SKEW QUADRUPOLE FOCUSING LATTICES AND APPLICATIONS.
PARKER,B.
2001-06-18
In this paper we revisit using skew quadrupole fields in place of traditional normal upright quadrupole fields to make beam focusing structures. We illustrate by example skew lattice decoupling, dispersion suppression and chromatic correction using the neutrino factory Study-II muon storage ring design. Ongoing BNL investigation of flat coil magnet structures that allow building a very compact muon storage ring arc and other flat coil configurations that might bring significant magnet cost reduction to a VLHC motivate our study of skew focusing.
Correcting Quadrupole Roll in Magnetic Lenses with Skew Quadrupoles
Walstrom, Peter Lowell
2014-11-10
Quadrupole rolls (i.e. rotation around the magnet axis) are known to be a significant source of image blurring in magnetic quadrupole lenses. These rolls may be caused by errors in mechanical mounting of quadrupoles, by uneven radiation-induced demagnetization of permanent-magnet quadrupoles, etc. Here a four-quadrupole ×10 lens with so-called ”Russian” or A -B B-A symmetry is used as a model problem. Existing SLAC 1/2 in. bore high-gradient quadrupoles are used in the design. The dominant quadrupole roll effect is changes in the first-order part of the transfer map (the R matrix) from the object to the image plane (Note effects on the R matrix can be of first order in rotation angle for some R-matrix elements and second order in rotation angle for other elements, as shown below). It is possible to correct roll-induced image blur by mechanically adjusting the roll angle of one or more of the quadrupoles. Usually, rotation of one quadrupole is sufficient to correct most of the combined effect of rolls in all four quadrupoles. There are drawbacks to this approach, however, since mechanical roll correction requires multiple entries into experimental area to make the adjustments, which are made according to their effect on images. An alternative is to use a single electromagnetic skew quadrupole corrector placed either between two of the quadrupoles or after the fourth quadrupole (so-called “non-local” correction). The basic feasibility of skew quadrupole correction of quadrupole roll effects is demonstrated here. Rolls of the third lens quadrupole of up to about 1 milliradian can be corrected with a 15 cm long skew quadrupole with a gradient of up to 1 T/m. Since the effect of rolls of the remaining three lens quadrupoles are lower, a weaker skew quadrupole can be used to correct them. Non-local correction of quadrupole roll effects by skew quadrupoles is shown to be about one-half as effective as local correction (i.e. rotating individual quadrupoles to zero
PRINCIPLE OF SKEW QUADRUPOLE MODULATION TO MEASURE BETATRON COUPLING.
LUO.Y.PILAT,F.ROSER,T.ET AL.
2004-07-05
The measurement of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of different skew quadrupole families the two eigentunes are precisely measured with the phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation directions are determined. The residual linear coupling could be corrected according to the measurement. An analytical solution for skew quadrupole modulation based on Hamiltonian perturbation approximation is given, and simulation code using smooth accelerator model is also developed. Some issues concerning the practical applications of this technique are discussed.
OPERATIONAL MEASUREMENT OF COUPLING BY SKEW QUADRUPOLE MODULATION.
LUO.Y.CAMERON,P.LEE,R.ET AL.
2004-07-05
The measurement and correction of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of the skew quadrupole families the two eigentune modulations are precisely measured with a high resolution phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation direction are determined. The residual linear coupling could be corrected according the measurement. We report the results from the dedicated beam studies carried on at RHIC injection, store and on the ramp. A capability of measuring coupling on the ramp opens possibility of continuous coupling corrections during acceleration.
SKEW QUADRUPOLES IN RHIC DIPOLE MAGNETS AT HIGH FIELDS.
JAIN, A.; GUPTA, P.; THOMPSON, P.; WANDERER, P.
1995-06-11
In the RHIC arc dipoles, the center of the cold mass lies above the center of the cryostat. At the maximum design field, the magnetic flux lines leak through the yoke to the asymmetrically located cryostat, which provides an additional return path. This introduces a systematic top-bottom asymmetry leading to a skew quadrupole term at high fields. A similar asymmetry is also created by any difference in weights of the upper and the lower yoke halves. Data from measurements of several RHIC dipoles are presented to study this effect. In the current production series of the RDIC dipoles, an attempt is made to compensate the effect of the cryostat by an asymmetry in the iron yoke. Seven dipoles with this type of yoke have been cold tested, and show a reduced saturation in the skew quadrupole term, as expected.
MEASURING LOCAL GRADIENT AND SKEW QUADRUPOLE ERRORS IN RHIC IRS.
CARDONA,J.; PEGGS,S.; PILAT,R.; PTITSYN,V.
2004-07-05
The measurement of local linear errors at RHIC interaction regions using an ''action and phase'' analysis of difference orbits has already been presented. This paper evaluates the accuracy of this technique using difference orbits that were taken when known gradient errors and skew quadrupole errors were intentionally introduced. It also presents action and phase analysis of simulated orbits when controlled errors are intentionally placed in a RHIC simulation model.
COMPENSATION OF FAST KICKER ROLLS WITH SKEW QUADRUPOLES
Pinayev, I.
2011-03-28
The development of the third generation light sources lead to the implementation of the top-up operation, when injection occurs while users collect data. The beam excursions due to the non-closure of the injection bump can spoil the data and need to be suppressed. In the horizontal plane compensation can be achieved by adjusting timing and kick amplitudes. The rolls of the kicker magnets create non-closure in the vertical plane and usually there is no means for correction. In the paper we describe proposed compensation scheme utilizing two skew quadrupoles placed inside the injection bump. The third generation light sources implement top-up operation firstly introduced at Advanced Photon Source. In this mode the circulating beam current is supported near constant by frequent injection of small charge, while photon beam is delivered for users. The beam perturbations caused by the mismatched injection bump can provide undesired noise in the user data. Usually the injection trigger is distributed to the users end stations so that those affected would be able to blank data acquisition. Nevertheless, as good operational practice such transients should be suppressed as much as possible. In the horizontal plane (which is commonly used for injection) one can adjust individual kicker strength as well as trigger delay while observing motion of the stored beam centroid. In the vertical plane such means are unavailable in the most cases. The possible solutions include dedicated weak vertical kickers and motorized adjustment of the roll angle of the injection kickers. Both abovementioned approaches are expensive and can significantly deteriorate reliability. We suggest two employ two skew quadrupoles (to correct both angle and position) placed inside the injection bump. In this case the beam position itself serves as measure of the kicker strength (assuming that kickers are well matched) and vertical kicks from the skew quadrupoles will be self synchronized with injection bump
Restoring the skew quadrupole moment in the Tevatron dipoles
Harding, D.J.; Bauer, P.C.; Blowers, J.N.; DiMarco, J.; Glass, H.D.; Hanft, R.W.; Carson, J.A.; Robotham, W.F.; Tartaglia, M.A.; Tompkins, J.C.; Velev, G.; /Fermilab
2005-05-01
In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 that will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets. In January 2003 two lines of inquiry converged, leading to the recognition that the severe betatron coupling that was hindering operation of the Tevatron could be explained by a systematic shift on the skew quadrupole field in the dipole magnets of the same size expected from observed mechanical movement of the coils inside the magnet yokes [1]. This paper reports on subsequent magnet studies that were conducted in parallel with additional beam studies and accelerator modeling [2] exploring the feasibility of the eventual remediation effort [3].
Permanent Magnet Skew Quadrupoles for the Low Emittance LER Lattice of PEP-II
Decker, F.-J.; Anderson, S.; Kharakh, D.; Sullivan, M.; /SLAC
2011-07-05
The vertical emittance of the low energy ring (LER) in the PEP-II B-Factory was reduced by using skew quadrupoles consisting of permanent magnet material. The advantages over electric quadrupoles or rotating existing normal quadrupoles are discussed. To assure a high field quality, a Biot-Savart calculation was used to cancel the natural 12-pole component by using different size poles over a few layers. A magnetic measurement confirmed the high quality of the magnets. After installation and adjusting the original electric 12 skew and 16 normal quadrupoles the emittance contribution from the region close to the interaction point, which was the biggest part in the original design, was considerably reduced. To strengthen the vertical behavior of the LER beam, a low emittance lattice was developed. It lowered the original vertical design emittance from 0.54 nm-rad to 0.034 nm-rad. In order to achieve this, additional skew quadrupoles were required to bring the coupling correction out of the arcs and closer to the detector solenoid in the straight (Fig. 1). It is important, together with low vertical dispersion, that the low vertical emittance is not coupled into the horizontal, which is what we get if the coupling correction continues into the arcs. Further details of the lattice work is described in another paper; here we concentrate on the development of the permanent skew (PSK) quadrupole solution. Besides the permanent magnets there are two other possibilities, using electric magnets or rotating normal quadrupoles. Electric magnets would have required much more additional equipment like magnets stands, power supply, and new vacuum chamber sections. Rotating existing quadrupoles was also not feasible since they are mostly mounted together with a bending magnet on the same support girder.
Coil Creep and Skew-Quadrupole Field Components in the Tevatron
Annala, G.; Harding, D.J.; Syphers, M.J.; /Fermilab
2011-07-11
During the start-up of Run II of the Tevatron Collider program, several issues surfaced which were not present, or not seen as detrimental, during Run I. These included the repeated deterioration of the closed orbit requiring orbit smoothing every two weeks or so, the inability to correct the closed orbit to desired positions due to various correctors running at maximum limits, regions of systematically strong vertical dipole corrections, and the identification of very strong coupling between the two transverse degrees-of-freedom. It became apparent that many of the problems being experienced operationally were connected to a deterioration of the main dipole magnet alignment, and remedial actions were undertaken. However, the alignment alone was not enough to explain the corrector strengths required to handle transverse coupling. With one exception, strong coupling had generally not been an issue in the Tevatron during Run I. Based on experience with the Main Ring, the Tevatron was designed with a very strong skew quadrupole circuit to compensate any quadrupole alignment and skew quadrupole field errors that might present themselves. The circuit was composed of 48 correctors placed evenly throughout the arcs, 8 per sector, evenly placed in every other cell. Other smaller circuits were installed but not initially needed or commissioned. These smaller circuits were composed of individual skew quadrupole correctors on either side of the long straight sections. These circuits were tuned by first bringing the horizontal and vertical tunes near each other. The skew quadrupoles were then adjusted to minimize tune split, usually to less than 0.003. Initially, the main skew quad circuit (designated T:SQ) could accomplish this global decoupling with only 4% of its possible current, and the smaller circuits were not required at all. The start-up of Run Ib was complicated by what was later discovered to be a rolled triplet quadrupole magnet in one of the Interaction Regions
Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam
Maschke, Alfred W.
1985-01-01
A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow throughout the assembly.
Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam
Maschke, A.W.
1984-04-16
A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow through the assembly.
Development of Superconducting Focusing Quadrupoles for Heavy Ion Drivers
Martovetsky, N; Manahan, R; Lietzke, A F
2001-09-10
Heavy Ion Fusion (HIF) is exploring a promising path to a practical inertial-confinement fusion reactor. The associated heavy ion driver will require a large number of focusing quadrupole magnets. A concept for a superconducting quadrupole array, using many simple racetrack coils, was developed at LLNL. Two, single-bore quadrupole prototypes of the same design, with distinctly different conductor, were designed, built, and tested. Both prototypes reached their short sample currents with little or no training. Magnet design, and test results, are presented and discussed.
Study of Row Phase Dependent Skew Quadrupole Fields in Apple-II Type EPUs at the ALS
Steier, C.; Marks, S.; Prestemon, Soren; Robin, David; Schlueter, Ross; Wolski, Andrzej
2004-05-07
Since about 5 years, Apple-II type Elliptically Polarizing Undulators (EPU) have been used very successfully at the ALS to generate high brightness photon beams with arbitrary polarization. However, both EPUs installed so far cause significant changes of the vertical beamsize, especially when the row phase is changed to change the polarization of the photons emitted. Detailed measurements indicate this is caused by a row phase dependent skew quadrupole term in the EPUs. Magnetic measurements revealed the same effect for the third EPU to be installed later this year. All measurements to identify and quantify the effect with beam will be presented, as well as some results of magnetic bench measurements and numeric field simulations.
Electrostatic quadrupole array for focusing parallel beams of charged particles
Brodowski, John
1982-11-23
An array of electrostatic quadrupoles, capable of providing strong electrostatic focusing simultaneously on multiple beams, is easily fabricated from a single array element comprising a support rod and multiple electrodes spaced at intervals along the rod. The rods are secured to four terminals which are isolated by only four insulators. This structure requires bias voltage to be supplied to only two terminals and eliminates the need for individual electrode bias and insulators, as well as increases life by eliminating beam plating of insulators.
Superconducting focusing quadrupoles for heavy ion fusion experiments
Sabbi, G.L.; Faltens, A.; Leitner, M.; Lietzke, A.; Seidl, P.; Barnard, J.; Lund, S.; Martovetsky, N.; Gung, C.; Minervini, J.; Radovinsky, A.; Schultz, J.; Meinke, R.
2003-05-01
The Heavy Ion Fusion (HIF) Program is developing superconducting focusing magnets for both near-term experiments and future driver accelerators. In particular, single bore quadrupoles have been fabricated and tested for use in the High Current Experiment (HCX) at Lawrence Berkeley National Laboratory (LBNL). The next steps involve the development of magnets for the planned Integrated Beam Experiment (IBX) and the fabrication of the first prototype multi-beam focusing arrays for fusion driver accelerators. The status of the magnet R&D program is reported, including experimental requirements, design issues and test results.
Design and operation of a laminar-flow electrostatic-quadrupole-focused acceleration column
Maschke, A.W.
1983-06-20
This report deals with the design principles involved in the design of a laminar-flow electrostatic-quadrupole-focused acceleration column. In particular, attention will be paid to making the parameters suitable for incorporation into a DC MEQALAC design.
Kinetic equilibrium of space charge dominated beams in a misaligned quadrupole focusing channel
Goswami, A.; Sing Babu, P.; Pandit, V. S.
2013-07-15
The dynamics of intense beam propagation through the misaligned quadrupole focusing channel has been studied in a self-consistent manner using nonlinear Vlasov-Maxwell equations. The equations of motion of the beam centroid have been developed and found to be independent of any specific beam distribution. A Vlasov equilibrium distribution and beam envelope equations have been obtained, which provide us a theoretical tool to investigate the dynamics of intense beam propagating in a misaligned quadrupole focusing channel. It is shown that the displaced quadrupoles only cause the centroid of the beam to wander off axis. The beam envelope around the centroid obeys the familiar Kapchinskij-Vladimirskij envelope equation that is independent of the centroid motion. However, the rotation of the quadrupole about its optical axis affects the beam envelope and causes an increase in the projected emittances in the two transverse planes due to the inter-plane coupling.
A compact beam focusing and steering element using quadrupoles with independently excited poles
NASA Astrophysics Data System (ADS)
Grime, Geoffrey W.
2013-07-01
Beam steering elements for accelerator beam transport are conventionally and conveniently incorporated into beamlines by fitting magnetic dipole elements around the vacuum tube of the line. Two steerers in each plane (X and Y) together with a quadrupole doublet constitute a module providing full control of the direction, position and focus of the beam. In some installations however, there may be insufficient space on the beamline to mount separate steerer elements. To provide steering capabilities in such a situation we have used a magnetic quadrupole doublet with the coils of each pole independently excited to synthesise the desired combination of quadrupole, horizontal dipole and vertical dipole fields. This paper describes the quadrupole steerer and its multichannel power supply and presents calculated magnetic field distributions together with raytracing simulation of its performance.
Design desiderata for a laminar flow quadrupole-focused acceleration column
Maschke, A.W.
1983-01-01
The Pierce design acceleration column has been widely used to accelerate high current beams. It operates well in the space charge limited condition, and will produce beams with a temperature comparable with that of the source. It is restricted in current density, however, by the Child-Langmuir relation. If the ion source itself is not the limiting constraint, then the achievable current density is limited by the electric field at which sparking occurs. One sees clearly that the achievable current density decreases as one goes to higher voltages. This can be easily overcome by using electrostatic quadrupole focusing in the acceleration column. Now it can be shown that the space charge limited current density in a constant energy quadrupole transport channel is greater than that if one assumes that the electric fields on the quadrupoles can be as high in the ion source extraction electric fields. In practice, this is a conservative assumption. It follows that if the beam can be transported a large distance at the C-L current density limit, it can surely be accelerated as it goes from quadrupole to quadrupole. Hence, the necessity of having a high gradient acceleration column goes away.
NASA Astrophysics Data System (ADS)
Nichols, Kimberley E. L.
Analysis of quadrupole focusing lattices for high-frequency TWT's is presented. This work is motivated by recent work performed at the Naval Research Laboratory (NRL) which demonstrated an advantageous case for strong focusing employing a Halbach quadrupole lattice. Using realistic Permanent Magnet Quadruple (PMQ) field cancellation, the advantage of using PMQ to transport higher current densities than Permanent Periodic Magnet (PPM) lattices disappears, while other advantages for employing quadrupole focusing remain. This dissertation gives a comprehensive analysis of the applicability of PMQ focusing in vacuum electronic devices.
Effects of quadrupole fringe fields in final focus systems for linear colliders
NASA Astrophysics Data System (ADS)
Patecki, Marcin; Tomás, Rogelio
2014-10-01
Quadrupole fringe fields in the final focus system can be a source of aberrations in the interaction point transverse beam sizes. This paper investigates the fringe field impact on the transverse beam size in the ATF2, ILC, and CLIC lattices in the linear and non-linear regimes. The linear effects are studied by replacing the hard-edge quadrupolar field by the more realistic gradient fall-off. To address the nonlinear effects, the fringe fields are represented as high order kicks added to both sides of the hard-edge magnets. It will be shown that the linear fringe fields effects can be easily cured by tuning the quadrupole strengths. On the other hand, mitigation of the nonlinear fringe fields effects is more difficult and requires use of octupole magnets or, alternatively, increasing the value of interaction point horizontal beta function βx*.
NASA Astrophysics Data System (ADS)
Chung, Moses; Qin, Hong; Gilson, Erik P.; Davidson, Ronald C.
2013-08-01
By extending the recently developed generalized Courant-Snyder theory for coupled transverse beam dynamics, we have constructed the Gaussian beam distribution and its projections with arbitrary mode emittance ratios. The new formulation has been applied to a continuously rotating quadrupole focusing channel because the basic properties of this channel are known theoretically and could also be investigated experimentally in a compact setup such as the linear Paul trap configuration. The new formulation retains a remarkably similar mathematical structure to the original Courant-Snyder theory, and thus, provides a powerful theoretical tool to investigate coupled transverse beam dynamics in general and more complex linear focusing channels.
H-mode accelerating structures with permanent-magnet quadrupole beam focusing
NASA Astrophysics Data System (ADS)
Kurennoy, S. S.; Rybarcyk, L. J.; O'Hara, J. F.; Olivas, E. R.; Wangler, T. P.
2012-09-01
We have developed high-efficiency normal-conducting rf accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of interdigital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3D modeling—electromagnetic computations, multiparticle beam-dynamics simulations with high currents, and thermal-stress analysis—for an IH-PMQ accelerator tank are presented. The accelerating-field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Measurements of a cold model of the IH-PMQ tank show a good agreement with the calculations. Examples of cross-bar H-mode structures with PMQ focusing for higher beam velocities are also presented. H-PMQ accelerating structures following a short radio-frequency quadrupole accelerator can be used both in the front end of ion linacs or in stand-alone applications.
NASA Astrophysics Data System (ADS)
Hofmann, Ingo
2013-04-01
Using laser accelerated protons or ions for various applications—for example in particle therapy or short-pulse radiographic diagnostics—requires an effective method of focusing and energy selection. We derive an analytical scaling for the performance of a solenoid compared with a doublet/triplet as function of the energy, which is confirmed by TRACEWIN simulations. Generally speaking, the two approaches are equivalent in focusing capability, if parameters are such that the solenoid length approximately equals its diameter. The scaling also shows that this is usually not the case above a few MeV; consequently, a solenoid needs to be pulsed or superconducting, whereas the quadrupoles can remain conventional. It is also important that the transmission of the triplet is found only 25% lower than that of the equivalent solenoid. Both systems are equally suitable for energy selection based on their chromatic effect as is shown using an initial distribution following the RPA simulation model by Yan et al. [Phys. Rev. Lett. 103, 135001 (2009PRLTAO0031-900710.1103/PhysRevLett.103.135001].
Kuroda, S.; Okugi, T.; Tauchi, T.; Fujisawa, H.; Ichikawa, M.; Iwashita, Y.; Tajima, Y.; Kumada, M.; Spencer, Cherrill M.; /SLAC
2008-01-18
An adjustable permanent magnet quadrupole has been developed for the final focus (FF) in a linear collider. Recent activities include a newly fabricated inner ring to demonstrate the strongest field gradient at a smaller bore diameter of 15mm and a magnetic field measurement system with a new rotating coil. The prospects of the R&D will be discussed.
Kim, C.H.
1987-04-01
This report compares two physics designs of the low energy end of an induction linac-ICF driver: one using electric quadrupole focusing of many parallel beams followed by transverse combining; the other using magnetic quadrupole focusing of fewer beams without beam combining. Because of larger head-to-tail velocity spread and a consequent rapid current amplification in a magnetic focusing channel, the overall accelerator size of the design using magnetic focusing is comparable to that using electric focusing.
Peggs, S.; Dell, G.F.
1994-12-31
The on-momentum description of linear coupling between horizontal and vertical betatron motion is extended to include off-momentum particles, introducing a vector quantity called the ``skew chromaticity``. This vector tends to be long in large superconducting storage rings, where it restricts the available working space in the tune plane, and modifies collective effect stability criteria. Skew chromaticity measurements at the Cornell Electron Storage Ring (CESR) and at the Fermilab Tevatron are reported, as well as tracking results from the Relativistic Heavy Ion Collider (RHIC). The observation of anomalous head-tail beam Iowa new the tune diagonal in the Tevatron are explained in terms of the extended theory, including modified criteria for headtail stability. These results are confirmed in head-tail simulations. Sources of skew chromaticity are investigated.
NASA Astrophysics Data System (ADS)
Apostolos, John; Mouyos, William; Feng, Judy; Chase, Walter
2015-05-01
The need for advanced techniques to detect improvised explosive devices (IED) at stand-off distances greater than ten (10) meters has driven AMI Research and Development (AMI) to develop a solution to detect and identify the threat utilizing a forward looking Synthetic Aperture Radar (SAR) combined with our CW radar technology Nuclear Quadrupole Resonance (NQR) detection system. The novel features include a near-field sub-wavelength focusing antenna, a wide band 300 KHz to 300 MHz rapidly scanning CW radar facilitated by a high Q antenna/tuner, and an advanced processor utilizing Rabi transitions where the nucleus oscillates between states under the time dependent incident electromagnetic field and alternately absorbs energy from the incident field while emitting coherent energy via stimulated emission. AMI's Sub-wavelength Focusing Wide Band Super Lens uses a Near-Field SAR, making detection possible at distances greater than ten (10) meters. This super lens is capable of operating on the near-field and focusing electromagnetic waves to resolutions beyond the diffraction limit. When applied to the case of a vehicle approaching an explosive hazard the methodologies of synthetic aperture radar is fused with the array based super resolution and the NQR data processing detecting the explosive hazard.
Anderson, O A; LoDestro, L L
2009-04-01
The Kapchinskij-Vladimirskij equations are widely used to study the evolution of the beam envelopes in a periodic system of quadrupole focusing cells. In this paper, we analyze the case of a matched beam. Our model is analogous to that used by Courant and Snyder [E.D. Courant and H.S. Snyder, Ann. Phys. 3, 1 (1958)], who obtained a first-order approximate solution for a synchrotron. Here, we treat a linear machine and obtain an exact solution. The model uses a full occupancy, piecewise-constant focusing function and neglects space charge. There are solutions in an infinite number of bands as the focus strength is increased. All these bands are stable. Our explicit results for the phase advance {sigma} and the envelopes a(z) and b(z) are exact for all phase advances except multiples of 180{sup o}, where the behavior is singular. We find that the peak envelope size is minimized for {delta} {approx} 81{sup o}. Actual operation in the higher bands would require very large, very accurate field strengths and would produce significantly larger envelope excursions. If such operation were found to be feasible, there would be interesting applications which we discuss.
An electrostatic quadrupole doublet focusing system for MeV heavy ions in MeV-SIMS
NASA Astrophysics Data System (ADS)
Seki, T.; Shitomoto, S.; Nakagawa, S.; Aoki, T.; Matsuo, J.
2013-11-01
The importance of imaging mass spectrometry (MS) for visualizing the spatial distribution of molecular species in biological tissues and cells is growing. In conventional SIMS with keV-energy ion beams, elastic collisions occur between projectiles and atoms in constituent molecules. The collisions produce fragments, making acquisition of molecular information difficult. In contrast, MeV-energy ion beams excite electrons near the surface and enhance the ionization of high-mass molecules, hence, fragment suppressed SIMS spectrum of ionized molecules can be obtained. This work is a further step on our previous report on the successful development of a MeV secondary ion mass spectrometry (MeV-SIMS) for biological samples. We have developed an electrostatic quadrupole doublet (EQ doublet) focusing system, made of two separate lenses, Q1 and Q2, to focus the MeV heavy ion beam and reduce measurement time. A primary beam of 6 MeV Cu4+ was focused with this EQ doublet. We applied 1120 V to the Q1 lens and 1430 V to the Q2 lens, and the current density increased by a factor of about 60. Using this arrangement, we obtained an MeV-SIMS image of 100 × 100 pixels of cholesterol-OH+ of cerebellum (m/z = 369.3) over a 4 mm × 4 mm field of view, with a pixel size of 40 μm within 5 min, showing that our EQ doublet reduces the measurement time of current imaging by a factor of about 30.
Muon Tracking Studies in a Skew Parametric Resonance Ionization Cooling Channel
Sy, Amy; Afanaciev, Andre; Derbenev, Yaroslav S.; Johnson, Rolland; Morozov, Vasiliy
2015-09-01
Skew Parametric-resonance Ionization Cooling (SPIC) is an extension of the Parametric-resonance Ionization Cooling (PIC) framework that has previously been explored as the final 6D cooling stage of a high-luminosity muon collider. The addition of skew quadrupoles to the PIC magnetic focusing channel induces coupled dynamic behavior of the beam that is radially periodic. The periodicity of the radial motion allows for the avoidance of unwanted resonances in the horizontal and vertical transverse planes, while still providing periodic locations at which ionization cooling components can be implemented. A first practical implementation of the magnetic field components required in the SPIC channel is modeled in MADX. Dynamic features of the coupled correlated optics with and without induced parametric resonance are presented and discussed.
Skew-Quad Parametric-Resonance Ionization Cooling: Theory and Modeling
Afanaciev, Andre; Derbenev, Yaroslav S.; Morozov, Vasiliy; Sy, Amy; Johnson, Rolland P.
2015-09-01
Muon beam ionization cooling is a key component for the next generation of high-luminosity muon colliders. To reach adequately high luminosity without excessively large muon intensities, it was proposed previously to combine ionization cooling with techniques using a parametric resonance (PIC). Practical implementation of PIC proposal is a subject of this report. We show that an addition of skew quadrupoles to a planar PIC channel gives enough flexibility in the design to avoid unwanted resonances, while meeting the requirements of radially-periodic beam focusing at ionization-cooling plates, large dynamic aperture and an oscillating dispersion needed for aberration corrections. Theoretical arguments are corroborated with models and a detailed numerical analysis, providing step-by-step guidance for the design of Skew-quad PIC (SPIC) beamline.
Audenaert, Koenraad M. R.
2014-11-15
In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.
Reproductive skew in the polygynandrous acorn woodpecker.
Haydock, Joseph; Koenig, Walter D
2002-05-14
Reproductive skew models, which focus on the degree to which reproduction is shared equally (low skew) or monopolized by a single individual (high skew) within groups, have been heralded as providing a general unifying framework for understanding the factors determining social evolution. Here, we test the ability of optimal skew, or "transactional," models, which predict the level of skew necessary to promote stable associations of dominants and subordinates, rather than independent breeding, to predict reproductive partitioning in the acorn woodpecker (Melanerpes formicivorus). This species provides a key test case because only a few vertebrates exhibit polygynandry (multiple breeders of both sexes within a group). Contrary to the predictions of the models, joint-nesting females share reproduction more equitably than expected, apparently because egg destruction and the inability of females to defend their eggs from cobreeders eliminate any possibility for one female to control reproduction. For males, however, reproductive skew is high, with the most successful male siring over three times as many young as the next most successful male. Although this result is consistent with optimal skew models, other aspects of male behavior are not; in particular, the reproductively most successful male frequently switches between nests produced by the same set of cobreeders, and we were unable to detect any phenotypic correlate of success. These results are consistent with an alternative null model in which cobreeder males have equal chance of paternity, but paternity of offspring within broods is nonindependent as a consequence of female, rather than male, control.
Startsev, Edward A.; Davidson, Ronald C.
2011-05-15
Identifying regimes for quiescent propagation of intense beams over long distances has been a major challenge in accelerator research. In particular, the development of systematic theoretical approaches that are able to treat self-consistently the applied oscillating force and the nonlinear self-field force of the beam particles simultaneously has been a major challenge of modern beam physics. In this paper, the recently developed Hamiltonian averaging technique [E. A. Startsev, R. C. Davidson, and M. Dorf, Phys. Rev. ST Accel. Beams 13, 064402 (2010)] which incorporates both the applied periodic focusing force and the self-field force of the beam particles, is generalized to the case of time-dependent beam distributions. The new formulation allows not only a determination of quasi-equilibrium solutions of the non-linear Vlasov-Poison system of equations but also a detailed study of their stability properties. The corrections to the well-known ''smooth-focusing'' approximation are derived, and the results are applied to a matched beam with thermal equilibrium distribution function. It is shown that the corrections remain small even for moderate values of the vacuum phase advance {sigma}{sub {upsilon}}. Nonetheless, because the corrections to the average self-field potential are non-axisymmetric, the stability properties of the different beam quasi-equilibria can change significantly.
Robust skew estimation using straight lines in document images
NASA Astrophysics Data System (ADS)
Koo, Hyung Il; Cho, Nam Ik
2016-05-01
A skew-estimation method using straight lines in document images is presented. Unlike conventional approaches exploiting the properties of text, we formulate the skew-estimation problem as an estimation task using straight lines in images and focus on robust and accurate line detection. To be precise, we adopt a block-based edge detector followed by a progressive line detector to take clues from a variety of sources such as text lines, boundaries of figures/tables, vertical/horizontal separators, and boundaries of textblocks. Extensive experiments on the datasets of skewed images and competition results reveal that the proposed method works robustly and yields accurate skew-estimation results.
Generalized Courant-Snyder Theory for Charged-Particle Dynamics in General Focusing Lattices
NASA Astrophysics Data System (ADS)
Qin, Hong; Davidson, Ronald C.; Chung, Moses; Burby, Joshua W.
2013-09-01
The Courant-Snyder (CS) theory for one degree of freedom is generalized to the case of coupled transverse dynamics in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D sympletic rotation. The envelope equation, the transfer matrix, and the CS invariant of the original CS theory all have their counterparts, with remarkably similar expressions, in the generalized theory.
Variable Permanent Magnet Quadrupole
Mihara, T.; Iwashita, Y.; Kumada, M.; Spencer, C.M.; /SLAC
2007-05-23
A permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens in a linear collider. An over 120 T/m strong variable permanent magnet quadrupole is achieved by the introduction of saturated iron and a 'double ring structure'. A fabricated PMQ achieved 24 T integrated gradient with 20 mm bore diameter, 100 mm magnet diameter and 20 cm pole length. The strength of the PMQ is adjustable in 1.4 T steps, due to its 'double ring structure': the PMQ is split into two nested rings; the outer ring is sliced along the beam line into four parts and is rotated to change the strength. This paper describes the variable PMQ from fabrication to recent adjustments.
Skew resisting hydrodynamic seal
Conroy, William T.; Dietle, Lannie L.; Gobeli, Jeffrey D.; Kalsi, Manmohan S.
2001-01-01
A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing material, provides a relatively stiff integral spring effect to minimize pressure-induced shuttling of the seal within the gland, and also maintains interfacial contact pressure within the dynamic sealing interface in an optimum range for efficient hydrodynamic lubrication and environment exclusion. The seal geometry also provides for complete support about the circumference of the seal to receive environmental pressure, as compared the interrupted character of seal support set forth in U.S. Pat. Nos. 5,873,576 and 6,036,192 and provides a hydrodynamic seal which is suitable for use with non-Newtonian lubricants.
