Science.gov

Sample records for 21-rod bundle flow

  1. PWR FLECHT SEASET 21-rod bundle flow blockage task data and analysis report. NRC/EPRI/Westinghouse Report No. 11. Appendices K-P

    SciTech Connect

    Loftus, M.J.; Hochreiter, L.E.; Lee, N.; McGuire, M.F.; Wenzel, A.H.; Valkovic, M.M.

    1982-09-01

    This report presents data and limited analysis from the 21-Rod Bundle Flow Blockage Task of the Full-Length Emergency Cooling Heat Transfer Separate Effects and Systems Effects Test Program (FLECHT SEASET). The tests consisted of forced and gravity reflooding tests utilizing electrical heater rods with a cosine axial power profile to simulate PWR nuclear core fuel rod arrays. Steam cooling and hydraulic characteristics tests were also conducted. These tests were utilized to determine effects of various flow blockage configurations (shapes and distributions) on reflooding behavior, to aid in development/assessment of computational models in predicting reflooding behavior of flow blockage configurations, and to screen flow blockage configurations for future 163-rod flow blockage bundle tests.

  2. PWR FLECHT SEASET 21-rod-bundle flow-blockage task: data and analysis report. NRC/EPRI/Westinghouse report No. 11, main report and appendices A-J

    SciTech Connect

    Loftus, M.J.; Hochreiter, L.E.; Lee, N.; McGuire, M.F.; Wenzel, A.H.; Valkovic, M.M.

    1982-09-01

    This report presents data and limited analysis from the 21-Rod Bundle Flow Blockage Task of the Full-Length Emergency Cooling Heat Transfer Separate Effects and Systems Effects Test Program (FLECHT SEASET). The tests consisted of forced and gravity reflooding tests utilizing electrical heater rods with a cosine axial power profile to simulate PWR nuclear core fuel rod arrays. Steam cooling and hydraulic characteristics tests were also conducted. These tests were utilized to determine effects of various flow blockage configurations (shapes and distributions) on reflooding behavior, to aid in development/assessment of computational models in predicting reflooding behavior of flow blockage configurations, and to screen flow blockage configurations for future 163-rod flow blockage bundle tests.

  3. Vertical, Bubbly, Cross-Flow Characteristics over Tube Bundles

    NASA Astrophysics Data System (ADS)

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    2005-12-01

    Two-phase flow over tube bundles is commonly observed in shell and tube-type heat exchangers. However, only limited amount of data concerning flow pattern and void fraction exists due to the flow complexity and the difficulties in measurement. The detailed flow structure in tube bundles needs to be understood for reliable and effective design. Therefore, the objective of this study was to clarify the two-phase structure of cross-flow in tube bundles by PIV. Experiments were conducted using two types of models, namely in-line and staggered arrays with a pitch-to-diameter ratio of 1.5. Each test section contains 20 rows of five 15 mm O.D. tubes in each row. The experiment’s data were obtained under very low void fraction (α<0.02). Liquid and gas velocity data in the whole flow field were measured successfully by optical filtering and image processing. The structures of bubbly flow in the two different configurations of tube bundles were described in terms of the velocity vector field, turbulence intensity and void fraction.

  4. Pressure and Flow Relations in Vascular Bundles of the Tomato Plant

    PubMed Central

    Dimond, A. E.

    1966-01-01

    In the tomato plant water flows through primary xylem in accordance with Poiseuille's law. This relation and the analogy between Poiseuille's and Ohm's law were employed to calculate rates of flow and differences in pressure within vascular bundles when transpiration rates from individual leaves were known. The resistance of vascular bundles to flow was calculated from a modification of Poiseuille's law and from measurements of vessels in all bundles. The rates of flow in all bundles were derived from a set of simultaneous linear equations of flow, written to correspond with the nature of the vascular network. Values of the difference in pressure associated with flow in bundles were derived from resistances and flow rates in individual bundles. These agreed substantially with values observed in a comparable plant. In large bundles, vessels occur in a frequency distribution that is approximately normal with respect either to the logarithms of their radii or to the fourth power of their radii. The largest vessels in a bundle transport most of the water when they are functioning. The tomato plant contains 2 types of vascular bundle. The large bundles of the stem form a network by joining above each node in combinations of 2 at a time. The small bundles of the stem and petiolar bundles are independent of other bundles from their origins at junctions to their termini. The small bundles offer high resistance to flow, whereas the resistance of large bundles is low. The average conductance of large bundles decreases from the base to the apex of the stem. That of small vascular bundles remains low and more or less constant throughout the plant. Only a small difference in pressure is required to maintain flow in large bundles. For lower leaves, the driving pressure required to move water to the base of a petiole is considerably less than that which moves water through petioles. The difference in pressure that maintains flow increases steadily for successively higher nodes

  5. Investigation of Swirling Flow in Rod Bundle Subchannels Using Computational Fluid Dynamics

    SciTech Connect

    Holloway, Mary V.; Beasley, Donald E.; Conner, Michael E.

    2006-07-01

    The fluid dynamics for turbulent flow through rod bundles representative of those used in pressurized water reactors is examined using computational fluid dynamics (CFD). The rod bundles of the pressurized water reactor examined in this study consist of a square array of parallel rods that are held on a constant pitch by support grids spaced axially along the rod bundle. Split-vane pair support grids are often used to create swirling flow in the rod bundle in an effort to improve the heat transfer characteristics for the rod bundle during both normal operating conditions and in accident condition scenarios. Computational fluid dynamics simulations for a two subchannel portion of the rod bundle were used to model the flow downstream of a split-vane pair support grid. A high quality computational mesh was used to investigate the choice of turbulence model appropriate for the complex swirling flow in the rod bundle subchannels. Results document a central swirling flow structure in each of the subchannels downstream of the split-vane pairs. Strong lateral flows along the surface of the rods, as well as impingement regions of lateral flow on the rods are documented. In addition, regions of lateral flow separation and low axial velocity are documented next to the rods. Results of the CFD are compared to experimental particle image velocimetry (PIV) measurements documenting the lateral flow structures downstream of the split-vane pairs. Good agreement is found between the computational simulation and experimental measurements for locations close to the support grid. (authors)

  6. Gas flow and thermal mixing in a helically wound tube bundle

    SciTech Connect

    Chiger, H.D.

    1980-07-01

    The thermal dissipation of a hot gas streak flowing across a segment of a helically wound tube bundle and the bypass flow streaming between the tubes and the bundle wall were investigated experimentally in the range of 8000 < Re < 50,000. Two different modes of creating a hot streak were employed. A planar hot streak was (1) injected at the entrance to the tube bundle and (2) generated by electrically heating several tubes past the bundle inlet. In the first case the mixing occurs in a region of lower turbulence since it occurs near the bundle inlet. In the second case the mixing occurs in a region of higher turbulence since the flow has already passed over several tube rows before the hot streak is generated.

  7. Lateral Flow Field Behavior Downstream of Mixing Vanes In a Simulated Nuclear Fuel Rod Bundle

    SciTech Connect

    Conner, Michael E.; Smith, L. David III; Holloway, Mary V.; Beasley, Donald E.

    2004-07-01

    To assess the fuel assembly performance of PWR nuclear fuel assemblies, average subchannel flow values are used in design analyses. However, for this highly complex flow, it is known that local conditions around fuel rods vary dependent upon the location of the fuel rod in the fuel assembly and upon the support grid design that maintains the fuel rod pitch. To investigate the local flow in a simulated nuclear fuel rod bundle, a testing technique has been employed to measure the lateral flow field in a 5 x 5 rod bundle. Particle Image Velocimetry was used to measure the lateral flow field downstream of a support grid with mixing vanes for four unique subchannels in the 5 x 5 bundle. The dominant lateral flow structures for each subchannel are compared in this paper including the decay of these flow structures. (authors)

  8. PIV measurement of the vertical cross-flow structure over tube bundles

    NASA Astrophysics Data System (ADS)

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    Shell and tube heat exchangers are among the most commonly used types of heat exchangers. Shell-side cross-flow in tube bundles has received considerable attention and has been investigated extensively. However, the microscopic flow structure including velocity distribution, wake, and turbulent structure in the tube bundles needs to be determined for more effective designs. Therefore, in this study, in order to clarify the detailed structure of cross-flow in tube bundles with particle image velocimetry (PIV), experiments were conducted using two types of model; in-line and staggered bundles with a pitch-to-diameter ratio of 1.5, containing 20 rows of five 15 mm O.D. tubes in each row. The velocity data in the whole flow field were measured successfully by adjusting the refractive index of the working fluid to that of the tube material. The flow features were characterized in different tube bundles with regards to the velocity vector field, vortex structure, and turbulent intensity.

  9. CFD Simulation of the Turbulent Flow and Heat Transfer in a Bare Rod Bundle

    SciTech Connect

    In, W.K.; Shin, C.H.; Oh, D.S.; Chun, T.H.

    2004-07-01

    A computational fluid dynamics(CFD) analysis has been performed to investigate the turbulent flow and heat transfer in a triangular rod bundle with pitch-to-diameter ratios(P/D) of 1.06 and 1.12. The CFD predictions using various turbulence models were compared with the experimental results. Anisotropic turbulence models(nonlinear k - {epsilon} and second-moment closure models) predicted the turbulence-driven secondary flow in the triangular subchannel and the distributions of the time mean velocity and temperature showing a significantly improved agreement with the measurements from the linear standard k - {epsilon} model. The anisotropic turbulence models predicted the turbulence structure for a rod bundle with a large P/D fairly well but could not predict the very high turbulent intensity of the azimuthal velocity observed in the narrow flow region(gap) for a rod bundle with a small P/D. (authors)

  10. Two-phase flow interfacial structures in a rod bundle geometry

    NASA Astrophysics Data System (ADS)

    Paranjape, Sidharth S.

    Interfacial structure of air-water two-phase flow in a scaled nuclear reactor rod bundle geometry was studied in this research. Global and local flow regimes were obtained for the rod bundle geometry. Local two-phase flow parameters were measured at various axial locations in order to understand the transport of interfacial structures. A one-dimensional two-group interfacial area transport model was evaluated using the local parameter database. Air-water two-phase flow experiments were performed in an 8 X 8 rod bundle test section to obtain flow regime maps at various axial locations. Area averaged void fraction was measured using parallel plate type impedance void meters. The cumulative probability distribution functions of the signals from the impedance void meters were used along with a self organizing neural network to identify flow regimes. Local flow regime maps revealed the cross-sectional distribution of flow regimes in the bundle. Local parameters that characterize interfacial structure, that is, void fraction alpha, interfacial area concentration, ai, bubble Sauter mean diameter, DSm and bubble velocity, vg were measured using four sensor conductivity probe technique. The local data revealed the distribution of the interfacial structure in the radial direction, as well as its development in the axial direction. In addition to this, the effect of spacer grid on the flow structure at different gas and liquid velocities was revealed by local parameter measurements across the spacer grids. A two-group interfacial area transport equation (IATE) specific to rod bundle geometry was derived. The derivation of two-group IATE required certain assumption on the bubble shapes in the subchannels and the bubbles spanning more than a subchannel. It was found that the geometrical relationship between the volume and the area of a cap bubble distorted by rods was similar to the one derived for a confined channel under a specific geometrical transformation. The one

  11. Study of the stratified-slug flow transition in a horizontal pipe containing a rod bundle

    SciTech Connect

    Krishnan, V.S.; Kowalski, J.E.

    1985-01-01

    The experimental measurements related to the stratified-slug flow transition in a horizontal pipe containing a 7-rod bundle are described. The experiments were carried out in air-water and Freon gas-water flows with liquid-to-gas density ratios in the range 46 to 392. The results are compared with the predictions of a modified form of the Taitel-Dukler theory. The predictions are also compared with other published experimental data on the stratified-slug flow transition in air-water and steam-water flows in pipes containing 37-rod bundles. Reasonable agreement is obtained in all cases. This work has particular application to the study of heat transfer in the horizontal fuel channels of a CANDU nuclear reactor under certain postulated fault conditions.

  12. CFD analyses of flow structures in air-ingress and rod bundle problems

    NASA Astrophysics Data System (ADS)

    Wei, Hong-Chan

    Two topics from nuclear engineering field are included in this dissertation. One study is the air-ingress phenomenon during a loss of coolant accident (LOCA) scenario, and the other is a 5-by-5 bundle assembly with a PWR design. The objectives were to investigate the Kelvin-Helmholtz instability of the gravity-driven stratified flows inside a coaxial pipe and the effects caused by two types of spacers at the downstream of the rod bundle. Richardson extrapolation was used for the grid independent study. The simulation results show good agreements with the experiments. Wavelet analysis and Proper Orthogonal Decomposition (POD) were used to study the flow behaviors and flow patterns. For the air-ingress phenomenon, Brunt-Vaisala frequency, or buoyancy frequency, predicts a frequency of 2.34 Hz; this is confirmed by the dominant frequency of 2.4 Hz obtained from the wavelet analysis between times 1.2 s and 1.85 s. For the rod bundle study, the dominant frequency at the center of the subchannel was determined to be 2.4 Hz with a secondary dominant frequency of 4 Hz and a much minor frequency of 6 Hz. Generally, wavelet analysis has much better performance than POD, in the air-ingress phenomenon, for a strongly transient scenario; they are both appropriate for the rod bundle study. Based on this study, when the fluid pair in a real condition is used, the time which air intrudes into the reactor is predictable.

  13. Numerical Study of Coolant Mixing Caused by the Flow Deflectors in a Nuclear Fuel Bundle

    SciTech Connect

    In, Wang Kee

    2001-05-15

    A numerical study was conducted to investigate the nuclear fuel assembly coolant flow mixing that is promoted by the flow deflectors on the grid spacer. Four typical flow deflectors (split vane, side-supported vane, swirl vane, and twisted vane) were chosen for this study. A single subchannel of one grid span is modeled using the flow symmetry. The predicted axial and lateral mean flow velocities, and the turbulent kinetic energy in the subchannel for the split-vane design, are in good agreement with the experimental results.The split vane and the twisted vane generate a large cross flow between the subchannels and a skewed elliptic swirling flow in the subchannel near the grid spacer. The cross flow rapidly decreases and the swirling flow becomes dominant downstream of the spacer. The side-supported vane induces a horizontally elongated elliptic swirl in the subchannel and a secondary flow in the near downstream of the spacer. The swirl vane produces a circular swirling flow in the subchannel and a negligible cross flow. For the twisted-vane and side-supported vane designs, the change in direction of the cross flow was predicted. The average turbulent kinetic energy in the subchannel sharply increases near the spacer and rapidly decreases to a fully developed level. In summary, the numerical results showed a somewhat large difference from the experimental results near the spacer but represented the overall characteristics of coolant mixing well in a nuclear fuel bundle with the flow deflectors on the grid spacer.

  14. Effects of oil on boiling of replacement refrigerants flowing normal to a tube bundle -- Part 1: R-123

    SciTech Connect

    Tatara, R.A.; Payvar, P.

    2000-07-01

    Local experimental heat transfer coefficients have been obtained for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-123 data with a structured enhanced boiling tube are available.The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual flooded evaporator bundle. Both heat flux, 2,607 to 10,427 Btu/h{center_dot}ft{sup 2} (8,224 to 32,893 W/m{sup 2}), and oil content, 0--15% (by weight), are varied; the mass flux is not varied independently but set by the heat flux. Local tube and bulk fluid temperatures are measured directly, by thermocouples, to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature set point (taken at the top of the tube bundle) is 40 F (4.4 C).

  15. Detailed flow and force measurements in a rotated triangular tube bundle subjected to two-phase cross-flow

    NASA Astrophysics Data System (ADS)

    Pettigrew, M. J.; Zhang, C.; Mureithi, N. W.; Pamfil, D.

    2005-05-01

    Two-phase cross-flow exists in many shell-and-tube heat exchangers. A detailed knowledge of the characteristics of two-phase cross-flow in tube bundles is required to understand and formulate flow-induced vibration parameters such as damping, fluidelastic instability, and random excitation due to turbulence. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures. The array is made of relatively large diameter cylinders (38 mm) to allow for detailed two-phase flow measurements between cylinders. Fiber-optic probes were developed to measure local void fraction. Local flow velocities and bubble diameters or characteristic lengths of the two-phase mixture are obtained by using double probes. Both the dynamic lift and drag forces were measured with a strain gauge instrumented cylinder.

  16. The Annular Two-phase Flow on Rod Bundle: The Effects of Spacers

    NASA Astrophysics Data System (ADS)

    Kunugi, Tomoaki; Pham, Son; Kawara, Zensaku; Yokomine, Takehiko

    2013-11-01

    The annular two-phase flow on rod bundle keeps an important role in many heat exchange systems but our knowledge about it, especially the interaction between the liquid film flowing on the rods' surfaces and the spacers is very limited. This study is aimed to the investigation of how the spacer affects the disturbance waves of the flow in a 3 × 3 simulating BWR fuel rod bundle test section. Firstly, the characteristics of the disturbance waves at both upstream and downstream locations of the spacer were obtained by using reflected light arrangement with a high speed camera Phantom V7.1 (Vision Research Inc.) and a Nikon macro lens 105mm f/2.8. The data showed that the parameters such as frequency and circumferential coherence of the disturbance waves are strongly modified when they go through the spacer. Then, the observations at the locations right before and after the spacer were performed by using the back light arrangement with the same high speed camera and a Cassegrain optical system (Seika Cooperation). The obtained images at micro-scale of time and space provided the descriptions of the wavy interface behaviors right before and after the spacer as well as different droplets creation processes caused by the presence of this spacer.

  17. Convective heat transfer in foams under laminar flow in pipes and tube bundles.

    PubMed

    Attia, Joseph A; McKinley, Ian M; Moreno-Magana, David; Pilon, Laurent

    2012-12-01

    The present study reports experimental data and scaling analysis for forced convection of foams and microfoams in laminar flow in circular and rectangular tubes as well as in tube bundles. Foams and microfoams are pseudoplastic (shear thinning) two-phase fluids consisting of tightly packed bubbles with diameters ranging from tens of microns to a few millimeters. They have found applications in separation processes, soil remediation, oil recovery, water treatment, food processes, as well as in fire fighting and in heat exchangers. First, aqueous solutions of surfactant Tween 20 with different concentrations were used to generate microfoams with various porosity, bubble size distribution, and rheological behavior. These different microfoams were flowed in uniformly heated circular tubes of different diameter instrumented with thermocouples. A wide range of heat fluxes and flow rates were explored. Experimental data were compared with analytical and semi-empirical expressions derived and validated for single-phase power-law fluids. These correlations were extended to two-phase foams by defining the Reynolds number based on the effective viscosity and density of microfoams. However, the local Nusselt and Prandtl numbers were defined based on the specific heat and thermal conductivity of water. Indeed, the heated wall was continuously in contact with a film of water controlling convective heat transfer to the microfoams. Overall, good agreement between experimental results and model predictions was obtained for all experimental conditions considered. Finally, the same approach was shown to be also valid for experimental data reported in the literature for laminar forced convection of microfoams in rectangular minichannels and of macrofoams across aligned and staggered tube bundles with constant wall heat flux.

  18. Convective heat transfer in foams under laminar flow in pipes and tube bundles

    PubMed Central

    Attia, Joseph A.; McKinley, Ian M.; Moreno-Magana, David; Pilon, Laurent

    2014-01-01

    The present study reports experimental data and scaling analysis for forced convection of foams and microfoams in laminar flow in circular and rectangular tubes as well as in tube bundles. Foams and microfoams are pseudoplastic (shear thinning) two-phase fluids consisting of tightly packed bubbles with diameters ranging from tens of microns to a few millimeters. They have found applications in separation processes, soil remediation, oil recovery, water treatment, food processes, as well as in fire fighting and in heat exchangers. First, aqueous solutions of surfactant Tween 20 with different concentrations were used to generate microfoams with various porosity, bubble size distribution, and rheological behavior. These different microfoams were flowed in uniformly heated circular tubes of different diameter instrumented with thermocouples. A wide range of heat fluxes and flow rates were explored. Experimental data were compared with analytical and semi-empirical expressions derived and validated for single-phase power-law fluids. These correlations were extended to two-phase foams by defining the Reynolds number based on the effective viscosity and density of microfoams. However, the local Nusselt and Prandtl numbers were defined based on the specific heat and thermal conductivity of water. Indeed, the heated wall was continuously in contact with a film of water controlling convective heat transfer to the microfoams. Overall, good agreement between experimental results and model predictions was obtained for all experimental conditions considered. Finally, the same approach was shown to be also valid for experimental data reported in the literature for laminar forced convection of microfoams in rectangular minichannels and of macrofoams across aligned and staggered tube bundles with constant wall heat flux. PMID:25552745

  19. Effects of oil on boiling R-123 and R-134a flowing normal to an integral-finned tube bundle

    SciTech Connect

    Tatara, R.A.; Payvar, P.

    1999-07-01

    Local, experimental heat transfer coefficients have been measured for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-123 and R-134a data with 26 fins per inch (1,024 fins per meter) tubes have been obtained. The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual flooded evaporator bundle. The nominal area heat flux was varied from 2,607 to 10,427 Btu/h{center{underscore}dot}ft{sup 2} (8,224 to 32,893 W/m{sup 2}) as the tube bundle oil content ranged from 0 to 15% (by weight) for each refrigerant/tube combination. The performance of R-22 without oil has also been determined. Local tube and bulk fluid temperatures were measured directly by thermocouples to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature set point (taken at the top of the tube bundle) is 40 F (4.4 C).

  20. Experimental Approach to Visualize Flow in a Stacked Hollow Fiber Bundle of an Artificial Lung With Particle Image Velocimetry.

    PubMed

    Kaesler, Andreas; Schlanstein, Peter C; Hesselmann, Felix; Büsen, Martin; Klaas, Michael; Roggenkamp, Dorothee; Schmitz-Rode, Thomas; Steinseifer, Ulrich; Arens, Jutta

    2016-12-07

    Flow distribution is key in artificial lungs, as it directly influences gas exchange performance as well as clot forming and blood damaging potential. The current state of computational fluid dynamics (CFD) in artificial lungs can only give insight on a macroscopic level due to model simplification applied to the fiber bundle. Based on our recent work on wound fiber bundles, we applied particle image velocimetry (PIV) to the model of an artificial lung prototype intended for neonatal use to visualize flow distribution in a stacked fiber bundle configuration to (i) evaluate the feasibility of PIV for artificial lungs, (ii) validate CFD in the fiber bundle of artificial lungs, and (iii) give a suggestion how to incorporate microscopic aspects into mainly macroscopic CFD studies. To this end, we built a fully transparent model of an artificial lung prototype. To increase spatial resolution, we scaled up the model by a factor of 5.8 compared with the original size. Similitude theory was applied to ensure comparability of the flow distribution between the device of original size and the scaled-up model. We focused our flow investigation on an area (20 × 70 × 43 mm) in a corner of the model with a Stereo-PIV setup. PIV data was compared to CFD data of the original sized artificial lung. From experimental PIV data, we were able to show local flow acceleration and declaration in the fiber bundle and meandering flow around individual fibers, which is not possible using state-of-the-art macroscopic CFD simulations. Our findings are applicable to clinically used artificial lungs with a similar stacked fiber arrangement (e.g., Novalung iLa and Maquet QUADROX-I). With respect to some limitations, we found PIV to be a feasible experimental flow visualization technique to investigate blood-sided flow in the stacked fiber arrangement of artificial lungs.

  1. Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

    PubMed Central

    Falcão, Andréa; Chalela, William; Giorgi, Maria Clementina; Imada, Rodrigo; Soares, José; Do Val, Renata; Oliveira, Marco Antonio; Izaki, Marisa; Filho, Roberto Kalil; Meneghetti, José C

    2015-01-01

    OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with

  2. Experimental study on cross-flow induced vibrations in heat exchanger tube bundle

    NASA Astrophysics Data System (ADS)

    Khushnood, Shahab; Nizam, Luqman Ahmad

    2017-03-01

    Vibration in heat exchangers is one of the main problems that the industry has faced over last few decades. Vibration phenomenon in heat exchangers is of major concern for designers and process engineers since it can lead to the tube damage, tube leakage, baffle damage, tube collision damage, fatigue, creep etc. In the present study, vibration response is analyzed on single tube located in the centre of the tube bundle having parallel triangular arrangement (60°) with P/ D ratio of 1.44. The experiment is performed for two different flow conditions. This kind of experiment has not been reported in the literature. Under the first condition, the tube vibration response is analyzed when there is no internal flow in the tube and under the second condition, the response is analyzed when the internal tube flow is maintained at a constant value of 0.1 m/s. The free stream shell side velocity ranges from 0.8 m/s to 1.3 m/s, the reduced gap velocity varies from 1.80 to 2.66 and the Reynolds number varies from 44500 to 66000. It is observed that the internal tube flow results in larger vibration amplitudes for the tube than that without internal tube flow. It is also established that over the current range of shell side flow velocity, the turbulence is the dominant excitation mechanism for producing vibration in the tube since the amplitude varies directly with the increase in the shell side velocity. Damping has no significant effect on the vibration behavior of the tube for the current velocity range.

  3. Estimation of anisotropic factor and turbulent mixing rate in rod bundles based on the flow pulsation phenomenon

    SciTech Connect

    Kim, S.; Park, G.C.

    1997-03-01

    The anisotropic turbulent diffusion and the turbulent mixing phenomena in rod bundle flow fields are studied. The former is a distinguishing feature of the flow through rod bundles, and the latter is essential to the subchannel thermal-hydraulic analysis. On the basis of the flow pulsation, which is suggested as a main process of turbulent mixing, scale relations for principal parameters such as the anisotropic factor and mixing rate are derived. To obtain a scale relation for the anisotropic factor, eddy viscosities are classified into isotropic and flow pulsation parts. Scales of each part are estimated using the scale analysis method. For the purpose of determining the length and velocity scales of the pulsating flow, a hypothetical circulating flow with a period corresponding to the frequency of the pulsation is assumed. The scale relation is compared with the experimental data and shows good agreement both with respect to trend and magnitude for various geometries. Thus, it is concluded that the flow pulsation is a significant contributor to the strong anisotropy in the rod bundle flow field. Also, the mixing rate is predicted by estimating the effective mixing velocity. The estimated mixing rate is transformed into well-known dimensionless numbers, which are compared with the experimental data and with correlations to verify the predictability.

  4. Algebraic stress model for axial flow in a bare rod-bundle

    SciTech Connect

    de Lemos, M.J.S.

    1987-01-01

    The problem of predicting transport properties for momentum and heat across the boundaries of interconnected channels has been the subject of many investigations. In the particular case of axial flow through rod-bundles, transport coefficients for channel faces aligned with rod centers are known to be considerably higher than those calculated by simple isotropic theories. And yet, it was been found that secondary flows play only a minor role in this overall transport, being turbulence highly enhanced across that hypothetical surface. In order to numerically predict the correct amount of the quantity being transported, the approach taken by many investigators was then to artificially increase the diffusion coefficient obtained via a simple isopropic theory (usually the standard k-epsilon model) and numerically match the correct experimentally observed mixing rates. The present paper reports an attempt to describe the turbulent stresses by means of an Algebraic Stress Model for turbulence. Relative turbulent kinetic energy distribution in all three directions are presented and compared with experiments in a square lattice. The strong directional dependence of transport terms are then obtained via a model for the Reynolds stresses. The results identify a need for a better representation of the mean-flow field part of the pressure-strain correlation term.

  5. Structure of Turbulent Flow in Subchannel of Rod Bundle Downstream of Spacer Grid With Hybrid Flow Mixing Device

    SciTech Connect

    Dong Seok Oh; Wang Kee In; Tae Hyun Chun

    2002-07-01

    An experiment was performed in a wind tunnel to investigate the flow structure in a rod bundle with a hybrid vane grid. The hybrid vane is a flow-mixing device, which consists of two pairs of primary and secondary vanes in a cell. The test section is a rectangular channel (300 mm x 300 mm x 2400 mm) including 3 x 3 rod (75 mm diameter) array with a spacer grid. The pitch to diameter ratio of the rod array is 1.33. The flow structures downstream the grid are measured at Reynolds number of 1.2 X 105 for 35-degree deflecting angle of the hybrid flow-mixing vane. The data are obtained for the distributions of the time mean axial velocity, lateral velocity, and turbulent intensities in 3 component directions over a center subchannel along axial locations and compared with the previous results of split vane grid that has two vanes in a cell. The results show that the mixing efficiency of the hybrid vane grid could be similar with that of the split vane grid because swirl factor of the hybrid vane grid is higher than that of split vane grid and the magnitude of axial turbulent intensity, turbulent diffusion coefficient, and cross flow factor is similar to each other in spite of differences of the vane numbers and shape in a cell between hybrid and split vane grids. (authors)

  6. Effects of oil on boiling of replacement refrigerants flowing normal to a tube bundle -- Part 2: R-134a

    SciTech Connect

    Tatara, R.A.; Payvar, P.

    2000-07-01

    Local, experimental heat transfer coefficients have been obtained for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-134a data with a structured enhanced boiling tube are available. This tube has reentrant cavities designed for higher saturation pressure of refrigerants. The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual evaporator bundle. Both heat flux, 2,607 to 10,427 Btu/h{center_dot}f{sup 2} (8,224 to 32,893 W/m{sup 2}), and oil content, 0--12% (by weight), are varied; the mass flux is not an independent variable but determined by the heat flux. Local tube and bulk fluid temperatures are measured directly, by thermocouples, to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature setpoint (taken at the top of the tube bundle) is 40 F (4.4 C).

  7. Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

    SciTech Connect

    Bates, J.M.; Khan, E.U.

    1980-10-01

    An experimental study was performed to obtain local fluid velocity and temperature measurements in the mixed (combined free and forced) convection regime for specific flow coastdown transients. A brief investigation of steady-state flows for the purely free-convection regime was also completed. The study was performed using an electrically heated 2 x 6 rod bundle contained in a flow housing. In addition a transient data base was obtained for evaluating the COBRA-WC thermal-hydraulic computer program (a modified version of the COBRA-IV code).

  8. Numerical Investigation of Cross Flow Phenomena in a Tight-Lattice Rod Bundle Using Advanced Interface Tracking Method

    NASA Astrophysics Data System (ADS)

    Zhang, Weizhong; Yoshida, Hiroyuki; Ose, Yasuo; Ohnuki, Akira; Akimoto, Hajime; Hotta, Akitoshi; Fujimura, Ken

    In relation to the design of an innovative FLexible-fuel-cycle Water Reactor (FLWR), investigation of thermal-hydraulic performance in tight-lattice rod bundles of the FLWR is being carried out at Japan Atomic Energy Agency (JAEA). The FLWR core adopts a tight triangular lattice arrangement with about 1 mm gap clearance between adjacent fuel rods. In view of importance of accurate prediction of cross flow between subchannels in the evaluation of the boiling transition (BT) in the FLWR core, this study presents a statistical evaluation of numerical simulation results obtained by a detailed two-phase flow simulation code, TPFIT, which employs an advanced interface tracking method. In order to clarify mechanisms of cross flow in such tight lattice rod bundles, the TPFIT is applied to simulate water-steam two-phase flow in two modeled subchannels. Attention is focused on instantaneous fluctuation characteristics of cross flow. With the calculation of correlation coefficients between differential pressure and gas/liquid mixing coefficients, time scales of cross flow are evaluated, and effects of mixing section length, flow pattern and gap spacing on correlation coefficients are investigated. Differences in mechanism between gas and liquid cross flows are pointed out.

  9. Ensemble phase averaging equations for multiphase flows in porous media, part I: the bundle-of-tubes model

    SciTech Connect

    Yang, Dali; Zhang, Duan; Currier, Robert

    2008-01-01

    A bundle-of-tubes construct is used as a model system to study ensemble averaged equations for multiphase flow in a porous material. Momentum equations for the fluid phases obtained from the method are similar to Darcy's law, but with additional terms. We study properties of the additional terms, and the conditions under which the averaged equations can be approximated by the diffusion model or the extended Darcy's law as often used in models for multiphase flows in porous media. Although the bundle-of-tubes model is perhaps the simplest model for a porous material, the ensemble averaged equation technique developed in this paper assumes the very same form in more general treatments described in Part 2 of the present work (Zhang 2009). Any model equation system intended for the more general cases must be understood and tested first using simple models. The concept of ensemble phase averaging is dissected here in physical terms, without involved mathematics through its application to the idealized bundle-of-tubes model for multiphase flow in porous media.

  10. Measurement of liquid film flow on nuclear rod bundle in micro-scale by using very high speed camera system

    NASA Astrophysics Data System (ADS)

    Pham, Son; Kawara, Zensaku; Yokomine, Takehiko; Kunugi, Tomoaki

    2012-11-01

    Playing important roles in the mass and heat transfer as well as the safety of boiling water reactor, the liquid film flow on nuclear fuel rods has been studied by different measurement techniques such as ultrasonic transmission, conductivity probe, etc. Obtained experimental data of this annular two-phase flow, however, are still not enough to construct the physical model for critical heat flux analysis especially at the micro-scale. Remain problems are mainly caused by complicated geometry of fuel rod bundles, high velocity and very unstable interface behavior of liquid and gas flow. To get over these difficulties, a new approach using a very high speed digital camera system has been introduced in this work. The test section simulating a 3×3 rectangular rod bundle was made of acrylic to allow a full optical observation of the camera. Image data were taken through Cassegrain optical system to maintain the spatiotemporal resolution up to 7 μm and 20 μs. The results included not only the real-time visual information of flow patterns, but also the quantitative data such as liquid film thickness, the droplets' size and speed distributions, and the tilt angle of wavy surfaces. These databases could contribute to the development of a new model for the annular two-phase flow. Partly supported by the Global Center of Excellence (G-COE) program (J-051) of MEXT, Japan.

  11. Analysis and generalization of experimental data on heat transfer to supercritical pressure water flow in annular channels and rod bundles

    NASA Astrophysics Data System (ADS)

    Deev, V. I.; Kharitonov, V. S.; Churkin, A. N.

    2017-02-01

    Experimental data on heat transfer to supercritical pressure water presented at ISSCWR-5, 6, and 7 international symposiums—which took place in 2011-2015 in Canada, China, and Finland—and data printed in recent periodical scientific publications were analyzed. Results of experiments with annular channels and three- and four-rod bundles of heating elements positioned in square or triangular grids were examined. Methodology used for round pipes was applied at generalization of experimental data and establishing of correlations suitable for engineering analysis of heat exchange coefficient in conditions of strongly changing water properties in the near-critical pressure region. Empiric formulas describing normal heat transfer to supercritical pressure water mowing in annular channels and rod bundles were obtained. As compared to existing recommendations, suggested correlations are distinguished by specified dependency of heat exchange coefficient on density of heat flux and mass flow velocity of water near pseudo-critical temperature. Differences between computed values of heat exchange coefficient and experimental data usually do not exceed ±25%. Detailed statistical analysis of deviations between computed and experimental results at different states of supercritical pressure water flow was carried out. Peculiarities of deteriorated heat exchange were considered and their existence boundaries were defined. Experimental results obtained for these regimes were generalized using criteria by J.D. Jackson that take the influence of thermal acceleration and Archimedes forces on heat exchange processes into account. Satisfactory agreement between experimental data on heat exchange at flowing of water in annular channels and rod bundles and data for round pipes was shown.

  12. Comparison of different approaches in the Trefftz method for analysis of fluid flow between regular bundles of cylindrical fibres

    NASA Astrophysics Data System (ADS)

    Mierzwiczak, M.; Grabski, J. K.; Kołodziej, J. A.

    2016-10-01

    In the paper three different approaches for the Trefftz method are compared in analysis of the fluid flow between regular bundles of cylindrical fibres. The approximate solution is a linear combination of such trial functions which fulfil exactly the governing equations. The trial functions can be defined in the Cartesian coordinate system (the first approach), in the cylindrical coordinate system (and can fulfil also some boundary conditions - the second approach) or be defined as a fundamental solutions (the third approach - the method of fundamental solutions).The average velocity and the product of the friction factor and the Reynolds number ƒ ṡ Re are compared for selected parameters of a considered region.

  13. PWR FLECHT SEASET 163-Rod Bundle Flow Blockage Task data report. NRC/EPRI/Westinghouse report No. 13, August-October 1982

    SciTech Connect

    Loftus, M J; Hochreiter, L E; McGuire, M F; Valkovic, M M

    1983-10-01

    This report presents data from the 163-Rod Bundle Blow Blockage Task of the Full-Length Emergency Cooling Heat Transfer Systems Effects and Separate Effects Test Program (FLECHT SEASET). The task consisted of forced and gravity reflooding tests utilizing electrical heater rods with a cosine axial power profile to simulate PWR nuclear core fuel rod arrays. These tests were designed to determine effects of flow blockage and flow bypass on reflooding behavior and to aid in the assessment of computational models in predicting the reflooding behavior of flow blockage in rod bundle arrays.

  14. Two-Phase Void Drift Phenomena in a 2 x 3 Rod Bundle: Flow Redistribution Data and Their Analysis

    SciTech Connect

    Sadatomi, Michio; Kawahara, Akimaro; Kuno, Tsukasa; Kano, Keiko

    2005-10-15

    To improve a void drift model used in a subchannel analysis, new experimental data are obtained for air-water two-phase flows in a vertical 2 x 3 rod channel consisting of six subchannels simulating a square array boiling water reactor fuel rod bundle. The data include the axial redistributions of flow rates of both phases and void fraction in the respective subchannels. By fitting the above data with the Lahey and Moody void settling model, we have determined a void diffusion coefficient in their model. It is found that the void diffusion coefficient for slug, churn, and annular flows could be well correlated in terms of a turbulent Peclet number developed in our previous study. Furthermore, a subchannel analysis code based on a two-fluid model proposed in our previous study is examined against the present data. In the code, the void settling model is incorporated with usual conservation equations of mass and momentum. From the examination, it is found that the subchannel analysis code can predict well the data on subchannel flow and void fraction for the 2 x 3 rod channel if appropriate correlations are adopted to evaluate wall and interfacial friction forces needed in the two-fluid model.

  15. Subchannel and bundle friction factors and flowsplit parameters for laminar, transition, and turbulent longitudinal flows in wire-wrap spaced hexagonal arrays. [LMFBR

    SciTech Connect

    Hawley, J.T.; Chiu, C.; Rohsenow, W.M.; Todreas, N.E.

    1980-08-01

    Correlations are presented for subchannel and bundle friction factors and flowsplit parameters for laminar, transition and turbulent longitudinal flows in wire wrap spaced hexagonal arrays. These results are obtained from pressure drop models of flow in individual subchannels. For turbulent flow, an existing pressure drop model for flow in edge subchannels is extended, and the resulting edge subchannel friction factor is identified. Using the expressions for flowsplit parameters and the equal pressured drop assumption, the interior subchannel and bundle friction factors are obtained. For laminar flow, models are developed for pressure drops of individual subchannels. From these models, expressions for the subchannel friction factors are identified and expressions for the flowsplit parameters are derived.

  16. A Hybrid Vortex Method for Two-Dimensional Flow Over Tube Bundles

    SciTech Connect

    Strickland, J.H.; Wolfe, W.P.

    1998-11-13

    A hybrid vortex method is presented for computing flows about objects that accurately resolves the boundary layer details while keeping the number of free vortices at a reasonable level. The method uses a wall layer model close to the body surface and discrete vortex blobs in the free wake. Details of the wall layer implementation are presented, and results of sample calculations are compared with known analytical solutions and with calculations from other vortex codes. These results show that the computed boundary layer details are accurate to approximately 0.3 percent of analytical solutions while using three orders of magnitude fewer vortices than other vortex simulations.

  17. Single- and Two-Phase Diversion Cross-Flows Between Triangle Tight Lattice Rod Bundle Subchannels - Data on Flow Resistance and Interfacial Friction Coefficients for the Cross-Flow

    SciTech Connect

    Tatsuya Higuchi; Akimaro Kawahara; Michio Sadatomi; Hiroyuki Kudo

    2006-07-01

    Single- and two-phase diversion cross-flows arising from the pressure difference between tight lattice subchannels are our concern in this study. In order to obtain a correlation of the diversion cross-flow, we conducted adiabatic experiments using a vertical multiple-channel with two subchannels simplifying the triangle tight lattice rod bundle for air-water flows at room temperature and atmospheric pressure. In the experiments, data were obtained on the axial variations in the pressure difference between the subchannels, the ratio of flow rate in one subchannel to the whole channel, the void fraction in each subchannel for slug-churn and annular flows in two-phase flow case. These data were analyzed by use of a lateral momentum equation based on a two-fluid model to determine both the cross-flow resistance coefficient between liquid phase and channel wall and the gas-liquid interfacial friction coefficient. The resulting coefficients have been correlated in a way similar to that developed for square lattice subchannel case by Kano et al. (2002); the cross-flow resistance coefficient data can be well correlated with a ratio of the lateral velocity due to the cross-flow to the axial one irrespective of single- and two-phase flows; the interfacial friction coefficient data were well correlated with a Reynolds number, which is based on the relative velocity between gas and liquid cross-flows as the characteristic velocity. (authors)

  18. Improvement of Predictive Accuracy on Subchannel Analysis Code (NASCA) for Tight-Lattice Rod Bundle Tests - Optimization of UEDA'S Entrainment Model Parameter and Cross Flow Model Parameters

    SciTech Connect

    Hiromasa Chitose; Akitoshi Hotta; Akira Ohnuki; Ken Fujimura

    2006-07-01

    The Reduced-Moderation Water Reactor (RMWR) is being developed at Japan Atomic Energy Agency and demonstration of the core heat removal performance is one of the most important issues. However, operation of the full-scale bundle experiment is difficult technically because the fuel rod bundle size is larger, which consumes huge electricity. Hence, it is expected to develop an analysis code for simulating RMWR core thermal-hydraulic performance with high accuracy. Subchannel analysis is the most powerful technique to resolve the problem. A subchannel analysis code NASCA (Nuclear-reactor Advanced Sub-Channel Analysis code) has been developed to improve capabilities of analyzing transient two-phase flow phenomena, boiling transition (BT) and post BT, and the NASCA code is applicable on the thermal-hydraulic analysis for the current BWR fuel. In the present study, the prediction accuracy of the NASCA code has been investigated using the reduced-scale rod bundle test data, and its applicability on the RMWR has been improved by optimizing the mechanistic constitutive models. (authors)

  19. The Effects of Swirl Flow on CHF by Various Spacer Grids in 2*2 Rod Bundle with R-134a

    SciTech Connect

    Byung Soo Shin; Soon Heung Chang

    2004-07-01

    Experimental works have shown that the effect of swirl flow on CHF by various spacer grid in the 2*2 rod bundle with R-134a. Test spacer grids have mixing vanes for generating swirl flow. The geometries of test section are as follows; rod diameter is 9.5 mm, rod pitch is 12.85 mm. For test spacer grid, two different types are used changing the angle of mixing vanes. In CHF test, experimental conditions are as follows; mass flux is from 1000 to 1800 kg/m{sup 2}s, inlet subcooling from 40.21 kJ/kg to 129.5 kJ/kg, and inlet pressure is from 15 bar to 25 bar. The locations of spacer grid are 200 mm upstream from the end of heating rod. Pressure drop was also measured in single phase experiment. Consequently, the magnitude of swirl flow is related to CHF. Namely, as swirl flow is stronger, the CHF enhance more. The type and angle of mixing vane are effective to swirl flow. And, because swirl flow decays along the flow stream, CHF enhancement decreases along the flow direction. Therefore, in nuclear fuel development, it is important to consider flow structure in a subchannel because CHF enhancement is up to 21% according to circumstances. (authors)

  20. Lattice Boltzmann simulation on liquid flow and mass transport in a bioreactor with cylinder bundle for hydrogen production

    NASA Astrophysics Data System (ADS)

    Liao, Qiang; Yang, Yan-Xia; Zhu, Xun; Wang, Hong; Ding, Yu-Dong

    2015-06-01

    The lattice Boltzmann method is adopted to simulate hydrodynamics and mass transfer accompanying with biochemical reaction in a channel with cylinder bundle, which is the scenario of biohydrogen production by photosynthetic bacteria in the biofilm attached on the surface of cylinder bundle in photobioreactor. The effects of cylinder spacing, Reynolds number and cylinder arrangement are investigated. The numerical results reveal that highest glucose concentration and the lowest hydrogen concentration are obtained at the front of the first row cylinders for all cases. The staggered arrangement leads to an increment in average drag coefficient, Sherwood number and consumption efficiency of substrate under a given condition, and the increment in Sherwood number reaches up to 30 %, while that in drag coefficient is around 1 %, moreover, the increment in consumption efficiency reaches the maximum value of 12 %. The results indicate that the staggered arrangement is beneficial to the mass transfer and biochemical reaction.

  1. Heat transfer and flow characteristics of fin-tube bundles with and without winglet-type vortex generators

    NASA Astrophysics Data System (ADS)

    Kwak, K. M.; Torii, K.; Nishino, K.

    2002-08-01

    The objective of this research is to investigate the effect of longitudinal vortices that can be applied to the heat transfer enhancement for fin-tube heat exchangers such as air-cooled condensers. A multichannel test core was designed and fabricated for the determination of overall heat transfer and pressure loss with circular tubes and winglet vortex generators. Heat transfer results were obtained using a transient method referred to as the modified single-blow method. For a three-row tube bundle in an in-line arrangement without winglets, the heat transfer and the pressure loss were 72% and 210% higher, respectively, than for a multichannel test core without any built-in tube or winglet. These increases were caused by vortices around the tube banks. The corresponding increases for a staggered tube bundle are 95% and 310%, respectively. The triangular winglets recommended by the previous studies in a fin-tube bundle in an in-line arrangement increase the overall heat transfer 10-25% and the pressure loss 20-35% for the Reynolds numbers ranging from 300 to 2700.

  2. Single-phase computational fluid dynamics applicability for the study of three-dimensional flow in 5' 5 rod bundles with spacer grids

    NASA Astrophysics Data System (ADS)

    Tian, Ruifeng; Mao, Xiaohui; Gao, Puzhen; Huang, Yanping

    2012-07-01

    Spacer grids play an important role in pressurized water reactor (PWR) fuel assembly in that they have significant influence on the thermal-hydraulic characteristics of the reactor core. But so far, the numerical studies are performed without regarding dimple and spring of spacer grids, just considering mixing vane. Moreover, these studies use k-ɛ turbulence model without considering the suitability of the other turbulence models upon the different spacer grids flow. A study is carried out to understand the 3-D single-phase flow in AFA-2G 5×5 rod bundles with spacer grids based on numerical method. In order to investigate the suitability of different turbulence models, k-ɛ model and k-ω model, the influence of different parts of spacer grid on the fluid flow is also predicted. By using second-order upwind scheme, hybrid grids technique, and improved SIMPLEC algorithm, the Reynolds averaged mass conservation and momentum conservation equations are solved, and the pressure and velocity field of flow are obtained. The numerical simulation results are compared with experiment results and the agreement is satisfactory. The simulation results show the influences of the spring, dimple and mixing vane, and the different characteristics of the k-ɛ model and k-ω model. Comparing with the experiment results, the simulation results suggest that the k-ω model is suitable for the simulation of the rod bundle flow with spacer grids; the spring and dimple are the main causes of the pressure loss in the spacer grid channel. The friction coefficient of the channel with spring and dimple is 1.5 times the coefficient of the channel with the vane. These results are beneficial to enhance the simulation ability of spacer grids flow and optimization design ability of spaces grid.

  3. Fuel bundle

    SciTech Connect

    Lui, C.K.

    1989-04-04

    This patent describes a method of forming a fuel bundle of a nuclear reactor. The method consists of positioning the fuel rods in the bottom plate, positioning the tie rod in the bottom plate with the key passed through the receptacle to the underside of the bottom plate and, after the tie rod is so positioned, turning the tie rod so that the key is in engagement with the underside of the bottom plate. Thereafter mounting the top plate is mounted in engagement with the fuel rods with the upper end of the tie rod extending through the opening in the top plate and extending above the top plate, and the tie rod is secured to the upper side of sid top plate thus simultaneously securing the key to the underside of the bottom plate.

  4. Fabrication of electrospun nanofibers bundles

    NASA Astrophysics Data System (ADS)

    Ye, Junjun; Sun, Daoheng

    2007-12-01

    Aligned nanofibers, filament bundle composed of large number of nanofibers have potential applications such as bio-material, composite material etc. A series of electrospinning experiments have been conducted to investigate the electrospinning process,in which some parameters such as polymer solution concentration, bias voltage, distance between spinneret and collector, solution flow rate etc have been setup to do the experiment of nanofibers bundles construction. This work firstly reports electrospun nanofiber bundle through non-uniform electrical field, and nanofibers distributed in different density on electrodes from that between them. Thinner nanofibers bundle with a few numbers of nanofiber is collected for 3 seconds; therefore it's also possible that the addressable single nanofiber could be collected to bridge two electrodes.

  5. Bundling of bacterial flagella

    NASA Astrophysics Data System (ADS)

    Powers, Thomas R.; van Parys, Annemarie J.; Breuer, Kenneth S.

    2002-03-01

    In bacterial chemotaxis, cells such as E. coli drift up chemical gradients by means of a directed random walk. Near the beginning of each step of a walk, the rotating helical flagella which propel the cell form a bundle. Using macroscopic experiments and numerical calculations, we study the viscous flows set up by two rotating helices. Our work illustrates the importance of geometry; for example, left-handed helices rotating counter-clockwise when viewed from the distal ends will inter-penetrate and synchronize when the pitch is shorter than the circumference. When the same helices turn clockwise, they fail to inter-penetrate.

  6. Experimental investigation of heat transfer performance coefficient in tube bundle of shell and tube heat exchanger in two-phase flow

    NASA Astrophysics Data System (ADS)

    Karaś, Marcin; Zając, Daniel; Ulbrich, Roman

    2014-03-01

    This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN)6 and K4Fe(CN)6 in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient) were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.

  7. A noninvasive technique for the evaluation of diversion cross flow at the inlet of a simulated fuel rod bundle

    SciTech Connect

    Sedaghat, A.; Castellana, F.S.; Hsu, R.H.; Macduff, R.B.

    1988-03-01

    Diversion cross flow was characterized from a two-subchannel simulation of a nuclear fuel assembly using a gamma camera. The gamma camera alllowed external monitoring over the length of the test assembly, thereby eliminating experimental problems associated with flow partitioning and an isokinetic withdrawal system, allowing the possibility of noninvasive measurement. The experiment was performed by providing fixed but different flow rates to each subchannel. The higher mass flow rate stream was traced with a gamma-emitting radionuclide, /sup 99m/Tc pertechnetate. Activity in each subchannel was measured by the camera. Diversion length was found to be relatively small and strongly dependent on gap spacing. Effective lateral velocity through the gap was also evaluated. With some exceptions, the results were in good agreement with the predictions of the subchannel analysis computer code COBRA IIIC. At a high inlet axial mass velocity ratio of 4, however, the agreement with the prediction was poor.

  8. Multiwalled carbon nanotube reinforced biomimetic bundled gel fibres.

    PubMed

    Kim, Young-Jin; Yamamoto, Seiichiro; Takahashi, Haruko; Sasaki, Naruo; Matsunaga, Yukiko T

    2016-08-19

    This work describes the fabrication and characterization of hydroxypropyl cellulose (HPC)-based biomimetic bundled gel fibres. The bundled gel fibres were reinforced with multiwalled carbon nanotubes (MWCNTs). A phase-separated aqueous solution with MWCNT and HPC was transformed into a bundled fibrous structure after being injected into a co-flow microfluidic device and applying the sheath flow. The resulting MWCNT-bundled gel fibres consist of multiple parallel microfibres. The mechanical and electrical properties of MWCNT-bundled gel fibres were improved and their potential for tissue engineering applications as a cell scaffold was demonstrated.

  9. Implementing sepsis bundles

    PubMed Central

    Jozwiak, Mathieu; Monnet, Xavier

    2016-01-01

    Sepsis bundles represent key elements of care regarding the diagnosis and treatment of patients with septic shock and allow ones to convert complex guidelines into meaningful changes in behavior. Sepsis bundles endorsed the early goal-directed therapy (EGDT) and their implementation resulted in an improved outcome of septic shock patients. They induced more consistent and timely application of evidence-based care and reduced practice variability. These benefits mainly depend on the compliance with sepsis bundles, highlighting the importance of dedicated performance improvement initiatives, such as multifaceted educational programs. Nevertheless, the interest of early goal directed therapy in septic shock patients compared to usual care has recently been questioned, leading to an update of sepsis bundles in 2015. These new sepsis bundles may also exhibit, as the previous bundles, some limits and pitfalls and the effects of their implementation still needs to be evaluated. PMID:27713890

  10. Polycation induced actin bundles.

    PubMed

    Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

    2011-04-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder.

  11. Experimental results of the QUENCH-16 bundle test on air ingress

    SciTech Connect

    Stuckert, J.; Steinbrueck, M.

    2012-07-01

    The out-of-pile bundle experiment QUENCH-16 on air ingress was conducted in the electrically heated 21-rod QUENCH facility at KIT in July 2011. It was performed in the frame of the EC supported LACOMECO program. The test scenario included the oxidation of the Zircaloy-4 claddings in air following a limited pre-oxidation in steam, and involved a long period of oxygen starvation to promote interaction with the nitrogen. The primary aim was to examine the influence of the formed oxide layer structure on bundle coolability and hydrogen release during the terminal flooding phase. QUENCH-16 was thus a companion test to the earlier air ingress experiment, QUENCH-10, which was performed with strongly pre-oxidized bundle. Unlike QUENCH-10, significant temperature escalation and intensive hydrogen release were observed during the reflood phase. Post-test investigations of bundle cross sections reveal residual nitride traces at various elevations. The external part of the oxide scale is of porous structure due to re-oxidation of nitrides during reflood. Relative thick internal oxide scales underneath this porous layer and residual nitrides were formed during reflood. At lower bundle elevations frozen partially oxidized melt was detected, relocated from upper elevations. (authors)

  12. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wold, L.

    1981-02-01

    Four tasks are reported on: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical determination of local temperature fields in LMFBR fuel rod bundles. (DLC)

  13. A Kinetic Model of Active Extensile Bundles

    NASA Astrophysics Data System (ADS)

    Goldstein, Daniel; Chakraborty, Bulbul; Baskaran, Aparna

    Recent experiments in active filament networks reveal interesting rheological properties (Dan Chen: APS March Meeting 2015 D49.00001). This system consumes ATP to produce an extensile motion in bundles of microtubules. This extension then leads to self generated stresses and spontaneous flows. We propose a minimal model where the activity is modeled by self-extending bundles that are part of a cross linked network. This network can reorganize itself through buckling of extending filaments and merging events that alter the topology of the network. We numerically simulate this minimal kinetic model and examine the emergent rheological properties and determine how stresses are generated by the extensile activity. We will present results that focus on the effects of confinement and network connectivity of the bundles on stress fluctuations and response of an active gel.

  14. Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles

    NASA Technical Reports Server (NTRS)

    Rickman, S. L.; Iamello, C. J.

    2016-01-01

    Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.

  15. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report, March 1, 1980-May 31, 1980

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wolf, L.

    1980-01-01

    Experimental and theoretical work is reported on four tasks: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical local temperature files in LMFBR fuel rod bundles. (DLC)

  16. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report, September 1, 1980-November 30, 1980

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wolf, L.

    1981-02-01

    Four tasks are reported: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical determination of local temperature fields in LMFBR fuel rod bundles. (DLC)

  17. Bundled monocapillary optics

    DOEpatents

    Hirsch, Gregory

    2002-01-01

    A plurality of glass or metal wires are precisely etched to form the desired shape of the individual channels of the final polycapillary optic. This shape is created by carefully controlling the withdrawal speed of a group of wires from an etchant bath. The etched wires undergo a subsequent operation to create an extremely smooth surface. This surface is coated with a layer of material which is selected to maximize the reflectivity of the radiation being used. This reflective surface may be a single layer of material, or a multilayer coating for optimizing the reflectivity in a narrower wavelength interval. The collection of individual wires is assembled into a close-packed multi-wire bundle, and the wires are bonded together in a manner which preserves the close-pack configuration, irrespective of the local wire diameter. The initial wires are then removed by either a chemical etching procedure or mechanical force. In the case of chemical etching, the bundle is generally segmented by cutting a series of etching slots. Prior to removing the wire, the capillary array is typically bonded to a support substrate. The result of the process is a bundle of precisely oriented radiation-reflecting hollow channels. The capillary optic is used for efficiently collecting and redirecting the radiation from a source of radiation which could be the anode of an x-ray tube, a plasma source, the fluorescent radiation from an electron microprobe, a synchrotron radiation source, a reactor or spallation source of neutrons, or some other source.

  18. Numerical modeling of anisotropic fiber bundle behavior in oxygenators.

    PubMed

    Bhavsar, Sonya S; Schmitz-Rode, Thomas; Steinseifer, Ulrich

    2011-11-01

    Prediction of flow patterns through oxygenator fiber bundles can allow shape optimization so that efficient gas exchange occurs with minimal thrombus formation and hemolysis. Computational fluid dynamics (CFD) simulations can be used to predict three-dimensional flow velocities and flow distribution from spatially dependent variables and they allow estimations of erythrocyte residence time within the fiber bundle. This study builds upon previous work to develop an accurate numerical model for oxygenators, which would allow for accelerated iterations in oxygenator shape and diffuser plate design optimization. Hollow fiber flow channels were developed to permit experimental calculation of fluid permeability in two directions: main flow along the hollow fiber and perpendicular to the hollow fibers. Commercial software was used to develop three-dimensional CFD models of the experimental flow channels and an anisotropic porous media model for oxygenators from these experimental results. The oxygenator model was used to predict pressure loss throughout the device, visualize blood distribution within the fiber bundle, and estimate erythrocyte residence time within the bundle. Experimental flow channels measurements produced a streamwise permeability of 1.143e(-8) m(2) and transverse permeability of 2.385e(-9) m(2) . These permeabilities, coupled with previous work with volume porosity, were used to develop the numerical model of anisotropic behavior through porous fiber bundles, which indicated a more uniform flow field throughout the oxygenator. Incorporation of known anisotropic fiber bundle behavior in previous numerical models more accurately represents fluid behavior through an oxygenator fiber bundle. CFD coupled with experimental validation can produce a powerful tool for oxygenator design and development.

  19. Hydraulic testing of accelerator-production-of-tritium rod bundles

    SciTech Connect

    Spatz, T.L.; Siebe, D.A.

    1999-01-01

    Hydraulic tests have been performed on small pitch-to-diameter-ratio rod bundles using light water (1.7 < P/D < 1.17, and d = 3.175 mm). Flows cover the range from greater-than-nominal Reynolds numbers (fully turbulent) to low-speed laminar flows. Differential pressure measurements were made across the support plates holding the rod bundles, across the rod bundles, and across the entire assembly. Flow rates, temperatures, and gauge pressures also were measured. The data from these hydraulic tests have been compared to correlating literature for tightly pitched rod bundles. The prototypic geometry of these tests did not compare directly to any geometry found in the literature because of the variety of subchannels along the outer wall of the rod bundle. Under that constraint, there was excellent comparison of the rod-bundle friction factor with those factors given in the literature. The results show a large range of the Reynolds number over which the flow is in transition from laminar to turbulent (e.g., 580 < Re{sub Tr} < 13,000). Also presented is the comparison of the overall rung pressure drop to a solution based on hydraulic-resistance handbook calculations.

  20. Bundle duct interaction studies for fuel assemblies. [LMFBR

    SciTech Connect

    Hsia, H.T.S.; Kaplan, S.

    1981-06-01

    It is known that the wire-wrapped rods and duct in an LMFBR are undergoing a gradual structural distortion from the initially uniform geometry under the combined effects of thermal expansion and irradiation induced swelling and creep. These deformations have a significant effect on flow characteristics, thus causing changes in thermal behavior such as cladding temperature and temperature distribution within a bundle. The temperature distribution may further enhance or retard irradiation induced deformation of the bundle. This report summarizes the results of the continuing effort in investigating the bundle-duct interaction, focusing on the need for the large development plant.

  1. Bundle Security Protocol for ION

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.; Birrane, Edward J.; Krupiarz, Christopher

    2011-01-01

    This software implements bundle authentication, conforming to the Delay-Tolerant Networking (DTN) Internet Draft on Bundle Security Protocol (BSP), for the Interplanetary Overlay Network (ION) implementation of DTN. This is the only implementation of BSP that is integrated with ION.

  2. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1999-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 degree C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire (2) bundle of 15 or more wires (3) 70 C environment (4) vacuum of 10(exp -5) torr or less To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  3. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire; (2) bundle of 15 or more wires; (3) 70 C environment: and (4) vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  4. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: 3.7 amps per wire, bundle of 15 or more wires, 70 C environment, and vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  5. Fiber bundle phase conjugate mirror

    DOEpatents

    Ward, Benjamin G.

