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Sample records for pressure-lung volume loops

  1. Relationship of end-expiratory pressure, lung volume, and /sup 99m/Tc-DTPA clearance

    SciTech Connect

    Cooper, J.A.; van der Zee, H.; Line, B.R.; Malik, A.B.

    1987-10-01

    We investigated the dose-response effect of positive end-expiratory pressure (PEEP) and increased lung volume on the pulmonary clearance rate of aerosolized technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). Clearance of lung radioactivity was expressed as percent decrease per minute. Base-line clearance was measured while anesthetized sheep (n = 20) were ventilated with 0 cmH/sub 2/O end-expiratory pressure. Clearance was remeasured during ventilation at 2.5, 5, 10, 15, or 20 cmH/sub 2/O PEEP. Further studies showed stepwise increases in functional residual capacity (FRC) (P less than 0.05) measured at 0, 2.5, 5, 10, 15, and 20 cmH/sub 2/O PEEP. At 2.5 cmH/sub 2/O PEEP, the clearance rate was not different from that at base line (P less than 0.05), although FRC was increased from base line. Clearance rate increased progressively with increasing PEEP at 5, 10, and 15 cmH/sub 2/O (P less than 0.05). Between 15 and 20 cmH/sub 2/O PEEP, clearance rate was again unchanged, despite an increase in FRC. The pulmonary clearance of aerosolized /sup 99m/Tc-DTPA shows a sigmoidal response to increasing FRC and PEEP, having both threshold and maximal effects. This relationship is most consistent with the hypothesis that alveolar epithelial permeability is increased by lung inflation.

  2. New volume and inverse volume operators for loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Yang, Jinsong; Ma, Yongge

    2016-08-01

    A new alternative volume operator is constructed for loop quantum gravity by using the so-called cotriad operators as building blocks. It is shown that the new volume operator shares the same qualitative properties with the standard volume operator. Moreover, a new alternative inverse volume operator is also constructed in the light of the construction of the alternative volume operator, which is possessed of the same qualitative properties as those of the alternative volume operator. The new inverse volume operator can be employed to construct the Hamiltonian operator of matter fields, which may lead to an anomaly-free on-shell quantum constraint algebra without any special restriction on the regularization procedure for gravity coupled to matter fields.

  3. Measuring Pressure Volume Loops in the Mouse.

    PubMed

    Townsend, DeWayne

    2016-01-01

    Understanding the causes and progression of heart disease presents a significant challenge to the biomedical community. The genetic flexibility of the mouse provides great potential to explore cardiac function at the molecular level. The mouse's small size does present some challenges in regards to performing detailed cardiac phenotyping. Miniaturization and other advancements in technology have made many methods of cardiac assessment possible in the mouse. Of these, the simultaneous collection of pressure and volume data provides a detailed picture of cardiac function that is not available through any other modality. Here a detailed procedure for the collection of pressure-volume loop data is described. Included is a discussion of the principles underlying the measurements and the potential sources of error. Anesthetic management and surgical approaches are discussed in great detail as they are both critical to obtaining high quality hemodynamic measurements. The principles of hemodynamic protocol development and relevant aspects of data analysis are also addressed. PMID:27166576

  4. Cardiovascular simulator improvement: pressure versus volume loop assessment.

    PubMed

    Fonseca, Jeison; Andrade, Aron; Nicolosi, Denys E C; Biscegli, José F; Leme, Juliana; Legendre, Daniel; Bock, Eduardo; Lucchi, Julio Cesar

    2011-05-01

    This article presents improvement on a physical cardiovascular simulator (PCS) system. Intraventricular pressure versus intraventricular volume (PxV) loop was obtained to evaluate performance of a pulsatile chamber mimicking the human left ventricle. PxV loop shows heart contractility and is normally used to evaluate heart performance. In many heart diseases, the stroke volume decreases because of low heart contractility. This pathological situation must be simulated by the PCS in order to evaluate the assistance provided by a ventricular assist device (VAD). The PCS system is automatically controlled by a computer and is an auxiliary tool for VAD control strategies development. This PCS system is according to a Windkessel model where lumped parameters are used for cardiovascular system analysis. Peripheral resistance, arteries compliance, and fluid inertance are simulated. The simulator has an actuator with a roller screw and brushless direct current motor, and the stroke volume is regulated by the actuator displacement. Internal pressure and volume measurements are monitored to obtain the PxV loop. Left chamber internal pressure is directly obtained by pressure transducer; however, internal volume has been obtained indirectly by using a linear variable differential transformer, which senses the diaphragm displacement. Correlations between the internal volume and diaphragm position are made. LabVIEW integrates these signals and shows the pressure versus internal volume loop. The results that have been obtained from the PCS system show PxV loops at different ventricle elastances, making possible the simulation of pathological situations. A preliminary test with a pulsatile VAD attached to PCS system was made. PMID:21595711

  5. [Aex - the area under the expiratory flow-volume loop].

    PubMed

    Stein, D; Stein, K; Ingrisch, S

    2015-04-01

    Preschool children often show total expiration times of less than one second in pulmonary function tests. Therefore, FEV1 cannot be used for evaluation of obstructive pulmonary diseases in small children. Aex, the area under the expiratory flow-volume loop, does not depend on the expiration time. The Aex value varies according to the convex or concave shape of the flow volume loop, can be quantified and is a valuable parameter in the diagnosis of obstructive airway diseases.In this study FEV1 und Aex values of 19882 flow-volume loops were measured and compared. The comparison shows a very high correlation coefficient of r = 0.99.The changes of both parameters in an individual after provocation or bronchospasmolysis also demonstrate a strong correlation. A 20 % change of FEV1 equals an Aex change of 36 %.We conclude that measuring Aex is a good alternative to measuring FEV1 especially if the FEV1 cannot be obtained due to short expiration times. PMID:25853269

  6. T-111 Rankine system corrosion test loop, volume 1

    NASA Technical Reports Server (NTRS)

    Harrison, R. W.; Hoffman, E. E.; Smith, J. P.

    1975-01-01

    Results are given of a program whose objective was to determine the performance of refractory metal alloys in a two loop Rankine test system. The test system consisted of a circulating lithium circuit heated to 1230 C maximum transferring heat to a boiling potassium circuit with a 1170 C superheated vapor temperature. The results demonstrate the suitability of the selected refractory alloys to perform from a chemical compatibility standpoint.

  7. Biphasic flow-volume loop in granulomatosis with polyangiitis related unilateral bronchus obstruction.

    PubMed

    Agrawal, Abhinav; Sahni, Sonu; Marder, Galina; Shah, Rakesh; Talwar, Arunabh

    2016-07-01

    Spirometry flow-volume measurement is used routinely in the outpatient setting to rule out obstructive lung diseases. Biphasic flow-volume loop is a classic presentation of unilateral bronchial stenosis due to multiple etiologies and it should raise clinical suspicion. Granulomatosis with polyangiitis (GPA) is a systemic inflammatory condition with pulmonary manifestations that may be infiltrative (e.g., pneumonia), hemorrhagic, and may rarely cause bronchial stenosis. Herein, we present a case of GPA-related, bronchial obstruction that caused biphasic flow-volume loop along with a literature review. PMID:27424828

  8. Non-Gaussian features from the inverse volume corrections in loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Li, Li-Fang; Cai, Rong-Gen; Guo, Zong-Kuan; Hu, Bin

    2012-08-01

    In this paper we study the non-Gaussian features of the primordial fluctuations in loop quantum cosmology with the inverse volume corrections. The detailed analysis is performed in the single field slow-roll inflationary models. However, our results reflect the universal characteristics of bispectrum in loop quantum cosmology. The main corrections to the scalar bispectrum come from two aspects: one is the modifications to the standard Bunch-Davies vacuum, and the other is the corrections to the background dependent variables, such as slow-roll parameters. Our calculations show that the loop quantum corrections make fNL of the inflationary models increase 0.1%. Moreover, we find that two new shapes of non-Gaussian signal arise, which we name F1 and F2. The former gives a unique loop quantum feature, which is less correlated with the local, equilateral, and single types, while the latter is highly correlated with the local one.

  9. Real time pressure-volume loops in mice using complex admittance: measurement and implications.

    PubMed

    Kottam, Anil T G; Porterfield, John; Raghavan, Karthik; Fernandez, Daniel; Feldman, Marc D; Valvano, Jonathan W; Pearce, John A

    2006-01-01

    Real time left ventricular (LV) pressure-volume (P-V) loops have provided a framework for understanding cardiac mechanics in experimental animals and humans. Conductance measurements have been used for the past 25 years to generate an instantaneous left ventricular (LV) volume signal. The standard conductance method yields a combination of blood and ventricular muscle conductance; however, only the blood signal is used to estimate LV volume. The state of the art techniques like hypertonic saline injection and IVC occlusion, determine only a single steady-state value of the parallel conductance of the cardiac muscle. This is inaccurate, since the cardiac muscle component should vary instantaneously throughout the cardiac cycle as the LV contracts and fills, because the distance from the catheter to the muscle changes. The capacitive nature of cardiac muscle can be used to identify its contribution to the combined conductance signal. This method, in contrast to existing techniques, yields an instantaneous estimate of the parallel admittance of cardiac muscle that can be used to correct the measurement in real time. The corrected signal consists of blood conductance alone. We present the results of real time in vivo measurements of pressure-admittance and pressure-phase loops inside the murine left ventricle. We then use the magnitude and phase angle of the measured admittance to determine pressure volume loops inside the LV on a beat by beat basis. These results may be used to achieve a substantial improvement in the state of the art in this measurement method by eliminating the need for hypertonic saline injection. PMID:17946238

  10. Cardiac Pressure-Volume Loop Analysis Using Conductance Catheters in Mice

    PubMed Central

    Abraham, Dennis; Mao, Lan

    2016-01-01

    Cardiac pressure-volume loop analysis is the “gold-standard” in the assessment of load-dependent and load-independent measures of ventricular systolic and diastolic function. Measures of ventricular contractility and compliance are obtained through examination of cardiac response to changes in afterload and preload. These techniques were originally developed nearly three decades ago to measure cardiac function in large mammals and humans. The application of these analyses to small mammals, such as mice, has been accomplished through the optimization of microsurgical techniques and creation of conductance catheters. Conductance catheters allow for estimation of the blood pool by exploiting the relationship between electrical conductance and volume. When properly performed, these techniques allow for testing of cardiac function in genetic mutant mouse models or in drug treatment studies. The accuracy and precision of these studies are dependent on careful attention to the calibration of instruments, systematic conduct of hemodynamic measurements and data analyses. We will review the methods of conducting pressure-volume loop experiments using a conductance catheter in mice. PMID:26436838

  11. Cardiac Pressure-Volume Loop Analysis Using Conductance Catheters in Mice.

    PubMed

    Abraham, Dennis; Mao, Lan

    2015-01-01

    Cardiac pressure-volume loop analysis is the "gold-standard" in the assessment of load-dependent and load-independent measures of ventricular systolic and diastolic function. Measures of ventricular contractility and compliance are obtained through examination of cardiac response to changes in afterload and preload. These techniques were originally developed nearly three decades ago to measure cardiac function in large mammals and humans. The application of these analyses to small mammals, such as mice, has been accomplished through the optimization of microsurgical techniques and creation of conductance catheters. Conductance catheters allow for estimation of the blood pool by exploiting the relationship between electrical conductance and volume. When properly performed, these techniques allow for testing of cardiac function in genetic mutant mouse models or in drug treatment studies. The accuracy and precision of these studies are dependent on careful attention to the calibration of instruments, systematic conduct of hemodynamic measurements and data analyses. We will review the methods of conducting pressure-volume loop experiments using a conductance catheter in mice. PMID:26436838

  12. NOTE: Comparison and evaluation of mouse cardiac MRI acquired with open birdcage, single loop surface and volume birdcage coils

    NASA Astrophysics Data System (ADS)

    Fan, Xiaobing; Markiewicz, Erica J.; Zamora, Marta; Karczmar, Gregory S.; Roman, Brian B.

    2006-12-01

    Although the quality and speed of MR images have vastly improved with the development of novel RF coil technologies, the engineering expertise required to implement them is often not available in many animal in vivo MR laboratories. We present here an open birdcage coil design which is easily constructed with basic RF coil expertise and produces high quality images. The quality and advantages of mouse cardiac MR images acquired with open birdcage coils were evaluated and compared to images acquired with a bent single loop surface, and standard birdcage coils acquired at 4.7 Tesla. Two low pass open birdcage coils, two single loop surface coils, and a low pass volume birdcage coil were constructed and their B1 distributions were evaluated and compared. The calculated average signal-to-noise ratio for the left ventricular wall was 10, 23 and 32 for the volume birdcage coil, single loop surface coil and open birdcage coil, respectively. The results demonstrate that the open birdcage coil provides greater sensitivity than the volume coil and a higher signal/contrast-to-noise ratio and B1 homogeneity than the single loop surface coil. The open birdcage coil offers easy access and better quality mouse cardiac imaging than both the single loop surface coil and volume birdcage coil and does not require extensive RF engineering expertise to construct.

  13. [Assessment of cardiac function by left heart catheterization: an analysis of left ventricular pressure-volume (length) loops].

    PubMed

    Sasayama, S; Nonogi, H; Sakurai, T; Kawai, C; Fujita, M; Eiho, S; Kuwahara, M

    1984-01-01

    The mechanical property of the cardiac muscle has been classically analyzed in two ways; shortening of muscle fiber, and the development of tension within the muscle. In the ejecting ventricle, left ventricular (LV) function can be analyzed by the analogous two-dimensional framework of pressure-volume loops, which are provided by plotting the instantaneous volume against corresponding LV pressure. The integral pressure with respect to volume allows to assess a total external ventricular work during ejection. The diastolic pressure-volume relations reflect a chamber stiffness of the ventricle. Force-velocity relations also provide an useful conceptual framework for understanding how the ventricle contracts under given afterload, with modification of preload. In the presence of coronary artery disease, the regional nature of left ventricular contractile function should be defined as well as the global ventricular function as described above, because the latter is determined by the complex interaction of dysfunction of the ischemic myocardium and of compensatory augmentation of shortening of the normally perfused myocardium. We utilized a computer technique to analyze the local wall motion of the ischemic heart by cineventriculography. The boundaries of serial ventricular images are automatically traced and superimposed using the external reference system. Radial grids are drawn from the center of gravity of the end-diastolic image. Measurement of length of each radial grid throughout cardiac cycle provides the analysis of movement of the ventricle at a particular point on the circumference. Using phasic pressure obtained simultaneously with opacification as the common parameter, segmental pressure-length loops are constructed simultaneously at various segments. The loops are similar over the entire circumference in the normal heart, being rectangular in morphology and with synchronous behavior during contraction and relaxation. However, the marked distortion of

  14. PILOT-SCALE INVESTIGATION OF CLOSED-LOOP FLY ASH SLUICING. VOLUME 2. APPENDICES

    EPA Science Inventory

    The report gives results of a pilot-scale demonstration of the technical feasibility of closed-loop operation of fly ash sluicing systems. Chemical species leached from the ash increase the dissolved solids concentration of recycled sluice water to a point where equipment scaling...

  15. PILOT-SCALE INVESTIGATION OF CLOSED-LOOP FLY ASH SLUICING. VOLUME 1. FINAL REPORT

    EPA Science Inventory

    The report gives results of a pilot-scale demonstration of the technical feasibility of closed-loop operation of fly ash sluicing systems. Chemical species leached from the ash increase the dissolved solids concentration of recycled sluice water to a point where equipment scaling...

  16. Evaluation of selected strapdown inertial instruments and pulse torque loops, volume 1

    NASA Technical Reports Server (NTRS)

    Sinkiewicz, J. S.; Feldman, J.; Lory, C. B.

    1974-01-01

    Design, operational and performance variations between ternary, binary and forced-binary pulse torque loops are presented. A fill-in binary loop which combines the constant power advantage of binary with the low sampling error of ternary is also discussed. The effects of different output-axis supports on the performance of a single-degree-of-freedom, floated gyroscope under a strapdown environment are illustrated. Three types of output-axis supports are discussed: pivot-dithered jewel, ball bearing and electromagnetic. A test evaluation on a Kearfott 2544 single-degree-of-freedom, strapdown gyroscope operating with a pulse torque loop, under constant rates and angular oscillatory inputs is described and the results presented. Contributions of the gyroscope's torque generator and the torque-to-balance electronics on scale factor variation with rate are illustrated for a SDF 18 IRIG Mod-B strapdown gyroscope operating with various pulse rebalance loops. Also discussed are methods of reducing this scale factor variation with rate by adjusting the tuning network which shunts the torque coil. A simplified analysis illustrating the principles of operation of the Teledyne two-degree-of-freedom, elastically-supported, tuned gyroscope and the results of a static and constant rate test evaluation of that instrument are presented.

  17. Strategies for Small Volume Resuscitation: Hyperosmotic-Hyperoncotic Solutions, Hemoglobin Based Oxygen Carriers and Closed-Loop Resuscitation

    NASA Technical Reports Server (NTRS)

    Kramer, George C.; Wade, Charles E.; Dubick, Michael A.; Atkins, James L.

    2004-01-01

    Introduction: Logistic constraints on combat casualty care preclude traditional resuscitation strategies which can require volumes and weights 3 fold or greater than hemorrhaged volume. We present a review of quantitative analyses of clinical and animal data on small volume strategies using 1) hypertonic-hyperosmotic solutions (HHS); 2) hemoglobin based oxygen carriers (HBOCs) and 3) closed-loop infusion regimens.Methods and Results: Literature searches and recent queries to industry and academic researchers have allowed us to evaluate the record of 81 human HHS studies (12 trauma trials), 19 human HBOCs studies (3trauma trials) and two clinical studies of closed-loop resuscitation.There are several hundreds animal studies and at least 82 clinical trials and reports evaluating small volume7.2%-7.5% hypertonic saline (HS) most often combined with colloids, e.g., dextran (HSD) or hetastarch(HSS). HSD and HSS data has been published for 1,108 and 392 patients, respectively. Human studies have documented volume sparing and hemodynamic improvements. Meta-analyses suggest improved survival for hypotensive trauma patients treated with HSD with significant reductions in mortality found for patients with blood pressure < 70 mmHg, head trauma, and penetrating injury requiring surgery. HSD and HSS have received regulatory approval in 14 and 3 countries, respectively, with 81,000+ units sold. The primary reported use was head injury and trauma resuscitation. Complications and reported adverse events are surprisingly rare and not significantly different from other solutions.HBOCs are potent volume expanders in addition to oxygen carriers with volume expansion greater than standard colloids. Several investigators have evaluated small volume hyperoncotic HBOCs or HS-HBOC formulations for hypotensive and normotensive resuscitation in animals. A consistent finding in resuscitation with HBOCs is depressed cardiac output. There is some evidence that HBOCs more efficiently unload

  18. Effects of control system failures on transients and accidents at a 3-loop Westinghouse pressurized water reactor. Volume 2. Appendices

    SciTech Connect

    Bruske, S.J.; Davis, C.B.; Ogden, D.M.; Ransom, C.B.; Stitt, B.D.; Stromberg, H.M.; Waterman, M.E.

    1985-10-01

    Safety Implications of Control Systems (A-47) was approved as an Unresolved Safety Issue (USI) by the Nuclear Regulatory Commission (NRC) in December of 1980. USI A-47 is concerned with the potential for transients or accidents being made more severe than previously analyzed as a result of control system failures. This report describes the work performed on the effects of control system failures on transients and accidents at a Westinghouse 3-loop pressurized water reactor. In this volume, the appendices contain detailed information consisting of the FMEA (failure mode and analysis) results, an in-depth description of the computer model, the deterministic computer analyses, and responses to comments made by Carolina Power and Light Company and Westinghouse Electric Corporation.

  19. The bosonic string measure at two and three loops and symplectic transformations of the volume form

    NASA Astrophysics Data System (ADS)

    Davis, Simon

    1995-08-01

    Symplectic modular invariance of the string integral has been verified at genus 2 and 3 using the period matrix coordinatization of moduli space. A calculation of the transformation of the product of holomorphic coordinates Π i⩽ j d τ ij shows that an extra phase arises together with the factor associated with a specific modular weight; the phase is cancelled in the transformation of the entire volume element including the complex conjugate. An argument is given for modular invariance of the reggeon measure at genus 12.

  20. Bio-telemetric device for measurement of left ventricular pressure-volume loops using the admittance technique in conscious, ambulatory rats

    PubMed Central

    Raghavan, Karthik; Feldman, Marc D; Porterfield, John E; Larson, Erik R; Jenkins, J Travis; Escobedo, Daniel; Pearce, John A

    2011-01-01

    This paper presents the design, construction and testing of a device to measure pressure volume loops in the left ventricle of conscious, ambulatory rats. Pressure is measured with a standard sensor, but volume is derived from data collected from a tetrapolar electrode catheter using a novel admittance technique. There are two main advantages of the admittance technique to measure volume. First, the contribution from the adjacent muscle can be instantaneously removed. Second, the admittance technique incorporates the nonlinear relationship between the electric field generated by the catheter and the blood volume. A low power instrument weighing 27 g was designed, which takes pressure-volume loops every 2 minutes and runs for 24 hours. Pressure-volume data are transmitted wirelessly to a base station. The device was first validated in thirteen rats with an acute preparation with 2-D echocardiography used to measure true volume. From an accuracy standpoint, the admittance technique is superior to both the conductance technique calibrated with hypertonic saline injections, and calibrated with cuvettes. The device was then tested in six rats with a 24-hour chronic preparation. Stability of the animal preparation and careful calibration are important factors affecting the success of the device. PMID:21606560

  1. Design of a wireless telemetric backpack device for real-time in vivo measurement of pressure-volume loops in conscious ambulatory rats.

    PubMed

    Raghavan, Karthik; Kottam, Anil T G; Valvano, Jonathan W; Pearce, John A

    2008-01-01

    Pressure - Volume (PV) analysis is the de facto standard for assessing myocardial function. Conductance based methods have been used for the past 27 years to generate instantaneous left ventricular (LV) volume signal. Our research group has developed the instrumentation and the algorithm for obtaining PV loops based on the measurement of real - time admittance magnitude and phase from the LV of anaesthetized mice and rats. In this study, the instrumentation will be integrated into an ASIC (Application Specific Integrated Circuit) and a backpack device will be designed along with this ASIC. This will enable measurement of real-time in vivo P-V loops from conscious and ambulatory rats, useful for both acute and chronic studies. PMID:19162825

  2. Probability of pipe failure in the reactor coolant loops of Babcock and Wilcox PWR plants. Volume 1. Summary report

    SciTech Connect

    Holman, G.S.; Chou, C.K.

    1986-05-01

    As part of its reevaluation of the double-ended guillotine break (DEGB) of reactor coolant piping as a design basis event for nuclear power plants, the US Nuclear Regulatory Commission (NRC) contracted the Lawrence Livermore National Laboratory (LLNL) to estimate the probability of occurrence of a DEGB, and to assess the effect that earthquakes have on DEGB probability. This report describes an evaluation of reactor coolant loop piping in PWR plants having nuclear steam supply systems designed by Babcock and Wilcox. Two causes of pipe break were considered: pipe fracture due to the growth of cracks at welded joints (''direct'' DEGB), and pipe rupture indirectly caused by failure of heavy component supports due to an earthquake (''indirect'' DEGB). Unlike in earlier evaluations of Westinghouse and Combustion Engineering reactor coolant loop piping, in which the probability of direct DEGB had been explicitly estimated using a probabilistic fracture mechanics model, no detailed fracture mechanics calculations were performed. Instead, a comparison of relevant plant data, mainly reactor coolant loop stresses, for one representative B and W plant with equivalent information for Westinghouse and C-E systems inferred that the probability of direct DEGB should be similarly low (less than le-10 per reactor year). The probability of indirect DEGB, on the other hand, was explicitly estimated for two representative plants. The results of this study indicate that the probability of a DEGB form either cause is very low for reactor coolant loop piping in these specific plants and, because of similarity in design, infer that the probability of DEGB is generally very low in B and W reactor coolant loop piping. The NRC should therefore consider eliminating DEGB as a design basis event in favor of more realistic criteria. 13 refs., 9 tabs.

  3. Probability of pipe failure in the reactor coolant loops of Westinghouse PWR Plants. Volume 1. Summary report

    SciTech Connect

    Holman, G.S.; Chou, C.K.

    1985-07-01

    As part of its reevaluation of the double-ended guillotine break (DEGB) of reactor coolant loop piping as a design basis event for nuclear power plants, the US Nuclear Regulatory Commission (NRC) contracted with the Lawrence Livermore National Laboratory (LLNL) to estimate the probability of occurrence probability. This report describes a probabilistic evaluation of reactor coolant loop piping in PWR plants having nuclear steam supply systems designed by Westinghouse. Two causes of pipe break were considered: pipe fracture due to the growth of cracks at welded joints (''direct'' DEGB), and pipe rupture indirectly caused by failure of component supports due to an earthquake (''indirect'' DEGB). The probability of direct DEGB was estimated using a probabilistic fracture mechanics model. The probability of indirect DEGB was estimated by estimating support fragility and then convolving fragility and seismic hazard. The results of this study indicate that the probability of a DEGB from either cause is very low for reactor coolant loop piping in these plants, and that NRC should therefore consider eliminating DEGB as a design basis event in favor of more realistic criteria. 17 refs., 15 figs., 11 tabs.

  4. Probability of pipe failure in the reactor coolant loops of Combustion Engineering PWR plants. Volume 1. Summary report

    SciTech Connect

    Holman, G.S.; Lo, T.; Chou, C.K.

    1985-01-01

    As part of its reevaluation of the double-ended guillotine break (DEGB) as a design requirement for reactor coolant piping, the US Nuclear Regulatory Commission (NRC) contracted with the Lawrence Livermore National Laboratory (LLNL) to estimate the probability of occurrence of a DEGB, and to assess the effect that earthquakes have on DEGB probability. This report describes a probabilistic evaluation of reactor coolant loop piping in PWR plants having nuclear steam supply systems designed by Combustion Engineering. Two causes of pipe break were considered: pipe fracture due to the growth of cracks at welded joints (direct DEGB), and pipe rupture indirectly caused by failure of component supports due to an earthquake (indirect DEGB). The probability of direct DEGB was estimated using a probabilistic fracture mechanics model. The probability of indirect DEGB was estimated by estimating support fragility and then convolving fragility with seismic hazard. The results of this study indicate that the probability of a DEGB from either cause is very low for reactor coolant loop piping in these plants, and that NRC should therefore consider eliminating DEGB as a design basis in favor of more realistic criteria.

  5. Regulative Loops, Step Loops and Task Loops

    ERIC Educational Resources Information Center

    VanLehn, Kurt

    2016-01-01

    This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, which…

  6. Probability of pipe fracture in the primary coolant loop of a PWR plant. Volume 6: failure mode analysis. Final report

    SciTech Connect

    Streit, R.D.

    1981-09-01

    Material properties and failure criteria were evaluated to assess the requirements for double-ended guillotine break in the primary coolant loop of the Zion Unit 1 pressurized water reactor. The properties of the 316 stainless steel piping materials were obtained from the literature. Statistical distributions of both the tensile and fracture properties at room and operating temperatures were developed. Yield and ultimate strength tensile properties were combined to estimate the material flow strength. The flow strength and fracture properties were used in the various failure models analyzed. Linear-elastic, elastic-plastic, and fully plastic fracture models were compared, and the governing fracture criterion was determined. For the particular case studied, the fully plastic flow requirement was found to be the controlling fracture criterion leading to a double-ended guillotine pipe break.

  7. A Closed-Loop Optimal Neural-Network Controller to Optimize Rotorcraft Aeromechanical Behaviour. Volume 1; Theory and Methodology

    NASA Technical Reports Server (NTRS)

    Leyland, Jane Anne

    2001-01-01

    Given the predicted growth in air transportation, the potential exists for significant market niches for rotary wing subsonic vehicles. Technological advances which optimise rotorcraft aeromechanical behaviour can contribute significantly to both their commercial and military development, acceptance, and sales. Examples of the optimisation of rotorcraft aeromechanical behaviour which are of interest include the minimisation of vibration and/or loads. The reduction of rotorcraft vibration and loads is an important means to extend the useful life of the vehicle and to improve its ride quality. Although vibration reduction can be accomplished by using passive dampers and/or tuned masses, active closed-loop control has the potential to reduce vibration and loads throughout a.wider flight regime whilst requiring less additional weight to the aircraft man that obtained by using passive methads. It is ernphasised that the analysis described herein is applicable to all those rotorcraft aeromechanical behaviour optimisation problems for which the relationship between the harmonic control vector and the measurement vector can be adequately described by a neural-network model.

  8. Inactivation and Anion Selectivity of Volume-regulated Anion Channels (VRACs) Depend on C-terminal Residues of the First Extracellular Loop.

    PubMed

    Ullrich, Florian; Reincke, S Momsen; Voss, Felizia K; Stauber, Tobias; Jentsch, Thomas J

    2016-08-12

    Canonical volume-regulated anion channels (VRACs) are crucial for cell volume regulation and have many other important roles, including tumor drug resistance and release of neurotransmitters. Although VRAC-mediated swelling-activated chloride currents (ICl,vol) have been studied for decades, exploration of the structure-function relationship of VRAC has become possible only after the recent discovery that VRACs are formed by differently composed heteromers of LRRC8 proteins. Inactivation of ICl,vol at positive potentials, a typical hallmark of VRACs, strongly varies between native cell types. Exploiting the large differences in inactivation between different LRRC8 heteromers, we now used chimeras assembled from isoforms LRRC8C and LRRC8E to uncover a highly conserved extracellular region preceding the second LRRC8 transmembrane domain as a major determinant of ICl,vol inactivation. Point mutations identified two amino acids (Lys-98 and Asp-100 in LRRC8A and equivalent residues in LRRC8C and -E), which upon charge reversal strongly altered the kinetics and voltage dependence of inactivation. Importantly, charge reversal at the first position also reduced the iodide > chloride permeability of ICl,vol This change in selectivity was stronger when both the obligatory LRRC8A subunit and the other co-expressed isoform (LRR8C or -E) carried such mutations. Hence, the C-terminal part of the first extracellular loop not only determines VRAC inactivation but might also participate in forming its outer pore. Inactivation of VRACs may involve a closure of the extracellular mouth of the permeation pathway. PMID:27325695

  9. Simultaneous and continuous multiple wavelength absorption spectroscopy on nanoliter volumes based on frequency-division multiplexing fiber-loop cavity ring-down spectroscopy.

    PubMed

    Waechter, Helen; Munzke, Dorit; Jang, Angela; Loock, Hans-Peter

    2011-04-01

    We demonstrate a method for measuring optical loss simultaneously at multiple wavelengths with cavity ring-down spectroscopy (CRD). Phase-shift CRD spectroscopy is used to obtain the absorption of a sample from the phase lag of intensity modulated light that is entering and exiting an optical cavity. We performed dual-wavelength detection by using two different laser light sources and frequency-division multiplexing. Each wavelength is modulated at a separate frequency, and a broadband detector records the total signal. This signal is then demodulated by lock-in amplifiers at the corresponding two frequencies allowing us to obtain the phase-shift and therefore the optical loss at several wavelengths simultaneously without the use of a dispersive element. In applying this method to fiber-loop cavity ring-down spectroscopy, we achieve detection at low micromolar concentrations in a 100 nL liquid volume. Measurements at two wavelengths (405 and 810 nm) were performed simultaneously on two dyes each absorbing at mainly one of the wavelengths. The respective concentrations could be quantified independently in pure samples as well as in mixtures. No crosstalk between the two channels was observed, and a minimal detectable absorbance of 0.02 cm(-1) was achieved at 405 nm. PMID:21355542

  10. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Evaluation of severe accident risk during mid-loop operations. Volume 6, Part 2: Appendices

    SciTech Connect

    Jo, J.; Lin, C.C.; Neymotin, L.; Mubayi, V.

    1995-05-01

    The objectives are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed. Volume 1 summarizes the results of the study. The scope of the level-1 study includes plant damage state analyses, and uncertainty analysis. The internal event analysis is documented in Volume 2. The internal fire and internal flood analysis are documented in Volumes 3 and 4, respectively. A separate study on seismic analysis, documented in Volume 5, was performed for the NRC by Future Resources Associated, Inc. A phased approach was used in the level 2/3 PRA program, however both phases addressed the risk from only mid-loop operation. The first phase of the level 2/3 PRA was initiated in late 1991 and consisted of an Abridged Risk Study. This study was completed in May 1992 and was focused on accident progression and consequences, conditional on core damage. Phase 2 is a more detailed study in which an evaluation of risk during mid-loop operation was performed. The results of the phase 2 level 2/3 study are the subject of this volume of NUREG/CR-6144, Volume 6. This report, Volume 6, Part 2, consists of five appendices containing supporting information for: the PDS (plant damage state) analysis; the accident progression analysis; the source term analysis; the consequence analysis; and the Melcor analysis. 73 figs., 21 tabs.

  11. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Analysis of core damage frequency from internal events during mid-loop operations. Appendix E (Sections E.9-E.16), Volume 2, Part 3B

    SciTech Connect

    Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J.; Wong, S.M.; Bley, D.; Johnson, D.

    1994-06-01

    Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The scope of the program includes that of a level-3 PRA. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed based on the results of the phase 1 study. The objective of the phase 2 study is to perform a detailed analysis of the potential accident scenarios that may occur during mid-loop operation, and compare the results with those of NUREG-1150. The scope of the level-1 study includes plant damage state analysis, and uncertainty analysis. Volume 1 summarizes the results of the study. Internal events analysis is documented in Volume 2. It also contains an appendix that documents the part of the phase 1 study that has to do with POSs other than mid-loop operation. Internal fire and internal flood analyses are documented in Volumes 3 and 4. A separate study on seismic analysis, documented in Volume 5, was performed for the NRC by Future Resources Associates, Inc. Volume 6 documents the accident progression, source terms, and consequence analysis.

  12. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit-1: Analysis of core damage frequency from internal events during mid-loop operations. Appendices F-H, Volume 2, Part 4

    SciTech Connect

    Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J.; Bley, D.; Johnson, D.; Holmes, B.

    1994-06-01

    Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The scope of the program includes that of a level-3 PRA. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed based on the results of the phase 1 study. The objective of the phase 2 study is to perform a detailed analysis of the potential accident scenarios that may occur during mid-loop operation, and compare the results with those of NUREG-1150. The scope of the level-1 study includes plant damage state analysis, and uncertainty analysis. Volume 1 summarizes the results of the study. Internal events analysis is documented in Volume 2. It also contains an appendix that documents the part of the phase 1 study that has to do with POSs other than mid-loop operation. Internal fire and internal flood analyses are documented in Volumes 3 and 4. A separate study on seismic analysis, documented in Volume 5, was performed for the NRC by Future Resources Associates, Inc. Volume 6 documents the accident progression, source terms, and consequence analysis.

  13. Loop-to-loop coupling.

    SciTech Connect

    Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald

    2012-05-01

    This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

  14. Admittance‐based pressure–volume loops versus gold standard cardiac magnetic resonance imaging in a porcine model of myocardial infarction

    PubMed Central

    van Hout, Gerardus P. J.; Jansen, Sanne J.; Gho, Johannes M. I. H.; Doevendans, Pieter A.; van Solinge, Wouter W.; Pasterkamp, Gerard; Chamuleau, Steven A. J.; Hoefer, Imo E.

    2014-01-01

    Abstract A novel admittance‐based pressure–volume system (AS) has recently been developed and introduced. Thus far, the new technique has been validated predominantly in small animals. In large animals it has only been compared to three‐dimensional echocardiography (3DE) where the AS showed to overestimate left ventricular (LV) volumes. To fully determine the accuracy of this device, we compared the AS with gold standard cardiac magnetic resonance imaging (CMRI) in a porcine model of chronic myocardial infarction (MI). Fourteen pigs were subjected to 90 min closed chest balloon occlusion of the left anterior descending artery. After 8 weeks of follow up, pigs were consecutively subjected to LV volume measurements by the AS, CMRI, and 3DE under general anesthesia. The AS overestimated end diastolic volume (EDV; +20.9 ± 30.6 mL, P = 0.024) and end systolic volume (ESV; +17.7 ± 29.4 mL, P = 0.042) but not ejection fraction (EF; +2.46 ± 6.16%, P = NS) compared to CMRI. Good correlations of EDV (R = 0.626, P = 0.017) and EF (R = 0.704, P = 0.005) between the AS and CMRI were observed. EF measured by the AS and 3DE also correlated significantly (R = 0.624, P = 0.030). After subjection of pigs to MI, the AS very moderately overestimates LV volumes and shows accurate measurements for EF compared to CMRI. This makes the AS a useful tool to determine cardiac function and dynamic changes in large animal models of cardiac disease. PMID:24771693

  15. Probability of pipe fracture in the primary coolant loop of a PWR Plant. Volume 6. Failure mode analysis load combination program. Project I, final report

    SciTech Connect

    Streit, R.D.

    1981-06-01

    Material properties and failure criteria were evaluated to assess the requirements for double-ended guillotine break in the primary coolant loop of the Zion Unit 1 pressurized water reactor. The properties of the 316 stainless steel piping materials were obtained from the literature. Statistical distributions of both the tensile and fracture properties at room and operating temperatures were developed. Yield and ultimate strength tensile properties were combined to estimate the material flow strength. The flow strength and fracture properties were used in the various failure models analyzed. Linear-elastic, elastic-plastic, and fully plastic fracture models were compared, and the governing fracture criterion was determined. For the particular case studied, the fully plastic requirement was found to be the controlling fracture criterion leading to a double-ended guillotine pipe break.

  16. Probability of pipe failure in the reactor coolant loops of Westinghouse PWR plants. Volume 4. Pipe failure induced by crack growth in west coast plants

    SciTech Connect

    Chinn, D.J.; Holman, G.S.; Lo, T.Y.; Mensing, R.W.

    1985-07-01

    The US Nuclear Regulatory Commission contracted with the Lawrence Livermore National Laboratory to conduct a study to determine if the probability of occurrence of a double-ended guillotine break (DEGB) in primary coolant piping warrants the current design requirements that safeguard against the effecs of such a break. This report assesses the reactor-coolant-loop piping system of west coast Westinghouse plants. The results indicate that directly induced DEGB is an unlikely event in the west coast Westinghouse plants. For the Trojan plant, leak is far more likely than a direct DEGB. Further, earthquakes have very little effect on the probabilities of leak and direct DEGB. At the Diablo Canyon plant, the increase in postulated seismic levels due to reevaluation of the site to account for the Hosgri Fault has caused directly induced DEGB failure probability to be dependent on earthquake occurrences. The resulting direct DEGB failure probability is still much lower than the indirect DEGB failure probability for Diablo Canyon.

  17. Probability of pipe failure in the reactor coolant loops of Combustion Engineering PWR plants. Volume 2. Pipe failure induced by crack growth

    SciTech Connect

    Lo, T.Y.; Mensing, R.W.; Woo, H.H.; Holman, G.S.

    1984-09-01

    A study was conducted to determine if the probability of occurrence of a double-ended guillotine break (DEGB) in the primary coolant piping warrants the current design requirements that safeguard against the effect of DEGB. This report describes the results of an assessment of reactor coolant loop piping systems designed by Combustion Engineering, Inc. A probabilistic fracture mechanics approach was used to estimate the crack growth and to assess the crack stability in the piping throughout the lifetime of the plant. The results of the assessment indicate that the probability of occurrence of DEGB due to crack growth and instability is extremely small, which supports the argument that the postulation of DEGB in design should be eliminated and replaced with more reasonable criteria.

  18. Probability of pipe fracture in the primary coolant loop of a PWR plant. Volume 1. Summary, Load Combination Program. Project I final report

    SciTech Connect

    Lu, S.; Streit, R.D.; Chou, C.K.

    1981-06-01

    This report summarizes work performed to establish a technical basis for the NRC to use in reassessing its requirement that earthquake and large loss-of-coolant accident (LOCA) loads be combined in the design of nuclear power plants. A systematic probabilistic approach is used to treat the random nature of earthquake and transient loading and to estimate the probability of large LOCAs that are directly and indirectly induced by earthquakes. A large LOCA is defined in this report as a double-ended guillotine break of the primary reactor coolant loop piping (the hot leg, cold leg, and crossover) of a pressurized water reactor (PWR). Unit 1 of the Zion Nuclear Power Plant, a four-loop PWR, is the demonstration plant used in this study. To estimate the probability of a large LOCA directly induced by earthquakes, only fatigue crack growth resulting from the combined effects of thermal, pressure, seismic, and other cyclic loads is considered. Fatigue crack growth is simulated by a deterministic fracture mechanics model with stochastic inputs of initial crack size distribution, material properties, stress histories, and leak detection probability. Results of the simulation indicate that the probability of a double-ended guillotine break, either with or without earthquake, is very small (on the order of 10/sup -12/). The probability of a leak was found to be several orders of magnitude greater than that of a large LOCA, complete pipe rupture. A limited investigation involving engineering judgment of a double-ended guillotine break indirectly induced by an earthquake is also reported.

  19. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Evaluation of severe accident risk during mid-loop operations. Main report. Volume 6. Part 1

    SciTech Connect

    Jo, J.; Lin, C.C.; Neymotin, L.

    1995-05-01

    During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Laboratory (BNL) and Sandia National Laboratories (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The scope of the program includes that of a level-3 PRA. A phased approach was used in the level-1 program. In phase 1 which was completed in Fall 1991, a coarse screening analysis including internal fire and flood was performed for all plant operational states (POSs). The objective of the phase 1 study was to identify potential vulnerable plant configurations, to characterize (on a high, medium, or low basis) the potential core damage accident scenarios, and to provide a foundation for a detailed phase 2 analysis. In phase 2, mid-loop operation was selected as the plant configuration to be analyzed based on the results of the phase 1 study. The objective of the phase 2 study is to perform a detailed analysis of the potential accident scenarios that may occur during mid-loop operation, and compare the results with those of NUREG-1150. The results of the phase 2 level 2/3 study are the subject of this volume of NUREG/CR-6144, Volume 6.

  20. Probability of pipe failure in the reactor coolant loops of Combustion Engineering PWR Plants. Volume 3. Double-ended guillotine break indirectly induced by earthquakes

    SciTech Connect

    Ravindra, M.K.; Campbell, R.D.; Kennedy, R.P.; Banon, H.

    1985-01-01

    The requirements to design nuclear power plants for the effects of an instantaneous double-ended guillotine break (DEGB) of reactor coolant loop (RCL) piping have led to excessive design costs, interference of normal plant operation and maintenance, and unnecessary radiation exposure of plant maintenance personnel. This report describes an aspect of the NRC/Lawrence Livermore National Laboratory sponsored research program aimed at investigating whether the probability of DEGB in RCL Piping of nuclear power plants is acceptably small and the requirements to design for the DEGB effects (e.g., provision of pipe whip restraints) may be removed. This study estimated the probability of indirect DEGB in RCL piping as a consequence of seismic-induced structural failures within the containment of Combustion Engineering supplied pressurized water reactor nuclear power plants in the United States. The median probability of indirect DEGB was estimated to be in the range of 10/sup -6/ per year for older plants, and less than 10/sup -8/ per year for modern plants; using very conservative assumptions, the 90% subjective probability value (confidence) of P/sub DEGB/ was found to be less than 5 x 10/sup -5/ per year for older plants and less than 3 x 10/sup -7/ per year for modern plants.

  1. Probability of pipe failure in the reactor coolant loops of Babcock and Wilcox PWR plants. Volume 2. Guillotine break indirectly induced by earthquakes

    SciTech Connect

    Ravindra, M.K.; Campbell, R.D.; Kipp, T.R.; Sues, R.H.

    1985-07-01

    The requirements to design nuclear power plants for the effects of an instantaneous double-ended guillotine break (DEGB) of the reactor coolant loop (RCL) piping have led to excessive design costs, interference with normal plant operation and maintenance, and unnecessary radiation exposure of plant maintenance personnel. This report describes an aspect of the NRC/Lawrence Livermore National Laboratory sponsored research program aimed at exploring whether the probability of DEGB in RCL Piping of nuclear power plants is acceptably small and the requirements to design for the DEGB effects (e.g., provision of pipe whip restraints) may be removed. This study estimates the probability of indirect DEGB in RCL piping as a consequence of seismic-induced structural failures within the containment of Babcock and Wilcox supplied pressurized water reactor nuclear power plants in the United States. The median probability of indirect DEGB was estimated to range between 6 x 10/sup -11/ and 1 x 10/sup -7/ per year. Using very conservative assumptions, the 90% subjective probability value (confidence) of P/sub DEGB/ was found to be less than 1 x 10/sup -5/ per year. 19 refs., 19 figs., 11 tabs.

  2. Probability of pipe failure in the reactor coolant loop of Westinghouse PWR plants. Volume 3. Guillotine break indirectly induced by earthquakes

    SciTech Connect

    Ravindra, M.K.; Campbell, R.D.; Kennedy, R.P.; Banon, H.

    1985-02-01

    The requirements to design nuclear power plants for the effects of an instantaneous double-ended guillotine break (DEGB) of reactor coolant loop (RCL) piping have led to excessive design costs, interference of normal plant operation and maintenance, and unnecessary radiation exposure of plant maintenance personnel. This report describes an aspect of the NRC/Lawrence Livermore National Laboratory sponsored research program aimed at investigating whether the probability of DEGB in RCL piping of nuclear power plants is acceptably small and the requirements to design for the DEGB effects (e.g., provision of pipe whip restraints) may be removed. This study estimated the probability of indirect DEGB in RCL piping as a consequence of seismic-induced structural failures within the containment of Westinghouse supplied pressurized water reactor nuclear power plants in the United States. The median probability of indirect DEGB was estimated to be about 3x10/sup -6/ per year with a 10% to 90% subjective probability range approximately from 1x10/sup -7/ per year to 5x10/sup -5/ per year.

  3. A Closed-Loop Optimal Neural-Network Controller to Optimize Rotorcraft Aeromechanical Behaviour. Volume 2; Output from Two Sample Cases

    NASA Technical Reports Server (NTRS)

    Leyland, Jane Anne

    2001-01-01

    A closed-loop optimal neural-network controller technique was developed to optimize rotorcraft aeromechanical behaviour. This technique utilities a neural-network scheme to provide a general non-linear model of the rotorcraft. A modem constrained optimisation method is used to determine and update the constants in the neural-network plant model as well as to determine the optimal control vector. Current data is read, weighted, and added to a sliding data window. When the specified maximum number of data sets allowed in the data window is exceeded, the oldest data set is and the remaining data sets are re-weighted. This procedure provides at least four additional degrees-of-freedom in addition to the size and geometry of the neural-network itself with which to optimize the overall operation of the controller. These additional degrees-of-freedom are: 1. the maximum length of the sliding data window, 2. the frequency of neural-network updates, 3. the weighting of the individual data sets within the sliding window, and 4. the maximum number of optimisation iterations used for the neural-network updates.

  4. Rollercoaster Loop Shapes

    ERIC Educational Resources Information Center

    Pendrill, Ann-Marie

    2005-01-01

    Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.

  5. Rollercoaster loop shapes

    NASA Astrophysics Data System (ADS)

    Pendrill, Ann-Marie

    2005-11-01

    Many modern rollercoasters feature loops. Although textbook loops are often circular, real rollercoaster loops are not. In this paper, we look into the mathematical description of various possible loop shapes, as well as their riding properties. We also discuss how a study of loop shapes can be used in physics education.

  6. Water Stream "Loop-the-Loop"

    ERIC Educational Resources Information Center

    Jefimenko, Oleg

    1974-01-01

    Discusses the design of a modified loop-the-loop apparatus in which a water stream is used to illustrate centripetal forces and phenomena of high-velocity hydrodynamics. Included are some procedures of carrying out lecture demonstrations. (CC)

  7. Probability of pipe fracture in the primary coolant loop of a PWR plant. Volume 8. Pipe fracture indirectly induced by an earthquake. Load Combination Program, Project I final report

    SciTech Connect

    Streit, R.D.

    1981-06-01

    This volume considers the probability that a double-ended guillotine break in the primary coolant loop of a pressurized water reactor occurs simultaneously with (and is indirectly caused by) a seismic event. The pipe break is a consequence of a seismically initiated failure in a system other than the primary piping itself. Events studied that can lead to an indirectly induced pipe break include structural and mechanical failures, missile impact, pressure transients, jet impingement, fire, and explosion. Structural failures of the supports for the reactor pressure vessel, reactor coolant pump, and steam generator have the highest probability of causing a double-ended pipe break. Furthermore, we found that structural failure of the containment dome and failure of the reactor coolant pump flywheel have the highest potential for a missile-caused pipe break. Since structural failure proved to be a major factor, we developed a model to estimate the probability of structural failure; this model is based on the engineering factors of safety and seismic hazard. preliminary results indicate that the probability of a double-ended pipe break indirectly caused by a seismic event during the plant life is on the order of 10/sup -9/.

  8. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Analysis of core damage frequency from internal events during mid-loop operations, Appendices A--D. Volume 2, Part 2

    SciTech Connect

    Chu, T.L.; Musicki, Z.; Kohut, P.

    1994-06-01

    During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the Potential risks during low Power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Laboratory (BNL) and Sandia National Laboratories (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the Plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this report is to document the approach utilized in the Surry plant and discuss the results obtained. A parallel report for the Grand Gulf plant is prepared by SNL. This study shows that the core-damage frequency during mid-loop operation at the Surry plant is comparable to that of power operation. We recognize that there is very large uncertainty in the human error probabilities in this study. This study identified that only a few procedures are available for mitigating accidents that may occur during shutdown. Procedures written specifically for shutdown accidents would be useful. This document, Volume 2, Pt. 2 provides appendices A through D of this report.

  9. Polyhedra in loop quantum gravity

    SciTech Connect

    Bianchi, Eugenio; Speziale, Simone; Dona, Pietro

    2011-02-15

    Intertwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a theorem by Minkowski allows us to interpret generic configurations in this space as bounded convex polyhedra in R{sup 3}: A polyhedron is uniquely described by the areas and normals to its faces. We provide a reconstruction of the geometry of the polyhedron: We give formulas for the edge lengths, the volume, and the adjacency of its faces. At the quantum level, this correspondence allows us to identify an intertwiner with the state of a quantum polyhedron, thus generalizing the notion of the quantum tetrahedron familiar in the loop quantum gravity literature. Moreover, coherent intertwiners result to be peaked on the classical geometry of polyhedra. We discuss the relevance of this result for loop quantum gravity. In particular, coherent spin-network states with nodes of arbitrary valence represent a collection of semiclassical polyhedra. Furthermore, we introduce an operator that measures the volume of a quantum polyhedron and examine its relation with the standard volume operator of loop quantum gravity. We also comment on the semiclassical limit of spin foams with nonsimplicial graphs.

  10. Polyhedra in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Bianchi, Eugenio; Doná, Pietro; Speziale, Simone

    2011-02-01

    Intertwiners are the building blocks of spin-network states. The space of intertwiners is the quantization of a classical symplectic manifold introduced by Kapovich and Millson. Here we show that a theorem by Minkowski allows us to interpret generic configurations in this space as bounded convex polyhedra in R3: A polyhedron is uniquely described by the areas and normals to its faces. We provide a reconstruction of the geometry of the polyhedron: We give formulas for the edge lengths, the volume, and the adjacency of its faces. At the quantum level, this correspondence allows us to identify an intertwiner with the state of a quantum polyhedron, thus generalizing the notion of the quantum tetrahedron familiar in the loop quantum gravity literature. Moreover, coherent intertwiners result to be peaked on the classical geometry of polyhedra. We discuss the relevance of this result for loop quantum gravity. In particular, coherent spin-network states with nodes of arbitrary valence represent a collection of semiclassical polyhedra. Furthermore, we introduce an operator that measures the volume of a quantum polyhedron and examine its relation with the standard volume operator of loop quantum gravity. We also comment on the semiclassical limit of spin foams with nonsimplicial graphs.

  11. OPE for super loops

    NASA Astrophysics Data System (ADS)

    Sever, Amit; Vieira, Pedro; Wang, Tianheng

    2011-11-01

    We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.

  12. The preprocessed doacross loop

    NASA Technical Reports Server (NTRS)

    Saltz, Joel H.; Mirchandaney, Ravi

    1990-01-01

    Dependencies between loop iterations cannot always be characterized during program compilation. Doacross loops typically make use of a-priori knowledge of inter-iteration dependencies to carry out required synchronizations. A type of doacross loop is proposed that allows the scheduling of iterations of a loop among processors without advance knowledge of inter-iteration dependencies. The method proposed for loop iterations requires that parallelizable preprocessing and postprocessing steps be carried out during program execution.

  13. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  14. Investigation, development and application of optimal output feedback theory. Volume 2: Development of an optimal, limited state feedback outer-loop digital flight control system for 3-D terminal area operation

    NASA Technical Reports Server (NTRS)

    Broussard, J. R.; Halyo, N.

    1984-01-01

    This report contains the development of a digital outer-loop three dimensional radio navigation (3-D RNAV) flight control system for a small commercial jet transport. The outer-loop control system is designed using optimal stochastic limited state feedback techniques. Options investigated using the optimal limited state feedback approach include integrated versus hierarchical control loop designs, 20 samples per second versus 5 samples per second outer-loop operation and alternative Type 1 integration command errors. Command generator tracking techniques used in the digital control design enable the jet transport to automatically track arbitrary curved flight paths generated by waypoints. The performance of the design is demonstrated using detailed nonlinear aircraft simulations in the terminal area, frequency domain multi-input sigma plots, frequency domain single-input Bode plots and closed-loop poles. The response of the system to a severe wind shear during a landing approach is also presented.

  15. Blind loop syndrome

    MedlinePlus

    Blind loop syndrome occurs when digested food slows or stops moving through part of the intestines. This ... The name of this condition refers to the "blind loop" formed by part of the intestine that ...