Female reproductive synchrony predicts skewed paternity across primates
Nunn, Charles L.; Schülke, Oliver
2008-01-01
Recent studies have uncovered remarkable variation in paternity within primate groups. To date, however, we lack a general understanding of the factors that drive variation in paternity skew among primate groups and across species. Our study focused on hypotheses from reproductive skew theory involving limited control and the use of paternity “concessions” by investigating how paternity covaries with the number of males, female estrous synchrony, and rates of extragroup paternity. In multivariate and phylogenetically controlled analyses of data from 27 studies on 19 species, we found strong support for a limited control skew model, with reproductive skew within groups declining as female reproductive synchrony and the number of males per group increase. Of these 2 variables, female reproductive synchrony explained more of the variation in paternity distributions. To test whether dominant males provide incentives to subordinates to resist matings by extragroup males, that is, whether dominants make concessions of paternity, we derived a novel prediction that skew is lower within groups when threat from outside the group exists. This prediction was not supported as a primary factor underlying patterns of reproductive skew among primate species. However, our approach revealed that if concessions occur in primates, they are most likely when female synchrony is low, as these conditions provide alpha male control of paternity that is assumed by concessions models. Collectively, our analyses demonstrate that aspects of male reproductive competition are the primary drivers of reproductive skew in primates. PMID:19018288
Magnetic Measurement Results of the LCLS Undulator Quadrupoles
Anderson, Scott; Caban, Keith; Nuhn, Heinz-Dieter; Reese, Ed; Wolf, Zachary; /SLAC
2011-08-18
This note details the magnetic measurements and the magnetic center fiducializations that were performed on all of the thirty-six LCLS undulator quadrupoles. Temperature rise, standardization reproducibility, vacuum chamber effects and magnetic center reproducibility measurements are also presented. The Linac Coherent Light Source (LCLS) undulator beam line has 33 girders, each with a LCLS undulator quadrupole which focuses and steers the beam through the beam line. Each quadrupole has main quadrupole coils, as well as separate horizontal and vertical trim coils. Thirty-six quadrupoles, thirty-three installed and three spares were, manufactured for the LCLS undulator system and all were measured to confirm that they met requirement specifications for integrated gradient, harmonics and for magnetic center shifts after current changes. The horizontal and vertical dipole trims of each quadrupole were similarly characterized. Each quadrupole was also fiducialized to its magnetic center. All characterizing measurements on the undulator quads were performed with their mirror plates on and after a standardization of three cycles from -6 to +6 to -6 amps. Since the undulator quadrupoles could be used as a focusing or defocusing magnet depending on their location, all quadrupoles were characterized as focusing and as defocusing quadrupoles. A subset of the undulator quadrupoles were used to verify that the undulator quadrupole design met specifications for temperature rise, standardization reproducibility and magnetic center reproducibility after splitting. The effects of the mirror plates on the undulator quadrupoles were also measured.
Utility functions predict variance and skewness risk preferences in monkeys.
Genest, Wilfried; Stauffer, William R; Schultz, Wolfram
2016-07-26
Utility is the fundamental variable thought to underlie economic choices. In particular, utility functions are believed to reflect preferences toward risk, a key decision variable in many real-life situations. To assess the validity of utility representations, it is therefore important to examine risk preferences. In turn, this approach requires formal definitions of risk. A standard approach is to focus on the variance of reward distributions (variance-risk). In this study, we also examined a form of risk related to the skewness of reward distributions (skewness-risk). Thus, we tested the extent to which empirically derived utility functions predicted preferences for variance-risk and skewness-risk in macaques. The expected utilities calculated for various symmetrical and skewed gambles served to define formally the direction of stochastic dominance between gambles. In direct choices, the animals' preferences followed both second-order (variance) and third-order (skewness) stochastic dominance. Specifically, for gambles with different variance but identical expected values (EVs), the monkeys preferred high-variance gambles at low EVs and low-variance gambles at high EVs; in gambles with different skewness but identical EVs and variances, the animals preferred positively over symmetrical and negatively skewed gambles in a strongly transitive fashion. Thus, the utility functions predicted the animals' preferences for variance-risk and skewness-risk. Using these well-defined forms of risk, this study shows that monkeys' choices conform to the internal reward valuations suggested by their utility functions. This result implies a representation of utility in monkeys that accounts for both variance-risk and skewness-risk preferences. PMID:27402743
Utility functions predict variance and skewness risk preferences in monkeys
Genest, Wilfried; Stauffer, William R.; Schultz, Wolfram
2016-01-01
Utility is the fundamental variable thought to underlie economic choices. In particular, utility functions are believed to reflect preferences toward risk, a key decision variable in many real-life situations. To assess the validity of utility representations, it is therefore important to examine risk preferences. In turn, this approach requires formal definitions of risk. A standard approach is to focus on the variance of reward distributions (variance-risk). In this study, we also examined a form of risk related to the skewness of reward distributions (skewness-risk). Thus, we tested the extent to which empirically derived utility functions predicted preferences for variance-risk and skewness-risk in macaques. The expected utilities calculated for various symmetrical and skewed gambles served to define formally the direction of stochastic dominance between gambles. In direct choices, the animals’ preferences followed both second-order (variance) and third-order (skewness) stochastic dominance. Specifically, for gambles with different variance but identical expected values (EVs), the monkeys preferred high-variance gambles at low EVs and low-variance gambles at high EVs; in gambles with different skewness but identical EVs and variances, the animals preferred positively over symmetrical and negatively skewed gambles in a strongly transitive fashion. Thus, the utility functions predicted the animals’ preferences for variance-risk and skewness-risk. Using these well-defined forms of risk, this study shows that monkeys’ choices conform to the internal reward valuations suggested by their utility functions. This result implies a representation of utility in monkeys that accounts for both variance-risk and skewness-risk preferences. PMID:27402743
Utility functions predict variance and skewness risk preferences in monkeys.
Genest, Wilfried; Stauffer, William R; Schultz, Wolfram
2016-07-26
Utility is the fundamental variable thought to underlie economic choices. In particular, utility functions are believed to reflect preferences toward risk, a key decision variable in many real-life situations. To assess the validity of utility representations, it is therefore important to examine risk preferences. In turn, this approach requires formal definitions of risk. A standard approach is to focus on the variance of reward distributions (variance-risk). In this study, we also examined a form of risk related to the skewness of reward distributions (skewness-risk). Thus, we tested the extent to which empirically derived utility functions predicted preferences for variance-risk and skewness-risk in macaques. The expected utilities calculated for various symmetrical and skewed gambles served to define formally the direction of stochastic dominance between gambles. In direct choices, the animals' preferences followed both second-order (variance) and third-order (skewness) stochastic dominance. Specifically, for gambles with different variance but identical expected values (EVs), the monkeys preferred high-variance gambles at low EVs and low-variance gambles at high EVs; in gambles with different skewness but identical EVs and variances, the animals preferred positively over symmetrical and negatively skewed gambles in a strongly transitive fashion. Thus, the utility functions predicted the animals' preferences for variance-risk and skewness-risk. Using these well-defined forms of risk, this study shows that monkeys' choices conform to the internal reward valuations suggested by their utility functions. This result implies a representation of utility in monkeys that accounts for both variance-risk and skewness-risk preferences.
Detecting skewness from summary information.
Altman, D G; Bland, J M
1996-11-01
Many statistical methods of analysis assume that the data have a normal distribution. When the data do not, they can often be changed to make them more normal. However, readers of published papers may wish to be certain that the authors have conducted a proper analysis. One can clearly see whether the distributional assumption is met when data are presented in the form of a histogram or scatter diagram. However, when only summary statistics are presented, the task becomes far more difficult. An idea of the distribution can be gleaned if the summary statistics include the range of the data. For example, a range from 7 to 41 around a mean of 15 suggests that the data are positively skewed. Belief in that assumption may be unreliable because the range is based upon the two most extreme, and atypical, values. Similar asymmetry affecting the lower and upper quartiles would better indicate a skewed distribution. it is suggested that for measurements which must be positive, if the mean is smaller than twice the standard deviation, the data are likely to be skewed. A second indicator of skewness can be used when there are data for several groups of individuals. Deviations from the normal distribution and a relation between the standard deviation and mean across groups often go together. A standard deviation which increases as the mean increases is a strong indication of positively skewed data, and specifically that a log transformation may be needed.
A Vibrating Wire System For Quadrupole Fiducialization
Wolf, Zachary
2010-12-13
A vibrating wire system is being developed to fiducialize the quadrupoles between undulator segments in the LCLS. This note provides a detailed analysis of the system. The LCLS will have quadrupoles between the undulator segments to keep the electron beam focused. If the quadrupoles are not centered on the beam axis, the beam will receive transverse kicks, causing it to deviate from the undulator axis. Beam based alignment will be used to move the quadrupoles onto a straight line, but an initial, conventional alignment must place the quadrupole centers on a straight line to 100 {micro}m. In the fiducialization step of the initial alignment, the position of the center of the quadrupole is measured relative to tooling balls on the outside of the quadrupole. The alignment crews then use the tooling balls to place the magnet in the tunnel. The required error on the location of the quadrupole center relative to the tooling balls must be less than 25 {micro}m. In this note, we analyze a system under construction for the quadrupole fiducialization. The system uses the vibrating wire technique to position a wire onto the quadrupole magnetic axis. The wire position is then related to tooling balls using wire position detectors. The tooling balls on the wire position detectors are finally related to tooling balls on the quadrupole to perform the fiducialization. The total 25 {micro}m fiducialization error must be divided between these three steps. The wire must be positioned onto the quadrupole magnetic axis to within 10 {micro}m, the wire position must be measured relative to tooling balls on the wire position detectors to within 15 {micro}m, and tooling balls on the wire position detectors must be related to tooling balls on the quadrupole to within 10 {micro}m. The techniques used in these three steps will be discussed. The note begins by discussing various quadrupole fiducialization techniques used in the past and discusses why the vibrating wire technique is our method
McInturff, A.D.
1985-07-01
The data base for this paper will represent the work from two different groups and two different Laboratories (Brookhaven National Laboratory and Fermi National Accelerator Laboratory). The majority of the data was that obtained by the Fermi National Accelerator Group and is the most recent, and is based on a larger number of coil windings. The coil winding sizes that will be discussed are 12 cm, (Figure 1) 7.6 cm and 5 cm, (Figure 2) for the inner diameter. The maximum gradients measured in the 5 cm sizes were 1.93 T/cm at 3.5 K and 1.79 T/cm at 4.2 K. In the 7.6 cm size were 1.35 T/cm at 2.0 K and 1.1 T/cm at 4.2 K and in the 12.0 cm size was 1.35 T/cm at 4.2 K. The 12 cm size used a cold iron shield, but had an older conductor, so one effect (increase due to Fe) offset the other (lower J/sub c/ (H) of the earlier superconductor). These gradients (especially the 12 cm measurements) can be improved using more modern conductors, (i.e., approx.20% + g/(cm A) and their higher current densities. These gradients represent an increase of 2 to 3+ times the value obtainable using conventional iron and copper magnets at a comparable aperature. The original purposes for these coils were for the 12 cm size, the Isabelle lattice, the 7.6 cm size, the Tevatron lattice and low ..beta.. insertion focus, and the 5 cm size, the final focus of SLC at SLAC and SSC size coils.
Bayesian partial linear model for skewed longitudinal data.
Tang, Yuanyuan; Sinha, Debajyoti; Pati, Debdeep; Lipsitz, Stuart; Lipshultz, Steven
2015-07-01
Unlike majority of current statistical models and methods focusing on mean response for highly skewed longitudinal data, we present a novel model for such data accommodating a partially linear median regression function, a skewed error distribution and within subject association structures. We provide theoretical justifications for our methods including asymptotic properties of the posterior and associated semiparametric Bayesian estimators. We also provide simulation studies to investigate the finite sample properties of our methods. Several advantages of our method compared with existing methods are demonstrated via analysis of a cardiotoxicity study of children of HIV-infected mothers.
Skew chromaticity in large accelerators
Peggs, S.; Dell, G.F.
1995-05-01
The 2-D ``skew chromaticity`` vector k is introduced when the standard on-momentum description of linear coupling is extended to include off-momentum particles. A lattice that is well decoupled on-momentum may be badly decoupled off-momentum, inside the natural momentum spread of the beam. There are two general areas of concern: (1) the free space in the tune plane is decreased; (2) collective phenomena may be destabilized. Two strong new criteria for head-tail stability in the presence of off-momentum coupling are derived, which are consistent with experimental and operational observations at the Tevatron, and with tracking data from RHIC.
Kinematic correction for roller skewing
NASA Technical Reports Server (NTRS)
Savage, M.; Loewenthal, S. H.
1980-01-01
A theory of kinematic stabilization of rolling cylinders is developed for high-speed cylindrical roller bearings. This stabilization requires race and roller crowning to product changes in the rolling geometry as the roller shifts axially. These changes put a reverse skew in the rolling elements by changing the rolling taper. Twelve basic possible bearing modifications are identified in this paper. Four have single transverse convex curvature in the rollers while eight have rollers with compound transverse curvature composed of a central cylindrical band of constant radius surrounded by symmetric bands with both slope and transverse curvature.
Mixture of Skewed α-Stable Distributions
NASA Astrophysics Data System (ADS)
Shojaei, S. R. Hosseini; Nassiri, V.; Mohammadian, Gh. R.; Mohammadpour, A.
2011-03-01
Expectation maximization (EM) algorithm and the Bayesian techniques are two approaches for statistical inference of mixture models [3, 4]. By noting the advantages of the Bayesian methods, practitioners prefer them. However, implementing Markov chain Monte Carlo algorithms can be very complicated for stable distributions, due to the non-analytic density or distribution function formulas. In this paper, we introduce a new class of mixture of heavy-tailed distributions, called mixture of skewed stable distributions. Skewed stable distributions belongs to the exponential family and they have analytic density representation. It is shown that skewed stable distributions dominate skew stable distribution functions and they can be used to model heavy-tailed data. The class of skewed stable distributions has an analytic representation for its density function and the Bayesian inference can be done similar to the exponential family of distributions. Finally, mixture of skewed stable distributions are compared to the mixture of stable distributions through a simulations study.
Superconducting magnetic quadrupole
Kim, J.W.; Shepard, K.W.; Nolen, J.A.
1995-08-01
A design was developed for a 350 T/m, 2.6-cm clear aperture superconducting quadrupole focussing element for use in a very low q/m superconducting linac as discussed below. The quadrupole incorporates holmium pole tips, and a rectangular-section winding using standard commercially-available Nb-Ti wire. The magnet was modeled numerically using both 2D and 3D codes, as a basis for numerical ray tracing using the quadrupole as a linac element. Components for a prototype singlet are being procured during FY 1995.
Roller skewing measurements in cylindrical roller bearings
NASA Technical Reports Server (NTRS)
Nypan, L. J.
1981-01-01
Measurements of roller skewing in a 118 mm bore roller bearing operating at shaft speeds to 12,000 rpm are reported. High speed motion pictures of a modified roller were taken through a derotation prism to record skewing as the roller moved through loaded and unloaded regions of the bearing. Subsequent frame by frame measurement of the photographic film provided information on roller skewing. Radial and tangential skew amplitudes of 0.4 to 0.5 degrees were observed with 0.5 degree misalignment.
Moreta, Cristina; Tena, María Teresa
2014-08-15
An analytical method is proposed to determine ten perfluorinated alkyl acids (PFAAs) [nine perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS)] in corn, popcorn and microwave popcorn packaging by focused ultrasound solid-liquid extraction (FUSLE) and ultra high performance liquid chromatography (UHPLC) coupled to quadrupole-time of flight mass spectrometry (QTOF-MS/MS). Selected PFAAs were extracted efficiently in only one 10-s cycle by FUSLE, a simple, safe and inexpensive technique. The developed method was validated for microwave popcorn bags matrix as well as corn and popcorn matrices in terms of linearity, matrix effect error, detection and quantification limits, repeatability and recovery values. The method showed good accuracy with recovery values around 100% except for the lowest chain length PFAAs, satisfactory reproducibility with RSDs under 16%, and sensitivity with limits of detection in the order of hundreds picograms per gram of sample (between 0.2 and 0.7ng/g). This method was also applied to the analysis of six microwave popcorn bags and the popcorn inside before and after cooking. PFCAs contents between 3.50ng/g and 750ng/g were found in bags, being PFHxA (perfluorohexanoic acid) the most abundant of them. However, no PFAAs were detected either corn or popcorn, therefore no migration was assumed.
Moreta, Cristina; Tena, María Teresa
2014-08-15
An analytical method is proposed to determine ten perfluorinated alkyl acids (PFAAs) [nine perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS)] in corn, popcorn and microwave popcorn packaging by focused ultrasound solid-liquid extraction (FUSLE) and ultra high performance liquid chromatography (UHPLC) coupled to quadrupole-time of flight mass spectrometry (QTOF-MS/MS). Selected PFAAs were extracted efficiently in only one 10-s cycle by FUSLE, a simple, safe and inexpensive technique. The developed method was validated for microwave popcorn bags matrix as well as corn and popcorn matrices in terms of linearity, matrix effect error, detection and quantification limits, repeatability and recovery values. The method showed good accuracy with recovery values around 100% except for the lowest chain length PFAAs, satisfactory reproducibility with RSDs under 16%, and sensitivity with limits of detection in the order of hundreds picograms per gram of sample (between 0.2 and 0.7ng/g). This method was also applied to the analysis of six microwave popcorn bags and the popcorn inside before and after cooking. PFCAs contents between 3.50ng/g and 750ng/g were found in bags, being PFHxA (perfluorohexanoic acid) the most abundant of them. However, no PFAAs were detected either corn or popcorn, therefore no migration was assumed. PMID:24986069
Modeling skewness in human transcriptomes.
Casellas, Joaquim; Varona, Luis
2012-01-01
Gene expression data are influenced by multiple biological and technological factors leading to a wide range of dispersion scenarios, although skewed patterns are not commonly addressed in microarray analyses. In this study, the distribution pattern of several human transcriptomes has been studied on free-access microarray gene expression data. Our results showed that, even in previously normalized gene expression data, probe and differential expression within probe effects suffer from substantial departures from the commonly assumed symmetric gaussian distribution. We developed a flexible mixed model for non-competitive microarray data analysis that accounted for asymmetric and heavy-tailed (Student's t distribution) dispersion processes. Random effects for gene expression data were modeled under asymmetric Student's t distributions where the asymmetry parameter (λ) took values from perfect symmetry (λ = 0) to right- (λ>0) or left-side (λ>0) over-expression patterns. This approach was applied to four free-access human data sets and revealed clearly better model performance when comparing with standard approaches accounting for traditional symmetric gaussian distribution patterns. Our analyses on human gene expression data revealed a substantial degree of right-hand asymmetry for probe effects, whereas differential gene expression addressed both symmetric and left-hand asymmetric patterns. Although these results cannot be extrapolated to all microarray experiments, they highlighted the incidence of skew dispersion patterns in human transcriptome; moreover, we provided a new analytical approach to appropriately address this biological phenomenon. The source code of the program accommodating these analytical developments and additional information about practical aspects on running the program are freely available by request to the corresponding author of this article. PMID:22701729
Portfolio optimization with skewness and kurtosis
NASA Astrophysics Data System (ADS)
Lam, Weng Hoe; Jaaman, Saiful Hafizah Hj.; Isa, Zaidi
2013-04-01
Mean and variance of return distributions are two important parameters of the mean-variance model in portfolio optimization. However, the mean-variance model will become inadequate if the returns of assets are not normally distributed. Therefore, higher moments such as skewness and kurtosis cannot be ignored. Risk averse investors prefer portfolios with high skewness and low kurtosis so that the probability of getting negative rates of return will be reduced. The objective of this study is to compare the portfolio compositions as well as performances between the mean-variance model and mean-variance-skewness-kurtosis model by using the polynomial goal programming approach. The results show that the incorporation of skewness and kurtosis will change the optimal portfolio compositions. The mean-variance-skewness-kurtosis model outperforms the mean-variance model because the mean-variance-skewness-kurtosis model takes skewness and kurtosis into consideration. Therefore, the mean-variance-skewness-kurtosis model is more appropriate for the investors of Malaysia in portfolio optimization.
Impact of final-focus ground motion on NLC luminosity
Irwin, J.; Zimmermann, F.
1996-06-01
Vertical displacements of final-focus quadrupoles due to ground motion can cause the two beams of the Next Linear Collider (NLC) to miss each other at the interaction point (IP) and, in addition, will increase the IP spot size, and thus degrade the luminosity, by generating dispersion and skew coupling. The sensitivity of the final-focus optics to plane ground waves is strongly wavelength dependent, which is formally expressed in terms of a lattice-response function. In this paper, the rms beam-beam separation and the rms IP spot-size increase are estimated for the NLC final focus, using the measured ground-motion power spectrum, a realistic orbit-feedback response curve, and the appropriate lattice-response function. The luminosity loss due to ground motion is shown to be insignificant.
Root waving and skewing: unexpectedly in micro-g.
Roux, Stanley J
2012-12-07
Gravity has major effects on both the form and overall length of root growth. Numerous papers have documented these effects (over 300 publications in the last 5 years), the most well-studied being gravitropism, which is a growth re-orientation directed by gravity toward the earth's center. Less studied effects of gravity are undulations due to the regular periodic change in the direction root tips grow, called waving, and the slanted angle of growth roots exhibit when they are growing along a nearly-vertical surface, called skewing. Although diverse studies have led to the conclusion that a gravity stimulus is needed for plant roots to show waving and skewing, the novel results just published by Paul et al. (2012) reveal that this conclusion is not correct. In studies carried out in microgravity on the International Space Station, the authors used a new imaging system to collect digital photographs of plants every six hours during 15 days of spaceflight. The imaging system allowed them to observe how roots grew when their orientation was directed not by gravity but by overhead LED lights, which roots grew away from because they are negatively phototropic. Surprisingly, the authors observed both skewing and waving in spaceflight plants, thus demonstrating that both growth phenomena were gravity independent. Touch responses and differential auxin transport would be common features of root waving and skewing at 1-g and micro-g, and the novel results of Paul et al. will focus the attention of cell and molecular biologists more on these features as they try to decipher the signaling pathways that regulate root skewing and waving.
Agrawal, Prateek; Chacko, Zackaria; Fortes, Elaine C. F. S.; Kilic, Can
2016-05-10
We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects minimal flavor violation and is, therefore, naturally consistent with flavor constraints. We study the phenomenology of a benchmark model in whichmore » dark matter couples to right-handed charged leptons. In large regions of parameter space, the dark matter can emerge as a thermal relic, while remaining consistent with the constraints from direct and indirect detection. The collider signatures of this scenario include events with multiple leptons and missing energy. In conclusion, these events exhibit a characteristic flavor pattern that may allow this class of models to be distinguished from other theories of dark matter.« less
SUPERCONDUCTING QUADRUPOLE ARRAYS FOR MULTIPLE BEAM TRANSPORT
Rainer Meinke Carl Goodzeit Penny Ball Roger Bangerter
2003-10-01
The goal of this research was to develop concepts for affordable, fully functional arrays of superconducting quadrupoles for multi-beam transport and focusing in heavy ion fusion (HIF)accelerators. Previous studies by the Virtual National Laboratory (VNL) collaboration have shown that the multi-beam transport system (consisting of alternating gradient quadrupole magnets, a beam vacuum system, and the beam monitor and control system) will likely be one of the most expensive and critical parts of such an accelerator. This statement is true for near-term fusion research accelerators as well as accelerators for the ultimate goal of power production via inertial fusion. For this reason, research on superconducting quadrupole arrays is both timely and important for the inertial fusion energy (IFE) research program. This research will also benefit near-term heavy ion fusion facilities such as the Integrated Research Experiment (IRE)and/or the Integrated Beam Experiment (IBX). We considered a 2-prong approach that addresses the needs of both the nearer and longer term requirements of the inertial fusion program. First, we studied the flat coil quadrupole design that was developed by LLNL; this magnet is 150 mm long with a 50 mm aperture and thus is suitable for near term experiments that require magnets of a small length to aperture ratio. Secondly, we studied the novel double-helix quadrupole (DHQ) design in a small (3 x 3) array configuration; this design can provide an important step to the longer term solution of low-cost, easy to manufacture array constructions. Our Phase I studies were performed using the AMPERES magnetostatic analysis software. Consideration of these results led to plans for future magnet R&D construction projects. The first objective of Phase I was to develop the concept of a superconducting focusing array that meets the specific requirements of a heavy ion fusion accelerator. Detailed parameter studies for such quadrupole arrays were performed
Tunable skewed edges in puckered structures
NASA Astrophysics Data System (ADS)
Grujić, Marko M.; Ezawa, Motohiko; Tadić, Milan Ž.; Peeters, François M.
2016-06-01
We propose a type of edges arising due to the anisotropy inherent in the puckered structure of a honeycomb system such as in phosphorene. Skewed-zigzag and skewed-armchair nanoribbons are semiconducting and metallic, respectively, in contrast to their normal edge counterparts. Their band structures are tunable, and a metal-insulator transition is induced by an electric field. We predict a field-effect transistor based on the edge states in skewed-armchair nanoribbons, where the edge state is gapped by applying arbitrary small electric field Ez. A topological argument is presented, revealing the condition for the emergence of such edge states.
Women's Memory Advantage Might Skew Alzheimer's Diagnosis
... https://medlineplus.gov/news/fullstory_161328.html Women's Memory Advantage Might Skew Alzheimer's Diagnosis Women tend to hold on to better verbal memory skills as they age compared to men, study ...
Skew estimation of document images using bagging.
Meng, Gaofeng; Pan, Chunhong; Zheng, Nanning; Sun, Chen
2010-07-01
This paper proposes a general-purpose method for estimating the skew angles of document images. Rather than to derive a skew angle merely from text lines, the proposed method exploits various types of visual cues of image skew available in local image regions. The visual cues are extracted by Radon transform and then outliers of them are iteratively rejected through a floating cascade. A bagging (bootstrap aggregating) estimator is finally employed to combine the estimations on the local image blocks. Our experimental results show significant improvements against the state-of-the-art methods, in terms of execution speed and estimation accuracy, as well as the robustness to short and sparse text lines, multiple different skews and the presence of nontextual objects of various types and quantities.
The Quadrupole Mass Spectrometer
ERIC Educational Resources Information Center
Matheson, E.; Harris, T. J.
1969-01-01
Describes the construction and operation of a quadrupole mass spectrometer for experiments in an advanced-teaching laboratory. Discusses the theory of operation of the spectrometer and the factors affecting the resolution. Some examples of mass spectra obtained with this instrument are presented and discussed. (LC)
High reproductive skew in tropical hover wasps.
Sumner, Seirian; Casiraghi, Maurizio; Foster, William; Field, Jeremy
2002-01-22
A plethora of recent models examines how genetic and environmental factors might influence partitioning of reproduction ('skew') in animal societies, but empirical data are sparse. We used three microsatellite loci to estimate skew on 13 nests of the Malaysian hover wasp, Liostenogaster flavolineata. Groups are small in L. flavolineata (1-10 females) and all females are capable of mating and laying eggs. Despite considerable variation between nests in parameters expected to influence skew, skew was uniformly high. On 11 of the 13 nests, all female eggs had been laid by a single dominant female. A second female had laid one to two out of 5-10 eggs respectively on the two remaining nests. A likelihood analysis suggested that on average, 90% of the male eggs had also been laid by the dominant. The slightly lower skew among male eggs might reflect the lower average relatedness of subordinates to male versus female offspring of the dominant. We suggest that high skew in L. flavolineata may result from strong ecological constraints and a relatively high probability that a subordinate will eventually inherit the dominant, egg-laying position.
Fieremans, Nathalie; Van Esch, Hilde; Holvoet, Maureen; Van Goethem, Gert; Devriendt, Koenraad; Rosello, Monica; Mayo, Sonia; Martinez, Francisco; Jhangiani, Shalini; Muzny, Donna M; Gibbs, Richard A; Lupski, James R; Vermeesch, Joris R; Marynen, Peter; Froyen, Guy
2016-08-01
Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males because of the hemizygous state of their X chromosome. Carrier females are generally unaffected because of the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analyzed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6%) had extreme skewing (>90%), which is significantly higher than observed in the general population (3.6%; P = 0.029). Whole-exome sequencing of 19 females with extreme skewing revealed causal variants in six females in the XLID genes DDX3X, NHS, WDR45, MECP2, and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in three of these patients. Moreover, variants likely accounting for skewing only were detected in MED12, HDAC8, and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients.
Stiening, R.
1984-07-12
Linac type QC and QCH quadrupoles are mounted on the accelerator with their power connection side facing the injector. The connections are on the top of the magnet. The correct polarity for magnets is shown. The magnetic centers of all magnets are measured. If the magnetic center is above the geometric center, the distance delta y is positive. If the magnetic center is to the right of the geometric center, the distance delta x is positive.
Static ocular counterroll reflex in skew deviation
Chandrakumar, M.; Blakeman, A.; Goltz, H.C.; Sharpe, J.A.
2011-01-01
Objective: The static ocular counterroll (OCR) reflex generates partially compensatory torsional eye movements during head roll. It is mediated by the utricle in the inner ear. Skew deviation is a vertical strabismus thought to be caused by imbalance in the utriculo-ocular pathway. We hypothesized that if skew deviation is indeed caused by damage to this reflex pathway, patients with skew deviation would show abnormal OCR. Methods: Eighteen patients with skew deviation caused by brainstem or cerebellar lesions and 18 normal participants viewed a target at 1 m. Ocular responses to static passive head roll-tilts of approximately 20° were recorded using search coils. Static OCR gain was calculated as the change in torsional eye position divided by the change in head position during sustained head roll. Perception of the subjective visual vertical (SVV) was also measured. Results: Group mean OCR gain was reduced by 45% in patients. At an individual level, OCR gains were asymmetric between eyes and between torsional directions in 90% of patients. In addition, the hypotropic eye incyclotorting gain was lower than the hypertropic eye excyclotorting gain during head roll toward the hypotropic eye in 94% of patients. No consistent pattern of gain asymmetry was found during head roll toward the hypertropic eye. The SVV was tilted toward the hypotropic eye. Conclusion: Static OCR gain is significantly reduced in skew deviation. Interocular and directional gain asymmetries are also prevalent. The asymmetries provide further evidence that disruption of the utriculo-ocular pathway is a mechanism for skew deviation. PMID:21813791
Commissioning a Vibrating Wire System for Quadrupole Fiducialization
Levashov, Michael Y
2010-12-03
Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of the quadrupoles. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing such a system. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). A previous study investigated the error associated with each step by using a permanent quadrupole magnet on an optical mover system. The study reported an error of 11{micro}m for step 1 and a repeatability of 4{micro}m for step 2. However, the set up used a FARO arm to measure tooling balls and didn't allow to accurately check step 2 for errors; an uncertainty of 100{micro}m was reported. Therefore, even though the repeatability was good, there was no way to check that the error in step 2 was small. Following the recommendations of
Skewness and Kurtosis in Statistical Kinetics
NASA Astrophysics Data System (ADS)
Barato, Andre C.; Seifert, Udo
2015-10-01
We obtain lower and upper bounds on the skewness and kurtosis associated with the cycle completion time of unicyclic enzymatic reaction schemes. Analogous to a well-known lower bound on the randomness parameter, the lower bounds on skewness and kurtosis are related to the number of intermediate states in the underlying chemical reaction network. Our results demonstrate that evaluating these higher order moments with single molecule data can lead to information about the enzymatic scheme that is not contained in the randomness parameter.
Skew chicane based betatron eigenmode exchange module
Douglas, David
2010-12-28
A skewed chicane eigenmode exchange module (SCEEM) that combines in a single beamline segment the separate functionalities of a skew quad eigenmode exchange module and a magnetic chicane. This module allows the exchange of independent betatron eigenmodes, alters electron beam orbit geometry, and provides longitudinal parameter control with dispersion management in a single beamline segment with stable betatron behavior. It thus reduces the spatial requirements for multiple beam dynamic functions, reduces required component counts and thus reduces costs, and allows the use of more compact accelerator configurations than prior art design methods.
Radio frequency quadrupole resonator for linear accelerator
Moretti, Alfred
1985-01-01
An RFQ resonator for a linear accelerator having a reduced level of interfering modes and producing a quadrupole mode for focusing, bunching and accelerating beams of heavy charged particles, with the construction being characterized by four elongated resonating rods within a cylinder with the rods being alternately shorted and open electrically to the shell at common ends of the rods to provide an LC parallel resonant circuit when activated by a magnetic field transverse to the longitudinal axis.
Muon cooling in a quadrupole magnet channel
Neuffer, David; Poklonskiy, A.; /Michigan State U.
2007-10-01
As discussed before,[1] a cooling channel using quadrupole magnets in a FODO transport channel can be used for initial cooling of muons. In the present note we discuss this possibility of a FODO focusing channel for cooling, and we present ICOOL simulations of muon cooling within a FODO channel. We explore a 1.5m cell-length cooling channel that could be used for the initial transverse cooling stage of a muon collider or neutrino factory.
Electrostatic quadrupole DC accelerators for BNCT applications
Kwan, J.W.; Anderson, O.A.; Reginato, L.L.; Vella, M.C.; Yu, S.S.
1994-04-01
A dc electrostatic quadrupole (ESQ) accelerator is capable of producing a 2.5 MeV, 100 mA proton beam for the purpose of generating neutrons for Boron Neutron Capture Therapy. The ESQ accelerator is better than the conventional aperture column in high beam current application due to the presence of stronger transverse field for beam focusing and for suppressing secondary electrons. The major challenge in this type of accelerator is in developing the proper power supply system.
