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Sample records for cone penetrometers

  1. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  2. Cone Penetrometer Off-Surface Sensor

    SciTech Connect

    Smail, T.R.; French, p.J.; Huffman, R.K.; Hebert, P.S.

    1999-10-20

    Cone penetrometer technology accounts for approximately 50 percent of the subsurface drilling done at the Savannah River Site. This technology provides a means of collecting data for use in the characterization of the subsurface. The cone penetrometer consists of a steel cone attached to a pipe column that is hydraulically inserted into the ground. To allow researchers to accurately measure subsurface properties, without the inherent problems of cone penetrometer equipment, the Savannah River Technology Center has developed the Cone Penetrometer Off-Surface Sensor (CPOSS). The CPOSS design consists of a knife-blade mechanism mounted along the surface of a module capable of attaching to existing cone penetrometer equipment and being deployed at depths of up to 200 feet. CPOSS development is the subject of this report.

  3. Cone penetrometer demonstration standard startup review checklist

    SciTech Connect

    KRIEG, S.A.

    1998-11-09

    Startup readiness for the Cone Penetrometer Demonstration in AX Tank Farm will be verified through the application of a Standard Startup Review Checklist. This is a listing of those items essential to demonstrating readiness to start the Cone Penetrometer Demonstration in AX Tank Farm.

  4. System design description cone penetrometer system

    SciTech Connect

    Seda, R.Y., Westinghouse Hanford

    1996-08-12

    The system design description documents in detail the design of the cone penetrometer system. The systems includes the cone penetrometer physical package, raman spectroscopy package and moisture sensor package. Information pertinent to the system design, development, fabrication and testing is provided.

  5. Final design report for cone penetrometer platform

    SciTech Connect

    Seda, R.Y., Westinghouse Hanford

    1996-08-13

    The final design report documents the completion of the design review meetings for acceptance of the cone penetrometer from the vendor. All design comments have been dispositioned and closed. Open items dealt with completion of the safety assessment,operational procedures, operational testing and readiness review.

  6. Internal Reflection Sensor for the Cone Penetrometer

    SciTech Connect

    Job Bello

    1998-05-29

    The objectives of this project are to design, assemble, test, and demonstrate a prototype Internal Reflection Sensor (IRS) for the cone penetrometer. The sensor will ultimately be deployed during site characterization with the goal of providing real-time, in situ detection of NonAqueous Phase Liquids (NAPLs) in the subsurface. In the first phase of this program, we have designed and assembled an IRS module that interfaces directly to a standard cone penetrometer system. Laboratory tests demonstrated that the sensor responds in real-time to a wide variety of free phase NAPLs without interference from natural materials such as water and soil of various types or dissolved contaminants. In a preliminary field test, the sensor was able to locate NAPLs at thin, discrete depths in a soil test pit when deployed with a cone penetrometer. Ruggedness of the device was tested with a series of penetrometer pushes to the depth of refusal at a clean location. There was no visible damage to the sensor and its performance did not change in the course of these experiments. Based on the successes of the Phase I program, it is recommended that the project proceed to full-scale demonstration in Phase II.

  7. Apparatus and process for an off-surface cone penetrometer sensor

    DOEpatents

    Smail, Timothy R.; French, Phillip J.; Huffman, Russell K.

    2003-04-29

    A cone penetrometer is provided having a pivoting arm which deploys a variable distance from the surface of the cone penetrometer. Sensors placed on the end of the deployable arm provide for data collection outside a compression zone created by the insertion of the cone penetrometer.

  8. Cone Penetrometer Load Cell Temperature and Radiation Testing Results

    SciTech Connect

    Follett, Jordan R.

    2013-08-28

    This report summarizes testing activities performed at the Pacific Northwest National Laboratory to verify the cone penetrometer load cell can withstand the tank conditions present in 241-AN-101 and 241-AN-106. The tests demonstrated the load cell device will operate under the elevated temperature and radiation levels expected to be encountered during tank farm deployment of the device.

  9. Engineering task plan HTI [Hanford Tank Initiative] cone penetrometer

    SciTech Connect

    Krieg, S.A.

    1998-03-19

    The Hanford Cone Penetrometer Platform (CPP) will be used to insert instrumented and soil sampling probes into the soil adjacent to Tank AX-104 to assist in characterizing the waste plume. The scope, deliverables, roles and responsibilities, safety, and environmental considerations are presented in the task plan.

  10. Geological interpretation of cone penetrometer tests in Norton Sound, Alaska

    USGS Publications Warehouse

    Hampton, M.A.; Lee, H.J.; Beard, R.M.

    1982-01-01

    In situ cone-penetrometer tests at 11 stations in Norton Sound, Alaska, complement previous studies of geologic processes and provide geotechnical data for an analysis of sediment response to loading. Assessment of the penetrometer records shows that various geologic factors influence penetration resistance. On the Yukon prodelta, penetration resistance increases with the level of storm wave or ice loading. In central and eastern Norton Sound, thermogenic and biogenic gas, as well as variations in sediment texture and composition, effect a wide range of resistance to penetration. ?? 1982 A. M. Dowden, Inc.

  11. Hanford tank initiative cone penetrometer stand alone grouting module

    SciTech Connect

    CALLAWAY, W.S.

    1998-10-15

    The HTI subsurface characterization task will use the Hanford Cone Penetrometer platform (CPP) to deploy contaminant sensor and soil sampling probes into the vadose zone surrounding SST 241-AX-104. Closure of the resulting penetration holes may be stipulated by WAC requirements. A stand alone grouting capability deployable by the CPP has been developed. This qualification test plan defines testing of this capability to be performed at the Immobilized Low Activity Waste Disposal Complex.

  12. Hanford Tanks Initiative cone penetrometer siting plan and progress report

    SciTech Connect

    IWATATE, D.F.

    1998-10-15

    The HTI subsurface characterization task will use the Hanford Cone Penetrometer platform (CPP) to deploy soil sensor and sampling probes into the vadose zone/soils around AX-104 during FY-99. This Siting Plan describes activities and actions undertaken in support of CPP deployment: deployment goals, maps of the deployment sites/locations, pre-activity (siting-related) documentation tasks, a summary of activities that have been completed to date, and an estimated schedule of additional planned activities.

  13. Cone penetrometer fiber optic raman spectroscopy probe assembly

    DOEpatents

    Kyle, Kevin R.; Brown, Steven B.

    2000-01-01

    A chemically and mechanically robust optical Raman spectroscopy probe assembly that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

  14. Grouting guidelines for Hanford Tanks Initiative cone penetrometer borings

    SciTech Connect

    Iwatate, D.F.

    1998-05-18

    Grouting of an open cone penetrometer (CP) borehole is done to construct a barrier that prevents the vertical migration of fluids and contaminants between geologic units and aquifers intersected by the boring. Whether to grout, the types of grout, and the method of deployment are functions of the site-specific conditions. This report recommends the strategy that should be followed both before and during HTI [Hanford Tanks Initiative] CP deployment to decide specific borehole grouting needs at Hanford SST farms. Topics discussed in this report that bear on this strategy include: Regulatory guidance, hydrogeologic conditions, operational factors, specific CP grouting deployment recommendations.

  15. Conceptual design of a Raman probe for inclusion in the in-tank cone penetrometer

    SciTech Connect

    Kyle, K.R.

    1994-09-30

    Currently, tank wastes are to be characterized by drilling and physically removing core samples. The cores are analyzed in laboratories in a hot cell environment. The purpose of the cone penetrometer is to bring the interrogative methods to the sample in its native environment, providing faster, safer, and more cost effective tank characterization, both in terms of time and effort. Probes currently exist for the physical characterization of tank wastes in terms of porosity, density, temperature, and electrical conductivity. The main tool for chemical analysis in the in-tank cone penetrometer will be a fiber optic Raman spectroscopy probe, which will be used to collect information about the molecular chemical constituents of the tank wastes. This report addresses the design and implementation of a Raman probe with the in-tank cone penetrometer. The scope of this document includes design specifications and recommendations for the following aspects of the in-tank Raman cone penetrometer probe: cone penetrometer probe interface--an unit for the inclusion of a Raman probe in the in-tank cone penetrometer will be described; window materials--chemically resistant and mechanically stable materials for the cone penetrometer probe interface window will be considered; Raman probes--Raman probes for inclusion in the penetrometer will be discussed.

  16. Evaluation of Cone Penetrometer Data for Permeability Correlation at the Savannah River Site

    SciTech Connect

    Harris, M.K.

    1997-02-01

    This report documents the results of an assessment of cone penetrometer technology (CPT) use at the Savannah River Site. The study is intended to provide valuable insight into methods of increasing the utility of CPT data for site characterization.

  17. Development of a Cone Penetrometer for Measuring Spectral Characteristics of Soils in Situ

    NASA Technical Reports Server (NTRS)

    Lee, Landris T., Jr.; Malone, Philip G.

    1993-01-01

    A patent was recently granted to the U.S. Army for an adaptation of a soil cone penetrometer that can be used to measure the spectral characteristics (fluorescence or reflectance) of soils adjacent to the penetrometer rod. The system can use a variety of light sources and spectral analytical equipment. A laser induced fluorescence measuring system has proven to be of immediate use in mapping the distribution of oil contaminated soil at waste disposal and oil storage areas. The fiber optic adaptation coupled with a cone penetrometer permits optical characteristics of the in-situ soil to be measured rapidly, safely, and inexpensively. The fiber optic cone penetrometer can be used to gather spectral data to a depth of approximately 25 to 30 m even in dense sands or stiff clays and can investigate 300 m of soil per day. Typical detection limits for oil contamination in sand is on the order of several hundred parts per million.

  18. Fiber optic/cone penetrometer system for subsurface heavy metals detection

    SciTech Connect

    Saggese, S.; Greenwell, R.

    1995-10-01

    The objective of this project is to develop an integrated fiber optic sensor/cone penetrometer system to analyze the heavy metals content of the subsurface. This site characterization tool will use an optical fiber cable assembly which delivers high power laser energy to vaporize and excite a sample in-situ and return the emission spectrum from the plasma produced for chemical analysis. The chemical analysis technique, often referred to as laser induced breakdown spectroscopy (LIBS), has recently shown to be an effective method for the quantitative analysis of contaminants soils. By integrating the fiber optic sensor with the cone penetrometer, we anticipate that the resultant system will enable in-situ, low cost, high resolution, real-time subsurface characterization of numerous heavy metal soil contaminants simultaneously. There are several challenges associated with the integration of the LIBS sensor and cone penetrometer. One challenge is to design an effective means of optically accessing the soil via the fiber probe in the penetrometer. A second challenge is to develop the fiber probe system such that the resultant emission signal is adequate for quantitative analysis. Laboratory techniques typically use free space delivery of the laser to the sample. The high laser powers used in the laboratory cannot be used with optical fibers, therefore, the effectiveness of the LIBS system at the laser powers acceptable to fiber delivery must be evaluated. The primary objectives for this project are: (1) Establish that a fiber optic LIBS technique can be used to detect heavy metals to the required concentration levels; (2) Design and fabricate a fiber optic probe for integration with the penetrometer system for the analysis of heavy metals in soil samples; (3) Design, fabricate, and test an integrated fiber/penetrometer system; (4) Fabricate a rugged, field deployable laser source and detection hardware system; and (6) Demonstrate the prototype in field deployments.

  19. National standards and code compliance for electrical equipment and instruments installed in hazardous locations for the cone penetrometer

    SciTech Connect

    Bussell, J.H.

    1996-03-01

    The cone penetrometer is designed to measure the material properties of waste tank contents at the Hanford Site. The penetrometer system consists of a skid-mounted assembly, a penetrometer assembly (composed of a guide tube and a push rod), an active neutron moisture measurement probe, decontamination unit, and a support trailer containing a diesel-engine-driven hydraulic pump and a generator. The skid-mounted assembly is about 8 feet wide by 23 feet long and 15 feet high. Its nominal weight is about 40,000 pounds with the provisions to add up to 54,500 pounds of additional ballast. This document describes the cone penetrometer electrical instruments and how it complies with national standards.

  20. Cone-penetrometer exploration of sinkholes: Stratigraphy and soil properties

    SciTech Connect

    Bloomberg, D.; Upchurch, S.B.; Hayden, M.L. ); Williams, R.C. )

    1988-10-01

    Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine transgressions. The resulting deposits include five stratigraphic units. 1 and 2 represent Plio-Pleistocene marine sediments with Unit 2 being the zone of soil clay accumulation. 3 and 4 are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units 1 and 2. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast, SPT indicates general, inconclusive trends.

  1. Maintenance of the Hanford cone penetrometer platform during fiscal year 1999

    SciTech Connect

    IWATATE, D.F.

    1998-11-30

    This SOW describes services requested of Applied Research and Associates, Inc. (ARA), as a commercial provider of cone penetrometer equipment and services, to provide routine inspection and minimum preventive maintenance on the Hanford CP Platform (CPP) during Fiscal Year 1999. This SOW specifically pertains to the maintenance of the CPP and associated support equipment and is limited in scope to routine preventive maintenance and identification of any deficiencies. ARA is the original manufacturer of the CPP and will conduct this work following the vendor-prepared maintenance schedule.

  2. Pavement performance monitoring using Dynamic Cone Penetrometer and Geogauge during construction

    NASA Astrophysics Data System (ADS)

    Ahsan, Ahmed Nawal

    Proper design life of road network system requires adequate quality control measures during the construction process to ensure proper material quality and sufficient strength in between the materials. Laboratory tests are often time consuming and sometimes, are not practical while the construction work is going on, in-situ techniques can efficiently evaluate the material properties through simple and less time consuming procedures. Dynamic Cone Penetrometer and Geogauge can play a vital role as an in-situ testing equipment because both have the potential to measure the change in material properties through field tests being performed in the field. Both in-situ techniques was not extensively used in North Texas area. Frequent use of these two equipment during the construction process can expedite the whole construction process because both are hand-held devices and can be conducted within a short amount of time, often in minutes. For this study, Dynamic Cone Penetrometer and Geogauge was used to assess the material properties from the tests performed on five construction sites of Horseshoe Project around Dallas, TX. Several points across the width of the pavement have been considered to perform these in-situ tests along with Nuclear Density Gauge test in two of these sites. A thorough analysis has been conducted for the material properties to be determined. Dynamic Cone Penetrometer and Geogauge both were consistent to measure the change in in-place material characteristics of the pavement materials. The design thickness of cement treated base layer where the tests were being performed was 6". DCP was efficient enough to detect the layer thickness up to a proximity of 0.5 inch and was also able to distinguish layer anomalies between the pavement layers. Cement stabilized base layer provided with a DCPI value which ranges from 0.5 mm/blow to 8 mm/blow whereas, DCPI values were observed to remain within a range of 2 mm/blow to 22 mm/ blow. For the top 6" cement

  3. Cone-penetrometer exploration of Sinkholes: Stratigraphy and soil properties

    NASA Astrophysics Data System (ADS)

    Bloomberg, D.; Upchurch, S. B.; Hayden, M. L.; Williams, R. C.

    1988-10-01

    Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine, transgressions. The resulting deposits include five stratigraphic units. I and II represent Plio-Pleistocene marine sediments with Unit II being the zone of soil clay accumulation. III and IV are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units I and II. Conduit fill is a mixture of materials with low cohesion. The fill materials indicate centripetal and downward movement of insoluble sediments derived from the surrounding strata. Loss of cohesion results in near-zero friction ratios. Very low friction ratios, coupled with materials with little cohesion, indicate potentially-liquefiable soils in the immediate vicinity of zones where piping failure may be imminent. SPT does not provide sufficient data to predict these zones of potential, failure. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast

  4. Experimental study of penetration-cavity expansion soil bioturbation models using miniature cone penetrometers

    NASA Astrophysics Data System (ADS)

    Ruiz, Siul; Or, Dani; Schymanski, Stan

    2015-04-01

    A recently developed model of soil penetration mechanics and energetics by earthworms and plant roots is based on analogy with cone penetration and cavity expansion. Model predicted resistive forces for different geometries were tested using miniature cone penetrometers at sizes compatible with burrowing earthworms and growing roots. Experiments using cones of different radii (1.0 to 2.5 mm) and different semi-apex angles (15-300) were conducted using an apparatus enabling insertion at constant (prescribed) rates while obtaining highly resolved penetration resistance force measurements. Penetration experiments used soils at different water contents where soil mechanical parameters were determined independently using Oedometer tests under confined and unconfined conditions. Measurements were compared with predictions by analytical expressions for earthworm or root burrowing mechanics. Model predictions for the insertion force as a function of cone geometry and soil mechanical properties were in excellent agreement with cone penetration measurements. The study provides the necessary experimental confirmation to support energetic estimates of bioturbation costs in terms of soil organic carbon consumption. The study provides a better understanding of the fundamental duality nature between penetration forces and stresses and the dependency on cone angle. The measurements suggest that friction plays a relatively minor role as confirmed by experiments using recessed cones (no soil-shaft friction). Differences in application of the model to plant roots and earthworms will be discussed.

  5. Laser Induced Breakdown Spectroscopy (LIBS) detection of heavy metal using a cone penetrometer: System design and field investigation results

    SciTech Connect

    Miles, B.H.; Cortes, J.; Cespedes, E.R.

    1997-12-31

    U.S. Army Engineer Waterways Experiment Station (WES) investigators have designed, fabricated and field tested a cone penetrometer sensor based on Laser Induced Breakdown Spectroscopy (LIBS). The patented LIBS penetrometer design presented here is a useful tool in the detection, identification and delineation of heavy metals in soils in the vadose zone. The LIBS penetrometer is forced into the ground using a hydraulic ram system mounted within the Site Characterization and Analysis Penetrometer System (SCAPS) truck. The probe design relies on a recessed window geometry to avoid output window damage and a 80 millijoule Nd:YAG laser inside the probe to create the plasma. The probe design is discussed with particular emphasis on design tradeoffs, strengths and limitations of this design.

  6. Hydrogeologic structure underlying a recharge pond delineated with shear-wave seismic reflection and cone penetrometer data

    USGS Publications Warehouse

    Haines, S.S.; Pidlisecky, A.; Knight, R.

    2009-01-01

    With the goal of improving the understanding of the subsurface structure beneath the Harkins Slough recharge pond in Pajaro Valley, California, USA, we have undertaken a multimodal approach to develop a robust velocity model to yield an accurate seismic reflection section. Our shear-wave reflection section helps us identify and map an important and previously unknown flow barrier at depth; it also helps us map other relevant structure within the surficial aquifer. Development of an accurate velocity model is essential for depth conversion and interpretation of the reflection section. We incorporate information provided by shear-wave seismic methods along with cone penetrometer testing and seismic cone penetrometer testing measurements. One velocity model is based on reflected and refracted arrivals and provides reliable velocity estimates for the full depth range of interest when anchored on interface depths determined from cone data and borehole drillers' logs. A second velocity model is based on seismic cone penetrometer testing data that provide higher-resolution ID velocity columns with error estimates within the depth range of the cone penetrometer testing. Comparison of the reflection/refraction model with the seismic cone penetrometer testing model also suggests that the mass of the cone truck can influence velocity with the equivalent effect of approximately one metre of extra overburden stress. Together, these velocity models and the depth-converted reflection section result in a better constrained hydrologic model of the subsurface and illustrate the pivotal role that cone data can provide in the reflection processing workflow. ?? 2009 European Association of Geoscientists & Engineers.

  7. A method for aquifer and piezometric surface mapping with a cone penetrometer

    SciTech Connect

    Aggarwal, P.K.; Burton, J.C.; Meyer, W.T.; Stefano, J.E.

    1994-04-01

    The electronic cone penetrometer (ECPT) is increasingly being used for environmental characterization of hazardous waste sites, especially to delineate subsurface lithology and to obtain samples of groundwater. A potentially powerful use of the ECPT is the mapping of subsurface hydrostratigraphic features and aquifer piezometric surface(s) by using measurements of pore pressure. Most published studies on the use of the ECPT have been limited to shallow sand-clay sequences and indicate only limited success in hydrogeologic characterization. In this paper, we discuss a method for delineating the depth and thicknesses of unsaturated and saturated zones on the basis of the nature and rate of pore pressure dissipation. We have used this method to depths of 110 ft at several sites underlaid by clay-sand or weathered shale-limestone sequences. The equilibrium pore pressures in the saturated zone should ideally indicate the depth of the water table or aquifer piezometric surface; however, our data indicate that an apparent equilibrium value for pore pressures may be obtained that may be lower or higher than the true value, depending on the composition and grain size of the material in the aquifer, the depth of the dissipation test within the saturated zone, and the history of use of the porous filter in the cone penetrometer assembly. Consequently, the data on dissipation must be carefully calibrated and tested with measurements in a monitoring well before the data are used to determine piezometric surfaces.

  8. Cone Penetrometer Shear Strength Measurements of Sludge Waste in Tanks 241-AN-101 and 241-AN-106

    SciTech Connect

    Follett, Jordan R.

    2014-03-06

    This document presents the resulting shear strength profiles for sludge waste in Tanks 241-AN-101 and 241-AN-106, as determined with a full-flow cone penetrometer. Full-flow penetrometer measurements indicate shear strength profiles that increase roughly uniformly with depth. For Tank 241-AN-101, the undrained shear strength was calculated to range from 500 Pa near the sludge surface to roughly 3,300 Pa at 15 inches above the tank bottom. For 241-AN-106, the undrained shear strength was calculated to range from 500 Pa near the sludge surface to roughly 5,000 Pa at 15 inches above the tank bottom.

  9. Cone penetrometer deployed in situ video microscope for characterizing sub-surface soil properties

    SciTech Connect

    Lieberman, S.H.; Knowles, D.S.; Kertesz, J.

    1997-12-31

    In this paper we report on the development and field testing of an in situ video microscope that has been integrated with a cone penetrometer probe in order to provide a real-time method for characterizing subsurface soil properties. The video microscope system consists of a miniature CCD color camera system coupled with an appropriate magnification and focusing optics to provide a field of view with a coverage of approximately 20 mm. The camera/optic system is mounted in a cone penetrometer probe so that the camera views the soil that is in contact with a sapphire window mounted on the side of the probe. The soil outside the window is illuminated by diffuse light provided through the window by an optical fiber illumination system connected to a white light source at the surface. The video signal from the camera is returned to the surface where it can be displayed in real-time on a video monitor, recorded on a video cassette recorder (VCR), and/or captured digitally with a frame grabber installed in a microcomputer system. In its highest resolution configuration, the in situ camera system has demonstrated a capability to resolve particle sizes as small as 10 {mu}m. By using other lens systems to increase the magnification factor, smaller particles could be resolved, however, the field of view would be reduced. Initial field tests have demonstrated the ability of the camera system to provide real-time qualitative characterization of soil particle sizes. In situ video images also reveal information on porosity of the soil matrix and the presence of water in the saturated zone. Current efforts are focused on the development of automated imaging processing techniques as a means of extracting quantitative information on soil particle size distributions. Data will be presented that compares data derived from digital images with conventional sieve/hydrometer analyses.

  10. Cone Penetrometer for Subsurface Heavy Metals Detection. Semiannual report, November 1, 1996--March 31, 1997

    SciTech Connect

    Grisanti, Ames A.; Timpe, Ronald C.; Foster, H.J.; Eylands, Kurt E.; Crocker, Charlene R.

    1997-12-31

    Surface and subsurface contamination of soils by heavy metals, including Pb, Cr, Cu, Zn, and Cd, has become an area of concern for many industrial and government organizations (1). Conventional sampling and analysis techniques for soil provide a high degree of sensitivity and selectivity for individual analytes. However, obtaining a representative sampling and analysis from a particular site using conventional techniques is time consuming and costly (2). Additionally, conventional methods are difficult to implement in the field for in situ and/or real-time applications. Therefore, there is a need for characterization and monitoring techniques for heavy metals in soils which allow cost-effective, rapid, in situ measurements. Laser-induced breakdown spectroscopy (LIBS) has been used to successfully measure metals content in a variety of matrices (3-15) including soil (16,17). Under the Department of Energy (DOE) Federal Energy Technology Center (FETC) Industry Program, Science {ampersand} Engineering Associates (SEA) is developing a subsurface cone penetrometer (CPT) probe for heavy metals detection that employs LIBS (18). The LIES-CPT unit is to be applied to in situ, real-time sampling and analysis of heavy metals in soil. As part of its contract with DOE FETC, SEA is scheduled to field test its LIBS-CPT system in September 1997.

  11. Three-dimensional analysis of a developing sinkhole using GPR and dynamic cone penetrometer (DCP) testing

    NASA Astrophysics Data System (ADS)

    Brook, Martin; Gaines, Andrew; Nobes, David

    2016-04-01

    Ground penetrating radar (GPR) imaging is one of the most promising non-destructive and non-invasive methods that have offered new opportunities for mapping shallow subsurface disturbances in urbanized and industrialized zones. However, difficulties often arise in choosing the optimum antenna frequency to image subsurface features. While high frequency antennas may provide lots of detail, lower frequency antennas may provide information on larger-scale features that provide more site context. In this study, we performed GPR surveys to investigate a zone of subtle surface subsidence and pavement cracking on reclaimed land at a quayside. A 3-stage approach was used, and included: (1) a 250 MHz antenna survey to delineate the spatial extent of the area of interest; (2) a 500 MHz antenna survey to yield greater detail; and (3) direct verification of some of the key features using dynamic cone penetrometer (DCP) testing to "ground-truth" anomalies. This staged approach proved successful in imaging the sub-grade, and minor voids within approximately 2 m depth. Moreover, the quality of the data can be further improved by using GPR-Slice software in conjunction with DCP data to develop a 3D ground model. Through this approach, a combination of GPR survey and direct testing, we demonstrate the efficiency and quality of this method in mapping shallow subsidence features. An interpretation of the process-origin of the collapse feature is also proposed.

  12. Savannah River Site A/M Area Southern Sector Characterization Cone Penetrometer Report

    SciTech Connect

    Raabe, B.A.

    1993-05-01

    The Savannah River Site (SRS) is located in the Atlantic Coastal Plaingeologic province. This area is characterized by low relief, predominantly unconsolidated sediments of Cretaceous though Tertiary age. A multiple aquifer system underlies the A/M Area and affects the definition and distribution of a contaminant plume. The water table and uppermost confined aquifer (Steed Pond Aquifer) are contaminated with elevated concentrations of trichloroethylene(TCE) and tetrachloroethylene (PCE) and their associated compounds. The deeper aquifers in this area have less widely spread chlorinated hydrocarbon contamination.Cone penetrometer testing was selected as the method of investigation because it is minimally invasive, offers advanced technological capabilities in gathering lithologic data, and offers groundwater sampling capabilities. CPT testing utilizes a hydraulic push tool system. The probe collects real-time data that is processed by computer into soil/lithology classifications. The system can also be used to collect sediment and soil vapor samples although these features were not utilized during this project. Advantages of the CPT system include a small borehole diameter which minimizes cross-contamination of lithologic units, virtual elimination of drill cuttings and fluids that require disposal, collection of various types of undisturbed sediment and water samples and plotting of hydrostratigraphic and lithologic data while in the field.

  13. A bayesian approach for determining velocity and uncertainty estimates from seismic cone penetrometer testing or vertical seismic profiling data

    USGS Publications Warehouse

    Pidlisecky, A.; Haines, S.S.

    2011-01-01

    Conventional processing methods for seismic cone penetrometer data present several shortcomings, most notably the absence of a robust velocity model uncertainty estimate. We propose a new seismic cone penetrometer testing (SCPT) data-processing approach that employs Bayesian methods to map measured data errors into quantitative estimates of model uncertainty. We first calculate travel-time differences for all permutations of seismic trace pairs. That is, we cross-correlate each trace at each measurement location with every trace at every other measurement location to determine travel-time differences that are not biased by the choice of any particular reference trace and to thoroughly characterize data error. We calculate a forward operator that accounts for the different ray paths for each measurement location, including refraction at layer boundaries. We then use a Bayesian inversion scheme to obtain the most likely slowness (the reciprocal of velocity) and a distribution of probable slowness values for each model layer. The result is a velocity model that is based on correct ray paths, with uncertainty bounds that are based on the data error. ?? NRC Research Press 2011.

  14. Tank 241-AX-104 upper vadose zone cone penetrometer demonstration sampling and analysis plan

    SciTech Connect

    FIELD, J.G.

    1999-02-02

    This sampling and analysis plan (SAP) is the primary document describing field and laboratory activities and requirements for the tank 241-AX-104 upper vadose zone cone penetrometer (CP) demonstration. It is written in accordance with Hanford Tank Initiative Tank 241-AX-104 Upper Vadose Zone Demonstration Data Quality Objective (Banning 1999). This technology demonstration, to be conducted at tank 241-AX-104, is being performed by the Hanford Tanks Initiative (HTI) Project as a part of Tank Waste Remediation System (TWRS) Retrieval Program (EM-30) and the Office of Science and Technology (EM-50) Tanks Focus Area. Sample results obtained as part of this demonstration will provide additional information for subsequent revisions to the Retrieval Performance Evaluation (RPE) report (Jacobs 1998). The RPE Report is the result of an evaluation of a single tank farm (AX Tank Farm) used as the basis for demonstrating a methodology for developing the data and analyses necessary to support making tank waste retrieval decisions within the context of tank farm closure requirements. The RPE includes a study of vadose zone contaminant transport mechanisms, including analysis of projected tank leak characteristics, hydrogeologic characteristics of tank farm soils, and the observed distribution of contaminants in the vadose zone in the tank farms. With limited characterization information available, large uncertainties exist as to the nature and extent of contaminants that may exist in the upper vadose zone in the AX Tank Farm. Traditionally, data has been collected from soils in the vadose zone through the installation of boreholes and wells. Soil samples are collected as the bore hole is advanced and samples are screened on site and/or sent to a laboratory for analysis. Some in-situ geophysical methods of contaminant analysis can be used to evaluate radionuclide levels in the soils adjacent to an existing borehole. However, geophysical methods require compensation for well

  15. In situ detection of TNT contamination using electrochemical sensors in cone penetrometer system

    NASA Astrophysics Data System (ADS)

    Cespedes, Ernesto R.; Cooper, Stafford S.; Davis, William M.; Buttner, William J.; Vickers, William C.

    1995-01-01

    The pyrolysis of TNT and other explosive compounds generates signature compounds that can be efficiently detected by electrochemical sensors. This concept was implemented in the development and testing of a sensor probe for the Site Characterization and Analysis Penetrometer System (SCAPS) for the in situ detection of TNT, RDX, HMX, and other nitrogen-containing soil contaminants. This paper describes the results of laboratory studies and field tests conducted to determine the feasibility of employing electrochemical sensors for detecting subsurface explosives contaminants. A method for the in situ pyrolysis of explosives contaminants in soils was developed, and laboratory tests determined that electrochemical sensing of the pyrolysis products was sensitive, selective, reversible, and capable of broad dynamic range. A penetrometer probe that accommodates the electrochemical sensors (including power supply and signal conditioning electronics), the pyrolyzer unit, the pneumatic components, and geophysical sensors for soil classification was designed and fabricated. Results of tests conducted at the Louisiana Army Ammunition Plant during September 1994, which demonstrated the performance of the SCAPS sensor under actual field conditions, are presented.

  16. EM Task 13 -- Cone penetrometer for subsurface heavy metals detection. Semi-annual report, April 1--September 30, 1997

    SciTech Connect

    Grisanti, A.A.; Timpe, R.C.; Foster, H.J.; Eylands, K.E.; Crocker, C.R.

    1997-12-31

    Surface and subsurface contamination of soils by heavy metals, including Pb, Cr, Cu, Zn, and Cd has become an area of concern for many industrial and government organizations. Conventional sampling and analysis techniques for soil provide a high degree of sensitivity and selectivity for individual analytes. However, obtaining a representative sampling and analysis from a particular site using conventional techniques is time-consuming and costly. Additionally, conventional methods are difficult to implement in the field for in situ and/or real-time applications. Therefore, there is a need for characterization and monitoring techniques for heavy metals in soils which allow cost-effective, rapid, in situ measurements. Laser induced breakdown spectroscopy (LIBS) has been used to successfully measure metals content in a variety of matrices including soil. Science and Engineering Associates (SEA) is developing a subsurface cone penetrometer (CPT) probe for heavy metal detection that employs LIBS. The LIBS/CPT unit is to be applied to in situ, real-time sampling and analysis of heavy metals in soil. The overall objectives of this project are to evaluate potential calibration techniques for the LIBS/CPT instrument and to provide a preliminary evaluation of the LIBS instrument calibration using samples obtained from the field.

  17. Validation of impact penetrometer data by cone penetration testing and shallow seismic data within the regional geology of the Southern North Sea

    NASA Astrophysics Data System (ADS)

    Stephan, Sebastian; Kaul, Norbert; Villinger, Heinrich

    2015-06-01

    This study presents the assessment of total cone resistance from in situ deceleration measurements using the Lance Insertion Retardation meter (LIRmeter) in the Southern North Sea. The penetrometer is equipped with a measurement lance that is up to 6 m in length. The aim was to validate LIRmeter data interpretation within the regional geological context by comparison with static velocity cone penetration testing (CPT) and sub-bottom profiles. In total, 13 datasets were taken, in addition to preexisting hydroacoustical and static velocity CPT datasets. The dynamically acquired data were processed and compared to the reference static velocity data. The validation encourages the use of acceleration-based dynamic penetration tests, since a high degree of agreement was demonstrated between independently acquired dynamic and static cone resistance data. Moreover, the results reveal evidence of two successive formations with different geotechnical properties, consistent with existing knowledge on the regional setting. Additionally, there is novel indication of an incised glacial valley with muddy low-permeability sediments extending much further than reported to date, which would necessitate updating of older maps. The main advantage of penetrometer-based deceleration measurements lies in the robustness of the method, and the reliability of the sensors. However, penetration depth is, for dimensioning reasons, limited to the order of a few meters. Additionally, data processing includes the dependency of knowledge about the soil type to correct the dynamic data. These limitations can be satisfactorily outweighed by combination with reference data from static velocity tests, as demonstrated by integrating these data into a soil classification scheme.

  18. Soil penetrometer

    NASA Technical Reports Server (NTRS)

    Howard, E. A.; Hotz, G. M.; Bryson, R. P. (Inventor)

    1968-01-01

    An auger-type soil penetrometer for burrowing into soil formations is described. The auger, while initially moving along a predetermined path, may deviate from the path when encountering an obstruction in the soil. Alterations and modifications may be made in the structure so that it may be used for other purposes.

  19. In-situ Measurements of Geotechnical and Geo-Acoustic Seabed Properties Using a Free Fall Cone Penetrometer

    NASA Astrophysics Data System (ADS)

    Osler, J.; Trevorrow, M.; Furlong, A.; Christian, H.

    2001-12-01

    The FFCPT is a free fall probe that has been developed to measure acceleration and dynamic sediment porewater pressure as a function of depth of penetration into the seafloor. It also records hydrostatic pressure and optical backscatter in the water column, for mudline detection capability. This combination of sensors permits the direct application of geotechnical analysis methods and parametric-based correlations already long established in engineering practice. The FFCPT provides two independent means of calculating the undrained shear strength, as well as other engineering variables that are used in sediment textural classification. Specifically, there are accepted empirical relationships between the dynamic pore pressure parameter, the normalized dynamic penetration resistance and sediment grain size characteristics. The probe has a modular design allowing additional sensor payloads to be integrated. The first module to be developed measures resistivity, as a means to determine sediment bulk density. Experimental results from the New Jersey Strataform area and the Scotian Shelf will be presented and compared with measurements using a Seabed Terminal Impact Newton Gradiometer (STING) and an eXpendable Bottom Penetrometer (XBP).

  20. Cone penetrometer acceptance test report

    SciTech Connect

    Boechler, G.N.

    1996-09-19

    This Acceptance Test Report (ATR) documents the results of acceptance test procedure WHC-SD-WM-ATR-151. Included in this report is a summary of the tests, the results and issues, the signature and sign- off ATP pages, and a summarized table of the specification vs. ATP section that satisfied the specification.

  1. SITE CHARACTERIZATION ANALYSIS PENETROMETER SYSTEM (SCAPS) - INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    In August 1994, a demonstration of cone penetrometer-mounted sensor technologies took place to evaluate their effectiveness in sampling and analyzing the physical and chemical characteristics of subsurface sod at hazardous waste sites. he effectiveness of each technology was eval...

  2. Miniature GC for in-situ monitoring of VOC`s within a cone penetrometer. Final report, July 1994--May 1996

    SciTech Connect

    1996-05-31

    The {open_quotes}Cone-GC{close_quotes} was developed in response to a need for down hole, in-situ characterization of volatile organics within the soil profile, in the vadose zone, or a water headspace. A design based on the use of a miniature gas chromatograph was selected since it was believed that such an instrument would be adaptable to a broad range of analytes and could be used in complex, real-world situations where the environmental contaminants to be monitored may exist in complex mixtures with other vapors. The Cone-GC is versatile and will also fit within many other soil probes, hole liners, and minimally intrusive emplacement systems where small size in addition to high performance are required. The Cone-GC was designed to allow environmental specialists for the first time to obtain immediate, in-situ chemical measurements in a soil probe and to make real-time, on-site decisions that will greatly reduce the time (and cost) of site characterization and remediation. It will no longer be necessary to collect samples (using long sampling lines that may become contaminated), send them to an off-site laboratory for analysis, and then wait hours or days for results.

  3. Steerable/distance enhanced penetrometer delivery system

    SciTech Connect

    Amini, A.; Shenhar, J.; Lum, K.D.

    1995-12-31

    The first steps toward contaminant plume contaminant and remediation are detection and mapping of the plume. Penetrometers can be used to map the plume efficiently and also provide the means for in-situ sampling and remediation. In traditional penetrometer applications, the instrumentation package located at the tip measures soil resistance. However, for environmental monitoring purposes, an array of environmental sensors is packed inside the penetrometer rods for in-situ sampling and analysis, or for collection of laboratory samples. At present, penetrometer applications are limited primarily to vertical pushes and because of their heavy weight, the use of penetrometer trucks over shallow buried storage tanks is restricted. To close the technology gap in the use of penetrometers for environmental purposes, UTD took the initiative by developing a new position location device referred to as POLO (short for POsition LOcator), which provides real-time position location without blocking downhole access for environmental sensors. The next step taken was the initiation of work to make penetrometers steerable and capable of greater penetration capabilities. The product of this work will be a relatively lightweight vibratory steerable penetrometer that can provide greater penetration capability than traditional penetrometers of the same weight, permitting applications over shallow buried storage tanks.

  4. Steerable/distance enhanced penetrometer delivery system

    SciTech Connect

    Amini, A.; Shenhar, J.; Lum, K.D.

    1995-10-01

    The first steps toward contaminant plume containment and remediation are detection and mapping of the plume. Penetrometers can be used to map the plume efficiently and also provide the means for in-situ sampling and remediation. In traditional penetrometer applications, the instrumentation package located at the tip measures soil resistance. However, for environmental monitoring purposes, an array of environmental sensors is packed inside the penetrometer rods for in-situ sampling and analysis, or for collection of laboratory samples. At present, penetrometer applications are limited primarily to vertical pushes and because of their heavy weight, the use of penetrometer trucks over shallow buried storage tanks is restricted. To close the technology gap in the use of penetrometers for environmental purposes, UTD took the initiative by developing a new position location device referred to as POLO (short for POsition LOcator), which provides real-time position location without blocking downhole access for environmental sensors. The next step taken was the initiation of work to make penetrometers steerable and capable of greater penetration capabilities. The product of this work will be a relatively lightweight vibratory steerable penetrometer that can provide greater penetration capability than traditional penetrometers of the same weight, permitting applications over shallow buried storage tanks.

  5. LASER FLUORESCENCE EEM PROBE FOR CONE PENETROMETER POLLUTION ANALYSIS

    EPA Science Inventory

    A fiber optic LIF (Laser induced fluorescence) EEM (Excitation emission matrix) instrument for CPT deployment has been successfully developed and field tested. The system employs a Nd: YAG laser and Raman shifter as a rugged field portable excitation source. This excitation sou...

  6. EM Task 13 - Cone Penetrometer for Subsurface Heavy Metals Detection

    SciTech Connect

    Ames A. Grisanti; Charlene R. Crocker

    1998-11-01

    Surface and subsurface contamination of soils by heavy metals, including Pb, Cr, Cu, Zn, and Cd has become an area of concern for many industrial and government organizations (1) Conventional sampling and analysis techniques for soil provide a high degree of sensitivity and selectivity for individual analytes. However, obtaining a representative sampling and analysis from a particular site using conventional techniques is time consuming and costly (2) Additionally, conventional methods are difficult to implement in the field for in situ and/or real-time applications. Therefore, there is a need for characterization and monitoring techniques for heavy metals in soils that allow cost-effective, rapid, in situ measurements. The overall objectives of this project are to evaluate potential calibration techniques for the laser-induced breakdown spectroscopy (LIBS)-CPT instrument, to provide a preliminary evaluation of the LIBS instrument calibration using samples obtained from the field and to provide technical support to field demonstration of the LIBS-CPT instrument at a DOE facility.

  7. Use of the site characterization and analysis penetrometer system at Grandville, Michigan superfund site. Final report

    SciTech Connect

    Sharp, M.K.; Kala, R.; Powell, J.

    1992-12-01

    This report documents the results of an investigation at the Organic Chemical, Inc. site in Grandville, Michigan. This site is on the National Priority List for cleanup, and is being overseen by the Environmental Protection Agency, Chicago, Region V office. The site was investigated utilizing the Site Characterization and Analysis Penetrometer System, with a fiber optic fluorimeter sensor. This sensor allows the detection of hydrocarbon contaminants in the subsurface. A total of fifty pushes were completed at the site to an average depth of approximately 15 ft, covering approximately 80 acres. A hydrocarbon contaminant plume was located at the site extending from the OCI facility in a northerly direction. This matches the flow of the groundwater in the area as it moves toward the Grand River. The plume was successfully bounded on the North, South, and West sides. The plume boundary on the East side could not be established due to property constraints. The concentrations of contaminants in certain areas of the site exceeded 5000 ppm. Cone penetrometer, Geophysics, Fiber optic fluorescence.

  8. Initial field trials of the site characterization and analysis penetrometer system (SCAPS). Reconnaissance of Jacksonville Naval Air Station waste oil and solvents disposal site. Final report

    SciTech Connect

    Cooper, S.S.; Douglas, D.H.; Sharp, M.K.; Olsen, R.A.; Comes, G.D.

    1993-12-01

    At the request of the Naval Facilities Engineering Command (NAVFAC), Southern Division, Charleston, SC, the U.S. Army Engineer Waterways Experiment Station (WES) conducted the initial field trial of the Site Characterization and Analysis Penetrometer System (SCAPS) at Jacksonville Naval Air Station (NAS), Jacksonville FL. This work was carried out by a field crew consisting of personnel from WES and the Naval Ocean Systems Center during the period of 16 July 1990 to 14 August 1990. The SCAPS investigation at the Jacksonville NAS has two primary objectives: (a) to provide data that could be useful in formulating remediation plans for the facility and (b) to provide for the initial field trial of the SCAPS currently under development by WES for the U.S. Army Toxic and Hazardous Materials Agency (USATHAMA), now the U.S. Army Environmental Center. The original concepts for the SCAPS was to develop an integrated site screening characterization system whose capabilities would include (a) surface mapping, (b) geophysical surveys using magnetic, induced electromagnetic, and radar instruments, (c) measurements of soil strength, soil electrical resistivity, and laser-induced soil fluorometry Cone penetrometer, Site Characterization and Analysis Laser Induced Fluorescence(LIF), Penetrometer System(SCAPS) POL Contamination, using screening instrumentation mounted in a soil penetrometer, (d) soil and fluid samplers, and (e) computerized data acquisition, interpretation, and visualization. The goal of the SCAPS program is to provide detailed, rapid, and cost-effective surface and subsurface data for input to site assessment/remediation efforts.

  9. A steerable/distance enhanced penetrometer delivery system: Phase II. Topical report

    SciTech Connect

    Amini, A.; Shenhar, J.; Lum, K.D.

    1996-05-01

    This report summarizes the phase II work on the Position Location Device (POLO) for penetrometers. Phase II was carried out to generate an integrated design of a full-scale steerable/distance enhanced penetrometer delivery system. Steering provides for the controlled and directional use of the penetrometer, while vibratory thrusting can provide greater penetration ability.

  10. Rapid Characterization of Near-Surface Seafloor Sediment using a Free Fall Penetrometer

    NASA Astrophysics Data System (ADS)

    Mulukutla, G. K.; Melton, J.

    2010-12-01

    The assessment of the mechanical properties of near-surface sediment is of critical importance to several studies of the seafloor. Key properties such as sediment type, grain size, shear strength or bearing capacity are required for most geophysical and geotechnical studies of the seafloor. Recently developed Free Fall Penetrometers (FFP), instrumented not only with accelerometers but also with pressure sensors and optical backscatter sensors, are deployable from an underway vessel to provide rapid data to characterize the seafloor over a wide areal extent. In existing practice FFP data is used to provide a qualitative description of the seabed sediment using models from quasi-static penetrometer testing or as soft, medium or hard and provide an estimate of penetration resistance. The mechanics of FFP impact and embedment is considerably different from quasi-static penetration of a Cone Penetrometer Testing (CPT) as result this study takes a different approach to formulating a model. In many cases the information on the bottom is not sufficient or the penetration resistance is overestimated due to the dilatory effects observed particularly in sediment with a coarse-grained fraction. In this study a model is described that uses acceleration (i.e the deceleration)-time histories to identify the sediment type and provide an estimate of grain size. Estimate of the sediment shear strength for soft-sediment is provided by the formulation of a strain-rate dependent model that accounts for the varying velocity during embedment. The response of the pressure and optical backscatter sensors to embedment are used to identify the mudline and understand the drainage conditions during the embedment and provide a picture of the bottom conditions. The work describes original analysis and uses data from more than 200 drops of two FFPs deployed in the Bering Sea (conducted using the NOAA ship Fairweather) and Gulf of Maine, along with groundtruthing from a bottom sampler and field

  11. Sediment identification using free fall penetrometer acceleration-time histories

    NASA Astrophysics Data System (ADS)

    Mulukutla, Gopal K.; Huff, Lloyd C.; Melton, Jeffrey S.; Baldwin, Kenneth C.; Mayer, Larry A.

    2011-09-01

    Knowledge of physical properties of near-surface sediments is an important requirement for many studies of the seafloor. Dynamic or Free Fall Penetrometers (FFP), instrumented with accelerometers, are widely used to assess the mechanical properties of the sediment by deriving penetration resistance from the deceleration response of the probe as it impacts and embeds the seabed. Other field investigations, a priori knowledge or a very basic description of the type of sediment (such as a description of the sediment as soft, medium or hard) derived from studying the deceleration response (accelerometer-time histories) are used for sediment identification prior to the application of an appropriate strength determination model. In many cases this information is site-specific and in others the penetration resistance is overestimated due to the dilatory effects observed in sediment with an undetected grain fraction. In this study variables affecting a dynamic penetrometer-sediment interaction system are identified. Using data from field investigations and literature we found a relationship among five variables: peak acceleration, embedment depth, total embedment time, velocity of impact and grain size. This is used to formulate a sediment identification model. The model accounts for variables that may vary widely within one deployment and it can be applied to other FFPs with different physical characteristics (such as a different mass or size). This may lead to the increased use of FFP as a deployment tool for rapid in situ characterization of the seafloor.

  12. Summary of raman cone penetrometer probe waste tank radiation and chemical environment test

    SciTech Connect

    Reich, F.R.

    1996-09-27

    This report summarizes the results of testing Raman sapphire windows that were braze mounted into a mockup Raman probe head and stainless steel coupons in a simulated tank waste environment. The simulated environment was created by exposing sapphire window components, immersed in a tank simulant, in a gamma pit. This work was completed for the U.S. Department of Energy (DOE) Office of Environmental Management (EM-50) for Technical Task Proposal RL4-6-WT-21.

  13. Preliminary numerical modeling results - cone penetrometer (CPT) tip used as an electrode

    SciTech Connect

    Ramirez, A L

    2006-12-19

    Figure 1 shows the resistivity models considered in this study; log10 of the resistivity is shown. The graph on the upper left hand side shows a hypothetical resisitivity well log measured along a well in the upper layered model; 10% Gaussian noise has been added to the well log data. The lower model is identical to the upper one except for one square area located within the second deepest layer. Figure 2 shows the electrode configurations considered. The ''reference'' case (upper frame) considers point electrodes located along the surface and along a vertical borehole. The ''CPT electrode'' case (middle frame) assumes that the CPT tip serves as an electrode that is electrically connected to the push rod; the surface electrodes are used in conjuction with the moving CPT electrode. The ''isolated CPT electrode'' case assumes that the electrode at the CPT tip is electrically isolated from the pushrod. Note that the separate CPT push rods in the middle and lower frames are shown separated to clarify the figure; in reality, there is only one pushrod that is changing length as the probe advances. Figure 3 shows three pole-pole measurement schemes were considered; in all cases, the ''get lost'' electrodes were the leftmost and rightmost surface electrodes. The top frame shows the reference scheme where all surface and borehole electrodes can be used. The middle frame shows two possible configurations available when a CPT mounted electrode is used. Note that only one of the four poles can be located along the borehole at any given time; electrode combinations such as the one depicted in blue (upper frame) are not possible in this case. The bottom frame shows a sample configuration where only the surface electrodes are used. Figure 4 shows the results obtained for the various measurement schemes. The white lines show the outline of the true model (shown in Figure 1, upper frame). The starting initial model for these inversions is based on the electrical resistivity log shown on the upper left. The results in the lower frame show what would be observed if the data collected by the CPT electrode have been corrected for the effects of the push rod. Figure 5 shows the results obtained when the starting initial model is a homogeneous half-space with a resistivity of 20 ohm-m. This figure can be compared with Figure 4 to see the effect that different starting models have on the inversion. Figure 6 shows results that are analogous to those in Figure 4. In this case, the true model is the one shown in the lower frame of Figure 1. Figure 7 compares corrected and uncorrected results. Both results only used data that can be collected when CPT electrodes are used. The top frame shows results when data is collected with point electrodes (no correction used). The bottom frame shows results when data is collected using a CPT electrode; a correction was applied to remove the effects of the electrically conducting pushrod. Figure 8 compares data collected using the CPT electrodes to data collected with point electrode. The blue diamonds represent the uncorrected CPT data and the red squares represent the corrected CPT data. The top frame (electrical gap = 0.0 m) corresponds to the case where the CPT electrode and the pushrod are connected together thorigh the metal. The bottom frame corresponds to the case where the CPT electrode and pushrod are separated by a 1.0 m gap; the electrical connection between rod and electrode is through the soil.

  14. The penetrometer - A technique for monitoring composite propellant ageing characteristics

    NASA Astrophysics Data System (ADS)

    Faulkner, G. S.

    The monitoring of the natural and accelerated aging of rubbery composite propellants by using a non-destructive mechanical properties tester, the 'penetrometer', is presented. This capability facilitates predictions of rocket-motor service life and also detects motors that may not have been stored correctly. The probe is inserted into the conduit of a motor and held in place by an integral, motor-specific, air-bag. The indenter is then driven into the charge in a low-stress region. Information obtained from the test is displayed graphically on a microcomputer, analyzed, and stored. It is concluded that, because not all of the rocket motors will have seen the same environment depending on the individual motor history, it will be possible to extend the lifetime before disposal since the charge can now be tested. This in turn will lead to financial savings if the charge's life can be said to have 'X' years of life left and does not need to be withdrawn from service.

  15. Demonstration of a VOC in-situ fiber optic sensor for use with a penetrometer analysis system

    NASA Astrophysics Data System (ADS)

    Hartenstein, Steven D.; Moore, Glenn A.; Nelson, Bruce N.; Kane, James; Lowe, Mark

    1996-11-01

    Researchers at the Idaho National Engineering Laboratory with their industrial CRADA partner GEO-CENTERS demonstrated a fiber optic based VOC sensor at the Army Environmental Center technology demonstration at Dover Air Force Base. The sensor used during the demonstration was a single fiber optic cable coupled to an in situ sensor element contained in a cone penetrometer tip. The sensor's fluorescence response was measured at the surface using an optical breadboard-based instrument. Results from this demonstration showed that the sensor provided semi-quantitative results for total VOCs comparable to the historical values of VOCs. In addition, the demonstration identified several technical challenges for improvement of the sensor. This paper describes the analytical properties of the reversible sensing materials, construction of an improved sensor system, and the planned demonstration of the modified in- situ VOC sensor system. This sensor system is tentatively scheduled for demonstration at the Army Environmental Center's Aberdeen Proving Ground Test site. Improvements to the VOC sensor system include an optical configuration that will correct for soil matrix interferences and multiple sensing substrates to learn whether VOC selectivity can be achieved.

  16. Distinct element analyses of inclined cone penetration test in granular ground

    NASA Astrophysics Data System (ADS)

    Jiang, Mingjing; Dai, Yongsheng; Shen, Zhifu; Zhang, Ning

    2013-06-01

    This paper is to investigate the mechanism of inclined cone penetration test (CPT) using the numerical discrete element approach. A series of penetration tests with the penetrometer inclined at different angles (i.e., 30°, 45°, 60°, 75° and 90°) were numerically performed. The velocity fields, displacements of soils adjacent to the cone tip, rotation of the principal stresses and the averaged pure rotation rate (APR) are analyzed. Special focus is placed on the penetration mechanism and the effect of inclination angle on the tip resistance. The DEM results show that soils around the cone tip experience complex displacement paths as the penetration proceeds and exhibit characteristic velocity fields corresponding to three different failure mechanisms. The principal stresses near the cone tip undergo apparent rotation, accompanied by large APR which indicates evident particle rotation adjacent to the cone. The normalized tip resistance qN( = qc/σν0) decays with penetration depth in a decreasing rate. At the same penetration depth, qN decreases with the increasing of the inclination angle of penetrometer.

  17. DEPTH CONTINUOUS HYDRAULIC CONDUCTIVITY PROFILING USING AN ACTIVE SOURCE PENETROMETER

    NASA Astrophysics Data System (ADS)

    Fitzgerald, M.; Elsworth, D.

    2009-12-01

    A method is developed to recover depth-continuous hydraulic conductivity profiles of an unconsolidated saturated aquifer using an active source penetrometer, the Hydraulic Profiling Tool (HPT). The tool yields estimates of K through continuous injection of fluid in the subsurface from a small port on the probe shaft while controlled measurements of net applied fluid pressure required to maintain a specified flow rate (typically 350 mL/min) are recorded. The tool gathers these data of flow rate and measured applied pressure during halted and constant-rate penetration (typically 2cm/sec) of the probe. The analysis is developed in two parts, first to explore the interplay between advective effects controlled by penetration rate and secondly flow volume effects controlled by the targeted flow rate. These two effects are analyzed through their respective influence on the measured applied pressure response in ΔP/σv’-Q/ΔP space, which shows a linear relationship for the flow rate to applied pressure response when Q/ΔP > 1 and when Q/ΔP < 1 the response tends towards an asymptotic limit representing soil failure limits as ΔP/σv’ > 1. The analysis shows that penetration rate does not significantly influence the applied pressure response at the tested penetration rates (0 ≤ U(cm/s)≤ 4). The targeted applied flow rate does however influence the applied pressure response as flow rates less than ~300 mL/min show a scattering of the data in ΔP/σv’-Q/ΔP space, where above 300 mL/min the data begins to form a linear response. A targeted flow rate of QT = 400mL/min is suggested as a suitable flow rate based on this analysis. Measurements of hydraulic conductivity are then obtained for the HPT data through the derivation of an equation based on a recast form of Darcy’s law where considerations of the flow geometry as K = (QHPT/ΔP)(δw/πΦ). K profiles obtained for the HPT system are then compared against K profiles obtained from an independent method (PSU

  18. Dynamic cone penetration tests in granular media: Determination of the tip's dynamic load-penetration curve

    NASA Astrophysics Data System (ADS)

    Escobar, E.; Benz, M.; Gourvès, R.; Breul, P.

    2013-06-01

    In this article a two-dimensional discrete numerical model, realized in PFC2D, is presented. This model is used in the dynamic penetration tests in a granular medium. Its objective being the validation of the measurement technique offered by Panda 3® (Benz et al. 2011) which is designed to calculate the tip's load-penetration curve for each impact in the soil where different parameters are used. To do so, we have compared the results obtained by calculation during the impacts to those measured directly in the model of a penetrometer through the installation of the gauges at the cone.

  19. A new method for comparing and matching snow profiles, application for profiles measured by penetrometers

    NASA Astrophysics Data System (ADS)

    Hagenmuller, Pascal; Pilloix, Thibault

    2016-05-01

    Hardness has long been recognized as a good predictor of snow mechanical properties and therefore as an indicator of snowpack stability at the measured point. Portable digital penetrometers enable the amassing of a large number of snow stratigraphic hardness profiles. Numerous probings can be performed to assess the snowpack spatial variability and to compensate for measurement errors. On a decameter scale, continuous internal layers are typically present in the snowpack. The variability in stratigraphic features observed in the measurement set mainly originates from the measured variations in internal layer thickness due to either a real heterogeneity in the snowpack or to errors in depth measurement. For the purpose of real time analysis of snowpack stability, a great amount of data collected by digital penetrometers must be quickly synthesized into a characterization representative of the test site. This paper presents a method with which to match and combine several hardness profiles by automatically adjusting their layer thicknesses. The objectives are to synthesize the information collected by several profiles into one representative profile of the measurement set, disentangle information about hardness and depth variabilities, and quantitatively compare hardness profiles measured by different penetrometers. The method was tested by using co-located hardness profiles measured with three different penetrometers --- the snow micropenetrometer (SMP), the Avatech SP1 and the ramsonde --- during the winter 2014-2015 at two sites in the French Alps. When applied to the SMP profiles of both sites, the method reveals a low spatial variability of hardness properties, which is usually masked by depth variations. The developed algorithm is further used to evaluate the new portable penetrometer SP1. The hardness measured with this instrument is shown to be in good agreement with the SMP measurements, but errors in the recovered depth are notable, with a standard

  20. Design of a horizontal penetrometer for measuring on-the-go soil resistance.

    PubMed

    Topakci, Mehmet; Unal, Ilker; Canakci, Murad; Celik, Huseyin Kursat; Karayel, Davut

    2010-01-01

    Soil compaction is one of the main negative factors that limits plant growth and crop yield. Therefore, it is important to determine the soil resistance level and map it for the field to find solutions for the negative effects of the compaction. Nowadays, high powered communication technology and computers help us on this issue within the approach of precision agriculture applications. This study is focused on the design of a penetrometer, which can make instantaneous soil resistance measurements in the soil horizontally and data acquisition software based on the GPS (Global Positioning System). The penetrometer was designed using commercial 3D parametric solid modelling design software. The data acquisition software was developed in Microsoft Visual Basic.NET programming language. After the design of the system, manufacturing and assembly of the system was completed and then a field experiment was carried out. According to the data from GPS and penetration resistance values which are collected in Microsoft SQL Server database, a Kriging method by ArcGIS was used and soil resistance was mapped in the field for a soil depth of 40 cm. During operation, no faults, either in mechanical and software parts, were seen. As a result, soil resistance values of 0.2 MPa and 3 MPa were obtained as minimum and maximum values, respectively. In conclusion, the experimental results showed that the designed system works quite well in the field and the horizontal penetrometer is a practical tool for providing on-line soil resistance measurements. This study contributes to further research for the development of on-line soil resistance measurements and mapping within the precision agriculture applications. PMID:22163410

  1. Design of a Horizontal Penetrometer for Measuring On-the-Go Soil Resistance

    PubMed Central

    Topakci, Mehmet; Unal, Ilker; Canakci, Murad; Celik, Huseyin Kursat; Karayel, Davut

    2010-01-01

    Soil compaction is one of the main negative factors that limits plant growth and crop yield. Therefore, it is important to determine the soil resistance level and map it for the field to find solutions for the negative effects of the compaction. Nowadays, high powered communication technology and computers help us on this issue within the approach of precision agriculture applications. This study is focused on the design of a penetrometer, which can make instantaneous soil resistance measurements in the soil horizontally and data acquisition software based on the GPS (Global Positioning System). The penetrometer was designed using commercial 3D parametric solid modelling design software. The data acquisition software was developed in Microsoft Visual Basic.NET programming language. After the design of the system, manufacturing and assembly of the system was completed and then a field experiment was carried out. According to the data from GPS and penetration resistance values which are collected in Microsoft SQL Server database, a Kriging method by ArcGIS was used and soil resistance was mapped in the field for a soil depth of 40 cm. During operation, no faults, either in mechanical and software parts, were seen. As a result, soil resistance values of 0.2 MPa and 3 MPa were obtained as minimum and maximum values, respectively. In conclusion, the experimental results showed that the designed system works quite well in the field and the horizontal penetrometer is a practical tool for providing on-line soil resistance measurements. This study contributes to further research for the development of on-line soil resistance measurements and mapping within the precision agriculture applications. PMID:22163410

  2. Design of a horizontal penetrometer for measuring on-the-go soil resistance.

    PubMed

    Topakci, Mehmet; Unal, Ilker; Canakci, Murad; Celik, Huseyin Kursat; Karayel, Davut

    2010-01-01

    Soil compaction is one of the main negative factors that limits plant growth and crop yield. Therefore, it is important to determine the soil resistance level and map it for the field to find solutions for the negative effects of the compaction. Nowadays, high powered communication technology and computers help us on this issue within the approach of precision agriculture applications. This study is focused on the design of a penetrometer, which can make instantaneous soil resistance measurements in the soil horizontally and data acquisition software based on the GPS (Global Positioning System). The penetrometer was designed using commercial 3D parametric solid modelling design software. The data acquisition software was developed in Microsoft Visual Basic.NET programming language. After the design of the system, manufacturing and assembly of the system was completed and then a field experiment was carried out. According to the data from GPS and penetration resistance values which are collected in Microsoft SQL Server database, a Kriging method by ArcGIS was used and soil resistance was mapped in the field for a soil depth of 40 cm. During operation, no faults, either in mechanical and software parts, were seen. As a result, soil resistance values of 0.2 MPa and 3 MPa were obtained as minimum and maximum values, respectively. In conclusion, the experimental results showed that the designed system works quite well in the field and the horizontal penetrometer is a practical tool for providing on-line soil resistance measurements. This study contributes to further research for the development of on-line soil resistance measurements and mapping within the precision agriculture applications.