  16. Loops and trees

    NASA Astrophysics Data System (ADS)

    Caron-Huot, S.

    2011-05-01

    We investigate relations between loop and tree amplitudes in quantum field theory that involve putting on-shell some loop propagators. This generalizes the so-called Feynman tree theorem which is satisfied at 1-loop. Exploiting retarded boundary conditions, we give a generalization to ℓ-loop expressing the loops as integrals over the on-shell phase space of exactly ℓ particles. We argue that the corresponding integrand for ℓ > 2 does not involve the forward limit of any physical tree amplitude, except in planar gauge theories. In that case we explicitly construct the relevant physical amplitude. Beyond the planar limit, abandoning direct integral representations, we propose that loops continue to be determined implicitly by the forward limit of physical connected trees, and we formulate a precise conjecture along this line. Finally, we set up technology to compute forward amplitudes in supersymmetric theories, in which specific simplifications occur.

  17. Laminated BEAM loops

    NASA Astrophysics Data System (ADS)

    Danisch, Lee A.

    1996-10-01

    BEAM sensors include treated loops of optical fiber that modulate optical throughput with great sensitivity and linearity, in response to curvature of the loop out of its plane. This paper describes BEAM sensors that have two loops treated in opposed fashion, hermetically sealed in flexible laminations. The sensors include an integrated optoelectronics package that extracts curvature information from the treated portion of the loops while rejecting common mode errors. The laminated structure is used to sense various parameters including displacement, force, pressure, flow, and acceleration.

  18. Observational Evidence for Loop-Loop Interaction

    NASA Astrophysics Data System (ADS)

    Guiping, W.; Guangli, H.; Yuhua, T.; Aoao, X.

    2004-01-01

    Through analysis of the data including the hard x-ray(BASTE) microwave(NoRP) and magnetogram(MDI from SOHO) as well as the images of soft x-ray(YHKOH) and EIT(SOHO) on Apr. 151998 solar flare in the active region 8203(N30W12) we found: (1) there are similar quasi period oscillation in the profile of hard x-ray flux (25-5050-100keV) and microwave flux(1GHz) with duration of 85+/-25s every peak includes two sub-peak structures; (2) in the preheat phase of the flare active magnetic field changes apparently and a s-pole spot emerges ; (3) several EIT and soft x-ray loops exist and turn into bright . All of these may suggest that loop-loop interaction indeed exist. Through reconnection the electrons may be accelerated and the hard x-ray and microwave emission take place.

  19. Space Station evolution study oxygen loop closure

    NASA Technical Reports Server (NTRS)

    Wood, M. G.; Delong, D.

    1993-01-01

    In the current Space Station Freedom (SSF) Permanently Manned Configuration (PMC), physical scars for closing the oxygen loop by the addition of oxygen generation and carbon dioxide reduction hardware are not included. During station restructuring, the capability for oxygen loop closure was deferred to the B-modules. As such, the ability to close the oxygen loop in the U.S. Laboratory module (LAB A) and the Habitation A module (HAB A) is contingent on the presence of the B modules. To base oxygen loop closure of SSF on the funding of the B-modules may not be desirable. Therefore, this study was requested to evaluate the necessary hooks and scars in the A-modules to facilitate closure of the oxygen loop at or subsequent to PMC. The study defines the scars for oxygen loop closure with impacts to cost, weight and volume and assesses the effects of byproduct venting. In addition, the recommended scenarios for closure with regard to topology and packaging are presented.

  20. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Analysis of core damage frequency from internal floods during mid-loop operations. Volume 4

    SciTech Connect

    Kohut, P.

    1994-07-01

    The major objective of the Surry internal flood analysis was to provide an improved understanding of the core damage scenarios arising from internal flood-related events. The mean core damage frequency of the Surry plant due to internal flood events during mid-loop operations is 4.8E-06 per year, and the 5th and 95th percentiles are 2.2E-07 and 1.8E-05 per year, respectively. Some limited sensitivity calculations were performed on three plant improvement options. The most significant result involves modifications of intake-level structure on the canal, which reduced core damage frequency contribution from floods in mid-loop by about 75%.

  1. Thermal power loops

    NASA Technical Reports Server (NTRS)

    Gottschlich, Joseph M.; Richter, Robert

    1991-01-01

    The concept of a thermal power loop (TPL) to transport thermal power over relatively large distances is presented as an alternative to heat pipes and their derivatives. The TPL is compared to heat pipes, and capillary pumped loops with respect to size, weight, conservation of thermal potential, start-up, and 1-g testing capability. Test results from a proof of feasibility demonstrator at the NASA JPL are discussed. This analysis demonstrates that the development of specific thermal power loops will result in substantial weight and cost savings for many spacecraft.

  2. Natively Unstructured Loops Differ from Other Loops

    PubMed Central

    Schlessinger, Avner; Liu, Jinfeng; Rost, Burkhard

    2007-01-01

    Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%–70% of all worm proteins observed to have more than seven protein–protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long

  3. Introduction to Loop Heat Pipes

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2015-01-01

    This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.

  4. In-situ Condition Monitoring of Components in Small Modular Reactors Using Process and Electrical Signature Analysis. Final report, volume 1. Development of experimental flow control loop, data analysis and plant monitoring

    SciTech Connect

    Upadhyaya, Belle; Hines, J. Wesley; Damiano, Brian; Mehta, Chaitanya; Collins, Price; Lish, Matthew; Cady, Brian; Lollar, Victor; de Wet, Dane; Bayram, Duygu

    2015-12-15

    The research and development under this project was focused on the following three major objectives: Objective 1: Identification of critical in-vessel SMR components for remote monitoring and development of their low-order dynamic models, along with a simulation model of an integral pressurized water reactor (iPWR). Objective 2: Development of an experimental flow control loop with motor-driven valves and pumps, incorporating data acquisition and on-line monitoring interface. Objective 3: Development of stationary and transient signal processing methods for electrical signatures, machinery vibration, and for characterizing process variables for equipment monitoring. This objective includes the development of a data analysis toolbox. The following is a summary of the technical accomplishments under this project: - A detailed literature review of various SMR types and electrical signature analysis of motor-driven systems was completed. A bibliography of literature is provided at the end of this report. Assistance was provided by ORNL in identifying some key references. - A review of literature on pump-motor modeling and digital signal processing methods was performed. - An existing flow control loop was upgraded with new instrumentation, data acquisition hardware and software. The upgrading of the experimental loop included the installation of a new submersible pump driven by a three-phase induction motor. All the sensors were calibrated before full-scale experimental runs were performed. - MATLAB-Simulink model of a three-phase induction motor and pump system was completed. The model was used to simulate normal operation and fault conditions in the motor-pump system, and to identify changes in the electrical signatures. - A simulation model of an integral PWR (iPWR) was updated and the MATLAB-Simulink model was validated for known transients. The pump-motor model was interfaced with the iPWR model for testing the impact of primary flow perturbations (upsets) on

  5. Coronal loops - Current-based heating processes

    NASA Technical Reports Server (NTRS)

    Beaufume, P.; Coppi, B.; Golub, L.

    1992-01-01

    Based on new observations, a theoretical model of magnetic-field related heating processes in the solar corona is given. In this model, field-aligned currents are induced along coronal loops in thin current sheaths. Excitation of instabilities involving magnetic reconnection converts the energy associated with the current-related magnetic field directly into particle energy, where the heating process proceeds via short bursts corresponding to an intermittent disruption of the current sheath configuration. Because of the relatively low transverse thermal conduction, only a small fraction of the loop volume is heated to a much higher temperature than the average value. This is consistent with experimental observations of low filling factors of hot plasmas in coronal loops. Thus the model involves a repeated sequence of dynamic events taking into account the observed loop topology, the differential emission measure distribution in the 10 exp 6 - 10 exp 7 K range, the energy balance requirements in the loop, and the probable duty cycles involved in the heating processes.

  6. Wilson-loop instantons

    NASA Technical Reports Server (NTRS)

    Lee, Kimyeong; Holman, Richard; Kolb, Edward W.

    1987-01-01

    Wilson-loop symmetry breaking is considered on a space-time of the form M4 x K, where M4 is a four-dimensional space-time and K is an internal space with nontrivial and finite fundamental group. It is shown in a simple model that the different vacua obtained by breaking a non-Abelian gauge group by Wilson loops are separated in the space of gauge potentials by a finite energy barrier. An interpolating gauge configuration is then constructed between these vacua and shown to have minimum energy. Finally some implications of this construction are discussed.

  7. Automatic one-loop calculations with Sherpa+OpenLoops

    NASA Astrophysics Data System (ADS)

    Cascioli, F.; Höche, S.; Krauss, F.; Maierhöfer, P.; Pozzorini, S.; Siegert, F.

    2014-06-01

    We report on the OpenLoops generator for one-loop matrix elements and its application to four-lepton production in association with up to one jet. The open loops algorithm uses a numerical recursion to construct the numerator of one-loop Feynman diagrams as functions of the loop momentum. In combination with tensor integrals this results in a highly efficient and numerically stable matrix element generator. In order to obtain a fully automated setup for the simulation of next-to-leading order scattering processes we interfaced OpenLoops to the Sherpa Monte Carlo event generator.

  8. Livermore Compiler Analysis Loop Suite

    Energy Science and Technology Software Center (ESTSC)

    2013-03-01

    LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizationsmore » and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.« less

  9. Livermore Compiler Analysis Loop Suite

    SciTech Connect

    Hornung, R. D.

    2013-03-01

    LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizations and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.

  10. NETL - Chemical Looping Reactor

    SciTech Connect

    2013-07-24

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  11. NETL - Chemical Looping Reactor

    ScienceCinema

    None

    2014-06-26

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  12. Loops: Twisting and Scaling

    NASA Astrophysics Data System (ADS)

    Walsh, R. W.

    2004-01-01

    Loop-like structures are the fundamental magnetic building blocks of the solar atmosphere. Recent space-based EUV and X-ray satellite observations (from Yohkoh SOHO and TRACE) have challenged the view that these features are simply static gravitationally stratified plasma pipes. Rather it is now surmised that each loop may consist of a bundle of fine plasma threads that are twisted around one another and can brighten independently. This invited review will outline the latest developments in ""untangling"" the topology of these features through three dimensional magnetohydrodynamic modelling and how their properties are being deduced through spectroscopic observations coupled to theoretical scaling laws. In particular recent interest has centred on how the observed thermal profile along loops can be employed as a tool to diagnose any localised energy input to the structure and hence constrain the presence of a particular coronal heating mechanism. The dynamic nature of loops will be highlighted and the implications of superior resolution plasma thread observations (whether spatial temporal or spectral) from future space missions (SolarB STEREO SDO and Solar Orbiter) will be discussed.

  13. RNA in the Loop

    PubMed Central

    Kung, Johnny T.Y.; Lee, Jeannie T.

    2013-01-01

    Long noncoding RNAs (lncRNAs) have been implicated in a variety of biological roles, particularly as cis or trans gene expression regulators. Reporting recently in Nature, Lai et al. (2013) show that a class of gene-activating lncRNAs combines two gene regulation paradigms: enhancer-directed chromosomal looping and RNA-mediated protein effector recruitment. PMID:23537627

  14. Closing the Loop Sampler.

    ERIC Educational Resources Information Center

    California Integrated Waste Management Board, Sacramento.

    Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

  15. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Analysis of core damage frequency from internal events during mid-loop operations, Appendices E (Sections E.1--E.8). Volume 2, Part 3A

    SciTech Connect

    Chu, T.L.; Musicki, Z.; Kohut, P.

    1994-06-01

    During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Laboratory (BNL) and Sandia National Laboratories (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this report is to document the approach utilized in the Surry plant and discuss the results obtained. A parallel report for the Grand Gulf plant is prepared by SNL. This study shows that the core-damage frequency during mid-loop operation at the Surry plant is comparable to that of power operation. The authors recognize that there is very large uncertainty in the human error probabilities in this study. This study identified that only a few procedures are available for mitigating accidents that may occur during shutdown. Procedures written specifically for shutdown accidents would be useful.

  16. Discrete state model and accurate estimation of loop entropy of RNA secondary structures.

    PubMed

    Zhang, Jian; Lin, Ming; Chen, Rong; Wang, Wei; Liang, Jie

    2008-03-28

    Conformational entropy makes important contribution to the stability and folding of RNA molecule, but it is challenging to either measure or compute conformational entropy associated with long loops. We develop optimized discrete k-state models of RNA backbone based on known RNA structures for computing entropy of loops, which are modeled as self-avoiding walks. To estimate entropy of hairpin, bulge, internal loop, and multibranch loop of long length (up to 50), we develop an efficient sampling method based on the sequential Monte Carlo principle. Our method considers excluded volume effect. It is general and can be applied to calculating entropy of loops with longer length and arbitrary complexity. For loops of short length, our results are in good agreement with a recent theoretical model and experimental measurement. For long loops, our estimated entropy of hairpin loops is in excellent agreement with the Jacobson-Stockmayer extrapolation model. However, for bulge loops and more complex secondary structures such as internal and multibranch loops, we find that the Jacobson-Stockmayer extrapolation model has large errors. Based on estimated entropy, we have developed empirical formulae for accurate calculation of entropy of long loops in different secondary structures. Our study on the effect of asymmetric size of loops suggest that loop entropy of internal loops is largely determined by the total loop length, and is only marginally affected by the asymmetric size of the two loops. Our finding suggests that the significant asymmetric effects of loop length in internal loops measured by experiments are likely to be partially enthalpic. Our method can be applied to develop improved energy parameters important for studying RNA stability and folding, and for predicting RNA secondary and tertiary structures. The discrete model and the program used to calculate loop entropy can be downloaded at http://gila.bioengr.uic.edu/resources/RNA.html. PMID:18376982

  17. COLD TEST LOOP INTEGRATED TEST LOOP RESULTS

    SciTech Connect

    Abraham, TJ

    2003-10-22

    A testing facility (Cold Test Loop) was constructed and operated to demonstrate the efficacy of the Accelerated Waste Retrieval (AWR) Project's planned sluicing approach to the remediation of Silos 1 and 2 at the Fernald Environmental Management Project near Cincinnati, Ohio. The two silos contain almost 10,000 tons of radium-bearing low-level waste, which consists primarily of solids of raffinates from processing performed on ores from the Democratic Republic of Congo (commonly referred to as ''Belgium Congo ores'') for the recovery of uranium. These silos are 80 ft in diameter, 36 ft high to the center of the dome, and 26.75 ft to the top of the vertical side walls. The test facility contained two test systems, each designed for a specific purpose. The first system, the Integrated Test Loop (ITL), a near-full-scale plant including the actual equipment to be installed at the Fernald Site, was designed to demonstrate the sluicing operation and confirm the selection of a slurry pump, the optimal sluicing nozzle operation, and the preliminary design material balance. The second system, the Component Test Loop (CTL), was designed to evaluate many of the key individual components of the waste retrieval system over an extended run. The major results of the initial testing performed during July and August 2002 confirmed that the AWR approach to sluicing was feasible. The ITL testing confirmed the following: (1) The selected slurry pump (Hazleton 3-20 type SHW) performed well and is suitable for AWR application. However, the pump's motor should be upgraded to a 200-hp model and be driven by a 150-hp variable-frequency drive (VFD). A 200-hp VFD is not much more expensive and would allow the pump to operate at full speed. (2) The best nozzle performance was achieved by using 15/16-in. nozzles operated alternately. This configuration appeared to most effectively mine the surrogate. (3) The Solartron densitometer, which was tested as an alternative mass flow measurement

  18. Can Thermal Nonequilibrium Explain Coronal Loops?

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.; Karpen, Judy T.; Antiochos, Spiro K.

    2010-01-01

    Any successful model of coronal loops must explain a number of observed properties. For warm (approx. 1 MK) loops, these include: 1. excess density, 2. flat temperature profile, 3. super-hydrostatic scale height, 4. unstructured intensity profile, and 5. 1000-5000 s lifetime. We examine whether thermal nonequilibrium can reproduce the observations by performing hydrodynamic simulations based on steady coronal heating that decreases exponentially with height. We consider both monolithic and multi-stranded loops. The simulations successfully reproduce certain aspects of the observations, including the excess density, but each of them fails in at least one critical way. -Xonolithic models have far too much intensity structure, while multi-strand models are either too structured or too long-lived. Storms of nanoflares remain the only viable explanation for warm loops that has been proposed so far. Our results appear to rule out the widespread existence of heating that is both highly concentrated low in the corona and steady or quasi-steady (slowly varying or impulsive with a rapid cadence). Active regions would have a very different appearance if the dominant heating mechanism had these properties. Thermal nonequilibrium may nonetheless play an important role in prominences and catastrophic cooling e(veen.gts..,coronal rain) that occupy a small fraction of the coronal volume. However, apparent inconsistencies between the models and observations of cooling events have yet to be understood.

  19. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1. Volume 5: Analysis of core damage frequency from seismic events during mid-loop operations

    SciTech Connect

    Budnitz, R.J.; Davis, P.R.; Ravindra, M.K.; Tong, W.H.

    1994-08-01

    In 1989 the US Nuclear Regulatory Commission (NRC) initiated an extensive program to examine carefully the potential risks during low-power and shutdown operations. The program included two parallel projects, one at Brookhaven National Laboratory studying a pressurized water reactor (Surry Unit 1) and the other at Sandia National Laboratories studying a boiling water reactor (Grand Gulf). Both the Brookhaven and Sandia projects have examined only accidents initiated by internal plant faults--so-called ``internal initiators.`` This project, which has explored the likelihood of seismic-initiated core damage accidents during refueling shutdown conditions, is complementary to the internal-initiator analyses at Brookhaven and Sandia. This report covers the seismic analysis at Surry Unit 1. All of the many systems modeling assumptions, component non-seismic failure rates, and human error rates that were used in the internal-initiator study at Surry have been adopted here, so that the results of the two studies can be as comparable as possible. Both the Brookhaven study and this study examine only two shutdown plant operating states (POSs) during refueling outages at Surry, called POS 6 and POS 10, which represent mid-loop operation before and after refueling, respectively. This analysis has been limited to work analogous to a level-1 seismic PRA, in which estimates have been developed for the core-damage frequency from seismic events during POSs 6 and 10. The results of the analysis are that the core-damage frequency of earthquake-initiated accidents during refueling outages in POS 6 and POS 10 is found to be low in absolute terms, less than 10{sup {minus}6}/year.

  20. Meyer's loop asymmetry and language lateralisation in epilepsy

    PubMed Central

    Nowell, Mark; Vos, Sjoerd B; Sidhu, Meneka; Wilcoxen, Kaitlin; Sargsyan, Narek; Ourselin, Sebastien; Duncan, John S

    2016-01-01

    Objectives Several studies have suggested an asymmetry in Meyer's loop in individuals, with the left loop anterior to the right. In this study we test the hypothesis that there is an association between Meyer's loop asymmetry (MLA) and language lateralisation. Methods 57 patients with epilepsy were identified with language functional MRI (fMRI) and diffusion MRI acquisition. Language lateralisation indices from fMRI(LI) and optic radiation and arcuate fasciculus probabilistic tractography was performed for each subject. The subjects were divided into left language dominant (LI>0.4) and non-left language groups (LI<0.4) according to their LI. Results A negative linear correlation was identified between language lateralisation and MLA, with greater left lateralised language associated with more anteriorly placed left Meyer's loops (R value −0.34, p=0.01). There was a significant difference in mean MLA between the two groups, with the left loop being anterior to the right loop in the LI>0.4 group and posterior to the right loop in the LI<0.4 group (p=0.003). No correlation was found between language lateralisation and arcuate fasciculus volume. Conclusions This study suggests an association between the extent of Meyer's loop asymmetry and the lateralisation of language determined by fMRI in patients with epilepsy. Further studies should be carried out to evaluate this association in control subjects and with other measures of language lateralisation. PMID:26384513

  1. Inner mappings of Bruck loops

    NASA Astrophysics Data System (ADS)

    Kreuzer, Alexander

    1998-01-01

    K-loops have their origin in the theory of sharply 2-transitive groups. In this paper a proof is given that K-loops and Bruck loops are the same. For the proof it is necessary to show that in a (left) Bruck loop the left inner mappings L(b)L(a) L(ab)[minus sign]1 are automorphisms. This paper generalizes results of Glauberman [3], Kist [8] and Kreuzer [9].

  2. Loop Heat Pipes and Capillary Pumped Loops: An Applications Perspective

    NASA Technical Reports Server (NTRS)

    Butler, Dan; Ku, Jentung; Swanson, Theodore; Obenschain, Arthur F. (Technical Monitor)

    2001-01-01

    Capillary pumped loops (CPLS) and loop heat pipes (LHPS) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed.

  3. Closed-loop anesthesia.

    PubMed

    LE Guen, Morgan; Liu, Ngai; Chazot, Thierry; Fischler, Marc

    2016-05-01

    Automated anesthesia which may offer to the physician time to control hemodynamic and to supervise neurological outcome and which may offer to the patient safety and quality was until recently consider as a holy grail. But this field of research is now increasing in every component of general anesthesia (hypnosis, nociception, neuromuscular blockade) and literature describes some successful algorithms - single or multi closed-loop controller. The aim of these devices is to control a predefined target and to continuously titrate anesthetics whatever the patients' co morbidities and surgical events to reach this target. Literature contains many randomized trials comparing manual and automated anesthesia and shows feasibility and safety of this system. Automation could quickly concern other aspects of anesthesia as fluid management and this review proposes an overview of closed-loop systems in anesthesia. PMID:26554614

  4. Verification of Loop Diagnostics

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Lionello, R.; Mok, Y.; Linker, J.; Mikic, Z.

    2014-01-01

    Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a 3D hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the loop background. We then determine the density, temperature and emission measure distribution as a function of time from the observations and compare with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details of the true temperature and density are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to inadequate background subtraction, but also indicate a limitation of the analysis methods.

  5. Chemical Looping Combustion Kinetics

    SciTech Connect

    Edward Eyring; Gabor Konya

    2009-03-31

    One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

  6. Loops of Jupiter

    NASA Astrophysics Data System (ADS)

    Opolski, Antoni

    2014-12-01

    Professor Antoni Opolski was actively interested in astronomy after his retirement in 1983. He especially liked to study the works of the famous astronomer Copernicus getting inspiration for his own work. Opolski started his work on planetary loops in 2011 continuing it to the end of 2012 . During this period calculations, drawings, tables, and basic descriptions of all the planets of the Solar System were created with the use of a piece of paper and a pencil only. In 2011 Antoni Opolski asked us to help him in editing the manuscript and preparing it for publication. We have been honored having the opportunity to work on articles on planetary loops with Antoni Opolski in his house for several months. In the middle of 2012 the detailed material on Jupiter was ready. However, professor Opolski improved the article by smoothing the text and preparing new, better drawings. Finally the article ''Loops of Jupiter'', written by the 99- year old astronomer, was published in the year of his 100th birthday.

  7. Novel Numerical Approaches to Loop Quantum Cosmology

    NASA Astrophysics Data System (ADS)

    Diener, Peter

    2015-04-01

    Loop Quantum Gravity (LQG) is an (as yet incomplete) approach to the quantization of gravity. When applied to symmetry reduced cosmological spacetimes (Loop Quantum Cosmology or LQC) one of the predictions of the theory is that the Big Bang is replaced by a Big Bounce, i.e. a previously existing contracting universe underwent a bounce at finite volume before becoming our expanding universe. The evolution equations of LQC take the form of difference equations (with the discretization given by the theory) that in the large volume limit can be approximated by partial differential equations (PDEs). In this talk I will first discuss some of the unique challenges encountered when trying to numerically solve these difference equations. I will then present some of the novel approaches that have been employed to overcome the challenges. I will here focus primarily on the Chimera scheme that takes advantage of the fact that the LQC difference equations can be approximated by PDEs in the large volume limit. I will finally also briefly discuss some of the results that have been obtained using these numerical techniques by performing simulations in regions of parameter space that were previously unreachable. This work is supported by a grant from the John Templeton Foundation and by NSF grant PHYS1068743.

  8. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit-1: Analysis of core damage frequency from internal events during mid-loop operations. Appendix I, Volume 2, Part 5

    SciTech Connect

    Chu, T.L.; Musicki, Z.; Kohut, P.; Yang, J.; Bozoki, G.; Hsu, C.J.; Diamond, D.J.; Bley, D.; Johnson, D.; Holmes, B.

    1994-06-01

    Traditionally, probabilistic risk assessments (PRA) of severe accidents in nuclear power plants have considered initiating events potentially occurring only during full power operation. Some previous screening analyses that were performed for other modes of operation suggested that risks during those modes were small relative to full power operation. However, more recent studies and operational experience have implied that accidents during low power and shutdown could be significant contributors to risk. During 1989, the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. The program includes two parallel projects being performed by Brookhaven National Lab. (BNL) and Sandia National Labs. (SNL). Two plants, Surry (pressurized water reactor) and Grand Gulf (boiling water reactor), were selected as the plants to be studied. The objectives of the program are to assess the risks of severe accidents initiated during plant operational states other than full power operation and to compare the estimated core damage frequencies, important accident sequences and other qualitative and quantitative results with those accidents initiated during full power operation as assessed in NUREG-1150. The objective of this volume of the report is to document the approach utilized in the level-1 internal events PRA for the Surry plant, and discuss the results obtained. A phased approach was used in the level-1 program. In phase 1, which was completed in Fall 1991, a coarse screening analysis examining accidents initiated by internal events (including internal fire and flood) was performed for all plant operational states (POSs). The objective of the phase 1 study was to identify potential vulnerable plant configurations, to characterize (on a high, medium, or low basis) the potential core damage accident scenarios, and to provide a foundation for a detailed phase 2 analysis.

  9. Coupled dual loop absorption heat pump

    DOEpatents

    Sarkisian, Paul H.; Reimann, Robert C.; Biermann, Wendell J.

    1985-01-01

    A coupled dual loop absorption system which utilizes two separate complete loops. Each individual loop operates at three temperatures and two pressures. This low temperature loop absorber and condenser are thermally coupled to the high temperature loop evaporator, and the high temperature loop condenser and absorber are thermally coupled to the low temperature generator.

  10. Closing the loop.

    PubMed

    Dassau, E; Atlas, E; Phillip, M

    2011-02-01

    Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging

  11. Gradiometer Using Middle Loops as Sensing Elements in a Low-Field SQUID MRI System

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin; Hahn, Inseob; Ho Eom, Byeong

    2009-01-01

    A new gradiometer scheme uses middle loops as sensing elements in lowfield superconducting quantum interference device (SQUID) magnetic resonance imaging (MRI). This design of a second order gradiometer increases its sensitivity and makes it more uniform, compared to the conventional side loop sensing scheme with a comparable matching SQUID. The space between the two middle loops becomes the imaging volume with the enclosing cryostat built accordingly.

  12. Ekpyrotic loop quantum cosmology

    SciTech Connect

    Wilson-Ewing, Edward

    2013-08-01

    We consider the ekpyrotic paradigm in the context of loop quantum cosmology. In loop quantum cosmology the classical big-bang singularity is resolved due to quantum gravity effects, and so the contracting ekpyrotic branch of the universe and its later expanding phase are connected by a smooth bounce. Thus, it is possible to explicitly determine the evolution of scalar perturbations, from the contracting ekpyrotic phase through the bounce and to the post-bounce expanding epoch. The possibilities of having either one or two scalar fields have been suggested for the ekpyrotic universe, and both cases will be considered here. In the case of a single scalar field, the constant mode of the curvature perturbations after the bounce is found to have a blue spectrum. On the other hand, for the two scalar field ekpyrotic model where scale-invariant entropy perturbations source additional terms in the curvature perturbations, the power spectrum in the post-bounce expanding cosmology is shown to be nearly scale-invariant and so agrees with observations.

  13. Accelerating the loop expansion

    SciTech Connect

    Ingermanson, R.

    1986-07-29

    This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

  14. On the sensitivity analysis of separated-loop MRS data

    NASA Astrophysics Data System (ADS)

    Behroozmand, A.; Auken, E.; Fiandaca, G.

    2013-12-01

    In this study we investigate the sensitivity analysis of separated-loop magnetic resonance sounding (MRS) data and, in light of deploying a separate MRS receiver system from the transmitter system, compare the parameter determination of the separated-loop with the conventional coincident-loop MRS data. MRS has emerged as a promising surface-based geophysical technique for groundwater investigations, as it provides a direct estimate of the water content. The method works based on the physical principle of NMR during which a large volume of protons of the water molecules in the subsurface is excited at the specific Larmor frequency. The measurement consists of a large wire loop (typically 25 - 100 m in side length/diameter) deployed on the surface which typically acts as both a transmitter and a receiver, the so-called coincident-loop configuration. An alternating current is passed through the loop deployed and the superposition of signals from all precessing protons within the investigated volume is measured in a receiver loop; a decaying NMR signal called Free Induction Decay (FID). To provide depth information, the FID signal is measured for a series of pulse moments (Q; product of current amplitude and transmitting pulse length) during which different earth volumes are excited. One of the main and inevitable limitations of MRS measurements is a relatively long measurement dead time, i.e. a non-zero time between the end of the energizing pulse and the beginning of the measurement, which makes it difficult, and in some places impossible, to record SNMR signal from fine-grained geologic units and limits the application of advanced pulse sequences. Therefore, one of the current research activities is the idea of building separate receiver units, which will diminish the dead time. In light of that, the aims of this study are twofold: 1) Using a forward modeling approach, the sensitivity kernels of different separated-loop MRS soundings are studied and compared with

  15. The double loop mattress suture

    PubMed Central

    Biddlestone, John; Samuel, Madan; Creagh, Terry; Ahmad, Tariq

    2014-01-01

    An interrupted stitch type with favorable tissue characteristics will reduce local wound complications. We describe a novel high-strength, low-tension repair for the interrupted closure of skin, cartilage, and muscle, the double loop mattress stitch, and compare it experimentally with other interrupted closure methods. The performance of the double loop mattress technique in porcine cartilage and skeletal muscle is compared with the simple, mattress, and loop mattress interrupted sutures in both a novel porcine loading chamber and mechanical model. Wound apposition is assessed by electron microscopy. The performance of the double loop mattress in vivo was confirmed using a series of 805 pediatric laparotomies/laparoscopies. The double loop mattress suture is 3.5 times stronger than the loop mattress in muscle and 1.6 times stronger in cartilage (p ≤ 0.001). Additionally, the double loop mattress reduces tissue tension by 66% compared with just 53% for the loop mattress (p ≤ 0.001). Wound gapping is equal, and wound eversion appears significantly improved (p ≤ 0.001) compared with the loop mattress in vitro. In vivo, the double loop mattress performs as well as the loop mattress and significantly better than the mattress stitch in assessments of wound eversion and dehiscence. There were no episodes of stitch extrusion in our series of patients. The mechanical advantage of its intrinsic pulley arrangement gives the double loop mattress its favorable properties. Wound dehiscence is reduced because this stitch type is stronger and exerts less tension on the tissue than the mattress stitch. We advocate the use of this novel stitch wherever a high-strength, low-tension repair is required. These properties will enhance wound repair, and its application will be useful to surgeons of all disciplines. PMID:24698436

  16. CAN THERMAL NONEQUILIBRIUM EXPLAIN CORONAL LOOPS?

    SciTech Connect

    Klimchuk, James A.; Karpen, Judy T.; Antiochos, Spiro K.

    2010-05-10

    Any successful model of coronal loops must explain a number of observed properties. For warm ({approx}1 MK) loops, these include (1) excess density, (2) flat temperature profile, (3) super-hydrostatic scale height, (4) unstructured intensity profile, and (5) 1000-5000 s lifetime. We examine whether thermal nonequilibrium can reproduce the observations by performing hydrodynamic simulations based on steady coronal heating that decreases exponentially with height. We consider both monolithic and multi-stranded loops. The simulations successfully reproduce certain aspects of the observations, including the excess density, but each of them fails in at least one critical way. Monolithic models have far too much intensity structure, while multi-strand models are either too structured or too long-lived. Our results appear to rule out the widespread existence of heating that is both highly concentrated low in the corona and steady or quasi-steady (slowly varying or impulsive with a rapid cadence). Active regions would have a very different appearance if the dominant heating mechanism had these properties. Thermal nonequilibrium may nonetheless play an important role in prominences and catastrophic cooling events (e.g., coronal rain) that occupy a small fraction of the coronal volume. However, apparent inconsistencies between the models and observations of cooling events have yet to be understood.

  17. A comprehensive sensitivity analysis of central-loop MRS data

    NASA Astrophysics Data System (ADS)

    Behroozmand, Ahmad; Auken, Esben; Dalgaard, Esben; Rejkjaer, Simon

    2014-05-01

    In this study we investigate the sensitivity analysis of separated-loop magnetic resonance sounding (MRS) data and, in light of deploying a separate MRS receiver system from the transmitter system, compare the parameter determination of the central-loop with the conventional coincident-loop MRS data. MRS, also called surface NMR, has emerged as a promising surface-based geophysical technique for groundwater investigations, as it provides a direct estimate of the water content and, through empirical relations, is linked to hydraulic properties of the subsurface such as hydraulic conductivity. The method works based on the physical principle of NMR during which a large volume of protons of the water molecules in the subsurface is excited at the specific Larmor frequency. The measurement consists of a large wire loop deployed on the surface which typically acts as both a transmitter and a receiver, the so-called coincident-loop configuration. An alternating current is passed through the loop deployed and the superposition of signals from all precessing protons within the investigated volume is measured in a receiver loop; a decaying NMR signal called Free Induction Decay (FID). To provide depth information, the FID signal is measured for a series of pulse moments (Q; product of current amplitude and transmitting pulse length) during which different earth volumes are excited. One of the main and inevitable limitations of MRS measurements is a relatively long measurement dead time, i.e. a non-zero time between the end of the energizing pulse and the beginning of the measurement, which makes it difficult, and in some places impossible, to record MRS signal from fine-grained geologic units and limits the application of advanced pulse sequences. Therefore, one of the current research activities is the idea of building separate receiver units, which will diminish the dead time. In light of that, the aims of this study are twofold: 1) Using a forward modeling approach, the

  18. Modeling of compact loop antennas

    SciTech Connect

    Baity, F.W.

    1987-01-01

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively-tuned resonant double loop (RDL) antennas the model treats stub-tuned resonant double loop antennas. Calculations using the model have been compared with measurements on full-scale mockups of resonant double loop antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and for the Compact Ignition Tokamak (CIT).

  19. Loop Heat Pipe Startup Behaviors

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2016-01-01

    A loop heat pipe must start successfully before it can commence its service. The startup transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe startup behaviors. Topics include the four startup scenarios, the initial fluid distribution between the evaporator and reservoir that determines the startup scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power startup, and methods to enhance the startup success. Also addressed are the pressure spike and pressure surge during the startup transient, and repeated cycles of loop startup and shutdown under certain conditions.

  20. Heating Profiles of Coronal Loops

    NASA Astrophysics Data System (ADS)

    Plowman, Joseph; Kankelborg, Charles C.; Martens, Petrus C.

    2016-05-01

    We analyze the temperature and density profiles of coronal loops, as a function of their length, using data from SDO/AIA and Hinode/EIS. The analysis considers the location of the heating along the loop's length, and we conduct a more throrough investigation of our previous preliminary result that heating is concentrated near the loop footpoints. The work now features a larger selection of coronal loops, compared to our previous presentations, and examines their scale-height temperatures to ascertain the extent to which they are hydrostatic.

  1. Modeling of compact loop antennas

    NASA Astrophysics Data System (ADS)

    Baity, F. W.

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively-tuned resonant double loop (RDL) antennas the model treats stub-tuned resonant double loop antennas. Calculations using the model have been compared with measurements on full-scale mockups of resonant double loop antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and for the Compact Ignition Tokamak (CIT).

  2. Unstable anisotropic loop quantum cosmology

    SciTech Connect

    Nelson, William; Sakellariadou, Mairi

    2009-09-15

    We study stability conditions of the full Hamiltonian constraint equation describing the quantum dynamics of the diagonal Bianchi I model in the context of loop quantum cosmology. Our analysis has shown robust evidence of an instability in the explicit implementation of the difference equation, implying important consequences for the correspondence between the full loop quantum gravity theory and loop quantum cosmology. As a result, one may question the choice of the quantization approach, the model of lattice refinement, and/or the role of the ambiguity parameters; all these should, in principle, be dictated by the full loop quantum gravity theory.

  3. Loop-the-Loop: Bringing Theory into Practice

    ERIC Educational Resources Information Center

    Suwonjandee, N.; Asavapibhop, B.

    2012-01-01

    During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

  4. Vortex loops and Majoranas

    SciTech Connect

    Chesi, Stefano; Jaffe, Arthur; Loss, Daniel; Pedrocchi, Fabio L.

    2013-11-15

    We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.

  5. Dynamic PID loop control

    SciTech Connect

    Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R.; DeGraff, B.; Darve, C.; /Fermilab

    2011-06-01

    The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.

  6. Uranyl Nitrate Flow Loop

    SciTech Connect

    Ladd-Lively, Jennifer L

    2008-10-01

    The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study

  7. Loop-the-Loop: An Easy Experiment, A Challenging Explanation

    NASA Astrophysics Data System (ADS)

    Asavapibhop, B.; Suwonjandee, N.

    2010-07-01

    A loop-the-loop built by the Institute for the Promotion of Teaching Science and Technology (IPST) was used in Thai high school teachers training program to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. We took videos using high speed camera to record the motions of a spherical steel ball moving down the aluminum inclined track at different released positions. The ball then moved into the circular loop and underwent a projectile motion upon leaving the track. We then asked the teachers to predict the landing position of the ball if we changed the height of the whole loop-the-loop system. We also analyzed the videos using Tracker, a video analysis software. It turned out that most teachers did not realize the effect of the friction between the ball and the track and could not obtain the correct relationship hence their predictions were inconsistent with the actual landing positions of the ball.

  8. RCD+: Fast loop modeling server

    PubMed Central

    López-Blanco, José Ramón; Canosa-Valls, Alejandro Jesús; Li, Yaohang; Chacón, Pablo

    2016-01-01

    Modeling loops is a critical and challenging step in protein modeling and prediction. We have developed a quick online service (http://rcd.chaconlab.org) for ab initio loop modeling combining a coarse-grained conformational search with a full-atom refinement. Our original Random Coordinate Descent (RCD) loop closure algorithm has been greatly improved to enrich the sampling distribution towards near-native conformations. These improvements include a new workflow optimization, MPI-parallelization and fast backbone angle sampling based on neighbor-dependent Ramachandran probability distributions. The server starts by efficiently searching the vast conformational space from only the loop sequence information and the environment atomic coordinates. The generated closed loop models are subsequently ranked using a fast distance-orientation dependent energy filter. Top ranked loops are refined with the Rosetta energy function to obtain accurate all-atom predictions that can be interactively inspected in an user-friendly web interface. Using standard benchmarks, the average root mean squared deviation (RMSD) is 0.8 and 1.4 Å for 8 and 12 residues loops, respectively, in the challenging modeling scenario in where the side chains of the loop environment are fully remodeled. These results are not only very competitive compared to those obtained with public state of the art methods, but also they are obtained ∼10-fold faster. PMID:27151199

  9. RCD+: Fast loop modeling server.

    PubMed

    López-Blanco, José Ramón; Canosa-Valls, Alejandro Jesús; Li, Yaohang; Chacón, Pablo

    2016-07-01

    Modeling loops is a critical and challenging step in protein modeling and prediction. We have developed a quick online service (http://rcd.chaconlab.org) for ab initio loop modeling combining a coarse-grained conformational search with a full-atom refinement. Our original Random Coordinate Descent (RCD) loop closure algorithm has been greatly improved to enrich the sampling distribution towards near-native conformations. These improvements include a new workflow optimization, MPI-parallelization and fast backbone angle sampling based on neighbor-dependent Ramachandran probability distributions. The server starts by efficiently searching the vast conformational space from only the loop sequence information and the environment atomic coordinates. The generated closed loop models are subsequently ranked using a fast distance-orientation dependent energy filter. Top ranked loops are refined with the Rosetta energy function to obtain accurate all-atom predictions that can be interactively inspected in an user-friendly web interface. Using standard benchmarks, the average root mean squared deviation (RMSD) is 0.8 and 1.4 Å for 8 and 12 residues loops, respectively, in the challenging modeling scenario in where the side chains of the loop environment are fully remodeled. These results are not only very competitive compared to those obtained with public state of the art methods, but also they are obtained ∼10-fold faster. PMID:27151199

  10. Atomistic simulations of the formation of -component dislocation loops in α-zirconium

    NASA Astrophysics Data System (ADS)

    Dai, Cong; Balogh, Levente; Yao, Zhongwen; Daymond, Mark R.

    2016-09-01

    The formation of -component dislocation loops in α-Zr is believed to be responsible for the breakaway irradiation growth experimentally observed under high irradiation fluences. However, while -loop growth is well described by existing models, the atomic mechanisms responsible for the nucleation of -component dislocation loops are still not clear. In the present work, both interstitial and vacancy -type dislocation loops are initially equilibrated at different temperatures. Cascades simulations in the vicinity of the -type loops are then performed by selecting an atom as the primary knock-on atoms (PKAs) with different kinetic energies, using molecular dynamics simulations. No -component dislocation loop was formed in cascades simulations with a 10 keV PKA, but -component interstitial loops were observed after the interaction between discontinuous 50 keV PKAs and pre-existing -type interstitial loops. The comparisons of cascades simulations in volumes having pre-existing -type interstitial and vacancy loops suggest that the reaction between the PKAs and -type interstitial loops is responsible for the formation of -component interstitial loops.

  11. Wilson Loop Diagrams and Positroids

    NASA Astrophysics Data System (ADS)

    Agarwala, Susama; Marin-Amat, Eloi

    2016-07-01

    In this paper, we study a new application of the positive Grassmannian to Wilson loop diagrams (or MHV diagrams) for scattering amplitudes in N= 4 Super Yang-Mill theory (N = 4 SYM). There has been much interest in studying this theory via the positive Grassmannians using BCFW recursion. This is the first attempt to study MHV diagrams for planar Wilson loop calculations (or planar amplitudes) in terms of positive Grassmannians. We codify Wilson loop diagrams completely in terms of matroids. This allows us to apply the combinatorial tools in matroid theory used to identify positroids (non-negative Grassmannians) to Wilson loop diagrams. In doing so, we find that certain non-planar Wilson loop diagrams define positive Grassmannians. While non-planar diagrams do not have physical meaning, this finding suggests that they may have value as an algebraic tool, and deserve further investigation.

  12. Higher dimensional loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong

    2016-07-01

    Loop quantum cosmology (LQC) is the symmetric sector of loop quantum gravity. In this paper, we generalize the structure of loop quantum cosmology to the theories with arbitrary spacetime dimensions. The isotropic and homogeneous cosmological model in n+1 dimensions is quantized by the loop quantization method. Interestingly, we find that the underlying quantum theories are divided into two qualitatively different sectors according to spacetime dimensions. The effective Hamiltonian and modified dynamical equations of n+1 dimensional LQC are obtained. Moreover, our results indicate that the classical big bang singularity is resolved in arbitrary spacetime dimensions by a quantum bounce. We also briefly discuss the similarities and differences between the n+1 dimensional model and the 3+1 dimensional one. Our model serves as a first example of higher dimensional loop quantum cosmology and offers the possibility to investigate quantum gravity effects in higher dimensional cosmology.

  13. Loop-bed combustion apparatus

    DOEpatents

    Shang, Jer-Yu; Mei, Joseph S.; Slagle, Frank D.; Notestein, John E.

    1984-01-01

    The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.

  14. Loop Heat Pipe Startup Behaviors

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2014-01-01

    A loop heat pipe must start successfully before it can commence its service. The start-up transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe start-up behaviors. Topics include the four start-up scenarios, the initial fluid distribution between the evaporator and reservoir that determines the start-up scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power start-up, and methods to enhance the start-up success. Also addressed are the thermodynamic constraint between the evaporator and reservoir in the loop heat pipe operation, the superheat requirement for nucleate boiling, pressure spike and pressure surge during the start-up transient, and repeated cycles of loop start-up andshutdown under certain conditions.

  15. On some 1/4 BPS Wilson-'t Hooft loops

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Yong; Qin, Li

    2015-10-01

    In this paper, we investigate the 1/4 BPS Wilson-'t Hooft loops in N=4 supersymmetric Yang-Mills theory. We use the bulk D3-brane solutions with both electric and magnetic charges on its world-volume to describe some of 1/4 BPS Wilson-'t Hooft loops. The D3-brane supersymmetric solutions are derived form requiring κ-symmetry. We find the two consistent constraints for Killing spinors and calculate the conserved charges of straight 1/4 BPS Wilson-'t Hooft loops and expectation values of circular 1/4 BPS Wilson-'t Hooft loops separately.

  16. Quantum reduced loop gravity: Universe on a lattice

    NASA Astrophysics Data System (ADS)

    Alesci, Emanuele; Cianfrani, Francesco

    2015-10-01

    We describe the quantum flat universe in Quantum Reduced Loop Gravity in terms of states based on cuboidal graphs with six-valent nodes. We investigate the action of the scalar constraint operator at each node, and we construct proper semiclassical states. This allows us to discuss the semiclassical effective dynamics of the quantum universe, which resembles that of Loop Quantum Cosmology. In particular, the regulator is identified with the third root of the inverse number of nodes within each homogeneous patch, while inverse-volume corrections are enhanced.

  17. Digital phase-locked loop

    NASA Technical Reports Server (NTRS)

    Cliff, R. A. (Inventor)

    1975-01-01

    An digital phase-locked loop is provided for deriving a loop output signal from an accumulator output terminal. A phase detecting exclusive OR gate is fed by the loop digital input and output signals. The output of the phase detector is a bi-level digital signal having a duty cycle indicative of the relative phase of the input and output signals. The accumulator is incremented at a first rate in response to a first output level of the phase detector and at a second rate in response to a second output level of the phase detector.

  18. Loop-mirror-based slot waveguide refractive index sensor

    NASA Astrophysics Data System (ADS)

    Kou, Jun-long; Xu, Fei; Lu, Yan-qing

    2012-12-01

    Loop mirror has been widely used in fiber optical devices and systems for it provides a smart way to make use of the fiber birefringence properties and can enhance the sensitivity greatly. On the other hand, slot waveguide is very promising for optical sensing applications because of their peculiar spatial mode profile. In this paper, we propose and analyze a loop-mirror-based slot waveguide (LMSW) sensor which can be routinely fabricated in modern high-volume complementary metal-oxide-semiconductor (CMOS) process. The finite element method (FEM) simulation results show that the birefringence can be as high as 0.8 which is orders of magnitude than that in conventional birefringent fiber loop mirror. High sensitivity up to 6 × 103 nm/RIU (refractive index unit) is achieved by this scheme.

  19. SDO Sees Brightening Magnetic Loops

    NASA Video Gallery

    Two active regions sprouted arches of bundled magnetic loops in this video from NASA’s Solar Dynamics Observatory taken on Nov. 11-12, 2015. Charged particles spin along the magnetic field, tracing...

  20. Automatic blocking of nested loops

    NASA Technical Reports Server (NTRS)

    Schreiber, Robert; Dongarra, Jack J.

    1990-01-01

    Blocked algorithms have much better properties of data locality and therefore can be much more efficient than ordinary algorithms when a memory hierarchy is involved. On the other hand, they are very difficult to write and to tune for particular machines. The reorganization is considered of nested loops through the use of known program transformations in order to create blocked algorithms automatically. The program transformations used are strip mining, loop interchange, and a variant of loop skewing in which invertible linear transformations (with integer coordinates) of the loop indices are allowed. Some problems are solved concerning the optimal application of these transformations. It is shown, in a very general setting, how to choose a nearly optimal set of transformed indices. It is then shown, in one particular but rather frequently occurring situation, how to choose an optimal set of block sizes.

  1. SDO Sees Flourishing Magnetic Loops

    NASA Video Gallery

    A bright set of loops near the edge of the sun’s face grew and shifted quickly after the magnetic field was disrupted by a small eruption on Nov. 25, 2015. Charged particles emitting light in extre...

  2. Loop Electrosurgical Excision Procedure (LEEP)

    MedlinePlus

    ... that acts like a scalpel (surgical knife). An electric current is passed through the loop, which cuts away ... A procedure in which an instrument works with electric current to destroy tissue. Local Anesthesia: The use of ...

  3. Observations of loops and prominences

    NASA Technical Reports Server (NTRS)

    Strong, Keith T.

    1994-01-01

    We review recent observations by the Yohkoh-SXT (Soft X-ray Telescope) in collaboration with other spacecraft and ground-based observatories of coronal loops and prominences. These new results point to problems that SoHO will be able to address. With a unique combination of rapid-cadence digital imaging (greater than or equal to 32 s full-disk and greater than or equal to 2 s partial-frame images), high spatial resolution (greater than or equal to 2.5 arcsec pixels), high sensitivity (EM less than or equal to 10(exp 42) cm(exp -3)), a low-scatter mirror, and large dynamic range, SXT can observe a vast range of targets on the Sun. Over the first 21 months of Yohkoh operations SXT has taken over one million images of the corona and so is building up an invaluable long-term database on the large-scale corona and loop geometry. The most striking thing about the SXT images is the range of loop sizes and shapes. The active regions are a bright tangle of magnetic field lines, surrounded by a network of large-scale quiet-Sun loops stretching over distances in excess of 105 km. The cross-section of most loops seems to be constant. Loops displaying significant Gamma's are the exception, not the rule, implying the presence of widespread currents in the corona. All magnetic structures show changes. Time scales range from seconds to months. The question of how these structures are formed, become filled with hot plasma, and are maintained is still open. While we see the propagation of brightenings along the length of active-region loops and in X-ray jets with velocities of several hundred km/s, much higher velocities are seen in the quiet Sun. In XBP flares, for example, velocities of over 1000 km/s are common. Active-region loops seem to be in constant motion, moving slowly outward, carrying plasma with them. During flares, loops often produce localized brightenings at the base and later at the apex of the loop. Quiescent filaments and prominences have been observed regularly

  4. Massless sunset diagrams in finite asymmetric volumes

    NASA Astrophysics Data System (ADS)

    Niedermayer, F.; Weisz, P.

    2016-06-01

    This paper discusses the methods and the results used in an accompanying paper describing the matching of effective chiral Lagrangians in dimensional and lattice regularizations. We present methods to compute 2-loop massless sunset diagrams in finite asymmetric volumes in the framework of these regularizations. We also consider 1-loop sums in both regularizations, extending the results of Hasenfratz and Leutwyler for the case of dimensional regularization and we introduce a new method to calculate precisely the expansion coefficients of the 1-loop lattice sums.

  5. Dynamical behaviour in coronal loops

    NASA Technical Reports Server (NTRS)

    Haisch, Bernhard M.

    1986-01-01

    Rapid variability has been found in two active region coronal loops observed by the X-ray Polychromator (XRP) and the Hard X-ray Imaging Spectrometer (HXIS) onboard the Solar Maximum Mission (SMM). There appear to be surprisingly few observations of the short-time scale behavior of hot loops, and the evidence presented herein lends support to the hypothesis that coronal heating may be impulsive and driven by flaring.

  6. The Coronal Loop Inventory Project

    NASA Astrophysics Data System (ADS)

    Schmelz, J. T.; Pathak, S.; Christian, G. M.; Dhaliwal, R. S. S.; Paul, K. S.

    2015-11-01

    Most coronal physicists now seem to agree that loops are composed of tangled magnetic strands and have both isothermal and multithermal cross-field temperature distributions. As yet, however, there is no information on the relative importance of each of these categories, and we do not know how common one is with respect to the other. In this paper, we investigate these temperature properties for all loop segments visible in the 171-Å image of AR 11294, which was observed by the Atmospheric Imaging Assembly (AIA) on 2011 September 15. Our analysis revealed 19 loop segments, but only 2 of these were clearly isothermal. Six additional segments were effectively isothermal, that is, the plasma emission to which AIA is sensitive could not be distinguished from isothermal emission, within measurement uncertainties. One loop had both isothermal transition region and multithermal coronal solutions. Another five loop segments require multithermal plasma to reproduce the AIA observations. The five remaining loop segments could not be separated reliably from the background in the crucial non-171-Å AIA images required for temperature analysis. We hope that the direction of coronal heating models and the efforts modelers spend on various heating scenarios will be influenced by these results.

  7. The Structure of Coronal Loops

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.

    2009-01-01

    It is widely believed that the simple coronal loops observed by XUV imagers, such as EIT, TRACE, or XRT, actually have a complex internal structure consisting of many (perhaps hundreds) of unresolved, interwoven "strands". According to the nanoflare model, photospheric motions tangle the strands, causing them to reconnect and release the energy required to produce the observed loop plasma. Although the strands, themselves, are unresolved by present-generation imagers, there is compelling evidence for their existence and for the nanoflare model from analysis of loop intensities and temporal evolution. A problem with this scenario is that, although reconnection can eliminate some of the strand tangles, it cannot destroy helicity, which should eventually build up to observable scales. we consider, therefore, the injection and evolution of helicity by the nanoflare process and its implications for the observed structure of loops and the large-scale corona. we argue that helicity does survive and build up to observable levels, but on spatial and temporal scales larger than those of coronal loops. we discuss the implications of these results for coronal loops and the corona, in general .