Direct focusing error correction with ring-wide TBT beam position data
Yang, M.J.; /Fermilab
2011-03-01
Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of free oscillations are taken in just few tens of milliseconds. With beam covering all positions and angles at every location TBT data can be used to diagnose focusing errors almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed. The procedure presented clearly has helped to reduce overall deviations significantly, with relative ease. Sextupoles, being a permanent feature of the ring, will need to be incorporated into the model. While cumulative effect from all sextupoles around the ring may be negligible on turn-to-turn basis it is not so in this transfer line analysis. It should be noted that this procedure is not limited to looking for quadrupole errors. By modifying the target of minimization it could in principle be used to look for skew quadrupole errors and sextupole errors as well.
Optimal Weak-Lensing Skewness Measurements
NASA Astrophysics Data System (ADS)
Zhang, Tong-Jie; Pen, Ue-Li; Zhang, Pengjie; Dubinski, John
2003-12-01
Weak-lensing measurements are starting to provide statistical maps of the distribution of matter in the universe that are increasingly precise and complementary to cosmic microwave background maps. The most common measurement is the correlation in alignments of background galaxies, which can be used to infer the variance of the projected surface density of matter. This measurement of the fluctuations is insensitive to the total mass content and is analogous to using waves on the ocean to measure its depths. However, when the depth is shallow, as happens near a beach, waves become skewed. Similarly, a measurement of skewness in the projected matter distribution directly measures the total matter content of the universe. While skewness has already been convincingly detected, its constraint on cosmology is still weak. We address optimal analyses for the Canada-France-Hawaii Telescope Legacy Survey in the presence of noise. We show that a compensated Gaussian filter with a width of 2.5‧ optimizes the cosmological constraint, yielding ΔΩm/Ωm~10%. This is significantly better than other filters that have been considered in the literature. This can be further improved with tomography and other sophisticated analyses.
Light transmission for polymer fibers using skew and meridional rays
NASA Astrophysics Data System (ADS)
Tekelioglu, Murat
This dissertation is concerned with the development of a light transmission model for polymer optical fibers having application in hybrid solar lighting (HSL) systems. Conceptually, the HSL system consists of a solar collector/receiver that focuses concentrated visible solar light onto a polymer optical fiber (up to 10-m-long) that transports the solar light to an interior space. For this study, the polymer optical fiber is a large-core (0.2-40 mm diameter) plastic optical fiber (POF) comprised of various lengths of straight and bent sections. Although there has been extensive research on the transmission of monochromatic light through optical fibers for the communications industry, there are relatively few publications for visible light transmission through POFs. These publications were critically reviewed in this research. It is shown that the light transmission can be described with either skew or meridional rays. For each ray type, the HSL system light transmission was determined as a function of fiber geometrical properties (core and cladding radii, bend radius, bend angle, and fiber length) and optical properties (core and clad refractive indices, absorption and scattering coefficients, core-clad rms roughness height, and core-clad interface defects loss coefficient). To do this, first, models were developed for separate straight and bent sections for multiple skew and meridional rays. Second, the straight and bent models were combined into a FORTRAN simulation program for an arbitrary fiber with a combination of arbitrary straight and bent sections. The input condition of the rays (arrangement of rays, incident angle, and intensity profile) is user-defined. Third, the simulation results were experimentally validated using two different POFs, twelve configurations of straight and bent fiber subsystems, and two ray types. These experimental comparisons show that the transmission model using meridional rays is slightly better than that with the skew rays. But
Generalized skew coefficients for flood-frequency analysis in Minnesota
Lorenz, D.L.
1997-01-01
This report presents an evaluation of generalized skew coefficients used in flood-frequency analysis. Station skew coefficients were computed for 267 long-term stream-gaging stations in Minnesota and the surrounding states of Iowa, North and South Dakota, Wisconsin, and the provinces of Manitoba and Ontario, Canada. Generalized skew coefficients were computed from station skew coefficients using a locally weighted regression technique. The resulting regression trend surface was the generalized skew coefficient map, except for the North Shore area, and has a mean square error of 0.182.
Crossover ensembles of random matrices and skew-orthogonal polynomials
Kumar, Santosh; Pandey, Akhilesh
2011-08-15
Highlights: > We study crossover ensembles of Jacobi family of random matrices. > We consider correlations for orthogonal-unitary and symplectic-unitary crossovers. > We use the method of skew-orthogonal polynomials and quaternion determinants. > We prove universality of spectral correlations in crossover ensembles. > We discuss applications to quantum conductance and communication theory problems. - Abstract: In a recent paper (S. Kumar, A. Pandey, Phys. Rev. E, 79, 2009, p. 026211) we considered Jacobi family (including Laguerre and Gaussian cases) of random matrix ensembles and reported exact solutions of crossover problems involving time-reversal symmetry breaking. In the present paper we give details of the work. We start with Dyson's Brownian motion description of random matrix ensembles and obtain universal hierarchic relations among the unfolded correlation functions. For arbitrary dimensions we derive the joint probability density (jpd) of eigenvalues for all transitions leading to unitary ensembles as equilibrium ensembles. We focus on the orthogonal-unitary and symplectic-unitary crossovers and give generic expressions for jpd of eigenvalues, two-point kernels and n-level correlation functions. This involves generalization of the theory of skew-orthogonal polynomials to crossover ensembles. We also consider crossovers in the circular ensembles to show the generality of our method. In the large dimensionality limit, correlations in spectra with arbitrary initial density are shown to be universal when expressed in terms of a rescaled symmetry breaking parameter. Applications of our crossover results to communication theory and quantum conductance problems are also briefly discussed.
Dynamic Modeling from Flight Data with Unknown Time Skews
NASA Technical Reports Server (NTRS)
Morelli, Eugene A.
2016-01-01
A method for estimating dynamic model parameters from flight data with unknown time skews is described and demonstrated. The method combines data reconstruction, nonlinear optimization, and equation-error parameter estimation in the frequency domain to accurately estimate both dynamic model parameters and the relative time skews in the data. Data from a nonlinear F-16 aircraft simulation with realistic noise, instrumentation errors, and arbitrary time skews were used to demonstrate the approach. The approach was further evaluated using flight data from a subscale jet transport aircraft, where the measured data were known to have relative time skews. Comparison of modeling results obtained from time-skewed and time-synchronized data showed that the method accurately estimates both dynamic model parameters and relative time skew parameters from flight data with unknown time skews.
Superconducting Focusing Lenses for the SSR1 Cryomodule of PXIE Test Stand at Fermilab
DiMarco, J.; Tartaglia, M.; Terechkine, I.
2016-01-01
Five solenoid-based focusing lenses designed for use inside the SSR1 cryomodule of the PXIE test stand at Fermilab have been fabricated and tested. In addition to a focusing solenoid, each lens is equipped with a set of windings that generate magnetic field in the transverse plane and can be used in the steering dipole mode or as a skew quadrupole corrector. The lenses will be installed between superconducting cavities in the cryomodule, so getting sufficiently low fringe magnetic field was one of the main design requirements. Beam dynamics simulations indicated a need for high accuracy positioning of the lenses in the cryomodule, which triggered a study towards understanding uncertainties of the magnetic axis position relative to the geometric features of the lens. This report summarizes the efforts towards certification of the lenses, including results of performance tests, fringe field data, and uncertainty of the magnetic axis position.
Purcaro, Giorgia; Tranchida, Peter Quinto; Ragonese, Carla; Conte, Lanfranco; Dugo, Paola; Dugo, Giovanni; Mondello, Luigi
2010-10-15
Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful technique which can enable a great increase in GC peak capacities. However, since secondary-column separations are very rapid, detectors with a fast acquisition rate are mandatory. Such a requirement has certainly limited the use of the quadrupole mass spectrometer in the GC×GC field. The present research is focused on the evaluation of a novel rapid-scanning quadrupole mass spectrometry (qMS) detector, characterized by a 20,000 amu/s scan speed and a 50 Hz scan frequency, using a 290 amu mass range (40-330 m/z). The performance of the MS system was assessed by analyzing mixtures of 24 allergens, as well as a perfume sample, through GC×GC/qMS. The MS parameters evaluated at different acquisition rates (50, 33, and 25 Hz), as well as in the (simultaneous) scan/selected ion monitoring (SIM) mode, were the number of data points per peak, mass spectrum quality, peak skewing, and sensitivity. Two GC×GC/qMS methods, using the 50 Hz acquisition rate and the scan/SIM mode, were validated. Both methods provided similar results in terms of repeatability, accuracy, and linearity, while a great increase in sensitivity was observed (ca. a factor of 10) under scan/SIM conditions. The validated method proved to be suitable for the analysis of perfume allergens, according to the requirements of Directive 2003/15/EC.
Inferring climate variability from skewed proxy records
NASA Astrophysics Data System (ADS)
Emile-Geay, J.; Tingley, M.
2013-12-01
Many paleoclimate analyses assume a linear relationship between the proxy and the target climate variable, and that both the climate quantity and the errors follow normal distributions. An ever-increasing number of proxy records, however, are better modeled using distributions that are heavy-tailed, skewed, or otherwise non-normal, on account of the proxies reflecting non-normally distributed climate variables, or having non-linear relationships with a normally distributed climate variable. The analysis of such proxies requires a different set of tools, and this work serves as a cautionary tale on the danger of making conclusions about the underlying climate from applications of classic statistical procedures to heavily skewed proxy records. Inspired by runoff proxies, we consider an idealized proxy characterized by a nonlinear, thresholded relationship with climate, and describe three approaches to using such a record to infer past climate: (i) applying standard methods commonly used in the paleoclimate literature, without considering the non-linearities inherent to the proxy record; (ii) applying a power transform prior to using these standard methods; (iii) constructing a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting the skewness in the proxy leads to erroneous conclusions and often exaggerates changes in climate variability between different time intervals. In contrast, an explicit treatment of the skewness, using either power transforms or a Bayesian inversion of the mechanistic model for the proxy, yields significantly better estimates of past climate variations. We apply these insights in two paleoclimate settings: (1) a classical sedimentary record from Laguna Pallcacocha, Ecuador (Moy et al., 2002). Our results agree with the qualitative aspects of previous analyses of this record, but quantitative departures are evident and hold implications for how such records are interpreted, and
GC skew and mitochondrial origins of replication.
Sahyoun, Abdullah H; Bernt, Matthias; Stadler, Peter F; Tout, Kifah
2014-07-01
The comprehensive understanding of mitochondrial genome evolution requires a detailed mechanistic picture of mitogenomic replication. Despite many previous efforts it has remained a non-trivial problem to determine the origins of replication and trace their fate across rearrangements of the gene order even in the small genomes of animal mitochondria. We elaborate here on the observation that the GC skew is correlated with the distance from the replication origins. This effect has been explained as a consequence of the standard model of mitochondrial DNA replication, i.e. the strand displacement model. According to this model chemical damage accumulates proportional to the duration that DNA is exposed in single-stranded form during replication (Dssh) which depends on the relative position with respect to the replication origins. Based on this model we developed a computational method to infer the positions of both the heavy strand and the light strand origin from nucleotide skew data. In a comprehensive survey of deuterostome mitochondria we infer conserved replication origins for the vast majority of vertebrates and cephalochordates. Deviations from the consensus picture are presumably associated with genome rearrangements.
Temperature-Compensated Clock Skew Adjustment
Castillo-Secilla, Jose María; Palomares, Jose Manuel; Olivares, Joaquín
2013-01-01
This work analyzes several drift compensation mechanisms in wireless sensor networks (WSN). Temperature is an environmental factor that greatly affects oscillators shipped in every WSN mote. This behavior creates the need of improving drift compensation mechanisms in synchronization protocols. Using the Flooding Time Synchronization Protocol (FTSP), this work demonstrates that crystal oscillators are affected by temperature variations. Thus, the influence of temperature provokes a low performance of FTSP in changing conditions of temperature. This article proposes an innovative correction factor that minimizes the impact of temperature in the clock skew. By means of this factor, two new mechanisms are proposed in this paper: the Adjusted Temperature (AT) and the Advanced Adjusted Temperature (A2T). These mechanisms have been combined with FTSP to produce AT-FTSP and A2T-FTSP Both have been tested in a network of TelosB motes running TinyOS. Results show that both AT-FTSP and A2T-FTSP improve the average synchronization errors compared to FTSP and other temperature-compensated protocols (Environment-Aware Clock Skew Estimation and Synchronization for WSN (EACS) and Temperature Compensated Time Synchronization (TCTS)). PMID:23966192
Evolution and models for skewed parton distribution
Musatov, I.C.; Radyushkin, A.V.
1999-05-17
The authors discuss the structure of the ''forward visible'' (FW) parts of double and skewed distributions related to usual distributions through reduction relations. They use factorized models for double distributions (DDs) {tilde f}(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DDs are used to construct skewed parton distributions (SPDs). For small skewedness, the FW parts of SPDs H ({tilde x},{xi}) can be obtained by averaging forward parton densities f({tilde x}-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution {tilde f}(x, {alpha}) at small x. They show that if the x{sup n} moments {tilde f}{sub n}({alpha}) of DDs have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha}-profile of {tilde f}(x,{alpha}) for small x is completely determined by small-x behavior of the usual parton distribution. They demonstrate that, for small {xi}, the model with asymptotic profiles for {tilde f}{sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPDs do not depend on {xi}. They perform a numerical investigation of the evolution patterns of SPDs and give interpretation of the results of these studies within the formalism of double distributions.
Quadrupole Induced Resonant Particle Transport
NASA Astrophysics Data System (ADS)
Gilson, Erik; Fajans, Joel
1998-11-01
We have performed experiments that explore the effects of a magnetic quadrupole field on a pure electron plasma confined in a Penning-Malmberg trap. A model that we have developed describes the shape of the plasma and shows that a certain class of resonant particles follows trajectories that take them out of the plasma. Even though the quadrupole field destroys the cylindrical symmetry of the system, our theory predicts that if the electrons are off resonance, then the lifetime of the plasma will not be greatly affected by the quadrupole field. Our preliminary experimental results show that the shape of the plasma and the plasma lifetime agree with our model. We are investigating the scaling of this behavior with various experimental parameters such as the plasma length, density, and strength of the quadrupole field. In addition to being an example of resonant particle transport, this effect may find practical applications in experiments that plan to use magnetic quadrupole neutral atom traps to confine anti-hydrogen created in double-well positron/anti-proton Penning-Malmberg traps. (ATHENA Collaboration.)
Quadrupole Induced Resonant Particle Transport
NASA Astrophysics Data System (ADS)
Gilson, Erik; Fajans, Joel
1999-11-01
We have performed experiments that explore the effects of a magnetic quadrupole field on a pure electron plasma confined in a Malmberg-Penning trap. A model that we have developed describes the shape of the plasma and shows that a certain class of resonant particles follows trajectories that take them out of the plasma. Even though the quadrupole field destroys the cylindrical symmetry of the system, our theory predicts that if the electrons are off resonance, then the lifetime of the plasma will not be greatly affected by the quadrupole field. Our preliminary experimental results show that the shape of the plasma and the plasma lifetime agree with our model. We are investigating the scaling of this behavior with various experimental parameters such as the plasma length, density, and strength of the quadrupole field. In addition to being an example of resonant particle transport, this effect may find practical applications in experiments that plan to use magnetic quadrupole neutral atom traps to confine anti-hydrogen created in double-well positron/anti-proton Malmberg-Penning traps. (ATHENA Collaboration.)
Coefficient of variation calculated from the range for skewed distributions.
Rhiel, G Steven
2006-02-01
In this research a coefficient of variation (CVS(high.low)) is developed that is calculated from the highest and lowest values in a set of data for samples from skewed distributions. A correction factor is determined such that CVS(high-low) is a dose estimate of the population coefficient of variation when sampling from three skewed chi-squared distributions and three skewed empirical distributions. The empirical distributions are from "real-world" data sets in psychology and education.
Analysis of skew plate problems with various constraints
NASA Astrophysics Data System (ADS)
Mizusawa, T.; Kajita, T.; Naruoka, M.
1980-12-01
This paper presents the application of the modified Rayleigh-Ritz method with Lagrange multipliers to analyze skew plate problems with various constraints. By this procedure one can satisfy both geometric and natural boundary conditions of skew plates. To demonstrate the accuracy and versatility of the method, several examples of bending, vibration and buckling of skew plates are solved, and results are compared with those obtained by other approximate methods.
Improving IRMPD in a quadrupole ion trap.
Newsome, G Asher; Glish, Gary L
2009-06-01
A focused laser is used to make infrared multiphoton photodissociation (IRMPD) more efficient in a quadrupole ion trap mass spectrometer. Efficient (up to 100%) dissociation at the standard operating pressure of 1 x 10(-3) Torr can be achieved without any supplemental ion activation and with shorter irradiation times. The axial amplitudes of trapped ion clouds are measured using laser tomography. Laser flux on the ion cloud is increased six times by focusing the laser so that the beam waist approximates the ion cloud size. Unmodified peptide ions from 200 Da to 3 kDa are completely dissociated in 2.5-10 ms at a bath gas pressure of 3.3 x 10(-4) Torr and in 3-25 ms at 1.0 x 10(-3) Torr. Sequential dissociation of product ions is increased by focusing the laser and by operating at an increased bath gas pressure to minimize the size of the ion cloud.
Cracked shells under skew-symmetric loading
NASA Technical Reports Server (NTRS)
Lelale, F.
1982-01-01
A shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and antiplane elasticity solutions. Extensive results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform inplane shearing, out of plane shearing, and torsion. The effect of orthotropy on the results is also studied.
Incorporating covariates in skewed functional data models.
Li, Meng; Staicu, Ana-Maria; Bondell, Howard D
2015-07-01
We introduce a class of covariate-adjusted skewed functional models (cSFM) designed for functional data exhibiting location-dependent marginal distributions. We propose a semi-parametric copula model for the pointwise marginal distributions, which are allowed to depend on covariates, and the functional dependence, which is assumed covariate invariant. The proposed cSFM framework provides a unifying platform for pointwise quantile estimation and trajectory prediction. We consider a computationally feasible procedure that handles densely as well as sparsely observed functional data. The methods are examined numerically using simulations and is applied to a new tractography study of multiple sclerosis. Furthermore, the methodology is implemented in the R package cSFM, which is publicly available on CRAN.
Accounting for Skewness in Ensemble Data Assimilation
NASA Astrophysics Data System (ADS)
Hodyss, D.
2011-12-01
I will discuss a new framework for understanding how a non-normal probability density function (pdf) may affect a state estimate and how one might usefully exploit the non-normal properties of the pdf when constructing a state estimate. A Bayesian framework is constructed that leads naturally to an expansion of the expected forecast error in a polynomial series consisting of powers of the innovation vector. This polynomial expansion in the innovation reveals a new view of the geometric nature of the state estimation problem. Among other things a direct relationship is shown between the degree to which the state estimate varies with the innovation and the moments of the distribution. A practical data assimilation algorithm will also be presented that explicitly accounts for skewness in the prior distribution. The algorithm operates as a global-solve using a conjugate-gradient technique and Schur/Hadamard (element-wise) localization, and as a general rule is only a factor of four more expensive than the traditional ensemble Kalman filter. The central feature of this technique is the squaring of the innovation and the ensemble perturbations so as to create an extended state-space that accounts for the second, third and fourth moments of the prior distribution. This new technique is illustrated in a simple scalar system as well as in a Boussinesq model of O(10000) variables configured to simulate nonlinearly evolving Kelvin-Helmholtz waves in shear flow. It is shown that ensemble sizes of at least 100 members is needed to adequately resolve the third and fourth moments required for the algorithm. For ensembles of this size it is shown that this new technique is superior to a state-of-the-art Ensemble Kalman Filter in situations with significant skewness, otherwise the new algorithm reduces to the performance of the Ensemble Kalman Filter.
Evolution and models for skewed parton distributions
Musatov, I. V.; Radyushkin, A. V.
2000-04-01
We discuss the structure of the ''forward visible'' (FV) parts of double and skewed distributions related to the usual distributions through reduction relations. We use factorized models for double distributions (DD's) f(tilde sign)(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DD's are used to construct skewed parton distributions (SPD's). For small skewedness, the FV parts of SPD's H(x(tilde sign),{xi}) can be obtained by averaging forward parton densities f(x(tilde sign)-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution f(tilde sign)(x,{alpha}) at small x. We show that if the x{sup n} moments f(tilde sign){sub n}({alpha}) of DD's have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha} profile of f(tilde sign)(x,{alpha}) for small x is completely determined by the small-x behavior of the usual parton distribution. We demonstrate that, for small {xi}, the model with asymptotic profiles for f(tilde sign){sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPD's do not depend on {xi}. We perform a numerical investigation of the evolution patterns of SPD's and give an interpretation of the results of these studies within the formalism of double distributions. (c) 2000 The American Physical Society.
Nuclear Quadrupole Moments and Nuclear Shell Structure
DOE R&D Accomplishments Database
Townes, C. H.; Foley, H. M.; Low, W.
1950-06-23
Describes a simple model, based on nuclear shell considerations, which leads to the proper behavior of known nuclear quadrupole moments, although predictions of the magnitudes of some quadrupole moments are seriously in error.
LCLS Undulator Quadrupole Fiducialization Plan
Wolf, Zachary; Levashov, Michael; Lundahl, Eric; Reese, Ed; LeCocq, Catherine; Ruland, Robert; /SLAC
2010-11-24
This note presents the fiducialization plan for the LCLS undulator quadrupoles. The note begins by summarizing the requirements for the fiducialization. A discussion of the measurement equipment is presented, followed by the methods used to perform the fiducialization and check the results. This is followed by the detailed fiducialization plan in which each step is enumerated. Finally, the measurement results and data storage formats are presented. The LCLS is made up of 33 assemblies consisting of an undulator, quadrupole, beam finder wire, and other components mounted on a girder. The components must be mounted in such a way that the beam passes down the axis of each component. In this note, we describe how the ideal beam axis is related to tooling balls on the quadrupole. This step, called fiducialization, is necessary because the ideal beam axis is determined magnetically, whereas tangible objects must be used to locate the quadrupole. The note begins with the list of fiducialization requirements. The laboratory in which the work will be performed and the relevant equipment is then briefly described. This is followed by a discussion of the methods used to perform the fiducialization and the methods used to check the results. A detailed fiducialization plan is presented in which all the steps of fiducialization are enumerated. A discussion of the resulting data files and directory structure concludes the note.
Learning a Novel Pattern through Balanced and Skewed Input
ERIC Educational Resources Information Center
McDonough, Kim; Trofimovich, Pavel
2013-01-01
This study compared the effectiveness of balanced and skewed input at facilitating the acquisition of the transitive construction in Esperanto, characterized by the accusative suffix "-n" and variable word order (SVO, OVS). Thai university students (N = 98) listened to 24 sentences under skewed (one noun with high token frequency) or…
A Method for Controlling Skew on Linked Surfaces
BENZLEY,STEVEN E.; KERR,ROBERT A.; MITCHELL,SCOTT A.; WHITE,DAVID R.
1999-09-27
A new method for lessening skew in mapped meshes is presented. This new method involves progressive subdivision of a surface into loops consisting of four sides. Using these loops, constraints can then be set on the curves of the surface, which will propagate interval assignments across the surface, allowing a mesh with a better skew metric to be generated.
Analysis of carbon dioxide concentration skewness at a rural site.
Pérez, Isidro A; Sánchez, M Luisa; García, M Ángeles; Ozores, Marta; Pardo, Nuria
2014-04-01
This paper provides evidence that symmetry of CO2 concentration distribution may indicate sources or dispersive processes. Skewness was calculated by different procedures with CO2 measured at a rural site using a Picarro G1301 analyser over a two-year period. The usual skewness coefficient was considered together with fourteen robust estimators. A noticeable contrast was obtained between day and night, and skewness decreased linearly with the logarithm of the height. One coefficient was selected from its satisfactory relationship with the median concentration in daily evolution. Three analyses based on the kernel smoothing method were conducted with this coefficient to investigate its response to yearly and daily evolutions, wind direction, and wind speed. Left-skewed distributions were linked to thermal turbulence during midday, especially in spring-summer, or with high wind speeds. Almost symmetric distributions were associated with sources, such as the Valladolid City plume reinforced with spring emissions and the lack of emissions in summer in the remaining directions. Finally, right-skewed distributions were related to low wind speeds and stable stratification at night, furthered by strong emissions in spring. Skewness intervals were proposed and their average median concentrations were calculated such that the relationship between skewness and concentration depends on the analysis performed. Since some skewness coefficients may also be negative, they provide better information about sources or dispersive processes than concentration.
Skew angle effects in shingled magnetic recording system with double/triple reader head array
NASA Astrophysics Data System (ADS)
Elidrissi, Moulay Rachid; Sann Chan, Kheong; Greaves, Simon; Kanai, Yasushi; Muraoka, Hiroaki
2014-05-01
Shingled Magnetic Recording (SMR) is a scheme used to extend the life of the current perpendicular magnetic recording technology. SMR enables writing narrow tracks with a wide writer. Currently, SMR employs a single reader and will suffer inter-track interference (ITI) as the tracks become comparable in width to the reader. ITI can be mitigated by using narrower readers; however, narrower readers suffer from increased reader noise. Another approach to combat ITI is to process 2D readback and use ITI cancellation schemes to retrieve the data track. Multiple readbacks can be obtained either with a single reader and multiple revolutions or with a reader array. The former suffers from increased readback latency. In this work, we focus on the latter. When using a reader array, the skew angle poses major challenges. During writing, there is increased adjacent track erasure, and during readback the effective reader pitch varies and there is an increase in the 2D intersymbol interference caused by the rotated reader profile. In this work, we run micromagnetic simulations at different skew angles to train the grain flipping probability model, and then evaluate raw bit channel error rate performance at skew. In particular, we investigate the performance degradation caused by skewing of the 2 or 3 read head array for various read-head geometries.
Radio-frequency quadrupole linear accelerator
Wangler, T.P.; Stokes, R.H.
1980-01-01
The radio-frequency quadrupole (RFQ) is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam. Because the RFQ can provide strong focusing at low velocities, it can capture a high-current dc ion beam from a low-voltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters. A recent experimental test at the Los Alamos Scientific Laboratory (LASL) has confirmed the expected performance of this structure and has stimulated interest in a wide variety of applications. The general properties of the RFQ are reviewed and examples of applications of this new accelerator are presented.
ERIC Educational Resources Information Center
Tabor, Josh
2010-01-01
On the 2009 AP[c] Statistics Exam, students were asked to create a statistic to measure skewness in a distribution. This paper explores several of the most popular student responses and evaluates which statistic performs best when sampling from various skewed populations. (Contains 8 figures, 3 tables, and 4 footnotes.)
SSC Quadrupole Magnet Performance at LBL
Lietzke, A.F.; Barale, P.; Benjegerdes, r.; Caspi, S.; Cortella, J.; Dell'Orco, D.; Gilbert, W.; Green, M.I.; Mirk, K.; Peters, C.; Scalan, R.; Taylor, C.E.; Wandesforde, A.
1992-10-01
Lawrence Berkeley Laboratory (LBL) contracted to design, construct, and test four short (1m) models and six full-size (5m) models of the Superconducting Super Collider (SSC) main-ring 5 meter focusing quadrupole magnet (211 Tesla/meter). The training performance of these magnets is summarized. Magnets were tested in a horizontal boiling helium (1 Atm) cryostat. The magnetic, strain-gage and training responses to two thermal cycles were measured. The quadrupole gradient, and relative multipole purity were determined from Fourier analysis of the rotating coil signals. Magnetic and strain-gage measurements were taken on-the-fly. The voltage-tap data was analyzed to determine quench-origin and propagation characteristics. Quench-training proceeded at 4.3K until a plateau was achieved or sub-cooling (2.5K) was used to accelerate the training process. The early short (1m) magnets were also trained at 1.8K (10kA) to help identify potential weak areas. The MIITs were calculated to compare various magnet protection methods. Except for modest training above the anticipated SSC operating point, the magnets performed very well and proved to be self-protecting. Some design flaws were identified and corrected. The last two 1 m models and all the 5m models have been reinstalled in cryostats at the SSC Laboratory, retested and used to achieve various milestones in their program.
Test of a NbTi Superconducting Quadrupole Magnet Based on Alternating Helical Windings
Caspi, S.; Trillaud, F.; Godeke, A.; Dietderich, D.; Ferracin, P.; Sabbi, G.; Giloux, C.; Perez, J. G.; Karppinen, M.
2009-08-16
It has been shown that by superposing two solenoid-like thin windings, that are oppositely skewed (tilted) with respect to the bore axis, the combined current density on the surface is cos({theta})-like and the resulting magnetic field in the bore is a pure dipole field. Following a previous test of such a superconducting dipole magnet, a quadrupole magnet was designed and built using similar principles. This paper describes the design, construction and test of a 75 mm bore 600 mm long superconducting quadrupole made with NbTi wire. The simplicity of the design, void of typical wedges, end-spacers and coil assembly, is especially suitable for future high field insert coils using Nb{sub 3}Sn as well as HTS wires. The 3 mm thick coil reached 46 T/m but did not achieve its current plateau.
Analytic formula for quadrupole-quadrupole matrix elements
NASA Astrophysics Data System (ADS)
Rosensteel, G.
1990-12-01
An analytic formula is reported for general matrix elements of the microscopic quadrupole-quadrupole operator in the U(3)-boson approximation. The complete infinite-dimensional basis of A-fermion wave functions is compatible with the harmonic-oscillator shell model and consists of np-nh configurations, with spurious center-of-mass excitations removed, which are symmetry adapted to the Elliott U(3) and symplectic Sp(3,R) models. The formula expresses the general Q2.Q2 matrix element with respect to this complete orthonormal basis as a Racah SU(3) U coefficient times a closed-shell matrix element. An oscillator closed-shell matrix element of Q2.Q2 is a square root of a rational function of the integer quantum numbers of the U(3) basis.
The low-energy quadrupole mode of nuclei
NASA Astrophysics Data System (ADS)
Frauendorf, S.
2015-08-01
The phenomenological classification of collective quadrupole excitations by means of the Bohr-Hamiltonian (BH) is reviewed with focus on signatures for triaxility. The variants of the microscopic BH derived by means of the Adiabatic Time-Dependent Mean Field theory from the Pairing-plus-quadrupole-quadrupole interaction, the Shell Correction Method, the Skyrme Energy Density Functional, the Relativistic Mean Field Theory and the Gogny interaction are discussed and applications to concrete nuclides reviewed. The Generator Coordinate Method for the five-dimensional quadrupole deformation space and first applications to triaxial nuclei are presented. The phenomenological classification in the framework of the Interacting Boson Model is discussed with a critical view on the boson number counting rule. The recent success in calculating the model parameters by mapping the mean field deformation energy surface on the bosonic one is discussed and the applications listed. A critical assessment of the models is given with focus on the limitations due to the adiabatic approximation. The Tidal Wave approach and the Triaxial Projected Shell Model are presented as practical approaches to calculate spectral properties outside the adiabatic region.
Spin Hall Effects Due to Phonon Skew Scattering
NASA Astrophysics Data System (ADS)
Gorini, Cosimo; Eckern, Ulrich; Raimondi, Roberto
2015-08-01
A diversity of spin Hall effects in metallic systems is known to rely on Mott skew scattering. In this work its high-temperature counterpart, phonon skew scattering, which is expected to be of foremost experimental relevance, is investigated. In particular, the phonon skew scattering spin Hall conductivity is found to be practically T independent for temperatures above the Debye temperature TD. As a consequence, in Rashba-like systems a high-T linear behavior of the spin Hall angle demonstrates the dominance of extrinsic spin-orbit scattering only if the intrinsic spin splitting is smaller than the temperature.
Focusing Electron Beams at SLAC.
ERIC Educational Resources Information Center
Taylor, Richard L.
1993-01-01
Describes the development of a set of magnets that focus high-energy electron and positron beams causing them to collide, annihilate each other, and generate new particles. Explains how dipoles bend the beam, how quadrupoles focus the beam, how the focal length is calculated, and the superconducting final focus. (MDH)
2. Skew Span on left to Span 3 on right ...
2. Skew Span on left to Span 3 on right from north bank-up river. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
4. From Skew Span to portal on span 1 looking ...
4. From Skew Span to portal on span 1 looking up grade toward the south end. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
3. Span 4 on right to Skew Span on leftfrom ...
3. Span 4 on right to Skew Span on left-from south bank-up river. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices
ERIC Educational Resources Information Center
Glaister, P.
2008-01-01
The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.
LOOKING WEST, BETWEEN READING DEPOT BRIDGE AND SKEW ARCH BRIDGE ...
LOOKING WEST, BETWEEN READING DEPOT BRIDGE AND SKEW ARCH BRIDGE (HAER No. PA-116). - Philadelphia & Reading Railroad, Reading Depot Bridge, North Sixth Street at Woodward Street, Reading, Berks County, PA
7. William E. Barrett, Photographer, 1974. SKEWED VIEW SHOWING CHEAT ...
7. William E. Barrett, Photographer, 1974. SKEWED VIEW SHOWING CHEAT RIVER VALLEY, REMAINS OF 1887 PIER AND c. 1900 MASONRY ARCHES. - Baltimore & Ohio Railroad, Tray Run Viaduct, Spanning Tray Run, Rowlesburg, Preston County, WV
Statistics on Cannabis Users Skew Perceptions of Cannabis Use
Burns, Rachel M.; Caulkins, Jonathan P.; Everingham, Susan S.; Kilmer, Beau
2013-01-01
Collecting information about the prevalence of cannabis use is necessary but not sufficient for understanding the size, dynamics, and outcomes associated with cannabis markets. This paper uses two data sets describing cannabis consumption in the United States and Europe to highlight (1) differences in inferences about sub-populations based on the measure used to quantify cannabis-related activity; (2) how different measures of cannabis-related activity can be used to more accurately describe trends in cannabis usage over time; and (3) the correlation between frequency of use in the past-month and average grams consumed per use-day. Key findings: focusing on days of use instead of prevalence shows substantially greater increases in U.S. cannabis use in recent years; however, the recent increase is mostly among adults, not youth. Relatively more rapid growth in use days also occurred among the college-educated and Hispanics. Further, data from a survey conducted in seven European countries show a strong positive correlation between frequency of use and quantity consumed per day of use, suggesting consumption is even more skewed toward the minority of heavy users than is suggested by days-of-use calculations. PMID:24223560
Vibration of skewed cantilever plates and helicoidal shells
NASA Technical Reports Server (NTRS)
Beres, D. P.; Bailey, C. D.