    2012-05-01

    An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

  6. Subchannel thermal-hydraulic modeling of an APT tungsten target rod bundle

    SciTech Connect

    Hamm, L.L.; Shadday, M.A. Jr.

    1997-09-01

    The planned target for the Accelerator Production of Tritium (APT) neutron source consists of an array of tungsten rod bundles through which D{sub 2}O coolant flows axially. Here, a scoping analysis of flow through an APT target rod bundle was conducted to demonstrate that lateral cross-flows are important, and therefore subchannel modeling is necessary to accurately predict thermal-hydraulic behavior under boiling conditions. A local reactor assembly code, FLOWTRAN, was modified to model axial flow along the rod bundle as flow through three concentric heated annular passages.

  7. Evaluating big deal journal bundles

    PubMed Central

    Bergstrom, Theodore C.; Courant, Paul N.; McAfee, R. Preston; Williams, Michael A.

    2014-01-01

    Large commercial publishers sell bundled online subscriptions to their entire list of academic journals at prices significantly lower than the sum of their á la carte prices. Bundle prices differ drastically between institutions, but they are not publicly posted. The data that we have collected enable us to compare the bundle prices charged by commercial publishers with those of nonprofit societies and to examine the types of price discrimination practiced by commercial and nonprofit journal publishers. This information is of interest to economists who study monopolist pricing, librarians interested in making efficient use of library budgets, and scholars who are interested in the availability of the work that they publish. PMID:24979785

  8. Evaluating big deal journal bundles.

    PubMed

    Bergstrom, Theodore C; Courant, Paul N; McAfee, R Preston; Williams, Michael A

    2014-07-01

    Large commercial publishers sell bundled online subscriptions to their entire list of academic journals at prices significantly lower than the sum of their á la carte prices. Bundle prices differ drastically between institutions, but they are not publicly posted. The data that we have collected enable us to compare the bundle prices charged by commercial publishers with those of nonprofit societies and to examine the types of price discrimination practiced by commercial and nonprofit journal publishers. This information is of interest to economists who study monopolist pricing, librarians interested in making efficient use of library budgets, and scholars who are interested in the availability of the work that they publish.

  9. Tube bundle system

    PubMed Central

    Marchewka, W.; Mohamed, K.; Addis, J.; Karnack, F.

    2015-01-01

    A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine. The gas samples are drawn via vacuum pump to the surface and are typically analyzed for oxygen, methane, carbon dioxide and carbon monoxide. Results of the gas analyses are displayed and recorded for further analysis. Trends in the composition of the mine atmosphere, such as increasing methane or carbon monoxide concentration, can be detected early, permitting rapid intervention that prevents problems, such as a potentially explosive atmosphere behind seals, fire or spontaneous combustion. TBS is a well-developed technology and has been used in coal mines around the world for more than 50 years. Most longwall coal mines in Australia deploy a TBS, usually with 30 to 40 monitoring points as part of their atmospheric monitoring. The primary uses of a TBS are detecting spontaneous combustion and maintaining sealed areas inert. The TBS might also provide mine atmosphere gas composition data after a catastrophe occurs in an underground mine, if the sampling tubes are not damaged. TBSs are not an alternative to statutory gas and ventilation airflow monitoring by electronic sensors or people; rather, they are an option to consider in an overall mine atmosphere monitoring strategy. This paper describes the hardware, software and operation of a TBS and presents one example of typical data from a longwall coal mine PMID:26306052

  10. Atrio-His bundle tracts.

    PubMed Central

    Brechenmacher, C

    1975-01-01

    The atrio-His bundle tracts are very rare; only two have been found in 687 hearts studied histologically. These tracts have a similar appearance to those of the atrioventricular bundle and form a complete bypass of the atrioventricular node. In their presence the electrocardiogram may show a short or normal PR interval. They may be responsible for some cases of very rapid ventricular response to supraventricular arrhythmias. Images PMID:1191446

  11. Connections on decorated path space bundles

    NASA Astrophysics Data System (ADS)

    Chatterjee, Saikat; Lahiri, Amitabha; Sengupta, Ambar N.

    2017-02-01

    For a principal bundle P → M equipped with a connection A ¯ , we study an infinite dimensional bundle PA¯ dec P over the space of paths on M, with the points of PA¯ dec P being horizontal paths on P decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting.

  12. Purification and alignment of arc-synthesis single-walled carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Huang, Houjin; Kajiura, Hisashi; Yamada, Atsuo; Ata, Masafumi

    2002-04-01

    We report here a scalable method for purification and alignment of single-walled carbon nanotubes (SWNT) in an aqueous solution. Arc-synthesis soot containing SWNTs is first treated with a concentrated nitric acid. After removal of most of the impurities and water, macroscopic and well-aligned SWNT bundles up to several centimeters long are formed in a rotary evaporator. Alignment of the SWNT bundles is ascribed to the liquid flow induced by rotary evaporation and van der Waals interactions among the bundles. The aligned SWNT bundles are further purified by ultrasonic Soxhlet extraction and annealing.

  13. Bundle Formation in Biomimetic Hydrogels.

    PubMed

    Jaspers, Maarten; Pape, A C H; Voets, Ilja K; Rowan, Alan E; Portale, Giuseppe; Kouwer, Paul H J

    2016-08-08

    Bundling of single polymer chains is a crucial process in the formation of biopolymer network gels that make up the extracellular matrix and the cytoskeleton. This bundled architecture leads to gels with distinctive properties, including a large-pore-size gel formation at very low concentrations and mechanical responsiveness through nonlinear mechanics, properties that are rarely observed in synthetic hydrogels. Using small-angle X-ray scattering (SAXS), we study the bundle formation and hydrogelation process of polyisocyanide gels, a synthetic material that uniquely mimics the structure and mechanics of biogels. We show how the structure of the material changes at the (thermally induced) gelation point and how factors such as concentration and polymer length determine the architecture, and with that, the mechanical properties. The correlation of the gel mechanics and the structural parameters obtained from SAXS experiments is essential in the design of future (synthetic) mimics of biopolymer networks.

  14. Procedure for dispersing fiber bundles

    NASA Technical Reports Server (NTRS)

    Padilla, D.

    1974-01-01

    Fiber bundles are dispersed and fibers are cleaned within enclosed container; therefore, safety clothing, masks, and eye protection are not required. Procedure also could be used wherever materials, such as fiberglass or insulation, require dispersion, fluffing, or cleaning. Process could be automated into continuous operation for handling large quantities of fiber.

  15. Fiber bundle design for an integrated wearable artificial lung.

    PubMed

    Madhani, Shalv P; Frankowski, Brian J; Federspiel, William J

    2017-02-07

    Mechanical ventilation and ECMO are the only viable treatment options for lung failure patients at the end stage, including ARDS and COPD. These treatments however are associated with high morbidity and mortality due to long wait times for lung transplant. Contemporary clinical literature has shown ambulation improves post-transplant outcomes in lung failure patients. Given this, we are developing the PAAL, a truly wearable artificial lung that allows for ambulation. In this study, we targeted 180 ml/min oxygenation and determined the form factor for a hollow fiber membrane (HFM) bundle for the PAAL.Based on a previously published mass transfer correlation we modeled oxygenation efficiency as a function of fiber bundle diameter. Three benchmark fiber bundles were fabricated to validate the model through in-vitro blood gas exchange at blood flow rates from 1 to 4 L/min according to ASTM standards. We used the model to determine a final design, which was characterized in-vitro through a gas exchange as well as a hemolysis study at 3.5 L/minThe percent difference between model predictions and experiment for the benchmark bundles ranged from 3% to 17.5% at the flowrates tested. Using the model, we predicted a 1.75 inch diameter bundle with 0.65 m surface area would produce 180 ml/min at 3.5 L/min blood flow rate. The oxygenation efficiency was 278 ml/min/m and the Normalized Index of Hemolysis (NIH) was less than 0.05g/100L. Future work involves integrating this bundle into the PAAL for which an experimental prototype is under development in our laboratory.

  16. Bundled capillary electrophoresis using microstructured fibres.

    PubMed

    Rogers, Benjamin; Gibson, Graham T T; Oleschuk, Richard D

    2011-01-01

    Joule heating, arising from the electric current passing through the capillary, causes many undesired effects in CE that ultimately result in band broadening. The use of narrow-bore capillaries helps to solve this problem as smaller cross-sectional area results in decreased Joule heating and the rate of heat dissipation is increased by the larger surface-to-volume ratio. Issues arising from such small capillaries, such as poor detection sensitivity, low loading capacity and high flow-induced backpressure (complicating capillary loading) can be avoided by using a bundle of small capillaries operating simultaneously that share buffer reservoirs. Microstructured fibres, originally designed as waveguides in the telecommunication industry, are essentially a bundle of parallel ∼5 μm id channels that extend the length of a fibre having otherwise similar dimensions to conventional CE capillaries. This work presents the use of microstructured fibres for CZE, taking advantage of their relatively high surface-to-volume ratio and the small individual size of each channel to effect highly efficient separations, particularly for dye-labelled peptides.

  17. Subroutine bundls, a fortran IV program to determine schreinemakers bundles

    NASA Astrophysics Data System (ADS)

    Linde, J.; Andrew, A. S.

    Given an entire set of relevant balanced equations, BUNDLS and associated subroutines select all invariant points and order univariant lines around these points. Invariant points are formed by taking every set of m absent phases from each reaction. All revelant univariant lines are ordered around each invariant point by a direct application of the rules of Schreinemakers. The program also calculates true angular values for PT, P-μ x1 or μ y-μ x diagrams.

  18. Reflooding of tight lattice bundles

    SciTech Connect

    Veteau, J.M.; Digonnet, A.; Deruaz, R. . Centre d'Etudes Nucleaires de Grenoble)

    1994-07-01

    Results regarding analytical bottom reflooding experiments in a 37- and a 127-heater rod bundle are presented for two different tight lattices. A comparison between these two geometries and with the standard pressurized water reactor (PWR) array shows a degradation of cooling efficiency when the cross section of the subchannels is decreased. The core heat sinks (guide thimbles and water tubes'') are seen to have a noticeable influence on the overall cooling of the bundle, and it is confirmed that a combined top/bottom injection does not significantly improve cooling efficiency. Calculations with CATHARE 1.3 code adjusted for the standard PWR array are presented (zero heat sinks), but results have to be confirmed over a wider range of parameters.

  19. Mathematical modelling for nanotube bundle oscillators

    NASA Astrophysics Data System (ADS)

    Thamwattana, Ngamta; Cox, Barry J.; Hill, James M.

    2009-07-01

    This paper investigates the mechanics of a gigahertz oscillator comprising a nanotube oscillating within the centre of a uniform concentric ring or bundle of nanotubes. The study is also extended to the oscillation of a fullerene inside a nanotube bundle. In particular, certain fullerene-nanotube bundle oscillators are studied, namely C60-carbon nanotube bundle, C60-boron nitride nanotube bundle, B36N36-carbon nanotube bundle and B36N36-boron nitride nanotube bundle. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the fullerene and the nanotube bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques which provides considerable insight into the underlying mechanisms. The paper presents a synopsis of the major results derived in detail by the present authors in [1, 2].

  20. Overhead electric power transmission line jumpering system for bundles of five or more subconductors

    DOEpatents

    Winkelman, Paul F.

    1982-01-01

    Jumpering of electric power transmission lines at a dead end tower. Two transmission line conductor bundles each contain five or more spaced apart subconductors (5) arranged in the shape of a cylinder having a circular cross section. The ends of each bundle of subconductors are attached with insulators to a dead end tower (1). Jumpering allows the electric current to flow between the two bundles of subconductors using jumper buses, internal jumper conductors, and external jumper conductors. One or more current collecting jumper buses (37) are located inside each bundle of subconductors with each jumper bus being attached to the end of a subconductor. Small-diameter internal jumper conductors (33) are located in the inherently electrically shielded area inside each bundle of subconductors with each subconductor (except ones having an attached jumper bus) having one internal jumper conductor connected between that subconductor's end and a jumper bus. Large-diameter external jumper conductors (9) are located outside each bundle of subconductors with one or more external jumper conductors being connected between the jumper buses in one bundle of subconductors and the jumper buses in the other bundle.

  1. A study of bacterial flagellar bundling.

    PubMed

    Flores, Heather; Lobaton, Edgar; Méndez-Diez, Stefan; Tlupova, Svetlana; Cortez, Ricardo

    2005-01-01

    Certain bacteria, such as Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium), use multiple flagella often concentrated at one end of their bodies to induce locomotion. Each flagellum is formed in a left-handed helix and has a motor at the base that rotates the flagellum in a corkscrew motion. We present a computational model of the flagellar motion and their hydrodynamic interaction. The model is based on the equations of Stokes flow to describe the fluid motion. The elasticity of the flagella is modeled with a network of elastic springs while the motor is represented by a torque at the base of each flagellum. The fluid velocity due to the forces is described by regularized Stokeslets and the velocity due to the torques by the associated regularized rotlets. Their expressions are derived. The model is used to analyze the swimming motion of a single flagellum and of a group of three flagella in close proximity to one another. When all flagellar motors rotate counterclockwise, the hydrodynamic interaction can lead to bundling. We present an analysis of the flow surrounding the flagella. When at least one of the motors changes its direction of rotation, the same initial conditions lead to a tumbling behavior characterized by the separation of the flagella, changes in their orientation, and no net swimming motion. The analysis of the flow provides some intuition for these processes.

  2. Laboratory manual for static pressure drop experiments in LMFBR wire wrapped rod bundles

    SciTech Connect

    Burns, K.J.; Todreas, N.E.

    1980-07-01

    Purpose of this experiment is to determine both interior and edge subchannel axial pressure drops for a range of Reynolds numbers. The subchannel static pressure drop is used to calculate subchannel and bundle average friction factors, which can be used to verify existing friction factor correlations. The correlations for subchannel friction factors are used as input to computer codes which solve the coupled energy, continuity, and momentum equations, and are also used to develop flow split correlations which are needed as input to codes which solve only the energy equation. The bundle average friction factor is used to calculate the overall bundle pressure drop, which determines the required pumping power.

  3. Bundle critical power predictions under normal and abnormal conditions in pressurized water reactors

    SciTech Connect

    Lin, W.S.; Pei, B.S. ); Lee, C.H. )

    1992-06-01

    In this paper a new approach to bundle critical power predictions is presented. In addition to a very accurate critical heat flux (CHF) model, correction factors that account for the effects of grid spacers, heat flux non-uniformities, and cold walls, which are needed for critical power predictions for practical fuel bundles, are developed. By using the subchannel analysis code COBRA IIIC/MIT-1, local flow conditions needed as input to CHF correlations are obtained. Critical power is therefore obtained iteratively to ensure that the bundle power value from the subchannel analysis will cause CHF at only one point in the bundle. Good agreement with the experimental data is obtained. The accuracy is higher than that of the W-3 and EPRI-1 correlations for the limited data base used in this study. The effects of three types of fuel abnormalities, namely, local heat flux spikes, local flow blockages, and rod bowing, on bundle critical power are also analyzed. The local heat flux spikes and flow blockages have no significant influence on critical power. However, rod bowing phenomena have some effect, the severity of which depends on system pressure, the gap closure between adjacent rods, and the presence or absence of thimble tubes (cold walls). A correlation for the influence of various rod bowing phenomena on bundle critical power is developed. Good agreement with experimental data is shown.

  4. Are central line bundles and ventilator bundles effective in critically ill neonates and children?

    PubMed

    Smulders, Charlotte A; van Gestel, Josephus P J; Bos, Albert P

    2013-08-01

    Central line-associated bloodstream infections (CLABSI) and ventilator-associated pneumonia (VAP) are common problems in adult, pediatric (PICU) and neonatal (NICU) intensive care unit patients. Care bundles have been developed to prevent these hospital-acquired infections and to provide best possible care. Studies in adults have proven that care bundles contribute to a decrease in CLABSI and VAP rates. The purpose of this literature review was to critically appraise the known evidence of the effectiveness of central line bundles and ventilator bundles in PICU and NICU patients. The number of publications of central line bundles and ventilator bundles in PICU and NICU patients is limited compared to adults. Ten studies in PICU patients demonstrated a significant decrease in the CLABSI or VAP rate after implementation of the bundle. Two studies in neonates demonstrated a reduction in the CLABSI rate after implementation of the central line bundle. No studies on the effectiveness of the ventilator bundle in neonates were found. Bundle elements differed between studies, and their scientific basis was not as robust as in adults. Monitoring of compliance to bundle elements seems required for optimal reduction of CLABSI and VAP. Bundle components that focus on maintenance of a central line probably are important to prevent CLABSI in children.

  5. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Final report

    SciTech Connect

    Todreas, N.E.; Cheng, S.K.; Basehore, K.

    1984-08-01

    This project principally undertook the investigation of the thermal hydraulic performance of wire wrapped fuel bundles of LMFBR configuration. Results obtained included phenomenological models for friction factors, flow split and mixing characteristics; correlations for predicting these characteristics suitable for insertion in design codes; numerical codes for analyzing bundle behavior both of the lumped subchannel and distributed parameter categories and experimental techniques for pressure velocity, flow split, salt conductivity and temperature measurement in water cooled mockups of bundles and subchannels. Flow regimes investigated included laminar, transition and turbulent flow under forced convection and mixed convection conditions. Forced convections conditions were emphasized. Continuing efforts are underway at MIT to complete the investigation of the mixed convection regime initiated here. A number of investigations on outlet plenum behavior were also made. The reports of these investigations are identified.

  6. Mass Transport Through Carbon Nanotube-Polystyrene Bundles

    NASA Astrophysics Data System (ADS)

    Lin, Rongzhou; Tran, Tuan

    2016-05-01

    Carbon nanotubes have been widely used as test channels to study nanofluidic transport, which has been found to have distinctive properties compared to transport of fluids in macroscopic channels. A long-standing challenge in the study of mass transport through carbon nanotubes (CNTs) is the determination of flow enhancement. Various experimental investigations have been conducted to measure the flow rate through CNTs, mainly based on either vertically aligned CNT membranes or individual CNTs. Here, we proposed an alternative approach that can be used to quantify the mass transport through CNTs. This is a simple method relying on the use of carbon nanotube-polystyrene bundles, which are made of CNTs pulled out from a vertically aligned CNT array and glued together by polystyrene. We experimentally showed by using fluorescent tagging that the composite bundles allowed measureable and selective mass transport through CNTs. This type of composite bundle may be useful in various CNT research areas as they are simple to fabricate, less likely to form macroscopic cracks, and offer a high density of CNT pores while maintaining the aligned morphology of CNTs.

  7. Delay Tolerant Networking - Bundle Protocol Simulation

    NASA Technical Reports Server (NTRS)

    SeGui, John; Jenning, Esther

    2006-01-01

    In this paper, we report on the addition of MACHETE models needed to support DTN, namely: the Bundle Protocol (BP) model. To illustrate the useof MACHETE with the additional DTN model, we provide an example simulation to benchmark its performance. We demonstrate the use of the DTN protocol and discuss statistics gathered concerning the total time needed to simulate numerous bundle transmissions.

  8. Damping Properties of the Hair Bundle

    NASA Astrophysics Data System (ADS)

    Baumgart, Johannes; Kozlov, Andrei S.; Risler, Thomas; Hudspeth, A. J.

    2011-11-01

    The viscous liquid surrounding a hair bundle dissipates energy and dampens oscillations, which poses a fundamental physical challenge to the high sensitivity and sharp frequency selectivity of hearing. To identify the mechanical forces at play, we constructed a detailed finite-element model of the hair bundle. Based on data from the hair bundle of the bullfrog's sacculus, this model treats the interaction of stereocilia both with the surrounding liquid and with the liquid in the narrow gaps between the individual stereocilia. The investigation revealed that grouping stereocilia in a bundle dramatically reduces the total drag. During hair-bundle deflections, the tip links potentially induce drag by causing small but very dissipative relative motions between stereocilia; this effect is offset by the horizontal top connectors that restrain such relative movements at low frequencies. For higher frequencies the coupling liquid is sufficient to assure that the hair bundle moves as a unit with a low total drag. This work reveals the mechanical characteristics originating from hair-bundle morphology and shows quantitatively how a hair bundle is adapted for sensitive mechanotransduction.

  9. Critical heat flux predictions in rod bundles

    SciTech Connect

    Kao, S.P.; Kazimi, M.S.

    1983-01-01

    The prediction of critical heat flux (CHF) in rod bundles has been studied with both subchannel and bundle-average methods. The correlations of Biasi, Bowring, CISE-4, and Barnett were considered. The General Electric 9-rod bundle CHF data were used in the comparisons. Calculations were performed by the two-fluid subchannel code THERMIT-2. The results indicate that the subchannel method yields more conservative CHF predictions than the bundleaverage method. This is attributed to the two-phase turbulent mixing phenomenon in the bundle, which can be modeled only on a subchannel basis. The results also indicate that the CISE-4 correlation had the smallest error in prediction of transition boiling for both subchannel and bundle-average methods.

  10. Line bundle embeddings for heterotic theories

    NASA Astrophysics Data System (ADS)

    Nibbelin, Stefan Groot; Ruehle, Fabian

    2016-04-01

    In heterotic string theories consistency requires the introduction of a non-trivial vector bundle. This bundle breaks the original ten-dimensional gauge groups E8 × E8 or SO(32) for the supersymmetric heterotic string theories and SO(16) × SO(16) for the non-supersymmetric tachyon-free theory to smaller subgroups. A vast number of MSSM-like models have been constructed up to now, most of which describe the vector bundle as a sum of line bundles. However, there are several different ways of describing these line bundles and their embedding in the ten-dimensional gauge group. We recall and extend these different descriptions and explain how they can be translated into each other.

  11. Rod Bundle Heat Transfer: Steady-State Steam Cooling Experiments

    SciTech Connect

    Spring, J.P.; McLaughlin, D.M.

    2006-07-01

    Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental rod bundle heat transfer (RBHT) facility was designed and built. The rod bundle consists of a 7 x 7 square pitch array with spacer grids and geometry similar to that found in a modern pressurized water reactor. From this facility, a series of steady-state steam cooling experiments were performed. The bundle inlet Reynolds number was varied from 1 400 to 30 000 over a pressure range from 1.36 to 4 bars (20 to 60 psia). The bundle inlet steam temperature was controlled to be at saturation for the specified pressure and the fluid exit temperature exceeded 550 deg. C in the highest power tests. One important quantity of interest is the local convective heat transfer coefficient defined in terms of the local bulk mean temperature of the flow, local wall temperature, and heat flux. Steam temperatures were measured at the center of selected subchannels along the length of the bundle by traversing miniaturized thermocouples. Using an analogy between momentum and energy transport, a method was developed for relating the local subchannel centerline temperature measurement to the local bulk mean temperature. Wall temperatures were measured using internal thermocouples strategically placed along the length of each rod and the local wall heat flux was obtained from an inverse conduction program. The local heat transfer coefficient was calculated from the data at each rod thermocouple location. The local heat transfer coefficients calculated for locations where the flow was fully developed were compared against several published correlations. The Weisman and El-Genk correlations were found to agree best with the RBHT steam cooling data, especially over the range of turbulent Reynolds numbers. The effect of spacer grids on the heat transfer enhancement was also determined from instrumentation placed downstream of the spacer grid locations. The local

  12. Preliminary report: NIF laser bundle review

    SciTech Connect

    Tietbohl, G.L.; Larson, D.W.; Erlandson, A.C.

    1995-08-31

    As requested in the guidance memo {sup 1}, this committe determined whether there are compelling reasons to recommend a change from the NIF CDR baseline laser. The baseline bundle design based on a tradeoff between cost and technical risk, which is replicated four times to create the required 192 beams. The baseline amplifier design uses bottom loading 1{times}4 slab and flashlamp cassettes for amplifier maintenance and large vacuum enclosures (2.5m high {times} 7m wide in cross-section for each of the two spatial filters in each of the four bundles. The laser beams are arranged in two laser bays configured in a u-shape around the target area. The entire bundle review effort was performed in a very short time (six weeks) and with limited resources (15 personnel part-time). This should be compared to the effort that produced the CDR design (12 months, 50 to 100 personnel). This committee considered three alternate bundle configurations (2{times}2, 4{times}2, and 4{times}4 bundles), and evaluated each bundle against the baseline design using the seven requested issues in the guidance memo: Cost; schedule; performance risk; maintainability/operability; hardware failure cost exposure; activation; and design flexibility. The issues were reviewed to identify differences between each alternate bundle configuration and the baseline.

  13. F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling

    PubMed Central

    1995-01-01

    Transverse sections though Drosophila bristles reveal 7-11 nearly round, plasma membrane-associated bundles of actin filaments. These filaments are hexagonally packed and in a longitudinal section they show a 12-nm periodicity in both the 1.1 and 1.0 views. From earlier studies this periodicity is attributable to cross-links and indicates that the filaments are maximally cross-linked, singed mutants also have 7-11 bundles, but the bundles are smaller, flattened, and the filaments within the bundles are randomly packed (not hexagonal); no periodicity can be detected in longitudinal sections. Another mutant, forked (f36a), also has 7-11 bundles but even though the bundles are very small, the filaments within them are hexagonally packed and display a 12-nm periodicity in longitudinal section. The singed-forked double mutant lacks filament bundles. Thus there are at least two species of cross-links between adjacent actin filaments. Hints of why two species of cross-links are necessary can be gleaned by studying bristle formation. Bristles sprout with only microtubules within them. A little later in development actin filaments appear. At early stages the filaments in the bundles are randomly packed. Later the filaments in the bundles become hexagonally packed and maximally cross-linked. We consider that the forked proteins may be necessary early in development to tie the filaments together in a bundle so that they can be subsequently zippered together by fascin (the singed gene product). PMID:7622563

  14. Validation of fuel bundle mechanical performance code ETOILE with bundle/duct interaction experimental data

    SciTech Connect

    Nakagawa, Masatoshi )

    1993-04-01

    Validation of the ETOILE code through a comparison with experimental bundle/duct interaction (BDI) data is discussed. ETOILE is a newly developed three-dimensional finite element program that uses a new analytical method to predict distortions and mechanical behavior in wire-wrapped-type fuel-pin bundles during irradiation in liquid-metal fast breeder reactor cores. Comparisons between the ETOILE solutions and the experimental data for bundle stiffnesses and minimum pin-to-pin and pin-to-duct clearances under bundle compression suggest that BDI performance can be predicted reasonably well with a suitable choice of friction coefficient and initial spiral wire displacement. Application of the code in the analysis of the mechanical behavior of soft bundles with distributed wireless pins is also presented to demonstrate the effectiveness of this design in reducing the interaction forces between a fuel-pin bundle and a duct wall under bundle compression. Agreement with the experimental data is fairly good for the reduction in bundle stiffness when the configuration is changed from the normal bundle to the soft bundle.

  15. Requirements for contractility in disordered cytoskeletal bundles

    NASA Astrophysics Data System (ADS)

    Lenz, Martin; Gardel, Margaret L.; Dinner, Aaron R.

    2012-03-01

    Actomyosin contractility is essential for biological force generation, and is well understood in highly organized structures such as striated muscle. Additionally, actomyosin bundles devoid of this organization are known to contract both in vivo and in vitro, which cannot be described by standard muscle models. To narrow down the search for possible contraction mechanisms in these systems, we investigate their microscopic symmetries. We show that contractile behavior requires non-identical motors that generate large-enough forces to probe the nonlinear elastic behavior of F-actin. This suggests a role for filament buckling in the contraction of these bundles, consistent with recent experimental results on reconstituted actomyosin bundles.

  16. Enhanced boiling heat transfer in horizontal test bundles

    SciTech Connect

    Trewin, R.R.; Jensen, M.K.; Bergles, A.E.

    1994-08-01

    Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.

  17. SU(5) heterotic Standard Model bundles

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Hoffmann, Norbert

    2012-04-01

    We construct a class of stable SU(5) bundles on an elliptically fibered Calabi-Yau threefold with two sections, a variant of the ordinary Weierstrass fibration, which admits a free involution. The bundles are invariant under the involution, solve the topological constraint imposed by the heterotic anomaly equation and give three generations of Standard Model fermions after symmetry breaking by Wilson lines of the intermediate SU(5) GUT-group to the Standard Model gauge group. Among the solutions we find some which can be perturbed to solutions of the Strominger system. Thus these solutions provide a step toward the construction of phenomenologically realistic heterotic flux compactifications via non-Kähler deformations of Calabi-Yau geometries with bundles. This particular class of solutions involves a rank two hidden sector bundle and does not require background fivebranes for anomaly cancellation.

  18. Robust incoherent fiber optic bundle decoder

    NASA Technical Reports Server (NTRS)

    Roberts, Hilary E. (Inventor); DePlachett, Charles P. (Inventor); Deason, Brent E. (Inventor); Pilgrim, Robert A. (Inventor); Sanford, Harold S. (Inventor)

    2003-01-01

    Apparatus and method for calibrating an incoherent fiber optic bundle for use in transmitting visual or infrared coherent images. The apparatus includes a computer, a computer video monitor, an objective lens adjacent to the input end of the bundle, a second lens adjacent the output end of the bundle, and a CCD camera. The camera transmits video data to the monitor to produce an illuminated fiber optic image. The coordinates for the center of each fiber is found through an imaging process and the output fibers coordinates are related to the input fiber coordinates and processed in the computer to produce a mapping lookup-table (LUT) unique to the specific fiber bundle. Remapping of the LUT due to changes in the lens focus, CCD camera, or the addition of an infrared filter is accomplished by a software utility in the computer.

  19. Sealed fiber-optic bundle feedthrough

    DOEpatents

    Tanner, Carol E.

    2002-01-01

    A sealed fiber-optic bundle feedthrough by which a multitude of fiber-optic elements may be passed through an opening or port in a wall or structure separating two environments at different pressures or temperatures while maintaining the desired pressure or temperature in each environment. The feedthrough comprises a rigid sleeve of suitable material, a bundle of individual optical fibers, and a resin-based sealing material that bonds the individual optical fibers to each other and to the rigid sleeve.

  20. Is It Complete Left Bundle Branch Block? Just Ablate the Right Bundle.

    PubMed

    Ali, Hussam; Lupo, Pierpaolo; Foresti, Sara; De Ambroggi, Guido; Epicoco, Gianluca; Fundaliotis, Angelica; Cappato, Riccardo

    2017-03-01

    Complete left bundle branch block (LBBB) is established according to standard electrocardiographic criteria. However, functional LBBB may be rate-dependent or can perpetuate during tachycardia due to repetitive concealed retrograde penetration of impulses through the contralateral bundle "linking phenomenon." In this brief article, we present two patients with basal complete LBBB in whom ablating the right bundle unmasked the actual antegrade conduction capabilities of the left bundle. These cases highlight intriguing overlap between electrophysiological concepts of complete block, linking, extremely slow, and concealed conduction.

  1. Estimate of the local cladding overheating caused by pin bundle distortion in an LMFBR assembly

    SciTech Connect

    Khan, E.U.; Rector, D.R.; Fort, J.M.; Patton, E.M.

    1983-02-01

    This paper presents a conservative estimate of the cladding temperature increase (over nominal temperature) caused by a bundle-duct interference of 100 mils (0 to 1 in.) in a typical LMFBR pin bundle. Parameters affecting global and local heating that is caused by bundle-duct interaction (BDI) are described. The highlights and shortcomings of previous work on the subject are discussed. The geometry of the distorted bundle is conservatively obtained by linearly superimposing calculated local distortions onto global distortions obtained from a bundle compression test. Significant local reduction in the area of hot the channel is predicted. The edge pins are expected to contact the duct wall, but no pin-to-pin contact is predicted. The thermal-hydraulic analysis is done in two steps. First, the COBRA-WC Code is used to determine the subchannel temperature distribution. Second, based on coolant flow velocity measurements in a scaled (6X) model of a distorted pin bundle, the cladding temperature at the contact is predicted as a function of the contact width.

  2. Subdiffusion in hair bundle dynamics: The role of protein conformational fluctuations

    NASA Astrophysics Data System (ADS)

    Sharma, Rati; Cherayil, Binny J.

    2012-12-01

    The detection of sound signals in vertebrates involves a complex network of different mechano-sensory elements in the inner ear. An especially important element in this network is the hair bundle, an antenna-like array of stereocilia containing gated ion channels that operate under the control of one or more adaptation motors. Deflections of the hair bundle by sound vibrations or thermal fluctuations transiently open the ion channels, allowing the flow of ions through them, and producing an electrical signal in the process, eventually causing the sensation of hearing. Recent high frequency (0.1-10 kHz) measurements by Kozlov et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 2896 (2012)], 10.1073/pnas.1121389109 of the power spectrum and the mean square displacement of the thermal fluctuations of the hair bundle suggest that in this regime the dynamics of the hair bundle are subdiffusive. This finding has been explained in terms of the simple Brownian motion of a filament connecting neighboring stereocilia (the tip link), which is modeled as a viscoelastic spring. In the present paper, the diffusive anomalies of the hair bundle are ascribed to tip link fluctuations that evolve by fractional Brownian motion, which originates in fractional Gaussian noise and is characterized by a power law memory. The predictions of this model for the power spectrum of the hair bundle and its mean square displacement are consistent with the experimental data and the known properties of the tip link.

  3. Properties of the microcirculation in capillary bundles of rat spinotrapezius muscle fascia

    NASA Astrophysics Data System (ADS)

    Jacobitz, Frank; Engebrecht, Cheryn; Metzger, Ian; Porterfield, Colin

    2006-11-01

    Properties of the microcirculation in capillary bundles of rat spinotrapezius muscle fascia are investigated using microscope observations, empirical modeling, and numerical simulations. Capillary bundles consist of a network of feeding arterioles, draining venules, and capillary vessels. A dozen samples of muscle fascia tissue were prepared for microscope observation. The chosen method of preparation allows for the long-term preservation of the tissue samples for future studies. Capillary bundles are photographed under a microscope with 40x magnification. From the images, the microvasculature of the tissue samples is reconstructed. It was found, for example, that the distribution of vessel length in a capillary bundle follows a log-normal law. In addition to a statistical analysis of the vessel data, the network topology is used for numerical simulations of the flow in the capillary bundles. The numerical approach uses a sparse-matrix solver and it considers vessel elasticity and blood rheology. The numerical simulations show, for example, a strong pressure drop across the capillary vessels of the bundle.

  4. A Mechanistic Approach for the Prediction of Critical Power in BWR Fuel Bundles

    NASA Astrophysics Data System (ADS)

    Chandraker, Dinesh Kumar; Vijayan, Pallipattu Krishnan; Sinha, Ratan Kumar; Aritomi, Masanori

    The critical power corresponding to the Critical Heat Flux (CHF) or dryout condition is an important design parameter for the evaluation of safety margins in a nuclear fuel bundle. The empirical approaches for the prediction of CHF in a rod bundle are highly geometric specific and proprietary in nature. The critical power experiments are very expensive and technically challenging owing to the stringent simulation requirements for the rod bundle tests involving radial and axial power profiles. In view of this, the mechanistic approach has gained momentum in the thermal hydraulic community. The Liquid Film Dryout (LFD) in an annular flow is the mechanism of CHF under BWR conditions and the dryout modeling has been found to predict the CHF quite accurately for a tubular geometry. The successful extension of the mechanistic model of dryout to the rod bundle application is vital for the evaluation of critical power in the rod bundle. The present work proposes the uniform film flow approach around the rod by analyzing individual film of the subchannel bounded by rods with different heat fluxes resulting in different film flow rates around a rod and subsequently distributing the varying film flow rates of a rod to arrive at the uniform film flow rate as it has been found that the liquid film has a strong tendency to be uniform around the rod. The FIDOM-Rod code developed for the dryout prediction in BWR assemblies provides detailed solution of the multiple liquid films in a subchannel. The approach of uniform film flow rate around the rod simplifies the liquid film cross flow modeling and was found to provide dryout prediction with a good accuracy when compared with the experimental data of 16, 19 and 37 rod bundles under BWR conditions. The critical power has been predicted for a newly designed 54 rod bundle of the Advanced Heavy Water Reactor (AHWR). The selected constitutive models for the droplet entrainment and deposition rates validated for the dryout in tube were

  5. Maximum allowable heat flux for a submerged horizontal tube bundle

    SciTech Connect

    McEligot, D.M.

    1995-08-14

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or {open_quotes}critical{close_quotes}) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration.

  6. Buckling behavior of individual and bundled microtubules.

    PubMed

    Soheilypour, Mohammad; Peyro, Mohaddeseh; Peter, Stephen J; Mofrad, Mohammad R K

    2015-04-07

    As the major structural constituent of the cytoskeleton, microtubules (MTs) serve a variety of biological functions that range from facilitating organelle transport to maintaining the mechanical integrity of the cell. Neuronal MTs exhibit a distinct configuration, hexagonally packed bundles of MT filaments, interconnected by MT-associated protein (MAP) tau. Building on our previous work on mechanical response of axonal MT bundles under uniaxial tension, this study is focused on exploring the compression scenarios. Intracellular MTs carry a large fraction of the compressive loads sensed by the cell and therefore, like any other column-like structure, are prone to substantial bending and buckling. Various biological activities, e.g., actomyosin contractility and many pathological conditions are driven or followed by bending, looping, and buckling of MT filaments. The coarse-grained model previously developed in our lab has been used to study the mechanical behavior of individual and bundled in vivo MT filaments under uniaxial compression. Both configurations show tip-localized, decaying, and short-wavelength buckling. This behavior highlights the role of the surrounding cytoplasm and MAP tau on MT buckling behavior, which allows MT filaments to bear much larger compressive forces. It is observed that MAP tau interconnections improve this effect by a factor of two. The enhanced ability of MT bundles to damp buckling waves relative to individual MT filaments, may be interpreted as a self-defense mechanism because it helps axonal MTs to endure harsher environments while maintaining their function. The results indicate that MT filaments in a bundle do not buckle simultaneously implying that the applied stress is not equally shared among the MT filaments, that is a consequence of the nonuniform distribution of MAP tau proteins along the bundle length. Furthermore, from a pathological perspective, it is observed that axonal MT bundles are more vulnerable to failure in

  7. Mechanism of Actin Filament Bundling by Fascin

    SciTech Connect

    Jansen, Silvia; Collins, Agnieszka; Yang, Changsong; Rebowski, Grzegorz; Svitkina, Tatyana; Dominguez, Roberto

    2013-03-07

    Fascin is the main actin filament bundling protein in filopodia. Because of the important role filopodia play in cell migration, fascin is emerging as a major target for cancer drug discovery. However, an understanding of the mechanism of bundle formation by fascin is critically lacking. Fascin consists of four {beta}-trefoil domains. Here, we show that fascin contains two major actin-binding sites, coinciding with regions of high sequence conservation in {beta}-trefoil domains 1 and 3. The site in {beta}-trefoil-1 is located near the binding site of the fascin inhibitor macroketone and comprises residue Ser-39, whose phosphorylation by protein kinase C down-regulates actin bundling and formation of filopodia. The site in {beta}-trefoil-3 is related by pseudo-2-fold symmetry to that in {beta}-trefoil-1. The two sites are {approx}5 nm apart, resulting in a distance between actin filaments in the bundle of {approx}8.1 nm. Residue mutations in both sites disrupt bundle formation in vitro as assessed by co-sedimentation with actin and electron microscopy and severely impair formation of filopodia in cells as determined by rescue experiments in fascin-depleted cells. Mutations of other areas of the fascin surface also affect actin bundling and formation of filopodia albeit to a lesser extent, suggesting that, in addition to the two major actin-binding sites, fascin makes secondary contacts with other filaments in the bundle. In a high resolution crystal structure of fascin, molecules of glycerol and polyethylene glycol are bound in pockets located within the two major actin-binding sites. These molecules could guide the rational design of new anticancer fascin inhibitors.

  8. Buckling Behavior of Individual and Bundled Microtubules

    PubMed Central

    Soheilypour, Mohammad; Peyro, Mohaddeseh; Peter, Stephen J.; Mofrad, Mohammad R.K.

    2015-01-01

    As the major structural constituent of the cytoskeleton, microtubules (MTs) serve a variety of biological functions that range from facilitating organelle transport to maintaining the mechanical integrity of the cell. Neuronal MTs exhibit a distinct configuration, hexagonally packed bundles of MT filaments, interconnected by MT-associated protein (MAP) tau. Building on our previous work on mechanical response of axonal MT bundles under uniaxial tension, this study is focused on exploring the compression scenarios. Intracellular MTs carry a large fraction of the compressive loads sensed by the cell and therefore, like any other column-like structure, are prone to substantial bending and buckling. Various biological activities, e.g., actomyosin contractility and many pathological conditions are driven or followed by bending, looping, and buckling of MT filaments. The coarse-grained model previously developed in our lab has been used to study the mechanical behavior of individual and bundled in vivo MT filaments under uniaxial compression. Both configurations show tip-localized, decaying, and short-wavelength buckling. This behavior highlights the role of the surrounding cytoplasm and MAP tau on MT buckling behavior, which allows MT filaments to bear much larger compressive forces. It is observed that MAP tau interconnections improve this effect by a factor of two. The enhanced ability of MT bundles to damp buckling waves relative to individual MT filaments, may be interpreted as a self-defense mechanism because it helps axonal MTs to endure harsher environments while maintaining their function. The results indicate that MT filaments in a bundle do not buckle simultaneously implying that the applied stress is not equally shared among the MT filaments, that is a consequence of the nonuniform distribution of MAP tau proteins along the bundle length. Furthermore, from a pathological perspective, it is observed that axonal MT bundles are more vulnerable to failure in

  9. The histology of retinal nerve fiber layer bundles and bundle defects.

    PubMed

    Radius, R L; Anderson, D R

    1979-05-01

    The fiber bundle striations recognized clinically in normal monkey eyes appear to be bundles of axons compartmentalized within glial tunnels formed by Müller's-cell processes, when viewed histologically. The dark boundaries that separate individual bundles are the broadened foot endings of these cells near the inner surface of the retina. Within one week after focal retinal photocoagulation, characteristic fundus changes could be seen in experimental eyes. In histologic sections of the involved retina, there was marked cystic degeneration of the retinal nerve fiber layer. Within one month, atrophy of distal axon segments was complete. With the drop-out of damaged axons and thinning of individual fiber bundles, retinal striations became less prominent. The resulting fundus picture in these experimental eyes is similar to fiber bundle defects that can be seen clinically in various neuro-ophthalmic disorders.

  10. Spectral bundles and the DRY-Conjecture

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Curio, Gottfried

    2012-04-01

    Supersymmetric heterotic string models, built from a Calabi-Yau threefold X endowed with a stable vector bundle V, usually start from a phenomenologically motivated choice of a bundle Vv in the visible sector, the spectral cover construction on an elliptically fibered X being a prominent example. The ensuing anomaly mismatch between c2(Vv) and c2(X), or rather the corresponding differential forms, is often 'solved', on the cohomological level, by including a fivebrane. This leads to the question whether the difference can be alternatively realized by a further stable bundle. The 'DRY'-conjecture of Douglas, Reinbacher and Yau in math.AG/0604597 gives a sufficient condition on cohomology classes on X to be realized as the Chern classes of a stable sheaf. In 1010.1644 [hep-th], we showed that infinitely many classes on X exist for which the conjecture is true. In this note, we give the sufficient condition for the mentioned fivebrane classes to be realized by a further stable bundle in the hidden sector. Using a result obtained in 1011.6246 [hep-th], we show that corresponding bundles exist, thereby confirming this version of the DRY-Conjecture.

  11. Photothermal imaging through coherent infrared bundles

    NASA Astrophysics Data System (ADS)

    Milstein, Yonat; Tepper, Michal; Harrington, James A.; Ben David, Moshe; Gannot, Israel

    2011-03-01

    This study aims to develop a photothermal imaging system through a coherent infrared bundle. This system will be used to determine the oxygenation level of various tissues, suspected malignant tissues in particular. The oxygenation estimation is preformed using a computerized algorithm. In order to evaluate the system, different bundle configurations were used for the determination of the optimal one. Bundle transmittance and the algorithm's estimation ability were measured, measurements were performed using agar phantoms consisting of varying ratios of Methylene Blue and ICG. A bundle consisting of 19 Teflon waveguides with a of 1.1mm was found to be the optimal configuration with an RMS of the error of 9.38%. At a second stage the system was validated on blood samples with varying oxygenation levels and there oxygenation levels were estimated. This stage had an RMS of the error of 10.16% for the oxygenation level estimation for samples with a 50% oxygenation level and higher. Once the basic system was validated successfully on agar phantoms and blood samples a portable system was designed and built in order to fit the system for portable use. The portable system consists of a white light illuminating source followed by filters transmitting certain wavelengths, a transmitting fiber, a thermal imaging bundle and a portable thermal camera. This portable system will be evaluated in order to have an adequate portable system for implementing the method out of the lab.

  12. Hydrodynamic interaction of bacterial flagella - flagellar bundling

    NASA Astrophysics Data System (ADS)

    Lim, Sookkyung

    2013-11-01

    Flagellar bundling is an important aspect of locomotion in bacteria such as Escherichia coli. To study the hydrodynamic behavior of helical flagella, we present a computational model that is based on the geometry of the bacterial flagellar filament at the micrometer scale. We consider two model flagella, each of which has a rotary motor at its base with the rotation rate of the motor set at 100 Hz. Bundling occurs when both flagella are left-handed helices turning counterclockwise (when viewed from the nonmotor end of the flagellum looking back toward the motor) or when both flagella are right-handed helices turning clockwise. Helical flagella of the other combinations of handedness and rotation direction do not bundle. In this work we use the generalized immersed boundary method combined with the unconstrained Kirchhoff rod theory, which allows us to study the complicated hydrodynamics of flagellar behavior. This is a joint work with Charlie Peskin at NYU. NSF

  13. Contour based object detection using part bundles

    PubMed Central

    Lu, ChengEn; Adluru, Nagesh; Ling, Haibin; Zhu, Guangxi; Latecki, Longin Jan

    2016-01-01

    In this paper we propose a novel framework for contour based object detection from cluttered environments. Given a contour model for a class of objects, it is first decomposed into fragments hierarchically. Then, we group these fragments into part bundles, where a part bundle can contain overlapping fragments. Given a new image with set of edge fragments we develop an efficient voting method using local shape similarity between part bundles and edge fragments that generates high quality candidate part configurations. We then use global shape similarity between the part configurations and the model contour to find optimal configuration. Furthermore, we show that appearance information can be used for improving detection for objects with distinctive texture when model contour does not sufficiently capture deformation of the objects.

  14. Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation

    SciTech Connect

    Yunus, Abdul S.; Jackson, Trent P.; Crisafi, Katherine; Burimski, Irina; Kilgore, Nicole R.; Zoumplis, Dorian; Allaway, Graham P.; Wild, Carl T.; Salzwedel, Karl

    2010-01-20

    Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 deg. C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of

  15. Determining the tube bundle streamlining critical parameters using the numerical experiment method

    NASA Astrophysics Data System (ADS)

    Kaplunov, S. M.; Val'es, N. G.; Samolysov, A. V.; Marchevskaya, O. A.

    2015-08-01

    The article is devoted to development and application of mathematical models describing the most dangerous mechanisms through which vibrations are excited in tube bundles and blunt cylindrically shaped structures, and to development of reliable calculation methods for describing these models, which would make it possible to obtain prompt data for designing and subsequent operation of the considered structural elements. For solving such problems, a comprehensive approach is required, which should be based on a combined use of numerical experiments on computers and experimental investigations on full-scale equipment. The authors have developed a procedure for numerically investigating the hydrodynamic forces arising during stalled streamlining and the tube bundle vibrations caused by these forces. The procedure is based on using the developed mathematical model describing fluid-elastic excitation of vibrations in a bundle of elastic tubes placed in external cross flow. The problem of studying fluid-elastic excitation is brought to stability analysis, which is carried out with the assumption about a linear behavior of destabilizing forces for undisturbed state of elastic tubes. A theoretical investigation of the developed mathematical model was carried out, from which the necessary and sufficient condition of system stability has been obtained in terms of system dimensionless parameters (mass, damping, and velocity). An algorithm for numerically determining the matrices of linear hydrodynamic coupling coefficients for particular tube bundles is developed. The validity of the algorithm and the computer programs developed on its basis are checked by comparing the results of test calculations with the bank of known experimental data. A procedure is proposed for determining the matrices of linear hydrodynamic coupling coefficients in bundles having a regular layout of their cross section and a large number of tubes through calculating these matrices for a relatively small

  16. Using the HELIOS facility for assessment of bundle-jacket thermal coupling in a CICC

    NASA Astrophysics Data System (ADS)

    Lacroix, B.; Rousset, B.; Cloez, H.; Decool, P.; Duchateau, J. L.; Hoa, C.; Luchier, N.; Nicollet, S.; Topin, F.

    2016-12-01

    In a Cable In Conduit Conductor (CICC) cooled by forced circulation of supercritical helium, the heat exchange in the bundle region can play a significant role for conductor safe operation, while remaining a quite uncertain parameter. Heat exchange between bundle and jacket depends on the relative contributions of convective heat transfer due to the helium flow inside the bundle and of thermal resistance due to the wrappings between the cable and the conduit. In order to qualify this thermal coupling at realistic operating conditions, a dedicated experiment on a 1.2 m sample of ITER Toroidal Field (TF) dummy conductor was designed and performed in the HELIOS test facility at CEA Grenoble. Several methods were envisaged, and the choice was made to assess bundle-jacket heat transfer coefficient by measuring the temperature of a solid copper cylinder inserted over the conductor jacket and submitted to heat deposition on its outer surface. The mock-up was manufactured and tested in spring 2015. Bundle-jacket heat transfer coefficient was found in the range 300-500 W m-2 K-1. Results analysis suggests that the order of magnitude of convective heat transfer coefficient inside bundle is closer to Colburn-Reynolds analogy than to Dittus-Boelter correlation, and that bundle-jacket thermal coupling is mainly limited by thermal resistance due to wrappings. A model based on an equivalent layer of stagnant helium between wraps and jacket was proposed and showed a good consistency with the experiment, with relevant values for the helium layer thickness.

  17. Photochemical Properties of Mesophyll and Bundle Sheath Chloroplasts of Maize 1

    PubMed Central

    Bazzaz, Maarib Bakri; Govindjee

    1973-01-01

    Several photochemical and spectral properties of maize (Zea mays) bundle sheath and mesophyll chloroplasts are reported that provide a better understanding of the photosynthetic apparatus of C4 plants. The difference absorption spectrum at 298 K and the fluorescence excitation and emission spectra of chlorophyll at 298 K and 77 K provide new information on the different forms of chlorophyll a in bundle sheath and mesophyll chloroplasts: the former contain, relative to short wavelength chlorophyll a forms, more long wavelength chlorophyll a form (e.g. chlorophyll a 693 and chlorophyll a 705) and less chlorophyll b than the latter. The degree of polarization of chlorophyll a fluorescence is 6% in bundle sheath and 4% in mesophyll chloroplasts. This result is consistent with the presence of relatively high amounts of oriented long wavelength forms of chlorophyll a in bundle sheath compared to mesophyll chloroplasts. The relative yield of variable, with respect to constant, chorophyll a fluorescence in mesophyll chloroplasts is more than twice that in bundle sheath chloroplast. Furthermore, the relative yield of total chlorophyll a fluorescence is 40% lower in bundle sheath compared to that in mesophyll chloroplasts. This is in agreement with the presence of the higher ratio of the weakly fluorescent pigment system I to pigment system II in bundle sheath than in mesophyll chloroplast. The efficiency of energy transfer from chlorophyll b and carotenoids to chlorophyll a are calculated to be 100 and 50%, respectively, in both types of chloroplasts. Fluorescence quenching of atebrin, reflecting high energy state of chloroplasts, is 10 times higher in mesophyll chloroplasts than in bundle sheath chloroplasts during noncyclic electron flow but is equal during cyclic flow. The entire electron transport chain is shown to be present in both types of chloroplasts, as inferred from the antagonistic effect of red (650 nm) and far red (710 nm) lights on the absorbance changes at

  18. Sodium boiling experiments in bundle geometries under fast transient and steady state conditions

    NASA Astrophysics Data System (ADS)

    Peppler, F. W.

    Flow loss experiments were carried out in tubular and 7 pin test-sections and in a sodium cooled 37 pin bundle with sinusoidal axial heat flux profile. Thermohydraulic behavior under fast loss of flow conditions, particularly three-dimensional phenomena such as the development of the temperature distribution, the boiling region, the onset and extension of dryout, and the flow regimes related to different boiling periods were studied. The experimental results provide data for the validation of three-dimensional two-phase hydrodynamic codes. Stationary boiling tests provide information on two-phase pressure drop in bundles, the flow regimes and the conditions prevailing during the approach to critical heat flux conditions.

  19. Effects of upper-plenum steam condensation phenomena on heat transfer in a rod bundle. [PWR

    SciTech Connect

    Chon, W.Y.; Addabbo, C.; Liao, N.S.

    1980-02-01

    System performance and thermohydraulic response to simultaneous bottom and top water injection were investigated in a 3 x 3 rod bundle Reflood Test Facility. An extensive series of tests, encompassing both simple bottom and combined injection reflooding, were carried out. A number of phenomenological events governing the thermodynamic coupling between the bottom reflood updraft and the top deluge were identified. Due to the countercurrent motion of the upflowing steam and water injected in the upper plenum counter current flow limiting phenomena hindered the penetration of water from inventory in the upper plenum into the bundle section. Consequently, condensation phenomena in the upper plenum and in the venting pipework characterized the thermohydraulic response of the bundle to simultaneous bottom and top water injection.

  20. Relaxation of ultralarge VWF bundles in a microfluidic-AFM hybrid reactor

    SciTech Connect

    Steppich, D.M.; Angerer, J.I.; Sritharan, K.; Schneider, S.W.; Thalhammer, S.; Wixforth, A.; Alexander-Katz, A.; Schneider, M.F.

    2008-05-02

    The crucial role of the biopolymer 'Von Willebrand factor' (VWF) in blood platelet binding is tightly regulated by the shear forces to which the protein is exposed in the blood flow. Under high-shear conditions, VWFs ability to immobilize blood platelets is strongly increased due to a change in conformation which at sufficient concentration is accompanied by the formation of ultra large VWF bundles (ULVWF). However, little is known about the dynamic and mechanical properties of such bundles. Combining a surface acoustic wave (SAW) based microfluidic reactor with an atomic force microscope (AFM) we were able to study the relaxation of stretched VWF bundles formed by hydrodynamic stress. We found that the dynamical response of the network is well characterized by stretched exponentials, indicating that the relaxation process proceeds through hopping events between a multitude of minima. This finding is in accordance with current ideas of VWF self-association. The longest relaxation time does not show a clear dependence on the length of the bundle, and is dominated by the internal conformations and effective friction within the bundle.

  1. Meromorphic Higgs bundles and related geometries

    NASA Astrophysics Data System (ADS)

    Dalakov, Peter

    2016-11-01

    The present note is mostly a survey on the generalised Hitchin integrable system and moduli spaces of meromorphic G-Higgs bundles. We also fill minor gaps in the existing literature, outline a calculation of the infinitesimal period map and review some related geometries.

  2. Social Bundles: Thinking through the Infant Body

    ERIC Educational Resources Information Center

    Brownlie, Julie; Leith, Valerie M. Sheach

    2011-01-01

    Drawing on a UK research study on immunization, this article investigates parents' understandings of the relationship between themselves, their infants, other bodies, the state, and cultural practices--material and symbolic. The article argues that infant bodies are best thought of as always social bundles, rather than as biobundles made social…

  3. Laughter-induced left bundle branch block.

    PubMed

    Chow, Grant V; Desai, Dipan; Spragg, David D; Zakaria, Sammy

    2012-10-01

    We present the case of a patient with ischemic heart disease and intermittent left bundle branch block, reproducibly induced by laughter. Following treatment of ischemia with successful deployment of a drug-eluting stent, no further episodes of inducible LBBB were seen. Transient ischemia, exacerbated by elevated intrathoracic pressure during laughter, may have contributed to onset of this phenomenon.

  4. Interplanetary Overlay Network Bundle Protocol Implementation

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    The Interplanetary Overlay Network (ION) system's BP package, an implementation of the Delay-Tolerant Networking (DTN) Bundle Protocol (BP) and supporting services, has been specifically designed to be suitable for use on deep-space robotic vehicles. Although the ION BP implementation is unique in its use of zero-copy objects for high performance, and in its use of resource-sensitive rate control, it is fully interoperable with other implementations of the BP specification (Internet RFC 5050). The ION BP implementation is built using the same software infrastructure that underlies the implementation of the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) built into the flight software of Deep Impact. It is designed to minimize resource consumption, while maximizing operational robustness. For example, no dynamic allocation of system memory is required. Like all the other ION packages, ION's BP implementation is designed to port readily between Linux and Solaris (for easy development and for ground system operations) and VxWorks (for flight systems operations). The exact same source code is exercised in both environments. Initially included in the ION BP implementations are the following: libraries of functions used in constructing bundle forwarders and convergence-layer (CL) input and output adapters; a simple prototype bundle forwarder and associated CL adapters designed to run over an IPbased local area network; administrative tools for managing a simple DTN infrastructure built from these components; a background daemon process that silently destroys bundles whose time-to-live intervals have expired; a library of functions exposed to applications, enabling them to issue and receive data encapsulated in DTN bundles; and some simple applications that can be used for system checkout and benchmarking.

  5. Empirical models for liquid metal heat transfer in the entrance region of tubes and rod bundles

    NASA Astrophysics Data System (ADS)

    Jaeger, Wadim

    2016-10-01

    Experiments focusing on liquid metals heat transfer in pipes and rod bundles with thermally and hydraulically developing flow are reviewed. Empirical heat transfer correlations are developed for engineering applications. In the developing regions the heat transfer is in-stationary. The heat transfer at the entrance is around 100 % higher due to the developing process including the lateral exchange of energy and momentum than for developed flow. Developing flow is not physically considered in the framework of system codes, which are used for thermal-hydraulic analysis of power and process plants with a multitude of components like pipes, tanks, valves and heat exchangers. Therefore, the application to liquid metal flows is limited to developed flow, which is independent of the distance from the flow entrance. The heat transfer enhancement in developing flows is important for the optimization of components like heat exchangers and helps to reduce unnecessary conservatism. In this work, empirical models are developed to account for developing flows in pipes and rod bundles. A literature review is performed to collect available experimental data for developing flow in liquid metal heat transfer. The evaluation shows that the length for pure thermally developing pipe flow is much larger (20-30 hydraulic diameters) than for combined thermally and hydraulically developing flow (10-15 hydraulic diameters). In rod bundles, fully combined developed flow is established after 30-40 hydraulic diameters downstream of the entrance. The derived empirical models for the heat transfer enhancement in the developing regions are implemented into a best estimate system code. The validation of these models by means of post-test analyses of 16 experiments shows that they are very well able to represent the heat transfer in developing regions.

  6. Computational models of hair cell bundle mechanics: III. 3-D utricular bundles.

    PubMed

    Silber, Joe; Cotton, John; Nam, Jong-Hoon; Peterson, Ellengene H; Grant, Wally

    2004-11-01

    Six utricular hair bundles from a red-eared turtle are modeled using 3-D finite element analysis. The mechanical model includes shear deformable stereocilia, realignment of all forces during force load increments, and tip and lateral link inter-stereocilia connections. Results show that there are two distinct bundle types that can be separated by mechanical bundle stiffness. The more compliant group has fewer total stereocilia and short stereocilia relative to kinocilium height; these cells are located in the medial and lateral extrastriola. The stiff group are located in the striola. They have more stereocilia and long stereocilia relative to kinocilia heights. Tip link tensions show parallel behavior in peripheral columns of the bundle and serial behavior in central columns when the tip link modulus is near or above that of collagen (1x10(9) N/m(2)). This analysis shows that lumped parameter models of single stereocilia columns can show some aspects of bundle mechanics; however, a distributed, 3-D model is needed to explore overall bundle behavior.

  7. Masquerading bundle branch block: a variety of right bundle branch block with left anterior fascicular block.

    PubMed

    Elizari, Marcelo V; Baranchuk, Adrian; Chiale, Pablo A

    2013-01-01

    The so-called 'masquerading' type of right bundle branch block is caused by the simultaneous presence of a high-degree left anterior fascicular block often accompanied with severe left ventricular enlargement and/or fibrotic block in the anterolateral wall of the left ventricle. These conditions tend to reorient the terminal electrical forces of the QRS complex towards the left and upwards, in such a way that the characteristic slurred S wave in lead I becomes smaller or even disappears. In many cases of standard masquerading right bundle branch block, a small Q wave in lead I is present due to the initial forces of the left anterior fascicular block, which are oriented rightwards and inferiorly. However, in some cases, the Q wave in lead I also vanishes, and the mimicking of a left bundle branch block becomes perfect in standard leads. This is commonly associated with an inferior myocardial infarction or severe inferior fibrosis in cardiomyopathies. The typical QRS changes of right bundle branch block may eventually be concealed even in the right precordial leads; under such circumstances, the ECG diagnosis may be mistaken and the right bundle branch block totally missed. The masquerading right bundle branch block carries a poor prognosis, since it always implies the presence of a severe underlying heart disease.