  3. The cone dystrophies.

    PubMed

    Simunovic, M P; Moore, A T

    1998-01-01

    The cone dystrophies are a heterogeneous group of inherited disorders that result in dysfunction of the cone photoreceptors and sometimes their post-receptoral pathways. The major clinical features of cone dystrophy are photophobia, reduced visual acuity and abnormal colour vision. Ganzfeld electroretinography shows reduced or absent cone responses. On the basis of their natural history, the cone dystrophies may be broadly divided into two groups: stationary and progressive cone dystrophies. The stationary cone dystrophies have received more attention, and subsequently our knowledge of their molecular genetic, psychophysical and clinical characteristics is better developed. Various methods of classification have been proposed for the progressive cone dystrophies, but none is entirely satisfactory, largely because the underlying disease mechanisms are poorly understood. Multidisciplinary studies involving clinical assessment, molecular genetics, electrophysiology and psychophysics should lead to an improved understanding of the pathogenesis of these disorders.

  4. Cold knife cone biopsy

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003910.htm Cold knife cone biopsy To use the sharing features on this page, please enable JavaScript. A cold knife cone biopsy (conization) is surgery to remove ...

  5. Cone-based electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Pidlisecky, Adam

    Determining the 3-D spatial distribution of subsurface properties is a critical part of managing the clean-up of contaminated sites. Most standard hydrologic methods sample small regions immediately adjacent to wells or testing devices. This provides data which are not representative of the entire region of interest. Furthermore, at many contaminated sites invasive methods are not acceptable, due to the risks associated with contacting and spreading the contaminants. To address these issues, I have developed a minimally invasive technology that provides information about the 3-D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), integrates the existing technologies of resistivity cone penetration testing (RCPT) with electrical resistivity tomography. Development of this tool included the creation of new software and modeling algorithms, the design of field equipment, field testing, and processing and interpretation of the resulting data. I present a 2.5-D forward modeling algorithm that incorporates an effective correction for the errors caused by boundary effects and source singularities. The algorithm includes an optimization technique for acquiring the Fourier coefficients required for the solution. A 3-D inversion algorithm is presented that has two major improvements over existing algorithms. First, it includes a 3-D version of the boundary correction/source singularity correction developed for the 2.5-D problem. Second, the algorithm can handle any type of acquisition geometry; this was a requirement for the development of C-bert. C-bert involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer and at the surface to measure the resultant potential field. In addition to these measurements, we obtain the standard suite of RCPT data, including high resolution resistivity logs. The RCPT data can be used to generate a realistic

  6. Determination of permeability of soils using the multiple piezo-element penetrometer

    NASA Astrophysics Data System (ADS)

    Song, Chung R.; Voyiadjis, George Z.; Tumay, Mehmet T.

    1999-11-01

    The current method of determining the hydraulic properties of soils using piezocone penetration test (PCPT) requires the advancement of the piezocone penetrometer to the desired depth and holding (or arresting) it for the dissipation test. In order to obtain the hydraulic properties, one analyses the pore water dissipation test results by two-dimensional or three-dimensional radial drainage consolidation. This conventional procedure is methodologically simple and presents relatively reliable values of permeability compared to other field test methods. However, it is still challenging for field engineers and needs to be improved. The piezocone penetrometer intrudes into the ground with the speed of 2 cm/s. Thus, the test mechanism is a kind of strain-controlled condition with partial drainage. Therefore, the excess pore pressure during the piezocone penetration is a function of the permeability of the soil as well as the stress-strain parameters. Thus, with the proper coupled theory of mixtures which can take into account the coupling of solid and pore water flow, one can predict the permeability of the soil from the pore pressure response during PCPT. In this study, the coupled theory of mixtures of the soil grains and the pore water is used in order to predict the permeability of the soil from the excess pore pressure generated from the multiple piezo-element PCPT on the fly. An elasto-plastic, finite strain constitutive equation in an updated Lagrangian reference frame is used in this work. Using the proposed method, a reliable value of the permeability of soil is obtained conveniently without the use of the pore pressure dissipation tests. Copyright

  7. INFLUENCE OF CONSOLIDATION CHARACTERISTICS ON CONE PENETRATION RESISTANCE AND LIQUEFACTION RESISTANCE IN SILTY SOILS

    NASA Astrophysics Data System (ADS)

    Ecemis, N.; Thevanayagam, S.

    2009-12-01

    A unique correlation between liquefaction resistance and penetration resistance is not possible to justify without considering the effects of hydraulic conductivity, k, compressibility, mv, and coefficient of consolidation, ch on cone penetration resistance (Thevanayagam and Martin 2002). Therefore, CPT liquefaction screening chart revised to take into account the consolidation characteristics on penetration resistance. Recently, it has been observed that k and ch magnitudes vary between sand and sand-silt mixtures even evaluated at the same liquefaction resistance. The combined effects of penetration rate, v, cone diameter, d, and ch also influences the cone penetration resistance. Silt content affects the liquefaction resistance as well. Several numerical simulations performed by Thevanayagam and Ecemis in 2008 to explore the transition from undrained to drained conditions by varying the non-dimensional parameter T(=vd/ch) with a range of coefficient of consolidation for a single soil type, Ottawa sand-silt mix. Numerical simulation suggested the drained and undrained limits for T are respectively around 0.01 and 10. Tests on circular foundations reported by Finnie and Randolph (1994) suggested the limits of 0.01 and 30. Tests with a cylindrical T-bar penetrometer suggested narrower limits of 0.1 and 10 (House et al. 2001). Finally, the correlation between T, normalized cone resistance and cyclic resistance to liquefaction is proposed and compared with the current liquefaction screening method by CPT (Fig.1). Fig.1: Proposed & Current Liquefaction Screening Method

  8. Cone Health and Retinoids.

    PubMed

    Kono, Masahiro

    2015-01-01

    Cones are photoreceptor cells used for bright light and color vision. Retinoids are vitamin A derivatives, one of which is the 11-cis aldehyde form that serves as the chromophore for both cone and rod visual pigments. In the visual disease, Type 2 Leber congenital amaurosis (LCA2), 11-cis-retinal generation is inhibited or abolished. Work by others has shown that patients with LCA2 have symptoms consistent with degenerating cones. In mouse models for LCA2, early cone degeneration is readily apparent: cone opsins and other proteins associated with the outer segment are delocalized and cell numbers decline rapidly within the first month. Rods would appear normal morphologically and functionally, if not for the absence of chromophore. Supplementation of mouse models of LCA2 with cis-retinoids has been shown to slow loss of cone photoreceptor cells if mice were maintained in darkness. Thus, 11-cis-retinal appears not only to have a role in the light response reaction but also to promote proper trafficking of the cone opsins and maintain viable cones. PMID:26310171

  9. Cone sampling array models

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Poirson, Allen

    1987-01-01

    A model is described for positioning cones in the retina. Each cone has a circular disk of influence, and the disks are tightly packed outward from the center. This model has three parameters that can vary with eccentricity: the mean radius of the cone disk, the standard deviation of the cone disk radius, and the standard deviation of postpacking jitter. Estimates for these parameters out to 1.6 deg are found by using measurements reported by Hirsch and Hylton (1985) and Hirsch and Miller (1987) of the positions of the cone inner segments of an adult macaque. The estimation is based on fitting measures of variation in local intercone distances, and the fit to these measures is good.

  10. Progressive cone dystrophy.

    PubMed Central

    Ripps, H; Noble, K G; Greenstein, V C; Siegel, I M; Carr, R E

    1987-01-01

    Psychophysical, reflectometric, and electrophysiological studies were performed on four members of a dominant pedigree with progressive cone dystrophy. The two youngest individuals were asymptomatic at the initial examination, and none of the subjects complained of problems associated with night vision. Absent or grossly reduced cone-mediated ERG responses revealed the widespread loss of cone function. Moderate elevations (1 log unit) in absolute threshold together with reductions in rhodopsin levels in the midperipheral retina provided evidence of a mild impairment of the rod system also, although not to the degree seen in a cone-rod dystrophy. The progressive nature of the disease was apparent from the case histories and the changes in visual performance that occurred on re-test after a 5-year interval. Likewise, the results of incremental threshold measurements at several retinal loci suggested that peripheral cones may be affected earlier and more severely than those in the central retina. PMID:3502298

  11. S-cone psychophysics.

    PubMed

    Smithson, Hannah E

    2014-03-01

    We review the features of the S-cone system that appeal to the psychophysicist and summarize the celebrated characteristics of S-cone mediated vision. Two factors are emphasized: First, the fine stimulus control that is required to isolate putative visual mechanisms and second, the relationship between physiological data and psychophysical approaches. We review convergent findings from physiology and psychophysics with respect to asymmetries in the retinal wiring of S-ON and S-OFF visual pathways, and the associated treatment of increments and decrements in the S-cone system. Beyond the retina, we consider the lack of S-cone projections to superior colliculus and the use of S-cone stimuli in experimental psychology, for example to address questions about the mechanisms of visually driven attention. Careful selection of stimulus parameters enables psychophysicists to produce entirely reversible, temporary, "lesions," and to assess behavior in the absence of specific neural subsystems. PMID:24759446

  12. Spatial variability of detrended soil plow layer penetrometer resistance transect in a sugarcane field

    NASA Astrophysics Data System (ADS)

    Pérez, Luis D.; Cumbrera, Ramiro; Mato, Juan; Millán, Humberto; Tarquis, Ana M.

    2015-04-01

    Spatial variability of soil properties is relevant for identifying those zones with physical degradation. In this sense, one has to face the problem of identifying the origin and distribution of spatial variability patterns (Brouder et al., 2001; Millán et al., 2012). The objective of the present work was to quantify the spatial structure of soil penetrometer resistance (PR) collected from a transect data consisted of 221 points equidistant. In each sampling, readings were obtained from 0 cm till 70 cm of depth, with an interval of 5 cm (Pérez, 2012). The study was conducted on a Vertisol (Typic Hapludert) dedicated to sugarcane (Saccharum officinarum L.) production during the last sixty years (Pérez et al., 2010). Recently, scaling approach has been applied on the determination of the scaling data properties (Tarquis et al., 2008; Millán et al., 2012; Pérez, 2012). We focus in the Hurst analysis to characterize the data variability for each depth. Previously a detrended analysis was conducted in order to better study de intrinsic variability of the series. The Hurst exponent (H) for each depth was estimated showing a characteristic pattern and differentiating PR evolution in depth. References Brouder, S., Hofmann, B., Reetz, H.F., 2001. Evaluating spatial variability of soil parameters for input management. Better Crops 85, 8-11. Millán, H; AM Tarquís, Luís D. Pérez, Juan Mato, Mario González-Posada, 2012. Spatial variability patterns of some Vertisol properties at a field scale using standardized data. Soil and Tillage Research, 120, 76-84. Pérez, Luís D. 2012. Influencia de la maquinaria agrícola sobre la variabilidad espacial de la compactación del suelo. Aplicación de la metodología geoestadística-fractal. PhD thesis, UPM (In Spanish). Pérez, Luís D., Humberto Millán, Mario González-Posada 2010. Spatial complexity of soil plow layer penetrometer resistance as influenced by sugarcane harvesting: A prefractal approach. Soil and Tillage

  13. The color cone.

    PubMed

    Logvinenko, Alexander D

    2015-02-01

    While the notion of a color cone can be found in writings of Maxwell, Helmholtz, Grassmann, and other scientists of the nineteenth century, it has not been clearly defined as yet. In this paper, the color cone is understood as the set of points in the cone excitation space produced by all possible lights. The spectral curve representing all the monochromatic lights is shown not to entirely belong to the color cone boundary, since its ends turn into the color cone interior. The monochromatic lights represented by the fragment of the spectral curve lying on the color cone boundary make up what is called the effective visible spectrum. The color cone is shown to be a convex hull of the conical surface through the fragment of the spectral curve representing the effective visible spectrum. The effective visible spectrum ends are shown to be determined by the photopigment spectral absorbance being independent of the prereceptor filters (e.g., the spectral transmittance of the lense and macular pigment).

  14. Growth cone collapse assay.

    PubMed

    Cook, Geoffrey M W; Jareonsettasin, Prem; Keynes, Roger J

    2014-01-01

    The growth cone collapse assay has proved invaluable in detecting and purifying axonal repellents. Glycoproteins/proteins present in detergent extracts of biological tissues are incorporated into liposomes, added to growth cones in culture and changes in morphology are then assessed. Alternatively purified or recombinant molecules in aqueous solution may be added directly to the cultures. In both cases after a defined period of time (up to 1 h), the cultures are fixed and then assessed by inverted phase contrast microscopy for the percentage of growth cones showing a collapsed profile with loss of flattened morphology, filopodia, and lamellipodia.

  15. 2017 Eclipse Shadow Cones

    NASA Video Gallery

    A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is complete...

  16. Lunar cinder cones.

    PubMed

    McGetchin, T R; Head, J W

    1973-04-01

    Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

  17. Lunar cinder cones.

    NASA Technical Reports Server (NTRS)

    Mcgetchin, T. R.; Head, J. W.

    1973-01-01

    Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

  18. Application of new combined penetrometer-moisture probe (CPMP) for hydro- geomorphological survey

    NASA Astrophysics Data System (ADS)

    Yamakawa, Y.; Masaoka, N.; Kosugi, K.; Mizuyama, T.

    2008-12-01

    In order to clarify generating mechanisms of shallow landslides on steep slopes and to predict their occurrences, it is important to grasp not only the geological structures but also the rainwater flow pathways in soil mantles. We developed combined penetrometer-moisture probe (CPMP) which enables us to directly and simultaneously measure vertical profiles of soil penetration resistance and water content. In terms of water content profiles measurement, CPMP provides less time-consuming and less destructive method than the conventional weighing method and the conventional soil moisture sensors which requires excavation of deep trenches. However, CPMP provides insufficient information on bedrock structures, and the application of the CPMP to large areas is still difficult. On the other hand, indirect geosurvey techniques, such as Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR), can be applied to detect the structures of large areas expanding from soil mantles through deep bedrocks. Measurements by these geosurvey techniques are, however, difficult to evaluate because both water content and bulk density of soils and rocks affect the results, namely, the electrical resistivities and the relative dielectric constant. In this study, we applied the CPMP, ERT, and GPR survey techniques to the same forested hillslope. The CPMP succeeded in accurate measurements of spatial distributions of soil water content and soil depth. The ERT succeeded in providing rough shapes of the soil mantle and the saturated region. Moreover, by comparing the ERT images to the soil mantle depths detected by the CPMP, the degree of bedrock weathering could be estimated. In contrast, the GPR was unable to detect precisely neither the ground water table nor the soil- bedrock interface, which might be attributed to the large heterogeneities in soil properties of the forested hillslope studied. The results of this study indicated a possibility that the combination of the

  19. Cone penetration and bevameter geotechnical tests in lunar regolith simulants: discrete element method analysis and experimentation

    NASA Astrophysics Data System (ADS)

    Kulchitsky, A. V.; Johnson, J.; Duvoy, P.; Wilkinson, A.; Creager, C. M.

    2012-12-01

    For in situ resource utilization on the Moon, asteroids, Mars, or other space body it is necessary to be able to simulate the interaction of mobile platforms and excavation machines with the regolith for engineering design, planning, and operations. For accurate simulations, tools designed to measure regolith properties will need to be deployed and interpreted. Two such tools are the penetrometer, used to measure a soil strength index as a function of depth, and the bevameter, used to characterize regolith surface properties of strength, friction and sinkage. The penetrometer interrogates regolith properties from the surface to a depth limited only by the capabilities of the instrument to penetrate the regolith while a bevameter interrogates only the upper few centimeters needed to describe a mobility platform's traction and sinkage. Interpretation of penetrometer and bevameter data can be difficult, especially on low gravity objects. We use the discrete element method (DEM) model to simulate the large regolith deformations and failures associated with the tests to determine regolith properties. The DEM simulates granular material behavior using large aggregates of distinct particles. Realistic physics of particle-particle interaction introduces many granular specific phenomena such as interlocking and force chain formation that cannot be represented using continuum methods. In this work, experiments using a cone penetrometer test (CPT) and bevameter on lunar simulants JSC-1A and GRC-1 were performed at NASA Glenn Research Center. These tests were used to validate the physics in the COUPi DEM model. COUPi is a general physical DEM code being developed to model machine/regolith interactions as part of a NASA Lunar Science Institute sponsored project on excavation and mobility modeling. The experimental results were used in this work to build an accurate model to simulate the lunar regolith. The CPT consists of driving an instrumented cone with opening angle of 60

  20. The cone dysfunction syndromes

    PubMed Central

    Aboshiha, Jonathan; Dubis, Adam M; Hardcastle, Alison J; Michaelides, Michel

    2016-01-01

    The cone dysfunction syndromes are a heterogeneous group of inherited, predominantly stationary retinal disorders characterised by reduced central vision and varying degrees of colour vision abnormalities, nystagmus and photophobia. This review details the following conditions: complete and incomplete achromatopsia, blue-cone monochromatism, oligocone trichromacy, bradyopsia and Bornholm eye disease. We describe the clinical, psychophysical, electrophysiological and imaging findings that are characteristic to each condition in order to aid their accurate diagnosis, as well as highlight some classically held notions about these diseases that have come to be challenged over the recent years. The latest data regarding the genetic aetiology and pathological changes observed in the cone dysfunction syndromes are discussed, and, where relevant, translational avenues of research, including completed and anticipated interventional clinical trials, for some of the diseases described herein will be presented. Finally, we briefly review the current management of these disorders. PMID:25770143

  1. Why rods and cones?

    PubMed

    Lamb, T D

    2016-02-01

    Under twenty-first-century metropolitan conditions, almost all of our vision is mediated by cones and the photopic system, yet cones make up barely 5% of our retinal photoreceptors. This paper looks at reasons why we additionally possess rods and a scotopic system, and asks why rods comprise 95% of our retinal photoreceptors. It considers the ability of rods to reliably signal the arrival of individual photons of light, as well as the ability of the retina to process these single-photon signals, and it discusses the advantages that accrue. Drawbacks in the arrangement, including the very slow dark adaptation of scotopic vision, are also considered. Finally, the timing of the evolution of cone and rod photoreceptors, the retina, and the camera-style eye is summarised.

  2. Developing a Penetrometer-Based Mapping System for Visualizing Silage Bulk Density from the Bunker Silo Face.

    PubMed

    Li, Menghua; Jungbluth, Kerstin H; Sun, Yurui; Cheng, Qiang; Maack, Christian; Buescher, Wolfgang; Lin, Jianhui; Zhou, Haiyang; Wang, Zhongyi

    2016-07-05

    For silage production, high bulk density (BD) is critical to minimize aerobic deterioration facilitated by oxygen intrusion. To precisely assess packing quality for bunker silos, there is a desire to visualize the BD distribution within the silage. In this study, a penetrometer-based mapping system was developed. The data processing included filtering of the penetration friction component (PFC) out of the penetration resistance (PR), transfer of the corrected penetration resistance (PRc) to BD, incorporation of Kriged interpolation for data expansion and map generation. The experiment was conducted in a maize bunker silo (width: 8 m, middle height: 3 m). The BD distributions near the bunker silo face were represented using two map groups, one related to horizontal- and the other to vertical-density distribution patterns. We also presented a comparison between the map-based BD results and core sampling data. Agreement between the two measurement approaches (RMSE = 19.175 kg·m(-3)) demonstrates that the developed penetrometer mapping system may be beneficial for rapid assessment of aerobic deterioration potential in bunker silos.

  3. Developing a Penetrometer-Based Mapping System for Visualizing Silage Bulk Density from the Bunker Silo Face

    PubMed Central

    Li, Menghua; Jungbluth, Kerstin H.; Sun, Yurui; Cheng, Qiang; Maack, Christian; Buescher, Wolfgang; Lin, Jianhui; Zhou, Haiyang; Wang, Zhongyi

    2016-01-01

    For silage production, high bulk density (BD) is critical to minimize aerobic deterioration facilitated by oxygen intrusion. To precisely assess packing quality for bunker silos, there is a desire to visualize the BD distribution within the silage. In this study, a penetrometer-based mapping system was developed. The data processing included filtering of the penetration friction component (PFC) out of the penetration resistance (PR), transfer of the corrected penetration resistance (PRc) to BD, incorporation of Kriged interpolation for data expansion and map generation. The experiment was conducted in a maize bunker silo (width: 8 m, middle height: 3 m). The BD distributions near the bunker silo face were represented using two map groups, one related to horizontal- and the other to vertical-density distribution patterns. We also presented a comparison between the map-based BD results and core sampling data. Agreement between the two measurement approaches (RMSE = 19.175 kg·m−3) demonstrates that the developed penetrometer mapping system may be beneficial for rapid assessment of aerobic deterioration potential in bunker silos. PMID:27399703

  4. Developing a Penetrometer-Based Mapping System for Visualizing Silage Bulk Density from the Bunker Silo Face.

    PubMed

    Li, Menghua; Jungbluth, Kerstin H; Sun, Yurui; Cheng, Qiang; Maack, Christian; Buescher, Wolfgang; Lin, Jianhui; Zhou, Haiyang; Wang, Zhongyi

    2016-01-01

    For silage production, high bulk density (BD) is critical to minimize aerobic deterioration facilitated by oxygen intrusion. To precisely assess packing quality for bunker silos, there is a desire to visualize the BD distribution within the silage. In this study, a penetrometer-based mapping system was developed. The data processing included filtering of the penetration friction component (PFC) out of the penetration resistance (PR), transfer of the corrected penetration resistance (PRc) to BD, incorporation of Kriged interpolation for data expansion and map generation. The experiment was conducted in a maize bunker silo (width: 8 m, middle height: 3 m). The BD distributions near the bunker silo face were represented using two map groups, one related to horizontal- and the other to vertical-density distribution patterns. We also presented a comparison between the map-based BD results and core sampling data. Agreement between the two measurement approaches (RMSE = 19.175 kg·m(-3)) demonstrates that the developed penetrometer mapping system may be beneficial for rapid assessment of aerobic deterioration potential in bunker silos. PMID:27399703

  5. Cap protects aircraft nose cone

    NASA Technical Reports Server (NTRS)

    Bryan, C. F., Jr.; Bryan, D. C.

    1981-01-01

    Inexpensive, easily fabricated cap protects aircraft nose cone from erosion. Made of molded polycarbonate, cap has been flight tested at both subsonic and supesonic speeds. Its strength and erosion characteristics are superior to those of fiberglass cones.

  6. Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

    SciTech Connect

    Delegard, Calvin H.; Schmidt, Andrew J.; Chenault, Jeffrey W.

    2011-12-06

    Spent fuel radioactive sludge present in the K East and K West spent nuclear fuel storage basins now resides in the KW Basin in six large underwater engineered containers. The sludge will be dispositioned in two phases under the Sludge Treatment Project: (1) hydraulic retrieval into sludge transport and storage containers (STSCs) and transport to interim storage in Central Plateau and (2) retrieval from the STSCs, treatment, and packaging for shipment to the Waste Isolation Pilot Plant. In the years the STSCs are stored, sludge strength is expected to increase through chemical reaction, intergrowth of sludge crystals, and compaction and dewatering by settling. Increased sludge strength can impact the type and operation of the retrieval equipment needed prior to final sludge treatment and packaging. It is important to determine whether water jetting, planned for sludge retrieval from STSCs, will be effective. Shear strength is a property known to correlate with the effectiveness of water jetting. Accordingly, the unconfined compressive strengths (UCS) of archive K Basin sludge samples and sludge blends were measured using a pocket penetrometer modified for hot cell use. Based on known correlations, UCS values can be converted to shear strengths. Twenty-six sludge samples, stored in hot cells for a number of years since last being disturbed, were identified as potential candidates for UCS measurement and valid UCS measurements were made for twelve, each of which was found as moist or water-immersed solids at least 1/2-inch deep. Ten of the twelve samples were relatively weak, having consistencies described as 'very soft' to 'soft'. Two of the twelve samples, KE Pit and KC-4 P250, were strong with 'very stiff' and 'stiff' consistencies described, respectively, as 'can be indented by a thumb nail' or 'can be indented by thumb'. Both of these sludge samples are composites collected from KE Basin floor and Weasel Pit locations. Despite both strong sludges having

  7. DEMONSTRATION BULLETIN: SITE CHARACTERIZATION ANALYSIS PENETROMETER SYSTEM (SCAPS) LIF SENSOR - U.S. ARMY, NAVY, AND AIR FORCE (TRI-SERVICES)

    EPA Science Inventory

    The Tri-Services Site Characterization Analysis Penetrometer System (SCAPS) was developed by the U.S. Army (U.S. Army Corps of Engineers, Waterways Experiment Station [WES] and the Army Environmental Center [AEC]), Navy (Naval Command, Control and Ocean Surveillance Center), and ...

  8. Task summary for cone penetrating testing sounding and soil and groundwater sampling Salmon Site, Lamar County, Mississippi

    SciTech Connect

    Not Available

    1994-10-01

    The Salmon Site (SS), located in Mississippi, was the site of two nuclear and two gas explosion testes conducted deep underground in the Tatum Salt Dome between 1964 and 1970. As a consequence radionuclides generated during the testing were released into the salt dome. During reentry drilling and other site activities, incidental liquid and solid wastes that contained radioactivity were generated, resulting in some soil, ground water and equipment contamination. US DOE is conducting a series of investigations as a part of the Remedial Investigation and Feasibility Study (under CERCLA) This report summarizes the cone penetrometer testing (CPT) and sampling program conducted in fall 1993, providing a description of the activities and a discussion of the results. The objectives of the CPT program were to determine subsurface conditions and stratification; determine the depth to the potentiometric surface; obtain soil samples from predetermined depths; obtain groundwater samples at predetermined depths.

  9. Light cone matrix product

    SciTech Connect

    Hastings, Matthew B

    2009-01-01

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {Delta} = 0.5, we simulate to a time of {approx} 22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  10. Shatter cones: Diagnostic impact signatures

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Dietz, R. S.

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  11. Shatter cones: Diagnostic impact signatures

    NASA Technical Reports Server (NTRS)

    Mchone, J. F.; Dietz, R. S.

    1988-01-01

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  12. Cone rod dystrophies.

    PubMed

    Hamel, Christian P

    2007-01-01

    Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently

  13. A/M Area Metallurgical Laboratory: Summary of Phase I Characterization Well Installation, Cone Penetrometer Testing and Soil Coring for Soil Headspace Analysis

    SciTech Connect

    Van Pelt, R.S.

    1999-11-05

    This report documents the Phase I characterization of chlorinated solvent contamination in the regulatory-defined uppermost aquifer (includes the M Area, Lost Lake and middle sand aquifer zones) within the Metallurgical Laboratory (Met Lab) of the A/M Area.

  14. Analytical results, database management and quality assurance for analysis of soil and groundwater samples collected by cone penetrometer from the F and H Area seepage basins

    SciTech Connect

    Boltz, D.R.; Johnson, W.H.; Serkiz, S.M.

    1994-10-01

    The Quantification of Soil Source Terms and Determination of the Geochemistry Controlling Distribution Coefficients (K{sub d} values) of Contaminants at the F- and H-Area Seepage Basins (FHSB) study was designed to generate site-specific contaminant transport factors for contaminated groundwater downgradient of the Basins. The experimental approach employed in this study was to collect soil and its associated porewater from contaminated areas downgradient of the FHSB. Samples were collected over a wide range of geochemical conditions (e.g., pH, conductivity, and contaminant concentration) and were used to describe the partitioning of contaminants between the aqueous phase and soil surfaces at the site. The partitioning behavior may be used to develop site-specific transport factors. This report summarizes the analytical procedures and results for both soil and porewater samples collected as part of this study and the database management of these data.

  15. The Holographic Entropy Cone

    SciTech Connect

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  16. The Holographic Entropy Cone

    DOE PAGES

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phasemore » space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.« less

  17. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  18. A marine dynamic penetrometer for the determination of sea floor geotechnical properties

    NASA Astrophysics Data System (ADS)

    Stephan, S.; Kaul, N. E.; Villinger, H. W.

    2013-12-01

    We present a seafloor lance penetration monitoring system: the Lance Insertion Retardation Meter (LIRmeter). The device can be used to infer geotechnical seafloor properties, such as bearing capacity by monitoring the deceleration of a free-fall penetrating lance. The deceleration record can be furthermore used to estimate mean grain size and mud content of the sea floor as well as total penetration depth. The LIRmeter is contained in a pressure vessel (440 x 110 mm) and equipped with accelerometers of different sensitivities to (i) determine sea floor resistance during penetration and (ii) to generate a depth axis. Typically, measurements are carried out in a pogo style fashion to allow a rapid measurement progress during field campaigns. The LIRmeter is intended to determine sea floor properties on the sole basis of deceleration measurements in order to achieve a mechanically and electronically robust system. Data is sampled at a resolution of 16 bit and at a rate of typically 500 Hz for each channel. The device can either be installed in any type of lance i.e. marine heat flow probes, gravity corers, piston corers or can be used in combination with a purpose built lance as a standalone instrument. It has a usable length of four meters, a total weight of 280 kg in air and can be operated up to full ocean depth (6000m). The bearing capacity of the sea floor is a critical factor for marine engineering projects such as burial of marine cables, pipeline laying and foundations. Knowledge of the mud content can provide constraints for the estimation of hydraulic conductivity. The identification of weak zones along a slope can moreover provide vital information for risk assessment studies. Traditionally, frame based, quasi static Cone Penetration Tests (CPT) or sampling methods like gravity coring are used to conduct these types of investigation. In comparison to established but time consuming and rather costly methods, the LIRmeter is intended (i) for near surface

  19. Determining the geotechnical properties of planetary regolith using Low Velocity Penetrometers

    NASA Astrophysics Data System (ADS)

    Seweryn, K.; Skocki, K.; Banaszkiewicz, M.; Grygorczuk, J.; Kolano, M.; Kuciński, T.; Mazurek, J.; Morawski, M.; Białek, A.; Rickman, H.; Wawrzaszek, R.

    2014-09-01

    Measurements of mechanical and thermophysical properties of planetary surface allow determining many important parameters useful for planetologists. For example, effective heat conductivity or thermal inertia of the regolith can help to better understand the processes occurring in the bodies interior. Chemical and mineralogical composition gives us a chance to determine the origin and evolution of moons and satellites. Mechanical properties of the surface are one of the key factors needed by civil engineers for developing future bases on space bodies. Space missions to planetary bodies highly restrict the payload concerning its mass and power consumption. Therefore, it is quite impossible to use a standard terrestrial technique like the Load Plate Test or Direct Shear Tests to determine the geotechnical parameters of the planetary regolith. Even the Dynamic Cone Penetration (DCP) method, which is frequently used for field testing, does not fit well with the constraints imposed by a space mission. Nevertheless, its operation principle is very similar to that of at the Low Velocity Penetrators (LVP), several of them being currently on their way to planetary bodies (e.g. the MUPUS instrument) or which were developed in the last couple of years (e.g. the CHOMIK instrument or the KRET device). In this paper we present a comparison between DCP method and LVP operation which was observed during several tests campaigns during mole KRET and CHOMIK instrument development. The tests were performed in different planetary analogues: JSC-1A, Chenobi and AGK-2010, Phobos analogue, cometary analogues F1, F2 and F3 (SRC) and dry quartz sand. In the last part of the paper the concept of results' interpretation is presented.

  20. Shatter cones: (Mis)understood?

    PubMed Central

    Osinski, Gordon R.; Ferrière, Ludovic

    2016-01-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and “double” cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship Dsc = 0.4 Da, where Dsc is the maximum spatial extent of in situ shatter cones, and Da is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  1. Shatter cones: (Mis)understood?

    PubMed

    Osinski, Gordon R; Ferrière, Ludovic

    2016-08-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and "double" cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact.

  2. Shatter cones: (Mis)understood?

    PubMed

    Osinski, Gordon R; Ferrière, Ludovic

    2016-08-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and "double" cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  3. RP cone-rod degeneration.

    PubMed Central

    Heckenlively, J R

    1987-01-01

    A group of patients with progressive retinal degeneration and visual field loss, who meet the basic definition of RP were investigated to better define the relationship of the findings on the ERG with clinical characteristics such as visual field size, presence or absence of scotomata or pseudo-altitudinal defects on visual field, amount of night blindness; and presence or absence of macular or optic nerve changes. These studies suggest that cone-rod degeneration patients of the RP type go through the following stages; early, the ERG has a definite cone-rod pattern where the rod ERG is larger than the cone ERG while both are abnormal. As the disease advances, there is more of a reduction in the scotopic ERG such that both the rod and cone ERGs become nearly equal. As the disease further progresses the ERG becomes non-recordable on single-flash technique, but there is good residual rod function and the final rod threshold remains good until the visual field is reduced, typically less than 10 degrees with the IV-4 isopter. Finally with advanced disease the patient becomes night blind and generally becomes very difficult to distinguished from patients who have advanced rod-cone degeneration. While it may seem logical to find that visual field size correlates with various ERG parameters; this has not been as consistent a finding in patients with rod-cone degeneration in the author's experience. The analysis shows several new pieces of information about visual field changes in cone-rod degeneration; enlarged blind spots are seen earlier in cases which have recordable cone-rod patterns (group I), and pseudo-altitudinal changes are more likely to occur in autosomal recessive patients. Patients with macular lesions and central scotomata had larger amplitudes than patients with normal appearing maculae and no central scotomata. Patients with temporal optic atrophy had an earlier onset of symptoms and significant correlation with both photopic a- and b-waves and bright flash

  4. Journey of water in pine cones

    PubMed Central

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-01-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system. PMID:25944117

  5. Journey of water in pine cones

    NASA Astrophysics Data System (ADS)

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-05-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system.

  6. Inside the cone of protection

    SciTech Connect

    Stahmann, J.R.

    1983-01-01

    Although lightning cones of protection and cones of attraction have been used for over 100 years, much confusion still remains as to their effectiveness, particularly as applied to personnel protection. At Kennedy Space Center, a 1:1 cone of protection with a straight side is standard for structure or equipment protection. However, at the launch pad, where a 400-foot lightning lightning rod on top of an insulating mast is used for pad lightning protection, the idea developed that personnel within a 400-foot radius of this mast would be safe from lightning and those outside it would not. Since it is obvious that a person 395 feet (120.4 m.) from the mast is only slightly safer than one at 405 feet (123.5 m.), an investigation was initiated to calculate the probabilities of a person being struck by lightning as he moves closer to the mast inside the cone of protection. Since the risk does not go to zero outside the structure, the risk level can then be estimated. To arrive at the expected strike frequency, it was necessary to measure the strike frequencies at KSC. Krider and others have found a mean area density of cloud-to-ground lightning at KSC of about 4.6 + or - 3.1 flashes per sq km per month in the summer. An overall frequency is estimated as about 20 flashes per sq km per year. With these data, the risk of exposure at various distances from the lightning mast can be calculated. Assuming continuous exposure during thunderstorms, this risk varies from about one strike per person in 1,400 years near the tower to one stroke per person in 300 years at about 400 foot (122 m.).

  7. Cardiac cone-beam CT

    SciTech Connect

    Manzke, Robert . E-mail: robert.manzke@philips.com

    2005-10-15

    This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net.

  8. Prescriptionless light-cone integrals

    NASA Astrophysics Data System (ADS)

    Suzuki, A. T.; Schmidt, A. G. M.

    2000-01-01

    Perturbative quantum gauge field theory as seen within the perspective of physical gauge choices such as the light-cone gauge entails the emergence of troublesome poles of the type (k\\cdot n)^{-α} in the Feynman integrals. These come from the boson field propagator, where α = 1,2,\\cdots and n^{μ} is the external arbitrary four-vector that defines the gauge proper. This becomes an additional hurdle in the computation of Feynman diagrams, since any graph containing internal boson lines will inevitably produce integrands with denominators bearing the characteristic gauge-fixing factor. How one deals with them has been the subject of research over decades, and several prescriptions have been suggested and tried in the course of time, with failures and successes. However, a more recent development at this fronteer which applies the negative dimensional technique to compute light-cone Feynman integrals shows that we can altogether dispense with prescriptions to perform the calculations. An additional bonus comes to us attached to this new technique, in that not only it renders the light-cone prescriptionless but, by the very nature of it, it can also dispense with decomposition formulas or partial fractioning tricks used in the standard approach to separate pole products of the type (k\\cdot n)^{-α}[(k-p)\\cdot n]^{-β} (β = 1,2,\\cdots ). In this work we demonstrate how all this can be done.

  9. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  10. Organization of the human trichromatic cone mosaic.

    PubMed

    Hofer, Heidi; Carroll, Joseph; Neitz, Jay; Neitz, Maureen; Williams, David R

    2005-10-19

    Using high-resolution adaptive-optics imaging combined with retinal densitometry, we characterized the arrangement of short- (S), middle- (M), and long- (L) wavelength-sensitive cones in eight human foveal mosaics. As suggested by previous studies, we found males with normal color vision that varied in the ratio of L to M cones (from 1.1:1 to 16.5:1). We also found a protan carrier with an even more extreme L:M ratio (0.37:1). All subjects had nearly identical S-cone densities, indicating independence of the developmental mechanism that governs the relative numerosity of L/M and S cones. L:M cone ratio estimates were correlated highly with those obtained in the same eyes using the flicker photometric electroretinogram (ERG), although the comparison indicates that the signal from each M cone makes a larger contribution to the ERG than each L cone. Although all subjects had highly disordered arrangements of L and M cones, three subjects showed evidence for departures from a strictly random rule for assigning the L and M cone photopigments. In two retinas, these departures corresponded to local clumping of cones of like type. In a third retina, the L:M cone ratio differed significantly at two retinal locations on opposite sides of the fovea. These results suggest that the assignment of L and M pigment, although highly irregular, is not a completely random process. Surprisingly, in the protan carrier, in which X-chromosome inactivation would favor L- or M-cone clumping, there was no evidence of clumping, perhaps as a result of cone migration during foveal development. PMID:16237171

  11. Coupled penetrometer, MBES and ADCP assessments of tidal variations in surface sediment layer characteristics along active subaqueous dunes, Danish Wadden Sea

    NASA Astrophysics Data System (ADS)

    Stark, Nina; Hanff, Hendrik; Svenson, Christian; Ernstsen, Verner B.; Lefebvre, Alice; Winter, Christian; Kopf, Achim

    2011-08-01

    In-situ geotechnical measurements of surface sediments were carried out along large subaqueous dunes in the Knudedyb tidal inlet channel in the Danish Wadden Sea using a small free-falling penetrometer. Vertical profiles showed a typical stratification pattern with a resolution of ˜1 cm depicting a thin surface layer of low sediment strength and a stiffer substratum below (quasi-static bearing capacity equivalent: 1-3 kPa in the top layer, 20-140 kPa in the underlying sediment; thickness of the top layer ca. 5-8 cm). Observed variations in the thickness and strength of the surface layer during a tidal cycle were compared to mean current velocities (measured using an acoustic Doppler current profiler, ADCP), high-resolution bathymetry (based on multibeam echo sounding, MBES) and qualitative estimates of suspended sediment distributions in the water column (estimated from ADCP backscatter intensity). The results revealed an ebb dominance in sediment remobilization, and a general accretion of the bed towards low water. A loose top layer occurred throughout the tidal cycle, likely influenced by bedload transport and small events of suspended sediment resettlement (thickness: 6 ± 2 cm). Furthermore, this layer showed a significant increase in thickness (e.g. from 8 cm to 16 cm) related to periods of overall deposition. These findings imply that dynamic penetrometers can conveniently serve to (1) quantify potentially mobile sediments by determining the thickness of a loose sediment surface layer, (2) unravel sediment strength development in potentially mobile sediments and (3) identify sediment accumulation. Such data are an important complement and add a new geotechnical perspective during investigations of sediment remobilization processes in highly dynamic coastal environments.

  12. Combination use of electrical resistivity imaging and a new combined penetrometer-moisture probe for measuring water content distribution in hillslopes

    NASA Astrophysics Data System (ADS)

    Yamakawa, Yosuke; Masaoka, Naoya; Kosugi, Ken'ichirou; Mizuyama, Takahisa

    2013-04-01

    Electrical resistivity imaging (ERI) as a method for effectively evaluating soil water content distribution on natural hill slopes was validated in site by combining ERI technique with the invasive measurement of volumetric water content (?) using a newly developed combined penetrometer-moisture probe (CPMP) in two head-water catchments underlain by weathered granite and weathered granite porphyry. The moisture sensor of a CPMP adopts time-domain reflectometry (TDR) and the probe, which is attached at the tip of the soil penetrometer, consists of two stainless steel wires coiled along grooves in acrylic pipe. The CPMP is a highly maneuverable technique and could provide simultaneous measurements of the penetration resistance and water content of soil layers. There was some reasonable correlation between ? and ? within each slope, indicating the potential of ERI for at least qualitatively evaluating moisture conditions within soil layers of natural hill slopes without directly measuring ? using any invasive method. These ? - ? datasets of two catchments with different geological condition were both roughly consistent with fitted functional models (Archie's equation), indicating the possibility of quantitatively evaluating ? of soil layer on natural hill slopes using ERI based on field-scale calibrations with invasive methods. The difference of the fitted functional models between the two catchments seems attributable to a difference in geological and soil conditions. Inconsistencies between ? and ? within each dataset of the two catchments may be significantly attributable to not only limitations on spatial resolution of ERI technique related to the issue of representative volumes of the technique and inversion analysis to obtain ? profiles but also the assumption that soil properties and pore-water resistivity of the entire slope are homogeneous. Using a CPMP as invasive method, detecting heterogeneous ? distribution more accurately than ERI technique, together

  13. Fundamental conical defects: The d-cone, its e-cone, and its p-cone

    NASA Astrophysics Data System (ADS)

    Seffen, Keith A.

    2016-07-01

    We consider well-known surface disclinations by cutting, joining, and folding pieces of paper card. The resulting shapes have a discrete, folded vertex whose geometry is described easily by Gauss's mapping, in particular, we can relate the degree of angular excess, or deficit, to the size of fold line rotations by the area enclosed by the vector diagram of these rotations. This is well known for the case of a so-called "d-cone" of zero angular deficit, and we formulate the same for a general disclination. This method allows us to observe kinematic properties in a meaningful way without needing to consider equilibrium. Importantly, the simple vector nature of our analysis shows that some disclinations are primitive; and that other types, such as d-cones, are amalgamations of them.

  14. Fundamental conical defects: The d-cone, its e-cone, and its p-cone.

    PubMed

    Seffen, Keith A

    2016-07-01

    We consider well-known surface disclinations by cutting, joining, and folding pieces of paper card. The resulting shapes have a discrete, folded vertex whose geometry is described easily by Gauss's mapping, in particular, we can relate the degree of angular excess, or deficit, to the size of fold line rotations by the area enclosed by the vector diagram of these rotations. This is well known for the case of a so-called "d-cone" of zero angular deficit, and we formulate the same for a general disclination. This method allows us to observe kinematic properties in a meaningful way without needing to consider equilibrium. Importantly, the simple vector nature of our analysis shows that some disclinations are primitive; and that other types, such as d-cones, are amalgamations of them. PMID:27575208

  15. Isolating prompt photons with narrow cones

    NASA Astrophysics Data System (ADS)

    Catani, S.; Fontannaz, M.; Guillet, J. Ph.; Pilon, E.

    2013-09-01

    We discuss the isolation of prompt photons in hadronic collisions by means of narrow isolation cones and the QCD computation of the corresponding cross sections. We reconsider the occurence of large perturbative terms with logarithmic dependence on the cone size and their impact on the fragmentation scale dependence. We cure the apparent perturbative violation of unitarity for small cone sizes, which had been noticed earlier in next-to-leading-order (NLO) calculations, by resumming the leading logarithmic dependence on the cone size. We discuss possible implications regarding the implementation of some hollow cone variants of the cone criterion, which simulate the experimental difficulty to impose isolation inside the region filled by the electromagnetic shower that develops in the calorimeter.

  16. Cone opsins, colour blindness and cone dystrophy: Genotype-phenotype correlations.

    PubMed

    Gardner, J C; Michaelides, M; Hardcastle, A J

    2016-05-25

    X-linked cone photoreceptor disorders caused by mutations in the OPN1LW (L) and OPN1MW (M) cone opsin genes on chromosome Xq28 include a range of conditions from mild stable red-green colour vision deficiencies to severe cone dystrophies causing progressive loss of vision and blindness. Advances in molecular genotyping and functional analyses of causative variants, combined with deep retinal phenotyping, are unravelling genetic mechanisms underlying the variability of cone opsin disorders.

  17. Ionic emission from Taylor cones

    NASA Astrophysics Data System (ADS)

    Castro Reina, Sergio

    Electrified Taylor cones have been seen as an efficient way to generate thrust for space propulsion. Especially the pure ionic regime (PIR) combines a very high specific impulse (thrust per unit mass) and efficiency, which is very important to reduce fuel transportation costs. The PIR has been primarily based on electrosprays of liquid metals [Swatik and Hendricks 1968, Swatik 1969]. However, emissions dominated by or containing exclusively ions have also been observed from nonmetallic purely ionic substances, initially sulfuric acid [Perel et al. 1969], and more recently room temperature molten salts referred to as ionic liquids (ILs) [Romero-Sanz et al. 2003]. The recent use of the liquid metal ion source (LMIS) with ILs, becoming this "new" source to be known as ionic liquid ion source (ILIS) [Lozano and Martinez-Sanchez 2005], has shown important differences on the emission from Taylor cones with the traditional hollow capillary. This new source seems to be more flexible than the capillary [Paulo, Sergio, carlos], although its low emission level (low thrust) is an important drawback from the space propulsion point of view. Throughout the thesis I have studied some aspects of the ionic emission from ionic liquid Taylor cones and the influence of the properties of the liquids and the characteristic of source on the emission. I have unraveled the reason why ILIS emits such low currents (˜200 nA) and found a way to solve this problem increasing the current up to capillary levels (˜1000 nA) [Castro and Fernandez de la Mora 2009]. I have also tried to reduce ion evaporation while reducing the emitted droplet size in order to increase the thrust generated while keeping the efficiency relatively high and I have measured the energy of evaporation of several cations composing ionic liquids, mandatory step to understand ionic evaporation.

  18. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, C.A.

    1991-05-28

    A plurality of conical transmission lines are concentrically nested to form an output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated. 6 figures.

  19. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, Carl A.

    1991-01-01

    A plurality of conical transmission lines are concentrically nested to form n output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated.

  20. Identification of appropriate cone length to avoid positive cone margin in high grade cervical intraepithelial neoplasia

    PubMed Central

    Tsuda, Naotake; Nishio, Shin; Ushijima, Kimio

    2016-01-01

    Objective To identify key factors for predicting positive cone margin and appropriate cone length. Methods We retrospectively reviewed the margin status of patients who received conization with high grade cervical intraepithelial neoplasia, along with other factors such as patient age, parity, preoperative cytology, size of disease, type of transformation zone, and cone length from patient records. Cut-off value of cone length was analyzed in women younger than 40 years old because we design conization with minimum length especially for women who wish for future pregnancy. Cut-off value of cone length was defined as length corresponds to estimated probability of positive cone margin equal to 0.1 by logistic regression analysis with variables selected by stepwise methods. Results Among 300 patients, 75 patients had positive cone margin. Multivariable analysis revealed that squamous cell carcinoma at preoperative cytology (p=0.001), 2 or more quadrant disease (p=0.011), and shorter cone length (p<0.001) were risk factors for positive cone margin. Stepwise methods identified cone length and size of lesion as important variables. With this condition, cut-off value of cone length was estimated as 15 mm in single quadrant disease and 20 mm in 2 or more quadrant disease, respectively. Conclusion We identified the independent risk factors of positive cone margin and identified the cut-off value of cone length to avoid positive cone margin in women younger than 40 years old. Conization should be performed not only according to colposcopic findings including type of transformation zone but size of disease and cone length. PMID:27401478

  1. The structure and emplacement of cinder cone fields

    NASA Technical Reports Server (NTRS)

    Settle, M.

    1979-01-01

    The paper examines the structure and emplacement of cinder cone fields. Terrestrial cinder cone fields occur in volcanic provinces upon the flanks of major volcanoes or within relatively flat-lying volcanic fields. Measurements of cone shape and distribution were made in three volcano cone fields and three platform cone fields, and it was found that modal average values of cone basal diameter are on the order of 300 to 400 m within volcano cone fields and 900 to 1000 m within platform cone fields. The average morphometric parameters for the six fields indicate that cone diameter is positively correlated with cone separation distance, and that the size and spacing of cinder cones formed on the flanks of volcanoes is less than the size and spacing of cones constructed in volcanic fields.

  2. Panoramic cone beam computed tomography

    SciTech Connect

    Chang Jenghwa; Zhou Lili; Wang Song; Clifford Chao, K. S.

    2012-05-15

    Purpose: Cone-beam computed tomography (CBCT) is the main imaging tool for image-guided radiotherapy but its functionality is limited by a small imaging volume and restricted image position (imaged at the central instead of the treatment position for peripheral lesions to avoid collisions). In this paper, the authors present the concept of ''panoramic CBCT,'' which can image patients at the treatment position with an imaging volume as large as practically needed. Methods: In this novel panoramic CBCT technique, the target is scanned sequentially from multiple view angles. For each view angle, a half scan (180 deg. + {theta}{sub cone} where {theta}{sub cone} is the cone angle) is performed with the imaging panel positioned in any location along the beam path. The panoramic projection images of all views for the same gantry angle are then stitched together with the direct image stitching method (i.e., according to the reported imaging position) and full-fan, half-scan CBCT reconstruction is performed using the stitched projection images. To validate this imaging technique, the authors simulated cone-beam projection images of the Mathematical Cardiac Torso (MCAT) thorax phantom for three panoramic views. Gaps, repeated/missing columns, and different exposure levels were introduced between adjacent views to simulate imperfect image stitching due to uncertainties in imaging position or output fluctuation. A modified simultaneous algebraic reconstruction technique (modified SART) was developed to reconstruct CBCT images directly from the stitched projection images. As a gold standard, full-fan, full-scan (360 deg. gantry rotation) CBCT reconstructions were also performed using projection images of one imaging panel large enough to encompass the target. Contrast-to-noise ratio (CNR) and geometric distortion were evaluated to quantify the quality of reconstructed images. Monte Carlo simulations were performed to evaluate the effect of scattering on the image quality and

  3. Recoverin depletion accelerates cone photoresponse recovery

    PubMed Central

    Zang, Jingjing; Keim, Jennifer; Kastenhuber, Edda; Gesemann, Matthias; Neuhauss, Stephan C. F.

    2015-01-01

    The neuronal Ca2+-binding protein Recoverin has been shown to regulate phototransduction termination in mammalian rods. Here we identify four recoverin genes in the zebrafish genome, rcv1a, rcv1b, rcv2a and rcv2b, and investigate their role in modulating the cone phototransduction cascade. While Recoverin-1b is only found in the adult retina, the other Recoverins are expressed throughout development in all four cone types, except Recoverin-1a, which is expressed only in rods and UV cones. Applying a double flash electroretinogram (ERG) paradigm, downregulation of Recoverin-2a or 2b accelerates cone photoresponse recovery, albeit at different light intensities. Exclusive recording from UV cones via spectral ERG reveals that knockdown of Recoverin-1a alone has no effect, but Recoverin-1a/2a double-knockdowns showed an even shorter recovery time than Recoverin-2a-deficient larvae. We also showed that UV cone photoresponse kinetics depend on Recoverin-2a function via cone-specific kinase Grk7a. This is the first in vivo study demonstrating that cone opsin deactivation kinetics determine overall photoresponse shut off kinetics. PMID:26246494

  4. Mechanochemical regulation of growth cone motility

    PubMed Central

    Kerstein, Patrick C.; Nichol IV, Robert H.; Gomez, Timothy M.

    2015-01-01

    Neuronal growth cones are exquisite sensory-motor machines capable of transducing features contacted in their local extracellular environment into guided process extension during development. Extensive research has shown that chemical ligands activate cell surface receptors on growth cones leading to intracellular signals that direct cytoskeletal changes. However, the environment also provides mechanical support for growth cone adhesion and traction forces that stabilize leading edge protrusions. Interestingly, recent work suggests that both the mechanical properties of the environment and mechanical forces generated within growth cones influence axon guidance. In this review we discuss novel molecular mechanisms involved in growth cone force production and detection, and speculate how these processes may be necessary for the development of proper neuronal morphogenesis. PMID:26217175

  5. Unique characteristics of cones in Central Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Noguchi, Rina; Kurita, Kei

    2015-06-01

    Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin of this flat plain. Cones in CEP are expected to be a key to resolve this controversy. In previous works, there are 2 models proposed for the origin of CEP cones: volcanic rootless cone (e.g. Jaeger et al., 2007) and periglacial pingo (e.g. Burr et al., 2002; Page et al., 2009). In this study, we described detail morphology, distribution and size of CEP cones by using high-resolution images and topographic data. CEP cones are classified into 3 morphological types: Single Cone (SC), Double Cone (DC), and Lotus Fruit Cone (LC). DC has an inner cone in the summit crater of the outer cone, and LC has several inner cones in the summit crater of the outer cone. Several cones have moat structure around the edifice with peripheral rise. DCs and LCs are located in very flat areas of Athabasca Valles in the vicinity of Cerberus Fossae, while SCs distribute in the entire region of CEP. We compared CEP cones with terrestrial rootless cones and pingos in aerial photos. In Lake Myvatn, Iceland, there exist rootless cones which resemble DCs and LCs in CEP. Based on the similarities with terrestrial analogies, we concluded that the most feasible origin of CEP cones is rootless cones.

  6. Primate Short-Wavelength Cones Share Molecular Markers with Rods

    PubMed Central

    Craft, Cheryl M.; Huang, Jing; Possin, Daniel E.; Hendrickson, Anita

    2015-01-01

    Macaca, Callithrix jacchus marmoset monkey, Pan troglodytes chim- panzee and human retinas were examined to define if short wavelength (S) cones share molecular markers with L&M cone or rod photoreceptors. S cones showed consistent differences in their immunohistochemical staining and expression levels compared to L&M cones for “rod” Arrestin1 (S-Antigen), “cone” Arrestin4, cone alpha transducin, and Calbindin. Our data verify a similar pattern of expression in these primate retinas and provide clues to the structural divergence of rods and S cones versus L&M cones, suggesting S cone retinal function is “intermediate” between them. PMID:24664680

  7. Gravity duals of boundary cones

    NASA Astrophysics Data System (ADS)

    Camps, Joan

    2016-09-01

    The replica trick defines Rényi entropies as partition functions on conically singular geometries. We discuss their gravity duals: regular bulk solutions to the Einstein equations inducing conically singular metrics at the boundary. When the conical singularity is supported on a flat or spherical surface, these solutions are rewritings of the hyperbolic black hole. For more general shapes, these solutions are new. We construct them perturbatively in a double expansion in the distance and strength of the conical singularity, and extract the vacuum polarisation due to the cone. Recent results about the structure of logarithmic divergences of Rényi entropies are reproduced — in particular, f b ≠ f c . We discuss in detail the dynamical resolution of the singularity in the bulk. This resolution is in agreement with a previous proposal, and indicates a non-minimal settling to the `splitting problem': an apparent ambiguity in the holographic entropy formula of certain theories with higher derivatives.

  8. Elastic cone for Chinese calligraphy

    NASA Astrophysics Data System (ADS)

    Cai, Fenglei; Li, Haisheng

    2014-01-01

    The brush plays an important role in creating Chinese calligraphy. We regard a single bristle of a writing brush as an elastic rod and the brush tuft absorbing ink as an elastic cone, which naturally deforms according to the force exerted on it when painting on a paper, and the brush footprint is formed by the intersection region between the deformed tuft and the paper plane. To efficiently generate brush strokes, this paper introduces interpolation and texture mapping approach between two adjacent footprints, and automatically applies bristle-splitting texture to the stroke after long-time painting. Experimental results demonstrate that our method is effective and reliable. Users can create realistic calligraphy in real time.

  9. Thyroid Hormone Signaling and Cone Photoreceptor Viability.

    PubMed

    Ma, Hongwei; Ding, Xi-Qin

    2016-01-01

    Thyroid hormone (TH) signaling regulates cell proliferation, differentiation, and apoptosis. In the retina, TH signaling plays a central role in cone opsin expression. TH signaling inhibits S opsin expression, stimulates M opsin expression, and promotes dorsal-ventral opsin patterning. TH signaling has also been associated with cone photoreceptor viability. Treatment with thyroid hormone triiodothyronine (T3) or induction of high T3 by deleting the hormone-inactivating enzyme type 3 iodothyronine deiodinase (DIO3) causes cone death in mice. This effect is reversed by deletion of the TH receptor (TR) gene. Consistent with the T3 treatment effect, suppressing TH signaling preserves cones in mouse models of retinal degeneration. The regulation of cone survival by TH signaling appears to be independent of its regulatory role in cone opsin expression. The mechanism by which TH signaling regulates cone viability remains to be identified. The current understanding of TH signaling regulation in photoreceptor viability suggests that suppressing TH signaling locally in the retina may represent a novel strategy for retinal degeneration management. PMID:26427466

  10. Modal content of living human cone photoreceptors

    PubMed Central

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-01-01

    Decades of experimental and theoretical investigations have established that photoreceptors capture light based on the principles of optical waveguiding. Yet considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors in the near infrared, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc = 785 nm) to noninvasively image in three dimensions the reflectance profile of cones. Modal content of reflections generated at the cone inner segment and outer segment junction (IS/OS) and cone outer segment tip (COST) was examined over a range of cone diameters in 1,802 cones from 0.6° to 10° retinal eccentricity. Second moment analysis in conjunction with theoretical predictions indicate cone IS and OS have optical properties consistent of waveguides, which depend on segment diameter and refractive index. Cone IS was found to support a single mode near the fovea (≤3°) and multiple modes further away (>4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, show no orientation preference, and are temporally stable. We tested mode predictions of a conventional step-index fiber model and found that in order to fit our AO-OCT results required a lower estimate of the IS refractive index and introduction of an IS focusing/tapering effect. PMID:26417509

  11. The Cone-specific Visual Cycle

    PubMed Central

    Wang, Jin-Shan; Kefalov, Vladimir J

    2010-01-01

    Cone photoreceptors mediate our daytime vision and function under bright and rapidly-changing light conditions. As their visual pigment is destroyed in the process of photoactivation, the continuous function of cones imposes the need for rapid recycling of their chromophore and regeneration of their pigment. The canonical retinoid visual cycle through the retinal pigment epithelium cells recycles chromophore and supplies it to both rods and cones. However, shortcomings of this pathway, including its slow rate and competition with rods for chromophore, have led to the suggestion that cones might use a separate mechanism for recycling of chromophore. In the past four decades biochemical studies have identified enzymatic activities consistent with recycling chromophore in the retinas of cone-dominant animals, such as chicken and ground squirrel. These studies have led to the hypothesis of a cone-specific retina visual cycle. The physiological relevance of these studies was controversial for a long time and evidence for the function of this visual cycle emerged only in very recent studies and will be the focus of this review. The retina visual cycle supplies chromophore and promotes pigment regeneration only in cones but not in rods. This pathway is independent of the pigment epithelium and instead involves the Müller cells in the retina, where chromophore is recycled and supplied selectively to cones. The rapid supply of chromophore through the retina visual cycle is critical for extending the dynamic range of cones to bright light and for their rapid dark adaptation following exposure to light. The importance of the retina visual cycle is emphasized also by its preservation through evolution as its function has now been demonstrated in species ranging from salamander to zebrafish, mouse, primate, and human. PMID:21111842

  12. Electrical coupling between cones in turtle retina.

    PubMed Central

    Detwiler, P B; Hodgkin, A L

    1979-01-01

    1. The electrical coupling between cones of known spectral sensitivity in the peripheral part of the turtle's retina was studied by passing current through a micro-electrode inserted into one cone and recording with a second micro-electrode inserted into a neighbouring cone. 2. Spatial sensitivity profiles were determined by recording flash responses to a long narrow strip of light which was moved across the impaled cones in orthogonal directions. These measurements gave both the length constant lambda of electrical spread in the cone network and the separation of the two cones. 3. The cone separation determined from the spatial profiles agreed closely with that measured directly by injecting a fluorescent dye into two cones. 4. The length constant lambda varied from 18 to 39 micron with a mean of 25 micron for red-sensitive cones and 26 micron for green-sensitive cones. 5. The majority of cone pairs studied were electrically coupled provided they had the same spectral sensitivity and were separated by less than 60 micron: thirty-two out of thirty-six red-red pairs, two out of two green-green pairs, none out of eight red-green pairs: no blue cones were observed. 6. The strength of electrical coupling was expressed as a mutual resistance defined as the voltage in one cell divided by the current flowing into the other. Mutual resistances decreased from a maximum value of about 30 M omega at separations close to zero to 0.2 M omega, the lower limit of detectable coupling at separations of about 60 micron. Mutual resistances were always positive and were independent of which cell was directly polarized. The coupling seemed to be ohmic and any rectification or non-linearity probably arose in the cone membranes rather than in the coupling resistances. 7. The results were analysed in terms of the Lamb & Simon (1977) theories of square and hexagonal lattices, which approximate to the continuous sheet model except in the case of the cone to which current is applied. 8. The

  13. Distribution and specificity of S-cone ("blue cone") signals in subcortical visual pathways.

    PubMed

    Martin, Paul R; Lee, Barry B

    2014-03-01

    We review here the distribution of S-cone signals and properties of S-cone recipient receptive fields in subcortical pathways. Nearly everything we know about S-cone signals in the subcortical visual system comes from the study of visual systems in cats and primates (monkeys); in this review, we concentrate on results from macaque and marmoset monkeys. We discuss segregation of S-cone recipient (blue-on and blue-off) receptive fields in the dorsal lateral geniculate nucleus and describe their receptive field properties. We treat in some detail the question of detecting weak S-cone signals as an introduction for newcomers to the field. Finally, we briefly consider the question on how S-cone signals are distributed among nongeniculate targets. PMID:24555883

  14. Distribution and specificity of S-cone ("blue cone") signals in subcortical visual pathways.

    PubMed

    Martin, Paul R; Lee, Barry B

    2014-03-01

    We review here the distribution of S-cone signals and properties of S-cone recipient receptive fields in subcortical pathways. Nearly everything we know about S-cone signals in the subcortical visual system comes from the study of visual systems in cats and primates (monkeys); in this review, we concentrate on results from macaque and marmoset monkeys. We discuss segregation of S-cone recipient (blue-on and blue-off) receptive fields in the dorsal lateral geniculate nucleus and describe their receptive field properties. We treat in some detail the question of detecting weak S-cone signals as an introduction for newcomers to the field. Finally, we briefly consider the question on how S-cone signals are distributed among nongeniculate targets.