1975-01-01
Theoretical vibration frequencies and mode shapes are obtained for skewed plates and helicoidal shells with a cantilever boundary. Using Hamilton's law of varying action, a power series solution is developed to obtain converged numerical results for the five lowest frequencies. Effects of geometrical variables such as aspect ratio, sweep angle and shell radius to thickness ratio are investigated. Accuracy of the solution method is substantiated by comparison with existing skewed plate spherical cap, and conical shell results.
LARP Long Quadrupole: A "Long" Step Toward an LHC
Giorgio Ambrosio
2016-07-12
The beginning of the development of Nb3Sn magnets for particle accelerators goes back to the 1960âs. But only very recently has this development begun to face the challenges of fabricating Nb3Sn magnets which can meet the requirements of modern particle accelerators. LARP (the LHC Accelerator Research Program) is leading this effort focusing on long models of the Interaction Region quadrupoles for a possible luminosity upgrade of the Large Hadron Collider. A major milestone in this development is to test, by the end of 2009, 4m-long quadrupole models, which will be the first Nb3Sn accelerator-type magnets approaching the length of real accelerator magnets. The Long Quadrupoles (LQ) are âProof-of-Principleâ magnets which are to demonstrate that Nb3Sn technology is sufficiently mature for use in high energy particle accelerators. Their design is based on the LARP Technological Quadrupole (TQ) models, under development at FNAL and LBNL, which have design gradients higher than 200 T/m and an aperture of 90 mm. Several challenges must be addressed for the successful fabrication of long Nb3Sn coils and magnets. These challenges and the solutions adopted will be presented together with the main features of the LQ magnets. Several R&D lines are participating to this effort and their contributions will be also presented.
Flow in Rotating Serpentine Coolant Passages With Skewed Trip Strips
NASA Technical Reports Server (NTRS)
Tse, David G.N.; Steuber, Gary
1996-01-01
Laser velocimetry was utilized to map the velocity field in serpentine turbine blade cooling passages with skewed trip strips. The measurements were obtained at Reynolds and Rotation numbers of 25,000 and 0.24 to assess the influence of trips, passage curvature and Coriolis force on the flow field. The interaction of the secondary flows induced by skewed trips with the passage rotation produces a swirling vortex and a corner recirculation zone. With trips skewed at +45 deg, the secondary flows remain unaltered as the cross-flow proceeds from the passage to the turn. However, the flow characteristics at these locations differ when trips are skewed at -45 deg. Changes in the flow structure are expected to augment heat transfer, in agreement with the heat transfer measurements of Johnson, et al. The present results show that trips are skewed at -45 deg in the outward flow passage and trips are skewed at +45 deg in the inward flow passage maximize heat transfer. Details of the present measurements were related to the heat transfer measurements of Johnson, et al. to relate fluid flow and heat transfer measurements.
Radio-frequency quadrupole resonator for linear accelerator
Moretti, A.
1982-10-19
An RFQ resonator for a linear accelerator having a reduced level of interfering modes and producing a quadrupole mode for focusing, bunching and accelerating beams of heavy charged particles, with the construction being characterized by four elongated resonating rods within a cylinder with the rods being alternately shorted and open electrically to the shell at common ends of the rods to provide an LC parallel resonant circuit when activated by a magnetic field transverse to the longitudinal axis.
Sample skewness as a statistical measurement of neuronal tuning sharpness.
Samonds, Jason M; Potetz, Brian R; Lee, Tai Sing
2014-05-01
We propose using the statistical measurement of the sample skewness of the distribution of mean firing rates of a tuning curve to quantify sharpness of tuning. For some features, like binocular disparity, tuning curves are best described by relatively complex and sometimes diverse functions, making it difficult to quantify sharpness with a single function and parameter. Skewness provides a robust nonparametric measure of tuning curve sharpness that is invariant with respect to the mean and variance of the tuning curve and is straightforward to apply to a wide range of tuning, including simple orientation tuning curves and complex object tuning curves that often cannot even be described parametrically. Because skewness does not depend on a specific model or function of tuning, it is especially appealing to cases of sharpening where recurrent interactions among neurons produce sharper tuning curves that deviate in a complex manner from the feedforward function of tuning. Since tuning curves for all neurons are not typically well described by a single parametric function, this model independence additionally allows skewness to be applied to all recorded neurons, maximizing the statistical power of a set of data. We also compare skewness with other nonparametric measures of tuning curve sharpness and selectivity. Compared to these other nonparametric measures tested, skewness is best used for capturing the sharpness of multimodal tuning curves defined by narrow peaks (maximum) and broad valleys (minima). Finally, we provide a more formal definition of sharpness using a shape-based information gain measure and derive and show that skewness is correlated with this definition.
NASA Astrophysics Data System (ADS)
Denner, Fabian; van Wachem, Berend G. M.
2015-10-01
Total variation diminishing (TVD) schemes are a widely applied group of monotonicity-preserving advection differencing schemes for partial differential equations in numerical heat transfer and computational fluid dynamics. These schemes are typically designed for one-dimensional problems or multidimensional problems on structured equidistant quadrilateral meshes. Practical applications, however, often involve complex geometries that cannot be represented by Cartesian meshes and, therefore, necessitate the application of unstructured meshes, which require a more sophisticated discretisation to account for their additional topological complexity. In principle, TVD schemes are applicable to unstructured meshes, however, not all the data required for TVD differencing is readily available on unstructured meshes, and the solution suffers from considerable numerical diffusion as a result of mesh skewness. In this article we analyse TVD differencing on unstructured three-dimensional meshes, focusing on the non-linearity of TVD differencing and the extrapolation of the virtual upwind node. Furthermore, we propose a novel monotonicity-preserving correction method for TVD schemes that significantly reduces numerical diffusion caused by mesh skewness. The presented numerical experiments demonstrate the importance of accounting for the non-linearity introduced by TVD differencing and of imposing carefully chosen limits on the extrapolated virtual upwind node, as well as the efficacy of the proposed method to correct mesh skewness.
Electrostatic quadrupoles for heavy-ion fusion
Seidl, P.; Faltens, A.
1993-05-01
Voltage-holding data for three quadrupole electrode sizes and inter-electrode spacings are reported. The dependence of the breakdown voltage on system size and its influence on the optimum quadrupole size for beam transport in a multiple beam array are discussed.
Quantum Fisher and skew information for Unruh accelerated Dirac qubit
NASA Astrophysics Data System (ADS)
Banerjee, Subhashish; Alok, Ashutosh Kumar; Omkar, S.
2016-08-01
We develop a Bloch vector representation of the Unruh channel for a Dirac field mode. This is used to provide a unified, analytical treatment of quantum Fisher and skew information for a qubit subjected to the Unruh channel, both in its pure form as well as in the presence of experimentally relevant external noise channels. The time evolution of Fisher and skew information is studied along with the impact of external environment parameters such as temperature and squeezing. The external noises are modelled by both purely dephasing phase damping and the squeezed generalised amplitude damping channels. An interesting interplay between the external reservoir temperature and squeezing on the Fisher and skew information is observed, in particular, for the action of the squeezed generalised amplitude damping channel. It is seen that for some regimes, squeezing can enhance the quantum information against the deteriorating influence of the ambient environment. Similar features are also observed for the analogous study of skew information, highlighting a similar origin of the Fisher and skew information.
Determining collective barrier operation skew in a parallel computer
Faraj, Daniel A.
2015-11-24
Determining collective barrier operation skew in a parallel computer that includes a number of compute nodes organized into an operational group includes: for each of the nodes until each node has been selected as a delayed node: selecting one of the nodes as a delayed node; entering, by each node other than the delayed node, a collective barrier operation; entering, after a delay by the delayed node, the collective barrier operation; receiving an exit signal from a root of the collective barrier operation; and measuring, for the delayed node, a barrier completion time. The barrier operation skew is calculated by: identifying, from the compute nodes' barrier completion times, a maximum barrier completion time and a minimum barrier completion time and calculating the barrier operation skew as the difference of the maximum and the minimum barrier completion time.
Uniqueness: skews bit occurrence frequencies in randomly generated fingerprint libraries.
Chen, Nelson G
2016-08-01
Requiring that randomly generated chemical fingerprint libraries have unique fingerprints such that no two fingerprints are identical causes a systematic skew in bit occurrence frequencies, the proportion at which specified bits are set. Observed frequencies (O) at which each bit is set within the resulting libraries systematically differ from frequencies at which bits are set at fingerprint generation (E). Observed frequencies systematically skew toward 0.5, with the effect being more pronounced as library size approaches the compound space, which is the total number of unique possible fingerprints given the number of bit positions each fingerprint contains. The effect is quantified for varying library sizes as a fraction of the overall compound space, and for changes in the specified frequency E. The cause and implications for this systematic skew are subsequently discussed. When generating random libraries of chemical fingerprints, the imposition of a uniqueness requirement should either be avoided or taken into account.
Power and Skew Aware Point Diffusion Clock Network
NASA Astrophysics Data System (ADS)
Jung, Gunok; Kim, Chunghee; Chae, Kyoungkuk; Park, Giho; Park, Sung Bae
This letter presents point diffusion clock network (PDCN) with local clock tree synthesis (CTS) scheme. The clock network is implemented with ten times wider metal line space than typical mesh networks for low power and utilized to nine times smaller area CTS execution for minimized clock skew amount. The measurement results show that skew amount of PDCN with local CTS is reduced to 36% and latency is shrunk to 45% of the amount in a 4.81mm2 CortexA-8 core with 65nm Samsung process.
Skewness of steady-state current fluctuations in nonequilibrium systems.
Belousov, Roman; Cohen, E G D; Wong, Chun-Shang; Goree, John A; Feng, Yan
2016-04-01
A skewness of the probability for instantaneous current fluctuations, in a nonequilibrium steady state, is observed experimentally in a dusty plasma. This skewness is attributed to the spatial asymmetry, which is imminent to the nonequilibrium systems due to the external hydrodynamic gradient. Using the modern framework of the large deviation theory, we extend the Onsager-Machlup ansatz for equilibrium fluctuations to systems with a preferred spatial direction, and provide a modulated Gaussian probability distribution, which is tested by simulations. This probability distribution is also of potential interest for other statistical disciplines. Connections with the principles of statistical mechanics, due to Boltzmann and Gibbs, are discussed as well. PMID:27176272
QUADRUPOLE BEAM-BASED ALIGNMENT AT RHIC.
NIEDZIELA, J.; MONTAG, C.; SATOGATA, T.
2005-05-16
Successful implementation of a beam-based alignment algorithm, tailored to different types of quadrupoles at RHIC, provides significant benefits to machine operations for heavy ions and polarized protons. This algorithm was used to calibrate beam position monitor centers relative to interaction region quadrupoles to maximize aperture. This approach was also used to determine the optimal orbit through transition jump quadrupoles to minimize orbit changes during the transition jump for heavy ion acceleration. This paper provides background discussion and results from first measurements during the RHIC 2005 run.
Jiang, Zhaolin; Shen, Nuo; Zhou, Jianwei
2013-01-01
We first give the style spectral decomposition of a special skew circulant matrix C and then get the style decomposition of arbitrary skew circulant matrix by making use of the Kronecker products between the elements of first row in skew circulant and the special skew circulant C. Besides that, we obtain the singular value of skew circulant matrix as well. Finally, we deal with the optimal backward perturbation analysis for the linear system with skew circulant coefficient matrix on the base of its style spectral decomposition. PMID:24369488
Thermocline Feedback Influence on Indian Ocean Dipole Skewness
NASA Astrophysics Data System (ADS)
Ng, B.; Cai, W.; Walsh, K. J.
2014-12-01
A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. These impacts from positive IODs range from drought over Australia and Indonesia, to flooding over East Africa and India. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming.
Skewness and Comparability of School Based Continuous Assessment Scores
ERIC Educational Resources Information Center
Gbore, Lawrence Olu; Olabode, Abe Thomas; Olufemi, Adodo Sunday
2011-01-01
This study examined skewness as means of determining the nature of distribution of school based continuous assessment (SBCA) scores in selected subjects among Secondary Schools in Ondo State, Nigeria, to determine whether or not there is need for moderation of the SBCA Scores. This is an ex-post-facto research design involving no treatment and…
4. North portal of Skew Span looking south and leading ...
4. North portal of Skew Span looking south and leading to Span 1 Main Bridge on the left and Span 1 Hot Metal Bridge on the right. - Monongahela Connecting Railroad Company, Main Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
Thermal Analysis of the ILC Superconductin Quadrupole
Ross, Ian; /Rose-Hulman Inst., Terre Haute /SLAC
2006-09-13
Critical to a particle accelerator's functioning, superconducting magnets serve to focus and aim the particle beam. The Stanford Linear Accelerator Center (SLAC) has received a prototype superconducting quadrupole designed and built by the Centro de Investigaciones Energ{acute e}ticas, Medioambientales y Tecnol{acute o}gicas (CIEMAT) to be evaluated for the International Linear Collider (ILC) project. To ensure proper functioning of the magnet, the device must be maintained at cryogenic temperatures by use of a cooling system containing liquid nitrogen and liquid helium. The cool down period of a low temperature cryostat is critical to the success of an experiment, especially a prototype setup such as this one. The magnet and the dewar each contain unique heat leaks and material properties. These differences can lead to tremendous thermal stresses. The system was analyzed mathematically, leading to ideal liquid helium and liquid nitrogen flow rates during the magnet's cool-down to 4.2 K, along with a reasonable estimate of how long this cool-down will take. With a flow rate of ten gaseous liters of liquid nitrogen per minute, the nitrogen shield will take approximately five hours to cool down to 77 K. With a gaseous helium flow rate of sixty liters per minute, the magnet will take at least nineteen hours to cool down to a temperature of 4.2 K.
Clusterization and quadrupole deformation in nuclei
Cseh, J.; Algora, A.; Antonenko, N. V.; Jolos, R. V.; Scheid, W.; Darai, J.; Hess, P. O.
2006-04-26
We study the interrelation of the clusterization and quadrupole deformation of atomic nuclei, by applying cluster models. Both the energetic stability and the exclusion principle is investigated. Special attention is paid to the relative orientations of deformed clusters.
Nonuniform radiation damage in permanent magnet quadrupoles
Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.
2014-08-15
We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL’s pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.
Permanent magnet edge-field quadrupole
Tatchyn, R.O.
1997-01-21
Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.
Permanent magnet edge-field quadrupole
Tatchyn, Roman O.
1997-01-01
Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.
Miniature quadrupole mass spectrometer array
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)
1997-01-01
The present invention provides a minature quadrupole mass spectrometer array for the separation of ions, comprising a first pair of parallel, planar, nonmagnetic conducting rods each having an axis of symmetry, a second pair of planar, nonmagnetic conducting rods each having an axis of symmetry parallel to said first pair of rods and disposed such that a line perpendicular to each of said first axes of symmetry and a line perpendicular to each of said second axes of symmetry bisect each other and form a generally 90 degree angle. A nonconductive top positioning plate is positioned generally perpendicular to the first and second pairs of rods and has an aperture for ion entrance along an axis equidistant from each axis of symmetry of each of the parallel rods, a nonconductive bottom positioning plate is generally parallel to the top positioning plate and has an aperture for ion exit centered on an axis equidistant from each axis of symmetry of each of the parallel rods, means for maintaining a direct current voltage between the first and second pairs of rods, and means for applying a radio frequency voltage to the first and second pairs of rods.
Miniature quadrupole mass spectrometer array
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)
1998-01-01
The present invention provides a minature quadrupole mass spectrometer array for the separation of ions, comprising a first pair of parallel, planar, nonmagnetic conducting rods each having an axis of symmetry, a second pair of planar, nonmagnetic conducting rods each having an axis of symmetry parallel to said first pair of rods and disposed such that a line perpendicular to each of said first axes of symmetry and a line perpendicular to each of said second axes of symmetry bisect each other and form a generally 90 degree angle. A nonconductive top positioning plate is positioned generally perpendicular to the first and second pairs of rods and has an aperture for ion entrance along an axis equidistant from each axis of symmetry of each of the parallel rods, a nonconductive bottom positioning plate is generally parallel to the top positioning plate and has an aperture for ion exit centered on an axis equidistant from each axis of symmetry of each of the parallel rods, means for maintaining a direct current voltage between the first and second pairs of rods, and means for applying a radio frequency voltage to the first and second pairs of rods.
Integrally formed radio frequency quadrupole
Abbott, Steven R.
1989-01-01
An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.
Set Up and Test Results for a Vibrating Wire System for Quadrupole Fiducialization
Not Available
2010-11-29
Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of a quadrupole. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing it. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). The following break up of error was suggested for the fiducialization steps: 10{micro}m for step 1 (finding the center), 20{micro}m for step 2 (finding the wire), and 10{micro}m for step 3 (tooling ball measurements). The purpose of this study is to investigate whether the vibrating wire system meets the requirements for LCLS. In particular, if it can reliably fiducialize a quadrupole magnetic center to within 25{micro}m in both vertical and horizontal directions. The behavior of individual system components is compared to the expected performance
Set Up and Test Results for a Vibrating Wire System for Quadrupole Fiducialization
Levashov, Michael Y.
2010-12-01
Quadrupoles will be placed between the undulator segments in LCLS to keep the electron beam focused as it passes through. The quadrupoles will be assembled with their respective undulator segments prior to being placed into the tunnel. Beam alignment will be used to center the quadrupoles, along with the corresponding undulators, on the beam. If there is any displacement between the undulator and the quadrupole axes in the assemblies, the beam will deviate from the undulator axis. If it deviates by more than 80{micro}m in vertical or 140{micro}m in horizontal directions, the undulator will not perform as required by LCLS. This error is divided between three sources: undulator axis fiducialization, quadrupole magnetic axis fiducialization, and assembly of the two parts. In particular, it was calculated that the quadrupole needs to be fiducialized to within 25{micro}m in both vertical and horizontal directions. A previous study suggested using a vibrating wire system for finding the magnetic axis of a quadrupole. The study showed that the method has high sensitivity (up to 1{micro}m) and laid out guidelines for constructing it. There are 3 steps in fiducializing the quadrupole with the vibrating wire system. They are positioning the wire at the magnet center (step 1), finding the wire with position detectors (step 2), and finding the quadrupole tooling ball positions relative to the position detector tooling balls (step 3). The following break up of error was suggested for the fiducialization steps: 10{micro}m for step 1 (finding the center), 20{micro}m for step 2 (finding the wire), and 10{micro}m for step 3 (tooling ball measurements). The purpose of this study is to investigate whether the vibrating wire system meets the requirements for LCLS. In particular, if it can reliably fiducialize a quadrupole magnetic center to within 25{micro}m in both vertical and horizontal directions. The behavior of individual system components is compared to the expected performance
Arc voltage distribution skewness as an indicator of electrode gap during vacuum arc remelting
Williamson, Rodney L.; Zanner, Frank J.; Grose, Stephen M.
1998-01-01
The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap.
Quench margin measurement in Nb3Sn quadrupole magnet
Kashikhin, V.V.; Bossert, R.; Chlachidze, G.; Lamm, M.; Novitski, I.; Zlobin, A.V.; /Fermilab
2008-08-01
One of the possible practical applications of the Nb{sub 3}Sn accelerator magnets is the LHC luminosity upgrade that involves replacing the present NbTi focusing quadrupoles in two high-luminosity interaction regions (IR). The IR magnets are exposed to strong radiation from the interaction point that requires a detailed investigation of the magnet operating margins under the expected radiation-induced heat depositions. This paper presents the results of simulation and measurement of quench limits and temperature margins for a Nb{sub 3}Sn model magnet using a special midplane strip heater.
Skewed Brownian Fluctuations in Single-Molecule Magnetic Tweezers
Burnham, Daniel R.; De Vlaminck, Iwijn; Henighan, Thomas; Dekker, Cees
2014-01-01
Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements. PMID:25265383
Quantifying Correlations via the Wigner-Yanase-Dyson Skew Information
NASA Astrophysics Data System (ADS)
Fan, Yajing; Cao, Huaixin
2016-09-01
In this paper, based on a discussion about the Wigner-Yanase-Dyson (WYD) skew information, the measure F a, α ( ρ a b ) for correlations in terms of the WYD skew information is introduced and discussed. The following conclusions are obtained. For a classical-quantum state ρ a b , F a, α ( ρ a b )=0 if and only if ρ a b is a product state; F a, α ( ρ a b ) is locally unitary invariant and convex on the set of states with the fixed marginal ρ a ; F a, α ( ρ a b ) decreases under local random unitary operation on H b ; For a quantum-classical state ρ a b , F a, α ( ρ a b ) decreases under local operation on H b ; Lastly, F a, α ( ρ a b ) is computed for the pure states and the Bell-diagonal states, respectively.
Identification of spots in rotated and skewed microarray images
NASA Astrophysics Data System (ADS)
Le Brese, Christopher; Zou, Ju Jia
2009-12-01
DNA microarray image processing has vast potential in the measurement of mass gene expression. A common approach to processing microarrays consists of spot identification, spot segmentation, and information extraction. We are concerned with spot identification. We aim to tackle the problem of identifying spots in rotated and skewed arrays via an automated process. The method proposed is composed of three steps, namely, array orientation calculation based on the Hough transform, affine calculation and correction, and gridding. The method is able to correctly identify spots in a microarray that has been rotated or skewed at an angle between 0 and +/-30 deg and corrupted by various types of noise such as high-intensity streaks, Gaussian noise, and salt-and-pepper noise.
Free vibration analyses of generally laminated tapered skew plates
NASA Astrophysics Data System (ADS)
Kapania, Rakesh K.; Singhvi, Sarvesh
1992-04-01
An efficient method is developed for the free vibration analyses of generally laminated composite skew plates having arbitrary edge conditions, such as clamped, simply supported or free. The procedure consists of the Rayleigh-Ritz method utilizing a strain energy functional containing both bending and stretching effects and accommodating arbitrary ply stacking sequences. A set of Chebyshev polynomials is used as trial functions to represent the three components of the displacement at a given point. The geometric boundary conditions are satisfied by providing appropriate springs with large stiffnesses at a given edge. Results are obtained for isotropic, specially orthotropic, symmetrically laminated and unsymmetrically laminated plates. Both rectangular and skewed tapered plates are analyzed. The capability to perform the static analysis of a composite plate is also demonstrated. To establish the correctness and effectiveness of the method, whenever possible, the numerical results are compared with those obtained by other researchers.
Universal relation between skewness and kurtosis in complex dynamics
NASA Astrophysics Data System (ADS)
Cristelli, Matthieu; Zaccaria, Andrea; Pietronero, Luciano
2012-06-01
We identify an important correlation between skewness and kurtosis for a broad class of complex dynamic systems and present a specific analysis of earthquake and financial time series. Two regimes of non-Gaussianity can be identified: a parabolic one, which is common in various fields of physics, and a power law one, with exponent 4/3, which at the moment appears to be specific of earthquakes and financial markets. For this property we propose a model and an interpretation in terms of very rare events dominating the statistics independently on the nature of the events considered. The predicted scaling relation between skewness and kurtosis matches very well the experimental pattern of the second regime. Regarding price fluctuations, this situation characterizes a universal stylized fact.
Incorporating Skew into RMS Surface Roughness Probability Distribution
NASA Technical Reports Server (NTRS)
Stahl, Mark T.; Stahl, H. Philip.
2013-01-01
The standard treatment of RMS surface roughness data is the application of a Gaussian probability distribution. This handling of surface roughness ignores the skew present in the surface and overestimates the most probable RMS of the surface, the mode. Using experimental data we confirm the Gaussian distribution overestimates the mode and application of an asymmetric distribution provides a better fit. Implementing the proposed asymmetric distribution into the optical manufacturing process would reduce the polishing time required to meet surface roughness specifications.
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, Lannie; Kalsi, Manmohan Singh
1999-01-01
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland.
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, L.; Kalsi, M.S.
1999-02-23
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. 14 figs.
Kurtosis, skewness, and non-Gaussian cosmological density perturbations
NASA Technical Reports Server (NTRS)
Luo, Xiaochun; Schramm, David N.
1993-01-01
Cosmological topological defects as well as some nonstandard inflation models can give rise to non-Gaussian density perturbations. Skewness and kurtosis are the third and fourth moments that measure the deviation of a distribution from a Gaussian. Measurement of these moments for the cosmological density field and for the microwave background temperature anisotropy can provide a test of the Gaussian nature of the primordial fluctuation spectrum. In the case of the density field, the importance of measuring the kurtosis is stressed since it will be preserved through the weakly nonlinear gravitational evolution epoch. Current constraints on skewness and kurtosis of primeval perturbations are obtained from the observed density contrast on small scales and from recent COBE observations of temperature anisotropies on large scales. It is also shown how, in principle, future microwave anisotropy experiments might be able to reveal the initial skewness and kurtosis. It is shown that present data argue that if the initial spectrum is adiabatic, then it is probably Gaussian, but non-Gaussian isocurvature fluctuations are still allowed, and these are what topological defects provide.
Caste load and the evolution of reproductive skew.
Holman, Luke
2014-01-01
Reproductive skew theory seeks to explain how reproduction is divided among group members in animal societies. Existing theory is framed almost entirely in terms of selection, though nonadaptive processes must also play some role in the evolution of reproductive skew. Here I propose that a genetic correlation between helper fecundity and breeder fecundity may frequently constrain the evolution of reproductive skew. This constraint is part of a wider phenomenon that I term "caste load," which is defined as the decline in mean fitness caused by caste-specific selection pressures, that is, differential selection on breeding and nonbreeding individuals. I elaborate the caste load hypothesis using quantitative and population genetic arguments and individual-based simulations. Although selection can sometimes erode genetic correlations and resolve caste load, this may be constrained when mutations have similar pleiotropic effects on breeder and helper traits. I document evidence for caste load, identify putative genomic adaptations to it, and suggest future research directions. The models highlight the value of considering adaptation within the boundaries imposed by genetic architecture and incidentally reaffirm that monogamy promotes the evolutionary transition to eusociality. PMID:24334738
Validation of an Acoustic Impedance Prediction Model for Skewed Resonators
NASA Technical Reports Server (NTRS)
Howerton, Brian M.; Parrott, Tony L.
2009-01-01
An impedance prediction model was validated experimentally to determine the composite impedance of a series of high-aspect ratio slot resonators incorporating channel skew and sharp bends. Such structures are useful for packaging acoustic liners into constrained spaces for turbofan noise control applications. A formulation of the Zwikker-Kosten Transmission Line (ZKTL) model, incorporating the Richards correction for rectangular channels, is used to calculate the composite normalized impedance of a series of six multi-slot resonator arrays with constant channel length. Experimentally, acoustic data was acquired in the NASA Langley Normal Incidence Tube over the frequency range of 500 to 3500 Hz at 120 and 140 dB OASPL. Normalized impedance was reduced using the Two-Microphone Method for the various combinations of channel skew and sharp 90o and 180o bends. Results show that the presence of skew and/or sharp bends does not significantly alter the impedance of a slot resonator as compared to a straight resonator of the same total channel length. ZKTL predicts the impedance of such resonators very well over the frequency range of interest. The model can be used to design arrays of slot resonators that can be packaged into complex geometries heretofore unsuitable for effective acoustic treatment.
Tide and skew surge independence: New insights for flood risk
NASA Astrophysics Data System (ADS)
Williams, Joanne; Horsburgh, Kevin J.; Williams, Jane A.; Proctor, Robert N. F.
2016-06-01
Storm surges are a significant hazard to coastal communities around the world, putting lives at risk and costing billions of dollars in damage. Understanding how storm surges and high tides interact is crucial for estimating extreme water levels so that we can protect coastal communities. We demonstrate that in a tidal regime the best measure of a storm surge is the skew surge, the difference between the observed and predicted high water within a tidal cycle. Based on tide gauge records spanning decades from the UK, U.S., Netherlands, and Ireland we show that the magnitude of high water exerts no influence on the size of the most extreme skew surges. This is the first systematic proof that any storm surge can occur on any tide, which is essential for understanding worst-case scenarios. The lack of surge generation dependency on water depth emphasizes the dominant natural variability of weather systems in an observation-based analysis. Weak seasonal relationships between skew surges and high waters were identified at a minority of locations where long-period changes to the tidal cycle interact with the storm season. Our results allow advances to be made in methods for estimating the joint probabilities of storm surges and tides.
NASA Astrophysics Data System (ADS)
Qin, Hong
2014-10-01
The dynamics of charged particles in general linear focusing lattices is analyzed using a generalized Courant-Snyder (CS) theory, which extends the original CS theory for one degree of freedom to higher dimensions. The general focusing lattices are allowed to include quadrupole, skew-quadrupole, solenoidal, and dipole components, as well as variation of beam energy and torsion of the fiducial orbit. The scalar envelope function is generalized into an envelope matrix, and the scalar envelope equation, also known as the Ermakov-Milne-Pinney equation in quantum mechanics, is generalized to an envelope matrix equation. The phase advance is generalized into a 4D symplectic rotation, or an U(2) element. Other components of the original CS theory, such as the CS invariant, transfer matrix, and Twiss functions all have their counterparts in the generalized theory with remarkably similar expressions. The gauge group of the generalized theory is analyzed. If the gauge freedom is fixed with a desired symmetry, the generalized CS parametrization assumes the form of the modified Iwasawa decomposition, whose importance in phase space quantum mechanics and optics has been recently realized. It is shown that the spectral and structural stability properties of a general focusing lattice are uniquely determined by the generalized phase advance. For structural stability, the generalized CS theory developed enables application of the Krein-Moser theory to significantly simplify the theoretical and numerical analysis. The generalized CS theory provides an effective tool to study the coupled dynamics of high-intensity charged particle beams and to discover more optimized lattice designs in the larger parameter space of general focusing lattices. Research supported by the U.S. Department of Energy.
Induced CMB quadrupole from pointing offsets
Moss, Adam; Scott, Douglas; Sigurdson, Kris E-mail: dscott@phas.ubc.ca
2011-01-01
Recent claims in the literature have suggested that the WMAP quadrupole is not primordial in origin, and arises from an aliasing of the much larger dipole field because of incorrect satellite pointing. We attempt to reproduce this result and delineate the key physics leading to the effect. We find that, even if real, the induced quadrupole would be smaller than the WMAP value. We discuss reasons why the WMAP data are unlikely to suffer from this particular systematic effect, including the implications for observations of point sources. Given this evidence against the reality of the effect, the similarity between the pointing-offset-induced signal and the actual quadrupole then appears to be quite puzzling. However, we find that the effect arises from a convolution between the gradient of the dipole field and anisotropic coverage of the scan direction at each pixel. There is something of a directional conspiracy here — the dipole signal lies close to the Ecliptic Plane, and its direction, together with the WMAP scan strategy, results in a strong coupling to the Y{sub 2,−1} component in Ecliptic co-ordinates. The dominant strength of this component in the measured quadrupole suggests that one should exercise increased caution in interpreting its estimated amplitude. The Planck satellite has a different scan strategy which does not so directly couple the dipole and quadrupole in this way and will soon provide an independent measurement.
Lamontagne, Jonathan R.; Stedinger, Jery R.; Berenbrock, Charles; Veilleux, Andrea G.; Ferris, Justin C.; Knifong, Donna L.
2012-01-01
Flood-frequency information is important in the Central Valley region of California because of the high risk of catastrophic flooding. Most traditional flood-frequency studies focus on peak flows, but for the assessment of the adequacy of reservoirs, levees, other flood control structures, sustained flood flow (flood duration) frequency data are needed. This study focuses on rainfall or rain-on-snow floods, rather than the annual maximum, because rain events produce the largest floods in the region. A key to estimating flood-duration frequency is determining the regional skew for such data. Of the 50 sites used in this study to determine regional skew, 28 sites were considered to have little to no significant regulated flows, and for the 22 sites considered significantly regulated, unregulated daily flow data were synthesized by using reservoir storage changes and diversion records. The unregulated, annual maximum rainfall flood flows for selected durations (1-day, 3-day, 7-day, 15-day, and 30-day) for all 50 sites were furnished by the U.S. Army Corps of Engineers. Station skew was determined by using the expected moments algorithm program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual flood-duration data. Bayesian generalized least squares regression procedures used in earlier studies were modified to address problems caused by large cross correlations among concurrent rainfall floods in California and to address the extensive censoring of low outliers at some sites, by using the new expected moments algorithm for fitting the LP3 distribution to rainfall flood-duration data. To properly account for these problems and to develop suitable regional-skew regression models and regression diagnostics, a combination of ordinary least squares, weighted least squares, and Bayesian generalized least squares regressions were adopted. This new methodology determined that a nonlinear model relating regional skew to mean basin elevation
Skewness and kurtosis as indicators of non-Gaussianity in galactic foreground maps
Ben-David, Assaf; Jackson, Andrew D.; Hausegger, Sebastian von E-mail: s.vonhausegger@nbi.dk
2015-11-01
Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non-Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the statistical properties of both maps in small local regions are predominantly Gaussian. This result was expected for the SMICA map. It is surprising that it also applies for the Haslam map given its evident large scale non-Gaussianity. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.