  8. Turkish and Native English Academic Writers' Use of Lexical Bundles

    ERIC Educational Resources Information Center

    Öztürk, Yusuf; Köse, Gül Durmusoglu

    2016-01-01

    Lexical bundles such as "on the other hand" and "as a result of" are extremely common and important in academic discourse. The appropriate use of lexical bundles typical of a specific academic discipline is important for writers and the absence of such bundles may not sound fluent and native-like. Recent studies (e.g. Adel…

  9. 76 FR 61365 - Bundled Payments for Care Improvement Initiative

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-04

    ... HUMAN SERVICES Centers for Medicare & Medicaid Services Bundled Payments for Care Improvement Initiative.... SUMMARY: This notice extends the deadlines for the submission of the Bundled Payments for Care Improvement.../patient-care-models/bundled-payments-for-care-improvement.html . Application Submission Deadline:...

  10. Cascading blockages in channel bundles.

    PubMed

    Barré, C; Talbot, J

    2015-11-01

    Flow in channel networks may involve a redistribution of flux following the blockage or failure of an individual link. Here we consider a simplified model consisting of N(c) parallel channels conveying a particulate flux. Particles enter these channels according to a homogeneous Poisson process and an individual channel blocks if more than N particles are simultaneously present. The behavior of the composite system depends strongly on how the flux of entering particles is redistributed following a blockage. We consider two cases. In the first, the intensity on each open channel remains constant while in the second the total intensity is evenly redistributed over the open channels. We obtain exact results for arbitrary N(c) and N for a system of independent channels and for arbitrary N(c) and N=1 for coupled channels. For N>1 we present approximate analytical as well as numerical results. Independent channels block at a decreasing rate due to a simple combinatorial effect, while for coupled channels the interval between successive blockages remains constant for N=1 but decreases for N>1. This accelerating cascade is due to the nonlinear dependence of the mean blocking time of a single channel on the entering particle flux that more than compensates for the decrease in the number of active channels.

  11. Cascading blockages in channel bundles

    NASA Astrophysics Data System (ADS)

    Barré, C.; Talbot, J.

    2015-11-01

    Flow in channel networks may involve a redistribution of flux following the blockage or failure of an individual link. Here we consider a simplified model consisting of Nc parallel channels conveying a particulate flux. Particles enter these channels according to a homogeneous Poisson process and an individual channel blocks if more than N particles are simultaneously present. The behavior of the composite system depends strongly on how the flux of entering particles is redistributed following a blockage. We consider two cases. In the first, the intensity on each open channel remains constant while in the second the total intensity is evenly redistributed over the open channels. We obtain exact results for arbitrary Nc and N for a system of independent channels and for arbitrary Nc and N =1 for coupled channels. For N >1 we present approximate analytical as well as numerical results. Independent channels block at a decreasing rate due to a simple combinatorial effect, while for coupled channels the interval between successive blockages remains constant for N =1 but decreases for N >1 . This accelerating cascade is due to the nonlinear dependence of the mean blocking time of a single channel on the entering particle flux that more than compensates for the decrease in the number of active channels.

  12. Characteristics of turbulent velocity and temperature in a wall channel of a heated rod bundle

    SciTech Connect

    Krauss, T.; Meyer, L.

    1995-09-01

    Turbulent air flow in a wall sub-channel of a heated 37-rod bundle (P/D = 1.12, W/D = 1.06) was investigated. measurements were performed with hot-wire probe with X-wires and a temperature wire. The mean velocity, the mean fluid temperature, the wall shear stress and wall temperature, the turbulent quantities such as the turbulent kinetic energy, the Reynolds-stresses and the turbulent heat fluxes were measured and are discussed with respect to data from isothermal flow in a wall channel and heated flow in a central channel of the same rod bundle. Also, data on the power spectral densities of the velocity and temperature fluctuations are presented. These data show the existence of large scale periodic fluctuations are responsible for the high intersubchannel heat and momentum exchange.

  13. Irreducible vector bundles on some elliptic non-Kahler threefolds

    NASA Astrophysics Data System (ADS)

    Brînzănescu, Vasile; Vuletescu, Victor

    2015-05-01

    We study rank-2 vector bundles on non-Kähler threefolds π : X → B, which are elliptic principal bundles with at least one non-zero Chern class over a complex surface B with no curves. In this case, we prove that every rank-2 irreducible vector bundle on X is a pull-back from B up to a twist by a line bundle. These 2-vector bundles are, via the Kobayashi-Hitchin correspondence, solutions of the Yang-Mills equations on the threefold X.

  14. Assembly of hair bundles, an amazing problem for cell biology.

    PubMed

    Barr-Gillespie, Peter-G

    2015-08-01

    The hair bundle--the sensory organelle of inner-ear hair cells of vertebrates--exemplifies the ability of a cell to assemble complex, elegant structures. Proper construction of the bundle is required for proper mechanotransduction in response to external forces and to transmit information about sound and movement. Bundles contain tightly controlled numbers of actin-filled stereocilia, which are arranged in defined rows of precise heights. Indeed, many deafness mutations that disable hair-cell cytoskeletal proteins also disrupt bundles. Bundle assembly is a tractable problem in molecular and cellular systems biology; the sequence of structural changes in stereocilia is known, and a modest number of proteins may be involved.

  15. A Comparison between Clinical Results of Selective Bundle and Double Bundle Anterior Cruciate Ligament Reconstruction

    PubMed Central

    Yoo, Yon-Sik; Song, Si Young; Yang, Cheol Jung; Ha, Jong Mun; Kim, Yoon Sang

    2016-01-01

    Purpose The purpose of this study was to compare the clinical outcomes of arthroscopic anatomical double bundle (DB) anterior cruciate ligament (ACL) reconstruction with either selective anteromedial (AM) or posterolateral (PL) bundle reconstruction while preserving a relatively healthy ACL bundle. Materials and Methods The authors evaluated 98 patients with a mean follow-up of 30.8±4.0 months who had undergone DB or selective bundle ACL reconstructions. Of these, 34 cases underwent DB ACL reconstruction (group A), 34 underwent selective AM bundle reconstruction (group B), and 30 underwent selective PL bundle reconstructions (group C). These groups were compared with respect to Lysholm and International Knee Documentation Committee (IKDC) score, side-to-side differences of anterior laxity measured by KT-2000 arthrometer at 30 lbs, and stress radiography and Lachman and pivot shift test results. Pre- and post-operative data were objectively evaluated using a statistical approach. Results The preoperative anterior instability measured by manual stress radiography at 90° of knee flexion in group A was significantly greater than that in groups B and C (all p<0.001). At last follow-up, mean side-to-side instrumented laxities measured by the KT-2000 and manual stress radiography were significantly improved from preoperative data in all groups (all p<0.001). There were no significant differences between the three groups in anterior instability measured by KT-2000 arthrometer, pivot shift, or functional scores. Conclusion Selective bundle reconstruction in partial ACL tears offers comparable clinical results to DB reconstruction in complete ACL tears. PMID:27401652

  16. Emitters of N-photon bundles.

    PubMed

    Muñoz, C Sánchez; Del Valle, E; Tudela, A González; Müller, K; Lichtmannecker, S; Kaniber, M; Tejedor, C; Finley, J J; Laussy, F P

    2014-07-01

    Controlling the ouput of a light emitter is one of the basic tasks of photonics, with landmarks such as the laser and single-photon sources. The development of quantum applications makes it increasingly important to diversify the available quantum sources. Here, we propose a cavity QED scheme to realize emitters that release their energy in groups, or "bundles" of N photons, for integer N. Close to 100% of two-photon emission and 90% of three-photon emission is shown to be within reach of state of the art samples. The emission can be tuned with system parameters so that the device behaves as a laser or as a N-photon gun. The theoretical formalism to characterize such emitters is developed, with the bundle statistics arising as an extension of the fundamental correlation functions of quantum optics. These emitters will be useful for quantum information processing and for medical applications.

  17. Care bundles reduce readmissions for COPD.

    PubMed

    Matthews, Healther; Tooley, Cathy; Nicholls, Carol; Lindsey-Halls, Anna

    In 2011, the respiratory nursing team at the James Paget University Hospital Foundation Trust were considering introducing a discharge care bundle for patients admitted with an acute exacerbation of chronic obstructive pulmonary disease. At the same time, the trust was asking for applications for Commissioning for Quality and Innovation schemes (CQUINs). These are locally agreed packages of quality improvement goals and indicators, which, if achieved in total, enable the provider to earn its full CQUIN payment. A CQUIN scheme should address the three domains of quality, safety and effectiveness, patient experience and also show innovation. This article discusses how the care bundle was introduced and how, over a 12-month period, it showed tangible results in improving the care pathway for COPD patients as well as reducing readmissions and saving a significant amount of money.

  18. Phase Slips in Oscillatory Hair Bundles

    NASA Astrophysics Data System (ADS)

    Roongthumskul, Yuttana; Shlomovitz, Roie; Bruinsma, Robijn; Bozovic, Dolores

    2013-04-01

    Hair cells of the inner ear contain an active amplifier that allows them to detect extremely weak signals. As one of the manifestations of an active process, spontaneous oscillations arise in fluid immersed hair bundles of in vitro preparations of selected auditory and vestibular organs. We measure the phase-locking dynamics of oscillatory bundles exposed to low-amplitude sinusoidal signals, a transition that can be described by a saddle-node bifurcation on an invariant circle. The transition is characterized by the occurrence of phase slips, at a rate that is dependent on the amplitude and detuning of the applied drive. The resultant staircase structure in the phase of the oscillation can be described by the stochastic Adler equation, which reproduces the statistics of phase slip production.

  19. Type IIB flux compactifications on twistor bundles

    NASA Astrophysics Data System (ADS)

    Imaanpur, Ali

    2014-02-01

    We construct a U(1) bundle over N(1,1), usually considered as an SO(3) bundle on CP2, and show that type IIB supergravity can be consistently compactified over it. With the five form flux turned on, there is a solution for which the metric becomes Einstein. We further turn on 3-form fluxes and show that there is a one parameter family of solutions. In particular, there is a limiting solution of large 3-form fluxes for which two U(1) fiber directions of the metric shrink to zero size. We also discuss compactifications over N(1,1) to AdS3. All solutions turn out to be non-supersymmetric.

  20. Non-abelian higher gauge theory and categorical bundle

    NASA Astrophysics Data System (ADS)

    Viennot, David

    2016-12-01

    A gauge theory is associated with a principal bundle endowed with a connection permitting to define horizontal lifts of paths. The horizontal lifts of surfaces cannot be defined into a principal bundle structure. An higher gauge theory is an attempt to generalize the bundle structure in order to describe horizontal lifts of surfaces. A such attempt is particularly difficult for the non-abelian case. Some structures have been proposed to realize this goal (twisted bundle, gerbes with connection, bundle gerbe, 2-bundle). Each of them uses a category in place of the total space manifold of the usual principal bundle structure. Some of them replace also the structure group by a category (more precisely a Lie crossed module viewed as a category). But the base space remains still a simple manifold (possibly viewed as a trivial category with only identity arrows). We propose a new principal categorical bundle structure, with a Lie crossed module as structure groupoid, but with a base space belonging to a bigger class of categories (which includes non-trivial categories), that we called affine 2-spaces. We study the geometric structure of the categorical bundles built on these categories (which are a more complicated structure than the 2-bundles) and the connective structures on these bundles. Finally we treat an example interesting for quantum dynamics which is associated with the Bloch wave operator theory.

  1. Uncovering ecosystem service bundles through social preferences.

    PubMed

    Martín-López, Berta; Iniesta-Arandia, Irene; García-Llorente, Marina; Palomo, Ignacio; Casado-Arzuaga, Izaskun; Amo, David García Del; Gómez-Baggethun, Erik; Oteros-Rozas, Elisa; Palacios-Agundez, Igone; Willaarts, Bárbara; González, José A; Santos-Martín, Fernando; Onaindia, Miren; López-Santiago, Cesar; Montes, Carlos

    2012-01-01

    Ecosystem service assessments have increasingly been used to support environmental management policies, mainly based on biophysical and economic indicators. However, few studies have coped with the social-cultural dimension of ecosystem services, despite being considered a research priority. We examined how ecosystem service bundles and trade-offs emerge from diverging social preferences toward ecosystem services delivered by various types of ecosystems in Spain. We conducted 3,379 direct face-to-face questionnaires in eight different case study sites from 2007 to 2011. Overall, 90.5% of the sampled population recognized the ecosystem's capacity to deliver services. Formal studies, environmental behavior, and gender variables influenced the probability of people recognizing the ecosystem's capacity to provide services. The ecosystem services most frequently perceived by people were regulating services; of those, air purification held the greatest importance. However, statistical analysis showed that socio-cultural factors and the conservation management strategy of ecosystems (i.e., National Park, Natural Park, or a non-protected area) have an effect on social preferences toward ecosystem services. Ecosystem service trade-offs and bundles were identified by analyzing social preferences through multivariate analysis (redundancy analysis and hierarchical cluster analysis). We found a clear trade-off among provisioning services (and recreational hunting) versus regulating services and almost all cultural services. We identified three ecosystem service bundles associated with the conservation management strategy and the rural-urban gradient. We conclude that socio-cultural preferences toward ecosystem services can serve as a tool to identify relevant services for people, the factors underlying these social preferences, and emerging ecosystem service bundles and trade-offs.

  2. Uncovering Ecosystem Service Bundles through Social Preferences

    PubMed Central

    Martín-López, Berta; Iniesta-Arandia, Irene; García-Llorente, Marina; Palomo, Ignacio; Casado-Arzuaga, Izaskun; Amo, David García Del; Gómez-Baggethun, Erik; Oteros-Rozas, Elisa; Palacios-Agundez, Igone; Willaarts, Bárbara; González, José A.; Santos-Martín, Fernando; Onaindia, Miren; López-Santiago, Cesar; Montes, Carlos

    2012-01-01

    Ecosystem service assessments have increasingly been used to support environmental management policies, mainly based on biophysical and economic indicators. However, few studies have coped with the social-cultural dimension of ecosystem services, despite being considered a research priority. We examined how ecosystem service bundles and trade-offs emerge from diverging social preferences toward ecosystem services delivered by various types of ecosystems in Spain. We conducted 3,379 direct face-to-face questionnaires in eight different case study sites from 2007 to 2011. Overall, 90.5% of the sampled population recognized the ecosystem’s capacity to deliver services. Formal studies, environmental behavior, and gender variables influenced the probability of people recognizing the ecosystem’s capacity to provide services. The ecosystem services most frequently perceived by people were regulating services; of those, air purification held the greatest importance. However, statistical analysis showed that socio-cultural factors and the conservation management strategy of ecosystems (i.e., National Park, Natural Park, or a non-protected area) have an effect on social preferences toward ecosystem services. Ecosystem service trade-offs and bundles were identified by analyzing social preferences through multivariate analysis (redundancy analysis and hierarchical cluster analysis). We found a clear trade-off among provisioning services (and recreational hunting) versus regulating services and almost all cultural services. We identified three ecosystem service bundles associated with the conservation management strategy and the rural-urban gradient. We conclude that socio-cultural preferences toward ecosystem services can serve as a tool to identify relevant services for people, the factors underlying these social preferences, and emerging ecosystem service bundles and trade-offs. PMID:22720006

  3. Mesophase Behavior in Carbon Fiber Bundles.

    DTIC Science & Technology

    1982-06-01

    Mesophase Coal-tar pitch Mesophase bloating Composite fabrication Mesophase wetting Ccmposite micrography Petroleum pitch 20. Atl RACT (Continue on reve...fiber in petroleum pitch were pyrolyzed under three conditions of constraint. The results confirm a recent report that the mesophase transformation...proceeds differently within a fiber bundle than in bulk pitch . In the early stages of transformation, both pitch and mesophase wet the fiber, and the

  4. Alpha1 LASSO data bundles Lamont, OK

    SciTech Connect

    Gustafson, William Jr; Vogelmann, Andrew; Endo, Satoshi; Toto, Tami; Xiao, Heng; Li, Zhijin; Cheng, Xiaoping; Krishna, Bhargavi

    2016-08-03

    A data bundle is a unified package consisting of LASSO LES input and output, observations, evaluation diagnostics, and model skill scores. LES input includes model configuration information and forcing data. LES output includes profile statistics and full domain fields of cloud and environmental variables. Model evaluation data consists of LES output and ARM observations co-registered on the same grid and sampling frequency. Model performance is quantified by skill scores and diagnostics in terms of cloud and environmental variables.

  5. An analytical fiber bundle model for pullout mechanics of root bundles

    NASA Astrophysics Data System (ADS)

    Cohen, D.; Schwarz, M.; Or, D.

    2011-09-01

    Roots in soil contribute to the mechanical stability of slopes. Estimation of root reinforcement is challenging because roots form complex biological networks whose geometrical and mechanical characteristics are difficult to characterize. Here we describe an analytical model that builds on simple root descriptors to estimate root reinforcement. Root bundles are modeled as bundles of heterogeneous fibers pulled along their long axes neglecting root-soil friction. Analytical expressions for the pullout force as a function of displacement are derived. The maximum pullout force and corresponding critical displacement are either derived analytically or computed numerically. Key model inputs are a root diameter distribution (uniform, Weibull, or lognormal) and three empirical power law relations describing tensile strength, elastic modulus, and length of roots as functions of root diameter. When a root bundle with root tips anchored in the soil matrix is pulled by a rigid plate, a unique parameter, ?, that depends only on the exponents of the power law relations, dictates the order in which roots of different diameters break. If ? < 1, small roots break first; if ? > 1, large roots break first. When ? = 1, all fibers break simultaneously, and the maximum tensile force is simply the roots' mean force times the number of roots in the bundle. Based on measurements of root geometry and mechanical properties, the value of ? is less than 1, usually ranging between 0 and 0.7. Thus, small roots always fail first. The model shows how geometrical and mechanical characteristics of roots and root diameter distribution affect the pullout force, its maximum and corresponding displacement. Comparing bundles of roots that have similar mean diameters, a bundle with a narrow variance in root diameter will result in a larger maximum force and a smaller displacement at maximum force than a bundle with a wide diameter distribution. Increasing the mean root diameter of a bundle without

  6. Modelling packing interactions in parallel helix bundles: pentameric bundles of nicotinic receptor M2 helices.

    PubMed

    Sankararamakrishnan, R; Sansom, M S

    1995-11-01

    The transbilayer pore of the nicotinic acetylcholine receptor (nAChR) is formed by a pentameric bundle of M2 helices. Models of pentameric bundles of M2 helices have been generated using simulated annealing via restrained molecular dynamics. The influence of: (a) the initial C alpha template; and (b) screening of sidechain electrostatic interactions on the geometry of the resultant M2 helix bundles is explored. Parallel M2 helices, in the absence of sidechain electrostatic interactions, pack in accordance with simple ridges-in-grooves considerations. This results in a helix crossing angle of ca. +12 degrees, corresponding to a left-handed coiled coil structure for the bundle as a whole. Tilting of M2 helices away from the central pore axis at their C-termini and/or inclusion of sidechain electrostatic interactions may perturb such ridges-in-grooves packing. In the most extreme cases right-handed coiled coils are formed. An interplay between inter-helix H-bonding and helix bundle geometry is revealed. The effects of changes in electrostatic screening on the dimensions of the pore mouth are described and the significance of these changes in the context of models for the nAChR pore domain is discussed.

  7. A thermal-hydraulic code for transient analysis in a channel with a rod bundle

    SciTech Connect

    Khodjaev, I.D.

    1995-09-01

    The paper contains the model of transient vapor-liquid flow in a channel with a rod bundle of core of a nuclear power plant. The computer code has been developed to predict dryout and post-dryout heat transfer in rod bundles of nuclear reactor core under loss-of-coolant accidents. Economizer, bubble, dispersed-annular and dispersed regimes are taken into account. The computer code provides a three-field representation of two-phase flow in the dispersed-annular regime. Continuous vapor, continuous liquid film and entrained liquid drops are three fields. For the description of dispersed flow regime two-temperatures and single-velocity model is used. Relative droplet motion is taken into account for the droplet-to-vapor heat transfer. The conservation equations for each of regimes are solved using an effective numerical technique. This technique makes it possible to determine distribution of the parameters of flows along the perimeter of fuel elements. Comparison of the calculated results with the experimental data shows that the computer code adequately describes complex processes in a channel with a rod bundle during accident.

  8. Bundled payment fails to gain a foothold In California: the experience of the IHA bundled payment demonstration.

    PubMed

    Ridgely, M Susan; de Vries, David; Bozic, Kevin J; Hussey, Peter S

    2014-08-01

    To determine whether bundled payment could be an effective payment model for California, the Integrated Healthcare Association convened a group of stakeholders (health plans, hospitals, ambulatory surgery centers, physician organizations, and vendors) to develop, through a consensus process, the methods and means of implementing bundled payment. In spite of a high level of enthusiasm and effort, the pilot did not succeed in its goal to implement bundled payment for orthopedic procedures across multiple payers and hospital-physician partners. An evaluation of the pilot documented a number of barriers, such as administrative burden, state regulatory uncertainty, and disagreements about bundle definition and assumption of risk. Ultimately, few contracts were signed, which resulted in insufficient volume to test hypotheses about the impact of bundled payment on quality and costs. Although bundled payment failed to gain a foothold in California, the evaluation provides lessons for future bundled payment initiatives.

  9. Historical dynamics in ecosystem service bundles.

    PubMed

    Renard, Delphine; Rhemtulla, Jeanine M; Bennett, Elena M

    2015-10-27

    Managing multiple ecosystem services (ES), including addressing trade-offs between services and preventing ecological surprises, is among the most pressing areas for sustainability research. These challenges require ES research to go beyond the currently common approach of snapshot studies limited to one or two services at a single point in time. We used a spatiotemporal approach to examine changes in nine ES and their relationships from 1971 to 2006 across 131 municipalities in a mixed-use landscape in Quebec, Canada. We show how an approach that incorporates time and space can improve our understanding of ES dynamics. We found an increase in the provision of most services through time; however, provision of ES was not uniformly enhanced at all locations. Instead, each municipality specialized in providing a bundle (set of positively correlated ES) dominated by just a few services. The trajectory of bundle formation was related to changes in agricultural policy and global trends; local biophysical and socioeconomic characteristics explained the bundles' increasing spatial clustering. Relationships between services varied through time, with some provisioning and cultural services shifting from a trade-off or no relationship in 1971 to an apparent synergistic relationship by 2006. By implementing a spatiotemporal perspective on multiple services, we provide clear evidence of the dynamic nature of ES interactions and contribute to identifying processes and drivers behind these changing relationships. Our study raises questions about using snapshots of ES provision at a single point in time to build our understanding of ES relationships in complex and dynamic social-ecological systems.

  10. The avalanche process of the fiber bundle model with defect

    NASA Astrophysics Data System (ADS)

    Hao, Da-Peng; Tang, Gang; Xia, Hui; Xun, Zhi-Peng; Han, Kui

    2017-04-01

    In order to explore the impacts of defect on the tensile fracture process of materials, the fiber bundle model with defect is constructed based on the classical fiber bundle model. In the fiber bundle model with defect, the two key parameters are the mean size and the density of defects. In both uniform and Weibull threshold distributions, the mean size and density all bring impacts on the threshold distribution of fibers. By means of analytical approximation and numerical simulation, we show that the two key parameters of the model have substantial effects on the failure process of the bundle. From macroscopic view, the defect described by the altering of threshold distribution of fibers will has a significant impact on the mechanical properties of the bundle. While in microscopic scale, the statistical properties of the model are still harmonious with the classical fiber bundle model.

  11. Morphology selection via geometric frustration in chiral filament bundles.

    PubMed

    Hall, Douglas M; Bruss, Isaac R; Barone, Justin R; Grason, Gregory M

    2016-07-01

    In assemblies, the geometric frustration of a locally preferred packing motif leads to anomalous behaviours, from self-limiting growth to defects in the ground state. Here, we demonstrate that geometric frustration selects the equilibrium morphology of cohesive bundles of chiral filaments, an assembly motif critical to a broad range of biological and synthetic nanomaterials. Frustration of inter-filament spacing leads to optimal shapes of self-twisting bundles that break the symmetries of packing and of the underlying inter-filament forces, paralleling a morphological instability in spherical two-dimensional crystals. Equilibrium bundle morphology is controlled by a parameter that characterizes the relative costs of filament bending and the straining of cohesive bonds between filaments. This parameter delineates the boundaries between stable, isotropic cylindrical bundles and anisotropic, twisted-tape bundles. We also show how the mechanical and interaction properties of constituent amyloid fibrils may be extracted from the mesoscale dimensions of the anisotropic bundles that they form.

  12. Synchronization of Spontaneous Active Motility of Hair Cell Bundles

    PubMed Central

    Zhang, Tracy-Ying; Ji, Seung; Bozovic, Dolores

    2015-01-01

    Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. PMID:26540409

  13. Expansion and Polarity Sorting in Microtubule-Dynein Bundles

    NASA Astrophysics Data System (ADS)

    Zemel, A.; Mogilner, A.

    Interactions of multiple molecular motors with dynamicpolymers, such as actin and microtubules, form the basis for many processes in the cell cytoskeleton. One example is the active `sorting' of microtubule bundles by dynein molecular motors into aster-like arrays of microtubules; in these bundles dynein motors cross-link and slide neighboring microtubules apart. A number of models have been suggested to quantify the active dynamics of cross-linked bundles of polar filaments. In the case of densely packed bundles, however, a major complication arises from the fact that each microtubule interacts with multiple neighboring filaments. To explicitly take these interactions into account we performed detailed computer simulations in which the equations of motion for all microtubules in the bundle were iteratively solved. Our simulations demonstrate the phenomenon of polarity sorting and reveal the variable-rate of the concurrent bundle expansion and its dependence on the nature of the microtubule-motor interactions.

  14. Monopoles and Modifications of Bundles over Elliptic Curves

    NASA Astrophysics Data System (ADS)

    Levin, Andrey M.; Olshanetsky, Mikhail A.; Zotov, Andrei V.

    2009-06-01

    Modifications of bundles over complex curves is an operation that allows one to construct a new bundle from a given one. Modifications can change a topological type of bundle. We describe the topological type in terms of the characteristic classes of the bundle. Being applied to the Higgs bundles modifications establish an equivalence between different classical integrable systems. Following Kapustin and Witten we define the modifications in terms of monopole solutions of the Bogomolny equation. We find the Dirac monopole solution in the case R × (elliptic curve). This solution is a three-dimensional generalization of the Kronecker series. We give two representations for this solution and derive a functional equation for it generalizing the Kronecker results. We use it to define Abelian modifications for bundles of arbitrary rank. We also describe non-Abelian modifications in terms of theta-functions with characteristic.

  15. Cooperativity and Frustration in Protein-Mediated Parallel Actin Bundles

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Drew, Kirstin R. Purdy; Bartles, James R.; Wong, Gerard C. L.; Grason, Gregory M.

    2009-12-01

    We examine the mechanism of bundling of cytoskeletal actin filaments by two representative bundling proteins, fascin and espin. Small-angle x-ray studies show that increased binding from linkers drives a systematic overtwist of actin filaments from their native state, which occurs in a linker-dependent fashion. Fascin bundles actin into a continuous spectrum of intermediate twist states, while espin only allows for untwisted actin filaments and fully overtwisted bundles. Based on a coarse-grained, statistical model of protein binding, we show that the interplay between binding geometry and the intrinsic flexibility of linkers mediates cooperative binding in the bundle. We attribute the respective continuous (discontinuous) bundling mechanisms of fascin (espin) to difference in the stiffness of linker bonds themselves.

  16. Higher order mechanics on graded bundles

    NASA Astrophysics Data System (ADS)

    Bruce, Andrew James; Grabowska, Katarzyna; Grabowski, Janusz

    2015-05-01

    In this paper we develop a geometric approach to higher order mechanics on graded bundles in both, the Lagrangian and Hamiltonian formalism, via the recently discovered weighted algebroids. We present the corresponding Tulczyjew triple for this higher order situation and derive in this framework the phase equations from an arbitrary (also singular) Lagrangian or Hamiltonian, as well as the Euler-Lagrange equations. As important examples, we geometrically derive the classical higher order Euler-Lagrange equations and analogous reduced equations for invariant higher order Lagrangians on Lie groupoids.

  17. Local load-sharing fiber bundle model in higher dimensions

    NASA Astrophysics Data System (ADS)

    Sinha, Santanu; Kjellstadli, Jonas T.; Hansen, Alex

    2015-08-01

    We consider the local load-sharing fiber bundle model in one to five dimensions. Depending on the breaking threshold distribution of the fibers, there is a transition where the fracture process becomes localized. In the localized phase, the model behaves as the invasion percolation model. The difference between the local load-sharing fiber bundle model and the equal load-sharing fiber bundle model vanishes with increasing dimensionality with the characteristics of a power law.

  18. Complete bundle moduli reduction in heterotic string compactifications

    NASA Astrophysics Data System (ADS)

    Curio, Gottfried

    2012-05-01

    A major problem in discussing heterotic string models is the stabilisation of the many vector bundle moduli via the superpotential generated by world-sheet instantons. In arXiv:1110.6315 we have discussed the method to make a discrete twist in a large and much discussed class of vector bundles such that the generation number gets new contributions (which can be tuned suitably) and at the same time the space of bundle moduli of the new, twisted bundle is a proper subspace (where the 'new', non-generic twist class exists) of the original bundle moduli space; one thus gets a model, closely related to the original model one started with, but with enhanced flexibility in the generation number and where on the other hand the number of bundle moduli is somewhat reduced. Whereas in the previous paper the emphasis was on examples for the new flexibility in the generation number we here classify and describe explicitly the twists and give the precise reduction formula (for the number of moduli) for SU(5) bundles leading to an SU(5) GUT group in four dimensions. Finally we give various examples where the bundle moduli space is reduced completely: the superpotential for such rigid bundles becomes a function of the complex structure moduli alone (besides the exponential Kahler moduli contribution).

  19. Robust Mapping of Incoherent Fiber-Optic Bundles

    NASA Technical Reports Server (NTRS)

    Roberts, Harry E.; Deason, Brent E.; DePlachett, Charles P.; Pilgrim, Robert A.; Sanford, Harold S.

    2007-01-01

    A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective. In a coherent fiber-optic bundle, the input and output ends of each fiber lie at identical positions in the input and output planes; therefore, the bundle can be used to transmit images without further modification. Unfortunately, the fabrication of coherent fiber-optic bundles is too labor-intensive and expensive for many applications. An incoherent fiber-optic bundle can be fabricated more easily and at lower cost, but it produces a scrambled image because the position of the end of each fiber in the input plane is generally different from the end of the same fiber in the output plane. However, the image transmitted by an incoherent fiber-optic bundle can be unscrambled (or, from a different perspective, decoded) by digital processing of the output image if the mapping between the input and output fiber-end positions is known. Thus, the present invention enables the use of relatively inexpensive fiber-optic bundles to transmit images.

  20. Isothermal microcalorimetry, a tool for probing SWNT bundles.

    PubMed

    Marquis, Renaud; Greco, Carla; Schultz, Patrick; Meunier, Stéphane; Mioskowski, Charles

    2009-11-01

    The bundling state of several dry single-walled carbon nanotube (SWNT) samples is compared using isothermal microcalorimetry (IMC). So as to get different dry samples with various bundling states, the pristine SWNTs were pretreated with a solution of an aromatic amphiphile with or without sonication, washed and dried before being studied by IMC. The bundling state of the different SWNT samples, which was first analyzed by TEM, was then correlated to the obtained IMC data thanks to the interpretation of the observed energy transfer phenomena. From our results, IMC appears to be an interesting technique for the surface probing of dry SWNT samples, and herein for the evaluation of the bundling state.

  1. Confinement-Dependent Friction in Peptide Bundles

    PubMed Central

    Erbaş, Aykut; Netz, Roland R.

    2013-01-01

    Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V → 0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. PMID:23528088

  2. Tangent Bundle Elastica and Computer Vision.

    PubMed

    Ben-Shahar, Ohad; Ben-Yosef, Guy

    2015-01-01

    Visual curve completion, an early visual process that completes the occluded parts between observed boundary fragments (a.k.a. inducers), is a major problem in perceptual organization and a critical step toward higher level visual tasks in both biological and machine vision. Most computational contributions to solving this problem suggest desired perceptual properties that the completed contour should satisfy in the image plane, and then seek the mathematical curves that provide them. Alternatively, few studies (including by the authors) have suggested to frame the problem not in the image plane but rather in the unit tangent bundleR (2) × S(1), the space that abstracts the primary visual cortex, where curve completion allegedly occurs. Combining both schools, here we propose and develop a biologically plausible theory of elastica in the tangent bundle that provides not only perceptually superior completion results but also a rigorous computational prediction that inducer curvatures greatly affects the shape of the completed curve, as indeed indicated by human perception.

  3. Constrained ripple optimization of Tokamak bundle divertors

    SciTech Connect

    Hively, L.M.; Rome, J.A.; Lynch, V.E.; Lyon, J.F.; Fowler, R.H.; Peng, Y-K.M.; Dory, R.A.

    1983-02-01

    Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ..xi.. B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have low on-axis ripple (<0.2%) so that, now, most banana-trapped fast ions are confined. Only those ions with banana tips near the outside region (absolute value theta < or equal to 45/sup 0/) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded.

  4. Bundle brunch reentrant ventricular tachycardia with two distinct conduction patterns in a patient with complete right bundle branch block.

    PubMed

    Enjoji, Yoshihisa; Mizobuchi, Masahiro; Shibata, Kensaku; Ono, Tsuyoshi; Funatsu, Atsushi; Kanbayashi, Daisuke; Kobayashi, Tomoko; Nakamura, Shigeru

    2006-12-01

    We report a rare case of bundle branch reentrant ventricular tachycardia [BBRVT]. A 67-year-old female was admitted for management of wide QRS tachycardia (right bundle branch block [RBBB] and a southwest axis). The mapping procedure revealed the tachycardia circuit consisted of the left anterior fascicle (LAF) as an antegrade, and the right bundle as a retrograde pathway. She presented RBBB during sinus rhythm. LAF ablation changed the tachycardia configuration to a northwest axis and prolonged the cycle length. Left posterior fascicle ablation terminated the tachycardia, and complete atrioventricular block occurred, which showed the unidirectional conduction over the right bundle.

  5. BUNDLE - A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2001-01-01

    indicating uniform axial heat flow. Delineation between the growing dendrites and eutectic structure with the "quenched-in" liquid was sharp, attesting to the efficacy of the helium quench. BUNDLE's conception, development, capability, and adaptability are presented (in view of Flight PI's needs and science requirements) through viewgraphs depicting actual hardware, generated thermal analysis, and micrographs prepared from BUNDLE processed, flight-like samples.

  6. BUNDLE: A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2000-01-01

    indicating uniform axial heat flow. Delineation between the growing dendrites and eutectic structure with the "quenched-in" liquid was sharp, attesting to the efficacy of the helium quench. BUNDLE's conception, development, capability, and adaptability are presented (in view of Flight PI's needs and science requirements) through viewgraphs depicting actual hardware, generated thermal analysis, and micrographs prepared from BUNDLE processed, flight-like samples.

  7. Coherent hollow-core waveguide bundles for thermal imaging.

    PubMed

    Gal, Udi; Harrington, James; Ben-David, Moshe; Bledt, Carlos; Syzonenko, Nicholas; Gannot, Israel

    2010-09-01

    There has been very little work done in the past to extend the wavelength range of fiber image bundles to the IR range. This is due, in part, to the lack of IR transmissive fibers with optical and mechanical properties analogous to the oxide glass fibers currently employed in the visible fiber bundles. Our research is aimed at developing high-resolution hollow-core coherent IR fiber bundles for transendoscopic infrared imaging. We employ the hollow glass waveguide (HGW) technology that was used successfully to make single-HGWs with Ag/AgI thin film coatings to form coherent bundles for IR imaging. We examine the possibility of developing endoscopic systems to capture thermal images using hollow waveguide fiber bundles adjusted to the 8-10?mum spectral range and investigate the applicability of such systems. We carried out a series of measurements in order to characterize the optical properties of the fiber bundles. These included the attenuation, resolution, and temperature response. We developed theoretical models and simulation tools that calculate the light propagation through HGW bundles, and which can be used to calculate the optical properties of the fiber bundles. Finally, the HGW fiber bundles were used to transmit thermal images of various heated objects; the results were compared with simulation results. The experimental results are encouraging, show an improvement in the resolution and thermal response of the HGW fiber bundles, and are consistent with the theoretical results. Nonetheless, additional improvements in the attenuation of the bundles are required in order to be able to use this technology for medical applications.

  8. A nano-microstructured artificial-hair-cell-type sensor based on topologically graded 3D carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Yilmazoglu, O.; Yadav, S.; Cicek, D.; Schneider, J. J.

    2016-09-01

    A design for a unique artificial-hair-cell-type sensor (AHCTS) based entirely on 3D-structured, vertically aligned carbon nanotube (CNT) bundles is introduced. Standard microfabrication techniques were used for the straightforward micro-nano integration of vertically aligned carbon nanotube arrays composed of low-layer multi-walled CNTs (two to six layers). The mechanical properties of the carbon nanotube bundles were intensively characterized with regard to various substrates and CNT morphology, e.g. bundle height. The CNT bundles display excellent flexibility and mechanical stability for lateral bending, showing high tear resistance. The integrated 3D CNT sensor can detect three-dimensional forces using the deflection or compression of a central CNT bundle which changes the contact resistance to the shorter neighboring bundles. The complete sensor system can be fabricated using a single chemical vapor deposition (CVD) process step. Moreover, sophisticated external contacts to the surroundings are not necessary for signal detection. No additional sensors or external bias for signal detection are required. This simplifies the miniaturization and the integration of these nanostructures for future microsystem set-ups. The new nanostructured sensor system exhibits an average sensitivity of 2100 ppm in the linear regime with the relative resistance change per micron (ppm μm-1) of the individual CNT bundle tip deflection. Furthermore, experiments have shown highly sensitive piezoresistive behavior with an electrical resistance decrease of up to ˜11% at 50 μm mechanical deflection. The detection sensitivity is as low as 1 μm of deflection, and thus highly comparable with the tactile hair sensors of insects, having typical thresholds on the order of 30-50 μm. The AHCTS can easily be adapted and applied as a flow, tactile or acceleration sensor as well as a vibration sensor. Potential applications of the latter might come up in artificial cochlear systems. In

  9. A thermal mixing model of crossflow in tube bundles for use with the porous body approximation

    SciTech Connect

    Ashcroft, J.; Kaminski, D.A.

    1996-06-01

    Diffusive thermal mixing in a heated tube bundle with a cooling fluid in crossflow was analyzed numerically. From the results of detailed two-dimensional models, which calculated the diffusion of heat downstream of one heated tube in an otherwise adiabatic flow field, a diffusion model appropriate for use with the porous body method was developed. The model accounts for both molecular and turbulent diffusion of heat by determining the effective thermal conductivity in the porous region. The model was developed for triangular shaped staggered tube bundles with pitch to diameter ratios between 1.10 and 2.00 and for Reynolds numbers between 1,000 and 20,000. The tubes are treated as nonconducting. Air and water were considered as working fluids. The effective thermal conductivity was found to be linearly dependent on the tube Reynolds number and fluid Prandtl number, and dependent on the bundle geometry. The porous body thermal mixing model was then compared against numerical models for flows with multiple heated tubes with very good agreement.

  10. Lexical Bundles: Facilitating University "Talk" in Group Discussions

    ERIC Educational Resources Information Center

    Heng, Chan Swee; Kashiha, Hadi; Tan, Helen

    2014-01-01

    Group discussion forms an integral language experience for most language learners, providing them with an opportunity to express themselves in a naturalistic setting. Multi-word expressions are commonly used and one of them is lexical bundles. Lexical bundles are types of extended collocations that occur more commonly than we expect; they are…

  11. Amplitude death of coupled hair bundles with stochastic channel noise

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2014-04-01

    Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.

  12. As Can Be Seen: Lexical Bundles and Disciplinary Variation

    ERIC Educational Resources Information Center

    Hyland, Ken

    2008-01-01

    An important component of fluent linguistic production is control of the multi-word expressions referred to as clusters, chunks or bundles. These are extended collocations which appear more frequently than expected by chance, helping to shape meanings in specific contexts and contributing to our sense of coherence in a text. Bundles have begun to…

  13. Lexical Bundles in University Spoken and Written Registers

    ERIC Educational Resources Information Center

    Biber, Douglas; Barbieri, Federica

    2007-01-01

    Lexical bundles--recurrent sequences of words--are important building blocks of discourse in spoken and written registers. Previous research has shown that lexical bundles are especially prevalent in university classroom teaching, where they serve three major discourse functions: stance expressions, discourse organizers, and referential…

  14. Sensory transduction: the 'swarm intelligence' of auditory hair bundles.

    PubMed

    Albert, Jörg

    2011-08-23

    In vertebrate hair cells, the hair bundle is responsible for the conversion of mechanical vibrations into electrical signals. In a combined experimental and computational tour de force, a group of researchers now presents a quantitative model that explains how the bundle's specific microarchitecture gives rise to its exquisite mechanosensory properties.

  15. Method of pressure pulse cleaning a tube bundle heat exchanger

    SciTech Connect

    Scharton, T.D.; Taylor, G.B.

    1987-04-07

    A method is described of removing the products of corrosion, oxidation, sedimentation and comparable chemical reactions collectively known as sludge which settle on the bottom of a tube bundle heat exchange and form a pile of sludge. The tube bundle heat exchanger is characterized by a tube bundle heat exchanger wall and a thick metal plate known as a tube sheet near the lower portion of the tube bundle heat exchanger wall's interior surface. The tube sheet serves to support the lower ends of a multiplicity of heat exchanger tubes within the tube bundle heat exchanger. The tube bundle heat exchange wall further comprises a multiplicity of small holes known as hand holes, manways, drain lines and vents, located around its circumference and above the tube sheet. The method is described of removing the pile of sludge which settles on the tube sheet comprising: a. locating at least one air-gun type pressure pulse shock wave source outside the tube bundle heat exchanger so as to be able to introduce pressure pulse shock waves through one or more of the multiplicity of hand holes, manways, drain lines and vents; and b. filling the tube bundle heat exchanger with a liquid to a level above the pile of sludge.

  16. Presenting Lexical Bundles for Explicit Noticing with Schematic Linguistic Representation

    ERIC Educational Resources Information Center

    Thomson, Haidee Elizabeth

    2016-01-01

    Lexical bundles are essential for fluency, but their incompleteness is a stumbling block for learners. In this study, two presentation methods to increase awareness of lexical bundles through explicit noticing are explored and compared with incidental exposure. The three conditions in this study were as follows: noticing with schematic linguistic…

  17. Zipping and entanglement in flagellar bundle of E. coli: Role of motile cell body

    NASA Astrophysics Data System (ADS)

    Adhyapak, Tapan Chandra; Stark, Holger

    2015-11-01

    The course of a peritrichous bacterium, such as E. coli, crucially depends on the level of synchronization and self-organization of several rotating flagella. However, the rotation of each flagellum generates countermovements of the body which in turn affect the flagellar dynamics. Using a detailed numerical model of an E. coli, we demonstrate that flagellar entanglement, besides fluid flow relative to the moving body, dramatically changes the dynamics of flagella from that compared to anchored flagella. In particular, bundle formation occurs through a zipping motion in a remarkably rapid time, affected little by initial flagellar orientation. A simplified analytical model supports our observations. Finally, we illustrate how entanglement, hydrodynamic interactions, and body movement contribute to zipping and bundling.

  18. Extendability of parallel sections in vector bundles

    NASA Astrophysics Data System (ADS)

    Kirschner, Tim

    2016-01-01

    I address the following question: Given a differentiable manifold M, what are the open subsets U of M such that, for all vector bundles E over M and all linear connections ∇ on E, any ∇-parallel section in E defined on U extends to a ∇-parallel section in E defined on M? For simply connected manifolds M (among others) I describe the entirety of all such sets U which are, in addition, the complement of a C1 submanifold, boundary allowed, of M. This delivers a partial positive answer to a problem posed by Antonio J. Di Scala and Gianni Manno (2014). Furthermore, in case M is an open submanifold of Rn, n ≥ 2, I prove that the complement of U in M, not required to be a submanifold now, can have arbitrarily large n-dimensional Lebesgue measure.

  19. Cyclic hardening in bundled actin networks.

    PubMed

    Schmoller, K M; Fernández, P; Arevalo, R C; Blair, D L; Bausch, A R

    2010-01-01

    Nonlinear deformations can irreversibly alter the mechanical properties of materials. Most soft materials, such as rubber and living tissues, display pronounced softening when cyclically deformed. Here we show that, in contrast, reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear. As a consequence, they exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain. This unique response is crucially determined by the network architecture: at lower crosslinker concentrations networks do not harden, but soften showing the classic Mullins effect known from rubber-like materials. By simultaneously performing macrorheology and confocal microscopy, we show that cyclic shearing results in structural reorganization of the network constituents such that the maximum applied strain is encoded into the network architecture.

  20. Bundled automobile insurance coverage and accidents.

    PubMed

    Li, Chu-Shiu; Liu, Chwen-Chi; Peng, Sheng-Chang

    2013-01-01

    This paper investigates the characteristics of automobile accidents by taking into account two types of automobile insurance coverage: comprehensive vehicle physical damage insurance and voluntary third-party liability insurance. By using a unique data set in the Taiwanese automobile insurance market, we explore the bundled automobile insurance coverage and the occurrence of claims. It is shown that vehicle physical damage insurance is the major automobile coverage and affects the decision to purchase voluntary liability insurance coverage as a complement. Moreover, policyholders with high vehicle physical damage insurance coverage have a significantly higher probability of filing vehicle damage claims, and if they additionally purchase low voluntary liability insurance coverage, their accident claims probability is higher than those who purchase high voluntary liability insurance coverage. Our empirical results reveal that additional automobile insurance coverage information can capture more driver characteristics and driving behaviors to provide useful information for insurers' underwriting policies and to help analyze the occurrence of automobile accidents.

  1. Advanced tube-bundle rocket thrust chamber

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Pavli, Albert J.

    1990-01-01

    An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

  2. Vision, healing brush, and fiber bundles

    NASA Astrophysics Data System (ADS)

    Georgiev, Todor

    2005-03-01

    The Healing Brush is a tool introduced for the first time in Adobe Photoshop (2002) that removes defects in images by seamless cloning (gradient domain fusion). The Healing Brush algorithms are built on a new mathematical approach that uses Fibre Bundles and Connections to model the representation of images in the visual system. Our mathematical results are derived from first principles of human vision, related to adaptation transforms of von Kries type and Retinex theory. In this paper we present the new result of Healing in arbitrary color space. In addition to supporting image repair and seamless cloning, our approach also produces the exact solution to the problem of high dynamic range compression of17 and can be applied to other image processing algorithms.

  3. Voltage- and calcium-dependent motility of saccular hair bundles

    NASA Astrophysics Data System (ADS)

    Quiñones, Patricia M.; Meenderink, Sebastiaan W. F.; Bozovic, Dolores

    2015-12-01

    Active bundle motility, which is hypothesized to supply feedback for mechanical amplification of signals, is thought to enhance sensitivity and sharpen tuning in vestibular and auditory organs. To study active hair bundle motility, we combined high-speed camera recordings of bullfrog sacculi, which were mounted in a two-compartment chamber, and voltage-clamp of the hair cell membrane potential. Using this paradigm, we measured three types of bundle motions: 1) spontaneous oscillations which can be analyzed to measure the physiological operating range of the transduction channel; 2) a sustained quasi-static movement of the bundle that depends on membrane potential; and 3) a fast, transient and asymmetric movement that resets the bundle position and depends on changes in the membrane potential. These data support a role for both calcium and voltage in the transduction-channel function.

  4. Historical dynamics in ecosystem service bundles

    PubMed Central

    Renard, Delphine; Rhemtulla, Jeanine M.; Bennett, Elena M.

    2015-01-01

    Managing multiple ecosystem services (ES), including addressing trade-offs between services and preventing ecological surprises, is among the most pressing areas for sustainability research. These challenges require ES research to go beyond the currently common approach of snapshot studies limited to one or two services at a single point in time. We used a spatiotemporal approach to examine changes in nine ES and their relationships from 1971 to 2006 across 131 municipalities in a mixed-use landscape in Quebec, Canada. We show how an approach that incorporates time and space can improve our understanding of ES dynamics. We found an increase in the provision of most services through time; however, provision of ES was not uniformly enhanced at all locations. Instead, each municipality specialized in providing a bundle (set of positively correlated ES) dominated by just a few services. The trajectory of bundle formation was related to changes in agricultural policy and global trends; local biophysical and socioeconomic characteristics explained the bundles’ increasing spatial clustering. Relationships between services varied through time, with some provisioning and cultural services shifting from a trade-off or no relationship in 1971 to an apparent synergistic relationship by 2006. By implementing a spatiotemporal perspective on multiple services, we provide clear evidence of the dynamic nature of ES interactions and contribute to identifying processes and drivers behind these changing relationships. Our study raises questions about using snapshots of ES provision at a single point in time to build our understanding of ES relationships in complex and dynamic social-ecological systems. PMID:26460005

  5. Big things come in bundled packages: implications of bundled payment systems in health care reimbursement reform.

    PubMed

    Delisle, Dennis R

    2013-01-01

    With passage of the Affordable Care Act, the ever-evolving landscape of health care braces for another shift in the reimbursement paradigm. As health care costs continue to rise, providers are pressed to deliver efficient, high-quality care at flat to minimally increasing rates. Inherent systemwide inefficiencies between payers and providers at various clinical settings pose a daunting task for enhancing collaboration and care coordination. A change from Medicare's fee-for-service reimbursement model to bundled payments offers one avenue for resolution. Pilots using such payment models have realized varying degrees of success, leading to the development and upcoming implementation of a bundled payment initiative led by the Center for Medicare and Medicaid Innovation. Delivery integration is critical to ensure high-quality care at affordable costs across the system. Providers and payers able to adapt to the newly proposed models of payment will benefit from achieving cost reductions and improved patient outcomes and realize a competitive advantage.

  6. Subchannel Analysis with Mechanistic Methods for Thermo-Hydro Dynamics in BWR Fuel Bundles

    SciTech Connect

    Kentaro Imura; Kenji Yoshida; Isao Kataoka; Masanori Naitoh

    2006-07-01

    In order to predict the critical power or void fraction in BWR fuel bundles and the DNB heat flux of PWR fuel assemblies, the boiling transition analysis code called 'CAPE' with mechanistic models has been developed in the IMPACT project by NUPEC. The objective of the CAPE code development is to perform with good accuracy the safety evaluation for a new type or improved fuel bundle design of BWR and PWR without full-scale experiments or any tuning parameters in the analysis code. In this study, the CAPE for BWR was validated by the test analysis for 8 x 8 fuel bundles comparing with the void distribution data of the experimental data, which was carried out under several operational conditions in a BWR. The computations were carried out by changing the operational parameter such as the inlet subcooling, mass flow rate and the power output of the fuel bundles. Resultantly, the thermal equilibrium quality at the outlet ranges from 2% to 25%. From these results, though the predictive accuracy of the analytical results are in close agreement with the experimental data, it was noted that the errors were relatively outstanding in some subchannels, which was surrounded by the heated fuel rods and partially unheated walls, such as an unheated rod, a water rod and a separation wall of the channel box. The reason for this error is thought to be that the cross sectional void distribution was partially distributed in such subchannels surrounded partially by unheated wall, so the multidimensional void distribution structure might be formed in these subchannels. Under such conditions, it is very important to take into consideration the multidimensional structure of the two-phase flow in subchannel, and perhaps improve the estimation or correlations for the distribution parameter, as well as the amount of void exchange between neighboring subchannels. (authors)

  7. His bundle recordings in right bundle-branch block coexisting with iatrogenic right ventricular pre-excitation

    PubMed Central

    Castellanos, Agustin; Castillo, Cesar A.

    1972-01-01

    Iatrogenic right ventricular pre-excitation failed to abolish right bundle-branch block in two patients. When `exclusive' His bundle pacing was performed, the QRS complexes, St-V, and St-LVE intervals were similar to the ventricular deflections, H-V, and V-LVE (intervals) recorded during sinus rhythm. `Exclusive' pacing of the ordinary muscle at the right ventricular inflow tract produced a complete left bundle-branch block pattern without abnormal left axis deviation. Pacing of both His bundle and ordinary muscle yielded combination complexes in which the right bundle-branch block pattern persisted. The ventricular activation process was studied in these beats, as well as during the right and left bundle-branch block induced by coupled atrial stimulation. It appeared as if certain areas of the right septal surface behaved, electrophysiologically, as if they belonged to the left ventricle. Impulses emerging from these sites were not propagated to the right ventricular free wall. The latter was activated by the excitation front emerging through the left bundle system. During right bundle-branch block the endocardium of the right ventricular inflow was activated before the peak of the R in V1. Bipolar leads, 1 mm apart (with the possible exception of the ones over the tricuspid valve), were helpful in mapping the spread of activation in the human heart. Images PMID:18610233

  8. Spontaneous Oscillation by Hair Bundles of the Bullfrog's Sacculus

    PubMed Central

    Martin, Pascal; Bozovic, D.; Choe, Y.; Hudspeth, A. J.

    2007-01-01

    One prominent manifestation of mechanical activity in hair cells is spontaneous otoacoustic emission, the unprovoked emanation of sound by an internal ear. Because active hair-bundle motility probably constitutes the active process of non-mammalian hair cells, we investigated the ability of hair bundles in the bullfrog's sacculus to produce oscillations that might underlie spontaneous otoacoustic emissions. When maintained in the ear's normal ionic milieu, many bundles oscillated spontaneously through distances as great as 80 nm at frequencies of 5-50 Hz. Whole-cell recording disclosed that the positive phase of movement was associated with the opening of transduction channels. Gentamicin, which blocks transduction channels, reversibly arrested oscillation; drugs that affect the cAMP phosphorylation pathway and might influence myosin's activity altered the rate of oscillation. Increasing the Ca2+ concentration rendered oscillations faster and smaller until they were suppressed; lowering the Ca2+ concentration moderately with chelators had the opposite effect. When a bundle was offset with a stimulus fiber, oscillations were transiently suppressed but gradually resumed. Loading a bundle by partial displacement clamping, which simulated the presence of the accessory structures to which a bundle is ordinarily attached, increased the frequency and diminished the magnitude of oscillation. These observations accord with a model in which oscillations arise from the interplay of the hair bundle's negative stiffness with the activity of adaptation motors and with Ca2+-dependent relaxation of gating springs. PMID:12805294

  9. Two-state approach to stochastic hair bundle dynamics

    NASA Astrophysics Data System (ADS)

    Clausznitzer, Diana; Lindner, Benjamin; Jülicher, Frank; Martin, Pascal

    2008-04-01

    Hair cells perform the mechanoelectrical transduction of sound signals in the auditory and vestibular systems of vertebrates. The part of the hair cell essential for this transduction is the so-called hair bundle. In vitro experiments on hair cells from the sacculus of the American bullfrog have shown that the hair bundle comprises active elements capable of producing periodic deflections like a relaxation oscillator. Recently, a continuous nonlinear stochastic model of the hair bundle motion [Nadrowski , Proc. Natl. Acad. Sci. U.S.A. 101, 12195 (2004)] has been shown to reproduce the experimental data in stochastic simulations faithfully. Here, we demonstrate that a binary filtering of the hair bundle's deflection (experimental data and continuous hair bundle model) does not change significantly the spectral statistics of the spontaneous as well as the periodically driven hair bundle motion. We map the continuous hair bundle model to the FitzHugh-Nagumo model of neural excitability and discuss the bifurcations between different regimes of the system in terms of the latter model. Linearizing the nullclines and assuming perfect time-scale separation between the variables we can map the FitzHugh-Nagumo system to a simple two-state model in which each of the states corresponds to the two possible values of the binary-filtered hair bundle trajectory. For the two-state model, analytical expressions for the power spectrum and the susceptibility can be calculated [Lindner and Schimansky-Geier, Phys. Rev. E 61, 6103 (2000)] and show the same features as seen in the experimental data as well as in simulations of the continuous hair bundle model.

  10. Systematic evaluation of bundled SPC water for biomolecular simulations.

    PubMed

    Gopal, Srinivasa M; Kuhn, Alexander B; Schäfer, Lars V

    2015-04-07

    In bundled SPC water models, the relative motion of groups of four water molecules is restrained by distance-dependent potentials. Bundled SPC models have been used in hybrid all-atom/coarse-grained (AA/CG) multiscale simulations, since they enable to couple atomistic SPC water with supra-molecular CG water models that effectively represent more than a single water molecule. In the present work, we systematically validated and critically tested bundled SPC water models as solvent for biomolecular simulations. To that aim, we investigated both thermodynamic and structural properties of various biomolecular systems through molecular dynamics (MD) simulations. Potentials of mean force of dimerization of pairs of amino acid side chains as well as hydration free energies of single side chains obtained with bundled SPC and standard (unrestrained) SPC water agree closely with each other and with experimental data. Decomposition of the hydration free energies into enthalpic and entropic contributions reveals that in bundled SPC, this favorable agreement of the free energies is due to a larger degree of error compensation between hydration enthalpy and entropy. The Ramachandran maps of Ala3, Ala5, and Ala7 peptides are similar in bundled and unrestrained SPC, whereas for the (GS)2 peptide, bundled water leads to a slight overpopulation of extended conformations. Analysis of the end-to-end distance autocorrelation times of the Ala5 and (GS)2 peptides shows that sampling in more viscous bundled SPC water is about two times slower. Pronounced differences between the water models were found for the structure of a coiled-coil dimer, which is instable in bundled SPC but not in standard SPC. In addition, the hydration of the active site of the serine protease α-chymotrypsin depends on the water model. Bundled SPC leads to an increased hydration of the active site region, more hydrogen bonds between water and catalytic triad residues, and a significantly slower exchange of water

  11. Dark-field illuminated reflectance fiber bundle endoscopic microscope

    NASA Astrophysics Data System (ADS)

    Liu, Xuan; Huang, Yong; Kang, Jin U.

    2011-04-01

    We propose a reflectance fiber bundle microscope using a dark-field illumination configuration for applications in endoscopic medical imaging and diagnostics. Our experiment results show that dark-field illumination can effectively suppress strong specular reflection from the proximal end of the fiber bundle. We realized a lateral resolution of 4.4 μm using the dark-field illuminated fiber bundle configuration. To demonstrate the feasibility of using the system to study cell morphology, we obtained still and video images of two thyroid cancer cell lines. Our results clearly allow differentiation of different cancer cell types.

  12. Characterization of a space orbited incoherent fiber optic bundle

    NASA Technical Reports Server (NTRS)

    Dewalt, Stephen A.; Taylor, Edward W.

    1993-01-01

    The results of a study performed to determine the effects of adverse space environments on a bundle of over 1800 optical fibers orbited for 69 months are reported. Experimental results are presented on an incoherent fiber optic bundle oriented in low Earth orbit aboard the Long Duration Exposure Facility (LDEF) satellite as part of the Space Environment Effects Experiment (M0006). Measurements were performed to determine if space induced radiation effects changed the fiber bundle characteristics. Data demonstrating the success of light transmitting fibers to withstand the adverse space environment are presented.

  13. Structural Transitions of F-Actin:Espin Bundles

    NASA Astrophysics Data System (ADS)

    Purdy, Kirstin; Bartles, James; Wong, Gerard

    2006-03-01

    Espin is an actin bundling protein involved in the formation of the parallel bundles of filamentous actin in hair cell stereocilia. Mutations in espin are implicated in deafness phenotypes in mice and humans. We present measurements of the F-actin structures induced by wild type and by mutated espin obtained via small angle x-ray scattering and fluorescence microscopy. We found that wild type espin induced a paracrystalline hexagonal array of twisted F-actin, whereas the mutated espin only condensed the F-actin into a nematic-like phase. The possibility of coexisting nematic and bundled actin in mixtures containing both mutant and wild type espins was also investigated.