  8. Loop quantum cosmology with self-dual variables

    NASA Astrophysics Data System (ADS)

    Wilson-Ewing, Edward

    2015-12-01

    Using the complex-valued self-dual connection variables, the loop quantum cosmology of a closed Friedmann space-time coupled to a massless scalar field is studied. It is shown how the reality conditions can be imposed in the quantum theory by choosing a particular inner product for the kinematical Hilbert space. While holonomies of the self-dual Ashtekar connection are not well defined in the kinematical Hilbert space, it is possible to introduce a family of generalized holonomylike operators of which some are well defined; these operators in turn are used in the definition of the Hamiltonian constraint operator where the scalar field can be used as a relational clock. The resulting quantum theory is closely related, although not identical, to standard loop quantum cosmology constructed from the Ashtekar-Barbero variables with a real Immirzi parameter. Effective Friedmann equations are derived which provide a good approximation to the full quantum dynamics for sharply peaked states whose volume remains much larger than the Planck volume, and they show that for these states quantum gravity effects resolve the big-bang and big-crunch singularities and replace them by a nonsingular bounce. Finally, the loop quantization in self-dual variables of a flat Friedmann space-time is recovered in the limit of zero spatial curvature and is identical to the standard loop quantization in terms of the real-valued Ashtekar-Barbero variables.

  9. Gas Test Loop Functional and Technical Requirements

    SciTech Connect

    Glen R. Longhurst; Soli T. Khericha; James L. Jones

    2004-09-01

    This document defines the technical and functional requirements for a gas test loop (GTL) to be constructed for the purpose of providing a high intensity fast-flux irradiation environment for developers of advanced concept nuclear reactors. This capability is needed to meet fuels and materials testing requirements of the designers of Generation IV (GEN IV) reactors and other programs within the purview of the Advanced Fuel Cycle Initiative (AFCI). Space nuclear power development programs may also benefit by the services the GTL will offer. The overall GTL technical objective is to provide developers with the means for investigating and qualifying fuels and materials needed for advanced reactor concepts. The testing environment includes a fast-flux neutron spectrum of sufficient intensity to perform accelerated irradiation testing. Appropriate irradiation temperature, gaseous environment, test volume, diagnostics, and access and handling features are also needed. This document serves to identify those requirements as well as generic requirements applicable to any system of this kind.

  10. Xerox's closed recycling loop still contains kinks

    SciTech Connect

    Not Available

    1995-02-01

    Xerox Corp. has established a recycling loop for plastics screw-top toner bottles and dry-ink containers used in most of the company's high-volume copiers. However, a severe shortage of post-consumer recycled plastic has been short-circuiting Xerox's good intentions. Last year, the Stamford, Conn.-based company stopped manufacturing toner containers from virgin plastics and instead began using recycled raw materials, such as discarded milk and water jugs collected from municipal curbside recycling programs. The bottles are ground and remolded into such products as air filters for vacuum cleaners, plastic lumber, compost bins, landscape ties, benches and fence posts. However, what sounds like a win-win situation actually is costing too much money. Contrary to popular belief, post-consumer recycled plastic costs more than virgin plastic. Despite the added expense, Xerox will continue to use recycled plastics when possible.

  11. Kalman Orbit Optimized Loop Tracking

    NASA Technical Reports Server (NTRS)

    Young, Lawrence E.; Meehan, Thomas K.

    2011-01-01

    Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

  12. Fabrication techniques for superconducting readout loops

    NASA Technical Reports Server (NTRS)

    Payne, J. E.

    1982-01-01

    Procedures for the fabrication of superconducting readout loops out of niobium on glass substrates were developed. A computer program for an existing fabrication system was developed. Both positive and negative resist procedures for the production of the readout loops were investigated. Methods used to produce satisfactory loops are described and the various parameters affecting the performance of the loops are analyzed.

  13. Filter for third order phase locked loops

    NASA Technical Reports Server (NTRS)

    Crow, R. B.; Tausworthe, R. C. (Inventor)

    1973-01-01

    Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.

  14. Volume accumulator design analysis computer codes

    NASA Technical Reports Server (NTRS)

    Whitaker, W. D.; Shimazaki, T. T.

    1973-01-01

    The computer codes, VANEP and VANES, were written and used to aid in the design and performance calculation of the volume accumulator units (VAU) for the 5-kwe reactor thermoelectric system. VANEP computes the VAU design which meets the primary coolant loop VAU volume and pressure performance requirements. VANES computes the performance of the VAU design, determined from the VANEP code, at the conditions of the secondary coolant loop. The codes can also compute the performance characteristics of the VAU's under conditions of possible modes of failure which still permit continued system operation.

  15. Quantum of volume in de Sitter space

    SciTech Connect

    Mielczarek, Jakub; Piechocki, Wlodzimierz

    2011-05-15

    We apply the nonstandard loop quantum cosmology method to quantize a flat Friedmann-Robertson-Walker cosmological model with a free scalar field and the cosmological constant {Lambda}>0. Modification of the Hamiltonian in terms of loop geometry parametrized by a length {lambda} introduces a scale dependence of the model. The spectrum of the volume operator is discrete and depends on {Lambda}. Relating quantum of the volume with an elementary lattice cell leads to an explicit dependence of {Lambda} on {lambda}. Based on this assumption, we investigate the possibility of interpreting {Lambda} as a running constant.

  16. Study of the Open Loop and Closed Loop Oscillator Techniques

    SciTech Connect

    Imel, George R.; Baker, Benjamin; Riley, Tony; Langbehn, Adam; Aryal, Harishchandra; Benzerga, M. Lamine

    2015-04-11

    This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.

  17. Gluing hexagons at three loops

    NASA Astrophysics Data System (ADS)

    Basso, Benjamin; Goncalves, Vasco; Komatsu, Shota; Vieira, Pedro

    2016-06-01

    We perform extensive three-loop tests of the hexagon bootstrap approach for structure constants in planar N = 4 SYM theory. We focus on correlators involving two BPS operators and one non-BPS operator in the so-called SL (2) sector. At three loops, such correlators receive wrapping corrections from mirror excitations flowing in either the adjacent or the opposing channel. Amusingly, we find that the first type of correction coincides exactly with the leading wrapping correction for the spectrum (divided by the one-loop anomalous dimension). We develop an efficient method for computing the second type of correction for operators with any spin. The results are in perfect agreement with the recently obtained three-loop perturbative data by Chicherin, Drummond, Heslop, Sokatchev [2] and by Eden [3]. We also derive the integrand for general multi-particle wrapping corrections, which turns out to take a remarkably simple form. As an application we estimate the loop order at which various new physical effects are expected to kick-in.

  18. Bandwidth controller for phase-locked-loop

    NASA Technical Reports Server (NTRS)

    Brockman, Milton H. (Inventor)

    1992-01-01

    A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.

  19. Digital phase-lock loop

    NASA Technical Reports Server (NTRS)

    Thomas, Jr., Jess B. (Inventor)

    1991-01-01

    An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.

  20. Criteria for saturated magnetization loop

    NASA Astrophysics Data System (ADS)

    Harres, A.; Mikhov, M.; Skumryev, V.; Andrade, A. M. H. de; Schmidt, J. E.; Geshev, J.

    2016-03-01

    Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe3O4 and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one.

  1. Waves in Solar Coronal Loops

    NASA Astrophysics Data System (ADS)

    Wang, T. J.

    2016-02-01

    The corona is visible in the optical band only during a total solar eclipse or with a coronagraph. Coronal loops are believed to be plasma-filled closed magnetic flux anchored in the photosphere. Based on the temperature regime, they are generally classified into cool, warm, and hot loops. The magnetized coronal structures support propagation of various types of magnetohydrodynamics (MHD) waves. This chapter reviews the recent progress made in studies based on observations of four types of wave phenomena mainly occurring in coronal loops of active regions, including: flare-excited slow-mode waves; impulsively excited kink-mode waves; propagating slow magnetoacoustic waves; and ubiquitous propagating kink (Alfvénic) waves. This review not only comprehensively discusses these waves and coronal seismology but also topics that are newly emerging or hotly debated in order to provide the reader with useful guidance on further studies.

  2. All digital pulsewidth control loop

    NASA Astrophysics Data System (ADS)

    Huang, Hong-Yi; Jan, Shiun-Dian; Pu, Ruei-Iun

    2013-03-01

    This work presents an all-digital pulsewidth control loop (ADPWCL). The proposed system accepts a wide range of input duty cycles and performs a fast correction to the target output pulsewidth. An all-digital delay-locked loop (DLL) with fast locking time using a simplified time to digital converter and a new differential two-step delay element is proposed. The area of the delay element is much smaller than that in conventional designs, while having the same delay range. A test chip is verified in a 0.18-µm CMOS process. The measured duty cycle ranges from 4% to 98% with 7-bit resolution.

  3. Loop quantum cosmology: an overview

    NASA Astrophysics Data System (ADS)

    Ashtekar, Abhay

    2009-04-01

    A brief overview of loop quantum cosmology of homogeneous isotropic models is presented with emphasis on the origin of and subtleties associated with the resolution of big bang and big crunch singularities. These results bear out the remarkable intuition that John Wheeler had. Discussion is organized at two levels. The the main text provides a bird’s eye view of the subject that should be accessible to non-experts. Appendices address conceptual and technical issues that are often raised by experts in loop quantum gravity and string theory.

  4. Modeling of compact loop antennas

    NASA Astrophysics Data System (ADS)

    Baity, F. W.

    1987-09-01

    A general compact loop antenna model which treats all elements of the antenna as lossy transmission lines has been developed. In addition to capacitively tuned resonant double loop (RDL) antennas, the model treats sub-tuned RDL antennas. Calculations using the model have been compared with measurements on full-scale mock-ups of RDL antennas for ATF and TFTR in order to refine the transmission line parameters. Results from the model are presented for RDL antenna designs for ATF, TFTR, Tore Supra, and the Compact Ignition Tokamak (CIT).

  5. Many Ways to Loop DNA

    PubMed Central

    Griffith, Jack D.

    2013-01-01

    In the 1960s, I developed methods for directly visualizing DNA and DNA-protein complexes using an electron microscope. This made it possible to examine the shape of DNA and to visualize proteins as they fold and loop DNA. Early applications included the first visualization of true nucleosomes and linkers and the demonstration that repeating tracts of adenines can cause a curvature in DNA. The binding of DNA repair proteins, including p53 and BRCA2, has been visualized at three- and four-way junctions in DNA. The trombone model of DNA replication was directly verified, and the looping of DNA at telomeres was discovered. PMID:24005675

  6. Space nuclear system volume accumulator development (SNAP program)

    NASA Technical Reports Server (NTRS)

    Whitaker, W. D.; Shimazaki, T. T.

    1973-01-01

    The engineering, design, and fabrication status of the volume accumulator units to be employed in the NaK primary and secondary coolant loops of the 5-kwe reactor thermoelectric system are described. Three identical VAU's are required - two for the primary coolant loop, and one for the secondary coolant loop. The VAU's utilize nested-formed bellows as the flexing member, are hermetically sealed, provide double containment and utilize a combination of gas pressure force and bellows spring force to obtain the desired pressure regulation of the coolant loops. All parts of the VAU, except the NaK inlet tube, are to be fabricated from Inconel 718.

  7. Cosmological perturbations in teleparallel Loop Quantum Cosmology

    NASA Astrophysics Data System (ADS)

    Haro, Jaime

    2013-11-01

    Cosmological perturbations in Loop Quantum Cosmology (LQC) are usually studied incorporating either holonomy corrections, where the Ashtekar connection is replaced by a suitable sinus function in order to have a well-defined quantum analogue, or inverse-volume corrections coming from the eigenvalues of the inverse-volume operator. In this paper we will develop an alternative approach to calculate cosmological perturbations in LQC based on the fact that, holonomy corrected LQC in the flat Friedmann-Lemaître-Robertson-Walker (FLRW) geometry could be also obtained as a particular case of teleparallel F(T) gravity (teleparallel LQC). The main idea of our approach is to mix the simple bounce provided by holonomy corrections in LQC with the non-singular perturbation equations given by F(T) gravity, in order to obtain a matter bounce scenario as a viable alternative to slow-roll inflation. In our study, we have obtained an scale invariant power spectrum of cosmological perturbations. However, the ratio of tensor to scalar perturbations is of order 1, which does not agree with the current observations. For this reason, we suggest a model where a transition from the matter domination to a quasi de Sitter phase is produced in order to enhance the scalar power spectrum.

  8. Modelling offset minor hysteresis loops with the modified Jiles-Atherton description

    NASA Astrophysics Data System (ADS)

    Chwastek, K.

    2009-08-01

    The paper addresses the issue of modelling offset minor hysteresis loops within the framework of the Jiles-Atherton model. Two of the model parameters are expressed in terms of scaling power laws with respect to the magnetization level. The approach is consistent with earlier theoretical considerations on the effective 'volume fraction' by Professor D Jiles. The influence of eddy currents on hysteresis loop is taken into account using an additional term of magnetic field.

  9. Formation process of dislocation loops in iron under irradiations with low-energy helium, hydrogen ions or high-energy electrons

    NASA Astrophysics Data System (ADS)

    Arakawa, K.; Mori, H.; Ono, K.

    2002-12-01

    Formation processes of interstitial-type dislocation loops (I loops) in high-purity Fe under irradiations with 5 keV H + ions or 1000 keV electrons are examined by in situ transmission electron microscopy at temperatures below room temperature, and the results are compared with that obtained under He + ion irradiation. For the electron irradiation, conventional model of I-loop nucleation based on the assumption that di-interstitial atoms are stable nuclei of I loops is questioned. The volume density of I loops by H + ion irradiation is one-order of magnitude higher than that by electron irradiation, and several times lower than that by He + ion irradiation. The temperature dependence of the volume density of I loops by H + ion irradiation supports the idea that such enhancement of I-loop formation is due to trapping of self-interstitial atoms by gas atom-vacancy complexes.

  10. Closed-Loop Neuromorphic Benchmarks

    PubMed Central

    Stewart, Terrence C.; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris

    2015-01-01

    Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of “minimal” simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820

  11. Closed-Loop Neuromorphic Benchmarks.

    PubMed

    Stewart, Terrence C; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris

    2015-01-01

    Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of "minimal" simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820

  12. Closing the Loop with Exercises

    ERIC Educational Resources Information Center

    Altizer, Andy

    2008-01-01

    Conducting exercises provides a critical bridge between the theory of an Emergency Action Plan and its effective implementation. When conducted properly, exercises can fill the gap between training and after-action review to close the preparedness loop--before an actual emergency occurs. Often exercises are planned and conducted on campus based on…

  13. Manchester transition tracking loop (MTTL)

    NASA Technical Reports Server (NTRS)

    Cellier, A.; Ma, L. N.; Huey, D. C.

    1977-01-01

    In new tracking loop, separate phase detection algorithm is incorporated for acquisition; programmed acquisition-to-track sequence includes automatic bandwidth switching. Additionally, system has very effective phase detection signal-to-noise ratio and can operate at any rate by changing master clock frequency. All system parameters remain constant.

  14. Bimodal loop-gap resonator

    NASA Astrophysics Data System (ADS)

    Piasecki, W.; Froncisz, W.; Hyde, James S.

    1996-05-01

    A bimodal loop-gap resonator for use in electron paramagnetic resonance (EPR) spectroscopy at S band is described. It consists of two identical one-loop-one-gap resonators in coaxial juxtaposition. In one mode, the currents in the two loops are parallel and in the other antiparallel. By introducing additional capacitors between the loops, the frequencies of the two modes can be made to coincide. Details are given concerning variable coupling to each mode, tuning of the resonant frequency of one mode to that of the other, and adjustment of the isolation between modes. An equivalent circuit is given and network analysis carried out both experimentally and theoretically. EPR applications are described including (a) probing of the field distributions with DPPH, (b) continuous wave (cw) EPR with a spin-label line sample, (c) cw electron-electron double resonance (ELDOR), (d) modulation of saturation, and (e) saturation-recovery (SR) EPR. Bloch induction experiments can be performed when the sample extends half way through the structure, but microwave signals induced by Mx and My components of magnetization cancel when it extends completely through. This latter situation is particularly favorable for SR, modulation of saturation, and ELDOR experiments, which depend on observing Mz indirectly using a second weak observing microwave source.

  15. The consistent histories approach to loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Craig, David A.

    2016-06-01

    We review the application of the consistent (or decoherent) histories formulation of quantum theory to canonical loop quantum cosmology. Conventional quantum theory relies crucially on “measurements” to convert unrealized quantum potentialities into physical outcomes that can be assigned probabilities. In the early universe and other physical contexts in which there are no observers or measuring apparatus (or indeed, in any closed quantum system), what criteria determine which alternative outcomes may be realized and what their probabilities are? In the consistent histories formulation it is the vanishing of interference between the branch wave functions describing alternative histories — as determined by the system’s decoherence functional — that determines which alternatives may be assigned probabilities. We describe the consistent histories formulation and how it may be applied to canonical loop quantum cosmology, describing in detail the application to homogeneous and isotropic cosmological models with scalar matter. We show how the theory may be used to make definite physical predictions in the absence of “observers”. As an application, we demonstrate how the theory predicts that loop quantum models “bounce” from large volume to large volume, while conventional “Wheeler-DeWitt”-quantized universes are invariably singular. We also briefly indicate the relation to other work.

  16. Evolution in a Braided Loop Ensemble

    NASA Video Gallery

    This braided loop has several loops near the 'base' that appear to be unwinding with significant apparent outflow. This is evidence of untwisting, and the braided structure also seeming to unwind w...

  17. Fragmentation of cosmic-string loops

    NASA Technical Reports Server (NTRS)

    York, Thomas

    1989-01-01

    The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.

  18. Chromosome Compaction by Active Loop Extrusion.

    PubMed

    Goloborodko, Anton; Marko, John F; Mirny, Leonid A

    2016-05-24

    During cell division, chromosomes are compacted in length by more than a 100-fold. A wide range of experiments demonstrated that in their compacted state, mammalian chromosomes form arrays of closely stacked consecutive ∼100 kb loops. The mechanism underlying the active process of chromosome compaction into a stack of loops is unknown. Here we test the hypothesis that chromosomes are compacted by enzymatic machines that actively extrude chromatin loops. When such loop-extruding factors (LEF) bind to chromosomes, they progressively bridge sites that are further away along the chromosome, thus extruding a loop. We demonstrate that collective action of LEFs leads to formation of a dynamic array of consecutive loops. Simulations and an analytically solved model identify two distinct steady states: a sparse state, where loops are highly dynamic but provide little compaction; and a dense state, where there are more stable loops and dramatic chromosome compaction. We find that human chromosomes operate at the border of the dense steady state. Our analysis also shows how the macroscopic characteristics of the loop array are determined by the microscopic properties of LEFs and their abundance. When the number of LEFs are used that match experimentally based estimates, the model can quantitatively reproduce the average loop length, the degree of compaction, and the general loop-array morphology of compact human chromosomes. Our study demonstrates that efficient chromosome compaction can be achieved solely by an active loop-extrusion process. PMID:27224481

  19. Hard thermal loops in static external fields

    SciTech Connect

    Frenkel, J.; Takahashi, N.; Pereira, S. H.

    2009-04-15

    We examine, in the imaginary-time formalism, the high temperature behavior of n-point thermal loops in static Yang-Mills and gravitational fields. We show that in this regime, any hard thermal loop gives the same leading contribution as the one obtained by evaluating the loop integral at zero external energies and momenta.

  20. The Statistical Loop Analyzer (SLA)

    NASA Technical Reports Server (NTRS)

    Lindsey, W. C.

    1985-01-01

    The statistical loop analyzer (SLA) is designed to automatically measure the acquisition, tracking and frequency stability performance characteristics of symbol synchronizers, code synchronizers, carrier tracking loops, and coherent transponders. Automated phase lock and system level tests can also be made using the SLA. Standard baseband, carrier and spread spectrum modulation techniques can be accomodated. Through the SLA's phase error jitter and cycle slip measurements the acquisition and tracking thresholds of the unit under test are determined; any false phase and frequency lock events are statistically analyzed and reported in the SLA output in probabilistic terms. Automated signal drop out tests can be performed in order to trouble shoot algorithms and evaluate the reacquisition statistics of the unit under test. Cycle slip rates and cycle slip probabilities can be measured using the SLA. These measurements, combined with bit error probability measurements, are all that are needed to fully characterize the acquisition and tracking performance of a digital communication system.

  1. Microgyroscope with closed loop output

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor); Cargille, Donald R. (Inventor)

    2002-01-01

    A micro-gyroscope (10) having closed loop operation by a control voltage (V.sub.TY), that is demodulated by an output signal of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis). The present invention provides wide-band, closed-loop operation for a micro-gyroscope (10) and allows the drive frequency to be closely tuned to a high Q sense axis resonance. A differential sense signal (S1-S2) is compensated and fed back by differentially changing the voltage on the drive electrodes to rebalance Coriolis torque. The feedback signal is demodulated in phase with the drive axis signal (K.sub..omega..crclbar..sub.x) to produce a measure of the Coriolis force.

  2. Loop connectors in dentogenic diastema.

    PubMed

    Nayar, Sanjna; Jayesh, Raghevendra; Venkateshwaran; Dinakarsamy, V

    2015-04-01

    Patients with a missing tooth along with diastema have limited treatment options to restore the edentulous space. The use of a conventional fixed partial denture (FPD) to replace the missing tooth may result in too wide anterior teeth leading to poor esthetics. Loss of anterior teeth with existing diastema may result in excess space available for pontic. This condition presents great esthetic challenge for prosthodontist. If implant supported prosthesis is not possible because of inadequate bone support, FPD along with loop connector may be a treatment option to maintain the diastema and provide optimal esthetic restoration. Here, we report a clinical case where FPD along with loop connector was used to achieve esthetic rehabilitation in maxillary anterior region in which midline diastema has been maintained. PMID:26015732

  3. Endoscopic management of afferent loop syndrome after a pylorus preserving pancreatoduodenecotomy presenting with obstructive jaundice and ascending cholangitis.

    PubMed

    Kim, Jae Kyung; Park, Chan Hyuk; Huh, Ji Hye; Park, Jeong Youp; Park, Seung Woo; Song, Si Young; Chung, Jaebock; Bang, Seungmin

    2011-09-01

    Afferent loop syndrome is a rare complication of gastrojejunostomy. Patients usually present with abdominal distention and bilious vomiting. Afferent loop syndrome in patients who have undergone a pylorus preserving pancreaticoduodenectomy can present with ascending cholangitis. This condition is related to a large volume of reflux through the biliary-enteric anastomosis and static materials with bacterial overgrowth in the afferent loop. Patients with afferent loop syndrome after pylorus preserving pancreaticoduodenectomy frequently cannot be confirmed as surgical candidates due to poor medical condition. In that situation, a non-surgical palliation should be considered. Herein, we report two patients with afferent loop syndrome presenting with obstructive jaundice and ascending cholangitis. The patients suffered from the recurrence of pancreatic cancer after pylorus preserving pancreaticoduodenectomy. The diagnosis of afferent loop syndrome was confirmed, and the patients were successfully treated by inserting an endoscopic metal stent using a colonoscopic endoscope. PMID:22741115

  4. Two Loop Higgs Unitarity Constraints

    NASA Astrophysics Data System (ADS)

    Maher, Peter Noel

    The perturbative approximation in the Symmetry Breaking sector of the Standard Model is investigated to two loops. The breakdown of perturbative unitarity seen at one loop is only slightly postponed. Attention is restricted to the coupled elastic scattering matrix of the neutral channels W^+W ^-, ZZ, HH, ZH. The high energy limit s gg M_sp{H} {2} gg M_sp{W}{2} and the Equivalence Theorem are used to simplify the calculation. The theory is renormalized on mass shell, in a way that automatically sums the tadpole graphs. Calculation of the counterterms was the most difficult part of the entire work. The running coupling and anomalous dimensions are calculated. The Landau pole of the running coupling is not significantly affected by the two loop contributions unless the coupling is large. Similarly, the anomalous dimensions are small. The eigen-amplitudes of the partial wave projected scattering matrix are analysed for breakdown of perturbative unitarity using Argand diagrams, and for term-wise convergence. It is found that if the Standard Model is to hold true up to sqrt{s} ~ 2TeV, the theory is strongly coupled and perturbative approximations are no longer trustworthy if M_{H} _sp{~}{>} 350 - 450 GeV. If the Standard Model is embedded in a perturbative grand unified theory, and assumed to hold true up to sqrt{s} = 10^ {15} GeV, then the Higgs mass is bounded M_{H} _sp{~ }{<} 160 GeV.

  5. Two-loop quantum gravity

    NASA Astrophysics Data System (ADS)

    van de Ven, Anton E. M.

    1992-07-01

    We prove the existence of a nonrenormalizable infinity in the two-loop effective action of perturbative quantum gravity by means of an explicit calculation. Our final result agrees with that obtained by earlier authors. We use the background-field method in coordinate space, combined with dimensional regularization and a heat kernel representation for the propagators. General covariance is manifestly preserved. Only vacuum graphs in the presence of an on-shell background metric need to be calculated. We extend the background covariant harmonic gauge to include terms nonlinear in the quantum gravitational fields and allow for general reparametrizations of those fields. For a particular gauge choice and field parametrization only two three-graviton and six four-graviton vertices are present in the action. Calculational labor is further reduced by restricting to backgrounds, which are not only Ricci-flat, but satisfy an additional constraint bilinear in the Weyl tensor. To handle the still formidable amount of algebra, we use the symbolic manipulation program FORM. We checked that the on-shell two-loop effective action is in fact independent of all gauge and field redefinition parameters. A two-loop analysis for Yang-Mills fields is included as well, since in that case we can give full details as well as simplify earlier analyses.

  6. Quantum reduced loop gravity and the foundation of loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Alesci, Emanuele; Cianfrani, Francesco

    2016-06-01

    Quantum reduced loop gravity is a promising framework for linking loop quantum gravity and the effective semiclassical dynamics of loop quantum cosmology. We review its basic achievements and its main perspectives, outlining how it provides a quantum description of the Universe in terms of a cuboidal graph which constitutes the proper framework for applying loop techniques in a cosmological setting.

  7. Twist-three at five loops, Bethe ansatz and wrapping

    NASA Astrophysics Data System (ADS)

    Beccaria, Matteo; Forini, Valentina; Łukowski, Tomasz; Zieme, Stefan

    2009-03-01

    We present a formula for the five-loop anomalous dimension of Script N = 4 SYM twist-three operators in the fraktur sfraktur l(2) sector. We obtain its asymptotic part from the Bethe Ansatz and finite volume corrections from the generalized Lüscher formalism, considering scattering processes of spin chain magnons with virtual particles that travel along the cylinder. The complete result respects the expected large spin scaling properties and passes non-trivial tests including reciprocity constraints. We analyze the pole structure and find agreement with a conjectured resummation formula. In analogy with the twist-two anomalous dimension at four-loops wrapping effects are of order (log2M/M2) for large values of the spin.

  8. [Performance of internal-loop air-lift nitrifying bioreactor].

    PubMed

    Lin, Feng-Mei; Zheng, Ping; Zhao, Yang-Yang; Hu, Bao-Lan; Chen, Jian-Song

    2002-07-01

    The performance of internal-loop air-lift nitrifying bioreactor was good with strong tolerance to influent ammonia concentration (78.49 mmol/L), high volume converting rate (163.18 mmol/L.d) and obvious working stability (ammonia removal > 94.42%). During operation of internal-loop air-lift bioreactor, the nitrifying activated sludge was granulated. The nitrifying granular activated sludge began to appear on day 45. Its average diameter was 0.83 mm, settling velocity was 55.53 m/h and specific ammonia removal rate was 0.95 mmol (NH4(+)-N)/g (VS).d. The nitrifying granular activated sludge had the activity for anaerobic ammonia oxidation with ammonia oxidation rate of 0.23 mmol (NH4(+)-N)/g(VS).d and nitrite reduction rate of 0.24 mmol (NO2(-)-N)/g(VS).d. PMID:12385250

  9. Influence of lung volume dependence of upper airway resistance during continuous negative airway pressure.

    PubMed

    Sériès, F; Marc, I

    1994-08-01

    To quantify the contribution of lung volume dependence of upper airway (UA) on continuous negative airway pressure (CNAP)-induced increase in upper airway resistance, we compared the changes in supralaryngeal resistance during an isolated decrease in lung volume and during CNAP in eight normal awake subjects. Inspiratory supralaryngeal resistance was measured at isoflow during four trials, during two CNAP trials where the pressure in a nasal mask was progressively decreased in 3- to 5-cmH2O steps and during two continuous positive extrathoracic pressure (CPEP) trials where the pressure around the chest (in an iron lung) was increased in similar steps. The CNAP and CPEP trials were done in random order. During the CPEP trial, the neck was covered by a rigid collar to prevent compression by the cervical seal of the iron lung. In each subject, resistance progressively increased during the experiments. The increase was linearily correlated with the pressure increase in the iron lung and with the square of the mask pressure during CNAP. There was a highly significant correlation between the rate of rise in resistance between CNAP and CPEP: the steeper the increase in resistance with decreasing lung volume, the steeper the increase in resistance with decreasing airway pressure. Lung volume dependence in UA resistance can account for 61% of the CNAP-induced increase in resistance. We conclude that in normal awake subjects the changes in supralaryngeal resistance induced by CNAP can partly be explained by the lung volume dependence of this resistance. PMID:8002537

  10. Premeasured Chordal Loops for Mitral Valve Repair.

    PubMed

    Gillinov, Marc; Quinn, Reed; Kerendi, Faraz; Gaudiani, Vince; Shemin, Richard; Barnhart, Glenn; Raines, Edward; Gerdisch, Marc W; Banbury, Michael

    2016-09-01

    Premeasured expanded polytetrafluoroethylene chordal loops with integrated sutures for attachment to the papillary muscle and leaflet edges facilitate correction of mitral valve prolapse. Configured as a group of 3 loops (length range 12 to 24 mm), the loops are attached to a pledget that is passed through the papillary muscle and tied. Each of the loops has 2 sutures with attached needles; these needles are passed through the free edge of the leaflet and then the sutures are tied to each other, securing the chordal loop to the leaflet. PMID:27549563

  11. Z-Sum approach to loop integrals

    NASA Astrophysics Data System (ADS)

    Rottmann, Paulo A.

    We study the applicability of the Z-Sum approach to multi-loop calculations with massive particles in perturbative quantum field theory. We systematically analyze the case of one-loop scalar integrals, which represent the building blocks of any higher-loop calculation. We focus in particular on triangle one-loop integrals and identify strengths and limitations of the Z-Sum approach, extending our results to the case of one-loop box integrals when appropriate. We conclude with the calculation of a specific physical example: the calculation of heavy flavor corrections to the renormalized scattering amplitude for deep inelastic scattering.

  12. Dynamic Aperture-based Solar Loop Segmentation

    NASA Technical Reports Server (NTRS)

    Lee, Jon Kwan; Newman, Timothy S.; Gary, G. Allen

    2006-01-01

    A new method to automatically segment arc-like loop structures from intensity images of the Sun's corona is introduced. The method constructively segments credible loop structures by exploiting the Gaussian-like shape of loop cross-sectional intensity profiles. The experimental results show that the method reasonably segments most of the well-defined loops in coronal images. The method is only the second published automated solar loop segmentation method. Its advantage over the other published method is that it operates independently of supplemental time specific data.

  13. Efficient Tiled Loop Generation: D-Tiling

    NASA Astrophysics Data System (ADS)

    Kim, Daegon; Rajopadhye, Sanjay

    Tiling is an important loop optimization for exposing coarse-grained parallelism and enhancing data locality. Tiled loop generation from an arbitrarily shaped polyhedron is a well studied problem. Except for the special case of a rectangular iteration space, the tiled loop generation problem has been long believed to require heavy machinery such as Fourier-Motzkin elimination and projection, and hence to have an exponential complexity. In this paper we propose a simple and efficient tiled loop generation technique similar to that for a rectangular iteration space. In our technique, each loop bound is adjusted only once, syntactically and independently. Therefore, our algorithm runs linearly with the number of loop bounds. Despite its simplicity, we retain several advantages of recent tiled code generation schemes - unified generation for fixed, parameterized and hybrid tiled loops, scalability for multi-level tiled loop generation with the ability to separate full tiles at any levels, and compact code. We also explore various schemes for multi-level tiled loop generation. We formally prove the correctness of our scheme and experimentally validate that the efficiency of our technique is comparable to existing parameterized tiled loop generation approaches. Our experimental results also show that multi-level tiled loop generation schemes have an impact on performance of generated code. The fact that our scheme can be implemented without sophisticated machinery makes it well suited for autotuners and production compilers.

  14. Hyperstaticity and loops in frictional granular packings

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Lam, Edward; Metzger, Philip T.

    2009-06-01

    The hyperstatic nature of granular packings of perfectly rigid disks is analyzed algebraically and through numerical simulation. The elementary loops of grains emerge as a fundamental element in addressing hyperstaticity. Loops consisting of an odd number of grains behave differently than those with an even number. For odd loops, the latent stresses are exterior and are characterized by the sum of frictional forces around each loop. For even loops, the latent stresses are interior and are characterized by the alternating sum of frictional forces around each loop. The statistics of these two types of loop sums are found to be Gibbsian with a "temperature" that is linear with the friction coefficient μ when μ<1.

  15. Loop quantum cosmology with complex Ashtekar variables

    NASA Astrophysics Data System (ADS)

    Ben Achour, Jibril; Grain, Julien; Noui, Karim

    2015-01-01

    We construct and study loop quantum cosmology (LQC) when the Barbero-Immirzi parameter takes the complex value γ =+/- i. We refer to this new approach to quantum cosmology as complex LQC. This formulation is obtained via an analytic continuation of the Hamiltonian constraint (with no inverse volume corrections) from real γ to γ =+/- i, in the simple case of a flat FLRW Universe coupled to a massless scalar field with no cosmological constant. For this, we first compute the non-local curvature operator (defined by the trace of the holonomy of the connection around a fundamental plaquette) evaluated in an arbitrary spin j representation, and find a new close formula for its expression. This allows us to define explicitly a one parameter family of regularizations of the Hamiltonian constraint in LQC, parametrized by the spin j. It is immediate to see that any spin j regularization leads to a bouncing scenario. Then, motivated in particular by previous results on black hole thermodynamics, we perform the analytic continuation of the Hamiltonian constraint to values of the Barbero-Immirzi parameter given by γ =+/- i and to spins j=\\frac{1}{2}(-1+is) where s is real. Even if the area spectrum then becomes continuous, we show that the complex LQC defined in this way does also replace the initial big-bang singularity by a big-bounce. In addition to this, the maximal density and the minimal volume of the Universe are obviously independent of γ . Furthermore, the dynamics before and after the bounce is not symmetrical anymore, which makes a clear distinction between these two phases of the evolution of the Universe.

  16. TEMPORAL VARIATIONS OF X-RAY SOLAR FLARE LOOPS: LENGTH, CORPULENCE, POSITION, TEMPERATURE, PLASMA PRESSURE, AND SPECTRA

    SciTech Connect

    Jeffrey, Natasha L. S.; Kontar, Eduard P.

    2013-04-01

    The spatial and spectral properties of three solar flare coronal X-ray loops are studied before, during, and after the peak X-ray emission. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we deduce the temporal changes in emitting X-ray length, corpulence, volume, position, number density, and thermal pressure. We observe a decrease in the loop length, width, and volume before the X-ray peak, and an increasing number density and thermal pressure. After the X-ray peak, volume increases and loop corpulence grows due to increasing width. The volume variations are more pronounced than the position variations, often known as magnetic field line contraction. We believe this is the first dedicated study examining the temporal evolution of X-ray loop lengths and widths. Collectively, the observations also show for the first time three temporal phases given by peaks in temperature, X-ray emission, and thermal pressure, with the minimum volume coinciding with the X-ray peak. Although the volume of the flaring plasma decreases before the peak in X-ray emission, the relationship between temperature and volume does not support simple compressive heating in a collapsing magnetic trap model. Within a low {beta} plasma, shrinking loop widths perpendicular to the guiding field can be explained by squeezing the magnetic field threading the region. Plasma heating leads to chromospheric evaporation and growing number density. This produces increasing thermal pressure and decreasing loop lengths as electrons interact at shorter distances and we believe after the X-ray peak, the increasing loop corpulence.

  17. Loop quantization of vacuum Bianchi I cosmology

    SciTech Connect

    Martin-Benito, M.; Mena Marugan, G. A.; Pawlowski, T.

    2008-09-15

    We analyze the loop quantization of the family of vacuum Bianchi I spacetimes, a gravitational system of which classical solutions describe homogeneous anisotropic cosmologies. We rigorously construct the operator that represents the Hamiltonian constraint, showing that the states of zero volume completely decouple from the rest of quantum states. This fact ensures that the classical cosmological singularity is resolved in the quantum theory. In addition, this allows us to adopt an equivalent quantum description in terms of a well-defined densitized Hamiltonian constraint. This latter constraint can be regarded in a certain sense as a difference evolution equation in an internal time provided by one of the triad components, which is polymerically quantized. Generically, this evolution equation is a relation between the projection of the quantum states in three different sections of constant internal time. Nevertheless, around the initial singularity the equation involves only the two closest sections with the same orientation of the triad. This has a double effect: on the one hand, physical states are determined just by the data on one section, on the other hand, the evolution defined in this way never crosses the singularity, without the need of any special boundary condition. Finally, we determine the inner product and the physical Hilbert space employing group averaging techniques, and we specify a complete algebra of Dirac observables. This completes the quantization program.

  18. Quantum volume

    NASA Astrophysics Data System (ADS)

    Ryabov, V. A.

    2015-08-01

    Quantum systems in a mechanical embedding, the breathing mode of a small particles, optomechanical system, etc. are far not the full list of examples in which the volume exhibits quantum behavior. Traditional consideration suggests strain in small systems as a result of a collective movement of particles, rather than the dynamics of the volume as an independent variable. The aim of this work is to show that some problem here might be essentially simplified by introducing periodic boundary conditions. At this case, the volume is considered as the independent dynamical variable driven by the internal pressure. For this purpose, the concept of quantum volume based on Schrödinger’s equation in 𝕋3 manifold is proposed. It is used to explore several 1D model systems: An ensemble of free particles under external pressure, quantum manometer and a quantum breathing mode. In particular, the influence of the pressure of free particle on quantum oscillator is determined. It is shown also that correction to the spectrum of the breathing mode due to internal degrees of freedom is determined by the off-diagonal matrix elements of the quantum stress. The new treatment not using the “force” theorem is proposed for the quantum stress tensor. In the general case of flexible quantum 3D dynamics, quantum deformations of different type might be introduced similarly to monopole mode.

  19. Loop Virasoro Lie conformal algebra

    SciTech Connect

    Wu, Henan Chen, Qiufan; Yue, Xiaoqing

    2014-01-15

    The Lie conformal algebra of loop Virasoro algebra, denoted by CW, is introduced in this paper. Explicitly, CW is a Lie conformal algebra with C[∂]-basis (L{sub i} | i∈Z) and λ-brackets [L{sub i} {sub λ} L{sub j}] = (−∂−2λ)L{sub i+j}. Then conformal derivations of CW are determined. Finally, rank one conformal modules and Z-graded free intermediate series modules over CW are classified.

  20. Genericness of a big bounce in isotropic loop quantum cosmology.

    PubMed

    Date, Ghanashyam; Hossain, Golam Mortuza

    2005-01-14

    The absence of isotropic singularity in loop quantum cosmology can be understood in an effective classical description as the Universe exhibiting a big bounce. We show that with a scalar matter field, the big bounce is generic in the sense that it is independent of quantization ambiguities and the details of scalar field dynamics. The volume of the Universe at the bounce point is parametrized by a single parameter. It provides a minimum length scale which serves as a cutoff for computations of density perturbations thereby influencing their amplitudes. PMID:15698060

  1. Element-specific recoil loops in Sm-Co/Fe exchange-spring magnets.

    SciTech Connect

    Choi, Y.; Jiang, J. S.; Pearson, J. E.; Bader, S. D.; Liu, J. P.; Materials Science Division; Univ. Texas at Arlington

    2008-04-01

    In two-phase nanocomposite magnets, open recoil loops have shown to be sensitive to interphase interfacial conditions and have been often used to characterize the interphase exchange coupling. Typically, the open recoil loops are attributed to the soft phase volume that is decoupled from the hard phase. Our element-specific magnetic measurements on bilayer Sm-Co/Fe exchange-spring magnets reveal that open recoil loops are present not only in the soft Fe layer but also in the hard Sm-Co layer and that the Fe- and Sm-specific remanence curves are similar to each other. The experimental results and micromagnetic modeling reveal that the observed open recoil loops can originate from the anisotropy variations in the hard Sm-Co layer.

  2. Closed-Loop Neuroscience and Non-Invasive Brain Stimulation: A Tale of Two Loops.

    PubMed

    Zrenner, Christoph; Belardinelli, Paolo; Müller-Dahlhaus, Florian; Ziemann, Ulf

    2016-01-01

    Closed-loop neuroscience is receiving increasing attention with recent technological advances that enable complex feedback loops to be implemented with millisecond resolution on commodity hardware. We summarize emerging conceptual and methodological frameworks that are available to experimenters investigating a "brain in the loop" using non-invasive brain stimulation and briefly review the experimental and therapeutic implications. We take the view that closed-loop neuroscience in fact deals with two conceptually quite different loops: a "brain-state dynamics" loop, used to couple with and modulate the trajectory of neuronal activity patterns, and a "task dynamics" loop, that is the bidirectional motor-sensory interaction between brain and (simulated) environment, and which enables goal-directed behavioral tasks to be incorporated. Both loops need to be considered and combined to realize the full experimental and therapeutic potential of closed-loop neuroscience. PMID:27092055

  3. Thermal Analysis of CDS Coronal Loops

    NASA Astrophysics Data System (ADS)

    Kimble, J. A.; Schmelz, J. T.; Nasraoui, K.; Rightmire, L. A.; Andrews, J. M.; Cirtain, J. W.

    2008-05-01

    The coronal loop data used for this analysis was obtained using the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory on 2003 January 17 at 14:24:43 UT. We use the Chianti atomic physics database and the hybrid coronal abundances to determine temperatures and densities for positions along several loops. We chose six pixels along each loop as well as background pixels. The intensities of the background pixels are subtracted from each loop pixel to isolate the emission from the loop pixel, and then spectral lines with significant contributions to the loop intensities are selected. The loops were then analyzed with a forward folding process to produce differential emission measure (DEM) curves. Emission measure loci plots and DEM automatic inversions are then used to verify those conclusions. We find different results for each of these loops. One appears to be isothermal at each loop position, and the temperature does not change with height. The second appears to be multithermal at each position and the third seems to be consistent with two DEM spikes, which might indicate that there are two isothermal loops so close together, that they are not resolved by CDS. Solar physics research at the University of Memphis is supported by a Hinode subcontract from NASA/SAO as well as NSF ATM-0402729.

  4. Multidimensional smooth loops with universal elasticity

    NASA Astrophysics Data System (ADS)

    Dzhukashev, K. R.; Shelekhov, A. M.

    2015-05-01

    Let \\widetilde E be a universal (isotopically invariant) identity that is derived from the elasticity identity E\\colon (xy)x=x(yx). One of the authors has previously shown that a) each local loop of dimension r with identity \\widetilde E (briefly, a loop \\widetilde E) is a smooth middle Bol loop of dimension r; b) smooth two-dimensional loops \\widetilde E are Lie groups; c) up to isotopy, there exist only two three-dimensional loops \\widetilde E: the loops E_1 and E_2. In this paper, the loops E_1 and E_2 are extended to the multidimensional case. The fact that each smooth loop \\widetilde E of dimension r corresponds to a unique multidimensional three-web on a manifold of dimension 2r is key to our work. In addition, the class of loops under investigation is characterized by the fact that the torsion tensor of the corresponding web has rank 1 (that is, the algebra generated by this tensor has a one-dimensional derived algebra). This enables us to express the differential equations of the problem in an invariant form. The system of equations thus obtained was found to be amenable to integration in the most general case, and the equations of the required loops have been obtained in local coordinates. Bibliography: 17 titles.

  5. Extended loop representation of quantum gravity

    SciTech Connect

    Di Bartolo, C. ); Gambini, R.; Griego, J. )

    1995-01-15

    A new representation of quantum gravity is developed. This formulation is based on an extension of the group of loops. The enlarged group that we call the extended loop group behaves locally as an infinite dimensional Lie group. Quantum gravity can be realized on the state space of extended loop-dependent wave functions. The extended representation generalizes the loop representation and contains this representation as a particular case. The resulting diffeomorphism and Hamiltonian constraints take a very simple form and allow us to apply functional methods and simplify the loop calculus. In particular we show that the constraints are linear in the momenta. The nondegenerate solutions known in the loop representation are also solutions of the constraints in the new representation. An approach to the regularization problems associated with the formal calculus is performed. We show that the solutions are generalized knot invariants, smooth in the extended variables, and any framing is unnecessary.

  6. Magnetic monopole in the loop representation

    SciTech Connect

    Leal, Lorenzo; Lopez, Alexander

    2006-01-15

    We quantize, within the Loop Representation formalism, the electromagnetic field in the presence of a static magnetic pole. It is found that the loop-dependent physical wave functionals of the quantum Maxwell theory become multivalued, through a topological phase factor depending on the solid angle subtended at the monopole by a surface bounded by the loop. It is discussed how this fact generalizes what occurs in ordinary quantum mechanics in multiply connected spaces.

  7. Biopolymer hairpin loops sustained by polarons

    NASA Astrophysics Data System (ADS)

    Chakrabarti, B.; Piette, B. M. A. G.; Zakrzewski, W. J.

    2012-08-01

    We show that polarons can sustain looplike configurations in flexible biopolymers and that the size of the loops depend on both the flexural rigidity of the polymer and the electron-phonon coupling constant. In particular we show that for single stranded DNA (ssDNA) and polyacetylene such loops can have as few as seven monomers. We also show that these configurations are very stable under thermal fluctuations and so could facilitate the formation of hairpin loops of ssDNA.

  8. LMFBR with booster pump in pumping loop

    DOEpatents

    Rubinstein, H.J.

    1975-10-14

    A loop coolant circulation system is described for a liquid metal fast breeder reactor (LMFBR) utilizing a low head, high specific speed booster pump in the hot leg of the coolant loop with the main pump located in the cold leg of the loop, thereby providing the advantages of operating the main pump in the hot leg with the reliability of cold leg pump operation.

  9. Loop anomalies in the causal approach

    NASA Astrophysics Data System (ADS)

    Grigore, Dan-Radu

    2015-01-01

    We consider gauge models in the causal approach and study one-loop contributions to the chronological products and the anomalies they produce. We prove that in order greater than 4 there are no one-loop anomalies. Next we analyze one-loop anomalies in the second- and third-order of the perturbation theory. We prove that the even parity contributions (with respect to parity) do not produce anomalies; for the odd parity contributions we reobtain the well-known result.

  10. [Multilevel revascularization of the lower extremities using loop endarterectomy].

    PubMed

    Losev, R Z; Burov, Iu A; Mikul'skaia, E G; Eliseev, A A; Bogdanova, N B; Skriabin, V V

    2006-01-01

    Results of 91 reconstructions of the ilio-femoro-popliteal segment in patients with multilevel injuries of the lower extremity arteries were analyzed. In 42 of the operations a method of operations associated with loop endarterectomy was used. The first stage in all the patients consisted of iliac deep femoral reconstructions or semi-closed loop endarterectomy from iliac arteries in order for inclusion in blood flow of the profound femoral artery. In the presence of the volumetric blood flow along the profound femoral artery less than 150 ml/min after the first stage of revascularization the operation volume was extended at the expense of the femoro-distal reconstructions and/or semi-closed loop endarterectomy from the femoral and popliteal arteries. It was found that revascularization of the ilio-femoral segment in combination with desobliteration of the popliteal artery allowed performing two-level reconstructions with little time and material costs followed by primary positive results in 92.9% of cases. PMID:17315682

  11. Genomic looping: a key principle of chromatin organization.

    PubMed

    van der Valk, Ramon A; Vreede, Jocelyne; Crémazy, Frédéric; Dame, Remus T

    2014-01-01

    The effective volume occupied by the genomes of all forms of life far exceeds that of the cells in which they are contained. Therefore, all organisms have developed mechanisms for compactly folding and functionally organizing their genetic material. Through recent advances in fluorescent microscopy and 3C-based technologies, we finally have a first glimpse into the complex mechanisms governing the 3-D folding of genomes. A key feature of genome organization in all domains of life is the formation of DNA loops. Here, we describe the main players in DNA organization with a focus on DNA-bridging proteins. Specifically, we discuss the properties of the bacterial DNA-bridging protein H-NS. Via two different modes of binding to DNA, this protein is a key driver of bacterial genome organization and provides a link between 3-D organization and transcription regulation. Importantly, H-NS function is modulated in response to environmental cues, which are translated into adapted gene expression patterns. We delve into the mechanisms underlying DNA looping and explore the complex and subtle modulation of these diverse, yet difficult-to-study, structures. DNA looping is universal and a conserved mechanism of genome organization throughout all domains of life. PMID:25732337

  12. Duality relation between radiation thermodynamics and cosmic string loop thermodynamics

    SciTech Connect

    Jou, D.; Mongiovi, M. S.; Sciacca, M.

    2011-05-15

    We discuss thermodynamics of electromagnetic radiation, with p=(1/3){rho} and S{proportional_to}T{sup 3}V, and of cosmic string loops, with p=-(1/3){rho} and S{proportional_to}T{sup -3}V, where p stands for pressure, T temperature, {rho} energy density, S entropy, and V volume. We write the thermodynamic formalisms under a common framework that illustrates their formal relationship and allows us to go from one to the other through a smooth transformation. From a microscopic perspective, these relations arise from the energy relations u({lambda})=hc/{lambda} for the photons of electromagnetic radiation, and u(l)=(c{sup 4}/a{sup 2}G)l for cosmic string loops, a being a numerical (dimensionless) constant and {lambda} and l the radiation wavelength and the length of a loop; G, c, and h are the gravitational constant, the speed of light in vacuo, and the Planck constant, respectively. The corresponding thermodynamic behaviors are seen to be connected through a related thermal duality corresponding to the change of T by T*=T{sub c}{sup 2}/T, with T{sub c} a reference temperature related to h, c, and G.

  13. Binary phase locked loops for Omega receivers

    NASA Technical Reports Server (NTRS)

    Chamberlin, K.

    1974-01-01

    An all-digital phase lock loop (PLL) is considered because of a number of problems inherent in an employment of analog PLL. The digital PLL design presented solves these problems. A single loop measures all eight Omega time slots. Memory-aiding leads to the name of this design, the memory-aided phase lock loop (MAPLL). Basic operating principles are discussed and the superiority of MAPLL over the conventional digital phase lock loop with regard to the operational efficiency for Omega applications is demonstrated.

  14. Loop statistics in polymers in crowded environment

    NASA Astrophysics Data System (ADS)

    Haydukivska, K.; Blavatska, V.

    2016-02-01

    We analyze the probability to find a single loop in a long flexible polymer chain in disordered environment in d dimensions. The structural defects are considered to be correlated on large distances r according to a power law ˜r-a. Working within the frames of continuous chain model and applying the direct polymer renormalization scheme, we obtain the values of critical exponents governing the scaling of probabilities to find the loops of various positions along the chain as function of loops' length. Our results quantitatively reveal that the presence of structural defects in environment decreases the probability of loop formation in polymer macromolecules.

  15. Multi-instrument observations of coronal loops

    NASA Astrophysics Data System (ADS)

    Scott, Jason Terrence

    This document exhibits results of analysis from data collected with multiple EUV satellites (SOHO, TRACE, STEREO, Hinode, and SDO). The focus is the detailed observation of coronal loops using multiple instruments, i.e. filter imagers and spectrometers. Techniques for comparing the different instruments and deriving loop parameters are demonstrated. Attention is given to the effects the different instruments may introduce into the data and their interpretation. The assembled loop parameters are compared to basic energy balance equations and scaling laws. Discussion of the blue-shifted, asymmetric, and line broadened spectral line profiles near the footpoints of coronal loops is made. The first quantitative analysis of the anti-correlation between intensity and spectral line broadening for isolated regions along loops and their footpoints is presented. A magnetic model of an active region shows where the separatrices meet the photospheric boundary. At the boundary, the spectral data reveal concentrated regions of increased blue-shifted outflows, blue wing asymmetry, and line broadening. This is found just outside the footpoints of bright loops. The intensity and line broadening in this region are anti-correlated. A comparison of the similarities in the spectroscopic structure near the footpoints of the arcade loops and more isolated loops suggests the notion of consistent structuring for the bright loops forming an apparent edge of an active region core.

  16. Interference Lattice-based Loop Nest Tilings for Stencil Computations

    NASA Technical Reports Server (NTRS)

    VanderWijngaart, Rob F.; Frumkin, Michael

    2000-01-01

    adjacent tiles are visited successively, there will be no replacement misses on the shared boundary. The iteration space may be covered with pencils larger than the size of the cache while avoiding data conflicts if the pencils are traversed by a scanning-face method. Replacement misses are incurred only on the boundaries of the pencils, and the number of misses is minimized by maximizing the volume of the scanning face, not the volume of the tile. We present an algorithm for constructing the most efficient scanning face for a given grid and stencil operator. In two dimensions it is based on a continued fraction algorithm. In three dimensions it follows Voronoi's successive minima algorithm. We show experimental results of using the scanning face, and compare with canonical loop orderings.