Near and Far Field Acoustic Pressure Skewness in a Heated Supersonic Jet
NASA Astrophysics Data System (ADS)
Gutmark, Ephraim; Mora, Pablo; Kastner, Jeff; Heeb, Nick; Kailasanath, Kailas; Liu, Junhui; University of Cincinnati Collaboration; Naval Research Laboratory Collaboration
2012-11-01
The dominant component of turbulent mixing noise in high speed jets is the Mach wave radiation generated by large turbulent structures in the shear layer The Over-All Sound Pressure Level (OASPL) in the far field peaks in a direction near the Mach wave angle. ``Crackle'' is another important component of high speed jet noise. Crackle cannot be recognized in the spectrum of the acoustic pressure signal, but it appears in the temporal waveform of the pressure as sharply rising peaks. Skewness levels of the pressure and dP/dt have been used as a measure of crackle in high specific thrust engines and rockets. In this paper, we focus on recognizing a technique that identifies the impact of different test conditions on the near-field and far-field statistics of the pressure and dP/dt signals of a supersonic jet with a design Mach number of Md=1.5 produced by a C-D conical nozzle. Cold and hot jets, T0=300K and 600K, are tested at over, design, and under-expanded conditions, with NPRs=2.5, 3.671, 4.5, respectively. Second, Third and Forth order statistics are examined in the near and far fields. Rms, skewness and kurtosis intensity levels and propagation are better identified in the dP/dt than in the pressure signal. Statistics of the dP/dt demonstrate to be a better measure for crackle. Project funded by ONR grant.
NASA Astrophysics Data System (ADS)
Buganu, Petricǎ; Fortunato, Lorenzo
2016-09-01
We review and discuss several recent approaches to quadrupole collectivity and developments of collective models and their solutions with many applications, examples and references. We focus in particular on analytic and approximate solutions of the Bohr hamiltonian of the last decade, because most of the previously published material has been already reviewed in other publications.
The nuclear electric quadrupole moment of copper.
Santiago, Régis Tadeu; Teodoro, Tiago Quevedo; Haiduke, Roberto Luiz Andrade
2014-06-21
The nuclear electric quadrupole moment (NQM) of the (63)Cu nucleus was determined from an indirect approach by combining accurate experimental nuclear quadrupole coupling constants (NQCCs) with relativistic Dirac-Coulomb coupled cluster calculations of the electric field gradient (EFG). The data obtained at the highest level of calculation, DC-CCSD-T, from 14 linear molecules containing the copper atom give rise to an indicated NQM of -198(10) mbarn. Such result slightly deviates from the previously accepted standard value given by the muonic method, -220(15) mbarn, although the error bars are superimposed.
Electric quadrupole transition probabilities for atomic lithium
Çelik, Gültekin; Gökçe, Yasin; Yıldız, Murat
2014-05-15
Electric quadrupole transition probabilities for atomic lithium have been calculated using the weakest bound electron potential model theory (WBEPMT). We have employed numerical non-relativistic Hartree–Fock wavefunctions for expectation values of radii and the necessary energy values have been taken from the compilation at NIST. The results obtained with the present method agree very well with the Coulomb approximation results given by Caves (1975). Moreover, electric quadrupole transition probability values not existing in the literature for some highly excited levels have been obtained using the WBEPMT.
Nuclear quadrupole resonance studies in semi-metallic structures
NASA Technical Reports Server (NTRS)
Murty, A. N.
1974-01-01
Both experimental and theoretical studies are presented on spectrum analysis of nuclear quadrupole resonance of antimony and arsenic tellurides. Numerical solutions for secular equations of the quadrupole interaction energy are also discussed.
Design of large aperture superferric quadrupole magnets for an in-flight fragment separator
NASA Astrophysics Data System (ADS)
Zaghloul, Aziz; Kim, Dogyun; Kim, Jangyoul; Kim, Mijung; Kim, Myeongjin; Yun, Chongcheoul; Kim, Jongwon
2014-01-01
Superferric quadrupole magnets to be used for in-flight fragment separator have been designed. A quadrupole magnet triplet for beam focusing is placed in a cryostat together with superconducting correction coils. To maximize acceptance of rare isotope beams produced by projectile fragmentation, it is essential to use large-aperture quadrupole magnets. The pole tip radius is 17 cm in the current design, and we tried to enlarge the aperture with 3D analysis on magnetic fields. In the front end of the separator, where a target and beam dump are located, we plan to use two sets of quadrupole triplets made of high-Tc superconductor (HTS) operating at 20-50 K considering high radiation heat load. The HTS magnet will use warm iron poles. Both low-Tc and high-Tc superconductors are acquired for test winding, and two kinds of dewar and cryostat are under construction to perform the coil and magnet tests. The magnetic design of superferric quadrupole is mainly discussed.
Design of large aperture superferric quadrupole magnets for an in-flight fragment separator
Zaghloul, Aziz; Kim, Dogyun; Kim, Jangyoul; Kim, Mijung; Kim, Myeongjin; Yun, Chongcheoul; Kim, Jongwon
2014-01-29
Superferric quadrupole magnets to be used for in-flight fragment separator have been designed. A quadrupole magnet triplet for beam focusing is placed in a cryostat together with superconducting correction coils. To maximize acceptance of rare isotope beams produced by projectile fragmentation, it is essential to use large-aperture quadrupole magnets. The pole tip radius is 17 cm in the current design, and we tried to enlarge the aperture with 3D analysis on magnetic fields. In the front end of the separator, where a target and beam dump are located, we plan to use two sets of quadrupole triplets made of high-Tc superconductor (HTS) operating at 20-50 K considering high radiation heat load. The HTS magnet will use warm iron poles. Both low-Tc and high-Tc superconductors are acquired for test winding, and two kinds of dewar and cryostat are under construction to perform the coil and magnet tests. The magnetic design of superferric quadrupole is mainly discussed.
NASA Astrophysics Data System (ADS)
Qin, Hong; Davidson, Ronald C.; Burby, Joshua W.; Chung, Moses
2014-04-01
The dynamics of charged particles in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy is parametrized using a generalized Courant-Snyder (CS) theory, which extends the original CS theory for one degree of freedom to higher dimensions. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D symplectic rotation, or a U(2) element. The 1D envelope equation, also known as the Ermakov-Milne-Pinney equation in quantum mechanics, is generalized to an envelope matrix equation in higher dimensions. Other components of the original CS theory, such as the transfer matrix, Twiss functions, and CS invariant (also known as the Lewis invariant) all have their counterparts, with remarkably similar expressions, in the generalized theory. The gauge group structure of the generalized theory is analyzed. By fixing the gauge freedom with a desired symmetry, the generalized CS parametrization assumes the form of the modified Iwasawa decomposition, whose importance in phase space optics and phase space quantum mechanics has been recently realized. This gauge fixing also symmetrizes the generalized envelope equation and expresses the theory using only the generalized Twiss function β. The generalized phase advance completely determines the spectral and structural stability properties of a general focusing lattice. For structural stability, the generalized CS theory enables application of the Krein-Moser theory to greatly simplify the stability analysis. The generalized CS theory provides an effective tool to study coupled dynamics and to discover more optimized lattice designs in the larger parameter space of general focusing lattices.
Qin, Hong; Davidson, Ronald C.; Burby, Joshua W.; Chung, Moses
2014-04-08
The dynamics of charged particles in general linear focusing lattices with quadrupole, skew-quadrupole, dipole, and solenoidal components, as well as torsion of the fiducial orbit and variation of beam energy is parametrized using a generalized Courant-Snyder (CS) theory, which extends the original CS theory for one degree of freedom to higher dimensions. The envelope function is generalized into an envelope matrix, and the phase advance is generalized into a 4D symplectic rotation, or a Uð2Þ element. The 1D envelope equation, also known as the Ermakov-Milne-Pinney equation in quantum mechanics, is generalized to an envelope matrix equation in higher dimensions. Other components of the original CS theory, such as the transfer matrix, Twiss functions, and CS invariant (also known as the Lewis invariant) all have their counterparts, with remarkably similar expressions, in the generalized theory. The gauge group structure of the generalized theory is analyzed. By fixing the gauge freedom with a desired symmetry, the generalized CS parametrization assumes the form of the modified Iwasawa decomposition, whose importance in phase space optics and phase space quantum mechanics has been recently realized. This gauge fixing also symmetrizes the generalized envelope equation and expresses the theory using only the generalized Twiss function β. The generalized phase advance completely determines the spectral and structural stability properties of a general focusing lattice. For structural stability, the generalized CS theory enables application of the Krein-Moser theory to greatly simplify the stability analysis. The generalized CS theory provides an effective tool to study coupled dynamics and to discover more optimized lattice designs in the larger parameter space of general focusing lattices.
Skew And Twist Resistant Hydrodynamic Rotary Shaft Seal
Dietle, Lannie; Kalsi, Manmohan Singh
2000-03-14
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. Compared to prior art, this invention provides a dramatic reduction of seal and shaft wear in abrasive environments and provides a significant increase in seal life.
Wigner-Yanase skew information as tests for quantum entanglement
Chen Zeqian
2005-05-15
A Bell-type inequality is proposed in terms of Wigner-Yanase skew information, which is quadratic and involves only one local spin observable at each site. This inequality presents a hierarchic classification of all states of multipartite quantum systems from separable to fully entangled states, which is more powerful than the one presented by quadratic Bell inequalities from two-entangled to fully entangled states. In particular, it is proved that the inequality provides an exact test to distinguish entangled from nonentangled pure states of two qubits. Our inequality sheds considerable light on relationships between quantum entanglement and information theory.
Effect of Resonator Axis Skew on Normal Incidence Impedance
NASA Technical Reports Server (NTRS)
Parrott, Tony L.; Jones, Michael G.; Homeijer, Brian
2003-01-01
High by-pass turbofan engines have fewer fan blades and lower rotation speeds than their predecessors. Consequently, the noise suppression at the low frequency end of the noise spectra has become an increasing concern. This has led to a renewed emphasis on improving noise suppression efficiency of passive, duct liner treatments at the lower frequencies. For a variety of reasons, passive liners are comprised of locally-reacting, resonant absorbers. One reason for this design choice is to satisfy operational and economic requirements. The simplest liner design consists of a single layer of honeycomb core sandwiched between a porous facesheet and an impervious backing plate. These resonant absorbing structures are integrated into the nacelle wall and are very ef- ficient over a limited bandwidth centered on their resonance frequency. Increased noise suppression bandwidth and greater suppression at lower frequencies is typically achieved for conventional liners by increasing the liner depth and incorporating thin porous septa into the honeycomb core. However, constraints on liner depth in modern high by-pass engine nacelles severely limit the suppression bandwidth extension to lower frequencies. Also, current honeycomb core liners may not be suitable for irregular geometric volumes heretofore not considered. It is of interest, therefore, to find ways to circumvent liner depth restrictions and resonator cavity shape constraints. One way to increase effective liner depth is to skew the honeycomb core axis relative to the porous facesheet surface. Other possibilities are to alter resonator cavity shape, e.g. high aspect ratio, narrow channels that possibly include right angle bends, 180. channel fold-backs, and splayed channel walls to conform to irregular geometric constraints. These possibilities constitute the practical motivation for expanding impedance modeling capability to include unconventional resonator orientations and shapes. The work reported in this paper is
Closed orbit response to quadrupole strength variation
Wolski, Andrzej; Zimmermann, Frank
2004-01-20
We derive two formulae relating the variation in closed orbit in a storage ring to variations in quadrupole strength, neglecting nonlinear and dispersive effects. These formulae correct results previously reported [1,2,3]. We compare the results of the formulae applied to the ATF with simulations using MAD, and consider their application to beam-based alignment.
Tevatron low-beta quadrupole triplet interconnects
Oleck, A.R.; Carson, J.A.; Koepke, K.; Sorenson, D.
1992-04-01
Installation of cold iron quadrupole magnets in the Low Beta (Superconducting High-Luminosity) upgrade at Fermilab required a newly designed magnet interconnect. The interconnect design and construction experience is presented. Considered are the connections carrying cryogenic fluids, beam vacuum, insulating vacuum, superconducting bus leads, their insulation and mechanical support. Details of the assembly and assembly experience are presented. 2 refs.
Design of general apochromatic drift-quadrupole beam lines
NASA Astrophysics Data System (ADS)
Lindstrøm, C. A.; Adli, E.
2016-07-01
Chromatic errors are normally corrected using sextupoles in regions of large dispersion. In low emittance linear accelerators, use of sextupoles can be challenging. Apochromatic focusing is a lesser-known alternative approach, whereby chromatic errors of Twiss parameters are corrected without the use of sextupoles, and has consequently been subject to renewed interest in advanced linear accelerator research. Proof of principle designs were first established by Montague and Ruggiero and developed more recently by Balandin et al. We describe a general method for designing drift-quadrupole beam lines of arbitrary order in apochromatic correction, including analytic expressions for emittance growth and other merit functions. Worked examples are shown for plasma wakefield accelerator staging optics and for a simple final focus system.
NASA Astrophysics Data System (ADS)
Murphy, Andrew; Aref, Thomas; Coskun, Ulas; Weinberg, Phillip; Levchenko, Alex; Vakaryuk, Victor; Bezryadin, Alexey
2013-03-01
We study statistical properties of the switching current in superconductor-graphene-superconductor proximity junctions and superconductor-nanowire-superconductor devices. The fluctuations of the switching current are related to Little's phase slips, generated by thermal and quantum fluctuations of the superconducting order parameter. The study focuses on higher moments of the statistical probability distributions of the switching current. Namely we study the skewness, which defines the asymmetry of the distribution, and kurtosis, which is a measure of the ``peakedness.'' The skewness is defined as sk= m3 /m23 / 2 where m2 is the second moment of the distribution, called the variance, and m3 is the third moment. Kurtosis is defined as kur= m4 /m22 , where m4 is the fourth moment of the distribution. It is known that for Gaussian distributions sk=0 and kur=3. On our devices we find, in most cases, sk ~ -1 and kur ~ 5. These results are in agreement with numerical simulations as well as an analytic model. Finally we present preliminary experimental results for a two-nanowire device. We have found that the standard deviation, skewness and kurtosis of the switching current distributions in these devices vary periodically with magnetic field.
Pattern formation of underwater sand ripples with a skewed drive.
Bundgaard, F; Ellegaard, C; Scheibye-Knudsen, K; Bohr, T; Sams, T
2004-12-01
In this paper we present an experimental study of the dynamics of underwater sand ripples when a regular pattern of ripples is subjected to a skewed oscillatory flow, i.e., one not perpendicular to the direction of the ripple crests. Striking patterns with new, superposed ripples on top of the original ones occur very quickly with a characteristic angle, which is, in general, not perpendicular to the flow. A slower, more complex transition then follows, leading to the final state where the ripples are again perpendicular to the flow. We investigate the variation of the superposed pattern as a function of the direction, amplitude, and frequency of the drive, and as a function of the viscosity (by changing the temperature). We quantify the dynamics of the entire transition process and finally study the grain motion around idealized (solid) skewed ripples. This leads to a characteristic mean path of a single particle. The path has a shape close to a parallelogram, with no apparent connection to the pattern of real, superposed ripples. On the other hand, a thin layer of sand sprinkled on the solid ripples leads to qualitatively similar patterns.
Characterising Uncertainty in Expert Assessments: Encoding Heavily Skewed Judgements
O’Leary, Rebecca A.; Low-Choy, Samantha; Fisher, Rebecca; Mengersen, Kerrie; Caley, M. Julian
2015-01-01
When limited or no observed data are available, it is often useful to obtain expert knowledge about parameters of interest, including point estimates and the uncertainty around these values. However, it is vital to elicit this information appropriately in order to obtain valid estimates. This is particularly important when the experts’ uncertainty about these estimates is strongly skewed, for instance when their best estimate is the same as the lowest value they consider possible. Also this is important when interest is in the aggregation of elicited values. In this paper, we compare alternative distributions for describing such estimates. The distributions considered include the lognormal, mirror lognormal, Normal and scaled Beta. The case study presented here involves estimation of the number of species in coral reefs, which requires eliciting counts within broader taxonomic groups, with highly skewed uncertainty estimates. This paper shows substantial gain in using the scaled Beta distribution, compared with Normal or lognormal distributions. We demonstrate that, for this case study on counting species, applying the novel encoding methodology developed in this paper can facilitate the acquisition of more rigorous estimates of (hierarchical) count data and credible bounds. The approach can also be applied to the more general case of enumerating a sampling frame via elicitation. PMID:26517835
Multiple mating and reproductive skew in Trinidadian guppies.
Becher, S. A.; Magurran, A. E.
2004-01-01
Male offspring production in promiscuously mating species is typically more skewed than female offspring production. It is therefore advantageous for males to seek as many mating partners as possible. However, given the documented benefits of polyandry we expect females, as well as males, to mate multiply. We tested these ideas using Trinidadian guppies, Poecilia reticulata. Fishes were collected from the wild, housed in groups of 10 males and 10 females and allowed to reproduce freely over a period of three months. We used hypervariable microsatellite loci to identify the parents of 840 offspring and to quantify the variance in mating success. As anticipated, and in line with the Bateman gradient, there was greater skew in the number of progeny produced by males. By contrast, we found no sex difference in mating partner number over the duration of the experiment. A median of two males fathered each brood and there was marked turnover in the identities of the sires of successive broods. Female partner turnover was, however, less than expected under random mating. We suggest that partner switching over time, as well as polyandry within broods, could contribute to the maintenance of genetic diversity in guppy populations. PMID:15293853
Experimental and finite element studies on free vibration of skew plates
NASA Astrophysics Data System (ADS)
Srinivasa, C. V.; Suresh, Y. J.; Prema Kumar, W. P.
2014-03-01
The present paper deals with the experimental and finite element studies carried out on free vibration of isotropic and laminated composite skew plates. The natural frequencies were determined using CQUAD8 finite element of MSC/NASTRAN and comparison made between the experimental values and the finite element solution. The effects of the skew angle and aspect ratio on the natural frequencies of isotropic skew plates were studied. The effects of skew angle, aspect ratio, fiber orientation angle and laminate stacking sequence (keeping total number of layers in the laminate constant) on the natural frequencies of antisymmetric laminated composite skew plates were also studied. The experimental values of the natural frequencies are in good agreement with the finite element solution. The natural frequencies generally increase with an increase in the skew angle for any given value of aspect ratio.
Performance of Nb3Sn Quadrupole Under High Stress
Felice, H.; Bajko, M.; Bingham, B.; Bordini, B.; Bottura, L.; Caspi, S.; Rijk, G. De; Dietderich, D.; Ferracin, P.; Giloux, C.; Godeke, A.; Hafalia, R.; Milanese, A.; Rossi, L.; Sabbi, G. L.
2010-08-01
Future upgrades of the Large Hadron Collider (LHC) will require large aperture and high gradient quadrupoles. Nb{sub 3}Sn is the most viable option for this application but is also known for its strain sensitivity. In high field magnets, with magnetic fields above 12 T, the Lorentz forces will generate mechanical stresses that may exceed 200 MPa in the windings. The existing measurements of critical current versus strain of Nb{sub 3}Sn strands or cables are not easily applicable to magnets. In order to investigate the impact of high mechanical stress on the quench performance, a series of tests was carried out within a LBNL/CERN collaboration using the magnet TQS03 (a LHC Accelerator Research Program (LARP) 1-meter long, 90-mm aperture Nb{sub 3}Sn quadrupole). The magnet was tested four times at CERN under various pre-stress conditions. The average mechanical compressive azimuthal pre-stress on the coil at 4.2 K ranged from 120 MPa to 200 MPa. This paper reports on the magnet performance during the four tests focusing on the relation between pre-stress conditions and the training plateau.
VIBRATION MEASUREMENTS IN A RHIC QUADRUPOLE AT CRYOGENIC TEMPERATURES.
JAIN, A.; AYDIN, S.; HE, P.; ANERELLA, M.; GANETIS, G.; HARRISON, M.; PARKER, B.; PLATE, S.
2005-10-17
One of the concerns in using compact superconducting magnets in the final focus region of the ILC is the influence of the cryogen flow on the vibration characteristics. As a first step towards characterizing such motion at nanometer levels, a project was undertaken at BNL to measure the vibrations in a spare RHIC quadrupole under cryogenic conditions. Given the constraints of cryogenic operation, and limited space available, it was decided to use a dual head laser Doppler vibrometer for this work. The performance of the laser vibrometer was tested in a series of room temperature tests and compared with results from Mark L4 geophones. The laser system was then used to measure the vibration of the cold mass of the quadrupole with respect to the outside warm enclosure. These measurements were carried out both with and without the flow of cold helium through the magnet. The results indicate only a minor increase in motion in the horizontal direction (where the cold mass is relatively free to move).
Bandyopadhyay, Dipankar; Lachos, Victor H.; Castro, Luis M.; Dey, Dipak K.
2012-01-01
Often in biomedical studies, the routine use of linear mixed-effects models (based on Gaussian assumptions) can be questionable when the longitudinal responses are skewed in nature. Skew-normal/elliptical models are widely used in those situations. Often, those skewed responses might also be subjected to some upper and lower quantification limits (viz. longitudinal viral load measures in HIV studies), beyond which they are not measurable. In this paper, we develop a Bayesian analysis of censored linear mixed models replacing the Gaussian assumptions with skew-normal/independent (SNI) distributions. The SNI is an attractive class of asymmetric heavy-tailed distributions that includes the skew-normal, the skew-t, skew-slash and the skew-contaminated normal distributions as special cases. The proposed model provides flexibility in capturing the effects of skewness and heavy tail for responses which are either left- or right-censored. For our analysis, we adopt a Bayesian framework and develop a MCMC algorithm to carry out the posterior analyses. The marginal likelihood is tractable, and utilized to compute not only some Bayesian model selection measures but also case-deletion influence diagnostics based on the Kullback-Leibler divergence. The newly developed procedures are illustrated with a simulation study as well as a HIV case study involving analysis of longitudinal viral loads. PMID:22685005
NASA Astrophysics Data System (ADS)
Liu, Yufang; Zhang, Weiguo; Fu, Junhui
2016-11-01
This paper presents the Binomial Markov-switching Multifractal (BMSM) model of asset returns with Skewed t innovations (BMSM-Skewed t for short), which considers the fat tails, skewness and multifractality in asset returns simultaneously. The parameters of BMSM-Skewed t model can be estimated by Maximum Likelihood (ML) methods, and volatility forecasting can be accomplished via Bayesian updating. In order to evaluate the performance of BMSM-Skewed t model, BMSM model with Normal innovations (BMSM-N), BMSM model with Student-t innovations (BMSM-t) and GARCH(1,1) models (GARCH-N, GARCH-t and GARCH-Skewed t) are chosen for comparison. Through empirical studies on Shanghai Stock Exchange Composite Index (SSEC), we find that for sample estimation, BMSM models outperform the GARCH(1,1) models through BIC and AIC rules, and BMSM-Skewed t performs the best among all the models due to its fat tails, skewness and multifractality. In addition, BMSM-Skewed t model dominates other models at most forecasting horizons for out-of-sample volatility forecasts in terms of MSE, MAE and SPA test.
Skewness and shock formation in laboratory-scale supersonic jet data.
Gee, Kent L; Neilsen, Tracianne B; Atchley, Anthony A
2013-06-01
Spatial properties of noise statistics near unheated, laboratory-scale supersonic jets yield insights into source characteristics and near-field shock formation. Primary findings are (1) waveforms with positive pressure skewness radiate from the source with a directivity upstream of maximum overall level and (2) skewness of the time derivative of the pressure waveforms increases significantly with range, indicating formation of shocks during propagation. These results corroborate findings of a previous study involving full-scale engine data. Further, a comparison of ideally and over-expanded laboratory data show that while derivative skewness maps are similar, waveform skewness maps are substantially different for the two cases. PMID:23742445
O'Connell, Megan E; Tuokko, Holly; Kadlec, Helena
2011-04-01
Demographic corrections for cognitive tests should improve classification accuracy by reducing age or education biases, but empirical support has been equivocal. Using a simulation procedure, we show that creating moderate or extreme skewness in cognitive tests compromises the classification accuracy of demographic corrections, findings that appear replicated within clinical data for the few neuropsychological test scores with an extreme degree of skew. For most neuropsychological tests, the dementia classification accuracy of raw and demographically corrected scores was equivalent. These findings suggest that the dementia classification accuracy of demographic corrections is robust to slight degrees of skew (i.e., skewness <1.5). PMID:21154077
NASA Astrophysics Data System (ADS)
Meier, J.; Bleile, A.; Ceballos Velasco, J.; Fischer, E.; Hess, G.; Macavei, J.; Spiller, P.
2015-12-01
The FAIR project (Facility for Antiproton and Ion Research) evolves and builds an international accelerator- and experimental facility for basic research activities in various fields of modern physics. Within the course of this project, integrated quadrupole doublet modules are in development. The quadrupole doublet modules provide a pair of superconducting main quadrupoles (focusing and defocusing), corrector magnets, cryogenic collimators and beam position monitors as integrated sets of ion-optical elements. Furthermore LHe cooled beam pipes and vacuum cold-warm transitions are used as ultra-high vacuum components for beam transportation. Superconducting bus bars are used for 13 kA current supply of the main quadrupole magnets. All components are integrated as one common cold mass into one cryostat. High temperature super conductor local current leads will be applied for the low current supply of corrector magnets. The quadrupole doublet modules will be operated in the SIS100 heavy ion accelerator, the core component of the FAIR project. A first version of a corrector magnet has already been manufactured at the Joint Institute for Nuclear Research (JINR), Russia, and is now ready for testing. The ion-optical lattice structure of SIS100 requires multiple configurations of named components. Eleven different configurations, organized in four categories, provide the required quadrupole doublet module setups. The high integration level of multiple ion-optical, mechanical and cryogenic functions, based on requirements of operation safety, is leading towards a sophisticated mechanical structure and cooling solution, to satisfy the demanding requirements on position preservation during thermal cycling. The mechanical and cryogenic design solutions will be discussed.
Bifacial Metasurface with Quadrupole Optical Response
NASA Astrophysics Data System (ADS)
Shevchenko, Andriy; Kivijärvi, Ville; Grahn, Patrick; Kaivola, Matti; Lindfors, Klas
2015-08-01
We design, fabricate, and characterize a metasurface, whose multipole optical response depends significantly on the illumination direction. The metasurface is composed of gold-nanodisc dimers embedded in glass. In spite of their nanoscale size, the dimers exhibit a dominating electric-current-quadrupole response in a wide range of wavelengths around 700 nm when illuminated from one side, and a primarily electric-dipole response when illuminated from the opposite side. This leads to two consequences. First, the reflection coefficient of the metasurface considerably differs for the two sides of illumination. Second, quadrupole excitation results in a significant local enhancement of both electric and magnetic fields around the dimers. Our experimental spectroscopic data are in good agreement with simulations obtained using a multipole expansion model.
LARP Long Nb3Sn Quadrupole Design
Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S.; Chlachidize, G.; Dietderich, D.; Feher, S.; Ferracin, P.; Ghosh, A.; Hafalia, R.; Hannaford, R.; Kashikhin, V.V.; Kerby, J.; Lamm, M.; Lietzke, A.; McInturff, A.; Muratore, J.; Nobrega, F.; Novitsky, I.; Sabbi, G.L.; Schmalzle, J.; Tartaglia, M.; Turrioni, D.; Wanderer, P.; Whitson, G.; Zlobin, A.V.
2008-06-01
A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb{sub 3}Sn conductor. The goal of these magnets is to be a proof of principle that Nb{sub 3}Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.
LARP Long Nb3Sn Quadrupole Design
Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S.; Chlachidze, G.; Dietderich, D.; Feher, S.; Felice, H.; Ferracin, P.; /Fermilab /Brookhaven /LBL, Berkeley /Texas A-M
2007-08-01
A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb3Sn conductor. The goal of these magnets is to be a proof of principle that Nb3Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.
15 T And Beyond - Dipoles and Quadrupoles
Sabbi, GianLuca
2008-05-19
Starting with the invention of the cyclotron by Lawrence, accelerator-based experiments have been the primary source of new discoveries in particle physics. In order to progress toward higher energy and luminosity, higher field magnets are required. R&D programs are underway to take advantage of new developments in superconducting materials, achieve better efficiency and simplify magnet fabrication while preserving accelerator-class field quality. A review of recent progress on high field dipole and quadrupole magnets is presented.
LHC INTERACTION REGION QUADRUPOLE ERROR IMPACT STUDIES
FISCHER,W.; PTITSIN,V.; WEI,J.
1999-09-07
The performance of the Large Hadron Collider (LHC) at collision energy is limited by the field quality of the interaction region (IR) quadrupoles and dipoles. In this paper the authors study the impact of the expected field errors of these magnets on the dynamic aperture. The authors investigate different magnet arrangements and error strength. Based on the results they propose and evaluate a corrector layout to meet the required dynamic aperture performance in a companion paper.
Table of nuclear electric quadrupole moments
NASA Astrophysics Data System (ADS)
Stone, N. J.
2016-09-01
This Table is a compilation of experimental measurements of static electric quadrupole moments of ground states and excited states of atomic nuclei throughout the periodic table. To aid identification of the states, their excitation energy, half-life, spin and parity are given, along with a brief indication of the method and any reference standard used in the particular measurement. Experimental data from all quadrupole moment measurements actually provide a value of the product of the moment and the electric field gradient [EFG] acting at the nucleus. Knowledge of the EFG is thus necessary to extract the quadrupole moment. A single recommended moment value is given for each state, based, for each element, wherever possible, upon a standard reference moment for a nuclear state of that element studied in a situation in which the electric field gradient has been well calculated. For several elements one or more subsidiary EFG/moment reference is required and their use is specified. The literature search covers the period to mid-2015.
Cracked shells under skew-symmetric loading. [Reissner theory
NASA Technical Reports Server (NTRS)
Delale, F.
1981-01-01
The general problem of a shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and anti-plane elasticity solutions. Results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform in-plane shearing, out of plane shearing, and torsion. The problem is formulated for specially orthostropic materials, therefore, the effect of orthotropy on the results is also studied.
Soft bounds on diffusion produce skewed distributions and Gompertz growth.
Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco
2014-09-01
Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.
Soft bounds on diffusion produce skewed distributions and Gompertz growth
NASA Astrophysics Data System (ADS)
Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco
2014-09-01
Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.
Ultra-High Energy Cosmic Rays: Composition, Early Air Shower Interactions, and Xmax Skewness
NASA Astrophysics Data System (ADS)
Stapleton, James
The composition of Ultra-High Energy Cosmic Rays (UHECRs) is still not completely understood, and must be inferred from Extended Air Shower (EAS), particle cascades which they initiate upon entering the atmosphere. The atmospheric depth at which the shower contains the maximum number of particles ( Xmax) is the most composition-sensitive property of the air shower, but its interpretation is hindered by intrinsic statistical fluctuations in EAS development which cause distinct compositions to produce overlapping Xmax distributions as well as our limited knowledge at these energies of hadronic physics which strongly impacts the Xmax distribution's shape. These issues ultimately necessitate a variety of complementary approaches to interpreting UHECR composition from Xmax data. The current work advances these approaches by connecting X max skewness to the uncertainties above. The study of X max has historically focused only on the mean and standard deviation of its distribution, but skewness is shown here to be strongly related to both the statistical fluctuations in EAS development as well as the least-understood hadronic cross-sections in the air shower. This leads into a treatment of the Exponentially-Modified Gaussian (EMG) distribution, whose little-known properties make it very useful for Xmax analysis and for data analysis in general. A powerful method emerges which uses only descriptive statistics in a robust check for energy-dependent changes in UHECR mass or EAS development. The application of these analyses to X max data provides tantalizing clues concerning issues of critical importance, such as the relationship between Xmax and the 'ankle' break in the UHECR energy spectrum, or the inferred properties of the UHECR mass distribution and its strong dependence on hadronic model systematics.
Super Strong Permanent Magnet Quadrupole for a Linear Collider
Mihara, Takanori
2004-02-19
The field strength generated by permanent magnets has been further extended by the introduction of saturated iron. A permanent magnet quadrupole (PMQ) lens with such saturated iron is one of the candidates for the final focus lens for an e{sup +}e{sup -} Linear Collider accelerator, because of its compactness and low power consumption. The first prototype of the PMQ has been fabricated and demonstrated to have an integrated strength of 28.5T with an overall length of 10 cm and a 7mm bore radius. Two drawbacks should be considered: its negative temperature coefficient of field strength and its fixed strength. A thermal compensation material is being tested to cure the first problem. The other problem may be solved by rotating sectioned magnet bricks, but that may lead to movement of the magnetic center and introduction of multipoles beyond some strict requirements.