  15. Design of a new sensor for determination of the effects of tractor field usage in southern Spain: soil sinkage and alterations in the cone index and dry bulk density.

    PubMed

    Valera, Diego L; Gil, Jesús; Agüera, Juan

    2012-01-01

    Variations in sinkage and cone index are of crucial importance when planning fieldwork, and for determining the trafficability of farm machinery. Many studies have highlighted the link between higher values of these parameters and dramatic decreases in crop yield. Variations in the dry bulk density and cone index of clayey soil in Southern Spain were measured following each of five successive passes over the same land with the three types of tractor most widely used in the area (tracked, two-wheel drive and four-wheel drive). In addition, sinkage (rut depth) of the running gear was measured using a laser microrelief profile meter. This device, which integrates three sensors, was specifically designed for these experiments, as was an electrical penetrometer to determine the cone index, and both instruments proved reliable and accurate in the field. The main goal of this study was to design, manufacture and test these new devices. The first pass caused most soil alteration when compared to successive passes for all types of tractor tested and soil conditions prevailing during the tests. (Heavier) four-wheel drive tractors were found to cause greater soil damage (sinkage, cone index and dry bulk density) than two-wheel drive and track tractors. There was no statistically significant difference between the two latter types. The greatest alterations were recorded in the top 10 cm of the soil. The results show that soil compaction should be avoided as much as possible. This can be achieved by ensuring that tractors always travel along the same tracks, especially in the wet season. At present these aspects are not considered by farmers in this area. PMID:23202006

  16. Design of a New Sensor for Determination of the Effects of Tractor Field Usage in Southern Spain: Soil Sinkage and Alterations in the Cone Index and Dry Bulk Density

    PubMed Central

    Valera, Diego L.; Gil, Jesús; Agüera, Juan

    2012-01-01

    Variations in sinkage and cone index are of crucial importance when planning fieldwork, and for determining the trafficability of farm machinery. Many studies have highlighted the link between higher values of these parameters and dramatic decreases in crop yield. Variations in the dry bulk density and cone index of clayey soil in Southern Spain were measured following each of five successive passes over the same land with the three types of tractor most widely used in the area (tracked, two-wheel drive and four-wheel drive). In addition, sinkage (rut depth) of the running gear was measured using a laser microrelief profile meter. This device, which integrates three sensors, was specifically designed for these experiments, as was an electrical penetrometer to determine the cone index, and both instruments proved reliable and accurate in the field. The main goal of this study was to design, manufacture and test these new devices. The first pass caused most soil alteration when compared to successive passes for all types of tractor tested and soil conditions prevailing during the tests. (Heavier) four-wheel drive tractors were found to cause greater soil damage (sinkage, cone index and dry bulk density) than two-wheel drive and track tractors. There was no statistically significant difference between the two latter types. The greatest alterations were recorded in the top 10 cm of the soil. The results show that soil compaction should be avoided as much as possible. This can be achieved by ensuring that tractors always travel along the same tracks, especially in the wet season. At present these aspects are not considered by farmers in this area. PMID:23202006

  17. Nonlinear Resonance Cones and Converging Plasma Blobs

    NASA Astrophysics Data System (ADS)

    Agmon, Nathan; Pribyl, Patrick; Gekelman, Walter; Wise, Joe; Katz, Cami; Ha, Chis; Baker, Bob

    2013-10-01

    Electric field resonance cones have been shown to create density disturbances in cold, magnetized plasmas. Two circular antennas in the LAPTAG experimental plasma device were used to create converging, nonlinear resonance cones. The nonlinear electrostatic field is produced by large amplitude RF (ERF/nkTe >> 1). A movable probe, powered by a computerized motor and consisting of three mutually orthogonal electric dipoles, is used to measure the electric field of the cones which become distorted at large amplitudes. A 2D movable Langmuir probe was used to determine localized density perturbations after turn-off of the RF power. A density blob moving at 3-5 times the ion sound speed has been observed to propagate away (for at least 20 cm) from the focus of the cone. Two ring antennas produced colliding blobs. The physics of the collision will be described. Work performed at the Basic Plasma Science Facility supported by DOE and NSF.

  18. Some inversion formulas for the cone transform

    NASA Astrophysics Data System (ADS)

    Terzioglu, Fatma

    2015-11-01

    Several novel imaging applications have lead recently to a variety of Radon type transforms, where integration is made over a family of conical surfaces. We call them cone transforms (in 2D they are also called V-line or broken ray transforms). Most prominently, they are present in the so called Compton camera imaging that arises in medical diagnostics, astronomy, and lately in homeland security applications. Several specific incarnations of the cone transform have been considered separately. In this paper, we address the most general (and overdetermined) cone transform, obtain integral relations between cone and Radon transforms in {{{R}}}n, and a variety of inversion formulas. In many applications (e.g., in homeland security), the signal to noise ratio is very low. So, if overdetermined data is collected (as in the case of Compton imaging), attempts to reduce the dimensionality might lead to essential elimination of the signal. Thus, our main concentration is on obtaining formulas involving overdetermined data.

  19. Homologies among Coniferophyte cones: further observations

    NASA Astrophysics Data System (ADS)

    Grauvogel-Stamm, Léa; Galtier, Jean

    1998-04-01

    A reinvestigation of the Triassic conifer pollen cone of Darneya shows evidence that clusters of pollen sacs are attached (adnate), at regular intervals, to the upper side of the stalk and that the distribution of stomata is restricted to the apical part of the abaxial side of the peltate scale. These features and others, such as the commissure visible on the stalk and the scale, suggest a dual nature of the male scale complex of Darneya which therefore is interpreted as an abaxial bract fused with an adaxial fertile shoot bearing several clusters of pollen sacs. This conifer pollen cone is thus considered as a compound strobilus (inflorescence) homologous with the female cone of the conifers and therefore with the cones, both male and female, of the cordaites.

  20. The cytoskeletons of isolated, neuronal growth cones.

    PubMed

    Gordon-Weeks, P R

    1987-06-01

    We have examined by electron microscopy the cytoskeletons of growth cones isolated from neonatal rat forebrain by the method of Gordon-Weeks and Lockerbie [Gordon-Weeks and Lockerbie (1984) Neuroscience 13, 119-136]. When fixed in suspension with conventional fixatives, isolated growth cones contain a central region filled with a branching system of smooth endoplasmic reticulum and a cortical region immediately beneath the plasma membrane that is relatively free of organelles and is composed of an amorphous granular cytoplasm. The filopodia of isolated growth cones are also devoid of organelles and contain a cytoplasm that is similar in appearance to that in the cortical region. No microtubules or neurofilaments have been found in these growth cones. When isolated growth cones were prepared for electron microscopy by a method which preserves actin filaments [Boyles, Anderson and Hutcherson (1985) J. Histochem. Cytochem. 33, 1116-1128], microfilaments were found throughout the cortical cytoplasm. In the filopodia, the microfilaments were bundled together and oriented longitudinally. Filopodial microfilament bundles often extended into the body of the growth cone and could traverse it completely. Inclusion of Triton X-100 (1% v/v) in the fixative solubilized the membranes and soluble cytoplasmic proteins of growth cones, allowing an unobscured view of the microfilament cytoskeleton including the core bundle of microfilaments in filopodia. Suspended within the cytoskeleton were the coats of coated vesicles. These were particularly numerous at the broad bases of filopodia. Microfilaments bound heavy meromyosin and were cytochalasin B (2.0 X 10(-7) M) sensitive. Individual microfilaments branched and within filopodia they were extensively cross-linked by thin (7 nm) filaments. Microtubules and neurofilaments were not seen in these cytoskeletons despite the fact that the fixative contained a Ca2+ chelator. When growth cones were preincubated in taxol (14 microM) their

  1. DEFORMATION OF SCORIA CONE BY CONDUIT PRESSURIZATION

    SciTech Connect

    E.S. Gaffney; B. Damjanac; D. Krier; G. Valentine

    2005-08-26

    A simplified mechanical model is used to simulate the deformation of a scoria cone due to pressurization of magma in a feeder conduit. The scoria cone is modeled as consisting of a cone of stabilized scoria with an axial region of loose scoria (height h{sub 1}), all overlying a vertically oriented cylindrical conduit intruded into rhyolite tuff country rock. For our analyses, the conduit is filled with basalt magma, usually with the upper length (h{sub 2}) solidified. The style of deformation of the cone depends on both h{sub 1} and h{sub 2}. If magma is prevented from hydrofracturing out of the conduit (as, for example, might be the case if the magma is surrounded by a solidified, but plastically deformable layer acting as a gasket backed up by the brittle country rock) pressures in the magma can build to 10s of MPa. When h{sub 1} is 100 m, not unusual for a small isolated basaltic cinder cone, the magma pressure needed to destabilize the cone when molten magma extends all the way to the original ground surface (h{sub 2} = 0) is only about one-third of the pressure when the upper part of the conduit is solidified (h{sub 2} = 25m). In the former case, almost the entire upper third of the cone is at failure in tension when the configuration becomes unstable. In the latter case, small portions of the surface of the cone are failing in tension when instability occurs, but a large volume in the central core of the cone is failing in shear or compressions. These results may provide insight into the status of volcanic plumbing, either past or present, beneath scoria cones. Field observations at the Lathrop Wells volcano in southern Nevada identify structures at the outer edge just below the crater rim that appear to be inward-dipping listric normal faults. This may indicate that, near the end of its active stage, the cone was close to failing in this fashion. A companion paper suggests that such a failure could have been quite energetic had it occurred.

  2. Substrate Deformation Predicts Neuronal Growth Cone Advance

    PubMed Central

    Athamneh, Ahmad I.M.; Cartagena-Rivera, Alexander X.; Raman, Arvind; Suter, Daniel M.

    2015-01-01

    Although pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 100–102 nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant. PMID:26445437

  3. Microspectrophotometric evidence for cone monochromacy in sharks

    NASA Astrophysics Data System (ADS)

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λmax 484-518 nm) and cone (λmax 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  4. Design of a trichromatic cone array.

    PubMed

    Garrigan, Patrick; Ratliff, Charles P; Klein, Jennifer M; Sterling, Peter; Brainard, David H; Balasubramanian, Vijay

    2010-02-01

    Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative. PMID:20168996

  5. Cone Tracing for Furry Object Rendering.

    PubMed

    Qin, Hao; Chai, Menglei; Hou, Qiming; Ren, Zhong; Zhou, Kun

    2014-08-01

    We present a cone-based ray tracing algorithm for high-quality rendering of furry objects with reflection, refraction and defocus effects. By aggregating many sampling rays in a pixel as a single cone, we significantly reduce the high supersampling rate required by the thin geometry of fur fibers. To reduce the cost of intersecting fur fibers with cones, we construct a bounding volume hierarchy for the fiber geometry to find the fibers potentially intersecting with cones, and use a set of connected ribbons to approximate the projections of these fibers on the image plane. The computational cost of compositing and filtering transparent samples within each cone is effectively reduced by approximating away in-cone variations of shading, opacity and occlusion. The result is a highly efficient ray tracing algorithm for furry objects which is able to render images of quality comparable to those generated by alternative methods, while significantly reducing the rendering time. We demonstrate the rendering quality and performance of our algorithm using several examples and a user study. PMID:26357369

  6. Crowding in the S-cone pathway.

    PubMed

    Coates, Daniel R; Chung, Susana T L

    2016-05-01

    The spatial extent of interference from nearby object or contours (the critical spacing of "crowding") has been thoroughly characterized across the visual field, typically using high contrast achromatic stimuli. However, attempts to link this measure with known properties of physiological pathways have been inconclusive. The S-cone pathway, with its ease of psychophysical isolation and known anatomical characteristics, offers a unique tool to gain additional insights into crowding. In this study, we measured the spatial extent of crowding in the S-cone pathway at several retinal locations using a chromatic adaptation paradigm. S-cone crowding was evident and extensive, but its spatial extent changed less markedly as a function of retinal eccentricity than the extent found using traditional achromatic stimuli. However, the spatial extent agreed with that of low contrast achromatic stimuli matched for isolated resolvability. This suggests that common cortical mechanisms mediate the crowding effect in the S-cone and achromatic pathway, but contrast is an important factor. The low contrast of S-cone stimuli makes S-cone vision more acuity-limited than crowding-limited.

  7. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology. PMID:21212930

  8. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  9. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Using a digital micromirror device to control both amplitude and phase, we inject arbitrary optical modes into our resonator. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We show that there is a conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  10. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    Creating photonic materials with nontrivial topological characteristics has seen burgeoning interest in recent years; however, a major route to topology, a magnetic field for continuum photons, has remained elusive. We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We will discuss the conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  11. Light responses of primate and other mammalian cones

    PubMed Central

    Cao, Li-Hui; Luo, Dong-Gen; Yau, King-Wai

    2014-01-01

    Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data. PMID:24550304

  12. Origin and Impact of Phototransduction Noise in Primate Cone Photoreceptors

    PubMed Central

    Angueyra, Juan Manuel; Rieke, Fred

    2013-01-01

    Noise in the responses of cone photoreceptors sets a fundamental limit to visual sensitivity, yet the origin of noise in mammalian cones and its relation to behavioral sensitivity are poorly understood. Our work here on primate cones improves understanding of these issues in three ways. First, we find that cone noise is not dominated by spontaneous photopigment activation or by quantal fluctuations in photon absorption but instead by other sources, namely channel noise and fluctuations in cGMP. Second, we find that adaptation in cones, unlike that in rods, affects signals and noise differently. This difference helps explain why thresholds for rod- and cone-mediated signals have different dependencies on background light level. Third, past estimates of noise in mammalian cones are too high to explain behavioral sensitivity. Our measurements indicate a lower level of cone noise, and thus help reconcile physiological and behavioral estimates of cone noise and sensitivity. PMID:24097042

  13. Light responses of primate and other mammalian cones.

    PubMed

    Cao, Li-Hui; Luo, Dong-Gen; Yau, King-Wai

    2014-02-18

    Retinal cones are photoreceptors for daylight vision. For lower vertebrates, cones are known to give monophasic, hyperpolarizing responses to light flashes. For primate cones, however, they have been reported to give strongly biphasic flash responses, with an initial hyperpolarization followed by a depolarization beyond the dark level, now a textbook dogma. We have reexamined this primate-cone observation and, surprisingly, found predominantly monophasic cone responses. Correspondingly, we found that primate cones began to adapt to steady light at much lower intensities than previously reported, explainable by a larger steady response to background light for a monophasic than for a biphasic response. Similarly, we have found a monophasic cone response for several other mammalian species. Thus, a monophasic flash response may in fact be the norm for primate and other mammalian cones as for lower-vertebrate cones. This revised information is important for ultimately understanding human retinal signal processing and correlating with psychophysical data. PMID:24550304

  14. Identifying quantitative trait loci and determining closely related stalk traits for rind penetrometer resistance in a high-oil maize population.

    PubMed

    Hu, Haixiao; Meng, Yujie; Wang, Hongwu; Liu, Hai; Chen, Shaojiang

    2012-05-01

    Stalk lodging in maize causes annual yield losses between 5 and 20% worldwide. Many studies have indicated that maize stalk strength significantly negatively correlates with lodging observed in the field. Rind penetrometer resistance (RPR) measurements can be used to effectively evaluate maize stalk strength, but little is known about the genetic basis of this parameter. The objective of this study was to explore a genetic model and detect quantitative trait loci (QTL) of RPR and determine relationships between RPR and other stalk traits, especially cell wall chemical components. RPR is quantitative trait in nature, and both additive and non-additive effects may be important to consider for the improvement of RPR. Nine additive-effect QTLs covering nine chromosomes, except chromosome 5, and one pair of epistatic QTLs were detected for RPR. CeSA11 involved in cellulose synthesis and colorless2 involved in lignin synthesis were identified as possible candidate genes for RPR. Internode diameter (InD), fresh weight of internode (FreW), dry weight of internode (DryW), fresh weight and dry weight as well as cell wall components per unit volume significantly positively correlated with RPR. The internode water content (InW) significantly negatively correlated with RPR. Notably, these traits significantly correlated with RPR, and the QTLs of these traits co-localized with those of RPR. The corresponding results obtained from correlation analysis and QTL mapping suggested the presence of pleitropism or linkage between genes and indicated that these different approaches may be used for cross authentication of relationships between different traits. PMID:22314785

  15. Regulated plasmalemmal expansion in nerve growth cones.

    PubMed

    Lockerbie, R O; Miller, V E; Pfenninger, K H

    1991-03-01

    To study the mechanisms underlying plasmalemmal expansion in the nerve growth cone, a cell-free assay was developed to quantify membrane addition, using ligand binding and sealed growth cone particles isolated by subcellular fractionation from fetal rat brain. Exposed versus total binding sites of 125I-wheat germ agglutinin were measured in the absence or presence of saponin, respectively, after incubation with various agents. Ca2(+)-ionophore A23187 in the presence of Ca2+ increases the number of binding sites (Bmax) but does not change their affinity (KD), indicating that new receptors appear on the plasma membrane. Similarly, membrane depolarization by high K+ or veratridine significantly induces, in a Ca2(+)-dependent manner, the externalization of lectin binding sites from an internal pool. Morphometric analysis of isolated growth cones indicates that A23187 and high K+ treatment cause a significant reduction in a specific cytoplasmic membrane compartment, thus confirming the lectin labeling results and identifying the plasmalemmal precursor. The isolated growth cones take up gamma-amino-butyric acid and serotonin, but show no evidence for Ca2(+)-dependent transmitter release so that transmitter exocytosis is dissociated from plasmalemmal expansion. The data demonstrate that plasmalemmal expansion in the growth cone is a regulated process and identify an internal pool of precursor membrane.

  16. Regulated plasmalemmal expansion in nerve growth cones

    PubMed Central

    1991-01-01

    To study the mechanisms underlying plasmalemmal expansion in the nerve growth cone, a cell-free assay was developed to quantify membrane addition, using ligand binding and sealed growth cone particles isolated by subcellular fractionation from fetal rat brain. Exposed versus total binding sites of 125I-wheat germ agglutinin were measured in the absence or presence of saponin, respectively, after incubation with various agents. Ca2(+)-ionophore A23187 in the presence of Ca2+ increases the number of binding sites (Bmax) but does not change their affinity (KD), indicating that new receptors appear on the plasma membrane. Similarly, membrane depolarization by high K+ or veratridine significantly induces, in a Ca2(+)-dependent manner, the externalization of lectin binding sites from an internal pool. Morphometric analysis of isolated growth cones indicates that A23187 and high K+ treatment cause a significant reduction in a specific cytoplasmic membrane compartment, thus confirming the lectin labeling results and identifying the plasmalemmal precursor. The isolated growth cones take up gamma-amino-butyric acid and serotonin, but show no evidence for Ca2(+)-dependent transmitter release so that transmitter exocytosis is dissociated from plasmalemmal expansion. The data demonstrate that plasmalemmal expansion in the growth cone is a regulated process and identify an internal pool of precursor membrane. PMID:1999470

  17. Whiskers, cones and pyramids created in sputtering by ion bombardment

    NASA Technical Reports Server (NTRS)

    Wehner, G. K.

    1979-01-01

    A thorough study of the role which foreign atoms play in cone formation during sputtering of metals revealed many experimental facts. Two types of cone formation were distinquished, deposit cones and seed cones. Twenty-six combinations of metals for seed cone formation were tested. The sputtering yield variations with composition for combinations which form seed cones were measured. It was demonstrated that whisker growth becomes a common occurrence when low melting point material is sputter deposited on a hot nonsputtered high melting point electrode.

  18. GABA release from mouse axonal growth cones

    PubMed Central

    Gao, Xiao-Bing; van den Pol, Anthony N

    2000-01-01

    Using developing hypothalamic neurons from transgenic mice that express high levels of green fluorescent protein in growing axons, and an outside-out patch from mature neuronal membranes that contain neurotransmitter receptors as a sensitive detector, we found that GABA is released by a vesicular mechanism from the growth cones of developing axons prior to synapse formation. A low level of GABA release occurs spontaneously from the growth cone, and this is substantially increased by evoked action potentials. Neurotransmitters such as acetylcholine can enhance protein kinase C (PKC) activity even prior to synapse formation; PKC activation caused a substantial increase in spontaneous GABA release from the growth cone, probably acting at the axon terminal. These data indicate that GABA is secreted from axons during a stage of neuronal development when GABA is excitatory, and that neuromodulators could alter GABA release from the growing axon, potentially enabling other developing neurons of different transmitter phenotype to modulate the early actions of GABA. PMID:10718743

  19. Hurricane track forecast cones from fluctuations

    NASA Astrophysics Data System (ADS)

    Meuel, T.; Prado, G.; Seychelles, F.; Bessafi, M.; Kellay, H.

    2012-06-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations.

  20. Hurricane track forecast cones from fluctuations.

    PubMed

    Meuel, T; Prado, G; Seychelles, F; Bessafi, M; Kellay, H

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations.

  1. Hurricane track forecast cones from fluctuations

    PubMed Central

    Meuel, T.; Prado, G.; Seychelles, F.; Bessafi, M.; Kellay, H.

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations. PMID:22701776

  2. Pure bending of a solid cone

    NASA Astrophysics Data System (ADS)

    Renton, J. D.

    1997-05-01

    The problems of torsion, axial loading and shear of a solid cone were solved around the turn of the century by Michell and Föppl. Surprisingly, no solution to the problem of the elastic response of a cone to the only other possible resultant applied to its apex seems to have been published until now. The method used here is based on certain theoretical considerations related to the author's work on generalizing the engineering theory of beams. This means that the result is derived rather than being the result of a trial-and-error process. A comparison is made with the usual engineering theory as modified for variable bending stiffness. The two analyses give the same results at the limit as the cone angle tends to zero.

  3. Lightcone: Light-cone generating script

    NASA Astrophysics Data System (ADS)

    Bernyk, Max

    2014-03-01

    Lightcone works with simulated galaxy data stored in a relational database to rearrange the data in a shape of a light-cone; simulated galaxy data is expected to be in a box volume. The light-cone constructing script works with output from the SAGE semi-analytic model, but will work with any other model that has galaxy positions (and other properties) saved per snapshots of the simulation volume distributed in time. The database configuration file is set up for PostgreSQL RDBMS, but can be modified for use with any other SQL database.

  4. Understanding Cone Photoreceptor Cell Death in Achromatopsia.

    PubMed

    Carvalho, Livia S; Vandenberghe, Luk H

    2016-01-01

    Colour vision is only achieved in the presence of healthy and functional cone photoreceptors found in the retina. It is an essential component of human vision and usually the first complaint patients undergoing vision degeneration have is the loss of daylight colour vision. Therefore, an understanding of the biology and basic mechanisms behind cone death under the degenerative state of retinal dystrophies and how the activation of the apoptotic pathway is triggered will provide valuable knowledge. It will also have broader applications for a spectrum of visual disorders and will be critical for future advances in translational research. PMID:26427416

  5. Basaltic Cone Suggests Constructional Origin of Some Guyots.

    PubMed

    Christensen, M N; Gilbert, C M

    1964-01-17

    A basaltic cinder cone was built beneath the waters of Mono Lake in Pleistocene time. This cone is now exposed. Its internal structure, external form, and petrography suggest that it was constructed with a flat top.

  6. Basaltic Cone Suggests Constructional Origin of Some Guyots.

    PubMed

    Christensen, M N; Gilbert, C M

    1964-01-17

    A basaltic cinder cone was built beneath the waters of Mono Lake in Pleistocene time. This cone is now exposed. Its internal structure, external form, and petrography suggest that it was constructed with a flat top. PMID:17753148

  7. Measurements of growth cone adhesion to culture surfaces by micromanipulation

    PubMed Central

    1994-01-01

    Neurons were grown on plastic surfaces that were untreated, or treated with polylysine, laminin, or L1 and their growth cones were detached from their culture surface by applying known forces with calibrated glass needles. This detachment force was taken as a measure of the force of adhesion of the growth cone. We find that on all surfaces, lamellipodial growth cones require significantly greater detachment force than filopodial growth cones, but this differences is, in general, due to the greater area of lamellipodial growth cones compared to filopodial growth cones. That is, the stress (force/unit area) required for detachment was similar for growth cones of lamellipodial and filopodial morphology on all surfaces, with the exception of lamellipodial growth cones on L1-treated surfaces, which had a significantly lower stress of detachment than on other surfaces. Surprisingly, the forces required for detachment (760-3,340 mudynes) were three to 15 times greater than the typical resting axonal tension, the force exerted by advancing growth cones, or the forces of retraction previously measured by essentially the same method. Nor did we observe significant differences in detachment force among growth cones of similar morphology on different culture surfaces, with the exception of lamellipodial growth cones on L1-treated surfaces. These data argue against the differential adhesion mechanism for growth cone guidance preferences in culture. Our micromanipulations revealed that the most mechanically resistant regions of growth cone attachment were confined to quite small regions typically located at the ends of filopodia and lamellipodia. Detached growth cones remained connected to the substratum at these regions by highly elastic retraction fibers. The closeness of contact of growth cones to the substratum as revealed by interference reflection microscopy (IRM) did not correlate with our mechanical measurements of adhesion, suggesting that IRM cannot be used as a

  8. The role of collapsing and cone rafting on eruption style changes and final cone morphology: Los Morados scoria cone, Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Németh, Karoly; Risso, Corina; Nullo, Francisco; Kereszturi, Gabor

    2011-06-01

    Payún Matru Volcanic Field is a Quaternary monogenetic volcanic field that hosts scoria cones with perfect to breached morphologies. Los Morados complex is a group of at least four closely spaced scoria cones (Los Morados main cone and the older Cones A, B, and C). Los Morados main cone was formed by a long lived eruption of months to years. After an initial Hawaiian-style stage, the eruption changed to a normal Strombolian, conebuilding style, forming a cone over 150 metres high on a northward dipping (˜4°) surface. An initial cone gradually grew until a lava flow breached the cone's base and rafted an estimated 10% of the total volume. A sudden sector collapse initiated a dramatic decompression in the upper part of the feeding conduit and triggered violent a Strombolian style eruptive stage. Subsequently, the eruption became more stable, and changed to a regular Strombolian style that partially rebuilt the cone. A likely increase in magma flux coupled with the gradual growth of a new cone caused another lava flow outbreak at the structurally weakened earlier breach site. For a second time, the unstable flank of the cone was rafted, triggering a second violent Strombolian eruptive stage which was followed by a Hawaiian style lava fountain stage. The lava fountaining was accompanied by a steady outpour of voluminous lava emission accompanied by constant rafting of the cone flank, preventing the healing of the cone. Santa Maria is another scoria cone built on a nearly flat pre-eruption surface. Despite this it went through similar stages as Los Morados main cone, but probably not in as dramatic a manner as Los Morados. In contrast to these examples of large breached cones, volumetrically smaller cones, associated to less extensive lava flows, were able to heal raft/collapse events, due to the smaller magma output and flux rates. Our evidence shows that scoria cone growth is a complex process, and is a consequence of the magma internal parameters (e.g. volatile

  9. Funnel cone for focusing intense ion beams on a target

    SciTech Connect

    Bieniosek, F.M.; Henestroza, E.; Ni, P.

    2009-10-05

    We describe a funnel cone for concentrating an ion beam on a target. The cone utilizes the reflection characteristic of ion beams on solid walls to focus the incident beam andincrease beam intensity on target. The cone has been modeled with the TRIM code. A prototype has been tested and installed for use in the 350-keV K+ NDCX target chamber.

  10. Vision. Realignment of cones after cataract removal.

    PubMed

    Smallman, H S; MacLeod, D I; Doyle, P

    2001-08-01

    Through unique observations of an adult case of bilateral congenital cataract removal, we have found evidence that retinal photoreceptors will swiftly realign towards the brightest regions in the pupils of the eye. Cones may be phototropic, actively orientating themselves towards light like sunflowers in a field.

  11. Performance analysis of cone detection algorithms.

    PubMed

    Mariotti, Letizia; Devaney, Nicholas

    2015-04-01

    Many algorithms have been proposed to help clinicians evaluate cone density and spacing, as these may be related to the onset of retinal diseases. However, there has been no rigorous comparison of the performance of these algorithms. In addition, the performance of such algorithms is typically determined by comparison with human observers. Here we propose a technique to simulate realistic images of the cone mosaic. We use the simulated images to test the performance of three popular cone detection algorithms, and we introduce an algorithm which is used by astronomers to detect stars in astronomical images. We use Free Response Operating Characteristic (FROC) curves to evaluate and compare the performance of the four algorithms. This allows us to optimize the performance of each algorithm. We observe that performance is significantly enhanced by up-sampling the images. We investigate the effect of noise and image quality on cone mosaic parameters estimated using the different algorithms, finding that the estimated regularity is the most sensitive parameter. PMID:26366758

  12. Visual Cone Arrestin 4 Contributes to Visual Function and Cone Health

    PubMed Central

    Deming, Janise D.; Pak, Joseph S.; Brown, Bruce M.; Kim, Moon K.; Aung, Moe H.; Eom, Yun Sung; Shin, Jung-a; Lee, Eun-Jin; Pardue, Machelle T.; Craft, Cheryl Mae

    2015-01-01

    Purpose Visual arrestins (ARR) play a critical role in shutoff of rod and cone phototransduction. When electrophysiological responses are measured for a single mouse cone photoreceptor, ARR1 expression can substitute for ARR4 in cone pigment desensitization; however, each arrestin may also contribute its own, unique role to modulate other cellular functions. Methods A combination of ERG, optokinetic tracking, immunohistochemistry, and immunoblot analysis was used to investigate the retinal phenotypes of Arr4 null mice (Arr4−/−) compared with age-matched control, wild-type mice. Results When 2-month-old Arr4−/− mice were compared with wild-type mice, they had diminished visual acuity and contrast sensitivity, yet enhanced ERG flicker response and higher photopic ERG b-wave amplitudes. In contrast, in older Arr4−/− mice, all ERG amplitudes were significantly reduced in magnitude compared with age-matched controls. Furthermore, in older Arr4−/− mice, the total cone numbers decreased and cone opsin protein immunoreactive expression levels were significantly reduced, while overall photoreceptor outer nuclear layer thickness was unchanged. Conclusions Our study demonstrates that Arr4−/− mice display distinct phenotypic differences when compared to controls, suggesting that ARR4 modulates essential functions in high acuity vision and downstream cellular signaling pathways that are not fulfilled or substituted by the coexpression of ARR1, despite its high expression levels in all mouse cones. Without normal ARR4 expression levels, cones slowly degenerate with increasing age, making this a new model to study age-related cone dystrophy. PMID:26284544

  13. Perturbation theory in light-cone quantization

    SciTech Connect

    Langnau, A.

    1992-01-01

    A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.

  14. Simulated and empiric wind pollination patterns of conifer ovulate cones

    PubMed Central

    Niklas, Karl J.

    1982-01-01

    Wind tunnel analyses of conifer ovulate cones indicate that the total geometry of the cone enhances the probability of pollen entrapment. Aerodynamic characteristics of cone scale-bract complexes are such that suspended pollen is directed toward the micropyles of attached ovules. Within the taxa examined, there appears to be a preferential entrapment by ovulate cones of pollen of the same species. The data are interpreted as evidence for an aerodynamic reciprocity between wind-suspended pollen and the structure of ovulate cones which increases the frequency of pollination and the potential for fertilization. Images PMID:16593147

  15. Characterizing the Human Cone Photoreceptor Mosaic via Dynamic Photopigment Densitometry

    PubMed Central

    Sabesan, Ramkumar; Hofer, Heidi; Roorda, Austin

    2015-01-01

    Densitometry is a powerful tool for the biophysical assessment of the retina. Until recently, this was restricted to bulk spatial scales in living humans. The application of adaptive optics (AO) to the conventional fundus camera and scanning laser ophthalmoscope (SLO) has begun to translate these studies to cellular scales. Here, we employ an AOSLO to perform dynamic photopigment densitometry in order to characterize the optical properties and spectral types of the human cone photoreceptor mosaic. Cone-resolved estimates of optical density and photosensitivity agree well with bulk estimates, although show smaller variability than previously reported. Photopigment kinetics of individual cones derived from their selective bleaching allowed efficient mapping of cone sub-types in human retina. Estimated uncertainty in identifying a cone as long vs middle wavelength was less than 5%, and the total time taken per subject ranged from 3–9 hours. Short wavelength cones were delineated in every subject with high fidelity. The lack of a third cone-type was confirmed in a protanopic subject. In one color normal subject, cone assignments showed 91% correspondence against a previously reported cone-typing method from more than a decade ago. Combined with cone-targeted stimulation, this brings us closer in studying the visual percept arising from a specific cone type and its implication for color vision circuitry. PMID:26660894

  16. Prospects for retinal cone-targeted gene therapy.

    PubMed

    Alexander, John J; Hauswirth, William W

    2008-06-01

    Gene therapy strategies that target therapeutic genes to retinal cones are a worthy goal both because cone photoreceptor diseases are severely vision limiting and because many retinal diseases that do not affect cones directly eventually lead to cone loss, the reason for eventual blindness. Human achromatopsia is a genetic disease of cones that renders them nonfunctional but otherwise intact. Thus, animal models of achromatopsia were used in conjunction with adeno-associated virus (AAV) vectors whose serotype efficiently transduces cones and with a promoter that limits transgene expression to cones. In the Gnat2(cpfl3) mouse model of one genetic form of human achromatopsia, we were able to demonstrate recovery of normal cone function and visual acuity after a single subretinal treatment of vector that supplied wild-type Gnat2 protein to cones. This validates the overall strategy of targeting cones using recombinant viral vectors and justifies a more complete examination of animal models of cone disease as a prelude to considering a clinical gene therapy trial. PMID:18596991

  17. Micro focusing of fast electrons with opened cone targets

    SciTech Connect

    Liu Feng; Liu Xiaoxuan; Ding Wenjun; Du Fei; Li Yutong; Ma Jinglong; Liu Xiaolong; Chen Liming; Lu Xin; Dong Quanli; Wang Weimin; Wang Zhaohua; Wei Zhiyi; Liu Bicheng; Sheng Zhengming; Zhang Jie

    2012-01-15

    Using opened reentrant cone silicon targets, we have demonstrated the effect of micro focusing of fast electrons generated in intense laser-plasma interactions. When an intense femtosecond laser pulse is focused tightly onto one of the side walls of the cone, fast electron beam emitted along the side wall is observed. When a line focus spot, which is long enough to irradiate both of the side walls of the cone simultaneously, is used, two electron beams emitted along each side wall, respectively, are observed. The two beams should cross each other near the open tip of the cone, resulting in micro focusing. We use a two-dimensional Particle-In-Cell code to simulate the electron emission both in opened and closed cone targets. The simulation results of the opened cone targets are in agreement with the experimental observation while the results of the closed cone targets do not show the micro focusing effect.

  18. WE-G-18A-03: Cone Artifacts Correction in Iterative Cone Beam CT Reconstruction

    SciTech Connect

    Yan, H; Folkerts, M; Jiang, S; Jia, X; Wang, X; Bai, T; Lu, W

    2014-06-15

    Purpose: For iterative reconstruction (IR) in cone-beam CT (CBCT) imaging, data truncation along the superior-inferior (SI) direction causes severe cone artifacts in the reconstructed CBCT volume images. Not only does it reduce the effective SI coverage of the reconstructed volume, it also hinders the IR algorithm convergence. This is particular a problem for regularization based IR, where smoothing type regularization operations tend to propagate the artifacts to a large area. It is our purpose to develop a practical cone artifacts correction solution. Methods: We found it is the missing data residing in the truncated cone area that leads to inconsistency between the calculated forward projections and measured projections. We overcome this problem by using FDK type reconstruction to estimate the missing data and design weighting factors to compensate the inconsistency caused by the missing data. We validate the proposed methods in our multi-GPU low-dose CBCT reconstruction system on multiple patients' datasets. Results: Compared to the FDK reconstruction with full datasets, while IR is able to reconstruct CBCT images using a subset of projection data, the severe cone artifacts degrade overall image quality. For head-neck case under a full-fan mode, 13 out of 80 slices are contaminated. It is even more severe in pelvis case under half-fan mode, where 36 out of 80 slices are affected, leading to inferior soft-tissue delineation. By applying the proposed method, the cone artifacts are effectively corrected, with a mean intensity difference decreased from ∼497 HU to ∼39HU for those contaminated slices. Conclusion: A practical and effective solution for cone artifacts correction is proposed and validated in CBCT IR algorithm. This study is supported in part by NIH (1R01CA154747-01)

  19. X-linked cone dystrophy caused by mutation of the red and green cone opsins.

    PubMed

    Gardner, Jessica C; Webb, Tom R; Kanuga, Naheed; Robson, Anthony G; Holder, Graham E; Stockman, Andrew; Ripamonti, Caterina; Ebenezer, Neil D; Ogun, Olufunmilola; Devery, Sophie; Wright, Genevieve A; Maher, Eamonn R; Cheetham, Michael E; Moore, Anthony T; Michaelides, Michel; Hardcastle, Alison J

    2010-07-01

    X-linked cone and cone-rod dystrophies (XLCOD and XLCORD) are a heterogeneous group of progressive disorders that solely or primarily affect cone photoreceptors. Mutations in exon ORF15 of the RPGR gene are the most common underlying cause. In a previous study, we excluded RPGR exon ORF15 in some families with XLCOD. Here, we report genetic mapping of XLCOD to Xq26.1-qter. A significant LOD score was detected with marker DXS8045 (Z(max) = 2.41 [theta = 0.0]). The disease locus encompasses the cone opsin gene array on Xq28. Analysis of the array revealed a missense mutation (c. 529T>C [p. W177R]) in exon 3 of both the long-wavelength-sensitive (LW, red) and medium-wavelength-sensitive (MW, green) cone opsin genes that segregated with disease. Both exon 3 sequences were identical and were derived from the MW gene as a result of gene conversion. The amino acid W177 is highly conserved in visual and nonvisual opsins across species. We show that W177R in MW opsin and the equivalent W161R mutation in rod opsin result in protein misfolding and retention in the endoplasmic reticulum. We also demonstrate that W177R misfolding, unlike the P23H mutation in rod opsin that causes retinitis pigmentosa, is not rescued by treatment with the pharmacological chaperone 9-cis-retinal. Mutations in the LW/MW cone opsin gene array can, therefore, lead to a spectrum of disease, ranging from color blindness to progressive cone dystrophy (XLCOD5). PMID:20579627

  20. Establishment of a cone photoreceptor transplantation platform based on a novel cone-GFP reporter mouse line

    PubMed Central

    Smiley, Sheila; Nickerson, Philip E.; Comanita, Lacrimioara; Daftarian, Narsis; El-Sehemy, Ahmed; Tsai, En Leh Samuel; Matan-Lithwick, Stuart; Yan, Keqin; Thurig, Sherry; Touahri, Yacine; Dixit, Rajiv; Aavani, Tooka; De Repentingy, Yves; Baker, Adam; Tsilfidis, Catherine; Biernaskie, Jeff; Sauvé, Yves; Schuurmans, Carol; Kothary, Rashmi; Mears, Alan J.; Wallace, Valerie A.

    2016-01-01

    We report successful retinal cone enrichment and transplantation using a novel cone-GFP reporter mouse line. Using the putative cone photoreceptor-enriched transcript Coiled-Coil Domain Containing 136 (Ccdc136) GFP-trapped allele, we monitored developmental reporter expression, facilitated the enrichment of cones, and evaluated transplanted GFP-labeled cones in wildtype and retinal degeneration mutant retinas. GFP reporter and endogenous Ccdc136 transcripts exhibit overlapping temporal and spatial expression patterns, both initiated in cone precursors of the embryonic retina and persisting to the adult stage in S and S/M opsin+ cones as well as rod bipolar cells. The trapped allele does not affect cone function or survival in the adult mutant retina. When comparing the integration of GFP+ embryonic cones and postnatal Nrl−/− ‘cods’ into retinas of adult wildtype and blind mice, both cell types integrated and exhibited a degree of morphological maturation that was dependent on donor age. These results demonstrate the amenability of the adult retina to cone transplantation using a novel transgenic resource that can advance therapeutic cone transplantation in models of age-related macular degeneration. PMID:26965927

  1. The S-cone contribution to luminance depends on the M- and L-cone adaptation levels: silent surrounds?

    PubMed

    Ripamonti, Caterina; Woo, Wen Ling; Crowther, Elizabeth; Stockman, Andrew

    2009-01-01

    Under dim background conditions, the S-cones make little or no contribution to luminance (A. Eisner & D. I. MacLeod, 1980; W. Verdon & A. J. Adams, 1987), yet under conditions of intense long-wavelength adaptation, a small but robust contribution to luminance--as defined by heterochromatic flicker photometry (A. Stockman, D. I. MacLeod, & D. D. DePriest, 1987, 1991) or motion (J. Lee & C. F. Stromeyer, 1989)--can be found. Here, by using selective adaptation and/or tritanopic metamers to isolate the S-cone response, we investigate the dependence of the S-cone luminance input on changes in background wavelength and radiance. Interestingly, the S-cone luminance input disappears completely when no adapting background is present, even though the same S-cone stimulus makes a clear contribution to luminance when a background is present. The dependence of the S-cone luminance input on the wavelength and radiance of the adapting background is surprising. We find that the S-cone signal can be measured on fields of 491 nm and longer wavelengths that exceed a criterion background radiance. These criterion radiances roughly follow an L + M spectral sensitivity, which suggests that the S-cone luminance input is silent unless the L- and M-cones are excited above a certain level. We hypothesize that the L + M cone signals produced by the steady adapting backgrounds somehow "gate" the S-cone luminance signals, perhaps by being modulated by them.

  2. Local Protein Synthesis in Axonal Growth Cones

    PubMed Central

    Šatkauskas, Saulius

    2007-01-01

    While initially thought to be essentially a developmental characteristic observed in artificial in vitro models, local protein synthesis in growth cones has been described in the adult, and more interestingly, during nerve regeneration. This emerging field is under intense investigation, revealing new functions of localized protein synthesis that include axon guidance, growth cone adaptation and sensitivity modulation at intermediate targets or axon regeneration. Here, we will review these functions and provide a short survey of the current knowledge on mechanisms of mRNA transport and regulation of localized protein synthesis. In addition, we will consider what lessons can be learned from localized protein synthesis in dendrites and what developments can be expected next in the field. This latter question relates to the crucial point of which technical strategy to adopt for an ideal and pertinent analysis of the phenomenon. PMID:19262143

  3. k-cones and kirigami metamaterials

    NASA Astrophysics Data System (ADS)

    Seffen, Keith A.

    2016-09-01

    We are inspired by the tensile buckling of a thin sheet with a slit to create a foldable planar metamaterial. The buckled shape comprises two pairs of identical e-cones connected to the slit, which we refer to as a k-cone. We approximate this shape as discrete vertices that can be folded out of plane as the slit is pulled apart. We determine their kinematics and we calculate generic shape properties using a simple elastic model of the folded shape. We then show how the folded sheet may be tessellated as a unit cell within a larger sheet, which may be constructed a priori by cutting and folding the latter in a regular way, in order to form a planar kirigami structure with a single degree of freedom.

  4. Instantons on Calabi-Yau cones

    NASA Astrophysics Data System (ADS)

    Sperling, Marcus

    2015-12-01

    The Hermitian Yang-Mills equations on certain vector bundles over Calabi-Yau cones can be reduced to a set of matrix equations; in fact, these are Nahm-type equations. The latter can be analysed further by generalising arguments of Donaldson and Kronheimer used in the study of the original Nahm equations. Starting from certain equivariant connections, we show that the full set of instanton equations reduce, with a unique gauge transformation, to the holomorphicity condition alone.

  5. Hadronic wavefunctions in light-cone quantization

    SciTech Connect

    Hyer, T.

    1994-05-01

    The analysis of light-cone wavefunctions seems the most promising theoretical approach to a detailed understanding of the structure of relativistic bound states, particularly hadrons. However, there are numerous complications in this approach. Most importantly, the light-cone approach sacrifices manifest rotational invariance in exchange for the elimination of negative-energy states. The requirement of rotational invariance of the full theory places important constraints on proposed light-cone wavefunctions, whether they are modelled or extracted from some numerical procedure. A formulation of the consequences of the hidden rotational symmetry has been sought for some time; it is presented in Chapter 2. In lattice gauge theory or heavy-quark effective theory, much of the focus is on the extraction of numerical values of operators which are related to the hadronic wavefunction. These operators are to some extent interdependent, with relations induced by fundamental constraints on the underlying wavefunction. The consequences of the requirement of unitarity are explored in Chapter 3, and are found to have startling phenomenological relevance. To test model light-cone wavefunctions, experimental predictions must be made. The reliability of perturbative QCD as a tool for making such predictions has been questioned. In Chapter 4, the author presents a computation of the rates for nucleon-antinucleon annihilation, improving the reliability of the perturbative computation by taking into account the Sudakov suppression of exclusive processes at large transverse impact parameter. In Chapter 5, he develops the analysis of semiexclusive production. This work focuses on processes in which a single isolated meson is produced perturbatively and recoils against a wide hadronizing system. At energies above about 10 GeV, semiexclusive processes are shown to be the most sensitive experimental probes of hadronic structure.

  6. Long polymers near wedges and cones

    NASA Astrophysics Data System (ADS)

    Hammer, Yosi; Kantor, Yacov

    2015-12-01

    We perform a Monte Carlo study of N -step self-avoiding walks, attached to the corner of an impenetrable wedge in two dimensions (d =2 ), or the tip of an impenetrable cone in d =3 , of sizes ranging up to N =106 steps. We find that the critical exponent γα, which determines the dependence of the number of available conformations on N for a cone or wedge with opening angle α , is in good agreement with the theory for d =2 . We study the end-point distribution of the walks in the allowed space and find similarities to the known behavior of random walks (ideal polymers) in the same geometry. For example, the ratio between the mean square end-to-end distances of a polymer near the cone or wedge and a polymer in free space depends linearly on γα, as is known for ideal polymers. We show that the end-point distribution of polymers attached to a wedge does not separate into a product of angular and radial functions, as it does for ideal polymers in the same geometry. The angular dependence of the end position of polymers near the wedge differs from theoretical predictions.

  7. Long polymers near wedges and cones.

    PubMed

    Hammer, Yosi; Kantor, Yacov

    2015-12-01

    We perform a Monte Carlo study of N-step self-avoiding walks, attached to the corner of an impenetrable wedge in two dimensions (d=2), or the tip of an impenetrable cone in d=3, of sizes ranging up to N=10(6) steps. We find that the critical exponent γ(α), which determines the dependence of the number of available conformations on N for a cone or wedge with opening angle α, is in good agreement with the theory for d=2. We study the end-point distribution of the walks in the allowed space and find similarities to the known behavior of random walks (ideal polymers) in the same geometry. For example, the ratio between the mean square end-to-end distances of a polymer near the cone or wedge and a polymer in free space depends linearly on γ(α), as is known for ideal polymers. We show that the end-point distribution of polymers attached to a wedge does not separate into a product of angular and radial functions, as it does for ideal polymers in the same geometry. The angular dependence of the end position of polymers near the wedge differs from theoretical predictions. PMID:26764719

  8. Numerical Simulation of Taylor Cone-Jet

    NASA Astrophysics Data System (ADS)

    Toledo, Ronne

    The Taylor cone-jet is a particular type of electrohydrodynamic phenomenon where electrostatic stresses and surface tension effects shape the interface of the jet in a peculiar conical shape. A thin jet is issued from the cone apex that further breaks up into a fine aerosol. Due to its monodispersive properties, this fine aerosol has found a number of applications, ranging from mass spectrometry, colloidal space propulsion, combustion, nano-fabrication, coating/painting, and many others. In this study, a general non-dimensional analysis is performed to derive the governing equations and boundary conditions. In accordance with the observations of Gamero-Castano (2010), noting that droplet electric potential is insensitive to the flow rate conditions, a particular set of characteristic parameters is proposed, based on the terminal jet diameter. In order to solve the non-dimensional set of governing equations and boundary conditions, a numerical method combining the Boundary Element Method and the Finite Volume Method is developed. Results of electric current have shown good agreement with numerical and experimental data available in the literature. The main feature of the algorithm developed is related to the decoupling of the electrostatic from the hydrodynamic problem, allowing us to accurately prescribe the far field electric potential boundary conditions away from the hydrodynamic computational domain used to solve the hydrodynamics of the transition region near the cone apex.

  9. Cusp formation in drops inside Taylor cones

    NASA Astrophysics Data System (ADS)

    Marin, Alvaro G.; Loscertales, Ignacio G.; Barrero, Antonio

    2005-11-01

    Here, we report the formation of cusp in insulating drops inside compound Taylor cones. The action of the electrical shear stress acting on the outer interface, which is transmitted by viscous forces inside the Taylor cone, tends to deform the drop of insulating liquid placed inside. For appropriate values of the capillary number, the insulating drop develops a steady cusp angle which depends on both the capillary number and the conducting to insulating viscosity ratio. A self-similar analysis has been developed to qualitatively describe the flow inside these compounds Taylor cones. Any perturbation of the cusp gives rise to an intermittent emission of tiny droplets; this effect may recall the tip-streaming observed by G.I. Taylor in his four-roll mill device. This emission can be stabilized by an appropriate control of the injected flow rate of the insulating liquid. When the capillary number increases, the cusped interface turns into a spout which flows coated by the conducting liquid forming the electrified coaxial jet which has been successfully employed for the production of nanocapsules, coaxial nanofibers and nanotubes (Science 295, n. 5560, 1695, 2002; JACS 126, 5376, 2004).

  10. Reconfiguration of broad leaves into cones

    NASA Astrophysics Data System (ADS)

    Miller, Laura

    2013-11-01

    Flexible plants, fungi, and sessile animals are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also exhibit this behavior. What is less understood is how the mechanical properties of a leaf in a three-dimensional flow will passively allow roll up and reduce drag. This presentation will begin by examining how leaves roll up into drag reducing shapes in strong flow. The dynamics of the flow around the leaf of the wild ginger Hexastylis arifolia are described using particle image velocimetry. The flows around the leaves are compared with those of simplified sheets using 3D numerical simulations and physical models. For some reconfiguration shapes, large forces and oscillations due to strong vortex shedding are produced. In the actual leaf, a stable recirculation zone is formed within the wake of the reconfigured cone. In physical and numerical models that reconfigure into cones, a similar recirculation zone is observed with both rigid and flexible tethers. These results suggest that the three-dimensional cone structure in addition to flexibility is significant to both the reduction of vortex-induced vibrations and the forces experienced by the leaf.

  11. CRALBP supports the mammalian retinal visual cycle and cone vision

    PubMed Central

    Xue, Yunlu; Shen, Susan Q.; Jui, Jonathan; Rupp, Alan C.; Byrne, Leah C.; Hattar, Samer; Flannery, John G.; Corbo, Joseph C.; Kefalov, Vladimir J.

    2015-01-01

    Mutations in the cellular retinaldehyde–binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor–mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus–mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone–driven vision and accelerating cone dark adaptation. PMID:25607845

  12. Growth cone behavior and production of traction force

    PubMed Central

    1990-01-01

    The growth cone must push its substrate rearward via some traction force in order to propel itself forward. To determine which growth cone behaviors produce traction force, we observed chick sensory growth cones under conditions in which force production was accommodated by movement of obstacles in the environment, namely, neurites of other sensory neurons or glass fibers. The movements of these obstacles occurred via three, different, stereotyped growth cone behaviors: (a) filopodial contractions, (b) smooth rearward movement on the dorsal surface of the growth cone, and (c) interactions with ruffling lamellipodia. More than 70% of the obstacle movements were caused by filopodial contractions in which the obstacle attached at the extreme distal end of a filopodium and moved only as the filopodium changed its extension. Filopodial contractions were characterized by frequent changes of obstacle velocity and direction. Contraction of a single filopodium is estimated to exert 50-90 microdyn of force, which can account for the pull exerted by chick sensory growth cones. Importantly, all five cases of growth cones growing over the top of obstacle neurites (i.e., geometry that mimics the usual growth cone/substrate interaction), were of the filopodial contraction type. Some 25% of obstacle movements occurred by a smooth backward movement along the top surface of growth cones. Both the appearance and rate of movements were similar to that reported for retrograde flow of cortical actin near the dorsal growth cone surface. Although these retrograde flow movements also exerted enough force to account for growth cone pulling, we did not observe such movements on ventral growth cone surfaces. Occasionally obstacles were moved by interaction with ruffling lamellipodia. However, we obtained no evidence for attachment of the obstacles to ruffling lamellipodia or for directed obstacle movements by this mechanism. These data suggest that chick sensory growth cones move forward by

  13. Biochemical pharmacology of isolated neuronal growth cones: implications for synaptogenesis.

    PubMed

    Lockerbie, R O

    1990-01-01

    The neuronal growth cone is critical to the establishment of neuronal polarity through its motile, pathfinding and target recognition properties exhibited during synaptogenesis. Subcellular fractionation procedures yielding milligram quantities of isolated growth cones has allowed for biochemical and pharmacological investigation of intrinsic growth cone components that are likely to be involved in regulation of growth cone function in neuronal development. These 'mapping' studies of growth cone components are prerequisites to elucidating the mechanisms by which extracellular factors influence the motility, adhesion and directed growth of the growth cone. For example, neurotransmitters and polypeptide growth factors which have been shown in other systems to modulate growth cone behavior are presumed to act through receptors on the growth cone, inducing second-messenger molecule formation and consequent modification and regulation of proteins effecting the response(s) of the growth cone (i.e. proteins involved in motility, adhesion and membrane turnover). In a relatively short period of time, work with the isolated growth cone preparation has identified, in independent studies, many of the elements involved in this proposed scheme of events, including transmitter receptors, second-messenger cascades, and second-messenger post-translational modifications. An obvious future goal will be to analyze in more detail the intracellular events, and the relationships between them, in the growth cone and how they transmit extracellular signals into responses such as motility and adhesivity which underly the growth cone's synaptogenic properties. It is to be expected that much of this information will come forth from experimentation with the isolated growth cone preparation.

  14. M-cone opsin gene number does not correlate with variation in L/M-cone sensitivity.

    PubMed

    Knau, H; Kremers, J; Schmidt, H-J; Wolf, S; Wissinger, B; Sharpe, L T

    2002-07-01

    Molecular genetic studies demonstrate that the human cone opsin gene array on the q-arm of the X-chromosome typically consists of one long-wave-sensitive (L) cone opsin gene and from one to several middle-wave-sensitive (M) cone opsin genes. Although the presence of the single L-cone opsin gene and at least one M-cone opsin gene is essential for normal red-green colour discrimination, the function of the additional M-cone opsin genes is still unclear. To investigate whether any variations in phenotype correlate with differences in the number of M-cone opsin genes, we selected 13 normal trichromat males, for whom four independent molecular techniques have exactly determined their number of M-cone opsin genes, ranging from one to four. Their phenotype was characterized by estimating their foveal L- to M-cone ratio from heterochromatic flicker photometric (HFP) thresholds, by measuring the wavelength corresponding to their 'unique yellow', and by determining their L- and M-cone modulation thresholds (CMTs). No correlation was found between these psychophysical measures and the number of M-cone opsin genes. Although, we found a reasonably good correlation between the L/M-cone ratios based on HFP and on CMT, we did not find any correlation between the estimated L/M-cone ratios and the settings of 'unique yellow'. Our results accord with previous molecular genetic studies that suggest that only the first two genes in the X-linked opsin gene array are expressed.

  15. Comparison of cone and cone shell configuration for depth sensitive fluorescence measurements in turbid media

    NASA Astrophysics Data System (ADS)

    Ong, Yi Hong; Liu, Quan

    2014-03-01

    We have developed a novel cone shell illumination and detection configurations using combination of axicon lenses for depth sensitive fluorescence spectroscopy. The probe was demonstrated experimentally to be able to selectively detecting fluorescence from different depths from a two-layered turbid agar phantom. In addition to enhanced contrast of subsurface fluorescence measurement as compared to a conventional cone configuration implemented by a microscope objective lens, the axicon lenses based setup eliminated the need of moving the objective lens up or down to achieve depth sensitive measurements, which effectively improves the consistency of optical coupling thus would be preferred in a clinical setting.

  16. Tantalum cones and bone defects in revision total knee arthroplasty.

    PubMed

    Boureau, F; Putman, S; Arnould, A; Dereudre, G; Migaud, H; Pasquier, G

    2015-04-01

    Management of bone loss is a major challenge in revision total knee arthroplasty (TKA). The development of preformed porous tantalum cones offers new possibilities, because they seem to have biological and mechanical qualities that facilitate osseointegration. Compared to the original procedure, when metaphyseal bone defects are too severe, a single tantalum cone may not be enough and we have developed a technique that could extend the indications for this cone in these cases. We used 2 cones to fill femoral bone defects in 7 patients. There were no complications due to wear of the tantalum cones. Radiological follow-up did show any migration or loosening. The short-term results confirm the interest of porous tantalum cones and suggest that they can be an alternative to allografts or megaprostheses in case of massive bone defects.

  17. Pulsar average waveforms and hollow cone beam models

    NASA Technical Reports Server (NTRS)

    Backer, D. C.

    1975-01-01

    An analysis of pulsar average waveforms at radio frequencies from 40 MHz to 15 GHz is presented. The analysis is based on the hypothesis that the observer sees one cut of a hollow-cone beam pattern and that stationary properties of the emission vary over the cone. The distributions of apparent cone widths for different observed forms of the average pulse profiles (single, double/unresolved, double/resolved, triple and multiple) are in modest agreement with a model of a circular hollow-cone beam with random observer-spin axis orientation, a random cone axis-spin axis alignment, and a small range of physical hollow-cone parameters for all objects.

  18. Heating distribution comparison between asymmetric and symmetric blunt cones

    NASA Technical Reports Server (NTRS)

    Stewart, D. A.; Kolodziej, P.

    1986-01-01

    An experiment was performed to compare the heating distribution between symmetric and asymmetric large-angle blunt cones, with cone angles of 100, 120, and 140 deg. These hot-wall data were obtained from models made from typical thermal protection insulation for proposed aeroassisted orbital transfer vehicles. Experimental data are compared with predictions using a boundary-layer integral matrix procedure with kinetics to determine how well the heating distribution over an asymmetric cone could be approximated using axisymmetric solutions for a cone and spherical segment. In addition, a relationship between the stagnation-point heat-transfer rate and the bow-shock standoff distance for these cones is discussed. The heat-distribution data from the symmetric and asymmetric cones were very similar. Numerical results compared well with the measured wall temperatures at the stagnation point but slightly underpredicted them over the conical portion of the models.

  19. Rod-cone interactions and analysis of retinal disease.

    PubMed Central

    Arden, G B; Hogg, C R

    1985-01-01

    Cone flicker threshold rises as the rods dark adapt, though the cone threshold to continuous light remains constant. The rise is normally about 1 log unit, but in certain patients who complain of night blindness it may be as great as 2.5 log units. In these persons the kinetics of the rod-cone interaction are those of the recovery of rod sensitivity. The rods impose a low-pass filter on the cones. This effect is absent in congenital nyctalopia and X-linked retinoschisis. We suggest that cone flicker is maintained through a feedback system involving horizontal cells, and when the rod dark current returns in dark adaptation this feedback is altered. Rod cone interaction thus tests rod dark current, and cases of abnormal interaction in patients with retinitis pigmentosa occur, which indicate that the transduction mechanism and the membrane dark current may be differentially affected. Images PMID:3873959

  20. Partial cone calix[4]arene-crown-6-ethers

    SciTech Connect

    Das, G.; Sachleben, R.A.; Descazeaud, T.; Bryan, J.C.; Moyer, B.A.

    1997-12-31

    Partial cone calix[4] arene crown ethers represents a new category of lariat ethers. In general, calix arene crown ethers have been previously shown to be efficient extractants for metal cations. Appropriately substituted cone and 1, 3-alt conformers of calix crowns exhibit selectivities for Na{sup +} and Cs{sup +}, respectively. The partial cone conformers have not been as throughly studied. We have developed an efficient method of synthesis of partial cone calix[4]arene-crown ethers and have synthesized a variety of partial cone calix[4]arene crowns. Solution and solid-state structures of representative examples have been determined by {sup 1}H NMR spectroscopy and X-ray crystallography. Relative affinities of these partial cone calix[4]arene crowns for alkali metal ions have been investigated by solvent extraction techniques.

  1. Photovoltage of Rods and Cones in the Macaque Retina

    NASA Astrophysics Data System (ADS)

    Schneeweis, David M.; Schnapf, Julie L.

    1995-05-01

    The kinetics, gain, and reliability of light responses of rod and cone photoreceptors are important determinants of overall visual sensitivity. In voltage recordings from photoreceptors in an intact primate retina, rods were found to be functionally isolated from each other, unlike the tightly coupled rods of cold-blooded vertebrates. Cones were observed to receive excitatory input from rods, which indicates that the cone pathway also processes rod signals. This input might be expected to degrade the spatial resolution of mesopic vision.

  2. The trip of the tip: understanding the growth cone machinery.

    PubMed

    Lowery, Laura Anne; Van Vactor, David

    2009-05-01

    The central component in the road trip of axon guidance is the growth cone, a dynamic structure that is located at the tip of the growing axon. During its journey, the growth cone comprises both 'vehicle' and 'navigator'. Whereas the 'vehicle' maintains growth cone movement and contains the cytoskeletal structural elements of its framework, a motor to move forward and a mechanism to provide traction on the 'road', the 'navigator' aspect guides this system with spatial bias to translate environmental signals into directional movement. The understanding of the functions and regulation of the vehicle and navigator provides new insights into the cell biology of growth cone guidance.

  3. Dynamics on the cone: Closed orbits and superintegrability

    SciTech Connect

    Brihaye, Y.; Kosiński, P.