  14. Experimental and theoretical study of horizontal tube bundle for passive condensation heat transfer

    NASA Astrophysics Data System (ADS)

    Song, Yong Jae

    The research in this thesis supports the design of a horizontal tube bundle condenser for passive heat removal system in nuclear reactors. From nuclear power plant containment, condensation of steam from a steam/noncondensable gas occurs on the primary side and boiling occurs on the secondary side; thus, heat exchanger modeling is a challenge. For the purpose of this experimental study, a six-tube bundle is used, where the outer diameter, inner diameter, and length of each stainless steel tube measures 38.10mm (1.5 inches), 31.75mm (1.25 inches) and 3.96m (156 inches), respectively. The pitch to diameter ratio was determined based on information gathered from literature surveys, and the dimensions were determined from calculations and experimental data. The objective of the calculations, correlations, and experimental data was to obtain complete condensation within the tube bundle. Experimental conditions for the tests in this thesis work were determined from Design Basis Accident (DBA). The applications are for an actual Passive Containment Cooling Systems (PCCS) condenser under postulated accident conditions in future light water reactors. In this research, steady state and transient experiments were performed to investigate the effect of noncondensable gas on steam condensation inside and boiling outside a tube bundle heat exchanger. The condenser tube inlet steam mass flow rate varied from 18.0 to 48.0 g/s, the inlet pressure varied from 100 kPa to 400 kPa, and the inlet noncondensable gas mass fraction varied from 1% to 10%. The effect of the noncondensable gas was examined by comparing the tube centerline temperatures for various inlet and system conditions. As a result, it was determined that the noncondensable gas accumulated near the condensate film causing a decrease of mass and energy transfer. In addition, the effect of the inlet steam flow rate gas was investigated by comparing the tube centerline temperatures, the conclusion being that, as the inlet

  15. Heat transfer characteristics of staggered wing-shaped tubes bundle at different angles of attack

    NASA Astrophysics Data System (ADS)

    Sayed Ahmed, Sayed Ahmed E.; Ibrahiem, Emad Z.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

    2014-08-01

    An experimental and numerical study has been conducted to clarify heat transfer characteristics and effectiveness of a cross-flow heat exchanger employing staggered wing-shaped tubes at different angels of attack. The water-side Rew and the air-side Rea were at 5 × 102 and at from 1.8 × 103 to 9.7 × 103, respectively. The tubes arrangements were employed with various angles of attack θ1,2,3 from 0° to 330° at the considered Rea range. Correlation of Nu, St, as well as the heat transfer per unit pumping power (ɛ) in terms of Rea and design parameters for the studied bundle were presented. The temperature fields around the staggered wing-shaped tubes bundle were predicted by using commercial CFD FLUENT 6.3.26 software package. Results indicated that the heat transfer increased with the angle of attack in the range from 0° to 45°, while the opposite was true for angles of attack from 135° to 180°. The best thermal performance and hence the efficiency η of studied bundle occurred at the lowest Rea and/or zero angle of attack. Comparisons between the experimental and numerical results of the present study and those, previously, obtained for similar available studies showed good agreements.

  16. Controlled production of aligned-nanotube bundles

    NASA Astrophysics Data System (ADS)

    Terrones, M.; Grobert, N.; Olivares, J.; Zhang, J. P.; Terrones, H.; Kordatos, K.; Hsu, W. K.; Hare, J. P.; Townsend, P. D.; Prassides, K.; Cheetham, A. K.; Kroto, H. W.; Walton, D. R. M.

    1997-07-01

    Carbon nanotubes might be usefully employed in nanometre-scale engineering and electronics. Electrical conductivity measurements on the bulk material, on individual multi-walled and single-walled nanotubes and on bundles of single-walled nanotubes have revealed that they may behave as metallic, insulating or semiconducting nanowires, depending on the method of production-which controls the degree of graphitization, the helicity and the diameter. Measurements of Young's modulus show that single nanotubes are stiffer than commercial carbon fibres. Methods commonly used to generate nanotubes-carbon-arc discharge techniques, catalytic pyrolysis of hydrocarbons and condensed-phase electrolysis-generally suffer from the drawbacks that polyhedral particles are also formed and that the dimensions of the nanotubes are highly variable. Here we describe a method for generating aligned carbon nanotubes by pyrolysis of 2-amino-4,6-dichloro-s-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching. The use of a patterned catalyst apparently encourages the formation of aligned nanotubes. The method offers control over length (up to about 50μm) and fairly uniform diameters (30-50nm), as well as producing nanotubes in high yield, uncontaminated by polyhedral particles.

  17. Concise Care Bundles In Acute Medicine

    PubMed Central

    Kivlin, Jude; Altemimi, Harith

    2015-01-01

    The Queen Elizabeth Hospital in King's Lynn, Norfolk is a 488 bed hospital providing services to approximately 331,000 people across 750 square miles. In 2012 a need was recognised for documentation (pathways) in a practical format to increase usage of national guidelines and facilitate adherence to best practice (gold standards of care) that could be easily version controlled, auditable and provide support in clinical decision-making by junior doctors. BMJ Action Sets[1] fulfilled the brief with expert knowledge, version control and support, though they were deemed too lengthy and unworkable in fast paced settings like the medical assessment unit; they formed the base creation of concise care bundles (CCB). CCB were introduced for 21 clinical presentations and one procedure. Outcomes were fully audited and showed significant improvement in a range of measures, including an increase in completions of CHADVASC score in atrial fibrillation, antibiotics prescribed per protocol in chronic obstructive pulmonary disease (COPD), and Blatchford score recorded for patients presenting with upper gastrointestinal bleed. PMID:26734437

  18. Nursing Care Management: Influence on Bundled Payments.

    PubMed

    Lentz, Shaynie; Luther, Brenda

    Fragmented and uncoordinated care is the third highest driver of U.S. healthcare costs. Although less than 10% of patients experience uncoordinated care, these patients represent 36% of total healthcare costs; care management interaction makes a significant impact on the utilization of healthcare dollars. A literature search was conducted to construct a model of care coordination for elective surgical procedures by collecting best practices for acute, transitions, and post-acute care periods. A case study was used to demonstrate the model developed. Care management defines care coordination as a model of care to address improving patient and caregiver engagement, communication across settings of care, and ultimately improved patient outcomes of care. Nurse-led care coordination in the presurgical, inpatient, and post-acute care settings requires systems change and administrative support to effectively meet the goals of the Affordable Care Act of reducing redundancy and costs while improving the patient experience. Nursing is the lynchpin of care management processes in all settings of care; thus, this model of care coordination for elective surgical admissions can provide nursing care management leaders a comprehensive view of coordinating care for these patient across settings of care during the predetermined time period of care. As bundled payment structures increasingly affect hospital systems, nursing leaders need to be ready to create or improve their care management processes; care coordination is one such process requiring immediate attention.

  19. Correlation of expression of the actin filament-bundling protein espin with stereociliary bundle formation in the developing inner ear.

    PubMed

    Li, Huawei; Liu, Hong; Balt, Steve; Mann, Sabine; Corrales, C Eduardo; Heller, Stefan

    2004-01-01

    The vertebrate hair cell is named for its stereociliary bundle or hair bundle that protrudes from the cell's apical surface. Hair bundles mediate mechanosensitivity, and their highly organized structure plays a critical role in mechanoelectrical transduction and amplification. The prototypical hair bundle is composed of individual stereocilia, 50-300 in number, depending on the animal species and on the type of hair cell. The assembly of stereocilia, in particular, the formation during development of individual rows of stereocilia with descending length, has been analyzed in great morphological detail. Electron microscopic studies have demonstrated that stereocilia are filled with actin filaments that are rigidly cross-linked. The growth of individual rows of stereocilia is associated with the addition of actin filaments and with progressively increasing numbers of cross-bridges between actin filaments. Recently, a mutation in the actin filament-bundling protein espin has been shown to underlie hair bundle degeneration in the deaf jerker mouse, subsequently leading to deafness. Our study was undertaken to investigate the appearance and developmental expression of espin in chicken inner ear sensory epithelia. We found that the onset of espin expression correlates with the initiation and growth of stereocilia bundles in vestibular and cochlear hair cells. Intense espin immunolabeling of stereocilia was colocalized with actin filament staining in all types of hair cells at all developmental stages and in adult animals. Our analysis of espin as a molecular marker for actin filament cross-links in stereocilia is in full accordance with previous morphological studies and implicates espin as an important structural component of hair bundles from initiation of bundle assembly to mature chicken hair cells.

  20. Bundles of Norms About Teen Sex and Pregnancy.

    PubMed

    Mollborn, Stefanie; Sennott, Christie

    2015-09-01

    Teen pregnancy is a cultural battleground in struggles over morality, education, and family. At its heart are norms about teen sex, contraception, pregnancy, and abortion. Analyzing 57 interviews with college students, we found that "bundles" of related norms shaped the messages teens hear. Teens did not think their communities encouraged teen sex or pregnancy, but normative messages differed greatly, with either moral or practical rationalizations. Teens readily identified multiple norms intended to regulate teen sex, contraception, abortion, childbearing, and the sanctioning of teen parents. Beyond influencing teens' behavior, norms shaped teenagers' public portrayals and post hoc justifications of their behavior. Although norm bundles are complex to measure, participants could summarize them succinctly. These bundles and their conflicting behavioral prescriptions create space for human agency in negotiating normative pressures. The norm bundles concept has implications for teen pregnancy prevention policies and can help revitalize social norms for understanding health behaviors.

  1. National Partnership for Maternal Safety: Consensus Bundle on Obstetric Hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-07-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and System Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  2. National Partnership for Maternal Safety Consensus Bundle on Obstetric Hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-01-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into 4 domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  3. National Partnership for Maternal Safety: consensus bundle on obstetric hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-07-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and System Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  4. 15. VIEW OF SHINGLES BUNDLED, PLACED ON PALLET, AND READIED ...

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

    15. VIEW OF SHINGLES BUNDLED, PLACED ON PALLET, AND READIED FOR FORKLIFT OPERATOR TO MOVE PALLET OF SHINGLES TO LOADING DOCK - Lester Shingle Mill, 1602 North Eighteenth Street, Sweet Home, Linn County, OR

  5. Assembly of mm-scale macrobridges with carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Cao, Anyuan; Ajayan, P. M.; Ramanath, G.

    2003-07-01

    We report a chemical vapor deposition method for in situ bridging of mm-scale metal-contact patterns with bundles of multiwalled carbon nanotubes. The nanotube bundles synthesized from a hexane-ferrocene-thiophene mixture have a diameter of <50 μm and lengths up to millimeters, typically consisting of tens to hundreds of aligned nanotubes. These bundles are transported to the downstream end of the furnace, where they are captured by relief patterns of metal-contact tips. We can control the orientation and length of the nanotube bridges by preorganizing the metal tips to receive the bundles. This method is amenable to both scaling up, e.g., to create large-area arrays of nanotubes with contact electrodes, as well as scaling down, e.g., to bridge closely spaced contact structures.

  6. Generalized holomorphic bundles and the B-field action

    NASA Astrophysics Data System (ADS)

    Hitchin, Nigel

    2011-01-01

    On a generalized complex manifold, there is an associated definition of a generalized holomorphic bundle, introduced by Gualtieri. In the case of an ordinary complex structure, this notion yields an object which we call a co-Higgs bundle, and we consider the B-field action of a closed form of type (1,1), both local and global. The effect makes contact with both Nahm's equations and holomorphic gerbes.

  7. Performance-based bundled payments: potential benefits and burdens.

    PubMed

    Satin, David J; Miles, Justin

    2009-10-01

    Performance-based bundled payments have emerged as the most recent iteration of pay for performance. These are programs in which providers are paid a single fee for a set of evidenced-based services related to a diagnosis. The payments are typically linked to outcomes as well as other quality measures. This paper reviews two prominent bundled payment programs--PROMETHEUS and ProvenCare--and discusses the potential pitfalls of these approaches.

  8. Tapered fiber bundles for combining high-power diode lasers.

    PubMed

    Kosterin, Andrey; Temyanko, Valery; Fallahi, Mahmoud; Mansuripur, Masud

    2004-07-01

    Tapered fiber bundles are often used to combine the output power of several semiconductor lasers into a multimode optical fiber for the purpose of pumping fiber lasers and amplifiers. It is generally recognized that the brightness of such combiners does not exceed the brightness of the individual input fibers. We report that the brightness of the tapered fibers (and fiber bundles) depends on both the taper ratio and the mode-filling properties of the beams launched into the individual fibers. Brightness, therefore, can be increased by selection of sources that fill a small fraction of the input fiber's modal capacity. As proof of concept, we present the results of measurements on tapered fiber-bundle combiners having a low-output étendue. Under low mode-filling conditions per input multimode fiber (i.e., fraction of filled modes < or =0.29), we report brightness enhancements of 8.0 dB for 19 x 1 bundles, 6.7 dB for 7 x 1 bundles, and 4.0 dB for 3 x 1 combiners. Our measured coupling efficiency variations of approximately 1%-2% among the various fibers in a given bundle confirm the uniformity and quality of the fabricated devices.

  9. Optical system design of subminiature endoscope with imaging fiber bundle

    NASA Astrophysics Data System (ADS)

    Lv, Juan; Xue, Bin; Li, Ting; He, Ying-hong; Ma, Xiao-long; Yan, Xing-tao

    2016-10-01

    A new subminiature endoscope which used for reconnaissance and diagnosis has been designed. This subminiature endoscope is designed based on imaging fiber bundle and consist of the front object lens whose aperture is only 0.5mm, imaging fiber bundle and the post coupling lens. It realized by using subminiature optical systems . The FOV(field of view) and the focal length of the front object lens are 50° and 0.59mm. And the object distance, F number and detected imaging high of the front object lens are 3mm, 6 and 0.5mm. The total number of the imaging fiber bundle are 10000 and it's pixel cell size is 5 μm. The effective aperture of the imaging fiber bundle is 0.46mm. The post coupling lens has a reduction ratio of 1.73. It's object distance and imaging height are 5mm and 0.8mm. The Numerical Aperture (NA) of the front object lens, imaging fiber bundle and the post coupling lens are matching will. The coupling efficiency of the imaging fiber bundle is above 93% and the system's design result can meet the need of the limit resolution of the imaging fiber. This kind of the fiber endoscope has the peculiarity of wide FOV, fine imaging quality, compact configuration, low finished cost and etc. It is meaningful to realize the objective of miniaturization, batch-type production and high imaging quality of the endoscope.

  10. Plantain fibre bundles isolated from Colombian agro-industrial residues.

    PubMed

    Gañán, Piedad; Zuluaga, Robin; Restrepo, Adriana; Labidi, Jalel; Mondragon, Iñaki

    2008-02-01

    Comestible fruit production from Musaceas plants is an important economical activity in developing countries like Colombia. However, it generates a large amount of agro-industrial residues. Some of them are a potential resource of natural fibres, which can be used as reinforcement for composite materials. In this work, a series of commercial plantain (Musa AAB, cv "Dominico Harton") fibre bundles extracted from pseudostem, leaf sheath and rachis agricultural wastes were analyzed. Mechanical decortication and biological retting processes were used during fiber extraction. No significant differences in composition of vascular bundles were observed for both extraction processes. Gross morphological characteristics and mechanical behavior have been evaluated. Conducting tissues with spiral-like arrangement are observed attached to fibre bundles. This fact suggests a big amount of these tissues in commercial plantain plants. Both used extraction methods are not enough to remove them. Pseudostem fibre bundles have higher specific strength and modulus and lower strain at break than leaf sheath and rachis fibre bundles, having values comparable to other lignocellulosic fibres bundles.

  11. Oscillation of carbon molecules inside carbon nanotube bundles.

    PubMed

    Thamwattana, Ngamta; Cox, Barry J; Hill, James M

    2009-04-08

    In this paper, we investigate the mechanics of a nanoscaled gigahertz oscillator comprising a carbon molecule oscillating within the centre of a uniform concentric ring or bundle of carbon nanotubes. Two kinds of oscillating molecules are considered, which are a carbon nanotube and a C(60) fullerene. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the nanotube-bundle and the C(60)-bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques, which provides considerable insight into the underlying mechanisms of the nanoscaled oscillators. The paper presents a synopsis of the major results derived in detail by the present authors (Cox et al 2007 Proc. R. Soc. A 464 691-710 and Cox et al 2007 J. Phys. A: Math. Theor. 40 13197-208).

  12. Oscillation of carbon molecules inside carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Thamwattana, Ngamta; Cox, Barry J.; Hill, James M.

    2009-04-01

    In this paper, we investigate the mechanics of a nanoscaled gigahertz oscillator comprising a carbon molecule oscillating within the centre of a uniform concentric ring or bundle of carbon nanotubes. Two kinds of oscillating molecules are considered, which are a carbon nanotube and a C60 fullerene. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the nanotube-bundle and the C60-bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques, which provides considerable insight into the underlying mechanisms of the nanoscaled oscillators. The paper presents a synopsis of the major results derived in detail by the present authors (Cox et al 2007 Proc. R. Soc. A 464 691-710 and Cox et al 2007 J. Phys. A: Math. Theor. 40 13197-208).

  13. A compactification of the moduli space of principal Higgs bundles over singular curves

    NASA Astrophysics Data System (ADS)

    Lo Giudice, Alessio; Pustetto, Andrea

    2016-12-01

    A principal Higgs bundle (P , ϕ) over a singular curve X is a pair consisting of a principal bundle P and a morphism ϕ : X →Ad P ⊗ ΩX1. We construct the moduli space of principal Higgs G-bundles over an irreducible singular curve X using the theory of decorated vector bundles. More precisely, given a faithful representation ρ : G → Sl(V) of G, we consider principal Higgs bundles as triples (E , q , φ) , where E is a vector bundle with rk(E) = dim V over the normalization X ˜ of X, q is a parabolic structure on E and φ :Ea,b → L is a morphism of bundles, L being a line bundle and Ea,b ≑(E⊗a) ⊕ b a vector bundle depending on the Higgs field ϕ and on the principal bundle structure.

  14. Electrolytic/fuel cell bundles and systems including a current collector in communication with an electrode thereof

    DOEpatents

    Hawkes, Grant L.; Herring, James S.; Stoots, Carl M.; O& #x27; Brien, James E.

    2013-03-05

    Electrolytic/fuel cell bundles and systems including such bundles include an electrically conductive current collector in communication with an anode or a cathode of each of a plurality of cells. A cross-sectional area of the current collector may vary in a direction generally parallel to a general direction of current flow through the current collector. The current collector may include a porous monolithic structure. At least one cell of the plurality of cells may include a current collector that surrounds an outer electrode of the cell and has at least six substantially planar exterior surfaces. The planar surfaces may extend along a length of the cell, and may abut against a substantially planar surface of a current collector of an adjacent cell. Methods for generating electricity and for performing electrolysis include flowing current through a conductive current collector having a varying cross-sectional area.

  15. Combustor having mixing tube bundle with baffle arrangement for directing fuel

    DOEpatents

    Hughes, Michael John; McConnaughhay, Johnie Franklin

    2016-08-23

    A combustor includes a tube bundle that extends radially across at least a portion of the combustor. The tube bundle includes an upstream surface axially separated from a downstream surface, and a plurality of tubes extend from the upstream surface through the downstream surface to provide fluid communication through the tube bundle. A barrier extends radially inside the tube bundle between the upstream and downstream surfaces, and a baffle extends axially inside the tube bundle between the upstream surface and the barrier.

  16. Vulnerability of Protoxylem and Metaxylem Vessels to Embolisms and Radial Refilling in a Vascular Bundle of Maize Leaves

    PubMed Central

    Hwang, Bae Geun; Ryu, Jeongeun; Lee, Sang Joon

    2016-01-01

    Regulation of water flow in an interconnected xylem vessel network enables plants to survive despite challenging environment changes that can cause xylem embolism. In this study, vulnerability to embolisms of xylem vessels and their water-refilling patterns in vascular bundles of maize leaves were experimentally investigated by employing synchrotron X-ray micro-imaging technique. A vascular bundle in maize consisted of a protoxylem vessel with helical thickenings between two metaxylem vessels with single perforation plates and nonuniformly distributed pits. When embolism was artificially induced in excised maize leaves by exposing them to air, protoxylem vessels became less vulnerable to dehydration compared to metaxylem vessels. After supplying water into the embolized vascular bundles, when water-refilling process stopped at the perforation plates in metaxylem vessels, discontinuous radial water influx occurred surprisingly in the adjacent protoxylem vessels. Alternating water refilling pattern in protoxylem and metaxylem vessels exhibited probable correlation between the incidence location and time of water refilling and the structural properties of xylem vessels. These results imply that the maintenance of water transport and modulation of water refilling are affected by hydrodynamic roles of perforation plates and radial connectivity in a xylem vascular bundle network. PMID:27446168

  17. Ultrastructure of the three anterior cruciate ligament bundles.

    PubMed

    Suzuki, Daisuke; Otsubo, Hidenori; Watanabe, Takafumi; Kamiya, Tomoaki; Nagoya, Satoshi; Yamashita, Toshihiko; Shino, Konsei

    2015-10-01

    The anterior cruciate ligament (ACL) can be morphologically separated into not only two, but three bundles: the anteromedial-medial bundle (AM-MB), the anteromedial-lateral bundle (AM-LB), and the posterolateral bundle (PLB). Our hypothesis was that the three bundles differ in their microstructures. The purpose of this study was to clarify the microstructural differences among the three bundles. The normal ACLs of six fresh frozen cadavers were harvested. After the AM-MB, AM-LB, and PLB were identified, their fibril structures were analyzed using a transmission electron microscope. The fibril orientation, distribution pattern, and the mass average diameter of the fibrils (MAD) were compared among the AM-MBs, AM-LBs, and PLBs. The AM-MB and AM-LB fibrils were arranged mostly in the longitudinal direction, while the PLB fibrils were not aligned in a uniform direction. The fibril diameter distribution pattern of AM-MBs showed a bi-modal pattern due to the existence of small-diameter (30-40 nm) and large-diameter fibrils (70-80 nm), while that of the AM-LBs and PLBs had a unimodal pattern with one prominent high peak at a diameter of 50-60 nm. The mean MAD of the AM-MBs (83.2 - 11.2 nm) was significantly larger than that of the PLBs (66.8 - 7.7 nm), while it showed no significant difference compared to that of the AM-LBs (77.6 - 12.3 nm). The three ACL bundles have different ultrastructures. The AM-MB predominantly includes thick, uni-directionally oriented fibrils like tendons, while the PLB consists of thinner, multi-directionally oriented fibrils. The AM-LB shows an intermediate structure between the AM-MB and the PLB.

  18. Verification of the FBR fuel bundle-duct interaction analysis code BAMBOO by the out-of-pile bundle compression test with large diameter pins

    NASA Astrophysics Data System (ADS)

    Uwaba, Tomoyuki; Ito, Masahiro; Nemoto, Junichi; Ichikawa, Shoichi; Katsuyama, Kozo

    2014-09-01

    The BAMBOO computer code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of the examined test bundles were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype fast breeder reactor (FBR) and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT) images and local parameters of bundle deformation such as pin-to-duct and pin-to-pin clearances were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms, the same as in the case of small diameter pin bundles. In addition, the BAMBOO analysis results confirmed that cladding oval distortion effectively suppresses BDI in large diameter pin bundles as well as in small diameter pin bundles.

  19. External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox

    NASA Astrophysics Data System (ADS)

    Börlin, Niclas; Grussenmeyer, Pierre

    2016-06-01

    The aim of this paper is to investigate whether the Matlab-based Damped Bundle Adjustment Toolbox (DBAT) can be used to provide independent verification of the BA computation of two popular software—PhotoModeler (PM) and PhotoScan (PS). For frame camera data sets with lens distortion, DBAT is able to reprocess and replicate subsets of PM results with high accuracy. For lens-distortion-free data sets, DBAT can furthermore provide comparative results between PM and PS. Data sets for the discussed projects are available from the authors. The use of an external verification tool such as DBAT will enable users to get an independent verification of the computations of their software. In addition, DBAT can provide computation of quality parameters such as estimated standard deviations, correlation between parameters, etc., something that should be part of best practice for any photogrammetric software. Finally, as the code is free and open-source, users can add computations of their own.

  20. Time-dependent fiber bundles with local load sharing.

    PubMed

    Newman, W I; Phoenix, S L

    2001-02-01

    Fiber bundle models, where fibers have random lifetimes depending on their load histories, are useful tools in explaining time-dependent failure in heterogeneous materials. Such models shed light on diverse phenomena such as fatigue in structural materials and earthquakes in geophysical settings. Various asymptotic and approximate theories have been developed for bundles with various geometries and fiber load-sharing mechanisms, but numerical verification has been hampered by severe computational demands in larger bundles. To gain insight at large size scales, interest has returned to idealized fiber bundle models in 1D. Such simplified models typically assume either equal load sharing (ELS) among survivors, or local load sharing (LLS) where a failed fiber redistributes its load onto its two nearest flanking survivors. Such models can often be solved exactly or asymptotically in increasing bundle size, N, yet still capture the essence of failure in real materials. The present work focuses on 1D bundles under LLS. As in previous works, a fiber has failure rate following a power law in its load level with breakdown exponent rho. Surviving fibers under fixed loads have remaining lifetimes that are independent and exponentially distributed. We develop both new asymptotic theories and new computational algorithms that greatly increase the bundle sizes that can be treated in large replications (e.g., one million fibers in thousands of realizations). In particular we develop an algorithm that adapts several concepts and methods that are well-known among computer scientists, but relatively unknown among physicists, to dramatically increase the computational speed with no attendant loss of accuracy. We consider various regimes of rho that yield drastically different behavior as N increases. For 1/2< or =rho< or =1, ELS and LLS have remarkably similar behavior (they have identical lifetime distributions at rho=1) with approximate Gaussian bundle lifetime statistics and a

  1. Ecosystem service bundles for analyzing tradeoffs in diverse landscapes.

    PubMed

    Raudsepp-Hearne, C; Peterson, G D; Bennett, E M

    2010-03-16

    A key challenge of ecosystem management is determining how to manage multiple ecosystem services across landscapes. Enhancing important provisioning ecosystem services, such as food and timber, often leads to tradeoffs between regulating and cultural ecosystem services, such as nutrient cycling, flood protection, and tourism. We developed a framework for analyzing the provision of multiple ecosystem services across landscapes and present an empirical demonstration of ecosystem service bundles, sets of services that appear together repeatedly. Ecosystem service bundles were identified by analyzing the spatial patterns of 12 ecosystem services in a mixed-use landscape consisting of 137 municipalities in Quebec, Canada. We identified six types of ecosystem service bundles and were able to link these bundles to areas on the landscape characterized by distinct social-ecological dynamics. Our results show landscape-scale tradeoffs between provisioning and almost all regulating and cultural ecosystem services, and they show that a greater diversity of ecosystem services is positively correlated with the provision of regulating ecosystem services. Ecosystem service-bundle analysis can identify areas on a landscape where ecosystem management has produced exceptionally desirable or undesirable sets of ecosystem services.

  2. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Simas, Tiffany A Moore; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    2017-04-06

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary work group to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  3. Surgical Management of Neurovascular Bundle in Uterine Fibroid Pseudocapsule

    PubMed Central

    Malvasi, Antonio; Hurst, Brad S.; Tsin, Daniel A.; Davila, Fausto; Dominguez, Guillermo; Dell'edera, Domenico; Cavallotti, Carlo; Negro, Roberto; Gustapane, Sarah; Teigland, Chris M.; Mettler, Liselotte

    2012-01-01

    The uterine fibroid pseudocapsule is a fibro-neurovascular structure surrounding a leiomyoma, separating it from normal peripheral myometrium. The fibroid pseudocapsule is composed of a neurovascular network rich in neurofibers similar to the neurovascular bundle surrounding a prostate. The nerve-sparing radical prostatectomy has several intriguing parallels to myomectomy. It may serve either as a useful model in modern fibroid surgical removal, or it may accelerate our understanding of the role of the fibrovascular bundle and neurotransmitters in the healing and restoration of reproductive potential after intracapsular myomectomy. Surgical innovations, such as laparoscopic or robotic myomectomy applied to the intracapsular technique with magnification of the fibroid pseudocapsule surrounding a leiomyoma, originated from the radical prostatectomy method that highlighted a careful dissection of the neurovascular bundle to preserve sexual functioning after prostatectomy. Gentle uterine leiomyoma detachment from the pseudocapsule neurovascular bundle has allowed a reduction in uterine bleeding and uterine musculature trauma with sparing of the pseudocapsule neuropeptide fibers. This technique has had a favorable impact on functionality in reproduction and has improved fertility outcomes. Further research should determine the role of the myoma pseudocapsule neurovascular bundle in the formation, growth, and pathophysiological consequences of fibroids, including pain, infertility, and reproductive outcomes. PMID:22906340

  4. Hair-bundle friction from transduction channels' gating forces

    NASA Astrophysics Data System (ADS)

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2015-12-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. We have shown recently that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle and thus provide a major source of damping [2]. We develop here a physical theory of passive hair-bundle mechanics that explains the origin of channel friction. We show that channel friction can be understood quantitatively by coupling the dynamics of the conformational change associated with channel gating to tip-link tension. As a result, varying channel properties affects friction, with faster channels producing smaller friction. The analysis emphasizes the dual role of transduction channels' gating forces, which affect both hair-bundle stiffness and drag. Friction originating from gating of ion channels is a general concept that is relevant to all mechanosensitive channels.

  5. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Moore Simas, Tiffany A; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary workgroup to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  6. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Moore Simas, Tiffany A; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    2017-03-01

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary workgroup to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  7. Variable recruitment in bundles of miniature pneumatic artificial muscles.

    PubMed

    DeLaHunt, Sylvie A; Pillsbury, Thomas E; Wereley, Norman M

    2016-09-13

    The natural compliance and force generation properties of pneumatic artificial muscles (PAMs) allow them to operate like human muscles in anthropomorphic robotic manipulators. Traditionally, manipulators use a single PAM or multiple PAMs actuated in unison in place of a human muscle. However, these standard manipulators can experience significant efficiency losses when operated outside their target performance ranges at low actuation pressures. This study considers the application of a variable recruitment control strategy to a parallel bundle of miniature PAMs as an attempt to mimic the selective recruitment of motor units in a human muscle. Bundles of miniature PAMs are experimentally characterized, their actuation behavior is modeled, and the efficiency gains and losses associated with the application of a variable recruitment control strategy are assessed. This bio-inspired control strategy allows muscle bundles to operate the fewest miniature PAMs necessary to achieve a desired performance objective, improving the muscle bundle's operating efficiency over larger ranges of force generation and displacement. The study also highlights the need for improved PAM fabrication techniques to facilitate the production of identical miniature PAMs for inclusion in muscle bundles.

  8. A statistical model of protein binding in parallel actin bundles

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Grason, Gregory; Purdy Drew, Kirstin; Wong, Gerard

    2010-03-01

    We propose a coarse-grained lattice model of cross-linking proteins in parallel actin bundles. Based on this model that captures the interplay between geometrical frustration of binding and the intrinsic flexibility of filaments and linkers, we predict a unique regular ground-state structure of fully cross-linked bundles. We also discuss the linker-dependent thermodynamic transition of actin filaments from their native state to the overtwisted state and map out the ``twist-state'' phase diagram in terms of linker flexibility as well as the chemical potential. A flexible linker regime exhibits a continuous spectrum of intermediate twist states, while a stiff linker regime only allows for untwisted actin filaments and fully overtwisted bundles. Our predictions compare well with small-angle scattering studies of bundles formed in the presence of two types of reconstituted cross-linking proteins, fascin and espin. Additionally, this study reveals how subtle differences in crosslinking agents themselves may be used by cells to achieve self-organized bundles with dramatically different properties.

  9. Statistical evaluation of fiber bundle imagery of wavelength multiplexing

    NASA Astrophysics Data System (ADS)

    Zhang, Yixin

    1994-09-01

    The effects of the wavelength multiplexing on the quality of an image transferred through a fiber bundle system is discussed by using the information capacity of an imaging system. The image transfer through a conventional fiber bundle can be thought of as a discrete sampling of the illuminance of the image at the entrance and of the bundle by each fiber element. This discrete sampling limits the band width of signals which can be transmitted. Also, the ends of the component fibers form an obtrusive pattern in the received image. Because, in the dispersion fiber bundle system, each fiber integrates the flux falling upon its entrance aperture, the entire picture format dispersion scan is reproduced at the frequency response characteristic of a uniform disk whose diameter is equal to that of the component fibers. Also, the individual fiber ends are thus blurred out and the obtrusive pattern formed by them is destroyed. It is shown, in theory, that the use of a dispersion method makes it possible to reduce the value of the light transmission nonuniformity contrast and to improve the resolution of fiber bundle image system, respectively.

  10. Dynamic response of fiber bundle under transverse impact.

    SciTech Connect

    Lu, Wei-Yang; Song, Bo

    2010-03-01

    There has been a very high demand in developing efficient soft body armors to protect the military and law enforcement personnel from ballistic or explosive attack. As a basic component in the soft body armor, fibers or fiber bundles play a key role in the performance against ballistic impact. In order to study the ballistic-resistant mechanism of the soft body armor, it is desirable to understand the dynamic response of the fiber bundle under transverse impact. Transverse wave speed is one important parameter because a faster transverse wave speed can make the impact energy dissipate more quickly. In this study, we employed split Hopkinson pressure bar (SHPB) to generate constant high-speed impact on a Kevlar fiber bundle in the transverse direction. The deformation of the fiber bundle was photographed with high-speed digital cameras. The transverse wave speeds were experimentally measured at various transverse impact velocities. The experimental results can also be used to quantitatively verify the current analytical models or to develop new models to describe the dynamic response of fiber bundle under transverse impact.

  11. Abnormal cingulum bundle development in autism: a probabilistic tractography study.

    PubMed

    Ikuta, Toshikazu; Shafritz, Keith M; Bregman, Joel; Peters, Bart D; Gruner, Patricia; Malhotra, Anil K; Szeszko, Philip R

    2014-01-30

    There is now considerable evidence that white matter abnormalities play a role in the neurobiology of autism. Little research has been directed, however, at understanding (a) typical white matter development in autism and how this relates to neurocognitive impairments observed in the disorder. In this study we used probabilistic tractography to identify the cingulum bundle in 21 adolescents and young adults with Autism Spectrum Disorder (ASD), and 21 age- and sex-matched healthy volunteers. We investigated group differences in the relationships between age and fractional anisotropy, a putative measure of white matter integrity, within the cingulum bundle. Moreover, in a preliminary investigation, we examined the relationship between cingulum fractional anisotropy and executive functioning using the Behavior Rating Inventory of Executive Function (BRIEF). The ASD participants demonstrated significantly lower fractional anisotropy within the cingulum bundle compared to the typically developing volunteers. There was a significant group-by-age interaction such that the ASD group did not show the typical age-associated increases in fractional anisotropy observed among healthy individuals. Moreover, lower fractional anisotropy within the cingulum bundle was associated with worse BRIEF behavioral regulation index scores in the ASD group. The current findings implicate a dysregulation in cingulum bundle white matter development occurring in late adolescence and early adulthood in ASD, and suggest that greater disturbances in this trajectory are associated with executive dysfunction in ASD.

  12. High thermodynamic stability of parametrically designed helical bundles

    SciTech Connect

    Huang, Po -Ssu; Oberdorfer, Gustav; Xu, Chunfu; Pei, Xue Y.; Nannenga, Brent L.; Rogers, Joseph M.; DiMaio, Frank; Gonen, Tamir; Luisi, Ben; Baker, David

    2014-10-24

    Here we describe a procedure for designing proteins with backbones produced by varying the parameters in the Crick coiled coil–generating equations. Combinatorial design calculations identify low-energy sequences for alternative helix supercoil arrangements, and the helices in the lowest-energy arrangements are connected by loop building. We design an antiparallel monomeric untwisted three-helix bundle with 80-residue helices, an antiparallel monomeric right-handed four-helix bundle, and a pentameric parallel left-handed five-helix bundle. The designed proteins are extremely stable (extrapolated ΔGfold > 60 kilocalories per mole), and their crystal structures are close to those of the design models with nearly identical core packing between the helices. The approach enables the custom design of hyperstable proteins with fine-tuned geometries for a wide range of applications.

  13. High-order synchronization of hair cell bundles

    NASA Astrophysics Data System (ADS)

    Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-Wook; Cheon, Jinwoo; Bozovic, Dolores

    2016-12-01

    Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells.

  14. Magnetic Propulsion of Microswimmers with DNA-Based Flagellar Bundles.

    PubMed

    Maier, Alexander M; Weig, Cornelius; Oswald, Peter; Frey, Erwin; Fischer, Peer; Liedl, Tim

    2016-02-10

    We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials.

  15. High-order synchronization of hair cell bundles

    PubMed Central

    Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-wook; Cheon, Jinwoo; Bozovic, Dolores

    2016-01-01

    Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells. PMID:27974743

  16. IKKε inhibits PKC to promote Fascin-dependent actin bundling

    PubMed Central

    Ogura, Yosuke; Misaki, Kazuyo; Maeda, Takuya; Kimpara, Akiyo; Yonemura, Shigenobu; Hayashi, Shigeo

    2016-01-01

    Signaling molecules have pleiotropic functions and are activated by various extracellular stimuli. Protein kinase C (PKC) is activated by diverse receptors, and its dysregulation is associated with diseases including cancer. However, how the undesired activation of PKC is prevented during development remains poorly understood. We have previously shown that a protein kinase, IKKε, is active at the growing bristle tip and regulates actin bundle organization during Drosophila bristle morphogenesis. Here, we demonstrate that IKKε regulates the actin bundle localization of a dynamic actin cross-linker, Fascin. IKKε inhibits PKC, thereby protecting Fascin from inhibitory phosphorylation. Excess PKC activation is responsible for the actin bundle defects in IKKε-deficient bristles, whereas PKC is dispensable for bristle morphogenesis in wild-type bristles, indicating that PKC is repressed by IKKε in wild-type bristle cells. These results suggest that IKKε prevents excess activation of PKC during bristle morphogenesis. PMID:27578797

  17. Magnetic Propulsion of Microswimmers with DNA-Based Flagellar Bundles

    PubMed Central

    2016-01-01

    We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials. PMID:26821214

  18. High thermodynamic stability of parametrically designed helical bundles

    DOE PAGES

    Huang, Po -Ssu; Oberdorfer, Gustav; Xu, Chunfu; ...

    2014-10-24

    Here we describe a procedure for designing proteins with backbones produced by varying the parameters in the Crick coiled coil–generating equations. Combinatorial design calculations identify low-energy sequences for alternative helix supercoil arrangements, and the helices in the lowest-energy arrangements are connected by loop building. We design an antiparallel monomeric untwisted three-helix bundle with 80-residue helices, an antiparallel monomeric right-handed four-helix bundle, and a pentameric parallel left-handed five-helix bundle. The designed proteins are extremely stable (extrapolated ΔGfold > 60 kilocalories per mole), and their crystal structures are close to those of the design models with nearly identical core packing between themore » helices. The approach enables the custom design of hyperstable proteins with fine-tuned geometries for a wide range of applications.« less

  19. Rheology of semiflexible bundle networks with transient linkers.

    PubMed

    Müller, Kei W; Bruinsma, Robijn F; Lieleg, Oliver; Bausch, Andreas R; Wall, Wolfgang A; Levine, Alex J

    2014-06-13

    We present a theoretical and computational analysis of the rheology of networks made up of bundles of semiflexible filaments bound by transient cross-linkers. Such systems are ubiquitous in the cytoskeleton and can be formed in vitro using filamentous actin and various cross-linkers. We find that their high-frequency rheology is characterized by a scaling behavior that is quite distinct from that of networks of the well-studied single semiflexible filaments. This regime can be understood theoretically in terms of a length-scale-dependent bending modulus for bundles. Next, we observe new dissipative dynamics associated with the shear-induced disruption of the network at intermediate frequencies. Finally, at low frequencies, we encounter a region of non-Newtonian rheology characterized by power-law scaling. This regime is dominated by bundle dissolution and large-scale rearrangements of the network driven by equilibrium thermal fluctuations.

  20. Betti numbers of graded modules and cohomology of vector bundles

    NASA Astrophysics Data System (ADS)

    Eisenbud, David; Schreyer, Frank-Olaf

    2009-07-01

    In the remarkable paper Graded Betti numbers of Cohen-Macaulay modules and the multiplicity conjecture, Mats Boij and Jonas Soederberg conjectured that the Betti table of a Cohen-Macaulay module over a polynomial ring is a positive linear combination of Betti tables of modules with pure resolutions. We prove a strengthened form of their conjectures. Applications include a proof of the Multiplicity Conjecture of Huneke and Srinivasan and a proof of the convexity of a fan naturally associated to the Young lattice. With the same tools we show that the cohomology table of any vector bundle on projective space is a positive rational linear combination of the cohomology tables of what we call supernatural vector bundles. Using this result we give new bounds on the slope of a vector bundle in terms of its cohomology.

  1. System for supporting bundled tube segments within a combustor

    DOEpatents

    Melton, Patrick Benedict

    2016-03-01

    A system for supporting bundled tube segments within a combustor includes an annular sleeve that extends circumferentially and axially within the combustor, a support lug that extends radially inward from the annular sleeve and an annular support frame that is disposed within the annular sleeve. The annular support frame includes an inner ring portion, an outer ring portion and a plurality of spokes that extend radially between the inner and outer ring portions. The inner ring portion, the outer ring portion and the plurality of spokes define an annular array of openings for receiving a respective bundled tube segment. The inner ring portion is connected to each bundled tube segment and the outer ring portion is coupled to the support lug.

  2. Preparation of superhydrophobic poly-p-phenylenebenzobisoxazole (PBO) fiber bundles

    NASA Astrophysics Data System (ADS)

    Jiang, Zai X.; Geng, Lin; Huang, Yu D.

    2011-02-01

    According to the reformed Cassie-Baxter equation, the superhydrophobic phenylenebenzobisoxazole (PBO) fiber bundle boats were fabricated from mimicking the lotus leaf venation using chemical surface modifications and roughness introduction. Water contact angles as high as 152.3° were achieved for PBO fiber bundles. Furthermore, the loading capacities of the superhydrophobic PBO fiber bundle boats were also measured. And the highest loading weight, 8.36 g, was obtained by the boats treated with 2.0 wt.% (heptadecafluoro-1,1,2,2,-tetradecyl)trimethoxysilane (HFTES). The large loading capacities were believed to arise from the air film surrounding the superhydrophobic surfaces of boats. The results of this study presented new applications of artificial hydrophobic surfaces in areas of miniature aquatic devices.

  3. Stable parabolic Higgs bundles as asymptotically stable decorated swamps

    NASA Astrophysics Data System (ADS)

    Beck, Nikolai

    2016-06-01

    Parabolic Higgs bundles can be described in terms of decorated swamps, which we studied in a recent paper. This description induces a notion of stability of parabolic Higgs bundles depending on a parameter, and we construct their moduli space inside the moduli space of decorated swamps. We then introduce asymptotic stability of decorated swamps in order to study the behaviour of the stability condition as one parameter approaches infinity. The main result is the existence of a constant, such that stability with respect to parameters greater than this constant is equivalent to asymptotic stability. This implies boundedness of all decorated swamps which are semistable with respect to some parameter. Finally, we recover the usual stability condition of parabolic Higgs bundles as asymptotic stability.

  4. One-sided ejaculation of echidna sperm bundles.

    PubMed

    Johnston, S D; Smith, B; Pyne, M; Stenzel, D; Holt, W V

    2007-12-01

    We report for the first time an unusual ejaculatory mechanism in the short-beaked echidna in which each side of the bilaterally symmetrical, rosettelike glans penis is used alternately, with the other being shut down. This is unparalleled in mammals but is reminiscent of the use of hemipenes in squamate reptiles, providing further reproductive evidence of a sauropsidian lineage in the Monotremata. Further, we describe the occurrence of motile sperm bundles in ejaculated echidna semen and provide scanning electron micrographs of their morphology. Sperm bundling appears to confer increased sperm motility, which may provide the potential for sperm competition between males.

  5. Dunkl Operators as Covariant Derivatives in a Quantum Principal Bundle

    NASA Astrophysics Data System (ADS)

    Durdevich, Micho; Sontz, Stephen Bruce

    2013-05-01

    A quantum principal bundle is constructed for every Coxeter group acting on a finite-dimensional Euclidean space E, and then a connection is also defined on this bundle. The covariant derivatives associated to this connection are the Dunkl operators, originally introduced as part of a program to generalize harmonic analysis in Euclidean spaces. This gives us a new, geometric way of viewing the Dunkl operators. In particular, we present a new proof of the commutativity of these operators among themselves as a consequence of a geometric property, namely, that the connection has curvature zero.

  6. Chern-Simons functional under gauge transformations on flat bundles

    NASA Astrophysics Data System (ADS)

    Byun, Yanghyun; Kim, Joohee

    2017-01-01

    We describe the effect of a gauge transformation on the Chern-Simons functional in a thorough and unifying manner. We use the assumptions that the structure group is compact and connected and, in particular, that the principal bundle is flat. The Chern-Simons functional we consider is the one defined by choosing a flat reference connection. The most critical step in arriving at the main result is to show both the existence and the uniqueness of a cohomology class on the adjoint bundle such that it is the class of the so-called Maurer-Cartan 3-form when restricted to each fiber.

  7. Calculation of Inter-Subchannel Turbulent Mixing Rate and Heat Transfer in a Triangular-Arrayed Rod Bundle Using Direct Numerical Simulation

    SciTech Connect

    Yudov, Yury V.

    2006-07-01

    The direct numerical simulation, extended to boundary - fitted coordinate, has been carried out for a fully-developed turbulent flow thermal hydraulics in a triangular rod bundle. The rod bundle is premised to be an infinite array. The spacer grid effects are ignored. The purpose of this work is to verify DNS methodology to be applied for deriving coefficients for inter-subchannel turbulent mixing and heat transfer on a rod. These coefficients are incorporated in subchannel analysis codes. To demonstrate the validity of this methodology, numerical calculation was performed for the bundle with the pitch to diameter ratio 1.2, at friction Reynolds number of 600 and Prandtl number of 1. The results for the hydraulic parameters are compared with published DNS data, and the results for the heat exchange coefficients -- with those obtained using semi-empirical correlations. (authors)

  8. Subchannel Thermal-Hydraulic Experimental Program (STEP). Volume 1. Mixing in a pressurized water reactor (PWR) rod bundle. Final report

    SciTech Connect

    Barber, A.R.; Zielke, L.A.

    1980-08-01

    This volume describes an experiment that was performed to determine the mixing characteristics of a pressurized water reactor (PWR) rod bundle. The objective of this project was to improve the subchannel computer code models of the reactor core. The experimental technique was isokinetic subchannel withdrawal of the entire flow from two sample subchannels. Once withdrawn, the sample fluid was condensed and its enthalpy was measured by regenerative heat exchange calorimetry. The test bundle was a 4 x 6 electrically heated array with a 50% power upset. The COBRA IIIC code was used to model the experiment and to determine the value of the thermal mixing coefficient, ..beta.., that was necessary to predict the measured results. Both single- and two-phase data were obtained over a range of PWR operating conditions. The results indicate that both single- and two-phase mixing is small. The COBRA model predicts the enthalpy data using a turbulent mixing coefficient, ..beta.. approx. = 0.002.

  9. Get ready: Bundled payments are in your future.

    PubMed

    2015-09-01

    The Centers for Medicare & Medicaid Services' (CMS') mandatory bundled payment pilot project makes clear that the agency intends to reform Medicare reimbursement. Hospitals in 75 geographic areas are required to participate in a five-year pilot project that puts them at risk for the cost of hip and knee replacements from the time of surgery until 90 days after discharge. Already, more than 6,500 providers are participating in the Bundled Payments for Care Improvement project, a voluntary program where participants can choose from 48 clinical episodes and four models. Even if they won't be part of a bundled payments arrangement, case managers need to shift their thinking to prepare for the future of reimbursement by developing close working relationships with post-acute providers, knowing the services and quality delivered by post-acute providers, and being aware of the costs for the entire episode of care. Case managers will not be able to handle all the responsibilities necessary in a bundled payment arrangement if they have large caseloads.

  10. Wire bundle formed into grids with minute interstices

    NASA Technical Reports Server (NTRS)

    Todd, H. H.

    1965-01-01

    Deforming the ends of a bundle of closely packed parallel wires to restrict the interstices to substantially uniform and minute dimensions produces grids or filters for ion engines. Porous metal structures made by this process are also used as fuel cell electrodes, diffusion membranes, and catalysts.

  11. Defect-driven shape instabilities in cohesive filament bundles

    NASA Astrophysics Data System (ADS)

    Bruss, Isaac; Grason, Gregory

    When defects are incorporated into the lattice of a flexible 2D crystalline membrane, it buckles into a new configuration. Specifically, 5- and 7-fold disclinations produce conical- and saddle-like geometries respectively. For bundles composed of a crystalline array of cohesive flexible filaments, we propose a similar phenomena of defect-induced buckling. This revelation is fueled by a recently discovered mapping between the metric properties of a curved surface, and the inter-filament spacing within a deformed bundle. Using a combination of continuum elasticity theory and numerical simulations, we investigate the effects of defects in the cross section on a bundle's global structure. We find that positive disclinations promote the twisting of filaments around a central axis within the bundle, while negative disclinations promote twisting around two parallel axes simultaneously. Both instabilities are interpreted by means of their equivalent Gaussian curvature, and map appropriately to the the corresponding membrane responses. Additionally, for 5-fold disclinations we uncover a new equilibria structure, torsional wrinkling, with the intriguing ability to focus gradients in filament tilt much like curvature-focusing for the analogous membrane. NSF (CAREER) DMR-0955760.

  12. A comprehensive in-pile test of PWR fuel bundle

    NASA Astrophysics Data System (ADS)

    Kang, Rixin; Zhang, Shucheng; Chen, Dianshan

    1991-02-01

    An in-pile test of PWR fuel bundle has been conducted in HWRR at IAE of China. This paper describes the structure of the test bundle (3 × 3-2), fabrication process and quality control of the fuel rod, irradiation conditions and the main Post Irradiation Examination (PIE) results. The test fuel bundle was irradiated under the PWR operation and water chemistry conditions with an average linear power of 381 W/cm and reached an average burnup of 25010 MWd/tU of the fuel bundle. After the test, destructive and non-destructive examination of the fuel rods was conducted at hot laboratories. The fission gas release was 10.4-23%. The ridge height of cladding was 3 to 8 μm. The hydrogen content of the cladding was 80 to 140 ppm. The fuel stack height was increased by 2.9 to 3.3 mm. The relative irradiation growth was about 0.11 to 0.17% of the fuel rod length. During the irradiation test, no fuel rod failure or other abnormal phenomena had been found by the on-line fuel failure monitoring system of the test loop and water sampling analysis. The structure of the test fuel assembly was left undamaged without twist and detectable deformation.

  13. Fission Yeast Scp3 Potentially Maintains Microtubule Orientation through Bundling

    PubMed Central

    Ozaki, Kanako; Chikashige, Yuji; Hiraoka, Yasushi; Matsumoto, Tomohiro

    2015-01-01

    Microtubules play important roles in organelle transport, the maintenance of cell polarity and chromosome segregation and generally form bundles during these processes. The fission yeast gene scp3+ was identified as a multicopy suppressor of the cps3-81 mutant, which is hypersensitive to isopropyl N-3-chlorophenylcarbamate (CIPC), a poison that induces abnormal multipolar spindle formation in higher eukaryotes. In this study, we investigated the function of Scp3 along with the effect of CIPC in the fission yeast Schizosaccharomyces pombe. Microscopic observation revealed that treatment with CIPC, cps3-81 mutation and scp3+ gene deletion disturbed the orientation of microtubules in interphase cells. Overexpression of scp3+ suppressed the abnormal orientation of microtubules by promoting bundling. Functional analysis suggested that Scp3 functions independently from Ase1, a protein largely required for the bundling of the mitotic spindle. A strain lacking the ase1+ gene was more sensitive to CIPC, with the drug affecting the integrity of the mitotic spindle, indicating that CIPC has a mitotic target that has a role redundant with Ase1. These results suggested that multiple systems are independently involved to ensure microtubule orientation by bundling in fission yeast. PMID:25767875

  14. Formation and Dissociation of Sperm Bundles in Monotremes.

    PubMed

    Nixon, Brett; Ecroyd, Heath; Dacheux, Jean-Louis; Dacheux, Francoise; Labas, Valerie; Johnston, Steve D; Jones, Russell C

    2016-10-01

    Because monotremes are the earliest offshoot of the mammalian lineage, the platypus and short-beaked echidna were studied as model animals to assess the origin and biological significance of adaptations considered unique to therian mammals: epididymal sperm maturation and subsequent capacitation. We show that spermatozoa from both species assemble into bundles of approximately 100 cells during passage through the epididymis and that an epididymal protein-secreted protein, acidic, cysteine-rich (osteonectin; SPARC)-is involved in bundle formation. The bundles persisted during incubation in vitro for at least 1 h under conditions that capacitate therian spermatozoa, and then underwent a time-dependent dissociation to release spermatozoa capable of fertilization. Only after this dissociation could the spermatozoa bind to the perivitelline membrane of a hen's egg, display an altered form of motility reminiscent of hyperactivation, and be induced to undergo an acrosome reaction. It is concluded that the development of sperm bundles in the monotreme epididymis mandates that they require a time-dependent process to be capable of fertilizing an ovum. However, because this functional end point was achieved without overt changes in protein tyrosine phosphorylation (a hallmark of capacitation in therians), it is concluded that the process in monotremes is distinctly different from capacitation in therian mammals.

  15. Metabolite Diffusion into Bundle Sheath Cells from C4 Plants

    PubMed Central

    Weiner, Hendrik; Burnell, James N.; Woodrow, Ian E.; Heldt, Hans W.; Hatch, Marshall D.

    1988-01-01

    The present studies provide the first measurements of the resistance to diffusive flux of metabolites between mesophyll and bundle sheath cells of C4 plants. Species examined were Panicum miliaceum, Urochloa panicoides, Atriplex spongiosa, and Zea mays. Diffusive flux of metabolites into isolated bundle sheath cells was monitored by following their metabolic transformation. Evidence was obtained that the observed rapid fluxes occurred via functional plasmodesmata. Diffusion constants were determined from the rate of transformation of limiting concentrations of metabolites via cytosolic enzymes with high potential velocities and favorable equilibrium constants. Values on a leaf chlorophyll basis ranged between 1 and 5 micromoles per minute per milligram of chlorophyll per millimolar gradient depending on the molecular weight of the metabolite and the source of bundle sheath cells. Diffusion of metabolites into these cells was unaffected by a wide variety of compounds including respiratory inhibitors, monovalent and divalent cations, and plant hormones, but it was interrupted by treatments inducing cell plasmolysis. The molecular weight exclusion limit for permeation of compounds into bundle sheath cells was in the range of 850 to 900. These cells provide an ideal system for the quantitative study of plasmodesmatal function. PMID:16666390

  16. Fuel bundle design for enhanced usage of plutonium fuel

    DOEpatents

    Reese, Anthony P.; Stachowski, Russell E.

    1995-01-01

    A nuclear fuel bundle includes a square array of fuel rods each having a concentration of enriched uranium and plutonium. Each rod of an interior array of the rods also has a concentration of gadolinium. The interior array of rods is surrounded by an exterior array of rods void of gadolinium. By this design, usage of plutonium in the nuclear reactor is enhanced.

  17. A Method of Assembling Compact Coherent Fiber-Optic Bundles

    NASA Technical Reports Server (NTRS)

    Martin, Stefan; Liu, Duncan; Levine, Bruce Martin; Shao, Michael; Wallace, James

    2007-01-01

    A method of assembling coherent fiber-optic bundles in which all the fibers are packed together as closely as possible is undergoing development. The method is based, straightforwardly, on the established concept of hexagonal close packing; hence, the development efforts are focused on fixtures and techniques for practical implementation of hexagonal close packing of parallel optical fibers.

  18. Exposure Control Using Adaptive Multi-Stage Item Bundles.

    ERIC Educational Resources Information Center

    Luecht, Richard M.

    This paper presents a multistage adaptive testing test development paradigm that promises to handle content balancing and other test development needs, psychometric reliability concerns, and item exposure. The bundled multistage adaptive testing (BMAT) framework is a modification of the computer-adaptive sequential testing framework introduced by…

  19. Fiber-bundle formalism for quantization in curved spaces

    SciTech Connect

    Wyrozumski, T. )

    1990-08-15

    We set up a geometrical formulation of the canonical quantization of a free Klein-Gordon field on a gravitational background. We introduce the notion of the Bogolubov bundle as the principal fiber bundle over the space of all Cauchy surfaces belonging to some fixed foliation of space-time, with the Bogolubov group as the structure group, as a tool in considering local Bogolubov transformations. Sections of the associated complex structure bundle have the meaning of attaching Hilbert spaces to Cauchy surfaces. We single out, as physical, sections defined by the equation of parallel transport on the Bogolubov bundle. The connection is then subjected to a certain nonlinear differential equation. We find a particular solution, which happens to coincide with a formula given by Parker for Robertson-Walker space-times. Finally, we adopt the adiabatic hypothesis as the physical input to the formalism and fix in this way a free parameter in the connection. Concluding, we comment on a possible geometrical interpretation of the regularization of the stress-energy tensor and on generalizations of the formalism toward quantum gravity.

  20. Thermal conversion of bundled carbon nanotubes into graphitic ribbons.

    PubMed

    Gutiérrez, H R; Kim, U J; Kim, J P; Eklund, P C

    2005-11-01

    High temperature heat treatment (HTT) of bundled single-walled carbon nanotubes (SWNTs) in vacuum ( approximately 10(-5) Torr) has been found to lead to the formation of two types of graphitic nanoribbons (GNRs), as observed by high-resolution transmission electron microscopy. Purified SWNT bundles were first found to follow two evolutionary steps, as reported previously, that is, tube coalescence (HTT approximately 1400 degrees C) and then massive bond rearrangement (HTT approximately 1600 degrees C), leading to the formation of bundled multiwall nanotubes (MWNTs) with 3-12 shells. At HTT > 1800 degrees C, we find that these MWNTs collapse into multishell GNRs. The first type of GNR we observed is driven by the collapse of diameter-doubled single-wall nanotubes, and their production is terminated at HTT approximately 1600 degrees C when the MWNTs also start to form. We propose that the collapse is driven by van der Waals forces between adjacent tubes in the same bundle. For HTT > 2000 degrees C, the heat-treated material is found to be almost completely in the multishell GNR form.

  1. Hair Cells: Bundles, Tuning, Transduction—A Moderated Discussion

    NASA Astrophysics Data System (ADS)

    Karavitaki, K. Domenica; Ricci, Anthony J.

    2011-11-01

    A discussion moderated by the authors on the topic "Hair Cells: Bundles, Tuning, Transduction" was held on 17 July 2011 at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The paper provides an edited transcript of the session.

  2. Masquerading Bundle Branch Block: A Poor Prognostic Sign Revisited

    PubMed Central

    Dhanse, Suheil; Kareem, Hashir; Devasia, Tom

    2016-01-01

    Masquerading bundle branch block is a rare but important finding on the Electrocardiogram (ECG). It is an indication of severe and diffuse conduction system disease and usually indicates poor prognosis. The precordial leads show a Right Bundle Branch Block (RBBB) pattern while the limb leads resemble a Left Bundle Branch Block (LBBB). This finding on an ECG is almost invariably associated with severe underlying heart disease. It is extremely important to be aware of this finding as it is a marker of poor cardiac outcomes. We report the case of a 68-year-old gentleman, who presented with progressive dyspnoea on exertion over three months. ECG showed a broad QRS complex with a RBBB pattern on the precordial leads and a LBBB pattern on the limb leads (suggestive of masquerading bundle branch block). A coronary angiogram revealed severe Triple Vessel Disease (TVD). The patient was scheduled for an early Coronary Artery By-Pass Grafting Surgery. However, his clinical condition deteriorated and he died while awaiting the surgery. PMID:27790494

  3. Product Bundling and Shared Information Goods: A Pricing Exercise

    ERIC Educational Resources Information Center

    Morrison, William G.

    2016-01-01

    In this article, the author describes an exercise in which two pricing problems (product bundling and the sharing of digital information goods) can be understood using the same analytical approach. The exercise allows students to calculate the correct numerical answers with relative ease, while the teaching plan demonstrates the importance of the…

  4. Electron diffraction and microscopy of single-wall carbon nanotube bundles produced by different methods

    NASA Astrophysics Data System (ADS)

    Colomer, J.-F.; Henrard, L.; Lambin, Ph.; van Tendeloo, G.