Massive higher spin states in string theory and gravitational quadrupoles
Giannakis, I. |; Liu, J.T.; Porrati, M. ||
1999-05-01
In this paper we study three point functions of the type II superstring involving one graviton and two massive states, focusing in particular on the spin- (7) /(2) fermions at the first mass level. Defining a gravitational quadrupole {open_quotes}{ital h} factor,{close_quotes} we find that the nonminimal interactions of string states in general are parametrized by h{ne}1, in contrast with the preferred field theory value of h=1 (for tree-level unitarity). This difference arises from the fact that consistent gravitational interactions of strings are related to the presence of a complete tower of massive states, not present in the ordinary field theory case. {copyright} {ital 1999} {ital The American Physical Society}
Photoassociation of a cold-atom-molecule pair: Long-range quadrupole-quadrupole interactions
Lepers, M.; Dulieu, O.; Kokoouline, V.
2010-10-15
The general formalism of the multipolar expansion of electrostatic interactions is applied to the calculation of the potential energy between an excited atom (without fine structure) and a ground-state diatomic molecule at large mutual separations. Both partners exhibit a permanent quadrupole moment so that their mutual long-range interaction is dominated by a quadrupole-quadrupole term, which is attractive enough to bind trimers. Numerical results are given for an excited Cs(6{sup 2}P) atom and a ground-state Cs{sub 2} molecule. The prospects for achieving photoassociation of a cold-atom-dimer pair are thus discussed and found promising. The formalism can be generalized to the long-range interaction between molecules to investigate the formation of cold tetramers.
GC skew is a conserved property of unmethylated CpG island promoters across vertebrates
Hartono, Stella R.; Korf, Ian F.; Chédin, Frédéric
2015-01-01
GC skew is a measure of the strand asymmetry in the distribution of guanines and cytosines. GC skew favors R-loops, a type of three stranded nucleic acid structures that form upon annealing of an RNA strand to one strand of DNA, creating a persistent RNA:DNA hybrid. Previous studies show that GC skew is prevalent at thousands of human CpG island (CGI) promoters and transcription termination regions, which correspond to hotspots of R-loop formation. Here, we investigated the conservation of GC skew patterns in 60 sequenced chordates genomes. We report that GC skew is a conserved sequence characteristic of the CGI promoter class in vertebrates. Furthermore, we reveal that promoter GC skew peaks at the exon 1/ intron1 junction and that it is highly correlated with gene age and CGI promoter strength. Our data also show that GC skew is predictive of unmethylated CGI promoters in a range of vertebrate species and that it imparts significant DNA hypomethylation for promoters with intermediate CpG densities. Finally, we observed that terminal GC skew is conserved for a subset of vertebrate genes that tend to be located significantly closer to their downstream neighbors, consistent with a role for R-loop formation in transcription termination. PMID:26253743
Assessment of seismic performance of skew reinforced concrete box girder bridges
NASA Astrophysics Data System (ADS)
Abdel-Mohti, Ahmed; Pekcan, Gokhan
2013-12-01
The seismic vulnerability of highway bridges remains an important problem and has received increased attention as a consequence of unprecedented damage observed during several major earthquakes. A significant number of research studies have examined the performance of skew bridges under service and seismic loads. The results of these studies are particularly sensitive to modeling assumptions in view of the interacting parameters. In the present study, three-dimensional improved beam-stick models of two-span highway bridges with skew angles varying from 0° to 60° are developed to investigate the seismic response characteristics of skew box girder bridges. The relative accuracy of beam-stick models is verified against counterpart finite element models. The effect of various parameters and conditions on the overall seismic response was examined such as skew angle, ground motion intensity, soil condition, abutment support conditions, bridge aspect ratio, and foundation-base conditions. The study shows that the improved beam-stick models can be used to conduct accurate nonlinear time history analysis of skew bridges. Skew angle and interacting parameters were found to have significant effect on the behavior of skewed highway bridges. Furthermore, the performance of shear keys may have a predominant effect on the overall seismic response of the skew bridges.
A proof for Rhiel's range estimator of the coefficient of variation for skewed distributions.
Rhiel, G Steven
2007-02-01
In this research study is proof that the coefficient of variation (CV(high-low)) calculated from the highest and lowest values in a set of data is applicable to specific skewed distributions with varying means and standard deviations. Earlier Rhiel provided values for d(n), the standardized mean range, and a(n), an adjustment for bias in the range estimator of micro. These values are used in estimating the coefficient of variation from the range for skewed distributions. The d(n) and an values were specified for specific skewed distributions with a fixed mean and standard deviation. In this proof it is shown that the d(n) and an values are applicable for the specific skewed distributions when the mean and standard deviation can take on differing values. This will give the researcher confidence in using this statistic for skewed distributions regardless of the mean and standard deviation.
Flexural Vibration Of Skew Mindlin Plates With Oblique Internal Line Supports
NASA Astrophysics Data System (ADS)
Xiang, Y.; Kitipornchai, S.; Liew, K. M.; Wang, C. M.
1994-12-01
A free vibration analysis of moderately thick skew plates with oblique internal line supports is presented. Mindlin's plate theory is employed and the pb -2 Rayleigh-Ritz method is applied to obtain the governing eigenvalue equation for internally supported skew plates. A set of natural frequencies for skew Mindlin plates with oblique internal line supports having different combinations of boundary conditions has been determined for various aspect ratios a/b, relative thickness ratios t/b and skew angles α. The validity of the approach is illustrated by comparing the results with other established values. From literature searches, it appears that no work has previously been done on the free vibration of moderately thick skew plates with oblique internal line supports. Thus this paper may provide some important information to designers and engineers for use in practical applications.
Electron Cloud Generation and Trapping in a Quadrupole Magnet at the Los Alamos Proton Storage Ring
Macek, Robert J.; Browman, Andrew A.; Ledford, John E.; Borden, Michael J.; O'Hara, James F.; McCrady, Rodney C.; Rybarcyk, Lawrence J.; Spickermann, Thomas; Zaugg, Thomas J.; Pivi, Mauro T.F.; /SLAC
2008-03-17
Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the 'prompt' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the 'swept' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to 100 {micro}s. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the quadrupole.
DESIGN OF A THIN QUADRUPOLE TO BE USED IN THE AGS SYNCHROTRON
TSOUPAS,N.; AHRENS, L.; ALFORQUE, R.; BAI, M.; BROWN, K.; COURANT, E.; ET AL.
2007-06-25
The Alternating Gradient Synchrotron (AGS) employs two partial helical snakes[l] to preserve the polarization of the proton beam during acceleration. In order to compensate for the focusing effect of the partial helical snakes on the beam optics in the AGS during acceleration of the beam, we introduced eight quadrupoles in straight sections of the AGS at the proximity of the partial snakes. At injection energies, the strength of each quad is set at a high value, and is ramped down to zero as the effect of the snakes diminishes by the square of beam's rigidity. Four of the eight compensation quadrupoles had to be placed in very short straight sections -30 cm in length, therefore the quadruples had be thin with an overall length of less than 30 cm. In this paper we will discus: (a) the mechanical and magnetic specifications of the ''thin'' quadrupole. (b) the method to minimize the strength of the dodecapole harmonic, (c) the method to optimize the thickness of the laminations that the magnet iron is made, (d) mechanical tolerances of the magnet, (e) comparison of the measured and calculated magnetic multipoles of the quadrupole.
Skewness of cloud droplet spectrum and an improved estimation for its relative dispersion
NASA Astrophysics Data System (ADS)
Liu, Yu; Lu, Chunsong; Li, Weiliang
2016-05-01
The relative dispersion of the cloud droplet spectrum is a very important parameter in describing and modeling cloud microphysical processes. Based on the definition of skewness as well as theoretical and data analyses, a linear fitting relationship (α = 2.91ɛ-0.59) between skewness (α) and relative dispersion (ɛ) is established and a new method is developed to estimate the relative dispersion of the cloud droplet spectrum. The new method does not depend on any assumption of a particular distribution for the cloud droplet spectrum and has broader applicability than the previous methods. Comparisons of the three methods for the relative dispersion with the observed data supported the following conclusions. (1) The skewness of the cloud droplet spectrum is asymmetrically distributed. An assumption of zero skewness in quantifying the relative dispersion inevitably results in relatively large deviations from the observations. Errors of the estimated relative dispersion due to the omission of the skewness term are not solely related to the skewness, but rather to the product of the skewness and relative dispersion. (2) The use of the assumption that the cloud droplet spectrum takes a gamma distribution is similar to the assumption that the skewness is twice the relative dispersion. This leads to a better accuracy in estimating the relative dispersion than that with zero skewness assumption. (3) Comparisons with observations show that the new method is more accurate than the one under gamma distribution assumption and is the best among all the three methods. (4) It is believed that finding a better correlation between the skewness and the relative dispersion would further reduce the deviations for the estimated relative dispersion.
Noise reduction in negative-ion quadrupole mass spectrometry
Chastagner, P.
1993-04-20
A quadrupole mass spectrometer (QMS) system is described having an ion source, quadrupole mass filter, and ion collector/recorder system. A weak, transverse magnetic field and an electron collector are disposed between the quadrupole and ion collector. When operated in negative ion mode, the ion source produces a beam of primarily negatively-charged particles from a sample, including electrons as well as ions. The beam passes through the quadrupole and enters the magnetic field, where the electrons are deflected away from the beam path to the electron collector. The negative ions pass undeflected to the ion collector where they are detected and recorded as a mass spectrum.
Noise reduction in negative-ion quadrupole mass spectrometry
Chastagner, Philippe
1993-01-01
A quadrupole mass spectrometer (QMS) system having an ion source, quadrupole mass filter, and ion collector/recorder system. A weak, transverse magnetic field and an electron collector are disposed between the quadrupole and ion collector. When operated in negative ion mode, the ion source produces a beam of primarily negatively-charged particles from a sample, including electrons as well as ions. The beam passes through the quadrupole and enters the magnetic field, where the electrons are deflected away from the beam path to the electron collector. The negative ions pass undeflected to the ion collector where they are detected and recorded as a mass spectrum.
Magnetic mirror structure for testing shell-type quadrupole coils
Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; Tartaglia, N.; Turrioni, D.; /Fermilab
2009-10-01
This paper presents magnetic and mechanical designs and analyses of the quadrupole mirror structure to test single shell-type quadrupole coils. Several quadrupole coils made of different Nb{sub 3}Sn strands, cable insulation and pole materials were tested using this structure at 4.5 and 1.9 K. The coils were instrumented with voltage taps, spot heaters, temperature sensors and strain gauges to study their mechanical and thermal properties and quench performance. The results of the quadrupole mirror model assembly and test are reported and discussed.
ANALYTICAL SOLUTIONS OF SINGULAR ISOTHERMAL QUADRUPOLE LENS
Chu Zhe; Lin, W. P.; Yang Xiaofeng E-mail: linwp@shao.ac.cn
2013-06-20
Using an analytical method, we study the singular isothermal quadrupole (SIQ) lens system, which is the simplest lens model that can produce four images. In this case, the radial mass distribution is in accord with the profile of the singular isothermal sphere lens, and the tangential distribution is given by adding a quadrupole on the monopole component. The basic properties of the SIQ lens have been studied in this Letter, including the deflection potential, deflection angle, magnification, critical curve, caustic, pseudo-caustic, and transition locus. Analytical solutions of the image positions and magnifications for the source on axes are derived. We find that naked cusps will appear when the relative intensity k of quadrupole to monopole is larger than 0.6. According to the magnification invariant theory of the SIQ lens, the sum of the signed magnifications of the four images should be equal to unity, as found by Dalal. However, if a source lies in the naked cusp, the summed magnification of the left three images is smaller than the invariant 1. With this simple lens system, we study the situations where a point source infinitely approaches a cusp or a fold. The sum of the magnifications of the cusp image triplet is usually not equal to 0, and it is usually positive for major cusps while negative for minor cusps. Similarly, the sum of magnifications of the fold image pair is usually not equal to 0 either. Nevertheless, the cusp and fold relations are still equal to 0 in that the sum values are divided by infinite absolute magnifications by definition.
Nuclear Quadrupole Resonance Studies in MICA
NASA Astrophysics Data System (ADS)
Sengupta, S.; Rhadakrishna, S.; Marino, R. A.
1986-02-01
Aluminum-27 NQR transitions were detected in Muscovite Mica at room temperature using double resonance by level crossing (DRLC) techniques. Three lines were observed with frequencies of 572.5, 1052.0, and 1624.5 kHz. These lines are assigned to the octahedrally coordinated site, AlO4(OH)2. The corresponding quadrupole coupling constant, e2q Q/h, and asymmetry parameter, η, are 3554.8 kHz and 0.265, respectively. The remaining tetrahedrally coordinated sites, AlO4, gave no discernible signal, perhaps due to the greater 27Al- 1H distance.
Multi-Pass Quadrupole Mass Analyzer
NASA Technical Reports Server (NTRS)
Prestage, John D.
2013-01-01
Analysis of the composition of planetary atmospheres is one of the most important and fundamental measurements in planetary robotic exploration. Quadrupole mass analyzers (QMAs) are the primary tool used to execute these investigations, but reductions in size of these instruments has sacrificed mass resolving power so that the best present-day QMA devices are still large, expensive, and do not deliver performance of laboratory instruments. An ultra-high-resolution QMA was developed to resolve N2 +/CO+ by trapping ions in a linear trap quadrupole filter. Because N2 and CO are resolved, gas chromatography columns used to separate species before analysis are eliminated, greatly simplifying gas analysis instrumentation. For highest performance, the ion trap mode is used. High-resolution (or narrow-band) mass selection is carried out in the central region, but near the DC electrodes at each end, RF/DC field settings are adjusted to allow broadband ion passage. This is to prevent ion loss during ion reflection at each end. Ions are created inside the trap so that low-energy particles are selected by low-voltage settings on the end electrodes. This is beneficial to good mass resolution since low-energy particles traverse many cycles of the RF filtering fields. Through Monte Carlo simulations, it is shown that ions are reflected at each end many tens of times, each time being sent back through the central section of the quadrupole where ultrahigh mass filtering is carried out. An analyzer was produced with electrical length orders of magnitude longer than its physical length. Since the selector fields are sized as in conventional devices, the loss of sensitivity inherent in miniaturizing quadrupole instruments is avoided. The no-loss, multi-pass QMA architecture will improve mass resolution of planetary QMA instruments while reducing demands on the RF electronics for high-voltage/high-frequency production since ion transit time is no longer limited to a single pass. The
Test results of Fermilab-built quadrupoles for the LHC interaction regions
Lamm, M.J.; Bossert, R.; DiMarco, J.; Feher, S.; Hocker, J.A.; Kerby, J.; Nobrega, F.; Novitski, I.; Rabehl, R.; Schlabach, P.; Strait, J.; /Fermilab
2006-06-01
As part of the US LHC Accelerator Project, Fermilab is nearing the completion of the Q2 optical elements for the LHC interaction region final focus. Each Q2 element (LQXB) consists of two identical high gradient quadrupoles (MQXB) with a dipole orbit corrector (MCBX). This paper summarizes the test results for the LQXB/MQXB program including quench performance, magnetic measurements and alignment, and gives the status of production and delivery of the LQXB magnets to the LHC.
A high gradient superconducting quadrupole for a low charge state ion linac
Kim, J.W.; Shepard, K.W.; Nolen, J.A.
1995-07-01
A superconducting quadrupole magnet has been designed for use as the focusing element in a low charge state linac proposed at Argonne. The expected field gradient is 350 T/m at an operating current of 53 A, and the bore diameter is 3 cm. The use of rare earth material holmium for pole tips provides about 10% more gradient then iron pole tips. The design and the status of construction of a prototype singlet magnet is described.
Skew redundant MEMS IMU calibration using a Kalman filter
NASA Astrophysics Data System (ADS)
Jafari, M.; Sahebjameyan, M.; Moshiri, B.; Najafabadi, T. A.
2015-10-01
In this paper, a novel calibration procedure for skew redundant inertial measurement units (SRIMUs) based on micro-electro mechanical systems (MEMS) is proposed. A general model of the SRIMU measurements is derived which contains the effects of bias, scale factor error and misalignments. For more accuracy, the effect of lever arms of the accelerometers to the center of the table are modeled and compensated in the calibration procedure. Two separate Kalman filters (KFs) are proposed to perform the estimation of error parameters for gyroscopes and accelerometers. The predictive error minimization (PEM) stochastic modeling method is used to simultaneously model the effect of bias instability and random walk noise on the calibration Kalman filters to diminish the biased estimations. The proposed procedure is simulated numerically and has expected experimental results. The calibration maneuvers are applied using a two-axis angle turntable in a way that the persistency of excitation (PE) condition for parameter estimation is met. For this purpose, a trapezoidal calibration profile is utilized to excite different deterministic error parameters of the accelerometers and a pulse profile is used for the gyroscopes. Furthermore, to evaluate the performance of the proposed KF calibration method, a conventional least squares (LS) calibration procedure is derived for the SRIMUs and the simulation and experimental results compare the functionality of the two proposed methods with each other.
Time Variations of Scour Below Submerged Skewed Pipelines
NASA Astrophysics Data System (ADS)
Yusoff, M. A. M.; Azamathulla, H. M.; Ghani, A. A.
2016-07-01
The presence of pipe across river initiates the piping effect combined with the stagnation eddy and vortex system in the vicinity of the pipeline. The main objective of the research is to investigate the physics of scour below skewed pipeline in river crossing as well as the time variations of the scour development. In this study, the experiments were conducted for four different angles of pipe (30°, 45°, 60° and 90°) across a channel and placed on the sediment bed with e/D = 0. The scour development for flow shallowness y/D = 3 and y/D = 4, initiated at downstream side of the pipe, where the bed sediment appeared to be ejected from the bed due to the piping effect process. At the initial stage, the scour process for 150mm flow depth enlarged rapidly. Whilst, the scour process for 200 mm flow depth slowly developed and after certain time, the sediment bed scoured rapidly. The scour depth increased considerably at development stage and the suspended load near the bed especially below the pipe decreased significantly compared to the initial stage. The rate of sediment eroded from the sediment bed decreased at the stabilization phase. The equilibrium phase of the scour depth considered achieved as the dimensions of the scour hole do not change significantly.
Abundant rich phase transitions in step-skew products
NASA Astrophysics Data System (ADS)
Díaz, L. J.; Gelfert, K.; Rams, M.
2014-09-01
We study phase transitions for the topological pressure of geometric potentials of transitive sets. The sets considered are partially hyperbolic having a step-skew product dynamics over a horseshoe with one-dimensional fibres corresponding to the central direction. The sets are genuinely non-hyperbolic, containing intermingled horseshoes of different hyperbolic, behaviour (contracting and expanding centre). We construct for every k ⩾ 1 a diffeomorphism F with a transitive set Λ as above such that the pressure map P(t) = P(t φ) of the potential \\varphi= -log \\,\\Vert \\rmd F|_{E^c}\\Vert (Ec the central direction) defined on Λ has k rich phase transitions. This means that there are parameters tℓ, ℓ = 0, …, k - 1, where P(t) is not differentiable and this lack of differentiability is due to the coexistence of two equilibrium states of tℓ φ with positive entropy and different Birkhoff averages. Each phase transition is associated with a gap in the central Lyapunov spectrum of F on Λ.
Regression for skewed biomarker outcomes subject to pooling.
Mitchell, Emily M; Lyles, Robert H; Manatunga, Amita K; Danaher, Michelle; Perkins, Neil J; Schisterman, Enrique F
2014-03-01
Epidemiological studies involving biomarkers are often hindered by prohibitively expensive laboratory tests. Strategically pooling specimens prior to performing these lab assays has been shown to effectively reduce cost with minimal information loss in a logistic regression setting. When the goal is to perform regression with a continuous biomarker as the outcome, regression analysis of pooled specimens may not be straightforward, particularly if the outcome is right-skewed. In such cases, we demonstrate that a slight modification of a standard multiple linear regression model for poolwise data can provide valid and precise coefficient estimates when pools are formed by combining biospecimens from subjects with identical covariate values. When these x-homogeneous pools cannot be formed, we propose a Monte Carlo expectation maximization (MCEM) algorithm to compute maximum likelihood estimates (MLEs). Simulation studies demonstrate that these analytical methods provide essentially unbiased estimates of coefficient parameters as well as their standard errors when appropriate assumptions are met. Furthermore, we show how one can utilize the fully observed covariate data to inform the pooling strategy, yielding a high level of statistical efficiency at a fraction of the total lab cost. PMID:24521420
Adiabatic Formation of a Matched-beam Distribution for an Alternating-gradient Quadrupole Lattice
Dorf, Mikhail A.; Davidson, Ronald C.; Startsev, Edward A.; Qin, Hong
2010-02-02
The formation of a quasiequilibrium beam distribution matched to an alternating-gradient quadrupole focusing lattice by means of the adiabatic turn-on of the oscillating focusing field is studied numerically using particle-in-cell simulations. Quiescent beam propagation over several hundred lattice periods is demonstrated for a broad range of beam intensities and vacuum phase advances describing the strength of the oscillating focusing field. Properties of the matched-beam distribution are investigated. In particular, self-similar evolution of the beam density profile is observed over a wide range of system parameters. The numerical simulations are performed using the WARP particle-in-cell code.
Field, J; Solís, C R; Queller, D C; Strassmann, J E
1998-06-01
Recent models postulate that the members of a social group assess their ecological and social environments and agree a "social contract" of reproductive partitioning (skew). We tested social contracts theory by using DNA microsatellites to measure skew in 24 cofoundress associations of paper wasps, Polistes bellicosus. In contrast to theoretical predictions, there was little variation in cofoundress relatedness, and relatedness either did not predict skew or was negatively correlated with it; the dominant/subordinate size ratio, assumed to reflect relative fighting ability, did not predict skew; and high skew was associated with decreased aggression by the rank 2 subordinate toward the dominant. High skew was associated with increased group size. A difficulty with measuring skew in real systems is the frequent changes in group composition that commonly occur in social animals. In P. bellicosus, 61% of egg layers and an unknown number of non-egg layers were absent by the time nests were collected. The social contracts models provide an attractive general framework linking genetics, ecology, and behavior, but there have been few direct tests of their predictions. We question assumptions underlying the models and suggest directions for future research.
Modulation of Root Skewing in Arabidopsis by Apyrases and Extracellular ATP.
Yang, Xingyan; Wang, Bochu; Farris, Ben; Clark, Greg; Roux, Stanley J
2015-11-01
When plant primary roots grow along a tilted surface that is impenetrable, they can undergo a slanted deviation from the direction of gravity called skewing. Skewing is induced by touch stimuli which the roots experience as they grow along the surface. Touch stimuli also induce the release of extracellular ATP (eATP) into the plant's extracellular matrix, and two apyrases (NTPDases) in Arabidopsis, APY1 and APY2, can help regulate the concentration of eATP. The primary roots of seedlings overexpressing APY1 show less skewing than wild-type plants. Plants suppressed in their expression of APY1 show more skewing than wild-type plants. Correspondingly, chemical inhibition of apyrase activity increased skewing in mutants and wild-type roots. Exogenous application of ATP or ATPγS also increased skewing in wild-type roots, which could be blocked by co-incubation with a purinergic receptor antagonist. These results suggest a model in which gradients of eATP set up by differential touch stimuli along roots help direct skewing in roots growing along an impenetrable surface.
Log Pearson type 3 quantile estimators with regional skew information and low outlier adjustments
Griffis, V.W.; Stedinger, J.R.; Cohn, T.A.
2004-01-01
[1] The recently developed expected moments algorithm (EMA) [Cohn et al., 1997] does as well as maximum likelihood estimations at estimating log-Pearson type 3 (LP3) flood quantiles using systematic and historical flood information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study compares the performance of Bulletin 17B using the entire sample with and without regional skew with estimators that use regional skew and censor low outliers, including an extended EMA estimator, the conditional probability adjustment (CPA) from Bulletin 17B, and an estimator that uses probability plot regression (PPR) to compute substitute values for low outliers. Estimators that neglect regional skew information do much worse than estimators that use an informative regional skewness estimator. For LP3 data the low outlier rejection procedure generally results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew are generally modest in the skewness range of real interest. Samples contaminated to model actual flood data demonstrate that estimators which give special treatment to low outliers significantly outperform estimators that make no such adjustment.
Bordered tug-of-war models are neither general nor predictive of reproductive skew.
Nonacs, Peter
2010-10-21
Models of reproductive skew assume reproductive shares are either conceded, competed over, or both. Previous mathematical evaluations found that simultaneous concessions and contests are evolutionarily unstable. Recently, Shen and Reeve (2010) challenged these conclusions and developed a series of sub-models they argued to be a unified approach to reproductive skew: the general bordered tug-of-war (BTOW). However, BTOW fails as a general model for two reasons: (1) the BTOW strategy cannot invade populations where individuals either only compete for or only concede reproductive shares and (2) contrary to Shen and Reeve's assertion, BTOW populations are easily invaded by strategies with fewer or no concessions, but competing at lower levels. The failure of BTOW as a general model has major implications for interpreting experiments on reproductive skew. A large number of studies have measured the effects of genetic relatedness and competitive ability on reproductive skew, with a great majority finding no significant correlation between variation in within-group relatedness or competitive ability and across-group differences in skew. No model of reproductive skew except one variant of the BTOW predicts such results. With the rejection of BTOW as a valid general model, it is clear that these results are contradictory to reproductive skew theory rather than supportive of it.
Explosives detection with quadrupole resonance analysis
NASA Astrophysics Data System (ADS)
Rayner, Timothy J.; Thorson, Benjamin D.; Beevor, Simon; West, Rebecca; Krauss, Ronald A.
1997-02-01
The increase in international terrorist activity over the past decade has necessitated the exploration of new technologies for the detection of plastic explosives. Quadrupole resonance analysis (QRA) has proven effective as a technique for detecting the presence of plastic, sheet, and military explosive compounds in small quantities, and can also be used to identify narcotics such as heroin and cocaine base. QRA is similar to the widely used magnetic resonance (MR) and magnetic resonance imaging (MRI) techniques, but has the considerable advantage that the item being inspected does not need to be immersed in a steady, homogeneous magnetic field. The target compounds are conclusively identified by their unique quadrupole resonance frequencies. Quantum magnetics has develop and introduced a product line of explosives and narcotics detection devices based upon QRA technology. The work presented here concerns a multi-compound QRA detection system designed to screen checked baggage, cargo, and sacks of mail at airports and other high-security facilities. The design philosophy and performance are discussed and supported by test results from field trials conducted in the United States and the United Kingdom. This detection system represents the current state of QRA technology for field use in both commercial and government sectors.
Quadrupole Polarizabilities in A ~150 Superdeformed Bands
NASA Astrophysics Data System (ADS)
Satula, Wojciech; Nazarewicz, Witold; Dobaczewski, Jacek; Dudek, Jerzy
1996-10-01
In this study, the quadrupole and hexadecapole moments of superdeformed (SD) bands in the A ~150 mass region have been analyzed in the cranking Skyrme-Hartree-Fock model. The analysis shows that the relative quadrupole moments, δ Q_20(X_A)≡ Q_20(X_A)-Q_20(^152Dy;yrast), follow experimental trends rather well and that they can be written as a sum of independent contributions from the single-particle/hole states around the doubly-magic SD core of ^152Dy with a surpisingly high accuracy. For more than 90% of the SD bands considered, the deviation |δ Q_20 ( X_A) - sum_Nn_zΛδ q^[Nn_zΛ]| is less than 0.04 b. It suggests that the SD high-spin bands around ^152Dy are excellent examples of an almost undisturbed single-particle motion, i.e., can be described by the extreme shell model.
Quadrupole Collectivity in Neutron Deficient Sn Isotopes
NASA Astrophysics Data System (ADS)
Gade, Alexandra
2014-03-01
One of the overarching goals of nuclear physics is the development of a comprehensive model of the atomic nucleus with predictive power across the nuclear chart. Of particular importance for the development of nuclear models is experimental data that consistently track the effect of isospin and changed binding, for example. The chain of Sn isotopes has been a formidable testing ground for nuclear models as some spectroscopic data is available from N = Z = 50 100Sn in the proximity of the proton dripline to 134Sn, beyond the very neutron-rich doubly magic nucleus 132Sn. In even-even nuclei, the electromagnetic quadrupole excitation strength is a measure of quadrupole collectivity, sensitive to the presence of shell gaps, nuclear deformation, and nucleon-nucleon correlations, for example. In the Sn isotopes, this transition strength has been reported from 104Sn to 130Sn, spanning a chain of 14 even-even Sn isotopes. The trend is asymmetric with respect to midshell and not even the largest-scale shell-model calculations have been able to describe the evolution of transition strength across the isotopic chain without varying effective charges. Implications will be discussed. This work was supported by the National Science Foundation under Grant No. PHY-1102511.
Means for the focusing and acceleration of parallel beams of charged particles. [Patent application
Maschke, A.W.
1980-09-23
Apparatus for focusing beams of charged particles comprising planar arrays of electrostatic quadrupoles. The array may be assembled from a single component which comprises a support plate containing uniform rows of poles. Each pole is separated by a hole through the plate designed to pass a beam. Two such plates may be positioned with their poles intermeshed to form a plurality of quadrupoles.
Means for the focusing and acceleration of parallel beams of charged particles
Maschke, Alfred W.
1982-09-21
Apparatus for focusing beams of charged particles comprising planar arrays of electrostatic quadrupoles. The array may be assembled from a single component which comprises a support plate containing uniform rows of poles. Each pole is separated by a hole through the plate designed to pass a beam. Two such plates may be positioned with their poles intermeshed to form a plurality of quadrupoles.
NASA Astrophysics Data System (ADS)
Koivisto, E.; Gordon, R.; Dyment, J.; Arkani-Hamed, J.
2006-12-01
Palaeomagnetic poles can be determined from asymmetry (skewness) of marine magnetic anomalies. Early works applying the skewness method were limited by the discovery of an apparently systematic error known as anomalous skewness (Cande 1976). Anomalous skewness can be thought of as the systematic difference between the observed skewness and the skewness predicted by a simple magnetization model with rectangular 2-D layer 2A prisms of alternating polarity separated by vertical boundaries. In the early works, anomalous skewness could be isolated for anomalies with counterparts across a mid-ocean ridge, but was much harder to estimate for anomalies with subducted counterparts, as is mostly the case in the Pacific plate. Petronotis et al. (1992) presented a solution to this problem by simultaneously estimating anomalous skewness and a best-fitting palaeomagnetic pole from skewness data from a single plate. In their approach, anomalous skewness is assumed to be identical for different crossings of the same plate and any spreading-rate dependence of anomalous skewness is neglected. Nonetheless, anomalous skewness of marine magnetic anomalies is observed to decrease with increasing spreading rate and become negligible above spreading rates of about 50 mm yr-1 (e.g. Roest et al. 1992; Dyment et al. 1994). Dyment &Arkani-Hamed (1995) proposed a model in which the magnetic structure of the oceanic lithosphere is dependent on spreading rate with parameters adjusted to fit the observed spreading- rate dependence of anomalous skewness for some key anomalies. Here we apply their model to determine a new Maastrichtian palaeomagnetic pole for the Pacific plate from skewness estimates of magnetic anomaly 32. Previously Petronotis &Gordon (1999) obtained a palaeopole assuming spreading-rate independent anomalous skewness for the same data used here. They also investigated the possible dependence of anomalous skewness on spreading rate and found it to have negligible effect on their
Differentially pumped dual linear quadrupole ion trap mass spectrometer
Owen, Benjamin C.; Kenttamaa, Hilkka I.
2015-10-20
The present disclosure provides a new tandem mass spectrometer and methods of using the same for analyzing charged particles. The differentially pumped dual linear quadrupole ion trap mass spectrometer of the present disclose includes a combination of two linear quadrupole (LQIT) mass spectrometers with differentially pumped vacuum chambers.
Feedback damper system for quadrupole oscillations after transition at RHIC.
Abreu,N.; Blaskiewicz, M.; Brennan, J.M.; Schultheiss, C.
2008-06-23
The heavy ion beam at RHIC undergoes strong quadrupole oscillations just after it crosses transition, which leads to an increase in bunch length making rebucketing less effective. A feedback system was built to damp these quadrupole oscillations and in this paper the characteristics of the system and the results obtained are presented and discussed.
NASA Astrophysics Data System (ADS)
Godfrey, B.; Majdalani, J.
2014-11-01
This study relies on computational fluid dynamics (CFD) tools to analyse a possible method for creating a stable quadrupole vortex within a simulated, circular-port, cylindrical rocket chamber. A model of the vortex generator is created in a SolidWorks CAD program and then the grid is generated using the Pointwise mesh generation software. The non-reactive flowfield is simulated using an open source computational program, Stanford University Unstructured (SU2). Subsequent analysis and visualization are performed using ParaView. The vortex generation approach that we employ consists of four tangentially injected monopole vortex generators that are arranged symmetrically with respect to the center of the chamber in such a way to produce a quadrupole vortex with a common downwash. The present investigation focuses on characterizing the flow dynamics so that future investigations can be undertaken with increasing levels of complexity. Our CFD simulations help to elucidate the onset of vortex filaments within the monopole tubes, and the evolution of quadrupole vortices downstream of the injection faceplate. Our results indicate that the quadrupole vortices produced using the present injection pattern can become quickly unstable to the extent of dissipating soon after being introduced into simulated rocket chamber. We conclude that a change in the geometrical configuration will be necessary to produce more stable quadrupoles.