    2014-05-15

    The generalization of Bertrand’s theorem to the case of the motion of point particle on the surface of a cone is presented. The superintegrability of such models is discussed. The additional integrals of motion are analysed for the case of Kepler and harmonic oscillator potentials. -- Highlights: •Bertrand’s theorem is generalized to the case of the motion on a cone. •The superintegrability of the dynamics on a cone is discussed. •The W-algebra of integrals of motion for Kepler and harmonic oscillator problems on a cone is derived.

  4. Associating color appearance with the cone chromaticity space.

    PubMed

    Cao, Dingcai; Pokorny, Joel; Smith, Vivianne C

    2005-07-01

    A cone chromaticity space, a transform of a colorimetric specification system into coordinates that represent cone excitations, does not provide color appearance information. Boynton and Olson (Color Research and Application 12, 94-105, 1987) gathered color naming for the 424 Optical Society of America Uniform Color Scales (OSA-UCS) color samples. Here, a computational algorithm was developed that converts OSA-UCS sample values into L, M, S cone excitations based on the 1964 CIE 10 degrees Standard Observer. This makes it possible to plot the cone chromaticities associated with the eight color names used by Boynton and Olsen's observers to describe the non-dark appearing colors.

  5. Psychophysical definition of S-cone stimuli in the macaque

    PubMed Central

    Hall, Nathan; Colby, Carol

    2013-01-01

    We used the perceptual reports of nonhuman primates to perform psychophysical calibrations of S-cone isolating stimuli. S-cone stimuli were calibrated separately at several spatial locations for each monkey. To do this we exploited the effect of transient tritanopia, which causes a selective decrease of sensitivity in the observer's S-cone channel. At the start of each transient tritanopia trial monkeys were visually adapted to a bright yellow background. This type of adaptation is known to induce transient tritanopia. Calibrated S-cone isolating stimuli were determined by finding a near S-cone stimulus whose detection threshold was maximally elevated during transient tritanopia. At the start of each control trial, monkeys were adapted to a bright white background. In these trials, monkeys' detection thresholds for near S-cone stimuli were unchanged. We found that S-cone isolating stimuli could be determined at most locations tested in each monkey. Calibrated S-cone stimuli were particular to both spatial location and animal. To understand the visual system as a whole in vivo requires physiological methods not possible in human subjects. The present results open the door to novel behavioral and physiological experiments by showing that S-cone isolating stimuli can be calibrated in monkeys. PMID:23412341

  6. Light-cone quantization and QCD phenomenology

    SciTech Connect

    Brodsky, S.J.; Robertson, D.G.

    1995-12-31

    In principle, quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of their elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. A crucial tool in analyzing such phenomena is the use of relativistic light-cone quantum mechanics and Fock state methods to provide tractable and consistent treatments of relativistic many-body systems. In this article we present an overview of this formalism applied to QCD, focusing in particular on applications to the final states in deep inelastic lepton scattering that will be relevant for the proposed European Laboratory for Electrons (ELFE), HERMES, HERA, SLAC, and CEBAF. We begin with a brief introduction to light-cone field theory, stressing how it many allow the derivation of a constituent picture, analogous to the constituent quark model, from QCD. We then discuss several applications of the light-cone Fock state formalism to QCD phenomenology. The Fock state representation includes all quantum fluctuations of the hadron wavefunction, including far off-shell configurations such as intrinsic charm and, in the case of nuclei, hidden color. In some applications, such as exclusive processes at large momentum transfer, one can make first-principle predictions using factorization theorems which separate the hard perturbative dynamics from the nonpertubative physics associated with hadron binding. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer.

  7. Cone Beam Computed Tomography - Know its Secrets

    PubMed Central

    Kumar, Mohan; Shanavas, Muhammad; Sidappa, Ashwin; Kiran, Madhu

    2015-01-01

    Cone-beam computed tomography (CBCT) is an advanced imaging modality that has high clinical applications in the field of dentistry. CBCT proved to be a successful investigative modality that has been used for dental and maxillofacial imaging. Radiation exposure dose from CBCT is 10 times less than from conventional CT scans during maxillofacial exposure. Furthermore, CBCT is highly accurate and can provide a three-dimensional volumetric data in axial, sagittal and coronal planes. This article describes the basic technique, difference in CBCT from CT and main clinical applications of CBCT. PMID:25859112

  8. Bistatic scattering from a cone frustum

    NASA Technical Reports Server (NTRS)

    Ebihara, W.; Marhefka, R. J.

    1986-01-01

    The bistatic scattering from a perfectly conducting cone frustum is investigated using the Geometrical Theory of Diffraction (GTD). The first-order GTD edge-diffraction solution has been extended by correcting for its failure in the specular region off the curved surface and in the rim-caustic regions of the endcaps. The corrections are accomplished by the use of transition functions which are developed and introduced into the diffraction coefficients. Theoretical results are verified in the principal plane by comparison with the moment method solution and experimental measurements. The resulting solution for the scattered fields is accurate, easy to apply, and fast to compute.

  9. Microcomputed tomography and shock microdeformation studies on shatter cones

    NASA Astrophysics Data System (ADS)

    Zaag, Patrice Tristan; Reimold, Wolf Uwe; Hipsley, Christy Anna

    2016-08-01

    One of the aspects of impact cratering that are still not fully understood is the formation of shatter cones and related fracturing phenomena. Yet, shatter cones have been applied as an impact-diagnostic criterion for decades without the role of shock waves and target rock defects in their formation having been elucidated ever. We have tested the application of the nondestructive microcomputed tomography (μCT) method to visualize the interior of shatter cones in order to possibly resolve links between fracture patterns and shatter cone surface features (striations and intervening "valleys"). Shatter-coned samples from different impact sites and in different lithologies were investigated for their μCT suitability, with a shatter cone in sandstone from the Serra da Cangalha impact structure (Brazil) remaining as the most promising candidate because of the fracture resolution achieved. To validate the obtained CT data, the scanned specimen was cut into three orthogonal sets of thin sections. Scans with 13 μm resolution were obtained. μCT scans and microscopic analysis unraveled an orientation of subplanar fractures and related fluid inclusion trails, and planar fracture (PF) orientations in the interior of shatter cones. Planar deformation features (PDF) were observed predominantly near the shatter cone surface. Previously undescribed varieties of feather features (FF), in the form of lamellae emanating from curviplanar and curved fractures, as well as an "arrowhead"-like FF development with microlamellae originating from both sides of a PF, were observed. The timing of shatter cone formation was investigated by establishing temporal relations to the generation of various shock microscopic effects. Shatter cones are, thus, generated post- or syn-formation of PF, FF, subplanar fractures, and PDF. The earliest possible time for shatter cone formation is during the late stage of the compressional phase, that is, shock wave passage, of an impact event.

  10. Real Gas/Blunt Cone. Phase 2

    NASA Technical Reports Server (NTRS)

    Deiwert, George S.; Eitelberg, Georg

    1998-01-01

    In this chapter recent activity in real-gas database definition and code validation will be summarized. In the Phase I report of the Working Group (WG) 181, aerothermodynamic problems were classified, for purpose of discussion, into seven types: aerodynamic parameters, viscous/shock interaction, boundary-layer transition, forebody-heating/heat-transfer, radiation and ablation, lee and base-region flow, and low-density flow. Several of these problem types were the subject of various chapters of the Phase 1 report describing real-gas effects and ground test facility issues. In this chapter some background and objectives outlined in the real-Gas effects Chapter V of the Phase 1 report will be reviewed. The results of the blunt cone test campaign developed under the auspices of the WG18 activity to study real-gas phenomena will be summarized, including the experimental and computational programs, issues and questions, and recommendations. Further, recent progress in other real-gas areas beyond the blunt cone test campaign will be discussed. Finally, a summary in which the present status of our understanding of real-gas issues will be presented.

  11. Light-cone quantization and hadron structure

    SciTech Connect

    Brodsky, S.J.

    1996-04-01

    Quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. In this talk, the author will discuss light-cone quantization and the light-cone Fock expansion as a tractable and consistent representation of relativistic many-body systems and bound states in quantum field theory. The Fock state representation in QCD includes all quantum fluctuations of the hadron wavefunction, including fax off-shell configurations such as intrinsic strangeness and charm and, in the case of nuclei, hidden color. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer. In other applications, such as the calculation of the axial, magnetic, and quadrupole moments of light nuclei, the QCD relativistic Fock state description provides new insights which go well beyond the usual assumptions of traditional hadronic and nuclear physics.

  12. Scatter corrections for cone beam optical CT

    NASA Astrophysics Data System (ADS)

    Olding, Tim; Holmes, Oliver; Schreiner, L. John

    2009-05-01

    Cone beam optical computed tomography (OptCT) employing the VISTA scanner (Modus Medical, London, ON) has been shown to have significant promise for fast, three dimensional imaging of polymer gel dosimeters. One distinct challenge with this approach arises from the combination of the cone beam geometry, a diffuse light source, and the scattering polymer gel media, which all contribute scatter signal that perturbs the accuracy of the scanner. Beam stop array (BSA), beam pass array (BPA) and anti-scatter polarizer correction methodologies have been employed to remove scatter signal from OptCT data. These approaches are investigated through the use of well-characterized phantom scattering solutions and irradiated polymer gel dosimeters. BSA corrected scatter solutions show good agreement in attenuation coefficient with the optically absorbing dye solutions, with considerable reduction of scatter-induced cupping artifact at high scattering concentrations. The application of BSA scatter corrections to a polymer gel dosimeter lead to an overall improvement in the number of pixel satisfying the (3%, 3mm) gamma value criteria from 7.8% to 0.15%.

  13. The Double Cone: A Mechanical Paradox or a Geometrical Constraint?

    ERIC Educational Resources Information Center

    Gallitto, Aurelio Agliolo; Fiordilino, Emilio

    2011-01-01

    In the framework of the Italian National Plan "Lauree Scientifiche" (PLS) in collaboration with secondary schools, we have investigated the mechanical paradox of the double cone. We have calculated the geometric condition for obtaining an upward movement. Based on this result, we have built a mechanical model with a double cone made of aluminum…

  14. Galileo Spacecraft Scan Platform Celestial Pointing Cone Control Gain Redesign

    NASA Technical Reports Server (NTRS)

    In, C-H. C.; Hilbert, K. B.

    1994-01-01

    During September and October 1991, pictures of the Gaspra asteroid and neighboring stars were taken by the Galileo Optical Navigation (OPNAV) Team for the purpose of navigation the spacecraft for a successful Gaspra encounter. The star tracks in these pictures showed that the scan platform celestial pointing cone controller performed poorly in compensating for wobble-induced cone offsets.

  15. Implosion of indirectly driven reentrant cone shell target

    SciTech Connect

    R.B. Stephens; S.P. Hatchett; R.E. Turner; K.A. Tanaka; R. Kodama

    2003-10-31

    In an x-ray driven reentrant cone fast ignition target the x-ray spectrum contains a high energy component that casuses preheating of the reentrant cone and mixing of the gold into the collapsing shell. Direct laser drive might avoid this problem.

  16. The dynamics of a steady Taylor cone electrospray

    NASA Astrophysics Data System (ADS)

    Bell, Martin; Rutgers, Maarten A.

    1998-11-01

    A liquid drop at the tip of a needle will become conical if a high voltage is supplied to the needle. This is known as a Zeleny^1-Taylor^2 cone. Due to the finite conductivity of most liquids, a thin liquid jet will emerge from the cone tip. This jet can be thinner than 1 micrometer and move with speeds in excess of 10 m/s! The jet breaks up due to a Rayleigh instability into a stream of monodisperse droplets. The particles themselves carry charge and can cause the droplet stream to break up into a diverging conical spray. De La Mora^3 has calculated the relation between the liquid and spray cone angles, but less in known about the dynamics with which the droplets move from the initial jet into the final electrospray cone. We have observed electrosprayed droplets in a regime where the Taylor cone oscillates axisymmetrically, leading to an interrupted spray. By periodically driving the volume of the Taylor cone, and illuminating the spray stroboscopically at the same frequency, we can essentially `freeze' the evolution of a packet of droplets in the spray cone. We clearly observe the disintegration of the initial jet of droplets into a growing spherical cloud. The expanding clouds can be inscribed in the cone of an uninterrupted electrospray. ^1J. Zeleny, Phys. Rev. 3:69, (1914), ^2G.I. Taylor, J. Fluid Mech. 2:1, (1965) ^3J.F. De La Mora, J. Fluid Mech. 243:561, (1992)

  17. Dosimetry characteristics of metallic cones for intraoperative radiotherapy.

    PubMed

    Nyerick, C E; Ochran, T G; Boyer, A L; Hogstrom, K R

    1991-07-01

    Dosimetry data were obtained on the first dedicated linear accelerator of its type designed for electron intraoperative radiotherapy (IORT) within an operating room. The linear accelerator uses a high dose rate, 9 Gy.min-1, to reduce the treatment time. Its chrome-plated brass treatment cones, designed with straight ends and 22.5 degrees beveled ends, are not mechanically attached to the collimator head, but are aligned using a laser projection system. Dosimetry measurements were made for each combination of energy (6, 9, 12, 15, and 16 MeV), cone size (diameters range from 5 to 12 cm), and cone type (22.5 degrees beveled or straight). From these data, depth-dose curves, cone output, and air-gap correction factors were generated that allow the calculation of the monitor setting for delivering a prescribed dose at any depth for any irradiation condition (energy, cone, air gap). Isodose data were measured for every cone using film in a solid water phantom. Scatter off the inside wall of the cone resulted in peripheral dose horns near the surface that were energy and cone dependent, being as large as 120%.

  18. Dosimetry characteristics of metallic cones for intraoperative radiotherapy

    SciTech Connect

    Nyerick, C.E.; Ochran, T.G.; Boyer, A.L.; Hogstrom, K.R. )

    1991-07-01

    Dosimetry data were obtained on the first dedicated linear accelerator of its type designed for electron intraoperative radiotherapy (IORT) within an operating room. The linear accelerator uses a high dose rate, 9 Gy.min-1, to reduce the treatment time. Its chrome-plated brass treatment cones, designed with straight ends and 22.5 degrees beveled ends, are not mechanically attached to the collimator head, but are aligned using a laser projection system. Dosimetry measurements were made for each combination of energy (6, 9, 12, 15, and 16 MeV), cone size (diameters range from 5 to 12 cm), and cone type (22.5 degrees beveled or straight). From these data, depth-dose curves, cone output, and air-gap correction factors were generated that allow the calculation of the monitor setting for delivering a prescribed dose at any depth for any irradiation condition (energy, cone, air gap). Isodose data were measured for every cone using film in a solid water phantom. Scatter off the inside wall of the cone resulted in peripheral dose horns near the surface that were energy and cone dependent, being as large as 120%.

  19. Scoria Cone Construction Mechanism, Lathrop Wells Volcano, Southern Nevada

    SciTech Connect

    G. Valentine; D. Krier; F. Perry; G. Heiken

    2005-01-18

    Scoria cones are commonly assumed to have been constructed by the accumulation of ballistically-ejected clasts from discrete and relatively coarse-grained Strombolian bursts and subsequent avalanching such that the cone slopes are at or near the angle of repose for loose scoria. The cone at the hawaiitic Lathrop Wells volcano, southern Nevada, contains deposits that are consistent with the above processes during early cone-building phases; these early deposits are composed mainly of coarse lapilli and fluidal bombs and are partially welded, indicating relatively little cooling during flight. However, the bulk of the cone is comprised of relatively fine-grained (ash and lapilli), planar beds with no welding, even within a few tens of meters of the vent. This facies is consistent with deposition by direct fallout from sustained eruption columns of relatively well-fragmented material, primarily mantling cone slopes and with a lesser degree of avalanching than is commonly assumed. A laterally extensive fallout deposit (up to 20 km from the vent) is inferred to have formed contemporaneously with these later cone deposits. This additional mechanism for construction of scoria cones may also be important at other locations, particularly where the magmas are relatively high in volatile content and where conditions promote the formation of abundant microlites in the rising mafic magma.

  20. Salamander Blue-sensitive Cones Lost During Metamorphosis†

    PubMed Central

    Chen, Ying; Znoiko, Sergey; DeGrip, Willem J.; Crouch, Rosalie K.; Ma, Jian-xing

    2009-01-01

    The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors—two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones. Here we show that after metamorphosis, the terrestrial salamander looses the blue-sensitive cones, while the density of the green rods increases. Moreover, the size of the green rod outer segments is increased in the terrestrial phase, compared to that in the aquatic phase. This switch from the blue-sensitive cones to the green rods may represent an adaptation to the dim light environment of the terrestrial phase. PMID:18331398

  1. Two-Step Reactivation of Dormant Cones in Retinitis Pigmentosa

    PubMed Central

    Wang, Wei; Lee, Sang Joon; Scott, Patrick A.; Lu, Xiaoqin; Emery, Douglas; Liu, Yongqin; Ezashi, Toshihiko; Roberts, Michael R.; Ross, Jason W.; Kaplan, Henry J.; Dean, Douglas C.

    2016-01-01

    Most Retinitis Pigmentosa (RP) mutations arise in rod photoreceptor genes, leading to diminished peripheral and nightime vision. Using a pig model of autosomal-dominant RP, we show glucose becomes sequestered in the retinal pigment epithelium (RPE), and thus is not transported to photoreceptors. The resulting starvation for glucose metabolites impairs synthesis of cone visual pigment -rich outer segments (OS), and then their mitochondrial-rich inner segments dissociate. Loss of these functional structures diminishes cone-dependent high-resolution central vision, which is utilized for most daily tasks. By transplanting wild-type rods, to restore glucose transport, or directly replacing glucose in the subretinal space, to bypass its retention in the RPE, we can regenerate cone functional structures, reactivating the dormant cells. Beyond providing metabolic building blocks for cone functional structures, we show glucose induces thioredoxin-interacting protein (Txnip) to regulate Akt signaling, thereby shunting metabolites toward aerobic glucose metabolism and regenerating cone OS synthesis. PMID:27050517

  2. Unsupervised Learning of Cone Spectral Classes from Natural Images

    PubMed Central

    Benson, Noah C.; Manning, Jeremy R.; Brainard, David H.

    2014-01-01

    The first step in the evolution of primate trichromatic color vision was the expression of a third cone class not present in ancestral mammals. This observation motivates a fundamental question about the evolution of any sensory system: how is it possible to detect and exploit the presence of a novel sensory class? We explore this question in the context of primate color vision. We present an unsupervised learning algorithm capable of both detecting the number of spectral cone classes in a retinal mosaic and learning the class of each cone using the inter-cone correlations obtained in response to natural image input. The algorithm's ability to classify cones is in broad agreement with experimental evidence about functional color vision for a wide range of mosaic parameters, including those characterizing dichromacy, typical trichromacy, anomalous trichromacy, and possible tetrachromacy. PMID:24967877

  3. Unsupervised learning of cone spectral classes from natural images.

    PubMed

    Benson, Noah C; Manning, Jeremy R; Brainard, David H

    2014-06-01

    The first step in the evolution of primate trichromatic color vision was the expression of a third cone class not present in ancestral mammals. This observation motivates a fundamental question about the evolution of any sensory system: how is it possible to detect and exploit the presence of a novel sensory class? We explore this question in the context of primate color vision. We present an unsupervised learning algorithm capable of both detecting the number of spectral cone classes in a retinal mosaic and learning the class of each cone using the inter-cone correlations obtained in response to natural image input. The algorithm's ability to classify cones is in broad agreement with experimental evidence about functional color vision for a wide range of mosaic parameters, including those characterizing dichromacy, typical trichromacy, anomalous trichromacy, and possible tetrachromacy. PMID:24967877

  4. Unsupervised learning of cone spectral classes from natural images.

    PubMed

    Benson, Noah C; Manning, Jeremy R; Brainard, David H

    2014-06-01

    The first step in the evolution of primate trichromatic color vision was the expression of a third cone class not present in ancestral mammals. This observation motivates a fundamental question about the evolution of any sensory system: how is it possible to detect and exploit the presence of a novel sensory class? We explore this question in the context of primate color vision. We present an unsupervised learning algorithm capable of both detecting the number of spectral cone classes in a retinal mosaic and learning the class of each cone using the inter-cone correlations obtained in response to natural image input. The algorithm's ability to classify cones is in broad agreement with experimental evidence about functional color vision for a wide range of mosaic parameters, including those characterizing dichromacy, typical trichromacy, anomalous trichromacy, and possible tetrachromacy.

  5. Two-Step Reactivation of Dormant Cones in Retinitis Pigmentosa.

    PubMed

    Wang, Wei; Lee, Sang Joon; Scott, Patrick A; Lu, Xiaoqin; Emery, Douglas; Liu, Yongqin; Ezashi, Toshihiko; Roberts, Michael R; Ross, Jason W; Kaplan, Henry J; Dean, Douglas C

    2016-04-12

    Most retinitis pigmentosa (RP) mutations arise in rod photoreceptor genes, leading to diminished peripheral and nighttime vision. Using a pig model of autosomal-dominant RP, we show glucose becomes sequestered in the retinal pigment epithelium (RPE) and, thus, is not transported to photoreceptors. The resulting starvation for glucose metabolites impairs synthesis of cone visual pigment-rich outer segments (OSs), and then their mitochondrial-rich inner segments dissociate. Loss of these functional structures diminishes cone-dependent high-resolution central vision, which is utilized for most daily tasks. By transplanting wild-type rods, to restore glucose transport, or directly replacing glucose in the subretinal space, to bypass its retention in the RPE, we can regenerate cone functional structures, reactivating the dormant cells. Beyond providing metabolic building blocks for cone functional structures, we show glucose induces thioredoxin-interacting protein (Txnip) to regulate Akt signaling, thereby shunting metabolites toward aerobic glucose metabolism and regenerating cone OS synthesis. PMID:27050517

  6. Cinder cone growth modeled after Northeast crater, Mount Etna, Sicily

    NASA Technical Reports Server (NTRS)

    Mcgetchin, T. R.; Settle, M.; Chouet, B. A.

    1974-01-01

    The structure, physical properties of ejecta, ballistics, and growth of Northeast crater, a young pyroclastic cone that originated in 1911 near the summit of Mount Etna, Sicily, were studied in order to form a model of volcano cinder cone growth. Four stages of growth were discerned: (1) a simple cone; (2) a cone with an outward-dipping talus slope; (3) destruction of rounded rim by the inward migration of the upper edge of the talus pile; and (4) extension of limits of talus pile beyond the ballistic limit of ejecta trajectories. The model is used to predict the features of lunar and Martian cones, assuming that they erupted under conditions qualitatively similar to Etna's Northeast crater.

  7. Shatter cones formed in large-scale experimental explosion craters

    NASA Technical Reports Server (NTRS)

    Roddy, D. J.; Davis, L. K.

    1977-01-01

    In 1968, a series of 0.5-ton and 100-ton TNT explosion experiments were conducted in granitic rock near Cedar City, Utah, as part of a basic research program on cratering and shock wave propagation. Of special interest was the formation of an important type of shock metamorphic feature, shatter cones. A description is presented of the first reported occurrence of shatter cones in high explosion trials. A background to shatter cone studies is presented and attention is given to the test program, geology and physical properties of the test medium, the observed cratering, and the formational pressures for shatter cones. The high explosion trials conducted demonstrate beyond any doubt, that shatter cones can be formed by shock wave processes during cratering and that average formational pressures in these crystalline rocks are in the 20-60 kb range.

  8. S cones: Evolution, retinal distribution, development, and spectral sensitivity.

    PubMed

    Hunt, David M; Peichl, Leo

    2014-03-01

    S cones expressing the short wavelength-sensitive type 1 (SWS1) class of visual pigment generally form only a minority type of cone photoreceptor within the vertebrate duplex retina. Hence, their primary role is in color vision, not in high acuity vision. In mammals, S cones may be present as a constant fraction of the cones across the retina, may be restricted to certain regions of the retina or may form a gradient across the retina, and in some species, there is coexpression of SWS1 and the long wavelength-sensitive (LWS) class of pigment in many cones. During retinal development, SWS1 opsin expression generally precedes that of LWS opsin, and evidence from genetic studies indicates that the S cone pathway may be the default pathway for cone development. With the notable exception of the cartilaginous fishes, where S cones appear to be absent, they are present in representative species from all other vertebrate classes. S cone loss is not, however, uncommon; they are absent from most aquatic mammals and from some but not all nocturnal terrestrial species. The peak spectral sensitivity of S cones depends on the spectral characteristics of the pigment present. Evidence from the study of agnathans and teleost fishes indicates that the ancestral vertebrate SWS1 pigment was ultraviolet (UV) sensitive with a peak around 360 nm, but this has shifted into the violet region of the spectrum (>380 nm) on many separate occasions during vertebrate evolution. In all cases, the shift was generated by just one or a few replacements in tuning-relevant residues. Only in the avian lineage has tuning moved in the opposite direction, with the reinvention of UV-sensitive pigments. PMID:23895771

  9. S cones: Evolution, retinal distribution, development, and spectral sensitivity.

    PubMed

    Hunt, David M; Peichl, Leo

    2014-03-01

    S cones expressing the short wavelength-sensitive type 1 (SWS1) class of visual pigment generally form only a minority type of cone photoreceptor within the vertebrate duplex retina. Hence, their primary role is in color vision, not in high acuity vision. In mammals, S cones may be present as a constant fraction of the cones across the retina, may be restricted to certain regions of the retina or may form a gradient across the retina, and in some species, there is coexpression of SWS1 and the long wavelength-sensitive (LWS) class of pigment in many cones. During retinal development, SWS1 opsin expression generally precedes that of LWS opsin, and evidence from genetic studies indicates that the S cone pathway may be the default pathway for cone development. With the notable exception of the cartilaginous fishes, where S cones appear to be absent, they are present in representative species from all other vertebrate classes. S cone loss is not, however, uncommon; they are absent from most aquatic mammals and from some but not all nocturnal terrestrial species. The peak spectral sensitivity of S cones depends on the spectral characteristics of the pigment present. Evidence from the study of agnathans and teleost fishes indicates that the ancestral vertebrate SWS1 pigment was ultraviolet (UV) sensitive with a peak around 360 nm, but this has shifted into the violet region of the spectrum (>380 nm) on many separate occasions during vertebrate evolution. In all cases, the shift was generated by just one or a few replacements in tuning-relevant residues. Only in the avian lineage has tuning moved in the opposite direction, with the reinvention of UV-sensitive pigments.

  10. Formation of shatter cones in MEMIN impact experiments

    NASA Astrophysics Data System (ADS)

    Wilk, J.; Kenkmann, T.

    2016-08-01

    Shatter cones are the only macroscopic feature considered as evidence for shock metamorphism. Their presence is diagnostic for the discovery and verification of impact structures. The occurrence of shatter cones is heterogeneous throughout the crater record and their geometry can diverge from the typical cone shape. The precise formation mechanism of shatter cones is still not resolved. In this study, we aim at better constraining the boundary conditions of shatter cone formation in impact experiments and test a novel approach to qualitatively and quantitatively describe shatter cone geometries by white light interferometry. We recovered several ejected fragments from MEMIN cratering experiments that show slightly curved, striated surfaces and conical geometries with apices of 36°-52°. These fragments fulfilling the morphological criteria of shatter cones were found in experiments with 20-80 cm sized target cubes of sandstone, quartzite and limestone, but not in highly porous tuff. Targets were impacted by aluminum, steel, and iron meteorite projectiles at velocities of 4.6-7.8 km s-1. The projectile sizes ranged from 2.5-12 mm in diameter and produced experimental peak pressures of up to 86 GPa. In experiments with lower impact velocities shatter cones could not be found. A thorough morphometric analysis of the experimentally generated shatter cones was made with 3D white light interferometry scans at micrometer accuracy. SEM analysis of the surfaces of recovered fragments showed vesicular melt films alternating with smoothly polished surfaces. We hypothesize that the vesicular melt films predominantly form at strain releasing steps and suggest that shatter cones are probably mixed mode fractures.

  11. Transition on elliptic cones at Mach 8

    NASA Astrophysics Data System (ADS)

    Huntley, Mark Bradford

    2000-10-01

    Flow visualizations of boundary layer transition on two sharp-nosed elliptic cones at Mach 8 are presented. The elliptic cone is a relevant three-dimensional flow field since it represents a generic hypersonic lifting vehicle shape. Experiments utilize carbon dioxide enhanced Filtered Rayleigh scattering to produce planar single-shot and motion picture images. CO2 is injected into the flow upstream of the tunnel stagnation chamber and subsequently condenses into nanoscale clusters during the nozzle expansion process. The clusters sublimate as they enter the hot boundary layer, and Rayleigh images capture the interface that exists between the regions of condensed (freestream) and sublimated (boundary layer) carbon dioxide. Boundary layers ranging from laminar to late-transitional in character are imaged using streamwise, spanwise, and planform laser sheet orientations. Characteristics of observed instabilities are quantified using pdf profiles, power spectrum analysis, and autocorrelation results derived from single-shot images. A new MHz-rate imaging system is also used to produce motion pictures images and volumetric reconstructions of the boundary layer. The pressure gradient and associated crossflow from the major axis to the minor axis of the cone causes increased growth and subsequent early transition of the centerline boundary layer. The convection velocity and temporal evolution of structures appearing on both the centerline and off-axis regions is studied using cross correlation procedures. Volumetric image sets of the centerline reveal hairpin structures characteristic of the early stages of subsonic turbulent spot formation. In the off-axis regions, planform single-shot images reveal a pattern of finger-like crests in the boundary layer. At higher Reynolds numbers the breakdown of these crests involves the formation of a series of chain-like structures. The behavior appears qualitatively similar to visualizations of crossflow vortex breakdown in

  12. Water coning in fractured basement reservoirs

    SciTech Connect

    Saad, S.E.D.M.; Darwich, T.D.; Asaad, Y.

    1995-11-01

    The problem of water coning in fractured basement reservoirs has been addressed in this work. The outcome of experimental and theoretical investigation to determine the critical production rate for single- and multi-fractured system, the capillary pressure effect, and the break-through time is presented. The results of the experimental work verify the presented theoretical relationship for different fluid viscosities, fracture angles, oil-water contacts (OWC), and rates for the case of single fracture system. The results also indicate that the capillary pressure effect may be generally neglected if the distance between the OWC and the fluid entry is sufficiently large compared to the capillary rise. The extension of the critical rate determination for a multi-fractured reservoir is also discussed. Finally, the main factors influencing the break-through time were investigated. The difference in viscosity between the oil and water phases has been fond to be the main factor affecting the breakthrough time.

  13. Nose-cone calorimeter: PHENIX forward upgrade

    NASA Astrophysics Data System (ADS)

    Chvala, Ondrej

    2009-07-01

    PHENIX is a high rate experiment efficient at measuring rare processes, but has limited acceptance in azimuth and pseudorapidity ( η). The Nose Cone Calorimeter (NCC), a W-Si sampling calorimeter in the region of 0.9< η<3, is one of the upgrades which will significantly increase coverage in both azimuth and pseudorapidity. The NCC will expand PHENIX’s precision measurements of electromagnetic probes in η, reconstruct jets, perform a wide scope of correlation measurements, and enhance triggering capabilities. The detector will significantly contribute to measurements of γ-jet correlations, quarkonia production, and low- x nuclear structure functions. This report discusses details of the detector design and its performance concerning a sample of the physics topics which will benefit from the NCC. In view of recent funding difficulties, outlook of the activities is discussed.

  14. Plasmonic corrugated cylinder-cone terahertz probe.

    PubMed

    Yao, Haizi; Zhong, Shuncong

    2014-08-01

    The spoof surface plasmon polariton (SPP) effect on the electromagnetic field distribution near the tip of a periodically corrugated metal cylinder-cone probe working at the terahertz regime was studied. We found that radially polarized terahertz radiation could be coupled effectively through a spoof SPP into a surface wave and propagated along the corrugated surface, resulting in more than 20× electric field enhancement near the tip of probe. Multiple resonances caused by the antenna effect were discussed in detail by finite element computation and theoretical analysis of dispersion relation for spoof SPP modes. Moreover, the key figures of merit such as the resonance frequency of the SPP can be flexibly tuned by modifying the geometry of the probe structure, making it attractive for application in an apertureless background-free terahertz near-field microscope. PMID:25121543

  15. Handling data redundancy in helical cone beam reconstruction with a cone-angle-based window function and its asymptotic approximation

    SciTech Connect

    Tang Xiangyang; Hsieh Jiang

    2007-06-15

    A cone-angle-based window function is defined in this manuscript for image reconstruction using helical cone beam filtered backprojection (CB-FBP) algorithms. Rather than defining the window boundaries in a two-dimensional detector acquiring projection data for computed tomographic imaging, the cone-angle-based window function deals with data redundancy by selecting rays with the smallest cone angle relative to the reconstruction plane. To be computationally efficient, an asymptotic approximation of the cone-angle-based window function is also given and analyzed in this paper. The benefit of using such an asymptotic approximation also includes the avoidance of functional discontinuities that cause artifacts in reconstructed tomographic images. The cone-angle-based window function and its asymptotic approximation provide a way, equivalent to the Tam-Danielsson-window, for helical CB-FBP reconstruction algorithms to deal with data redundancy, regardless of where the helical pitch is constant or dynamically variable during a scan. By taking the cone-parallel geometry as an example, a computer simulation study is conducted to evaluate the proposed window function and its asymptotic approximation for helical CB-FBP reconstruction algorithm to handle data redundancy. The computer simulated Forbild head and thorax phantoms are utilized in the performance evaluation, showing that the proposed cone-angle-based window function and its asymptotic approximation can deal with data redundancy very well in cone beam image reconstruction from projection data acquired along helical source trajectories. Moreover, a numerical study carried out in this paper reveals that the proposed cone-angle-based window function is actually equivalent to the Tam-Danielsson-window, and rigorous mathematical proofs are being investigated.

  16. Magma supply rates inferred from cinder cone volumes

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Borgia, A.; Neri, M.; Kervyn, M.

    2010-12-01

    Revisiting the question of how cinder cones grow suggests the possibility of inferring magma supply rates from cinder cones sizes. We start with a conceptual model of cinder cone growth: (1) Eruption volume flux increases rapidly and then decreases exponentially. (2) Cinder cones get steeper during the initiation of the eruption and then maintain a constant steepness. (3) The initial basal diameter varies with volume flux into the cone. Based on these constraints, we propose a general form for the relationship between cinder cone volume and magma supply rate: V = Q(exp(-t/b)/b - exp(-t/a)/a), where V is volume (in m3), Q is the maximum potential magma flux (in m3/s), t is time (in s), a is a damping factor (in s) controlling the decline in volume flux, and b is a factor controlling the initial increase in volume flux. Then we use the data available on the growth of cinder cones from four modern eruptions to show the relevance of our model and to constrain the supply curves. All four modern cones (Paricutin, Mexico which erupted 1943-1974; Tolbachik, Kamchatka which erupted in 1975-1976; Cono del Laghetto, Mount Etna, Italy which formed in 2001; and a small cone on the summit of Oldoinyo Lengai, Tanzania, which formed during the 2007 eruption) show the basic growth pattern: initial rapid growth followed by declining growth (Figure 1). The regression results yeild the following magma supply rates: The southern Tolbachik cones have the largest predicted magma supply at ~100 m3/s. Paricutin and Laghetto are around 9 m3/s. The Oldoinyo Lengai cone has a magma supply of ~0.5 m3/s. The northern Tolbachik cone has the lowest magma supply of ~0.1 m3/s. In contrast, the damping factor a is generally on the order of 107 (it varies from 8 x 106 at southern Tolbachik to 4 x 107 at northern Tolbachik). The parameter b controlling the initial increase is generally small (<1). The predicted magma supply does not seem to be very sensitive to either parameter. Thus we suggest that

  17. Cytoskeletal remodeling during growth cone-target interactions

    PubMed Central

    1993-01-01

    Reorganization of the cytoskeleton of neuronal growth cones in response to environmental cues underlies the process of axonal guidance. Most previous studies addressing cytoskeletal changes during growth cone pathfinding have focused on the dynamics of a single cytoskeletal component. We report here an investigation of homophilic growth cone- target interactions between Aplysia bag cell neurons using digitally enhanced video microscopy, which addresses dynamic interactions between actin filaments and microtubules. After physical contact of a growth cone with a physiological target, mechanical coupling occurred after a delay; and then the growth cone exerted forces on and displaced the target object. Subsequent to coupling, F-actin accumulation was observed at the target contact zone, followed by preferential microtubule extension to the same site. After successful target interactions, growth cones typically moved off highly adhesive poly-L- lysine substrates into native target cell surfaces. These events were associated with modulation of both the direction and rate of neurite outgrowth: growth cone migration was typically reoriented to a trajectory along the target interaction axis and rates of advance increased by about one order of magnitude. Directed microtubule movements toward the contact site appeared to be F-actin dependent as target site-specific microtubule extension and bundling could be reversibly randomized by micromolar levels of cytochalasin B in a characteristic manner. Our results suggest that target contacts can induce focal F-actin assembly and reorganization which, in turn, guides target site-directed microtubule redistribution. PMID:8509456

  18. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus).

    PubMed

    Wilby, David; Toomey, Matthew B; Olsson, Peter; Frederiksen, Rikard; Cornwall, M Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C; Roberts, Nicholas W

    2015-10-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones. PMID:26423439

  19. L and M cone proportions in polymorphic New World monkeys.

    PubMed

    Jacobs, Gerald H; Williams, Gary A

    2006-01-01

    Platyrrhine monkeys typically have only a single X-chromosome opsin gene. Alleles of this gene code for multiple versions of middle- to long-wavelength cone photopigments. X-chromosome inactivation provides heterozygous females with a retinal mosaic of cones containing either of two types of M and L pigment, thus establishing the photopigment basis for trichromatic color vision. This study examined the proportions of L and M cones created by this process. For that purpose, electroretinogram flicker photometry was used to obtain complete spectral sensitivity functions from 60 heterozygous female monkeys drawn from seven genera of platyrrhine monkeys. To obtain estimates of cone proportions, these functions were subsequently fit with linear combinations of L and M cone fundamentals that were derived from similar recordings made on conspecific animals having only one type of M/L pigment. Consistent with a random X-chromosome inactivation process, the average L:M cone weighting across the sample was close to unity. At the same time, there were significant individual variations in L:M cone proportions. The genesis of this variation and its implications for seeing are discussed. PMID:16961968

  20. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus).

    PubMed

    Wilby, David; Toomey, Matthew B; Olsson, Peter; Frederiksen, Rikard; Cornwall, M Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C; Roberts, Nicholas W

    2015-10-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones.

  1. Coupled local translation and degradation regulate growth cone collapse

    PubMed Central

    Deglincerti, Alessia; Colak, Dilek; Hengst, Ulrich; Liu, Yaobin; Xu, Guoqiang; Jaffrey, Samie R.

    2015-01-01

    Local translation mediates axonal responses to Semaphorin3A (Sema3A) and other guidance cues. However, only a subset of the axonal proteome is locally synthesized, while most proteins are trafficked from the soma. The reason why only specific proteins are locally synthesized is unknown. Here we show that local protein synthesis and degradation are linked events in growth cones. We find that growth cones exhibit high levels of ubiquitination and that local signaling pathways trigger the ubiquitination and degradation of RhoA, a mediator of Sema3A-induced growth cone collapse. Inhibition of RhoA degradation is sufficient to remove the protein-synthesis requirement for Sema3A-induced growth cone collapse. In addition to RhoA, we find that locally translated proteins are the main targets of the ubiquitin-proteasome system in growth cones. Thus, local protein degradation is a major feature of growth cones and creates a requirement for local translation to replenish proteins needed to maintain growth cone responses. PMID:25901863

  2. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus)

    PubMed Central

    Wilby, David; Toomey, Matthew B.; Olsson, Peter; Frederiksen, Rikard; Cornwall, M. Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C.; Roberts, Nicholas W.

    2015-01-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones. PMID:26423439

  3. Mouse rods signal through gap junctions with cones

    PubMed Central

    Asteriti, Sabrina; Gargini, Claudia; Cangiano, Lorenzo

    2014-01-01

    Rod and cone photoreceptors are coupled by gap junctions (GJs), relatively large channels able to mediate both electrical and molecular communication. Despite their critical location in our visual system and evidence that they are dynamically gated for dark/light adaptation, the full impact that rod–cone GJs can have on cone function is not known. We recorded the photovoltage of mouse cones and found that the initial level of rod input increased spontaneously after obtaining intracellular access. This process allowed us to explore the underlying coupling capacity to rods, revealing that fully coupled cones acquire a striking rod-like phenotype. Calcium, a candidate mediator of the coupling process, does not appear to be involved on the cone side of the junctional channels. Our findings show that the anatomical substrate is adequate for rod–cone coupling to play an important role in vision and, possibly, in biochemical signaling among photoreceptors. DOI: http://dx.doi.org/10.7554/eLife.01386.001 PMID:24399457

  4. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

    PubMed

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H; Rodgers, Karla K; Smith, Marci L; Wang, Jin-Shan; Pittler, Steven J; Kefalov, Vladimir J

    2016-04-15

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors.

  5. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

    PubMed

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H; Rodgers, Karla K; Smith, Marci L; Wang, Jin-Shan; Pittler, Steven J; Kefalov, Vladimir J

    2016-04-15

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors. PMID:26893377

  6. Comparison of Cone Model Parameters for Halo Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Na, Hyeonock; Moon, Y.-J.; Jang, Soojeong; Lee, Kyoung-Sun; Kim, Hae-Yeon

    2013-11-01

    Halo coronal mass ejections (HCMEs) are a major cause of geomagnetic storms, hence their three-dimensional structures are important for space weather. We compare three cone models: an elliptical-cone model, an ice-cream-cone model, and an asymmetric-cone model. These models allow us to determine three-dimensional parameters of HCMEs such as radial speed, angular width, and the angle [ γ] between sky plane and cone axis. We compare these parameters obtained from three models using 62 HCMEs observed by SOHO/LASCO from 2001 to 2002. Then we obtain the root-mean-square (RMS) error between the highest measured projection speeds and their calculated projection speeds from the cone models. As a result, we find that the radial speeds obtained from the models are well correlated with one another ( R > 0.8). The correlation coefficients between angular widths range from 0.1 to 0.48 and those between γ-values range from -0.08 to 0.47, which is much smaller than expected. The reason may be the different assumptions and methods. The RMS errors between the highest measured projection speeds and the highest estimated projection speeds of the elliptical-cone model, the ice-cream-cone model, and the asymmetric-cone model are 376 km s-1, 169 km s-1, and 152 km s-1. We obtain the correlation coefficients between the location from the models and the flare location ( R > 0.45). Finally, we discuss strengths and weaknesses of these models in terms of space-weather application.

  7. Directionality of individual cone photoreceptors in the parafoveal region.

    PubMed

    Morris, Hugh J; Blanco, Leonardo; Codona, Johanan L; Li, Simone L; Choi, Stacey S; Doble, Nathan

    2015-12-01

    The pointing direction of cone photoreceptors can be inferred from the Stiles-Crawford Effect of the First Kind (SCE-I) measurement. Healthy retinas have tightly packed cones with a SCE-I function peak either centered in the pupil or with a slight nasal bias. Various retinal pathologies can change the profile of the SCE-I function implying that the arrangement or the light capturing properties of the cone photoreceptors are affected. Measuring the SCE-I may reveal early signs of photoreceptor change before actual cell apoptosis occurs. In vivo retinal imaging with adaptive optics (AO) was used to measure the pointing direction of individual cones at eight retinal locations in four control human subjects. Retinal images were acquired by translating an aperture in the light delivery arm through 19 different locations across a subject's entrance pupil. Angular tuning properties of individual cones were calculated by fitting a Gaussian to the reflected intensity profile of each cone projected onto the pupil. Results were compared to those from an accepted psychophysical SCE-I measurement technique. The maximal difference in cone directionality of an ensemble of cones, ρ¯, between the major and minor axes of the Gaussian fit was 0.05 versus 0.29mm(-2) in one subject. All four subjects were found to have a mean nasal bias of 0.81mm with a standard deviation of ±0.30mm in the peak position at all retinal locations with mean ρ¯ value decreasing by 23% with increasing retinal eccentricity. Results show that cones in the parafoveal region converge towards the center of the pupillary aperture, confirming the anterior pointing alignment hypothesis. PMID:26494187

  8. Light-driven calcium signals in mouse cone photoreceptors.

    PubMed

    Wei, Tao; Schubert, Timm; Paquet-Durand, François; Tanimoto, Naoyuki; Chang, Le; Koeppen, Katja; Ott, Thomas; Griesbeck, Oliver; Seeliger, Mathias W; Euler, Thomas; Wissinger, Bernd

    2012-05-16

    Calcium mediates various neuronal functions. The complexity of neuronal Ca²⁺ signaling is well exemplified by retinal cone photoreceptors, which, with their distinct compartmentalization, offer unique possibilities for studying the diversity of Ca²⁺ functions in a single cell. Measuring subcellular Ca²⁺ signals in cones under physiological conditions is not only fundamental for understanding cone function, it also bears important insights into pathophysiological processes governing retinal neurodegeneration. However, due to the proximity of light-sensitive outer segments to other cellular compartments, optical measurements of light-evoked Ca²⁺ responses in cones are challenging. We addressed this problem by generating a transgenic mouse (HR2.1:TN-XL) in which both short- and middle-wavelength-sensitive cones selectively express the genetically encoded ratiometric Ca²⁺ biosensor TN-XL. We show that HR2.1:TN-XL allows recording of light-evoked Ca²⁺ responses using two-photon imaging in individual cone photoreceptor terminals and to probe phototransduction and its diverse regulatory mechanisms with pharmacology at subcellular resolution. To further test this system, we asked whether the classical, nitric oxide (NO)-soluble guanylyl-cyclase (sGC)-cGMP pathway could modulate Ca²⁺ in cone terminals. Surprisingly, NO reduced Ca²⁺ resting levels in mouse cones, without evidence for direct sGC involvement. In conclusion, HR2.1:TN-XL mice offer unprecedented opportunities to elucidate light-driven Ca²⁺ dynamics and their (dys)regulation in cone photoreceptors.

  9. Oscillatory flow in a cone-and-plate bioreactor.

    PubMed

    Chung, C A; Tzou, M R; Ho, R W

    2005-08-01

    Motivated by biometric applications, we analyze oscillatory flow in a cone-and-plate geometry. The cone is rotated in a simple harmonic way on a stationary plate. Based on assuming that the angle between the cone and plate is small, we describe the flow analytically by a perturbation method in terms of two small parameters, the Womersley number and the Reynolds number, which account for the influences of the local acceleration and centripetal force, respectively. Working equations for the shear stresses induced both by laminar primary and secondary flows on the plate surface are presented. PMID:16121530

  10. Pulsar average wave forms and hollow-cone beam models

    NASA Technical Reports Server (NTRS)

    Backer, D. C.

    1976-01-01

    Pulsar wave forms have been analyzed from observations conducted over a wide radio-frequency range to assess the wave-form morphologies and to measure wave-form widths. The results of the analysis compare favorably with the predictions of a model with a hollow-cone beam of fixed dimensions and with random orientation of both the observer and the cone axis with respect to the pulsar spin axis. A class of three-component wave forms is included in the model by adding a central pencil beam to the hollow-cone hypothesis. The consequences of a number of discrepancies between observations and quantitative predictions of the model are discussed.

  11. Shock tunnel measurements of hypervelocity blunted cone drag

    SciTech Connect

    Porter, L.M.; Paull, A.; Mee, D.J.; Simmons, J.M.

    1994-12-01

    Presented here are results obtained from an investigation into the effects of nose bluntness on slender cone drag in the hypervelocity flight regime. The results indicate that, for small cone angles, the drag of a blunt cone is reasonably well predicted by the Newtonian sine-square law modified for blunt bodies. This suggests the absence of any real gas effects on the total drag. The effect of nose bluntness at the smaller bluntness ratios is relatively small. This is encouraging for the design of a hypervelocity space plane or a centerbody for an axisymmetric scramjet where a slightly blunted nose is required to reduce stagnation point heating. 7 refs.

  12. The multifocal visual evoked potential and cone-isolating stimuli: implications for L- to M-cone ratios and normalization.

    PubMed

    Hood, Donald C; Yu, Alice L; Zhang, Xian; Albrecht, Johannes; Jägle, Herbert; Sharpe, Lindsay T

    2002-01-01

    Multifocal visual evoked potentials (mfVEP) were recorded with a pattern-reversing display that modulated only the long wavelength-sensitive (L) cones or only the middle wavelength-sensitive (M) cones. Outside the central 5.8 degrees (radius), the ratio of the amplitudes of the mfVEP responses to L- and M-cone modulation varied across the six subjects, ranging from 1.1 to 1.7. The responses from the central 1 degrees (radius) showed a substantially lower ratio, ranging from 0.8 to 1.1 (average of 0.9). The variation among individuals outside the central fovea is probably due to differences in the ratio of the L/M cone input to both magno- and parvocellular pathways. The substantially lower ratios for the central responses is consistent with an L/M cone ratio closer to 1.0 in the central 1 degrees and/or an adjustment in the gain of the L- versus M-cone contributions to the central parvocellular pathways. Taking into consideration evidence from other techniques, we believe it is unlikely that most individuals have a L/M cone ratio of 1.0 in the fovea. Instead, it appears that there is a change in gain before the mfVEP is generated in area 17.

  13. Shape measurement and vibration analysis of moving speaker cone

    NASA Astrophysics Data System (ADS)

    Zhang, Qican; Liu, Yuankun; Lehtonen, Petri

    2014-06-01

    Surface three-dimensional (3-D) shape information is needed for many fast processes such as structural testing of material, standing waves on loudspeaker cone, etc. Usually measurement is done from limited number of points using electrical sensors or laser distance meters. Fourier Transform Profilometry (FTP) enables fast shape measurement of the whole surface. Method is based on angled sinusoidal fringe pattern projection and image capturing. FTP requires only one image of the deformed fringe pattern to restore the 3-D shape of the measured object, which makes real-time or dynamic data processing possible. In our experiment the method was used for loudspeaker cone distortion measurement in dynamic conditions. For sound quality issues it is important that the whole cone moves in same phase and there are no partial waves. Our imaging resolution was 1280x1024 pixels and frame rate was 200 fps. Using our setup we found unwanted spatial waves in our sample cone.

  14. Conifer ovulate cones accumulate pollen principally by simple impaction

    PubMed Central

    Cresswell, James E.; Henning, Kevin; Pennel, Christophe; Lahoubi, Mohamed; Patrick, Michael A.; Young, Phillipe G.; Tabor, Gavin R.

    2007-01-01

    In many pine species (Family Pinaceae), ovulate cones structurally resemble a turbine, which has been widely interpreted as an adaptation for improving pollination by producing complex aerodynamic effects. We tested the turbine interpretation by quantifying patterns of pollen accumulation on ovulate cones in a wind tunnel and by using simulation models based on computational fluid dynamics. We used computer-aided design and computed tomography to create computational fluid dynamics model cones. We studied three species: Pinus radiata, Pinus sylvestris, and Cedrus libani. Irrespective of the approach or species studied, we found no evidence that turbine-like aerodynamics made a significant contribution to pollen accumulation, which instead occurred primarily by simple impaction. Consequently, we suggest alternative adaptive interpretations for the structure of ovulate cones. PMID:17986613

  15. 26. LONE CONE AND OLD ROAD GRADE TO LEFT SEEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    26. LONE CONE AND OLD ROAD GRADE TO LEFT SEEN FROM PARKING LOT ADJACENT TO LAUNDROMAT AT MOREFIELD CAMPGROUND STORE, FACING NW. - Mesa Verde National Park Main Entrance Road, Cortez, Montezuma County, CO

  16. On the dynamics of a particle on a cone

    SciTech Connect

    Kowalski, K. Rembielinski, J.

    2013-02-15

    A detailed study of the classical and quantum mechanics of a free particle on a double cone and a particle bound to its tip by a harmonic oscillator potential is presented. - Highlights: Black-Right-Pointing-Pointer We study the classical and quantum free particle and harmonic oscillator on a double cone. Black-Right-Pointing-Pointer We analyze the solutions of classical equations and show that the motion in a generator is unstable. Black-Right-Pointing-Pointer We identify the observables and Hilbert space for the quantum particle on a double cone. Black-Right-Pointing-Pointer The case of the quantization on the double cone is compared with a single-nappe case. Black-Right-Pointing-Pointer We solve the Schroedinger equations and discuss them in the context of the classical instabilities.

  17. Identification of cone mechanisms in monkey ganglion cells

    PubMed Central

    Gouras, Peter

    1968-01-01

    1. Blue, green, and red sensitive cone mechanisms have been studied in two types of on-centre ganglion cells in the Rhesus monkey's retina. 2. One type of cell receives signals from both green and red sensitive cone mechanisms, both of which excite in the centre and inhibit in the periphery of the cell's receptive field. These cells discharge transiently to maintained stimuli of any wave-length and are called phasic. 3. The second type of cell receives excitatory signals from only one cone mechanism, either blue, green or red sensitive, in the centre, and inhibition from another cone mechanism in the periphery of its receptive field. These cells discharge continuously to maintained stimuli of appropriate wave-length and are called tonic. 4. Tonic cells outnumber phasic cells although both are found adjacent to one another throughout the retina. Phasic cells are relatively more common toward the periphery and tonic cells relatively more common toward the fovea. PMID:4974745

  18. Testing the reliability of ice-cream cone model

    NASA Astrophysics Data System (ADS)

    Pan, Zonghao; Shen, Chenglong; Wang, Chuanbing; Liu, Kai; Xue, Xianghui; Wang, Yuming; Wang, Shui

    2015-04-01

    Coronal Mass Ejections (CME)'s properties are important to not only the physical scene itself but space-weather prediction. Several models (such as cone model, GCS model, and so on) have been raised to get rid of the projection effects within the properties observed by spacecraft. According to SOHO/ LASCO observations, we obtain the 'real' 3D parameters of all the FFHCMEs (front-side full halo Coronal Mass Ejections) within the 24th solar cycle till July 2012, by the ice-cream cone model. Considering that the method to obtain 3D parameters from the CME observations by multi-satellite and multi-angle has higher accuracy, we use the GCS model to obtain the real propagation parameters of these CMEs in 3D space and compare the results with which by ice-cream cone model. Then we could discuss the reliability of the ice-cream cone model.

  19. 128. Moses H. Cone Memorial Park. View of the stone ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    128. Moses H. Cone Memorial Park. View of the stone faced bridge on the bass lake carriage trail. Facing west. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  20. 127. Moses H. Cone Memorial Park. View of the flat ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    127. Moses H. Cone Memorial Park. View of the flat top manor from the bass lake carriage road. Looking north-northwest. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  1. Ideal illuminants for rod/L-cone color

    NASA Astrophysics Data System (ADS)

    McCann, John J.

    2006-01-01

    Humans see multicolor complex images with illuminants that have very low amounts of 400 to 580nm light when there is enough long-wave light greater than 590nm. Interactions between rods and long-wave (L) cones generate these colors. They are observed when there is insufficient light for a threshold response from M- and S-cones. This paper measures the spectral emission of a wood fire and a wax candle and it compares these low-color temperature spectral radiant exitances with the sensitivities of rods and long-wave cones. The paper reviews some of the literature on the evolution of human cone pigments and the early use of fire by hominids.

  2. Supersonic flow around circular cones at angles of attack

    NASA Technical Reports Server (NTRS)

    Ferri, Antonio

    1951-01-01

    The properties of conical flow without axial symmetry are analyzed. The flow around cones of circular cross section at small angles of attack is determined by correctly considering the effect of the entropy gradients in the flow.

  3. Further observations on resonance cones in non-Maxwellian plasmas

    NASA Technical Reports Server (NTRS)

    Thiemann, H.; Singh, N.

    1983-01-01

    Results on the angular distribution of the electrostatic potential of a pulsating point charge in a warm magnetized plasma permeated by an electron beam are presented. The theoretical formulation for a finite magnetic field is given, and the solution of the resonance cone dispersion relation is presented. Numerical results on the angular distribution of the potential are shown, and the propagation of waves outside the resonance cones is described. It is demonstrated that with the inclusions of a finite magnetic field, the field patterns of a point charge are qualitatively similar to those obtained for a uniaxial plasma. The Cerenkov radiation occurs at angles much smaller than the cold-cone angle, even with the finite magnetic field. When the beam velocity is well above the thermal velocity of the background electrons, a characteristic wave propagation occurs between the cold-cone angles.

  4. Microhabitats within venomous cone snails contain diverse actinobacteria.

    PubMed

    Peraud, Olivier; Biggs, Jason S; Hughen, Ronald W; Light, Alan R; Concepcion, Gisela P; Olivera, Baldomero M; Schmidt, Eric W

    2009-11-01

    Actinomycetes can be symbionts in diverse organisms, including both plants and animals. Some actinomycetes benefit their host by producing small molecule secondary metabolites; the resulting symbioses are often developmentally complex. Actinomycetes associated with three cone snails were studied. Cone snails are venomous tropical marine gastropods which have been extensively examined because of their production of peptide-based neurological toxins, but no microbiological studies have been reported on these organisms. A microhabitat approach was used in which dissected tissue from each snail was treated as an individual sample in order to explore bacteria in the tissues separately. Our results revealed a diverse, novel, and highly culturable cone snail-associated actinomycete community, with some isolates showing promising bioactivity in a neurological assay. This suggests that cone snails may represent an underexplored reservoir of novel actinomycetes of potential interest for drug discovery.

  5. The mitochondrial genome of the venomous cone snail Conus consors.

    PubMed

    Brauer, Age; Kurz, Alexander; Stockwell, Tim; Baden-Tillson, Holly; Heidler, Juliana; Wittig, Ilka; Kauferstein, Silke; Mebs, Dietrich; Stöcklin, Reto; Remm, Maido

    2012-01-01

    Cone snails are venomous predatory marine neogastropods that belong to the species-rich superfamily of the Conoidea. So far, the mitochondrial genomes of two cone snail species (Conus textile and Conus borgesi) have been described, and these feed on snails and worms, respectively. Here, we report the mitochondrial genome sequence of the fish-hunting cone snail Conus consors and describe a novel putative control region (CR) which seems to be absent in the mitochondrial DNA (mtDNA) of other cone snail species. This possible CR spans about 700 base pairs (bp) and is located between the genes encoding the transfer RNA for phenylalanine (tRNA-Phe, trnF) and cytochrome c oxidase subunit III (cox3). The novel putative CR contains several sequence motifs that suggest a role in mitochondrial replication and transcription.

  6. Estimating individual cone fundamentals from their color-matching functions.

    PubMed

    Andersen, Casper F; Finlayson, Graham D; Connah, David

    2016-08-01

    Estimation of individual spectral cone fundamentals from color-matching functions is a classical and longstanding problem in color science. In this paper we propose a novel method to carry out this estimation based on a linear optimization technique, employing an assumption of a priori knowledge of the retinal absorptance functions. The result is an estimation of the combined lenticular and macular filtration for an individual, along with the nine coefficients in the linear combination that relates their color-matching functions to their estimated spectral-cone fundamentals. We test the method on the individual Stiles and Burch color-matching functions and derive cone-fundamental estimations for different viewing fields and matching experiment repetition. We obtain cone-fundamental estimations that are remarkably similar to those available in the literature. This suggests that the method yields results that are close to the true fundamentals.

  7. 124. Moses H. Cone Memorial Park. View of the flat ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    124. Moses H. Cone Memorial Park. View of the flat top manor porch, carriage road, and pasture. View looking south-southwest. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  8. The Mitochondrial Genome of the Venomous Cone Snail Conus consors

    PubMed Central

    Brauer, Age; Kurz, Alexander; Stockwell, Tim; Baden-Tillson, Holly; Heidler, Juliana; Wittig, Ilka; Kauferstein, Silke; Mebs, Dietrich; Stöcklin, Reto; Remm, Maido

    2012-01-01

    Cone snails are venomous predatory marine neogastropods that belong to the species-rich superfamily of the Conoidea. So far, the mitochondrial genomes of two cone snail species (Conus textile and Conus borgesi) have been described, and these feed on snails and worms, respectively. Here, we report the mitochondrial genome sequence of the fish-hunting cone snail Conus consors and describe a novel putative control region (CR) which seems to be absent in the mitochondrial DNA (mtDNA) of other cone snail species. This possible CR spans about 700 base pairs (bp) and is located between the genes encoding the transfer RNA for phenylalanine (tRNA-Phe, trnF) and cytochrome c oxidase subunit III (cox3). The novel putative CR contains several sequence motifs that suggest a role in mitochondrial replication and transcription. PMID:23236512

  9. Cone monochromacy and visual pigment spectral tuning in wobbegong sharks.

    PubMed

    Theiss, Susan M; Davies, Wayne I L; Collin, Shaun P; Hunt, David M; Hart, Nathan S

    2012-12-23

    Much is known regarding the evolution of colour vision in nearly every vertebrate class, with the notable exception of the elasmobranchs. While multiple spectrally distinct cone types are found in some rays, sharks appear to possess only a single class of cone and, therefore, may be colour blind. In this study, the visual opsin genes of two wobbegong species, Orectolobus maculatus and Orectolobus ornatus, were isolated to verify the molecular basis of their monochromacy. In both species, only two opsin genes are present, RH1 (rod) and LWS (cone), which provide further evidence to support the concept that sharks possess only a single cone type. Examination of the coding sequences revealed substitutions that account for interspecific variation in the photopigment absorbance spectra, which may reflect the difference in visual ecology between these species.

  10. On the nonstationary Stokes system in a cone

    NASA Astrophysics Data System (ADS)

    Kozlov, Vladimir; Rossmann, Jürgen

    2016-06-01

    The authors consider the Dirichlet problem for the nonstationary Stokes system in a threedimensional cone. They obtain existence and uniqueness results for solutions in weighted Sobolev spaces and prove a regularity assertion for the solutions.

  11. Aberrant lacrimal gland and pleomorphic adenoma within the muscle cone.

    PubMed

    Mueller, E C; Borit, A

    1979-04-01

    Aberrant lacrimal gland tissue within the muscle cone formed a pleomorphic adenoma (benign mixed tumor). Histopathologically, the lesion was identical to similar neoplasms originating from lacrimal and other salivary glands as well as from other serous glands of the body.