    2002-05-01

    The atomic structure of single-wall carbon nanotube bundles produced by three different techniques (laser ablation, electric arc discharge and catalytic chemical vapor deposition (CCVD)) has been characterized by electron diffraction and microscopy. Information on the helicity and the lattice packing has been obtained. Concerning the helicity, small bundles produced by CCVD exhibit only one or two tube helicities within a single bundle. The diffraction patterns of laser-ablation produced bundles also present well-defined but more diversified chiralities within a single bundle. By contrast the data acquired on bundles formed by arc discharge show a more diffuse pattern, characteristic of a random chirality dispersion within a single bundle. Concerning the lattice packing, informations are obtained via a detailed study of the equatorial line of the diffraction pattern for bundles produced by the three techniques. This electron diffraction study is completed by high-resolution electron microscopy.

  5. 76 FR 53137 - Bundled Payments for Care Improvement Initiative: Request for Applications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-25

    ... HUMAN SERVICES Centers for Medicare & Medicaid Services Bundled Payments for Care Improvement Initiative... of the initial four models under the Bundled Payments for Care Improvement initiative beginning in... described on the CMS Innovation Center Web site...

  6. 75 FR 8353 - Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold AGENCY: Federal Election Commission. ACTION: Notice of adjustments to expenditure limitations and lobbyist... Commission'') is adjusting certain expenditure limitations and the lobbyist bundling disclosure threshold...

  7. Infinitesimal moduli of G2 holonomy manifolds with instanton bundles

    NASA Astrophysics Data System (ADS)

    de la Ossa, Xenia; Larfors, Magdalena; Svanes, Eirik E.

    2016-11-01

    We describe the infinitesimal moduli space of pairs ( Y, V) where Y is a manifold with G 2 holonomy, and V is a vector bundle on Y with an instanton connection. These structures arise in connection to the moduli space of heterotic string compactifications on compact and non-compact seven dimensional spaces, e.g. domain walls. Employing the canonical G 2 cohomology developed by Reyes-Carrión and Fernández and Ugarte, we show that the moduli space decomposes into the sum of the bundle moduli {H}_{{overset{ěe }{d}}_A}^1(Y,End(V)) plus the moduli of the G 2 structure preserving the instanton condition. The latter piece is contained in {H}_{overset{ěe }{d}θ}^1(Y,TY) , and is given by the kernel of a map overset{ěe }{F} which generalises the concept of the Atiyah map for holomorphic bundles on complex manifolds to the case at hand. In fact, the map overset{ěe }{F} is given in terms of the curvature of the bundle and maps {H}_{overset{ěe }{d}θ}^1(Y,TY) into {H}_{{overset{ěe }{d}}_A}^2(Y,End(V)) , and moreover can be used to define a cohomology on an extension bundle of TY by End( V). We comment further on the resemblance with the holomorphic Atiyah algebroid and connect the story to physics, in particular to heterotic compactifications on ( Y, V) when α' = 0.

  8. Geometric principles in the assembly of α-helical bundles.

    PubMed

    Pratap, J V; Luisi, B F; Calladine, C R

    2013-06-28

    α-Helical coiled coils are usually stabilized by hydrophobic interfaces between the two constituent α-helices, in the form of 'knobs-into-holes' packing of non-polar residues arranged in repeating heptad patterns. Here we examine the corresponding 'hydrophobic cores' that stabilize bundles of four α-helices. In particular, we study three different kinds of bundle, involving four α-helices of identical sequence: two pack in a parallel and one in an anti-parallel orientation. We point out that the simplest way of understanding the packing of these 4-helix bundles is to use Crick's original idea that the helices are held together by 'hydrophobic stripes', which are readily visualized on the cylindrical surface lattice of the α-helices; and that the 'helix-crossing angle'--which determines, in particular, whether supercoiling is left- or right-handed--is fixed by the slope of the lattice lines that contain the hydrophobic residues. In our three examples the constituent α-helices have hydrophobic repeat patterns of 7, 11 and 4 residues, respectively; and we associate the different overall conformations with 'knobs-into-holes' packing along the 7-, 11- and 4-start lines, respectively, of the cylindrical surface lattices of the constituent α-helices. For the first two examples, all four interfaces between adjacent helices are geometrically equivalent; but in the third, one of the four interfaces differs significantly from the others. We provide a geometrical explanation for this non-equivalence in terms of two different but equivalent ways of assembling this bundle, which may possibly constitute a bistable molecular 'switch' with a coaxial throw of about 12 Å. The geometrical ideas that we deploy in this paper provide the simplest and clearest description of the structure of helical bundles. In an appendix, we describe briefly a computer program that we have devised in order to search for 'knobs-into-holes' packing between α-helices in proteins.

  9. Experimental study of heat transfer in a 7-element bundle cooled with supercritical Freon-12

    SciTech Connect

    Richards, G.; Shelegov, A. S.; Kirillov, P. L.; Pioro, I. L.; Harvel, G.

    2012-07-01

    Experimental data on Supercritical-Water (SCW) cooled bundles are very limited. Major problems with performing such experiments are technical difficulties in testing and experimental costs at high pressures, temperatures and heat fluxes. Also, there are only a few SCW experimental setups currently in the world capable of providing data. Supercritical Water-cooled nuclear Reactors (SCWRs), as one of the six concepts of Generation IV reactors, cannot be designed without such data. Therefore, a preliminary approach uses modeling fluids such as carbon dioxide and refrigerants instead of water is practical. In particularly, experiments in supercritical refrigerant-cooled bundles can be used. One of the SC modeling fluids typically used is Freon-12 (R-12) with the critical pressure of 4.136 MPa and the critical temperature of 111.97 deg. C. These conditions correspond to the critical pressure of 22.064 MPa and critical temperature of 373.95 deg. C in water. A set of experimental data obtained at the Inst. of Physics and Power Engineering (IPPE, Obninsk, Russia) in a vertically-oriented bundle cooled with supercritical R-12 was analyzed. This dataset consisted of 20 runs. The test section was 7-element bundle installed in a hexagonal flow channel with 3 grid spacers. Data was collected at pressures of approximately 4.65 MPa for several different combinations of wall and bulk-fluid temperatures that were below, at, or above the pseudo-critical temperature. The values of mass flux were ranged from 400 to 1320 kg/m{sup 2}s and inlet temperatures ranged from 72 to 120 deg. C. The test section consisted of fuel-element simulators that were 9.5 mm in OD with the total heated length of about 1 m. Bulk-fluid and wall temperature profiles were recorded using a combination of 8 different thermocouples. Analysis of the data has confirmed that there are three distinct heat-transfer regimes for forced convention in supercritical fluids: 1) Normal heat transfer; 2) Deteriorated heat

  10. Coupling a sensory hair-cell bundle to cyber clones enhances nonlinear amplification.

    PubMed

    Barral, Jérémie; Dierkes, Kai; Lindner, Benjamin; Jülicher, Frank; Martin, Pascal

    2010-05-04

    The vertebrate ear benefits from nonlinear mechanical amplification to operate over a vast range of sound intensities. The amplificatory process is thought to emerge from active force production by sensory hair cells. The mechano-sensory hair bundle that protrudes from the apical surface of each hair cell can oscillate spontaneously and function as a frequency-selective, nonlinear amplifier. Intrinsic fluctuations, however, jostle the response of a single hair bundle to weak stimuli and seriously limit amplification. Most hair bundles are mechanically coupled by overlying gelatinous structures. Here, we assayed the effects of mechanical coupling on the hair-bundle amplifier by combining dynamic force clamp of a hair bundle from the bullfrog's saccule with real-time stochastic simulations of hair-bundle mechanics. This setup couples the hair bundle to two virtual hair bundles, called cyber clones, and mimics a situation in which the hair bundle is elastically linked to two neighbors with similar characteristics. We found that coupling increased the coherence of spontaneous hair-bundle oscillations. By effectively reducing noise, the synergic interplay between the hair bundle and its cyber clones also enhanced amplification of sinusoidal stimuli. All observed effects of coupling were in quantitative agreement with simulations. We argue that the auditory amplifier relies on hair-bundle cooperation to overcome intrinsic noise limitations and achieve high sensitivity and sharp frequency selectivity.

  11. 78 FR 29139 - Medicare Program; Bundled Payments for Care Improvement Model 1 Open Period

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-17

    ... participation in Model 1 of the Bundled Payments for Care Improvement initiative. DATES: Model 1 of the Bundled Payments for Care Improvement Deadline: Interested organizations must submit a Model 1 Open Period... regarding Model 1 of the Bundled Payments for Care Improvement initiative. For additional information...

  12. Exploring Differential Bundle Functioning in Mathematics by Gender: The Effect of Hierarchical Modelling

    ERIC Educational Resources Information Center

    Ong, Yoke Mooi; Williams, Julian; Lamprianou, Iasonas

    2013-01-01

    Researchers interested in exploring substantive group differences are increasingly attending to bundles of items (or testlets): the aim is to understand how gender differences, for instance, are explained by differential performances on different types or bundles of items, hence differential bundle functioning (DBF). Some previous work has…

  13. Analyzing the Light Energy Distribution in the Photosynthetic Apparatus of C4 Plants Using Highly Purified Mesophyll and Bundle-Sheath Thylakoids.

    PubMed Central

    Pfundel, E.; Nagel, E.; Meister, A.

    1996-01-01

    The chlorophyll fluorescence characteristics of mesophyll and bundle-sheath thylakoids from plant species with the C4 dicarboxylic acid pathway of photosynthesis were investigated using flow cytometry. Ten species with the NADP-malic enzyme (NADP-ME) biochemical type of C4 photosynthesis were tested: Digitaria sanguinalis (L.) Scop., Euphorbia maculata L., Portulaca grandiflora Hooker, Saccharum officinarum L., Setaria viridis (L.) Beauv., Zea mays L., and four species of the genus Flaveria. This study also included three species with NAD-ME biochemistry (Atriplex rosea L., Atriplex spongiosa F. Muell., and Portulaca oleracea L.). Two C4 species of unknown biochemical type were investigated: Cyperus papyrus L. and Atriplex tatarica L. Pure mesophyll and bundle-sheath thylakoids were prepared by flow cytometry and characterized by low-temperature fluorescence spectroscopy. In pure bundle-sheath thylakoids from many species with C4 photosynthesis of the NADP-ME type, significant amounts of photosystem II (PSII) emission can be detected by fluorescence spectroscopy. Simulation of fluorescence excitation spectra of these thylakoids showed that PSII light absorption contributes significantly to the apparent excitation spectrum of photosystem I. Model calculations indicated that the excitation energy of PSII is efficiently transferred to photosystem I in bundle-sheath thylakoids of many NADP-ME species. PMID:12226432

  14. Development of Design Technology on Thermal-Hydraulic Performance in Tight-Lattice Rod Bundle: IV Large Paralleled Simulation by the Advanced Two-fluid Model Code

    NASA Astrophysics Data System (ADS)

    Misawa, Takeharu; Yoshida, Hiroyuki; Akimoto, Hajime

    In Japan Atomic Energy Agency (JAEA), the Innovative Water Reactor for Flexible Fuel Cycle (FLWR) has been developed. For thermal design of FLWR, it is necessary to develop analytical method to predict boiling transition of FLWR. Japan Atomic Energy Agency (JAEA) has been developing three-dimensional two-fluid model analysis code ACE-3D, which adopts boundary fitted coordinate system to simulate complex shape channel flow. In this paper, as a part of development of ACE-3D to apply to rod bundle analysis, introduction of parallelization to ACE-3D and assessments of ACE-3D are shown. In analysis of large-scale domain such as a rod bundle, even two-fluid model requires large number of computational cost, which exceeds upper limit of memory amount of 1 CPU. Therefore, parallelization was introduced to ACE-3D to divide data amount for analysis of large-scale domain among large number of CPUs, and it is confirmed that analysis of large-scale domain such as a rod bundle can be performed by parallel computation with keeping parallel computation performance even using large number of CPUs. ACE-3D adopts two-phase flow models, some of which are dependent upon channel geometry. Therefore, analyses in the domains, which simulate individual subchannel and 37 rod bundle, are performed, and compared with experiments. It is confirmed that the results obtained by both analyses using ACE-3D show agreement with past experimental result qualitatively.

  15. Air/water subchannel measurements of the equilibrium quality and mass-flux distribution in a rod bundle. [BWR

    SciTech Connect

    Sterner, R.W.; Lahey, R.T. Jr.

    1983-07-01

    Subchannel measurements were performed in order to determine the equilibrium quality and mass flux distribution in a four rod bundle, using air/water flow. An isokinetic technique was used to sample the flow in the center, side and corner subchannels of this test section. Flow rates of the air and water in each sampled subchannel were measured. Experiments were performed for two test-section-average mass fluxes (0.333x10/sup 6/ and 0.666x10/sup 6/ lb/sub m//h-ft/sup 2/), and the test-section-average quality was varied from 0% to 0.54% for each mass flux. Single-phase liquid, bubbly, slug and churn-turbulent two-phase flow regimes were achieved. The observed data trends agreed with previous diabatic measurements in which the center subchannel had the highest quality and mass flux, while the corner subchannel had the lowest.

  16. Medical catheters thermally manipulated by fiber optic bundles

    DOEpatents

    Chastagner, Philippe

    1992-01-01

    A maneuverable medical catheter comprising a flexible tube having a functional tip. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts.

  17. Medical catheters thermally manipulated by fiber optic bundles

    DOEpatents

    Chastagner, P.

    1992-10-06

    A maneuverable medical catheter comprising a flexible tube having a functional tip is described. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts. 10 figs.

  18. Dimer model for Tau proteins bound in microtubule bundles

    NASA Astrophysics Data System (ADS)

    Hall, Natalie; Kluber, Alexander; Hayre, N. Robert; Singh, Rajiv; Cox, Daniel

    2013-03-01

    The microtubule associated protein tau is important in nucleating and maintaining microtubule spacing and structure in neuronal axons. Modification of tau is implicated as a later stage process in Alzheimer's disease, but little is known about the structure of tau in microtubule bundles. We present preliminary work on a proposed model for tau dimers in microtubule bundles (dimers are the minimal units since there is one microtubule binding domain per tau). First, a model of tau monomer was created and its characteristics explored using implicit solvent molecular dynamics simulation. Multiple simulations yield a partially collapsed form with separate positively/negatively charged clumps, but which are a factor of two smaller than required by observed microtubule spacing. We argue that this will elongate in dimer form to lower electrostatic energy at a cost of entropic ``spring'' energy. We will present preliminary results on steered molecular dynamics runs on tau dimers to estimate the actual force constant. Supported by US NSF Grant DMR 1207624.

  19. Quantum Turbulence: Vortex Bundle Collapse and Kolmogorov Spectrum

    NASA Astrophysics Data System (ADS)

    Nemirovskii, Sergey K.

    2016-12-01

    The statement of problem is motivated by the idea of modeling the classical turbulence with a set of chaotic quantized vortex filaments in superfluids. Among various arguments supporting the idea of quasi-classic behavior of quantum turbulence, the strongest, probably, is the k dependence of the spectra of energy, E(k)∝ k^{-5/3} obtained in numerical simulations and experiments. At the same time, the mechanism of classical vs. quantum turbulence is not clarified and the source of the k^{-5/3} dependence is unclear. In this work, we concentrated on the nonuniform vortex bundles. This choice is related to the actively discussed question concerning a role of collapses in the vortex dynamics in formation of turbulent spectra. We demonstrate that the nonuniform vortex bundles, which appear in result of nonlinear vortex dynamics, generates an energy spectrum which is close to the Kolmogorov dependence ∝ k^{-5/3}.

  20. Synthesis of bundled tungsten oxide nanowires with controllable morphology

    SciTech Connect

    Sun Shibin Zou Zengda; Min Guanghui

    2009-05-15

    Bundled tungsten oxide nanowires with controllable morphology were synthesized by a simple solvothermal method with tungsten hexachloride (WCl{sub 6}) as precursor and cyclohexanol as solvent. The as-synthesized products were systematically characterized by using scanning electron microscopy, X-ray diffraction and transition electron microscopy. Brunauer-Emmett-Teller gas-sorption measurements were also employed. Accompanied by an apparent drop of specific surface area from 151 m{sup 2} g{sup -1} for the longer nanowires synthesized using a lower concentration of WCl{sub 6} to 106 m{sup 2} g{sup -1} for the shorter nanowires synthesized using a higher concentration of WCl{sub 6}, a dramatically morphological evolution was also observed. With increasing concentration of tungsten hexachloride (WCl{sub 6}) in cyclohexanol, the nanostructured bundles became larger, shorter and straighter, and finally a block-shape product occurred.

  1. Curved Space-Times by Crystallization of Liquid Fiber Bundles

    NASA Astrophysics Data System (ADS)

    Hélein, Frédéric; Vey, Dimitri

    2017-01-01

    Motivated by the search for a Hamiltonian formulation of Einstein equations of gravity which depends in a minimal way on choices of coordinates, nor on a choice of gauge, we develop a multisymplectic formulation on the total space of the principal bundle of orthonormal frames on the 4-dimensional space-time. This leads quite naturally to a new theory which takes place on 10-dimensional manifolds. The fields are pairs of ((α ,ω ),π), where (α ,ω ) is a 1-form with coefficients in the Lie algebra of the Poincaré group and π is an 8-form with coefficients in the dual of this Lie algebra. The dynamical equations derive from a simple variational principle and imply that the 10-dimensional manifold looks locally like the total space of a fiber bundle over a 4-dimensional base manifold. Moreover this base manifold inherits a metric and a connection which are solutions of a system of Einstein-Cartan equations.

  2. Nanostructured Composites: Effective Mechanical Property Determination of Nanotube Bundles

    NASA Technical Reports Server (NTRS)

    Saether, E.; Pipes, R. B.; Frankland, S. J. V.

    2002-01-01

    Carbon nanotubes naturally tend to form crystals in the form of hexagonally packed bundles or ropes that should exhibit a transversely isotropic constitutive behavior. Although the intratube axial stiffness is on the order of 1 TPa due to a strong network of delocalized bonds, the intertube cohesive strength is orders of magnitude less controlled by weak, nonbonding van der Waals interactions. An accurate determination of the effective mechanical properties of nanotube bundles is important to assess potential structural applications such as reinforcement in future composite material systems. A direct method for calculating effective material constants is developed in the present study. The Lennard-Jones potential is used to model the nonbonding cohesive forces. A complete set of transverse moduli are obtained and compared with existing data.

  3. Buckling of a fiber bundle embedded in epoxy

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Sohi, M. M.

    1986-01-01

    Buckling of a fiber bundle embedded in epoxy resin was studied to gain insight into compressive failure mechanisms in unidirectional composites. The fibers used were E-glass, T300 graphite, T700 graphite, and P75 graphite. These fibers were combined with two different resins: Epon 815/V140 and Epon 828/Z. In both resins the failure mode of the bundle was found to be microbuckling of fibers for the first three types of fibers; however, the high-modulus P75 fibers failed in shear without any sign of microbuckling. The strains at which microbuckling occurred were higher than the compressive failure strains of the corresponding unidirectional composites. In the soft resin, Epon 815/V140, fibers buckled at lower strains than in the stiff resin, Epon 828/Z. The buckling strains and the segment lengths followed the trends predicted for a single filament embedded in an infinite matrix.

  4. CAT reconstruction and potting comparison of a LMFBR fuel bundle

    SciTech Connect

    Betten, P.R.; Tow, D.M.

    1984-04-01

    A standard Liquid Metal Fast Breeder Reactor (LMFBR) subassembly used in the Experimental Breeder Reactor II (EBR-II) was investigated, by remote techniques, for fuel bundle distortion by both nondestructive and destructive methods, and the results from both methods were compared. The non-destructive method employed neutron tomography to reconstruct the locations of fuel elements through the use of a maximum entropy reconstruction algorithm known as MENT. The destructive method consisted of ''potting'' (a technique that embeds and permanently fixes the fuel elements in a solid matrix) the subassembly, and then cutting and polishing the individual sections. The comparison indicated that the tomography reconstruction provided good results in describing the bundle geometry and spacer-wire locations, with the overall resolution being on the order of a spacer-wire diameter. A dimensional consistency check indicated that the element and spacer-wire dimensions were accurately reproduced in the reconstruction.

  5. Cofilin-mediated actin dynamics promotes actin bundle formation during Drosophila bristle development

    PubMed Central

    Wu, Jing; Wang, Heng; Guo, Xuan; Chen, Jiong

    2016-01-01

    The actin bundle is an array of linear actin filaments cross-linked by actin-bundling proteins, but its assembly and dynamics are not as well understood as those of the branched actin network. Here we used the Drosophila bristle as a model system to study actin bundle formation. We found that cofilin, a major actin disassembly factor of the branched actin network, promotes the formation and positioning of actin bundles in the developing bristles. Loss of function of cofilin or AIP1, a cofactor of cofilin, each resulted in increased F-actin levels and severe defects in actin bundle organization, with the defects from cofilin deficiency being more severe. Further analyses revealed that cofilin likely regulates actin bundle formation and positioning by the following means. First, cofilin promotes a large G-actin pool both locally and globally, likely ensuring rapid actin polymerization for bundle initiation and growth. Second, cofilin limits the size of a nonbundled actin-myosin network to regulate the positioning of actin bundles. Third, cofilin prevents incorrect assembly of branched and myosin-associated actin filament into bundles. Together these results demonstrate that the interaction between the dynamic dendritic actin network and the assembling actin bundles is critical for actin bundle formation and needs to be closely regulated. PMID:27385345

  6. Structural characterizations and electronic properties of boron nitride nanotube crystalline bundles

    NASA Astrophysics Data System (ADS)

    Zheng, Fawei; Zhou, Gang; Hao, Shaogang; Duan, Wenhui

    2005-09-01

    The structural characterizations and electronic properties of aligned armchair single-walled boron nitride nanotube (BNNT) bundles are theoretically investigated. In the spontaneous bundling process, the cylindrical shapes of bundled BNNTs are preserved all along, whereas their diameters expand, then shrink, and return back to the initial dimensions. Owing to the nonuniform distribution of positive and negative charges among BNNTs, the multipole interaction in bundles is completely dependent upon the chirality of each BNNT and the arrangement of bundled BNNTs. The effect of intertube coupling on the dispersions of BNNT bundles is demonstrated. Our systematical simulations might be helpful for the understanding of potential applications of BNNT bundles in the nanometer manufacturing techniques such as doping, adsorption, and derivative synthesis.

  7. Determinants of contractile forces generated in disorganized actomyosin bundles.

    PubMed

    Kim, Taeyoon

    2015-04-01

    Actomyosin machinery is a fundamental engine consisting mostly of actin filaments, molecular motors, and passive cross-linkers, generating mechanical forces required for biological processes of non-muscle cells such as cell migration, cytokinesis, and morphogenesis. Although the molecular and physical properties of key elements in the actomyosin machinery have been characterized well, it still remains unclear how macroscopic force buildup and dissipation in actomyosin networks and bundles depend on the microscopic properties of individual cytoskeletal components and their local interactions. To bridge such a gap between macroscopic and microscopic scales, we have developed a three-dimensional computational model of actomyosin bundles clamped to an elastic substrate with minimal components: actin filaments, passive cross-linkers, and active motors. Our model accounts for several key features neglected by previous studies despite their significance for force generation, such as realistic structure and kinetics of the motors. Using the model, we systematically investigated how net tension in actomyosin bundles is governed via interplay between motors and cross-linkers. We demonstrated motors can generate large tension on a bundle in the absence of cross-linkers in a very inefficient, unstable manner. Cross-linkers help motors to generate their maximum potential forces as well as enhance overall connectivity, leading to much higher efficiency and stability. We showed further that the cross-linkers behave as a molecular clutch with tunable friction which has quite distinct effects on net tension depending on their cross-linking angles. We also examined the source of symmetry breaking between tensile and compressive forces during tension generation process and discussed how the length and dynamics of actin filaments and the stiffness of the elastic substrate can affect the generated tension.

  8. Arrays of Bundles of Carbon Nanotubes as Field Emitters

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Bronkowski, Michael

    2007-01-01

    Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

  9. Fuel bundle design for enhanced usage of plutonium fuel

    DOEpatents

    Reese, A.P.; Stachowski, R.E.

    1995-08-08

    A nuclear fuel bundle includes a square array of fuel rods each having a concentration of enriched uranium and plutonium. Each rod of an interior array of the rods also has a concentration of gadolinium. The interior array of rods is surrounded by an exterior array of rods void of gadolinium. By this design, usage of plutonium in the nuclear reactor is enhanced. 10 figs.

  10. Image processing for cameras with fiber bundle image relay.

    PubMed

    Olivas, Stephen J; Arianpour, Ashkan; Stamenov, Igor; Morrison, Rick; Stack, Ron A; Johnson, Adam R; Agurok, Ilya P; Ford, Joseph E

    2015-02-10

    Some high-performance imaging systems generate a curved focal surface and so are incompatible with focal plane arrays fabricated by conventional silicon processing. One example is a monocentric lens, which forms a wide field-of-view high-resolution spherical image with a radius equal to the focal length. Optical fiber bundles have been used to couple between this focal surface and planar image sensors. However, such fiber-coupled imaging systems suffer from artifacts due to image sampling and incoherent light transfer by the fiber bundle as well as resampling by the focal plane, resulting in a fixed obscuration pattern. Here, we describe digital image processing techniques to improve image quality in a compact 126° field-of-view, 30 megapixel panoramic imager, where a 12 mm focal length F/1.35 lens made of concentric glass surfaces forms a spherical image surface, which is fiber-coupled to six discrete CMOS focal planes. We characterize the locally space-variant system impulse response at various stages: monocentric lens image formation onto the 2.5 μm pitch fiber bundle, image transfer by the fiber bundle, and sensing by a 1.75 μm pitch backside illuminated color focal plane. We demonstrate methods to mitigate moiré artifacts and local obscuration, correct for sphere to plane mapping distortion and vignetting, and stitch together the image data from discrete sensors into a single panorama. We compare processed images from the prototype to those taken with a 10× larger commercial camera with comparable field-of-view and light collection.

  11. "Bundle Data" Approach at GES DISC Targeting Natural Hazards

    NASA Astrophysics Data System (ADS)

    Shie, C. L.; Shen, S.; Kempler, S. J.

    2015-12-01

    Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the "Big", i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served "Big" Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard/event, we have thus initiated a "Bundle Data" approach in 2014, first targeting the hurricane event/topic. We have recently worked on new topics such as volcano and blizzard. The "bundle data" of a specific hazard/event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant ("knowledge-based") data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online "Data Cookbook" site at GES DISC is the current host for the "bundle data". We are now also planning on developing an "Automated Virtual Collection Framework" that shall eventually accommodate the "bundle data", as well as further improve our management in "Big Data".

  12. The Business of Bundling: Joining Forces on Joint Replacement.

    PubMed

    Kaldy, Joanne

    2016-03-01

    A mandated bundled-payment program for joint replacement is in place in several regions across the country, and practitioners such as pharmacists are still sorting out their roles in this federal initiative. To get involved, pharmacists need to establish connections with area hospitals and physician groups to promote and document their ability to manage medications, reduce and eliminate medication-related problems and rehospitalizations, and work with patients to maximize adherence and improve communication for those undergoing hip and knee replacement.

  13. Topological Aharonov-Bohm Effect and Pseudo-Particle Bundles

    NASA Astrophysics Data System (ADS)

    Payandeh, Farrin

    2016-10-01

    Exploiting a topological approach, we discuss the outstanding Aharonov-Bohm effect and try to explain it in the context of the principal P(M, U(1)) bundle. We show that this could be done by excluding a specific region from the main manifold which acts as the solenoid around which the effect is observed. Moreover, we discuss the impacts of pseudo-particles in this topological approach.

  14. Background independent noncommutative gravity from Fedosov quantization of endomorphism bundle

    NASA Astrophysics Data System (ADS)

    Dobrski, Michał

    2017-04-01

    A model of noncommutative gravity is constructed by means of Fedosov deformation quantization of an endomorphism bundle. The fields describing noncommutativity—symplectic form and symplectic connection—are dynamical, and the resulting theory is coordinate covariant and background independent. Its interpretation in terms of a Seiberg–Witten map is provided. Also, a new action for ordinary (commutative) general relativity is given, which in the present context appears as a commutative limit of noncommutative theory.

  15. Bundle Data Approach at GES DISC Targeting Natural Hazards

    NASA Technical Reports Server (NTRS)

    Shie, Chung-Lin; Shen, Suhung; Kempler, Steven J.

    2015-01-01

    Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the Big, i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served Big Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard event, we have thus initiated a Bundle Data approach in 2014, first targeting the hurricane event topic. We have recently worked on new topics such as volcano and blizzard. The bundle data of a specific hazard event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant (knowledge--based) data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online Data Cookbook site at GES DISC is the current host for the bundle data. We are now also planning on developing an Automated Virtual Collection Framework that shall eventually accommodate the bundle data, as well as further improve our management in Big Data.

  16. Ab initio study of MoS2 nanotube bundles

    NASA Astrophysics Data System (ADS)

    Verstraete, Matthieu; Charlier, Jean-Christophe

    2003-07-01

    Recently, the synthesis of a new phase of MoS2I1/3 stoichiometry was reported [M. Remskar, A. Mrzel, Z. Skraba, A. Jesih, M. Ceh, J. Demšar, P. Stadelmann, F. Lévy, and D. Mihailovic, Science 292, 479 (2001)]. Electron microscope images and diffraction data were interpreted to indicate bundles of sub-nanometer-diameter single-wall MoS2 nanotubes. After experimental characterization, the structure was attributed to an assembly of “armchair” nanotubes with interstitial iodine. Using first-principles total-energy calculations, bundles of MoS2 nanotubes with different topologies and stoichiometries are investigated. All of the systems are strongly metallic. Configurations with “zigzag” structures are found to be more stable energetically than the “armchair” ones, though all of the structures have similar stabilities. After relaxation, there remain several candidates which give a lattice parameter in relative agreement with experiment. Further, spin-polarized calculations indicate that a structure with armchair tubes iodine atoms in their center acquires a very large spontaneous magnetic moment of 12μB, while the other structures are nonmagnetic. Our ab initio calculations show that in most of the other structures, the tubes are very strongly bound together, and that the compounds should be considered as a crystal, rather than as a bundle of tubes in the habitual sense.

  17. Frontostriatal fiber bundle compromise in HIV infection without dementia

    PubMed Central

    Pfefferbaum, Adolf; Rosenbloom, Margaret J.; Rohlfing, Torsten; Kemper, Carol A.; Deresinski, Stanley; Sullivan, Edith V.

    2010-01-01

    Background Quantitative fiber tracking derived from diffusion tensor imaging (DTI) was used to determine whether white matter association, projection, or commissural tracts are affected in nondemented individuals with HIV infection and to identify the regional distribution of sparing and impairment of fiber systems. Methods DTI measured fractional anisotropy and diffusivity, quantified separately for longitudinal (λL) diffusivity (index of axonal injury) and transverse (λT) diffusivity (index of myelin injury), in 11 association and projection white matter tracts and six commissural tracts in 29 men and 13 women with HIV infection and 88 healthy, age-matched controls (42 men and 46 women). Results The total group of HIV-infected individuals had higher diffusivity (principally longitudinal) than controls in the posterior sectors of the corpus callosum, internal and external capsules, and superior cingulate bundles. High longitudinal diffusivity, indicative of axonal compromise, was especially prominent in posterior callosal sectors, fornix, and superior cingulate bundle in HIV with AIDS. Unmedicated patients had notably high transverse diffusivity, indicative of myelin compromise, in the occipital forceps, inferior cingulate bundle, and superior longitudinal fasciculus. Pontocerebellar projection fibers were resistant to HIV effects as were commissural fibers coursing through premotor and sensorimotor callosal sectors. Conclusion This quantitative survey of brain fiber tract integrity indicates that even nondemented HIV patients can have neuroradiological evidence for damage to association and commissural tracts. These abnormalities were vulnerable to exacerbation with AIDS and possibly mitigated by HAART. PMID:19730350

  18. Creep rupture of fiber bundles: A molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Linga, G.; Ballone, P.; Hansen, Alex

    2015-08-01

    The creep deformation and eventual breaking of polymeric samples under a constant tensile load F is investigated by molecular dynamics based on a particle representation of the fiber bundle model. The results of the virtual testing of fibrous samples consisting of 40 000 particles arranged on Nc=400 chains reproduce characteristic stages seen in the experimental investigations of creep in polymeric materials. A logarithmic plot of the bundle lifetime τ versus load F displays a marked curvature, ruling out a simple power-law dependence of τ on F . A power law τ ˜F-4 , however, is recovered at high load. We discuss the role of reversible bond breaking and formation on the eventual fate of the sample and simulate a different type of creep testing, imposing a constant stress rate on the sample up to its breaking point. Our simulations, relying on a coarse-grained representation of the polymer structure, introduce new features into the standard fiber bundle model, such as real-time dynamics, inertia, and entropy, and open the way to more detailed models, aiming at material science aspects of polymeric fibers, investigated within a sound statistical mechanics framework.

  19. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2011-03-01

    Assemblies of filamentous biopolymers are hierarchical materials in which the properties of the overall assemblage are determined by structure and interactions between constituent particles at all hierarchical levels. For example, the overall bending rigidity of a two bundled filaments greatly depends on the bending rigidity of, and the adhesion strength between individual filaments. However, another property of importance is the ability for the filaments to slide freely against one another. Everyday experience indicates that it is much easier to bend a stack of papers in which individual sheets freely slide past each other than the same stack of papers in which all the sheets are irreversibly glued together. Similarly, in filamentous structures the ability for local re-arrangement is of the utmost importance in determining the properties of the structures observed. In order to study this phenomenon we create bundles of biopolymers by inducing attractive interactions between actin filaments via the depletion mechanism. We find that bundles of actin filaments to do not slide freely across one another. In order to characterize these sliding interactions, we perform active experiments using laser tweezers to pull one filament across the other at constant velocity.

  20. Evaluating pulp stiffness from fibre bundles by ultrasound

    NASA Astrophysics Data System (ADS)

    Karppinen, Timo; Montonen, Risto; Määttänen, Marjo; Ekman, Axel; Myllys, Markko; Timonen, Jussi; Hæggström, Edward

    2012-06-01

    A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The developed tester employs (933 ± 15) kHz tweezer-like ultrasonic transducers and time-of-flight measurement through (9.0 ± 2.5) mm long and (0.8 ± 0.1) mm thick fibre bundles kept at (19.1 ± 0.4) °C and (62 ± 1)% RH. We determined the stiffness of soft wood pulps produced by three kraft pulping modifications: standard kraft pulp, (5.2 ± 0.4) GPa, prehydrolysis kraft pulp, (4.3 ± 0.4) GPa, and alkali extracted prehydrolysis kraft pulp, (3.3 ± 0.4) GPa. Prehydrolysis and alkali extraction processes mainly lowered the hemicellulose content of the pulps, which essentially decreased the fibre-wall stiffness hence impairing the stiffness of the fibre networks. Our results indicate that the method allows ranking of pulps according to their stiffness determined from bundle-like samples taken at an early phase of the papermaking process.

  1. Medicare's bundling pilot: including post-acute care services.

    PubMed

    Dummit, Laura A

    2011-03-28

    Fee-for-service Medicare, in which a separate payment is made for each service, rewards health care providers for delivering more services, but not necessarily coordinating those services over time or across settings. To help address these concerns, the Patient Protection and Affordable Care Act of 2010 requires Medicare to experiment with making a bundled payment for a hospitalization plus post-acute care, that is, the recuperative or rehabilitative care following a hospital discharge. This bundled payment approach is intended to promote more efficient care across the acute/post-acute episode because the entity that receives the payment has financial incentives to keep episode costs below the payment. Although the entity is expected to control costs through improved care coordination and efficiency, it could stint on care or avoid expensive patients instead. This issue brief focuses on the unique challenges posed by the inclusion of post-acute care services in a payment bundle and special considerations in implementing and evaluating the episode payment approach.

  2. Increasing silk fibre strength through heterogeneity of bundled fibrils.

    PubMed

    Cranford, Steven W

    2013-05-06

    Can naturally arising disorder in biological materials be beneficial? Materials scientists are continuously attempting to replicate the exemplary performance of materials such as spider silk, with detailed techniques and assembly procedures. At the same time, a spider does not precisely machine silk-imaging indicates that its fibrils are heterogeneous and irregular in cross section. While past investigations either focused on the building material (e.g. the molecular scale protein sequence and behaviour) or on the ultimate structural component (e.g. silk threads and spider webs), the bundled structure of fibrils that compose spider threads has been frequently overlooked. Herein, I exploit a molecular dynamics-based coarse-grain model to construct a fully three-dimensional fibril bundle, with a length on the order of micrometres. I probe the mechanical behaviour of bundled silk fibrils with variable density of heterogenic protrusions or globules, ranging from ideally homogeneous to a saturated distribution. Subject to stretching, the model indicates that cooperativity is enhanced by contact through low-force deformation and shear 'locking' between globules, increasing shear stress transfer by up to 200 per cent. In effect, introduction of a random and disordered structure can serve to improve mechanical performance. Moreover, addition of globules allows a tuning of free volume, and thus the wettability of silk (with implications for supercontraction). These findings support the ability of silk to maintain near-molecular-level strength at the scale of silk threads, and the mechanism could be easily adopted as a strategy for synthetic fibres.

  3. F-actin bundles in Drosophila bristles are assembled from modules composed of short filaments

    PubMed Central

    1996-01-01

    The actin bundles in Drosophila bristles run the length of the bristle cell and are accordingly 65 microns (microchaetes) or 400 microns (macrochaetes) in length, depending on the bristle type. Shortly after completion of bristle elongation in pupae, the actin bundles break down as the bristle surface becomes chitinized. The bundles break down in a bizarre way; it is as if each bundle is sawed transversely into pieces that average 3 microns in length. Disassembly of the actin filaments proceeds at the "sawed" surfaces. In all cases, the cuts in adjacent bundles appear in transverse register. From these images, we suspected that each actin bundle is made up of a series of shorter bundles or modules that are attached end-to-end. With fluorescent phalloidin staining and serial thin sections, we show that the modular design is present in nondegenerating bundles. Decoration of the actin filaments in adjacent bundles in the same bristle with subfragment 1 of myosin reveals that the actin filaments in every module have the same polarity. To study how modules form developmentally, we sectioned newly formed and elongating bristles. At the bristle tip are numerous tiny clusters of 6-10 filaments. These clusters become connected together more basally to form filament bundles that are poorly organized, initially, but with time become maximally cross-linked. Additional filaments are then added to the periphery of these organized bundle modules. All these observations make us aware of a new mechanism for the formation and elongation of actin filament bundles, one in which short bundles are assembled and attached end-to-end to other short bundles, as are the vertical girders between the floors of a skyscraper. PMID:8947552

  4. Flow map layout via spiral trees.

    PubMed

    Verbeek, Kevin; Buchin, Kevin; Speckmann, Bettina

    2011-12-01

    Flow maps are thematic maps that visualize the movement of objects, such as people or goods, between geographic regions. One or more sources are connected to several targets by lines whose thickness corresponds to the amount of flow between a source and a target. Good flow maps reduce visual clutter by merging (bundling) lines smoothly and by avoiding self-intersections. Most flow maps are still drawn by hand and only few automated methods exist. Some of the known algorithms do not support edge-bundling and those that do, cannot guarantee crossing-free flows. We present a new algorithmic method that uses edge-bundling and computes crossing-free flows of high visual quality. Our method is based on so-called spiral trees, a novel type of Steiner tree which uses logarithmic spirals. Spiral trees naturally induce a clustering on the targets and smoothly bundle lines. Our flows can also avoid obstacles, such as map features, region outlines, or even the targets. We demonstrate our approach with extensive experiments.

  5. Physical modeling and numerical simulation of subcooled boiling in one- and three-dimensional representation of bundle geometry

    SciTech Connect

    Bottoni, M.; Lyczkowski, R.; Ahuja, S.

    1995-07-01

    Numerical simulation of subcooled boiling in one-dimensional geometry with the Homogeneous Equilibrium Model (HEM) may yield difficulties related to the very low sonic velocity associated with the HEM. These difficulties do not arise with subcritical flow. Possible solutions of the problem include introducing a relaxation of the vapor production rate. Three-dimensional simulations of subcooled boiling in bundle geometry typical of fast reactors can be performed by using two systems of conservation equations, one for the HEM and the other for a Separated Phases Model (SPM), with a smooth transition between the two models.

  6. Experimental study on convective heat transfer coefficient around a vertical hexagonal rod bundle

    NASA Astrophysics Data System (ADS)

    Makhmalbaf, M. H. M.

    2012-06-01

    Research on convective heat transfer coefficient around a rod bundle has many diverse applications in industry. So far, many studies have been conducted in correlations related to internal and turbulent fully-developed flow. Comparison shows that Dittus-Boelter, Sieder-Tate and Petukhov have so far been the most practical correlations in fully-developed turbulent fluid flow heat transfer. The present study conducts an experimental examination of the validity of these frequently-applied correlations and introduces a manufactured test facility as well. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) can fulfil extensive applications. The paper also studies the major deviation sources in data measurements, calibrations and turbulence of fluid flow in this. Finally, regarding to sufficient number of experiments in a vast fluid mean velocity range (3,800 < Re < 40,000), a new curve and correlation are presented and the results are compared with the above mentioned commonly-applied correlations.

  7. CHF Performance of Hybrid Mixing Vane Grid for a Nuclear Fuel Bundle

    SciTech Connect

    Shin, Chang-Hwan; Chun, Tae-Hyun; Choo, Yeon-Jun; Moon, Sang-Ki; Chun, Se-Young

    2007-07-01

    Numerous studies have shown that the mixing vanes of the spacer grids in a nuclear fuel rod bundle increase the Critical Heat Flux (CHF) significantly. The amount of the CHF enhancement depends strongly on the design of the mixing vanes such as the vane shape and vane bending angle. Recently a new mixing vane design was developed for an advanced spacer grid. It is called a Hybrid Mixing Vane. The main objective of this work is to evaluate the CHF performance of the hybrid vane grid and to compare it with that of a split vane grid. Three kinds of rod bundles were tested for the above objectives: no mixing vane grids, the hybrid mixing vane grids, and the split mixing vane grids. To measure the CHF data, 5x5 rod bundle experiments were conducted in the FTHEL (Freon Thermal Hydraulic Experiment Loop). Each experiment was performed by maintaining the following system conditions as constant: inlet pressure, inlet temperature, and mass flow rate. The experiments were performed in ranges of the inlet pressure, P{sub in} = 2000{approx}3000 kPa, mass flux, G = 1000{approx}3000 kg/m{sup 2}s, and inlet subcooling, {delta}h{sub in}= 10{approx}55 kJ/kg, which simulates the PWR operating conditions for a water equivalence through a fluid-to-fluid modeling. The CHF performances were compared with the data belonging to a PWR's operating conditions; a pressure of 2000{approx}3000 kPa and a mass flux of 1500{approx}3000 kg/m{sup 2}s. The average of the CHF increase for the hybrid mixing grids for 20 data sets is 18.2% higher than that for the no vane grids. While the average of the CHF increase for the split mixing vane grids for 20 data sets is 14.5% higher than that for the no vane grids. Consequently, the CHF performance of the hybrid mixing vane grid is superior by about 4% to that of the split mixing vane grid near the normal PWR operating conditions even under a longer grid span than usual. (authors)

  8. Increasing silk fibre strength through heterogeneity of bundled fibrils

    PubMed Central

    Cranford, Steven W.

    2013-01-01

    Can naturally arising disorder in biological materials be beneficial? Materials scientists are continuously attempting to replicate the exemplary performance of materials such as spider silk, with detailed techniques and assembly procedures. At the same time, a spider does not precisely machine silk—imaging indicates that its fibrils are heterogeneous and irregular in cross section. While past investigations either focused on the building material (e.g. the molecular scale protein sequence and behaviour) or on the ultimate structural component (e.g. silk threads and spider webs), the bundled structure of fibrils that compose spider threads has been frequently overlooked. Herein, I exploit a molecular dynamics-based coarse-grain model to construct a fully three-dimensional fibril bundle, with a length on the order of micrometres. I probe the mechanical behaviour of bundled silk fibrils with variable density of heterogenic protrusions or globules, ranging from ideally homogeneous to a saturated distribution. Subject to stretching, the model indicates that cooperativity is enhanced by contact through low-force deformation and shear ‘locking’ between globules, increasing shear stress transfer by up to 200 per cent. In effect, introduction of a random and disordered structure can serve to improve mechanical performance. Moreover, addition of globules allows a tuning of free volume, and thus the wettability of silk (with implications for supercontraction). These findings support the ability of silk to maintain near-molecular-level strength at the scale of silk threads, and the mechanism could be easily adopted as a strategy for synthetic fibres. PMID:23486175

  9. Photothermal imaging bundle system for estimating tissue oxygen saturation

    NASA Astrophysics Data System (ADS)

    Milstein, Yonat; Allon, Dror M.; Harrington, James; Bledt, Carlos; Gannot, Israel

    2012-01-01

    The objective of this study is to validate a method for the measurement of tissue oxygen saturation level via a thermal imaging bundle in-vitro and in-vivo. The method consists of a thermal imaging system and an algorithm which estimates the compound concentration according to the temperature rise of the tissue. A temperature rise is obtained by illuminating the tissue in the NIR range and is measured using a thermal camera and a coherent thermal imaging bundle for non-invasive transendoscopic use. The system was validated using agar phantoms of varying concentrations of Methylene Blue and ICG as well as blood samples. The algorithm estimated the Methylene Blue relative amount and the results were compared to the real relative amount. The calculated RMS of the error was 5.12%, a satisfying value for this stage. In the blood samples, for oxygenation levels higher than 50% the RMS of the error was 5.79%. Once the system was verified a portable system was built for clinical use, this system was also evaluated on agar phantoms and the RMS of the error was 10.64%. As a result of the encouraging experiments in-vivo, animal trials were performed. The oxygenation levels of mice were decreased and were estimated respectively using our system. The system determined a small decrease in the tissue oxygen saturation of the mice. These results verify the algorithm's and bundle's suitability for the use in a non-invasive system. They provide motivation for performing more complex in-vitro experiments and moving on to clinical trials.

  10. "Bundle" Practices and Ventilator-Associated Events: Not Enough.

    PubMed

    O'Horo, John C; Lan, Haitao; Thongprayoon, Charat; Schenck, Louis; Ahmed, Adil; Dziadzko, Mikhail

    2016-12-01

    OBJECTIVE Ventilator-associated events (VAEs) are nosocomial events correlated with length of stay, costs, and mortality. Current ventilator bundle practices target the older definition of ventilator-associated pneumonia and have not been systematically evaluated for their impact on VAEs. DESIGN Retrospective cohort study. SETTING Tertiary medical center between January 2012 and August 2014. PARTICIPANTS All adult patients ventilated for at least 24 hours at our institution. INTERVENTIONS We conducted univariate analyses for compliance with each element; we focused on VAEs occurring within a 2-day window of failure to meet any ventilator bundle element. We used Cox proportional hazard models to assess the effect of stress ulcer prophylaxis, deep vein thrombosis (DVT) prophylaxis, oral care, and sedation breaks on VAEs. We adjusted models for gender, age, and Acute Physiology and Chronic Health Evaluation (APACHE) III scores. RESULTS Our cohort comprised 2,660 patients with 16,858 ventilator days and 77 VAEs. Adjusting for APACHE score and gender, only oral care was associated with a reduction in the risk of VAE (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.26-0.77). The DVT prophylaxis and sedation breaks did not show any significant impact on VAEs. Stress ulcer prophylaxis trended toward an increased risk of VAE (HR, 1.59; 95% CI, 1.00-2.56). CONCLUSION Although limited by a low baseline rate of VAEs, existing ventilator bundle practices do not appear to target VAEs well. Oral care is clearly important, but the impact of DVT prophylaxis, sedation breaks, and especially stress ulcer prophylaxis are questionable at best. Infect Control Hosp Epidemiol 2016;1453-1457.

  11. Noise alters hair-bundle mechanics at the cochlear apex

    NASA Astrophysics Data System (ADS)

    Strimbu, C. Elliott; Fridberger, Anders

    2015-12-01

    Exposure to loud sounds can lead to both permanent and short term changes in auditory sensitivity. Permanent hearing loss is often associated with gross changes in cochlear morphology including the loss of hair cells and auditory nerve fibers while the mechanisms of short term threshold shifts are much less well understood and may vary at different locations across the cochlea. Previous reports suggest that exposure to loud sounds leads to a decrease in the cochlear microphonic potential and in the stiffness of the organ of Corti. Because the cochlear microphonic reflects changes in the membrane potential of the hair cells, this suggests that hair-bundle motion should be reversibly altered following exposure to loud sounds. Using an in vitro preparation of the guinea pig temporal bone we investigate changes in the micro-mechanical response near the cochlear apex following a brief (up to 10 - 20 minutes) exposure to loud (˜ 120 dB) tones near the best frequency at this location. We use time-resolved confocal imaging to record the motion of outer hair cell bundles before and after acoustic overstimulation. We have also recorded larger-scale structural views of the organ of Corti before and after exposure to the loud sound. Conventional electrophysiological techniques are used measure the cochlear microphonic potential. As has been previously reported, following acoustic overexposure the cochlear microphonic declines in value and typically recovers on the order of 30 - 60 minutes. Hair-bundle trajectories are affected following the loud sound and typically recover on a somewhat faster time scale than the microphonic potential, although the results vary considerably across preparations. Preliminary results also suggest reversible changes in the hair cell's resting potential following the loud sound.

  12. Local Pixel Bundles: Bringing the Pixels to the People

    NASA Astrophysics Data System (ADS)

    Anderson, Jay

    2014-12-01

    The automated galaxy-based alignment software package developed for the Frontier Fields program (hst2galign, see Anderson & Ogaz 2014 and http://www.stsci.edu/hst/campaigns/frontier-fields/) produces a direct mapping from the pixels of the flt frame of each science exposure into a common master frame. We can use these mappings to extract the flt-pixels in the vicinity of a source of interest and package them into a convenient "bundle". In addition to the pixels, this data bundle can also contain "meta" information that will allow users to transform positions from the flt pixels to the reference frame and vice-versa. Since the un-resampled pixels in the flt frames are the only true constraints we have on the astronomical scene, the ability to inter-relate these pixels will enable many high-precision studies, such as: point-source-fitting and deconvolution with accurate PSFs, easy exploration of different image-combining algorithms, and accurate faint-source finding and photometry. The data products introduced in this ISR are a very early attempt to provide the flt-level pixel constraints in a package that is accessible to more than the handful of experts in HST astrometry. The hope is that users in the community might begin using them and will provide feedback as to what information they might want to see in the bundles and what general analysis packages they might find useful. For that reason, this document is somewhat informally written, since I know that it will be modified and updated as the products and tools are optimized.

  13. Bound constrained bundle adjustment for reliable 3D reconstruction

    PubMed Central

    Gong, Yuanzheng; Meng, De; Seibel, Eric J.

    2015-01-01

    Bundle adjustment (BA) is a common estimation algorithm that is widely used in machine vision as the last step in a feature-based three-dimensional (3D) reconstruction algorithm. BA is essentially a non-convex non-linear least-square problem that can simultaneously solve the 3D coordinates of all the feature points describing the scene geometry, as well as the parameters of the camera. The conventional BA takes a parameter either as a fixed value or as an unconstrained variable based on whether the parameter is known or not. In cases where the known parameters are inaccurate but constrained in a range, conventional BA results in an incorrect 3D reconstruction by using these parameters as fixed values. On the other hand, these inaccurate parameters can be treated as unknown variables, but this does not exploit the knowledge of the constraints, and the resulting reconstruction can be erroneous since the BA optimization halts at a dramatically incorrect local minimum due to its non-convexity. In many practical 3D reconstruction applications, unknown variables with range constraints are usually available, such as a measurement with a range of uncertainty or a bounded estimate. Thus to better utilize these pre-known, constrained, but inaccurate parameters, a bound constrained bundle adjustment (BCBA) algorithm is proposed, developed and tested in this study. A scanning fiber endoscope (the camera) is used to capture a sequence of images above a surgery phantom (the object) of known geometry. 3D virtual models are reconstructed based on these images and then compared with the ground truth. The experimental results demonstrate BCBA can achieve a more reliable, rapid, and accurate 3D reconstruction than conventional bundle adjustment. PMID:25969115

  14. Heterotic non-Kähler geometries via polystable bundles on Calabi-Yau threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Garcia-Fernandez, Mario

    2012-02-01

    In arXiv:1008.1018 it is shown that a given stable vector bundle V on a Calabi-Yau threefold X which satisfies c2(X)=c2(V) can be deformed to a solution of the Strominger system and the equations of motion of heterotic string theory. In this note we extend this result to the polystable case and construct explicit examples of polystable bundles on elliptically fibered Calabi-Yau threefolds where it applies. The polystable bundle is given by a spectral cover bundle, for the visible sector, and a suitably chosen bundle, for the hidden sector. This provides a new class of heterotic flux compactifications via non-Kähler deformation of Calabi-Yau geometries with polystable bundles. As an application, we obtain examples of non-Kähler deformations of some three generation GUT models.

  15. Synthesis and Self-Assembly of Bundle-Forming α-Helical Peptide-Dendron Hybrids.

    PubMed

    Marine, Jeannette E; Song, Shuang; Liang, Xiaoli; Rudick, Jonathan G

    2016-01-11

    Dendronized helix bundle assemblies combine the sequence diversity and folding properties of proteins with the tailored physical properties of dendrimers. Assembly of peptide-dendron hybrids into α-helical bundles encapsulates the helix bundle motif in a dendritic sheath that will allow the functional, protein-like domain to be transplanted to nonbiological environments. A bioorthogonal graft-to synthetic strategy for preparing helix bundle-forming peptide-dendron hybrids is described herein for hybrids 1a, 1b, and 2. Titration experiments monitored by circular dichroism spectroscopy support our self-assembly model for how the peptide-dendron hybrids self-assemble into α-helical bundles with the dendrons on outside of the bundle.

  16. Synthesis and Self-Assembly of Bundle-Forming α-Helical Peptide–Dendron Hybrids

    PubMed Central

    Marine, Jeannette E.; Song, Shuang; Liang, Xiaoli; Rudick, Jonathan G.

    2015-01-01

    Dendronized helix bundle assemblies combine the sequence diversity and folding properties of proteins with the tailored physical properties of dendrimers. Assembly of peptide-dendron hybrids into α-helical bundles encapsulates the helix bundle motif in a dendritic sheath that will allow the functional, protein-like domain to be transplanted to non-biological environments. A bioorthogonal graft-to synthetic strategy for preparing helix bundle-forming peptide-dendron hybrids is described herein for hybrids 1a, 1b, and 2. Titration experiments monitored by circular dichroism spectroscopy support our self-assembly model for how the peptide-dendron hybrids self-assemble into α-helical bundles with the dendrons on outside of the bundle. PMID:26674475

  17. Results of international standard problem No. 36 severe fuel damage experiment of a VVER fuel bundle

    SciTech Connect

    Firnhaber, M.; Yegorova, L.; Brockmeier, U.

    1995-09-01

    International Standard Problems (ISP) organized by the OECD are defined as comparative exercises in which predictions with different computer codes for a given physical problem are compared with each other and with a carefully controlled experimental study. The main goal of ISP is to increase confidence in the validity and accuracy of analytical tools used in assessing the safety of nuclear installations. In addition, it enables the code user to gain experience and to improve his competence. This paper presents the results and assessment of ISP No. 36, which deals with the early core degradation phase during an unmitigated severe LWR accident in a Russian type VVER. Representatives of 17 organizations participated in the ISP using the codes ATHLET-CD, ICARE2, KESS-III, MELCOR, SCDAP/RELAP5 and RAPTA. Some participants performed several calculations with different codes. As experimental basis the severe fuel damage experiment CORA-W2 was selected. The main phenomena investigated are thermal behavior of fuel rods, onset of temperature escalation, material behavior and hydrogen generation. In general, the calculations give the right tendency of the experimental results for the thermal behavior, the hydrogen generation and, partly, for the material behavior. However, some calculations deviate in important quantities - e.g. some material behavior data - showing remarkable discrepancies between each other and from the experiments. The temperature history of the bundle up to the beginning of significant oxidation was calculated quite well. Deviations seem to be related to the overall heat balance. Since the material behavior of the bundle is to a great extent influenced by the cladding failure criteria a more realistic cladding failure model should be developed at least for the detailed, mechanistic codes. Regarding the material behavior and flow blockage some models for the material interaction as well as for relocation and refreezing requires further improvement.

  18. Tangent bundle geometry from dynamics: Application to the Kepler problem

    NASA Astrophysics Data System (ADS)

    Cariñena, J. F.; Clemente-Gallardo, J.; Jover-Galtier, J. A.; Marmo, G.

    In this paper, we consider a manifold with a dynamical vector field and enquire about the possible tangent bundle structures which would turn the starting vector field into a second-order one. The analysis is restricted to manifolds which are diffeomorphic with affine spaces. In particular, we consider the problem in connection with conformal vector fields of second-order and apply the procedure to vector fields conformally related with the harmonic oscillator (f-oscillators). We select one which covers the vector field describing the Kepler problem.

  19. Cotangent bundle reduction and Poincaré-Birkhoff normal forms

    NASA Astrophysics Data System (ADS)

    Çiftçi, Ünver; Waalkens, Holger; Broer, Henk W.

    2014-02-01

    In this paper we study a systematic and natural construction of canonical coordinates for the reduced space of a cotangent bundle with a free Lie group action. The canonical coordinates enable us to compute Poincaré-Birkhoff normal forms of relative equilibria using standard algorithms. The case of simple mechanical systems with symmetries is studied in detail. As examples we compute Poincaré-Birkhoff normal forms for a Lagrangian equilateral triangle configuration of a three-body system with a Morse-type potential and the stretched-out configuration of a double spherical pendulum.

  20. Solutions of the Strominger System via Stable Bundles on Calabi-Yau Threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Garcia-Fernandez, Mario

    2012-10-01

    We prove that a given Calabi-Yau threefold with a stable holomorphic vector bundle can be perturbed to a solution of the Strominger system provided that the second Chern class of the vector bundle is equal to the second Chern class of the tangent bundle. If the Calabi-Yau threefold has strict SU(3) holonomy then the equations of motion derived from the heterotic string effective action are also satisfied by the solutions we obtain.

  1. Analysis of multimode fiber bundles for endoscopic spectral-domain optical coherence tomography

    PubMed Central

    Risi, Matthew D.; Makhlouf, Houssine; Rouse, Andrew R.; Gmitro, Arthur F.

    2016-01-01

    A theoretical analysis of the use of a fiber bundle in spectral-domain optical coherence tomography (OCT) systems is presented. The fiber bundle enables a flexible endoscopic design and provides fast, parallelized acquisition of the OCT data. However, the multimode characteristic of the fibers in the fiber bundle affects the depth sensitivity of the imaging system. A description of light interference in a multimode fiber is presented along with numerical simulations and experimental studies to illustrate the theoretical analysis. PMID:25967012

  2. Formation and structural organization of the egg-sperm bundle of the scleractinian coral Montipora capitata

    NASA Astrophysics Data System (ADS)

    Padilla-Gamiño, J. L.; Weatherby, T. M.; Waller, R. G.; Gates, R. D.

    2011-06-01

    The majority of scleractinian corals are hermaphrodites that broadcast spawn their gametes separately or packaged as egg-sperm bundles during spawning events that are timed to the lunar cycle. The egg-sperm bundle is an efficient way of transporting gametes to the ocean surface where fertilization takes place, while minimizing sperm dilution and maximizing the opportunity for gamete encounters during a spawning event. To date, there are few studies that focus on the formation and structure of egg-sperm bundle. This study explores formation, ultrastructure, and longevity of the egg-sperm bundle in Montipora capitata, a major reef building coral in Hawai`i. Our results show that the egg-sperm bundle is formed by a mucus layer secreted by the oocytes. The sperm package is located at the center of each bundle, possibly reflecting the development of male and female gametes in different mesenteries. Once the egg-sperm bundle has reached the ocean surface, it breaks open within 10-35 min, depending on the environmental conditions (i.e., wind, water turbulence). Although the bundle has an ephemeral life span, the formation of an egg-sperm bundle is a fundamental part of the reproductive process that could be strongly influenced by climate change and deterioration of water quality (due to anthropogenic effects) and thus requires further investigation.