Double-photoionization of helium including quadrupole radiation effects
Colgan, James; Ludlow, J A; Lee, Teck - Ghee; Pindzola, M S; Robicheaux, F
2009-01-01
Non-perturbative time-dependent close-coupling calculations are carried out for the double photoionization of helium including both dipole and quadrupole radiation effects. At a photon energy of 800 eV, accessible at CUlTent synchrotron light sources, the quadrupole interaction contributes around 6% to the total integral double photoionization cross section. The pure quadrupole single energy differential cross section shows a local maxima at equal energy sharing, as opposed to the minimum found in the pure dipole single energy differential cross section. The sum of the pure dipole and pure quadrupole single energy differentials is insensitive to non-dipole effects at 800 eV. However, the triple differential cross section at equal energy sharing of the two ejected electrons shows strong non-dipole effects due to the quadrupole interaction that may be experimentally observable.
Quadrupole photoionization of hydrogen atoms in Debye plasmas
Lin, C. Y.; Ho, Y. K.
2010-09-15
Although a great deal of effort has been devoted to investigating dipole photoionization of plasma-embedded atoms, far less is known about the corresponding quadrupole transitions. In the present work, quadrupole photoionization processes for the ground and excited states of hydrogen atoms in Debye plasma are explored using the method of complex coordinate rotation. The plasma shielding effects on the quadrupole photoionization cross sections are reported for a variety of Debye screening lengths and compared to the dipole results accordingly. Under the perturbation of plasma screening, shape resonances and Cooper-type minima occurring in both dipole and quadrupole photoionization cross sections are presented and discussed. Comparisons are made to other theoretical calculations for the dipole photoionization with good agreement. The present quadrupole results are the first predictions for hydrogen photoionization in Debye plasmas.
Effect of Surface Motion on the Rotational Quadrupole Alignment Parameter of D2 Reacting on Cu(111)
NASA Astrophysics Data System (ADS)
Nattino, Francesco; Díaz, Cristina; Jackson, Bret; Kroes, Geert-Jan
2012-06-01
Ab initio molecular dynamics (AIMD) calculations using the specific reaction parameter approach to density functional theory are presented for the reaction of D2 on Cu(111) at high surface temperature (Ts=925K). The focus is on the dependence of reaction on the alignment of the molecule’s angular momentum relative to the surface. For the two rovibrational states for which measured energy resolved rotational quadrupole alignment parameters are available, and for the energies for which statistically accurate rotational quadrupole alignment parameters could be computed, statistically significant results of our AIMD calculations are that, on average, (i) including the effect of the experimental surface temperature (925 K) in the AIMD simulations leads to decreased rotational quadrupole alignment parameters, and (ii) including this effect leads to increased agreement with experiment.
Supersonic Quadrupole Noise Theory for High-Speed Helicopter Rotors
NASA Technical Reports Server (NTRS)
Farassat, F.; Brentner, Kenneth S.
1997-01-01
High-speed helicopter rotor impulsive noise prediction is an important problem of aeroacoustics. The deterministic quadrupoles have been shown to contribute significantly to high-speed impulsive (HSI) noise of rotors, particularly when the phenomenon of delocalization occurs. At high rotor-tip speeds, some of the quadrupole sources lie outside the sonic circle and move at supersonic speed. Brentner has given a formulation suitable for efficient prediction of quadrupole noise inside the sonic circle. In this paper, we give a simple formulation based on the acoustic analogy that is valid for both subsonic and supersonic quadrupole noise prediction. Like the formulation of Brentner, the model is exact for an observer in the far field and in the rotor plane and is approximate elsewhere. We give the full analytic derivation of this formulation in the paper. We present the method of implementation on a computer for supersonic quadrupoles using marching cubes for constructing the influence surface (Sigma surface) of an observer space- time variable (x; t). We then present several examples of noise prediction for both subsonic and supersonic quadrupoles. It is shown that in the case of transonic flow over rotor blades, the inclusion of the supersonic quadrupoles improves the prediction of the acoustic pressure signature. We show the equivalence of the new formulation to that of Brentner for subsonic quadrupoles. It is shown that the regions of high quadrupole source strength are primarily produced by the shock surface and the flow over the leading edge of the rotor. The primary role of the supersonic quadrupoles is to increase the width of a strong acoustic signal.
Skewness in large-scale structure and non-Gaussian initial conditions
NASA Technical Reports Server (NTRS)
Fry, J. N.; Scherrer, Robert J.
1994-01-01
We compute the skewness of the galaxy distribution arising from the nonlinear evolution of arbitrary non-Gaussian intial conditions to second order in perturbation theory including the effects of nonlinear biasing. The result contains a term identical to that for a Gaussian initial distribution plus terms which depend on the skewness and kurtosis of the initial conditions. The results are model dependent; we present calculations for several toy models. At late times, the leading contribution from the initial skewness decays away relative to the other terms and becomes increasingly unimportant, but the contribution from initial kurtosis, previously overlooked, has the same time dependence as the Gaussian terms. Observations of a linear dependence of the normalized skewness on the rms density fluctuation therefore do not necessarily rule out initially non-Gaussian models. We also show that with non-Gaussian initial conditions the first correction to linear theory for the mean square density fluctuation is larger than for Gaussian models.
NASA Astrophysics Data System (ADS)
Song, Shiyu; Wang, Suxin; Wang, Yongjin
2016-08-01
Motivated by the close connection between the skew Brownian motion and the random particle motion in heterogeneous media, we investigate the reflected skew Brownian motion and try to find out its relationship with the corresponding dispersion problem when there exists a reflecting boundary. Through the use of the knowledge of stochastic analysis, we provide some basic properties of reflected skew Brownian motions, including the transition density, the Laplace transform of the first passage time, and some related results. A simple method to generate the sample path is also proposed. At the end of this paper, we reveal the strong relationship between the reflected skew Brownian motion and the solute dispersion in the presence of a sharp interface and a reflecting boundary.
Fast frequency domain method to detect skew in a document image
NASA Astrophysics Data System (ADS)
Mehta, Sunita; Walia, Ekta; Dutta, Maitreyee
2015-12-01
In this paper, a new fast frequency domain method based on Discrete Wavelet Transform and Fast Fourier Transform has been implemented for the determination of the skew angle in a document image. Firstly, image size reduction is done by using two-dimensional Discrete Wavelet Transform and then skew angle is computed using Fast Fourier Transform. Skew angle error is almost negligible. The proposed method is experimented using a large number of documents having skew between -90° and +90° and results are compared with Moments with Discrete Wavelet Transform method and other commonly used existing methods. It has been determined that this method works more efficiently than the existing methods. Also, it works with typed, picture documents having different fonts and resolutions. It overcomes the drawback of the recently proposed method of Moments with Discrete Wavelet Transform that does not work with picture documents.
Asymptotic performance of the quadratic discriminant function to skewed training samples.
Adebanji, Atinuke; Asamoah-Boaheng, Michael; Osei-Tutu, Olivia
2016-01-01
This study investigates the asymptotic performance of the quadratic discriminant function (QDF) under skewed training samples. The main objective of this study is to evaluate the performance of the QDF under skewed distribution considering different sample size ratios, varying the group centroid separators and the number of variables. Three populations [Formula: see text] with increasing group centroid separator function were considered. A multivariate normal distributed data was simulated with MatLab R2009a. There was an increase in the average error rates of the sample size ratios 1:2:2 and 1:2:3 as the total sample size increased asymptotically in the skewed distribution when the centroid separator increased from 1 to 3. The QDF under the skewed distribution performed better for the sample size ratio 1:1:1 as compared to the other sampling ratios and under centroid separator [Formula: see text]. PMID:27652103
12. Underside of Skew SpanHot Metal system on right, toward ...
12. Underside of Skew Span-Hot Metal system on right, toward Rocker Bent. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
Mondello, Luigi; Sciarrone, Danilo; Casilli, Alessandro; Tranchida, Peter Quinto; Dugo, Paola; Dugo, Giovanni
2007-08-01
The Scientific Committee for Cosmetics and NonFood Products in the 7th Amendment to the European Cosmetics Directive established 26 fragrance components, widely used in cosmetic products, as being responsible for a series of contact allergies (Directive 2003/15/EC, Official Journal of the European Union, L66/26, 11.3.2003). The regulation foresees that any allergen, present in excess of 100 mg/kg in rinse-off and of 10 mg/kg in leave-on formulations, must be reported on the label of the product. The present research reports a fast GC-full scan quadrupole mass spectrometric method (under 5 min) for the qualitative/quantitative analysis of allergens in perfumes. Reliable peak identification was achieved through a twin-filtered MS library matching procedure, considering a minimum degree of spectral similarity (90%) and retention data (a linear retention index window was applied). Peak quantification was carried out by using a specific extracted ion. In case a suspected allergen fell within its retention time window but presented a low degree of spectral purity (< 90%), analyte determination was achieved by using three extracted ions (one quantifier and two qualifiers). The fast GC-MS method was validated in terms of intraday retention time and peak area precision, LODs and LOQs, and method linearity. Finally, peak skewing was also evaluated and was within more than acceptable limits.
Vibration Measurements to Study the Effect of Cryogen Flow in Superconducting Quadrupole.
He,P.; Anerella, M.; aydin, S.; Ganetis, G. Harrison, M.; Jain, A.; Parker, B.
2007-06-25
The conceptual design of compact superconducting magnets for the International Linear Collider final focus is presently under development. A primary concern in using superconducting quadrupoles is the potential for inducing additional vibrations from cryogenic operation. We have employed a Laser Doppler Vibrometer system to measure the vibrations in a spare RHIC quadrupole magnet under cryogenic conditions. Some preliminary results of these studies were limited in resolution due to a rather large motion of the laser head as well as the magnet. As a first step towards improving the measurement quality, a new set up was used that reduces the motion of the laser holder. The improved setup is described, and vibration spectra measured at cryogenic temperatures, both with and without helium flow, are presented.
Explosives detection by nuclear quadrupole resonance (NQR)
NASA Astrophysics Data System (ADS)
Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.; Krauss, Ronald A.
1994-10-01
Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a laboratory prototype NQR explosives detector which interrogates a volume of 300 liters (10 ft3). This paper presents abbreviated results from a demonstration of the laboratory prototype NQR explosives detector conducted at the Federal Aviation Administration Technical Center in May 1994 on RDX-based explosives.
Quadrupole resonance scanner for narcotics detection
NASA Astrophysics Data System (ADS)
Shaw, Julian D.; Moeller, C. R.; Magnuson, Erik E.; Sheldon, Alan G.
1994-10-01
Interest in non-invasive, non-hazardous, bulk detection technologies for narcotics interdiction has risen over the last few years. As part of our continuing research and development programs in detection of narcotics and explosives using sensitive magnetic measuring devices, we present the first commercially available prototype Quadrupole Resonance (QR) scanner for narcotics detection. The portable narcotics detection system was designed in modular form such that a single QR base system could be easily used with a variety of custom detection heads. The QR system presented in this paper is suitable for scanning items up to 61 X 35 X 13 cm in size, and was designed to scan mail packages and briefcase-sized items for the presence of narcotics. System tests have shown that detection sensitivity is comparable that obtained in laboratory systems.
Development of a quadrupole resonance confirmation system
NASA Astrophysics Data System (ADS)
Barrall, Geoffrey A.; Derby, Kevin A.; Drew, Adam J.; Ermolaev, Konstantine V.; Huo, Shouqin; Lathrop, Daniel K.; Petrov, Todor R.; Steiger, Matthew J.; Stewart, Stanley H.; Turner, Peter J.
2004-09-01
Quantum Magnetics has developed a Quadrupole Resonance (QR) system for the detection of anti-tank and anti-vehicle landmines. The QR confirmation sensor (QRCS) is a part of the Army GSTAMIDS Block 1 program and is designed to confirm the presence of landmines initially flagged by a primary sensor system. The ultimate goal is to significantly reduce the number of sites that require neutralization or other time consuming investigation into the presence of a landmine. Government tests in 2002 and 2003 demonstrated the performance of the system in a wide variety of conditions including high radio frequency interference (RFI) and piezo electric ringing (PER) environments. Field test results are presented along with an overall description of the system design and methods used to solve prior issues with RFI and PER.
Atomic Quadrupole Moment Measurement Using Dynamic Decoupling.
Shaniv, R; Akerman, N; Ozeri, R
2016-04-01
We present a method that uses dynamic decoupling of a multilevel quantum probe to distinguish small frequency shifts that depend on m_{j}^{2}, where m_{j}^{2} is the angular momentum of level |j⟩ along the quantization axis, from large noisy shifts that are linear in m_{j}, such as those due to magnetic field noise. Using this method we measured the electric-quadrupole moment of the 4D_{5/2} level in ^{88}Sr^{+} to be 2.973_{-0.033}^{+0.026}ea_{0}^{2}. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in ^{88}Sr^{+} based optical atomic clocks and verifies complicated many-body quantum calculations.
Atomic Quadrupole Moment Measurement Using Dynamic Decoupling.
Shaniv, R; Akerman, N; Ozeri, R
2016-04-01
We present a method that uses dynamic decoupling of a multilevel quantum probe to distinguish small frequency shifts that depend on m_{j}^{2}, where m_{j}^{2} is the angular momentum of level |j⟩ along the quantization axis, from large noisy shifts that are linear in m_{j}, such as those due to magnetic field noise. Using this method we measured the electric-quadrupole moment of the 4D_{5/2} level in ^{88}Sr^{+} to be 2.973_{-0.033}^{+0.026}ea_{0}^{2}. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in ^{88}Sr^{+} based optical atomic clocks and verifies complicated many-body quantum calculations. PMID:27104691
An improved integrally formed radio frequency quadrupole
Abbott, S.R.
1987-10-05
An improved radio frequency quadrupole is provided having an elongate housing with an elongate central axis and top, bottom and two side walls symmetrically disposed about the axis, and vanes formed integrally with the walls, the vanes each having a cross-section at right angles to the central axis which tapers inwardly toward the axis to form electrode tips spaced from each other by predetermined distances. Each of the four walls, and the vanes integral therewith, is a separate structural element having a central lengthwise plane passing through the tip of the vane, the walls having flat mounting surfaces at right angles to and parallel to the control plane, respectively, which are butted together to position the walls and vane tips relative to each other. 4 figs.
RADIATION RESISTANT HTS QUADRUPOLES FOR RIA.
GUPTA,R.; ANERELLA,M.; HARRISON,M.; ET AL.
2004-10-03
Extremely high radiation, levels with accumulated doses comparable to those in nuclear reactors than in accelerators, and very high heat loads ({approx}15 kw) make the quadrupole magnets in the fragment separator one of the most challenging elements of the proposed Rare Isotope Accelerator (RIA). Removing large heat loads, protecting the superconducting coils against quenching, the long term survivability of magnet components, and in particular, insulation that can retain its functionality in such a harsh environment, are the major challenges associated with such magnets. A magnet design based on commercially available high temperature superconductor (HTS) and stainless steel tape insulation has been developed. HTS will efficiently remove these large heat loads and stainless steel can tolerate these large radiation doses. Construction of a model magnet has been started with several coils already built and tested. This paper presents the basic magnet design, results of the coil tests, the status and the future plans. In addition, preliminary results of radiation calculations are also presented.
Cryostat design for SSC quadrupole magnets
Lehmann, G.A.; Grut, K.E.; Hiller, M.W.; Huang, X.; Stutzki, D.T.; Waynert, J.A.
1994-12-31
The baseline design of the SSC Collider Quadrupole Magnet (CQM) cryostat is complete. The cryostat is designed to minimize cost and maximize system reliability. Many components have already been procured. Material characterization and component tests for many of the parts have been completed or are ongoing. The first CQM cryostat will be assembled in September of 1993. This paper describes the cryostat design for the CQM developed at Babcock & Wilcox (B&W). The CQM cryostat operates at cryogenic temperatures with a very stringent heat load budget. The cryostat supports the cold mass within the cryostat and insulates the cold mass against heating by conduction, thermal radiation and residual gas conduction. A description of the major components highlighting the key design features is given. The tradeoff studies performed for each component are summarized. The results of a static thermal analysis of the cryostat are presented.
Quadrupole magnet for a rapid cycling synchrotron
Witte, H.; Berg, J. S.
2015-05-03
Rapid Cycling Synchrotrons (RCS) feature interleaved warm and cold dipole magnets; the field of the warm magnets is used to modulate the average bending field depending on the particle energy. It has been shown that RCS can be an attractive option for fast acceleration of particles, for example, muons, which decay quickly. In previous studies it was demonstrated that in principle warm dipole magnets can be designed which can provide the required ramp rates, which are equivalent to frequencies of about 1 kHz. To reduce the losses it is beneficial to employ two separate materials for the yoke; it was also shown that by employing an optimized excitation coil geometry the eddy current losses are acceptable. In this paper we show that the same principles can be applied to quadrupole magnets targeting 30 T/m with a repetition rate of 1kHz and good field quality.
An Adaptive Method for Reducing Clock Skew in an Accumulative Z-Axis Interconnect System
NASA Technical Reports Server (NTRS)
Bolotin, Gary; Boyce, Lee
1997-01-01
This paper will present several methods for adjusting clock skew variations that occur in a n accumulative z-axis interconnect system. In such a system, delay between modules in a function of their distance from one another. Clock distribution in a high-speed system, where clock skew must be kept to a minimum, becomes more challenging when module order is variable before design.
A study on the effects of a skewed distribution on the EWMA and MA charts
NASA Astrophysics Data System (ADS)
Liew, Jeng Young; Khoo, Michael Boon Chong; Neoh, Siang Gee
2014-07-01
The control chart is the most powerful tool in statistical process control. A control chart is a graphical display used to determine the presence of assignable causes so that prompt corrective actions can be taken to remove such causes before many nonconforming products are produced. The exponentially weighted moving average (EWMA) and moving average (MA) charts are very effective in detecting small and moderate shifts in the process mean. These two charts are constructed based on the properties of the normal distribution. In many practical applications, the validity of the normality assumption is always doubted as the process distribution could be skewed. A skewed distribution can result in a higher incidence of false alarms. This is due to the inconsistencies between the spread of a skewed distribution and the normality assumption employed in setting up a control chart. This paper studies the effects of a skewed distribution on the performances of the EWMA and MA charts, in terms of the charts' false alarm rates. We compare the in-control average run length (ARL0) performance of these two charts when the underlying distributions are normal and skewed. The gamma distribution is selected to represent the skewed distribution. A Monte Carlo simulation using the Statistical Analysis System (SAS) software is carried out to compute the necessary ARL0s. The findings of this study show that the ARL0 performance of the EWMA and MA charts is substantially affected by the skewed distribution. However, the MA chart is not as robust as the EWMA chart, in terms of the ARL0, when the distribution is skewed.
Landfors, Mattias; Philip, Philge; Rydén, Patrik; Stenberg, Per
2011-01-01
Genome-wide analysis of gene expression or protein binding patterns using different array or sequencing based technologies is now routinely performed to compare different populations, such as treatment and reference groups. It is often necessary to normalize the data obtained to remove technical variation introduced in the course of conducting experimental work, but standard normalization techniques are not capable of eliminating technical bias in cases where the distribution of the truly altered variables is skewed, i.e. when a large fraction of the variables are either positively or negatively affected by the treatment. However, several experiments are likely to generate such skewed distributions, including ChIP-chip experiments for the study of chromatin, gene expression experiments for the study of apoptosis, and SNP-studies of copy number variation in normal and tumour tissues. A preliminary study using spike-in array data established that the capacity of an experiment to identify altered variables and generate unbiased estimates of the fold change decreases as the fraction of altered variables and the skewness increases. We propose the following work-flow for analyzing high-dimensional experiments with regions of altered variables: (1) Pre-process raw data using one of the standard normalization techniques. (2) Investigate if the distribution of the altered variables is skewed. (3) If the distribution is not believed to be skewed, no additional normalization is needed. Otherwise, re-normalize the data using a novel HMM-assisted normalization procedure. (4) Perform downstream analysis. Here, ChIP-chip data and simulated data were used to evaluate the performance of the work-flow. It was found that skewed distributions can be detected by using the novel DSE-test (Detection of Skewed Experiments). Furthermore, applying the HMM-assisted normalization to experiments where the distribution of the truly altered variables is skewed results in considerably higher
NASA Technical Reports Server (NTRS)
Majumdar, A. K.
1979-01-01
Expressions are derived for higher-order skewness and excess coefficients using central moments and cumulants up to 8th order. These coefficients are then calculated for three probability distributions: (1) Log-normal, (2) Rice-Nakagami, and (3) Gamma distributions. Curves are given to shown the variation of skewness with excess coefficients for these distributions. These curves are independent of the particular distribution parameters. This method is useful for studying fluctuating phenomena, which obey non-Gaussian statistics.
Bukh, Boris; Lund, Steven M.
2003-05-01
We present an analysis of envelope perturbations evolving in the limit of a fully space-charge depressed (zero emittance) beam in periodic, thin-lens focusing channels. Both periodic solenoidal and FODO quadrupole focusing channels are analyzed. The phase advance and growth rate of normal mode perturbations are analytically calculated as a function of the undepressed particle phase advance to characterize the evolution of envelope perturbations.
Automated beam based alignment of the ALS quadrupoles
Portmann, G.; Robin, D.; Schachinger, L.
1995-04-01
Knowing the electrical offset of the storage ring beam position monitors (BPM) to an adjacent quadrupole magnetic center is important in order to correct the orbit in the ring. The authors describe a simple, fast and reliable technique to measure the BPM electrical centers relative to the quadrupole magnetic centers. By varying individual quadrupole magnets and observing the effects on the orbit they were able to measure the BPM offsets in half the horizontal and vertical BPMs (48) in the ALS. These offsets were measured to an accuracy of better than 50{mu}m. The technique is completely automated and takes less than 3 hours for the whole ring.
2014-01-01
Background In insect societies, intracolonial genetic variation is predicted to affect both colony efficiency and reproductive skew. However, because the effects of genetic variation on these two colony characteristics have been tested independently, it remains unclear whether they are affected by genetic variation independently or in a related manner. Here we test the effect of genetic variation on colony efficiency and reproductive skew in a rhinotermitid termite, Reticulitermes speratus, a species in which female-female pairs can facultatively found colonies. We established colonies using two types of female-female pairs: colonies founded by sisters (i.e., sister-pair colonies) and those founded by females from different colonies (i.e., unrelated-pair colonies). Colony growth and reproductive skew were then compared between the two types of incipient colonies. Results At 15 months after colony foundation, unrelated-pair colonies were larger than sister-pair colonies, although the caste ratio between workers and nymphs, which were alternatively differentiated from young larvae, did not differ significantly. Microsatellite DNA analyses of both founders and their parthenogenetically produced offspring indicated that, in both sister-pair and unrelated-pair colonies, there was no significant skew in the production of eggs, larvae, workers and soldiers. Nymph production, however, was significantly more skewed in the sister-pair colonies than in unrelated-pair colonies. Because nymphs can develop into winged adults (alates) or nymphoid reproductives, they have a higher chance of direct reproduction than workers in this species. Conclusions Our results support the idea that higher genetic variation among colony members could provide an increase in colony productivity, as shown in hymenopteran social insects. Moreover, this study suggests that low genetic variation (high relatedness) between founding females increases reproductive skew via one female preferentially
Static performance investigation of a skewed-throat multiaxis thrust-vectoring nozzle concept
NASA Technical Reports Server (NTRS)
Wing, David J.
1994-01-01
The static performance of a jet exhaust nozzle which achieves multiaxis thrust vectoring by physically skewing the geometric throat has been characterized in the static test facility of the 16-Foot Transonic Tunnel at NASA Langley Research Center. The nozzle has an asymmetric internal geometry defined by four surfaces: a convergent-divergent upper surface with its ridge perpendicular to the nozzle centerline, a convergent-divergent lower surface with its ridge skewed relative to the nozzle centerline, an outwardly deflected sidewall, and a straight sidewall. The primary goal of the concept is to provide efficient yaw thrust vectoring by forcing the sonic plane (nozzle throat) to form at a yaw angle defined by the skewed ridge of the lower surface contour. A secondary goal is to provide multiaxis thrust vectoring by combining the skewed-throat yaw-vectoring concept with upper and lower pitch flap deflections. The geometric parameters varied in this investigation included lower surface ridge skew angle, nozzle expansion ratio (divergence angle), aspect ratio, pitch flap deflection angle, and sidewall deflection angle. Nozzle pressure ratio was varied from 2 to a high of 11.5 for some configurations. The results of the investigation indicate that efficient, substantial multiaxis thrust vectoring was achieved by the skewed-throat nozzle concept. However, certain control surface deflections destabilized the internal flow field, which resulted in substantial shifts in the position and orientation of the sonic plane and had an adverse effect on thrust-vectoring and weight flow characteristics. By increasing the expansion ratio, the location of the sonic plane was stabilized. The asymmetric design resulted in interdependent pitch and yaw thrust vectoring as well as nonzero thrust-vector angles with undeflected control surfaces. By skewing the ridges of both the upper and lower surface contours, the interdependency between pitch and yaw thrust vectoring may be eliminated
Quadrupole beam-based alignment in the RHIC interaction regions
Ziegler, J.; Satogata, T.
2011-03-28
Continued beam-based alignment (BBA) efforts have provided significant benefit to both heavy ion and polarized proton operations at RHIC. Recent studies demonstrated previously unknown systematic beam position monitor (BPM) offset errors and produced accurate measurements of individual BPM offsets in the experiment interaction regions. Here we describe the algorithm used to collect and analyze data during the 2010 and early 2011 RHIC runs and the results of these measurements. BBA data has been collected over the past two runs for all three of the active experimental IRs at RHIC, updating results from the 2005 run which were taken with incorrectly installed offsets. The technique was successfully applied to expose a systematic misuse of the BPM survey offsets in the control system. This is likely to benefit polarized proton operations as polarization transmission through acceleration ramps depends on RMS orbit control in the arcs, but a quantitative understanding of its impact is still under active investigation. Data taking is ongoing as are refinements to the BBA technique aimed at reducing systematic errors and properly accounting for dispersive effects. Further development may focus on non-triplet BPMs such as those located near snakes, or arc quadrupoles that do not have individually shunted power supplies (a prerequisite for the current method) and as such, will require a modified procedure.
LARP NB3SN QUADRUPOLE MAGNETS FOR THE LHC LUMINOSITY UPGRADE
Ferracin, P.
2009-06-01
The US LHC Accelerator Research Program (LARP) is a collaboration between four US laboratories (BNL, FNAL, LBNL, and SLAC) aimed at contributing to the commissioning and operation of the LHC and conducting R&D on its luminosity upgrade. Within LARP, the Magnet Program's main goal is to demonstrate that Nb{sub 3}Sn superconducting magnets are a viable option for a future upgrade of the LHC Interaction Regions. Over the past four years, LARP has successfully fabricated and tested several R&D magnets: (1) the subscale quadrupole magnet SQ, to perform technology studies with 300 mm long racetrack coils, (2) the technology quadrupole TQ, to investigate support structure behavior with 1 m long cos2{theta} coils, and (3) the long racetrack magnet LR, to test 3.6 m long racetrack coils. The next milestone consists in the fabrication and test of the 3.7 m long quadrupole magnet LQ, with the goal of demonstrating that ND{sub 3}Sn technology is mature for use in high energy accelerators. After an overview of design features and test results of the LARP magnets fabricated so far, this paper focuses on the status of the fabrication of LQ: we describe the production of the 3.4 m long cos2{theta} coils, and the qualification of the support structure. Finally, the status of the development of the next 1 m long model HQ, conceived to explore stress and field limits of Nb{sub 3}Sn superconducting magnets, is presented.
Cryo-technical design aspects of the superconducting SIS100 quadrupole doublet modules
Meier, J. P.; Bleile, A.; Fischer, E.; Hess, G.; Macavei, J.; Spiller, P.
2014-01-29
The FAIR project was initiated to build an international accelerator and experimental facility for basic research activities in various fields of modern physics. The core component of the project will be the SIS100 heavy ion accelerator, producing heavy ion beams of uniquely high intensities and qualities. The superconducting main quadrupoles and corrector magnets are assembled within complex quadrupole doublet modules (QDMs), combining two superconducting quadrupole (focusing and defocusing), sextupole and steering magnets in one cryostat. In addition a cryo-catcher, a beam position monitor and a cold beam pipe will be integrated. In accordance with the magnet lattice structure, the QDM series for the SIS100 consists of four main families composed of eleven different configurations. The common technical feature of all configurations is a sophisticated common girder structure, mechanically integrating all functional components in one cold mass and being suspended in a corresponding cryostat system. The requirements to position preservation during thermal cycling are to be fulfilled by a precise and stable support of the functional elements, as well as by a reliable, reproducible and stable cold mass suspension system. The main design aspects of the QDMs will be discussed as a result of these requirements.
Final focus system for high intensity beams
Henestroza, E.; Bieniosek, F.M.; Eylon, S.; Roy, P.K.; Yu, S.S.
2003-05-01
The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high perveance heavy ion beams. The NTX final focus system produces a converging beam at the entrance to the neutralized drift section where it focuses to a small spot. The final focus lattice consists of four pulsed quadrupole magnets. The main issues are the control of emittance growth due to high order fields from magnetic multipoles and image fields. We will present experimental results from NTX on beam envelope and phase space distributions, and compare these results with particle simulations using the particle-in-cell code WARP.
Quadrupole resonance spectroscopic study of narcotic materials
NASA Astrophysics Data System (ADS)
Rayner, Timothy J.; West, Rebecca; Garroway, Allen N.; Lyndquist, R.; Yesinowski, James P.
1997-02-01
Bulk narcotic detection systems based upon Quadrupole Resonance Analysis (QRA) technology have a major advantage over imaging technologies, in that QRA is chemical-specific and consequently has a lower rate of false alarms. QRA is a magnetic resonance technology which occurs as a result of the inherent molecular properties of the atomic nuclei in crystalline and amorphous solids. The QRA response is characterized by 1) the precessional frequency of the nucleus, and 2) the nature of the electric field gradient experienced by the nucleus,due to its molecular environment. Another important detection parameter is linewidth, resonant quality. All of these parameters depend on sample purity and manufacturing process. Quantum Magnetics recently carried out a study on the QRA signatures of various narcotic materials with the support of the US Army, US Customs, and the Office of National Drug Control Policy. The aim of the study was to fully characterize the variation in QRA spectroscopic parameters of different samples of cocaine base and cocaine hydrochloride. The results from this study ar discussed here.
Adjustable rare earth quadrupole drift tube magnets
Feinberg, B.; Tanabe, J.; Halbach, K.; Koehler, G.; Green, M.I.
1987-03-01
A prototype permanent-magnet drift tube quadrupole with adjustable field strength has been constructed and tested. The magnet uses iron pole pieces to provide the required field shape along with rare earth permanent-magnet material (samarium cobalt) to energize the magnet. A unique feature of the configuration is the adjustability of the field, accomplished by rotating the outer rings consisting of permanent magnets and iron. In contrast with a previous prototype magnet, this new design uses ball bearings in place of slide bearings to eliminate potential failures. The rotation is now achieved with a bevel gear mechanism. The prototype design also incorporates a new drift tube shell vacuum seal to allow easy disassembly. Tests were made of the magnetic properties and the mechanical performance of this magnet. Field errors are extremely small, and the magnet passed an accelerated ten year lifetime test. It is planned to use this type of magnet to replace 24 of the SuperHILAC prestripper drift tubes.
Autonomously Calibrating a Quadrupole Mass Spectrometer
NASA Technical Reports Server (NTRS)
Lee, Seungwon; Bornstein, Benjamin J.
2009-01-01
A computer program autonomously manages the calibration of a quadrupole ion mass spectrometer intended for use in monitoring concentrations and changes in concentrations of organic chemicals in the cabin air of the International Space Station. The instrument parameters calibrated include the voltage on a channel electron multiplier, a discriminator threshold, and an ionizer current. Calibration is achieved by analyzing the mass spectrum obtained while sweeping the parameter ranges in a heuristic procedure, developed by mass spectrometer experts, that involves detection of changes in signal trends that humans can easily recognize but cannot necessarily be straightforwardly codified in an algorithm. The procedure includes calculation of signal-to-noise ratios, signal-increase rates, and background-noise-increase rates; finding signal peaks; and identifying peak patterns. The software provides for several recovery-from-error scenarios and error-handling schemes. The software detects trace amounts of contaminant gases in the mass spectrometer and notifies associated command- and-data-handling software to schedule a cleaning. Furthermore, the software autonomously analyzes the mass spectrum to determine whether the parameters of a radio-frequency ramp waveform are set properly so that the peaks of the mass spectrum are at expected locations.