  17. Closed-Loop Neuroscience and Non-Invasive Brain Stimulation: A Tale of Two Loops

    PubMed Central

    Zrenner, Christoph; Belardinelli, Paolo; Müller-Dahlhaus, Florian; Ziemann, Ulf

    2016-01-01

    Closed-loop neuroscience is receiving increasing attention with recent technological advances that enable complex feedback loops to be implemented with millisecond resolution on commodity hardware. We summarize emerging conceptual and methodological frameworks that are available to experimenters investigating a “brain in the loop” using non-invasive brain stimulation and briefly review the experimental and therapeutic implications. We take the view that closed-loop neuroscience in fact deals with two conceptually quite different loops: a “brain-state dynamics” loop, used to couple with and modulate the trajectory of neuronal activity patterns, and a “task dynamics” loop, that is the bidirectional motor-sensory interaction between brain and (simulated) environment, and which enables goal-directed behavioral tasks to be incorporated. Both loops need to be considered and combined to realize the full experimental and therapeutic potential of closed-loop neuroscience. PMID:27092055

  18. UWB communication receiver feedback loop

    DOEpatents

    Spiridon, Alex; Benzel, Dave; Dowla, Farid U.; Nekoogar, Faranak; Rosenbury, Erwin T.

    2007-12-04

    A novel technique and structure that maximizes the extraction of information from reference pulses for UWB-TR receivers is introduced. The scheme efficiently processes an incoming signal to suppress different types of UWB as well as non-UWB interference prior to signal detection. Such a method and system adds a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. Moreover, sampling the second order statistical function such as, for example, the autocorrelation function (ACF) of the received signal and matching it to the ACF samples of the original pulses for each transmitted bit provides a more robust UWB communications method and system in the presence of channel distortions.

  19. Closed loop steam cooled airfoil

    SciTech Connect

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  20. Delay locked loop integrated circuit.

    SciTech Connect

    Brocato, Robert Wesley

    2007-10-01

    This report gives a description of the development of a Delay Locked Loop (DLL) integrated circuit (IC). The DLL was developed and tested as a stand-alone IC test chip to be integrated into a larger application specific integrated circuit (ASIC), the Quadrature Digital Waveform Synthesizer (QDWS). The purpose of the DLL is to provide a digitally programmable delay to enable synchronization between an internal system clock and external peripherals with unknown clock skew. The DLL was designed and fabricated in the IBM 8RF process, a 0.13 {micro}m CMOS process. It was designed to operate with a 300MHz clock and has been tested up to 500MHz.

  1. Closing the loop with blur

    NASA Astrophysics Data System (ADS)

    Tani, Jacopo

    A great variety of systems use image sensors to provide measurements for closed loop operation. A drawback of using image sensors in real-time feedback is that they provide measurements at slower sampling rates as compared to the actuators, typically around 30 Hz for CCD cameras, hence acting as the bottleneck for closed loop control bandwidths. While high speed cameras exist, higher frame rates imply an upper bound on exposures which lowers the signal-to-noise-ratio (SNR), reducing measurements accuracy. The integrative nature of image sensors though offers the opportunity to prolong the exposure window and collect motion blurred measurements. This research describes how to exploit the dynamic information of observed system outputs, encoded in motion blur, to control fast systems at the fast rate through slow rate image sensors. In order to achieve this objective it is necessary to (a) design a controller providing fast rate input to the system based on the slow image measurements. Ideally such a controller would require a fast rate estimate of the system's state variables in order to provide the necessary control action, therefore an (b) image blur based estimator is to be developed. State estimators typically need a model of the system in order to provide their estimates, so (c) a system identification problem has to be addressed, where a reliable model describing the frequency content of the system, up to frequencies corresponding to the fast rate, has to be determined through slow rate image sensor measurements. Alternatively when such a procedure is not possible for lack, e.g., of knowledge of the input to the system, then (d) a method to reconstruct the output signal frequency content up to frequencies above those set by the limitations of the sampling theorem is to be devised. Therefore in order to "close the loop with blur", this work describes how to pose and solve the problems of, namely: system identification , state estimation, closed loop control and

  2. Three-loop cusp anomalous dimension and a conjecture for n loops

    NASA Astrophysics Data System (ADS)

    Kidonakis, Nikolaos

    2016-05-01

    I present analytical expressions for the massive cusp anomalous dimension in QCD through three loops, first calculated in 2014, in terms of elementary functions and ordinary polylogarithms. I observe interesting relations between the results at different loops and provide a conjecture for the n-loop cusp anomalous dimension in terms of the lower-loop results. I also present numerical results and simple approximate formulas for the cusp anomalous dimension relevant to top-quark production.

  3. Dihedral-like constructions of automorphic loops

    NASA Astrophysics Data System (ADS)

    Aboras, Mouna

    In this dissertation we study dihedral-like constructions of automorphic loops. Automorphic loops are loops in which all inner mappings are automorphisms. We start by describing a generalization of the dihedral construction for groups. Namely, if (G, +) is an abelian group, m > 1 and alpha ∈2 Aut(G), let Dih(m, G, alpha) on Zm x G be defined by. (i, u)(j, v) = (i + j, ((--1)ju + v)alpha ij). We prove that the resulting loop is automorphic if and only if m = 2 or (alpha2 = 1 and m is even) or (m is odd, alpha = 1 and exp(G) ≤ 2). In the last case, the loop is a group. The case m = 2 was introduced by Kinyon, Kunen, Phillips, and Vojtechovsky. We study basic structural properties of dihedral-like automorphic loops. We describe certain subloops, including: nucleus, commutant, center, associator subloop and derived subloop. We prove theorems for dihedral-like automorphic loops analogous to the Cauchy and Lagrange theorems for groups, and further we discuss the coset decomposition in dihedral-like automorphic loops. We show that two finite dihedral-like automorphic loops Dih( m, G, alpha) and Dih(m¯, G¯, [special character omitted]) are isomorphic if and only if m = m¯, G ≅ G¯ and alpha is conjugate to [special character omitted] in Aut(G). We describe the automorphism group of Q and its subgroup consisting of inner mappings of Q. Finally, due to the solution to the isomorphism problem, we are interested in studying conjugacy classes of automorphism groups of finite abelian groups. Then we describe all dihedral-like automorphic loops of order < 128 up to isomorphism. We conclude with a description of all dihedral-like automorphic loops of order < 64 up to isotopism.

  4. Magnetic loop emergence within a granule

    NASA Astrophysics Data System (ADS)

    Gömöry, P.; Beck, C.; Balthasar, H.; Rybák, J.; Kučera, A.; Koza, J.; Wöhl, H.

    2010-02-01

    Aims: We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center. Methods: We combined IR spectropolarimetry of high angular resolution performed in two Fe i lines at 1565 nm with speckle-reconstructed G-band imaging. We determined the magnetic field parameters by a LTE inversion of the full Stokes vector using the SIR code, and followed their evolution in time. To interpret the observations, we created a geometrical model of a rising loop in 3D. The relevant parameters of the loop were matched to the observations where possible. We then synthesized spectra from the 3D model for a comparison to the observations. Results: We found signatures of magnetic flux emergence within a growing granule. In the early phases, a horizontal magnetic field with a distinct linear polarization signal dominated the emerging flux. Later on, two patches of opposite circular polarization signal appeared symmetrically on either side of the linear polarization patch, indicating a small loop-like structure. The mean magnetic flux density of this loop was roughly 450 G, with a total magnetic flux of around 3 × 1017 Mx. During the ~12 min episode of loop occurrence, the spatial extent of the loop increased from about 1 to 2 arcsec. The middle part of the appearing feature was blueshifted during its occurrence, supporting the scenario of an emerging loop. There is also clear evidence for the interaction of one loop footpoint with a preexisting magnetic structure of opposite polarity. The temporal evolution of the observed spectra is reproduced to first order by the spectra derived from the geometrical model. During the phase of clearest visibility of the loop in the observations, the observed and synthetic spectra match quantitatively. Conclusions: The observed event can be explained as a case of flux emergence in the shape of a small-scale loop. The fast disappearance of the loop at the end could possibly be due to magnetic

  5. QCD at zero baryon density and the Polyakov loop paradox

    SciTech Connect

    Kratochvila, Slavo; Forcrand, Philippe de

    2006-06-01

    We compare the grand-canonical partition function at fixed chemical potential {mu} with the canonical partition function at fixed baryon number B, formally and by numerical simulations at {mu}=0 and B=0 with four flavors of staggered quarks. We verify that the free energy densities are equal in the thermodynamic limit, and show that they can be well described by the hadron resonance gas at TT{sub c}. Small differences between the two ensembles, for thermodynamic observables characterizing the deconfinement phase transition, vanish with increasing lattice size. These differences are solely caused by contributions of nonzero baryon density sectors, which are exponentially suppressed with increasing volume. The Polyakov loop shows a different behavior: for all temperatures and volumes, its expectation value is exactly zero in the canonical formulation, whereas it is always nonzero in the commonly used grand-canonical formulation. We clarify this paradoxical difference, and show that the nonvanishing Polyakov loop expectation value is due to contributions of nonzero triality states, which are not physical, because they give zero contribution to the partition function.

  6. Quantitation of interactions between two DNA loops demonstrates loop domain insulation in E. coli cells.

    PubMed

    Priest, David G; Kumar, Sandip; Yan, Yan; Dunlap, David D; Dodd, Ian B; Shearwin, Keith E

    2014-10-21

    Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loops--that aid or inhibit enhancer-promoter contact--are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage λ CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each other's formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each other's formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions. PMID:25288735

  7. High dynamic, low volume GPS receiver

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.

    1983-01-01

    A new GPS receiver concept and design are presented to meet the high dynamic and low volume requirements for range applications in missiles and drones. The receiver has the potential to satisfy all range requirements with one basic receiver, which has significant potential economic benefit over the alternate approach of using a family of receivers, each tailored for specific applications. The main new concept is to use approximate maximum likelihood estimates of pseudo range and range-rate, rather than tracking with carrier phase locked loops and code delay locked loops. Preliminary analysis indicates that receivers accelerating at 50 g or more can track with position errors due to acceleration of approximately 0.2 m/g, or 10 m at 50 g. Implementation is almost entirely digital to meet the low volume requirements.

  8. Loop calculus for lattice gauge theories

    SciTech Connect

    Gambini, R.; Leal, L.; Trias, A.

    1989-05-15

    Hamiltonian calculations are performed using a loop-labeled basis where the full set of identities for the SU(/ital N/) gauge models has been incorporated. The loops are classified as clusterlike structures and the eigenvalue problem leads to a linear set of finite-difference equations easily amenable to numerical treatment. Encouraging results are reported for SU(2) at spatial dimension 2.

  9. Feedback loop compensates for rectifier nonlinearity

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Signal processing circuit with two negative feedback loops rectifies two sinusoidal signals which are 180 degrees out of phase and produces a single full-wave rectified output signal. Each feedback loop incorporates a feedback rectifier to compensate for the nonlinearity of the circuit.

  10. The Cygnus Loop: An Older Supernova Remnant.

    ERIC Educational Resources Information Center

    Straka, William

    1987-01-01

    Describes the Cygnus Loop, one of brightest and most easily studied of the older "remnant nebulae" of supernova outbursts. Discusses some of the historical events surrounding the discovery and measurement of the Cygnus Loop and makes some projections on its future. (TW)

  11. Loop polymer brushes from polymer single crystals

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Li, Christopher

    2014-03-01

    Loop polymer brushes represent a category of polymer brushes with both chain ends being tethered to a surface or interface with sufficiently high density. Due to this morphological difference, loop brushes exhibit distinct properties compared with traditional polymer brushes with single chain end being tethered. In our study, α, ω-functionalized polycaprolactone (PCL) single crystals were prepared as templates for polymer brush synthesis. By carefully controlling crystallization condition and immobilization, looped polymer brushes were successfully prepared. Comprehensive studies on the morphology and physical properties of these polymer brushes were carried out using Atomic Force Microscopy and FTIR. Advantages of using this method include exclusive loop morphology, high grafting density, controlled tethering sites and tunable loop size.

  12. Transient brightenings of interconnecting loops. II - Dynamics of the brightened loops

    NASA Technical Reports Server (NTRS)

    Svestka, Z.; Howard, R.

    1981-01-01

    Three different kinds of dynamic events related to interconnecting loops observed in soft X-rays aboard Skylab are discussed: (1) a newly born transequatorial loop that was either emerging from subphotospheric layers or gradually filled in with hot plasma; (2) large-scale twists of interconnecting loops which never relax, and often only form after the loop brightenings, and (3) three events where the loop that later interconnected two active regions had been visible long before one of the interconnecting regions was born. Several impacts this observation might have upon the understanding of the process of flux emergence are suggested.

  13. A communication scheme for the distrubted execution of loop nests with while loops

    SciTech Connect

    Griebl, M.; Lengauer, C.

    1995-10-01

    The mathematical model for the parallelization, or {open_quotes}space-time mapping,{close_quotes} of loop nests is the polyhedron model. The presence of while loops in the nest complicates matters for two reasons: (1) the parallelized loop nest does not correspond to a polyhedron but instead to a subset that resembles a (multi-dimensional) comb and (2) it is not clear when the entire loop nest has terminated. We describe a communication scheme which can deal with both problems and which can be added to the parallel target loop nest by a compiler.

  14. Loop heat pipes and capillary pumped loops-an applications perspective

    NASA Astrophysics Data System (ADS)

    Butler, Dan; Ku, Jentung; Swanson, Theodore

    2002-01-01

    Capillary pumped loops (CPLs) and loop heat pipes (LHPs) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed. .

  15. Multiple volume compressor for hot gas engine

    DOEpatents

    Stotts, Robert E.

    1986-01-01

    A multiple volume compressor for use in a hot gas (Stirling) engine having a plurality of different volume chambers arranged to pump down the engine when decreased power is called for and return the working gas to a storage tank or reservoir. A valve actuated bypass loop is placed over each chamber which can be opened to return gas discharged from the chamber back to the inlet thereto. By selectively actuating the bypass valves, a number of different compressor capacities can be attained without changing compressor speed whereby the capacity of the compressor can be matched to the power available from the engine which is used to drive the compressor.

  16. Cygnus Loop Supernova Blast Wave

    NASA Technical Reports Server (NTRS)

    1993-01-01

    This is an image of a small portion of the Cygnus Loop supernova remnant, which marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion, occurring about 15,000 years ago. The HST image shows the structure behind the shock waves, allowing astronomers for the first time to directly compare the actual structure of the shock with theoretical model calculations. Besides supernova remnants, these shock models are important in understanding a wide range of astrophysical phenomena, from winds in newly-formed stars to cataclysmic stellar outbursts. The supernova blast is slamming into tenuous clouds of insterstellar gas. This collision heats and compresses the gas, causing it to glow. The shock thus acts as a searchlight revealing the structure of the interstellar medium. The detailed HST image shows the blast wave overrunning dense clumps of gas, which despite HST's high resolution, cannot be resolved. This means that the clumps of gas must be small enough to fit inside our solar system, making them relatively small structures by interstellar standards. A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova; this interstellar 'bullet' traveling over three million miles per hour (5 million kilometres) is just catching up with the shock front, which has slowed down by ploughing into interstellar material. The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full Moon), located in the northern constellation, Cygnus the Swan. The supernova remnant is within the plane of our Milky Way galaxy and is 2,600 light-years away. The photo is a combination of separate images taken in three colors, oxygen atoms (blue) emit light at temperatures of 30,000 to 60,000 degrees Celsius (50,000 to 100,000 degrees Farenheit). Hydrogen atoms (green) arise throughout the region of shocked gas. Sulfur atoms (red) form when the gas cools to

  17. Quantitation of interactions between two DNA loops demonstrates loop domain insulation in E. coli cells

    PubMed Central

    Priest, David G.; Kumar, Sandip; Yan, Yan; Dunlap, David D.; Dodd, Ian B.; Shearwin, Keith E.

    2014-01-01

    Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loops—that aid or inhibit enhancer–promoter contact—are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage λ CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each other’s formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each other’s formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions. PMID:25288735

  18. Towards conformal loop quantum gravity

    NASA Astrophysics Data System (ADS)

    H-T Wang, Charles

    2006-03-01

    A discussion is given of recent developments in canonical gravity that assimilates the conformal analysis of gravitational degrees of freedom. The work is motivated by the problem of time in quantum gravity and is carried out at the metric and the triad levels. At the metric level, it is shown that by extending the Arnowitt-Deser-Misner (ADM) phase space of general relativity (GR), a conformal form of geometrodynamics can be constructed. In addition to the Hamiltonian and Diffeomorphism constraints, an extra first class constraint is introduced to generate conformal transformations. This phase space consists of York's mean extrinsic curvature time, conformal three-metric and their momenta. At the triad level, the phase space of GR is further enlarged by incorporating spin-gauge as well as conformal symmetries. This leads to a canonical formulation of GR using a new set of real spin connection variables. The resulting gravitational constraints are first class, consisting of the Hamiltonian constraint and the canonical generators for spin-gauge and conformorphism transformations. The formulation has a remarkable feature of being parameter-free. Indeed, it is shown that a conformal parameter of the Barbero-Immirzi type can be absorbed by the conformal symmetry of the extended phase space. This gives rise to an alternative approach to loop quantum gravity that addresses both the conceptual problem of time and the technical problem of functional calculus in quantum gravity.

  19. Direct Demonstration That Loop1 of Scap Binds to Loop7: A CRUCIAL EVENT IN CHOLESTEROL HOMEOSTASIS.

    PubMed

    Zhang, Yinxin; Lee, Kwang Min; Kinch, Lisa N; Clark, Lindsay; Grishin, Nick V; Rosenbaum, Daniel M; Brown, Michael S; Goldstein, Joseph L; Radhakrishnan, Arun

    2016-06-10

    Cholesterol homeostasis is mediated by Scap, a polytopic endoplasmic reticulum (ER) protein that transports sterol regulatory element-binding proteins from the ER to Golgi, where they are processed to forms that activate cholesterol synthesis. Scap has eight transmembrane helices and two large luminal loops, designated Loop1 and Loop7. We earlier provided indirect evidence that Loop1 binds to Loop7, allowing Scap to bind COPII proteins for transport in coated vesicles. When ER cholesterol rises, it binds to Loop1. We hypothesized that this causes dissociation from Loop7, abrogating COPII binding. Here we demonstrate direct binding of the two loops when expressed as isolated fragments or as a fusion protein. Expressed alone, Loop1 remained intracellular and membrane-bound. When Loop7 was co-expressed, it bound to Loop1, and the soluble complex was secreted. A Loop1-Loop7 fusion protein was also secreted, and the two loops remained bound when the linker between them was cleaved by a protease. Point mutations that disrupt the Loop1-Loop7 interaction prevented secretion of the Loop1-Loop7 fusion protein. These data provide direct documentation of intramolecular Loop1-Loop7 binding, a central event in cholesterol homeostasis. PMID:27068746

  20. Mitotic chromosome compaction via active loop extrusion

    NASA Astrophysics Data System (ADS)

    Goloborodko, Anton; Imakaev, Maxim; Marko, John; Mirny, Leonid; MIT-Northwestern Team

    During cell division, two copies of each chromosome are segregated from each other and compacted more than hundred-fold into the canonical X-shaped structures. According to earlier microscopic observations and the recent Hi-C study, chromosomes are compacted into arrays of consecutive loops of ~100 kilobases. Mechanisms that lead to formation of such loop arrays are largely unknown. Here we propose that, during cell division, chromosomes can be compacted by enzymes that extrude loops on chromatin fibers. First, we use computer simulations and analytical modeling to show that a system of loop-extruding enzymes on a chromatin fiber self-organizes into an array of consecutive dynamic loops. Second, we model the process of loop extrusion in 3D and show that, coupled with the topo II strand-passing activity, it leads to robust compaction and segregation of sister chromatids. This mechanism of chromosomal condensation and segregation does not require additional proteins or specific DNA markup and is robust against variations in the number and properties of such loop extruding enzymes. Work at NU was supported by the NSF through Grants DMR-1206868 and MCB-1022117, and by the NIH through Grants GM105847 and CA193419. Work at MIT was supported by the NIH through Grants GM114190 R01HG003143.

  1. Direct Volume Rendering of Curvilinear Volumes

    NASA Technical Reports Server (NTRS)

    Vaziri, Arsi; Wilhelms, J.; Challinger, J.; Alper, N.; Ramamoorthy, S.; Kutler, Paul (Technical Monitor)

    1998-01-01

    Direct volume rendering can visualize sampled 3D scalar data as a continuous medium, or extract features. However, it is generally slow. Furthermore, most algorithms for direct volume rendering have assumed rectilinear gridded data. This paper discusses methods for using direct volume rendering when the original volume is curvilinear, i.e. is divided into six-sided cells which are not necessarily equilateral hexahedra. One approach is to ray-cast such volumes directly. An alternative approach is to interpolate the sample volumes to a rectilinear grid, and use this regular volume for rendering. Advantages and disadvantages of the two approaches in terms of speed and image quality are explored.

  2. The ionospheric outflow feedback loop

    NASA Astrophysics Data System (ADS)

    Moore, T. E.; Fok, M.-C.; Garcia-Sage, K.

    2014-08-01

    Following a long period of observation and investigation beginning in the early 1970s, it has been firmly established that Earth's magnetosphere is defined as much by the geogenic plasma within it as by the geomagnetic field. This plasma is not confined to the ionosphere proper, defined as the region within a few density scale heights of the F-region plasma density peak. Rather, it fills the flux tubes on which it is created, and circulates throughout the magnetosphere in a pattern driven by solar wind plasma that becomes magnetically connected to the ionosphere by reconnection through the dayside magnetopause. Under certain solar wind conditions, plasma and field energy is stored in the magnetotail rather than being smoothly recirculated back to the dayside. Its release into the downstream solar wind is produced by magnetotail disconnection of stored plasma and fields both continuously and in the form of discrete plasmoids, with associated generation of energetic Earthward-moving bursty bulk flows and injection fronts. A new generation of global circulation models is showing us that outflowing ionospheric plasmas, especially O+, load the system in a different way than the resistive F-region load of currents dissipating energy in the plasma and atmospheric neutral gas. The extended ionospheric load is reactive to the primary dissipation, forming a time-delayed feedback loop within the system. That sets up or intensifies bursty transient behaviors that would be weaker or absent if the ionosphere did not “strike back” when stimulated. Understanding this response appears to be a necessary, if not sufficient, condition for us to gain accurate predictive capability for space weather. However, full predictive understanding of outflow and incorporation into global simulations requires a clear observational and theoretical identification of the causal mechanisms of the outflows. This remains elusive and requires a dedicated mission effort.

  3. Open-loop digital frequency multiplier

    NASA Technical Reports Server (NTRS)

    Moore, R. C.

    1977-01-01

    Monostable multivibrator is implemented by using digital integrated circuits where multiplier constant is too large for conventional phase-locked-loop integrated circuit. A 400 Hz clock is generated by divide-by-N counter from 1 Hz timing reference.

  4. The universal one-loop effective action

    NASA Astrophysics Data System (ADS)

    Drozd, Aleksandra; Ellis, John; Quevillon, Jérémie; You, Tevong

    2016-03-01

    We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.

  5. Loop Diuretics in the Treatment of Hypertension.

    PubMed

    Malha, Line; Mann, Samuel J

    2016-04-01

    Loop diuretics are not recommended in current hypertension guidelines largely due to the lack of outcome data. Nevertheless, they have been shown to lower blood pressure and to offer potential advantages over thiazide-type diuretics. Torsemide offers advantages of longer duration of action and once daily dosing (vs. furosemide and bumetanide) and more reliable bioavailability (vs. furosemide). Studies show that the previously employed high doses of thiazide-type diuretics lower BP more than furosemide. Loop diuretics appear to have a preferable side effect profile (less hyponatremia, hypokalemia, and possibly less glucose intolerance). Studies comparing efficacy and side effect profiles of loop diuretics with the lower, currently widely prescribed, thiazide doses are needed. Research is needed to fill gaps in knowledge and common misconceptions about loop diuretic use in hypertension and to determine their rightful place in the antihypertensive arsenal. PMID:26951244

  6. Mathematical Modeling of Loop Heat Pipes

    NASA Technical Reports Server (NTRS)

    Kaya, Tarik; Ku, Jentung; Hoang, Triem T.; Cheung, Mark L.

    1998-01-01

    The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.

  7. A magnetohydrodynamic theory of coronal loop transients

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1982-01-01

    The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.

  8. A multiple-pass ring oscillator based dual-loop phase-locked loop

    NASA Astrophysics Data System (ADS)

    Danfeng, Chen; Junyan, Ren; Jingjing, Deng; Wei, Li; Ning, Li

    2009-10-01

    A dual-loop phase-locked loop (PLL) for wideband operation is proposed. The dual-loop architecture combines a coarse-tuning loop with a fine-tuning one, enabling a wide tuning range and low voltage-controlled oscillator (VCO) gain without poisoning phase noise and reference spur suppression performance. An analysis of the phase noise and reference spur of the dual-loop PLL is emphasized. A novel multiple-pass ring VCO is designed for the dual-loop application. It utilizes both voltage-control and current-control simultaneously in the delay cell. The PLL is fabricated in Jazz 0.18-μm RF CMOS technology. The measured tuning range is from 4.2 to 5.9 GHz. It achieves a low phase noise of -99 dBc/Hz @ 1 MHz offset from a 5.5 GHz carrier.

  9. Thermal and non-thermal emission from reconnecting twisted coronal loops

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Gordovskyy, M.; Browning, P. K.; Vilmer, N.

    2016-01-01

    Context. Twisted magnetic fields should be ubiquitous in the solar corona, particularly in flare-producing active regions where the magnetic fields are strongly non-potential. The magnetic energy contained in such twisted fields can be released during solar flares and other explosive phenomena. It has recently been shown that reconnection in helical magnetic coronal loops results in plasma heating and particle acceleration distributed within a large volume, including the lower coronal and chromospheric sections of the loops. Hence, the magnetic reconnection and particle acceleration scenario involving magnetic helicity can be a viable alternative to the standard flare model, where particles are accelerated only in a small volume located in the upper corona. Aims: The key goal of this study is to investigate the links and observational signatures of plasma heating and particle acceleration in kink-unstable twisted coronal loops. Methods: We used a combination of magnetohydrodynamic (MHD) simulations and test-particle methods. These simulations describe the development of kink instability and magnetic reconnection in twisted coronal loops using resistive compressible MHD and incorporate atmospheric stratification and large-scale loop curvature. The resulting distributions of hot plasma let us estimate thermal X-ray emission intensities. With the electric and magnetic fields we obtained, we calculated electron trajectories using the guiding-centre approximation. These trajectories combined with the MHD plasma density distributions let us deduce synthetic hard X-ray bremsstrahlung intensities. Results: Our simulations emphasise that the geometry of the emission patterns produced by hot plasma in flaring twisted coronal loops can differ from the actual geometry of the underlying magnetic fields. In particular, the twist angles revealed by the emission threads (soft X-ray thermal emission; SXR) are consistently lower than the field-line twist present at the onset of the

  10. Loop quantum cosmology in 2 +1 dimension

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong

    2014-12-01

    As a first step to generalize the structure of loop quantum cosmology to the theories with the spacetime dimension other than four, the isotropic model of loop quantum cosmology in 2 +1 dimension is studied in this paper. We find that the classical big bang singularity is again replaced by a quantum bounce in the model. The similarities and differences between the (2 +1 )-dimensional model and the (3 +1 )-dimensional one are also discussed.

  11. Onset of inflation in loop quantum cosmology

    SciTech Connect

    Germani, Cristiano; Nelson, William; Sakellariadou, Mairi

    2007-08-15

    Using a Liouville measure, similar to the one proposed recently by Gibbons and Turok, we investigate the probability that single-field inflation with a polynomial potential can last long enough to solve the shortcomings of the standard hot big bang model, within the semiclassical regime of loop quantum cosmology. We conclude that, for such a class of inflationary models and for natural values of the loop quantum cosmology parameters, a successful inflationary scenario is highly improbable.

  12. Deployable radiator with flexible line loop

    NASA Technical Reports Server (NTRS)

    Keeler, Bryan V. (Inventor); Lehtinen, Arthur Mathias (Inventor); McGee, Billy W. (Inventor)

    2003-01-01

    Radiator assembly (10) for use on a spacecraft (12) is provided including at least one radiator panel assembly (26) repeatably movable between a panel stowed position (28) and a panel deployed position (36), at least two flexible lines (40) in fluid communication with the at least one radiator panel assembly (26) and repeatably movable between a stowage loop (42) and a flattened deployed loop (44).

  13. Bonus symmetry for super Wilson loops

    NASA Astrophysics Data System (ADS)

    Münkler, Hagen

    2016-05-01

    The Yangian level-one hypercharge generator for the super Wilson loop in { N }=4 supersymmetric Yang-Mills theory is constructed. Moreover, evidence for the presence of a corresponding symmetry generator at all higher levels is provided. The derivation is restricted to the strong-coupling description of the super Wilson loop and based on the construction of novel conserved charges for type IIB superstrings on {{AdS}}5× {{{S}}}5.

  14. Cyclic universe from Loop Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Cianfrani, Francesco; Kowalski-Glikman, Jerzy; Rosati, Giacomo

    2016-02-01

    We discuss how a cyclic model for the flat universe can be constructively derived from Loop Quantum Gravity. This model has a lower bounce, at small values of the scale factor, which shares many similarities with that of Loop Quantum Cosmology. We find that Quantum Gravity corrections can be also relevant at energy densities much smaller than the Planckian one and that they can induce an upper bounce at large values of the scale factor.

  15. Tachyon matter in loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Sen, A. A.

    2006-08-01

    An analytical approach for studying the cosmological scenario with a homogeneous tachyon field within the framework of loop quantum gravity is developed. Our study is based on the semiclassical regime where space time can be approximated as a continuous manifold, but matter Hamiltonian gets nonperturbative quantum corrections. A formal correspondence between classical and loop quantum cosmology is also established. The Hamilton-Jacobi method for getting exact solutions is constructed and some exact power law as well as bouncing solutions are presented.

  16. Can Chemical Looping Combustion Use CFB Technology?

    SciTech Connect

    Gamwo, I.K.

    2006-11-01

    Circulating Fluidized Bed (CFB) technology has demonstrated an unparalleled ability to achieve low SO2 and NOx emissions for coal-fired power plants without CO2 capture. Chemical Looping combustion (CLC) is a novel fuel combustion technology which appears as a leading candidate in terms of competitiveness for CO2 removal from flue gas. This presentaion deals with the adaptation of circulating fluidized bed technology to Chemical looping combustion

  17. Multiple Flow Loop SCADA System Implemented on the Production Prototype Loop

    SciTech Connect

    Baily, Scott A.; Dalmas, Dale Allen; Wheat, Robert Mitchell; Woloshun, Keith Albert; Dale, Gregory E.

    2015-11-16

    The following report covers FY 15 activities to develop supervisory control and data acquisition (SCADA) system for the Northstar Moly99 production prototype gas flow loop. The goal of this effort is to expand the existing system to include a second flow loop with a larger production-sized blower. Besides testing the larger blower, this system will demonstrate the scalability of our solution to multiple flow loops.

  18. Flare Half-Loops: What Are They?

    NASA Astrophysics Data System (ADS)

    McKenzie, David Eugene; Guidoni, S. E.; Longcope, D. W.; Yoshimura, K.

    2012-05-01

    The M1.4 flare of 28 January 2011 has a remarkable resemblance to the famous "Tsuneta candle-flame" flare of 1992. It was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting in higher resolution, greater temperature coverage, and stereoscopic views of this iconic structure. The high temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the arcade. They also show that loops which are successively connected to this tower develop a density increase in one of their legs that can exceed twice the density of the other leg, giving the appearance of "half loops". These jumps in density last for an extended period of time. On the other hand, XRT filter ratios suggest that temperature is approximately uniform along the entire loop. XRT filter-ratio density maps corroborate that the brighter legs have higher density than the fainter halves. The tower is associated with a localized density increase, with even higher densities than either leg of the loop. This spatial variation of density may correspond to a shock at the top of the loops. We use STEREO images to show that the half loop brightening is not a line-of-sight projection effect of the type suggested by Forbes & Acton. This work is supported under contract SP02H3901R from Lockheed-Martin to MSU, and under contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory.

  19. Hybrid Combustion-Gasification Chemical Looping

    SciTech Connect

    Herbert Andrus; Gregory Burns; John Chiu; Gregory Lijedahl; Peter Stromberg; Paul Thibeault

    2009-01-07

    For the past several years Alstom Power Inc. (Alstom), a leading world-wide power system manufacturer and supplier, has been in the initial stages of developing an entirely new, ultra-clean, low cost, high efficiency power plant for the global power market. This new power plant concept is based on a hybrid combustion-gasification process utilizing high temperature chemical and thermal looping technology The process consists of the oxidation, reduction, carbonation, and calcination of calcium-based compounds, which chemically react with coal, biomass, or opportunity fuels in two chemical loops and one thermal loop. The chemical and thermal looping technology can be alternatively configured as (i) a combustion-based steam power plant with CO{sub 2} capture, (ii) a hybrid combustion-gasification process producing a syngas for gas turbines or fuel cells, or (iii) an integrated hybrid combustion-gasification process producing hydrogen for gas turbines, fuel cells or other hydrogen based applications while also producing a separate stream of CO{sub 2} for use or sequestration. In its most advanced configuration, this new concept offers the promise to become the technology link from today's Rankine cycle steam power plants to tomorrow's advanced energy plants. The objective of this work is to develop and verify the high temperature chemical and thermal looping process concept at a small-scale pilot facility in order to enable AL to design, construct and demonstrate a pre-commercial, prototype version of this advanced system. In support of this objective, Alstom and DOE started a multi-year program, under this contract. Before the contract started, in a preliminary phase (Phase 0) Alstom funded and built the required small-scale pilot facility (Process Development Unit, PDU) at its Power Plant Laboratories in Windsor, Connecticut. Construction was completed in calendar year 2003. The objective for Phase I was to develop the indirect combustion loop with CO{sub 2

  20. Consistency of loop regularization method and divergence structure of QFTs Beyond one-loop order

    NASA Astrophysics Data System (ADS)

    Huang, Da; Li, Ling-Fong; Wu, Yue-Liang

    2013-04-01

    We study the problem how to deal with tensor-type two-loop integrals in the Loop Regularization (LORE) scheme. We use the two-loop photon vacuum polarization in the massless Quantum Electrodynamics (QED) as the example to present the general procedure. In the processes, we find a new divergence structure: the regulated result for each two-loop diagram contains a gauge-violating quadratic harmful divergent term even combined with their corresponding counterterm insertion diagrams. Only when we sum up over all the relevant diagrams do these quadratic harmful divergences cancel, recovering the gauge invariance and locality.

  1. A Warm Magnetoactive Plasma in a Large Volume of Space

    NASA Technical Reports Server (NTRS)

    Heiles, C.

    1984-01-01

    A diffuse ionized warm gas fills a large volume of space in the general direction of Radio Loop II. There are three types of observational evidence: Faraday rotation measures (RM's) of extragalactic sources; emission measures (EM's) derived from the H alpha emission line in the diffuse interstellar medium; and magnetic field strengths in HI clouds derived from Zeeman splitting observations.

  2. A hybrid mock circulation loop for a total artificial heart.

    PubMed

    Nestler, Frank; Bradley, Andrew P; Wilson, Stephen J; Timms, Daniel L; Frazier, O Howard; Cohn, William E

    2014-09-01

    Rotary blood pumps are emerging as a viable technology for total artificial hearts, and the development of physiological control algorithms is accelerated with new evaluation environments. In this article, we present a novel hybrid mock circulation loop (HMCL) designed specifically for evaluation of rotary total artificial hearts (rTAH). The rTAH is operated in the physical domain while all vasculature elements are embedded in the numerical domain, thus combining the strengths of both approaches: fast and easy exchange of the vasculature model together with improved controllability of the pump. Parameters, such as vascular resistance, compliance, and blood volume, can be varied dynamically in silico during operation. A hydraulic-numeric interface creates a real-time feedback loop between the physical and numerical domains. The HMCL uses computer-controlled resistance valves as actuators, thereby reducing the size and number of hydraulic elements. Experimental results demonstrate a stable interaction over a wide operational range and a high degree of flexibility. Therefore, we demonstrate that the newly created design environment can play an integral part in the hydraulic design, control development, and durability testing of rTAHs. PMID:25234760

  3. Genericness of inflation in isotropic loop quantum cosmology.

    PubMed

    Date, Ghanashyam; Hossain, Golam Mortuza

    2005-01-14

    Nonperturbative corrections from loop quantum cosmology (LQC) to the scalar matter sector are already known to imply inflation. We prove that the LQC modified scalar field generates exponential inflation in the small scale factor regime, for all positive definite potentials, independent of initial conditions and independent of ambiguity parameters. For positive semidefinite potentials it is always possible to choose, without fine-tuning, a value of one of the ambiguity parameters such that exponential inflation results, provided zeros of the potential are approached at most as a power law in the scale factor. In conjunction with the generic occurrence of bounce at small volumes, particle horizon is absent, thus eliminating the horizon problem of the standard big bang model. PMID:15698059

  4. Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling

    NASA Astrophysics Data System (ADS)

    Dahlburg, R. B.; Einaudi, G.; Taylor, B. D.; Ugarte-Urra, I.; Warren, H. P.; Rappazzo, A. F.; Velli, M.

    2016-01-01

    The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is nonuniformly distributed so that only a fraction of the coronal mass and volume gets heated at any time. Temperature and density are highly structured at scales that, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multithermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Numerical simulations of coronal loops of 50,000 km length and axial magnetic field intensities ranging from 0.01 to 0.04 T are presented. To connect these simulations to observations, we use the computed number densities and temperatures to synthesize the intensities expected in emission lines typically observed with the Extreme Ultraviolet Imaging Spectrometer on Hinode. These intensities are used to compute differential emission measure distributions using the Monte Carlo Markov Chain code, which are very similar to those derived from observations of solar active regions. We conclude that coronal heating is found to be strongly intermittent in space and time, with only small portions of the coronal loop being heated: in fact, at any given time, most of the corona is cooling down.

  5. Thermal stability of static coronal loops: Part 1: Effects of boundary conditions

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.; Shoub, E. C.; An, C. H.; Emslie, A. G.

    1985-01-01

    The linear stability of static coronal-loop models undergoing thermal perturbations was investigated. The effect of conditions at the loop base on the stability properties of the models was considered in detail. The question of appropriate boundary conditions at the loop base was considered and it was concluded that the most physical assumptions are that the temperature and density (or pressure) perturbations vanish there. However, if the base is taken to be sufficiently deep in the chromosphere, either several chromospheric scale heights or several coronal loop lengths in depth, then the effect of the boundary conditions on loop stability becomes negligible so that all physically acceptable conditions are equally appropriate. For example, one could as well assume that the velocity vanishes at the base. The growth rates and eigenmodes of static models in which gravity is neglected and in which the coronal heating is a relatively simple function, either constant per-unit mass or per-unit volume were calculated. It was found that all such models are unstable with a growth rate of the order of the coronal cooling time. The physical implications of these results for the solar corona and transition region are discussed.

  6. Dangling bond deflection model: Growth of gel network with loop structure

    NASA Astrophysics Data System (ADS)

    Ma, Hang-Shing; Jullien, Rémi; Scherer, George W.

    2002-04-01

    It has been shown that the closed-loop structure in the model gel networks is responsible for their stiffness. However, the creation of loops has been underestimated in most of the existing kinetic aggregation models [e.g., DLCA (diffusion-limited cluster-cluster aggregation) and derivatives]. A dangling bond deflection (DEF) mechanism is proposed to model the fluctuation of dangling branches or dead ends under thermal excitation. The random deflections of the dangling branches can create loops in the network by forming intracluster bonds, and proceed during both the gelling and aging processes. The resulting DLCADEF networks have extensive loop structure with a negligible number of dangling branches. Its growth kinetics and fractal behavior resemble those of real gels, including volume-invariant gel time and fractal dimension of about 2. The DLCADEF model is the first attempt to model the gel growth with loop formation by the physically realistic fluctuation mechanism. The mechanical properties of the resulting networks will be studied and verified by comparison with real gels.

  7. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-08-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  8. Modeling the Effect of Multiple Matrix Cracking Modes on Cyclic Hysteresis Loops of 2D Woven Ceramic-Matrix Composites

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2016-02-01

    In this paper, the effect of multiple matrix cracking modes on cyclic loading/unloading hysteresis loops of 2D woven ceramic-matrix composites (CMCs) has been investigated. The interface slip between fibers and the matrix existed in matrix cracking mode 3 and mode 5, in which matrix cracking and interface debonding occurred in longitudinal yarns, are considered as the major reason for hysteresis loops of 2D woven CMCs. The effects of fiber volume content, peak stress, matrix crack spacing, interface properties, matrix cracking mode proportion and interface wear on interface slip and hysteresis loops have been analyzed. The cyclic loading/unloading hysteresis loops of 2D woven SiC/SiC composite corresponding to different peak stresses have been predicted using the present analysis. It was found that the damage parameter, i.e., the proportion of matrix cracking mode 3 in the entire cracking modes of the composite, increases with increasing peak stress.

  9. LOOP CALCULUS AND BELIEF PROPAGATION FOR Q-ARY ALPHABET: LOOP TOWER

    SciTech Connect

    CHERTKOV, MICHAEL; CHERNYAK, VLADIMIR

    2007-01-10

    Loop calculus introduced in [1], [2] constitutes a new theoretical tool that explicitly expresses symbol Maximum-A-Posteriori (MAP) solution of a general statistical inference problem via a solution of the Belief Propagation (BP) equations. This finding brought a new significance to the BP concept, which in the past was thought of as just a loop-free approximation. In this paper they continue a discussion of the Loop Calculus, partitioning the results into three Sections. In Section 1 they introduce a new formulation of the Loop Calculus in terms of a set of transformations (gauges) that keeping the partition function of the problem invariant. The full expression contains two terms referred to as the 'ground state' and 'excited states' contributions. The BP equations are interpreted as a special (BP) gauge fixing condition that emerges as a special orthogonality constraint between the ground state and excited states, which also selects loop contributions as the only surviving ones among the excited states. In Section 2 they demonstrate how the invariant interpretation of the Loop Calculus, introduced in Section 1, allows a natural extension to the case of a general q-ary alphabet, this is achieved via a loop tower sequential construction. The ground level in the tower is exactly equivalent to assigning one color (out of q available) to the 'ground state' and considering all 'excited' states colored in the remaining (q-1) colors, according to the loop calculus rule. Sequentially, the second level in the tower corresponds to selecting a loop from the previous step, colored in (q-1) colors, and repeating the same ground vs excited states splitting procedure into one and (q-2) colors respectively. The construction proceeds till the full (q-1)-levels deep loop tower (and the corresponding contributions to the partition function) are established. In Section 3 they discuss an ultimate relation between the loop calculus and the Bethe-Free energy variational approach of [3].

  10. An Antibody Loop Replacement Design Feasibility Study and a Loop-Swapped Dimer Structure

    SciTech Connect

    Clark, L.; Boriack-Sjodin, P; Day, E; Eldredge, J; Fitch, C; Jarpe, M; Miller, S; Li, Y; Simon, K; van Vlijmen, H

    2009-01-01

    A design approach was taken to investigate the feasibility of replacing single complementarity determining region (CDR) antibody loops. This approach may complement simpler mutation-based strategies for rational antibody design by expanding conformation space. Enormous crystal structure diversity is available, making CDR loops logical targets for structure-based design. A detailed analysis for the L1 loop shows that each loop length takes a distinct conformation, thereby allowing control on a length scale beyond that accessible to simple mutations. The L1 loop in the anti-VLA1 antibody was replaced with the L2 loop residues longer in an attempt to add an additional hydrogen bond and fill space on the antibody-antigen interface. The designs expressed well, but failed to improve affinity. In an effort to learn more, one design was crystallized and data were collected at 1.9 {angstrom} resolution. The designed L1 loop takes the qualitatively desired conformation; confirming that loop replacement by design is feasible. The crystal structure also shows that the outermost loop (residues Leu51-Ser68) is domain swapped with another monomer. Tryptophan fluorescence measurements were used to monitor unfolding as a function of temperature and indicate that the loop involved in domain swapping does not unfold below 60C. The domain-swapping is not directly responsible for the affinity loss, but is likely a side-effect of the structural instability which may contribute to affinity loss. A second round of design was successful in eliminating the dimerization through mutation of a residue (Leu51Ser) at the joint of the domain-swapped loop.

  11. Mechanics of Protein-Mediated DNA Looping

    NASA Astrophysics Data System (ADS)

    Meiners, Jens-Christian

    2009-03-01

    The formation of looped DNA-protein complexes in which a protein or protein assembly binds to multiple distant operator sites on the DNA is a common feature for many regulatory schemes on the transcriptional level. In a living cell, a multitude of mechanical forces and constraints act on these complexes, and it is imperative to understand their effects on biological function. For this aim, we study the lactose repressor as a model system for protein-mediated DNA looping in single-molecule experiments. Using a novel axial constant-force optical trapping scheme that allows us to manipulate sub-micron DNA fragments with well-controlled forces down to the 10 fN range, we show that mechanical tension in the substrate DNA of hundred femtonewton is sufficient to disrupt the loop formation process, which suggests that such mechanical tension may provide a mechanical pathway to controlling gene expression in vivo. From the force sensitivity of the loop formation process, we can also infer the topology of the looped complex; in our case an antiparallel conformation. In addition, we will present new tethered-particle microscopy data that shows lifetimes of the looped complexes that are two to three orders of magnitude shorter than those measured in biochemical competition assays and discuss possible interpretations, including the suggestion that operator binding of the lactose repressor tetramer leads to a destabilization of the dimer-dimer interface and that thus the loop breakdown process is mostly a dissociation of the tetramer into two dimers, instead, as widely assumed, an unbinding of the tetramer from the DNA.

  12. NASA MSFC hardware in the loop simulations of automatic rendezvous and capture systems

    NASA Technical Reports Server (NTRS)

    Tobbe, Patrick A.; Naumann, Charles B.; Sutton, William; Bryan, Thomas C.

    1991-01-01

    Two complementary hardware-in-the-loop simulation facilities for automatic rendezvous and capture systems at MSFC are described. One, the Flight Robotics Laboratory, uses an 8 DOF overhead manipulator with a work volume of 160 by 40 by 23 feet to evaluate automatic rendezvous algorithms and range/rate sensing systems. The other, the Space Station/Station Operations Mechanism Test Bed, uses a 6 DOF hydraulic table to perform docking and berthing dynamics simulations.

  13. EUV spectroscopy of cool stars. III. Interpretation of EUVE spectra in terms of quasi-static loops.

    NASA Astrophysics Data System (ADS)

    van den Oord, G. H. J.; Schrijver, C. J.; Camphens, M.; Mewe, R.; Kaastra, J. S.

    1997-10-01

    We discuss the limitations of coronal spectroscopy to derive physical parameters of stellar magnetic loops. We distinguish between the intrinsic non-uniqueness of emitted spectra for models of quasi-static coronal loops, and the supplemental ambiguity introduced by both instrumental effects and spectral line formation. We demonstrate that the spectrum emitted by loops with constant cross-sections is the same for a large range of values of the conductive flux at the base when the apex temperature is fixed. Because it is impossible to estimate the conductive flux at the base from observations, it is also impossible to determine the volume heating rate and the loop length uniquely. For geometrically expanding (tapered) loops, the emitted spectrum depends on the expansion and on the conductive flux at the base, and there is a trade off between them without significant changes in the spectrum. We show that loop length and heating rate can only be derived if the density is known, but that even then a large intrinsic uncertainty remains for these loop parameters. We conclude that there is no unambiguous relationship between loop parameters and emitted spectra: modeling the spectra as the sum of spectra from discrete loops cannot result in a unique determination of coronal structure. Based on spectra observed with the Extreme Ultra Violet Explorer (EUVE) we find that quasi-static loop models allow adequate modeling of stellar coronal spectra. We show that coronal loops on active cool stars must expand with height. The minimum required areal expansion between base and apex is not very large, lying between 2 and 5. For three stars (α Cen, Capella and ξ UMa) the observations suggest the presence of two distinct, dominant loop populations, while for χ^1^ Ori a single population, characterized by a single apex temperature, suffices. The high electron densities (10^12^-10^13^cm^-3^) for coronal components on Capella and ξ UMa require abnormally large heating rates. It is

  14. Measurement of Hydrogen Absorption in Ternary Alloys with Volumetric (Sieverts Loop) Techniques

    SciTech Connect

    Aceves, S.

    2015-10-26

    The Sieverts loop is an inexpensive, robust and reliable methodology for calculating hydrogen absorption in materials [1]. In this approach, we start by storing a sample of the material being tested in the volume Vcell (Figure 1) and initiate the process by producing a high vacuum in the system while the material sample is heated to eliminate (most of) the hydrogen and other impurities previously absorbed. The system typically operates isothermally, with the volume Vref at ambient temperature and the sample at a temperature of interest – high enough to liquefy the alloy for the current application to nuclear fusion.

  15. TRANSVERSE OSCILLATIONS OF A COOLING CORONAL LOOP

    SciTech Connect

    Morton, R. J.; Erdelyi, R. E-mail: Robertus@sheffield.ac.u

    2009-12-10

    Here we present an investigation into how cooling of the plasma influences the oscillation properties (e.g., eigenfunctions and eigenfrequencies) of transverse (i.e., kink) magnetohydrodynamic (MHD) waves in a compressible magnetic flux tube embedded in a gravitationally stratified and uniformly magnetized atmosphere. The cooling is introduced via a temperature-dependent density profile. A time-dependent governing equation is derived and an approximate zeroth-order solution is then obtained. From this the influence of cooling on the behavior of the eigenfrequencies and eigenfunctions of the transverse MHD waves is determined for representative cooling timescales. It is shown analytically, as the loop cools, how the amplitude of the perturbations is found to decrease as time increases. For cooling timescales of 900-2000 s (as observed in typical EUV loops), it is shown that the cooling has important and relevant influence on the damping times of loop oscillations. Next, the theory is put to the test. The damping due to cooling is fitted to a representative observation of standing kink oscillation of EUV loops. It is also shown with an explicit approximate analytical form, how the period of the fundamental and first harmonic of the kink mode changes with time as the loop cools. A consequence of this is that the value of the period ratio P {sub 1}/P {sub 2}, a tool that is popular in magneto-seismological studies in coronal diagnostics, decreases from the value of a uniform loop, 2, as the temperature decreases. The rate of change in P {sub 1}/P {sub 2} is dependent upon the cooling timescale and is well within the observable range for typical EUV loops. Further to this, the magnitude of the anti-node shift of the eigenfunctions of the first harmonic is shown to continually increase as the loop cools, giving additional impetus to the use of spatial magneto-seismology of the solar atmosphere. Finally, we suggest that measurements of the rate of change in the

  16. Students' Understanding of Loops and Nested Loops in Computer Programming: An APOS Theory Perspective

    ERIC Educational Resources Information Center

    Cetin, Ibrahim

    2015-01-01

    The purpose of this study is to explore students' understanding of loops and nested loops concepts. Sixty-three mechanical engineering students attending an introductory programming course participated in the study. APOS (Action, Process, Object, Schema) is a constructivist theory developed originally for mathematics education. This study is the…

  17. Teachers' Attitudes and Perceptions of Looping and the Effect of Looping on Students' Academic Achievement

    ERIC Educational Resources Information Center

    Williams-Wright, Vera

    2013-01-01

    The purpose of this research study was two-fold. The first purpose was to investigate the impact of looping on academic achievement of students in selected public schools in Mississippi. The students' results on the 2010 and 2011 Mississippi Curriculum Test, Second Edition (MCT2) were used to determine whether looping students score differently in…

  18. Discretization parameter and operator ordering in loop quantum cosmology with the cosmological constant

    SciTech Connect

    Tanaka, Tomo; Amemiya, Fumitoshi; Shimano, Masahiro; Harada, Tomohiro; Tamaki, Takashi

    2011-05-15

    In loop quantum cosmology, the Hamiltonian reduces to a finite difference operator and quantum dynamics are controlled by the difference equation. In this framework, Bojowald [M. Bojowald, Phys. Rev. Lett. 86, 5227 (2001).] showed that the initial singularity is absent in the twofold sense: (i) the spectrum of the inverse scale factor operator is bounded from above; (ii) the wave function of the Universe can be uniquely extended beyond the point which was the initial singularity in classical theory. In this paper, we study the initial singularity in this sense and the large-volume limit against the ambiguities in the discretization and the operator ordering within a homogeneous, isotropic and spatially flat model with the cosmological constant. We find that the absence of the singularity strongly depends on the choice of the operator ordering and the requirement for the absence singles out a very small class of orderings. Moreover we find a general ordering rule required for the absence of the singularity. We also find that the large-volume limit naturally recovers a smooth wave function in the discretization where each step corresponds to a fixed volume increment but not in the one where each step corresponds to a fixed area increment. If loop quantum cosmology is to be a phenomenological realization of full loop quantum gravity, these results are important to fix the theoretical ambiguities.

  19. Multithermal Analysis of EIS Coronal Loops

    NASA Astrophysics Data System (ADS)

    Worley, Brian T.; Schmelz, J. T.; Pathak, S.

    2012-05-01

    Four separate active regions containing multiple coronal loops were selected for Differential Emission Measure (DEM) analysis from Hinode Extreme ultraviolet Imaging Spectrometer (EIS) data. Each loop was chosen based on its location and our ability to find a clean nearby area for background subtraction. Our analysis uses iron lines with ionization stages from Fe VIII to Fe XVI in the wavelength ranges 170 - 210 and 250 - 290 A. The twelve selected loops were then analyzed to determine if their cross-field temperature was isothermal or multithermal. This was accomplished by averaging the intensities of ten individual pixels along the length of each loop and subtracting the average intensity of ten nearby background pixels. We then used these background-subtracted values, the density from a density-sensitive line ratio, and the atomic data from the CHIANTI database to create a DEM curve for each loop. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 as well as a Hinode subcontract from NASA/SAO.

  20. Modeling of protein loops by simulated annealing.

    PubMed Central

    Collura, V.; Higo, J.; Garnier, J.