  12. Dimensional regularization and dimensional reduction in the light cone

    SciTech Connect

    Qiu, J.

    2008-06-15

    We calculate all of the 2 to 2 scattering process in Yang-Mills theory in the light cone gauge, with the dimensional regulator as the UV regulator. The IR is regulated with a cutoff in q{sup +}. It supplements our earlier work, where a Lorentz noncovariant regulator was used, and the final results bear some problems in gauge fixing. Supersymmetry relations among various amplitudes are checked by using the light cone superfields.

  13. Cones perform a non-linear transformation on natural stimuli

    PubMed Central

    Endeman, D; Kamermans, M

    2010-01-01

    Visual information in natural scenes is distributed over a broad range of intensities and contrasts. This distribution has to be compressed in the retina to match the dynamic range of retinal neurons. In this study we examined how cones perform this compression and investigated which physiological processes contribute to this operation. M- and L-cones of the goldfish were stimulated with a natural time series of intensities (NTSI) and their responses were recorded. The NTSI displays an intensity distribution which is skewed towards the lower intensities and has a long tail into the high intensity region. Cones transform this skewed distribution into a more symmetrical one. The voltage responses of the goldfish cones were compared to those of a linear filter and a non-linear biophysical model of the photoreceptor. The results show that the linear filter under-represents contrasts at low intensities compared to the actual cone whereas the non-linear biophysical model performs well over the whole intensity range used. Quantitative analysis of the two approaches indicates that the non-linear biophysical model can capture 91 ± 5% of the coherence rate (a biased measure of information rate) of the actual cone, where the linear filter only reaches 48 ± 8%. These results demonstrate that cone photoreceptors transform an NTSI in a non-linear fashion. The comparison between current clamp and voltage clamp recordings and analysis of the behaviour of the biophysical model indicates that both the calcium feedback loop in the outer segment and the hydrolysis of cGMP are the major components that introduce the specific non-linear response properties found in the goldfish cones. PMID:20008463

  14. Elliptic Cones Alone and with Wings at Supersonic Speed

    NASA Technical Reports Server (NTRS)

    Jorgensen, Leland H

    1958-01-01

    To help fill the gap in the knowledge of aerodynamics of shapes intermediate between bodies of revolution and flat triangular wings, force and moment characteristics for elliptic cones have been experimentally determined for Mach numbers of 1.97 and 2.94. Elliptic cones having cross-sectional axis ratios from 1 through 6 and with lengths and base areas equal to circular cones of fineness ratios 3.67 and 5 have been studied for angles of bank of 0 degree and 90 degrees. Elliptic and circular cones in combination with triangular wings of aspect ratios 1 and 1.5 also have been considered. The angle-of-attack range was from 0 degree to about 16 degrees, and the Reynolds number was 8 x 10(6), based on model length. In addition to the forces and moments at angle of attack, pressure distributions for elliptic cones at zero angle of attack have been determined. The results of this investigation indicate that there are distinct aerodynamic advantages to the use of elliptic cones.

  15. Numerical Modeling of Shatter Cones Development in Impact Craters

    NASA Technical Reports Server (NTRS)

    Baratoux, D.; Melosh, H. J.

    2003-01-01

    Shatter cones are the characteristic forms of rock fractures in impact structures. They have been used for decades as unequivocal fingerprints of meteoritic impacts on Earth. The abundant data about shapes, apical angles, sizes and distributions of shatter cones for many terrestrial impact structures should provide insights for the determination of impact conditions and characteristics of shock waves produced by high-velocity projectiles in geologic media. However, previously proposed models for the formation of shatter cones do not agree with observations. For example, the widely accepted Johnson-Talbot mechanism requires that the longitudinal stress drops to zero between the arrival of the elastic precursor and the main plastic wave. Unfortunately, observations do not support such a drop. A model has been also proposed to explain the striated features on the surface of shatter cones but can not invoked for their conical shape. The mechanism by which shatter cones form thus remains enigmatic to date. In this paper we present a new model for the formation of shatter cones. Our model has been tested by means of numerical simulations using the hydrocodes SALE 2D enhanced with the Grady-Kipp-Melosh fragmentation model.

  16. Organizational motifs for ground squirrel cone bipolar cells.

    PubMed

    Light, Adam C; Zhu, Yongling; Shi, Jun; Saszik, Shannon; Lindstrom, Sarah; Davidson, Laura; Li, Xiaoyu; Chiodo, Vince A; Hauswirth, William W; Li, Wei; DeVries, Steven H

    2012-09-01

    In daylight vision, parallel processing starts at the cone synapse. Cone signals flow to On and Off bipolar cells, which are further divided into types according to morphology, immunocytochemistry, and function. The axons of the bipolar cell types stratify at different levels in the inner plexiform layer (IPL) and can interact with costratifying amacrine and ganglion cells. These interactions endow the ganglion cell types with unique functional properties. The wiring that underlies the interactions among bipolar, amacrine, and ganglion cells is poorly understood. It may be easier to elucidate this wiring if organizational rules can be established. We identify 13 types of cone bipolar cells in the ground squirrel, 11 of which contact contiguous cones, with the possible exception of short-wavelength-sensitive cones. Cells were identified by antibody labeling, tracer filling, and Golgi-like filling following transduction with an adeno-associated virus encoding for green fluorescent protein. The 11 bipolar cell types displayed two organizational patterns. In the first pattern, eight to 10 of the 11 types came in pairs with partially overlapping axonal stratification. Pairs shared morphological, immunocytochemical, and functional properties. The existence of similar pairs is a new motif that might have implications for how signals first diverge from a cone to bipolar cells and then reconverge onto a costratifying ganglion cell. The second pattern is a mirror symmetric organization about the middle of the IPL involving at least seven bipolar cell types. This anatomical symmetry may be associated with a functional symmetry in On and Off ganglion cell responses.

  17. LSP Calculations of Cone-Wire Experiments

    SciTech Connect

    Town, R J; Cottrill, L A; Key, M H; Kruer, W L; Langdon, A B; Lasinski, B F; McCandless, B C; Myatt, J F; Park, H S; Remington, B A; Snavely, R A; Still, C H; Tabak, M; Welch, D R; Wilks, S C

    2005-06-13

    Recent experiments at the Institute of Laser Engineering (ILE) in Japan [1] and at Rutherford Appleton Laboratory (RAL) in the United Kingdom [2] have shown good coupling of short-pulse high-intensity laser light into high-energy electrons channeled down a narrow fiber. Such target configurations are being considered as backlighter targets on the National Ignition Facility (NIF). We will report on LSP calculations of these cone-wire experiments and other candidate target configurations. These calculations also give insight into the transport of MeV-electrons, which remains the critical issue for the achievement of fast ignition [3]. The LSP code uses a direct implicit particle-in-cell (PIC) algorithm in 2 or 3 dimensions to solve for beam particle transport, while treating the background particles as a fluid [4]. We have modified LSP to produce K{alpha} photons in a non-interfering manner and will show calculated absolute K{alpha} yields for the experiments reported by Key [2].

  18. Giant scattering cones in obscured quasars

    NASA Astrophysics Data System (ADS)

    Obied, Georges; Zakamska, Nadia L.; Wylezalek, Dominika; Liu, Guilin

    2016-03-01

    We analyse Hubble Space Telescope observations of scattering regions in 20 luminous obscured quasars at 0.24 < z < 0.65 (11 new observations and nine archival ones) observed at rest frame ˜3000 Å. We find spectacular 5-10 kpc-scale scattering regions in almost all cases. The median scattering efficiency at this wavelength (the ratio of observed to estimated intrinsic flux) is 2.3, and 73 per cent of the observed flux at this wavelength is due to scattered light, which if unaccounted for may strongly bias estimates of quasar hosts' star formation rates. Modelling these regions as illuminated dusty cones, we estimate the radial density distributions of the interstellar medium as well as the geometric properties of circumnuclear quasar obscuration - inclinations and covering factors. Small derived opening angles (median half-angle and standard deviation 27° ± 9°) are inconsistent with a 1:1 type 1/type 2 ratio. We suggest that quasar obscuration is patchy and that the observer has an ˜40 per cent chance of seeing a type 1 source even through the obscuration. We estimate median density profile of the scattering medium to be nH = 0.04-0.5 (1 kpc/r)2 cm-3, depending on the method. Quasars in our sample likely exhibit galaxy-wide winds, but if these consist of optically thick clouds then only a small fraction of the wind mass ( ≲ 10 per cent) contributes to scattering.

  19. Manipulation of Dirac Cones in Mechanical Graphene.

    PubMed

    Kariyado, Toshikaze; Hatsugai, Yasuhiro

    2015-01-01

    Recently, quantum Hall state analogs in classical mechanics attract much attention from topological points of view. Topology is not only for mathematicians but also quite useful in a quantum world. Further it even governs the Newton's law of motion. One of the advantages of classical systems over solid state materials is its clear controllability. Here we investigate mechanical graphene, which is a spring-mass model with the honeycomb structure as a typical mechanical model with nontrivial topological phenomena. The vibration spectrum of mechanical graphene is characterized by Dirac cones serving as sources of topological nontriviality. We find that the spectrum has dramatic dependence on the spring tension at equilibrium as a natural control parameter, i.e., creation and annihilation of the Dirac particles are realized as the tension increases. Just by rotating the system, the manipulated Dirac particles lead to topological transition, i.e., a jump of the "Chern number" occurs associated with flipping of propagating direction of chiral edge modes. This is a bulk-edge correspondence governed by the Newton's law. A simple observation that in-gap edge modes exist only at the fixed boundary, but not at the free one, is attributed to the symmetry protection of topological phases. PMID:26667580

  20. Manipulation of Dirac Cones in Mechanical Graphene

    NASA Astrophysics Data System (ADS)

    Kariyado, Toshikaze; Hatsugai, Yasuhiro

    2015-12-01

    Recently, quantum Hall state analogs in classical mechanics attract much attention from topological points of view. Topology is not only for mathematicians but also quite useful in a quantum world. Further it even governs the Newton’s law of motion. One of the advantages of classical systems over solid state materials is its clear controllability. Here we investigate mechanical graphene, which is a spring-mass model with the honeycomb structure as a typical mechanical model with nontrivial topological phenomena. The vibration spectrum of mechanical graphene is characterized by Dirac cones serving as sources of topological nontriviality. We find that the spectrum has dramatic dependence on the spring tension at equilibrium as a natural control parameter, i.e., creation and annihilation of the Dirac particles are realized as the tension increases. Just by rotating the system, the manipulated Dirac particles lead to topological transition, i.e., a jump of the “Chern number” occurs associated with flipping of propagating direction of chiral edge modes. This is a bulk-edge correspondence governed by the Newton’s law. A simple observation that in-gap edge modes exist only at the fixed boundary, but not at the free one, is attributed to the symmetry protection of topological phases.

  1. Manipulation of Dirac Cones in Mechanical Graphene

    PubMed Central

    Kariyado, Toshikaze; Hatsugai, Yasuhiro

    2015-01-01

    Recently, quantum Hall state analogs in classical mechanics attract much attention from topological points of view. Topology is not only for mathematicians but also quite useful in a quantum world. Further it even governs the Newton’s law of motion. One of the advantages of classical systems over solid state materials is its clear controllability. Here we investigate mechanical graphene, which is a spring-mass model with the honeycomb structure as a typical mechanical model with nontrivial topological phenomena. The vibration spectrum of mechanical graphene is characterized by Dirac cones serving as sources of topological nontriviality. We find that the spectrum has dramatic dependence on the spring tension at equilibrium as a natural control parameter, i.e., creation and annihilation of the Dirac particles are realized as the tension increases. Just by rotating the system, the manipulated Dirac particles lead to topological transition, i.e., a jump of the “Chern number” occurs associated with flipping of propagating direction of chiral edge modes. This is a bulk-edge correspondence governed by the Newton’s law. A simple observation that in-gap edge modes exist only at the fixed boundary, but not at the free one, is attributed to the symmetry protection of topological phases. PMID:26667580

  2. Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

    SciTech Connect

    G. Valentine; D.J. Krier; F.V. Perry; G. Heiken

    2006-08-03

    The {approx}80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching {approx}800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to {approx}20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km{sup 3}, scoria cone--0.02 km{sup 3}, and lavas--0.03 km{sup 3}. Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of {approx}21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of

  3. Theseus Nose and Pod Cones Being Unloaded

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Crew members are seen here unloading the nose and pod cones of the Theseus prototype research aircraft at NASA's Dryden Flight Research Center, Edwards, California, in May of 1996. The Theseus aircraft, built and operated by Aurora Flight Sciences Corporation, Manassas, Virginia, was a unique aircraft flown at NASA's Dryden Flight Research Center, Edwards, California, under a cooperative agreement between NASA and Aurora. Dryden hosted the Theseus program, providing hangar space and range safety for flight testing. Aurora Flight Sciences was responsible for the actual flight testing, vehicle flight safety, and operation of the aircraft. The Theseus remotely piloted aircraft flew its maiden flight on May 24, 1996, at Dryden. During its sixth flight on November 12, 1996, Theseus experienced an in-flight structural failure that resulted in the loss of the aircraft. As of the beginning of the year 2000, Aurora had not rebuilt the aircraft. Theseus was built for NASA under an innovative, $4.9 million fixed-price contract by Aurora Flight Sciences Corporation and its partners, West Virginia University, Morgantown, West Virginia, and Fairmont State College, Fairmont, West Virginia. The twin-engine, unpiloted vehicle had a 140-foot wingspan, and was constructed largely of composite materials. Powered by two 80-horsepower, turbocharged piston engines that drove twin 9-foot-diameter propellers, Theseus was designed to fly autonomously at high altitudes, with takeoff and landing under the active control of a ground-based pilot in a ground control station 'cockpit.' With the potential ability to carry 700 pounds of science instruments to altitudes above 60,000 feet for durations of greater than 24 hours, Theseus was intended to support research in areas such as stratospheric ozone depletion and the atmospheric effects of future high-speed civil transport aircraft engines. Instruments carried aboard Theseus also would be able to validate satellite-based global environmental

  4. Towards cone-beam CT thermometry

    NASA Astrophysics Data System (ADS)

    Li, Ming; Abi-Jaoudeh, Nadine; Kapoor, Ankur; Kadoury, Samuel; Xu, Sheng; Noordhoek, Niels; Radaelli, Alessandro; Carelsen, Bart; Wood, Bradford J.

    2013-03-01

    Temperature monitoring and therefore the final treatment zone achieved during a cone-beam CT (CBCT) guided ablation can prevent overtreatment and undertreatment. A novel method is proposed to detect changes in consecutive CBCT images obtained from projection reconstructions during an ablation procedure. The possibility is explored of using this method to generate thermometry maps from CBCT images, which can be used as an input function for ablation treatment planning. This novel method uses a baseline and an intermittent CBCT scan, which are routinely acquired to confirm the needle position and monitor progress of the ablation. Accurate registration is required and assumed in vitro and ex vivo. A Wronskian change detector algorithm is applied on the compensated images to obtain a difference image between the intermittent and baseline scans. Finally, a thermal map created by applying a calibration determined experimentally is used to obtain the corresponding temperature at each pixel or voxel. We applied Wronskian change detector to detect the difference of two CBCT images, which have low signal to noise ratio, and calibrate Wronskian change model to temperature data using a gel phantom. We tested the temperature mapping with water and gel phantoms as well as pig shoulder. The experimental results show this method can detect temperature change within 5°C for a voxel size of 1mm3 (within clinical relevancy), and by consequence delineate the ablation zone. The preliminary experimental results show that CBCT thermometry is possible and promising, but may require pre-processing, such as registration for motion compensation between the baseline and intermittent scans. Further, quantitative evaluations have to be conducted for validation prior to clinical assessment and translation. CBCT is a widely available technology that could make thermometry clinically practical as an enabling component of iterative ablation treatment planning.

  5. Double Cones as a Basis for Polarization Sensitivity in Vertebrates

    NASA Astrophysics Data System (ADS)

    Rowe, Manoel

    1995-01-01

    Over the course of the past 50 years there has been an increasing number of claims that certain vertebrates are sensitive to the linear polarization state of visible radiation. However, the mechanism(s) that mediates this polarization sensitivity remains elusive at the present time. The retinas of most vertebrates contain anatomical structures loosely referred to as double cones--composite entities constituted by the apposition of two independently developed, diurnally active photoreceptors. The significance of this apposition for visual function also remains elusive. It is possible that double cones mediate polarization sensitivity as a consequence of geometric birefringence; light polarized parallel to the axis joining the centers of the two halves of a double cone can potentially stimulate the receptors more strongly than light polarized in the direction perpendicular to both that axis and the normal axis of light propagation down the length of the double cone. The feasibility of this mechanism for polarization sensitivity has been examined here with specific reference to the retina of a representative animal, the green sunfish (Lepomis cyanellus). Transmission electron micrographs of thin sections from a sunfish retina were analyzed in order to develop simple models of waveguiding down the long axis of a sunfish double cone. The results of the computations indicate that the mechanism is feasible only if there are refractive index gradients in the photoreceptors of sunfish. Isolated receptors were thus examined with scanning microinterferometry to demonstrate the presence of such gradients. In the course of the investigation, the literature pertaining to vertebrate polarization sensitivity and retinal anatomy were reviewed to delimit the generality of the conclusions drawn from sunfish photoreceptors. As a result of this analysis, it should be concluded that much future research is needed to clarify what (if any) role optical polarization plays in the sensory

  6. Detailed topographical, distributional, and material analyses of rootless cones in Myvatn, Iceland

    NASA Astrophysics Data System (ADS)

    Noguchi, Rina; Höskuldsson, Ármann; Kurita, Kei

    2016-05-01

    Unique types of rootless cones have been found both on Earth and on Mars. They have inner cones inside their summit craters, and we call them double cones (DCs) and multiple cones. Though previous studies have mentioned their existence, there are no quantitative data on their topography, distribution, or constituent materials. Having this information available as a comparative reference could promote our understanding of Martian cones. For this study, we conducted a field campaign on terrestrial cones in Myvatn, Iceland. To provide high-quality reference data about the morphology of rootless cones, we performed kinematic Global Positioning System (GPS) measurements. In the study area DCs and multiple cones are located in the vicinity of the lake (Lake Myvatn) within 15 km of a fissure vent. There are no such cones on the paleo-riverbed. In crosscut outcrops of DCs on Geitey Island, a clearly recognizable structural boundary between the inner and outer cones shows that the inner cone was formed by a separate explosion episode. We propose a probable formation scenario for DCs here. We posit that the inner cones of DCs are formed by delayed explosions due to percolation of water through the lacustrine sediments. These unique characteristics of rootless cones are useful in the interpretation of Martian cones.

  7. Comparison of cone beam artifacts reduction: two pass algorithm vs TV-based CS algorithm

    NASA Astrophysics Data System (ADS)

    Choi, Shinkook; Baek, Jongduk

    2015-03-01

    In a cone beam computed tomography (CBCT), the severity of the cone beam artifacts is increased as the cone angle increases. To reduce the cone beam artifacts, several modified FDK algorithms and compressed sensing based iterative algorithms have been proposed. In this paper, we used two pass algorithm and Gradient-Projection-Barzilai-Borwein (GPBB) algorithm to reduce the cone beam artifacts, and compared their performance using structural similarity (SSIM) index. In two pass algorithm, it is assumed that the cone beam artifacts are mainly caused by extreme-density(ED) objects, and therefore the algorithm reproduces the cone beam artifacts(i.e., error image) produced by ED objects, and then subtract it from the original image. GPBB algorithm is a compressed sensing based iterative algorithm which minimizes an energy function for calculating the gradient projection with the step size determined by the Barzilai- Borwein formulation, therefore it can estimate missing data caused by the cone beam artifacts. To evaluate the performance of two algorithms, we used testing objects consisting of 7 ellipsoids separated along the z direction and cone beam artifacts were generated using 30 degree cone angle. Even though the FDK algorithm produced severe cone beam artifacts with a large cone angle, two pass algorithm reduced the cone beam artifacts with small residual errors caused by inaccuracy of ED objects. In contrast, GPBB algorithm completely removed the cone beam artifacts and restored the original shape of the objects.

  8. ERM proteins regulate growth cone responses to Sema3A

    PubMed Central

    Mintz, C. David; Carcea, Ioana; McNickle, Daniel G.; Dickson, Tracey C.; Ge, Yongchao; Salton, Stephen R.J.; Benson, Deanna L.

    2008-01-01

    Axonal growth cones initiate and sustain directed growth in response to cues in their environment. A variety of events such as receptor internalization, kinase activation, and actin rearrangement can be stimulated by guidance cues and are essential for mediating targeted growth cone behavior. Surprisingly little is known about how such disparate actions are coordinated. Our data suggest that ezrin, radixin, and moesin (ERMs), a family of highly homologous, multifunctional proteins may be able to coordinate growth cone responses to the guidance cue, Sema3A. We show that active ERMs concentrate asymmetrically in neocortical growth cones, are rapidly and transiently inactivated by Sema3A, and are required for Sema3A-mediated growth cone collapse and guidance. The FERM domain of active ERMs regulates internalization of the Sema3A receptor, Npn1 and its co-receptor, L1CAM, while the ERM C-terminal domain binds and caps F-actin. Our data support a model in which ERMs can coordinate membrane and actin dynamics in response to Sema3A. PMID:18651636

  9. Noise masking of S-cone increments and decrements

    PubMed Central

    Wang, Quanhong; Richters, David P.; Eskew, Rhea T.

    2014-01-01

    S-cone increment and decrement detection thresholds were measured in the presence of bipolar, dynamic noise masks. Noise chromaticities were the L-, M-, and S-cone directions, as well as L−M, L+M, and achromatic (L+M+S) directions. Noise contrast power was varied to measure threshold Energy versus Noise (EvN) functions. S+ and S− thresholds were similarly, and weakly, raised by achromatic noise. However, S+ thresholds were much more elevated by S, L+M, L–M, L- and M-cone noises than were S− thresholds, even though the noises consisted of two symmetric chromatic polarities of equal contrast power. A linear cone combination model accounts for the overall pattern of masking of a single test polarity well. L and M cones have opposite signs in their effects upon raising S+ and S− thresholds. The results strongly indicate that the psychophysical mechanisms responsible for S+ and S− detection, presumably based on S-ON and S-OFF pathways, are distinct, unipolar mechanisms, and that they have different spatiotemporal sampling characteristics, or contrast gains, or both. PMID:25391300

  10. Strong topological metal material with multiple Dirac cones

    NASA Astrophysics Data System (ADS)

    Ji, Huiwen; Pletikosić, I.; Gibson, Q. D.; Sahasrabudhe, Girija; Valla, T.; Cava, R. J.

    2016-01-01

    We report a new, cleavable, strong topological metal, Zr2Te2P , which has the same tetradymite-type crystal structure as the topological insulator B i2T e2Se . Instead of being a semiconductor, however, Zr2Te2P is metallic with a pseudogap between 0.2 and 0.7 eV above the Fermi energy (EF). Inside this pseudogap, two Dirac dispersions are predicted: one is a surface-originated Dirac cone protected by time-reversal symmetry (TRS), while the other is a bulk-originated and slightly gapped Dirac cone with a largely linear dispersion over a 2 eV energy range. A third surface TRS-protected Dirac cone is predicted, and observed using angle-resolved photoemission spectroscopy, making Zr2Te2P the first system, to our knowledge, to realize TRS-protected Dirac cones at M ¯ points. The high anisotropy of this Dirac cone is similar to the one in the hypothetical Dirac semimetal Bi O2 . We propose that if EF can be tuned into the pseudogap where the Dirac dispersions exist, it may be possible to observe ultrahigh carrier mobility and large magnetoresistance in this material.

  11. Molecular mechanism of spontaneous pigment activation in retinal cones.

    PubMed Central

    Sampath, Alapakkam P; Baylor, Denis A

    2002-01-01

    Spontaneous current and voltage fluctuations (dark noise) in the photoreceptor cells of the retina limit the ability of the visual system to detect dim light. We recorded the dark current noise of individual salamander L cones. Previous work showed that the dark noise in these cells arises from thermal activation of the visual pigment. From the temperature dependence of the rate of occurrence of elementary noise events, we found an Arrhenius activation energy E(a) of 25 +/- 7 kcal/mol (mean +/- SD). This E(a) is similar to that reported for the thermal isomerization of 11-cis retinal in solution, suggesting that the cone pigment noise results from isomerization of the retinal chromophore. E(a) for the cone noise is similar to that previously reported for the "photon-like" noise of rods, but the preexponential factor is five orders of magnitude higher. To test the hypothesis that thermal isomerization can only occur in molecules whose Schiff base linkage is unprotonated, we changed the pH of the solution bathing the cone outer segment. This had little effect on the rate of occurrence of elementary noise events. The rate was also unchanged when the cone was exposed to Ringer solution made up from heavy water, whose solvent isotope effect should reduce the probability, that the Schiff base nitrogen is naked. PMID:12080111

  12. Glycine receptors are functionally expressed on bullfrog retinal cone photoreceptors.

    PubMed

    Ge, L-H; Lee, S-C; Liu, J; Yang, X-L

    2007-04-25

    Using immunocytochemical and whole cell recording techniques, we examined expression of glycine receptors on bullfrog retinal cone photoreceptors. Immunofluorescence double labeling experiments conducted on retinal sections and isolated cell preparations showed that terminals and inner segments of cones were immunoreactive to both alpha1 and beta subunits of glycine receptors. Moreover, application of glycine induced a sustained inward current from isolated cones, which increased in amplitude in a dose-dependent manner, with an EC50 (concentration of glycine producing half-maximal response) of 67.3+/-4.9 microM, and the current was blocked by the glycine receptor antagonist strychnine, but not 5,7-dichlorokynurenic acid (DCKA) of 200 microM, a blocker of the glycine recognition site at the N-methyl-D-aspartate (NMDA) receptor. The glycine-induced current reversed in polarity at a potential close to the calculated chloride equilibrium potential, and the reversal potential was changed as a function of the extracellular chloride concentration. These results suggest that strychnine-sensitive glycine receptors are functionally expressed in bullfrog cones, which may mediate signal feedback from glycinergic interplexiform cells to cones in the outer retina. PMID:17346892

  13. Lipid rafts mediate chemotropic guidance of nerve growth cones.

    PubMed

    Guirland, Carmine; Suzuki, Shingo; Kojima, Masami; Lu, Bai; Zheng, James Q

    2004-04-01

    Axon guidance requires signal transduction of extracellular cues through the plasma membrane for directional motility. Here we present evidence that cholesterol- and sphingolipid-enriched membrane microdomains (lipid rafts) mediate specific guidance responses of nerve growth cones. Disruption of lipid rafts by various approaches targeting cholesterol or gangliosides selectively abolished growth cone attraction and repulsion in BDNF and netrin-1 gradients, respectively, without affecting glutamate-induced attraction. Interestingly, local raft disruption on one side of the growth cone in bath BDNF or netrin-1 produced opposite turning responses to that induced by the gradients. Raft manipulation also blocked Semaphorin 3A-induced growth cone repulsion, inhibition, and collapse. Finally, guidance responses appeared to involve raft-dependent activation of p42/p44 MAPK and ligand-induced receptor recruitment to lipid rafts. Together with the observation of asymmetric receptor-raft associations at the growth cone in guidance gradients, our findings indicate that localized signaling through membrane rafts plays a role in mediating guidance actions of extracellular cues on developing axons. PMID:15066264

  14. Basal bodies exhibit polarized positioning in zebrafish cone photoreceptors

    PubMed Central

    Ramsey, Michelle; Perkins, Brian D.

    2012-01-01

    The asymmetric positioning of basal bodies, and therefore cilia, is often critical for proper cilia function. This planar polarity is critical for motile cilia function but has not been extensively investigated for non-motile cilia or for sensory cilia such as vertebrate photoreceptors. Zebrafish photoreceptors form an organized mosaic ideal for investigating cilia positioning. We report that in the adult retina, the basal bodies of red, green-, and blue-sensitive cone photoreceptors localized asymmetrically on the cell edge nearest to the optic nerve. In contrast, no patterning was seen in the basal bodies of ultraviolet-sensitive cones or in rod photoreceptors. The asymmetric localization of basal bodies was consistent in all regions of the adult retina. Basal body patterning was unaffected in the cones of the XOPS-mCFP transgenic line, which lacks rod photoreceptors. Finally, the adult pattern was not seen in 7 day post fertilization (dpf) larvae as basal bodies were randomly distributed in all the photoreceptor subtypes. These results establish the asymmetrical localization of basal bodies in red-, green-, and blue-sensitive cones in adult zebrafish retinas but not in larvae. This pattern suggests an active cellular mechanism regulated the positioning of basal bodies after the transition to the adult mosaic and that rods do not seem to be necessary for the patterning of cone basal bodies. PMID:23171982

  15. AN IONIZATION CONE IN THE DWARF STARBURST GALAXY NGC 5253

    SciTech Connect

    Zastrow, Jordan; Oey, M. S.; Veilleux, Sylvain; McDonald, Michael; Martin, Crystal L.

    2011-11-01

    There are few observational constraints on how the escape of ionizing photons from starburst galaxies depends on galactic parameters. Here we report on the first major detection of an ionization cone in NGC 5253, a nearby starburst galaxy. This high-excitation feature is identified by mapping the emission-line ratios in the galaxy using [S III] {lambda}9069, [S II] {lambda}6716, and H{alpha} narrowband images from the Maryland-Magellan Tunable Filter at Las Campanas Observatory. The ionization cone appears optically thin, which suggests the escape of ionizing photons. The cone morphology is narrow with an estimated solid angle covering just 3% of 4{pi} steradians, and the young, massive clusters of the nuclear starburst can easily generate the radiation required to ionize the cone. Although less likely, we cannot rule out the possibility of an obscured active galactic nucleus source. An echelle spectrum along the minor axis shows complex kinematics that are consistent with outflow activity. The narrow morphology of the ionization cone supports the scenario that an orientation bias contributes to the difficulty in detecting Lyman continuum emission from starbursts and Lyman break galaxies.

  16. Inferring conduit process from population studies of cinder cone craters

    NASA Astrophysics Data System (ADS)

    Bemis, Karen G.

    2014-05-01

    One of the most observable aspects of magma conduits is of course their exit to the Earth's surface: the volcanic crater. The craters resulting from small mostly-monogenetic volcanic eruptions vary in considerable in size and shape, even after accounting for variation in size. Presumably, these variations tell us something about the state of the conduit at least in the ending stages of eruption. But what? This work explores the statistical properties of crater populations in Guatemala and elsewhere and speculates on the conduit processes that may explain the complex behavior. Crater depths are strongly correlated with cone slopes even when normalized by cone diameter, which suggests the importance of the impact of the volatile content (which may influence slope through fragmentation and the resulting grain size) and the duration of eruption (which may influence whether the cone is built to its maximum slope) despite erosion acting to reduce observed crater depths (cone slopes are known to decrease with erosion but cone diameters increase).

  17. Strong topological metal material with multiple Dirac cones

    DOE PAGES

    Ji, Huiwen; Valla, T.; Pletikosic, I.; Gibson, Q. D.; Sahasrabudhe, Girija; Cava, R. J.

    2016-01-25

    We report a new, cleavable, strong topological metal, Zr2Te2P, which has the same tetradymite-type crystal structure as the topological insulator Bi2Te2Se. Instead of being a semiconductor, however, Zr2Te2P is metallic with a pseudogap between 0.2 and 0.7 eV above the Fermi energy (EF). Inside this pseudogap, two Dirac dispersions are predicted: one is a surface-originated Dirac cone protected by time-reversal symmetry (TRS), while the other is a bulk-originated and slightly gapped Dirac cone with a largely linear dispersion over a 2 eV energy range. A third surface TRS-protected Dirac cone is predicted, and observed using angle-resolved photoemission spectroscopy, making Zr2Te2Pmore » the first system, to our knowledge, to realize TRS-protected Dirac cones at M¯ points. The high anisotropy of this Dirac cone is similar to the one in the hypothetical Dirac semimetal BiO2. As a result, we propose that if EF can be tuned into the pseudogap where the Dirac dispersions exist, it may be possible to observe ultrahigh carrier mobility and large magnetoresistance in this material.« less

  18. Fast Electron Generation in Cones with Ultra-Intense Laser Pulses

    SciTech Connect

    Mackinnon, A; VanWoerkom, L; Akli, K; Bartal, T; Beg, F; Chawla, S; Chen, C; Chowdhury, E; Freeman, R; Hey, D; Key, M; King, J; Link, A; MacPhee, A; Offermann, D; Ovchinnikov, V; Patel, P; Schumacher, D; Stephens, R; Tsui, Y; Ma, T

    2007-12-07

    Experimental results from copper cones irradiated with ultra-intense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {micro}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser cone interaction is dominated by preplasma created from the long duration, low energy pre-pulse from the laser.

  19. Discrimination of cone contrast changes as evidence for colour constancy in cerebral achromatopsia.

    PubMed

    Hurlbert, A C; Bramwell, D I; Heywood, C; Cowey, A

    1998-11-01

    One proposed mechanism for underpinning colour constancy is computation of the relative activity of cones within one class--cone ratios, or cone contrasts--between surfaces in a fixed scene undergoing a change in illuminant. Although there is evidence that cone ratios do determine colour appearance under many conditions, the site or sites of their computation is unknown. Here, we report that a cerebrally achromatopsic observer, MS, displayed evidence of colour constancy in asymmetric colour matching tasks and was able to discriminate changes in cone ratios for simple, but not complex scenes. We hypothesise that the site of local cone-ratio computation is therefore early in the visual system, probably retinal.

  20. Skeletal dosimetry in cone beam computed tomography

    SciTech Connect

    Walters, B. R. B.; Ding, G. X.; Kramer, R.; Kawrakow, I.

    2009-07-15

    Cone beam computed tomography (CBCT) is a relatively new patient imaging technique that has proved invaluable for treatment target verification and patient positioning during image-guided radiotherapy (IGRT). It has been shown that CBCT results in additional dose to bone that may amount to 10% of the prescribed dose. In this study, voxelized human phantoms, FAX06 (adult female) and MAX06 (adult male), are used together with phase-space data collected from a realistic model of a CBCT imager to calculate dose in the red bone marrow (RBM) and bone surface cells (BSCs), the two organs at risk within the bone spongiosa, during simulated head and neck, chest and pelvis CBCT scans. The FAX06/MAX06 phantoms model spongiosa based on micro-CT images, filling the relevant phantom voxels, which are 0.12x0.12x0.12 cm{sup 3}, with 17x17x17 {mu}m{sup 3} microvoxels to form a micromatrix of trabecular bone and bone marrow. FAX06/MAX06 have already been implemented in an EGSnrc-based Monte Carlo code to simulate radiation transport in the phantoms; however, this study required significant modifications of the code to allow use of phase-space data from a simulated CBCT imager as a source and to allow scoring of total dose, RBM dose and BSC dose on a voxel-by-voxel basis. In simulated CBCT scans, the BSC dose is significantly greater than the dose to other organs at risk. For example, in a simulated head and neck scan, the average BSC dose is 25% higher than the average dose to eye lens ({approx}8.3 cGy), and 80% greater than the average dose to brain (5.7 cGy). Average dose to RBM, on the other hand, is typically only {approx}50% of the average BSC dose and less than the dose to other organs at risk (54% of the dose to eye lens and 76% of dose to brain in a head and neck scan). Thus, elevated dose in bone due to CBCT results in elevated BSC dose. This is potentially of concern when using CBCT in conjunction with radiotherapy treatment.

  1. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  2. Cones of positive maps and their duality relations

    NASA Astrophysics Data System (ADS)

    Skowronek, Łukasz; Størmer, Erling; Życzkowski, Karol

    2009-06-01

    The structure of cones of positive and k-positive maps acting on a finite-dimensional Hilbert space is investigated. Special emphasis is given to their duality relations to the sets of superpositive and k-superpositive maps. We characterize k-positive and k-superpositive maps with regard to their properties under taking compositions. A number of results obtained for maps are also rephrased for the corresponding cones of block positive, k-block positive, separable, and k-entangled operators due to the Jamiołkowski-Choi isomorphism. Generalizations to a situation where no such simple isomorphism is available are also made, employing the idea of mapping cones. As a side result to our discussion, we show that extreme entanglement witnesses, which are optimal, should be of special interest in entanglement studies.

  3. Testing the reliability of ice-cream cone model

    NASA Astrophysics Data System (ADS)

    Pan, Z.; Shen, C.; Wang, Y.; Liu, K.

    2013-12-01

    Coronal Mass Ejections (CME)'s properties are important to not only the physical scene itself but spaceweather prediction. Several models(such as cone model, GCS model, and so on) have been raised to get rid of the projection effects within the properties observated by spacecraft. According to SOHO/ LASCO observations, we obtain the 'real' 3D parameters of 33 FFHCMEs (front-side full halo Coronal Mass Ejections) within the 24th solar cycle by the ice-cream cone model. Considering that the method to obtain 3D parameters from the CME observations by multi-satellite and multi-angle has higher accuracy, we use the GCS model to obtain the real propagation parameters of these CMEs in 3D space and compare the results with which by ice-cream cone model. It was demonstrated that the correlation coefficient for the speeds by using these both methods is 0.97.

  4. An ice-cream cone model for coronal mass ejections

    NASA Astrophysics Data System (ADS)

    Xue, X. H.; Wang, C. B.; Dou, X. K.

    2005-08-01

    In this study, we use an ice-cream cone model to analyze the geometrical and kinematical properties of the coronal mass ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an ice-cream cone. This model is improved by (1) using an ice-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.

  5. Wind tunnel experiments on two blunt cones at Ma6

    NASA Astrophysics Data System (ADS)

    Zhang, Yunchi; Li, Cunbiao; State Key LaboratoryTurbulence; Complex Systems Team

    2015-11-01

    Wind tunnel experiments are performed on two 5° half-angle blunt cones over Mach 6 flow for 0° and 10° angle of attack. The temperature distributions on both windward and leeward sides are obtained by temperature sensitive painting (TSP) technique and the fluctuation pressure is measured by PCB pressure sensors for 7 meridian lines between the central meridian lines of the windward and the leeward by 30° step. Boundary layer transition is implied by the temperature distribution and power spectral evolution of the fluctuation pressure. It is found there exists a streamwise high-temperature strip near the central meridian line of the leeward side and transition is most likely to occur along the strip (earlier than the windward side and 0° angle of attack). Besides, the radius of the cone tip has an effective influence on the transition location. Transition is more likely to occur on the cone with the sharper tip.

  6. Optimization of pyrolysis properties using TGA and cone calorimeter test

    NASA Astrophysics Data System (ADS)

    Park, Won-Hee; Yoon, Kyung-Beom

    2013-04-01

    The present paper describes an optimization work to obtain the properties related to a pyrolysis process in the solid material such as density, specific heat, conductivity of virgin and char, heat of pyrolysis and kinetic parameters used for deciding pyrolysis rate. A repulsive particle swarm optimization algorithm is used to obtain the pyrolysis-related properties. In the previous study all properties obtained only using a cone calorimeter but in this paper both the cone calorimeter and thermo gravimetric analysis (TGA) are used for precisely optimizing the pyrolysis properties. In the TGA test a very small mass is heated up and conduction and heat capacity in the specimen is negligible so kinetic parameters can first be optimized. Other pyrolysis-related properties such as virgin/char specific heat and conductivity and char density are also optimized in the cone calorimeter test with the already decided parameters in the TGA test.

  7. Spin-Cherenkov effect and magnonic Mach cones

    NASA Astrophysics Data System (ADS)

    Yan, Ming; Kákay, Attila; Andreas, Christian; Hertel, Riccardo

    2013-12-01

    We report on the Cherenkov-type excitation of spin waves (SWs) in ferromagnets. Our micromagnetic simulations show that a localized magnetic field pulse moving sufficiently fast along the surface of a ferromagnet generates a SW boom, with a Mach-type cone of propagating wave fronts. The SWs are formed when the velocity of the source exceeds the propagation speed of SWs. Unlike the single cone of the usual Cherenkov effect, we find that the magnetic Mach cone consists of two wave fronts with different wave numbers. In patterned thin strips, this magnetic analog of the Cherenkov effect should enable the excitation of SWs with well-defined and velocity-dependent frequency. It thereby provides a promising route towards tunable SW generation, with important potential for applications in magnonic devices.

  8. Concrescence: Cone-Beam Computed Tomography Imaging Perspective

    PubMed Central

    Alluri, LeelaSubhashini Choudary; Mallela, Dhiraj

    2016-01-01

    Concrescence is a form of twinning, formed by the confluence of cementum of two teeth at the root level. The diagnosis of concrescence has largely relied on the conventional 2D imaging. The 2D imaging has inherent limitations such as distortion and superimposition. Cone-Beam CT eliminates these limitations. The aim of this article was to describe a case of dental abnormality using Cone-Beam CT imaging modality. Volumetric data demonstrated confluence of left mandibular third molar with a paramolar, a supernumerary tooth. To our knowledge, this is the second case in the dental literature reported demonstrating the use of Cone-Beam CT in the diagnosis of concrescence. PMID:27800194

  9. The oral cone of Anomalocaris is not a classic ``peytoia''

    NASA Astrophysics Data System (ADS)

    Daley, Allison C.; Bergström, Jan

    2012-06-01

    The Cambro-Ordovician anomalocaridids are large ecdysozoans commonly regarded as ancestors of the arthropods and apex predators. Predation is indicated partly by the presence of an unusual "peytoia"-type oral cone, which is a tetraradial outer ring of 32 plates, four of which are enlarged and in perpendicular arrangement. This oral cone morphology was considered a highly consistent and defining characteristic of well-known Burgess Shale taxa. It is here shown that Anomalocaris has a different oral cone, with only three large plates and a variable number of smaller and medium plates. Its functional morphology suggests that suction, rather than biting, was used for food ingestion, and that anomalocaridids in general employed a range of different scavenging and predatory feeding strategies. Removing anomalocaridids from the position of highly specialized trilobite predators forces a reconsideration of the ecological structure of the earliest marine animal communities in the Cambrian.

  10. X-ray cone beam CT system calibration

    NASA Astrophysics Data System (ADS)

    Sire, Pascal; Rizo, Philippe; Martin, M.

    1993-12-01

    Recently x-ray cone beam computed tomography (CT) has become of interest for nondestructive testing (NDT) of advanced materials. Such a technique takes advantage of the cone beam geometry, to reduce the acquisition time and increase the resolution. Performances of CT systems rely mainly on geometric precision and measurement quality. Inaccurate geometry or incorrect data produce artifacts and blurring which limit the spatial resolution. A precise geometric calibration procedure is required and some corrections must be applied to the raw attenuation data in order to obtain accurate measurements. An x-ray cone beam CT system has been developed at the LETI. This machine was designed to control small parts limited to a few centimeters, with a high spatial resolution close to 30 microns. This paper introduces the machine setup and describes the calibration computing resources involved in the system. Then, we discuss the performances on experimental data.

  11. Evolution of a Hybrid Roller Cone/PDC core bit

    SciTech Connect

    Pettitt, R.; Laney, R.; George, D.; Clemens, G.

    1980-01-01

    The development of the hot dry rock (HDR) geothermal resource, as presently being accomplished by the Los Alamos Scientific Laboratory (LASL), requires that sufficient quantities of good quality core be obtained at a reasonable cost. The use of roller cone core bits, with tungsten carbide inserts, was initiated by the Deep Sea Drilling Program. These bits were modified for continental drilling in deep, hot, granitic rock for the LASL HDR Geothermal Site at Fenton Hill, New Mexico in 1974. After the advent of monocrystalline diamond Stratapax pads, a prototype hybrid roller cone/Stratapax core bit was fabricated by Smith Tool, and tested at Fenton Hill in 1978. During the drilling for a deeper HDR reservoir system in 1979 and 1980, six of the latest generation of these bits, now called Hybrid Roller Cone/Polycrystalline Diamond Cutter (PDC) core bits, were successfully used in granitic rock at depths below 11,000 ft.

  12. CONE - An STS-based cryogenic fluid management experiment

    NASA Technical Reports Server (NTRS)

    Bell, R. S.; Vento, D. M.; Hanna, G. J.

    1992-01-01

    An overview of the CONE program is presented which includes a definition of the technology addressed by CONE and a baseline experiment set, a description of the experimental and support subsystems, interface requirements between the STS and the experiment carrier (Hitchhiker M), and the reusability and expansion capacity for additional experiment flights. CONE evaluates three primary technologies: the active thermodynamic vent system, the passive thermodynamic vent system, and liquid acquisition device performance. The cryogenic fluid management technology database that the system offers will allow for efficient subcritical cryogenic system designs for operation in a low-gravity environment. This system maximizes the balance between existing component technology and the need for the development of a cryogenic-fluid-management (CFM) test bed to investigate and demonstrate methods of storage and handling arenas.

  13. THz radiation properties of silver V-cone antenna arrays

    NASA Astrophysics Data System (ADS)

    Qian, Jun; Huang, Mengya; Hu, Mingzhe

    2012-12-01

    In the present article, silver cone antenna and its arrays are designed according to the requirement of wide bandwidth terahertz irradiation property. Coordinate transformation method is employed to analyze the solution process of the integrate equation of the irradiated electromagnetic field. And CST microwave studio software is employed to simulate the terahertz irradiation properties of Ag cone antenna arrays. Theoretical analysis and simulation results both manifest that the single Ag cone antenna with micrometer scale size can irradiate a wide bandwidth THz wave with the gain of 22.7dBi, while its corresponding antenna arrays with proper configuration can further improve the radiation pattern and enhance the gain to 42.5dBi. The theoretical analysis and CST simulation results will be useful for the guidance of experimental investigation of terahertz irradiation sources.

  14. [The forms and frequency of renal parenchymal cones].

    PubMed

    Kara, Murat; Tuma, Jan

    2014-02-12

    The renal parenchymal cone (RPC) is an important differential diagnosis to the real kidney tumors. It is defined as at least 15 mm large part of the normal renal parenchyma which protrudes into the space of the renal sinus. If the RPC is solely formed from renal cortical tissue, it is called "Column of Bertin" renal parenchymal cones (CB-RPC). If the renal medulla is part of RPC, together with the renal cortex, it is called lobular renal parenchymal cones (L-RPC). The aim of this prospective study was to determine the frequency of CB-RPC and the L-RPC. 200 kidneys from 100 patients were evaluated. At least one RPC was found in 53 patients. 27 RPC were on both sides. CB-RPC was present in 27,5% of the kidneys, a L-RPC in 12,5%. The high frequency of RPC underlines its importance in the diagnosis of focal renal parenchymal changes.

  15. Dirac cones in transition metal doped boron nitride

    SciTech Connect

    Feng, Min; Cao, Xuewei; Shao, Bin; Zuo, Xu

    2015-05-07

    The transition metal (TM) doped zinc blende boron nitride (c-BN) is studied by using the first principle calculation. TM atoms fill in the interstitials in c-BN and form two-dimensional honeycomb lattice. The generalized gradient approximation and projector augmented wave method are used. The calculated density of states and band structures show that d electrons of TM atoms form impurity bands in the gap of c-BN. When the TM-BN system is in ferromagnetic or non-magnetic state, Dirac cones emerge at the K point in Brillouin zone. When TM is Ti and Co, the Dirac cones are spin polarized and very close to the Fermi level, which makes them promising candidates of Dirac half-metal [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012)]. While TM is Ni and Cu, the system is non-magnetic and Dirac cones located above the Fermi level.

  16. Dirac cones in transition metal doped boron nitride

    NASA Astrophysics Data System (ADS)

    Feng, Min; Shao, Bin; Cao, Xuewei; Zuo, Xu

    2015-05-01

    The transition metal (TM) doped zinc blende boron nitride (c-BN) is studied by using the first principle calculation. TM atoms fill in the interstitials in c-BN and form two-dimensional honeycomb lattice. The generalized gradient approximation and projector augmented wave method are used. The calculated density of states and band structures show that d electrons of TM atoms form impurity bands in the gap of c-BN. When the TM-BN system is in ferromagnetic or non-magnetic state, Dirac cones emerge at the K point in Brillouin zone. When TM is Ti and Co, the Dirac cones are spin polarized and very close to the Fermi level, which makes them promising candidates of Dirac half-metal [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012)]. While TM is Ni and Cu, the system is non-magnetic and Dirac cones located above the Fermi level.

  17. Retinal cone photoreceptors of the deer mouse Peromyscus maniculatus: development, topography, opsin expression and spectral tuning.

    PubMed

    Arbogast, Patrick; Glösmann, Martin; Peichl, Leo

    2013-01-01

    A quantitative analysis of photoreceptor properties was performed in the retina of the nocturnal deer mouse, Peromyscus maniculatus, using pigmented (wildtype) and albino animals. The aim was to establish whether the deer mouse is a more suitable model species than the house mouse for photoreceptor studies, and whether oculocutaneous albinism affects its photoreceptor properties. In retinal flatmounts, cone photoreceptors were identified by opsin immunostaining, and their numbers, spectral types, and distributions across the retina were determined. Rod photoreceptors were counted using differential interference contrast microscopy. Pigmented P. maniculatus have a rod-dominated retina with rod densities of about 450.000/mm(2) and cone densities of 3000-6500/mm(2). Two cone opsins, shortwave sensitive (S) and middle-to-longwave sensitive (M), are present and expressed in distinct cone types. Partial sequencing of the S opsin gene strongly supports UV sensitivity of the S cone visual pigment. The S cones constitute a 5-15% minority of the cones. Different from house mouse, S and M cone distributions do not have dorsoventral gradients, and coexpression of both opsins in single cones is exceptional (<2% of the cones). In albino P. maniculatus, rod densities are reduced by approximately 40% (270.000/mm(2)). Overall, cone density and the density of cones exclusively expressing S opsin are not significantly different from pigmented P. maniculatus. However, in albino retinas S opsin is coexpressed with M opsin in 60-90% of the cones and therefore the population of cones expressing only M opsin is significantly reduced to 5-25%. In conclusion, deer mouse cone properties largely conform to the general mammalian pattern, hence the deer mouse may be better suited than the house mouse for the study of certain basic cone properties, including the effects of albinism on cone opsin expression. PMID:24260509

  18. Spawning rings of exceptional points out of Dirac cones.

    PubMed

    Zhen, Bo; Hsu, Chia Wei; Igarashi, Yuichi; Lu, Ling; Kaminer, Ido; Pick, Adi; Chua, Song-Liang; Joannopoulos, John D; Soljačić, Marin

    2015-09-17

    The Dirac cone underlies many unique electronic properties of graphene and topological insulators, and its band structure--two conical bands touching at a single point--has also been realized for photons in waveguide arrays, atoms in optical lattices, and through accidental degeneracy. Deformation of the Dirac cone often reveals intriguing properties; an example is the quantum Hall effect, where a constant magnetic field breaks the Dirac cone into isolated Landau levels. A seemingly unrelated phenomenon is the exceptional point, also known as the parity-time symmetry breaking point, where two resonances coincide in both their positions and widths. Exceptional points lead to counter-intuitive phenomena such as loss-induced transparency, unidirectional transmission or reflection, and lasers with reversed pump dependence or single-mode operation. Dirac cones and exceptional points are connected: it was theoretically suggested that certain non-Hermitian perturbations can deform a Dirac cone and spawn a ring of exceptional points. Here we experimentally demonstrate such an 'exceptional ring' in a photonic crystal slab. Angle-resolved reflection measurements of the photonic crystal slab reveal that the peaks of reflectivity follow the conical band structure of a Dirac cone resulting from accidental degeneracy, whereas the complex eigenvalues of the system are deformed into a two-dimensional flat band enclosed by an exceptional ring. This deformation arises from the dissimilar radiation rates of dipole and quadrupole resonances, which play a role analogous to the loss and gain in parity-time symmetric systems. Our results indicate that the radiation existing in any open system can fundamentally alter its physical properties in ways previously expected only in the presence of material loss and gain. PMID:26352476

  19. Numerical simulation of electrospray in the cone-jet mode.

    PubMed

    Herrada, M A; López-Herrera, J M; Gañán-Calvo, A M; Vega, E J; Montanero, J M; Popinet, S

    2012-08-01

    We present a robust and computationally efficient numerical scheme for simulating steady electrohydrodynamic atomization processes (electrospray). The main simplification assumed in this scheme is that all the free electrical charges are distributed over the interface. A comparison of the results with those calculated with a volume-of-fluid method showed that the numerical scheme presented here accurately describes the flow pattern within the entire liquid domain. Experiments were performed to partially validate the numerical predictions. The simulations reproduced accurately the experimental shape of the liquid cone jet, providing correct values of the emitted electric current even for configurations very close to the cone-jet stability limit. PMID:23005852

  20. Numerical simulation of electrospray in the cone-jet mode.

    PubMed

    Herrada, M A; López-Herrera, J M; Gañán-Calvo, A M; Vega, E J; Montanero, J M; Popinet, S

    2012-08-01

    We present a robust and computationally efficient numerical scheme for simulating steady electrohydrodynamic atomization processes (electrospray). The main simplification assumed in this scheme is that all the free electrical charges are distributed over the interface. A comparison of the results with those calculated with a volume-of-fluid method showed that the numerical scheme presented here accurately describes the flow pattern within the entire liquid domain. Experiments were performed to partially validate the numerical predictions. The simulations reproduced accurately the experimental shape of the liquid cone jet, providing correct values of the emitted electric current even for configurations very close to the cone-jet stability limit.

  1. Does the Dirac Cone Exist in Silicene on Metal Substrates?

    PubMed Central

    Quhe, Ruge; Yuan, Yakun; Zheng, Jiaxin; Wang, Yangyang; Ni, Zeyuan; Shi, Junjie; Yu, Dapeng; Yang, Jinbo; Lu, Jing

    2014-01-01

    Absence of the Dirac cone due to a strong band hybridization is revealed to be a common feature for epitaxial silicene on metal substrates according to our first-principles calculations for silicene on Ir, Cu, Mg, Au, Pt, Al, and Ag substrates. The destroyed Dirac cone of silicene, however, can be effectively restored with linear or parabolic dispersion by intercalating alkali metal atoms between silicene and the metal substrates, offering an opportunity to study the intriguing properties of silicene without further transfer of silicene from the metal substrates. PMID:24969493

  2. Comparison of cone directionality determined by psychophysical and reflectometric techniques

    PubMed Central

    He, J.C.; Marcos, S; Burns, S.A.

    2010-01-01

    We measured the directionality of the cones using both a psychophysical (Stiles-Crawford I) technique and an optical technique. Both sets of measurements were made in the same subjects using as similar stimuli as possible. Both types of measurements gave similar estimates of the location in the pupil towards which the cones were optimally aligned. However, the two measurements gave very dissimilar estimates of the width of the directional sensitivity. On average optical measurements were half as broad as psychophysical measurements in the fovea, but there were substantial individual differences. At 2 deg retinal eccentricty the difference between techniques was even more marked. PMID:10517020

  3. Configuration of singular optical cones in gyrotropic crystals with dichroism

    SciTech Connect

    Merkulov, V. S.

    2015-02-15

    Optical conic singularities in crystals with linear dichroism and natural optical activity at the point of intersection of dispersion curves for the main refractive indices are considered. The possible existence of singularities like a nodal point, tangency point, triple point, and cusps of the first and second order is demonstrated. Forty-nine different types of irreducible fourth-order optical cones obtained by sequential bifurcations of eight main singular cones are established. The classification is based on the concept of roughness of systems depending on parameters.

  4. Cone snail venomics: from novel biology to novel therapeutics.

    PubMed

    Prashanth, Jutty Rajan; Brust, Andreas; Jin, Ai-Hua; Alewood, Paul F; Dutertre, Sébastien; Lewis, Richard J

    2014-10-01

    Peptide neurotoxins from cone snails called conotoxins are renowned for their therapeutic potential to treat pain and several neurodegenerative diseases. Inefficient assay-guided discovery methods have been replaced by high-throughput bioassays integrated with advanced MS and next-generation sequencing, ushering in the era of 'venomics'. In this review, we focus on the impact of venomics on the understanding of cone snail biology as well as the application of venomics to accelerate the discovery of new conotoxins. We also discuss the continued importance of medicinal chemistry approaches to optimize conotoxins for clinical use, with a descriptive case study of MrIA featured.

  5. Does the Dirac cone exist in silicene on metal substrates?

    PubMed

    Quhe, Ruge; Yuan, Yakun; Zheng, Jiaxin; Wang, Yangyang; Ni, Zeyuan; Shi, Junjie; Yu, Dapeng; Yang, Jinbo; Lu, Jing

    2014-06-27

    Absence of the Dirac cone due to a strong band hybridization is revealed to be a common feature for epitaxial silicene on metal substrates according to our first-principles calculations for silicene on Ir, Cu, Mg, Au, Pt, Al, and Ag substrates. The destroyed Dirac cone of silicene, however, can be effectively restored with linear or parabolic dispersion by intercalating alkali metal atoms between silicene and the metal substrates, offering an opportunity to study the intriguing properties of silicene without further transfer of silicene from the metal substrates.

  6. Cyclic nucleotides of cone-dominant retinas. Reduction of cyclic AMP levels by light and by cone degeneration.

    PubMed

    Farber, D B; Souza, D W; Chase, D G; Lolley, R N

    1981-01-01

    Dark-adapted retinas or whole eyes of 13-line ground squirrels (Citellus tridecemlineatus) and western fence lizards (Sceloporus occidentalis) contain higher levels of cyclic AMP than of cyclic GMP. In these cone-dominant retinas, light reduces cyclic AMP content selectively. Freezing of dark- or light-adapted retinas or eyes also reduces cyclic AMP content, with only minimal changes in cyclic GMP levels. In addition, exposure of frozen retinas of dark-adapted ground squirrel to light results in a significant decrease in cyclic AMP content. The destruction of cone visual cells of ground squirrel retina by iodoacetic acid injection decreases the cyclic nucleotide content of the dark-adapted retina. Considering the relative loss of cyclic nucleotides from cone degeneration, we estimate that the content of cyclic AMP in visual cells of ground squirrel retina is about four times greater than that of cyclic GMP. PMID:6256308

  7. Horizontal Cells of the Primate Retina: Cone Specificity Without Spectral Opponency

    NASA Astrophysics Data System (ADS)

    Dacey, Dennis M.; Lee, Barry B.; Stafford, Donna K.; Pokorny, Joel; Smith, Vivianne C.

    1996-02-01

    The chromatic dimensions of human color vision have a neural basis in the retina. Ganglion cells, the output neurons of the retina, exhibit spectral opponency; they are excited by some wavelengths and inhibited by others. The hypothesis that the opponent circuitry emerges from selective connections between horizontal cell interneurons and cone photoreceptors sensitive to long, middle, and short wavelengths (L-, M-, and S-cones) was tested by physiologically and anatomically characterizing cone connections of horizontal cell mosaics in macaque monkeys. H1 horizontal cells received input only from L- and M-cones, whereas H2 horizontal cells received a strong input from S-cones and a weaker input from L- and M-cones. All cone inputs were the same sign, and both horizontal cell types lacked opponency. Despite cone type selectivity, the horizontal cell cannot be the locus of an opponent transformation in primates, including humans.

  8. Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development.

    PubMed

    Özel, Mehmet Neset; Langen, Marion; Hassan, Bassem A; Hiesinger, P Robin

    2015-10-29

    Filopodial dynamics are thought to control growth cone guidance, but the types and roles of growth cone dynamics underlying neural circuit assembly in a living brain are largely unknown. To address this issue, we have developed long-term, continuous, fast and high-resolution imaging of growth cone dynamics from axon growth to synapse formation in cultured Drosophila brains. Using R7 photoreceptor neurons as a model we show that >90% of the growth cone filopodia exhibit fast, stochastic dynamics that persist despite ongoing stepwise layer formation. Correspondingly, R7 growth cones stabilize early and change their final position by passive dislocation. N-Cadherin controls both fast filopodial dynamics and growth cone stabilization. Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers. Hence, growth cone dynamics can influence wiring specificity without a direct role in target recognition and implement simple rules during circuit assembly.

  9. Aerodynamic characteristics of the standard dynamics model in coning motion at Mach 0.6

    NASA Technical Reports Server (NTRS)

    Jermey, C.; Schiff, L. B.

    1985-01-01

    A wind tunnel test was conducted on the Standard Dynamics Model (a simplified generic fighter aircraft shape) undergoing coning motion at Mach 0.6. Six component force and moment data are presented for a range of angle of attack, sideslip, and coning rates. At the relatively low non-dimensional coning rate employed (omega b/2V less than or equal to 0.04), the lateral aerodynamic characteristics generally show a linear variation with coning rate.