  3. Sperm competition promotes diversity of sperm bundles in Ohomopterus ground beetles

    NASA Astrophysics Data System (ADS)

    Takami, Yasuoki; Sota, Teiji

    2007-07-01

    Diversification of sperm morphology has been investigated in the context of sperm competition, but the adaptive significance of sperm bundles is still unclear. In analyzing 10 taxa of the genus Carabus subgenus Ohomopterus and one related Carabus ground beetles, we found that dimorphic sperm bundles occurred in most species with varied degrees of bimodality, whereas sperm were generally monomorphic. Comparative analyses with phylogenetically independent contrasts revealed that the sizes of large and small sperm bundles evolved more rapidly than, and were not correlated with, the length of sperm, suggesting more intense selection on sperm bundle sizes and their independent responses to different evolutionary forces. The size of large sperm bundles was positively correlated with male genital morphology (pertinent to displacement of rival spermatophores) and postcopulatory guarding duration as well as male body length, suggesting that larger sperm bundles have been favored when the risk of spermatophore displacement is high. Larger sperm bundles may be advantageous because of their ability to migrate more rapidly into the spermatheca. In contrast, no clear association was detected between the small sperm bundle size and mating traits despite its rapid diversification. The present study provides the first record of heteromorphic sperm bundles, the diversity of which may be promoted by sperm competition.

  4. Significance of the resting angles of hair-cell bundles for Hopf bifurcation criticality

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2016-08-01

    We investigate the significance of the inclined angle of a hair bundle at equilibrium. We find that, while the angle gives a geometrical conversion factor between the bundle deflection and the ion channel displacement, it also controls the dynamics of the bundle. We show that a Hopf bifurcation, which enhances sensitivity, can be driven by the geometrical factor. However, existing experimental data indicate that mammalian auditory hair-cell bundles are located far away from the Hopf bifurcation point, suggesting that the high sensitivity of mammalian hearing might come from other mechanisms.

  5. Geometry of moduli stacks of (k , l) -stable vector bundles over algebraic curves

    NASA Astrophysics Data System (ADS)

    Mata-Gutiérrez, O.; Neumann, Frank

    2017-01-01

    We study the geometry of the moduli stack of vector bundles of fixed rank and degree over an algebraic curve by introducing a filtration made of open substacks build from (k , l) -stable vector bundles. The concept of (k , l) -stability was introduced by Narasimhan and Ramanan to study the geometry of the coarse moduli space of stable bundles. We will exhibit the stacky picture and analyse the geometric and cohomological properties of the moduli stacks of (k , l) -stable vector bundles. For particular pairs (k , l) of integers we also show that these moduli stacks admit coarse moduli spaces and we discuss their interplay.

  6. Bundles over nearly-Kahler homogeneous spaces in heterotic string theory

    NASA Astrophysics Data System (ADS)

    Klaput, Michael; Lukas, Andre; Matti, Cyril

    2011-09-01

    We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is SU(3)/U(1)2. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.

  7. Role of the actin bundling protein fascin in growth cone morphogenesis: localization in filopodia and lamellipodia.

    PubMed

    Cohan, C S; Welnhofer, E A; Zhao, L; Matsumura, F; Yamashiro, S

    2001-02-01

    Growth cones at the distal tips of growing nerve axons contain bundles of actin filaments distributed throughout the lamellipodium and that project into filopodia. The regulation of actin bundling by specific actin binding proteins is likely to play an important role in many growth cone behaviors. Although the actin binding protein, fascin, has been localized in growth cones, little information is available on its functional significance. We used the large growth cones of the snail Helisoma to determine whether fascin was involved in temporal changes in actin filaments during growth cone morphogenesis. Fascin localized to radially oriented actin bundles in lamellipodia (ribs) and filopodia. Using a fascin antibody and a GFP fascin construct, we found that fascin incorporated into actin bundles from the beginning of growth cone formation at the cut end of axons. Fascin associated with most of the actin bundle except the proximal 6--12% adjacent to the central domain, which is the region associated with actin disassembly. Later, during growth cone morphogenesis when actin ribs shortened, the proximal fascin-free zone of bundles increased, but fascin was retained in the distal, filopodial portion of bundles. Treatment with tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), which phosphorylates fascin and decreases its affinity for actin, resulted in loss of all actin bundles from growth cones. Our findings suggest that fascin may be particularly important for the linear structure and dynamics of filopodia and for lamellipodial rib dynamics by regulating filament organization in bundles.

  8. Redesign and replacement of Connecticut Yankee moisture separator/reheater (MSR) tube bundles

    SciTech Connect

    Gibson, J.N.

    1981-01-01

    This paper describes the various aspects of the tube bundle redesign and replacement coordinated by Northeast Utilities Service Company for the Connecticut Yankee Atomic Power Company during the plant's 1980 refueling outage. The main objective of the replacement was to improve the operating reliability along with secondary plant chemistry through the use of new bundle design and tube material. The considerations leading to the selection of material and design of the new bundles, the highlights of fabrication and bundle change-out, and the eddy current test experience and performance monitoring techniques and results are presented. 6 refs.

  9. Bagger-Witten line bundles on moduli spaces of elliptic curves

    NASA Astrophysics Data System (ADS)

    Gu, Wei; Sharpe, Eric

    2016-12-01

    In this paper, we discuss Bagger-Witten line bundles over moduli spaces of SCFTs. We review how in general they are “fractional” line bundles, not honest line bundles, twisted on triple overlaps. We discuss the special case of moduli spaces of elliptic curves in detail. There, the Bagger-Witten line bundle does not exist as an ordinary line bundle, but rather is necessarily fractional. As a fractional line bundle, it is nontrivial (though torsion) over the uncompactified moduli stack, and its restriction to the interior, excising corners with enhanced stabilizers, is also fractional. It becomes an honest line bundle on a moduli stack defined by a quotient of the upper half plane by a metaplectic group, rather than SL(2, ℤ). We review and compare to results of recent work arguing that well-definedness of the worldsheet metric implies that the Bagger-Witten line bundle admits a flat connection (which includes torsion bundles as special cases), and gives general arguments on the existence of universal structures on moduli spaces of SCFTs, in which superconformal deformation parameters are promoted to nondynamical fields ranging over the SCFT moduli space.

  10. Sperm competition promotes diversity of sperm bundles in Ohomopterus ground beetles.

    PubMed

    Takami, Yasuoki; Sota, Teiji

    2007-07-01

    Diversification of sperm morphology has been investigated in the context of sperm competition, but the adaptive significance of sperm bundles is still unclear. In analyzing 10 taxa of the genus Carabus subgenus Ohomopterus and one related Carabus ground beetles, we found that dimorphic sperm bundles occurred in most species with varied degrees of bimodality, whereas sperm were generally monomorphic. Comparative analyses with phylogenetically independent contrasts revealed that the sizes of large and small sperm bundles evolved more rapidly than, and were not correlated with, the length of sperm, suggesting more intense selection on sperm bundle sizes and their independent responses to different evolutionary forces. The size of large sperm bundles was positively correlated with male genital morphology (pertinent to displacement of rival spermatophores) and postcopulatory guarding duration as well as male body length, suggesting that larger sperm bundles have been favored when the risk of spermatophore displacement is high. Larger sperm bundles may be advantageous because of their ability to migrate more rapidly into the spermatheca. In contrast, no clear association was detected between the small sperm bundle size and mating traits despite its rapid diversification. The present study provides the first record of heteromorphic sperm bundles, the diversity of which may be promoted by sperm competition.

  11. Modern Methods of Bundle Adjustment on the Gpu

    NASA Astrophysics Data System (ADS)

    Hänsch, R.; Drude, I.; Hellwich, O.

    2016-06-01

    The task to compute 3D reconstructions from large amounts of data has become an active field of research within the last years. Based on an initial estimate provided by structure from motion, bundle adjustment seeks to find a solution that is optimal for all cameras and 3D points. The corresponding nonlinear optimization problem is usually solved by the Levenberg-Marquardt algorithm combined with conjugate gradient descent. While many adaptations and extensions to the classical bundle adjustment approach have been proposed, only few works consider the acceleration potentials of GPU systems. This paper elaborates the possibilities of time and space savings when fitting the implementation strategy to the terms and requirements of realizing a bundler on heterogeneous CPUGPU systems. Instead of focusing on the standard approach of Levenberg-Marquardt optimization alone, nonlinear conjugate gradient descent and alternating resection-intersection are studied as two alternatives. The experiments show that in particular alternating resection-intersection reaches low error rates very fast, but converges to larger error rates than Levenberg-Marquardt. PBA, as one of the current state-of-the-art bundlers, converges slower in 50 % of the test cases and needs 1.5-2 times more memory than the Levenberg- Marquardt implementation.

  12. A four-helix bundle stores copper for methane oxidation.

    PubMed

    Vita, Nicolas; Platsaki, Semeli; Baslé, Arnaud; Allen, Stephen J; Paterson, Neil G; Crombie, Andrew T; Murrell, J Colin; Waldron, Kevin J; Dennison, Christopher

    2015-09-03

    Methane-oxidizing bacteria (methanotrophs) require large quantities of copper for the membrane-bound (particulate) methane monooxygenase. Certain methanotrophs are also able to switch to using the iron-containing soluble methane monooxygenase to catalyse methane oxidation, with this switchover regulated by copper. Methane monooxygenases are nature's primary biological mechanism for suppressing atmospheric levels of methane, a potent greenhouse gas. Furthermore, methanotrophs and methane monooxygenases have enormous potential in bioremediation and for biotransformations producing bulk and fine chemicals, and in bioenergy, particularly considering increased methane availability from renewable sources and hydraulic fracturing of shale rock. Here we discover and characterize a novel copper storage protein (Csp1) from the methanotroph Methylosinus trichosporium OB3b that is exported from the cytosol, and stores copper for particulate methane monooxygenase. Csp1 is a tetramer of four-helix bundles with each monomer binding up to 13 Cu(I) ions in a previously unseen manner via mainly Cys residues that point into the core of the bundle. Csp1 is the first example of a protein that stores a metal within an established protein-folding motif. This work provides a detailed insight into how methanotrophs accumulate copper for the oxidation of methane. Understanding this process is essential if the wide-ranging biotechnological applications of methanotrophs are to be realized. Cytosolic homologues of Csp1 are present in diverse bacteria, thus challenging the dogma that such organisms do not use copper in this location.

  13. Cortactin Adopts a Globular Conformation and Bundles Actin into Sheets

    SciTech Connect

    Cowieson, Nathan P.; King, Gordon; Cookson, David; Ross, Ian; Huber, Thomas; Hume, David A.; Kobe, Bostjan; Martin, Jennifer L.

    2008-08-21

    Cortactin is a filamentous actin-binding protein that plays a pivotal role in translating environmental signals into coordinated rearrangement of the cytoskeleton. The dynamic reorganization of actin in the cytoskeleton drives processes including changes in cell morphology, cell migration, and phagocytosis. In general, structural proteins of the cytoskeleton bind in the N-terminal region of cortactin and regulatory proteins in the C-terminal region. Previous structural studies have reported an extended conformation for cortactin. It is therefore unclear how cortactin facilitates cross-talk between structural proteins and their regulators. In the study presented here, circular dichroism, chemical cross-linking, and small angle x-ray scattering are used to demonstrate that cortactin adopts a globular conformation, thereby bringing distant parts of the molecule into close proximity. In addition, the actin bundling activity of cortactin is characterized, showing that fully polymerized actin filaments are bundled into sheet-like structures. We present a low resolution structure that suggests how the various domains of cortactin interact to coordinate its array of binding partners at sites of actin branching.

  14. Faster and improved microchip electrophoresis using a capillary bundle.

    PubMed

    Sun, Yi; Kwok, Yien Chian; Nguyen, Nam Trung

    2007-12-01

    Joule heating generated in CE microchips is known to affect temperature gradient, electrophoretic mobility, diffusion of analytes, and ultimately the efficiency and reproducibility of the separation. One way of reducing the effect of Joule heating is to decrease the cross-section area of microchannels. Currently, due to the limit of fabrication technique and detection apparatus, the typical dimensions of CE microchannels are in the range of 50-200 microm. In this paper, we propose a novel approach of performing microchip CE in a bundle of extremely narrow channels by using photonic crystal fiber (PCF) as separation column. The PCF was simply encapsulated in a poly(methyl methacrylate) (PMMA) microchannel right after a T-shaped injector. CE was simultaneously but independently carried out in 54 narrow capillaries, each capillary with diameter of 3.7 microm. The capillary bundle could sustain high electric field strength up to 1000 V/cm due to efficient heat dissipation, thus faster and enhanced separation was attained.

  15. Prostaglandins temporally regulate cytoplasmic actin bundle formation during Drosophila oogenesis.

    PubMed

    Spracklen, Andrew J; Kelpsch, Daniel J; Chen, Xiang; Spracklen, Cassandra N; Tootle, Tina L

    2014-02-01

    Prostaglandins (PGs)--lipid signals produced downstream of cyclooxygenase (COX) enzymes--regulate actin dynamics in cell culture and platelets, but their roles during development are largely unknown. Here we define a new role for Pxt, the Drosophila COX-like enzyme, in regulating the actin cytoskeleton--temporal restriction of actin remodeling during oogenesis. PGs are required for actin filament bundle formation during stage 10B (S10B). In addition, loss of Pxt results in extensive early actin remodeling, including actin filaments and aggregates, within the posterior nurse cells of S9 follicles; wild-type follicles exhibit similar structures at a low frequency. Hu li tai shao (Hts-RC) and Villin (Quail), an actin bundler, localize to all early actin structures, whereas Enabled (Ena), an actin elongation factor, preferentially localizes to those in pxt mutants. Reduced Ena levels strongly suppress early actin remodeling in pxt mutants. Furthermore, loss of Pxt results in reduced Ena localization to the sites of bundle formation during S10B. Together these data lead to a model in which PGs temporally regulate actin remodeling during Drosophila oogenesis by controlling Ena localization/activity, such that in S9, PG signaling inhibits, whereas at S10B, it promotes Ena-dependent actin remodeling.

  16. Contrast limiting factors of optical fiber bundles for flexible endoscopy

    NASA Astrophysics Data System (ADS)

    Ortega-Quijano, N.; Arce-Diego, J. L.; Fanjul-Vélez, F.

    2008-11-01

    Medical endoscopy constitutes a basic device for the development of minimally invasive procedures for a wide range of medical applications, involving diagnosis, treatment and surgery, as well as biopsy sampling. Its minimally invasive nature results in no surgery, or only small incisions, which involves a minimal hospitalization time. The medical relevance of endoscopes relies on the fact that they are one of the most effective means of early stages of cancer diagnosis, with the subsequent improvement in the patient's quality of life. Flexible endoscopy by means of coherent optical fiber bundles shows both flexibility and a high active area. However, the parallel arrangement of the fibers within the bundle produces interference phenomena between them, which results in optical crosstalk. As a consequence, there is a power exchange between contiguous fibers, producing a worsening in the contrast of the image. In this work, this quality limiting factor is deeply studied. We quantitatively analyze crosstalk, performing several studies that show the limitations imposed to the endoscopic system. Finally, we propose some solutions by an analytical method to accurately determine the appropriate optical fibers for each particular design. The method is also applied to endoscopic OCT.

  17. The helix bundle: A reversible lipid binding motif

    PubMed Central

    Narayanaswami, Vasanthy; Kiss, Robert S.; Weers, Paul M.M.

    2009-01-01

    Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic α-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the α-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions. PMID:19770066

  18. CFD Validation Benchmark Dataset for Natural Convection in Nuclear Fuel Rod Bundles

    NASA Astrophysics Data System (ADS)

    Smith, Barton; Jones, Kyle

    2016-11-01

    The present study provide CFD validation benchmark data for coupled fluid flow/convection heat transfer on the exterior of heated rods arranged in a 2 × 2 array. The rod model incorporates grids with swirling veins to resemble a nuclear fuel bundle. The four heated aluminum rods are suspended in an open-circuit wind tunnel. Boundary conditions (BCs) are measured and uncertainties calculated to provide all quantities necessary to successfully conduct a CFD validation exercise. System response quantities (SRQs) are measured for comparing the simulation output to the experiment. Stereoscopic Particle Image Velocimetry (SPIV) is used to non-intrusively measure 3-component velocity fields. A through-plane measurement is used for the inflow while laser sheet planes aligned with the flow direction at several downstream locations are used for system response quantities. Two constant heat flux rod surface conditions are presented (400 W/m2 and 700 W/m2) achieving a peak Rayleigh number of 1010 . Uncertainty for all measured variables is reported. The boundary conditions, system response, and all material properties are now available online for download. The U.S. Department of Energy Nuclear Engineering University Program provided the funding for these experiments under Grant 00128493.

  19. System design description for GCFR-core flow test loop

    SciTech Connect

    Huntley, W.R.; Grindell, A.G.

    1980-12-01

    The Core Flow Test Loop is a high-pressure, high-temperature, out-of-reactor helium circulation system that is being constructed to permit detailed study of the thermomechanical and thermal performance at prototypic steady-state and transient operating conditions of simulated segments of core assemblies for a GCFR Demonstration Plant, as designed by General Atomic Company. It will also permit the expermental verification of predictive analytical models of the GCFR core assemblies needed to reduce operational and safety uncertainties of the GCFR. Full-sized blanket assemblies and segments of fuel rod and control rod fuel assemblies will be simulated with test bundles of electrically powered fuel rod or blanket rod simulators. The loop will provide the steady-state and margin test requirements of bundle power and heat removal, and of helium coolant flow rate, pressure, and temperature for test bundles having up to 91 rods; these requirements set the maximum power, coolant helium flow, and thermal requirements for the loop. However, the size of the test vessel that contains the test bundles will be determined by the bundles that simulate a full-sized GCFR blanket assembly. The loop will also provide for power and coolant transients to simulate transient operation of GCFR core assemblies, including the capability for rapid helium depressurization to simulate the depressurization class of GCFR accidents. In addition, the loop can be used as an out-of-reactor test bed for characterizing in-reactor test bundle configurations.

  20. Incorporating Endmember Variability into Spectral Mixture Analysis Through Endmember Bundles

    NASA Technical Reports Server (NTRS)

    Bateson, C. Ann; Asner, Gregory P.; Wessman, Carol A.

    1998-01-01

    Variation in canopy structure and biochemistry induces a concomitant variation in the top-of-canopy spectral reflectance of a vegetation type. Hence, the use of a single endmember spectrum to track the fractional abundance of a given vegetation cover in a hyperspectral image may result in fractions with considerable error. One solution to the problem of endmember variability is to increase the number of endmembers used in a spectral mixture analysis of the image. For example, there could be several tree endmembers in the analysis because of differences in leaf area index (LAI) and multiple scatterings between leaves and stems. However, it is often difficult in terms of computer or human interaction time to select more than six or seven endmembers and any non-removable noise, as well as the number of uncorrelated bands in the image, limits the number of endmembers that can be discriminated. Moreover, as endmembers proliferate, their interpretation becomes increasingly difficult and often applications simply need the aerial fractions of a few land cover components which comprise most of the scene. In order to incorporate endmember variability into spectral mixture analysis, we propose representing a landscape component type not with one endmember spectrum but with a set or bundle of spectra, each of which is feasible as the spectrum of an instance of the component (e.g., in the case of a tree component, each spectrum could reasonably be the spectral reflectance of a tree canopy). These endmember bundles can be used with nonlinear optimization algorithms to find upper and lower bounds on endmember fractions. This approach to endmember variability naturally evolved from previous work in deriving endmembers from the data itself by fitting a triangle, tetrahedron or, more generally, a simplex to the data cloud reduced in dimension by a principal component analysis. Conceptually, endmember variability could make it difficult to find a simplex that both surrounds the data

  1. "The Purpose of This Study Is to": Connecting Lexical Bundles and Moves in Research Article Introductions

    ERIC Educational Resources Information Center

    Cortes, Viviana

    2013-01-01

    This article presents a group of lexical bundles identified in a corpus of research article introductions as the first step in the analysis of these expressions in the different sections of the research article. A one-million word corpus of research article introductions from various disciplines was compiled and the lexical bundles identified in…

  2. Bundled Slash: A Potential New Biomass Resource for Fuels and Chemicals

    NASA Astrophysics Data System (ADS)

    Steele, Philip H.; Mitchell, Brian K.; Cooper, Jerome E.; Arora, S.

    Postharvest residues for southern pine species have not previously been quantified to compare volumes produced from both thinnings and clearcut volumes. A John Deere 1490 Slash Bundler bundled postharvest residues following a first thinning of a 14-year-old stand, a second thinning of a 25-year-old stand, and a clearcut of a naturally regenerated mature stand of 54 years of age. Regardless of stand type, nearly one-fifth of merchantable volume harvested was collected as postharvest residue. Initial bundle moisture contents were 127.3, 81.1, and 49.4% dry basis (db) for the first and second thinnings and mature stands, respectively. Bundle needles content was found to significantly influence the relative moisture contents of the bundles by stand type due to the high moisture content of needles compared to other bundle components. Bundles were stored outside and exposed to very hot and dry conditions and dried very rapidly to lowest moisture contents of 22.8, 14.5, and 13.5% (db) for first and second thinnings and mature stands, respectively. Response to moderating temperatures and higher precipitation resulted in rapid moisture content increase to 69.9, 46.2, and 38.1% (db) for the first and second thinnings and mature stand bundles by the end of the study. Temperature and precipitation and bundle percentage needles content all significantly influenced the rapid moisture content variations observed over the study periods.

  3. Liquid-like bundles of crosslinked actin filaments contract without motors

    NASA Astrophysics Data System (ADS)

    Weirich, Kimberly

    The actin cytoskeleton is a dynamic, structural material that drives cellular-scale deformations during processes such as cell migration and division. Motor proteins are responsible for actively driving many deformations by buckling and translocating actin filaments. However, there is evidence that deformations, such as the constriction of the actin bundle that drives the separation of cells during division, can occur without motors, mediated instead by crosslinker proteins. How might crosslinkers, independent of motors, drive contraction of a bundle? Using a model system of purified proteins, we show that crosslinkers, analogous to molecular cohesion, create an effective surface tension that induces bundle contraction. Crosslinked short actin filaments form micron-sized spindle-shaped bundles. Similar to tactoid granules found at the isotropic-nematic phase transition in liquid crystals, these bundles coarsen and coalesce like liquid droplets. In contrast, crosslinked long filaments coarsen into a steady state of bundles that are frozen in a solid-like network. Near the liquid-solid boundary, filaments of intermediate length initially form bundles that spontaneously contract into tactoid droplets. Our results, that crosslinked actin bundles are liquid-like with an effective surface tension, provide evidence for a mechanism of motor-independent contractility in biological materials.

  4. On the existence of stable bundles with prescribed Chern classes on Calabi-Yau threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Curio, Gottfried

    2014-02-01

    We prove a case of the conjecture of Douglas, Reinbacher and Yau about the existence of stable vector bundles with prescribed Chern classes on a Calabi-Yau threefold. For this purpose we prove the existence of certain stable vector bundle extensions over elliptically fibered Calabi-Yau threefolds.

  5. Bundled slash: a potential new biomass resource for fuels and chemicals.

    PubMed

    Steele, Philip H; Mitchell, Brian K; Cooper, Jerome E; Arora, S

    2008-03-01

    Postharvest residues for southern pine species have not previously been quantified to compare volumes produced from both thinnings and clearcut volumes. A John Deere 1490 Slash Bundler bundled postharvest residues following a first thinning of a 14-year-old stand, a second thinning of a 25-year-old stand, and a clearcut of a naturally regenerated mature stand of 54 years of age. Regardless of stand type, nearly one-fifth of merchantable volume harvested was collected as postharvest residue. Initial bundle moisture contents were 127.3, 81.1, and 49.4% dry basis (db) for the first and second thinnings and mature stands, respectively. Bundle needles content was found to significantly influence the relative moisture contents of the bundles by stand type due to the high moisture content of needles compared to other bundle components. Bundles were stored outside and exposed to very hot and dry conditions and dried very rapidly to lowest moisture contents of 22.8, 14.5, and 13.5% (db) for first and second thinnings and mature stands, respectively. Response to moderating temperatures and higher precipitation resulted in rapid moisture content increase to 69.9, 46.2, and 38.1% (db) for the first and second thinnings and mature stand bundles by the end of the study. Temperature and precipitation and bundle percentage needles content all significantly influenced the rapid moisture content variations observed over the study periods.

  6. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  7. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  8. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  9. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  10. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  11. Nucleate Boiling Characteristics of R-113 in a Small Enhanced Tube Bundle

    DTIC Science & Technology

    1991-09-26

    kettle reboilers and full bundle boilers. The difference is described in detail in Payvar [Ref. 5]. To summarize, in the kettle type reboiler the...Liquid levels", BuilleinJME, Vol. 10, p.3 2 8 . 5. Payvar , P., "Analysis of Performance of Full Bundle Submerged Boilers," ASME HMII , Vol. 44, pp. 11

  12. Bundled payment: hospitals see the advantages, but face big challenges too.

    PubMed

    Burns, Joseph

    2013-04-01

    What you need to know about bundled payment. While most hospital leaders see the advantages of moving to bundled payments for an episode of care, many are unprepared either for the mindset or the mechanics required to implement the emerging reimbursement model. Here the concers and possible strategies you should consider.

  13. A retracting wire knife for cutting fiber bundles and making sheet lesions of brain tissue.

    PubMed

    Shibata, M; Russell, I S

    1979-07-01

    A retracting knife which has two cutting wires for the transection of fiber bundles is described. The knife holds the fiber bundles of the stria terminalis between the two cutting wires and transects them by a shearing movement as the wires close. In addition, the feasability of such a knife producing a sheet lesion around the n. caudatus is also described.

  14. Vestibular Deprivation and the Development of Dendrite Bundles in the Rat

    PubMed Central

    Geisler, Hildegard C.; IJkema-Paassen, Jos; Westerga, Johan; Gramsbergen, Albert

    2000-01-01

    Motoneuronal pools of muscles that subserve postural tasks contain dendrite bundles. We investigated in the rat the development of these bundles in the pools of the long back muscles and related this to postural development. Motoneurons and their dendrites were retrogradely labeled by injecting unconjugated cholera toxin subunit B (CTB) into the muscles of 54 normal rats from birth until adulthood and into 18 rats that were vestibularly deprived from the 5th postnatal day (P5). Dendrite bundles coursing in a transverse direction already occurred at P1. From P4, the first longitudinal bundles could be observed, but the major spurt in development occurred between P6 and P9, when conspicuous bundles developed coursing in rostro-caudal and tranverse directions. This is the age when rats become able to stand freely and walk a few steps. Around P20, the dendrite bundles attained their adult characteristics. Vestibular deprivation by plugging both semicircular horizontal canals did not lead to a retarded development of dendrite bundles nor to a changed morphology. This finding is remarkable, as behavioral analysis showed a delay in postural development by about 3 days. We hypothesize that dendrite bundles in the pools of the long back muscles function to synchronize the motoneurons in different spinal cord segments. PMID:11147461

  15. A bundle strategy including patient hand hygiene to decrease clostridium difficile infections.

    PubMed

    Pokrywka, Marian; Feigel, Jody; Douglas, Barbara; Grossberger, Susan; Hensler, Amelia; Hensler, Amelia; Weber, David

    2014-01-01

    Prevention strategies for Clostridium difficile infection traditionally have addressed barrier precautions, environmental disinfection, and health care worker hand hygiene. When applied as a bundle, this approach has been used widely as an evidence-based strategy to prevent hospital-acquired C. difficile infection. Expanding the bundle to include patient hand hygiene is a nurse-driven approach to prevent C. difficile transmission.

  16. Lexical Bundles in Discourse Structure: A Corpus-Based Study of Classroom Discourse

    ERIC Educational Resources Information Center

    Csomay, Eniko

    2013-01-01

    The present study applies corpus-based methods to document the distributional patterns of previously reported lexical bundle functions as they relate to discourse structure. Specifically, 84 lexical bundles and their discourse functions (Biber "et al." 2004a) were tracked in 1,176 discourse units extracted from the initial phases of 196 university…

  17. Assessing the Effect of Language Demand in Bundles of Math Word Problems

    ERIC Educational Resources Information Center

    Banks, Kathleen; Jeddeeni, Ahmad; Walker, Cindy M.

    2016-01-01

    Differential bundle functioning (DBF) analyses were conducted to determine whether seventh and eighth grade second language learners (SLLs) had lower probabilities of answering bundles of math word problems correctly that had heavy language demands, when compared to non-SLLs of equal math proficiency. Math word problems on each of four test forms…

  18. Textbook-Bundled Metacognitive Tools: A Study of LearnSmart's Efficacy in General Chemistry

    ERIC Educational Resources Information Center

    Thadani, Vandana; Bouvier-Brown, Nicole C.

    2016-01-01

    College textbook publishers increasingly bundle sophisticated technology-based study tools with their texts. These tools appear promising, but empirical work on their efficacy is needed. We examined whether LearnSmart, a study tool bundled with McGraw-Hill's textbook "Chemistry" (Chang & Goldsby, 2013), improved learning in an…

  19. Characterization of midrib vascular bundles of selected medicinal species in Rubiaceae

    NASA Astrophysics Data System (ADS)

    Nurul-Syahirah, M.; Noraini, T.; Latiff, A.

    2016-11-01

    An anatomical study was carried out on mature leaves of five selected medicinal species of Rubiaceae from Peninsular Malaysia. The chosen medicinal species were Aidia densiflora, Aidia racemosa, Chasallia chartacea, Hedyotis auricularia and Ixora grandifolia. The objective of this study is to determine the taxonomic value of midrib anatomical characteristics. Leaves samples were collected from Taman Paku Pakis, Universiti Kebangsaan Malaysia, Bangi, Selangor and Kledang Saiong Forest Reserve, Perak, Malaysia. Leaves samples then were fixed in spirit and acetic acid (3:1), the midrib parts then were sectioned using sliding microtome, cleared using Clorox, stained in Safranin and Alcian blue, mounted in Euparal and were observed under light microscope. Findings in this study have shown all species have collateral bundles. The midrib vascular bundles characteristics that can be used as tool to differentiate between species or genus are vascular bundles system (opened or closed), shape and arrangement of main vascular bundles, presence of both additional and medullary vascular bundles, position of additional vascular bundles, shape of medullary vascular bundles, presence of sclerenchyma cells ensheathed the vascular bundles. As a conclusion, midrib anatomical characteristics can be used to identify and discriminate medicinal plants species studied in the Rubiaceae.

  20. The MIMIC Model as a Tool for Differential Bundle Functioning Detection

    ERIC Educational Resources Information Center

    Finch, W. Holmes

    2012-01-01

    Increasingly, researchers interested in identifying potentially biased test items are encouraged to use a confirmatory, rather than exploratory, approach. One such method for confirmatory testing is rooted in differential bundle functioning (DBF), where hypotheses regarding potential differential item functioning (DIF) for sets of items (bundles)…

  1. Unwrapping the Bundle: An Examination of Research Libraries and the "Big Deal"

    ERIC Educational Resources Information Center

    Strieb, Karla L.; Blixrud, Julia C.

    2014-01-01

    This study presents and analyzes the findings of a 2012 survey of member libraries belonging to the Association of Research Libraries (ARL) about publishers' large journal bundles and compares the results to earlier surveys. The data illuminate five research questions: market penetration, journal bundle construction, collection format shifts,…

  2. Structural reorganization of parallel actin bundles by crosslinking proteins: Incommensurate states of twist

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Grason, Gregory M.

    2010-11-01

    We construct a coarse-grained model of parallel actin bundles crosslinked by compact globular bundling proteins, such as fascin and espin, necessary components of filopodial and mechanosensory bundles. Consistent with structural observations of bundles, we find that the optimal geometry for crosslinking is overtwisted, requiring a coherent structural change of the helical geometry of the filaments. We study the linker-dependent thermodynamic transition of bundled actin filaments from their native state to the overtwisted state and map out the “twist-state” phase diagram in terms of the availability as well as the flexibility of crosslinker proteins. We predict that the transition from the uncrosslinked to fully crosslinked state is highly sensitive to linker flexibility: flexible crosslinking smoothly distorts the twist state of bundled filaments, while rigidly crosslinked bundles undergo a phase transition, rapidly overtwisting filaments over a narrow range of free crosslinker concentrations. Additionally, we predict a rich spectrum of intermediate structures, composed of alternating domains of sparsely bound (untwisted) and strongly bound (overtwisted) filaments. This model reveals that subtle differences in crosslinking agents themselves modify not only the detailed structure of parallel actin bundles, but also the thermodynamic pathway by which they form.

  3. 48 CFR 7.107 - Additional requirements for acquisitions involving bundling.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the agency must conduct market research to determine whether bundling is necessary and justified (15 U.S.C. 644(e)(2)). Market research may indicate that bundling is necessary and justified if an agency... if a cost comparison analysis will be performed in accordance with OMB Circular A-76....

  4. Active hair-bundle motility harnesses noise to operate near an optimum of mechanosensitivity.

    PubMed

    Nadrowski, Björn; Martin, Pascal; Jülicher, Frank

    2004-08-17

    The ear relies on nonlinear amplification to enhance its sensitivity and frequency selectivity to oscillatory mechanical stimuli. It has been suggested that this active process results from the operation of dynamical systems that operate in the vicinity of an oscillatory instability, a Hopf bifurcation. In the bullfrog's sacculus, a hair cell can display spontaneous oscillations of its mechanosensory hair bundle. The behavior of an oscillatory hair bundle resembles that of a critical oscillator. We present here a theoretical description of the effects of intrinsic noise on active hair-bundle motility. An oscillatory instability can result from the interplay between a region of negative stiffness in the bundle's force-displacement relation and the Ca(2+)-regulated activity of molecular motors. We calculate a state diagram that describes the possible dynamical states of the hair bundle in the absence of fluctuations. Taking into account thermal fluctuations, the stochastic nature of transduction channels' gating, and of the forces generated by molecular motors, we discuss conditions that yield a response function and spontaneous noisy movements of the hair bundle in quantitative agreement with previously published experiments. We find that the magnitude of the fluctuations resulting from the active processes that mediate mechanical amplification remains just below that of thermal fluctuations. Fluctuations destroy the phase coherence of spontaneous oscillations and restrict the bundle's sensitivity as well as frequency selectivity to small oscillatory stimuli. We show, however, that a hair bundle studied experimentally operates near an optimum of mechanosensitivity in our state diagram.

  5. Parallel helix bundles and ion channels: molecular modeling via simulated annealing and restrained molecular dynamics.

    PubMed Central

    Kerr, I D; Sankararamakrishnan, R; Smart, O S; Sansom, M S

    1994-01-01

    A parallel bundle of transmembrane (TM) alpha-helices surrounding a central pore is present in several classes of ion channel, including the nicotinic acetylcholine receptor (nAChR). We have modeled bundles of hydrophobic and of amphipathic helices using simulated annealing via restrained molecular dynamics. Bundles of Ala20 helices, with N = 4, 5, or 6 helices/bundle were generated. For all three N values the helices formed left-handed coiled coils, with pitches ranging from 160 A (N = 4) to 240 A (N = 6). Pore radius profiles revealed constrictions at residues 3, 6, 10, 13, and 17. A left-handed coiled coil and a similar pattern of pore constrictions were observed for N = 5 bundles of Leu20. In contrast, N = 5 bundles of Ile20 formed right-handed coiled coils, reflecting loosened packing of helices containing beta-branched side chains. Bundles formed by each of two classes of amphipathic helices were examined: (a) M2a, M2b, and M2c derived from sequences of M2 helices of nAChR; and (b) (LSSLLSL)3, a synthetic channel-forming peptide. Both classes of amphipathic helix formed left-handed coiled coils. For (LSSLLSL)3 the pitch of the coil increased as N increased from 4 to 6. The M2c N = 5 helix bundle is discussed in the context of possible models of the pore domain of nAChR. Images FIGURE 1 FIGURE 3 PMID:7529585

  6. Lexical bundles in an advanced INTOCSU writing class and engineering texts: A functional analysis

    NASA Astrophysics Data System (ADS)

    Alquraishi, Mohammed Abdulrahman

    The purpose of this study is to investigate the functions of lexical bundles in two corpora: a corpus of engineering academic texts and a corpus of IEP advanced writing class texts. This study is concerned with the nature of formulaic language in Pathway IEPs and engineering texts, and whether those types of texts show similar or distinctive formulaic functions. Moreover, the study looked into lexical bundles found in an engineering 1.26 million-word corpus and an ESL 65000-word corpus using a concordancing program. The study then analyzed the functions of those lexical bundles and compared them statistically using chi-square tests. Additionally, the results of this investigation showed 236 unique frequent lexical bundles in the engineering corpus and 37 bundles in the pathway corpus. Also, the study identified several differences between the density and functions of lexical bundles in the two corpora. These differences were evident in the distribution of functions of lexical bundles and the minimal overlap of lexical bundles found in the two corpora. The results of this study call for more attention to formulaic language at ESP and EAP programs.

  7. Drosophila singed, a fascin homolog, is required for actin bundle formation during oogenesis and bristle extension

    PubMed Central

    1994-01-01

    Drosophila singed mutants were named for their gnarled bristle phenotype but severe alleles are also female sterile. Recently, singed protein was shown to have 35% peptide identity with echinoderm fascin. Fascin is found in actin filament bundles in microvilli of sea urchin eggs and in filopodial extensions in coelomocytes. We show that Drosophila singed is required for actin filament bundle formation in the cytoplasm of nurse cells during oogenesis; in severe mutants, the absence of cytoplasmic actin filament bundles allows nurse cell nuclei to lodge in ring canals and block nurse cell cytoplasm transport. Singed is also required for organized actin filament bundle formation in the cellular extension that forms a bristle; in severe mutants, the small disorganized actin filament bundles lack structural integrity and allow bristles to bend and branch during extension. Singed protein is also expressed in migratory cells of the developing egg chamber and in the socket cell of the developing bristle, but no defect is observed in these cells in singed mutants. Purified, bacterially expressed singed protein bundles actin filaments in vitro with the same stoichiometry reported for purified sea urchin fascin. Singed-saturated actin bundles have a molar ratio of singed/actin of approximately 1:4.3 and a transverse cross-banding pattern of 12 nm seen using electron microscopy. Our results suggest that singed protein is required for actin filament bundle formation and is a Drosophila homolog of echinoderm fascin. PMID:8163553

  8. A Clinical and Follow-up Study of Right and Left Bundle Branch Block

    DTIC Science & Technology

    1974-09-03

    I’SAFSAM) The pur- pose of the study was to group subjects with bundle branch block into various fascicular combinations and to compare and...and left bundle branch block with no clinically apparent cardiovascular disease have revealed a mild diffuse abnormality of the ventricular

  9. Influence of the angle of inclination of round-finned tubes in a staggered tube bundle on the free convective heat exchange between it and an unbounded air space

    NASA Astrophysics Data System (ADS)

    Kuntysh, V. B.; Samorodov, A. V.

    2010-05-01

    Results of experimental investigations of the average heat transfer from five-row staggered bundles of tubes with knurled spiral fins, operating in the free air-convection regime, in the case where the angel of inclination of the longitudinal axis of the tubes changed from 0 to 60° are presented. The investigations were carried out by the method of complete heat simulation. The average heat transfer was measured in the direction of a free air flow in each row of a tube bundle. The experimental data were generalized by similarity equations for calculating the average heat transfer from the tube bundles and their individual rows in the range of change in the Rayleigh number characteristic of the operating conditions of industrial heat exchangers assembled from finned tubes of the type of the above-indicated tubes.

  10. The electrochemical properties of bundles of single-walled nanotubes

    SciTech Connect

    Zawodzinski, T.A. Jr.; Haridoss, P.; Uribe, F.A.

    1998-12-31

    This is the final report of a Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors studied electrochemical properties of single-walled fullerene nanotube bundles. The materials exhibited a highly anisotropic conductivity. Electrochemical cycling in solutions of alkyl ammonium salts in propylene carbonate revealed that the nanotubes are stable to at least {+-}1.5 V and have a fairly high accessible surface area. Double-layer charging currents of approximately 30 farads per gram were observed. This is on the same order of magnitude, though somewhat lower, than state-of-the-art values for ultra-capacitor materials. Electrochemical insertion of lithium was attempted. Though several features were observed in a slow cyclic voltammetric scan, these features were not reversible, indicating little reversible insertion. Several possible reasons for this behavior are discussed.

  11. Cap assembly for a bundled tube fuel injector

    SciTech Connect

    LeBegue, Jeffrey Scott; Melton, Patrick Benedict; Westmoreland, III, James Harold; Flanagan, James Scott

    2016-04-26

    A cap assembly for a bundled tube fuel injector includes an impingement plate and an aft plate that is disposed downstream from the impingement plate. The aft plate includes a forward side that is axially separated from an aft side. A tube passage extends through the impingement plate and the aft plate. A tube sleeve extends through the impingement plate within the tube passage towards the aft plate. The tube sleeve includes a flange at a forward end and an aft end that is axially separated from the forward end. A retention plate is positioned upstream from the impingement plate. A spring is disposed between the retention plate and the flange. The spring provides a force so as to maintain contact between at least a portion of the aft end of the tube sleeve and the forward side of the aft plate.

  12. Liquid behavior of cross-linked actin bundles.

    PubMed

    Weirich, Kimberly L; Banerjee, Shiladitya; Dasbiswas, Kinjal; Witten, Thomas A; Vaikuntanathan, Suriyanarayanan; Gardel, Margaret L

    2017-02-28

    The actin cytoskeleton is a critical regulator of cytoplasmic architecture and mechanics, essential in a myriad of physiological processes. Here we demonstrate a liquid phase of actin filaments in the presence of the physiological cross-linker, filamin. Filamin condenses short actin filaments into spindle-shaped droplets, or tactoids, with shape dynamics consistent with a continuum model of anisotropic liquids. We find that cross-linker density controls the droplet shape and deformation timescales, consistent with a variable interfacial tension and viscosity. Near the liquid-solid transition, cross-linked actin bundles show behaviors reminiscent of fluid threads, including capillary instabilities and contraction. These data reveal a liquid droplet phase of actin, demixed from the surrounding solution and dominated by interfacial tension. These results suggest a mechanism to control organization, morphology, and dynamics of the actin cytoskeleton.

  13. Rare Manifestation of Digoxin Toxicity: Right Bundle Branch Block

    PubMed Central

    Gill, Dalvir; Zaidi, Samana

    2016-01-01

    A 76-year-old female, with medical history significant for systolic congestive heart failure, who presented to the emergency department with lethargy and abdominal pain with diarrhea for the past 3 weeks. Due to hypotension, the patient received multiple boluses of isotonic saline and was started on norepinephrine. Laboratories were significant for severe digoxin toxicity (29 ng/mL), in setting of acute kidney injury. Electrocardiogram (EKG) revealed a new right bundle branch block (RBBB). She was given Digibind and her repeat digoxin level was 20 ng/mL. Repeat EKG showed resolved RBBB. This case identifies that patients with digoxin toxicity are at risk for RBBB. This is a rare finding and is not commonly recognized. Emergency medicine physicians are often the first to encounter patients with digoxin toxicity and need to be aware of such EKG findings. PMID:28104974

  14. Superconductivity in bundles of double-wall carbon nanotubes.

    PubMed

    Shi, Wu; Wang, Zhe; Zhang, Qiucen; Zheng, Yuan; Ieong, Chao; He, Mingquan; Lortz, Rolf; Cai, Yuan; Wang, Ning; Zhang, Ting; Zhang, Haijing; Tang, Zikang; Sheng, Ping; Muramatsu, Hiroyuki; Kim, Yoong Ahm; Endo, Morinobu; Araujo, Paulo T; Dresselhaus, Mildred S

    2012-01-01

    We present electrical and thermal specific heat measurements that show superconductivity in double-wall carbon nanotube (DWCNT) bundles. Clear evidence, comprising a resistance drop as a function of temperature, magnetoresistance and differential resistance signature of the supercurrent, suggest an intrinsic superconducting transition below 6.8 K for one particular sample. Additional electrical data not only confirm the existence of superconductivity, but also indicate the T(c) distribution that can arise from the diversity in the diameter and chirality of the DWCNTs. A broad superconducting anomaly is observed in the specific heat of a bulk DWCNT sample, which yields a T(c) distribution that correlates well with the range of the distribution obtained from the electrical data. As quasi one dimensionality of the DWCNTs dictates the existence of electronic density of state peaks, confirmation of superconductivity in this material system opens the exciting possibility of tuning the T(c) through the application of a gate voltage.

  15. Brownian dynamics simulation of sickle hemoglobin bundle formation

    NASA Astrophysics Data System (ADS)

    Liu, Ya; Gunton, James; Chakrabarti, Amit

    2010-03-01

    The physical properties of biopolymer fibers, such as their stability and degree of aggregation, are implicated in many diseases, including sickle cell anemia. The natural chirality of protofilaments plays a crucial role in the formation of sickle hemoglobin fiber which leads to the permanent blockage of microvessels. We use Brownian dynamics to investigate the kinetics of fiber aggregation. The geometrical helical structure and chirality of the filaments are modeled by anisotropic patch-like interactions. We present the kinetics of fiber formation and study the possibility of a finite critical fiber bundle size. We compare our results with various experimental and theoretical results. This work is supported by grants from the NSF and the G. Harold and Leila Y. Mathers Foundation.

  16. MENT reconstruction and potting comparison of a LMFBR fuel bundle

    SciTech Connect

    Betten, P.R.; Tow, D.M.

    1984-01-01

    Since the advent of computer-assisted-tomography (CAT), the CAT techniques have been rapidly expanded to the nuclear industry. A number of investigators have applied these techniques to reconstruct the fuel bundle configuration inside a subassembly with various degrees of resolution; however, there has been little data available on the accuracy of these reconstructions, and no comparisons have been made with the internal structure of actual irradiated subassemblies. Some efforts have utilized pretest mock-ups to calibrate the CAT algorithms, but the resulting mock-up configurations do not necessarily represent an actual subassembly, so an exact comparison has been lacking. The purpose of this paper is to present the results of a comparison between a CAT reconstruction of an irradiated subassembly and the destructive examination of the same subassembly.

  17. Numerical Hermitian Yang-Mills connections and vector bundle stability in heterotic theories

    NASA Astrophysics Data System (ADS)

    Anderson, Lara B.; Braun, Volker; Karp, Robert L.; Ovrut, Burt A.

    2010-06-01

    A numerical algorithm is presented for explicitly computing the gauge connection on slope-stable holomorphic vector bundles on Calabi-Yau manifolds. To illustrate this algorithm, we calculate the connections on stable monad bundles defined on the K3 twofold and Quintic threefold. An error measure is introduced to determine how closely our algorithmic connection approximates a solution to the Hermitian Yang-Mills equations. We then extend our results by investigating the behavior of non slope-stable bundles. In a variety of examples, it is shown that the failure of these bundles to satisfy the Hermitian Yang-Mills equations, including field-strength singularities, can be accurately reproduced numerically. These results make it possible to numerically determine whether or not a vector bundle is slope-stable, thus providing an important new tool in the exploration of heterotic vacua.

  18. Defects in crystalline packings of twisted filament bundles. II. Dislocations and grain boundaries

    NASA Astrophysics Data System (ADS)

    Azadi, Amir; Grason, Gregory M.

    2012-03-01

    Twisted and ropelike assemblies of filamentous molecules are common and vital structural elements in cells and tissues of living organisms. We study the intrinsic frustration occurring in these materials between the two-dimensional organization of filaments in cross section and out-of-plane interfilament twist in bundles. Using nonlinear continuum elasticity theory of columnar materials, we study the favorable coupling of twist-induced stresses to the presence of edge dislocations in the lattice packing of bundles, which leads to a restructuring of the ground-state order of these materials at intermediate twist. The stability of dislocations increases as both the degree of twist and lateral bundle size grow. We show that in ground states of large bundles, multiple dislocations pile up into linear arrays, radial grain boundaries, whose number and length grows with bundle twist, giving rise to a rich class of “polycrystalline” packings.

  19. Topological Defects in Twisted Bundles of Two-Dimensionally Ordered Filaments

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2010-07-01

    Twisted assemblies of filaments in ropes, cables, and bundles are essential structural elements in both macroscopic materials and living organisms. We develop the unique, nonlinear elastic properties of twisted filament bundles that derive from generic properties of two-dimensional line-ordered materials. Continuum elasticity reveals a formal equivalence between the elastic stresses induced by bundle twist and those induced by the positive curvature in thin, elastic sheets. These geometrically induced stresses are screened by fivefold disclination defects in the lattice packing, and we predict a discrete spectrum of elastic-energy ground states associated with integer numbers of disclinations in cylindrical bundles. Finally, we show that elastic-energy ground states are extremely sensitive to the defect position in the cross section, with off-center disclinations driving the entire bundle to buckle and writhe.

  20. The dual specificity phosphatase Cdc14B bundles and stabilizes microtubules

    SciTech Connect

    Plumley, Hyekyung; Liu, Yie; Gomez, Marla V; Wang, Yisong

    2005-01-01

    The Cdc14 dual-specificity phosphatases regulate key events in the eukaryotic cell cycle. However, little is known about the function of mammalian CDC14B family members. Here, we demonstrate that subcellular localization of CDC14B protein is cell cycle regulated. CDC14B can bind, bundle, and stabilize microtubules in vitro independently of its catalytic activity. Basic amino acid residues within the nucleolar targeting domain are important for both retaining CDC14B in the nucleolus and preventing microtubule bundling. Overexpression of CDC14B resulted in the formation of cytoplasmic CDC14B and microtubule bundles in interphase cells. These microtubule bundles were resistant to microtubule depolymerization reagents and enriched in acetylated -tubulin. Expression of cytoplasmic forms of CDC14B impaired microtubule nucleation from the microtubule organization center. CDC14B is thus a novel microtubule-bundling and -stabilizing protein, whose regulated subcellular localization may help modulate spindle and microtubule dynamics in mitosis.

  1. Ordered bundles of infrared-transmitting AgClBr fibers: optical characterization of individual fibers.

    PubMed

    Rave, E; Nagli, L; Katzir, A

    2000-09-01

    Silver halide (AgCl(x) Br(1-x)) crystals were extruded to form polycrystalline fibers that are highly transparent in the spectral range 3-30 mum. Ordered bundles consisting of as many as 9000 fibers were fabricated by multiple extrusion steps. The transmission loss of an individual fiber in the 100-fiber bundles was 0.12 dB/cm, and the cross talk between neighboring fibers in the 900-fiber bundles was 25%. Thermal images of bodies at room temperature have been transmitted through the bundles. Such ordered bundles provide a solution for the problem of thermal imaging in regions where there is no line of sight between a thermal camera and a warm object.

  2. Increased reliability of nuclear magnetic resonance protein structures by consensus structure bundles.

    PubMed

    Buchner, Lena; Güntert, Peter

    2015-02-03

    Nuclear magnetic resonance (NMR) structures are represented by bundles of conformers calculated from different randomized initial structures using identical experimental input data. The spread among these conformers indicates the precision of the atomic coordinates. However, there is as yet no reliable measure of structural accuracy, i.e., how close NMR conformers are to the "true" structure. Instead, the precision of structure bundles is widely (mis)interpreted as a measure of structural quality. Attempts to increase precision often overestimate accuracy by tight bundles of high precision but much lower accuracy. To overcome this problem, we introduce a protocol for NMR structure determination with the software package CYANA, which produces, like the traditional method, bundles of conformers in agreement with a common set of conformational restraints but with a realistic precision that is, throughout a variety of proteins and NMR data sets, a much better estimate of structural accuracy than the precision of conventional structure bundles.

  3. Photoacoustic imaging by using a bundle of thin hollow-optical fibers

    NASA Astrophysics Data System (ADS)

    Seki, A.; Iwai, K.; Katagiri, T.; Matsuura, Y.

    2016-03-01

    We propose a photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers that enables endoscopic diagnosis. The hollow-fiber bundle involves 37 fibers with an inner diameter of 100 μm and the total diameter of the bundle is 1.2 mm. A laser beam for photoacoustic excitation is scanned at the input end of fiber bundle and therefore, no scanning mechanism is necessary at the distal end. In addition, owing to the small numerical aperture of hollow optical fibers, a high resolution image is obtained without using a micro-lens array at the end. By using the fiber bundle probe, photoacoustic imaging of blood vessels in the ovarian membrane of fish were successfully obtained with a laser fluence of around 2.8 mJ/cm2.

  4. Load sharing in the growth of bundled biopolymers

    NASA Astrophysics Data System (ADS)

    Wang, Ruizhe; Carlsson, A. E.

    2014-11-01

    To elucidate the nature of load sharing in the growth of multiple biopolymers, we perform stochastic simulations of the growth of biopolymer bundles against obstacles under a broad range of conditions and varying assumptions. The obstacle motion due to thermal fluctuations is treated explicitly. We assume the ‘perfect Brownian ratchet’ model, in which the polymerization rate equals the free-filament rate as soon as the filament-obstacle distance exceeds the monomer size. Accurate closed-form formulas are obtained for the case of a rapidly moving obstacle. We find the following: (1) load sharing is usually sub-perfect in the sense that polymerization is slower than for a single filament carrying the same average force; (2) the sub-perfect behavior becomes significant at a total force proportional to the logarithm or the square root of the number of filaments, depending on the alignment of the filaments; (3) for the special case of slow barrier diffusion and low opposing force, an enhanced obstacle velocity for an increasing number of filaments is possible; (4) the obstacle velocity is very sensitive to the alignment of the filaments in the bundle, with a staggered alignment being an order of magnitude faster than an unstaggered one at forces of only 0.5 pN per filament for 20 filaments; (5) for large numbers of filaments, the power is maximized at a force well below 1 pN per filament; (6) for intermediate values of the obstacle diffusion coefficient, the shape of the force velocity relation is very similar to that for rapid obstacle diffusion.

  5. A four-helix bundle stores copper for methane oxidation

    PubMed Central

    Vita, Nicolas; Platsaki, Semeli; Baslé, Arnaud; Allen, Stephen J.; Paterson, Neil G.; Crombie, Andrew T.; Murrell, J. Colin; Waldron, Kevin J.; Dennison, Christopher

    2015-01-01

    Methane-oxidising bacteria (methanotrophs) require large quantities of copper for the membrane-bound (particulate) methane monooxygenase (pMMO)1,2. Certain methanotrophs are also able to switch to using the iron-containing soluble MMO (sMMO) to catalyse methane oxidation, with this switchover regulated by copper3,4. MMOs are Nature’s primary biological mechanism for suppressing atmospheric levels of methane, a potent greenhouse gas. Furthermore, methanotrophs and MMOs have enormous potential in bioremediation and for biotransformations producing bulk and fine chemicals, and in bioenergy, particularly considering increased methane availability from renewable sources and hydraulic fracturing of shale rock5,6. We have discovered and characterised a novel copper storage protein (Csp1) from the methanotroph Methylosinus trichosporium OB3b that is exported from the cytosol, and stores copper for pMMO. Csp1 is a tetramer of 4-helix bundles with each monomer binding up to 13 Cu(I) ions in a previously unseen manner via mainly Cys residues that point into the core of the bundle. Csp1 is the first example of a protein that stores a metal within an established protein-folding motif. This work provides a detailed insight into how methanotrophs accumulate copper for the oxidation of methane. Understanding this process is essential if the wide-ranging biotechnological applications of methanotrophs are to be realised. Cytosolic homologues of Csp1 are present in diverse bacteria thus challenging the dogma that such organisms do not use copper in this location. PMID:26308900

  6. Compressive nonlinearity in the hair bundle's active response to mechanical stimulation.

    PubMed

    Martin, P; Hudspeth, A J

    2001-12-04

    The auditory system's ability to interpret sounds over a wide range of amplitudes rests on the nonlinear responsiveness of the ear. Whether measured by basilar-membrane vibration, nerve-fiber activity, or perceived loudness, the ear is most sensitive to small signals and grows progressively less responsive as stimulation becomes stronger. Seeking a correlate of this behavior at the level of mechanoelectrical transduction, we examined the responses of hair bundles to direct mechanical stimulation. As reported by the motion of an attached glass fiber, an active hair bundle from the bullfrog's sacculus oscillates spontaneously. Sinusoidal movement of the fiber's base by as little as +/-1 nm, corresponding to the application at the bundle's top of a force of +/-0.3 pN, causes detectable phase-locking of the bundle's oscillations to the stimulus. Although entrainment increases as the stimulus grows, the amplitude of the hair-bundle movement does not rise until phase-locking is nearly complete. A bundle is most sensitive to stimulation at its frequency of spontaneous oscillation. Far from that frequency, the sensitivity of an active hair bundle resembles that of a passive bundle. Over most of its range, an active hair bundle's response grows as the one-third power of the stimulus amplitude; the bundle's sensitivity declines accordingly in proportion to the negative two-thirds power of the excitation. This scaling behavior, also found in the response of the mammalian basilar membrane to sound, signals the operation of an amplificatory process at the brink of an oscillatory instability, a Hopf bifurcation.

  7. MRI depiction and 3D visualization of three anterior cruciate ligament bundles.

    PubMed

    Otsubo, H; Akatsuka, Y; Takashima, H; Suzuki, T; Suzuki, D; Kamiya, T; Ikeda, Y; Matsumura, T; Yamashita, T; Shino, K

    2017-03-01

    The anterior cruciate ligament (ACL) is divided into three fiber bundles (AM-M: anteromedial-medial, AM-L: anteromedial-lateral, PL: posterolateral). We attempted to depict the three bundles of the human ACL on MRI images and to obtain 3-dimensional visualization of them. Twenty-four knees of healthy volunteers (14 males, 10 females) were scanned by 3T-MRI using the fat suppression 3D coherent oscillatory state acquisition for the manipulation of imaging contrast (FS 3D-COSMIC). The scanned images were reconstructed after the isotropic voxel data, which allows the images to be reconstructed in any plane, was acquired. We conducted statistical examination on the identification rate of the three ACL bundles by 2D planes. Segmentation and 3D visualization of the fiber bundles using volume rendering were performed. The triple-bundle ACL was best depicted in the oblique axial plane. While the AM-M and AM-L bundles were clearly depicted in all cases, the PL bundle was not clearly visualized in two knees (8%). Therefore, the three ACL bundles were depicted in 22 knees (92%). The results of 3D visualization of the fiber arrangement agreed well with macroscopic findings of previous anatomical studies. 3T-MRI and the isotropic voxel data from FS 3D-COSMIC made it possible to demonstrate the identifiable depiction of three ACL bundles in nearly all cases. 3D visualization of the bundles could be a useful tool to understand the ACL fiber arrangement. Clin. Anat. 30:276-283, 2017. 2016 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

  8. Rewetting of Vertical Hot Surface in a Centrally Heated Annulus and a 6 x 6 Rod Bundle Geometry During Reflood Phase

    SciTech Connect

    Seok Cho; Sang-Ki Moon; Ki-Yong Choi; Se-Young Chun; Moon-Ki Chung; Won-Pil Baek

    2006-07-01

    A series of bottom reflood tests were carried out to investigate thermal-hydraulic characteristics during the reflood phase. This paper includes descriptions of three related groups of reflood tests categorized by the geometry of a flow channel and an electric power shape of heater rods. A centrally-heated annular geometry with an outer-visualizing tube was adopted for the first two groups of tests (group-A and -B), and a 6 x 6 rod bundle geometry for the other group of tests (group-C). The ranges of experimental parameters are 2{approx}8 cm/s of flooding velocity, 20{approx}80 deg. C of inlet subcooling temperature, and 500{approx}700 deg. C of initial wall temperature. In the single rod annular flow channel reflood test, quench front behavior can be easily observed through the visualizing window and a dominant flow regime near downstream of quench front is inverted annular film boiling regardless of the flooding velocity. For the case of the 6 x 6 rod bundle experiments, on the other hand, the dominant flow regime is dispersed flow film boiling (DFFB), and therefore the thermal hydraulic behavior becomes more complicated and chaotic due to the interaction between liquid phase such as droplet and liquid film and vapor phase generated from liquid-wall heat transfer. (authors)

  9. Intercalation of heavy alkali metals (K, Rb and Cs) in the bundles of single wall nanotubes

    NASA Astrophysics Data System (ADS)

    Duclaux, L.; Méténier, K.; Lauginie, P.; Salvetat, J. P.; Bonnamy, S.; Beguin, F.

    2000-11-01

    The electric-arc discharge carbon deposits (collaret) containing Single Wall Carbon Nanotubes (SWNTs) were heat treated at 1600 °C during 2 days under N2 flow in order to eliminate the Ni catalyst by sublimation, without modifications of the SWNTs ropes. Sorting this deposit by gravity enabled to obtain in the coarsest particles higher amount of SWNTs ropes than in other particle sizes. The coarser particles of the carbon deposits were reacted with the alkali metals vapor giving intercalated samples with a MC8 composition. The intercalation led to an expansion of the 2D lattice of the SWNTs so that the alkali metals were intercalated in between the tubes within the bundles. Disordered lattices were observed after intercalation of Rb and Cs. The simulations of the X-ray diffractograms of SWNTs reacted with K, gave the best fit for three K ions occupying the inter-tubes triangular cavities. The investigations by EPR, and 13C NMR, showed that doped carbon deposits are metallic.