    1993-01-01

    A method is presented to model loops of protein to be used in homology modeling of proteins. This method employs the ESAP program of Higo et al. (Higo, J., Collura, V., & Garnier, J., 1992, Biopolymers 32, 33-43) and is based on a fast Monte Carlo simulation and a simulated annealing algorithm. The method is tested on different loops or peptide segments from immunoglobulin, bovine pancreatic trypsin inhibitor, and bovine trypsin. The predicted structure is obtained from the ensemble average of the coordinates of the Monte Carlo simulation at 300 K, which exhibits the lowest internal energy. The starting conformation of the loop prior to modeling is chosen to be completely extended, and a closing harmonic potential is applied to N, CA, C, and O atoms of the terminal residues. A rigid geometry potential of Robson and Platt (1986, J. Mol. Biol. 188, 259-281) with a united atom representation is used. This we demonstrate to yield a loop structure with good hydrogen bonding and torsion angles in the allowed regions of the Ramachandran map. The average accuracy of the modeling evaluated on the eight modeled loops is 1 A root mean square deviation (rmsd) for the backbone atoms and 2.3 A rmsd for all heavy atoms. PMID:8401234

  1. Crack interaction with 3-D dislocation loops

    NASA Astrophysics Data System (ADS)

    Gao, Huajian

    CRACKS in a solid often interact with other crystal defects such as dislocation loops. The interaction effects are of 3-D character yet their analytical treatment has been mostly limited to the 2-D regime due to mathematical complications. This paper shows that distribution of the stress intensity factors along a crack front due to arbitrary dislocation loops may be expressed as simple line integrals along the loop contours. The method of analysis is based on the 3-D Bueckner-Rice weight function theory for elastic crack analysis. Our results have significantly simplified the calculations for 3-D dislocation loops produced in the plastic processes at the crack front due to highly concentrated crack tip stress fields. Examples for crack-tip 3-D loops and 2-D straight dislocations emerging from the crack tip are given to demonstrate applications of the derived formulae. The results are consistent with some previous analytical solutions existing in the literature. As further applications we also analyse straight dislocations that are parallel or perpendicular to the crack plane but are not parallel to the crack front.

  2. Bootstrapping the Three-Loop Hexagon

    SciTech Connect

    Dixon, Lance J.; Drummond, James M.; Henn, Johannes M.; /Humboldt U., Berlin /Santa Barbara, KITP

    2011-11-08

    We consider the hexagonal Wilson loop dual to the six-point MHV amplitude in planar N = 4 super Yang-Mills theory. We apply constraints from the operator product expansion in the near-collinear limit to the symbol of the remainder function at three loops. Using these constraints, and assuming a natural ansatz for the symbol's entries, we determine the symbol up to just two undetermined constants. In the multi-Regge limit, both constants drop out from the symbol, enabling us to make a non-trivial confirmation of the BFKL prediction for the leading-log approximation. This result provides a strong consistency check of both our ansatz for the symbol and the duality between Wilson loops and MHV amplitudes. Furthermore, we predict the form of the full three-loop remainder function in the multi-Regge limit, beyond the leading-log approximation, up to a few constants representing terms not detected by the symbol. Our results confirm an all-loop prediction for the real part of the remainder function in multi-Regge 3 {yields} 3 scattering. In the multi-Regge limit, our result for the remainder function can be expressed entirely in terms of classical polylogarithms. For generic six-point kinematics other functions are required.

  3. Wilson loops in supersymmetric gauge theories

    NASA Astrophysics Data System (ADS)

    Pestun, Vasily

    This thesis is devoted to several exact computations in four-dimensional supersymmetric gauge field theories. In the first part of the thesis we prove conjecture due to Erickson-Semenoff-Zarembo and Drukker-Gross which relates supersymmetric circular Wilson loop operators in the N = 4 supersymmetric Yang-Mills theory with a Gaussian matrix model. We also compute the partition function and give a new matrix model formula for the expectation value of a supersymmetric circular Wilson loop operator for the pure N = 2 and the N* = 2 supersymmetric Yang-Mills theory on a four-sphere. Circular supersymmetric Wilson loops in four-dimensional N = 2 superconformal gauge theory are treated similarly. In the second part we consider supersymmetric Wilson loops of arbitrary shape restricted to a two-dimensional sphere in the four-dimensional N = 4 supersymmetric Yang-Mills theory. We show that expectation value for these Wilson loops can be exactly computed using a two-dimensional theory closely related to the topological two-dimensional Higgs-Yang-Mills theory, or two-dimensional Yang-Mills theory for the complexified gauge group.

  4. Fatigue-Resistant Metal Hook-And-Loop Fastener

    NASA Technical Reports Server (NTRS)

    Sawaf, Bernard

    1994-01-01

    Proposed metal hook-and-loop fastener engaged and disengaged many hundreds of times without breaking. Fastener opens by mechanical action. Translation moves hooks out of loops or pushes loops away from hooks. Hooks not required to flex and, therefore, do not fail by fatigue. Lifetime much greater than that of other metal hook-and-loop fasteners, depending on flexure for disengagement such as article, "Hook-and-Loop Metal Fastener" (MSC-21586).

  5. A numerical study of the thermal stability of solar loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, J. A.; Antiochos, S. K.; Mariska, J. T.

    1987-01-01

    An important property of all loops is their thermal stability. If low lying hot loops were thermally unstable, for example, a great majority of the low loops on the Sun might be expected to be cool. How small perturbations evolve in low lying, linearly unstable hot loops was determined and how high lying, linearly stable hot loops respond to large amplitude disturbances such as might be expected on the Sun were examined. Only general descriptions and results are given.

  6. A tree-loop duality relation at two loops and beyond

    NASA Astrophysics Data System (ADS)

    Bierenbaum, Isabella; Catani, Stefano; Draggiotis, Petros; Rodrigo, Germán

    2010-10-01

    The duality relation between one-loop integrals and phase-space integrals, developed in a previous work, is extended to higher-order loops. The duality relation is realized by a modification of the customary + i0 prescription of the Feynman propagators, which compensates for the absence of the multiple-cut contributions that appear in the Feynman tree theorem. We rederive the duality theorem at one-loop order in a form that is more suitable for its iterative extension to higher-loop orders. We explicitly show its application to two-and three-loop scalar master integrals, and we discuss the structure of the occurring cuts and the ensuing results in detail.

  7. Linear phase demodulator including a phase locked loop with auxiliary feedback loop

    NASA Technical Reports Server (NTRS)

    Rippy, R. R. (Inventor)

    1976-01-01

    A phase modulated wave that may have no carrier power is demodulated by a phase locked loop including a phase detector for deriving an A.C. data output signal having a magnitude and a phase indicative of the phase of the modulated wave. A feedback loop responsive to the data output signal restores power to the carrier frequency component to the loop. In one embodiment, the feedback loop includes a phase modulator responsive to the phase modulated wave and the data output signal. In a second embodiment, carrier frequency power is restored by differentiating the data output signal and supplying the differentiated signal to an input of a voltage controlled oscillator included in the phase locked loop.

  8. Three-loop hard-thermal-loop free energy for QED

    SciTech Connect

    Andersen, Jens O.; Strickland, Michael; Su, Nan

    2009-10-15

    We calculate the free energy of a hot gas of electrons and photons to three loops using the hard-thermal-loop perturbation theory reorganization of finite-temperature perturbation theory. We calculate the free energy through three loops by expanding in a power series in m{sub D}/T, m{sub f}/T, and e{sup 2}, where m{sub D} and m{sub f} are thermal masses and e is the coupling constant. We demonstrate that the hard-thermal-loop perturbation reorganization improves the convergence of the successive approximations to the QED free energy at large coupling, e{approx}2. The reorganization is gauge invariant by construction, and due to cancellation among various contributions, we obtain a completely analytic result for the resummed thermodynamic potential at three loops. Finally, we compare our result with similar calculations that use the {phi}-derivable approach.

  9. Hot topic, warm loops, cooling plasma? Multithermal analysis of active region loops

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Christian, G. M.; Dhaliwal, R. S.; Brooks, D. H.

    2014-11-10

    We have found indications of a relationship between the differential emission measure (DEM) weighted temperature and the cross-field DEM width for coronal loops. The data come from the Hinode X-ray Telescope, the Hinode EUV Imaging Spectrometer, and the Solar Dynamics Observatory Atmospheric Imaging Assembly. These data show that cooler loops tend to have narrower DEM widths. If most loops observed by these instruments are composed of bundles of unresolved magnetic strands and are only observed in their cooling phase, as some studies have suggested, then this relationship implies that the DEM of a coronal loop narrows as it cools. This could imply that fewer strands are seen emitting in the later cooling phase, potentially resolving the long standing controversy of whether the cross-field temperatures of coronal loops are multithermal or isothermal.

  10. Loop quantum Brans-Dicke cosmology

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong; Artymowski, Michal; Ma, Yongge

    2013-04-01

    The spatially flat and isotropic cosmological model of Brans-Dicke theory with coupling parameter ω≠-(3)/(2) is quantized by the approach of loop quantum cosmology. An interesting feature of this model is that although the Brans-Dicke scalar field is nonminimally coupled with curvature, it can still play the role of an emergent time variable. In the quantum theory, the classical differential equation which represents cosmological evolution is replaced by a quantum difference equation. The effective Hamiltonian and modified dynamical equations of loop quantum Brans-Dicke cosmology are also obtained, which lay a foundation for the phenomenological investigation to possible quantum gravity effects in cosmology. The effective equations indicate that the classical big bang singularity is again replaced by a quantum bounce in loop quantum Brans-Dicke cosmology.

  11. Double reference pulsed phase locked loop

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1986-01-01

    A double reference pulse phase locked loop is described which measures the phase shift between tone burst signals initially derived from the same periodic signal source (voltage controlled oscillator) and delayed by different amounts because of two different paths. A first path is from the transducer to the surface of a sample and back. A second path is from the transducer to the opposite surface and back. A first pulse phase locked loop including a phase detector and a phase shifter forces the tone burst signal delayed by the second path in phase quadrature with the periodic signal source. A second pulse phase locked loop including a second phase detector forces the tone burst signals delayed by the first path into phase quadrature with the phase shifted periodic signal source.

  12. Torus Knot Polynomials and Susy Wilson Loops

    NASA Astrophysics Data System (ADS)

    Giasemidis, Georgios; Tierz, Miguel

    2014-12-01

    We give, using an explicit expression obtained in (Jones V, Ann Math 126:335, 1987), a basic hypergeometric representation of the HOMFLY polynomial of ( n, m) torus knots, and present a number of equivalent expressions, all related by Heine's transformations. Using this result, the symmetry and the leading polynomial at large N are explicit. We show the latter to be the Wilson loop of 2d Yang-Mills theory on the plane. In addition, after taking one winding to infinity, it becomes the Wilson loop in the zero instanton sector of the 2d Yang-Mills theory, which is known to give averages of Wilson loops in = 4 SYM theory. We also give, using matrix models, an interpretation of the HOMFLY polynomial and the corresponding Jones-Rosso representation in terms of q-harmonic oscillators.

  13. Hierarchical curiosity loops and active sensing.

    PubMed

    Gordon, Goren; Ahissar, Ehud

    2012-08-01

    A curious agent acts so as to optimize its learning about itself and its environment, without external supervision. We present a model of hierarchical curiosity loops for such an autonomous active learning agent, whereby each loop selects the optimal action that maximizes the agent's learning of sensory-motor correlations. The model is based on rewarding the learner's prediction errors in an actor-critic reinforcement learning (RL) paradigm. Hierarchy is achieved by utilizing previously learned motor-sensory mapping, which enables the learning of other mappings, thus increasing the extent and diversity of knowledge and skills. We demonstrate the relevance of this architecture to active sensing using the well-studied vibrissae (whiskers) system, where rodents acquire sensory information by virtue of repeated whisker movements. We show that hierarchical curiosity loops starting from optimally learning the internal models of whisker motion and then extending to object localization result in free-air whisking and object palpation, respectively. PMID:22386787

  14. Coronal Loops: New Insights from EIS Observations

    NASA Astrophysics Data System (ADS)

    Del Zanna, G.; Bradshaw, S. J.

    2009-12-01

    Multi-instrument observations of coronal loops of different active regions have been studied. The general features discussed in Del Zanna (2003) and Del Zanna and Mason (2003) based on SOHO/CDS are confirmed. Hinode/EIS high-cadence observations clearly show how dynamic loops are at all temperatures. This clearly reflects the fast changes in the photospheric magnetic fields measured by SOT over a minute timescale. Despite that, persistent patterns are present. In particular, the pattern of Doppler shifts and non-thermal widths, found for the first time in NOAA 10926 (cf. Del Zanna 2007, 2008), is actually a common feature in all active regions. It is likely that the majority of cool (0.5--1 MK) loops are observed during their radiatively cooling phase.

  15. Current loop signal conditioning: Practical applications

    NASA Technical Reports Server (NTRS)

    Anderson, Karl F.

    1995-01-01

    This paper describes a variety of practical application circuits based on the current loop signal conditioning paradigm. Equations defining the circuit response are also provided. The constant current loop is a fundamental signal conditioning circuit concept that can be implemented in a variety of configurations for resistance-based transducers, such as strain gages and resistance temperature detectors. The circuit features signal conditioning outputs which are unaffected by extremely large variations in lead wire resistance, direct current frequency response, and inherent linearity with respect to resistance change. Sensitivity of this circuit is double that of a Wheatstone bridge circuit. Electrical output is zero for resistance change equals zero. The same excitation and output sense wires can serve multiple transducers. More application arrangements are possible with constant current loop signal conditioning than with the Wheatstone bridge.

  16. Coronal Loops: Evolving Beyond the Isothermal Approximation

    NASA Astrophysics Data System (ADS)

    Schmelz, J. T.; Cirtain, J. W.; Allen, J. D.

    2002-05-01

    Are coronal loops isothermal? A controversy over this question has arisen recently because different investigators using different techniques have obtained very different answers. Analysis of SOHO-EIT and TRACE data using narrowband filter ratios to obtain temperature maps has produced several key publications that suggest that coronal loops may be isothermal. We have constructed a multi-thermal distribution for several pixels along a relatively isolated coronal loop on the southwest limb of the solar disk using spectral line data from SOHO-CDS taken on 1998 Apr 20. These distributions are clearly inconsistent with isothermal plasma along either the line of sight or the length of the loop, and suggested rather that the temperature increases from the footpoints to the loop top. We speculated originally that these differences could be attributed to pixel size -- CDS pixels are larger, and more `contaminating' material would be expected along the line of sight. To test this idea, we used CDS iron line ratios from our data set to mimic the isothermal results from the narrowband filter instruments. These ratios indicated that the temperature gradient along the loop was flat, despite the fact that a more complete analysis of the same data showed this result to be false! The CDS pixel size was not the cause of the discrepancy; rather, the problem lies with the isothermal approximation used in EIT and TRACE analysis. These results should serve as a strong warning to anyone using this simplistic method to obtain temperature. This warning is echoed on the EIT web page: ``Danger! Enter at your own risk!'' In other words, values for temperature may be found, but they may have nothing to do with physical reality. Solar physics research at the University of Memphis is supported by NASA grant NAG5-9783. This research was funded in part by the NASA/TRACE MODA grant for Montana State University.

  17. Quasi-periodic processes in the flare loop generated by sudden temperature enhancements at loop footpoints

    NASA Astrophysics Data System (ADS)

    Karlický, M.; Jelínek, P.

    2016-05-01

    Aims: During the impulsive flare phase, the plasma at the flare loop footpoints is rapidly heated by particle beams. In the present paper, we study processes that occur after this sudden heating in a two-dimensional magnetic loop. Methods: We adopt a 2D magnetohydrodynamic (MHD) model, in which we solve a full set of the ideal time-dependent MHD equations by means of the FLASH code, using the adaptive mesh refinement (AMR) method. Periods in the processes are estimated by the wavelet analysis technique. Results: We consider a model of the solar atmosphere with a symmetric magnetic loop. The length of this loop in the corona is approximately 21.5 Mm. At both loop footpoints, at the transition region, we initiate the Gaussian temperature (pressure) perturbation with the maximum temperature 14, 7, or 3.5 times higher than the unperturbed temperature. In the corona, the perturbations produce supersonic blast shocks with the Mach number of about 1.1, but well below Alfvén velocities. We consider cases with the same perturbations at both footpoints (symmetric case) and one with different perturbations (asymmetric case). In the symmetric case, the shocks move along both loop legs upwards to the top of the loop, where they interact and form a transient compressed region. Then they continue in their motion to the transition region at the opposite side of the loop, where they are reflected upwards, and so on. At the top of the loop, the shock appears periodically with the period of about 170 s. In the loop legs during this period, a double peak of the plasma parameters, which is connected with two arrivals of shocks, is detected: firstly, when the shock moves up and then when the shock, propagating from the opposite loop leg, moves down. Increasing the distance of the detection point in the loop leg from the top of the loop, the time interval between these shock arrivals increases. Thus, at these detection points, the processes with shorter periods can be detected. After

  18. Similarity Metrics for Closed Loop Dynamic Systems

    NASA Technical Reports Server (NTRS)

    Whorton, Mark S.; Yang, Lee C.; Bedrossian, Naz; Hall, Robert A.

    2008-01-01

    To what extent and in what ways can two closed-loop dynamic systems be said to be "similar?" This question arises in a wide range of dynamic systems modeling and control system design applications. For example, bounds on error models are fundamental to the controller optimization with modern control design methods. Metrics such as the structured singular value are direct measures of the degree to which properties such as stability or performance are maintained in the presence of specified uncertainties or variations in the plant model. Similarly, controls-related areas such as system identification, model reduction, and experimental model validation employ measures of similarity between multiple realizations of a dynamic system. Each area has its tools and approaches, with each tool more or less suited for one application or the other. Similarity in the context of closed-loop model validation via flight test is subtly different from error measures in the typical controls oriented application. Whereas similarity in a robust control context relates to plant variation and the attendant affect on stability and performance, in this context similarity metrics are sought that assess the relevance of a dynamic system test for the purpose of validating the stability and performance of a "similar" dynamic system. Similarity in the context of system identification is much more relevant than are robust control analogies in that errors between one dynamic system (the test article) and another (the nominal "design" model) are sought for the purpose of bounding the validity of a model for control design and analysis. Yet system identification typically involves open-loop plant models which are independent of the control system (with the exception of limited developments in closed-loop system identification which is nonetheless focused on obtaining open-loop plant models from closed-loop data). Moreover the objectives of system identification are not the same as a flight test and

  19. Pressure structure of solar coronal loops

    NASA Technical Reports Server (NTRS)

    Krishan, V.

    1987-01-01

    The steady state pressure structure of a coronal loop is discussed in terms of the MHD global invariants of an incompressible plasma. The steady state is represented by the superposition of two Chandrasekhar-Kendall functions corresponding to (n=m=0) and (n=m=1) modes. The relative contribution of the two modes (epsilon) is found to depend on the surface pressure of the coronal loop which is also the pressure of the external medium. The mixed mode state does not exist for high values of the external pressure because epsilon becomes complex.

  20. Loop transformations to prevent false sharing

    SciTech Connect

    Granston, E.D.; Montaut, T.; Bodin, F.

    1995-08-01

    To date, page management in shared virtual memory (SVM) systems has been primarily the responsibility of the run-time system. However, there are some problems that are difficult to resolve efficiently at run time. Chief among these is false sharing. In this paper, a loop transformation theory is developed for identifying and eliminating potential sources of multiple-writer false sharing and other sources of page migration resulting from regular references in numerical applications. Loop nests of one and two dimensions (before blocking) with single-level, DOALL-style parallelism are covered. The potential of these transformations is demonstrated experimentally.

  1. Slipping magnetic reconnection in coronal loops.

    PubMed

    Aulanier, Guillaume; Golub, Leon; Deluca, Edward E; Cirtain, Jonathan W; Kano, Ryouhei; Lundquist, Loraine L; Narukage, Noriyuki; Sakao, Taro; Weber, Mark A

    2007-12-01

    Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep gradients: The field lines may slip across each other. Soft x-ray observations of fast bidirectional motions of coronal loops, observed by the Hinode spacecraft, support the existence of this slipping magnetic reconnection regime in the Sun's corona. This basic process should be considered when interpreting reconnection, both on the Sun and in laboratory-based plasma experiments. PMID:18063789

  2. How current loops and solenoids curve spacetime

    NASA Astrophysics Data System (ADS)

    Füzfa, André

    2016-01-01

    The curved spacetime around current loops and solenoids carrying arbitrarily large steady electric currents is obtained from the numerical resolution of the coupled Einstein-Maxwell equations in cylindrical symmetry. The artificial gravitational field associated to the generation of a magnetic field produces gravitational redshift of photons and deviation of light. Null geodesics in the curved spacetime of current loops and solenoids are also presented. We finally propose an experimental setup achievable with current technology of superconducting coils, that produces a phase shift of light of the same order of magnitude as astrophysical signals in ground-based gravitational wave observatories.

  3. Temperature Oscillations in Loop Heat Pipe Operation

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Ottenstein, Laura; Kobel, Mark; Rogers, Paul; Kaya, Tarik; Paquin, Krista C. (Technical Monitor)

    2000-01-01

    Loop heat pipes (LHPs) are versatile two-phase heat transfer devices that have gained increasing acceptance for space and terrestrial applications. The operating temperature of an LHP is a function of its operating conditions. The LHP usually reaches a steady operating temperature for a given heat load and sink temperature. The operating temperature will change when the heat load and/or the sink temperature changes, but eventually reaches another steady state in most cases. Under certain conditions, however, the loop operating temperature never really reaches a true steady state, but instead becomes oscillatory. This paper discusses the temperature oscillation phenomenon using test data from a miniature LHP.

  4. A double-loop tracking system.

    NASA Technical Reports Server (NTRS)

    Yuen, J. H.

    1972-01-01

    A nonlinear analysis which can be used to assess certain statistical characteristics of double-loop tracking systems is presented. It takes into account the mutual coupling effects of the loops in the system. Two approaches are taken to obtain steady-state probability density functions (pdf's) of the system phase errors. From these pdf's, important system performance statistics, e.g., the phase-error variances, can be calculated, thus illustrating the application and usefulness of the analysis. The analysis is applied to a satellite transponder as an example.

  5. Stabilizing gene regulatory networks through feedforward loops

    NASA Astrophysics Data System (ADS)

    Kadelka, C.; Murrugarra, D.; Laubenbacher, R.

    2013-06-01

    The global dynamics of gene regulatory networks are known to show robustness to perturbations in the form of intrinsic and extrinsic noise, as well as mutations of individual genes. One molecular mechanism underlying this robustness has been identified as the action of so-called microRNAs that operate via feedforward loops. We present results of a computational study, using the modeling framework of stochastic Boolean networks, which explores the role that such network motifs play in stabilizing global dynamics. The paper introduces a new measure for the stability of stochastic networks. The results show that certain types of feedforward loops do indeed buffer the network against stochastic effects.

  6. Coronal Loops: Observations and Modeling of Confined Plasma

    NASA Astrophysics Data System (ADS)

    Reale, Fabio

    2014-07-01

    Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops) are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC) and impulsive (DC) heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.

  7. Effect of ambient pressure variation on closed loop gas system for India based Neutrino Observatory (INO)

    NASA Astrophysics Data System (ADS)

    Satyanarayana, B.; Majumder, G.; Mondal, N. K.; Kalmani, S. D.; Shinde, R. R.; Joshi, A.

    2014-10-01

    Pilot unit of a closed loop gas mixing and distribution system for the INO project was designed and is being operated with 1.8meters × 1.9meters RPCs for about two years. A number of studies on controlling the flow and optimisation of the gas mixture through the RPC stack were carried out during this period. The gas system essentially measures and attempts to maintain absolute pressure inside the RPC gas volume. During typical Mumbai monsoon seasons, the barometric pressure changes rather rapidly, due to which the gas system fails to maintain the set differential pressure between the ambience and the RPC gas volume. As the safety bubblers on the RPC gas input lines are set to work on fixed pressure differentials, the ambient pressure changes lead to either venting out and thus wasting gas through safety bubblers or over pressuring the RPCs gas volume and thus degrading its performance. The above problem also leads to gas mixture contamination through minute leaks in gas gap. The problem stated above was solved by including the ambient barometric pressure as an input parameter in the closed loop. Using this, it is now possible to maintain any set differential pressure between the ambience and RPC gas volumes between 0 to 20mm of water column, thus always ensuring a positive pressure inside the RPC gas volume with respect to the ambience. This has resulted in improved performance of the gas system by maintaining the constant gas flow and reducing the gas toping up frequency. In this paper, we will highlight the design features and improvements of the closed loop gas system. We will present some of the performance studies and considerations for scaling up the system to be used with the engineering module and then followed by Iron Calorimeter detector (ICAL), which is designed to deploy about 30,000 RPCs of 1.8meters × 1.9 meters in area.

  8. Radiation Enhanced Absorption of Frank Loops by Nanovoids in Cu

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Zhang, X.; Wang, J.

    2016-01-01

    Neutron and heavy ion irradiations generally induce voids in metallic materials, and continuous radiations typically result in void swelling and mechanical failure of the irradiated materials. Recent experiments showed that nanovoids in nanotwinned copper could act as sinks for radiation-induced Frank loops, significantly mitigating radiation damage. In this paper, we report on structural evolution of Frank loops under cascades and address the role of nanovoids in absorbing Frank loops in detail by using molecular dynamics simulations. Results show that a stand-alone Frank loop is stable under cascades. When Frank loops are adjacent to nanovoids, the diffusion of a group of atoms from the loop into nanovoids is accomplished via the formation and propagation of dislocation loops. The loop-nanovoid interactions result in the shrinkage of the nanovoids and the Frank loops.

  9. Run-time parallelization and scheduling of loops

    NASA Technical Reports Server (NTRS)

    Saltz, Joel H.; Mirchandaney, Ravi; Crowley, Kay

    1990-01-01

    Run time methods are studied to automatically parallelize and schedule iterations of a do loop in certain cases, where compile-time information is inadequate. The methods presented involve execution time preprocessing of the loop. At compile-time, these methods set up the framework for performing a loop dependency analysis. At run time, wave fronts of concurrently executable loop iterations are identified. Using this wavefront information, loop iterations are reordered for increased parallelism. Symbolic transformation rules are used to produce: inspector procedures that perform execution time preprocessing and executors or transformed versions of source code loop structures. These transformed loop structures carry out the calculations planned in the inspector procedures. Performance results are presented from experiments conducted on the Encore Multimax. These results illustrate that run time reordering of loop indices can have a significant impact on performance. Furthermore, the overheads associated with this type of reordering are amortized when the loop is executed several times with the same dependency structure.

  10. PHOTOSPHERIC PROPERTIES OF WARM EUV LOOPS AND HOT X-RAY LOOPS

    SciTech Connect

    Kano, R.; Ueda, K.; Tsuneta, S.

    2014-02-20

    We investigate the photospheric properties (vector magnetic fields and horizontal velocity) of a well-developed active region, NOAA AR 10978, using the Hinode Solar Optical Telescope specifically to determine what gives rise to the temperature difference between ''warm loops'' (1-2 MK), which are coronal loops observed in EUV wavelengths, and ''hot loops'' (>3 MK), coronal loops observed in X-rays. We found that outside sunspots, the magnetic filling factor in the solar network varies with location and is anti-correlated with the horizontal random velocity. If we accept that the observed magnetic features consist of unresolved magnetic flux tubes, this anti-correlation can be explained by the ensemble average of flux-tube motion driven by small-scale random flows. The observed data are consistent with a flux tube width of ∼77 km and horizontal flow at ∼2.6 km s{sup –1} with a spatial scale of ∼120 km. We also found that outside sunspots, there is no significant difference between warm and hot loops either in the magnetic properties (except for the inclination) or in the horizontal random velocity at their footpoints, which are identified with the Hinode X-Ray Telescope and the Transition Region and Coronal Explorer. The energy flux injected into the coronal loops by the observed photospheric motion of the magnetic fields is estimated to be 2 × 10{sup 6} erg s{sup –1} cm{sup –2}, which is the same for both warm and hot loops. This suggests that coronal properties (e.g., loop length) play a more important role in giving rise to temperature differences of active-region coronal loops than photospheric parameters.

  11. Photospheric Properties of Warm EUV Loops and Hot X-Ray Loops

    NASA Astrophysics Data System (ADS)

    Kano, R.; Ueda, K.; Tsuneta, S.

    2014-02-01

    We investigate the photospheric properties (vector magnetic fields and horizontal velocity) of a well-developed active region, NOAA AR 10978, using the Hinode Solar Optical Telescope specifically to determine what gives rise to the temperature difference between "warm loops" (1-2 MK), which are coronal loops observed in EUV wavelengths, and "hot loops" (>3 MK), coronal loops observed in X-rays. We found that outside sunspots, the magnetic filling factor in the solar network varies with location and is anti-correlated with the horizontal random velocity. If we accept that the observed magnetic features consist of unresolved magnetic flux tubes, this anti-correlation can be explained by the ensemble average of flux-tube motion driven by small-scale random flows. The observed data are consistent with a flux tube width of ~77 km and horizontal flow at ~2.6 km s-1 with a spatial scale of ~120 km. We also found that outside sunspots, there is no significant difference between warm and hot loops either in the magnetic properties (except for the inclination) or in the horizontal random velocity at their footpoints, which are identified with the Hinode X-Ray Telescope and the Transition Region and Coronal Explorer. The energy flux injected into the coronal loops by the observed photospheric motion of the magnetic fields is estimated to be 2 × 106 erg s-1 cm-2, which is the same for both warm and hot loops. This suggests that coronal properties (e.g., loop length) play a more important role in giving rise to temperature differences of active-region coronal loops than photospheric parameters.

  12. Time loops in a gravitational theory

    SciTech Connect

    Choudhury, A.L.

    1993-06-01

    We demonstrate here that time loops can be constructed by pasting different wormhole solutions with higher order perturbative terms in a model originated by Gidding and Strominger and subsequently improved by Coule and Maeda. In this model a scalar field interacts with a gravitational axion in Euclidean space. 6 refs., 2 figs.

  13. Lorentz invariance in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Pullin, Jorge; Rastgoo, Saeed; Gambini, Rodolfo

    2011-04-01

    We reconsider the argument of Collins, Perez, Sudarsky, Urrutia and Vucetich concerning violations of Lorentz invariance in the context of loop quantum gravity. We show that even if one introduces a lattice that violates Lorentz invariance at the Planck scale, this does not translate itself into large violations that would conflict with experiment.

  14. Extrasensitive phase-locked-loop circuit

    NASA Technical Reports Server (NTRS)

    Nyiri, E. J.

    1977-01-01

    Modified phase-locked loop (PLL) generates clock from incoming data signal. To minimize effects of threshold phase-detector gain variations, the PLL uses a dither oscillator, a dither band-pass filter, and correlator instead of coherent amplitude detector.

  15. Interstitial loop transformations in FeCr

    DOE PAGESBeta

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientationmore » depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.« less

  16. Interstitial loop transformations in FeCr

    SciTech Connect

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientation depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.

  17. BIOREACTOR DESIGN - OUTER LOOP LANDFILL, LOUISVILLE, KY

    EPA Science Inventory

    Bioreactor field demonstration projects are underway at the Outer Loop Landfill in Louisville, KY, USA. The research effort is a cooperative research effort between US EPA and Waste Management Inc. Two primary kinds of municipal waste bioreactors are under study at this site. ...

  18. Numerical multi-loop integrals and applications

    NASA Astrophysics Data System (ADS)

    Freitas, A.

    2016-09-01

    Higher-order radiative corrections play an important role in precision studies of the electroweak and Higgs sector, as well as for the detailed understanding of large backgrounds to new physics searches. For corrections beyond the one-loop level and involving many independent mass and momentum scales, it is in general not possible to find analytic results, so that one needs to resort to numerical methods instead. This article presents an overview of a variety of numerical loop integration techniques, highlighting their range of applicability, suitability for automatization, and numerical precision and stability. In a second part of this article, the application of numerical loop integration methods in the area of electroweak precision tests is illustrated. Numerical methods were essential for obtaining full two-loop predictions for the most important precision observables within the Standard Model. The theoretical foundations for these corrections will be described in some detail, including aspects of the renormalization, resummation of leading log contributions, and the evaluation of the theory uncertainty from missing higher orders.

  19. Mars Pathfinder mechanically pumped cooling loop

    NASA Technical Reports Server (NTRS)

    Birur, G. C.

    2001-01-01

    A mechanically pumped single-phase cooling loop was successfully flown on the Mars Pathfinder (MPF) Spacecraft which safely landed on the Martian surface on July 4, 1997. One of the key technologies that enabled the mission to succeed was an active heat rejection system (HRS) used to cool the electronics on the spacecraft during its seven-month cruise from Earth to Mars.

  20. Magnetic reconnection and solar flare loops

    NASA Technical Reports Server (NTRS)

    Forbes, T. G.

    1987-01-01

    Reconnection models of the main phase of large solar flares are used to explain the energetics and the motions of the large flare loops that occur during this phase. Correct predictions for the density and temperature of the X-ray emitting loops are obtained by coupling magnetic reconnection with chromospheric ablation. In the reconnection models the ablation is driven by the thermal conduction of heat along magnetic field lines connecting the reconnection shocks in the corona with the flare ribbons in the chromosphere. Combining the compressible reconnection theory of Soward and Priest (1982) with the magnetohydrodynamic (MHD) subshock criteria of Coroniti (1970) shows that the Petschek-type slow-mode shocks in the vicinity of the x-line always dissociate into pairs of isothermal slow-mode subshocks and thermal conduction fronts. The rate of expansion of the loops is a function of the reconnection rate, and loops can be evolving self-similarly in time with their height increasing as sq root t and the reconnection rate decreasing as t to the minus 1.

  1. Selective purge for hydrogenation reactor recycle loop

    DOEpatents

    Baker, Richard W.; Lokhandwala, Kaaeid A.

    2001-01-01

    Processes and apparatus for providing improved contaminant removal and hydrogen recovery in hydrogenation reactors, particularly in refineries and petrochemical plants. The improved contaminant removal is achieved by selective purging, by passing gases in the hydrogenation reactor recycle loop or purge stream across membranes selective in favor of the contaminant over hydrogen.

  2. Warm inflationary model in loop quantum cosmology

    SciTech Connect

    Herrera, Ramon

    2010-06-15

    A warm inflationary universe model in loop quantum cosmology is studied. In general we discuss the condition of inflation in this framework. By using a chaotic potential, V({phi}){proportional_to}{phi}{sup 2}, we develop a model where the dissipation coefficient {Gamma}={Gamma}{sub 0}=constant. We use recent astronomical observations for constraining the parameters appearing in our model.

  3. Closed Loop System Identification with Genetic Algorithms

    NASA Technical Reports Server (NTRS)

    Whorton, Mark S.

    2004-01-01

    High performance control design for a flexible space structure is challenging since high fidelity plant models are di.cult to obtain a priori. Uncertainty in the control design models typically require a very robust, low performance control design which must be tuned on-orbit to achieve the required performance. Closed loop system identi.cation is often required to obtain a multivariable open loop plant model based on closed-loop response data. In order to provide an accurate initial plant model to guarantee convergence for standard local optimization methods, this paper presents a global parameter optimization method using genetic algorithms. A minimal representation of the state space dynamics is employed to mitigate the non-uniqueness and over-parameterization of general state space realizations. This control-relevant system identi.cation procedure stresses the joint nature of the system identi.cation and control design problem by seeking to obtain a model that minimizes the di.erence between the predicted and actual closed-loop performance.

  4. Loop realizations of quantum affine algebras

    SciTech Connect

    Cautis, Sabin; Licata, Anthony

    2012-12-15

    We give a simplified description of quantum affine algebras in their loop presentation. This description is related to Drinfeld's new realization via halves of vertex operators. We also define an idempotent version of the quantum affine algebra which is suitable for categorification.

  5. Loop Evolution Observed with AIA and Hi-C

    NASA Technical Reports Server (NTRS)

    Mulu-Moore, Fana; Winebarger, Amy R.; Cirtain, Jonathan W.; Kobayashi, Ken; Korreck, Kelly E.; Golub, Leon; Kuzin, Sergei; Walsh, Robert William; DeForest, Craig E.; De Pontieu, Bart; Title, Alan M.; Weber, Mark

    2012-01-01

    In the past decade, the evolution of EUV loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this presentation we discuss the first results of loop analysis comparing AIA and Hi-C data. In the past decade, the evolution of EUV loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this presentation we discuss the first results of loop analysis comparing AIA and Hi-C data.

  6. Oriented matroids—combinatorial structures underlying loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Brunnemann, Johannes; Rideout, David

    2010-10-01

    We analyze combinatorial structures which play a central role in determining spectral properties of the volume operator (Ashtekar A and Lewandowski J 1998 Adv. Theor. Math. Phys. 1 388) in loop quantum gravity (LQG). These structures encode geometrical information of the embedding of arbitrary valence vertices of a graph in three-dimensional Riemannian space and can be represented by sign strings containing relative orientations of embedded edges. We demonstrate that these signature factors are a special representation of the general mathematical concept of an oriented matroid (Ziegler G M 1998 Electron. J. Comb.; Björner A et al 1999 Oriented Matroids (Cambridge: Cambridge University Press)). Moreover, we show that oriented matroids can also be used to describe the topology (connectedness) of directed graphs. Hence, the mathematical methods developed for oriented matroids can be applied to the difficult combinatorics of embedded graphs underlying the construction of LQG. As a first application we revisit the analysis of Brunnemann and Rideout (2008 Class. Quantum Grav. 25 065001 and 065002), and find that enumeration of all possible sign configurations used there is equivalent to enumerating all realizable oriented matroids of rank 3 (Ziegler G M 1998 Electron. J. Comb.; Björner A et al 1999 Oriented Matroids (Cambridge: Cambridge University Press)), and thus can be greatly simplified. We find that for 7-valent vertices having no coplanar triples of edge tangents, the smallest non-zero eigenvalue of the volume spectrum does not grow as one increases the maximum spin jmax at the vertex, for any orientation of the edge tangents. This indicates that, in contrast to the area operator, considering large jmax does not necessarily imply large volume eigenvalues. In addition we give an outlook to possible starting points for rewriting the combinatorics of LQG in terms of oriented matroids.

  7. Sfermion loop contribution to the two-loop level fermion electric dipole moment in R-parity violating supersymmetric models

    NASA Astrophysics Data System (ADS)

    Yamanaka, Nodoka

    2012-10-01

    We evaluate the Barr-Zee-type two-loop level contribution to the fermion electric and chromo-electric dipole moments with sfermion loop in R-parity violating supersymmetric models. It is found that the Barr-Zee-type fermion dipole moment with sfermion loop acts destructively to the currently known fermion loop contribution, and that it has small effect when the mass of squarks or charged sleptons in the loop is larger than or comparable to that of the sneutrinos, but cannot be neglected if the sneutrinos are much heavier than loop sfermions.

  8. Direct measurement of loop gain and bandwidth of phase-locked loop for mode-locked laser.

    PubMed

    Hou, Dong; Tian, Jie; Sun, Fuyu; Huang, Xianhe

    2016-07-25

    A simple and robust technique for measuring the loop gain and bandwidth of a phase-locking loop (PLL) for mode-locked laser is proposed. This technique can be used for the real-time measurement of the PLL's real loop gain and bandwidth in a closed loop without breaking its locking state. The agreement of the experimental result and theoretical calculation proves the validity of the proposed technique for measuring the loop gain and bandwidth. This technique with a simple configuration can be easily expanded to other laser's locking system whose loop gain and bandwidth should be measured in advance. PMID:27464173

  9. Polyakov loop and correlator of Polyakov loops at next-to-next-to-leading order

    SciTech Connect

    Brambilla, Nora; Vairo, Antonio; Ghiglieri, Jacopo; Petreczky, Peter

    2010-10-01

    We study the Polyakov loop and the correlator of two Polyakov loops at finite temperature in the weak-coupling regime. We calculate the Polyakov loop at order g{sup 4}. The calculation of the correlator of two Polyakov loops is performed at distances shorter than the inverse of the temperature and for electric screening masses larger than the Coulomb potential. In this regime, it is accurate up to order g{sup 6}. We also evaluate the Polyakov-loop correlator in an effective field theory framework that takes advantage of the hierarchy of energy scales in the problem and makes explicit the bound-state dynamics. In the effective field theory framework, we show that the Polyakov-loop correlator is at leading order in the multipole expansion the sum of a color-singlet and a color-octet quark-antiquark correlator, which are gauge invariant, and compute the corresponding color-singlet and color-octet free energies.

  10. Closed-loop and decision-assist resuscitation of burn patients.

    PubMed

    Salinas, Jose; Drew, Guy; Gallagher, James; Cancio, Leopoldo C; Wolf, Steven E; Wade, Charles E; Holcomb, John B; Herndon, David N; Kramer, George C

    2008-04-01

    Effective resuscitation is critical in reducing mortality and morbidity rates of patients with acute burns. To this end, guidelines and formulas have been developed to define infusion rates and volume requirements during the first 48 hours postburn. Even with these standardized resuscitation guidelines, however, over- and under-resuscitation are not uncommon. Two approaches to adjust infusion rate are decision-assist and closed-loop algorithms based on levels of urinary output. Specific decision assist guidelines or a closed-loop system using computer-controlled feedback technology that supplies automatic control of infusion rates can potentially achieve better control of urinary output. In a properly designed system, closed-loop control has the potential to provide more accurate titration rates, while lowering the incidence of over- and under-resuscitation. Because the system can self-adjust based on monitoring inputs, the technology can be pushed to environments such as combat zones where burn resuscitation expertise is limited. A closed-loop system can also assist in the management of mass casualties, another scenario in which medical expertise is often in short supply. This article reviews the record of fluid balance of contemporary burn resuscitation and approaches, as well as the engineering efforts, animal studies, and algorithm development of our most recent autonomous systems for burn resuscitation. PMID:18385584

  11. A loop resonator for slice-selective in vivo EPR imaging in rats.

    PubMed

    Hirata, Hiroshi; He, Guanglong; Deng, Yuanmu; Salikhov, Ildar; Petryakov, Sergey; Zweier, Jay L

    2008-01-01

    A loop resonator was developed for 300 MHz continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy and imaging in live rats. A single-turn loop (55 mm in diameter) was used to provide sufficient space for the rat body. Efficiency for generating a radiofrequency magnetic field of 38 microT/W(1/2) was achieved at the center of the loop. For the resonator itself, an unloaded quality factor of 430 was obtained. When a 350 g rat was placed in the resonator at the level of the lower abdomen, the quality factor decreased to 18. The sensitive volume in the loop was visualized with a bottle filled with an aqueous solution of the nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-CP). The resonator was shown to enable EPR imaging in live rats. Imaging was performed for 3-CP that had been infused intravenously into the rat and its distribution was visualized within the lower abdomen. PMID:18006343

  12. The simulation of thermohydraulic phenomena in a pressurized water reactor primary loop

    SciTech Connect

    Popp, M

    1987-01-01

    Several important fluid flow and heat transfer phenomena essential to nuclear power reactor safety were investigated. Scaling and modeling laws for pressurized water reactors are reviewed and a new scaling approach focusing on the overall loop behavior is presented. Scaling criteria for one- and two-phase natural circulation are developed, as well as a simplified model describing the first phase of a small break loss of coolant accident. Reactor vessel vent valve effects are included in the analysis of steady one-phase natural circulation flow. Two new dimensionless numbers, which uniquely describe one-phase flow in natural circulation loops, were deduced and are discussed. A scaled model of the primary loop of a typical Babcock and Wilcox reactor was designed, built, and tested. The particular prototype modeled was the TMI unit 2 reactor. The electrically heated, stainless steel model operates at a maximum pressure of 300 psig and has a maximum heat input of 188 kW. The model is about 4 times smaller in height than the prototype reactor, with a nominal volume scale of 1:500. Experiments were conducted establishing subcooled natural circulation in the model loop. Both steady flow and power transients were investigated.

  13. High-LET Patterns of DSBs in DNA Loops, the HPRT Gene and Phosphorylation Foci

    NASA Technical Reports Server (NTRS)

    Ponomarev, Artem L.; Huff, Janice L.; Cucinotta, Francis A.

    2007-01-01

    We present new results obtained with our model based on the track structure and chromatin geometry that predicts the DSB spatial and genomic distributions in a cell nucleus with the full genome represented. The model generates stochastic patterns of DSBs in the physical space of the nucleus filled with the realistic configuration of human chromosomes. The model was re-used to find the distribution of DSBs in a physical volume corresponding to a visible phosphorylation focus believed to be associated with a DSB. The data shows whether there must more than one DSB per foci due to finite size of the visible focus, even if a single DSB is radiochemically responsible for the phosphorylation of DNA in its vicinity. The same model can predict patterns of closely located DSBs in a given gene, or in a DNA loop, one of the large-scale chromatin structures. We demonstrated for the example of the HPRT gene, how different sorts of radiation lead to proximity effect in DSB locations, which is important for modeling gene deletions. The spectrum of intron deletions and total gene deletions was simulated for the HPRT gene. The same proximity effect of DSBs in a loop can hinder DSB restitutions, as parts of the loop between DSBs is deleted with a higher likelihood. The distributions of DSBs and deletions of DNA in a loop are presented.

  14. Parametric Multi-Level Tiling of Imperfectly Nested Loops

    SciTech Connect

    Hartono, Albert; Baskaran, Muthu M.; Bastoul, Cedric; Cohen, Albert; Krishnamoorthy, Sriram; Norris, Boyana; Ramanujam, J.; Sadayappan, Ponnuswamy

    2009-05-18

    Tiling is a critical loop transformation for generating high-performance code on modern architectures. Efficient generation of multilevel tiled code is essential to exploit several levels of parallelism and/or to maximize data reuse in deep memory hierarchies. Tiled loops with parameterized tile sizes (not compile time constants) facilitate runtime feedback and dynamic optimizations used in iterative compilation and automatic tuning. The existing parametric multilevel tiling approach has focused on transformation for perfectly nested loops, where all assignment statements are contained inside the innermost loop of a loop nest. Previous solutions to tiling for imperfect loop nests are limited to the case where tile sizes are fixed. In this paper, we present an approach to parameterized multilevel tiling for imperfectly nested loops. Our tiling algorithm generates loops that iterate over full rectangular tiles that are amenable for potential compiler optimizations such as register tiling. Experimental results using a number of computational benchmarks demonstrate the effectiveness of our tiling approach.

  15. The Seasonality Of The Loop Current

    NASA Astrophysics Data System (ADS)

    Hall, Cody Alan

    A total of 20 Loop Current eddy separation event dates were derived from Seasat and ERS-1 satellite altimetry, Coastal Zone Color Scanner chlorophyll-a images, Advanced Very High Resolution Radiometer sea surface temperature images, Horizon Marine, Inc. EddyWatch(TM) reports, and Climatology and Simulation of Eddies Eddy Joint Industry Project Gulf Eddy Model analyses spanning mid-1978 - 1992. There were many inconsistencies between the new "pre-altimetry" reanalysis dates derived from mostly non-altimeter data and dates published in past literature based on earlier versions of the pre-altimetry record. The reanalysis dates were derived from a larger compilation of data types and, consequently, were not as affected by intermittent and seasonal data outages common with past records. Therefore, the reanalysis dates are likely more accurate. About 30 Loop Current eddy separation dates were derived from altimetry data spanning 1993 -- 2012. The pre-altimetry and altimetry reanalysis dates along with similar altimetry dates published in other literature exhibit statistically significant seasonality. Eddy separation events are more likely in the months March, August, and September, and less likely in December. Reanalysis event dates were objectively divided into "spring" and "fall" seasons using a k-means clustering algorithm. The estimated spring and fall season centers are March 2nd and August 23 rd, respectively, with seasonal boundaries on May 22nd and December 3rd. The altimetry data suggest that Loop Current intrusion/retreat is dominantly an annual process. Loop Current metrics such as maximum northern boundary latitude and area are relatively high from January through about July and low in September and October. February metrics are statistically different than metrics in either October or November or both. This annual process is primarily driven by and dynamically linked to geostrophic currents seaward of the Campeche Bank shelf break forced by Kelvin waves

  16. Multivariate volume rendering

    SciTech Connect

    Crawfis, R.A.

    1996-03-01

    This paper presents a new technique for representing multivalued data sets defined on an integer lattice. It extends the state-of-the-art in volume rendering to include nonhomogeneous volume representations. That is, volume rendering of materials with very fine detail (e.g. translucent granite) within a voxel. Multivariate volume rendering is achieved by introducing controlled amounts of noise within the volume representation. Varying the local amount of noise within the volume is used to represent a separate scalar variable. The technique can also be used in image synthesis to create more realistic clouds and fog.

  17. Microscopic origin of volume modulus inflation

    SciTech Connect

    Cicoli, Michele; Muia, Francesco; Pedro, Francisco Gil

    2015-12-21

    High-scale string inflationary models are in well-known tension with low-energy supersymmetry. A promising solution involves models where the inflaton is the volume of the extra dimensions so that the gravitino mass relaxes from large values during inflation to smaller values today. We describe a possible microscopic origin of the scalar potential of volume modulus inflation by exploiting non-perturbative effects, string loop and higher derivative perturbative corrections to the supergravity effective action together with contributions from anti-branes and charged hidden matter fields. We also analyse the relation between the size of the flux superpotential and the position of the late-time minimum and the inflection point around which inflation takes place. We perform a detailed study of the inflationary dynamics for a single modulus and a two moduli case where we also analyse the sensitivity of the cosmological observables on the choice of initial conditions.

  18. Large volume axionic Swiss cheese inflation

    NASA Astrophysics Data System (ADS)

    Misra, Aalok; Shukla, Pramod

    2008-09-01

    Continuing with the ideas of (Section 4 of) [A. Misra, P. Shukla, Moduli stabilization, large-volume dS minimum without anti-D3-branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi Yau's, arXiv: 0707.0105 [hep-th], Nucl. Phys. B, in press], after inclusion of perturbative and non-perturbative α corrections to the Kähler potential and (D1- and D3-) instanton generated superpotential, we show the possibility of slow roll axionic inflation in the large volume limit of Swiss cheese Calabi Yau orientifold compactifications of type IIB string theory. We also include one- and two-loop corrections to the Kähler potential but find the same to be subdominant to the (perturbative and non-perturbative) α corrections. The NS NS axions provide a flat direction for slow roll inflation to proceed from a saddle point to the nearest dS minimum.

  19. Microscopic origin of volume modulus inflation

    NASA Astrophysics Data System (ADS)

    Cicoli, Michele; Muia, Francesco; Gil Pedro, Francisco

    2015-12-01

    High-scale string inflationary models are in well-known tension with low-energy supersymmetry. A promising solution involves models where the inflaton is the volume of the extra dimensions so that the gravitino mass relaxes from large values during inflation to smaller values today. We describe a possible microscopic origin of the scalar potential of volume modulus inflation by exploiting non-perturbative effects, string loop and higher derivative perturbative corrections to the supergravity effective action together with contributions from anti-branes and charged hidden matter fields. We also analyse the relation between the size of the flux superpotential and the position of the late-time minimum and the inflection point around which inflation takes place. We perform a detailed study of the inflationary dynamics for a single modulus and a two moduli case where we also analyse the sensitivity of the cosmological observables on the choice of initial conditions.

  20. Digital simulation of hybrid loop operation in RFI backgrounds.

    NASA Technical Reports Server (NTRS)

    Ziemer, R. E.; Nelson, D. R.

    1972-01-01

    A digital computer model for Monte-Carlo simulation of an imperfect second-order hybrid phase-locked loop (PLL) operating in radio-frequency interference (RFI) and Gaussian noise backgrounds has been developed. Characterization of hybrid loop performance in terms of cycle slipping statistics and phase error variance, through computer simulation, indicates that the hybrid loop has desirable performance characteristics in RFI backgrounds over the conventional PLL or the costas loop.

  1. An estimator-predictor approach to PLL loop filter design

    NASA Technical Reports Server (NTRS)

    Statman, Joseph I.; Hurd, William J.

    1990-01-01

    The design of digital phase locked loops (DPLL) using estimation theory concepts in the selection of a loop filter is presented. The key concept, that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor, is discussed. The estimator provides recursive estimates of phase, frequency, and higher-order derivatives, and the predictor compensates for the transport lag inherent in the loop.

  2. The dangers of metal-loop intraocular lenses.

    PubMed

    Shepard, D D

    1977-10-01

    The author implanted 500 intraocular lenses (IOLs) during intracapsular surgery. Data from the 60 lenses with metal posterior loops showed a markedly high incidence of complication compared to plastic loops: twice as many overall complications, three times the cystoid mascular edema, three times the rate for subsequent corrective surgical procedures, and 30 times more IOLs had to be removed. IOL manufacturers are advised to abandon metal loops for intracapsular implantation. Polypropylene is suggested as the apparent ideal loop material. PMID:304550

  3. Various options for electronic rebalancing loops of strapdown floated gyroscopes

    NASA Astrophysics Data System (ADS)

    Ribeiro, Jose Francisco

    1991-07-01

    A general view is presented of the different concepts for the problem of electronic rebalancing loops of strapdown floated gyroscopes. The loops of rebalancing analyzed are analogue, binary, ternary, and time modulated types. In particular, the errors are discussed along with the interfaces and the electronic implementation of each one of the loops. The rebalancing control loops are compared and one of them is selected for future analysis and simulation.