  10. Variability in human cone topography assessed by adaptive optics scanning laser ophthalmoscopy

    PubMed Central

    Zhang, Tianjiao; Godara, Pooja; Blanco, Ernesto R.; Griffin, Russell L; Wang, Xiaolin; Curcio, Christine A.; Zhang, Yuhua

    2015-01-01

    Purpose To assess between- and within-individual variability of macular cone topography in the eyes of young adults. Design Observational case series. Methods Cone photoreceptors in 40 eyes of 20 subjects aged 19–29 years with normal maculae were imaged using a research adaptive optics scanning laser ophthalmoscope. Refractive errors ranged from −3.0 D to 0.63 D and differed by <0.50 D in fellow eyes. Cone density was assessed on a two-dimensional sampling grid over the central 2.4 mm × 2.4 mm. Between-individual variability was evaluated by coefficient of variation (CV). Within-individual variability was quantified by maximum difference and root-mean-square (RMS). Cones were cumulated over increasing eccentricity. Results Peak densities of foveal cones are 168,162 ± 23,529 cones/mm2 (mean ± SD) (CV = 0.14). The number of cones within the cone-dominated foveola (0.8–0.9 mm diameter) is 38,311 ± 2,319 (CV = 0.06). The RMS cone density difference between fellow eyes is 6.78%, and the maximum difference is 23.6%. Mixed model statistical analysis found no difference in the association between eccentricity and cone density in the superior/nasal (p=0.8503), superior/temporal (p=0.1551), inferior/nasal (p=0.8609), and inferior/temporal (p=0.6662) quadrants of fellow eyes. Conclusions New instrumentation imaged the smallest foveal cones, thus allowing accurate assignment of foveal centers and assessment of variability in macular cone density in a large sample of eyes. Though cone densities vary significantly in the fovea, the total number of foveolar cones are very similar both between- and within-subjects. Thus, the total number of foveolar cones may be an important measure of cone degeneration and loss. PMID:25935100

  11. Changes of cone electroretinograms to colour flash stimuli after successful retinal detachment surgery

    PubMed Central

    Hayashi, M; Yamamoto, S

    2001-01-01

    AIM—To examine the changes in the short wavelength (S) and mixed long (L) and middle (M) wavelength sensitive cone (L,M-cone) electroretinograms (ERGs) after successful retinal detachment surgery.
METHODS—Cone ERGs elicited by different colour flashes were recorded from 19 eyes with unilateral rhegmatogenous retinal detachment treated successfully by conventional buckling surgery. Ganzfeld colour flashes on a bright white background were used to elicit S-cone and L,M-cone ERGs. The ratio (operated eye/fellow eye) of the S-cone b-wave elicited by a 450 nm stimulus and the ratio (operated eye/fellow eye) of the L,M-cone b-wave elicited by a 633 nm stimulus were evaluated preoperatively and 1, 3, and 6 months after surgery.
RESULTS—Preoperatively, no significant difference was observed between the ratio of the S-cone ERG amplitudes and the ratio of the L,M-cone ERG amplitudes. Postoperatively, the ratio of the L,M-cone ERGs increased significantly over the preoperative value (p=0.001) but the ratio of the S-cone ERG did not improve. There were significant differences between the ratios of the S-cone and the L,M-cone ERGs at 1, 3, and 6 months after surgery. The postoperative recovery of the S-cone ERG was significantly greater in eyes treated within 4 weeks after the onset of the detachment than in eyes treated later than 4 weeks.
CONCLUSIONS—These results indicate that the impairment of the L,M-cone system caused by retinal detachment may be reversible. However, the S-cone system may have more profound permanent damage.

 PMID:11264128

  12. Mach cone shocks in a two-dimensional Yukawa solid using a complex plasma

    PubMed

    Samsonov; Goree; Thomas; Morfill

    2000-05-01

    Mach cones were studied experimentally in a two-dimensional Yukawa solid consisting of charged micrometer particles suspended as a layer in a plasma. These cones were V-shaped shocks produced spontaneously by a supersonic particle moving below the main two-dimensional particle layer. The cones had a double structure. The first cone was compressional and particles moved forward, and it was followed by a second cone, which was rarefactional, where particles moved backward. Over the limited range of speed V attained by the supersonic particles in this experiment, the angle mu of the cone was found to obey the Mach cone rule sin mu = c/V, where c is the medium's sound speed. The cones caused only elastic deformations in the crystal lattice, except in a narrow track behind the cone's vertex. The wings of the cones can be analyzed as linear shocks in two dimensions. Using spatially resolved measurements of the particle number density and velocity and applying the Hugoniot relations for shocks in two dimensions, we found that the pressure inside the first Mach cone was greater than in the undisturbed medium by a factor of 1.3-1.6. The cone angle was also used to measure the charge in this experiment. PMID:11031610

  13. Rootless Cone? Pingo? or Mud Volcano? in Central Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Noguchi, R.; Kurita, K.

    2011-03-01

    It is possible that Mars has experienced recent (~100 Ma) magmatism. In central Elysium Planitia, the identification of cone-like landforms are discussed: rootless cones, pingos, or mud volcanos. From their morphology, the landforms are thought to be rootless cones.

  14. The eddy-eliminating method of guide cone in the closed sump

    NASA Astrophysics Data System (ADS)

    Wang, Y. J.; Cheng, L.; Xia, C. Z.; Zhou, J. R.; Yan, H. Q.; Jiang, H. Y.

    2016-05-01

    In order to explore the effect on eddy-eliminating method of guide cone in the closed sump, the simple factor analysis and CFD numerical simulation are applied to calculate the flow field of closed sump and select ω-shaped back wall. ω-shaped back wall is consistent with the stream line in the suction sump, on this basis, CFD numerical simulation is conducted with the eddy-eliminating of the triangle guide cone and traditional guide cone. The results show that, for eddy-eliminating measures, with the height of triangular guide cone from 0 to 0.407HZ/DL , the excessive triangle guide cone hinder water into the flared pipe. With the width of triangular guide cone from 0.5 to 1.0BZ/DL , increasing width of triangular guide cone may increase the pumping hydraulic performance and pumping efficiency. However with the width of triangular guide cone from 0.5 to 1.0 BZ/DL , too broad traditional guide cone hinder water into the flared pipe. In the design discharge, whether triangle guide cone or traditional guide cone have a little effect on the efficiency of the pumping station. But in terms of the eddy-eliminating on the bottom of suction sump, it is necessary to set up guide cone.

  15. The Na(+)/Ca(2+), K(+) exchanger 2 modulates mammalian cone phototransduction.

    PubMed

    Sakurai, Keisuke; Vinberg, Frans; Wang, Tian; Chen, Jeannie; Kefalov, Vladimir J

    2016-01-01

    Calcium ions (Ca(2+)) modulate the phototransduction cascade of vertebrate cone photoreceptors to tune gain, inactivation, and light adaptation. In darkness, the continuous current entering the cone outer segment through cGMP-gated (CNG) channels is carried in part by Ca(2+), which is then extruded back to the extracellular space. The mechanism of Ca(2+) extrusion from mammalian cones is not understood. The dominant view has been that the cone-specific isoform of the Na(+)/Ca(2+), K(+) exchanger, NCKX2, is responsible for removing Ca(2+) from their outer segments. However, indirect evaluation of cone function in NCKX2-deficient (Nckx2(-/-)) mice by electroretinogram recordings revealed normal photopic b-wave responses. This unexpected result suggested that NCKX2 may not be involved in the Ca(2+) homeostasis of mammalian cones. To address this controversy, we examined the expression of NCKX2 in mouse cones and performed transretinal recordings from Nckx2(-/-) mice to determine the effect of NCKX2 deletion on cone function directly. We found that Nckx2(-/-) cones exhibit compromised phototransduction inactivation, slower response recovery and delayed background adaptation. We conclude that NCKX2 is required for the maintenance of efficient Ca(2+) extrusion from mouse cones. However, surprisingly, Nckx2(-/-) cones adapted normally in steady background light, indicating the existence of additional Ca(2+)-extruding mechanisms in mammalian cones. PMID:27580676

  16. The Na+/Ca2+, K+ exchanger 2 modulates mammalian cone phototransduction

    PubMed Central

    Sakurai, Keisuke; Vinberg, Frans; Wang, Tian; Chen, Jeannie; Kefalov, Vladimir J.

    2016-01-01

    Calcium ions (Ca2+) modulate the phototransduction cascade of vertebrate cone photoreceptors to tune gain, inactivation, and light adaptation. In darkness, the continuous current entering the cone outer segment through cGMP-gated (CNG) channels is carried in part by Ca2+, which is then extruded back to the extracellular space. The mechanism of Ca2+ extrusion from mammalian cones is not understood. The dominant view has been that the cone-specific isoform of the Na+/Ca2+, K+ exchanger, NCKX2, is responsible for removing Ca2+ from their outer segments. However, indirect evaluation of cone function in NCKX2-deficient (Nckx2−/−) mice by electroretinogram recordings revealed normal photopic b-wave responses. This unexpected result suggested that NCKX2 may not be involved in the Ca2+ homeostasis of mammalian cones. To address this controversy, we examined the expression of NCKX2 in mouse cones and performed transretinal recordings from Nckx2−/− mice to determine the effect of NCKX2 deletion on cone function directly. We found that Nckx2−/− cones exhibit compromised phototransduction inactivation, slower response recovery and delayed background adaptation. We conclude that NCKX2 is required for the maintenance of efficient Ca2+ extrusion from mouse cones. However, surprisingly, Nckx2−/− cones adapted normally in steady background light, indicating the existence of additional Ca2+-extruding mechanisms in mammalian cones. PMID:27580676

  17. Neuronal growth cones respond to laser-induced axonal damage

    PubMed Central

    Wu, Tao; Mohanty, Samarendra; Gomez-Godinez, Veronica; Shi, Linda Z.; Liaw, Lih-Huei; Miotke, Jill; Meyer, Ronald L.; Berns, Michael W.

    2012-01-01

    Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons in vitro. The axons underwent a localized decrease in thickness (‘thinning’) within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model. PMID:21831892

  18. Nonperturbative renormalization of QED in light-cone quantization

    SciTech Connect

    Hiller, J.R.; Brodsky, S.J.

    1996-08-01

    As a precursor to work on QCD, we study the dressed electron in QED non-perturbatively. The calculational scheme uses an invariant mass cutoff, discretized light cone quantization, a Tamm-Dancoff truncation of the Fock space, and a small photon mass. Nonperturbative renormalization of the coupling and electron mass is developed.

  19. S-cones in thin shells under indentation

    NASA Astrophysics Data System (ADS)

    Nasto, Alice; Ajdari, Amin; Lazarus, Arnaud; Vaziri, Ashkan; Reis, Pedro

    2012-02-01

    We perform a hybrid experimental and numerical investigation of the localization of deformation in indented thin spherical elastic shells. Past the initial linear response, an inverted cap develops as a Pogorelov circular ridge. For further indentation, this ridge looses axis-symmetry and sharp points of localized curvature form. We refer to these localized objects as s-cones (for shell-cones), in contrast with their developable cousins in plates (d-cones). We quantify the effect of systematically varying the indenter's radius of curvature (from point to plate load) on the formation and evolution of s-cones. In our precision desktop-scale experiments we use rapid prototyped elastomeric shells and rigid indenters of various shape. The mechanical response is measured through load-displacement compression tests and the deformation process is further characterized through digital imaging. In parallel, the experimental results are contrasted against nonlinear Finite Element simulations. Merging these two complementary approaches allows us to gain further physical insight towards rationalizing this geometrically nonlinear process.

  20. Cardiac cone-beam CT volume reconstruction using ART

    SciTech Connect

    Nielsen, T.; Manzke, R.; Proksa, R.; Grass, M.

    2005-04-01

    Modern computed tomography systems allow volume imaging of the heart. Up to now, approximately two-dimensional (2D) and 3D algorithms based on filtered backprojection are used for the reconstruction. These algorithms become more sensitive to artifacts when the cone angle of the x-ray beam increases as it is the current trend of computed tomography (CT) technology. In this paper, we investigate the potential of iterative reconstruction based on the algebraic reconstruction technique (ART) for helical cardiac cone-beam CT. Iterative reconstruction has the advantages that it takes the cone angle into account exactly and that it can be combined with retrospective cardiac gating fairly easily. We introduce a modified ART algorithm for cardiac CT reconstruction. We apply it to clinical cardiac data from a 16-slice CT scanner and compare the images to those obtained with a current analytical reconstruction method. In a second part, we investigate the potential of iterative reconstruction for a large area detector with 256 slices. For the clinical cases, iterative reconstruction produces excellent images of diagnostic quality. For the large area detector, iterative reconstruction produces images superior to analytical reconstruction in terms of cone-beam artifacts.

  1. Long-term results of the Wagner cone prosthesis

    PubMed Central

    Schraml, Annemarie; Hohenberger, Gerd

    2007-01-01

    The Wagner cone prosthesis is indicated in uncemented total hip replacement of cases with cylinder-shaped femurs, deformed femurs, femurs with increased antetorsion, and in conditions of intramedullary bony scar tissue after previous osteotomies. The objective of this study is to present long-term results. From January 1, 1993 to December 31, 1995, 132 implantations were made with the Wagner cone prosthesis. We report the clinical and radiographic results of 94 cone prostheses with a mean observation period of 11.5 years. The Merle d’Aubigné score improved from a preoperative mean value of 8.8 to a postoperative mean of 16.3. The radiographic evaluation revealed 32 cases with cortical hypertrophy, 73 cases with atrophy of the proximal femur, and 18 cases with complete pedestal formation. Radiolucencies over Gruen zones 1 and 7 occurred in 42 cases; only zone 1 was affected in 24 cases. Complications included three deep infections, three acetabular revisions, five total joint revisions, one recurrent luxation, and three heterotopic ossifications. In spite of the fact that the examined cohort often included patients who had undergone multiple previous operations (a maximum of six) of the proximal femur or the acetabulum, the long-term results of the Wagner cone prostheses were very promising. PMID:17932669

  2. Growth Cone Biomechanics in Peripheral and Central Nervous System Neurons

    NASA Astrophysics Data System (ADS)

    Urbach, Jeffrey; Koch, Daniel; Rosoff, Will; Geller, Herbert

    2012-02-01

    The growth cone, a highly motile structure at the tip of an axon, integrates information about the local environment and modulates outgrowth and guidance, but little is known about effects of external mechanical cues and internal mechanical forces on growth-cone mediated guidance. We have investigated neurite outgrowth, traction forces and cytoskeletal substrate coupling on soft elastic substrates for dorsal root ganglion (DRG) neurons (from the peripheral nervous system) and hippocampal neurons (from the central) to see how the mechanics of the microenvironment affect different populations. We find that the biomechanics of DRG neurons are dramatically different from hippocampal, with DRG neurons displaying relatively large, steady traction forces and maximal outgrowth and forces on substrates of intermediate stiffness, while hippocampal neurons display weak, intermittent forces and limited dependence of outgrowth and forces on substrate stiffness. DRG growth cones have slower rates of retrograde actin flow and higher density of localized paxillin (a protein associated with substrate adhesion complexes) compared to hippocampal neurons, suggesting that the difference in force generation is due to stronger adhesions and therefore stronger substrate coupling in DRG growth cones.

  3. 95. VIEW OF ZINC FEEDER FROM SOUTHEAST. NOTE FEEDER CONE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    95. VIEW OF ZINC FEEDER FROM SOUTHEAST. NOTE FEEDER CONE AND PIPING FROM VACUUM RECEIVER ON LEFT. PRECIPITATE PUMP MOTOR MOUNT VISIBLE BELOW FEEDER STAIRS, PUMP AND MOTOR MISSING. SUMPS ARE LOCATED UNDER THIS FLOOR, WITH ACCESS TO HATCH TO THE RIGHT OF FEEDER STAIR. - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD

  4. 63. Historic detail drawing of inlet duct cone on exhaust ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. Historic detail drawing of inlet duct cone on exhaust scrubber at building 202, June 18, 1955. NASA GRC drawing no. CD-101266. (On file at NASA Glenn Research Center). - Rocket Engine Testing Facility, GRC Building No. 202, NASA Glenn Research Center, Cleveland, Cuyahoga County, OH

  5. Dirac cones in the spectrum of bond-decorated graphenes

    SciTech Connect

    Van den Heuvel, Willem Soncini, Alessandro

    2014-06-21

    We present a two-band model based on periodic Hückel theory, which is capable of predicting the existence and position of Dirac cones in the first Brillouin zone of an infinite class of two-dimensional periodic carbon networks, obtained by systematic perturbation of the graphene connectivity by bond decoration, that is by inclusion of arbitrary π-electron Hückel networks into each of the three carbon–carbon π-bonds within the graphene unit cell. The bond decoration process can fundamentally modify the graphene unit cell and honeycomb connectivity, representing a simple and general way to describe many cases of graphene chemical functionalization of experimental interest, such as graphyne, janusgraphenes, and chlorographenes. Exact mathematical conditions for the presence of Dirac cones in the spectrum of the resulting two-dimensional π-networks are formulated in terms of the spectral properties of the decorating graphs. Our method predicts the existence of Dirac cones in experimentally characterized janusgraphenes and chlorographenes, recently speculated on the basis of density functional theory calculations. For these cases, our approach provides a proof of the existence of Dirac cones, and can be carried out at the cost of a back of the envelope calculation, bypassing any diagonalization step, even within Hückel theory.

  6. 36. EASTERN VIEW OF BOTTOM CONE OF GAS COOLING TOWER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    36. EASTERN VIEW OF BOTTOM CONE OF GAS COOLING TOWER No. 1 AND TWO GAS COOLING TOWER SERVICE WATER PUMPS IN THE GAS WASHER PUMP HOUSE. - U.S. Steel Duquesne Works, Basic Oxygen Steelmaking Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  7. Euler Cone Aperture in a Special Euler-Poinsot Case

    NASA Astrophysics Data System (ADS)

    Ciobanu, Monica

    2008-09-01

    We try to give a personal explanation to the difference between Euler and Chandler periods in Earth's rotation. Continuing to analyze the Euler-Poinsot motion in a special case (gyroscope), we address the question: is the aperture of the Euler cone nonzero?

  8. Variability and Reliabiltiy in Axon Growth Cone Navigation Decision Making

    NASA Astrophysics Data System (ADS)

    Garnelo, Marta; Ricoult, Sébastien G.; Juncker, David; Kennedy, Timothy E.; Faisal, Aldo A.

    2015-03-01

    The nervous system's wiring is a result of axon growth cones navigating through specific molecular environments during development. In order to reach their target, growth cones need to make decisions under uncertainty as they are faced with stochastic sensory information and probabilistic movements. The overall system therefore exhibits features of whole organisms (perception, decision making, action) in the subset of a single cell. We aim to characterise growth cone navigation in defined nano-dot guidance cue environments, by using the tools of computational neuroscience to conduct ``molecular psychophysics.'' We start with a generative model of growth cone behaviour and we 1. characterise sensory and internal sources of noise contributing to behavioural variables, by combining knowledge of the underlying stochastic dynamics in cue sensing and the growth of the cytoskeleton. This enables us to 2. produce bottom-up lower limit estimates of behavioural response reliability and visualise it as probability distributions over axon growth trajectories. Given this information we can match our in silico model's ``psychometric'' decision curves with empirical data. Finally we use a Monte-Carlo approach to predict response distributions of axon trajectories from our model.

  9. Model based scatter correction for cone-beam computed tomography

    NASA Astrophysics Data System (ADS)

    Wiegert, Jens; Bertram, Matthias; Rose, Georg; Aach, Til

    2005-04-01

    Scattered radiation is a major source of image degradation and nonlinearity in flat detector based cone-beam CT. Due to the bigger irradiated volume the amount of scattered radiation in true cone-beam geometry is considerably higher than for fan beam CT. This on the one hand reduces the signal to noise ratio, since the additional scattered photons contribute only to the noise and not to the measured signal, and on the other hand cupping and streak artifacts arise in the reconstructed volume. Anti-scatter grids composed of lead lamellae and interspacing material decrease the SNR for flat detector based CB-CT geometry, because the beneficial scatter attenuating effect is overcompensated by the absorption of primary radiation. Additionally, due to the high amount of scatter that still remains behind the grid, cupping and streak artifacts cannot be reduced sufficiently. Computerized scatter correction schemes are therefore essential for achieving artifact-free reconstructed images in cone-beam CT. In this work, a fast model based scatter correction algorithm is proposed, aiming at accurately estimating the level and spatial distribution of scattered radiation background in each projection. This will allow for effectively reducing streak and cupping artifacts due to scattering in cone-beam CT applications.

  10. Functional significance of the taper of vertebrate cone photoreceptors

    PubMed Central

    Hárosi, Ferenc I.

    2012-01-01

    Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between

  11. Relationship Between Foveal Cone Specialization and Pit Morphology in Albinism

    PubMed Central

    Wilk, Melissa A.; McAllister, John T.; Cooper, Robert F.; Dubis, Adam M.; Patitucci, Teresa N.; Summerfelt, Phyllis; Anderson, Jennifer L.; Stepien, Kimberly E.; Costakos, Deborah M.; Connor, Thomas B.; Wirostko, William J.; Chiang, Pei-Wen; Dubra, Alfredo; Curcio, Christine A.; Brilliant, Murray H.; Summers, C. Gail; Carroll, Joseph

    2014-01-01

    Purpose. Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. Methods. We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. Results. We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. Conclusions. Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue. PMID:24845642

  12. Calcium regulates vesicle replenishment at the cone ribbon synapse.

    PubMed

    Babai, Norbert; Bartoletti, Theodore M; Thoreson, Wallace B

    2010-11-24

    Cones release glutamate-filled vesicles continuously in darkness, and changing illumination modulates this release. Because sustained release in darkness is governed by vesicle replenishment rates, we analyzed how cone membrane potential regulates replenishment. Synaptic release from cones was measured by recording postsynaptic currents in Ambystoma tigrinum horizontal or OFF bipolar cells evoked by depolarization of simultaneously voltage-clamped cones. We measured replenishment after attaining a steady state between vesicle release and replenishment using trains of test pulses. Increasing Ca(2+) currents (I(Ca)) by changing the test step from -30 to -10 mV increased replenishment. Lengthening -30 mV test pulses to match the Ca(2+) influx during 25 ms test pulses to -10 mV produced similar replenishment rates. Reducing Ca(2+) driving force by using test steps to +30 mV slowed replenishment. Using UV flashes to reverse inhibition of I(Ca) by nifedipine accelerated replenishment. Increasing [Ca(2+)](i) by flash photolysis of caged Ca(2+) also accelerated replenishment. Replenishment, but not the initial burst of release, was enhanced by using an intracellular Ca(2+) buffer of 0.5 mm EGTA rather than 5 mm EGTA, and diminished by 1 mm BAPTA. This suggests that although release and replenishment exhibited similar Ca(2+) dependencies, release sites are <200 nm from Ca(2+) channels but replenishment sites are >200 nm away. Membrane potential thus regulates replenishment by controlling Ca(2+) influx, principally by effects on replenishment mechanisms but also by altering releasable pool size. This in turn provides a mechanism for converting changes in light intensity into changes in sustained release at the cone ribbon synapse. PMID:21106825

  13. A quantitative study of growth cone filopodial extension.

    PubMed

    Argiro, V; Bunge, M B; Johnson, M I

    1985-01-01

    The extension of filopodia from growth cones of regenerating neurites from rat superior cervical ganglion neurons in tissue culture was studied. Cultures were grown on a thin layer of fibrous collagen and maintained in a medium containing serum and nerve growth factor. Time-lapse cinematography and computer-assisted morphometry were used to observe and measure the kinetics of extension of individual filopodia. Filopodia extended from the growth cone margin, trailing neurite, or from each other. Frequently, extension was preceded by the appearance at the cone margin of a nodule of cytoplasm which appeared dense in phase-contrast optics. Branch points between adjacent extending filopodia remained fixed with respect to the growth cone while the filopodia lengthened. The rate of extension was maximum just after initiation (0.12 +/- 0.4 micron/sec; mean +/- SD; n = 36) and declined thereafter until the filopodium collapsed. This initial rate of extension was directly correlated with the eventual length of the filopodium (r = 0.67). Filopodia of growth cones arising from embryonic neurons exhibited higher initial extension rates (range: 0.07 to 0.20 micron/sec; mean = 0.13 micron/sec) than those of postnatal neurons (range: 0.01 to 0.13 micron/sec; mean = 0.09 micron/sec). These data are discussed in relation to a model proposed by Tilney and Inoue [1982] for the extension, by distal addition of G-actin to growing filaments, of another type of elongating process filled with microfilaments, the acrosomal process of Thyone sperm.

  14. Anti-scatter grid evaluation for wide-cone CT

    NASA Astrophysics Data System (ADS)

    Melnyk, Roman; Boudry, John; Liu, Xin; Adamak, Mark

    2014-03-01

    Scatter is a significant source of image artifacts in wide-cone CT. Scatter management includes both scatter rejection and scatter correction. The common scatter rejection approach is to use an anti-scatter grid (ASG). Conventional CT scanners (with detector coverage not exceeding 40mm along the patient axis) typically employ one-dimensional (1D) ASGs. Such grids are quite effective for small cone angles. For larger cone angles, however, simply increasing the aspect ratio of a 1D ASG is not sufficient. In addition, a 1D ASG offers no scatter rejection along the patient axis. To ensure adequate image quality in wide-cone CT, a two-dimensional (2D) ASG is needed. In this work, we measured the amount of scatter and the degree of image artifacts typically attributable to scatter for four prototype 2D ASG designs, and we compared those to a 1D ASG. The scatter was measured in terms of the scatter-toprimary ratio (SPR). The cupping and ghosting artifacts were assessed through quantitative metrics. For the 2D ASGs, when compared to the 1D ASG, the SPR decreased by up to 66% and 75% for 35cm water and 48cm polyethylene, respectively, phantoms, at 80-160mm apertures (referenced to isocenter), as measured by the pinhole method. As measured by the two-aperture method, the SPR reduction was 59%-68% at isocenter for the 35cm water phantom at 160mm aperture. The cupping artifact was decreased by up to ~80%. The ghosting artifact was reduced as well. The results of the evaluation clearly demonstrate the advantage of using a 2D ASG for wide-cone CT.

  15. Evolutionary loss of cone photoreception in balaenid whales reveals circuit stability in the mammalian retina.

    PubMed

    Schweikert, Lorian E; Fasick, Jeffry I; Grace, Michael S

    2016-10-01

    The classical understanding of mammalian vision is that it occurs through "duplex" retinae containing both rod and cone photoreceptors, the signals from which are processed through rod- and/or cone-specific signaling pathways. The recent discovery of rod monochromacy in some cetacean lineages provides a novel opportunity to investigate the effects of an evolutionary loss of cone photoreception on retinal organization. Sequence analysis of right whale (Eubalaena glacialis; family Balaenidae) cDNA derived from long-wavelength sensitive (LWS) cone opsin mRNA identified several mutations in the opsin coding sequence, suggesting the loss of cone cell function, but maintenance of non-photosensitive, cone opsin mRNA-expressing cells in the retina. Subsequently, we investigated the retina of the closely related bowhead whale (Balaena mysticetus; family Balaenidae) to determine how the loss of cone-mediated photoreception affects light signaling pathways in the retina. Anti-opsin immunofluorescence demonstrated the total loss of cone opsin expression in B. mysticetus, whereas light microscopy, transmission electron microscopy, and bipolar cell (protein kinase C-α [PKC-α] and recoverin) immunofluorescence revealed the maintenance of cone soma, putative cone pedicles, and both rod and cone bipolar cell types. These findings represent the first immunological and anatomical evidence of a naturally occurring rod-monochromatic mammalian retina, and suggest that despite the loss of cone-mediated photoreception, the associated cone signaling structures (i.e., cone synapses and cone bipolar cells) may be maintained for multichannel rod-based signaling in balaenid whales. J. Comp. Neurol. 524:2873-2885, 2016. © 2016 Wiley Periodicals, Inc. PMID:26972896

  16. Cone selection by Eurasian red squirrels in mixed conifer forests in the Italian Alps

    NASA Astrophysics Data System (ADS)

    Molinari, A.; Wauters, L. A.; Airoldi, G.; Cerinotti, F.; Martinoli, A.; Tosi, G.

    2006-07-01

    Tree squirrels are arboreal granivores that harvest and consume tree seeds both prior to and after seed-dispersal. Inter- and intraspecific patterns of seed predation suggest that squirrels may exert strong selective pressure on cone morphology and patterns of cone production, and suggest coevolutionary interactions between squirrels and conifers. In some pine species (genus Pinus), mutualistic relationships have evolved between cone (seed) traits and seed-dispersal behaviour by birds and rodents. In other species, feeding by seed predators has selected for cone traits that decrease intensity of seed consumption. In mixed conifer forests, red squirrels ( Sciurus vulgaris) feed intensively in some (target) trees but avoid others (nontarget trees). Here we explore defensive cone traits and seed traits correlated with tree selection for conifer species with different seed-dispersal strategies. No selection for cone traits existed in Pinus cembra, which has large wingless seeds, dispersed by birds and rodents. In Picea abies, the most favoured species, target trees had cones with more seeds per cone than nontarget trees, and number of seeds increased with cone length. Cone selection was most pronounced in Pinus sylvestris, where target trees had bigger cones with more seeds and higher total seed mass than nontarget trees. However, ratio of seed mass on cone mass did not differ among target and nontarget trees, suggesting that bigger cones also had more protective tissue, probably increasing difficulties for seed predators to gain access to seeds. Our results suggest that cone and seed traits of P. cembra facilitate seed consumption by squirrels, but that defensive cone traits of small-seeded conifers, in combination with annual differences in seed production (masting), might be the result of coevolution with seed-eating squirrels.

  17. Three Different Cone Opsin Gene Array Mutational Mechanisms with Genotype–Phenotype Correlation and Functional Investigation of Cone Opsin Variants

    PubMed Central

    Gardner, Jessica C; Liew, Gerald; Quan, Ying-Hua; Ermetal, Burcu; Ueyama, Hisao; Davidson, Alice E; Schwarz, Nele; Kanuga, Naheed; Chana, Ravinder; Maher, Eamonn R; Webster, Andrew R; Holder, Graham E; Robson, Anthony G; Cheetham, Michael E; Liebelt, Jan; Ruddle, Jonathan B; Moore, Anthony T; Michaelides, Michel; Hardcastle, Alison J

    2014-01-01

    Mutations in the OPN1LW (L-) and OPN1MW (M-)cone opsin genes underlie a spectrum of cone photoreceptor defects from stationary loss of color vision to progressive retinal degeneration. Genotypes of 22 families with a range of cone disorders were grouped into three classes: deletions of the locus control region (LCR); missense mutation (p.Cys203Arg) in an L-/M-hybrid gene; and exon 3 single-nucleotide polymorphism (SNP) interchange haplotypes in an otherwise normal gene array. Moderate-to-high myopia was observed in all mutation categories. Individuals with LCR deletions or p.Cys203Arg mutations were more likely to have nystagmus and poor vision, with disease progression in some p.Cys203Arg patients. Three disease-associated exon 3 SNP haplotypes encoding LIAVA, LVAVA, or MIAVA were identified in our cohort. These patients were less likely to have nystagmus but more likely to show progression, with all patients over the age of 40 years having marked macular abnormalities. Previously, the haplotype LIAVA has been shown to result in exon 3 skipping. Here, we show that haplotypes LVAVA and MIAVA also result in aberrant splicing, with a residual low level of correctly spliced cone opsin. The OPN1LW/OPN1MW:c.532A>G SNP, common to all three disease-associated haplotypes, appears to be principally responsible for this mutational mechanism. PMID:25168334

  18. Short Wavelength Cone Opsin Is Not Expressed in the Retina of Arboreal African Pangolin (Manis tricuspis).

    PubMed

    Adekanmbi, Adejoke J; Adekanmbi, Adefisayo A; Akinola, Oluwole B

    2016-01-01

    This paper reports a study of cone photoreceptors present in the retina of Manis tricuspis. Specifically, the LWS (L-) opsin expressed in longwave-sensitive cones and SWS1 (S-) opsin shortwave-sensitive cones were targeted. Vertical sections revealed reactivity to a cone marker, peanut agglutinin (PNA), and to an LWS antibody, but not to an SWS1 antibody. This suggests that the Manis tricuspis visual system is not able to discriminate shorter wavelengths from longer wavelengths because the short wavelength cones are not expressed in their retina. PMID:27242946

  19. Cone photopigment in older subjects: decreased optical density in early age-related macular degeneration

    NASA Astrophysics Data System (ADS)

    Elsner, Ann E.; Burns, Stephen A.; Weiter, John J.

    2002-01-01

    We measured changes to cone photoreceptors in patients with early age-related macular degeneration. The data of 53 patients were compared with normative data for color matching measurements of long- and middle-wavelength-sensitive cones in the central macula. A four-parameter model quantified cone photopigment optical density and kinetics. Cone photopigment optical density was on average less for the patients than for normal subjects and was uncorrelated with visual acuity. More light was needed to reduce the photopigment density by 50% in the steady state for patients. These results imply that cone photopigment optical density is reduced by factors other than slowed kinetics.

  20. Short Wavelength Cone Opsin Is Not Expressed in the Retina of Arboreal African Pangolin (Manis tricuspis)

    PubMed Central

    Adekanmbi, Adejoke J.; Adekanmbi, Adefisayo A.; Akinola, Oluwole B.

    2016-01-01

    This paper reports a study of cone photoreceptors present in the retina of Manis tricuspis. Specifically, the LWS (L-) opsin expressed in longwave-sensitive cones and SWS1 (S-) opsin shortwave-sensitive cones were targeted. Vertical sections revealed reactivity to a cone marker, peanut agglutinin (PNA), and to an LWS antibody, but not to an SWS1 antibody. This suggests that the Manis tricuspis visual system is not able to discriminate shorter wavelengths from longer wavelengths because the short wavelength cones are not expressed in their retina. PMID:27242946

  1. Short Wavelength Cone Opsin Is Not Expressed in the Retina of Arboreal African Pangolin (Manis tricuspis).

    PubMed

    Adekanmbi, Adejoke J; Adekanmbi, Adefisayo A; Akinola, Oluwole B

    2016-01-01

    This paper reports a study of cone photoreceptors present in the retina of Manis tricuspis. Specifically, the LWS (L-) opsin expressed in longwave-sensitive cones and SWS1 (S-) opsin shortwave-sensitive cones were targeted. Vertical sections revealed reactivity to a cone marker, peanut agglutinin (PNA), and to an LWS antibody, but not to an SWS1 antibody. This suggests that the Manis tricuspis visual system is not able to discriminate shorter wavelengths from longer wavelengths because the short wavelength cones are not expressed in their retina.

  2. Possible Rootless Cones or Pseudo craters on Mars

    NASA Technical Reports Server (NTRS)

    1999-01-01

    High-resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) have revealed small cone-shaped structures on lava flows in southern Elysium Planitia, Marte Valles, and northwestern Amazonis Planitia in the northern hemisphere of the red planet. The most likely interpretation of these cones is that they may be volcanic features known as 'pseudo craters' or 'rootless cones.' They share several key characteristics with pseudo craters on Earth: they are distributed in small clusters independent of structural patterns, are superimposed on fresh lava flows, and they do not appear to have erupted lavas themselves. The white box in the picture above left shows the location of one of the MOC images of possible pseudocraters on Mars. The white box is drawn upon a MOC red wide angle context image acquired at the same time as the high resolution view, shown on the right above. Located in northwestern Amazonis Planitia near 24.8oN, 171.3oW, both the context image and high-resolution view are illuminated from the lower left. The high resolution view shows several possible pseudocraters (cone-shaped features with holes or pits at their summits) that occur on top of a rough-textured lava plain. The context frame covers an area 115 km (71 mi) across, the high-resolution view is 3 km (1.9 mi) across. Pseudocraters form by explosions due to the interaction of molten lava with a water-rich surface. Possible martian pseudocraters are of interest because they may mark the locations of shallow water or ice at the time the lava was emplaced. Viking Orbiter images have shown structures in other regions of Mars that were interpreted to be pseudocraters, but the interpretations were uncertain because the morphology was poorly resolved, it was unclear if they occurred on volcanic surfaces, and they have diameters as much as a factor of 3 larger than terrestrial pseudocraters. The cone-shaped morphology is well resolved in the cones imaged by MOC, and they have

  3. Development of a full ice-cream cone model for halo CME structures

    NASA Astrophysics Data System (ADS)

    Na, Hyeonock; Moon, Yong-Jae

    2015-04-01

    The determination of three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) is very important for space weather forecast. To estimate these parameters, several cone models based on a flat cone or a shallow ice-cream cone with spherical front have been suggested. In this study, we investigate which cone model is proper for halo CME morphology using 33 CMEs which are identified as halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From geometrical parameters of these CMEs such as their front curvature, we find that near full ice-cream cone CMEs (28 events) are dominant over shallow ice-cream cone CMEs (5 events). So we develop a new full ice-cream cone model by assuming that a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, (4) minimize the difference between the estimated projection points with the observed ones. We apply this model to several halo CMEs and compare the results with those from other methods such as a Graduated Cylindrical Shell model and a geometrical triangulation method.

  4. The uniqueness of the solution of cone-like inversion models for halo CMEs

    NASA Astrophysics Data System (ADS)

    Zhao, X. P.

    2006-12-01

    Most of elliptic halo CMEs are believed to be formed by the Thompson scattering of the photospheric light by the 3-D cone-like shell of the CME plasma. To obtain the real propagation direction and angular width of the halo CMEs, such cone-like inversion models as the circular cone, the elliptic cone and the ice-cream cone models have been suggested recently. Because the number of given parameters that are used to characterize 2-D elliptic halo CMEs observed by one spacecraft are less than the number of unknown parameters that are used to characterize the 3-D elliptic cone model, the solution of the elliptic cone model is not unique. Since it is difficult to determine whether or not an observed halo CME is formed by an circular cone or elliptic cone shell, the solution of circular cone model may often be not unique too. To fix the problem of the uniqueness of the solution of various 3-D cone-like inversion models, this work tries to develop the algorithm for using the data from multi-spacecraft, such as the STEREO A and B, and the Solar Sentinels.

  5. Activated mTORC1 promotes long-term cone survival in retinitis pigmentosa mice

    PubMed Central

    Venkatesh, Aditya; Ma, Shan; Le, Yun Z.; Hall, Michael N.; Rüegg, Markus A.; Punzo, Claudio

    2015-01-01

    Retinitis pigmentosa (RP) is an inherited photoreceptor degenerative disorder that results in blindness. The disease is often caused by mutations in genes that are specific to rod photoreceptors; however, blindness results from the secondary loss of cones by a still unknown mechanism. Here, we demonstrated that the mammalian target of rapamycin complex 1 (mTORC1) is required to slow the progression of cone death during disease and that constitutive activation of mTORC1 in cones is sufficient to maintain cone function and promote long-term cone survival. Activation of mTORC1 in cones enhanced glucose uptake, retention, and utilization, leading to increased levels of the key metabolite NADPH. Moreover, cone death was delayed in the absence of the NADPH-sensitive cell death protease caspase 2, supporting the contribution of reduced NADPH in promoting cone death. Constitutive activation of mTORC1 preserved cones in 2 mouse models of RP, suggesting that the secondary loss of cones is caused mainly by metabolic deficits and is independent of a specific rod-associated mutation. Together, the results of this study address a longstanding question in the field and suggest that activating mTORC1 in cones has therapeutic potential to prolong vision in RP. PMID:25798619

  6. Adaptive optics retinal imaging reveals S-cone dystrophy in tritan color-vision deficiency

    NASA Astrophysics Data System (ADS)

    Baraas, Rigmor C.; Carroll, Joseph; Gunther, Karen L.; Chung, Mina; Williams, David R.; Foster, David H.; Neitz, Maureen

    2007-05-01

    Tritan color-vision deficiency is an autosomal dominant disorder associated with mutations in the short-wavelength-sensitive- (S-) cone-pigment gene. An unexplained feature of the disorder is that individuals with the same mutation manifest different degrees of deficiency. To date, it has not been possible to examine whether any loss of S-cone function is accompanied by physical disruption in the cone mosaic. Two related tritan subjects with the same novel mutation in their S-cone-opsin gene, but different degrees of deficiency, were examined. Adaptive optics was used to obtain high-resolution retinal images, which revealed distinctly different S-cone mosaics consistent with their discrepant phenotypes. In addition, a significant disruption in the regularity of the overall cone mosaic was observed in the subject completely lacking S-cone function. These results taken together with other recent findings from molecular genetics indicate that, with rare exceptions, tritan deficiency is progressive in nature.

  7. Neurosurgeon as innovator: William V. Cone (1897-1959).

    PubMed

    Preul, M C; Stratford, J; Bertrand, G; Feindel, W

    1993-10-01

    Neurosurgeons are well known for being productive researchers and innovators. Few, however, have possessed the prolific ingenuity of William Cone. In 1934, he and William Penfield were cofounders of the Montreal Neurological Institute where, until 1959, he filled the twin roles of neurosurgeon-in-chief and neuropathologist. Because he did not find writing easy, many of his technical inventions and refinements remained unpublished. His numerous innovations included the extensive use of twist-drill technique for biopsy, drainage for subdural hematoma and cerebral abscess, and ventriculography. In the mid-1940's, he developed power tools driven by nitrogen that led to the modern, universally used air-driven tool systems. He had a special interest in the treatment of spinal dysfunction, for which he invented the Cone-Barton skull-traction tongs along with the Cone spinal operating table. He also devised operative procedures for vertebral fracture-dislocation and craniospinal anomalies. For the maintenance of muscle tone in the paralyzed bladder, he constructed a tidal drainage system. He introduced and popularized ventriculoperitoneal shunting techniques and carried out some of the earliest experimental trails to treat brain infections with sulphonamide and antibiotic drugs. He designed his own set of surgical suction devices, bone rongeurs, and a personal suction "air-conditioning" system for each surgeon. He had a keen early interest in intracranial tumors, and also demonstrated on monkeys how subdural mass lesions caused pupillary dilation and mesial temporal lobe damage due to cerebral compression. His work for the military during World War II on effects of altitude on brain pressure remained classified for many years. The first clipping and excision of an intracranial aneurysm is attributed to Cone. Although Penfield was known as "the Chief," Cone was referred to as "the Boss." His fervent dedication to provide total care to his patients was expressed in round

  8. Determination of HCME 3-D parameters using a full ice-cream cone model

    NASA Astrophysics Data System (ADS)

    Na, Hyeonock; Moon, Yong-Jae; Lee, Harim

    2016-05-01

    It is very essential to determine three dimensional parameters (e.g., radial speed, angular width, source location) of Coronal Mass Ejections (CMEs) for space weather forecast. Several cone models (e.g., an elliptical cone model, an ice-cream cone model, an asymmetric cone model) have been examined to estimate these parameters. In this study, we investigate which cone type is close to a halo CME morphology using 26 CMEs: halo CMEs by one spacecraft (SOHO or STEREO-A or B) and as limb CMEs by the other ones. From cone shape parameters of these CMEs such as their front curvature, we find that near full ice-cream cone type CMEs are much closer to observations than shallow ice-cream cone type CMEs. Thus we develop a new cone model in which a full ice-cream cone consists of many flat cones with different heights and angular widths. This model is carried out by the following steps: (1) construct a cone for given height and angular width, (2) project the cone onto the sky plane, (3) select points comprising the outer boundary, and (4) minimize the difference between the estimated projection speeds with the observed ones. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3-D parameters from our method are similar to those from other stereoscopic methods (a geometrical triangulation method and a Graduated Cylindrical Shell model) based on multi-spacecraft data. We are developing a general ice-cream cone model whose front shape is a free parameter determined by observations.

  9. Avian Cone Photoreceptors Tile the Retina as Five Independent, Self-Organizing Mosaics

    PubMed Central

    Kram, Yoseph A.; Mantey, Stephanie; Corbo, Joseph C.

    2010-01-01

    The avian retina possesses one of the most sophisticated cone photoreceptor systems among vertebrates. Birds have five types of cones including four single cones, which support tetrachromatic color vision and a double cone, which is thought to mediate achromatic motion perception. Despite this richness, very little is known about the spatial organization of avian cones and its adaptive significance. Here we show that the five cone types of the chicken independently tile the retina as highly ordered mosaics with a characteristic spacing between cones of the same type. Measures of topological order indicate that double cones are more highly ordered than single cones, possibly reflecting their posited role in motion detection. Although cones show spacing interactions that are cell type-specific, all cone types use the same density-dependent yardstick to measure intercone distance. We propose a simple developmental model that can account for these observations. We also show that a single parameter, the global regularity index, defines the regularity of all five cone mosaics. Lastly, we demonstrate similar cone distributions in three additional avian species, suggesting that these patterning principles are universal among birds. Since regular photoreceptor spacing is critical for uniform sampling of visual space, the cone mosaics of the avian retina represent an elegant example of the emergence of adaptive global patterning secondary to simple local interactions between individual photoreceptors. Our results indicate that the evolutionary pressures that gave rise to the avian retina's various adaptations for enhanced color discrimination also acted to fine-tune its spatial sampling of color and luminance. PMID:20126550

  10. The effects of longitudinal chromatic aberration and a shift in the peak of the middle-wavelength sensitive cone fundamental on cone contrast.

    PubMed

    Rucker, F J; Osorio, D

    2008-09-01

    Longitudinal chromatic aberration is a well-known imperfection of visual optics, but the consequences in natural conditions, and for the evolution of receptor spectral sensitivities are less well understood. This paper examines how chromatic aberration affects image quality in the middle-wavelength sensitive (M-) cones, viewing broad-band spectra, over a range of spatial frequencies and focal planes. We also model the effects on M-cone contrast of moving the M-cone fundamental relative to the long- and middle-wavelength (L- and M-cone) fundamentals, while the eye is accommodated at different focal planes or at a focal plane that maximizes luminance contrast. When the focal plane shifts towards longer (650 nm) or shorter wavelengths (420 nm) the effects on M-cone contrast are large: longitudinal chromatic aberration causes total loss of M-cone contrast above 10-20 c/d. In comparison, the shift of the M-cone fundamental causes smaller effects on M-cone contrast. At 10 c/d a shift in the peak of the M-cone spectrum from 560 to 460 nm decreases M-cone contrast by 30%, while a 10 nm blue-shift causes only a minor loss of contrast. However, a noticeable loss of contrast may be seen if the eye is focused at focal planes other than that which maximizes luminance contrast. The presence of separate long- and middle-wavelength sensitive cones therefore has a small, but not insignificant cost to the retinal image via longitudinal chromatic aberration. This aberration may therefore be a factor limiting evolution of visual pigments and trichromatic color vision. PMID:18639571

  11. The multifocal electroretinogram (mfERG) and cone isolating stimuli: variation in L- and M-cone driven signals across the retina.

    PubMed

    Albrecht, Johannes; Jägle, Herbert; Hood, Donald C; Sharpe, Lindsay T

    2002-01-01

    Multifocal electroretinograms (mfERG) were recorded from 38 normal trichromats with a pattern-reversing display that modulated only their long-wavelength sensitive (L) or only their middle-wavelength sensitive (M) cones at equal cone contrasts and average quantal catches. The display consisted of scaled, 103 hexagonal elements, subtending 84 degrees x 75 degrees of visual angle. Typically, the amplitude of the L-cone driven signal was greater than that for the M-cone driven one at all retinal eccentricities, but large differences were found among observers. These values correlated with L- to M-cone ratios obtained psychophysically in the same observers using 2 degrees (dia.) heterochromatic flicker photometry. Interestingly, the L- to M-cone driven amplitude ratios differed between the central and peripheral retina. For the central fovea (5 degrees dia.), the mean ratio was 1.4 +/- 0.6 (for the N1P1 component), whereas for the annular ring centered at 40 degrees in the periphery, it was 2.3 +/- 2.0. The mean P1 latency of the summed M-cone driven mfERG (28.0 +/- 2.6 ms) was significantly advanced relative to the L-cone driven signal (29.0 +/- 1.9 ms), but the mean N1 latencies were similar (15.6 +/- 1.7 ms and 16.2 +/- 1.3 ms, respectively). The P1 latency difference between the L- and M-cone driven waveforms was not found in the central 5 degrees (dia.) of the retina. However, it increased with retinal eccentricity. The regional differences in the amplitudes and latencies of the L- and M-cone driven mfERG signals can be related to variations in the L- to M-cone ratios and/or the receptor to bipolar gain factors that depend on eccentricity.

  12. On generalized gravitational entropy, squashed cones and holography

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Arpan; Sharma, Menika; Sinha, Aninda

    2014-01-01

    We consider generalized gravitational entropy in various higher derivative theories of gravity dual to four dimensional CFTs using the recently proposed regularization of squashed cones. We derive the universal terms in the entanglement entropy for spherical and cylindrical surfaces. This is achieved by constructing the Fefferman-Graham expansion for the leading order metrics for the bulk geometry and evaluating the generalized gravitational entropy. We further show that the Wald entropy evaluated in the bulk geometry constructed for the regularized squashed cones leads to the correct universal parts of the entanglement entropy for both spherical and cylindrical entangling surfaces. We comment on the relation with the Iyer-Wald formula for dynamical horizons relating entropy to a Noether charge. Finally we show how to derive the entangling surface equation in Gauss-Bonnet holography.

  13. Human cone pigment expressed in transgenic mice yields altered vision.

    PubMed

    Jacobs, G H; Fenwick, J C; Calderone, J B; Deeb, S S

    1999-04-15

    Genetically driven alterations in the complement of retinal photopigments are fundamental steps in the evolution of vision. We sought to determine how a newly added photopigment might impact vision by studying a transgenic mouse that expresses a human cone photopigment. Electroretinogram (ERG) measurements indicate that the added pigment works well, significantly changing spectral sensitivity without deleteriously affecting the operation of the native cone pigments. Visual capacities of the transgenic mice were established in behavioral tests. The new pigment was found to provide a significant expansion of the spectral range over which mice can perceive light, thus underlining the immediate utility of acquiring a new photopigment. The transgenic mouse also has the receptor basis for a novel color vision capacity, but tests show that potential was not realized. This failure likely reflects limitations in the organizational arrangement of the mouse retina.

  14. Feasibility study for the Cryogenic Orbital Nitrogen Experiment (CONE)

    NASA Technical Reports Server (NTRS)

    Bell, R. S.; Crouch, M. A.; Hanna, G. J.; Cady, E. C.; Meserole, J. S.

    1991-01-01

    An improved understanding of low gravity subcritical cryogenic fluid behavior is critical for the continued development of space based systems. Although early experimental programs provided some fundamental understanding of zero gravity cryogenic fluid behavior, more extensive flight data are required to design space based cryogenic liquid storage and transfer systems with confidence. As NASA's mission concepts evolve, the demand for optimized in-space cryogenic systems is increasing. Cryogenic Orbital Nitrogen Experiment (CONE) is an attached shuttle payload experiment designed to address major technological issues associated with on-orbit storage and supply of cryogenic liquids. During its 7 day mission, CONE will conduct experiments and technology demonstrations in active and passive pressure control, stratification and mixing, liquid delivery and expulsion efficiency, and pressurant bottle recharge. These experiments, conducted with liquid nitrogen as the test fluid, will substantially extend the existing low gravity fluid data base and will provide future system designers with vital performance data from an orbital environment.

  15. Disclinations, e-cones, and their interactions in extensible sheets.

    PubMed

    Chopin, Julien; Kudrolli, Arshad

    2016-05-11

    We investigate the nucleation, growth, and spatial organization of topological defects with a ribbon shaped elastic sheet which is stretched and twisted. Singularities are found to spontaneously arrange in a triangular lattice in the form of vertices connected by stretched ridges that result in a self-rigidified structure. The vertices are shown to be negative disclinations or e-cones which occur in sheets with negative Gaussian curvature, in contrast with d-cones in sheets with zero-Gaussian curvature. We find the growth of the wrinkled width of the ribbon to be consistent with a far-from-threshold approach assuming a compression-free base state. The system is found to show a transition from a regime where the wavelength is given by the ribbon geometry, to where it is given by its elasticity as a function of the ratio of the applied tension to the elastic modulus and cross-sectional area of the ribbon.

  16. Migraine photophobia originating in cone-driven retinal pathways.

    PubMed

    Noseda, Rodrigo; Bernstein, Carolyn A; Nir, Rony-Reuven; Lee, Alice J; Fulton, Anne B; Bertisch, Suzanne M; Hovaguimian, Alexandra; Cestari, Dean M; Saavedra-Walker, Rodrigo; Borsook, David; Doran, Bruce L; Buettner, Catherine; Burstein, Rami

    2016-07-01

    Migraine headache is uniquely exacerbated by light. Using psychophysical assessments in patients with normal eyesight we found that green light exacerbates migraine headache significantly less than white, blue, amber or red lights. To delineate mechanisms, we used electroretinography and visual evoked potential recording in patients, and multi-unit recording of dura- and light-sensitive thalamic neurons in rats to show that green activates cone-driven retinal pathways to a lesser extent than white, blue and red; that thalamic neurons are most responsive to blue and least responsive to green; and that cortical responses to green are significantly smaller than those generated by blue, amber and red lights. These findings suggest that patients' experience with colour and migraine photophobia could originate in cone-driven retinal pathways, fine-tuned in relay thalamic neurons outside the main visual pathway, and preserved by the cortex. Additionally, the findings provide substrate for the soothing effects of green light. PMID:27190022

  17. Pentamode metamaterials with asymmetric double-cone elements

    NASA Astrophysics Data System (ADS)

    Cai, Chengxin; Wang, Zhaohong; Li, Qingwei; Xu, Zhuo; Tian, Xiaogeng

    2015-05-01

    Pentamode metamaterials are a very interesting set of artificial solids. They are difficult to compress but flow easily, hence imitating somehow the behaviours of liquids. In this paper, three-dimensional (3D) pentamode metamaterials based on the asymmetric double-cone element (ADCE) are proposed. The ADCE is composed by two connected truncated cones with different thin diameters. The phonon band structures of the ADCEs pentamode metamaterials are numerically analysed by using the finite element method (FEM). Besides the single phonon mode, the complete 3D band gaps are also found in the phonon band structures. Here, the influence of the degree of asymmetry of ADCE to the figure of merit (FOM), which is the ratio of bulk modulus and shear modulus, is discussed. The FOM can be increased by 21-30% (at FOM ≥ 103) when the degree of asymmetry m ranges from 0.4 to 0.6.

  18. Light-cone fluctuations in the cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bezerra de Mello, E. R.; Bessa, C. H. G.; Bezerra, V. B.

    2016-07-01

    In this paper we consider light-cone fluctuations arising as a consequence of the nontrivial topology of the locally flat cosmic string spacetime. By setting the light-cone along the z -direction we are able to develop a full analysis to calculate the renormalized graviton two-point function, as well as the mean square fluctuation in the geodesic interval function and the time delay (or advance) in the propagation of a light pulse. We found that all these expressions depend upon the parameter characterizing the conical topology of the cosmic string spacetime and vanish in the absence of it. We also point out that at large distances from the cosmic string the mean square fluctuation in the geodesic interval function is extremely small while in the opposite limit it logarithmically increases.

  19. Observation of Dirac cone warping and chirality effects in silicene.

    PubMed

    Feng, Baojie; Li, Hui; Liu, Cheng-Cheng; Shao, Ting-Na; Cheng, Peng; Yao, Yugui; Meng, Sheng; Chen, Lan; Wu, Kehui

    2013-10-22

    We performed low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) studies on the electronic properties of (√3 × √3)R30° phase of silicene on Ag(111) surface. We found the existence of Dirac Fermion chirality through the observation of -1.5 and -1.0 power law decay of quasiparticle interference (QPI) patterns. Moreover, in contrast to the trigonal warping of Dirac cone in graphene, we found that the Dirac cone of silicene is hexagonally warped, which is further confirmed by density functional calculations and explained by the unique superstructure of silicene. Our results demonstrate that the (√3 × √3)R30° phase is an ideal system to investigate the unique Dirac Fermion properties of silicene.

  20. Use of Cone Beam Computed Tomography in Endodontics

    PubMed Central

    Scarfe, William C.; Levin, Martin D.; Gane, David; Farman, Allan G.

    2009-01-01

    Cone Beam Computed Tomography (CBCT) is a diagnostic imaging modality that provides high-quality, accurate three-dimensional (3D) representations of the osseous elements of the maxillofacial skeleton. CBCT systems are available that provide small field of view images at low dose with sufficient spatial resolution for applications in endodontic diagnosis, treatment guidance, and posttreatment evaluation. This article provides a literature review and pictorial demonstration of CBCT as an imaging adjunct for endodontics. PMID:20379362

  1. Structure of the Nucleon Spin on the Light Cone

    SciTech Connect

    Pasquini, B.

    2008-10-13

    The spin structure of the nucleon is studied in a light-cone description of the nucleon where the Fock expansion is truncated to consider only valence quarks. Transverse momentum dependent parton distributions and transverse-spin densities, defined through the generalized parton distributions in the impact parameter space, are investigated as new tools to reveal the spin-spin and spin-orbit correlations for different quark and nucleon polarizations.

  2. Development of an advanced 3D cone beam tomographic system

    NASA Astrophysics Data System (ADS)

    Sire, Pascal; Rizo, Philippe; Martin, M.; Grangeat, Pierre; Morisseau, P.

    Due to its high spatial resolution, the 3D X-ray cone-beam tomograph (CT) maximizes understanding of test object microstructure. In order for the present X-ray CT NDT system to control ceramics and ceramic-matrix composites, its spatial resolution must exceed 50 microns. Attention is given to two experimental data reconstructions that have been conducted to illustrate system capabilities.

  3. Holographic entanglement entropy for hollow cones and banana shaped regions

    NASA Astrophysics Data System (ADS)

    Dorn, Harald

    2016-06-01

    We consider banana shaped regions as examples of compact regions, whose boundary has two conical singularities. Their regularised holographic entropy is calculated with all divergent as well as finite terms. The coefficient of the squared logarithmic divergence, also in such a case with internally curved boundary, agrees with that calculated in the literature for infinite circular cones with their internally flat boundary. For the otherwise conformally invariant coefficient of the ordinary logarithmic divergence an anomaly under exceptional conformal transformations is observed.

  4. Multi-Cone Model for Estimating GPS Ionospheric Delays

    NASA Technical Reports Server (NTRS)

    Sparks, Lawrence; Komjathy, Attila; Mannucci, Anthony

    2009-01-01

    The multi-cone model is a computational model for estimating ionospheric delays of Global Positioning System (GPS) signals. It is a direct descendant of the conical-domain model. A primary motivation for the development of this model is the need to find alternatives for modeling slant delays at low latitudes, where ionospheric behavior poses an acute challenge for GPS signal-delay estimates based upon the thin-shell model of the ionosphere.

  5. Cone beam computed tomography scanning and diagnosis for dental implants.

    PubMed

    Greenberg, Alex M

    2015-05-01

    Cone beam computed tomography (CBCT) has become an important new technology for oral and maxillofacial surgery practitioners. CBCT provides improved office-based diagnostic capability and applications for surgical procedures, such as CT guidance through the use of computer-generated drill guides. A thorough knowledge of the basic science of CBCT as well as the ability to interpret the images correctly and thoroughly is essential to current practice.

  6. Coherent Cone-Beam X-ray Microscopy

    SciTech Connect

    Harder, R.; Xiao, X.

    2011-09-09

    A novel full-field imaging method using the (111) Bragg diffraction of a sub-micron gold crystal as the divergent cone-beam for sample illumination is reported. The divergence of the illumination allows for very high magnification, limited only by the achievable ratio of the crystal-to-sample and sample-to-detector distances. In this case an x-ray magnification of approximately 115 was achieved.

  7. 126. Moses H. Cone Memorial Park. View of barbed wire ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    126. Moses H. Cone Memorial Park. View of barbed wire fence along carriage trail with a concrete box culvert for the carriage trail in the background. It is the only culvert on the parkway with stone veneer finished with a roman arch. It was constructed in 1960. Looking south-southeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  8. Riemannian light cone from vanishing birefringence in premetric vacuum electrodynamics

    SciTech Connect

    Laemmerzahl, Claus; Hehl, Friedrich W.

    2004-11-15

    We consider premetric electrodynamics with a local and linear constitutive law for the vacuum. Within this framework, we find quartic Fresnel wave surfaces for the propagation of light. If we require (i) the Fresnel equation to have only real solutions and (ii) the vanishing of birefringence in vacuum, then a Riemannian light cone is implied. No proper Finslerian structure can occur. This is generalized to dynamical equations of any order.

  9. Distribution and development of short-wavelength cones differ between Macaca monkey and human fovea.

    PubMed

    Bumsted, K; Hendrickson, A

    1999-01-25

    Macaca monkey and humans have three cone types containing either long-wavelength (L), medium-wavelength (M), or short-wavelength (S)-specific opsin. The highest cone density is found in the fovea, which mediates high visual acuity. Most studies agree that the adult human fovea has a small S cone-free area, but data are conflicting concerning S-cone numbers in the adult Macaca monkey fovea, and little evidence exists for how either primate fovea develops its characteristic cone pattern. Single- and double-label in situ hybridization and immunocytochemistry have been used to determine the pattern of foveal S cones in both the fetal and adult Macaca and human. Both labels find a clear difference at all ages between monkey and human. Adult humans have a distinct but variable central zone about 100 microm wide that lacks S cones and is surrounded by a ring in which the S-cone density is 8%. This S cone-free zone is detectable at fetal week 15.5 (Fwk15.5), shortly after S opsin is expressed, and is similar to the adult by Fwk20.5. Adult monkey foveas have an overall S-cone foveal density of 10%, with several areas lacking a few S cones that are not coincident with the area of highest cone density. A surrounding zone at 200-microm eccentricity has an S-cone density averaging 25%, but, by 800 microm, this has decreased to 11%. Fetal day 77-135 monkeys all have a distribution and density of foveal S cones similar to adults, although the high-density ring is not obvious in fetal retinas. Estimates of the numbers of S cones missing in the fetal human fovea range from 234 to 328, whereas no more than 40 are missing in the fetal monkey. These results show that, in these two trichromatic primates, S-cone distribution and the developmental mechanisms determining S-cone topography are markedly different from the time that S cones are first detected.

  10. Loss-cone instability: Wave saturation by particle trapping

    SciTech Connect

    Zaslavsky, A.; Krafft, C.; Volokitin, A.

    2007-12-15

    The nonlinear mechanisms governing the interactions between whistler or lower hybrid waves and loss-cone type particles' distributions in magnetized plasmas are of great importance if one considers the major role that waves of frequency below the electron cyclotron frequency play in space and thermonuclear fusion plasmas. Up to now, most of the numerical simulations have been devoted to study the nonlinear processes at work when the plasma is weakly relativistic and when the anisotropy of the particles' distributions leads to the so-called maser instability. However, in many interesting cases, the particles' energies are sufficiently weak to ensure the validity of the nonrelativistic approximation. In this framework, the paper studies the interaction at normal cyclotron resonances between lower hybrid waves and electron distributions presenting loss-cone like features. A theoretical Hamiltonian model and a corresponding numerical symplectic code are used to evidence and to explain the nonlinear mechanisms at work at the saturation stage of the loss-cone instability. Moreover, simple analytical expressions and scaling laws have been derived for the linear growth rates and the wave amplitude at saturation.

  11. On trajectories of rolling marbles in cones and other funnels

    NASA Astrophysics Data System (ADS)

    White, Gary D.