  10. Comprehensive Spatial Display of the Microcirculation in a Capillary Bundle from Rat Spinotrapezius Muscle Fascia Tissue

    NASA Astrophysics Data System (ADS)

    Yamamura, Niki; Jacobitz, Frank; Schmid-Schönbein, Geert

    2012-11-01

    Previous investigations of the microcirculation in skeletal muscle have utilized a statistical display of fundamental hemodynamic variables without regard of actual microvascular details. The focus of this project is the development of a software tool to perform a spatial analysis of hemodynamic results. The vessel network considered in this study is a capillary bundle in rat spinotrapezius muscle fascia with transverse arterioles supplying blood, capillary vessels, and collecting venules removing blood. The software tool represents information about blood vessel location and connectivity in two matrices. The first matrix holds spatial locations of vessel intersections or nodes. This matrix is used to create a second matrix containing the locations of all microvessels. The second matrix is then used to produce result matrices holding the values of flow properties at the locations at which they are observed in the vessel network. The resulting images provide a full display, for example, of the pressure drop in the network. The highest velocities are obtained in the transverse arterioles and adjacent capillaries, while other vessels in the network show lower velocities. An area of elevated hematocrit is observed in the periphery of the network.

  11. Existence of automaticity in anomalous bundle of Wolff-Parkinson-White syndrome.

    PubMed Central

    Przybylski, J; Chiale, P A; Halpern, M S; Lázzari, J O; Elizari, M V; Rosenbaum, M B

    1978-01-01

    Escape beats probably arising from the anomalous bundle were documented in 2 patients with the Wolff-Parkinson-White (WPW) syndrome. A third patient, in whom complete AV block developed both in the anomalous bundle and the normal pathway, showed the occurrence of escape beats (an escape-bigeminy pattern), as well as a regular idioventricular rhythm arising from the anomalous bundle. Phase 4 block in the anomalous bundle occurred in 7 other patients, in 4 of them spontaneously and in 3 only after the administration of ajmaline or amiodarone. Only 4 of 14 fully investigated patients (out of a total number of 23) showed absence of both escape beats and phase 4 block. The escape beats were considered as direct evidence, and the phase 4 block as indirect evidence, for the existence of automaticity in the anomalous bundle. Such evidence supports the view that the anomalous bundle, like the His bundle-branch system, may be composed of specialised tissue endowed with the property of automaticity. PMID:656241

  12. Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear

    PubMed Central

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2014-01-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force–displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness. PMID:24799674

  13. Comparative effects of ajmaline on intermittent bundle branch block and the Wolff-Parkinson-White syndrome.

    PubMed

    Chiale, P A; Przybylski, J; Halpern, M S; Lazzari, J O; Elizari, M V; Rosenbaum, M B

    1977-05-04

    Phase 4 or phase 3 block or both occurred in the His bundle branch system of 11 patients with intermittent bundle branch block and in the anomalous bundle of 6 of 46 patients with the Wolff-Parkinson-White syndrome (13%). Administration of a single dose of ajmaline (50 mg intravenously) in these patients caused a similar response: expansion of the range of phase 3 and phase 4 block at the expense of the intermediate normal conduction range and total interruption of conduction in the affected fascicle when the effect of the drug was maximal. The great similarity in physiologic behavior and pharmacologic response in these groups of patients suggests that the anomalous bundle was probably diseased or abnormal in the six patients with Wolff-Parkinson-White conduction. In addition, ajmaline caused the first appearance of phase 4 or phase 3 block, or both, but not total interruption of conduction in 26 of the 46 patients with Wolff-Parkinson-White conduction (56.5%). Ajmaline does not cause fascicular block in normal subjects; thus this finding suggests either that the anomalous bundle is diseased or that the safety margin for conduction in the anomalous bundle is much narrower than in the bundle branch system. The conduction-depressing action of ajmaline may be greater at relatively rapid or relatively slow rates of stimulation, and smaller or absent at intermediate rates.

  14. Performance of a Novel PMMA Polymer Imaging Bundle for Field Acquisition and Wavefront Sensing

    NASA Astrophysics Data System (ADS)

    Richards, S. N.; Leon-Saval, S.; Goodwin, M.; Zheng, J.; Lawrence, J. S.; Bryant, J. J.; Bland-Hawthorn, J.; Norris, B.; Cvetojevic, N.; Argyros, A.

    2017-01-01

    Imaging bundles provide a convenient way to translate a spatially coherent image, yet conventional imaging bundles made from silica fibre optics typically remain expensive with large losses due to poor filling factors ( 40%). We present the characterisation of a novel polymer imaging bundle made from poly(methyl methacrylate) (PMMA) that is considerably cheaper and a better alternative to silica imaging bundles over short distances ( 1 m; from the middle to the edge of a telescope's focal plane). The large increase in filling factor (92% for the polymer imaging bundle) outweighs the large increase in optical attenuation from using PMMA (1 dB/m) instead of silica (10-3 dB/m). We present and discuss current and possible future multi-object applications of the polymer imaging bundle in the context of astronomical instrumentation including: field acquisition, guiding, wavefront sensing, narrow-band imaging, aperture masking, and speckle imaging. The use of PMMA limits its use in low-light applications (e.g., imaging of galaxies); however, it is possible to fabricate polymer imaging bundles from a range of polymers that are better suited to the desired science.

  15. Two-dimensional evaluation of 3D needled Cf/SiC composite fiber bundle surface

    NASA Astrophysics Data System (ADS)

    Wei, Jinhua; Lin, Bin; Cao, Xiaoyan; Zhang, Xiaofeng; Fang, Sheng

    2015-11-01

    The variations of fiber bundle surface microstructure have direct influence on the material performance, especially the friction and wear properties. Therefore, fiber bundle is the smallest evaluation unit of Cf/SiC composite surface. However, due to the anisotropy and inhomogeneity of Cf/SiC composite, it is difficult to evaluate the surface characteristics. Researchers think that two-dimensional evaluation is not suitable for the composites surface assessment any more because of its complex composition and varied surface structure. In this paper, a novel method is introduced for the evaluation of 3D needled Cf/SiC composite fiber bundle surface. On the level of Cf/SiC composite fiber bundle surface, two-dimensional evaluation method is adopted, with which the fiber bundle surface quality can be quantitatively evaluated by the two-dimensional surface roughness Ra. As long as the extracted surface profiles averagely distributed on Cf/SiC composite fiber bundle surface, with appropriate sampling length and sampling number, the mean value of Ra can estimate the whole surface roughness, thus reflecting the roughness degree of surface accurately. This study not only benefits the detection of 3D needled Cf/SiC composite fiber bundle surface quality, and lays a foundation on the evaluation of material functional features in further. And it corresponds to the convenient application in engineering practice.

  16. Optical design of endoscopic shape-tracker using quantum dots embedded in fiber bundles

    NASA Astrophysics Data System (ADS)

    Eisenstein, Jessica; Gavalis, Robb; Wong, Peter Y.; Cao, Caroline G. L.

    2009-08-01

    Colonoscopy is the current gold standard for colon cancer screening and diagnosis. However, the near-blind navigation process employed during colonoscopy results in endoscopist disorientation and scope looping, leading to missed detection of tumors, incorrect localization, and pain for the patient. A fiber optic bend sensor, which would fit into the working channel of a colonoscope, is developed to aid navigation through the colon during colonoscopy. The bend sensor is comprised of a bundle of seven fibers doped with quantum dots (QDs). Each fiber within the bundle contains a unique region made up of three zones with differently-colored QDs, spaced 120° apart circumferentially on the fiber. During bending at the QD region, light lost from the fiber's core is coupled into one of the QD zones, inducing fluorescence of the corresponding color whose intensity is proportional to the degree of bending. A complementary metal oxide semiconductor camera is used to obtain an image of the fluorescing end faces of the fiber bundle. The location of the fiber within the bundle, the color of fluorescence, and the fluorescence intensity are used to determine the bundle's bending location, direction, and degree of curvature, respectively. Preliminary results obtained using a single fiber with three QD zones and a seven-fiber bundle containing one active fiber with two QDs (180° apart) demonstrate the feasibility of the concept. Further developments on fiber orientation during bundling and the design of a graphical user interface to communicate bending information are also discussed.

  17. Actin-binding proteins sensitively mediate F-actin bundle stiffness

    NASA Astrophysics Data System (ADS)

    Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

    2006-09-01

    Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

  18. Sperm bundle and reproductive organs of carabid beetles tribe Pterostichini (Coleoptera: Carabidae).

    PubMed

    Sasakawa, Kôji

    2007-05-01

    The morphological characteristics of sperm and reproductive organs may offer clues as to how reproductive systems have evolved. In this paper, the morphologies of the sperm and male reproductive organs of carabid beetles in the tribe Pterostichini (Coleoptera: Carabidae) are described, and the morphological associations among characters are examined. All species form sperm bundles in which the head of the sperm was embedded in a rod-shaped structure, i.e., spermatodesm. The spermatodesm shape (left-handed spiral, right-handed spiral, or without conspicuous spiral structure) and the condition of the sperm on the spermatodesm surface (with the tail free-moving or forming a thin, sheetlike structure) vary among species. In all species, the spiral directions of the convoluted seminal vesicles and vasa deferentia are the same on both sides of the body; that is, they show an asymmetric structure. The species in which the sperm bundle and the seminal vesicles both have a spiral structure could be classified into two types, with significant differences in sperm-bundle length between the two types. The species with a sperm-bundle spiral and seminal-vesicle spiral of almost the same diameter have longer sperm bundles than the species with a sperm-bundle spiral and seminal-vesicle tube of almost the same diameter. In the former type, the spiral directions of the sperm bundles and seminal vesicles are inevitably the same, whereas they differ in some species with the later type. Therefore, increased sperm bundle length appears to have been facilitated by the concordance of the sperm bundle's coiling direction with the coiling direction of the seminal vesicle.

  19. Coupling and elastic loading affect the active response by the inner ear hair cell bundles.

    PubMed

    Strimbu, Clark Elliott; Fredrickson-Hemsing, Lea; Bozovic, Dolores

    2012-01-01

    Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non-mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the otolithic membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the otolithic membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in the system of coupled hair bundles by external input is sufficient to displace large overlying structures.

  20. Education alone is not enough in ventilator associated pneumonia care bundle compliance

    PubMed Central

    Hamishehkar, Hadi; Vahidinezhad, Mahdi; Mashayekhi, Simin Ozar; Asgharian, Parina; Hassankhani, Hadi; Mahmoodpoor, Ata

    2014-01-01

    Objective: Ventilator-associated pneumonia (VAP) described as a secondary and preventable consequence in mechanically ventilated patients, emerges 48 h or more after patients intubation. Considering the high morbidity and mortality rate of VAP and the fact that VAP is preventable, it seemed necessary to evaluate care bundle compliance rate and effect of education on its improvement. Methods: This observational study was conducted on 10 Intensive Care Units (ICUs) of four university affiliated hospitals in three steps. In the first step, VAP care bundle compliance including head of bed (HOB) elevation, endotracheal cuff pressure (ETCP), mouthwash time, utilizing close suction systems, subglottic secretion drainage, type of suction package, and hand wash before suctioning was evaluated. In the second and third steps, ICU staffs were trained and its effect on VAP care bundle compliance was investigated. Finally, an inquiry from nurses was conducted to evaluate the obtained results. Findings: A total of 552 checklists consisting of 294 observations in the pre-education group and 258 observations in the posteducation group were filled. Mean VAP care bundle compliance in pre-education and posteducation stages was 36.5% and 41.2%, respectively (P > 0.05). Except for patients' mouth washing, there were no improvement in HOB elevation (>30°), hand washing and ETCP after education. Based on the results of questionnaire received from nurses at the end of study, more than 90% of nurses believed that lack of rigid monitoring of VAP care bundle is a main reason of low adherence for VAP care bundle compliance. Conclusion: The adherence to VAP care bundle was inappropriate. Education seems to be ineffective on improving VAP care bundle compliance. Frequent recall of the necessity of the VAP care bundle and the continuous supervision of ICU staffs is highly recommended. PMID:25114937

  1. Analytical Deriving of the Field Capacity through Soil Bundle Model

    NASA Astrophysics Data System (ADS)

    Arnone, E.; Viola, F.; Antinoro, C.; Noto, L. V.

    2015-12-01

    The concept of field capacity as soil hydraulic parameter is widely used in many hydrological applications. Althought its recurring usage, its definition is not univocal. Traditionally, field capacity has been related to the amount of water that remains in the soil after the excess water has drained away and the water downward movement experiences a significant decresase. Quantifying the drainage of excess of water may be vague and several definitions, often subjective, have been proposed. These definitions are based on fixed thresholds either of time, pressure, or flux to which the field capacity condition is associated. The flux-based definition identifies the field capacity as the soil moisture value corresponding to an arbitrary fixed threshold of free drainage flux. Recently, many works have investigated the flux-based definition by varying either the drainage threshold, the geometry setting and mainly the description of the drainage flux. Most of these methods are based on the simulation of the flux through a porous medium by using the Darcy's law or Richard's equation. Using the above-mentioned flux-based definition, in this work we propose an alternative analytical approach for deriving the field capacity based on a bundle-of-tubes model. The pore space of a porous medium is conceptualized as a bundle of capillary tubes of given length of different radii, derived from a known distribution. The drainage from a single capillary tube is given by the analytical solution of the differential equation describing the water height evolution within the capillary tube. This equation is based on the Poiseuille's law and describes the drainage flux with time as a function of tube radius. The drainage process is then integrated for any portion of soil taking into account the tube radius distribution which in turns depends on the soil type. This methodology allows to analytically derive the dynamics of drainage water flux for any soil type and consequently to define the

  2. All-optical photoacoustic imaging system using fiber ultrasound probe and hollow optical fiber bundle.

    PubMed

    Miida, Yusuke; Matsuura, Yuji

    2013-09-23

    An all-optical 3D photoacoustic imaging probe that consists of an optical fiber probe for ultrasound detection and a bundle of hollow optical fibers for excitation of photoacoustic waves was developed. The fiber probe for ultrasound is based on a single-mode optical fiber with a thin polymer film attached to the output end surface that works as a Fabry Perot etalon. The input end of the hollow fiber bundle is aligned so that each fiber in the bundle is sequentially excited. A thin and flexible probe can be obtained because the probe system does not have a scanning mechanism at the distal end.

  3. Atmospheric effects in the intensity of muon bundles and geometrical mechanism of their formation

    NASA Astrophysics Data System (ADS)

    Kokoulin, R. P.; Bogdanov, A. G.; Dmitrieva, A. N.; Romanenkova, E. V.; Shutenko, V. V.; Yurina, E. A.

    2016-02-01

    Temporal changes in the intensity of muon bundles produced as a result of interactions of primary cosmic ray particles with energies of the order of 1015 eV and detected at the ground level are analyzed. Seasonal variations, barometric and temperature effects, and correlations with the altitudes of various levels of residual pressure are considered. It is shown that muon bundle intensity variations are well explained in frame of a simple mechanism related with changes of the muon lateral distribution function at the observation level caused by geometrical changes of the effective altitude of the formation of the bundles.

  4. [Bundle of His tachycardia and chronic reciprocating rhythm: rare forms of prenatal tachycardia].

    PubMed

    Lupoglazoff, J M; Denjoy, I; Magnier, S; Oury, J F; Blot, P; Casasoprana, A; Azancot, A

    2000-05-01

    In cases of permanent tachycardia, ante-natal diagnosis of chronic reciprocating rhythms with long RP' intervals or His bundle tachycardias is difficult. The authors report two cases of permanent foetal tachycardia with 1/1 atrioventricular conduction. In one case, the tachycardia rate was 170/min with anasarca treated by amiodarone in view of a family history of His bundle tachycardia. In the other case, the tachycardia rate was 200/min but with no signs of cardiac failure and was, therefore, not treated. The ECG at birth confirmed the diagnosis of His bundle tachycardia in the first case and identified a chronic reciprocating rhythm in the other.

  5. Experimental investigations of uncovered-bundle heat transfer and two-phase mixture-level swell under high-pressure low heat-flux conditions. [PWR

    SciTech Connect

    Anklam, T. M.; Miller, R. J.; White, M. D.

    1982-03-01

    Results are reported from a series of uncovered-bundle heat transfer and mixture-level swell tests. Experimental testing was performed at Oak Ridge National Laboratory in the Thermal Hydraulic Test Facility (THTF). The THTF is an electrically heated bundle test loop configured to produce conditions similar to those in a small-break loss-of-coolant accident. The objective of heat transfer testing was to acquire heat transfer coefficients and fluid conditions in a partially uncovered bundle. Testing was performed in a quasi-steady-state mode with the heated core 30 to 40% uncovered. Linear heat rates varied from 0.32 to 2.22 kW/m.rod (0.1 to 0.68 kW/ft.rod). Under these conditions peak clad temperatures in excess of 1050 K (1430/sup 0/F) were observed, and total heat transfer coefficients ranged from 0.0045 to 0.037 W/cm/sup 2/.K (8 to 65 Btu/h.ft/sup 2/./sup 0/F). Spacer grids were observed to enhance heat transfer at, and downstream of, the grid. Radiation heat transfer was calculated to account for as much as 65% of total heat transfer in low-flow tests.

  6. Robustness of power systems under a democratic-fiber-bundle-like model.

    PubMed

    Yağan, Osman

    2015-06-01

    We consider a power system with N transmission lines whose initial loads (i.e., power flows) L(1),...,L(N) are independent and identically distributed with P(L)(x)=P[L≤x]. The capacity C(i) defines the maximum flow allowed on line i and is assumed to be given by C(i)=(1+α)L(i), with α>0. We study the robustness of this power system against random attacks (or failures) that target a p fraction of the lines, under a democratic fiber-bundle-like model. Namely, when a line fails, the load it was carrying is redistributed equally among the remaining lines. Our contributions are as follows. (i) We show analytically that the final breakdown of the system always takes place through a first-order transition at the critical attack size p(☆)=1-(E[L]/max(x)(P[L>x](αx+E[L|L>x])), where E[·] is the expectation operator; (ii) we derive conditions on the distribution P(L)(x) for which the first-order breakdown of the system occurs abruptly without any preceding diverging rate of failure; (iii) we provide a detailed analysis of the robustness of the system under three specific load distributions-uniform, Pareto, and Weibull-showing that with the minimum load L(min) and mean load E[L] fixed, Pareto distribution is the worst (in terms of robustness) among the three, whereas Weibull distribution is the best with shape parameter selected relatively large; (iv) we provide numerical results that confirm our mean-field analysis; and (v) we show that p(☆) is maximized when the load distribution is a Dirac delta function centered at E[L], i.e., when all lines carry the same load. This last finding is particularly surprising given that heterogeneity is known to lead to high robustness against random failures in many other systems.

  7. Skeletal cubic, lamellar, and ribbon phases of bundled thermotropic bolapolyphiles.

    PubMed

    Liu, Feng; Prehm, Marko; Zeng, Xiangbing; Tschierske, Carsten; Ungar, Goran

    2014-05-14

    A series of T-shaped polyphilic molecules composed of a rigid linear biphenyl core with a polar glycerol group at each end and one swallow-tail semiperfluorinated lateral chain were synthesized and their thermotropic liquid crystalline (LC) phases were investigated by X-ray diffraction, calorimetry, and microscopy. The compounds have a long alkyl spacer between the aromatic core and the fluorinated C(n)F(2n+1) ends, where n = 4, 6, 8, and 10. Upon melting, all compounds start with lamellar LC phases, followed on heating by a rectangular columnar ribbon phase with c2mm symmetry. Unusually, a ribbon is a flat bundle of molecular cores highly aligned parallel to the ribbon axis. On further heating, for n = 8 and 10, this phase is succeeded by a bicontinuous cubic phase with Ia3d symmetry. This is a new variant of the "gyroid" phase, with axially oriented rod-like molecular cores forming the skeleton of the two infinite networks and junctions separated by exactly two molecular lengths. In this tricontinuous core-shell structure (aromatic-aliphatic-perfluoroalkyl), the polar glycerol domains of appreciable size, contained within the skeleton, can be considered as micellar.

  8. RBA: Reduced Bundle Adjustment for oblique aerial photogrammetry

    NASA Astrophysics Data System (ADS)

    Sun, Yanbiao; Sun, Huabo; Yan, Lei; Fan, Shiyue; Chen, Rui

    2016-11-01

    This study proposes an efficient Bundle Adjustment (BA) model for oblique aerial photogrammetry to reduce the number of unknown parameters and the dimensions of a non-linear optimization problem. Instead of serving as independent exterior orientations, oblique camera poses are parameterized with nadir camera poses and constant relative poses between oblique and nadir cameras. New observation functions are created with image points as a function of the nadir pose and the relative pose parameters. With these observation functions, the problem of BA is defined as finding optimal unknown parameters by minimizing the total difference between estimated and observed image points. A Gauss-Newton optimization method is utilized to provide a solution for this least-square problem with a reduced normal equation, which plays a very critical role in the convergence and efficiency of BA. Compared with traditional BA methods, the number of unknown parameters and the dimension of the normal equations decrease, this approach dramatically reduces the computational complexity and memory cost especially for large-scale scenarios with a number of oblique images. Four synthetic datasets and a real dataset were used to check the validation and the accuracy of the proposed method. The accuracy of the proposed method is very close to that of the traditional BA method, but the efficiency can be significantly improved by the proposed method. For very large-scale scenarios, the proposed method can still address the limitation of memory and orientate all images captured by an oblique aerial multi-camera system.

  9. Bundled-Optode Method in Functional Near-Infrared Spectroscopy

    PubMed Central

    Nguyen, Hoang-Dung; Hong, Keum-Shik; Shin, Yong-Il

    2016-01-01

    In this paper, a theory for detection of the absolute concentrations of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) from hemodynamic responses using a bundled-optode configuration in functional near-infrared spectroscopy (fNIRS) is proposed. The proposed method is then applied to the identification of two fingers (i.e., little and thumb) during their flexion and extension. This experiment involves a continuous-wave-type dual-wavelength (760 and 830 nm) fNIRS and five healthy male subjects. The active brain locations of two finger movements are identified based on the analysis of the t- and p-values of the averaged HbOs, which are quite distinctive. Our experimental results, furthermore, revealed that the hemodynamic responses of two-finger movements are different: The mean, peak, and time-to-peak of little finger movements are higher than those of thumb movements. It is noteworthy that the developed method can be extended to 3-dimensional fNIRS imaging. PMID:27788178

  10. Neurovascular Bundle Decompression without Excessive Dissection for Tarsal Tunnel Syndrome

    PubMed Central

    KIM, Kyongsong; ISU, Toyohiko; MORIMOTO, Daijiro; SASAMORI, Toru; SUGAWARA, Atsushi; CHIBA, Yasuhiro; ISOBE, Masahiro; KOBAYASHI, Shiro; MORITA, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion. PMID:25367582

  11. Neurovascular bundle decompression without excessive dissection for tarsal tunnel syndrome.

    PubMed

    Kim, Kyongsong; Isu, Toyohiko; Morimoto, Daijiro; Sasamori, Toru; Sugawara, Atsushi; Chiba, Yasuhiro; Isobe, Masahiro; Kobayashi, Shiro; Morita, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion.

  12. Tube bundle system: for monitoring of coal mine atmosphere.

    PubMed

    Zipf, R Karl; Marchewka, W; Mohamed, K; Addis, J; Karnack, F

    2013-05-01

    A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine. The gas samples are drawn via vacuum pump to the surface and are typically analyzed for oxygen, methane, carbon dioxide and carbon monoxide. Results of the gas analyses are displayed and recorded for further analysis. Trends in the composition of the mine atmosphere, such as increasing methane or carbon monoxide concentration, can be detected early, permitting rapid intervention that prevents problems, such as a potentially explosive atmosphere behind seals, fire or spontaneous combustion. TBS is a well-developed technology and has been used in coal mines around the world for more than 50 years. Most longwall coal mines in Australia deploy a TBS, usually with 30 to 40 monitoring points as part of their atmospheric monitoring. The primary uses of a TBS are detecting spontaneous combustion and maintaining sealed areas inert. The TBS might also provide mine atmosphere gas composition data after a catastrophe occurs in an underground mine, if the sampling tubes are not damaged. TBSs are not an alternative to statutory gas and ventilation airflow monitoring by electronic sensors or people; rather, they are an option to consider in an overall mine atmosphere monitoring strategy. This paper describes the hardware, software and operation of a TBS and presents one example of typical data from a longwall coal mine.

  13. The left bundle branch block revised with novel imaging modalities

    PubMed Central

    van Dijk, J.; Mannaerts, H.F.J.; Germans, T.; Hauer, H.A.; Knaapen, P.; Visser, C.A.; Kamp, O.

    2006-01-01

    Left bundle branch block (LBBB) is related to abnormal cardiac conduction and mechanical asynchrony and is associated with hypertension and coronary artery disease. Improved evaluation of left ventricular (LV) mechanical asynchrony is needed, because of the increasing number of patients with LBBB and heart failure. In this paper, we describe tissue Doppler imaging (TDI), strain (rate) imaging and tissue tracking in LBBB patients. A variety of patterns of mechanical activation can be observed in LBBB patients. A recent development, referred to as tissue synchronisation imaging, colour codes TDI time-to-peak systolic velocities of segments and displays mechanical asynchrony. Furthermore, real-time 3D echocardiography provides new regional information about mechanical asynchrony. Contained in an LV model and projected on a bull's eye plot, this modality helps to display the spatial distribution of mechanical asynchrony. Finally, segmental time-to-peak circumferential strain curves, produced by cardiac magnetic resonance imaging, provide additional quantification of LV mechanical asynchrony. Effects of LBBB on regional and global cardiac function are impressive, myocardial involvement seems to play a role and with the help of these novel imaging modalities, new insights continue to develop. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7 PMID:25696572

  14. Temperature response of bundle-sheath conductance in maize leaves

    PubMed Central

    Yin, Xinyou; van der Putten, Peter E.L.; Driever, Steven M.; Struik, Paul C.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  15. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2012-02-01

    Assemblies of filamentous biopolymers are hierarchical materials in which the properties of the overall assemblage are determined by structure and interactions between constituent particles at all hierarchical levels. For example, the overall bending rigidity of a two bundled filaments greatly depends on the bending rigidity of, and the adhesion strength between individual filaments. However, another property of importance is the ability for the filaments to slide freely against one another. Everyday experience indicates that it is much easier to bend a stack of papers in which individual sheets freely slide past each other than the same stack of papers in which all the sheets are irreversibly glued together. Similarly, in filamentous structures the ability for local re-arrangement is of the utmost importance in determining the properties of the structures observed. We have developed a method to directly measure the frictional interactions between a pair of aligned filaments in a well-defined and controllable configuration. This enables us to systematically investigate the role of adhesion strength, filament orientation, length, and surface structure.

  16. Oscillatory characteristics of carbon nanotubes inside carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Alipour, A.; Sadeghi, F.

    2012-12-01

    This article presents a comprehensive study on the mechanics of carbon nanotubes (CNTs) oscillating in CNT bundles. Using the continuum approximation along with Lennard-Jones (LJ) potential function, new semi-analytical expressions in terms of double integrals are presented to evaluate van der Waals (vdW) potential energy and interaction force upon which the equation of motion is directly solved. The obtained potential expression enables one to arrive at a new semi-analytical formula for the exact evaluation of oscillation frequency. Also, an algebraic frequency formula is extracted on the basis of the simplifying assumption of constant vdW force. Based on the present expressions, a thorough study on various aspects of operating frequencies under different system parameters is given, which permits fresh insight into the problem. The strong dependence of oscillation frequency on system parameters, such as the extrusion distance and initial velocity of the core as initial conditions for the motion is indicated. Interestingly, a specific initial velocity is found at which the oscillation frequency is independent of the core length. In addition, a relation between this specific initial velocity and the escape velocity is disclosed.

  17. Corrosion of Palo Verde 2 upper bundle steam generator tubing

    SciTech Connect

    Magee, T.P.; Molkenthin, J.P.; Hall, J.F.; Melton, M.A.; Sachs, D.E.; Sweeney, K.M.; Begley, J.

    1995-12-31

    Palo Verde Unit-2 (PV-2) has experienced degradation in the upper bundle region of some of its Alloy 600 steam generator (SG) tubes. Arizona Public Service (APS) initiated several mitigating actions, including a 1994 chemical cleaning to remove tube deposits. Eddy current tests (ECT) conducted after chemical cleaning showed an increase in the number of indications. To detail the bend region indications, APS elected to remove the hot leg bend portion of 21 tubes for laboratory examination. The examination showed that the degradation mode was outside diameter initiated intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC). The most severe corrosion occurred beneath ridge-like deposits, although shallow IGA was discovered on large areas of free-span tubing. In some cases, degradation was associated with scratches or gouges on the tubes. Some wear was apparently caused by periodic tube-to-tube contact. Degradation was found in tubing with both poor and partial correspondence between grain boundaries and carbides. The chemical conditions that caused the tube degradation were likely neutral to alkaline solutions containing residual sulfur (sulfide) species. The burst strength of all tubes tested significantly exceeded Regulatory Guide 1.121 requirements. These results confirmed past PV-2 tube corrosion examination results.

  18. Bundle-forming pilus retraction enhances enteropathogenic Escherichia coli infectivity

    PubMed Central

    Zahavi, Eitan E.; Lieberman, Joshua A.; Donnenberg, Michael S.; Nitzan, Mor; Baruch, Kobi; Rosenshine, Ilan; Turner, Jerrold R.; Melamed-Book, Naomi; Feinstein, Naomi; Zlotkin-Rivkin, Efrat; Aroeti, Benjamin

    2011-01-01

    Enteropathogenic Escherichia coli (EPEC) is an important human pathogen that causes acute infantile diarrhea. The type IV bundle-forming pili (BFP) of typical EPEC strains are dynamic fibrillar organelles that can extend out and retract into the bacterium. The bfpF gene encodes for BfpF, a protein that promotes pili retraction. The BFP are involved in bacterial autoaggregation and in mediating the initial adherence of the bacterium with its host cell. Importantly, BFP retraction is implicated in virulence in experimental human infection. How pili retraction contributes to EPEC pathogenesis at the cellular level remains largely obscure, however. In this study, an effort has been made to address this question using engineered EPEC strains with induced BFP retraction capacity. We show that the retraction is important for tight-junction disruption and, to a lesser extent, actin-rich pedestal formation by promoting efficient translocation of bacterial protein effectors into the host cells. A model is proposed whereby BFP retraction permits closer apposition between the bacterial and the host cell surfaces, thus enabling timely and effective introduction of bacterial effectors into the host cell via the type III secretion apparatus. Our studies hence suggest novel insights into the involvement of pili retraction in EPEC pathogenesis. PMID:21613538

  19. Strategies and tactics for successful implementation of bundled payments: bundled payment for care improvement at a large, urban, academic medical center.

    PubMed

    Iorio, Richard

    2015-03-01

    As health care reform continues to evolve, there will need to be an emphasis on generating value, quality improvement, and cost control. In 2011, the Centers for Medicare and Medicaid Services (CMS) initiated a new Bundled Payment for Care Improvement initiative. Early results from this CMS bundled payment initiative at an urban, tertiary, academic medical center demonstrate decreased length of stay and increased discharge to home, with decreasing readmission rates, which can result in cost-savings without compromise of the quality of care. Changes in care coordination, clinical care pathways, and evidence-based protocols are the key to improving the quality metrics and cost effectiveness within the implementation of the bundled payment for care initiative, thus bringing increased value to our total joint arthroplasty patients.

  20. The degree of the logarithmic extension of the cotangent bundle to the moduli of pointed curves and Hitchin systems, spectral curves and KP equations

    NASA Astrophysics Data System (ADS)

    Hodge, Andrew Richard

    This dissertation is divided into two parts. In the first part we prove a recursive relation for the Kahler-Einsein volume of the moduli space of genus g curves with n marked points in terms of the intersection of the Kahler-Einstein form with kappa classes. We will show that in the case where the genus is zero, the cohomology classes of the Kahler-Einstein form and kappa1 coincide. We will also show that if the genus is one, then the Kahler-Einstein volume can be computed in terms of kappa1 volume of moduli spaces of curves with either a smaller genus or less marked points. Using this we will show that the generating function for kappa1 volumes of genus one pointed curves satisfies a non-linear second order ordinary differential equation. In the section part of this dissertation we examine the moduli space of stable Higgs bundles. We determine an effective family of spectral curves that appear in the Hitchin fibration. This effective family will provide an embedding into the Sato Grassmannian. The Hitchin integrable system will be shown to be the pull back of the KP-flows on the Sto Grassmannian. We will show that the formal adjoint on the space of pseudo-differential operators corresponds to the Serre duality operation on the moduli space of stable Higgs bundles. Using this correspondence, we can identify the moduli space of stable Sp2m-Higgs bundles as a reduction of the KP equations. The dual abelian fibration associated to the Sp2m-Higgs moduli space is constructed as the symplectic quotient of a Lie algebra action on the moduli space of GL-Higgs bundles.

  1. 77 FR 9925 - Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-21

    ... From the Federal Register Online via the Government Publishing Office FEDERAL ELECTION COMMISSION...: Federal Election Commission. ACTION: Notice of adjustments to expenditure limitations and lobbyist bundling disclosure threshold. SUMMARY: As mandated by provisions of the Federal Election Campaign Act...

  2. Modeling of imaging fiber bundles and adapted signal processing for fringe projection

    NASA Astrophysics Data System (ADS)

    Matthias, Steffen; Kästner, Markus; Reithmeier, Eduard

    2016-12-01

    Fringe projection profilometry is an established technique for capturing three-dimensional (3-D)-geometry data with high-point densities in short time. By combining fringe projection with endoscopy techniques, it is possible to perform inline inspection of industrial manufacturing processes. A new fringe projection system is presented, which uses flexible image fiber bundles to achieve versatile positioning of a compact sensor head. When measuring specimens with highly varying reflectivity, such as technical surfaces on tool geometries, measurement errors increase especially due to the crosstalk between individual fibers in the bundle. A detailed analysis of the transmission properties of the utilized fiber bundles is presented. It is shown that aliasing is avoided due to the non-regular grid structure of a bundle. Different techniques are demonstrated to reduce the effect of crosstalk on the phase evaluation. Measurements of highly reflective technical surfaces with different geometrical properties are shown.

  3. Unmasking of left free wall ventricular preexcitation by His bundle ablation.

    PubMed Central

    Visman, A G; Hauer, R N; Robles de Medina, E O

    1993-01-01

    His bundle ablation was performed in a 48 year old man with drug refractory orthodromic atrioventricular reentrant tachycardia and paroxysmal atrial fibrillation. Reentry was caused by a left free wall concealed accessory pathway. Interruption of the His bundle by low energy direct current shock (25 J) was quickly followed by anterograde conduction via the accessory pathway, with various forms of advanced block. The combined effect of unfavourable anterograde conduction (prolonged anterograde effective refractory period and decremental conduction), the left lateral location of the accessory pathway and intra-atrial conduction delay on one side, and normal conduction via the atrioventricular node and His bundle with retrograde concealed conduction into the accessory pathway on the other side resulted in masking of the anterograde conduction capability of the anomalous pathway. This observation does not seem to invalidate the choice of His bundle ablation in similar cases. PMID:8518069

  4. Fabrication of a 10-m-length IR imaging bundle from arsenic trisulfide glass fibers

    NASA Astrophysics Data System (ADS)

    Hilton, Albert R., Sr.; McCord, James; Whaley, Glen; Loretz, Thomas J.; Modlin, Paul

    1999-04-01

    Amorphous Materials (AMI) has been engaged for several years in developing a process suitable for forming coherent imaging bundles from small diameter chalcogenide glass fibers. Currently, in a SBIR II program funded by the Navy Air Warfare Center at Patuxent River, Md., efforts are directed towards forming a bundle 10 meters in length from arsenic trisulfide glass fibers using the stacked ribbon method. A drum 10 meters in circumference was constructed on which to wind the ribbons. The fiber core diameter goal is 50 micrometer. The bundle will be 7 mm square with an active fiber area greater than 50% and an overall transmission goal of 50%. Anti-reflection coatings on both ends are provided using the AMI coating facility. A unique method of forming imaging bundles will be discussed. Images formed during evaluation will be shown.

  5. Dressed elliptic genus of heterotic compactifications with torsion and general bundles

    NASA Astrophysics Data System (ADS)

    Israël, Dan; Sarkis, Matthieu

    2016-08-01

    We define and compute the dressed elliptic genus of {N}=2 heterotic compactifications with torsion that are principal two-torus bundles over a K3 surface. We consider a large class of gauge bundles compatible with supersymmetry, consisting of a stable holomorphic vector bundle over the base together with an Abelian bundle over the total space, generalizing the computation previously done by the authors in the absence of the latter. Starting from a (0,2) gauged linear sigma-model with torsion we use supersymmetric localization to obtain the result. We provide also a mathematical definition of the dressed elliptic genus as a modified Euler characteristic and prove that both expressions agree for hypersurfaces in weighted projective spaces. Finally we show that it admits a natural decomposition in terms of {N}=4 superconformal characters, that may be useful to investigate moonshine phenomena for this wide class of {N}=2 vacua, that includes K3 × T 2 compactifications as special cases.

  6. Microcrystalline sodium tungsten bronze nanowire bundles as efficient visible light-responsive photocatalysts.

    PubMed

    Wang, Lei; Zhan, Jinhua; Fan, Weiliu; Cui, Guanwei; Sun, Honggang; Zhuo, Linhai; Zhao, Xian; Tang, Bo

    2010-12-14

    Microcrystalline sodium tungsten bronze nanowire bundles were obtained via a facile hydrothermal synthesis, and were applied in water purification as visible-light-driven photocatalysts for the first time.

  7. The myosin X motor is optimized for movement on actin bundles

    PubMed Central

    Ropars, Virginie; Yang, Zhaohui; Isabet, Tatiana; Blanc, Florian; Zhou, Kaifeng; Lin, Tianming; Liu, Xiaoyan; Hissier, Pascale; Samazan, Frédéric; Amigues, Béatrice; Yang, Eric D.; Park, Hyokeun; Pylypenko, Olena; Cecchini, Marco; Sindelar, Charles V.; Sweeney, H. Lee; Houdusse, Anne

    2016-01-01

    Myosin X has features not found in other myosins. Its structure must underlie its unique ability to generate filopodia, which are essential for neuritogenesis, wound healing, cancer metastasis and some pathogenic infections. By determining high-resolution structures of key components of this motor, and characterizing the in vitro behaviour of the native dimer, we identify the features that explain the myosin X dimer behaviour. Single-molecule studies demonstrate that a native myosin X dimer moves on actin bundles with higher velocities and takes larger steps than on single actin filaments. The largest steps on actin bundles are larger than previously reported for artificially dimerized myosin X constructs or any other myosin. Our model and kinetic data explain why these large steps and high velocities can only occur on bundled filaments. Thus, myosin X functions as an antiparallel dimer in cells with a unique geometry optimized for movement on actin bundles. PMID:27580874

  8. Some recent developments in the theory of acoustic transmission in tube bundles

    NASA Astrophysics Data System (ADS)

    Heckl, Maria A.; Mulholland, L. S.

    1995-01-01

    A comprehensive theoretical model for acoustic transmission in a tube bundle is presented. The tube bundle is considered as a series of diffraction gratings. Each grating consists of periodically spaced cylindrical tubes which obey the equations of motion of a cylindrical shell. Fluid loading is included. The model can be used for numerical simulations to calculate the sound field at any point in a tube bundle. Various phenomena can be predicted which are of interest for the development of acoustic diagnostics in heat exchangers. These include diffraction of a plane incident wave into several directions, the occurrence of passing and stopping bands in the transmission spectrum, features specific to oblique waves and the effect of dissipative losses. Tube bundles with baffle plates are also examined. The validity of the theoretical model is confirmed by comparison with experimental results.

  9. Adsorption behavior of ternary mixtures of noble gases inside single-walled carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Foroutan, Masumeh; Nasrabadi, Amir Taghavi

    2010-09-01

    In order to study the gas-storage and gas-filtering capability of carbon nanotube (CNT) bundles simultaneously, we considered the adsorption behavior of a ternary mixture of noble gases, including Argon (Ar), Krypton (Kr), and Xenon (Xe), i.e., Ar-Kr-Xe mixture, on (10, 10) single-walled carbon nanotube (SWCNT) bundles. Molecular dynamics (MD) simulations at different temperatures of (75, 100, 150, 200, 250, and 300) K were performed, and adsorption energies, self-diffusion coefficients, activation energies, and radial distribution functions (RDFs) were computed to analyze the thermodynamics, transport and structural properties of the adsorption systems. It is observed that the SWCNT bundles have larger contents of heavier noble gases compared to the lighter ones. This interesting behavior of SWCNT bundles makes them proper candidates for gas-storage and gas molecular-sieving processes.

  10. Correlations between nuclear morphology and bundles of cytoplasmic fibrils in 50 cases of acute myeloid leukaemia.

    PubMed Central

    Pearson, E C

    1986-01-01

    An electron microscopic examination was carried out of peripheral blood or bone marrow samples, or both, from 50 patients entered into the Medical Research Council 9th Acute Myeloid Leukaemia Trial. The results showed a striking correlation between the presence of conspicuous bundles of fibrils within the cytoplasm of the leukaemic cells and the degree of convolution or lobulation of the nuclei. In none of the samples were predominantly convoluted or lobed nuclei observed in the absence of prominent fibrillar bundles and in only two cases were nuclei of a more regular outline seen in association with many conspicuous bundles of cytoplasmic fibrils. No correlation was found between the apparent degree of maturity of the nuclei, as assessed by the degree of chromatin condensation, and the absence or abundance of fibrillar bundles. Images PMID:3456357

  11. Defect induced photoluminescence and ferromagnetic properties of bio-compatible SWCNT/Ni hybrid bundles.

    PubMed

    Gupta, Vinay; Gupta, Bipin Kumar; Kotnala, R K; Narayanan, T N; Grover, Vaneet; Shah, Jyoti; Agrawal, Vikash; Chand, Suresh; Shanker, Virendra

    2011-10-15

    Designing of bio-compatible nanomagnets with multiple functionalities receives immense scientific attention due to their potential applications in bio-labeling, medical diagnosis and treatment. Here we report the synthesis of Nickel (Ni) incorporated single-walled carbon nanotube (SWCNT) hybrid and bio-compatible bundles having interesting magnetic and photoluminescence (PL) properties. The SWCNT exhibits a high-crystallinity and it has an average diameter of ∼1.7 nm. Ni particles of 10-20 nm were incorporated within the SWCNT bundles. These hybrid bundles exhibit PL and it is attributed to the presence of delocalized π electrons and their recombination at the defective sites of SWCNT. Magnetic characterization revealed that the SWCNT/Ni hybrid bundle possesses a high (50 Oe) coercivity compared to bulk Ni and a long range ferromagnetic ordering at room temperature. MTT-assay has been conducted to study the cytotoxicity of these hybrid nanostructures.

  12. Contractile Units in Disordered Actomyosin Bundles Arise from F-Actin Buckling

    NASA Astrophysics Data System (ADS)

    Lenz, Martin; Thoresen, Todd; Gardel, Margaret L.; Dinner, Aaron R.

    2012-06-01

    Bundles of filaments and motors are central to contractility in cells. The classic example is striated muscle, where actomyosin contractility is mediated by highly organized sarcomeres which act as fundamental contractile units. However, many contractile bundles in vivo and in vitro lack sarcomeric organization. Here we propose a model for how contractility can arise in bundles without sarcomeric organization and validate its predictions with experiments on a reconstituted system. In the model, internal stresses in frustrated arrangements of motors with diverse velocities cause filaments to buckle, leading to overall shortening. We describe the onset of buckling in the presence of stochastic motor head detachment and predict that buckling-induced contraction occurs in an intermediate range of motor densities. We then calculate the size of the “contractile units” associated with this process. Consistent with these results, our reconstituted actomyosin bundles show contraction at relatively high motor density, and we observe buckling at the predicted length scale.

  13. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of the electron density for an individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closest neighbours reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  14. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of electron density for na individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closet neighbors reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  15. Carbon nanotube bundles/polystyrene composites as high-performance flexible thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Suemori, Kouji; Watanabe, Yuichi; Hoshino, Satoshi

    2015-03-01

    Lightweight and flexible thermoelectric devices consisting of carbon nanotube (CNT)-based materials have the potential to be used for the various applications, such as energy harvesting from the low-temperature waste heat that exists ubiquitously in living areas. Because high-performance CNT-based materials are crucial for the broad-ranging employment of CNT-based thermoelectric devices, considerable efforts are being made to improve the power-generation capability of CNT-based thermoelectric materials. Here, we report high-performance thermoelectric composites consisting of CNT bundles and polystyrene fabricated by a planetary ball milling-based dispersion technique, which allows for the direct dispersion of the CNT bundles within the polystyrene matrix without causing the disaggregation of the bundled CNTs into individual ones. The CNT-bundles/polystyrene composites reported here exhibit a power factor of 413 μW/K2.m.

  16. 78 FR 8530 - Price Index Adjustments for Contribution and Expenditure Limitations and Lobbyist Bundling...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-06

    ... Price Index Adjustments for Contribution and Expenditure Limitations and Lobbyist Bundling Disclosure Threshold AGENCY: Federal Election Commission. ACTION: Notice of adjustments to contribution and expenditure...'' or ``the Commission'') is adjusting certain contribution and expenditure limitations and the...

  17. 76 FR 8368 - Price Index Adjustments for Contribution and Expenditure Limits and Lobbyist Bundling Disclosure...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-14

    ... Price Index Adjustments for Contribution and Expenditure Limits and Lobbyist Bundling Disclosure Threshold AGENCY: Federal Election Commission. ACTION: Notice of adjustments to contribution and expenditure...'' or ``the Commission'') is adjusting certain contribution and expenditure limits and the...

  18. Bundled payments for care improvement initiative: the next evolution of payment formulations: AAHKS Bundled Payment Task Force.

    PubMed

    Froimson, Mark I; Rana, Adam; White, Richard E; Marshall, Amanda; Schutzer, Steve F; Healy, William L; Naas, Peggy; Daubert, Gail; Iorio, Richard; Parsley, Brian

    2013-09-01

    The Patient Protection and Affordable Care Act contains a number of provision for improving the delivery of healthcare in the United States, among the most impactful of which may be the call for modifications in the packaging of and payment for care that is bundled into episodes. The move away from fee for service payment models to payment for coordinated care delivered as comprehensive episodes is heralded as having great potential to enhance quality and reduce cost, thereby increasing the value of the care delivered. This effort builds on the prior experience around delivering care for arthroplasty under the Acute Care Episode Project and offers extensions and opportunities to modify the experience moving forward. Total hip and knee arthroplasties are viewed as ideal treatments to test the effectiveness of this payment model. Providers must learn the nuances of these modified care delivery concepts and evaluate whether their environment is conducive to success in this arena. This fundamental shift in payment for care offers both considerable risk and tremendous opportunity for physicians. Acquiring an understanding of the recent experience and the determinants of future success will best position orthopaedic surgeons to thrive in this new environment. Although this will remain a dynamic exercise for some time, early experience may enhance the chances for long term success, and physicians can rightfully lead the care delivery redesign process.

  19. An Exploration of Human Well-Being Bundles as Identifiers of Ecosystem Service Use Patterns

    PubMed Central

    Biggs, Reinette; Reyers, Belinda

    2016-01-01

    We take a social-ecological systems perspective to investigate the linkages between ecosystem services and human well-being in South Africa. A recent paper identified different types of social-ecological systems in the country, based on distinct bundles of ecosystem service use. These system types were found to represent increasingly weak direct feedbacks between nature and people, from rural “green-loop” communities to urban “red-loop” societies. Here we construct human well-being bundles and explore whether the well-being bundles can be used to identify the same social-ecological system types that were identified using bundles of ecosystem service use. Based on national census data, we found three distinct well-being bundle types that are mainly characterized by differences in income, unemployment and property ownership. The distribution of these well-being bundles approximates the distribution of ecosystem service use bundles to a substantial degree: High levels of income and education generally coincided with areas characterised by low levels of direct ecosystem service use (or red-loop systems), while the majority of low well-being areas coincided with medium and high levels of direct ecosystem service use (or transition and green-loop systems). However, our results indicate that transformations from green-loop to red-loop systems do not always entail an immediate improvement in well-being, which we suggest may be due to a time lag between changes in the different system components. Using human well-being bundles as an indicator of social-ecological dynamics may be useful in other contexts since it is based on socio-economic data commonly collected by governments, and provides important insights into the connections between ecosystem services and human well-being at policy-relevant sub-national scales. PMID:27695120

  20. An Exploration of Human Well-Being Bundles as Identifiers of Ecosystem Service Use Patterns.

    PubMed

    Hamann, Maike; Biggs, Reinette; Reyers, Belinda

    2016-01-01

    We take a social-ecological systems perspective to investigate the linkages between ecosystem services and human well-being in South Africa. A recent paper identified different types of social-ecological systems in the country, based on distinct bundles of ecosystem service use. These system types were found to represent increasingly weak direct feedbacks between nature and people, from rural "green-loop" communities to urban "red-loop" societies. Here we construct human well-being bundles and explore whether the well-being bundles can be used to identify the same social-ecological system types that were identified using bundles of ecosystem service use. Based on national census data, we found three distinct well-being bundle types that are mainly characterized by differences in income, unemployment and property ownership. The distribution of these well-being bundles approximates the distribution of ecosystem service use bundles to a substantial degree: High levels of income and education generally coincided with areas characterised by low levels of direct ecosystem service use (or red-loop systems), while the majority of low well-being areas coincided with medium and high levels of direct ecosystem service use (or transition and green-loop systems). However, our results indicate that transformations from green-loop to red-loop systems do not always entail an immediate improvement in well-being, which we suggest may be due to a time lag between changes in the different system components. Using human well-being bundles as an indicator of social-ecological dynamics may be useful in other contexts since it is based on socio-economic data commonly collected by governments, and provides important insights into the connections between ecosystem services and human well-being at policy-relevant sub-national scales.

  1. Laboratory manual for salt-mixing test in 37- and 217-pin bundles. [LMFBR

    SciTech Connect

    Chan, Y.N.; Todreas, N.E.

    1980-08-01

    This laboratory manual deals with the procedure employed during salt tracer experiments used in evaluating the hydraulic characteristics of a rod bundle. A description of the standard equipment used is given together with the details of manufacture of probes used for detecting the salt concentration. Details of the bundle construction have been excluded as they are availble in the reference cited. An attempt has been made to point out potential trouble areas and procedures.

  2. Force Generation by Molecular-Motor-Powered Microtubule Bundles; Implications for Neuronal Polarization and Growth

    PubMed Central

    Jakobs, Maximilian; Franze, Kristian; Zemel, Assaf

    2015-01-01

    The heavily cross-linked microtubule (MT) bundles found in neuronal processes play a central role in the initiation, growth and maturation of axons and dendrites; however, a quantitative understanding of their mechanical function is still lacking. We here developed computer simulations to investigate the dynamics of force generation in 1D bundles of MTs that are cross-linked and powered by molecular motors. The motion of filaments and the forces they exert are investigated as a function of the motor type (unipolar or bipolar), MT density and length, applied load, and motor connectivity. We demonstrate that only unipolar motors (e.g., kinesin-1) can provide the driving force for bundle expansion, while bipolar motors (e.g., kinesin-5) oppose it. The force generation capacity of the bundles is shown to depend sharply on the fraction of unipolar motors due to a percolation transition that must occur in the bundle. Scaling laws between bundle length, force, MT length and motor fraction are presented. In addition, we investigate the dynamics of growth in the presence of a constant influx of MTs. Beyond a short equilibration period, the bundles grow linearly in time. In this growth regime, the bundle extends as one mass forward with most filaments sliding with the growth velocity. The growth velocity is shown to be dictated by the inward flux of MTs, to inversely scale with the load and to be independent of the free velocity of the motors. These findings provide important molecular-level insights into the mechanical function of the MT cytoskeleton in normal axon growth and regeneration after injury. PMID:26617489

  3. Cotangent bundle over all the compact Hermitian symmetric spaces and projective superspace

    NASA Astrophysics Data System (ADS)

    Arai, Masato

    2014-05-01

    We construct the N = 2 supersymmetric nonlinear sigma model on the cotangent bundle over the compact Hermitian symmetric space E7/E6 × U(1) by using the projective superspace formalism which is an off-shell superfield formulation in four-dimensional space-time. We also give a simple formula giving the hyper-Kahler potential of the cotangent bundle over all the compact Hermitian symmetric spaces.

  4. Force Generation by Molecular-Motor-Powered Microtubule Bundles; Implications for Neuronal Polarization and Growth.

    PubMed

    Jakobs, Maximilian; Franze, Kristian; Zemel, Assaf

    2015-01-01

    The heavily cross-linked microtubule (MT) bundles found in neuronal processes play a central role in the initiation, growth and maturation of axons and dendrites; however, a quantitative understanding of their mechanical function is still lacking. We here developed computer simulations to investigate the dynamics of force generation in 1D bundles of MTs that are cross-linked and powered by molecular motors. The motion of filaments and the forces they exert are investigated as a function of the motor type (unipolar or bipolar), MT density and length, applied load, and motor connectivity. We demonstrate that only unipolar motors (e.g., kinesin-1) can provide the driving force for bundle expansion, while bipolar motors (e.g., kinesin-5) oppose it. The force generation capacity of the bundles is shown to depend sharply on the fraction of unipolar motors due to a percolation transition that must occur in the bundle. Scaling laws between bundle length, force, MT length and motor fraction are presented. In addition, we investigate the dynamics of growth in the presence of a constant influx of MTs. Beyond a short equilibration period, the bundles grow linearly in time. In this growth regime, the bundle extends as one mass forward with most filaments sliding with the growth velocity. The growth velocity is shown to be dictated by the inward flux of MTs, to inversely scale with the load and to be independent of the free velocity of the motors. These findings provide important molecular-level insights into the mechanical function of the MT cytoskeleton in normal axon growth and regeneration after injury.

  5. Structure and Characterization of Vertically Aligned Single-Walled Carbon Nanotube Bundles

    DOE PAGES

    Márquez, Francisco; López, Vicente; Morant, Carmen; ...

    2010-01-01

    Arrmore » ays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800°C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30 nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.« less

  6. Sperm bundle and reproductive organs of carabid beetles tribe Pterostichini (Coleoptera: Carabidae)

    NASA Astrophysics Data System (ADS)

    Sasakawa, Kôji

    2007-05-01

    The morphological characteristics of sperm and reproductive organs may offer clues as to how reproductive systems have evolved. In this paper, the morphologies of the sperm and male reproductive organs of carabid beetles in the tribe Pterostichini (Coleoptera: Carabidae) are described, and the morphological associations among characters are examined. All species form sperm bundles in which the head of the sperm was embedded in a rod-shaped structure, i.e., spermatodesm. The spermatodesm shape (left-handed spiral, right-handed spiral, or without conspicuous spiral structure) and the condition of the sperm on the spermatodesm surface (with the tail free-moving or forming a thin, sheetlike structure) vary among species. In all species, the spiral directions of the convoluted seminal vesicles and vasa deferentia are the same on both sides of the body; that is, they show an asymmetric structure. The species in which the sperm bundle and the seminal vesicles both have a spiral structure could be classified into two types, with significant differences in sperm-bundle length between the two types. The species with a sperm-bundle spiral and seminal-vesicle spiral of almost the same diameter have longer sperm bundles than the species with a sperm-bundle spiral and seminal-vesicle tube of almost the same diameter. In the former type, the spiral directions of the sperm bundles and seminal vesicles are inevitably the same, whereas they differ in some species with the later type. Therefore, increased sperm bundle length appears to have been facilitated by the concordance of the sperm bundle’s coiling direction with the coiling direction of the seminal vesicle.

  7. Exposed inferior alveolar neurovascular bundle during surgical removal of a residual cyst.

    PubMed

    Boffano, Paolo; Gallesio, Cesare

    2010-01-01

    Iatrogenic neurodeficiency is one of the most distressing complications to any surgical procedure. The prediction of close proximity of the oral lesions to the inferior alveolar neurovascular bundle is extremely important. Furthermore, iatrogenic neurosensory dysfunctions of the facial region involve important medicolegal issues. In this report, we describe the case of a patient who did not show either paresthesia or anesthesia after the surgical removal of a mandibular residual cyst that exhibited adherence to the inferior alveolar nerve bundle.

  8. Method of fabricating high-density hermetic electrical feedthroughs using insulated wire bundles

    DOEpatents

    Shah, Kedar G.; Benett, William J.; Pannu, Satinderpall S.

    2016-05-10

    A method of fabricating electrical feedthroughs coats of a plurality of electrically conductive wires with an electrically insulating material and bundles the coated wires together in a substantially parallel arrangement. The bundled coated wires are secured to each other by joining the electrically insulating material of adjacent wires together to form a monolithic block which is then cut transverse to the wires to produce a block section having opposing first and second sides with a plurality of electrically conductive feedthroughs extending between them.

  9. Toward endoscopes with no distal optics: video-rate scanning microscopy through a fiber bundle.

    PubMed

    Andresen, Esben Ravn; Bouwmans, Géraud; Monneret, Serge; Rigneault, Hervé

    2013-03-01

    We report a step toward scanning endomicroscopy without distal optics. The focusing of the beam at the distal end of a fiber bundle is achieved by imposing a parabolic phase profile across the exit face with the aid of a spatial light modulator. We achieve video-rate images by galvanometric scanning of the phase tilt at the proximal end. The approach is made possible by the bundle, designed to have very low coupling between cores.

  10. Coolant mass flow equalizer for nuclear fuel

    DOEpatents

    Betten, Paul R.

    1978-01-01

    The coolant mass flow distribution in a liquid metal cooled reactor is enhanced by restricting flow in sub-channels defined in part by the peripheral fuel elements of a fuel assembly. This flow restriction, which results in more coolant flow in interior sub-channels, is achieved through the use of a corrugated liner positioned between the bundle of fuel elements and the inner wall of the fuel assembly coolant duct. The corrugated liner is expandable to accommodate irradiation induced growth of fuel assembly components.

  11. Electrocardiographic criteria of left ventricular hypertrophy in left bundle-branch block.

    PubMed Central

    Cokkinos, D V; Demopoulos, J N; Heimonas, E T; Mallios, C; Papazoglou, N; Vorides, E M

    1978-01-01

    In order to determine whether the electrocardiographic criteria of left ventricular hypertrophy apply in the presence of left bundle-branch block we studied 79 cases of intermittent left bundle-branch block and compared the QRS voltage and axis before and after its onset. Cases of incomplete left bundle-branch block were excluded. There was a statistically significant correlation between pre- and post-left bundle-branch block values of R or S wave voltage in leads I, V1, V2, V5, and V6, the Sokolow index (R V5 or V6 + S V1), and the QRS axis. There was a statistically significant reduction in R wave voltage in leads I, V5, and V6, an increase in S wave voltage in V1 and V2, and leftward shift of QRS axis, but the Sokolow index remained unchanged, after the onset of left bundle-branch block. The Sokolow criteria for left ventricular hypertrophy apply satisfactorily even in the presence of left bundle-branch block, though specificity is low, but QRS axis is unhelpful. Images PMID:147697

  12. Two Helpful MRI Signs for Evaluation of Posterolateral Bundle Tears of the Anterior Cruciate Ligament

    PubMed Central

    Volokhina, Yulia V.; Syed, Hasan M.; Pham, Peter H.; Blackburn, Allie K.

    2015-01-01

    Background: Diagnosis of partial anterior cruciate ligament (ACL) tears is difficult on magnetic resonance imaging (MRI), particularly the isolated tears of the posterolateral bundle. Purpose: To describe 2 MRI signs of partial ACL tear involving the posterolateral bundle on conventional knee MRI sequences, specifically, the “gap” and “footprint” signs. Study Design: Case-control study. Methods: We retrospectively reviewed the MRI appearance of the ACL in 11 patients with arthroscopically proven partial ACL tears isolated to the posterolateral bundle, as well as in 10 patients with arthroscopically proven intact ACLs, and evaluated for the presence of gap and/or footprint signs. Results: There was high degree of sensitivity and specificity associated with the MRI findings of “gap” and “footprint” signs with arthroscopically proven isolated posterolateral bundle tears. Conclusion: Gap and footprint signs are suggestive of posterolateral bundle tear of the ACL, and the presence of 1 or both of these imaging findings should alert the radiologist to the possibility of a posterolateral bundle tear. PMID:26535387

  13. Total evaluation of in bundle void fraction measurement test of PWR fuel assembly

    SciTech Connect

    Hori, Keiichi; Miyazaki, Keiji; Akiyama, Yoshiei; Nishioka, Hiromasa; Takeda, Naoki

    1996-08-01

    Nuclear Power Engineering Corporation is performing the various proof or verification tests on safety and reliability of nuclear power plants under the sponsorship of the Ministry of International Trade and Industry. As one program of these Japanese national projects, an in bundle void fraction measurement test of a pressurized water reactor (PWR) fuel assembly was started in 1987 and finished at the end of 1994. The experiments were performed using the 5 x 5 square array rod bundle test sections. The rod bundle test section simulates the partial section and full length of a 17 x 17 type Japanese PWR fuel assembly. A distribution of subchannel averaged void fraction in a rod bundle test section was measured by the gamma-ray attenuation method using the stationary multi beam systems. The additional single channel test was performed to obtain the required information for the calibration of the rod bundle test data and the assessment of the void prediction method. Three test rod bundles were prepared to analyze an axial power distribution effect, an unheated rod effect, and a grid spacer effect. And, the obtained data were used for the assessment of the void prediction method relevant to the subchannel averaged void fraction of PWR fuel assemblies. This paper describes the outline of the experiments, the evaluation of the experimental data and the assessment of void prediction method.