  4. Formation and evolution of the Waiho Loop terminal moraine, New Zealand

    NASA Astrophysics Data System (ADS)

    Alexander, David; Davies, Tim; Shulmeister, James

    2015-04-01

    The terminal moraine of the Franz Josef Glacier in New Zealand, known as the Waiho Loop, has been subject to intense scientific research since it was identified as potential evidence of a Southern Hemisphere Younger Dryas (~12000 yrs BP) event in the late 1980s and early 1990s. As a result, the large, arcuate moraine has been interpreted to indicate inter-hemispheric connectivity and synchronicity of climate change, and in turn has been inferred to indicate a major late-glacial cooling event in New Zealand. In recent times, it has been postulated that the Loop moraine may not reflect climate variation at all, but rather it may have been the result of a landslide sourced from the upper Franz Josef catchment due to its rock-avalanche-debris-dominated composition. New evidence from shallow seismic studies between the Loop and the range front (~3 km) suggests (i) that the presence of an overdeepened trough may be a critical component influencing glacier behaviour and moraine formation; and (ii) that the volume of the Waiho Loop is significantly greater than previously thought. Using a one-dimensional flowline model, two rock-avalanche-based scenarios for the formation of Loop are tested: first, that a rock avalanche generated a significant advance of the glacier terminus from a location within the confined mountain valley to the Loop; and second, that the rock avalanche occurred while the glacier was retreating from its long-occupied terminus at the distal margin of its overdeepened trough close to the position of the Loop during the Last Glacial Interglacial Transition (LGIT) 13000-11000 yrs BP. Results from the first test demonstrate that a rock avalanche could not have generated a significant advance of the Franz Josef Glacier terminus from a location within the confined mountain valley to form the Loop, because most of the rock avalanche debris could not be advected to the terminus to form a sufficiently high moraine before the ice in the upper catchment becomes

  5. Loop observations and the coronal heating problem

    NASA Astrophysics Data System (ADS)

    López Fuentes, M. C.; Klimchuk, J. A.

    2015-08-01

    Coronal heating continues to be one of the fundamental problems of solar physics. In recent years, instrumental advances and the availability of data from space observatories produced important progress, imposing restrictions to the models proposed. However, since the physical processes occur at spatial scales below the present instrumental resolution, definitive answers are still due. Since the corona is strongly dominated by the magnetic field, active region plasma is confined in closed structures or loops. These are the basic observable blocks of the corona, so the analysis of their structure and evolution is essential to understand the heating. In this report, mainly addressed to astronomers not necessarily familiarized with the subject, we review some of the proposed heating models and we pay special attention to the sometimes confusing and apparently contradictory observations of coronal loops. We discuss the consequences of these observations for some of the heating models proposed, in particular those based on impulsive events known as nanoflares.

  6. Adaptive Inner-Loop Rover Control

    NASA Technical Reports Server (NTRS)

    Kulkarni, Nilesh; Ippolito, Corey; Krishnakumar, Kalmanje; Al-Ali, Khalid M.

    2006-01-01

    Adaptive control technology is developed for the inner-loop speed and steering control of the MAX Rover. MAX, a CMU developed rover, is a compact low-cost 4-wheel drive, 4-wheel steer (double Ackerman), high-clearance agile durable chassis, outfitted with sensors and electronics that make it ideally suited for supporting research relevant to intelligent teleoperation and as a low-cost autonomous robotic test bed and appliance. The design consists of a feedback linearization based controller with a proportional - integral (PI) feedback that is augmented by an online adaptive neural network. The adaptation law has guaranteed stability properties for safe operation. The control design is retrofit in nature so that it fits inside the outer-loop path planning algorithms. Successful hardware implementation of the controller is illustrated for several scenarios consisting of actuator failures and modeling errors in the nominal design.

  7. String theory effective action; String loop corrections

    SciTech Connect

    Tseytlin, A.A. )

    1988-01-01

    The authors discuss the general ideology of the computation of string loop corrections to the effective action for the massless modes of the string. Both the S-matrix and the sigma-model approaches are presented. It is emphasized that the effective action is more general and better defined object than the S-matrix. In particular, it is finite in spite of modular infinities that may be present in loop amplitudes computed near a wrong vacuum. The case of the disc topology in the open-closed string theory is treated in some detail. Some issues concerning the soft dilation vertex operators related to the infinities of the string amplitudes are discussed.

  8. The Fundamental Structure of Coronal Loops

    NASA Technical Reports Server (NTRS)

    Winebarger, Amy; Warren, Harry; Cirtain, Jonathan; Kobayashi, Ken; Korreck, Kelly; Golub, Leon; Kuzin, Sergey; Walsh, Robert; DePontieu, Bart; Title, Alan; Weber, Mark

    2012-01-01

    During the past ten years, solar physicists have attempted to infer the coronal heating mechanism by comparing observations of coronal loops with hydrodynamic model predictions. These comparisons often used the addition of sub ]resolution strands to explain the observed loop properties. On July 11, 2012, the High Resolution Coronal Imager (Hi ]C) was launched on a sounding rocket. This instrument obtained images of the solar corona was 0.2 ]0.3'' resolution in a narrowband EUV filter centered around 193 Angstroms. In this talk, we will compare these high resolution images to simultaneous density measurements obtained with the Extreme Ultraviolet Imaging Spectrograph (EIS) on Hinode to determine whether the structures observed with Hi ]C are resolved.

  9. Adaptive autofocusing: a closed-loop perspective.

    PubMed

    Zhang, Ying; Wen, Changyun; Soh, Yeng Chai; Fong, Aik Meng

    2005-04-01

    We present an adaptive autofocusing scheme. In this scheme, the focus measure is updated with focus tuning. To achieve this, we construct the focus measure by using image moments and develop an adaptive focus-tuning strategy to estimate the measure in closed loop. It is shown that the adaptive updating of the focus measure enables us to overcome the dependence of autofocusing on the image contents. Such an adaptive closed-loop focusing operation also effectively suppresses both the effect of the noise in optical imaging and the effect of time delay due to image processing time. Therefore a high accuracy of autofocusing is guaranteed. The effectiveness of the proposed scheme is demonstrated by simulations and experiments. PMID:15839269

  10. Closed Loop Welding Controller for Manufacturing Process

    NASA Astrophysics Data System (ADS)

    Bonaccorso, F.; Bruno, C.; Cantelli, L.; Longo, D.; Muscato, G.; Rapisarda, S.

    2011-12-01

    The aim of this paper is to investigate on the closed loop welding controller of a rapid manufacturing Shaped Metal Deposition (SMD) process. SMD was developed and patented by Rolls-Royce in order to produce mechanical parts directly from a CAD model. A simplified SMD plant has been set up in order to investigate the welding dynamics and parameters and to develop a SMD automatic controller. On the basis of the experience acquired, some basic control laws have been developed, and a closed loop controller has been implemented. This controller permits to find and to maintain the process stability condition, so that the final process results totally automatic. The control is performed adjusting the welding conditions on the basis of arc voltage information obtained from the welding machine during the deposition. The experimental results reported confirm the validity of the proposed strategy.

  11. DNA loops generate intracentromere tension in mitosis

    PubMed Central

    Lawrimore, Josh; Vasquez, Paula A.; Falvo, Michael R.; Taylor, Russell M.; Vicci, Leandra; Yeh, Elaine; Forest, M. Gregory

    2015-01-01

    The centromere is the DNA locus that dictates kinetochore formation and is visibly apparent as heterochromatin that bridges sister kinetochores in metaphase. Sister centromeres are compacted and held together by cohesin, condensin, and topoisomerase-mediated entanglements until all sister chromosomes bi-orient along the spindle apparatus. The establishment of tension between sister chromatids is essential for quenching a checkpoint kinase signal generated from kinetochores lacking microtubule attachment or tension. How the centromere chromatin spring is organized and functions as a tensiometer is largely unexplored. We have discovered that centromere chromatin loops generate an extensional/poleward force sufficient to release nucleosomes proximal to the spindle axis. This study describes how the physical consequences of DNA looping directly underlie the biological mechanism for sister centromere separation and the spring-like properties of the centromere in mitosis. PMID:26283798

  12. A multifilter phase-lock loop.

    NASA Technical Reports Server (NTRS)

    Carden, F.; Thompson, W. E.; Cheng, E.

    1971-01-01

    The phase model for the generalized multifilter phase-lock loop (M PLL) is considered and state equations for this model are derived. A linear analysis is presented to aid in the preliminary design of an M PLL and to indicate the noise improvement over a conventional phase-lock loop (PLL). Performance characteristics are examined for an M PLL with low-pass and bandpass characteristics used in a specific FM communication system. Both single and double sinusoidal FM are used and a region of proper operation of the M PLL is determined in terms of modulation index and modulati ng frequency. These results are obtained from both analog and digital computer simulation of the nonlinear system.

  13. Capillary pumped loop body heat exchanger

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore D. (Inventor); Wren, deceased, Paul (Inventor)

    1998-01-01

    A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.

  14. Analysis of CREVONA sodium loop material

    NASA Astrophysics Data System (ADS)

    Ganesan, Vaidehi; Ganesan, V.; Borgstedt, H. U.

    2003-02-01

    Stainless steel specimens equivalent to AISI type 304 taken from the CREVONA sodium loop (Forschungszentrum Karlsruhe, Germany), which was operated for more than 80 000 h, were analysed for microstructures and changes in chemical composition of depleted layers using SEM/EDAX. SEM micrographs were obtained in the cross-section of the specimens to reveal the thickness of the corroded layer. EDX analysis confirms depletion of Ni and Cr in the corroded layer. The leaching rates of chromium and nickel are obtained from the depleted layer width. These results are compared with the degraded layer and corrosion resistant node formation in sodium-exposed AISI type 316 SS specimens. The corroded layer widths of the specimens taken from the CREVONA loop determined using known models for life prediction like those proposed by Thorley and Tyzack are found to be much less than the actual layer widths observed experimentally after sodium exposure. The materials were exposed to flowing sodium for about 10 years.

  15. The wire anchor loop traction (WALT) maneuver.

    PubMed

    Effendi, Khaled; Sacho, Raphael Hillel; Belzile, François; Marotta, Thomas R

    2016-02-01

    Crossing the neck of large complex intracranial aneurysms for the purposes of stent deployment can be challenging using standard over the wire techniques. We describe a novel yet simple technique for straightening out the loop formed within a large intracranial aneurysm, which is often required in order to cross the aneurysm neck into the distal branch. Both the microcatheter and microwire are initially introduced into the distal vasculature, followed by withdrawal of the microwire to a point parallel to the distal exiting branch. The microcatheter and microwire are then gently withdrawn and a series of maneuvers to gradually reduce the loop is performed, obviating the need for distal purchase in the form of a stent, balloon, or coil, which have previously been described to maintain distal purchase. PMID:25634903

  16. Molecular motor driven transportation on microtubule loops

    NASA Astrophysics Data System (ADS)

    Sikora, Aurelien; Federici, Filippo; Kim, Kyongwan; Nakazawa, Hikaru; Umetsu, Mitsuo; Hwang, Wonmuk; Teizer, Winfried

    2015-03-01

    Molecular motors such as kinesin are naturally fitted for the transport of cargo. By offering an unlimited path, microtubule loops allow the study of kinesin motility on distances exceeding that offered by a single microtubule. Moreover, the periodicity of the path allows the comparisons of trajectories between laps. Here we study the motility of quantum dot labeled kinesin on microtubule loops. Motility of kinesins over multiple laps is observed and their trajectories are extracted from kymograph using a custom algorithm. Distribution of velocities at given locations do not vary randomly but show a correlation with the presence of obstacles. Possible mechanisms responsible for the long range transport are discussed in the context of available theories.

  17. Coronal seismology using transverse loop oscillations

    NASA Astrophysics Data System (ADS)

    Verwichte, E.; Foullon, C.; Van Doorsselaere, T.; Smith, H. M.; Nakariakov, V. M.

    2009-12-01

    Coronal seismology exploits the properties of magnetohydrodynamics in the corona of the Sun to diagnose the local plasma. Therefore, seismology complements direct diagnostic techniques, which suffer from line-of-sight integration or may not give access to all physical quantities. In particular, the seismological exploitation of fast magnetoacoustic oscillations in coronal loops provides information about the global magnetic and density structuring of those loops acting as wave guides. From the oscillation period and damping time it is shown how to obtain information about the local coronal magnetic field as well as the longitudinal and transverse structuring. Furthermore, such studies motivate the development of coronal wave theories, which are also relevant to the coronal heating problem.

  18. Separable Hilbert space in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Fairbairn, Winston; Rovelli, Carlo

    2004-07-01

    We study the separability of the state space of loop quantum gravity. In the standard construction, the kinematical Hilbert space of the diffeomorphism-invariant states is nonseparable. This is a consequence of the fact that the knot space of the equivalence classes of graphs under diffeomorphisms is noncountable. However, the continuous moduli labeling these classes do not appear to affect the physics of the theory. We investigate the possibility that these moduli could be only the consequence of a poor choice in the fine-tuning of the mathematical setting. We show that by simply choosing a minor extension of the functional class of the classical fields and coordinates, the moduli disappear, the knot classes become countable, and the kinematical Hilbert space of loop quantum gravity becomes separable.

  19. Loop parallelism on Tera MTA using SISAL

    SciTech Connect

    Mitrovic, S.

    1995-11-01

    The difficulty of programming parallel computers has impeded their wide-spread use. The problems are caused by existing hardware and software tools. The software problems on shared-memory and vector computers can be solved by using deterministic high-performance functional languages like SISAL. Distributed-memory computers have even more obstacles than shared-memory parallel machines. Research indicates that multithreaded architectures can hide long latency of distributed memories and that they can solve the problems of locality. Tera`s MTA multiprocessor is based on the concept of multithreading and provides the programmer with a real shared-memory model. This paper investigates the performance of parallel loops written in SISAL and executed on the Tera MTA using the Livermore Loops benchmarks.

  20. Loop quantization of the Schwarzschild black hole.

    PubMed

    Gambini, Rodolfo; Pullin, Jorge

    2013-05-24

    We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian, and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes. PMID:23745855

  1. Analytic structure of one-loop coefficients

    NASA Astrophysics Data System (ADS)

    Feng, Bo; Wang, Honghui

    2013-05-01

    By the unitarity cut method, analytic expressions of one-loop coefficients have been given in spinor forms. In this paper, we present one-loop coefficients of various bases in Lorentz-invariant contraction forms of external momenta. Using these forms, the analytic structure of these coefficients becomes manifest. Firstly, coefficients of bases contain only second-type singularities while the first-type singularities are included inside scalar bases. Secondly, the highest degree of each singularity is correlated with the degree of the inner momentum in the numerator. Thirdly, the same singularities will appear in different coefficients, thus our explicit results could be used to provide a clear physical picture under various limits (such as soft or collinear limits) when combining contributions from all bases.

  2. Mutual inductance between piecewise-linear loops

    NASA Astrophysics Data System (ADS)

    Cristina Barroso, Ana; Silva, J. P.

    2013-11-01

    We consider a current-carrying wire loop made out of linear segments of arbitrary sizes and directions in three-dimensional space. We develop expressions to calculate its vector potential and magnetic field at all points in space. We then calculate the mutual inductance between two such (non-intersecting) piecewise-linear loops. As simple applications, we consider in detail the mutual inductance between two square wires of equal length that either lie in the same plane or lie in parallel horizontal planes with their centers on the same vertical axis. Our expressions can also be used to obtain approximations to the mutual inductance between wires of arbitrary three-dimensional shapes.

  3. Square-loop cobalt/gold multilayers

    NASA Astrophysics Data System (ADS)

    Gambino, R. J.; Ruf, R. R.

    1990-05-01

    Multilayers of Co and Au with perpendicular hysteresis loop squareness ratios of ˜1 have been prepared by e-beam evaporation. These films have perpendicular anisotropy in the as-deposited condition in contrast to other work in which Co/Au multilayers, prepared by ion beam sputtering, showed perpendicular anisotropy only after annealing at 300 °C. The Faraday rotation of these square-loop multilayers is about 9×105 deg/cm of Co or 1×105 deg/cm of total thickness at a wavelength of 633 nm. These values indicate an enhancement of the Faraday rotation of Co at this wavelength by about a factor of 2. This may be a plasma-edge enhancement effect similar to that reported by Katayama et al. [Phys. Rev. Lett. 60, 1426 (1988)] in the Kerr effect of Fe/Au multilayers.

  4. Closed-Loop Optogenetic Intervention in Mice

    PubMed Central

    Oijala, Mikko; Soltesz, Ivan

    2014-01-01

    Optogenetic interventions offer novel ways of probing, in a temporally specific manner, the roles of specific cell types in neuronal network functions of awake, behaving animals. Despite the unique potential for temporally specific optogenetic interventions in disease states, a major hurdle in its broad application to unpredictable brain states in a laboratory setting is constructing a real-time responsive system. We recently created a closed-loop system for stopping spontaneous seizures in chronically epileptic mice using optogenetic intervention. This system performs with very high sensitivity and specificity, and the strategy is relevant not only to epilepsy, but can also be used to react in real time, with optogenetic or other interventions, to diverse brain states. The protocol presented here is highly modular and requires variable time to perform. We describe the basic construction of a complete system, and include our downloadable custom closed-loop detection software which can be employed for this purpose. PMID:23845961

  5. Force distribution in a semiflexible loop

    NASA Astrophysics Data System (ADS)

    Waters, James T.; Kim, Harold D.

    2016-04-01

    Loops undergoing thermal fluctuations are prevalent in nature. Ringlike or cross-linked polymers, cyclic macromolecules, and protein-mediated DNA loops all belong to this category. Stability of these molecules are generally described in terms of free energy, an average quantity, but it may also be impacted by local fluctuating forces acting within these systems. The full distribution of these forces can thus give us insights into mechanochemistry beyond the predictive capability of thermodynamics. In this paper, we study the force exerted by an inextensible semiflexible polymer constrained in a looped state. By using a simulation method termed "phase-space sampling," we generate the equilibrium distribution of chain conformations in both position and momentum space. We compute the constraint forces between the two ends of the loop in this chain ensemble using Lagrangian mechanics, and show that the mean of these forces is equal to the thermodynamic force. By analyzing kinetic and potential contributions to the forces, we find that the mean force acts in the direction of increasing extension not because of bending stress, but in spite of it. Furthermore, we obtain a distribution of constraint forces as a function of chain length, extension, and stiffness. Notably, increasing contour length decreases the average force, but the additional freedom allows fluctuations in the constraint force to increase. The force distribution is asymmetric and falls off less sharply than a Gaussian distribution. Our work exemplifies a system where large-amplitude fluctuations occur in a way unforeseen by a purely thermodynamic framework, and offers computational tools useful for efficient, unbiased simulation of a constrained system.

  6. Revisiting Wilson loops for nonrelativistic backgrounds

    NASA Astrophysics Data System (ADS)

    Araujo, Thiago R.

    2015-12-01

    We consider several configurations that describe Wilson loops in nonrelativistic field theories, and for some of them we find systems of coupled nonlinear differential equations. Also, we find a nontrivial drag force at zero temperature, which suggests that the parameter controlling the deviation of the nonrelativistic space from the relativistic space may be related to the chemical potential of these systems. Moreover, we reconsider some known configurations in the literature and we perform further analysis.

  7. Orion Suit Loop Variable Pressure Regulator Development

    NASA Technical Reports Server (NTRS)

    Mosher, Michael; Vassallo, Andrew; Lewis, John F.; Campbell, Melissa

    2014-01-01

    The Orion Multi Purpose Crew Vehicle (MPCV) integrates the cabin and pressure suits with the core life support systems to provide life support during contingency depressurized cabin operations. To provide the multipule suit pressures between nominal pressurized cabin suited operations, suit leak checks, depressurized cabin suited operations, and elevated suit pressure for denitrification, a variable pressure regulator is needed. This paper documents the development and integrated testing of the suit loop regulator for Orion.

  8. Orion Suit Loop Variable Pressure Regulator Development

    NASA Technical Reports Server (NTRS)

    Mosher, Michael; Lewis, John F.; Campbell, Melissa

    2012-01-01

    The Orion Multi Purpose Crew Vehicle (MPCV) integrates the cabin and pressure suits with the core life support systems to provide life support during contingency depressurized cabin operations. To provide the multiple suit pressures between nominal pressurized cabin suited operations, suit leak checks, depressurized cabin suited operations, and elevated suit pressure for denitrification, a variable pressure regulator is needed. This paper documents the development of the suit loop regulator for Orion.

  9. Pumped two-phase heat transfer loop

    NASA Technical Reports Server (NTRS)

    Edelstein, Fred

    1988-01-01

    A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

  10. Pumped two-phase heat transfer loop

    NASA Technical Reports Server (NTRS)

    Edelstein, Fred (Inventor)

    1987-01-01

    A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

  11. Closed-loop pulsed helium ionization detector

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detector for gas chromatography is operated in a constant current, pulse-modulated mode by configuring the detector, electrometer and a high voltage pulser in a closed-loop control system. The detector current is maintained at a fixed level by varying the frequency of fixed-width, high-voltage bias pulses applied to the detector. An output signal proportional to the pulse frequency is produced which is indicative of the charge collected for a detected species.

  12. Semi-Infinite Cohomology of Loop Spaces

    NASA Astrophysics Data System (ADS)

    Shutler, Paul Maurice Edmund

    Available from UMI in association with The British Library. Requires signed TDF. This thesis attempts to construct a de Rham model for the Floer homology of the space of free loops on a symplectic manifold. It derives its inspiration principally from the work of Witten on topological quantum field theories. Chapter 1 consist of a review of background material followed by a number of elementary results. It is seen how Floer homology should naturally be representable by a semi-infinite generalisation of the ordinary de Rham theory associated to a manifold. In Chapter 2 the main attempt at constructing such a semi-infinite theory is made by defining an exterior derivative. Two different kinds of divergences are encountered and resolved. A suitable space of semi-infinite forms is constructed and some remarks are made about the likelihood that this model captures the Floer homology. In Chapter 3 the obstruction to the existence of a chiral factorisation of the bundle of fermionic Fock spaces over the loop space of the two-sphere is computed. For this purpose the ordinary cohomology ring of the loop space is calculated, also the action of the deck transformation on the cohomology of the simply connected covering space. In Chapter 4 the supersymmetric path integral approach to quantising topological field theories is developed formally. The semi-infinite dimensionality of the differential forms involved emerges naturally. The Floer homology of loop space is shown to be a ring. Its structure is calculated for the simple case of complex projective space. Chapter 5 concludes the thesis with some remarks about the action of the super-Virasoro algebra on the space of ordinary and semi-infinite differential forms respectively. Two short appendices are included describing a polynomial generating function for spherical harmonics and the spectrum of curl on vector fields on the three -sphere.

  13. Einstein Gyrogroup as a B-loop

    NASA Astrophysics Data System (ADS)

    Suksumran, Teerapong; Wiboonton, Keng

    2015-08-01

    Using the Clifford algebra formalism, we give an algebraic proof that the open unit ball B = v ∈Rn : ‖ v ‖ < 1 } of Rn equipped with Einstein addition ⊕E forms a B-loop or, equivalently, a uniquely 2-divisible gyrocommutative gyrogroup. We obtain a compact formula for Einstein addition in terms of Möbius addition. We then give a characterization of associativity and commutativity of vectors in B with respect to Einstein addition.

  14. Wilson loops and Riemann theta functions II

    NASA Astrophysics Data System (ADS)

    Kruczenski, Martin; Ziama, Sannah

    2014-05-01

    In this paper we extend and simplify previous results regarding the computation of Euclidean Wilson loops in the context of the AdS/CFT correspondence, or, equivalently, the problem of finding minimal area surfaces in hyperbolic space (Euclidean AdS3). If the Wilson loop is given by a boundary curve( s) we define, using the integrable properties of the system, a family of curves ( λ, s) depending on a complex parameter λ known as the spectral parameter. This family has remarkable properties. As a function of λ, ( λ, s) has cuts and therefore is appropriately defined on a hyperelliptic Riemann surface, namely it determines the spectral curve of the problem. Moreover, ( λ, s) has an essential singularity at the origin λ = 0. The coefficients of the expansion of ( λ, s) around λ = 0, when appropriately integrated along the curve give the area of the corresponding minimal area surface. Furthermore we show that the same construction allows the computation of certain surfaces with one or more boundaries corresponding to Wilson loop correlators. We extend the area formula for that case and give some concrete examples. As the main example we consider a surface ending on two concentric circles and show how the boundary circles can be deformed by introducing extra cuts in the spectral curve.

  15. Toward precision holography with supersymmetric Wilson loops

    NASA Astrophysics Data System (ADS)

    Faraggi, Alberto; Pando Zayas, Leopoldo A.; Silva, Guillermo A.; Trancanelli, Diego

    2016-04-01

    We consider certain 1/4 BPS Wilson loop operators in SU( N) N=4 supersymmetric Yang-Mills theory, whose expectation value can be computed exactly via supersymmetric localization. Holographically, these operators are mapped to fundamental strings in AdS 5 × S 5. The string on-shell action reproduces the large N and large coupling limit of the gauge theory expectation value and, according to the AdS/CFT correspondence, there should also be a precise match between subleading corrections to these limits. We perform a test of such match at next-to-leading order in string theory, by deriving the spectrum of quantum fluctuations around the classical string solution and by computing the corresponding 1-loop effective action. We discuss in detail the supermultiplet structure of the fluctuations. To remove a possible source of ambiguity in the ghost zero mode measure, we compare the 1/4 BPS configuration with the 1/2 BPS one, dual to a circular Wilson loop. We find a discrepancy between the string theory result and the gauge theory prediction, confirming a previous result in the literature. We are able to track the modes from which this discrepancy originates, as well as the modes that by themselves would give the expected result.

  16. Leptogenesis from loop effects in curved spacetime

    NASA Astrophysics Data System (ADS)

    McDonald, Jamie I.; Shore, Graham M.

    2016-04-01

    We describe a new mechanism — radiatively-induced gravitational leptogenesis — for generating the matter-antimatter asymmetry of the Universe. We show how quantum loop effects in C and CP violating theories cause matter and antimatter to propagate differently in the presence of gravity, and prove this is forbidden in flat space by CPT and translation symmetry. This generates a curvature-dependent chemical potential for leptons, allowing a matter-antimatter asymmetry to be generated in thermal equilibrium in the early Universe. The time-dependent dynamics necessary for leptogenesis is provided by the interaction of the virtual self-energy cloud of the leptons with the expanding curved spacetime background, which violates the strong equivalence principle and allows a distinction between matter and antimatter. We show here how this mechanism is realised in a particular BSM theory, the see-saw model, where the quantum loops involve the heavy sterile neutrinos responsible for light neutrino masses. We demonstrate by explicit computation of the relevant two-loop Feynman diagrams how the size of the radiative corrections relevant for leptogenesis becomes enhanced by increasing the mass hierarchy of the sterile neutrinos, and show how the induced lepton asymmetry may be sufficiently large to play an important rôle in determining the baryon-to-photon ratio of the Universe.

  17. Closed-Loop, Open-Source Electrophysiology

    PubMed Central

    Rolston, John D.; Gross, Robert E.; Potter, Steve M.

    2010-01-01

    Multiple extracellular microelectrodes (multi-electrode arrays, or MEAs) effectively record rapidly varying neural signals, and can also be used for electrical stimulation. Multi-electrode recording can serve as artificial output (efferents) from a neural system, while complex spatially and temporally targeted stimulation can serve as artificial input (afferents) to the neuronal network. Multi-unit or local field potential (LFP) recordings can not only be used to control real world artifacts, such as prostheses, computers or robots, but can also trigger or alter subsequent stimulation. Real-time feedback stimulation may serve to modulate or normalize aberrant neural activity, to induce plasticity, or to serve as artificial sensory input. Despite promising closed-loop applications, commercial electrophysiology systems do not yet take advantage of the bidirectional capabilities of multi-electrodes, especially for use in freely moving animals. We addressed this lack of tools for closing the loop with NeuroRighter, an open-source system including recording hardware, stimulation hardware, and control software with a graphical user interface. The integrated system is capable of multi-electrode recording and simultaneous patterned microstimulation (triggered by recordings) with minimal stimulation artifact. The potential applications of closed-loop systems as research tools and clinical treatments are broad; we provide one example where epileptic activity recorded by a multi-electrode probe is used to trigger targeted stimulation, via that probe, to freely moving rodents. PMID:20859448

  18. Tracking Loop Current eddies with satellite altimetry

    NASA Astrophysics Data System (ADS)

    Leben, Robert R.; Born, George H.

    1993-11-01

    Geosat altimeter derived sea surface height (SSH) anomaly fields have been optimally interpolated onto a regular space time grid using both crossover data from the nonrepeating Geodetic Mission (Geosat-GM) and collinear data from the Exact Repeat Mission (Geosat-ERM). Over four years of data were collected from the combined missions, spanning the time period from April 1985 through August 1989, during which six major and at least two minor Loop Current eddies were directly observed. Eddy paths determined by automated tracking of the local maximum values in the SSH anomaly fields were compared with eddy centers estimated from drifting buoy trajectories, validating the data processing and tracking techniques. Accurate tracking of eddy centers allowed transits of 90°W to be used as a benchmark for determination of eddy shedding periods. For this data set the average period between major eddy transits was 9.8 months, with individual separation periods ranging from 6 to 14 months. The two minor eddies observed were associated with the deepest penetrations of the Loop Current into the gulf, and were nearly coincident with the shedding of the strongest major Loop Current eddies.

  19. Phase-locked loop FM demodulator

    NASA Technical Reports Server (NTRS)

    Kirkham, Harold (Inventor); Jackson, Shannon P. (Inventor)

    1992-01-01

    A conventional phase-locked loop is improved by replacing its phase detector with one comprising a linear ramp generator and a sample-and-hold circuit, thus eliminating the need for a lowpass loop filter, although the output of the sample-and-hold circuit may be filtered in the case of a very low level modulating signal on the incoming FM signal, but then filtering is not a difficult problem as in a conventional phase-locked loop. The result is FM demodulation by zero-order estimation. For FM demodulation by first-order estimation, the arithmetic difference between adjacent samples is formed, and using a second sample-and-hold circuit an arithmetic difference signal is produced as an input to a second ramp generator that is reset after each sampling cycle to generate a ramp the slope of which is a function of the arithmetic difference signal stored in the second sample-and-hold circuit. The ramp thus generated by the second ramp generator is arithmetically summed with the zero-estimation signal from the first sample-and-hold circuit to form a first-order estimation signal. Filtering such a first-order estimation signal is less of a problem than filtering a zero-order estimation signal.

  20. Closed-loop, open-source electrophysiology.

    PubMed

    Rolston, John D; Gross, Robert E; Potter, Steve M

    2010-01-01

    Multiple extracellular microelectrodes (multi-electrode arrays, or MEAs) effectively record rapidly varying neural signals, and can also be used for electrical stimulation. Multi-electrode recording can serve as artificial output (efferents) from a neural system, while complex spatially and temporally targeted stimulation can serve as artificial input (afferents) to the neuronal network. Multi-unit or local field potential (LFP) recordings can not only be used to control real world artifacts, such as prostheses, computers or robots, but can also trigger or alter subsequent stimulation. Real-time feedback stimulation may serve to modulate or normalize aberrant neural activity, to induce plasticity, or to serve as artificial sensory input. Despite promising closed-loop applications, commercial electrophysiology systems do not yet take advantage of the bidirectional capabilities of multi-electrodes, especially for use in freely moving animals. We addressed this lack of tools for closing the loop with NeuroRighter, an open-source system including recording hardware, stimulation hardware, and control software with a graphical user interface. The integrated system is capable of multi-electrode recording and simultaneous patterned microstimulation (triggered by recordings) with minimal stimulation artifact. The potential applications of closed-loop systems as research tools and clinical treatments are broad; we provide one example where epileptic activity recorded by a multi-electrode probe is used to trigger targeted stimulation, via that probe, to freely moving rodents. PMID:20859448

  1. Wilson loops from supergravity and string theory

    NASA Astrophysics Data System (ADS)

    Sonnenschein, J.

    2000-03-01

    We present a theorem that determines the value of the Wilson loop associated with a Nambu-Goto action which generalizes the action of the AdS 5 × S 5 model. In particular, we derive sufficient conditions for confining behaviour. We then apply this theorem to various string models. We go beyond the classical string picture by incorporating quadratic quantum fluctuations. We show that the bosonic determinant of Dp -branes with 16 supersymmetries yields a Lüscher term. We confirm that the free energy associated with a BPS configuration of a single quark is free from divergences. We show that unlike for a string in flat spacetime in the case of AdS 5 × S 5 the fermionic determinant does not cancel the bosonic one. For a set-up that corresponds to a confining gauge theory the correction to the potential is attractive. We determine the form of the Wilson loop for actions that include non-trivial B µicons/Journals/Common/nu" ALT="nu" ALIGN="TOP"/> field. The issue of an exact determination of the value of the stringy Wilson loop is discussed.

  2. One-loop effective lagrangians after matching

    NASA Astrophysics Data System (ADS)

    del Aguila, F.; Kunszt, Z.; Santiago, J.

    2016-05-01

    We discuss the limitations of the covariant derivative expansion prescription advocated to compute the one-loop Standard Model (SM) effective lagrangian when the heavy fields couple linearly to the SM. In particular, one-loop contributions resulting from the exchange of both heavy and light fields must be explicitly taken into account through matching because the proposed functional approach alone does not account for them. We review a simple case with a heavy scalar singlet of charge -1 to illustrate the argument. As two other examples where this matching is needed and this functional method gives a vanishing result, up to renormalization of the heavy sector parameters, we re-evaluate the one-loop corrections to the T-parameter due to a heavy scalar triplet with vanishing hypercharge coupling to the Brout-Englert-Higgs boson and to a heavy vector-like quark singlet of charged 2 / 3 mixing with the top quark, respectively. In all cases we make use of a new code for matching fundamental and effective theories in models with arbitrary heavy field additions.

  3. MAGNETIC LOOPS IN THE QUIET SUN

    SciTech Connect

    Wiegelmann, T.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Borrero, J. M.; Schmidt, W.; Pillet, V. MartInez; Bonet, J. A.; Domingo, V.; Knoelker, M.; Title, A. M.

    2010-11-10

    We investigate the fine structure of magnetic fields in the atmosphere of the quiet Sun. We use photospheric magnetic field measurements from SUNRISE/IMaX with unprecedented spatial resolution to extrapolate the photospheric magnetic field into higher layers of the solar atmosphere with the help of potential and force-free extrapolation techniques. We find that most magnetic loops that reach into the chromosphere or higher have one footpoint in relatively strong magnetic field regions in the photosphere. Ninety-one percent of the magnetic energy in the mid-chromosphere (at a height of 1 Mm) is in field lines, whose stronger footpoint has a strength of more than 300 G, i.e., above the equipartition field strength with convection. The loops reaching into the chromosphere and corona are also found to be asymmetric in the sense that the weaker footpoint has a strength B < 300 G and is located in the internetwork (IN). Such loops are expected to be strongly dynamic and have short lifetimes, as dictated by the properties of the IN fields.

  4. Magnetic Loops in the Quiet Sun

    NASA Astrophysics Data System (ADS)

    Wiegelmann, T.; Solanki, S. K.; Borrero, J. M.; Martínez Pillet, V.; del Toro Iniesta, J. C.; Domingo, V.; Bonet, J. A.; Barthol, P.; Gandorfer, A.; Knölker, M.; Schmidt, W.; Title, A. M.

    2010-11-01

    We investigate the fine structure of magnetic fields in the atmosphere of the quiet Sun. We use photospheric magnetic field measurements from SUNRISE/IMaX with unprecedented spatial resolution to extrapolate the photospheric magnetic field into higher layers of the solar atmosphere with the help of potential and force-free extrapolation techniques. We find that most magnetic loops that reach into the chromosphere or higher have one footpoint in relatively strong magnetic field regions in the photosphere. Ninety-one percent of the magnetic energy in the mid-chromosphere (at a height of 1 Mm) is in field lines, whose stronger footpoint has a strength of more than 300 G, i.e., above the equipartition field strength with convection. The loops reaching into the chromosphere and corona are also found to be asymmetric in the sense that the weaker footpoint has a strength B < 300 G and is located in the internetwork (IN). Such loops are expected to be strongly dynamic and have short lifetimes, as dictated by the properties of the IN fields.

  5. Aeration and mass transfer optimization in a rectangular airlift loop photobioreactor for the production of microalgae.

    PubMed

    Guo, Xin; Yao, Lishan; Huang, Qingshan

    2015-08-01

    Effects of superficial gas velocity and top clearance on gas holdup, liquid circulation velocity, mixing time, and mass transfer coefficient are investigated in a new airlift loop photobioreactor (PBR), and empirical models for its rational control and scale-up are proposed. In addition, the impact of top clearance on hydrodynamics, especially on the gas holdup in the internal airlift loop reactor, is clarified; a novel volume expansion technique is developed to determine the low gas holdup in the PBR. Moreover, a model strain of Chlorella vulgaris is cultivated in the PBR and the volumetric power is analyzed with a classic model, and then the aeration is optimized. It shows that the designed PBR, a cost-effective reactor, is promising for the mass cultivation of microalgae. PMID:25958141

  6. Cutting a Drop of Water Pinned by Wire Loops Using a Superhydrophobic Surface and Knife

    PubMed Central

    Yanashima, Ryan; García, Antonio A.; Aldridge, James; Weiss, Noah; Hayes, Mark A.; Andrews, James H.

    2012-01-01

    A water drop on a superhydrophobic surface that is pinned by wire loops can be reproducibly cut without formation of satellite droplets. Drops placed on low-density polyethylene surfaces and Teflon-coated glass slides were cut with superhydrophobic knives of low-density polyethylene and treated copper or zinc sheets, respectively. Distortion of drop shape by the superhydrophobic knife enables a clean break. The driving force for droplet formation arises from the lower surface free energy for two separate drops, and it is modeled as a 2-D system. An estimate of the free energy change serves to guide when droplets will form based on the variation of drop volume, loop spacing and knife depth. Combining the cutting process with an electrofocusing driving force could enable a reproducible biomolecular separation without troubling satellite drop formation. PMID:23029297

  7. Large loop EMI sensor for detection of deeply buried munitions in magnetic soils

    NASA Astrophysics Data System (ADS)

    Miller, Jonathan S.; Billings, Stephen; Keranen, Joe; Schultz, Gregory; Bassani, Chet

    2012-06-01

    This paper presents an active source Electromagnetic Induction (EMI) sensor that offers extended detection ranges (> 2m) with minimal sensitivity to magnetic geology. The Ultra Deep Search (ULTRA) EMI system employs a large (20 - 40m), stationary, surface-laid transmitter loop that produces a relatively uniform magnetic field within the search region. This primary field decays slowly with depth due to the non-dipolar nature of the field within the search volume. An array of 3-axis receiver cubes measures the time derivative of secondary field decays produced by subsurface metallic objects. The large-loop transmitter combined with the vector sensing induction coil receivers produces a deep search capability that remains robust in environments containing highly magnetic soils. In this paper, we assess the general detection capabilities of the ULTRA system and present data collected over a set of standardized UXO targets. Additionally, we evaluate the potential for target feature extraction through dipole fit analysis of several data sets.

  8. Comments on large-N volume independence

    SciTech Connect

    Poppitz, Erich; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.

    2010-06-02

    We study aspects of the large-N volume independence on R{sup 3} X L{sup {Gamma}}, where L{sup {Gamma}} is a {Gamma}site lattice for Yang-Mills theory with adjoint Wilson-fermions. We find the critical number of lattice sites above which the center-symmetry analysis on L{sup {Gamma}} agrees with the one on the continuum S{sup 1}. For Wilson parameter set to one and {Gamma}{>=}2, the two analyses agree. One-loop radiative corrections to Wilson-line masses are finite, reminiscent of the UV-insensitivity of the Higgs mass in deconstruction/Little-Higgs theories. Even for theories with {Gamma}=1, volume independence in QCD(adj) may be guaranteed to work by tuning one low-energy effective field theory parameter. Within the parameter space of the theory, at most three operators of the 3d effective field theory exhibit one-loop UV-sensitivity. This opens the analytical prospect to study 4d non-perturbative physics by using lower dimensional field theories (d=3, in our example).

  9. Assessing catchment connectivity using hysteretic loops

    NASA Astrophysics Data System (ADS)

    Keesstra, Saskia; Masselink, Rens; Goni, Mikel; Campo, Miguel Angel; Gimenez, Rafael; Casali, Javier; Seeger, Manuel

    2015-04-01

    Sediment connectivity is a concept which can explain the origin, pathways and sinks of sediments within landscapes. This information is valuable for land managers to be able to take appropriate action at the correct place. Hysteresis between sediment and water discharge can give important information about the sources , pathways and conditions of sediment that arrives at the outlet of a catchment. "Hysteresis" happens when the sediment concentration associated with a certain flow rate is different depending on the direction in which the analysis is performed -towards the increase or towards the diminution of the flow. This phenomenon to some extent reflects the way in which the runoff generation processes are conjugated with those of the production and transport of sediments, hence the usefulness of hysteresis as a diagnostic hydrological parameter. However, the complexity of the phenomena and factors which determine hysteresis make its interpretation uncertain or, at the very least, problematic. Many types of hysteretic loops have been described as well as the cause for the shape of the loop, mainly describing the origin of the sediments. In this study, several measures to objectively classify hysteretic loops in an automated way were developed. These were consecutively used to classify several hundreds of loops from several agricultural catchments in Northern Spain. The data set for this study comes from four experimental watersheds in Navarre (Spain), owned and maintained by the Government of Navarre. These experimental watersheds have been monitored and studied since 1996 (La Tejería and Latxaga) and 2001 (Oskotz "principal", Op, and Oskotz "woodland", Ow). La Tejería and Latxaga watersheds, located in the Central Western part of Navarre, are roughly similar to each other regarding size (approximately 200 ha), geology (marls and sandstones), soils (fine texture topsoil), climate (humid sub Mediterranean) and land use (80-90% cultivated with winter grain crops

  10. A dual-loop model of the human controller

    NASA Technical Reports Server (NTRS)

    Hess, R. A.

    1977-01-01

    A representative model of the human controller in single-axis compensatory tracking tasks that exhibits an internal feedback loop which is not evident in single-loop models now in common use is presented. This hypothetical inner-loop involves a neuromuscular command signal derived from the time rate of change of controlled element output which is due to control activity. It is not contended that the single-loop human controller models now in use are incorrect, but that they contain an implicit but important internal loop closure, which, if explicitly considered, can account for a good deal of the adaptive nature of the human controller in a systematic manner.

  11. Te homogeneous precipitation in Ge dislocation loop vicinity

    NASA Astrophysics Data System (ADS)

    Perrin Toinin, J.; Portavoce, A.; Texier, M.; Bertoglio, M.; Hoummada, K.

    2016-06-01

    High resolution microscopies were used to study the interactions of Te atoms with Ge dislocation loops, after a standard n-type doping process in Ge. Te atoms neither segregate nor precipitate on dislocation loops, but form Te-Ge clusters at the same depth as dislocation loops, in contradiction with usual dopant behavior and thermodynamic expectations. Atomistic kinetic Monte Carlo simulations show that Te atoms are repulsed from dislocation loops due to elastic interactions, promoting homogeneous Te-Ge nucleation between dislocation loops. This phenomenon is enhanced by coulombic interactions between activated Te2+ or Te1+ ions.

  12. Temperature, Density, and Heating Profiles of Coronal Loops

    NASA Astrophysics Data System (ADS)

    Plowman, Joseph; Martens, P. C.; Kankelborg, C.; Ritchie, M.; Scott, J.; Sharma, R.

    2013-07-01

    We show detailed results of a combined DEM and density-sensitive line ratio analysis of coronal loops observed simultaneously by EIS and AIA. The temperature and density profiles of the loop are compared to and isolated from those of the surrounding material, and these properties are fit to an analytic strand heating model developed by Martens (2010). This research builds on our previously reported work by analyzing a number of coronal loops (including one observed by the Hi-C rocket), improved background subtraction and loop fitting. These improvements allow us to place significant constraints on the heating distribution of coronal loops.

  13. Loop residues and catalysis in OMP synthase.

    PubMed

    Wang, Gary P; Hansen, Michael Riis; Grubmeyer, Charles

    2012-06-01

    Residue-to-alanine mutations and a two-amino acid deletion have been made in the highly conserved catalytic loop (residues 100-109) of Salmonella typhimurium OMP synthase (orotate phosphoribosyltransferase, EC 2.4.2.10). As described previously, the K103A mutant enzyme exhibited a 10(4)-fold decrease in k(cat)/K(M) for PRPP; the K100A enzyme suffered a 50-fold decrease. Alanine mutations at His105 and Glu107 produced 40- and 7-fold decreases in k(cat)/K(M), respectively, and E101A, D104A, and G106A were slightly faster than the wild-type (WT) in terms of k(cat), with minor effects on k(cat)/K(M). Equilibrium binding of OMP or PRPP in binary complexes was affected little by loop mutation, suggesting that the energetics of ground-state binding have little contribution from the catalytic loop, or that a favorable binding energy is offset by costs of loop reorganization. Pre-steady-state kinetics for mutants showed that K103A and E107A had lost the burst of product formation in each direction that indicated rapid on-enzyme chemistry for WT, but that the burst was retained by H105A. Δ102Δ106, a loop-shortened enzyme with Ala102 and Gly106 deleted, showed a 10(4)-fold reduction of k(cat) but almost unaltered K(D) values for all four substrate molecules. The 20% (i.e., 1.20) intrinsic [1'-(3)H]OMP kinetic isotope effect (KIE) for WT is masked because of high forward and reverse commitment factors. K103A failed to express intrinsic KIEs fully (1.095 ± 0.013). In contrast, H105A, which has a smaller catalytic lesion, gave a [1'-(3)H]OMP KIE of 1.21 ± 0.0005, and E107A (1.179 ± 0.0049) also gave high values. These results are interpreted in the context of the X-ray structure of the complete substrate complex for the enzyme [Grubmeyer, C., Hansen, M. R., Fedorov, A. A., and Almo, S. C. (2012) Biochemistry 51 (preceding paper in this issue, DOI 10.1021/bi300083p )]. The full expression of KIEs by H105A and E107A may result from a less secure closure of the catalytic loop

  14. Equilibrium Models of Coronal Loops That Involve Curvature and Buoyancy

    NASA Astrophysics Data System (ADS)

    Hindman, Bradley W.; Jain, Rekha

    2013-12-01

    We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.

  15. Equilibrium models of coronal loops that involve curvature and buoyancy

    SciTech Connect

    Hindman, Bradley W.; Jain, Rekha

    2013-12-01

    We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.

  16. Coupled AGC-Costas loops with AM/PM conversion

    NASA Astrophysics Data System (ADS)

    Gagliardi, R. M.

    1980-01-01

    Costas loops are invariably designed in conjunction with an automatic gain control (AGC) loop for stabilizing performance. In such systems an inherent coupling between the AGC and Costas loops develops, complicating the standard phase referencing analysis. This coupling is further emphasized if the gain control amplifier introduces an AM/PM conversion, which causes power variations to enter the Costas loop as phase variations. In this paper the coupling effect between AGC and Costas loops is developed, leading to a pair of joint, interconnected dynamical tracking loops. Some degree of solution is attainable by assuming a first order AGC loop, and resorting to quasi-stationary analysis for evaluating the phase referencing generation. Results with and without AM/PM are presented, and illustrate how an improper AGC may in fact degrade the phase referencing from the expected performance.

  17. Research on phase locked loop in optical memory servo system

    NASA Astrophysics Data System (ADS)

    Qin, Liqin; Ma, Jianshe; Zhang, Jianyong; Pan, Longfa; Deng, Ming

    2005-09-01

    Phase locked loop (PLL) is a closed loop automatic control system, which can track the phase of input signal. It widely applies in each area of electronic technology. This paper research the phase locked loop in optical memory servo area. This paper introduces the configuration of digital phase locked loop (PLL) and phase locked servo system, the control theory, and analyses system's stability. It constructs the phase locked loop experiment system of optical disk spindle servo, which based on special chip. DC motor is main object, this system adopted phase locked servo technique and digital signal processor (DSP) to achieve constant linear velocity (CLV) in controlling optical spindle motor. This paper analyses the factors that affect the stability of phase locked loop in spindle servo system, and discusses the affection to the optical disk readout signal and jitter due to the stability of phase locked loop.

  18. Acquisition and Tracking Behavior of Phase-Locked Loops

    NASA Technical Reports Server (NTRS)

    Viterbi, A. J.

    1958-01-01

    Phase-locked or APC loops have found increasing applications in recent years as tracking filters, synchronizing devices, and narrowband FM discriminators. Considerable work has been performed to determine the noise-squelching properties of the loop when it is operating in or near phase lock and is functioning as a linear coherent detector. However, insufficient consideration has been devoted to the non-linear behavior of the loop when it is out of lock and in the process of pulling in. Experimental evidence has indicated that there is a strong tendency for phase-locked loops to achieve lock under most circumstances. However, the analysis which has appeared in the literature iis limited to the acquisition of a constant frequency reference signal with only one phase-locked loop filter configuration. This work represents an investigation of frequency acquisition properties of phase-locked loops for a variety of reference-signal behavior and loop configurations

  19. Method of implementing digital phase-locked loops

    NASA Technical Reports Server (NTRS)

    Stephens, Scott A. (Inventor); Thomas, Jess Brooks, Jr. (Inventor)

    1993-01-01

    In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with simple and direct physical meaning in terms of loop noise bandwidth, root-specific decay rate, or root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (BLT yields 0) and in a discrete-update formulation with arbitrary BLT. Deficiencies of the continuous-update approximation in large-BLT applications are avoided in the new discrete-update formulation. A new method for direct, transient-free acquisition with third- and fourth-order loops can improve the versatility and reliability of acquisition with such loops.

  20. Current loop coalescence studied by 3-D electromagnetic particle code

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi; Sakai, Jun-Ichi; Koide, Shinji; Buneman, O.; Neubert, T.

    1993-01-01

    Solar flare plasma data from the Yohkoh satellite is analyzed. The interactions of current loops were observed in the active regions on the Sun. This observation pointed out the importance of the idea that the solar flare is generated by the coalescence of current loops. The three dimensional electromagnetic particle simulations are to help in understanding the global interaction between two current loops including the evolution of the twist of loops due to instabilities. Associated rapid dynamics of current loop coalescence such as reconnection, shock waves and associated kinetic processes such as energy transfer, acceleration of particles, and electromagnetic emissions are to be studied by the code to complement analytical theories and magnetohydrodynamic simulations of the current loop coalescence. The simulation results show the strong interactions between two current loops, beam and whistler instabilities, and associated parallel and perpendicular particle heating.

  1. Energy Conversion Advanced Heat Transport Loop and Power Cycle

    SciTech Connect

    Oh, C. H.

    2006-08-01

    The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in its early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed in order to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. Three configurations of the power conversion unit were demonstrated in this study. A three-shaft design with 3 turbines and 4 compressors, a combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated cycle with 3 stages of reheat were investigated. An intermediate heat transport loop for transporting process heat to a High Temperature Steam Electrolysis (HTSE) hydrogen production plant was used. Helium, CO2, and an 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative component size were estimated for the different working fluids. The relative size of the turbomachinery was measured by comparing the power input/output of the component. For heat exchangers the volume was computed and compared. Parametric studies away from the baseline values of the three-shaft and combined cycles were performed to determine the effect of varying conditions in the cycle. This gives some insight into the sensitivity of these cycles to various

  2. A quantum reduction to spherical symmetry in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Bodendorfer, N.; Lewandowski, J.; Świeżewski, J.

    2015-07-01

    Based on a recent purely geometric construction of observables for the spatial diffeomorphism constraint, we propose two distinct quantum reductions to spherical symmetry within full 3 + 1-dimensional loop quantum gravity. The construction of observables corresponds to using the radial gauge for the spatial metric and allows to identify rotations around a central observer as unitary transformations in the quantum theory. Group averaging over these rotations yields our first proposal for spherical symmetry. Hamiltonians of the full theory with angle-independent lapse preserve this spherically symmetric subsector of the full Hilbert space. A second proposal consists in implementing the vanishing of a certain vector field in spherical symmetry as a constraint on the full Hilbert space, leading to a close analogue of diffeomorphisms invariant states. While this second set of spherically symmetric states does not allow for using the full Hamiltonian, it is naturally suited to implement the spherically symmetric midisuperspace Hamiltonian, as an operator in the full theory, on it. Due to the canonical structure of the reduced variables, the holonomy-flux algebra behaves effectively as a one parameter family of 2 + 1-dimensional algebras along the radial coordinate, leading to a diagonal non-vanishing volume operator on 3-valent vertices. The quantum dynamics thus becomes tractable, including scenarios like spherically symmetric dust collapse.

  3. Noncontractible loops in the dense O(n) loop model on the cylinder.

    PubMed

    Alcaraz, F C; Brankov, J G; Priezzhev, V B; Rittenberg, V; Rogozhnikov, A M

    2014-11-01

    A lattice model of critical dense polymers O(n) is considered for finite cylinder geometry. Due to the presence of noncontractible loops with a fixed fugacity ξ, the model at n=0 is a generalization of the critical dense polymers solved by Pearce, Rasmussen, and Villani. We found the free energy for any height N and circumference L of the cylinder. The density ρ of noncontractible loops is obtained for N→∞ and large L. The results are compared with those found for the anisotropic quantum chain with twisted boundary conditions. Using the latter method, we derived ρ for any O(n) model and an arbitrary fugacity. PMID:25493770

  4. Mock Circulatory Loop Compliance Chamber Employing a Novel Real-Time Control Process.

    PubMed

    Taylor, Charles E; Miller, Gerald E

    2012-12-01

    The use of compliance chambers in mock circulatory loop construction is the predominant means of simulating arterial compliance. Utilizing mock circulatory loops as bench test methods for cardiac assist technologies necessitates that they must be capable of reproducing the circulatory conditions that would exist physiologically. Of particular interest is the ability to determine instantaneous compliance of the system, and the ability to change the compliance in real-time. This capability enables continuous battery testing of conditions without stopping the flow to change the compliance chamber settings, and the simulation of dynamic changes in arterial compliance. The method tested involves the use of a compliance chamber utilizing a circular natural latex rubber membrane separating the fluid and air portions of the device. Change in system compliance is affected by the airspace pressure, which creates more reaction force at the membrane to the fluid pressure. A pressure sensor in the fluid portion of the chamber and a displacement sensor monitoring membrane center deflection allow for real-time inputs to the control algorithm. A predefined numerical model correlates the displacement sensor data to the volume displacement of the membrane. The control algorithm involves a tuned π loop maintaining the volume distention of the membrane via regulation of the air space pressure. The proportional integral (PI) controller tuning was achieved by creating a computational model of the compliance chamber using Simulink™ Simscape(®) toolboxes. These toolboxes were used to construct a model of the hydraulic, mechanical, and pneumatic elements in the physical design. Parameter Estimation™ tools and Design Optimization™ methods were employed to determine unknown physical parameters in the system, and tune the process controller used to maintain the compliance setting. It was found that the resulting control architecture was capable of maintaining compliance along a

  5. Causal Loop Analysis of coastal geomorphological systems

    NASA Astrophysics Data System (ADS)

    Payo, Andres; Hall, Jim W.; French, Jon; Sutherland, James; van Maanen, Barend; Nicholls, Robert J.; Reeve, Dominic E.