    2013-12-01

    We report on theoretical and experimental results for a ball that rolls without slipping on a surface of revolution, whose symmetry axis is aligned with a uniform gravitational field, particularly investigating both near-circular orbits and scattering-type orbits in cones. The experimental data give support for the theoretical treatment, a non-trivial application of Newton's second law that expands on our previous work and related work of others. Our findings refine those from a recent article in this journal, and largely replicate those obtained from an earlier Lagrangian approach, adding some new details and commentary. While the orbits of marbles rolling in cones do not match inverse-square-law orbits quantitatively (e.g., instead of Kepler's 3rd law, we have T2∝R), we argue that students should experience these qualitative phenomena—precession of orbits, escape velocity behavior, spin-orbit coupling, conservation laws for angular momentum, energy, and spin projection—as much for the fun and kinesthetic impressions as for the raw learning. We also report on a heretofore largely ignored variable in the exploration of rolling orbits in a gravity well: the marble's spin about its own axis as it rolls. Experimenters can, intentionally or not, vary this initial condition and produce different orbital periods for a given orbital radius—a distinctly non-celestial behavior. Careful selection of the initial spin direction and speed for a particular cone can result in marble orbits that mimic the planetary ellipses.

  12. Development of DLC cone for fast ignition experiment

    NASA Astrophysics Data System (ADS)

    Koga, Mayuko; Ono, Takuma; Tokunaga, Takuma; Kadota, Hayato; Hashimoto, Takashi; Kanda, Kazuhiro; Norimatsu, Takayoshi

    2015-09-01

    In fast ignition research, a divergence of laser-generated hot electrons is a serious problem. Using DLC cones is one of actions against this problem. However, it is difficult to make a stand alone DLC cone because it needs a thick DLC layer. In this reserch, we studied preparation conditions for thick DLC layers and characteristics of DLC layers. We prepared a DLC layer on a brass conical bar by using a plasma-based ion implantation and deposition (PBIID) system. Acetylene gas or toluene vapor was used as a source. It was found that low gas pressure and low RF pulse power is suitable for thick DLC layer deposition. It was found that the toluene vapor had an advantage in thick layer deposition because of its high deposition rate. These DLC layers showed SP3 rich property in Near edge X-ray absorption fine structures (NEXAFS) spectra. Based on these results, we succeeded in making stand alone DLC cones. This work was supported by JSPS KAKENHI Grant Number 26420853 and Collaboration Research Program by NIFS (NIFS12KUGK063).

  13. Raked circular-cone aerobraking orbital transfer vehicle

    NASA Technical Reports Server (NTRS)

    Park, Chul (Inventor); Davies, Carol B. (Inventor)

    1990-01-01

    An aerobraking orbital transfer vehicle (AOTV) (80) has aerobrake (82) with a blunted raked-off circular-cone configuration. The other components of the AOTV, including command/control module (95), fuel tanks (86, 88, 89 and 91), rocket engines (94) and afterbody (84), are positioned substantially along resultant force axis (104) of the AOTV (80). The axis (104) coincides with the resultant (sum of lift and drag) force vector. Afterbody (84) is mounted behind the aerobrake (82) with its length extending rearwardly from the aerobrake. The base flow clearance angle .phi. of the aerobrake (80) is 25.degree., thus allowing the afterbody (84) to extend rearwardly from the aerobrake (82) to a much greater extent than possible with a raked-off elliptic-cone aerobraking shield configuration. Afterbody size limitation and other problems associated with the raked-off elliptic-cone aerobraking shield configuration are alleviated by the combination of the aerobrake shape and positioning of the fuel tanks (86, 88, 89 and 91), rocket engines (94) and afterbody (84).

  14. IMPLOSION OF INDIRECTLY DRIVEN REENTRANT CONE SHELL TARGET

    SciTech Connect

    STEPHENS,RB

    2003-08-01

    OAK-B135 The authors have examined the implosion of an indirectly driven reentrant-cone shell target to clarify the issues attendant on compressing fuel for a fast ignition target. The target design is roughly hydrodynamic equivalent to a NIF cryo-ignition target, but scaled down to be driven by Omega. A sequence of backlit x-radiographs recorded each implosion. The collapse was also modeled with LASNEX, generating simulated radiographs. They compare experimental and simulated diameter, density and symmetry as functions of time near stagnation. The simulations were generally in good agreement with the experiments with respect to the shell, but did not show the opacity due to ablation of gold off the cone; non-thermal gold M-line radiation from the hohlraum wall penetrates the shell and drives this ablation causing some Au to mix into the low density center of the core and into the region between the core and cone. This might be a problem in a cryo-ignition target.

  15. Resin Transfer Moulding Of An Engine Thrust Frame Cone Cap

    NASA Astrophysics Data System (ADS)

    Brodsjo, Anders; Fatemi, Javad; de Vries, Henri

    2012-07-01

    For the Ariane 5 Midlife Evolution, a new Engine Thrust Frame for the upper stage is being developed. Part of this Engine Thrust Frame is the so-called Cone Cap, which closes the inverted cone shape of the structure. This part is highly loaded, as it transfers all the loads from the engines to the cone shape, and includes the hinge points for the mechanism that steer the engines. Besides strength to cope with the loads, stiffness is a very important design parameter. A composite design of this structure has been developed, which is approximately 15 kg’s lighter than the aluminium structure. To manufacture such a part in composites is challenging, because of the complexity of the shape and large laminate thickness. Due to these requirements, Resin Transfer Moulding has been selected as manufacturing method, which allows this highly integrated structure to be made in one step. As part of this project, a quarter segment of the full-scale design has been manufactured. From the design model, a detailed design for the dry fibre preform has been made using advanced composite laminate software tools. This preform was placed inside a heated, double sided tool and injected with the resin.

  16. The inviscid stability of supersonic flow past a sharp cone

    NASA Technical Reports Server (NTRS)

    Duck, Peter W.; Shaw, Stephen J.

    1990-01-01

    The laminar boundary layer which forms on a sharp cone in a supersonic freestream, where lateral curvature plays a key role in the physics of the problem is considered. This flow is then analyzed from the point of view of linear, temporal, inviscid stability. The basic, non-axisymmetric disturbance equations are derived for general flows of this class, and a so called triply generalized inflexion condition is found for the existence of subsonic neutral modes of instability. This condition is analogous to the well-known generalized inflexion condition found in planar flows, although in the present case the condition depends on both axial and aximuthal wavenumbers. Extensive numerical results are presented for the stability problem at a freestream Mach number of 3.8, for a range of streamwise locations. These results reveal that a new mode of instability may occur, peculiar to flows of this type involving curvature. Additionally, asymptotic analyses valid close to the tip of the cone, far downstream of the cone are presented, and these give a partial (asymptotic) description of this additional mode of instability.

  17. SWCX Emission from the Helium Focusing Cone - Preliminary Results

    NASA Technical Reports Server (NTRS)

    Snowden, S. L.; Kuntz, K. D.; Collier, M. R.

    2008-01-01

    Preliminary results from an XMM-Newton campaign to study solar wind charge exchange (SWCX) emission from the heliospheric focusing cone of interstellar helium are presented. The detections of enhanced O VII and O VIII emission from the cone are at the 2(sigma) and 4(sigma) levels. The solar wind charge exchange (SWCX) emission in the heliosphere not associated with distinct objects (e.g., comets and planets including exospheric material in and near Earth s magnetosheath) is proportional to the flux of the solar wind and the space density of neutral material. The neutral material originates in the interstellar medium (ISM) and passes through the solar system due to the relative motion of the Sun and the ISM. The flow of the neutral material through the solar system is strongly perturbed by the Sun both by gravity and by radiation pressure. Because of the relative radiative scattering cross sections and the effect of solar gravitation the density of interstellar hydrogen near the Sun is reduced while interstellar helium is gravitationally focused. This creates a helium focusing cone downstream of the Sun [e.g., 1, and references therein].

  18. Fundamentals of cone beam computed tomography for a prosthodontist

    PubMed Central

    John, George Puthenpurayil; Joy, Tatu Elenjickal; Mathew, Justin; Kumar, Vinod R. B.

    2015-01-01

    Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT) is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone.[1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10–70 s) and radiation dosages reportedly up to 15–100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled. PMID:26929479

  19. Camera Layout Design for the Upper Stage Thrust Cone

    NASA Technical Reports Server (NTRS)

    Wooten, Tevin; Fowler, Bart

    2010-01-01

    Engineers in the Integrated Design and Analysis Division (EV30) use a variety of different tools to aid in the design and analysis of the Ares I vehicle. One primary tool in use is Pro-Engineer. Pro-Engineer is a computer-aided design (CAD) software that allows designers to create computer generated structural models of vehicle structures. For the Upper State thrust cone, Pro-Engineer was used to assist in the design of a layout for two camera housings. These cameras observe the separation between the first and second stage of the Ares I vehicle. For the Ares I-X, one standard speed camera was used. The Ares I design calls for two separate housings, three cameras, and a lighting system. With previous design concepts and verification strategies in mind, a new layout for the two camera design concept was developed with members of the EV32 team. With the new design, Pro-Engineer was used to draw the layout to observe how the two camera housings fit with the thrust cone assembly. Future analysis of the camera housing design will verify the stability and clearance of the camera with other hardware present on the thrust cone.

  20. Vitreal delivery of AAV vectored Cnga3 restores cone function in CNGA3−/−/Nrl−/− mice, an all-cone model of CNGA3 achromatopsia†

    PubMed Central

    Du, Wei; Tao, Ye; Deng, Wen-Tao; Zhu, Ping; Li, Jie; Dai, Xufeng; Zhang, Yuxin; Shi, Wei; Liu, Xuan; Chiodo, Vince A.; Ding, Xi-Qin; Zhao, Chen; Michalakis, Stylianos; Biel, Martin; Zhang, Zuoming; Qu, Jia; Hauswirth, William W.; Pang, Ji-jing

    2015-01-01

    The CNGA3−/−/Nrl−/− mouse is a cone-dominant model with Cnga3 channel deficiency, which partially mimics the all cone foveal structure of human achromatopsia 2 with CNGA3 mutations. Although subretinal (SR) AAV vector administration can transfect retinal cells efficiently, the injection-induced retinal detachment can cause retinal damage, particularly when SR vector bleb includes the fovea. We therefore explored whether cone function–structure could be rescued in CNGA3−/−/Nrl−/− mice by intravitreal (IVit) delivery of tyrosine to phenylalanine (Y-F) capsid mutant AAV8. We find that AAV-mediated CNGA3 expression can restore cone function and rescue structure following IVit delivery of AAV8 (Y447, 733F) vector. Rescue was assessed by restoration of the cone-mediated electroretinogram (ERG), optomotor responses, and cone opsin immunohistochemistry. Demonstration of gene therapy in a cone-dominant mouse model by IVit delivery provides a potential alternative vector delivery mode for safely transducing foveal cones in achromatopsia patients and in other human retinal diseases affecting foveal function. PMID:25855802

  1. Channeling of red and green cone inputs to the zebrafish optomotor response.

    PubMed

    Orger, Michael B; Baier, Herwig

    2005-01-01

    Visual systems break scenes down into individual features, processed in distinct channels, and then selectively recombine those features according to the demands of particular behavioral tasks. In primates, for example, there are distinct pathways for motion and form processing. While form vision utilizes color information, motion pathways receive input from only a subset of cone photoreceptors and are generally colorblind. To explore the link between early channeling of visual information and behavioral output across vertebrate species, we measured the chromatic inputs to the optomotor response of larval zebrafish. Using cone-isolating gratings, we found that there is a strong input from both red and green cones but not short-wavelength cones, which nevertheless do contribute to another behavior, phototaxis. Using a motion-nulling method, we measured precisely the input strength of gratings that stimulated cones in combination. The fish do not respond to gratings that stimulate different cone types out of phase, but have an enhanced response when the cones are stimulated together. This shows that red and green cone signals are pooled at a stage before motion detection. Since the two cone inputs are combined into a single 'luminance' channel, the response to sinusoidal gratings is colorblind. However, we also find that the relative contributions of the two cones at isoluminance varies with spatial frequency. Therefore, natural stimuli, which contain a mixture of spatial frequencies, are likely to be visible regardless of their chromatic composition. PMID:16079003

  2. Comparison of Asymmetric and Ice-cream Cone Models for Halo Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Na, H.; Moon, Y.

    2011-12-01

    Halo coronal mass ejections (HCMEs) are major cause of the geomagnetic storms. To minimize the projection effect by coronagraph observation, several cone models have been suggested: an ice-cream cone model, an asymmetric cone model etc. These models allow us to determine the three dimensional parameters of HCMEs such as radial speed, angular width, and the angle between sky plane and central axis of the cone. In this study, we compare these parameters obtained from different models using 48 well-observed HCMEs from 2001 to 2002. And we obtain the root mean square error (RMS error) between measured projection speeds and calculated projection speeds for both cone models. As a result, we find that the radial speeds obtained from the models are well correlated with each other (R = 0.86), and the correlation coefficient of angular width is 0.6. The correlation coefficient of the angle between sky plane and central axis of the cone is 0.31, which is much smaller than expected. The reason may be due to the fact that the source locations of the asymmetric cone model are distributed near the center, while those of the ice-cream cone model are located in a wide range. The average RMS error of the asymmetric cone model (85.6km/s) is slightly smaller than that of the ice-cream cone model (87.8km/s).

  3. Volcanic cones in Hydraotes chaos : implications for the chaotic terrains formation

    NASA Astrophysics Data System (ADS)

    Meresse, S.; Costard, F.; Mangold, N.; Masson, P.; Neukum, G.

    2006-12-01

    Numerous geologic scenarios have been proposed for the chaotic terrains formation. They include (1) sub-ice volcanism and other magma-ice interactions and (2) catastrophic release of groundwater from confined aquifers. The lack of volcanic morphology in the chaos was an handicap for the hypothesis of magma-ice interactions but the HRSC (High Resolution Stereo Camera) images have recently revealed possible volcanic cones inside the Hydraotes chaos. About thirty cones lie on the lowest parts of the chaos at elevation between -4300 and -5100 meters. They have basal diameters of 500-1900 m and heights exceeding 100 m. They are observed on young surface: the south smooth floor and inside the narrow valleys separating the mesas. The cones are relatively fresh. Similar morphologies of small cone-shaped structures have been previously identified in the northern lowlands of Mars (Chryse, Acidalia, Amazonis, Isidis and Elysuim Planitia) but their origin remains uncertain. A number of volcanic or cold climate landforms were proposed as potential terrestrial analogues : Icelandic pseudocraters (or rootless cones), cinder cones, tuff cones, pingos and spatter cones. The morphologic measurements made on the Hydraotes cones argue rather for a volcanic origin in comparison with terrestrial analogues. These first volcanic cones observed in Hydraotes chaos suggest that volcanic or subvolcanic activity might have played an important part in the chaotic terrains formation and outflow channels genesis.

  4. Increase in Growth Cone Size Correlates with Decrease in Neurite Growth Rate

    PubMed Central

    Ren, Yuan

    2016-01-01

    Several important discoveries in growth cone cell biology were made possible by the use of growth cones derived from cultured Aplysia bag cell neurons, including the characterization of the organization and dynamics of the cytoskeleton. The majority of these Aplysia studies focused on large growth cones induced by poly-L-lysine substrates at early stages in cell culture. Under these conditions, the growth cones are in a steady state with very little net advancement. Here, we offer a comprehensive cellular analysis of the motile behavior of Aplysia growth cones in culture beyond this pausing state. We found that average growth cone size decreased with cell culture time whereas average growth rate increased. This inverse correlation of growth rate and growth cone size was due to the occurrence of large growth cones with a peripheral domain larger than 100 μm2. The large pausing growth cones had central domains that were less consistently aligned with the direction of growth and could be converted into smaller, faster-growing growth cones by addition of a three-dimensional collagen gel. We conclude that the significant lateral expansion of lamellipodia and filopodia as observed during these culture conditions has a negative effect on neurite growth. PMID:27274874

  5. Development of partial ontogenic resistance to powdery mildew in hop cones and its management implications.

    PubMed

    Twomey, Megan C; Wolfenbarger, Sierra N; Woods, Joanna L; Gent, David H

    2015-01-01

    Knowledge of processes leading to crop damage is central to devising rational approaches to disease management. Multiple experiments established that infection of hop cones by Podosphaera macularis was most severe if inoculation occurred within 15 to 21 days after bloom. This period of infection was associated with the most pronounced reductions in alpha acids, cone color, and accelerated maturation of cones. Susceptibility of cones to powdery mildew decreased progressively after the transition from bloom to cone development, although complete immunity to the disease failed to develop. Maturation of cone tissues was associated with multiple significant affects on the pathogen manifested as reduced germination of conidia, diminished frequency of penetration of bracts, lengthening of the latent period, and decreased sporulation. Cones challenged with P. macularis in juvenile developmental stages also led to greater frequency of colonization by a complex of saprophytic, secondary fungi. Since no developmental stage of cones was immune to powdery mildew, the incidence of powdery mildew continued to increase over time and exceeded 86% by late summer. In field experiments with a moderately susceptible cultivar, the incidence of cones with powdery mildew was statistically similar when fungicide applications were made season-long or targeted only to the juvenile stages of cone development. These studies establish that partial ontogenic resistance develops in hop cones and may influence multiple phases of the infection process and pathogen reproduction. The results further reinforce the concept that the efficacy of a fungicide program may depend largely on timing of a small number of sprays during a relatively brief period of cone development. However in practice, targeting fungicide and other management tactics to periods of enhanced juvenile susceptibility may be complicated by a high degree of asynchrony in cone development and other factors that are situation-dependent.

  6. Development of Partial Ontogenic Resistance to Powdery Mildew in Hop Cones and Its Management Implications

    PubMed Central

    Twomey, Megan C.; Wolfenbarger, Sierra N.; Woods, Joanna L.; Gent, David H.

    2015-01-01

    Knowledge of processes leading to crop damage is central to devising rational approaches to disease management. Multiple experiments established that infection of hop cones by Podosphaera macularis was most severe if inoculation occurred within 15 to 21 days after bloom. This period of infection was associated with the most pronounced reductions in alpha acids, cone color, and accelerated maturation of cones. Susceptibility of cones to powdery mildew decreased progressively after the transition from bloom to cone development, although complete immunity to the disease failed to develop. Maturation of cone tissues was associated with multiple significant affects on the pathogen manifested as reduced germination of conidia, diminished frequency of penetration of bracts, lengthening of the latent period, and decreased sporulation. Cones challenged with P. macularis in juvenile developmental stages also led to greater frequency of colonization by a complex of saprophytic, secondary fungi. Since no developmental stage of cones was immune to powdery mildew, the incidence of powdery mildew continued to increase over time and exceeded 86% by late summer. In field experiments with a moderately susceptible cultivar, the incidence of cones with powdery mildew was statistically similar when fungicide applications were made season-long or targeted only to the juvenile stages of cone development. These studies establish that partial ontogenic resistance develops in hop cones and may influence multiple phases of the infection process and pathogen reproduction. The results further reinforce the concept that the efficacy of a fungicide program may depend largely on timing of a small number of sprays during a relatively brief period of cone development. However in practice, targeting fungicide and other management tactics to periods of enhanced juvenile susceptibility may be complicated by a high degree of asynchrony in cone development and other factors that are situation

  7. Condensing efficiency of the truncated cone condenser and its comparison with the Winston cone condenser in terahertz region

    NASA Astrophysics Data System (ADS)

    Aoki, Makoto; Hiromoto, Norihisa

    2015-01-01

    The angle-dependent condensing efficiency of a truncated cone condenser (TCC) in the terahertz (THz) region has been examined by 2D ray tracing and 3D electromagnetic simulation. The condensing efficiency in the THz region is transferred to that in the optical region by theoretical dispersive reflection from a rough surface, and it is confirmed that the latter is consistent with the measured condensing efficiency in the optical region. Although the TCC has a gradual field of view (FOV) compared with the Winston cone condenser (WCC), we improved the steepness of the FOV by adding a baffle before the input aperture of the TCC. We also proved that the TCC has a high condensing efficiency at around normal incidence in comparison with the WCC in the THz region.

  8. The role of cytoskeleton in organizing growth cones: a microfilament- associated growth cone component depends upon microtubules for its localization

    PubMed Central

    1989-01-01

    We are interested in the relationship between the cytoskeleton and the organization of polarized cell morphology. We show here that the growth cones of hippocampal neurons in culture are specifically stained by a monoclonal antibody called 13H9. In other systems, the antigen recognized by 13H9 is associated with marginal bands of chicken erythrocytes and shows properties of both microtubule-and microfilament- associated proteins (Birgbauer, E., and F. Solomon. 1989 J. Cell Biol. 109:1609-1620). This dual nature is manifest in hippocampal neurons as well. At early stages after plating, the antibody stains the circumferential lamellipodia that mediate initial cell spreading. As processes emerge, 13H9 staining is heavily concentrated in the distal regions of growth cones, particularly in lamellipodial fans. In these cells, the 13H9 staining is complementary to the localization of assembled microtubules. It colocalizes partially, but not entirely, with phalloidin staining of assembled actin. Incubation with nocodazole rapidly induces microtubule depolymerization, which proceeds in the distal-to-proximal direction in the processes. At the same time, a rapid and dramatic redistribution of the 13H9 staining occurs; it delocalizes along the axon shaft, becoming clearly distinct from the phalloidin staining and always remaining distal to the receding front of assembled microtubules. After longer times without assembled microtubules, no staining of 13H9 can be detected. Removal of the nocodazole allows the microtubules to reform, in an ordered proximal-to- distal fashion. The 13H9 immunoreactivity also reappears, but only in the growth cones, not in any intermediate positions along the axon, and only after the reformation of microtubules is complete. The results indicate that the antigen recognized by 13H9 is highly concentrated in growth cones, closely associated with polymerized actin, and that its proper localization depends upon intact microtubules. PMID:2677024

  9. An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9

    PubMed Central

    Goldstein, Orly; Mezey, Jason G.; Boyko, Adam R.; Gao, Chuan; Wang, Wei; Bustamante, Carlos D.; Anguish, Lynne J.; Jordan, Julie Ann; Pearce-Kelling, Susan E.; Aguirre, Gustavo D.

    2010-01-01

    Purpose To identify the causative mutation in a canine cone-rod dystrophy (crd3) that segregates as an adult onset disorder in the Glen of Imaal Terrier breed of dog. Methods Glen of Imaal Terriers were ascertained for crd3 phenotype by clinical ophthalmoscopic examination, and in selected cases by electroretinography. Blood samples from affected cases and non-affected controls were collected and used, after DNA extraction, to undertake a genome-wide association study using Affymetrix Version 2 Canine single nucleotide polymorphism chips and 250K Sty Assay protocol. Positional candidate gene analysis was undertaken for genes identified within the peak-association signal region. Retinal morphology of selected crd3-affected dogs was evaluated by light and electron microscopy. Results A peak association signal exceeding genome-wide significance was identified on canine chromosome 16. Evaluation of genes in this region suggested A Disintegrin And Metalloprotease domain, family member 9 (ADAM9), identified concurrently elsewhere as the cause of human cone-rod dystrophy 9 (CORD9), as a strong positional candidate for canine crd3. Sequence analysis identified a large genomic deletion (over 20 kb) that removed exons 15 and 16 from the ADAM9 transcript, introduced a premature stop, and would remove critical domains from the encoded protein. Light and electron microscopy established that, as in ADAM9 knockout mice, the primary lesion in crd3 appears to be a failure of the apical microvilli of the retinal pigment epithelium to appropriately invest photoreceptor outer segments. By electroretinography, retinal function appears normal in very young crd3-affected dogs, but by 15 months of age, cone dysfunction is present. Subsequently, both rod and cone function degenerate. Conclusions Identification of this ADAM9 deletion in crd3-affected dogs establishes this canine disease as orthologous to CORD9 in humans, and offers opportunities for further characterization of the disease

  10. Multiple rod-cone and cone-rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression.

    PubMed

    Simões, Bruno F; Sampaio, Filipa L; Loew, Ellis R; Sanders, Kate L; Fisher, Robert N; Hart, Nathan S; Hunt, David M; Partridge, Julian C; Gower, David J

    2016-01-27

    In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor 'transmutation'. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1, sws1 and lws, in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.

  11. Uptake and release of [3H]GABA by growth cones isolated from neonatal rat brain.

    PubMed

    Gordon-Weeks, P R; Lockerbie, R O; Pearce, B R

    1984-11-23

    A subcellular fraction highly enriched in neuronal growth cones was isolated from 5-day-old rat forebrain by a recently described method. The growth cone fraction was shown to have a sodium- and temperature-dependent, high-affinity (Km = 4.4 microM) uptake system for [3H]GABA. Electron microscopic autoradiography confirmed that this uptake was into growth cones since only these structures were heavily labelled with silver grains. High potassium induced the release of newly accumulated [3H]GABA from the growth cone fraction, about half of which was Ca2+-dependent. The presence of uptake and release systems for GABA in growth cones may simply reflect the development of growth cones into nerve terminals. Alternatively, these observations may indicate a role for neurotransmitter release in synaptogenesis.

  12. A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors

    PubMed Central

    Jackman, Skyler L.; Babai, Norbert; Chambers, James J.; Thoreson, Wallace B.; Kramer, Richard H.

    2011-01-01

    Cone photoreceptors and horizontal cells (HCs) have a reciprocal synapse that underlies lateral inhibition and establishes the antagonistic center-surround organization of the visual system. Cones transmit to HCs through an excitatory synapse and HCs feed back to cones through an inhibitory synapse. Here we report that HCs also transmit to cone terminals a positive feedback signal that elevates intracellular Ca2+ and accelerates neurotransmitter release. Positive and negative feedback are both initiated by AMPA receptors on HCs, but positive feedback appears to be mediated by a change in HC Ca2+, whereas negative feedback is mediated by a change in HC membrane potential. Local uncaging of AMPA receptor agonists suggests that positive feedback is spatially constrained to active HC-cone synapses, whereas the negative feedback signal spreads through HCs to affect release from surrounding cones. By locally offsetting the effects of negative feedback, positive feedback may amplify photoreceptor synaptic release without sacrificing HC-mediated contrast enhancement. PMID:21559323

  13. The study on stress-cone based on HTS cable terminal

    NASA Astrophysics Data System (ADS)

    Wu, C. Y.; Fang, J.; Huang, X. H.; Lu, W. J.; Li, D.; Guo, L. J.

    2013-01-01

    Our research aims at improving the performance of 35 kV class stress-cone for HTS cable terminal. Firstly, the equivalent circuit model of a stress-cone is constructed for simulation. The relation between the sag voltage of each layer can be characterized by structural and material parameters, such as the stress-cone’s plate length, plate radius, insulating material thickness and dielectric constant. Secondly, the simulation based on ANSYS is developed for analyzing the electric field of stress cone of HTS cable terminal, by altering the length of step and insulation material parameter of stress cone, we get the voltage of each plate layer, horizontal electric field and vertical electric field, and the influence of stress-cone parameter on stress cone electric field is analyzed.

  14. Use of scanning ion conductance microscopy to guide and redirect neuronal growth cones.

    PubMed

    Pellegrino, Mario; Orsini, Paolo; De Gregorio, Francesca

    2009-07-01

    Scanning ion conductance microscopy has been applied to neuronal growth cones of the leech either to image or to stimulate them. Growth cone advance was recorded in non-contact mode using a 2% ion current decrease criterion for pipette-membrane distance control. We demonstrate effective growth cone remodelling using a 5% criterion (near-scanning). Recurrent line near-scanning aligned growth cone processes along the scan line. The new membrane protrusions, marked by DiI, started a few minutes after scanning onset and progressively grew in thickness. Using scanning patterns suitable for connecting distinct growth cones, new links were consistently developed. Although the underlying mechanism is still a matter for investigation, a mechanical perturbation produced by the moving probe appeared to induce the process formation. Thanks to its deterministic and interactive features, this novel approach to guiding growth cones is a promising way to develop networks of identified neurons as well as link them with artificial structures. PMID:19447298

  15. The influence of retinal illuminance on L- and M-cone driven electroretinograms.

    PubMed

    Kremers, Jan; Parry, Neil R A; Panorgias, Athanasios; Murray, Ian J

    2011-03-01

    The electroretinographic response to L- and M-cone isolating stimuli was measured at different luminance levels to study the effect of retinal illuminance on amplitude and phase, and how this may influence estimates of L:M ratios in the retina. It was found that the amplitude of L- and M-cone driven responses increases differently with increasing retinal illuminance: L-cone responses increase more quickly than those of M-cones. The L:M ratio does not change strongly with retinal illuminance. The phase of both L- and M-cone driven responses advances with increasing retinal illuminance. There is considerable interindividual variability in the phase difference between the two, but generally M-cone driven responses are phase advanced.

  16. A tetrachromatic display for the spatiotemporal control of rod and cone stimulation.

    PubMed

    Bayer, Florian S; Paulun, Vivian C; Weiss, David; Gegenfurtner, Karl R

    2015-08-01

    We present an apparatus that allows independent stimulation of rods and short (S)-, middle (M)-, and long (L)-wavelength-sensitive cones. Previously presented devices allow rod and cone stimulation independently, but only for a spatially invariant stimulus design (Pokorny, Smithson, & Quinlan, 2004; Sun, Pokorny, & Smith, 2001b). We overcame this limitation by using two spectrally filtered projectors with overlapping projections. This approach allows independent rod and cone stimulation in a dynamic two-dimensional scene with appropriate resolution in the spatial, temporal, and receptor domains. Modulation depths were ±15% for M-cones and L-cones, ±20% for rods, and ±50% for S-cones, all with respect to an equal-energy mesopic background at 3.4 cd/m2. Validation was provided by radiometric measures and behavioral data from two trichromats, one protanope, one deuteranope, and one night-blind observer. PMID:26305863

  17. Semi-automated identification of cones in the human retina using circle Hough transform

    PubMed Central

    Bukowska, Danuta M.; Chew, Avenell L.; Huynh, Emily; Kashani, Irwin; Wan, Sue Ling; Wan, Pak Ming; Chen, Fred K

    2015-01-01

    A large number of human retinal diseases are characterized by a progressive loss of cones, the photoreceptors critical for visual acuity and color perception. Adaptive Optics (AO) imaging presents a potential method to study these cells in vivo. However, AO imaging in ophthalmology is a relatively new phenomenon and quantitative analysis of these images remains difficult and tedious using manual methods. This paper illustrates a novel semi-automated quantitative technique enabling registration of AO images to macular landmarks, cone counting and its radius quantification at specified distances from the foveal center. The new cone counting approach employs the circle Hough transform (cHT) and is compared to automated counting methods, as well as arbitrated manual cone identification. We explore the impact of varying the circle detection parameter on the validity of cHT cone counting and discuss the potential role of using this algorithm in detecting both cones and rods separately. PMID:26713186

  18. Radixin Is Involved in Lamellipodial Stability during Nerve Growth Cone Motility

    PubMed Central

    Castelo, Leslie; Jay, Daniel G.

    1999-01-01

    Immunocytochemistry and in vitro studies have suggested that the ERM (ezrin-radixin-moesin) protein, radixin, may have a role in nerve growth cone motility. We tested the in situ role of radixin in chick dorsal root ganglion growth cones by observing the effects of its localized and acute inactivation. Microscale chromophore-assisted laser inactivation (micro-CALI) of radixin in growth cones causes a 30% reduction of lamellipodial area within the irradiated region whereas all control treatments did not affect lamellipodia. Micro-CALI of radixin targeted to the middle of the leading edge often split growth cones to form two smaller growth cones during continued forward movement (>80%). These findings suggest a critical role for radixin in growth cone lamellipodia that is similar to ezrin function in pseudopodia of transformed fibroblasts. They are consistent with radixin linking actin filaments to each other or to the membrane during motility. PMID:10233159

  19. Time-size trade-offs in responses of cycads to male cone herbivory.

    PubMed

    Marler, Thomas E

    2010-11-01

    Plant-arthropod pollination mutualisms based on adults as pollinators and juveniles as predators of reproductive structures are understood to be successful by balancing the benefits of pollination with the antagonisms of herbivory. In a recent paper, I showed that Cycas micronesica male cone herbivory by larvae of the pollinator moth Anatrachyntis species hastened the plant's subsequent reproductive event. In this mutualism, both pollination and predation elicit distinct increases in plant fitness. The results support a resource tradeoff within an optimal-allocation model whereby cone disposal by the pollinator juveniles reduces reproductive costs. Many cycad species exhibit an annual coning season that is fixed by the environment, and in those cases the trade-off may be expressed as plasticity in cone size or cone number. Conservation plans would benefit from understanding the consequences of the lack of natural cone herbivory in ex situ germplasm management. PMID:21331253

  20. Time-size trade-offs in responses of cycads to male cone herbivory.

    PubMed

    Marler, Thomas E

    2010-11-01

    Plant-arthropod pollination mutualisms based on adults as pollinators and juveniles as predators of reproductive structures are understood to be successful by balancing the benefits of pollination with the antagonisms of herbivory. In a recent paper, I showed that Cycas micronesica male cone herbivory by larvae of the pollinator moth Anatrachyntis species hastened the plant's subsequent reproductive event. In this mutualism, both pollination and predation elicit distinct increases in plant fitness. The results support a resource tradeoff within an optimal-allocation model whereby cone disposal by the pollinator juveniles reduces reproductive costs. Many cycad species exhibit an annual coning season that is fixed by the environment, and in those cases the trade-off may be expressed as plasticity in cone size or cone number. Conservation plans would benefit from understanding the consequences of the lack of natural cone herbivory in ex situ germplasm management.

  1. When Do Short-Wave Cones Signal Blue or Red? A Solution Introducing the Concept of Primary and Secondary Cone Outputs

    PubMed Central

    2016-01-01

    A recent paper by Oh and Sakata investigates the “incompletely solved mystery” of how the three cone responses map onto perceived hue, and particularly the S cone’s well-known problematic contribution to blueness and redness. Citing previous workers, they argue the twentieth century traditional multistage model does not satisfactorily account for color appearance. In their experiment, increasing S cone excitation with shortening wavelength from about 480–460 nm increased perceived blueness up to the unique Blue point at 470 nm, when (a) it began decreasing and (b) redness perception began increasing. The authors asked, What mechanism can be responsible for such functions? I demonstrate a solution. First, it is shown the problem does not lie in the traditional opponent color chromatic responses yellow-blue, red-green (y-b, r-g, which accurately predict the above functions), but in the traditional multistage model of mapping cone responses to chromatic response functions. Arguably, this is due to the S cone’s hypothetically signaling both blueness and redness by the same mechanism rather than by different, independent, mechanisms. Hence a new distinction or mechanism is proposed for a more accurate model, that introduces the new terms primary and secondary cone outputs. However, this distinction requires that the cones S, M, L each directly produce one of the three spectral chromatic responses b, g, y. Such a model was recently published, based on extremely high correlation of SML cone responsivities with the three spectral (bgy) chromatic responses. This model encodes the former directly onto the latter one-to-one as cone primary outputs, whilst S and L cones have a further or secondary function where each produces one of the two spectral lobes of r chromatic response. The proposed distinction between primary and secondary cone outputs is a new concept and useful tool in detailing cone outputs to chromatic channels, and provides a solution to the above

  2. Integrins and cAMP mediate netrin-induced growth cone collapse

    PubMed Central

    Lemons, M.L.; Abanto, M.L.; Dambrouskas, N.; Clements, C.C.; DeLoughery, Z.; Garozzo, J.; Condic, M.L.

    2013-01-01

    Growth cones integrate a remarkably complex concert of chemical cues to guide axons to their appropriate destinations. Recent work suggests that integrins contribute to axon guidance by interacting with a wide range of extracellular molecules including axon guidance molecules, by mechanisms that are not fully understood. Here, we describe an interaction between integrins and netrin-1 in growth cones that contributes to growth cone collapse. Our data show that netrin-1 causes growth cone collapse in a substratum-specific manner and is integrin-dependent. Netrin-1 causes collapse of cultured chick dorsal root ganglion (DRG) growth cones extending on high levels of laminin-1 (LN) but not growth cones extending on low levels of LN or on fibronectin. Blocking integrin function significantly decreases netrin-induced growth cone collapse on high LN. Netrin-1 and integrins interact on growth cones; netrin-1 causes integrin activation, a conformational shift to a high ligand-affinity state. Netrin-1 directly binds to integrin α3 and α6 peptides, further suggesting a netrin-integrin interaction. Interestingly, our data reveal netrin-1 increases growth cone levels of cAMP in a substratum-specific manner and that netrin-induced growth cone collapse requires increased cAMP in combination with integrin activation. Manipulations that either decrease cAMP levels or integrin activation block netrin-induced collapse. These results imply a common mechanism for growth cone collapse and novel interactions between integrins, netrin-1 and cAMP that contribute to growth cone guidance. PMID:24001590

  3. On the shielding of sound from a source near one or two coaxial cones

    NASA Astrophysics Data System (ADS)

    Campos, L. M. B. C.; Gil, P. J. S.

    2016-06-01

    The shielding of the sound from a source near a cone or two coaxial circular cones is addressed by an exact analytical method, considering free spherical waves satisfying a rigid or impedance boundary condition on the wall of the cone(s); the boundary condition is applied for impedance proportional to the distance from the vertex. The exact solution involves the eigenvalues of the problem that are generally real or complex (not integers), and coincide with the degree of the associated Legendre functions and order of the spherical Bessel functions which specify respectively the latitudinal and radial dependencies of the wave field. These eigenfunctions or 'conical wave harmonics' can be chosen in more than one way, e.g. (a) as standing wave modes which are finite at the vertex of the cone(s), but do not satisfy a radiation condition at infinity; (b) as propagating waves satisfying a radiation condition at infinity, and generally singular at the vertex of the cone(s). The method of calculation of eigenvalues and eigenfunctions is presented both for a single cone and two coaxial cones with the same vertex, and arbitrary aperture(s). The method specifies the eigenvalues, and the corresponding radial, azimuthal and latitudinal eigenfunctions. An asymptotic formula is obtained for the eigenvalues which gives reasonable good agreement with the exact results. The eigenvalues and eigenfunctions appear with suitable amplitudes in the Green function representing a monopole source near the vertex of the cone(s). The acoustic field is plotted also for a longitudinal and a transverse dipole and mixed quadrupole source near the vertex.

  4. Formation of shatter cones by symmetric fracture bifurcation: Phenomenological modeling and validation

    NASA Astrophysics Data System (ADS)

    Kenkmann, Thomas; Hergarten, Stefan; Kuhn, Thomas; Wilk, Jakob

    2016-08-01

    Several models of shatter cone formation require a heterogeneity at the cone apex of high impedance mismatch to the surrounding bulk rock. This heterogeneity is the source of spherically expanding waves that interact with the planar shock front or the following release wave. While these models are capable of explaining the overall conical shape of shatter cones, they are not capable of explaining the subcone structure and the diverging and branching striations that characterize the surface of shatter cones and lead to the so-called horse-tailing effect. Here, we use the hierarchical arrangement of subcone ridges of shatter cone surfaces as key for understanding their formation. Tracing a single subcone ridge from its apex downward reveals that each ridge branches after some distance into two symmetrically equivalent subcone ridges. This pattern is repeated to form new branches. We propose that subcone ridges represent convex-curved fracture surfaces and their intersection corresponds to the bifurcation axis. The characteristic diverging striations are interpreted as the intersection lineations delimiting each subcone. Multiple symmetric crack branching is the result of rapid fracture propagation that may approach the Raleigh wave speed. We present a phenomenological model that fully constructs the shatter cone geometry to any order. The overall cone geometry including apex angle of the enveloping cone and the degree of concavity (horse-tailing) is largely governed by the convexity of the subcone ridges. Straight cones of various apical angles, constant slope, and constant bifurcation angles form if the subcone convexity is low (30°). Increasing subcone convexity leads to a stronger horse-tailing effect and the bifurcation angles increase with increasing distance from the enveloping cone apex. The model predicts possible triples of enveloping cone angle, bifurcation angle, and subcone angle. Measurements of these quantities on four shatter cones from different

  5. Morphometry of volcanic cones on Mars in perspective of Astrobiological Research

    NASA Astrophysics Data System (ADS)

    Gilichinsky, Michael; Demidov, Nikita; Rivkina, Elizaveta

    2015-10-01

    The permanently frozen volcanic sediment is one of the most promising geological objects for searching life on Mars. On Earth, volcanic intrusions into permafrost result in formation of the unique microbial communities. We propose several terrestrial analogues of Martian polar volcanoes, such as the permanently frozen volcanic sediments on the Kamchatka peninsula and in Antarctica. The present study shows applicability of the morphometric analysis for demonstration of the morphological similarity between the terrestrial and Martian cinder cones. In the present work, the morphometric analysis of young Martian landforms is based on the assumption that the conical structures identified on digital terrain model (DTM) are volcanic cinder cones. Morphometric analysis of the studied cones showed a range of degradation. The extent of degradation may be an indicator of age based on comparison with volcanic cinder cones on Earth. A morphometric analysis of potentially young volcanic cones in the North Polar Region of Mars was performed to estimate their relative age. The 14 potential cinder cones were identified using the DTM provided by Mars Express High Resolution Stereo Camera (HRSC), allowing for the basic morphometric calculations. The majority of the cinder cones are localized in the Chasma Boreale region within the area 79°-81°N and 261°-295°E. The calculated morphometric parameters showed that the cone average steepness varied from 3.4° to 11.8°, cone height-to-width ratio varied from 0.025 to 0.12, and the ratio between surface and basal area of the cone varied from 1.005 to 1.131. The studied cinder cones were classified with respect to the morphometric ratios assuming that larger values correspond to the younger structures. Employing the terrestrial analogy of morphometric ratios as a proxy for relative geological age, we suggest that existing microorganisms may be found in permafrost of young Martian cinder cones.

  6. Differential encoding of spatial information among retinal on cone bipolar cells.

    PubMed

    Purgert, Robert J; Lukasiewicz, Peter D

    2015-09-01

    The retina is the first stage of visual processing. It encodes elemental features of visual scenes. Distinct cone bipolar cells provide the substrate for this to occur. They encode visual information, such as color and luminance, a principle known as parallel processing. Few studies have directly examined whether different forms of spatial information are processed in parallel among cone bipolar cells. To address this issue, we examined the spatial information encoded by mouse ON cone bipolar cells, the subpopulation excited by increments in illumination. Two types of spatial processing were identified. We found that ON cone bipolar cells with axons ramifying in the central inner plexiform layer were tuned to preferentially encode small stimuli. By contrast, ON cone bipolar cells with axons ramifying in the proximal inner plexiform layer, nearest the ganglion cell layer, were tuned to encode both small and large stimuli. This dichotomy in spatial tuning is attributable to amacrine cells providing stronger inhibition to central ON cone bipolar cells compared with proximal ON cone bipolar cells. Furthermore, background illumination altered this difference in spatial tuning. It became less pronounced in bright light, as amacrine cell-driven inhibition became pervasive among all ON cone bipolar cells. These results suggest that differential amacrine cell input determined the distinct spatial encoding properties among ON cone bipolar cells. These findings enhance the known parallel processing capacity of the retina. PMID:26203104

  7. Horizontal cells of the rabbit retina are non-selectively connected to the cones.

    PubMed

    Hack, I; Peichl, L

    1999-07-01

    Mammalian horizontal cells have generally been assumed to be spectrally non-selective in their cone contacts until recently, when specific contacts have been found for some species. The rabbit retina is frequently studied as a representative of dichromatic mammalian retinae. These are the reasons for elucidating the connections of the two types of horizontal cells (A-HCs and B-HCs) with the green-sensitive and blue-sensitive cones of the rabbit retina. Individual A-HCs and B-HCs were revealed by Lucifer Yellow injections, the total cone population overlying them was stained using peanut agglutinin, and the blue cones among these were identified by the antiserum JH 455 against blue cone opsin. Both A-HCs and B-HCs indiscriminately contact the two cone types available. This holds for the green cone-dominated dorsal retina and the blue cone-dominated ventral retina. No evidence was found for a third, potentially blue cone-selective, horizontal cell type [postulated by Famiglietti, E. V. (1990) Brain Res., 535, 174-179].

  8. Peripheral detection and resolution with mid-/long-wavelength and short-wavelength sensitive cone systems.

    PubMed

    Zhu, Hai-Feng; Zele, Andrew J; Suheimat, Marwan; Lambert, Andrew J; Atchison, David A

    2016-08-01

    This study compared neural resolution and detection limits of the human mid-/long-wavelength and short-wavelength cone systems with anatomical estimates of photoreceptor and retinal ganglion cell spacings and sizes. Detection and resolution limits were measured from central fixation out to 35° eccentricity across the horizontal visual field using a modified Lotmar interferometer. The mid-/long-wavelength cone system was studied using a green (550 nm) test stimulus to which S-cones have low sensitivity. To bias resolution and detection to the short-wavelength cone system, a blue (450 nm) test stimulus was presented against a bright yellow background that desensitized the M- and L-cones. Participants were three trichromatic males with normal visual functions. With green stimuli, resolution showed a steep central-peripheral gradient that was similar between participants, whereas the detection gradient was shallower and patterns were different between participants. Detection and resolution with blue stimuli were poorer than for green stimuli. The detection of blue stimuli was superior to resolution across the horizontal visual field and the patterns were different between participants. The mid-/long-wavelength cone system's resolution is limited by midget ganglion cell spacing and its detection is limited by the size of the M- and L-cone photoreceptors, consistent with previous observations. We found that no such simple relationships occur for the short-wavelength cone system between resolution and the bistratified ganglion cell spacing, nor between detection and the S-cone photoreceptor sizes.

  9. Peripheral detection and resolution with mid-/long-wavelength and short-wavelength sensitive cone systems.

    PubMed

    Zhu, Hai-Feng; Zele, Andrew J; Suheimat, Marwan; Lambert, Andrew J; Atchison, David A

    2016-08-01

    This study compared neural resolution and detection limits of the human mid-/long-wavelength and short-wavelength cone systems with anatomical estimates of photoreceptor and retinal ganglion cell spacings and sizes. Detection and resolution limits were measured from central fixation out to 35° eccentricity across the horizontal visual field using a modified Lotmar interferometer. The mid-/long-wavelength cone system was studied using a green (550 nm) test stimulus to which S-cones have low sensitivity. To bias resolution and detection to the short-wavelength cone system, a blue (450 nm) test stimulus was presented against a bright yellow background that desensitized the M- and L-cones. Participants were three trichromatic males with normal visual functions. With green stimuli, resolution showed a steep central-peripheral gradient that was similar between participants, whereas the detection gradient was shallower and patterns were different between participants. Detection and resolution with blue stimuli were poorer than for green stimuli. The detection of blue stimuli was superior to resolution across the horizontal visual field and the patterns were different between participants. The mid-/long-wavelength cone system's resolution is limited by midget ganglion cell spacing and its detection is limited by the size of the M- and L-cone photoreceptors, consistent with previous observations. We found that no such simple relationships occur for the short-wavelength cone system between resolution and the bistratified ganglion cell spacing, nor between detection and the S-cone photoreceptor sizes. PMID:27580041

  10. Short-wavelength cone-opponent retinal ganglion cells in mammals

    PubMed Central

    MARSHAK, DAVID W.; MILLS, STEPHEN L.

    2014-01-01

    In all of the mammalian species studied to date, the short-wavelength-sensitive (S) cones and the S-cone bipolar cells that receive their input are very similar, but the retinal ganglion cells that receive synapses from the S-cone bipolar cells appear to be quite different. Here, we review the literature on mammalian retinal ganglion cells that respond selectively to stimulation of S-cones and respond with opposite polarity to longer wavelength stimuli. There are at least three basic mechanisms to generate these color-opponent responses, including: (1) opponency is generated in the outer plexiform layer by horizontal cells and is conveyed to the ganglion cells via S-cone bipolar cells, (2) inputs from bipolar cells with different cone inputs and opposite response polarity converge directly on the ganglion cells, and (3) inputs from S-cone bipolar cells are inverted by S-cone amacrine cells. These are not mutually exclusive; some mammalian ganglion cells that respond selectively to S-cone stimulation seem to utilize at least two of them. Based on these findings, we suggest that the small bistratified ganglion cells described in primates are not the ancestral type, as proposed previously. Instead, the known types of ganglion cells in this pathway evolved from monostratified ancestral types and became bistratified in some mammalian lineages. PMID:24759445

  11. Short-wavelength cone-opponent retinal ganglion cells in mammals.

    PubMed

    Marshak, David W; Mills, Stephen L

    2014-03-01

    In all of the mammalian species studied to date, the short-wavelength-sensitive (S) cones and the S-cone bipolar cells that receive their input are very similar, but the retinal ganglion cells that receive synapses from the S-cone bipolar cells appear to be quite different. Here, we review the literature on mammalian retinal ganglion cells that respond selectively to stimulation of S-cones and respond with opposite polarity to longer wavelength stimuli. There are at least three basic mechanisms to generate these color-opponent responses, including: (1) opponency is generated in the outer plexiform layer by horizontal cells and is conveyed to the ganglion cells via S-cone bipolar cells, (2) inputs from bipolar cells with different cone inputs and opposite response polarity converge directly on the ganglion cells, and (3) inputs from S-cone bipolar cells are inverted by S-cone amacrine cells. These are not mutually exclusive; some mammalian ganglion cells that respond selectively to S-cone stimulation seem to utilize at least two of them. Based on these findings, we suggest that the small bistratified ganglion cells described in primates are not the ancestral type, as proposed previously. Instead, the known types of ganglion cells in this pathway evolved from monostratified ancestral types and became bistratified in some mammalian lineages. PMID:24759445

  12. Spatial and temporal expression of cone opsins during monkey retinal development.

    PubMed

    Bumsted, K; Jasoni, C; Szél, A; Hendrickson, A

    1997-02-01

    The primate retina requires a coordinated series of developmental events to form its specialized photoreceptor topography. In this study, the temporal expression of cone photoreceptor opsin was determined in Macaca monkey retina. Markers for mRNA and protein that recognize short wavelength (S) and long/medium wavelength (L/M) opsin were used to determine (1) the temporal and spatial patterns of opsin expression, (2) the spatial relationship between S and L/M cones at the time of initial opsin expression, and (3) the relative time of cone and rod opsin expression (Dorn et al. [1995] Invest. Ophthalmol. Vis. Sci. 36:2634-2651). Adult cone outer segments were recognized by either L/M or S opsin antiserum. Of all adult cone inner segments, 88-90% contained L/M opsin mRNA, whereas 10-12% contained S opsin mRNA. Fetal cones initially showed cell membrane as well as outer segment labeling for opsin protein, but cell membrane labeling disappeared by birth. No cones at any age contained markers for both S and L/M opsin mRNA or protein. S and L/M opsin protein appeared in the fovea at fetal day 75. Once opsin expression progressed beyond the fovea, both mRNA and protein for S opsin were consistently detected more peripherally than L/M opsin. Cones at the peripheral edge of S opsin expression had basal telodendria that appeared to reach toward neighboring cones. Because interactions between cone populations could organize the cone mosaic, the spatial relationship between S cones and the first cones to express L/M protein was analyzed quantitatively by using double-label immunocytochemistry. No consistent relationship was found between these two cone populations. Cones are generated at least 1 week before rods across monkey retina. However, rod opsin protein appears in and around the fovea at fetal day 66, 1 week before cone opsin protein. This suggests that independent local factors control differentiation in these two photoreceptor populations.

  13. Meniscus Shape and Wetting Competition of a Drop between a Cone and a Plane.

    PubMed

    Liang, Yu-En; Weng, Yu-Hsuan; Tsao, Heng-Kwong; Sheng, Yu-Jane

    2016-08-23

    The formation of a liquid bridge between a cone and a plane is related to dip-pen nanolithography. The meniscus shape and rupture process of a liquid meniscus between a cone and a plane are investigated by Surface Evolver, many-body dissipative particle dynamics, and macroscopic experiments. Dependent on the cone geometry, cone-plane separation, and wetting properties of cone and plane, three types of menisci can be observed before rupture and two types of wetting competition outcomes are seen after breakup. It is interesting to find that after rupture, the bulk of the liquid bridge volume is not necessarily retained by the cone which is more wettable. In fact, a sharp hydrophilic cone often loses wetting competition to a hydrophobic plane. To explain our findings, the "apparent" contact angle of the cone is introduced and the behavior of drop-on-cone/plane system is analogous to that of a liquid bridge between two parallel planes based on this concept. PMID:27483140

  14. Hydrovolcanic (Tuff?) Rings and Cones on Mars: Evidence for Phreatomagmatic Explosive Eruptions?

    NASA Astrophysics Data System (ADS)

    Broz, P.; Hauber, E.

    2012-09-01

    We present observations of two fields of small pitted and mostly breached cones; one located along the dichotomy boundary in the Amenthes region (southern Utopia); the second located in an unnamed impact crater in the Xanthe Terra region. The aim of our study is to test the hypothesis of a (hydro)volcanic origin of these cones, which would be an alternative to the mud volcano scenario put forward by [1] for cones in Amenthes region. To aid our analysis, we also examine morphological and morphometrical data of possible terrestrial analogues (tuff rings and cones, mud volcanoes in Azerbaijan).

  15. Hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on Mars

    NASA Astrophysics Data System (ADS)

    Brož, P.; Hauber, E.

    2013-08-01

    is a common natural phenomenon on Earth and should be common on Mars, too, since its surface shows widespread evidence for volcanism and near-surface water. We investigate fields of pitted cones in the Nephentes/Amenthes region at the southern margin of the ancient impact basin, Utopia, which were previously interpreted as mud volcanoes. The cone fields contain pitted and breached cones with associated outgoing flow-like landforms. Based on stratigraphic relations, we determined a Hesperian or younger model age. We test the hypothesis of a (hydro)volcanic origin. Based on a detailed morphological and morphometrical analysis and an analysis of the regional context, an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible. Several lines of evidence suggest the existence of subsurface water ice. The pitted cones display well-developed wide central craters with floor elevations below the preeruptive surface. Their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings. Mounds that are also observed in the same region resemble terrestrial lava domes. The hydrovolcanic interaction between ascending magma and subsurface water and/or water ice may explain the formation of the pitted cones, although other scenarios such as mud volcanism cannot be ruled out. Together with the mounds, the cones might represent effusive and explosive edifices of a monogenetic volcanic field composed of lava domes, tuff rings, tuff cones, and possibly maars.

  16. Auto calibration of a cone-beam-CT

    SciTech Connect

    Gross, Daniel; Heil, Ulrich; Schulze, Ralf; Schoemer, Elmar; Schwanecke, Ulrich

    2012-10-15

    Purpose: This paper introduces a novel autocalibration method for cone-beam-CTs (CBCT) or flat-panel CTs, assuming a perfect rotation. The method is based on ellipse-fitting. Autocalibration refers to accurate recovery of the geometric alignment of a CBCT device from projection images alone, without any manual measurements. Methods: The authors use test objects containing small arbitrarily positioned radio-opaque markers. No information regarding the relative positions of the markers is used. In practice, the authors use three to eight metal ball bearings (diameter of 1 mm), e.g., positioned roughly in a vertical line such that their projection image curves on the detector preferably form large ellipses over the circular orbit. From this ellipse-to-curve mapping and also from its inversion the authors derive an explicit formula. Nonlinear optimization based on this mapping enables them to determine the six relevant parameters of the system up to the device rotation angle, which is sufficient to define the geometry of a CBCT-machine assuming a perfect rotational movement. These parameters also include out-of-plane rotations. The authors evaluate their method by simulation based on data used in two similar approaches [L. Smekal, M. Kachelriess, S. E, and K. Wa, 'Geometric misalignment and calibration in cone-beam tomography,' Med. Phys. 31(12), 3242-3266 (2004); K. Yang, A. L. C. Kwan, D. F. Miller, and J. M. Boone, 'A geometric calibration method for cone beam CT systems,' Med. Phys. 33(6), 1695-1706 (2006)]. This allows a direct comparison of accuracy. Furthermore, the authors present real-world 3D reconstructions of a dry human spine segment and an electronic device. The reconstructions were computed from projections taken with a commercial dental CBCT device having two different focus-to-detector distances that were both calibrated with their method. The authors compare their reconstruction with a reconstruction computed by the manufacturer of the CBCT device to

  17. Synaptic Elements for GABAergic Feed-Forward Signaling between HII Horizontal Cells and Blue Cone Bipolar Cells Are Enriched beneath Primate S-Cones

    PubMed Central

    Puller, Christian; Haverkamp, Silke; Neitz, Maureen; Neitz, Jay

    2014-01-01

    The functional roles and synaptic features of horizontal cells in the mammalian retina are still controversial. Evidence exists for feedback signaling from horizontal cells to cones and feed-forward signaling from horizontal cells to bipolar cells, but the details of the latter remain elusive. Here, immunohistochemistry and confocal microscopy were used to analyze the expression patterns of the SNARE protein syntaxin-4, the GABA receptor subunits α1 and ρ, and the cation-chloride cotransporters NKCC and KCC2 in the outer plexiform layer of primate retina. In macaque retina, as observed previously in other species, syntaxin-4 was expressed on dendrites and axon terminals of horizontal cells at cone pedicles and rod spherules. At cones, syntaxin-4 appeared densely clustered in two bands, at horizontal cell dendritic tips and at the level of desmosome-like junctions. Interestingly, in the lower band where horizontal cells may synapse directly onto bipolar cells, syntaxin-4 was highly enriched beneath short-wavelength sensitive (S) cones and colocalized with calbindin, a marker for HII horizontal cells. The enrichment at S-cones was not observed in either mouse or ground squirrel. Furthermore, high amounts of both GABA receptor and cation-chloride cotransporter subunits were found beneath primate S-cones. Finally, while syntaxin-4 was expressed by both HI and HII horizontal cell types, the intense clustering and colocalization with calbindin at S-cones indicated an enhanced expression in HII cells. Taken together, GABA receptors beneath cone pedicles, chloride transporters, and syntaxin-4 are putative constituents of a synaptic set of proteins which would be required for a GABA-mediated feed-forward pathway via horizontal cells carrying signals directly from cones to bipolar cells. PMID:24586460

  18. Light-cone averages in a Swiss-cheese universe

    SciTech Connect

    Marra, Valerio; Kolb, Edward W.; Matarrese, Sabino

    2008-01-15

    We analyze a toy Swiss-cheese cosmological model to study the averaging problem. In our Swiss-cheese model, the cheese is a spatially flat, matter only, Friedmann-Robertson-Walker solution (i.e., the Einstein-de Sitter model), and the holes are constructed from a Lemaitre-Tolman-Bondi solution of Einstein's equations. We study the propagation of photons in the Swiss-cheese model, and find a phenomenological homogeneous model to describe observables. Following a fitting procedure based on light-cone averages, we find that the expansion scalar is unaffected by the inhomogeneities (i.e., the phenomenological homogeneous model is the cheese model). This is because of the spherical symmetry of the model; it is unclear whether the expansion scalar will be affected by nonspherical voids. However, the light-cone average of the density as a function of redshift is affected by inhomogeneities. The effect arises because, as the universe evolves, a photon spends more and more time in the (large) voids than in the (thin) high-density structures. The phenomenological homogeneous model describing the light-cone average of the density is similar to the {lambda}CDM concordance model. It is interesting that, although the sole source in the Swiss-cheese model is matter, the phenomenological homogeneous model behaves as if it has a dark-energy component. Finally, we study how the equation of state of the phenomenological homogeneous model depends on the size of the inhomogeneities, and find that the equation-of-state parameters w{sub 0} and w{sub a} follow a power-law dependence with a scaling exponent equal to unity. That is, the equation of state depends linearly on the distance the photon travels through voids. We conclude that, within our toy model, the holes must have a present size of about 250 Mpc to be able to mimic the concordance model.

  19. Light-cone averages in a Swiss-cheese universe

    NASA Astrophysics Data System (ADS)

    Marra, Valerio; Kolb, Edward W.; Matarrese, Sabino

    2008-01-01

    We analyze a toy Swiss-cheese cosmological model to study the averaging problem. In our Swiss-cheese model, the cheese is a spatially flat, matter only, Friedmann-Robertson-Walker solution (i.e., the Einstein-de Sitter model), and the holes are constructed from a Lemaître-Tolman-Bondi solution of Einstein’s equations. We study the propagation of photons in the Swiss-cheese model, and find a phenomenological homogeneous model to describe observables. Following a fitting procedure based on light-cone averages, we find that the expansion scalar is unaffected by the inhomogeneities (i.e., the phenomenological homogeneous model is the cheese model). This is because of the spherical symmetry of the model; it is unclear whether the expansion scalar will be affected by nonspherical voids. However, the light-cone average of the density as a function of redshift is affected by inhomogeneities. The effect arises because, as the universe evolves, a photon spends more and more time in the (large) voids than in the (thin) high-density structures. The phenomenological homogeneous model describing the light-cone average of the density is similar to the ΛCDM concordance model. It is interesting that, although the sole source in the Swiss-cheese model is matter, the phenomenological homogeneous model behaves as if it has a dark-energy component. Finally, we study how the equation of state of the phenomenological homogeneous model depends on the size of the inhomogeneities, and find that the equation-of-state parameters w0 and wa follow a power-law dependence with a scaling exponent equal to unity. That is, the equation of state depends linearly on the distance the photon travels through voids. We conclude that, within our toy model, the holes must have a present size of about 250 Mpc to be able to mimic the concordance model.

  20. The Southern Cone: A critical element in North American geology

    SciTech Connect

    Dalziel, I.W.D. . Inst. for Geophysics)

    1993-02-01

    The Pacific and Atlantic-Gulf of Mexico continental margins converge towards southern Mexico, delimiting the Southern Cone of North American. The margins are controlled by late Precambrian to early Paleozoic rift systems. The Neoproterozoic rifts along the Pacific margin truncate the 1.3--1.0 Ga Grenville-Llano front and still older structural boundaries within the craton, such as the Snowbird line. The Atlantic margin originated by separation from another continent within the Grenville orogen near the time of the Precambrian-Cambrian boundary. The Gulf of Mexico margin was initiated with rifting at that time, but appears to truncate the Ordovician Taconian orogen in Georgia. The continental margins of the Southern Cone may prove critical in understanding the origin of North America as a discrete continent. A possible continuation of the Grenville-Llano front has now been identified along the Pacific margin of the East Antarctic craton; the opposite side of the Grenville orogen may be present in South America and East Antarctic; a southern continuation of the Taconic Appalachians may have been identified in southern South American and Antarctica (L. Dalla Salda et al., Geology, 1992 a;b: I. Dalziel, Geology, 1991, and GSA Today, 1992; P. Hoffman, Science, 1991; E. Moores, Geology, 1991). Thus the geology of the Southern Cone of North America provides opportunities for critical testing of these globally important hypotheses, notably through geochronometry, isotope geochemistry, stratigraphy, and paleobiogeography. Conversely, East Antarctica, southern Africa, and the proto-Andean margin of South America may offer exciting opportunities to further understanding of pre-Pangea geology across southern North America.