  14. Confinement effects and why carbon nanotube bundles can work as gas sensors.

    PubMed

    Amorim, Rodrigo G; Fazzio, A; da Silva, Antônio J R; Rocha, Alexandre R

    2013-04-07

    Carbon nanotubes have been at the forefront of nanotechnology, leading not only to a better understanding of the basic properties of charge transport in one dimensional materials, but also to the perspective of a variety of possible applications, including highly sensitive sensors. Practical issues, however, have led to the use of bundles of nanotubes in devices, instead of isolated single nanotubes. From a theoretical perspective, the understanding of charge transport in such bundles, and how it is affected by the adsorption of molecules, has been very limited, one of the reasons being the sheer size of the calculations. A frequent option has been the extrapolation of knowledge gained from single tubes to the properties of bundles. In the present work we show that such procedure is not correct, and that there are qualitative differences in the effects caused by molecules on the charge transport in bundles versus isolated nanotubes. Using a combination of density functional theory and recursive Green's function techniques we show that the adsorption of molecules randomly distributed onto the walls of carbon nanotube bundles leads to changes in the charge density and consequently to significant alterations in the conductance even in pristine tubes. We show that this effect is driven by confinement which is not present in isolated nanotubes. Furthermore, a low concentration of dopants randomly adsorbed along a two-hundred nm long bundle drives a change in the transport regime; from ballistic to diffusive, which can account for the high sensitivity to different molecules.

  15. The impact of Lean bundles on hospital performance: does size matter?

    PubMed

    Al-Hyari, Khalil; Abu Hammour, Sewar; Abu Zaid, Mohammad Khair Saleem; Haffar, Mohamed

    2016-10-10

    Purpose The purpose of this paper is to study the effect of the implementation of Lean bundles on hospital performance in private hospitals in Jordan and evaluate how much the size of organization can affect the relationship between Lean bundles implementation and hospital performance. Design/methodology/approach The research is considered as quantitative method (descriptive and hypothesis testing). Three statistical techniques were adopted to analyse the data. Structural equation modeling techniques and multi-group analysis were used to examine the research's hypothesis, and to perform the required statistical analysis of the data from the survey. Reliability analysis and confirmatory factor analysis were used to test the construct validity, reliability and measurement loadings that were performed. Findings Lean bundles have been identified as an effective approach that can dramatically improve the organizational performance of private hospitals in Jordan. Main Lean bundles - just in time, human resource management, and total quality management are applicable to large, small and medium hospitals without significant differences in advantages that depend on size. Originality/value According to the researchers' best knowledge, this is the first research that studies the impact of Lean bundles implementation in healthcare sector in Jordan. This research also makes a significant contribution for decision makers in healthcare to increase their awareness of Lean bundles.

  16. Large scale implementation of a medicines reconciliation care bundle in NHS GGC GP practices

    PubMed Central

    Bruce, Rachel

    2016-01-01

    Medicines reconciliation (MR) is an essential process for patient safety, promoting safer use of medicines with effective communication at the interface, particularly when patients are admitted and discharged from hospital. Much of the work on MR has been focussed in secondary care, however, the principles are equally important in primary care. The aim of the work was to test the Scottish Patient Safety in Primary Care (SPSP-PC) MR care bundle and consider scale up and spread across all NHS Greater Glasgow and Clyde (NHS GGC) GP practices. Care bundles are a quality improvement tool which can drive improvement by standardising processes to deliver optimum care. Pilot work and testing began with 5 GP practices in 2011 and was spread to over 200 practices by 2015/16. A care bundle compliance process measure was measured monthly, with practices sampling 10 patients per month. Practices could view their run charts in real time and identify which measures resulted in “non-compliance” and PDSA cycles were promoted to test and implement improvements. Data was collated at NHS GGC level with an aim of 95% compliance with the care bundle by March 2016. MR care bundle compliance started at 40% (5 practices reporting) in 2011 with final data in March 2016 demonstrating 92% compliance (192 practices reporting). A sustained “reliability” of 92-93% across >200 practices has been observed since January 2015. In conclusion, the bundle was implemented by 97% of NHS GGC GP practices and resulted in process improvements. PMID:27933147

  17. Hair-bundle proteomes of avian and mammalian inner-ear utricles

    PubMed Central

    Wilmarth, Phillip A.; Krey, Jocelyn F.; Shin, Jung-Bum; Choi, Dongseok; David, Larry L.; Barr-Gillespie, Peter G.

    2015-01-01

    Examination of multiple proteomics datasets within or between species increases the reliability of protein identification. We report here proteomes of inner-ear hair bundles from three species (chick, mouse, and rat), which were collected on LTQ or LTQ Velos ion-trap mass spectrometers; the constituent proteins were quantified using MS2 intensities, which are the summed intensities of all peptide fragmentation spectra matched to a protein. The data are available via ProteomeXchange with identifiers PXD002410 (chick LTQ), PXD002414 (chick Velos), PXD002415 (mouse Velos), and PXD002416 (rat LTQ). The two chick bundle datasets compared favourably to a third, already-described chick bundle dataset, which was quantified using MS1 peak intensities, the summed intensities of peptides identified by high-resolution mass spectrometry (PXD000104; updated analysis in PXD002445). The mouse bundle dataset described here was comparable to a different mouse bundle dataset quantified using MS1 intensities (PXD002167). These six datasets will be useful for identifying the core proteome of vestibular hair bundles. PMID:26645194

  18. Focal loss of actin bundles causes microtubule redistribution and growth cone turning.

    PubMed

    Zhou, Feng-Quan; Waterman-Storer, Clare M; Cohan, Christopher S

    2002-05-27

    It is commonly believed that growth cone turning during pathfinding is initiated by reorganization of actin filaments in response to guidance cues, which then affects microtubule structure to complete the turning process. However, a major unanswered question is how changes in actin cytoskeleton are induced by guidance cues and how these changes are then translated into microtubule rearrangement. Here, we report that local and specific disruption of actin bundles from the growth cone peripheral domain induced repulsive growth cone turning. Meanwhile, dynamic microtubules within the peripheral domain were oriented into areas where actin bundles remained and were lost from areas where actin bundles disappeared. This resulted in directional microtubule extension leading to axon bending and growth cone turning. In addition, this local actin bundle loss coincided with localized growth cone collapse, as well as asymmetrical lamellipodial protrusion. Our results provide direct evidence, for the first time, that regional actin bundle reorganization can steer the growth cone by coordinating actin reorganization with microtubule dynamics. This suggests that actin bundles can be potential targets of signaling pathways downstream of guidance cues, providing a mechanism for coupling changes in leading edge actin with microtubules at the central domain during turning.

  19. Liquefaction of H{sub 2} molecules upon exterior surfaces of carbon nanotube bundles

    SciTech Connect

    Han, Sang Soo; Kang, Jeung Ku; Lee, Hyuck Mo; Duin, Adri C.T. van; Goddard, William A. III

    2005-05-16

    We have used molecular dynamics simulations to investigate interaction of H{sub 2} molecules on the exterior surfaces of carbon nanotubes (CNTs): single and bundle types. At 80 K and 10 MPa, it is found that charge transfer occurs from a low curvature region to a high curvature region of the deformed CNT bundle, which develops charge polarization only on the deformed structure. The long-range electrostatic interactions of polarized charges on the deformed CNT bundle with hydrogen molecules are observed to induce a high local-ordering of H{sub 2} gas that results in hydrogen liquefaction. Our predicted heat of hydrogen liquefaction on the CNT bundle is 97.6 kcal kg{sup -1}. On the other hand, hydrogen liquefaction is not observed in the CNT of a single type. This is because charge polarization is not developed on the single CNT as it is symmetrically deformed under the same pressure. Consequently, the hydrogen storage capacity on the CNT bundle is much higher due to liquefaction than that on the single CNT. Additionally, our results indicate that it would also be possible to liquefy H{sub 2} gas on a more strongly polarized CNT bundle at temperatures higher than 80 K.

  20. Espin cross-links cause the elongation of microvillus-type parallel actin bundles in vivo.

    PubMed

    Loomis, Patricia A; Zheng, Lili; Sekerková, Gabriella; Changyaleket, Benjarat; Mugnaini, Enrico; Bartles, James R

    2003-12-08

    The espin actin-bundling proteins, which are the target of the jerker deafness mutation, caused a dramatic, concentration-dependent lengthening of LLC-PK1-CL4 cell microvilli and their parallel actin bundles. Espin level was also positively correlated with stereocilium length in hair cells. Villin, but not fascin or fimbrin, also produced noticeable lengthening. The espin COOH-terminal peptide, which contains the actin-bundling module, was necessary and sufficient for lengthening. Lengthening was blocked by 100 nM cytochalasin D. Espin cross-links slowed actin depolymerization in vitro less than twofold. Elimination of an actin monomer-binding WASP homology 2 domain and a profilin-binding proline-rich domain from espin did not decrease lengthening, but made it possible to demonstrate that actin incorporation was restricted to the microvillar tip and that bundles continued to undergo actin treadmilling at approximately 1.5 s-1 during and after lengthening. Thus, through relatively subtle effects on actin polymerization/depolymerization reactions in a treadmilling parallel actin bundle, espin cross-links cause pronounced barbed-end elongation and, thereby, make a longer bundle without joining shorter modules.

  1. Class III myosins shape the auditory hair bundles by limiting microvilli and stereocilia growth

    PubMed Central

    Lelli, Andrea; Michel, Vincent; Boutet de Monvel, Jacques; Cortese, Matteo; Bosch-Grau, Montserrat; Aghaie, Asadollah; Perfettini, Isabelle; Dupont, Typhaine; Avan, Paul

    2016-01-01

    The precise architecture of hair bundles, the arrays of mechanosensitive microvilli-like stereocilia crowning the auditory hair cells, is essential to hearing. Myosin IIIa, defective in the late-onset deafness form DFNB30, has been proposed to transport espin-1 to the tips of stereocilia, thereby promoting their elongation. We show that Myo3a−/−Myo3b−/− mice lacking myosin IIIa and myosin IIIb are profoundly deaf, whereas Myo3a-cKO Myo3b−/− mice lacking myosin IIIb and losing myosin IIIa postnatally have normal hearing. Myo3a−/−Myo3b−/− cochlear hair bundles display robust mechanoelectrical transduction currents with normal kinetics but show severe embryonic abnormalities whose features rapidly change. These include abnormally tall and numerous microvilli or stereocilia, ungraded stereocilia bundles, and bundle rounding and closure. Surprisingly, espin-1 is properly targeted to Myo3a−/−Myo3b−/− stereocilia tips. Our results uncover the critical role that class III myosins play redundantly in hair-bundle morphogenesis; they unexpectedly limit the elongation of stereocilia and of subsequently regressing microvilli, thus contributing to the early hair bundle shaping. PMID:26754646

  2. Experimental observation of spatially resolved photo-luminescence intensity distribution in dual mode upconverting nanorod bundles

    PubMed Central

    Kumar, Pawan; Singh, Satbir; Singh, V. N.; Singh, Nidhi; Gupta, R. K.; Gupta, Bipin Kumar

    2017-01-01

    A novel method for demonstration of photoluminescence intensity distribution in upconverting nanorod bundles using confocal microscopy is reported. Herein, a strategy for the synthesis of highly luminescent dual mode upconverting/downshift Y1.94O3:Ho3+0.02/Yb3+0.04 nanorod bundles by a facile hydrothermal route has been introduced. These luminescent nanorod bundles exhibit strong green emission at 549 nm upon excitations at 449 nm and 980 nm with quantum efficiencies of ~6.3% and ~1.1%, respectively. The TEM/HRTEM results confirm that these bundles are composed of several individual nanorods with diameter of ~100 nm and length in the range of 1–3 μm. Furthermore, two dimensional spatially resolved photoluminescence intensity distribution study has been carried out using confocal photoluminescence microscope throughout the nanorod bundles. This study provides a new direction for the potential use of such emerging dual mode nanorod bundles as photon sources for next generation flat panel optical display devices, bio-medical applications, luminescent security ink and enhanced energy harvesting in photovoltaic applications. PMID:28211891

  3. Experimental observation of spatially resolved photo-luminescence intensity distribution in dual mode upconverting nanorod bundles

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Singh, Satbir; Singh, V. N.; Singh, Nidhi; Gupta, R. K.; Gupta, Bipin Kumar

    2017-02-01

    A novel method for demonstration of photoluminescence intensity distribution in upconverting nanorod bundles using confocal microscopy is reported. Herein, a strategy for the synthesis of highly luminescent dual mode upconverting/downshift Y1.94O3:Ho3+0.02/Yb3+0.04 nanorod bundles by a facile hydrothermal route has been introduced. These luminescent nanorod bundles exhibit strong green emission at 549 nm upon excitations at 449 nm and 980 nm with quantum efficiencies of ~6.3% and ~1.1%, respectively. The TEM/HRTEM results confirm that these bundles are composed of several individual nanorods with diameter of ~100 nm and length in the range of 1–3 μm. Furthermore, two dimensional spatially resolved photoluminescence intensity distribution study has been carried out using confocal photoluminescence microscope throughout the nanorod bundles. This study provides a new direction for the potential use of such emerging dual mode nanorod bundles as photon sources for next generation flat panel optical display devices, bio-medical applications, luminescent security ink and enhanced energy harvesting in photovoltaic applications.

  4. Visualization of the medial forebrain bundle using diffusion tensor imaging.

    PubMed

    Hana, Ardian; Hana, Anisa; Dooms, Georges; Boecher-Schwarz, Hans; Hertel, Frank

    2015-01-01

    Diffusion tensor imaging is a technique that enables physicians the portrayal of white matter tracts in vivo. We used this technique in order to depict the medial forebrain bundle (MFB) in 15 consecutive patients between 2012 and 2015. Men and women of all ages were included. There were six women and nine men. The mean age was 58.6 years (39-77). Nine patients were candidates for an eventual deep brain stimulation. Eight of them suffered from Parkinson's disease and one had multiple sclerosis. The remaining six patients suffered from different lesions which were situated in the frontal lobe. These were 2 metastasis, 2 meningiomas, 1 cerebral bleeding, and 1 glioblastoma. We used a 3DT1-sequence for the navigation. Furthermore T2- and DTI- sequences were performed. The FOV was 200 × 200 mm(2), slice thickness 2 mm, and an acquisition matrix of 96 × 96 yielding nearly isotropic voxels of 2 × 2 × 2 mm. 3-Tesla-MRI was carried out strictly axial using 32 gradient directions and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2. b-value was 800 s/mm(2). The maximal angle was 50°. Additional scanning time was < 9 min. We were able to visualize the MFB in 12 of our patients bilaterally and in the remaining three patients we depicted the MFB on one side. It was the contralateral side of the lesion. These were 2 meningiomas and one metastasis. Portrayal of the MFB is possible for everyday routine for neurosurgical interventions. As part of the reward circuitry it might be of substantial importance for neurosurgeons during deep brain stimulation in patients with psychiatric disorders. Surgery in this part of the brain should always take the preservation of this white matter tract into account.

  5. Direct His-bundle pacing: present and future.

    PubMed

    Deshmukh, Pramod M; Romanyshyn, Mary

    2004-06-01

    Direct His-bundle pacing (DHBP) produces rapid sequential multisite synchronous ventricular activation and, therefore, would be an ideal alternative to right ventricular apical (RVA) pacing. In 54 patients with cardiomyopathy, ejection fraction (EF) 0.23 +/- 0.11, persistent atrial fibrillation, and normal QRS < 120 ms. DHBP was attempted. This was successful in 39 patients. In seven patients, the effect of increasing heart rate on contractility (Treppe effect) was investigated. Twelve patients who also received a RVA lead underwent cardiopulmonary testing. After a mean follow-up of 42 months, 29 patients are still alive with EF improving from 0.23 +/- 0.11 to 0.33 +/- 0.15. Functional class improved from 3.5 to 2.2. DP/dt increased at each pacing site (P < 0.05) as the heart rate increased to 60, 100, and 120 beats/min. Rise in dP/dt by DHBP pacing at 120 beats/min was at least 170 +/- mmHg/s, greater than any other site in the ventricle (P < 0.05). Cardiopulmonary testing revealed longer exercise time (RVA 255 +/- 110 s) (His 280 +/- 104 s) (P < 0.05), higher O2 uptake (RVA 15 +/- 4 mL/kg per minute) (His 16 +/- 4 mL/kg minute) (P < 0.05), and later anaerobic threshold (RVA 126 +/- 71 s) (His 145 +/- 74 s) (P < 0.05) with DHBP compared to RVA pacing. Long-term DHBP is safe and effective in humans. DHBP is associated with a superior Treppe effect and increased cardiopulmonary reserve when compared to RVA pacing.

  6. Ventricular fibrillation associated with complete right bundle branch block

    PubMed Central

    Aizawa, Yoshiyasu; Takatsuki, Seiji; Kimura, Takehiro; Nishiyama, Nobuhiro; Fukumoto, Kotaro; Tanimoto, Yoko; Tanimoto, Kojiro; Miyoshi, Shunichiro; Suzuki, Makoto; Yokoyama, Yasuhiro; Chinushi, Masaomi; Watanabe, Ichiro; Ogawa, Satoshi; Aizawa, Yoshifusa; Antzelevitch, Charles; Fukuda, Keiichi

    2013-01-01

    BACKGROUND A substantial number of patients with idiopathic ventricular fibrillation (IVF) present with no specific electrocardiographic (ECG) findings. OBJECTIVE To evaluate complete right bundle branch block (RBBB) in patients with IVF. METHODS Patients with IVF showing complete RBBB were included in the present study. Structural and primary electrical diseases were excluded, and provocation tests were performed to exclude the presence of spastic angina or Brugada syndrome (BrS). The prevalence of complete RBBB and the clinical and ECG parameters were compared either in patients with IVF who did not show RBBB or in the general population and age and sex comparable controls with RBBB. RESULTS Of 96 patients with IVF, 9 patients were excluded for the presence of BrS. Of 87 patients studied, 10 (11.5%) patients showed complete RBBB. None had structural heart diseases, BrS, or coronary spasms. The mean age was 44 ± 15 years, and 8 of 10 patients were men. Among the ECG parameters, only the QRS duration was different from that of the other patients with IVF who did not show complete RBBB. Ventricular fibrillation recurred in 3:2 in the form of storms, which were well suppressed by isoproterenol. Complete RBBB was found less often in control subjects (1.37%; P < .0001), and the QRS duration was more prolonged in patients with IVF: 139 ± 10 ms vs 150 ± 14 ms (P = .0061). CONCLUSIONS Complete RBBB exists more often in patients with IVF than in controls. A prolonged QRS complex suggests a conduction abnormality. Our findings warrant further investigation of the role of RBBB in the development of arrhythmias in patients with IVF. PMID:23499623

  7. Visualization of the medial forebrain bundle using diffusion tensor imaging

    PubMed Central

    Hana, Ardian; Hana, Anisa; Dooms, Georges; Boecher-Schwarz, Hans; Hertel, Frank

    2015-01-01

    Diffusion tensor imaging is a technique that enables physicians the portrayal of white matter tracts in vivo. We used this technique in order to depict the medial forebrain bundle (MFB) in 15 consecutive patients between 2012 and 2015. Men and women of all ages were included. There were six women and nine men. The mean age was 58.6 years (39–77). Nine patients were candidates for an eventual deep brain stimulation. Eight of them suffered from Parkinson‘s disease and one had multiple sclerosis. The remaining six patients suffered from different lesions which were situated in the frontal lobe. These were 2 metastasis, 2 meningiomas, 1 cerebral bleeding, and 1 glioblastoma. We used a 3DT1-sequence for the navigation. Furthermore T2- and DTI- sequences were performed. The FOV was 200 × 200 mm2, slice thickness 2 mm, and an acquisition matrix of 96 × 96 yielding nearly isotropic voxels of 2 × 2 × 2 mm. 3-Tesla-MRI was carried out strictly axial using 32 gradient directions and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2. b-value was 800 s/mm2. The maximal angle was 50°. Additional scanning time was < 9 min. We were able to visualize the MFB in 12 of our patients bilaterally and in the remaining three patients we depicted the MFB on one side. It was the contralateral side of the lesion. These were 2 meningiomas and one metastasis. Portrayal of the MFB is possible for everyday routine for neurosurgical interventions. As part of the reward circuitry it might be of substantial importance for neurosurgeons during deep brain stimulation in patients with psychiatric disorders. Surgery in this part of the brain should always take the preservation of this white matter tract into account. PMID:26581828

  8. Conductive Polymer Combined Silk Fiber Bundle for Bioelectrical Signal Recording

    PubMed Central

    Tsukada, Shingo; Nakashima, Hiroshi; Torimitsu, Keiichi

    2012-01-01

    Electrode materials for recording biomedical signals, such as electrocardiography (ECG), electroencephalography (EEG) and evoked potentials data, are expected to be soft, hydrophilic and electroconductive to minimize the stress imposed on living tissue, especially during long-term monitoring. We have developed and characterized string-shaped electrodes made from conductive polymer with silk fiber bundles (thread), which offer a new biocompatible stress free interface with living tissue in both wet and dry conditions. An electroconductive polyelectrolyte, poly(3,4-ethylenedioxythiophene) -poly(styrenesulfonate) (PEDOT-PSS) was electrochemically combined with silk thread made from natural Bombyx mori. The polymer composite 280 µm thread exhibited a conductivity of 0.00117 S/cm (which corresponds to a DC resistance of 2.62 Mohm/cm). The addition of glycerol to the PEDOT-PSS silk thread improved the conductivity to 0.102 S/cm (20.6 kohm/cm). The wettability of PEDOT-PSS was controlled with glycerol, which improved its durability in water and washing cycles. The glycerol treated PEDOT-PSS silk thread showed a tensile strength of 1000 cN in both wet and dry states. Without using any electrolytes, pastes or solutions, the thread directly collects electrical signals from living tissue and transmits them through metal cables. ECG, EEG, and sensory evoked potential (SEP) signals were recorded from experimental animals by using this thread placed on the skin. PEDOT-PSS silk glycerol composite thread offers a new class of biocompatible electrodes in the field of biomedical and health promotion that does not induce stress in the subjects. PMID:22493670

  9. Flow in a model of the SSME main injector bowl

    NASA Technical Reports Server (NTRS)

    Thompson, B. E.; Senaldi, J.; Vafidis, C.; Whitelaw, J. H.; Mcdonald, H.

    1989-01-01

    Mean-flow and turbulence quantities obtained in a 32-percent acrylic model of the SSME main injector bowl are presented. Flow visualization obtained with laser sheets and conventional photography shows the basic patterns and identifies regions of recirculating flow. Measurements of mean-flow and turbulence normal stresses are obtained with laser velocimetry to confirm these results and to quantify flow characteristics in the inlet ducts, entrance region, racetrack, LOX-post bundle, and exit nozzle. Measured velocity distributions show the upstream effect of the injector bowl in the transfer ducts, the plenum effect of the racetrack and LOX-post bundle, and the nonuniform distribution of flow into the main exit nozzle.

  10. Effect of temperature on the formation of macroporous ZnO bundles and its application in photocatalysis.

    PubMed

    Muruganandham, M; Chen, I S; Wu, J J

    2009-12-30

    In this article, the effects of temperature on the formation of macroporous zinc oxide bundles and its photocatalytic activity under a variety of experimental conditions were reported. Thermal decomposition of zinc oxalate dihydrate yields hexagonal wurtzite-type ZnO bundles. Increased the decomposition temperatures resulted in decreased time required for bundle formation, with a corresponding increase in nanoparticles agglomeration. ZnO bundle formation was facilitated up to 200 degrees C after complete decomposition of zinc oxalate into ZnO at 400 degrees C in 15 min. However, low temperature (such as 100 degrees C) was not facilitated nanobundle formation, suggesting the importance of temperature on ZnO bundles formation. In addition, nitrogen adsorption experiments confirmed the presence of macroporous structure in the bundles. The photocatalytic decolorization and adsorption of methylene blue dye (MB) on ZnO bundles were investigated under UV light irradiation. The adsorption and decolorization efficiency of macroporous bundles were higher than the fused bundles. In conclusion, ZnO bundles are efficient and easily recyclable photocatalyst.

  11. Measurement and Analysis of Void Fraction in a Multiple-Channel Simplifying Triangle Tight Lattice Rod Bundle

    SciTech Connect

    Michio Sadatomi; Akimaro Kawahara; Hiroyuki Kudo; Hiroshi Shirai

    2006-07-01

    In order to know the effects of reduced surface tension on void fraction, adiabatic experiments were conducted for both air-water and air-water with surfactant systems at room temperature and pressure. Void fraction data were obtained for bubbly, slug, churn and annular flows in a vertical channel with two subchannels simplifying a triangle tight lattice rod bundle. The void fraction was found to be lower in air-water system than air-water with surfactant one. In addition, the void fractions for both systems were found to be lower than those calculated by various correlations in literatures for circular pipe flow. In order to study the cause of the above data trend, for annular flows as a first step, the void fraction has been calculated by a subchannel analysis using wall and interfacial friction correlations in literatures as constitutive equations, and by assuming the liquid film to be uniform over the wall perimeter. The best agreement between the calculation and the experiment has been obtained when NASCA correlation for wall friction force and modified RELAP5/MOD2 correlation incorporating reduced surface tension effects for interfacial friction force were used. (authors)

  12. Orifice plate for controlling solids flow, methods of use thereof and articles comprising the same

    DOEpatents

    Jukkola, Glen D.; Teigen, Bard C.

    2017-01-31

    Disclosed herein is an orifice plate comprising one or more plates having orifices disposed therein; the orifices being operative to permit the flow of solids from a moving bed heat exchanger to a solids flow control system; where the orifice plate is downstream of a tube bundle of the moving bed heat exchanger and upstream of the solids flow control system and wherein the orifice plate is operative to evenly distribute the flow of solids in the solids flow control system.

  13. The role of localized inductive electric fields in electron injections around dipolarizing flux bundles

    NASA Astrophysics Data System (ADS)

    Gabrielse, Christine; Harris, Camilla; Angelopoulos, Vassilis; Artemyev, Anton; Runov, Andrei

    2016-10-01

    We study energetic electron injections by using an analytical model that self-consistently describes electric and magnetic field perturbations of a transient, localized dipolarizing flux bundle (DFB). This simple model reproduces most injection signatures at multiple locations simultaneously, reaffirming earlier findings that an earthward-traveling DFB can both transport and accelerate electrons to suprathermal energies, and can thus be considered an important driver of short-lived ( < 10 min) injections. We find that energetic electron drift paths are greatly influenced by the sharp magnetic field gradients around a localized DFB. Because a DFB is so localized (only a few RE wide across the tail), there are strong duskward magnetic field gradients on the DFB's dawn flank and strong dawnward magnetic field gradients on its dusk flank. Electrons on the DFB's dawnside therefore ∇B drift farther earthward from the reconnection site, whereas electrons on its duskside can potentially evacuate the inner magnetosphere by ∇B drifting tailward. This results in flux decrease at the front's duskside. As a result, the source of electrons observed during injection depends sensitively on the spacecraft location relative to the DFB and on the DFB's properties. We similarly find that the process of electron energization depends on how the electrons interact with the DFB. The initial injection signature is from electrons that interact with the front and gain the majority of their energy from the increasing magnetic field (∂B/∂t), whereas populations that arrive later gain most of their energy from ∇B drifting across the flow channel and against the DFB's electric fields.

  14. [Wall motion abnormalities and hemodynamic parameters in patients with left bundle branch block during exercise echocardiography].

    PubMed

    Dupliakov, D V; Vozhdaeva, Z I; Sysuenkova, E V; Zemlianova, M E; Lotina, A S; Goleva, S V; Svetlakova, A P; Khokhlunov, S M

    2011-01-01

    Study aim was to investigate dynamics of local contractility and hemodynamic parameters during exercise stress echocardiography (EEcho) in patients with left bundle branch block (LBBB). We examined 23 patients (15 men, 8 women) aged 48-65 years (mean age 53.9+/-8.1 years). Bicycle EEcho was accomplished according to standard protocol. Patients without clinical signs of ischemic heart disease (n=11) comprised group 1, patients after myocardial infarction (n=12) - group 2 (subgroup 2A - with negative test result, subgroup 2B - with worsening of local left ventricular contractility during EEcho). At baseline group 1 patients had significantly better hemodynamic parameters (ejection fraction - EF, left ventricular end diastolic volume - LVEDV) and no abnormalities of local contractility. Exercise tolerance was also the highest in this group. Insignificant worsening of postexercise EF occurred in patients of subgroup 2B (from 46+/-10.5 to 44,2+/-9.4%). In group 1 EF significantly increased (from 56.8+/-10.5% to 64.7+/-15.4%, <0.05), in subgroup 2A tendency to EF increase up to 48.7+/-9.9% was registered. Lowering of local contractility abnormalities index was noted also only in patients of subgroup 2B (from 1.54+/-0.4 to 2.17+/-0.37 (p<0.01). LVEDV compared with initial values tended to decrease in both groups (however differences between groups were not significant). Positive echocardiographic response was associated with significant changes of transmitral blood flow. Angiographically clean coronary arteries were found in 8 of 10 patients in group 1. Six group 2 patients with history of typical clinical picture of angina and myocardial infarction) had multivessel lesions in coronary vascular bed. EEcho result was positive in 5 of 6 group 2 patients. Thus EEcho possesses high potential for diagnosis of coronary atherosclerosis in patients with LBBB. This allows recommending it as a first line method in patients with this pathology.

  15. Why Are Two Different Cross-linkers Necessary for Actin Bundle Formation In Vivo and What Does Each Cross-link Contribute?

    PubMed Central

    Tilney, Lewis G.; Connelly, Patricia S.; Vranich, Kelly A.; Shaw, Michael K.; Guild, Gregory M.

    1998-01-01

    In developing Drosophila bristles two species of cross-linker, the forked proteins and fascin, connect adjacent actin filaments into bundles. Bundles form in three phases: (a) tiny bundles appear; (b) these bundles aggregate into larger bundles; and (c) the filaments become maximally cross-linked by fascin. In mutants that completely lack forked, aggregation of the bundles does not occur so that the mature bundles consist of <50 filaments versus ∼700 for wild type. If the forked concentration is genetically reduced to half the wild type, aggregation of the tiny bundles occurs but the filaments are poorly ordered albeit with small patches of fascin cross-linked filaments. In mutants containing an excess of forked, all the bundles tend to aggregate and the filaments are maximally crossbridged by fascin. Alternatively, if fascin is absent, phases 1 and 2 occur normally but the resultant bundles are twisted and the filaments within them are poorly ordered. By extracting fully elongated bristles with potassium iodide which removes fascin but leaves forked, the bundles change from being straight to twisted and the filaments within them become poorly ordered. From these observations we conclude that (a) forked is used early in development to aggregate the tiny bundles into larger bundles; and (b) forked facilitates fascin entry into the bundles to maximally cross-link the actin filaments into straight, compact, rigid bundles. Thus, forked aligns the filaments and then directs fascin binding so that inappropriate cross-linking does not occur. PMID:9763425

  16. Creation of a whole brain short association bundle atlas using a hybrid approach.

    PubMed

    Guevara, M; Roman, C; Houenou, J; Duclap, D; Poupon, C; Mangin, J-F; Guevara, P; Guevara, M; Roman, C; Houenou, J; Duclap, D; Poupon, C; Mangin, J-F; Guevara, P; Mangin, J-F; Roman, C; Duclap, D; Poupon, C; Houenou, J; Guevara, P; Guevara, M

    2016-08-01

    The Human brain connection map is far from being complete. In particular the study of the superficial white matter (SWM) is an unachieved task. Its description is essential for the understanding of human brain function and the study of pathogenesis triggered by abnormal connectivity. In this work we expanded a previously developed method for the automatic creation of a whole brain SWM bundle atlas. The method is based on a hybrid approach. First a cortical parcellation is used to extract fibers connecting two regions. Then an intra-and inter-subject hierarchical clustering are applied to find well-defined SWM bundles reproducible across subjects. In addition to the fronto-parietal and insula regions of the left hemisphere, the analysis was extended to the temporal and occipital lobes, including all their internal regions, for both hemispheres. Validation steps are performed in order to test the robustness of the method and the reproducibility of the obtained bundles. First the method was applied to two independent groups of subjects, in order to discard bundles without match across the two independent atlases. Then, the resulting intersection atlas was projected on a third independent group of subjects in order to filter out bundles without reproducible and reliable projection. The final multi-subject U-fiber atlas is composed of 100 bundles in total, 50 per hemisphere, from which 35 are common to both hemispheres. The atlas can be used in clinical studies for segmentation of the SWM bundles in new subjects, and measure DW values or complement functional data.

  17. Detection of the opening of the bundle crossing in KcsA with fluorescence lifetime spectroscopy reveals the existence of two gates for ion conduction.

    PubMed

    Blunck, Rikard; Cordero-Morales, Julio F; Cuello, Luis G; Perozo, Eduardo; Bezanilla, Francisco

    2006-11-01

    The closed KcsA channel structure revealed a crossing of the cytosolic ends of the transmembrane helices blocking the permeation pathway. It is generally agreed that during channel opening this helical bundle crossing has to widen in order to enable access to the inner cavity. Here, we address the question of whether the opening of the inner gate is sufficient for ion conduction, or if a second gate, located elsewhere, may interrupt the ion flow. We used fluorescence lifetime measurements on KcsA channels labeled with tetramethylrhodamine at residues in the C-terminal end of TM2 to report on the opening of the lower pore region. We found two populations of channels with different fluorescence lifetimes, whose relative distribution agrees with the open probability of the channel. The absolute fraction of channels found with an open bundle crossing is too high to explain the low open probability of the KcsA-WT channel. We found the same distribution as in the WT channel between open and closed bundle crossing for two KcsA mutants, A73E and E71A, which significantly increase open probability at low pH. These two results strongly suggest that a second gate in the ion permeation pathway exists. The location of the mutations A73E and E71A suggests that the second gate may be the selectivity filter, which resides in an inactivated state under steady-state conditions. Since the long closed times observed in KcsA-WT are not present in KcsA-A73E or -E71A, we propose that KcsA-WT remains predominantly in a state with an open bundle crossing but closed (inactivated) second gate, while the mutations A73E and E71A sharply decrease the tendency to enter in the inactivated state, and as a consequence, the second gate is predominantly open at steady state. The ability to monitor the opening of the bundle crossing optically enables the direct recording of the movement of the pore helices while the channel is functioning.

  18. Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

    SciTech Connect

    Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Jiang, H.; Kauppinen, E. I.; Susi, T.; Nasibulin, A. G.

    2015-07-06

    We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3–4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ∼10{sup 5 }cm{sup −3} prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

  19. Bundling ecosystem services in the Panama Canal watershed.

    PubMed

    Simonit, Silvio; Perrings, Charles

    2013-06-04

    Land cover change in watersheds affects the supply of a number of ecosystem services, including water supply, the production of timber and nontimber forest products, the provision of habitat for forest species, and climate regulation through carbon sequestration. The Panama Canal watershed is currently being reforested to protect the dry-season flows needed for Canal operations. Whether reforestation of the watershed is desirable depends on its impacts on all services. We develop a spatially explicit model to evaluate the implications of reforestation both for water flows and for other services. We find that reforestation does not necessarily increase water supply, but does increase carbon sequestration and timber production.

  20. Bundling ecosystem services in the Panama Canal watershed

    PubMed Central

    Simonit, Silvio; Perrings, Charles

    2013-01-01

    Land cover change in watersheds affects the supply of a number of ecosystem services, including water supply, the production of timber and nontimber forest products, the provision of habitat for forest species, and climate regulation through carbon sequestration. The Panama Canal watershed is currently being reforested to protect the dry-season flows needed for Canal operations. Whether reforestation of the watershed is desirable depends on its impacts on all services. We develop a spatially explicit model to evaluate the implications of reforestation both for water flows and for other services. We find that reforestation does not necessarily increase water supply, but does increase carbon sequestration and timber production. PMID:23690598

  1. Congenitally corrected transposition of the great vessels: localization of the site of complete atrioventricular block using his bundle electrograms.

    PubMed

    Foster, J R; Damato, A N; Kline, L E; Akhtar, M; Ruskin, J N

    1976-09-01

    Complete atrioventricular block proximal to the bundle of His in a patient with congenitally corrected transposition of the great vessels was documented using His bundle electrograms. The spontaneous rhythnm probably originated from the bundle of His and was responsive to carotid sinus massage, atropine and isometric and treadmill exercise. These electrophysiologic observations are consistent with recent anatomic studies of congenitally corrected transposition of the great vessels.

  2. Microtubule bundling and shape transitions: Mechanics, interactions, and self-assemblies

    NASA Astrophysics Data System (ADS)

    Needleman, Daniel Joseph

    Microtubules associate to form bundles in vivo in a wide variety of contexts including the mitotic spindle, neuronal processes, and the cortical array in plant cells. These supramolecular assemblies differ in size and shape, and in their internal structure, but the principles that determine this variation in morphology are not understood. To help elucidate such principals we constructed microtubule bundles in vitro using a variety of bundling agents. We have characterized the structure of these supramolecular assemblies of microtubules from the nanoscale to the mesoscale using synchrotron x-ray scattering and diffraction, video enhanced DIC and fluorescence microscopy, and electron microscopy. In the presence of inert polymers, an osmotic pressure imbalance between the inside and the outside of the microtubules may cause them to buckle to a non-circular cross-section. Depletion effects cause these distorted microtubules to bundle into a lattice with rectangular symmetry. The critical buckling pressure provides a measure of the stiffness of the inter-protofilament bond, and we determined that microtubule associated proteins enhance the strength of this bond, while the chemotherapeutic drug taxol has no effect. Multivalent ions cause microtubules to associate into bundles whose morphology depends on the condensing ion. Tightly packed hexagonal bundles with controllable diameters are observed for large tri-, tetra-, and pentavalent counterions. Unexpectedly, in the presence of small divalent cations, we have discovered a living necklace bundle phase, comprised of dynamical assemblies of MT nematic membranes with linear, branched, and loop topologies. Cations may also cause tubulin to assemble into non-microtubule structures. For example, in the presence of spermine, over time the microtubule bundles transform into a columnar phase of inverted tubules, such that the surface which was facing outside of the microtubules switches to the inside. This rearrangement between

  3. Enhanced Load Transfer in Carbon Nanotube Bundles via Carbon-Ion Bombardment

    NASA Astrophysics Data System (ADS)

    Carpena-Nunez, Jennifer; Hernandez, Jose A.; Siochi, Emilie J.; Kim, Jae-Woo; Fonseca, Luis F.

    2014-03-01

    Carbon Nanotubes (CNTs) are ideal candidates for structural composites due to their high modulus and strength, and low weight and density. However, achieving their exceptional mechanical performance at the macroscale is an ongoing challenge, as individual CNTs within bundles are held together by weak van der Waals forces. The current work aims to address issues related to crosslinking CNTs via carbon-ion irradiation to achieve the mechanical performance promised by CNTs. Samples irradiated with a carbon-ion dose of ~ 1013-1014 cm-2 and kinetic energies ranging from 9-25keV show partial amorphization at the outermost layer of the CNT bundle, as theoretically predicted. Mechanical data collected via in-situ Transmission Electron Microscopy-Atomic Force Microscopy (TEM-AFM) shows an increase in tensile and shear strength for irradiated CNT bundles of ~ 6.6GPa and ~ 100MPa, respectively. The adhesion energy between CNT bundles showed an increase from ~ 0.12-0.48 Jm-2 for pristine CNTs up to ~ 42 Jm-2 for carbon-ion irradiated bundles. In addition, enhanced shear interaction exceeding a strength value of ~ 1GPa was observed when exposed to additional amorphous carbon binding, providing a route for improved adhesion to polymer components used in structural composites. This work was supported by a NASA Space Technology Research Fellowship.

  4. Calculation of Non-Bonded Forces Due to Sliding of Bundled Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Frankland, S. J. V.; Bandorawalla, T.; Gates, T. S.

    2003-01-01

    An important consideration for load transfer in bundles of single-walled carbon nanotubes is the nonbonded (van der Waals) forces between the nanotubes and their effect on axial sliding of the nanotubes relative to each other. In this research, the non-bonded forces in a bundle of seven hexagonally packed (10,10) single-walled carbon nanotubes are represented as an axial force applied to the central nanotube. A simple model, based on momentum balance, is developed to describe the velocity response of the central nanotube to the applied force. The model is verified by comparing its velocity predictions with molecular dynamics simulations that were performed on the bundle with different force histories applied to the central nanotube. The model was found to quantitatively predict the nanotube velocities obtained from the molecular dynamics simulations. Both the model and the simulations predict a threshold force at which the nanotube releases from the bundle. This force converts to a shear yield strength of 10.5-11.0 MPa for (10,10) nanotubes in a bundle.

  5. The Calcium-Dependent Switch Helix of L-Plastin Regulates Actin Bundling

    PubMed Central

    Ishida, Hiroaki; Jensen, Katharine V.; Woodman, Andrew G.; Hyndman, M. Eric; Vogel, Hans J.

    2017-01-01

    L-plastin is a calcium-regulated actin-bundling protein that is expressed in cells of hematopoietic origin and in most metastatic cancer cells. These cell types are mobile and require the constant remodeling of their actin cytoskeleton, where L-plastin bundles filamentous actin. The calcium-dependent regulation of the actin-bundling activity of L-plastin is not well understood. We have used NMR spectroscopy to determine the solution structure of the EF-hand calcium-sensor headpiece domain. Unexpectedly, this domain does not bind directly to the four CH-domains of L-plastin. A novel switch helix is present immediately after the calcium-binding region and it binds tightly to the EF-hand motifs in the presence of calcium. We demonstrate that this switch helix plays a major role during actin-bundling. Moreover a peptide that competitively inhibits the association between the EF-hand motifs and the switch helix was shown to deregulate the actin-bundling activity of L-plastin. Overall, these findings may help to develop new drugs that target the L-plastin headpiece and interfere in the metastatic activity of cancer cells. PMID:28145401

  6. Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

    NASA Technical Reports Server (NTRS)

    Toda, Risaku; Bronikowski, Michael; Luong, Edward; Manohara, Harish

    2008-01-01

    A continuing effort to develop carbon-nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime a concept that was discussed in more detail in Arrays of Bundles of Carbon Nanotubes as Field Emitters (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located, such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

  7. Towards a bimodal proximity sensor for in situ neurovascular bundle detection during dental implant surgery

    PubMed Central

    Weber, Jessie R.; Baribeau, François; Grenier, Paul; Émond, Frédéric; Dubois, Sylvain; Duchesne, François; Girard, Marc; Pope, Timothy; Gallant, Pascal; Mermut, Ozzy; Moghadam, Hassan Ghaderi

    2013-01-01

    Proof of concept results are presented towards an in situ bimodal proximity sensor for neurovascular bundle detection during dental implant surgery using combined near infrared absorption (NIR) and optical coherence tomography (OCT) techniques. These modalities are shown to have different sensitivity to the proximity of optical contrast from neurovascular bundles. NIR AC and DC signals from the pulsing of an artery enable qualitative ranging of the bundle in the millimeter range, with best sensitivity around 0.5-3mm distance in a custom phantom setup. OCT provides structural mapping of the neurovascular bundle at sub-millimeter distances in an ex vivo human jaw bone. Combining the two techniques suggests a novel ranging system for the surgeon that could be implemented in a “smart drill.” The proximity to the neurovascular bundle can be tracked in real time in the range of a few millimeters with NIR signals, after which higher resolution imaging OCT to provide finer ranging in the sub-millimeter distances. PMID:24466473

  8. Myosin di-phosphorylation and peripheral actin bundle formation as initial events during endothelial barrier disruption.

    PubMed

    Hirano, Mayumi; Hirano, Katsuya

    2016-02-11

    The phosphorylation of the 20-kD myosin light chain (MLC) and actin filament formation play a key role in endothelial barrier disruption. MLC is either mono- or di-phosphorylated (pMLC and ppMLC) at T18 or S19. The present study investigated whether there are any distinct roles of pMLC and ppMLC in barrier disruption induced by thrombin. Thrombin induced a modest bi-phasic increase in pMLC and a robust mono-phasic increase in ppMLC. pMLC localized in the perinuclear cytoplasm during the initial phase, while ppMLC localized in the cell periphery, where actin bundles were formed. Later, the actin bundles were rearranged into stress fibers, where pMLC co-localized. Rho-kinase inhibitors inhibited thrombin-induced barrier disruption and peripheral localization of ppMLC and actin bundles. The double, but not single, mutation of phosphorylation sites abolished the formation of peripheral actin bundles and the barrier disruption, indicating that mono-phosphorylation of MLC at either T18 or S19 is functionally sufficient for barrier disruption. Namely, the peripheral localization, but not the degree of phosphorylation, is suggested to be essential for the functional effect of ppMLC. These results suggest that MLC phosphorylation and actin bundle formation in cell periphery are initial events during barrier disruption.

  9. Standardization of Type 2 Diabetes Outpatient Expenditure with Bundled Payment Method in China

    PubMed Central

    Xu, Guo-Chao; Luo, Yun; Li, Qian; Wu, Meng-Fan; Zhou, Zi-Jun

    2016-01-01

    Background: In recent years, the prevalence of type 2 diabetes among Chinese population has been increasing by years, directly leading to an average annual growth rate of 19.90% of medical expenditure. Therefore, it is urgent to work on strategies to control the growth of medical expenditure on type 2 diabetes on the basis of the reality of China. Therefore, in this study, we explored the feasibility of implementing bundled payment in China through analyzing bundled payment standards of type 2 diabetes outpatient services. Methods: This study analyzed the outpatient expenditure on type 2 diabetes with Beijing Urban Employee's Basic Medical Insurance from 2010 to 2012. Based on the analysis of outpatient expenditure and its influential factors, we adopted decision tree approach to conduct a case-mix analysis. In the end, we built a case-mix model to calculate the standard expenditure and the upper limit of each combination. Results: We found that age, job status, and whether with complication were significant factors that influence outpatient expenditure for type 2 diabetes. Through the analysis of the decision tree, we used six variables (complication, age, diabetic foot, diabetic nephropathy, cardiac-cerebrovascular disease, and neuropathy) to group the cases, and obtained 11 case-mix groups. Conclusions: We argued that it is feasible to implement bundled payment on type 2 diabetes outpatient services. Bundled payment is effective to control the increase of outpatient expenditure. Further improvements are needed for the implementation of bundled payment reimbursement standards, together with relevant policies and measures. PMID:27064041

  10. Molecular Basis for the Dual Function of Eps8 on Actin Dynamics: Bundling and Capping

    PubMed Central

    Hazelwood, Larnele; Disanza, Andrea; Liu, HongJun; Perlade, Emilie; Malabarba, Maria Grazia; Pasqualato, Sebastiano; Maiolica, Alessio; Confalonieri, Stefano; Le Clainche, Christophe; Offenhauser, Nina; Block, Jennifer; Rottner, Klemens; Di Fiore, Pier Paolo; Carlier, Marie-France; Volkmann, Niels; Hanein, Dorit; Scita, Giorgio

    2010-01-01

    Actin capping and cross-linking proteins regulate the dynamics and architectures of different cellular protrusions. Eps8 is the founding member of a unique family of capping proteins capable of side-binding and bundling actin filaments. However, the structural basis through which Eps8 exerts these functions remains elusive. Here, we combined biochemical, molecular, and genetic approaches with electron microscopy and image analysis to dissect the molecular mechanism responsible for the distinct activities of Eps8. We propose that bundling activity of Eps8 is mainly mediated by a compact four helix bundle, which is contacting three actin subunits along the filament. The capping activity is mainly mediated by a amphipathic helix that binds within the hydrophobic pocket at the barbed ends of actin blocking further addition of actin monomers. Single-point mutagenesis validated these modes of binding, permitting us to dissect Eps8 capping from bundling activity in vitro. We further showed that the capping and bundling activities of Eps8 can be fully dissected in vivo, demonstrating the physiological relevance of the identified Eps8 structural/functional modules. Eps8 controls actin-based motility through its capping activity, while, as a bundler, is essential for proper intestinal morphogenesis of developing Caenorhabditis elegans. PMID:20532239

  11. Structural implications of Ca2+-dependent actin-bundling function of human EFhd2/Swiprosin-1

    PubMed Central

    Park, Kyoung Ryoung; Kwon, Min-Sung; An, Jun Yop; Lee, Jung-Gyu; Youn, Hyung-Seop; Lee, Youngjin; Kang, Jung Youn; Kim, Tae Gyun; Lim, Jia Jia; Park, Jeong Soon; Lee, Sung Haeng; Song, Woo Keun; Cheong, Hae-Kap; Jun, Chang-Duk; Eom, Soo Hyun

    2016-01-01

    EFhd2/Swiprosin-1 is a cytoskeletal Ca2+-binding protein implicated in Ca2+-dependent cell spreading and migration in epithelial cells. EFhd2 domain architecture includes an N-terminal disordered region, a PxxP motif, two EF-hands, a ligand mimic helix and a C-terminal coiled-coil domain. We reported previously that EFhd2 displays F-actin bundling activity in the presence of Ca2+ and this activity depends on the coiled-coil domain and direct interaction of the EFhd2 core region. However, the molecular mechanism for the regulation of F-actin binding and bundling by EFhd2 is unknown. Here, the Ca2+-bound crystal structure of the EFhd2 core region is presented and structures of mutants defective for Ca2+-binding are also described. These structures and biochemical analyses reveal that the F-actin bundling activity of EFhd2 depends on the structural rigidity of F-actin binding sites conferred by binding of the EF-hands to Ca2+. In the absence of Ca2+, the EFhd2 core region exhibits local conformational flexibility around the EF-hand domain and C-terminal linker, which retains F-actin binding activity but loses the ability to bundle F-actin. In addition, we establish that dimerisation of EFhd2 via the C-terminal coiled-coil domain, which is necessary for F-actin bundling, occurs through the parallel coiled-coil interaction. PMID:27974828

  12. Efficient formation of bipolar microtubule bundles requires microtubule-bound γ-tubulin complexes

    PubMed Central

    Janson, Marcel E.; Setty, Thanuja Gangi; Paoletti, Anne; Tran, P.T.

    2005-01-01

    The mechanism for forming linear microtubule (MT) arrays in cells such as neurons, polarized epithelial cells, and myotubes is not well understood. A simpler bipolar linear array is the fission yeast interphase MT bundle, which in its basic form contains two MTs that are bundled at their minus ends. Here, we characterize mto2p as a novel fission yeast protein required for MT nucleation from noncentrosomal γ-tubulin complexes (γ-TuCs). In interphase mto2Δ cells, MT nucleation was strongly inhibited, and MT bundling occurred infrequently and only when two MTs met by chance in the cytoplasm. In wild-type 2, we observed MT nucleation from γ-TuCs bound along the length of existing MTs. We propose a model on how these nucleation events can more efficiently drive the formation of bipolar MT bundles in interphase. Key to the model is our observation of selective antiparallel binding of MTs, which can both explain the generation and spatial separation of multiple bipolar bundles. PMID:15837798

  13. [Does radiofrequency ablation of the bundle of Kent results in a lower risk of atrial fibrillation?].

    PubMed

    Brembilla-Perrot, B; Beurrier, D; Houriez, P

    2002-02-01

    Radiofrequency ablation of the Bundle of Kent is a common method of treating malignant forms of the Wolff-Parkinson-White syndrome and the paroxysmal junctional tachycardia which may complicate this condition. The aim of this study was to investigate the effects of ablation of a latent or patent Bundle of Kent on the prevention of atrial fibrillation. One hundred and thirty eight patients aged 15 to 81 years of age with one or more patent (Group I) (n = 96) or latent Bundles of Kent (Group II) (n = 42) underwent successful ablation of the Bundle of Kent. Five patients in Group I (5%) and 4 in Group II (9.5%) had spontaneous paroxysmal atrial fibrillation before ablation. During electrophysiological investigation, AF was induced in 7 patients, 2 of whom had spontaneous AF in Group I and 3 in Group II. During follow-up (3 +/- 1 years), 3 patients of Group I went on to develop AF: 2 of them had never had the arrhythmia before: 4 patients of Group II, including 2 with previous AF, went on to develop AF. The risk of spontaneous AF was correlated to older ages. The authors conclude that persistence of the risk of spontaneous AF after ablation of a Bundle of Kent should be investigated especially in patients over 45 years of age.

  14. EsxB, a secreted protein from Bacillus anthracis forms two distinct helical bundles

    DOE PAGES

    Fan, Yao; Tan, Kemin; Chhor, Gekleng; ...

    2015-07-03

    The EsxB protein from Bacillus anthracis belongs to the WXG100 family, a group of proteins secreted by a specialized secretion system. We have determined the crystal structures of recombinant EsxB and discovered that the small protein (~10 kDa), comprised of a helix-loop-helix (HLH) hairpin, is capable of associating into two different helical bundles. The two basic quaternary assemblies of EsxB are an antiparallel (AP) dimer and a rarely observed bisecting U (BU) dimer. This structural duality of EsxB is believed to originate from the heptad repeat sequence diversity of the first helix of its HLH hairpin, which allows for twomore » alternative helix packing. The flexibility of EsxB and the ability to form alternative helical bundles underscore the possibility that this protein can serve as an adaptor in secretion and can form hetero-oligomeric helix bundle(s) with other secreted members of the WXG100 family, such as EsxW. The highly conserved WXG motif is located within the loop of the HLH hairpin and is mostly buried within the helix bundle suggesting that its role is mainly structural. The exact functions of the motif, including a proposed role as a secretion signal, remain unknown.« less

  15. Combining high power diode lasers using fiber bundles for beam delivery in optoacoustic endoscopy applications

    NASA Astrophysics Data System (ADS)

    Gawali, Sandeep Babu; Leggio, Luca; Sánchez, Miguel; Rodríguez, Sergio; Dadrasnia, Ehsan; Gallego, Daniel C.; Lamela, Horacio

    2016-05-01

    Optoacoustic (OA) effect refers to the generation of the acoustic waves due to absorption of light energy in a biological tissue. The incident laser pulse is absorbed by the tissue, resulting in the generation of ultrasound that is typically detected by a piezoelectric detector. Compared to other techniques, the advantage of OA imaging (OAI) technique consists in combining the high resolution of ultrasound technique with the high contrast of optical imaging. Generally, Nd:YAG and OPO systems are used for the generation of OA waves but their use in clinical environment is limited for many aspects. On the other hand, high-power diode lasers (HPDLs) emerge as potential alternative. However, the power of HPDLs is still relatively low compared to solid-state lasers. We show a side-by-side combination of several HPDLs in an optical fiber bundle to increase the amount of power for OA applications. Initially, we combine the output optical power of several HPDLs at 905 nm using two 7 to 1 round optical fiber bundles featuring a 675 μm and 1.2 mm bundle aperture. In a second step, we couple the output light of these fiber bundles to a 600 μm core diameter endoscopic fiber, reporting the corresponding coupling efficiencies. The fiber bundles with reasonable small diameter are likely to be used for providing sufficient light energy to potential OA endoscopy (OAE) applications.

  16. Forward-viewing photoacoustic imaging probe with bundled ultra-thin hollow optical fibers

    NASA Astrophysics Data System (ADS)

    Seki, A.; Iwai, K.; Katagiri, T.; Matsuura, Y.

    2016-07-01

    A photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers is proposed for endoscopic diagnosis. In this system, a bundle of 127 hollow-optical fibers with an inner diameter of 100 μm was fabricated. The total diameter of the bundle was 2.1 mm, and the minimum bending radius was around 10 mm. Owing to the small numerical aperture of hollow optical fibers, a high resolution image was obtained without using a lens array at the distal end. In the imaging system, the hollow fibers in the bundle were aligned at the input end, so the hollow fibers were sequentially excited by linearly scanning the laser beam at the input end. Photoacoustic imaging systems consisting of the bundled fibers for excitation of acoustic wave and piezoelectric probes for detection of photoacoustic signals were built. By using the systems, photoacoustic images of blood vessels in the ovarian membrane of fish were taken to test the feasibility of the system. As a result, photoacoustic images of the vessel were successfully obtained with a laser fluence of around 6.6 mJ cm-2.

  17. Stochastic mechanical degradation of multi-cracked fiber bundles with elastic and viscous interactions.

    PubMed

    Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio

    2015-05-01

    The mechanics of fiber bundles has been largely investigated in order to understand their complex failure modes. Under a mechanical load, the fibers fail progressively while the load is redistributed among the unbroken fibers. The classical fiber bundle model captures the most important features of this rupture process. On the other hand, the homogenization techniques are able to evaluate the stiffness degradation of bulk solids with a given population of cracks. However, these approaches are inadequate to determine the effective response of a degraded bundle where breaks are induced by non-mechanical actions. Here, we propose a method to analyze the behavior of a fiber bundle, undergoing a random distribution of breaks, by considering the intrinsic response of the fibers and the visco-elastic interactions among them. We obtain analytical solutions for simple configurations, while the most general cases are studied by Monte Carlo simulations. We find that the degradation of the effective bundle stiffness can be described by two scaling regimes: a first exponential regime for a low density of breaks, followed by a power-law regime at increasingly higher break density. For both regimes, we find analytical effective expressions described by specific scaling exponents.

  18. A comparison of results from LANCER02 and MCNP on a series of two-dimensional multiple BWR bundle configurations

    SciTech Connect

    Knott, D.; Wehlage, E.; Sawada, A.; Zino, J.

    2006-07-01

    This paper discusses recent extensions to the LANCER02 lattice physics code that allow for the analysis of multiple bundles lying along a two-dimensional plane of a reactor core. The paper presents results from LANCER02 on a study consisting of analyses on single assemblies, 2 x 2 arrays of bundles, and 4 x 4 arrays of bundles at different operating conditions. LANCER02 eigenvalues and rod-by-rod fission rates are compared against results from corresponding MCNP analyses. Results indicate that the LANCER02 multi-bundle modelling option is equivalent in accuracy to its single-assembly capability. (authors)

  19. [Care bundle to reduce central venous catheter-related bloodstream infection: an integrative review].

    PubMed

    Brachine, Juliana Dane Pereira; Peterlini, Maria Angélica Sorgini; Pedreira, Mavilde da Luz Gonçalves

    2012-12-01

    This is an integrative review of literature aimed to identify evidence-based interventions which make up care bundles to reduce central venous catheter-related or associated bloodstream infections. To collect data in Brazilian and international databases were used the key word bundle and the descriptors catheter-related infection, infection control and central venous catheterization, resulting in fifteen articles, after inclusion criteria application. This work showed five interventions as those commonly employed in the bundles methods: hand hygiene, chlorhexidine gluconate for skin antisepsis, use of maximal sterile barrier precaution during the catheter insertion, avoid the femoral access and daily review of catheter necessity with prompt removal as no longer essential. The majority of the studies showed a significant reduction in bloodstream infection related to or associated with central venous catheters.

  20. Size distributions of air showers accompanied with high energy gamma ray bundles observed at Mt. Chacaltaya

    NASA Technical Reports Server (NTRS)

    Matano, T.; Machida, M.; Tsuchima, I.; Kawasumi, N.; Honda, K.; Hashimoto, K.; Martinic, N.; Zapata, J.; Navia, C. E.; Aquirre, C.

    1985-01-01

    Size distributions of air showers accompanied with bundle of high energy gamma rays and/or large size bursts under emulsion chambers, to study the composition of primary cosmic rays and also characteristics of high energy nuclear interaction. Air showers initiated by particles with a large cross section of interaction may develop from narrow region of the atmosphere near the top. Starting levels of air showers by particles with smaller cross section fluctuate in wider region of the atmosphere. Air showers of extremely small size accompanied with bundle of gamma rays may be ones initiated by protons at lower level after penetrating deep atmosphere without interaction. It is determined that the relative size distribution according to the total energy of bundle of gamma rays and the total burst size observed under 15 cm lead absorber.