    2016-03-01

    As geomorphologists embrace ever more sophisticated theoretical frameworks that shift from simple notions of evolution towards single steady equilibria to recognise the possibility of multiple response pathways and outcomes, morphodynamic modellers are facing the problem of how to keep track of an ever-greater number of system feedbacks. Within coastal geomorphology, capturing these feedbacks is critically important, especially as the focus of activity shifts from reductionist models founded on sediment transport fundamentals to more synthesist ones intended to resolve emergent behaviours at decadal to centennial scales. This paper addresses the challenge of mapping the feedback structure of processes controlling geomorphic system behaviour with reference to illustrative applications of Causal Loop Analysis at two study cases: (1) the erosion-accretion behaviour of graded (mixed) sediment beds, and (2) the local alongshore sediment fluxes of sand-rich shorelines. These case study examples are chosen on account of their central role in the quantitative modelling of geomorphological futures and as they illustrate different types of causation. Causal loop diagrams, a form of directed graph, are used to distil the feedback structure to reveal, in advance of more quantitative modelling, multi-response pathways and multiple outcomes. In the case of graded sediment bed, up to three different outcomes (no response, and two disequilibrium states) can be derived from a simple qualitative stability analysis. For the sand-rich local shoreline behaviour case, two fundamentally different responses of the shoreline (diffusive and anti-diffusive), triggered by small changes of the shoreline cross-shore position, can be inferred purely through analysis of the causal pathways. Explicit depiction of feedback-structure diagrams is beneficial when developing numerical models to explore coastal morphological futures. By explicitly mapping the feedbacks included and neglected within a

  6. Gas Test Loop Booster Fuel Hydraulic Testing

    SciTech Connect

    Gas Test Loop Hydraulic Testing Staff

    2006-09-01

    The Gas Test Loop (GTL) project is for the design of an adaptation to the Advanced Test Reactor (ATR) to create a fast-flux test space where fuels and materials for advanced reactor concepts can undergo irradiation testing. Incident to that design, it was found necessary to make use of special booster fuel to enhance the neutron flux in the reactor lobe in which the Gas Test Loop will be installed. Because the booster fuel is of a different composition and configuration from standard ATR fuel, it is necessary to qualify the booster fuel for use in the ATR. Part of that qualification is the determination that required thermal hydraulic criteria will be met under routine operation and under selected accident scenarios. The Hydraulic Testing task in the GTL project facilitates that determination by measuring flow coefficients (pressure drops) over various regions of the booster fuel over a range of primary coolant flow rates. A high-fidelity model of the NW lobe of the ATR with associated flow baffle, in-pile-tube, and below-core flow channels was designed, constructed and located in the Idaho State University Thermal Fluids Laboratory. A circulation loop was designed and constructed by the university to provide reactor-relevant water flow rates to the test system. Models of the four booster fuel elements required for GTL operation were fabricated from aluminum (no uranium or means of heating) and placed in the flow channel. One of these was instrumented with Pitot tubes to measure flow velocities in the channels between the three booster fuel plates and between the innermost and outermost plates and the side walls of the flow annulus. Flow coefficients in the range of 4 to 6.5 were determined from the measurements made for the upper and middle parts of the booster fuel elements. The flow coefficient for the lower end of the booster fuel and the sub-core flow channel was lower at 2.3.

  7. Closing the loop of deep brain stimulation.

    PubMed

    Carron, Romain; Chaillet, Antoine; Filipchuk, Anton; Pasillas-Lépine, William; Hammond, Constance

    2013-01-01

    High-frequency deep brain stimulation is used to treat a wide range of brain disorders, like Parkinson's disease. The stimulated networks usually share common electrophysiological signatures, including hyperactivity and/or dysrhythmia. From a clinical perspective, HFS is expected to alleviate clinical signs without generating adverse effects. Here, we consider whether the classical open-loop HFS fulfills these criteria and outline current experimental or theoretical research on the different types of closed-loop DBS that could provide better clinical outcomes. In the first part of the review, the two routes followed by HFS-evoked axonal spikes are explored. In one direction, orthodromic spikes functionally de-afferent the stimulated nucleus from its downstream target networks. In the opposite direction, antidromic spikes prevent this nucleus from being influenced by its afferent networks. As a result, the pathological synchronized activity no longer propagates from the cortical networks to the stimulated nucleus. The overall result can be described as a reversible functional de-afferentation of the stimulated nucleus from its upstream and downstream nuclei. In the second part of the review, the latest advances in closed-loop DBS are considered. Some of the proposed approaches are based on mathematical models, which emphasize different aspects of the parkinsonian basal ganglia: excessive synchronization, abnormal firing-rate rhythms, and a deficient thalamo-cortical relay. The stimulation strategies are classified depending on the control-theory techniques on which they are based: adaptive and on-demand stimulation schemes, delayed and multi-site approaches, stimulations based on proportional and/or derivative control actions, optimal control strategies. Some of these strategies have been validated experimentally, but there is still a large reservoir of theoretical work that may point to ways of improving practical treatment. PMID:24391555

  8. Uniqueness of measures in loop quantum cosmology

    SciTech Connect

    Hanusch, Maximilian

    2015-09-15

    In Ashtekar and Campiglia [Classical Quantum Gravity 29, 242001 (2012)], residual diffeomorphisms have been used to single out the standard representation of the reduced holonomy-flux algebra in homogeneous loop quantum cosmology (LQC). We show that, in the homogeneous isotropic case, unitarity of the translations with respect to the extended ℝ-action (exponentiated reduced fluxes in the standard approach) singles out the Bohr measure on both the standard quantum configuration space ℝ{sub Bohr} as well as on the Fleischhack one (ℝ⊔ℝ{sub Bohr}). Thus, in both situations, the same condition singles out the standard kinematical Hilbert space of LQC.

  9. Shocked clouds in the Cygnus Loop

    NASA Technical Reports Server (NTRS)

    Raymond, John C.

    1994-01-01

    This grant covers the analysis of ROSAT PSPC and HRI images of the Cygnus Loop, an elderly supernova remnant. The project, as proposed, includes not only the usual analysis of ROSAT data; the ROSAT data is being combined with optical and UV data, and new model calculations are being performed. The status is reported on optical imagery, echelle data, IUE data, ROSAT data, and the grain model. The major question being addressed is whether the blastwave-cloud interaction in the feature known as XA is basically a converging shock in a fairly large cloud or turbulent stripping of material from the edges of a smaller cloud.

  10. Wilson loop invariants from WN conformal blocks

    NASA Astrophysics Data System (ADS)

    Alekseev, Oleg; Novaes, Fábio

    2015-12-01

    Knot and link polynomials are topological invariants calculated from the expectation value of loop operators in topological field theories. In 3D Chern-Simons theory, these invariants can be found from crossing and braiding matrices of four-point conformal blocks of the boundary 2D CFT. We calculate crossing and braiding matrices for WN conformal blocks with one component in the fundamental representation and another component in a rectangular representation of SU (N), which can be used to obtain HOMFLY knot and link invariants for these cases. We also discuss how our approach can be generalized to invariants in higher-representations of WN algebra.

  11. Vector fields and Loop Quantum Cosmology

    SciTech Connect

    Artymowski, Michał; Lalak, Zygmunt E-mail: Zygmunt.Lalak@fuw.edu.pl

    2011-09-01

    In the context of the Loop Quantum Cosmology we have analysed the holonomy correction to the classical evolution of the simplified Bianchi I model in the presence of vector fields. For the Universe dominated by a massive vector field or by a combination of a scalar field and a vector field a smooth transition between Kasner-like and Kasner-unlike solutions for a Bianchi I model has been demonstrated. In this case a lack of initial curvature singularity and a finite maximal energy density appear already at the level of General Relativity, which simulates a classical Big Bounce.

  12. Are feedback loops destructive to synchronization?

    NASA Astrophysics Data System (ADS)

    Sheshbolouki, A.; Zarei, M.; Sarbazi-Azad, H.

    2015-08-01

    We study the effects of directionality on synchronization of dynamical networks. Performing the linear stability analysis and the numerical simulation of the Kuramoto model in directed networks, we show that balancing in- and out-degrees of all nodes enhances the synchronization of sparse networks, especially in networks with high clustering coefficient and homogeneous degree distribution. Furthermore, by omitting all the feedback loops, we show that while hierarchical directed acyclic graphs are structurally highly synchronizable, their global synchronization is too sensitive to the choice of natural frequencies and is strongly affected by noise.

  13. Regularization ambiguities in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Perez, Alejandro

    2006-02-01

    One of the main achievements of loop quantum gravity is the consistent quantization of the analog of the Wheeler-DeWitt equation which is free of ultraviolet divergences. However, ambiguities associated to the intermediate regularization procedure lead to an apparently infinite set of possible theories. The absence of an UV problem—the existence of well-behaved regularization of the constraints—is intimately linked with the ambiguities arising in the quantum theory. Among these ambiguities is the one associated to the SU(2) unitary representation used in the diffeomorphism covariant “point-splitting” regularization of the nonlinear functionals of the connection. This ambiguity is labeled by a half-integer m and, here, it is referred to as the m ambiguity. The aim of this paper is to investigate the important implications of this ambiguity. We first study 2+1 gravity (and more generally BF theory) quantized in the canonical formulation of loop quantum gravity. Only when the regularization of the quantum constraints is performed in terms of the fundamental representation of the gauge group does one obtain the usual topological quantum field theory as a result. In all other cases unphysical local degrees of freedom arise at the level of the regulated theory that conspire against the existence of the continuum limit. This shows that there is a clear-cut choice in the quantization of the constraints in 2+1 loop quantum gravity. We then analyze the effects of the ambiguity in 3+1 gravity exhibiting the existence of spurious solutions for higher representation quantizations of the Hamiltonian constraint. Although the analysis is not complete in 3+1 dimensions—due to the difficulties associated to the definition of the physical inner product—it provides evidence supporting the definitions quantum dynamics of loop quantum gravity in terms of the fundamental representation of the gauge group as the only consistent possibilities. If the gauge group is SO(3) we

  14. High heat flux loop heat pipes

    NASA Technical Reports Server (NTRS)

    North, Mark T.; Sarraf, David B.; Rosenfeld, John H.; Maidanik, Yuri F.; Vershinin, Sergey

    1997-01-01

    Loop heat pipes (LHPs) can transport very large thermal power loads over long distances, through flexible, small diameter tubes against gravitational heads. In order to overcome the evaporator limit of LHPs, which is of about 0.07 MW/sq m, work was carried out to improve the efficiency by threefold to tenfold. The vapor passage geometry for the high heat flux conditions is shown. A bidisperse wick material within the circumferential vapor passages was used. Along with heat flux enhancement, several underlying issues were demonstrated, including the fabrication of bidisperse powder with controlled properties and the fabrication of a device geometry capable of replacing vapor passages with bidisperse powder.

  15. Observation of coronal loop torsional oscillation

    NASA Astrophysics Data System (ADS)

    Zaqarashvili, T. V.

    2003-02-01

    We suggest that the global torsional oscillation of solar coronal loop may be observed by the periodical variation of a spectral line width. The amplitude of the variation must be maximal at the velocity antinodes and minimal at the nodes of the torsional oscillation. Then the spectroscopic observation as a time series at different heights above the active region at the solar limb may allow to determine the period and wavelength of global torsional oscillation and consequently the Alfvén speed in corona. From the analysis of early observation (Egan & Schneeberger \\cite{egan}) we suggest the value of coronal Alfvén speed as ~ 500 km s-1.

  16. FORTE hardware-in-loop simulation

    SciTech Connect

    Ruud, K.K.; Murray, H.S.; Moore, T.K.

    1997-12-01

    Fast On-Orbit Recording of Transient Events (FORTE) is a small, low Earth orbit satellite scheduled for launch in August 1997. FORTE is a momentum-biased, gravity-gradient stabilized spacecraft. This paper describes the use of a hardware-in-loop simulator, developed by Ithaco Inc. and Los Alamos National Laboratory, in performing FORTE mission simulations. Scenarios studied include separation, acquisition on orbit, control system parameter sensitivity studies, sensor noise simulations, antenna deployment and momentum desaturation. Use of the simulator to refine control algorithms and sequences is also described.

  17. A Measurable Difference: Bridge Versus Loop

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Trig-Tek, Inc.'s Model 251A ACL-8 Anderson Current Loop (ACL) Conditioner is an eight channel device designed to condition variable-resistant sensor signals from Strain Gage and RTD's (Resistance Temperature Device)s. It uses NASA's patented ACL technology instead of the classic wheatstone bridge. The electronic measurement circuit delivers accuracy far beyond previous methods and prevents errors caused by variation in the wires that connect sensors to data collection equipment. This is the first license to market a NASA Dryden Flight Research Center patent.

  18. Phase-locked loops and their application

    NASA Technical Reports Server (NTRS)

    Lindsey, W. C. (Editor); Simon, M. K.

    1978-01-01

    A collection of papers is presented on the characteristics and capabilities of phase-locked loops (PLLs), along with some applications of interest. The discussion covers basic theory (linear and nonlinear); acquisition; threshold; stability; frequency demodulation and detection; tracking; cycle slipping and loss of lock; phase-locked oscillators; operation and performance in the presence of noise; AGC, AFC, and APC circuits and systems; digital PLL; and applications and miscellaneous. With the rapid development of IC technology, PLLs are expected to be used widely in consumer electronics.

  19. Thermoelectric power generator with intermediate loop

    SciTech Connect

    Bell, Lon E; Crane, Douglas Todd

    2013-05-21

    A thermoelectric power generator is disclosed for use to generate electrical power from heat, typically waste heat. An intermediate heat transfer loop forms a part of the system to permit added control and adjustability in the system. This allows the thermoelectric power generator to more effectively and efficiently generate power in the face of dynamically varying temperatures and heat flux conditions, such as where the heat source is the exhaust of an automobile, or any other heat source with dynamic temperature and heat flux conditions.

  20. Affective loop experiences: designing for interactional embodiment

    PubMed Central

    Höök, Kristina

    2009-01-01

    Involving our corporeal bodies in interaction can create strong affective experiences. Systems that both can be influenced by and influence users corporeally exhibit a use quality we name an affective loop experience. In an affective loop experience, (i) emotions are seen as processes, constructed in the interaction, starting from everyday bodily, cognitive or social experiences; (ii) the system responds in ways that pull the user into the interaction, touching upon end users' physical experiences; and (iii) throughout the interaction the user is an active, meaning-making individual choosing how to express themselves—the interpretation responsibility does not lie with the system. We have built several systems that attempt to create affective loop experiences with more or less successful results. For example, eMoto lets users send text messages between mobile phones, but in addition to text, the messages also have colourful and animated shapes in the background chosen through emotion-gestures with a sensor-enabled stylus pen. Affective Diary is a digital diary with which users can scribble their notes, but it also allows for bodily memorabilia to be recorded from body sensors mapping to users' movement and arousal and placed along a timeline. Users can see patterns in their bodily reactions and relate them to various events going on in their lives. The experiences of building and deploying these systems gave us insights into design requirements for addressing affective loop experiences, such as how to design for turn-taking between user and system, how to create for ‘open’ surfaces in the design that can carry users' own meaning-making processes, how to combine modalities to create for a ‘unity’ of expression, and the importance of mirroring user experience in familiar ways that touch upon their everyday social and corporeal experiences. But a more important lesson gained from deploying the systems is how emotion processes are co-constructed and

  1. Phase transition in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Mäkelä, Jarmo

    2016-04-01

    We point out that with a specific counting of states loop quantum gravity implies that black holes perform a phase transition at a certain characteristic temperature TC . In this phase transition the punctures of the spin network on the stretched horizon of the black hole jump, in effect, from the vacuum to the excited states. The characteristic temperature TC may be regarded as the lowest possible temperature of the hole. From the point of view of a distant observer at rest with respect to the hole, the characteristic temperature TC corresponds to the Hawking temperature of the hole.

  2. Quantum black holes in loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Olmedo, Javier

    2016-03-01

    In this contribution I will comment on the last advances in relation to the loop quantization of spherically symmetric spacetimes. I will briefly summarize the vacuum case, where the physical states and observables are known explicitly. The main physical consequences are i) a genuine discretization of the geometry and ii) singularity resolution. Afterwards I will consider the coupling with a thin spherically symmetric null-dust shell. This is one of the simplest collapse scenarios with nontrivial dynamics. I will provide a representation for the scalar constraint that is consistent with the Dirac quantization approach, and the quantum observables of the model. Finally, I comment on the possible physical consequences of this model.

  3. Star-formation in the Coalsack Loop

    NASA Astrophysics Data System (ADS)

    Golev, V.; Kaltcheva, N.

    The giant Galactic H II region known as the Coalsack Loop, which is associated with the H I supershell GSH 305+01-24, provides a unique opportunity to study the OB-star influence on the surrounding interstellar material. The bright OB-stars within this region contribute a sufficient wind injection energy consistent with the observed size and expansion velocity of the supershell. The derived age distribution of the OB-stars is suggestive for a continuous star-formation where the youngest stars are located at the supershell's periphery.

  4. Shocked clouds in the Cygnus Loop

    NASA Astrophysics Data System (ADS)

    Raymond, John C.

    1994-02-01

    This grant covers the analysis of ROSAT PSPC and HRI images of the Cygnus Loop, an elderly supernova remnant. The project, as proposed, includes not only the usual analysis of ROSAT data; the ROSAT data is being combined with optical and UV data, and new model calculations are being performed. The status is reported on optical imagery, echelle data, IUE data, ROSAT data, and the grain model. The major question being addressed is whether the blastwave-cloud interaction in the feature known as XA is basically a converging shock in a fairly large cloud or turbulent stripping of material from the edges of a smaller cloud.

  5. Loops in Reeb Graphs of 2-Manifolds

    SciTech Connect

    Cole-McLaughlin, K; Edelsbrunner, H; Harer, J; Natarajan, V; Pascucci, V

    2004-12-16

    Given a Morse function f over a 2-manifold with or without boundary, the Reeb graph is obtained by contracting the connected components of the level sets to points. We prove tight upper and lower bounds on the number of loops in the Reeb graph that depend on the genus, the number of boundary components, and whether or not the 2-manifold is orientable. We also give an algorithm that constructs the Reeb graph in time O(n log n), where n is the number of edges in the triangulation used to represent the 2-manifold and the Morse function.

  6. Loops in Reeb Graphs of 2-Manifolds

    SciTech Connect

    Cole-McLaughlin, K; Edelsbrunner, H; Harer, J; Natarajan, V; Pascucci, V

    2003-02-11

    Given a Morse function f over a 2-manifold with or without boundary, the Reeb graph is obtained by contracting the connected components of the level sets to points. We prove tight upper and lower bounds on the number of loops in the Reeb graph that depend on the genus, the number of boundary components, and whether or not the 2-manifold is orientable. We also give an algorithm that constructs the Reeb graph in time O(n log n), where n is the number of edges in the triangulation used to represent the 2-manifold and the Morse function.

  7. Quenching phenomena in natural circulation loop

    SciTech Connect

    Umekawa, Hisashi; Ozawa, Mamoru; Ishida, Naoki

    1995-09-01

    Quenching phenomena has been investigated experimentally using circulation loop of liquid nitrogen. During the quenching under natural circulation, the heat transfer mode changes from film boiling to nucleate boiling, and at the same time flux changes with time depending on the vapor generation rate and related two-phase flow characteristics. Moreover, density wave oscillations occur under a certain operating condition, which is closely related to the dynamic behavior of the cooling curve. The experimental results indicates that the occurrence of the density wave oscillation induces the deterioration of effective cooling of the heat surface in the film and the transition boiling regions, which results in the decrease in the quenching velocity.

  8. Thermoelectric power generator with intermediate loop

    DOEpatents

    Bel,; Lon E.; Crane, Douglas Todd

    2009-10-27

    A thermoelectric power generator is disclosed for use to generate electrical power from heat, typically waste heat. An intermediate heat transfer loop forms a part of the system to permit added control and adjustability in the system. This allows the thermoelectric power generator to more effectively and efficiently generate power in the face of dynamically varying temperatures and heat flux conditions, such as where the heat source is the exhaust of an automobile, or any other heat source with dynamic temperature and heat flux conditions.

  9. Affective loop experiences: designing for interactional embodiment.

    PubMed

    Höök, Kristina

    2009-12-12

    Involving our corporeal bodies in interaction can create strong affective experiences. Systems that both can be influenced by and influence users corporeally exhibit a use quality we name an affective loop experience. In an affective loop experience, (i) emotions are seen as processes, constructed in the interaction, starting from everyday bodily, cognitive or social experiences; (ii) the system responds in ways that pull the user into the interaction, touching upon end users' physical experiences; and (iii) throughout the interaction the user is an active, meaning-making individual choosing how to express themselves-the interpretation responsibility does not lie with the system. We have built several systems that attempt to create affective loop experiences with more or less successful results. For example, eMoto lets users send text messages between mobile phones, but in addition to text, the messages also have colourful and animated shapes in the background chosen through emotion-gestures with a sensor-enabled stylus pen. Affective Diary is a digital diary with which users can scribble their notes, but it also allows for bodily memorabilia to be recorded from body sensors mapping to users' movement and arousal and placed along a timeline. Users can see patterns in their bodily reactions and relate them to various events going on in their lives. The experiences of building and deploying these systems gave us insights into design requirements for addressing affective loop experiences, such as how to design for turn-taking between user and system, how to create for 'open' surfaces in the design that can carry users' own meaning-making processes, how to combine modalities to create for a 'unity' of expression, and the importance of mirroring user experience in familiar ways that touch upon their everyday social and corporeal experiences. But a more important lesson gained from deploying the systems is how emotion processes are co-constructed and experienced

  10. Brief Review on Black Hole Loop Quantization

    NASA Astrophysics Data System (ADS)

    Olmedo, Javier

    2016-06-01

    Here, we present a review about the quantization of spherically-symmetric spacetimes adopting loop quantum gravity techniques. Several models that have been studied so far share similar properties: the resolution of the classical singularity and some of them an intrinsic discretization of the geometry. We also explain the extension to Reissner---Nordstr\\"om black holes. Besides, we review how quantum test fields on these quantum geometries allow us to study phenomena, like the Casimir effect or Hawking radiation. Finally, we briefly describe a recent proposal that incorporates spherically-symmetric matter, discussing its relevance for the understanding of black hole evolution.

  11. An innovative work-loop calorimeter for in vitro measurement of the mechanics and energetics of working cardiac trabeculae.

    PubMed

    Taberner, Andrew J; Han, June-Chiew; Loiselle, Denis S; Nielsen, Poul M F; Nielsen, Paul M F

    2011-12-01

    We describe a unique work-loop calorimeter with which we can measure, simultaneously, the rate of heat production and force-length work output of isolated cardiac trabeculae. The mechanics of the force-length work-loop contraction mimic those of the pressure-volume work-loops experienced by the heart. Within the measurement chamber of a flow-through microcalorimeter, a trabecula is electrically stimulated to respond, under software control, in one of three modes: fixed-end, isometric, or isotonic. In each mode, software controls the position of a linear motor, with feedback from muscle force, to adjust muscle length in the desired temporal sequence. In the case of a work-loop contraction, the software achieves seamless transitions between phases of length control (isometric contraction, isometric relaxation, and restoration of resting muscle length) and force control (isotonic shortening). The area enclosed by the resulting force-length loop represents the work done by the trabecula. The change of enthalpy expended by the muscle is given by the sum of the work term and the associated amount of evolved heat. With these simultaneous measurements, we provide the first estimation of suprabasal, net mechanical efficiency (ratio of work to change of enthalpy) of mammalian cardiac trabeculae. The maximum efficiency is at the vicinity of 12%. PMID:21903883

  12. Fluid reabsorption in Henle's loop and urinary excretion of sodium and water in normal rats and rats with chronic hypertension

    PubMed Central

    Stumpe, Klaus O.; Lowitz, Hans D.; Ochwadt, Bruno

    1970-01-01

    The function of the short loops of Henle was investigated by micropuncture technique in normal rats, in rats with spontaneous hypertension, and in the untouched kidney of rats with experimental renal hypertension. All animals received a standard infusion of 1.2 ml of isotonic saline per hr. With increasing arterial blood pressure (range from 90 to 220 mm Hg), a continuous decrease in transit time of Lissamine green through Henle's loop from 32 to 10 sec was observed. Fractional water reabsorption along the loop declined progressively from 26 to 10%, and fractional sodium reabsorption decreased from 40 to 36% of the filtered load. The fluid volume in Henle's loop calculated from transit time and mean flow rate also decreased with increasing blood pressure. There was no change in superficial single nephron filtration rate but there was a slight increase in total glomerular filtration rate (GFR). Sodium and water reabsorption in the proximal tubule remained unchanged. Urine flow rate, sodium excretion, osmolar clearance, and negative free water clearance increased with increasing blood pressure. The osmolal urine to plasma (U/P) ratio declined but did not fall below a value of 1.5. It is concluded that the increase in sodium and water excretion with chronic elevation of arterial blood pressure is caused by a decrease of sodium and water reabsorption along the loop of Henle, presumably as a consequence of increased medullary blood pressure. PMID:5422022

  13. Two-loop perturbative quark mass renormalization from large {beta} Monte Carlo

    SciTech Connect

    Keisuke Jimmy Juge

    2001-02-14

    We present the calculation of heavy Wilson quark mass renormalization constants from large beta Monte Carlo simulations. Simulations were performed at various beta larger than 9, each on several spatial lattice sizes to allow for an infinite volume extrapolation. We use twisted boundary conditions to suppress tunneling and work in Coulomb gauge with appropriate adjustments for the temporal links. The one-loop coefficient obtained from this method is in agreement with the analytical result and a preliminary result for the second order coefficient is reported.

  14. TRANSVERSE OSCILLATIONS OF A LONGITUDINALLY STRATIFIED CORONAL LOOP SYSTEM

    SciTech Connect

    Fathalian, N.; Safari, H. E-mail: safari@znu.ac.i

    2010-11-20

    Collective transverse coronal loop oscillations seem to be detected in observational studies. In this regard, Luna et al. modeled the collective kink-like normal modes of several cylindrical loop systems using the T-matrix theory. This paper investigates the effects of longitudinal density stratification along the loop axis on the collective kink-like modes of the system of coronal loops. The coronal loop system is modeled as cylinders of parallel flux tubes, with two ends of each loop at the dense photosphere. The flux tubes are considered as uniform magnetic fields, with stratified density along the loop axis which changes discontinuously at the lateral surface of each cylinder. The MHD equations are reduced to solve a set of two coupled dispersion relations for frequencies and wavenumbers, in the presence of a stratification parameter. The fundamental and first overtone frequencies and longitudinal wavenumbers are computed. The previous results are verified for an unstratified coronal loop system. Finally, we conclude that an increased longitudinal density stratification parameter will result in an increase of the frequencies. The frequency ratios, first overtones to fundamentals, are very sensitive functions of the density scale height parameter. Therefore, stratification should be included in dynamics of coronal loop systems. For unstratified coronal loop systems, these ratios are the same as monoloop ones.

  15. Saccade learning with concurrent cortical and subcortical basal ganglia loops

    PubMed Central

    N'Guyen, Steve; Thurat, Charles; Girard, Benoît

    2014-01-01

    The Basal Ganglia (BG) is a central structure involved in multiple cortical and subcortical loops. Some of these loops are believed to be responsible for saccade target selection. We study here how the very specific structural relationships of these saccadic loops can affect the ability of learning spatial and feature-based tasks. We propose a model of saccade generation with reinforcement learning capabilities based on our previous BG and superior colliculus models. It is structured around the interactions of two parallel cortico-basal loops and one tecto-basal loop. The two cortical loops separately deal with spatial and non-spatial information to select targets in a concurrent way. The subcortical loop is used to make the final target selection leading to the production of the saccade. These different loops may work in concert or disturb each other regarding reward maximization. Interactions between these loops and their learning capabilities are tested on different saccade tasks. The results show the ability of this model to correctly learn basic target selection based on different criteria (spatial or not). Moreover the model reproduces and explains training dependent express saccades toward targets based on a spatial criterion. Finally, the model predicts that in absence of prefrontal control, the spatial loop should dominate. PMID:24795615

  16. A Rapid, Manual Method to Map Coronal-Loop Structures of an Active Region Using Cubic Bézier Curves and Its Applications to Misalignment Angle Analysis

    NASA Astrophysics Data System (ADS)

    Gary, G. Allen; Hu, Qiang; Lee, Jong Kwan

    2014-03-01

    A rapid and flexible manual method is described that maps individual coronal loops of a 2D EUV image as Bézier curves using only four points per loop. Using the coronal loops as surrogates of magnetic-field lines, the mapping results restrict the magnetic-field models derived from extrapolations of magnetograms to those admissible and inadmissible via a fitness parameter. We outline explicitly how the coronal loops can be employed in constraining competing magnetic-field models by transforming 2D coronal-loop images into 3D field lines. The magnetic-field extrapolations must satisfy not only the lower boundary conditions of the vector field (the vector magnetogram) but also must have a set of field lines that satisfies the mapped coronal loops in the volume, analogous to an upper boundary condition. This method uses the minimization of the misalignment angles between the magnetic-field model and the best set of 3D field lines that match a set of closed coronal loops. The presented method is an important tool in determining the fitness of magnetic-field models for the solar atmosphere. The magnetic-field structure is crucial in determining the overall dynamics of the solar atmosphere.

  17. Inflation and deflation pressure-volume loops in anesthetized pinnipeds confirms compliant chest and lungs

    PubMed Central

    Fahlman, Andreas; Loring, Stephen H.; Johnson, Shawn P.; Haulena, Martin; Trites, Andrew W.; Fravel, Vanessa A.; Van Bonn, William G.

    2014-01-01

    We examined structural properties of the marine mammal respiratory system, and tested Scholander's hypothesis that the chest is highly compliant by measuring the mechanical properties of the respiratory system in five species of pinniped under anesthesia (Pacific harbor seal, Phoca vitulina; northern elephant seal, Mirounga angustirostris; northern fur seal Callorhinus ursinus; California sea lion, Zalophus californianus; and Steller sea lion, Eumetopias jubatus). We found that the chest wall compliance (CCW) of all five species was greater than lung compliance (airways and alveoli, CL) as predicted by Scholander, which suggests that the chest provides little protection against alveolar collapse or lung squeeze. We also found that specific respiratory compliance was significantly greater in wild animals than in animals raised in an aquatic facility. While differences in ages between the two groups may affect this incidental finding, it is also possible that lung conditioning in free-living animals may increase pulmonary compliance and reduce the risk of lung squeeze during diving. Overall, our data indicate that compliance of excised pinniped lungs provide a good estimate of total respiratory compliance. PMID:25426080

  18. Inflation and deflation pressure-volume loops in anesthetized pinnipeds confirms compliant chest and lungs.

    PubMed

    Fahlman, Andreas; Loring, Stephen H; Johnson, Shawn P; Haulena, Martin; Trites, Andrew W; Fravel, Vanessa A; Van Bonn, William G

    2014-01-01

    We examined structural properties of the marine mammal respiratory system, and tested Scholander's hypothesis that the chest is highly compliant by measuring the mechanical properties of the respiratory system in five species of pinniped under anesthesia (Pacific harbor seal, Phoca vitulina; northern elephant seal, Mirounga angustirostris; northern fur seal Callorhinus ursinus; California sea lion, Zalophus californianus; and Steller sea lion, Eumetopias jubatus). We found that the chest wall compliance (CCW) of all five species was greater than lung compliance (airways and alveoli, CL) as predicted by Scholander, which suggests that the chest provides little protection against alveolar collapse or lung squeeze. We also found that specific respiratory compliance was significantly greater in wild animals than in animals raised in an aquatic facility. While differences in ages between the two groups may affect this incidental finding, it is also possible that lung conditioning in free-living animals may increase pulmonary compliance and reduce the risk of lung squeeze during diving. Overall, our data indicate that compliance of excised pinniped lungs provide a good estimate of total respiratory compliance. PMID:25426080

  19. Open-loop and closed-loop excitation of the wake behind a circular cylinder

    NASA Astrophysics Data System (ADS)

    Williams, David; Cohen, Kelly; Siegel, Stefan; McLaughlin, Tom

    2006-11-01

    Both open loop and closed loop control were used to modify the flow around a circular cylinder at Re = 20,000. Independent plasma actuators were installed on the sides of the cylinder at +/- 90^o from the forward stagnation line. The actuators could be excited in-phase or 180^o out of phase with one another. In the case of open-loop forcing, in-phase excitation at twice the von Karman vortex shedding frequency produced large changes in the wake structure, similar to the experiments done by Williams, Mansy & Amato (JFM, 1992.) Negligible changes in wake structure occurred when the out-of-phase actuation was used, although the lock-on phenomenon was observed, suggesting that the wake structure modification resulting from the interaction between the forcing field and near wake is independent of Reynolds number. Closed-loop excitation using a proportional-derivative controller was done using a hot-film probe positioned at x/D=1.5, y/D = 1.5. The amplitude of the wake oscillation was shown to be sensitive to both the gain and phase of the controller. The amplitude of oscillations at a fixed controller gain are enhanced or suppressed relative to the non-forced level, depending on the controller phase. The vortex shedding frequency is changed when the PD controller is in a region of suppression. The expert assistance of SSgt. Mary S. Church is gratefully acknowledged.

  20. Fast loop modeling for protein structures

    NASA Astrophysics Data System (ADS)

    Zhang, Jiong; Nguyen, Son; Shang, Yi; Xu, Dong; Kosztin, Ioan

    2015-03-01

    X-ray crystallography is the main method for determining 3D protein structures. In many cases, however, flexible loop regions of proteins cannot be resolved by this approach. This leads to incomplete structures in the protein data bank, preventing further computational study and analysis of these proteins. For instance, all-atom molecular dynamics (MD) simulation studies of structure-function relationship require complete protein structures. To address this shortcoming, we have developed and implemented an efficient computational method for building missing protein loops. The method is database driven and uses deep learning and multi-dimensional scaling algorithms. We have implemented the method as a simple stand-alone program, which can also be used as a plugin in existing molecular modeling software, e.g., VMD. The quality and stability of the generated structures are assessed and tested via energy scoring functions and by equilibrium MD simulations. The proposed method can also be used in template-based protein structure prediction. Work supported by the National Institutes of Health [R01 GM100701]. Computer time was provided by the University of Missouri Bioinformatics Consortium.

  1. High temperature storage loop : final design report.

    SciTech Connect

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650%C2%B0C) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOE's SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  2. Embedding loop quantum cosmology without piecewise linearity

    NASA Astrophysics Data System (ADS)

    Engle, Jonathan

    2013-04-01

    An important goal is to understand better the relation between full loop quantum gravity (LQG) and the simplified, reduced theory known as loop quantum cosmology (LQC), directly at the quantum level. Such a firmer understanding would increase confidence in the reduced theory as a tool for formulating predictions of the full theory, as well as permitting lessons from the reduced theory to guide further development in the full theory. This paper constructs an embedding of the usual state space of LQC into that of standard LQG, that is, LQG based on piecewise analytic paths. The embedding is well defined even prior to solving the diffeomorphism constraint, at no point is a graph fixed and at no point is the piecewise linear category used. This motivates for the first time a definition of operators in LQC corresponding to holonomies along non-piecewise linear paths, without changing the usual kinematics of LQC in any way. The new embedding intertwines all operators corresponding to such holonomies, and all elements in its image satisfy an operator equation which classically implies homogeneity and isotropy. The construction is made possible by a recent result proven by Fleischhack. Communicated by P Singh

  3. Wilson loops in warped resolved deformed conifolds

    SciTech Connect

    Bennett, Stephen

    2011-11-15

    We calculate quark-antiquark potentials using the relationship between the expectation value of the Wilson loop and the action of a probe string in the string dual. We review and categorise the possible forms of the dependence of the energy on the separation between the quarks. In particular, we examine the possibility of there being a minimum separation for probe strings which do not penetrate close to the origin of the bulk space, and derive a condition which determines whether this is the case. We then apply these considerations to the flavoured resolved deformed conifold background of Gaillard et al. (2010) . We suggest that the unusual behaviour that we observe in this solution is likely to be related to the IR singularity which is not present in the unflavoured case. - Highlights: > We calculate quark-antiquark potentials using the Wilson loop and the action of a probe string in the string dual. > We review and categorise the possible forms of the dependence of the energy on the separation between the quarks. > We look in particular at the flavoured resolved deformed conifold. > There appears to be unusual behaviour which seems likely to be related to the IR singularity introduced by flavours.

  4. Emerging singularities in the bouncing loop cosmology

    NASA Astrophysics Data System (ADS)

    Mielczarek, Jakub; Szydłowski, Marek

    2008-06-01

    In this paper we calculate O(μ4) corrections from holonomies in the loop quantum gravity, usually not taken into account. Allowance of the corrections of this kind is equivalent with the choice of the new quatization scheme. Quantization ambiguities in the loop quantum cosmology allow for this additional freedom and presented corrections are consistent with the standard approach. We apply these corrections to the flat Friedmann-Robertson-Walker cosmological model and calculate the modified Friedmann equation. We show that the bounce appears in the models with the standard O(μ2) quantization scheme and is shifted to the higher energies ρbounce=3ρc. Also, a pole in the Hubble parameter appears for ρpole=(3)/(2)ρc corresponding to hyperinflation/deflation phases. This pole represents a curvature singularity at which the scale factor is finite. In this scenario the singularity and bounce coexist. Moreover, we find that an ordinary bouncing solution appears only when quantum corrections in the lowest order are considered. Higher order corrections can lead to nonperturbative effects.

  5. Loop quantization of the Schwarzschild interior revisited

    NASA Astrophysics Data System (ADS)

    Corichi, Alejandro; Singh, Parampreet

    2016-03-01

    The loop quantization of the Schwarzschild interior region, as described by a homogeneous anisotropic Kantowski-Sachs model, is re-examined. As several studies of different—inequivalent—loop quantizations have shown, to date there exists no fully satisfactory quantum theory for this model. This fact poses challenges to the validity of some scenarios to address the black hole information problem. Here we put forward a novel viewpoint to construct the quantum theory that builds from some of the models available in the literature. The final picture is a quantum theory that is both independent of any auxiliary structure and possesses a correct low curvature limit. It represents a subtle but non-trivial modification of the original prescription given by Ashtekar and Bojowald. It is shown that the quantum gravitational constraint is well defined past the singularity and that its effective dynamics possesses a bounce into an expanding regime. The classical singularity is avoided, and a semiclassical spacetime satisfying vacuum Einstein’s equations is recovered on the ‘other side’ of the bounce. We argue that such a metric represents the interior region of a white-hole spacetime, but for which the corresponding ‘white hole mass’ differs from the original black hole mass. Furthermore, we find that the value of the white hole mass is proportional to the third power of the starting black hole mass.

  6. BAYESIAN MAGNETOHYDRODYNAMIC SEISMOLOGY OF CORONAL LOOPS

    SciTech Connect

    Arregui, I.; Asensio Ramos, A. E-mail: aasensio@iac.es

    2011-10-10

    We perform a Bayesian parameter inference in the context of resonantly damped transverse coronal loop oscillations. The forward problem is solved in terms of parametric results for kink waves in one-dimensional flux tubes in the thin tube and thin boundary approximations. For the inverse problem, we adopt a Bayesian approach to infer the most probable values of the relevant parameters, for given observed periods and damping times, and to extract their confidence levels. The posterior probability distribution functions are obtained by means of Markov Chain Monte Carlo simulations, incorporating observed uncertainties in a consistent manner. We find well-localized solutions in the posterior probability distribution functions for two of the three parameters of interest, namely the Alfven travel time and the transverse inhomogeneity length scale. The obtained estimates for the Alfven travel time are consistent with previous inversion results, but the method enables us to additionally constrain the transverse inhomogeneity length scale and to estimate real error bars for each parameter. When observational estimates for the density contrast are used, the method enables us to fully constrain the three parameters of interest. These results can serve to improve our current estimates of unknown physical parameters in coronal loops and to test the assumed theoretical model.

  7. Acromioclavicular separation. Reconstruction using synthetic loop augmentation.

    PubMed

    Morrison, D S; Lemos, M J

    1995-01-01

    A total of 110 patients with a diagnosis of acromioclavicular joint separation were seen at our clinic between 1986 and 1991. Of these, 14 patients (12.7%) with grade III, IV, or V injuries required surgical reconstruction and were examined 2 years after surgery. All 14 patients underwent acromioclavicular reconstruction using a synthetic loop passed through drill holes in the base of the coracoid and the anterior third of the clavicle. When the loop is tightened, the clavicle is reduced anatomically without the anterior subluxation caused by simple clavicular cerclage. At an average followup of 44.2 months, patients were evaluated using the University of California, Los Angeles, rating scale. Twelve of the 14 had good or excellent results and returned to normal sport and work activities at 6 months. Of the two initial poor results, one required revision 1 month post-operatively because the patient was noncompliant, and the other required manipulation under anesthesia 3 months after surgery. The results in these two patients at 2 years were good and excellent, respectively. We concluded that, when medically indicated, fixation of the clavicle to the coracoid using this technique yields satisfactory results in an athletic population. PMID:7726339

  8. BOOK REVIEW: A First Course in Loop Quantum Gravity A First Course in Loop Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Dittrich, Bianca

    2012-12-01

    Students who are interested in quantum gravity usually face the difficulty of working through a large amount of prerequisite material before being able to deal with actual quantum gravity. A First Course in Loop Quantum Gravity by Rodolfo Gambini and Jorge Pullin, aimed at undergraduate students, marvellously succeeds in starting from the basics of special relativity and covering basic topics in Hamiltonian dynamics, Yang Mills theory, general relativity and quantum field theory, ending with a tour on current (loop) quantum gravity research. This is all done in a short 173 pages! As such the authors cannot cover any of the subjects in depth and indeed this book should be seen more as a motivation and orientation guide so that students can go on to follow the hints for further reading. Also, as there are many subjects to cover beforehand, slightly more than half of the book is concerned with more general subjects (special and general relativity, Hamiltonian dynamics, constrained systems, quantization) before the starting point for loop quantum gravity, the Ashtekar variables, are introduced. The approach taken by the authors is heuristic and uses simplifying examples in many places. However they take care in motivating all the main steps and succeed in presenting the material pedagogically. Problem sets are provided throughout and references for further reading are given. Despite the shortness of space, alternative viewpoints are mentioned and the reader is also referred to experimental results and bounds. In the second half of the book the reader gets a ride through loop quantum gravity; the material covers geometric operators and their spectra, the Hamiltonian constraints, loop quantum cosmology and, more broadly, black hole thermodynamics. A glimpse of recent developments and open problems is given, for instance a discussion on experimental predictions, where the authors carefully point out the very preliminary nature of the results. The authors close with an

  9. Coronal Loop Evolution Observed with AIA and Hi-C

    NASA Technical Reports Server (NTRS)

    Mulu-Moore, Fana; Winebarger, A.; Cirtain, J.; Kobayashi, K.; Korreck, K.; Golub, L.; Kuzin. S.; Walsh, R.; DeForest, C.; DePontieu, B.; Weber, M.

    2012-01-01

    Despite much progress toward understanding the dynamics of the solar corona, the physical properties of coronal loops are not yet fully understood. Recent investigations and observations from different instruments have yielded contradictory results about the true physical properties of coronal loops. In the past, the evolution of loops has been used to infer the loop substructure. With the recent launch of High Resolution Coronal Imager (Hi-C), this inference can be validated. In this poster we discuss the first results of loop analysis comparing AIA and Hi-C data. We find signatures of cooling in a pixel selected along a loop structure in the AIA multi-filter observations. However, unlike previous studies, we find that the cooling time is much longer than the draining time. This is inconsistent with previous cooling models.

  10. Loop Integrands for Scattering Amplitudes from the Riemann Sphere

    NASA Astrophysics Data System (ADS)

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2015-09-01

    The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n -gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory.

  11. Iterative LQG Controller Design Through Closed-Loop Identification

    NASA Technical Reports Server (NTRS)

    Hsiao, Min-Hung; Huang, Jen-Kuang; Cox, David E.

    1996-01-01

    This paper presents an iterative Linear Quadratic Gaussian (LQG) controller design approach for a linear stochastic system with an uncertain open-loop model and unknown noise statistics. This approach consists of closed-loop identification and controller redesign cycles. In each cycle, the closed-loop identification method is used to identify an open-loop model and a steady-state Kalman filter gain from closed-loop input/output test data obtained by using a feedback LQG controller designed from the previous cycle. Then the identified open-loop model is used to redesign the state feedback. The state feedback and the identified Kalman filter gain are used to form an updated LQC controller for the next cycle. This iterative process continues until the updated controller converges. The proposed controller design is demonstrated by numerical simulations and experiments on a highly unstable large-gap magnetic suspension system.

  12. Structure Prediction of RNA Loops with a Probabilistic Approach

    PubMed Central

    Li, Jun; Zhang, Jian; Wang, Jun; Li, Wenfei; Wang, Wei

    2016-01-01

    The knowledge of the tertiary structure of RNA loops is important for understanding their functions. In this work we develop an efficient approach named RNApps, specifically designed for predicting the tertiary structure of RNA loops, including hairpin loops, internal loops, and multi-way junction loops. It includes a probabilistic coarse-grained RNA model, an all-atom statistical energy function, a sequential Monte Carlo growth algorithm, and a simulated annealing procedure. The approach is tested with a dataset including nine RNA loops, a 23S ribosomal RNA, and a large dataset containing 876 RNAs. The performance is evaluated and compared with a homology modeling based predictor and an ab initio predictor. It is found that RNApps has comparable performance with the former one and outdoes the latter in terms of structure predictions. The approach holds great promise for accurate and efficient RNA tertiary structure prediction. PMID:27494763

  13. Structure Prediction of RNA Loops with a Probabilistic Approach.

    PubMed

    Li, Jun; Zhang, Jian; Wang, Jun; Li, Wenfei; Wang, Wei

    2016-08-01

    The knowledge of the tertiary structure of RNA loops is important for understanding their functions. In this work we develop an efficient approach named RNApps, specifically designed for predicting the tertiary structure of RNA loops, including hairpin loops, internal loops, and multi-way junction loops. It includes a probabilistic coarse-grained RNA model, an all-atom statistical energy function, a sequential Monte Carlo growth algorithm, and a simulated annealing procedure. The approach is tested with a dataset including nine RNA loops, a 23S ribosomal RNA, and a large dataset containing 876 RNAs. The performance is evaluated and compared with a homology modeling based predictor and an ab initio predictor. It is found that RNApps has comparable performance with the former one and outdoes the latter in terms of structure predictions. The approach holds great promise for accurate and efficient RNA tertiary structure prediction. PMID:27494763

  14. Loops and multiple edges in modularity maximization of networks

    NASA Astrophysics Data System (ADS)

    Cafieri, Sonia; Hansen, Pierre; Liberti, Leo

    2010-04-01

    The modularity maximization model proposed by Newman and Girvan for the identification of communities in networks works for general graphs possibly with loops and multiple edges. However, the applications usually correspond to simple graphs. These graphs are compared to a null model where the degree distribution is maintained but edges are placed at random. Therefore, in this null model there will be loops and possibly multiple edges. Sharp bounds on the expected number of loops, and their impact on the modularity, are derived. Then, building upon the work of Massen and Doye, but using algebra rather than simulation, we propose modified null models associated with graphs without loops but with multiple edges, graphs with loops but without multiple edges and graphs without loops nor multiple edges. We validate our models by using the exact algorithm for clique partitioning of Grötschel and Wakabayashi.

  15. Loop Integrands for Scattering Amplitudes from the Riemann Sphere.

    PubMed

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2015-09-18

    The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n-gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory. PMID:26430983

  16. The "loop with anchor" technique to repair mitral valve prolapse.

    PubMed

    Isoda, Susumu; Osako, Motohiko; Kimura, Tamizo; Mashiko, Yuji; Yamanaka, Nozomu; Nakamura, Shingo; Maehara, Tadaaki

    2012-01-01

    The current surgical technique of using an artificial chord (composed of expanded polytetrafluoroethylene [ePTFE] sutures) to repair mitral prolapse is technically difficult to perform. Slippery knot tying and the difficulty of changing the chordae length after the hydrostatic test are frustrating problems. The loop technique solves the problem of slippery knot tying but not the problem of changing the chordae length. Our "loop with anchor" technique consists of the following elements: construction of an anchor at the papillary muscle; determining the loop length; tying the loop to the anchor; suturing the loop to the mitral valve; the hydrostatic test; and re-suturing or changing the loop, if needed. Adjustments can be made for the entire procedure or for a portion of the procedure. PMID:22156285

  17. One-loop radiative corrections to the QED Casimir energy

    NASA Astrophysics Data System (ADS)

    Moazzemi, Reza; Mojavezi, Amirhosein

    2016-05-01

    In this paper, we investigate one-loop radiative corrections to the Casimir energy in the presence of two perfectly conducting parallel plates for QED theory within the renormalized perturbation theory. In fact, there are three contributions for radiative corrections to the Casimir energy, up to order α . Only the two-loop diagram, which is of order α , has been computed by Bordag et. al (Ann. Phys. 165:192, 1985), approximately. Here, up to this order, we consider corrections due to two one-loop terms, i.e., photonic and fermionic loop corrections resulting from renormalized QED Lagrangian, more precisely. Our results show that only the fermionic loop has a very minor correction and the correction of photonic loop vanishes.

  18. Isolated and coupled superquadric loop antennas for mobile communications applications

    NASA Technical Reports Server (NTRS)

    Jensen, Michael A.; Rahmat-Samii, Yahya

    1993-01-01

    This work provides an investigation of the performance of loop antennas for use in mobile communications applications. The analysis tools developed allow for high flexibility by representing the loop antenna as a superquadric curve, which includes the case of circular, elliptical, and rectangular loops. The antenna may be in an isolated environment, located above an infinite ground plane, or placed near a finite conducting plate or box. In cases where coupled loops are used, the two loops may have arbitrary relative positions and orientations. Several design examples are included to illustrate the versatility of the analysis capabilities. The performance of coupled loops arranged in a diversity scheme is also evaluated, and it is found that high diversity gain can be achieved even when the antennas are closely spaced.

  19. Renormalization of the Polyakov loop with gradient flow

    NASA Astrophysics Data System (ADS)

    Petreczky, P.; Schadler, H.-P.

    2015-11-01

    We use the gradient flow for the renormalization of the Polyakov loop in various representations. Using 2 +1 flavor QCD with highly improved staggered quarks and lattices with temporal extents of Nτ=6 , 8, 10 and 12 we calculate the renormalized Polyakov loop in many representations including fundamental, sextet, adjoint, decuplet, 15-plet, 24-plet and 27-plet. This approach allows for the calculations of the renormalized Polyakov loops over a large temperature range from T =116 MeV up to T =815 MeV , with small errors not only for the Polyakov loop in fundamental representation, but also for the Polyakov loops in higher representations. We compare our results with standard renormalization schemes and discuss the Casimir scaling of the Polyakov loops.

  20. Two-loop gap equations for the magnetic mass

    NASA Astrophysics Data System (ADS)

    Eberlein, F.

    1998-10-01

    One-loop gap equations have recently been used by several authors to estimate the non-perturbative mass gap in a 3-dimensional gauge theory. I extend the method to two loops and demonstrate that the resulting gap equation has a real and positive solution m~=0.34g2, which is in good agreement with the one-loop results and lattice data.

  1. Decision feedback loop for tracking a polyphase modulated carrier

    NASA Technical Reports Server (NTRS)

    Simon, M. K. (Inventor)

    1974-01-01

    A multiple phase modulated carrier tracking loop for use in a frequency shift keying system is described in which carrier tracking efficiency is improved by making use of the decision signals made on the data phase transmitted in each T-second interval. The decision signal is used to produce a pair of decision-feedback quadrature signals for enhancing the loop's performance in developing a loop phase error signal.

  2. Exploiting loop level parallelism in nonprocedural dataflow programs

    NASA Technical Reports Server (NTRS)

    Gokhale, Maya B.

    1987-01-01

    Discussed are how loop level parallelism is detected in a nonprocedural dataflow program, and how a procedural program with concurrent loops is scheduled. Also discussed is a program restructuring technique which may be applied to recursive equations so that concurrent loops may be generated for a seemingly iterative computation. A compiler which generates C code for the language described below has been implemented. The scheduling component of the compiler and the restructuring transformation are described.