  1. Moon Farside, Quiet Cone and the "RLI" Experiment

    NASA Astrophysics Data System (ADS)

    Maccone, C.

    The Farside of the Moon is a unique place. Radio emissions coming from the Earth, and notably the from Telecommunication Satellites orbiting the Earth, don't get there since shielded by the Moon's spherical body. A radio telescope placed inside Crater Daedalus (just at the center of the Farside) would thus sense no man-made RFI (Radio Frequency Interference) and would be ideal for all radio astronomical and SETI searches. Above the Farside, a conical region extends into space, the ``Quiet Cone'', tangent to the Moon surface and with apex a few thousands of kilometers above the Moon. The size of the Quiet Cone, however, is only vaguely known, and changes in time, because the orbits of secret military satellites around the Earth are of course unknown. The only way to know the current, actual size of the Quiet Cone is to send a radiometer into orbit around the Moon and find out where the RFI coming from the Earth is actually shielded and where it is not. The RLI Experiment (RLI is an acronym for ``Radiometro Lunare Italiano'', i.e. Italian Moon Radiometer), is currently under construction by an Italian team coordinated by this author as Principal Investigator. The RLI is hopefully going to be put into orbit around the Moon before 2007. This will be done by placing the RLI radiometer aboard the ``Trailbalzer'', the first American commercial Moon spacecraft, built by TransOrbital Inc.. The RLI Experiment will take direct measurements of the intensity of man-made RFI around two frequencies: The band in between 10.7 and 11.8 GHz (main frequency band of European TV transmissions and, in part, also of American TV transmissions) and The band in between 10 Hz and 10 kHz, to get a Fourier spectrum of the very thin Moon atmosphere. A scientific and technical description of the RLI mission is given in this paper.

  2. Isometric immersions of a cone and a cylinder

    NASA Astrophysics Data System (ADS)

    Shtogrin, Mikhail I.

    2009-02-01

    We thoroughly analyse the method used by Pogorelov to construct piecewise-smooth tubular surfaces in \\mathbb R^3 isometric to the surface of a right circular cylinder. The properties of the inverse images of edges of any tubular surface on its planar unfolding are investigated in detail. We find conditions on plane curves lying on the unfolding that enable them to be the inverse images of edges of some tubular surface. We make a refinement concerning the number of smooth pieces that form a piecewise-smooth tubular surface. We generalize Pogorelov's method from the surface of a right circular cylinder to that of a right circular cone.

  3. Clinical analysis of molar fissures by Cone-beam tomography.

    PubMed

    Cruvinel, V R N; Azevedo, B C; Gravina, D B L; Toledo, O A; Bezerra, A C B

    2007-01-01

    This study aimed to validate clinical analysis of 20 pediatric dentists on occlusal groove-fossa-system of molar depth comparing to Cone-beam tomography. The 48 sound third molars were visually classified from the shallowest to the deepest. Images were taken from the Accuitomo 3DX. There was a fair correlation between clinical analysis and the tomographic scorings (rs = 0.238; P = 0.103). It was concluded that pediatric dentists were not able to classify the fissures depth by visual analysis correctly. PMID:19161057

  4. Areal geology of the Little Cone quadrangle, Colorado

    USGS Publications Warehouse

    Bush, Alfred Lerner; Marsh, O.T.; Taylor, Richard Bartlett

    1958-01-01

    The Little Cone quadrangle includes an area of about 59 square miles in eastern San Miguel County in southwestern Colorado. It lies within and adjacent to the northeastern boundary of the Colorado Plateau physiographic province. The precipitous front of the San Juan Mountains lies a few miles to the east and northeast, and an outlier of the San Juans, the San Miguel Mountains, lies about a mile to the south. The quadrangle contains features characteristic of both the plateaus and the mountains, and has been affected by geologic events and processes of two different geologic environments.

  5. Nose-Cone Calorimeter: upgrade of PHENIX detector

    NASA Astrophysics Data System (ADS)

    Chvala, Ondrej

    2008-10-01

    PHENIX experiment at RHIC is efficient at measuring processes involving rare probes, but has limited acceptance in azimuth and pseudorapidity (η). The Nose Cone Calorimeter (NCC), a W-Si sampling calorimeter in the region of 0.9,<η<,, is one of the upgrades which will dramatically increase coverage in azimuth and pseudorapidity. The NCC will expand PHENIX's precision measurements of electromagnetic probes in η, reconstruct jets, and enhance triggering capabilities. It will significantly contribute to measurements of γ-jets, quarkonia, and low-x nuclear structure functions. Details of the detector design, performance, and a sample of the physics topics which will benefit from the NCC, will be discussed.

  6. Viscous flow over spinning cones at angle of attack.

    NASA Technical Reports Server (NTRS)

    Lin, T. C.; Rubin, S. G.

    1973-01-01

    A numerical finite-difference method is developed for evaluating the Magnus coefficients on spinning cones in laminar flow. The merged layer, the strong interaction region, and the downstream boundary layer are all considered. The numerical method is a predictor-corrector scheme developed for three-dimensional flows with or without crossflow diffusion. This method is particularly useful in problems in which a symmetry plane does not exist. Several contributions to the Magnus force and moments are considered. These include asymmetries in displacement thickness, centrifugal force and crossflow shear, and the effects of crossflow separation and vortex formation. Comparisons are made with experimental data and other analyses.

  7. Large-sized tubular graphite cones with nanotube tips

    SciTech Connect

    Shang, N.G.; Jiang, X.

    2005-10-17

    Tubular graphite cones (TGCs) have been grown on planar steel substrates by microwave plasma-assisted chemical vapor deposition with a high concentration of methane and at a high substrate temperature. The largest TGCs can reach 110 {mu}m in length and 10 {mu}m in diameter at the root. Unique TGCs terminated in long extruding carbon nanotube tips are realized. Scanning micro-Raman spectroscopy of individual TGCs shows a high crystallinity of the tips and more disordered structure of the roots. A possible growth mechanism of TGCs is presented.

  8. Light-Cone Sum Rule Approach for Baryon Form Factors

    NASA Astrophysics Data System (ADS)

    Offen, Nils

    2016-10-01

    We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.

  9. Azimuthal spin asymmetries in light-cone constituent quark models

    SciTech Connect

    Boffi, S.; Pasquini, B.; Efremov, A. V.; Schweitzer, P.

    2009-05-01

    We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with available experimental data and present predictions to be further tested by future CLAS, COMPASS, and HERMES data.

  10. Closed-form expressions for ray geometries on a cone

    NASA Astrophysics Data System (ADS)

    Jha, Rakesh Mohan; Bokhari, S. A.; Sudhakar, V.; Balakrishnan, N.

    Closed-form expressions for the geometric parameters required in the UTD (uniform geometric theory of diffraction) analysis are derived which are readily suited for the mutual coupling computations. The derivation is based upon the theory of differential geometry, and does not require the use of the developability property of the surface. It is demonstrated that the number of geodesics between any two points on a cone is finite. The inclusion of the second order geodesics results in considerable improvement in the results in certain regions, and in a closer match with the experimental results. The regions in which the mutual coupling and field computations are most affected have been identified.

  11. Light-Cone Sum Rule Approach for Baryon Form Factors

    NASA Astrophysics Data System (ADS)

    Offen, Nils

    2016-08-01

    We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.

  12. Isolation and partial characterisation of neuronal growth cones from neonatal rat forebrain.

    PubMed

    Gordon-Weeks, P R; Lockerbie, R O

    1984-09-01

    We have devised a method for the isolation of viable neuronal growth cones from neonatal rat forebrain. The method involves differential and density gradient centrifugation and exploits the relatively low buoyant density (approximately 1.018 g/cm3) of growth cones. There are no known biochemical markers for growth cones and it was necessary therefore to monitor for their presence during the isolation using transmission electron microscopy. Several criteria were used to identify isolated growth cones including the presence of filopodia, an extensive system of branching, tubular smooth endoplasmic reticulum and a region rich in microfilaments subjacent to the plasma membrane. These morphological features are similar to those of growth cones identified unequivocally in intact developing brain and in tissue culture. Electron microscopical analysis showed that greater than 90% of membrane-bound, identifiable objects in one fraction were growth cones by these criteria. The major contaminant consisted of membrane sacs and vesicles of unidentified origin. There were only small amounts of isolated rough endoplasmic reticulum and mitochondria. Isolated growth cones were roughly spherical in shape with a diameter of 1.9 +/- 0.5 micron (mean +/- 1 SD). They usually contained mitochondria, large granular vesicles and small vesicles, and occasionally contained coated vesicles, lysosomes, lamellar bodies and multivesicular bodies, and only very rarely, intermediate filaments. Occasionally, growth cones had rudimentary synapses on them. The viability of isolated growth cones was investigated by observing their behaviour in short-term culture. After a few hours in culture on poly-D-lysine-coated coverslips, growth cones flattened down and extended filopodia-like processes. This behaviour was inhibited by cytochalasin B and reversibly by cold (4 degrees C). We conclude that physiologically active growth cones can be isolated rapidly and in large numbers by the method described here.

  13. Technical Factors Influencing Cone Packing Density Estimates in Adaptive Optics Flood Illuminated Retinal Images

    PubMed Central

    Lombardo, Marco; Serrao, Sebastiano; Lombardo, Giuseppe

    2014-01-01

    Purpose To investigate the influence of various technical factors on the variation of cone packing density estimates in adaptive optics flood illuminated retinal images. Methods Adaptive optics images of the photoreceptor mosaic were obtained in fifteen healthy subjects. The cone density and Voronoi diagrams were assessed in sampling windows of 320×320 µm, 160×160 µm and 64×64 µm at 1.5 degree temporal and superior eccentricity from the preferred locus of fixation (PRL). The technical factors that have been analyzed included the sampling window size, the corrected retinal magnification factor (RMFcorr), the conversion from radial to linear distance from the PRL, the displacement between the PRL and foveal center and the manual checking of cone identification algorithm. Bland-Altman analysis was used to assess the agreement between cone density estimated within the different sampling window conditions. Results The cone density declined with decreasing sampling area and data between areas of different size showed low agreement. A high agreement was found between sampling areas of the same size when comparing density calculated with or without using individual RMFcorr. The agreement between cone density measured at radial and linear distances from the PRL and between data referred to the PRL or the foveal center was moderate. The percentage of Voronoi tiles with hexagonal packing arrangement was comparable between sampling areas of different size. The boundary effect, presence of any retinal vessels, and the manual selection of cones missed by the automated identification algorithm were identified as the factors influencing variation of cone packing arrangements in Voronoi diagrams. Conclusions The sampling window size is the main technical factor that influences variation of cone density. Clear identification of each cone in the image and the use of a large buffer zone are necessary to minimize factors influencing variation of Voronoi diagrams of the cone

  14. Differential regulation of cone calcium signals by different horizontal cell feedback mechanisms in the mouse retina.

    PubMed

    Kemmler, Robin; Schultz, Konrad; Dedek, Karin; Euler, Thomas; Schubert, Timm

    2014-08-27

    Controlling neurotransmitter release by modulating the presynaptic calcium level is a key mechanism to ensure reliable signal transmission from one neuron to the next. In this study, we investigated how the glutamatergic output of cone photoreceptors (cones) in the mouse retina is shaped by different feedback mechanisms from postsynaptic GABAergic horizontal cells (HCs) using a combination of two-photon calcium imaging and pharmacology at the level of individual cone axon terminals. We provide evidence that hemichannel-mediated (putative ephaptic) feedback sets the cone output gain by defining the basal calcium level, a mechanism that may be crucial for adapting cones to the ambient light level. In contrast, pH-mediated feedback did not modulate the cone basal calcium level but affected the size and shape of light-evoked cone calcium signals in a contrast-dependent way: low-contrast light responses were amplified, whereas high-contrast light responses were reduced. Finally, we provide functional evidence that GABA shapes light-evoked calcium signals in cones. Because we could not localize ionotropic GABA receptors on cone axon terminals using electron microscopy, we suggest that GABA may act through GABA autoreceptors on HCs, thereby possibly modulating hemichannel- and/or pH-mediated feedback. Together, our results suggest that at the cone synapse, hemichannel-mediated (ephaptic) and pH-mediated feedback fulfill distinct functions to adjust the output of cones to changing ambient light levels and stimulus contrasts and that the efficacy of these feedback mechanisms is likely modulated by GABA release in the outer retina.

  15. Selective stimulation of penumbral cones reveals perception in the shadow of retinal blood vessels.

    PubMed

    Spitschan, Manuel; Aguirre, Geoffrey K; Brainard, David H

    2015-01-01

    In 1819, Johann Purkinje described how a moving light source that displaces the shadow of the retinal blood vessels to adjacent cones can produce the entopic percept of a branching tree. Here, we describe a novel method for producing a similar percept. We used a device that mixes 56 narrowband primaries under computer control, in conjunction with the method of silent substitution, to present observers with a spectral modulation that selectively targeted penumbral cones in the shadow of the retinal blood vessels. Such a modulation elicits a clear Purkinje-tree percept. We show that the percept is specific to penumbral L and M cone stimulation and is not produced by selective penumbral S cone stimulation. The Purkinje-tree percept was strongest at 16 Hz and fell off at lower (8 Hz) and higher (32 Hz) temporal frequencies. Selective stimulation of open-field cones that are not in shadow, with penumbral cones silenced, also produced the percept, but it was not seen when penumbral and open-field cones were modulated together. This indicates the need for spatial contrast between penumbral and open-field cones to create the Purkinje-tree percept. Our observation provides a new means for studying the response of retinally stabilized images and demonstrates that penumbral cones can support spatial vision. Further, the result illustrates a way in which silent substitution techniques can fail to be silent. We show that inadvertent penumbral cone stimulation can accompany melanopsin-directed modulations that are designed only to silence open-field cones. This in turn can result in visual responses that might be mistaken as melanopsin-driven.

  16. Selective Stimulation of Penumbral Cones Reveals Perception in the Shadow of Retinal Blood Vessels

    PubMed Central

    Spitschan, Manuel; Aguirre, Geoffrey K.; Brainard, David H.

    2015-01-01

    In 1819, Johann Purkinje described how a moving light source that displaces the shadow of the retinal blood vessels to adjacent cones can produce the entopic percept of a branching tree. Here, we describe a novel method for producing a similar percept. We used a device that mixes 56 narrowband primaries under computer control, in conjunction with the method of silent substitution, to present observers with a spectral modulation that selectively targeted penumbral cones in the shadow of the retinal blood vessels. Such a modulation elicits a clear Purkinje-tree percept. We show that the percept is specific to penumbral L and M cone stimulation and is not produced by selective penumbral S cone stimulation. The Purkinje-tree percept was strongest at 16 Hz and fell off at lower (8 Hz) and higher (32 Hz) temporal frequencies. Selective stimulation of open-field cones that are not in shadow, with penumbral cones silenced, also produced the percept, but it was not seen when penumbral and open-field cones were modulated together. This indicates the need for spatial contrast between penumbral and open-field cones to create the Purkinje-tree percept. Our observation provides a new means for studying the response of retinally stabilized images and demonstrates that penumbral cones can support spatial vision. Further, the result illustrates a way in which silent substitution techniques can fail to be silent. We show that inadvertent penumbral cone stimulation can accompany melanopsin-directed modulations that are designed only to silence open-field cones. This in turn can result in visual responses that might be mistaken as melanopsin-driven. PMID:25897842

  17. Independent variation of retinal S and M cone photoreceptor topographies: A survey of four families of mammals.

    PubMed

    Ahnelt, Peter Kurt; Schubert, Christian; Kübber-Heiss, Anna; Schiviz, Alexandra; Anger, Elisabeth

    2006-01-01

    In mammals, cone photoreceptor subtypes are thought to establish topographies that reflect the species-relevant properties of the visual environment. Middle- to long-wavelength-sensitive (M) cones are the dominant population and in most species they form an area centralis at the visual axis. Short-wavelength-sensitive (S) cone topographies do not always match this pattern. We here correlate the interrelationship of S and M cone topographies in representatives of several mammalian orders with different visual ecology, including man, cheetah, cat, Eurasian lynx, African lion, wild hog, roe deer, and red deer. Retinas were labeled with opsin antisera and S and M cone distributions as well as S/M cone ratios were mapped. We find that species inhabiting open environments show M cone horizontal streaks (cheetah, pig, deer). Species living in structured habitats (tiger, lynx, red deer) have increased S cone densities along the retinal margin. In species with active vision (cheetah, bear, tiger, man), S cone distributions are more likely to follow the centripetal M cone gradients. Small species show a ventral bias of peak S cone density which either matches the peak of M cone density in a temporal area centralis (diurnal sciurid rodents, tree shrews) or not (cat, manul, roe deer). Thus, in addition to habitat structure, physical size and specific lifestyle patterns (e.g. food acquisition) appear to underlie the independent variations of M and S cone topographies.

  18. Arrestin 1 and Cone Arrestin 4 Have Unique Roles in Visual Function in an All-Cone Mouse Retina

    PubMed Central

    Deming, Janise D.; Pak, Joseph S.; Shin, Jung-a; Brown, Bruce M.; Kim, Moon K.; Aung, Moe H.; Lee, Eun-Jin; Pardue, Machelle T.; Craft, Cheryl Mae

    2015-01-01

    Purpose Previous studies discovered cone phototransduction shutoff occurs normally for Arr1−/− and Arr4−/−; however, it is defective when both visual arrestins are simultaneously not expressed (Arr1−/−Arr4−/−). We investigated the roles of visual arrestins in an all-cone retina (Nrl−/−) since each arrestin has differential effects on visual function, including ARR1 for normal light adaptation, and ARR4 for normal contrast sensitivity and visual acuity. Methods We examined Nrl−/−, Nrl−/−Arr1−/−, Nrl−/−Arr4−/−, and Nrl−/−Arr1−/−Arr4−/− mice with photopic electroretinography (ERG) to assess light adaptation and retinal responses, immunoblot and immunohistochemical localization analysis to measure retinal expression levels of M- and S-opsin, and optokinetic tracking (OKT) to measure the visual acuity and contrast sensitivity. Results Study results indicated that Nrl−/− and Nrl−/−Arr4−/− mice light adapted normally, while Nrl−/−Arr1−/− and Nrl−/−Arr1−/−Arr4−/− mice did not. Photopic ERG a-wave, b-wave, and flicker amplitudes followed a general pattern in which Nrl−/−Arr4−/− amplitudes were higher than the amplitudes of Nrl−/−, while the amplitudes of Nrl−/−Arr1−/− and Nrl−/−Arr1−/−Arr4−/− were lower. All three visual arrestin knockouts had faster implicit times than Nrl−/− mice. M-opsin expression is lower when ARR1 is not expressed, while S-opsin expression is lower when ARR4 is not expressed. Although M-opsin expression is mislocalized throughout the photoreceptor cells, S-opsin is confined to the outer segments in all genotypes. Contrast sensitivity is decreased when ARR4 is not expressed, while visual acuity was normal except in Nrl−/−Arr1−/−Arr4−/−. Conclusions Based on the opposite visual phenotypes in an all-cone retina in the Nrl−/−Arr1−/− and Nrl−/−Arr4−/− mice, we conclude that ARR1 and ARR4 perform unique

  19. A geometric calibration method for cone beam CT systems

    SciTech Connect

    Yang, Kai; Kwan, Alexander L. C.; Miller, DeWitt F.; Boone, John M.

    2006-06-15

    Cone beam CT systems are being deployed in large numbers for small animal imaging, dental imaging, and other specialty applications. A new high-precision method for cone beam CT system calibration is presented in this paper. It uses multiple projection images acquired from rotating point-like objects (metal ball bearings) and the angle information generated from the rotating gantry system is also used. It is assumed that the whole system has a mechanically stable rotation center and that the detector does not have severe out-of-plane rotation (<2 deg.). Simple geometrical relationships between the orbital paths of individual BBs and five system parameters were derived. Computer simulations were employed to validate the accuracy of this method in the presence of noise. Equal or higher accuracy was achieved compared with previous methods. This method was implemented for the geometrical calibration of both a micro CT scanner and a breast CT scanner. The reconstructed tomographic images demonstrated that the proposed method is robust and easy to implement with high precision.

  20. Development of a 3D CT scanner using cone beam

    NASA Astrophysics Data System (ADS)

    Endo, Masahiro; Kamagata, Nozomu; Sato, Kazumasa; Hattori, Yuichi; Kobayashi, Shigeo; Mizuno, Shinichi; Jimbo, Masao; Kusakabe, Masahiro

    1995-05-01

    In order to acquire 3D data of high contrast objects such as bone, lung and vessels enhanced by contrast media for use in 3D image processing, we have developed a 3D CT-scanner using cone beam x ray. The 3D CT-scanner consists of a gantry and a patient couch. The gantry consists of an x-ray tube designed for cone beam CT and a large area two-dimensional detector mounted on a single frame and rotated around an object in 12 seconds. The large area detector consists of a fluorescent plate and a charge coupled device video camera. The size of detection area was 600 mm X 450 mm capable of covering the total chest. While an x-ray tube was rotated around an object, pulsed x ray was exposed 30 times a second and 360 projected images were collected in a 12 second scan. A 256 X 256 X 256 matrix image (1.25 mm X 1.25 mm X 1.25 mm voxel) was reconstructed by a high-speed reconstruction engine. Reconstruction time was approximately 6 minutes. Cylindrical water phantoms, anesthetized rabbits with or without contrast media, and a Japanese macaque were scanned with the 3D CT-scanner. The results seem promising because they show high spatial resolution in three directions, though there existed several point to be improved. Possible improvements are discussed.

  1. Incidental findings on cone beam computed tomography images.

    PubMed

    Allareddy, Veeratrishul; Vincent, Steven D; Hellstein, John W; Qian, Fang; Smoker, Wendy R K; Ruprecht, Axel

    2012-01-01

    Background. Cone beam computed tomography (CBCT) has gained widespread acceptance in dentistry for a variety of applications. Most dentists who are not radiologists/trained in radiology are generally not familiar with interpretation of anatomical structures and/or pathosis outside their area of primary interest, as often this was not within the scope of their training. Objectives. To assess that the number of incidental findings on a CBCT scan is high both within and outside of the primary area of interest, thereby emphasizing the importance of interpretation of all areas visualized on the scan. Materials and Methods. An oral and maxillofacial radiologist reviewed 1000 CBCT scans (382 males and 618 females) for findings both in- and outside the area of interest. Results. Of the 1000 subjects that were reviewed, 943 scans showed findings in the primary regions of interest and/or outside the regions of interest, and 76 different conditions were visualized in these scans both in and outside the areas of interest. Conclusion. From the wide scope of findings noted on these scans, it can be concluded that it is essential that a person trained in advanced interpretation techniques in radiology interprets cone beam computed tomography scans.

  2. Effects of scoria-cone eruptions upon nearby human communities

    USGS Publications Warehouse

    Ort, M.H.; Elson, M.D.; Anderson, K.C.; Duffield, W.A.; Hooten, J.A.; Champion, D.E.; Waring, G.

    2008-01-01

    Scoria-cone eruptions are typically low in volume and explosivity compared with eruptions from stratovolcanoes, but they can affect local populations profoundly. Scoria-cone eruption effects vary dramatically due to eruption style, tephra blanket extent, climate, types of land use, the culture and complexity of the affected group, and resulting governmental action. A comparison of a historic eruption (Pari??cutin, Me??xico) with prehistoric eruptions (herein we primarily focus on Sunset Crater in northern Arizona, USA) elucidates the controls on and effects of these variables. Long-term effects of lava flows extend little beyond the flow edges. These flows, however, can be used for defensive purposes, providing refuges from invasion for those who know them well. In arid lands, tephra blankets serve as mulches, decreasing runoff and evaporation, increasing infiltration, and regulating soil temperature. Management and retention of these scoria mulches, which can open new areas for agriculture, become a priority for farming communities. In humid areas, though, the tephra blanket may impede plant growth and increase erosion. Cultural responses to eruptions vary, from cultural collapse, through fragmentation of society, dramatic changes, and development of new technologies, to little apparent change. Eruptions may also be viewed as retribution for poor behavior, and attempts are made to mollify angry gods. ?? 2008 Geological Society of America.

  3. DSCAM Localization and Function at the Mouse Cone Synapse

    PubMed Central

    de Andrade, Gabriel Belem; Long, Samuel S.; Fleming, Harrison; Li, Wei; Fuerst, Peter G.

    2014-01-01

    The Down Syndrome Cell Adhesion Molecule (DSCAM) is required for regulation of cell number, soma spacing and cell type specific dendrite avoidance in many types of retinal ganglion and amacrine cells. In this study we assay the organization of cells making up the outer plexiform layer of the retina in the absence of Dscam. Some types of OFF bipolar cells, type 3b and type 4 bipolar cells, had defects in dendrite arborization in the Dscam mutant retina, while other cell types appeared similar to wild type. The cone synapses that these cells project their dendrites to were intact, as visualized by electron microscopy, and had a distribution and density that was not significantly different than wild type. The spacing of type 3b bipolar cell dendrites was further analyzed by Voronoi domain analysis, Density Recovery Profiling (DRP) analysis and Nearest Neighbor Analysis (NNA). Spacing was found to be significantly different when comparing wild type and mutant type 3b bipolar cell dendrites. Defects in arborization of these bipolar cells could not be attributed to the disorganization of inner plexiform layer cells that occurs in the Dscam mutant retina or an increase in cell number, as they arborized when Dscam was targeted in retinal ganglion cells only or in the bax null retina. Localization of DSCAM was assayed and the protein was localized near to cone synapses in mouse, macaque and ground squirrel retinas. DSCAM protein was detected in several types of bipolar cells, including type 3b and type 4 bipolar cells. PMID:24477985

  4. XCone: N-jettiness as an exclusive cone jet algorithm

    NASA Astrophysics Data System (ADS)

    Stewart, Iain W.; Tackmann, Frank J.; Thaler, Jesse; Vermilion, Christopher K.; Wilkason, Thomas F.

    2015-11-01

    We introduce a new jet algorithm called XCone, for eXclusive Cone, which is based on minimizing the event shape N -jettiness. Because N -jettiness partitions every event into N jet regions and a beam region, XCone is an exclusive jet algorithm that always returns a fixed number of jets. We use a new "conical geometric" measure for which well-separated jets are bounded by circles of radius R in the rapidity-azimuth plane, while overlapping jet regions automatically form nearest-neighbor "clover jets". This avoids the split/merge criteria needed in inclusive cone algorithms. A key feature of XCone is that it smoothly transitions between the resolved regime where the N signal jets of interest are well separated and the boosted regime where they overlap. The returned value of N -jettiness also provides a quality criterion of how N -jet-like the event looks. We also discuss the N -jettiness factorization theorems that occur for various jet measures, which can be used to compute the associated exclusive N -jet cross sections. In a companion paper [1], the physics potential of XCone is demonstrated using the examples of dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs.

  5. RGBA packing for fast cone beam reconstruction on the GPU

    NASA Astrophysics Data System (ADS)

    Ino, Fumihiko; Yoshida, Seiji; Hagihara, Kenichi

    2009-02-01

    This paper presents a fast cone beam reconstruction method accelerated on the graphics processing unit (GPU). We implement the Feldkamp, Davis, and Kress (FDK) algorithm on the OpenGL graphics pipeline, which allows us to exploit the full resources and capabilities available on the GPU. The proposed method differs from previous GPU-based methods in having an RGBA packing scheme capable of directly dealing with projections without rebinning. It also reduces the amount of computation by using a data reuse scheme, which is useful to save the memory bandwidth for this memory-intensive problem. Both schemes contribute to reduce the number of rendering passes, namely the number of kernel invocations on the GPU, realizing fast cone beam reconstruction. We show some experimental results obtained on a desktop PC with an nVIDIA GeForce 8800 GTX card. As a result, the proposed method takes 8.1 seconds to reconstruct a 5123-voxel volume from 360 5122-pixel projection images. This execution time is equivalent to a 15.6-fold speedup over a CPU implementation, showing 10% higher performance as compared with a previous OpenGL-based method that requires the single-slice rebinning of projections for acceleration. With respect to non-rebinned data, our method provides approximately three times higher performance than the previous method.

  6. Receptivity of Hypersonic Boundary Layers over Straight and Flared Cones

    NASA Technical Reports Server (NTRS)

    Balakumar, Ponnampalam; Kegerise, Michael A.

    2010-01-01

    The effects of adverse pressure gradients on the receptivity and stability of hypersonic boundary layers were numerically investigated. Simulations were performed for boundary layer flows over a straight cone and two flared cones. The steady and the unsteady flow fields were obtained by solving the two-dimensional Navier-Stokes equations in axi-symmetric coordinates using the 5th order accurate weighted essentially non-oscillatory (WENO) scheme for space discretization and using third-order total-variation-diminishing (TVD) Runge-Kutta scheme for time integration. The mean boundary layer profiles were analyzed using local stability and non-local parabolized stability equations (PSE) methods. After the most amplified disturbances were identified, two-dimensional plane acoustic waves were introduced at the outer boundary of the computational domain and time accurate simulations were performed. The adverse pressure gradient was found to affect the boundary layer stability in two important ways. Firstly, the frequency of the most amplified second-mode disturbance was increased relative to the zero pressure gradient case. Secondly, the amplification of first- and second-mode disturbances was increased. Although an adverse pressure gradient enhances instability wave growth rates, small nose-tip bluntness was found to delay transition due to the low receptivity coefficient and the resulting weak initial amplitude of the instability waves. The computed and measured amplitude-frequency spectrums in all three cases agree very well in terms of frequency and the shape except for the amplitude.

  7. A review of an attempt to create shatter cones with magnetic flyer plate technology

    NASA Technical Reports Server (NTRS)

    Linnerud, H. J.

    1981-01-01

    The feasibility of creating shatter cones in a controlled laboratory environment is discussed. Magnetic flyer plate technology, which generates high amplitude shock waves in test materials is discribed. Considerable sample shear and break up was observed, however, no shatter cones are found in the tested samples.

  8. Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development

    PubMed Central

    Özel, Mehmet Neset; Langen, Marion; Hassan, Bassem A; Hiesinger, P Robin

    2015-01-01

    Filopodial dynamics are thought to control growth cone guidance, but the types and roles of growth cone dynamics underlying neural circuit assembly in a living brain are largely unknown. To address this issue, we have developed long-term, continuous, fast and high-resolution imaging of growth cone dynamics from axon growth to synapse formation in cultured Drosophila brains. Using R7 photoreceptor neurons as a model we show that >90% of the growth cone filopodia exhibit fast, stochastic dynamics that persist despite ongoing stepwise layer formation. Correspondingly, R7 growth cones stabilize early and change their final position by passive dislocation. N-Cadherin controls both fast filopodial dynamics and growth cone stabilization. Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers. Hence, growth cone dynamics can influence wiring specificity without a direct role in target recognition and implement simple rules during circuit assembly. DOI: http://dx.doi.org/10.7554/eLife.10721.001 PMID:26512889

  9. The contribution of single and double cones to spectral sensitivity in budgerigars during changing light conditions.

    PubMed

    Lind, Olle; Chavez, Johanna; Kelber, Almut

    2014-03-01

    Bird colour vision is mediated by single cones, while double cones and rods mediate luminance vision in bright and dim light, respectively. In daylight conditions, birds use colour vision to discriminate large objects such as fruit and plumage patches, and luminance vision to detect fine spatial detail and motion. However, decreasing light intensity favours achromatic mechanisms and eventually, in dim light, luminance vision outperforms colour vision in all visual tasks. We have used behavioural tests in budgerigars (Melopsittacus undulatus) to investigate how single cones, double cones and rods contribute to spectral sensitivity for large (3.4°) static monochromatic stimuli at light intensities ranging from 0.08 to 63.5 cd/m². We found no influences of rods at any intensity level. Single cones dominate the spectral sensitivity function at intensities above 1.1 cd/m², as predicted by a receptor noise-limited colour discrimination model. Below 1.1 cd/m², spectral sensitivity is lower than expected at all wavelengths except 575 nm, which corresponds to double cone function. We suggest that luminance vision mediated by double cones restores visual sensitivity when single cone sensitivity quickly decreases at light intensities close to the absolute threshold of colour vision. PMID:24366429

  10. The Mythical Retention Chart and the Corruption of Dale's Cone of Experience

    ERIC Educational Resources Information Center

    Subramony, Deepak Prem; Molenda, Michael; Betrus, Anthony K.; Thalheimer, Will

    2014-01-01

    In response to the wide-scale proliferation of "the cone of learning"--a fanciful retention chart confounded with Dale's Cone of Experience--the authors make four major claims debunking this fantasy and provide documentary evidence to support these claims. The first claim is that the data in the mythical retention chart do not make…

  11. Spatial structure of cone inputs to receptive fields in primate lateral geniculate nucleus

    NASA Astrophysics Data System (ADS)

    Reid, R. Clay; Shapley, Robert M.

    1992-04-01

    HUMAN colour vision depends on three classes of cone photoreceptors, those sensitive to short (S), medium (M) or long (L) wavelengths, and on how signals from these cones are combined by neurons in the retina and brain. Macaque monkey colour vision is similar to human, and the receptive fields of macaque visual neurons have been used as an animal model of human colour processing1. P retinal ganglion cells and parvocellular neurons are colour-selective neurons in macaque retina and lateral geniculate nucleus. Interactions between cone signals feeding into these neurons are still unclear. On the basis of experimental results with chromatic adaptation, excitatory and inhibitory inputs from L and M cones onto P cells (and parvocellular neurons) were thought to be quite specific2,3 (Fig. la). But these experiments with spatially diffuse adaptation did not rule out the 'mixed-surround' hypothesis: that there might be one cone-specific mechanism, the receptive field centre, and a surround mechanism connected to all cone types indiscriminately (Fig. le). Recent work has tended to support the mixed-surround hypothesis4-8. We report here the development of new stimuli to measure spatial maps of the linear L-, M- and S-cone inputs to test the hypothesis definitively. Our measurements contradict the mixed-surround hypothesis and imply cone specificity in both centre and surround.

  12. Discovery of Possible Meteoritic Matter on Shatter Cones and Slickensides — 1. Ries Crater, Southern Germnay

    NASA Astrophysics Data System (ADS)

    Buchner, E.; Schmieder, M.

    2016-08-01

    In the frame of the “Shatter Cone Coatings Project”, we investigated shatter cones and slickensides from the Ries crater that locally contain high concentrations of Fe, Ni, P, and particles of Fe-Ni-Co metal and metal oxide, and of Fe-Ni phosphide.

  13. Processing of the S-cone signals in the early visual cortex of primates

    PubMed Central

    XIAO, YOUPING

    2013-01-01

    The short-wavelength-sensitive (S) cones play an important role in color vision of primates, and may also contribute to the coding of other visual features, such as luminance and motion. The color signals carried by the S cones and other cone types are largely separated in the subcortical visual pathway. Studies on nonhuman primates or humans have suggested that these signals are combined in the striate cortex (V1) following a substantial amplifi cation of the S-cone signals in the same area. In addition to reviewing these studies, this review describes the circuitry in V1 that may underlie the processing of the S-cone signals and the dynamics of this processing. It also relates the interaction between various cone signals in V1 to the results of some psychophysical and physiological studies on color perception, which leads to a discussion of a previous model, in which color perception is produced by a multistage processing of the cone signals. Finally, I discuss the processing of the S-cone signals in the extrastriate area V2. PMID:23941664

  14. The current state of knowledge about shatter cones: Introduction to the special issue

    NASA Astrophysics Data System (ADS)

    Baratoux, David; Reimold, Wolf Uwe

    2016-08-01

    Shatter cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments. The occurrence of shatter cones is the only accepted meso- to macroscopic recognition criterion for impact structures. Shatter cones exhibit a number of geometric characteristics (orientation, apical angles, striation angles, sizes) that can be best described as varied, from case to case. Possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of shatter cones does not offer a physical framework to discuss or understand them. A database of shatter cone occurrences has been produced for this introduction paper to the special issue of Meteoritics and Planetary Science on shatter cones. Distribution of shatter cones with respect to crater size and lithology suggests that shatter cones do not occur in impact craters less than a few kilometers in diameter, with a few, currently questionable exceptions. All pertinent hypotheses of formation are presented and discussed. Several may be discarded in light of the most recent observations. The branching fracture mechanism and the interference models proposed, respectively, by Sagy et al. (2002) and Baratoux and Melosh (2003) require further evaluation. New observations, experiments, or theoretical considerations presented in this special issue promise an important step forward, based on a renewed effort to resolve the enigmatic origin of these important features.

  15. Worldsheet theory of light-cone gauge noncritical strings on higher genus Riemann surfaces

    NASA Astrophysics Data System (ADS)

    Ishibashi, Nobuyuki; Murakami, Koichi

    2016-06-01

    It is possible to formulate light-cone gauge string field theory in noncritical dimensions. Such a theory corresponds to conformal gauge worldsheet theory with nonstandard longitudinal part. We study the longitudinal part of the worldsheet theory on higher genus Riemann surfaces. The results in this paper shall be used to study the dimensional regularization of light-cone gauge string field theory.

  16. Discovery of Possible Meteoritic Matter on Shatter Cones — 3. Marquez Dome, Texas, USA

    NASA Astrophysics Data System (ADS)

    Schmieder, M.; Buchner, E.

    2016-08-01

    In the frame of the “Shatter Cone Coatings Project”, we investigated shatter cones from the Marquez Dome impact structure that contain Fe-Ni-Co particles (kamacite); the composition of a Fe-sulfide particle suggests the particle is troilite.

  17. Ablation and cone formation mechanism on CR-39 by ArF laser irradiation

    SciTech Connect

    Shakeri Jooybari, B. E-mail: hafarideh@aut.ac.ir; Afarideh, H. E-mail: hafarideh@aut.ac.ir; Lamehi-Rachti, M.; Ghergherehchi, M.

    2015-03-07

    In this work, chemical properties, surface modification, and micro structures formation on ablated polyallyl di-glycol carbonate (CR-39) polymer by ArF laser irradiation (λ = 193 nm) at various fluences and pulse number were investigated. CR-39 samples have been irradiated with an ArF laser (193 nm) at a repetition rate of 1 Hz. Threshold fluence of ablation and effective absorption coefficient of CR-39 were determined. Conical microstructures (Taylor cone) formed on laser-ablated CR-39 exhibit: smooth, Taylor cone shape walls and sharp tips together with interference and well defined fringe-structure with a period of 230 nm, around cone base. Mechanism of cone formation and cone evolution of CR-39 ablated surface were investigated by change of fluences (at a given pulse number) and pulse number (at a given fluence). Cone height, cone base, and region of interface were increased in micrometer steps by increasing the total fluence. Depression on the base of the cone and the circular fringe were simulated. FTIR spectra were measured and energy dispersive x-ray analysis of irradiated and un-irradiated samples was performed.

  18. Rootless cone eruption processes informed by dissected tephra deposits and conduits

    NASA Astrophysics Data System (ADS)

    Reynolds, P.; Brown, R. J.; Thordarson, T.; Llewellin, E. W.; Fielding, K.

    2015-09-01

    Rootless cones result from the explosive interaction between lava flows and underlying water-saturated sediment or volcaniclastic deposits. Rootless explosions can represent a significant far-field hazard during basaltic eruptions, but there are few detailed studies of their deposits. A rootless cone field in the 8.5 Ma Ice Harbor flow field of the Columbia River Basalt Province, NW USA, is revealed by sections through rootless conduit and cone structures. The Ice Harbor lava flow hosting the rootless cones was emplaced across a floodplain or lacustrine environment that had recently been mantled by a layer of silicic volcanic ash from a major explosive eruption. Our observations indicate a two-stage growth model for the rootless cones: (1) initial explosions generated sediment-rich tephra emplaced by fallout and pyroclastic density currents and (2) later weaker explosions that generated spatter-rich fountains. Variable explosive activity resulted in a wide range of pyroclast morphologies and vesicularities. Cross-sections through funnel-shaped conduits also show how the conduits were constructed and stabilised. The growth model is consistent with decreasing water availability with time, as inferred for rootless cones described in Iceland. The Ice Harbor rootless cones provide further lithological data to help distinguish between rootless cone-derived tephra and tephra generated above an erupting dyke.

  19. The Two-Cone Model of Second Language Teaching/Learning: Some Further Thoughts.

    ERIC Educational Resources Information Center

    Hammerly, Hector

    The developer of the two-cone model of second language teaching and learning outlines the original model and its concepts, and presents some further ideas concerning it. The model represents the native and second languages as two cones with pronunciation at the apex, morphology and syntax (grammar) at the center, and vocabulary around grammar and…

  20. Processing of the S-cone signals in the early visual cortex of primates.

    PubMed

    Xiao, Youping

    2014-03-01

    The short-wavelength-sensitive (S) cones play an important role in color vision of primates, and may also contribute to the coding of other visual features, such as luminance and motion. The color signals carried by the S cones and other cone types are largely separated in the subcortical visual pathway. Studies on nonhuman primates or humans have suggested that these signals are combined in the striate cortex (V1) following a substantial amplification of the S-cone signals in the same area. In addition to reviewing these studies, this review describes the circuitry in V1 that may underlie the processing of the S-cone signals and the dynamics of this processing. It also relates the interaction between various cone signals in V1 to the results of some psychophysical and physiological studies on color perception, which leads to a discussion of a previous model, in which color perception is produced by a multistage processing of the cone signals. Finally, I discuss the processing of the S-cone signals in the extrastriate area V2.

  1. Cone bipolar cells in the retina of the microbat Carollia perspicillata.

    PubMed

    Butz, Elisabeth; Peichl, Leo; Müller, Brigitte

    2015-04-15

    We studied the retinal cone bipolar cells of Carollia perspicillata, a microchiropteran bat of the phyllostomid family. Microchiroptera are strongly nocturnal, with small eyes and rod-dominated retinae. However, they also possess a significant cone population (2-4%) comprising two spectral types, which are hence the basis for daylight and color vision. We used antibodies against the calcium-binding protein recoverin and the carbohydrate epitope 15 (CD15) as reliable markers for certain cone bipolar cells. Dye injections of recoverin- or CD15-prelabeled cone bipolar cells in vertical slices revealed the morphology of the axon terminal system of individual bipolar cells. Seven distinct cone bipolar cell types were identified. They differed in the morphology and stratification level of their axon terminal system in the inner plexiform layer and in immunoreactivity for recoverin and/or CD15. Additional immunocytochemical markers were used to assess the functional ON/OFF subdivision of the inner plexiform layer. In line with the extended thickness of the ON sublayer of the inner plexiform layer in the microbat retina, more ON than OFF cone bipolar cell types were found, namely, four versus three. Most likely, in the bats' predominantly dark environment, ON signals have greater importance for contrast perception. We conclude that the microbat retina conforms to the general mammalian blueprint, in which light signals of intensities above rod sensitivity are detected by cones and transmitted to various types of ON and OFF cone bipolar cells. PMID:25521284

  2. A Complete Description of Cones and Polytopes Including Hypervolumes of All Facets of a Polytope

    ERIC Educational Resources Information Center

    Jubete, F.; Castillo, E.

    2007-01-01

    In this paper methods and algorithms for identifying the main elements (edges and facets of any dimension) of a cone and a polytope, and calculating the corresponding hypervolumes are presented. The cones and polytopes are supposed to be given as the non-negative linear combination and the convex hull generated by a, not necessarily minimal, set…

  3. Clinical utility of dental cone-beam computed tomography: current perspectives

    PubMed Central

    Jaju, Prashant P; Jaju, Sushma P

    2014-01-01

    Panoramic radiography and computed tomography were the pillars of maxillofacial diagnosis. With the advent of cone-beam computed tomography, dental practice has seen a paradigm shift. This review article highlights the potential applications of cone-beam computed tomography in the fields of dental implantology and forensic dentistry, and its limitations in maxillofacial diagnosis. PMID:24729729

  4. Therapeutic strategy for handling inherited retinal degenerations in a gene-independent manner using rod-derived cone viability factors.

    PubMed

    Léveillard, Thierry; Fridlich, Ram; Clérin, Emmanuelle; Aït-Ali, Najate; Millet-Puel, Géraldine; Jaillard, Céline; Yang, Ying; Zack, Donald; van-Dorsselaer, Alain; Sahel, José-Alain

    2014-03-01

    The most common hereditary retinal degeneration, retinitis pigmentosa (RP), leads to blindness by degeneration of cone photoreceptors. Meanwhile, genetic studies have shown that a significant proportion of RP genes is expressed only by rods, which raises the question of the mechanism leading to the degeneration of cones. Following the concept of sustainability factor cones, rods secrete survival factors that are necessary to maintain the cones, named Rod-derived Cone Viability Factors (RdCVFs). In patients suffering from RP, loss of rods results in the loss of RdCVFs expression and followed by cone degeneration. We have identified the bifunctional genes nucleoredoxin-like 1 and 2 that encode for, by differential splicing, a thioredoxin enzyme and a cone survival factor, respectively RdCVF and RdCVF2. The administration of these survival factors would maintain cones and central vision in most patients suffering from RP.

  5. Incremental and decremental L- and M-cone-driven ERG responses: I. Square-wave pulse stimulation.

    PubMed

    McKeefry, Declan; Kremers, Jan; Kommanapalli, Deepika; Challa, Naveen K; Murray, Ian J; Maguire, John; Parry, Neil R A

    2014-04-01

    Electroretinograms (ERGs) elicited by transient, square-wave L- and M-cone isolating stimuli were recorded from human trichromatic (n=19) and dichromatic (n=4) observers. The stimuli were generated on a four primary LED stimulator and were equated in terms of cone modulation (cone contrast=0.11) and retinal illuminance (12,000 trolands). L- and M-cone isolated ERGs had waveforms similar to those observed for luminance responses. However, M-cone ERGs exhibited a phase reversal in their responses to onset and offset stimuli relative to the L-cone responses. This on-off response reversal was observed in trichromats but not dichromats. Simultaneous counterphase and inphase combinations of L- and M-cone isolating stimuli generated responses that reflected chromatic and luminance processing, respectively. We conclude that L- and M-cone specific ERGs provide a measure of how photoreceptors contribute to postreceptoral mechanisms. PMID:24695165

  6. Estimates of L:M cone ratio from ERG flicker photometry and genetics.

    PubMed

    Carroll, Joseph; Neitz, Jay; Neitz, Maureen

    2002-01-01

    Estimates of L:M cone ratio for males with normal color vision were derived using the flicker-photometric electroretinogram (ERG). These were obtained by best fitting ERG spectral sensitivity functions to a weighted sum of long (L)- and middle (M)-wavelength-sensitive cone spectral absorption curves. Using the ERG, measurements can be made with extremely high precision, which leaves variation in the wavelength of maximal sensitivity (lambda(max)) of the cone photopigments as the major remaining source of inaccuracy in determining the ratio of cone contributions. Here that source of inaccuracy was largely eliminated through the use of individualized L-cone spectral absorption curves deduced from L-pigment gene sequences. The method was used on 62 normal males as part of an effort to obtain a true picture of how normal variations in L:M cone ratio are distributed. The percentage of L cones in the average eye was 65%L [where %L = 100 X L / (L+M)]. There were huge individual differences ranging from 28%-93%L, corresponding to more than a 30-fold range in L:M ratio (0.4-13). However, the most extreme values were relatively rare; 80% of the subjects fell within +/-15 %L of the mean, corresponding to a 4-fold range in L:M ratio (1-4). The method remedies major weaknesses inherent in earlier applications of flicker photometry to estimate cone ratio; however, it continues to depend on the assumption that the average L cone produces a response with an identical amplitude to that of the average M cone. A comparison of the ERG results with the distribution of cone ratios estimated from cone pigment messenger RNA in cadaver eyes indicates that the assumption generally holds true. However, there may be a small number of exceptions in which individuals have normally occurring (but relatively rare) amino acid substitutions in one of their pigments that significantly affect the physiology of the cone class containing that pigment, so as to reduce the amplitude of its contribution

  7. Contribution of human short-wave cones to luminance and motion detection.

    PubMed Central

    Lee, J; Stromeyer, C F

    1989-01-01

    1. Human short-wave S cone signals are important for colour vision and here we examine whether the S cone signals also contribute to motion and luminance. 2. Detection was measured with moving patterns that selectively stimulated S cones-violet sine-wave gratings of 1 cycle deg-1 on an intense yellowish field. For rates up to 12 Hz, detection was governed by non-directional mechanisms, possibly of a chromatic nature, as shown by three findings: moving gratings had to be suprathreshold for their direction to be identified; the threshold ratio of counterphase flickering versus moving gratings was low; and direction-selective adaptation was essentially absent. 3. Evidence for less sensitive, directional mechanisms includes the following: at high velocity, the direction of movement of the violet gratings can be identified just slightly above the detection threshold; directional adaptation was strong with a suprathreshold test pattern; velocity was seen veridically for clearly suprathreshold patterns; and a counterphase flickering test, added in spatial-temporal quadrature phase to a similar suprathreshold mask, had identical detection and direction-identification thresholds. 4. Interactions of long-wave L cone and S cone signals in direction-selective mechanisms were measured with an orange counterphase grating and a violet counterphase test, both flickering at the same rate and presented in spatial quadrature phase on the yellowish adapting field. Direction identification thresholds, measured as a function of the temporal phase of two gratings, demonstrated both that the S cone signal lags considerably behind the L cone signal (an effect that strongly varies with S cone light adaptation), and more strikingly, the S cone signal summates with a negative sign and thus is effectively inverted in direction-selective mechanisms. 5. Quantitatively similar temporal phase functions were obtained with uniform violet and orange flicker when a luminance discrimination criterion

  8. Comparison of the WSA-ENLIL model with three CME cone types

    NASA Astrophysics Data System (ADS)

    Jang, Soojeong; Moon, Y.; Na, H.

    2013-07-01

    We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the prediction of geomagnetic storms.Abstract (2,250 Maximum Characters): We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the

  9. The similarity of shock waves generated by a cone-shaped plasma and by a solid cone in a supersonic airflow

    SciTech Connect

    Kuo, Spencer P.; Bivolaru, Daniel

    2007-02-15

    A truncated 60 deg. cone with a slender central spike, which protrudes to the tip location of a perfect cone, is designed as a wind tunnel model. It generates a bow shock in a supersonic airflow. This model is featured with an on-board discharge arrangement with the central spike and the truncated cone as two electrodes. When the central electrode is designated as the cathode, a dc pulsed discharge produces a hollow cone-shaped plasma that envelops the spike. The results show that this plasma has changed the original bow shock to a conical shock, equivalent to reinstating the model into a perfect cone and to generate a 70% increase in the body aspect ratio. A significant drag reduction in each discharge is inferred from the pressure measurements; at the discharge maximum, the pressure on the frontal surface of the body decreases by more than 30%, the pressure on the cone surface increases by about 5%, while the pressure on the cylinder surface remains unchanged. The energy loss due to wave drag is reduced to make up for the two-thirds of the energy consumed in the electric discharge for plasma generation. The measurements also show that the plasma effect on shock structure lasts much longer than the discharge period.

  10. Contamination of gutta-percha and Resilon cones taken directly from the manufacturer.

    PubMed

    Seabra Pereira, Osvaldo L; Siqueira, José F

    2010-06-01

    Any substance and material placed in the root canal either temporarily or definitively must be free of microbial contamination. The purpose of the present study was to evaluate the percentage of contamination of Resilon cones, a polycaprolactone-based material, and seven different brands of gutta-percha cones available in the specialized market. Cones were removed from their original manufacturer boxes and immediately transferred to tubes containing thioglycolate broth. Tests were carried out in triplicate. In addition, for quantitative analysis of possible contaminants, cones were taken from their packages, transferred to tubes containing saline solution, agitated, and aliquots of this solution were seeded onto Mueller-Hinton agar plates. No sample showed contamination in any of the tests performed. Despite the absence of detectable contamination before the first use, a rationale for routinely disinfecting cones before placing them into root canals is given.

  11. Numerical investigation of cone angle effect on the flow field and separation efficiency of deoiling hydrocyclones

    NASA Astrophysics Data System (ADS)

    Saidi, Maysam; Maddahian, Reza; Farhanieh, Bijan

    2013-02-01

    In this study, the effect of cone angle on the flow field and separation efficiency of deoiling hydrocyclones is investigated taking advantage of large eddy simulation. The dynamic Smagorinsky is employed to determine the residual stress tensor of the continuous phase. The method of Lagrangian particle tracking with an optimized search algorithm (closest cell) is applied to evaluate the separation efficiency of deoiling hydrocyclone. Simulations are performed on a 35-mm deoiling hydrocyclone with the three different cone angles of 6, 10 and 20 degree. The numerical results revealed that the changes in the cone angle would affect the velocity and pressure distribution inside hydrocyclone, and lead to changes in the separation efficiency. However, the large cone angle increases the tangential velocity and pressure gradient inside the hydrocyclone, but reduces the separation efficiency. The reasons behind the decrease in the separation efficiency are the flow structure and reduction of oil droplets residence time in hydrocyclones with large cone angles.

  12. ‘Parabolic’ trapped modes and steered Dirac cones in platonic crystals

    PubMed Central

    McPhedran, R. C.; Movchan, A. B.; Movchan, N. V.; Brun, M.; Smith, M. J. A.

    2015-01-01

    This paper discusses the properties of flexural waves governed by the biharmonic operator, and propagating in a thin plate pinned at doubly periodic sets of points. The emphases are on the design of dispersion surfaces having the Dirac cone topology, and on the related topic of trapped modes in plates for a finite set (cluster) of pinned points. The Dirac cone topologies we exhibit have at least two cones touching at a point in the reciprocal lattice, augmented by another band passing through the point. We show that these Dirac cones can be steered along symmetry lines in the Brillouin zone by varying the aspect ratio of rectangular lattices of pins, and that, as the cones are moved, the involved band surfaces tilt. We link Dirac points with a parabolic profile in their neighbourhood, and the characteristic of this parabolic profile decides the direction of propagation of the trapped mode in finite clusters. PMID:27547089

  13. Observation of an anisotropic Dirac cone reshaping and ferrimagnetic spin polarization in an organic conductor.

    PubMed

    Hirata, Michihiro; Ishikawa, Kyohei; Miyagawa, Kazuya; Tamura, Masafumi; Berthier, Claude; Basko, Denis; Kobayashi, Akito; Matsuno, Genki; Kanoda, Kazushi

    2016-01-01

    The Coulomb interaction among massless Dirac fermions in graphene is unscreened around the isotropic Dirac points, causing a logarithmic velocity renormalization and a cone reshaping. In less symmetric Dirac materials possessing anisotropic cones with tilted axes, the Coulomb interaction can provide still more exotic phenomena, which have not been experimentally unveiled yet. Here, using site-selective nuclear magnetic resonance, we find a non-uniform cone reshaping accompanied by a bandwidth reduction and an emergent ferrimagnetism in tilted Dirac cones that appear on the verge of charge ordering in an organic compound. Our theoretical analyses based on the renormalization-group approach and the Hubbard model show that these observations are the direct consequences of the long-range and short-range parts of the Coulomb interaction, respectively. The cone reshaping and the bandwidth renormalization, as well as the magnetic behaviour revealed here, can be ubiquitous and vital for many Dirac materials. PMID:27578363

  14. S-cone discrimination in the presence of two adapting fields: data and model.

    PubMed

    Cao, Dingcai

    2014-04-01

    This study investigated S-cone discrimination using a test annulus surrounded by an inner and outer adapting field with systematic manipulation of the adapting l=L/(L+M) or s=S/(L+M) chromaticities. The results showed that different adapting l chromaticities altered S-cone discrimination for a high adapting s chromaticity due to parvocellular input to the koniocellular pathway. In addition, S-cone discrimination was determined by the combined spectral signals arising from both adapting fields. The "white" adapting field or an adapting field with a different l chromaticity from the other fields was more likely to have a stronger influence on discrimination thresholds. These results indicated that the two cardinal axes are not independent in S-cone discrimination, and the two adapting fields jointly contribute to S-cone discrimination through a cortical summation mechanism.

  15. Local Resonance Broadband Gap in a Homogeneous Plate with Periodic Truncated Cones

    NASA Astrophysics Data System (ADS)

    Chen, Jiu-jiu; Zhang, Hong-bo; Han, Xu

    2013-03-01

    We investigate the band structures in a homogeneous plate with periodic truncated cones for the square lattice based on finite element method (FEM). The radius of the truncated cone is gradually reduced from the lower base to the upper base. Compared to the classical stubbed phononic plates, a considerable enlargement of the bandwidth by a factor of 2.04 is obtained by varying the semiangle of the truncated cone, while the truncated cone's weight is only 65.19% of that of the cylinder of the stubbed case. Moreover the relative bandwidth is also enlarged by a factor of 1.68. We show that this band gap enlargement is due to the acoustic waves of different wavelengths is localized at the different parts of the truncated cone. These characteristics of elastic or acoustic waves suggest potential applications in aerospace.

  16. Physical properties of thin-film field emission cathodes with molybdenum cones

    NASA Technical Reports Server (NTRS)

    Spindt, C. A.; Brodie, I.; Humphrey, L.; Westerberg, E. R.

    1976-01-01

    Field emission cathodes fabricated using thin-film techniques and electron beam microlithography are described, together with effects obtained by varying the fabrication parameters. The emission originates from the tip of molybdenum cones that are about 1.5 micron tall with a tip radius around 500 A. Such cathodes have been produced in closely packed arrays containing 100 and 5000 cones as well as singly. Maximum currents in the range 50-150 microamp per cone can be drawn. Life tests with the 100-cone arrays drawing 2 mA total emission (or 3 A per sq cm) have proceeded in excess of 7000 hr with about a 10% drop in emission current. Studies are presented of the emission characteristics and current fluctuation phenomena. It is tentatively concluded that the emission arises from only one or a few atomic sites on the cone tips.

  17. Heat transfer analysis in an annular cone subjected to power law variations

    NASA Astrophysics Data System (ADS)

    Salman Ahmed, N. J.; Al-Rashed, Abdullah A. A. A.; Yunus Khan, T. M.; Kamangar, Sarfaraz; Athani, Abdulgaphur; Anjum Badruddin, Irfan

    2016-09-01

    Present study deals with the analysis of heat transfer and fluid flow behavior in an annular cone fixed with saturated porous medium. The inner surface of the cone is assumed to have power law variable wall temperature. The governing partial differential equations are solved using well known Finite Element Method (FEM). The coupled nonlinear differential equations are converted into the algebraic equations by using Galerkin method. A 3 noded triangular element is used to divide the porous domain into smaller segments. The effects of various geometrical parameters on the cone angle are presented. It is found that the effect of cone angle on the heat transfer characteristics and fluid flow behavior is considerably significant. The fluid moment is found to shift towards the upper side of cone with increase in the power law coefficient. The fluid velocity decreases with increase in the power law coefficient.

  18. Observation of an anisotropic Dirac cone reshaping and ferrimagnetic spin polarization in an organic conductor

    NASA Astrophysics Data System (ADS)

    Hirata, Michihiro; Ishikawa, Kyohei; Miyagawa, Kazuya; Tamura, Masafumi; Berthier, Claude; Basko, Denis; Kobayashi, Akito; Matsuno, Genki; Kanoda, Kazushi

    2016-08-01

    The Coulomb interaction among massless Dirac fermions in graphene is unscreened around the isotropic Dirac points, causing a logarithmic velocity renormalization and a cone reshaping. In less symmetric Dirac materials possessing anisotropic cones with tilted axes, the Coulomb interaction can provide still more exotic phenomena, which have not been experimentally unveiled yet. Here, using site-selective nuclear magnetic resonance, we find a non-uniform cone reshaping accompanied by a bandwidth reduction and an emergent ferrimagnetism in tilted Dirac cones that appear on the verge of charge ordering in an organic compound. Our theoretical analyses based on the renormalization-group approach and the Hubbard model show that these observations are the direct consequences of the long-range and short-range parts of the Coulomb interaction, respectively. The cone reshaping and the bandwidth renormalization, as well as the magnetic behaviour revealed here, can be ubiquitous and vital for many Dirac materials.

  19. Spatial order in short-wavelength-sensitive cone photoreceptors: a comparative study of the primate retina.

    PubMed

    Martin, P R; Grünert, U; Chan, T L; Bumsted, K

    2000-03-01

    We compared the spatial distribution of short-wavelength-sensitive (SWS or blue) cone photoreceptors in the retinas of eight primate species. The regularity of the SWS cone array was quantified with a statistic (packing factor) that varies between a random distribution (0) and a triangular array (1). We find wide variability among species, with packing factors varying between 0.06 and 0.3. The SWS cone array in at least two New World monkey species is indistinguishable from a random array. The SWS cone density gradient across the retina was measured in the capuchin monkey Cebus apella and the squirrel monkey Saimiri sciureus. Both species show a peak density of 5,000-8,000 cells/mm2 at the fovea and a 50-fold central-peripheral density gradient. In contrast to the wide variation in local regularity, the spatial density and the topography of SWS cones are well preserved across primates.

  20. Observation of an anisotropic Dirac cone reshaping and ferrimagnetic spin polarization in an organic conductor

    PubMed Central

    Hirata, Michihiro; Ishikawa, Kyohei; Miyagawa, Kazuya; Tamura, Masafumi; Berthier, Claude; Basko, Denis; Kobayashi, Akito; Matsuno, Genki; Kanoda, Kazushi

    2016-01-01

    The Coulomb interaction among massless Dirac fermions in graphene is unscreened around the isotropic Dirac points, causing a logarithmic velocity renormalization and a cone reshaping. In less symmetric Dirac materials possessing anisotropic cones with tilted axes, the Coulomb interaction can provide still more exotic phenomena, which have not been experimentally unveiled yet. Here, using site-selective nuclear magnetic resonance, we find a non-uniform cone reshaping accompanied by a bandwidth reduction and an emergent ferrimagnetism in tilted Dirac cones that appear on the verge of charge ordering in an organic compound. Our theoretical analyses based on the renormalization-group approach and the Hubbard model show that these observations are the direct consequences of the long-range and short-range parts of the Coulomb interaction, respectively. The cone reshaping and the bandwidth renormalization, as well as the magnetic behaviour revealed here, can be ubiquitous and vital for many Dirac materials. PMID:27578363