  3. The Energy Landscape of Hyperstable LacI-DNA Loops

    NASA Astrophysics Data System (ADS)

    Kahn, Jason

    2009-03-01

    The Escherichia coli LacI protein represses transcription of the lac operon by blocking access to the promoter through binding at a promoter-proximal DNA operator. The affinity of tetrameric LacI (and therefore the repression efficiency) is enhanced by simultaneous binding to an auxiliary operator, forming a DNA loop. Hyperstable LacI-DNA loops were previously shown to be formed on DNA constructs that include a sequence-directed bend flanked by operators. Biochemical experiments showed that two such constructs (9C14 and 11C12) with different helical phasing between the operators and the DNA bend form different DNA loop shapes. The geometry and topology of the loops and the relevance of alternative conformations suggested by probable flexible linkers in LacI remain unclear. Bulk and single molecule fluorescence resonance energy transfer (SM-FRET, with D. English) experiments on a dual fluorophore-labeled 9C14-LacI loop demonstrate that it adopts a single, stable, rigid closed-form loop conformation. Here, we characterize the LacI-9C14 loop by SM-FRET as a function of inducer isopropyl-β,D-thiogalactoside (IPTG) concentration. Energy transfer measurements reveal partial but incomplete destabilization of loop formation by IPTG. Surprisingly, there is no change in the energy transfer efficiency of the remaining looped population. Models for the regulation of the lac operon often assume complete disruption of LacI-operator complexes upon inducer binding to LacI. Our work shows that even at saturating IPTG there is still a significant population of LacI-DNA complexes in a looped state, in accord with previous in vivo experiments that show incomplete induction (with J. Maher). Finally, we will report progress on characterizing the ``energy landscape'' for DNA looping upon systematic variation of the DNA linkers between the operators and the bending locus. Rod mechanics simulations (with N. Perkins) provide testable predictions on loop stability, topology, and FRET.

  4. Kinematic calibration of manipulators with closed loop actuated joints

    NASA Technical Reports Server (NTRS)

    Everett, Louis J.; Lin, C. Y.

    1988-01-01

    A method for performing forward kinematic calibration of manipulators having one or more closed-loop-actuated joints is presented. The technique is an extension of algorithms designed for open-loop jointed manipulators. The calibration is equivalent to minimizing an objective function subject to constraints. The objective function is taken as the integral of end-effector position and orientation error. The constraints arise from the closed-loop mechanisms present in the manipulator.

  5. Direct-contact closed-loop heat exchanger

    DOEpatents

    Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

    1984-01-01

    A high temperature heat exchanger with a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

  6. Neuron-like dynamics of a phase-locked loop

    NASA Astrophysics Data System (ADS)

    Matrosov, Valery V.; Mishchenko, Mikhail A.; Shalfeev, Vladimir D.

    2013-10-01

    Dynamics of two coupled phase-controlled generators based on phase-locked loop systems with a high frequency filter in the control loop was studied. It was found that beating modes are synchronized in the systems and shown that different synchronization states form an overlapping structure in parameters space of the coupled systems. Usage of the phase-locked loop as a neuron-like element is proposed.

  7. Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates

    NASA Astrophysics Data System (ADS)

    Hayata, Tomoya; Yamamoto, Arata

    2015-05-01

    We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.

  8. Synthesis of nano precipitated calcium carbonate by using a carbonation process through a closed loop reactor

    NASA Astrophysics Data System (ADS)

    Thriveni, Thenepalli; Ahn, Ji Whan; Ramakrishna, Chilakala; Ahn, Young Jun; Han, Choon

    2016-01-01

    Nano calcium carbonate particles have a wide range of industrial applications due to their beneficial properties such as high porosity and high surface area to volume ratio and due to their strengthening the mechanical properties of plastics and paper. Consequently, significant research has been done to deliver a new approach for the synthesis of precipitated nano calcium carbonate by using a carbonation process through a closed loop reactor. Both the experimental and the instrumental parameters, i.e. the CO2 flow rate, the concentration of the starting materials (Ca(OH)2 and CaO), the pH, the orifice diameter, etc., were investigated. The carbonation efficiency was increased due to the diffusion process involved in the loop reactor. The particle size was affected by the CO2 flow rate, reaction time, and orifice diameter. Finally, precipitated nano calcite calcium carbonate (50 to 100 nm) was synthesized by optimizing all the experimental and the instrumental parameters. The synthesized precipitated nano calcium carbonate was characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. This study has proved that the carbonation efficiency can be enhanced for a short time by using a loop reactor and that the carbonation process was more energy efficient and cost effective than other conventional methods.

  9. Bright EUV knots on post-flare loops: Are we seeing slow shocks?

    NASA Astrophysics Data System (ADS)

    Unverferth, John; Longcope, Dana; Reeves, Katharine

    2015-04-01

    Post flare loops imaged in the EUV sometimes show bright knots of emission at their apices. Knots from the loops in an arcade often line up to form a bar of coronal emission parallel to the polarity inversion line. These features have been variously interpreted as the results of colliding evaporation flows or volume enhancement at the point of weakest magnetic field. Here we consider the possibility that the features are produced through density enhancement resulting from shock compression during the reconnection process. We present simulations of thin flux tube dynamics following reconnection, which capture the essential physics of Petschek's fast reconnection model. The slow shock present during reconnection and subsequent retraction produce a high density region which persists even after the loop has achieved its ultimate equilibrium configuration. This high density produces enhanced emission at the bottom of the current sheet. Evaporation flows impinge on the high density region resulting in further enhancement to the density and the emission at the same position: the bottom of the current sheet. We compare these results to those from more conventional simulation where ad hoc heating drives evaporation from both feet.

  10. Differential Emission Measure Studies of Solar Coronal Loops for AIA

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, D.; Weber, M. A.; Sette, A. L.

    2004-12-01

    The Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory scheduled to launch in 2008 will provide an unprecedented quantity of information about the solar corona at rapid cadence in 6 EUV channels. We discuss the study of coronal loops through differential emission measure (DEM) analysis of coronal plasma using mock AIA observations. We select a loop structure in the coronal model and evaluate various DEM estimation methods (including background subtraction) against the known loop properties. We find that coronal loops can be successfully identified by their DEM signatures. Such signatures provide observational data essential to furthering our understanding of hot coronal plasmas.

  11. Inverse spin Hall effect in a closed loop circuit

    SciTech Connect

    Omori, Y.; Auvray, F.; Wakamura, T.; Niimi, Y.; Fert, A.

    2014-06-16

    We present measurements of inverse spin Hall effects (ISHEs), in which the conversion of a spin current into a charge current via the ISHE is detected not as a voltage in a standard open circuit but directly as the charge current generated in a closed loop. The method is applied to the ISHEs of Bi-doped Cu and Pt. The derived expression of ISHE for the loop structure can relate the charge current flowing into the loop to the spin Hall angle of the SHE material and the resistance of the loop.

  12. Entropy mode loops and cosmological correlations during perturbative reheating

    SciTech Connect

    Kaya, Ali; Kutluk, Emine Seyma E-mail: seymakutluk@gmail.com

    2015-01-01

    Recently, it has been shown that during preheating the entropy modes circulating in the loops, which correspond to the inflaton decay products, meaningfully modify the cosmological correlation functions at superhorizon scales. In this paper, we determine the significance of the same effect when reheating occurs in the perturbative regime. In a typical two scalar field model, the magnitude of the loop corrections are shown to depend on several parameters like the background inflaton amplitude in the beginning of reheating, the inflaton decay rate and the inflaton mass. Although the loop contributions turn out to be small as compared to the preheating case, they still come out larger than the loop effects during inflation.

  13. Man-in-the-control-loop simulation of manipulators

    NASA Technical Reports Server (NTRS)

    Chang, J. L.; Lin, Tsung-Chieh; Yae, K. Harold

    1989-01-01

    A method to achieve man-in-the-control-loop simulation is presented. Emerging real-time dynamics simulation suggests a potential for creating an interactive design workstation with a human operator in the control loop. The recursive formulation for multibody dynamics simulation is studied to determine requirements for man-in-the-control-loop simulation. High speed computer graphics techniques provides realistic visual cues for the simulator. Backhoe and robot arm simulations are implemented to demonstrate the capability of man-in-the-control-loop simulation.

  14. Capillary-Condenser-Pumped Heat-Transfer Loop

    NASA Technical Reports Server (NTRS)

    Silverstein, Calvin C.

    1989-01-01

    Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

  15. TOPLOSS - A thermal analyzer for two-phase loops

    NASA Astrophysics Data System (ADS)

    Schwarzott, Walter; Faust, Thomas; Rothmeyer, Markus

    Two phase flow cooling loops are an answer to the new thermal requirements established by future space missions which tend to larger size and higher power demand. The software package TOPLOSS simulates the thermal, fluid- and thermodynamic behavior of two and single phase cooling loops of arbitrary geometry including all relevant components. TOPLOSS structure is modular, the different loop components are modeled in separate adaptable subroutines. The fluid properties module is an improved version of GASP, a NASA-developed fluid property program. TOPLOSS is linked to the thermal network analyzer SINDA which is used to manage the thermal boundaries for the loop. An example illustrates TOPLOSS performance.

  16. Violation of the holographic principle in the loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Sargın, Ozan; Faizal, Mir

    2016-02-01

    In this paper, we analyze the holographic principle using loop quantum gravity (LQG). This will be done by using polymeric quantization for analysing Yurtsever's holographic bound on the entropy, which is obtained from local quantum field theories. As the polymeric quantization is the characteristic feature of loop quantum gravity, we will argue that this calculation will indicate the effect of loop quantum gravity on the holographic principle. Thus, we will be able to explicitly demonstrate the violation of the holographic principle in the loop quantum gravity.

  17. Bosonic (meta)stabilization of cosmic string loops

    NASA Astrophysics Data System (ADS)

    Morris, J. R.

    2013-02-01

    We consider the possibility of a bosonic (meta)stabilization of a cosmic gauge string loop due to the presence of a gas of low-mass bosonic particles which become trapped within the string core. This boson gas exerts a pressure which tends to counteract the string tension, allowing a circular string loop to find a finite equilibrium radius, provided that gas particles do not escape the string core. However, high-energy bosons do escape, and, consequently, the loop shrinks, and the temperature rises. Estimates indicate that the bosonic stabilization mechanism is ineffective, and the loop is unstable against decay.

  18. Solar flares as cascades of reconnecting magnetic loops.

    PubMed

    Hughes, D; Paczuski, M; Dendy, R O; Helander, P; McClements, K G

    2003-04-01

    A model for the solar coronal magnetic field is proposed where multiple directed loops evolve in space and time. Loops injected at small scales are anchored by footpoints of opposite polarity moving randomly on a surface. Nearby footpoints of the same polarity aggregate, and loops can reconnect when they collide. This may trigger a cascade of further reconnection, representing a solar flare. Numerical simulations show that a power law distribution of flare energies emerges, associated with a scale-free network of loops, indicating self-organized criticality. PMID:12689272

  19. Spin and orbital magnetization loops obtained using magnetic Compton scattering

    SciTech Connect

    Itou, M.; Sakurai, Y.; Koizumi, A.

    2013-02-25

    We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl{sub 2} was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.

  20. Investigation of Low Power Operation in a Loop Heat Pipe

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Powers, Edward I. (Technical Monitor)

    2001-01-01

    This paper presents test results of an experimental study of low power operation in a loop heat pipe. The main objective was to demonstrate how changes in the vapor void fraction inside the evaporator core would affect the loop behavior, The fluid inventory and the relative tilt between the evaporator and the compensation chamber were varied so as to create different vapor void fractions in the evaporator core. The effect on the loop start-up, operating temperature, and capillary limit was investigated. Test results indicate that the vapor void fraction inside the evaporator core is the single most important factor in determining the loop operation at low powers.

  1. Taxonomy and conformational analysis of loops in proteins.

    PubMed

    Ring, C S; Kneller, D G; Langridge, R; Cohen, F E

    1992-04-01

    We propose a general classification scheme for loops, aperiodic segments of protein structure. In an effort to avoid the geometric complexity created by non-repeating phi psi angles, a morphologic definition that focuses upon the linearity and planarity of loops is utilized. Out of 432 loops (4 to 20 residues in length) extracted from 67 proteins, 205 are classified as linear (straps), 133 as non-linear and planar (omegas), and 86 as non-linear and non-planar (zetas). The remaining 8 are classified as compound loops because they contain a combination of strap, omega, and zeta morphologies. We introduce a structural alphabet as a shorthand notation for describing local conformation. The symbols of this alphabet are based on the virtual dihedral angle joining four consecutive alpha carbons. The notation is used to provide a compact description of loop motifs in phosphate binding and calcium binding proteins. Since similar loop conformations form similar "words", the structural sequence facilitates the search for common structural motifs in a family of loops. Contrary to the view of loops as "random coils", we find loops to have positional preferences for amino acid residues analogous to those previously described for beta-turns. PMID:1569550

  2. Efficient static scheduling of loops on synchronous multiprocessors

    SciTech Connect

    Zaky, A.M.

    1989-01-01

    This dissertation investigates efficient compile-time scheduling techniques for exploiting parallelism on synchronous multiprocessors. Synchronous multiprocessors, e.g. Very Long Instruction Word (VLIW) machines, are very effective in utilizing unstructured fine-grained parallelism in programs. The effectiveness of such machines is crucially dependent on the static compile-time analysis and detection of potential parallelism. The first part of the dissertation focuses on scheduling sequential loops on multiprocessors with multiple identical processor units. The problem of determining the maximal initiation rate for the execution of a sequential loop with uniform dependence distances on a synchronous multiprocessor is addressed and cast as an eigenvalue problem in a path algebra. A low-order polynomial algorithm for the determination of the optimal loop initiation rate is developed, and a schedule that exploits fine-grained parallelism and achieves the optimal initiation rate is developed under an idealized unbounded processor model. Next, the concepts developed above are extended to deal with perfectly-nested loops with uniform dependences. A strategy is developed to identify both the loop level and fine-grained expression level parallelism in nested loops, and to efficiently schedule such loops on synchronous multiprocessors. Loop scheduling techniques such as Do-Across, Wavefront scheduling, and fine-grained scheduling techniques such as loop unfolding are shown to be derivable within the presented framework.

  3. Observational evidence for atmospheric modulation of the Loop Current migrations

    NASA Astrophysics Data System (ADS)

    Lindo-Atichati, D.; Sangrà, P.

    2015-12-01

    Recent modeling studies on the shedding of Loop Current rings suggest that the intensification of the dominant zonal wind field delays the detachment of rings and affects the Loop Current migrations. The atmospheric modulation of the Loop Current migrations is analyzed here using reanalysis winds and altimetry-derived observations. A newly developed methodology is applied to locate the Loop Current front, and a wavelet-based semblance analysis is used to explore correlations with atmospheric forcing. The results show that weakening (intensification) of the zonal wind stress in the eastern Gulf of Mexico is related with the Loop Current excursions to the north (south). Semblance analyses confirm negative correlations between the zonal wind stress and the Loop Current migrations during the past 20 years. The intrusions of the Loop Current might involve an increase of the Yucatan Transport, which would balance the westward Rossby wave speed of a growing loop and delay the ring shedding. The results of this study have consequences for the interpretation of the chaotic processes of ring detachment and Loop Current intrusions, which might be modulated by wind stress.

  4. Experimental study on sintered powder wick loop heat pipe

    NASA Astrophysics Data System (ADS)

    Putra, Nandy; Saputra, Bimo, M. Iqbal; Irwansyah, Ridho; Wayan, S. Nata

    2012-06-01

    Increased of heat flux generated by electronic equipment in particular components of a computer (CPU) should always be accompanied with a good cooling in order to achieve optimal operating capability with a high level of reliability. The use of loop heat pipes in thermal management of electronic cooling becomes one of alternative solution. Before LHPs are implemented as an alternative cooling method for electronic device, a quantity of reliability factors should be considered and evaluated such as wick structure and material, type of working fluid, long term life tests, and other tests. The purposes of this experimental study are to examine and analyze the application of sintered copper powder as a wick on a loop heat pipe, type of cooling system on LHP and the orientation of LHP. The performace of nanofluid as working fluid in loop heat pipe were also investigated in this experiment. The performance of the loop heat pipe was also affected by the type of condenser; the water cooled loop heat pipe has the highest temperature reducing value compared to the heat sink fan. The orientation of loop heat pipe also affected the performance of loop heat pipe. This proved that gravity and capillary pressure affecting the performance of loop heat pipes. Temperature differences between the evaporator and condenser sections with nanofluids were less that pure water, i.e. thermal resistance of the LHP when charged with nanofluids was less. It makes nanofluid attractive as working fluid in loop heat pipe technology.

  5. Modelling of Nonthermal Microwave Emission from Twisted Magnetic Loops

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Kuznetsov, A. A.

    2016-05-01

    Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand the impact of a twisted magnetic field topology on radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with a particular polarisation distribution. The polarisation sign inversion line is inclined relatively to the axis of the loop. The radio emission source is more compact in the case of a less twisted loop, assuming an anisotropic pitch-angle distribution of nonthermal electrons.

  6. False lock performance of Shuttle Costas loop receivers

    NASA Technical Reports Server (NTRS)

    Woo, K. T.; Holmes, J. K.; Huth, G. K.; Lindsey, W. C.

    1978-01-01

    The false (sideband) lock problem in Shuttle Costas loop receivers, in the presence of noise, is assessed. False lock margin is defined depending on symbol signal-to-noise ratio rather than in the absence of noise. Closed-form results are given for the case where the arm filters of the Costas loop are one-pole Butterworth filters as used in the Shuttle receivers. However, the approach taken is also general enough to cover filters of arbitrary characteristics. As part of the development of the false lock margin, it is shown that the false lock phenomenon of the squaring loop is identical to that of the Costas loop.

  7. Modelling of Nonthermal Microwave Emission from Twisted Magnetic Loops

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Kuznetsov, A. A.

    2016-06-01

    Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand the impact of a twisted magnetic field topology on radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with a particular polarisation distribution. The polarisation sign inversion line is inclined relatively to the axis of the loop. The radio emission source is more compact in the case of a less twisted loop, assuming an anisotropic pitch-angle distribution of nonthermal electrons.

  8. One-loop QCD contribution to the potential of QQ¯

    NASA Astrophysics Data System (ADS)

    Liu, Li-Quan; Zhao, Shu-Min; Zhang, Jian-Jun; Yang, Bao-Zhu; Huang, De-Bao

    2011-02-01

    Without the non-relativistic approximation in one-loop function, the dominating one-loop contribution to the quark-antiquark potential is studied numerically in terms of perturbative Quantum Chromo Dynamics (QCD). For Coulomb-like potential, the ratio of the one-loop correction to the tree diagram contribution is presented, whose absolute value is about 20%. Our result is consistent with the analysis that the one-loop contribution should be suppressed by a factor αs/π to the leading order contribution. This work can deepen the comprehension of αs in Cornel potential.

  9. Monitoring Digital Closed-Loop Feedback Systems

    NASA Technical Reports Server (NTRS)

    Katz, Richard; Kleyner, Igor

    2011-01-01

    A technique of monitoring digital closed-loop feedback systems has been conceived. The basic idea is to obtain information on the performances of closed-loop feedback circuits in such systems to aid in the determination of the functionality and integrity of the circuits and of performance margins. The need for this technique arises as follows: Some modern digital systems include feedback circuits that enable other circuits to perform with precision and are tolerant of changes in environment and the device s parameters. For example, in a precision timing circuit, it is desirable to make the circuit insensitive to variability as a result of the manufacture of circuit components and to the effects of temperature, voltage, radiation, and aging. However, such a design can also result in masking the indications of damaged and/or deteriorating components. The present technique incorporates test circuitry and associated engineering-telemetry circuitry into an embedded system to monitor the closed-loop feedback circuits, using spare gates that are often available in field programmable gate arrays (FPGAs). This technique enables a test engineer to determine the amount of performance margin in the system, detect out of family circuit performance, and determine one or more trend(s) in the performance of the system. In one system to which the technique has been applied, an ultra-stable oscillator is used as a reference for internal adjustment of 12 time-to-digital converters (TDCs). The feedback circuit produces a pulse-width-modulated signal that is fed as a control input into an amplifier, which controls the circuit s operating voltage. If the circuit s gates are determined to be operating too slowly or rapidly when their timing is compared with that of the reference signal, then the pulse width increases or decreases, respectively, thereby commanding the amplifier to increase or reduce, respectively, its output level, and "adjust" the speed of the circuits. The nominal

  10. Excluded volume effects on the kinetic assembling of a structural motif for RNA catalysis

    NASA Astrophysics Data System (ADS)

    Fernández, Ariel

    1991-09-01

    We establish the role of excluded volume effects on the loss of conformational entropy due to pseudoknot formation in RNA. This pseudoknot appears to be the structural motif responsible for shaping the splicing site of certain noncoding RNA transcriptional products. Focusing on the illustrative example of the YC4 intron, we show that the emergence of this motif is kinetically driven and prevails over competing catalytically inert secondary structure due to excluded volume effects which favor the correlation of interacting intramolecular loops.

  11. Inorganic nutrients, bacteria, and the microbial loop.

    PubMed

    Caron, D A

    1994-09-01

    The realization that natural assemblages of planktonic bacteria may acquire a significant fraction of their nitrogen and phosphorus via the uptake of dissolved inorganic nutrients has modified our traditional view of these microorganisms as nutrient remineralizers in plankton communities. Bacterial uptake of inorganic nitrogen and phosphorus may place bacteria and phytoplankton in competition for growth-limiting nutrients, rather than in their traditional roles as the respective "source" and "sink" for these nutrients in the plankton. Bacterial nutrient uptake also implies that bacterivorous protozoa may play a pivotal role in the remineralization of these elements in the microbial loop. The overall contribution of bacterial utilization of inorganic nutrients to total nutrient uptake in the ocean is still poorly understood, but some generalizations are emerging with respect to the geographical areas and community physiological conditions that might elicit this behavior. PMID:24186457

  12. Calculating soft radiation at one loop

    NASA Astrophysics Data System (ADS)

    Kasemets, Tomas; Waalewijn, Wouter J.; Zeune, Lisa

    2016-03-01

    We present an efficient way to calculate the effect of soft QCD radiation at one loop, which is needed for predictions at next-to-next-to-leading logarithmic accuracy. We use rapidity coordinates and isolate the divergences in the integrand. By performing manipulations with cumulative variables, we avoid complications from plus distributions. We address rapidity divergences, divergences with an azimuthal dependence, complicated jet boundaries and multi-differential measurements. The process and measurements can be easily adjusted, as we demonstrate by reproducing many existing soft functions. The results for a general LHC process with multiple Wilson lines are obtained by treating Wilson lines that are not back-to-back using a boost. We also obtain, for the first time, the N-jettiness soft function for generic jet angularities, and the collinear-soft function for the measurement of two angularities.

  13. Generalized effective description of loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Ashtekar, Abhay; Gupt, Brajesh

    2015-10-01

    The effective description of loop quantum cosmology (LQC) has proved to be a convenient platform to study phenomenological implications of the quantum bounce that resolves the classical big bang singularity. Originally, this description was derived using Gaussian quantum states with small dispersions. In this paper we present a generalization to incorporate states with large dispersions. Specifically, we derive the generalized effective Friedmann and Raychaudhuri equations and propose a generalized effective Hamiltonian which are being used in an ongoing study of the phenomenological consequences of a broad class of quantum geometries. We also discuss an interesting interplay between the physics of states with larger dispersions in standard LQC, and of sharply peaked states in (hypothetical) LQC theories with larger area gap.

  14. Covariant entropy bound and loop quantum cosmology

    SciTech Connect

    Ashtekar, Abhay; Wilson-Ewing, Edward

    2008-09-15

    We examine Bousso's covariant entropy bound conjecture in the context of radiation filled, spatially flat, Friedmann-Robertson-Walker models. The bound is violated near the big bang. However, the hope has been that quantum gravity effects would intervene and protect it. Loop quantum cosmology provides a near ideal setting for investigating this issue. For, on the one hand, quantum geometry effects resolve the singularity and, on the other hand, the wave function is sharply peaked at a quantum corrected but smooth geometry, which can supply the structure needed to test the bound. We find that the bound is respected. We suggest that the bound need not be an essential ingredient for a quantum gravity theory but may emerge from it under suitable circumstances.

  15. Thermal stability of idealized folded carbyne loops.

    PubMed

    Cranford, Steven W

    2013-01-01

    Self-unfolding items provide a practical convenience, wherein ring-like frames are contorted into a state of equilibrium and subsequently  pop up' or deploy when perturbed from a folded structure. Can the same process be exploited at the molecular scale? At the limiting scale is a closed chain of single atoms, used here to investigate the limits of stability of such folded ring structures via full atomistic molecular dynamics. Carbyne is a one-dimensional carbon allotrope composed of sp-hybridized carbon atoms. Here, we explore the stability of idealized carbyne loops as a function of chain length, curvature, and temperature, and delineate an effective phase diagram between folded and unfolded states. We find that while overall curvature is reduced, in addition to torsional and self-adhesive energy barriers, a local increase in curvature results in the largest impedance to unfolding. PMID:24252156

  16. Compact, closed-loop controlled waste incinerator

    SciTech Connect

    Schadow, K.C.; Seeker, W.R.

    1999-07-01

    Technologies for solid and liquid waste destruction in compact incinerators are being developed in collaboration between industry, universities, and a Government laboratory. This paper reviews progress on one technology, namely active combustion control to achieve efficient and controlled afterburning of air-starved reaction products. This technology which uses synchronized waste gas injection into acoustically stabilized air vortices was transitioned to a simplified afterburner design and practical operational conditions. The full-scale, simplified afterburner, which achieved CO and NO{sub x} emissions of about 30 ppm with a residence time of less than 50 msec, was integrated with a commercially available marine incinerator to increase throughput and reduce emissions. Closed-loop active control with diode laser sensors and novel control strategies was demonstrated on a sub-scale afterburner.

  17. Geothermal Loop Experimental Facility. Final report

    SciTech Connect

    Not Available

    1980-04-01

    Research at the Geothermal Loop Experimental Facility was successfully concluded in September 1979. In 13,000 hours of operation over a three and one half year period, the nominal 10 megawatt electrical equivalent GLEF provided the opportunity to identify problems in working with highly saline geothermal fluids and to develop solutions that could be applied to a commercial geothermal power plant producing electricity. A seven and one half year period beginning in April 1972, with early well flow testing and ending in September 1979, with the completion of extensive facility and reservoir operations is covered. During this period, the facility was designed, constructed and operated in several configurations. A comprehensive reference document, addressing or referencing documentation of all the key areas investigated is presented.

  18. Simple device for treating prolapsing loop colostomy.

    PubMed

    Hsieh, Ming-Yu; Liu, Chinsu; Ho, Shin-Huei; Wung, Shin-Huev; Chin, Taiwai; Wei, Choufu

    2006-03-01

    Stoma prolapse is a common complication of intestinal stoma. Although various surgical methods yield satisfactory results, nonsurgical treatment may be better for a temporary stoma. We report a case of a patient with a distal limb prolapse of a right transverse colostomy who received nonsurgical treatment with satisfactory results. For the treatment of a temporary transverse loop colostomy with distal limb prolapse, we designed a simple device consisting of a pediatric plastic medicine cup, which was rolled into a towel to shape the bottom of the cup into a compressor. The towel was put on the stoma outside of the colostomy bag with the compressor above the prolapsing limb of the colostomy. An abdominal binder was applied to fix the towel. PMID:16599021

  19. Open-loop heat-recovery dryer

    SciTech Connect

    TeGrotenhuis, Ward Evan

    2013-11-05

    A drying apparatus is disclosed that includes a drum and an open-loop airflow pathway originating at an ambient air inlet, passing through the drum, and terminating at an exhaust outlet. A passive heat exchanger is included for passively transferring heat from air flowing from the drum toward the exhaust outlet to air flowing from the ambient air inlet toward the drum. A heat pump is also included for actively transferring heat from air flowing from the passive heat exchanger toward the exhaust outlet to air flowing from the passive heat exchanger toward the drum. A heating element is also included for further heating air flowing from the heat pump toward the drum.

  20. Loop quantization of Schwarzschild interior revisited

    NASA Astrophysics Data System (ADS)

    Singh, Parampreet; Corichi, Alejandro

    2016-03-01

    Several studies of different inequivalent loop quantizations have shown, that there exists no fully satisfactory quantum theory for the Schwarzschild interior. Existing quantizations fail either on dependence on the fiducial structure or on the lack of the classical limit. Here we put forward a novel viewpoint to construct the quantum theory that overcomes all of the known problems of the existing quantizations. It is shown that the quantum gravitational constraint is well defined past the singularity and that its effective dynamics possesses a bounce into an expanding regime. The classical singularity is avoided, and a semiclassical spacetime satisfying vacuum Einstein's equations is recovered on the ``other side'' of the bounce. We argue that such metric represents the interior region of a white-hole spacetime, but for which the corresponding ``white-hole mass'' differs from the original black hole mass. We compare the differences in physical implications with other quantizations.

  1. Loop Group Parakeet Virtual Cable Concept Demonstrator

    NASA Astrophysics Data System (ADS)

    Dowsett, T.; McNeill, T. C.; Reynolds, A. B.; Blair, W. D.

    2002-07-01

    The Parakeet Virtual Cable (PVC) concept demonstrator uses the Ethernet Local Area Network (LAN) laid for the Battle Command Support System (BCSS) to connect the Parakeet DVT(DA) (voice terminal) to the Parakeet multiplexer. This currently requires pairs of PVC interface units to be installed for each DVT(DA) . To reduce the cost of a PVC installation, the concept of a Loop Group Parakeet Virtual Cable (LGPVC) was proposed. This device was designed to replace the up to 30 PVC boxes and the multiplexer at the multiplexer side of a PVC installation. While the demonstrator is largely complete, testing has revealed an incomplete understanding of how to emulate the proprietary handshaking occurring between the circuit switch and the multiplexer. The LGPVC concept cannot yet be demonstrated.

  2. Pulsed phase locked loop strain monitor

    NASA Technical Reports Server (NTRS)

    Froggatt, Mark E. (Inventor)

    1995-01-01

    A pulse phase locked loop system according to the present invention is described. A frequency generator such as a voltage controlled oscillator (VCO) generates an output signal and a reference signal having a frequency equal to that of the output signal. A transmitting gate gates the output frequency signal and this gated signal drives a transmitting transducer which transmits an acoustic wave through a material. A sample/hold samples a signal indicative of the transmitted wave which is received by a receiving transducer. Divide-by-n counters control these gating and sampling functions in response to the reference signal of the frequency generator. Specifically, the output signal is gated at a rate of F/h, wherein F is the frequency of the output signal and h is an integer; and the received signal is sampled at a delay of F/n wherein n is an integer.

  3. An excitatory GABA loop operating in vivo

    PubMed Central

    Astorga, Guadalupe; Bao, Jin; Marty, Alain; Augustine, George J.; Franconville, Romain; Jalil, Abdelali; Bradley, Jonathan; Llano, Isabel

    2015-01-01

    While it has been proposed that the conventional inhibitory neurotransmitter GABA can be excitatory in the mammalian brain, much remains to be learned concerning the circumstances and the cellular mechanisms governing potential excitatory GABA action. Using a combination of optogenetics and two-photon calcium imaging in vivo, we find that activation of chloride-permeable GABAA receptors in parallel fibers (PFs) of the cerebellar molecular layer of adult mice causes parallel fiber excitation. Stimulation of PFs at submaximal stimulus intensities leads to GABA release from molecular layer interneurons (MLIs), thus creating a positive feedback loop that enhances excitation near the center of an activated PF bundle. Our results imply that elevated chloride concentration can occur in specific intracellular compartments of mature mammalian neurons and suggest an excitatory role for GABAA receptors in the cerebellar cortex of adult mice. PMID:26236197

  4. Closed Loop Requirements and Analysis Management

    NASA Technical Reports Server (NTRS)

    Lamoreaux, Michael; Verhoef, Brett

    2015-01-01

    Effective systems engineering involves the use of analysis in the derivation of requirements and verification of designs against those requirements. The initial development of requirements often depends on analysis for the technical definition of specific aspects of a product. Following the allocation of system-level requirements to a product's components, the closure of those requirements often involves analytical approaches to verify that the requirement criteria have been satisfied. Meanwhile, changes that occur in between these two processes need to be managed in order to achieve a closed-loop requirement derivation/verification process. Herein are presented concepts for employing emerging Team center capabilities to jointly manage requirements and analysis data such that analytical techniques are utilized to effectively derive and allocate requirements, analyses are consulted and updated during the change evaluation processes, and analyses are leveraged during the design verification process. Recommendations on concept validation case studies are also discussed.

  5. Experimental studies on coaxial vortex loops

    NASA Astrophysics Data System (ADS)

    Mariani, R.; Kontis, K.

    2010-12-01

    An experimental study has been conducted on the formation and propagation of coaxial vortex loops using a shock tube facility. The study aimed at evaluating the flow characteristics of pairs of corotating vortex rings that generate the leapfrogging phenomenon. The driver and driven gas of the shock tube were air. Three driver pressures were used (4, 8, and 12 bars) with the driven gas being at ambient conditions. The Mach numbers of the shock wave generated inside the shock tube were 1.34, 1.54, and 1.66, respectively. The sudden expansion present at the diaphragm location effectively decreased the Mach number value of the traveling shock wave. Results showed that a pair of vortex rings staggered with respect to time and with the same direction rotation lead to leapfrogging. Results also indicated that the number of leapfrogging occurrences is related to the Reynolds number of the vortex ring pairs with a decrease in leapfrogs at higher Reynolds numbers.

  6. Open loop model for WDM links

    NASA Astrophysics Data System (ADS)

    D, Meena; Francis, Fredy; T, Sarath K.; E, Dipin; Srinivas, T.; K, Jayasree V.

    2014-10-01

    Wavelength Division Multiplexing (WDM) techniques overfibrelinks helps to exploit the high bandwidth capacity of single mode fibres. A typical WDM link consisting of laser source, multiplexer/demultiplexer, amplifier and detectoris considered for obtaining the open loop gain model of the link. The methodology used here is to obtain individual component models using mathematical and different curve fitting techniques. These individual models are then combined to obtain the WDM link model. The objective is to deduce a single variable model for the WDM link in terms of input current to system. Thus it provides a black box solution for a link. The Root Mean Square Error (RMSE) associated with each of the approximated models is given for comparison. This will help the designer to select the suitable WDM link model during a complex link design.

  7. Closed-Loop Life Support Systems

    NASA Technical Reports Server (NTRS)

    Fisher, John W.

    2003-01-01

    Contents include the following: 1. Advanced life support requirements document-high level: (a) high level requirements and standards, (b) advanced life support requirements documents-air, food, water. 2. Example technologies that satisfy requrements: air system-carbon dioxide removal. 3. Air-sabatter. 4. International Space Station water treatment subsystem.5. Direct osmotic concentrator. 6. Mass, volume and power estimates.

  8. Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 2: Data

    NASA Technical Reports Server (NTRS)

    Waszak, M. R.; Schmidt, D. K.

    1985-01-01

    Two analysis methods are applied to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop modal analysis technique. This method considers the effect of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Both analyses indicated that dynamic aeroelastic effects caused a degradation in vehicle tracking performance, based on the evaluation of some simulation results. Volume 2 consists of the presentation of the state variable models of the flexible aircraft configurations used in the analysis applications mode shape plots for the structural modes, numerical results from the modal analysis frequency response plots from the pilot in the loop analysis and a listing of the modal analysis computer program.

  9. Design of Accumulators and Liquid/Gas Charging of Single Phase Mechanically Pumped Fluid Loop Heat Rejection Systems

    NASA Technical Reports Server (NTRS)

    Bhandari, Pradeep; Dudik, Brenda; Birur, Gajanana; Karlmann, Paul; Bame, David; Mastropietro, A. J.

    2012-01-01

    For single phase mechanically pumped fluid loops used for thermal control of spacecraft, a gas charged accumulator is typically used to modulate pressures within the loop. This is needed to accommodate changes in the working fluid volume due to changes in the operating temperatures as the spacecraft encounters varying thermal environments during its mission. Overall, the three key requirements on the accumulator to maintain an appropriate pressure range throughout the mission are: accommodation of the volume change of the fluid due to temperature changes, avoidance of pump cavitation and prevention of boiling in the liquid. The sizing and design of such an accumulator requires very careful and accurate accounting of temperature distribution within each element of the working fluid for the entire range of conditions expected, accurate knowledge of volume of each fluid element, assessment of corresponding pressures needed to avoid boiling in the liquid, as well as the pressures needed to avoid cavitation in the pump. The appropriate liquid and accumulator strokes required to accommodate the liquid volume change, as well as the appropriate gas volumes, require proper sizing to ensure that the correct pressure range is maintained during the mission. Additionally, a very careful assessment of the process for charging both the gas side and the liquid side of the accumulator is required to properly position the bellows and pressurize the system to a level commensurate with requirements. To achieve the accurate sizing of the accumulator and the charging of the system, sophisticated EXCEL based spreadsheets were developed to rapidly come up with an accumulator design and the corresponding charging parameters. These spreadsheets have proven to be computationally fast and accurate tools for this purpose. This paper will describe the entire process of designing and charging the system, using a case study of the Mars Science Laboratory (MSL) fluid loops, which is en route to

  10. ACSYNT inner loop flight control design study

    NASA Technical Reports Server (NTRS)

    Bortins, Richard; Sorensen, John A.

    1993-01-01

    The NASA Ames Research Center developed the Aircraft Synthesis (ACSYNT) computer program to synthesize conceptual future aircraft designs and to evaluate critical performance metrics early in the design process before significant resources are committed and cost decisions made. ACSYNT uses steady-state performance metrics, such as aircraft range, payload, and fuel consumption, and static performance metrics, such as the control authority required for the takeoff rotation and for landing with an engine out, to evaluate conceptual aircraft designs. It can also optimize designs with respect to selected criteria and constraints. Many modern aircraft have stability provided by the flight control system rather than by the airframe. This may allow the aircraft designer to increase combat agility, or decrease trim drag, for increased range and payload. This strategy requires concurrent design of the airframe and the flight control system, making trade-offs of performance and dynamics during the earliest stages of design. ACSYNT presently lacks means to implement flight control system designs but research is being done to add methods for predicting rotational degrees of freedom and control effector performance. A software module to compute and analyze the dynamics of the aircraft and to compute feedback gains and analyze closed loop dynamics is required. The data gained from these analyses can then be fed back to the aircraft design process so that the effects of the flight control system and the airframe on aircraft performance can be included as design metrics. This report presents results of a feasibility study and the initial design work to add an inner loop flight control system (ILFCS) design capability to the stability and control module in ACSYNT. The overall objective is to provide a capability for concurrent design of the aircraft and its flight control system, and enable concept designers to improve performance by exploiting the interrelationships between

  11. An integrated tool for loop calculations: AITALC

    NASA Astrophysics Data System (ADS)

    Lorca, Alejandro; Riemann, Tord

    2006-01-01

    AITALC, a new tool for automating loop calculations in high energy physics, is described. The package creates Fortran code for two-fermion scattering processes automatically, starting from the generation and analysis of the Feynman graphs. We describe the modules of the tool, the intercommunication between them and illustrate its use with three examples. Program summaryTitle of the program:AITALC version 1.2.1 (9 August 2005) Catalogue identifier:ADWO Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWO Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Computer:PC i386 Operating system:GNU/ LINUX, tested on different distributions SuSE 8.2 to 9.3, Red Hat 7.2, Debian 3.0, Ubuntu 5.04. Also on SOLARIS Programming language used:GNU MAKE, DIANA, FORM, FORTRAN77 Additional programs/libraries used:DIANA 2.35 ( QGRAF 2.0), FORM 3.1, LOOPTOOLS 2.1 ( FF) Memory required to execute with typical data:Up to about 10 MB No. of processors used:1 No. of lines in distributed program, including test data, etc.:40 926 No. of bytes in distributed program, including test data, etc.:371 424 Distribution format:tar gzip file High-speed storage required:from 1.5 to 30 MB, depending on modules present and unfolding of examples Nature of the physical problem:Calculation of differential cross sections for ee annihilation in one-loop approximation. Method of solution:Generation and perturbative analysis of Feynman diagrams with later evaluation of matrix elements and form factors. Restriction of the complexity of the problem:The limit of application is, for the moment, the 2→2 particle reactions in the electro-weak standard model. Typical running time:Few minutes, being highly depending on the complexity of the process and the FORTRAN compiler.

  12. Overview of Loop Heat Pipe Operation

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    1999-01-01

    Loop heat pipes (LHP's) are two-phase heat transfer devices that utilize the evaporation and condensation of a working fluid to transfer heat, and the capillary forces developed in the porous wicks to circulate the fluid. The LHP was first developed in the former Soviet Union in the early 1980s, about the same time that the capillary pumped loop (CPL) was developed in the United States. The LHP is known for its high pumping capability and robust operation mainly due to the use of fine-pored metal wicks and an integral evaporator/hydro-accumulator design. The LHP technology is rapidly gaining acceptance in aerospace community. It is the baseline design for thermal control of several spacecraft, including NASA's GLAS and Chemistry, ESA's ATLID, CNES' STENTOR, RKA's OBZOR, and several commercial satellites. Numerous LHP papers have been published since the mid-1980's. Most papers presented test results and discussions on certain specific aspects of the LHP operation. LHP's and CPL's show many similarities in their operating principles and performance characteristics. However, they also display significant differences in many aspects of their operation. Some of the LHP behaviors may seem strange or mysterious, even to experienced CPL practitioners. The main purpose of this paper is to present a systematic description of the operating principles and thermal-hydraulic behaviors of LHP'S. LHP operating principles will be given first, followed by a description of the thermal-hydraulics involved in LHP operation. Operating characteristics and important parameters affecting the LHP operation will then be described in detail. Peculiar behaviors of the LHP, including temperature hysteresis and temperature overshoot during start-up, will be explained. For simplicity, most discussions will focus upon LHP's with a single evaporator and a single condenser, but devices with multiple evaporators and condensers will also be discussed. Similarities and differences between LHP's and

  13. Constant cross section of loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Peter, H.; Bingert, S.

    2012-12-01

    Context. The corona of the Sun is dominated by emission from loop-like structures. When observed in X-ray or extreme ultraviolet emission, these million K hot coronal loops show a more or less constant cross section. Aims: In this study we show how the interplay of heating, radiative cooling, and heat conduction in an expanding magnetic structure can explain the observed constant cross section. Methods: We employ a three-dimensional magnetohydrodynamics (3D MHD) model of the corona. The heating of the coronal plasma is the result of braiding of the magnetic field lines through footpoint motions and subsequent dissipation of the induced currents. From the model we synthesize the coronal emission, which is directly comparable to observations from, e.g., the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO). Results: We find that the synthesized observation of a coronal loop seen in the 3D data cube does match actually observed loops in count rate and that the cross section is roughly constant, as observed. The magnetic field in the loop is expanding and the plasma density is concentrated in this expanding loop; however, the temperature is not constant perpendicular to the plasma loop. The higher temperature in the upper outer parts of the loop is so high that this part of the loop is outside the contribution function of the respective emission line(s). In effect, the upper part of the plasma loop is not bright and thus the loop actually seen in coronal emission appears to have a constant width. Conclusions: From this we can conclude that the underlying field-line-braiding heating mechanism provides the proper spatial and temporal distribution of the energy input into the corona - at least on the observable scales. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  14. The ejector-loop fermenter: Description and performance of the apparatus.

    PubMed

    Moresi, M; Bartolo Gianturco, G; Sebastiani, E

    1983-12-01

    A novel fermentation unit, the ejector-loop fermenter (ELF), consisting of an outer-loop tower fermenter, a centrifugal pump, a plate-heat exchanger, and a gas-liquid ejector, was designed and constructed. Aeration was achieved by continuously recirculating the fermentation medium through two different nozzle devices instead of using the traditional expensive air compressor. By carrying out a whey fermentation with Kluyveromyces fragilis as the test organism, either in the ELF or in conventional stirred fermenter, it was possible to confirm that the high sheat streses and mixing shock occurring in the ejector nozzle and diffuser sections did not affect microbial growth. Within the range of experimental power consumption per unit volume (-0.1-5 kW/m(3)), the oxygen transfer capability of the ELF per unit power input was found to vary from 1 to 2.5 kg O(2) kW(-1)h(-1). Moreover, it is shown that there is suficient room for improvement in the performance of the ELF unit by care fully designing the aeration device. In fact, at constant volumetric oxygen transfer coefficient, the power consumpotion per unit volume in a 4-mm nozzle was found to be about 40% less than that in a 6-mm nozzle. PMID:18548625

  15. Utilizing the eigenvectors of freeway loop data spatiotemporal schematic for real time crash prediction.

    PubMed

    Fang, Shou'en; Xie, Wenjing; Wang, Junhua; Ragland, David R

    2016-09-01

    The concept of crash precursor identification is gaining more practicality due to the recent advancements in Advanced Transportation Management and Information Systems. Investigating the shortcomings of the existing models, this paper proposes a new method to model the real time crash likelihood based on loop data through schematic eigenvectors. Firstly, traffic volume, occupancy and density spatiotemporal schematics in certain duration before an accident occurrence were constructed to describe the traffic flow status. Secondly, eigenvectors and eigenvalues of the spatiotemporal schematics were extracted to represent traffic volume, occupancy and density situation before the crash occurrence. Thirdly, by setting the vectors in crash time as case and those at crash free time as control, a logistic model is constructed to identify the crash precursors. Results show that both the eigenvectors and eigenvalues can significantly impact the accident likelihood compared to the previous study, the proposed model has the advantage of avoiding multicollinearity, better reflection of the overall traffic flow status before the crash, and improving missing data problem of loop detectors. PMID:27258946

  16. Mock circulation loop to investigate hemolysis in a pulsatile total artificial heart.

    PubMed

    Gräf, Felix; Finocchiaro, Thomas; Laumen, Marco; Mager, Ilona; Steinseifer, Ulrich

    2015-05-01

    Hemocompatibility of blood pumps is a crucial parameter that has to be ensured prior to in vivo testing. In contrast to rotary blood pumps, a standard for testing a pulsatile total artificial heart (TAH) has not yet been established. Therefore, a new mock circulation loop was designed to investigate hemolysis in the left ventricle of the ReinHeart TAH. Its main features are a high hemocompatibility, physiological conditions, a low priming volume, and the conduction of blood through a closed tubing system. The mock circulation loop consists of a noninvasive pressure chamber, an aortic compliance chamber, and an atrium directly connected to the ventricle. As a control pump, the clinically approved Medos-HIA ventricular assist device (VAD) was used. The pumps were operated at 120 beats per minute with an aortic pressure of 120 to 80 mm Hg and a mean atrial pressure of 10 mm Hg, generating an output flow of about 5 L/min. Heparinized porcine blood was used. A series of six identical tests were performed. A test method was established that is comparable to ASTM F 1841, which is standard practice for the assessment of hemolysis in continuous-flow blood pumps. The average normalized index of hemolysis (NIH) values of the VAD and the ReinHeart TAH were 0.018 g/100 L and 0.03 g/100 L, respectively. The standard deviation of the NIH was 0.0033 for the VAD and 0.0034 for the TAH. Furthermore, a single test with a BPX-80 Bio-Pump was performed to verify that the hemolysis induced by the mock circulation loop was negligible. The performed tests showed a good reproducibility and statistical significance. The mock circulation loop and test protocol developed in this study are valid methods to investigate the hemolysis induced by a pulsatile blood pump. PMID:25586541

  17. Automated Droplet Manipulation Using Closed-Loop Axisymmetric Drop Shape Analysis.

    PubMed

    Yu, Kyle; Yang, Jinlong; Zuo, Yi Y

    2016-05-17

    Droplet manipulation plays an important role in a wide range of scientific and industrial applications, such as synthesis of thin-film materials, control of interfacial reactions, and operation of digital microfluidics. Compared to micron-sized droplets, which are commonly considered as spherical beads, millimeter-sized droplets are generally deformable by gravity, thus introducing nonlinearity into control of droplet properties. Such a nonlinear drop shape effect is especially crucial for droplet manipulation, even for small droplets, at the presence of surfactants. In this paper, we have developed a novel closed-loop axisymmetric drop shape analysis (ADSA), integrated into a constrained drop surfactometer (CDS), for manipulating millimeter-sized droplets. The closed-loop ADSA generalizes applications of the traditional drop shape analysis from a surface tension measurement methodology to a sophisticated tool for manipulating droplets in real time. We have demonstrated the feasibility and advantages of the closed-loop ADSA in three applications, including control of drop volume by automatically compensating natural evaporation, precise control of surface area variations for high-fidelity biophysical simulations of natural pulmonary surfactant, and steady control of surface pressure for in situ Langmuir-Blodgett transfer from droplets. All these applications have demonstrated the accuracy, versatility, applicability, and automation of this new ADSA-based droplet manipulation technique. Combining with CDS, the closed-loop ADSA holds great promise for advancing droplet manipulation in a variety of material and surface science applications, such as thin-film fabrication, self-assembly, and biophysical study of pulmonary surfactant. PMID:27132978

  18. Some finite terms from ladder diagrams in three and four loop maximal supergravity

    NASA Astrophysics Data System (ADS)

    Basu, Anirban

    2015-10-01

    We consider the finite part of the leading local interactions in the low energy expansion of the four graviton amplitude from the ladder skeleton diagrams in maximal supergravity on T 2, at three and four loops. At three loops, we express the {D}8{{R}}4 and {D}10{{R}}4 amplitudes as integrals over the moduli space of an underlying auxiliary geometry. These amplitudes are evaluated exactly for special values of the the moduli of the auxiliary geometry, where the integrand simplifies. We also perform a similar analysis for the {D}8{{R}}4 amplitude at four loops that arise from the ladder skeleton diagrams for a special value of a parameter in the moduli space of the auxiliary geometry. While the dependence of the amplitudes on the volume of the T 2 is very simple, the dependence on the complex structure of the T 2 is quite intricate. In some of the cases, the amplitude consists of terms each of which factorizes into a product of two {SL}(2,{{Z}}) invariant modular forms. While one of the factors is a non-holomorphic Eisenstein series, the other factor splits into a sum of modular forms each of which satisfies a Poisson equation on moduli space with source terms that are bilinear in the Eisenstein series. This leads to several possible perturbative contributions unto genus 5 in type II string theory on S1. Unlike the one and two loop supergravity analysis, these amplitudes also receive non-perturbative contributions from bound states of three D-(anti)instantons in the IIB theory.

  19. Bovine embryo sex determination by multiplex loop-mediated isothermal amplification.

    PubMed

    Khamlor, Trisadee; Pongpiachan, Petai; Parnpai, Rangsun; Punyawai, Kanchana; Sangsritavong, Siwat; Chokesajjawatee, Nipa

    2015-03-15

    In cattle, the ability to determine the sex of embryos before embryo transfer is beneficial for increasing the number of animals with the desired sex. This study therefore developed a new modification of loop-mediated isothermal amplification in a multiplex format (multiplex LAMP) for highly efficient bovine embryo sexing. Two chromosomal regions, one specific for males (Y chromosome, S4 region) and the other common to both males and females (1.715 satellite DNA), were amplified in the same reaction tube. Each target was amplified by specifically designed inner primers, outer primers, and loop primers, where one of the S4 loop primers was labeled with the fluorescent dye 6-carboxyl-X-rhodamine (emitting a red color), whereas both satellite loop primers were labeled with the fluorescent dye fluorescein isothiocyanate (emitting a green color). After amplification at 63 °C for 1 hour, the amplified products were precipitated by a small volume of cationic polymer predispensed inside the reaction tube cap. Green precipitate indicated the presence of only control DNA without the Y chromosome, whereas orange precipitate indicated the presence of both target DNAs, enabling interpretation as female and male, respectively. Accuracy of the multiplex LAMP assay was evaluated using 46 bovine embryos with known sex (25 male and 21 female) generated by somatic cell nuclear transfer and confirmed by multiplex polymerase chain reaction. The multiplex LAMP showed 100% accuracy in identifying the actual sex of the embryos and provides a fast, simple, and cost-effective tool for bovine embryo sexing. PMID:25542460

  20. Blood flow dynamics of one cardiac cycle and relationship to mechanotransduction and trabeculation during heart looping

    PubMed Central

    Garita, Barbara; Jenkins, Michael W.; Han, Mingda; Zhou, Chao; VanAuker, Michael; Rollins, Andrew M.; Watanabe, Michiko; Fujimoto, J. G.

    2011-01-01

    Analyses of form-function relationships during heart looping are directly related to technological advances. Recent advances in four-dimensional optical coherence tomography (OCT) permit observations of cardiac dynamics at high-speed acquisition rates and high resolution. Real-time observation of the avian stage 13 looping heart reveals that interactions between the endocardial and myocardial compartments are more complex than previously depicted. Here we applied four-dimensional OCT to elucidate the relationships of the endocardium, myocardium, and cardiac jelly compartments in a single cardiac cycle during looping. Six cardiac levels along the longitudinal heart tube were each analyzed at 15 time points from diastole to systole. Using image analyses, the organization of mechanotransducing molecules, fibronectin, tenascin C, α-tubulin, and nonmuscle myosin II was correlated with specific cardiac regions defined by OCT data. Optical coherence microscopy helped to visualize details of cardiac architectural development in the embryonic mouse heart. Throughout the cardiac cycle, the endocardium was consistently oriented between the midline of the ventral floor of the foregut and the outer curvature of the myocardial wall, with multiple endocardial folds allowing high-volume capacities during filling. The cardiac area fractional shortening is much higher than previously published. The in vivo profile captured by OCT revealed an interaction of the looping heart with the extra-embryonic splanchnopleural membrane providing outside-in information. In summary, the combined dynamic and imaging data show the developing structural capacity to accommodate increasing flow and the mechanotransducing networks that organize to effectively facilitate formation of the trabeculated four-chambered heart. PMID:21239637