Modeling absolute differences in life expectancy with a censored skew-normal regression approach
Clough-Gorr, Kerri; Zwahlen, Marcel
2015-01-01
Parameter estimates from commonly used multivariable parametric survival regression models do not directly quantify differences in years of life expectancy. Gaussian linear regression models give results in terms of absolute mean differences, but are not appropriate in modeling life expectancy, because in many situations time to death has a negative skewed distribution. A regression approach using a skew-normal distribution would be an alternative to parametric survival models in the modeling of life expectancy, because parameter estimates can be interpreted in terms of survival time differences while allowing for skewness of the distribution. In this paper we show how to use the skew-normal regression so that censored and left-truncated observations are accounted for. With this we model differences in life expectancy using data from the Swiss National Cohort Study and from official life expectancy estimates and compare the results with those derived from commonly used survival regression models. We conclude that a censored skew-normal survival regression approach for left-truncated observations can be used to model differences in life expectancy across covariates of interest. PMID:26339544
Eggert, Anne-Katrin; Otte, Tobias; Müller, Josef K
2008-01-01
Proximate mechanisms underlying reproductive skew are obscure in many animals that breed communally. Here, we address causes of reproductive skew in brood-parasitic associations of burying beetles (Nicrophorus vespilloides). Male and female burying beetles feed and defend their larvae on buried carcasses. When several females locate the same small carcass, they engage in violent physical altercations. The subordinate then acts as an intraspecific brood parasite, laying eggs, but not providing care. The dominant female largely monopolizes access to the carcass; she alone provides parental care and her share of the brood is much larger than the subordinate's. On larger carcasses, subordinates have greater access to the carcass than on small ones, and reproductive skew is reduced. Differential fecundity, ovicide and larvicide have been suggested as causes of skew on small carcasses. Here, we report the results of the experiments pertaining to the first two of these potential mechanisms. Ovicide did not significantly contribute to reproductive skew on small carcasses, but differential fecundity did. Fecundity differences were due to dominance status, not body size per se. Fecundity differences disappeared when supplemental food was available, suggesting that reduced access to the carcass limits fecundity by causing nutritional deficiencies. Supplemental food prevented such nutritional deficiencies and allowed subordinates to produce as many eggs as dominants. Apparently, aggressive behaviour by dominants functions in the context of reproductive competition, limiting subordinate reproduction by preventing food intake on the carcass. PMID:18647719
Dynamics of a charged drop in a quadrupole electric field
NASA Astrophysics Data System (ADS)
Das, Sudip; Mayya, Y. S.; Thaokar, Rochish
2015-07-01
Quadrupole electric fields are commonly employed for confining charged conducting drops in Paul traps for studying Rayleigh instability characteristics. We investigate the effect of these fields on the deformation and stability characteristics of a charged liquid drop, using the axisymmetric boundary integral method (BIM). Different combinations of the amount of charge and strength of the electric field give rise to different equilibrium shapes. Interestingly, unlike in the case of uniform fields, stable oblate equilibrium drop shapes are sustained in quadrupole fields. In a positive endcap configuration of the quadrupole setup a drop carrying a small negative charge displays a transition from oblate to prolate as the field strength increases. On the other hand, for the case of a highly charged drop, a shift in the Rayleigh critical charge is observed in the presence of a weak quadrupole field. The Rayleigh instability displays imperfect transcritical bifurcation characteristics with respect to imposed prolate and oblate perturbations. Results are of significance in i) interpreting deformation and the Rayleigh stability effects using Paul traps with quadrupole fields, ii) designing more efficient quadrupole-field-based technologies for emulsification of water in oil.
Peng, Shixiang Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Zhang, Ailing; Chen, Jia'er
2014-02-15
A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 π mm mrad and the fraction of He+ is about 99%.
Peng, Shixiang; Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Zhang, Ailing; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Chen, Jia'er
2014-02-01
A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 π mm mrad and the fraction of He+ is about 99%.
Julià, Olga; Vidal-Mas, Jaume; Panikov, Nicolai S; Vives-Rego, Josep
2010-01-01
We report a skew-Laplace statistical analysis of both flow cytometry scatters and cell size from microbial strains primarily grown in batch cultures, others in chemostat cultures and bacterial aquatic populations. Cytometry scatters best fit the skew-Laplace distribution while cell size as assessed by an electronic particle analyzer exhibited a moderate fitting. Unlike the cultures, the aquatic bacterial communities clearly do not fit to a skew-Laplace distribution. Due to its versatile nature, the skew-Laplace distribution approach offers an easy, efficient, and powerful tool for distribution of frequency analysis in tandem with the flow cytometric cell sorting.
Julià, Olga; Vidal-Mas, Jaume; Panikov, Nicolai S.; Vives-Rego, Josep
2010-01-01
We report a skew-Laplace statistical analysis of both flow cytometry scatters and cell size from microbial strains primarily grown in batch cultures, others in chemostat cultures and bacterial aquatic populations. Cytometry scatters best fit the skew-Laplace distribution while cell size as assessed by an electronic particle analyzer exhibited a moderate fitting. Unlike the cultures, the aquatic bacterial communities clearly do not fit to a skew-Laplace distribution. Due to its versatile nature, the skew-Laplace distribution approach offers an easy, efficient, and powerful tool for distribution of frequency analysis in tandem with the flow cytometric cell sorting. PMID:20592754
NASA Astrophysics Data System (ADS)
Kim, Tae-Woo; Chang, Jung-Hwan
2013-08-01
This paper suggests an effective step-skew method to reduce the cogging torque of a surface-mounted permanent magnet synchronous motor (SPMSM). The main concept of the proposed method is to adjust each step length by considering the non-uniform air gap flux density distribution in the axial direction. The results show that the proposed step-skew method reduces the net cogging torque compared with the conventional step-skew method and is more effective for smaller stacking lengths and larger skew steps.
Watermann, J.; McNamara, A.G. ); Sofko, G.J.; Koehler, J.A. )
1989-06-01
Some 7,700 radio aurora spectra obtained from a six link 50-MHz CW radar network set up on the Canadian prairies were analyzed with respect to the distributions of mean Doppler shift, spectral width and skewness. A comparison with recently published SABRE results obtained at 153 MHz shows substantial differences in the distributions which are probably due to different experimental and geophysical conditions. The spectra are mostly broad with mean Doppler shifts close to zero (type II spectra). The typical groupings of type I and type III spectra are clearly identified. All types appear to be in general much more symmetric than those recorded with SABRE, and the skewness is only weakly dependent on the sign of the mean Doppler shift. Its distribution peaks near zero and shows a weak positive correlation with the type II Doppler shifts while the mostly positive type I Doppler shifts are slightly negatively correlated with the skewness.
A Berger-type theorem for metric connections with skew-symmetric torsion
NASA Astrophysics Data System (ADS)
Reggiani, Silvio
2013-03-01
We prove a Berger-type theorem which asserts that if the orthogonal subgroup generated by the torsion tensor (pulled back to a point by parallel transport) of a metric connection with skew-symmetric torsion is not transitive on the sphere, then the space must be locally isometric to a Lie group with a bi-invariant metric or its symmetric dual (we assume the space to be locally irreducible). We also prove that a (simple) Lie group with a bi-invariant metric admits only two flat metric connections with skew-symmetric torsion: the two flat canonical connections. In particular, we get a refinement of a well-known theorem of Cartan and Schouten. Finally, we show that the holonomy group of a metric connection with skew-symmetric torsion on these spaces generically coincides with the Riemannian holonomy.
Modeling the effects of wave skewness and beach cusps on littoral sand transport
Haas, K.A.; Check, L.A.; Hanes, D.M.
2008-01-01
A process-based numerical modeling system is utilized for predicting littoral sand transport. The intent is to examine conditions slightly more complex than linear waves impinging upon a plane beach. Two factors that we examine are wave skewness and longshore varying bathymetry. An empirical model is used for calculating the skewed bottom wave orbital velocity. The advection of sediment due to the skewed wave velocity is larger and in the direction of the waves, opposite to the results with sinusoidal wave velocities, due to the increase in the bottom shear stress under the wave crests. The model system is also applied to bathymetry containing beach cusps. When the wave field has relatively weak longshore wave power, the currents and the littoral transport exhibit significant longshore variability, thereby altering the overall mean littoral transport.
Perceived quality of wood images influenced by the skewness of image histogram
NASA Astrophysics Data System (ADS)
Katsura, Shigehito; Mizokami, Yoko; Yaguchi, Hirohisa
2015-08-01
The shape of image luminance histograms is related to material perception. We investigated how the luminance histogram contributed to improvements in the perceived quality of wood images by examining various natural wood and adhesive vinyl sheets with printed wood grain. In the first experiment, we visually evaluated the perceived quality of wood samples. In addition, we measured the colorimetric parameters of the wood samples and calculated statistics of image luminance. The relationship between visual evaluation scores and image statistics suggested that skewness and kurtosis affected the perceived quality of wood. In the second experiment, we evaluated the perceived quality of wood images with altered luminance skewness and kurtosis using a paired comparison method. Our result suggests that wood images are more realistic if the skewness of the luminance histogram is slightly negative.
Gaudin-type models, non-skew-symmetric classical r-matrices and nested Bethe ansatz
NASA Astrophysics Data System (ADS)
Skrypnyk, T.
2015-02-01
We consider quantum integrable systems associated with the Lie algebra gl (n) and Cartan-invariant non-dynamical non-skew-symmetric classical r-matrices. We describe the sub-class of Cartan-invariant non-skew-symmetric r-matrices for which exists the standard procedure of the nested Bethe ansatz associated with the chain of embeddings gl (n) ⊃ gl (n - 1) ⊃ gl (n - 2) ⊃ ⋯ ⊃ gl (1). We diagonalize the corresponding quantum integrable systems by its means. We illustrate the obtained results by the examples of the generalized Gaudin systems with and without external magnetic field associated with three classes of non-dynamical non-skew-symmetric classical r-matrices.
Skewness in CMB temperature fluctuations from curved cosmic (super-)strings
Yamauchi, Daisuke; Sendouda, Yuuiti; Yoo, Chul-Moon; Naruko, Atsushi; Sasaki, Misao; Takahashi, Keitaro E-mail: sendouda@yukawa.kyoto-u.ac.jp E-mail: keitaro@a.phys.nagoya-u.ac.jp E-mail: misao@yukawa.kyoto-u.ac.jp
2010-05-01
We compute the one-point probability distribution function of small-angle cosmic microwave background temperature fluctuations due to curved cosmic (super-)strings with a simple model of string network by performing Monte Carlo simulations. Taking into account of the correlation between the curvature and the velocity of string segments, there appear non-Gaussian features, specifically non-Gaussian tails and a skewness, in the one-point pdf. The obtained sample skewness for the conventional field-theoretic cosmic strings is g{sub 1} ≈ −0.14, which is consistent with the result reported by Fraisse et al. We also discuss the dependence of the pdf on the intercommuting probability. We find that the standard deviation of the Gaussian part increases and non-Gaussian features are suppressed as the intercommuting probability decreases. For sufficiently small intercommuting probability, the skewness is given by ∼< (a few) × 10{sup −2}.
The log-dynamic brain: how skewed distributions affect network operations
Buzsáki, György; Mizuseki, Kenji
2014-01-01
We often assume that the variables of functional and structural brain parameters — such as synaptic weights, the firing rates of individual neurons, the synchronous discharge of neural populations, the number of synaptic contacts between neurons and the size of dendritic boutons — have a bell-shaped distribution. However, at many physiological and anatomical levels in the brain, the distribution of numerous parameters is in fact strongly skewed with a heavy tail, suggesting that skewed (typically lognormal) distributions are fundamental to structural and functional brain organization. This insight not only has implications for how we should collect and analyse data, it may also help us to understand how the different levels of skewed distributions — from synapses to cognition — are related to each other. PMID:24569488
NASA Astrophysics Data System (ADS)
Fan, Ya-Jing; Cao, Huai-Xin; Meng, Hui-Xian; Chen, Liang
2016-09-01
The uncertainty principle in quantum mechanics is a fundamental relation with different forms, including Heisenberg's uncertainty relation and Schrödinger's uncertainty relation. In this paper, we prove a Schrödinger-type uncertainty relation in terms of generalized metric adjusted skew information and correlation measure by using operator monotone functions, which reads, U_ρ ^{(g,f)}(A)U_ρ ^{(g,f)}(B)≥ f(0)^2l/k| {Corr}_ρ ^{s(g,f)}(A,B)| ^2 for some operator monotone functions f and g, all n-dimensional observables A, B and a non-singular density matrix ρ . As applications, we derive some new uncertainty relations for Wigner-Yanase skew information and Wigner-Yanase-Dyson skew information.
NASA Astrophysics Data System (ADS)
Skrypnyk, T.
2010-08-01
Using non-skew-symmetric classical r-matrices r12(u,v) with spectral parameters, we generalize Fuchsian systems and Schlesinger equations (isomonodromy equations) viewing the last as the nonautonomous Hamiltonian equations corresponding to the generalized Gaudin Hamiltonians. Quantizing these systems we construct generalization of Knizhnik-Zamolodchikov equations corresponding to the non-skew-symmetric classical r-matrices r12(u,v) with spectral parameters. In the case of an ordinary skew-symmetric classical r-matrix r12(u-v) depending on the difference of the spectral parameters, we reobtain, as special partial cases, a standard generalization of Fuchsian systems, Schlesinger, and Knizhnik-Zamolodchikov equations.
Zheng, Shimin; Rao, Uma; Bartolucci, Alfred A.; Singh, Karan P.
2011-01-01
Bartolucci et al.(2003) extended the distribution assumption from the normal (Lyles et al., 2000) to the elliptical contoured distribution (ECD) for random regression models used in analysis of longitudinal data accounting for both undetectable values and informative drop-outs. In this paper, the random regression models are constructed on the multivariate skew ECD. A real data set is used to illustrate that the skew ECDs can fit some unimodal continuous data better than the Gaussian distributions or more general continuous symmetric distributions when the symmetric distribution assumption is violated. Also, a simulation study is done for illustrating the model fitness from a variety of skew ECDs. The software we used is SAS/STAT, V. 9.13. PMID:21637734
Radio frequency focused interdigital linear accelerator
Swenson, Donald A.; Starling, W. Joel
2006-08-29
An interdigital (Wideroe) linear accelerator employing drift tubes, and associated support stems that couple to both the longitudinal and support stem electromagnetic fields of the linac, creating rf quadrupole fields along the axis of the linac to provide transverse focusing for the particle beam. Each drift tube comprises two separate electrodes operating at different electrical potentials as determined by cavity rf fields. Each electrode supports two fingers, pointing towards the opposite end of the drift tube, forming a four-finger geometry that produces an rf quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to one half of the particle wavelength .beta..lamda., where .beta. is the particle velocity in units of the velocity of light and .lamda. is the free space wavelength of the rf. Particles are accelerated in the gaps between drift tubes. The particle beam is focused in regions inside the drift tubes.
Separating the effects of mutation and selection in producing DNA skew in bacterial chromosomes
Morton, Richard A; Morton, Brian R
2007-01-01
Background Many bacterial chromosomes display nucleotide asymmetry, or skew, between the leading and lagging strands of replication. Mutational differences between these strands result in an overall pattern of skew that is centered about the origin of replication. Such a pattern could also arise from selection coupled with a bias for genes coded on the leading strand. The relative contributions of selection and mutation in producing compositional skew are largely unknown. Results We describe a model to quantify the contribution of mutational differences between the leading and lagging strands in producing replication-induced skew. When the origin and terminus of replication are known, the model can be used to estimate the relative accumulation of G over C and of A over T on the leading strand due to replication effects in a chromosome with bidirectional replication arms. The model may also be implemented in a maximum likelihood framework to estimate the locations of origin and terminus. We find that our estimations for the origin and terminus agree very well with the location of genes that are thought to be associated with the replication origin. This indicates that our model provides an accurate, objective method of determining the replication arms and also provides support for the hypothesis that these genes represent an ancestral cluster of origin-associated genes. Conclusion The model has several advantages over other methods of analyzing genome skew. First, it quantifies the role of mutation in generating skew so that its effect on composition, for example codon bias, can be assessed. Second, it provides an objective method for locating origin and terminus, one that is based on chromosome-wide accumulation of leading vs lagging strand nucleotide differences. Finally, the model has the potential to be utilized in a maximum likelihood framework in order to analyze the effect of chromosome rearrangements on nucleotide composition. PMID:17935620
Atypical AT Skew in Firmicute Genomes Results from Selection and Not from Mutation
Charneski, Catherine A.; Honti, Frank; Bryant, Josephine M.
2011-01-01
The second parity rule states that, if there is no bias in mutation or selection, then within each strand of DNA complementary bases are present at approximately equal frequencies. In bacteria, however, there is commonly an excess of G (over C) and, to a lesser extent, T (over A) in the replicatory leading strand. The low G+C Firmicutes, such as Staphylococcus aureus, are unusual in displaying an excess of A over T on the leading strand. As mutation has been established as a major force in the generation of such skews across various bacterial taxa, this anomaly has been assumed to reflect unusual mutation biases in Firmicute genomes. Here we show that this is not the case and that mutation bias does not explain the atypical AT skew seen in S. aureus. First, recently arisen intergenic SNPs predict the classical replication-derived equilibrium enrichment of T relative to A, contrary to what is observed. Second, sites predicted to be under weak purifying selection display only weak AT skew. Third, AT skew is primarily associated with largely non-synonymous first and second codon sites and is seen with respect to their sense direction, not which replicating strand they lie on. The atypical AT skew we show to be a consequence of the strong bias for genes to be co-oriented with the replicating fork, coupled with the selective avoidance of both stop codons and costly amino acids, which tend to have T-rich codons. That intergenic sequence has more A than T, while at mutational equilibrium a preponderance of T is expected, points to a possible further unresolved selective source of skew. PMID:21935355
Iwashita, Y.; Mihara, T.; Kumada, M.; Spencer, C.; /SLAC
2006-02-06
A superstrong permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens for the International Linear Collider (ILC). Our prototype PMQ can produce variable strengths from 3.5T to 24.2T in 1.4T steps. The magnetic center of the PMQ must not move more than a few microns during a 20% strength change to enable a Beam-Based Alignment (BBA) process to work. Our PMQ can be mechanically adjusted to suppress the center movement from more than 30{micro}m to less than 10{micro}m during strength changes.
Rhiel, G Steven
2010-02-01
In 2007, Rhiel presented a technique to estimate the coefficient of variation from the range when sampling from skewed distributions. To provide an unbiased estimate, a correction factor (a(n)) for the mean was included. Numerical correction factors for a number of skewed distributions were provided. In a follow-up paper, he provided a proof he claimed showed the correction factor was independent of the mean and standard deviation, making the factors useful as these parameters vary; however, that proof did not establish independence. Herein is a proof which establishes the independence.
Mixed-derivative skewness for high Prandtl and Reynolds numbers in homogeneous isotropic turbulence
NASA Astrophysics Data System (ADS)
Briard, Antoine; Gomez, Thomas
2016-08-01
The mixed-derivative skewness Suθ of a passive scalar field in high Reynolds and Prandtl numbers decaying homogeneous isotropic turbulence is studied numerically using eddy-damped quasi-normal Markovian closure, for Reλ ≥ 103 up to Pr = 105. A convergence of Suθ for Pr ≥ 103 is observed for any high enough Reynolds number. This asymptotic high Pr regime can be interpreted as a saturation of the mixing properties of the flow at small scales. The decay of the derivative skewnesses from high to low Reynolds numbers and the influence of large scales initial conditions are investigated as well.
Multivariate skew- t approach to the design of accumulation risk scenarios for the flooding hazard
NASA Astrophysics Data System (ADS)
Ghizzoni, Tatiana; Roth, Giorgio; Rudari, Roberto
2010-10-01
The multivariate version of the skew- t distribution provides a powerful analytical description of the joint behavior of multivariate processes. It enjoys valuable properties: from the aptitude to model skewed as well as leptokurtic datasets to the availability of moments and likelihood analytical expressions. Moreover, it offers a wide range of extremal dependence strength, allowing for upper and lower tail dependence. The idea underneath this work is to employ the multivariate skew- t distribution to provide an estimation of the joint probability of flood events in a multi-site multi-basin approach. This constitutes the basis for the design and evaluation of flood hazard scenarios for large areas in terms of their intensity, extension and frequency, i.e. those information required by civil protection agencies to put in action mitigation strategies and by insurance companies to price the flooding risk and to evaluate portfolios. Performances of the skew- t distribution and the corresponding t copula function, introduced to represent the state of the art for multivariate simulations, are discussed with reference to the Tanaro Basin, North-western Italy. To enhance the characteristics of the correlation structure, three nested and non-nested gauging stations are selected with contributing areas from 1500 to 8000 km 2. A dataset of 76 trivariate flood events is extracted from a mean daily discharges database available for the time period from January 1995 to December 2003. Applications include the generation of multivariate skew- t and t copula samples and models' comparison through the principle of minimum cross-entropy, here revised for the application to multivariate samples. Copula and skew- t based scenario return period estimations are provided for the November 1994 flood event, i.e. the worst on record in the 1801-2001 period. Results are encouraging: the skew- t distribution seems able to describe the joint behavior, being close to the observations. Marginal
Alternating skew deviation in association with anti-glutamic acid decarboxylase antibodies
Farooq, Asim V.; Soin, Ketki; Moss, Heather E.
2015-01-01
The presence of an elevated anti-glutamic acid decarboxylase (GAD) antibody level has been associated with a number of eye movement abnormalities, as well as other findings including cerebellar ataxia and insulin dependent diabetes mellitus. Skew deviation in association with anti-GAD antibodies has not been previously reported. Here we report a case of alternating skew deviation along with cerebellar-brainstem signs in a patient with an elevated anti-GAD antibody titer. Follow-up neurologic evaluation after treatment with intravenous immunoglobulin revealed improvement in cerebellar-brainstem signs, while ophthalmic evaluation was stable. PMID:26594078
Gulyuz, Kerim; Stedwell, Corey N.; Wang Da; Polfer, Nick C.
2011-05-15
We present a laboratory-constructed mass spectrometer optimized for recording infrared multiple photon dissociation (IRMPD) spectra of mass-selected ions using a benchtop tunable infrared optical parametric oscillator/amplifier (OPO/A). The instrument is equipped with two ionization sources, an electrospray ionization source, as well as an electron ionization source for troubleshooting. This hybrid mass spectrometer is composed of a quadrupole mass filter for mass selection, a reduced pressure ({approx}10{sup -5} Torr) quadrupole ion trap (QIT) for OPO irradiation, and a reflectron time-of-flight drift tube for detecting the remaining precursor and photofragment ions. A helium gas pulse is introduced into the QIT to temporarily increase the pressure and hence enhance the trapping efficiency of axially injected ions. After a brief pump-down delay, the compact ion cloud is subjected to the focused output from the continuous wave OPO. In a recent study, we implemented this setup in the study of protonated tryptophan, TrpH{sup +}, as well as collision-induced dissociation products of this protonated amino acid [W. K. Mino, Jr., K. Gulyuz, D. Wang, C. N. Stedwell, and N. C. Polfer, J. Phys. Chem. Lett. 2, 299 (2011)]. Here, we give a more detailed account on the figures of merit of such IRMPD experiments. The appreciable photodissociation yields in these measurements demonstrate that IRMPD spectroscopy of covalently bound ions can be routinely carried out using benchtop OPO setups.
Higher order parametric excitation modes for spaceborne quadrupole mass spectrometers
Gershman, D. J.; Block, B. P.; Rubin, M.; Zurbuchen, T. H.; Benna, M.; Mahaffy, P. R.
2011-12-15
This paper describes a technique to significantly improve upon the mass peak shape and mass resolution of spaceborne quadrupole mass spectrometers (QMSs) through higher order auxiliary excitation of the quadrupole field. Using a novel multiresonant tank circuit, additional frequency components can be used to drive modulating voltages on the quadrupole rods in a practical manner, suitable for both improved commercial applications and spaceflight instruments. Auxiliary excitation at frequencies near twice that of the fundamental quadrupole RF frequency provides the advantages of previously studied parametric excitation techniques, but with the added benefit of increased sensed excitation amplitude dynamic range and the ability to operate voltage scan lines through the center of upper stability islands. Using a field programmable gate array, the amplitudes and frequencies of all QMS signals are digitally generated and managed, providing a robust and stable voltage control system. These techniques are experimentally verified through an interface with a commercial Pfeiffer QMG422 quadrupole rod system. When operating through the center of a stability island formed from higher order auxiliary excitation, approximately 50% and 400% improvements in 1% mass resolution and peak stability were measured, respectively, when compared with traditional QMS operation. Although tested with a circular rod system, the presented techniques have the potential to improve the performance of both circular and hyperbolic rod geometry QMS sensors.
Theoretical investigation of flute modes in a magnetic quadrupole
Wu, H.S.
1988-01-01
This research developed theories and conducted numerical investigations of electrostatic flute modes in a plasma confined in a magnetic quadrupole. Chapter I presents the discussion of relevant background. Chapter II contains a brief discussion of the basic flute-mode operator L{sub 0} for intermediate- and low-frequency regimes. Chapter III develops a simple theory for a flute mode with frequency between the electron and ion bounce frequencies in the uniform density and temperature regions of a magnetic quadrupole. The frequency is predicted to be inversely proportional to the wave number. Chapter IV describes the kinetic approach. Chapter V contains the derivation of an eigenvalue equation for electrostatic waves with frequencies below the ion frequency in the private flux region of a magnetic quadrupole. Chapter VI develops a theory for electrostatic waves with frequency below the ion bounce frequency in the shared flux region of a magnetic quadrupole. Chapter VII contains the derivation of a dispersion equation for flute modes with frequencies between the electron and ion bounce frequencies in a plasma confined to a magnetic quadrupole. Chapter VIII presents a summary of the research described.
Theoretical investigation of flute modes in a magnetic quadrupole
Wu, H.S.
1988-01-01
The objective of this research is to develop theories and conduct numerical investigations of electrostatic flute modes in a plasma confined in magnetic quadrupole. Chapter I presents the discussion of relevant background. Chapter II contains a brief discussion of the basic flute-mode operator L{sub 0} for intermediate- and low frequency regimes. Chapter III develops a simple theory for a flute mode with frequency between the electron and ion bounce frequencies in the uniform density and temperature regions of a magnetic quadrupole. Chapter IV describes the kinetic approach. Chapter V contains the derivation of an eigenvalue equation for electrostatic waves with frequencies below the ion frequency in the private flux region of a magnetic quadrupole. Chapter VI develops a theory for electrostatic waves with frequency below the ion bounce frequency in the shared flux region of a magnetic quadrupole. Chapter VII contains the derivation of a dispersion equation for flute modes with frequencies between the electron and ion ounce frequencies in a plasma confined to a magnetic quadrupole. Two intermediate-frequency modes are predicted.
Detecting body cavity bombs with nuclear quadrupole resonance
NASA Astrophysics Data System (ADS)
Collins, Michael London
Nuclear Quadrupole Resonance (NQR) is a technology with great potential for detecting hidden explosives. Past NQR research has studied the detection of land mines and bombs concealed within luggage and packages. This thesis focuses on an NQR application that has received less attention and little or no publicly available research: detecting body cavity bombs (BCBs). BCBs include explosives that have been ingested, inserted into orifices, or surgically implanted. BCBs present a threat to aviation and secure facilities. They are extremely difficult to detect with the technology currently employed at security checkpoints. To evaluate whether or not NQR can be used to detect BCBs, a computational model is developed to assess how the dielectric properties of biological tissue affect the radio frequency magnetic field employed in NQR (0.5-5MHz). The relative permittivity of some biological tissue is very high (over 1,000 at 1MHz), making it conceivable that there is a significant effect on the electromagnetic field. To study this effect, the low-frequency approximation known as the Darwin model is employed. First, the electromagnetic field of a coil is calculated in free space. Second, a dielectric object or set of objects is introduced, and the free-space electric field is modified to accommodate the dielectric object ensuring that the relevant boundary conditions are obeyed. Finally, the magnetic field associated with the corrected electric field is calculated. This corrected magnetic field is evaluated with an NQR simulation to estimate the impact of dielectric tissue on NQR measurements. The effect of dielectric tissue is shown to be small, thus obviating a potential barrier to BCB detection. The NQR model presented may assist those designing excitation and detection coils for NQR. Some general coil design considerations and strategies are discussed.
An analytical algorithm for skew-slit imaging geometry with nonuniform attenuation correction
Huang Qiu; Zeng, Gengsheng L.
2006-04-15
The pinhole collimator is currently the collimator of choice in small animal single photon emission computed tomography (SPECT) imaging because it can provide high spatial resolution and reasonable sensitivity when the animal is placed very close to the pinhole. It is well known that if the collimator rotates around the object (e.g., a small animal) in a circular orbit to form a cone-beam imaging geometry with a planar trajectory, the acquired data are not sufficient for an exact artifact-free image reconstruction. In this paper a novel skew-slit collimator is mounted instead of the pinhole collimator in order to significantly reduce the image artifacts caused by the geometry. The skew-slit imaging geometry is a more generalized version of the pinhole imaging geometry. The multiple pinhole geometry can also be extended to the multiple-skew-slit geometry. An analytical algorithm for image reconstruction based on the tilted fan-beam inversion is developed with nonuniform attenuation compensation. Numerical simulation shows that the axial artifacts are evidently suppressed in the skew-slit images compared to the pinhole images and the attenuation correction is effective.
Using social parasitism to test reproductive skew models in a primitively eusocial wasp.
Green, Jonathan P; Cant, Michael A; Field, Jeremy
2014-08-22
Remarkable variation exists in the distribution of reproduction (skew) among members of cooperatively breeding groups, both within and between species. Reproductive skew theory has provided an important framework for understanding this variation. In the primitively eusocial Hymenoptera, two models have been routinely tested: concessions models, which assume complete control of reproduction by a dominant individual, and tug-of-war models, which assume on-going competition among group members over reproduction. Current data provide little support for either model, but uncertainty about the ability of individuals to detect genetic relatedness and difficulties in identifying traits conferring competitive ability mean that the relative importance of concessions versus tug-of-war remains unresolved. Here, we suggest that the use of social parasitism to generate meaningful variation in key social variables represents a valuable opportunity to explore the mechanisms underpinning reproductive skew within the social Hymenoptera. We present a direct test of concessions and tug-of-war models in the paper wasp Polistes dominulus by exploiting pronounced changes in relatedness and power structures that occur following replacement of the dominant by a congeneric social parasite. Comparisons of skew in parasitized and unparasitized colonies are consistent with a tug-of-war over reproduction within P. dominulus groups, but provide no evidence for reproductive concessions.
The curious anomaly of skewed judgment distributions and systematic error in the wisdom of crowds.
Nash, Ulrik W
2014-01-01
Judgment distributions are often skewed and we know little about why. This paper explains the phenomenon of skewed judgment distributions by introducing the augmented quincunx (AQ) model of sequential and probabilistic cue categorization by neurons of judges. In the process of developing inferences about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can be inferred from how skewed their judgment distributions are, and in what direction they tilt. This implies not just that judgment distributions are shaped by cues, but that judgment distributions are cues themselves for the wisdom of crowds. The AQ model also predicts that judgment variance correlates positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support, and implications are discussed with reference to three central ideas on collective intelligence, these being Galton's conjecture on the distribution of judgments, Muth's rational expectations hypothesis, and Page's diversity prediction theorem. PMID:25406078
Large-scale age-dependent skewed sex ratio in a sexually dimorphic avian scavenger.
Lambertucci, Sergio A; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando
2012-01-01
Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed.
Large-Scale Age-Dependent Skewed Sex Ratio in a Sexually Dimorphic Avian Scavenger
Lambertucci, Sergio A.; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando
2012-01-01
Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed. PMID:23029488
On Some Confidence Intervals for Estimating the Mean of a Skewed Population
ERIC Educational Resources Information Center
Shi, W.; Kibria, B. M. Golam
2007-01-01
A number of methods are available in the literature to measure confidence intervals. Here, confidence intervals for estimating the population mean of a skewed distribution are considered. This note proposes two alternative confidence intervals, namely, Median t and Mad t, which are simple adjustments to the Student's t confidence interval. In…
Tan, Kun; An, Lei; Miao, Kai; Ren, Likun; Hou, Zhuocheng; Tao, Li; Zhang, Zhenni; Wang, Xiaodong; Xia, Wei; Liu, Jinghao; Wang, Zhuqing; Xi, Guangyin; Gao, Shuai; Sui, Linlin; Zhu, De-Sheng; Wang, Shumin; Wu, Zhonghong; Bach, Ingolf; Chen, Dong-bao; Tian, Jianhui
2016-01-01
Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications. PMID:26951653
Skewing (n +1) Tensor Indices where the Index Range is n
ERIC Educational Resources Information Center
Agacy, R. L.
2005-01-01
It is known that any totally skew quantity with (n + 1) indices, each of which ranges over n values, vanishes identically. The aim of this short note is to show that this is equivalent to the simple fact that any (n + 1) vectors in an n-dimensional vector space are linearly dependent.
A Monte Carlo Study of Skewed Theta Distributions on DIF Indices.
ERIC Educational Resources Information Center
Monaco, Malina
The effects of skewed theta distributions on indices of differential item functioning (DIF) were studied, comparing Mantel Haenszel (N. Mantel and W. Haenszel, 1959) and DFIT (N. S. Raju, W. J. van der Linden, and P. F. Fleer) (noncompensatory DIF). The significance of the study is that in educational and psychological data, the distributions one…
Bayesian Comparison of GARCH Processes with Skewness Mechanism in Conditional Distributions
NASA Astrophysics Data System (ADS)
Pipien, M.
2006-11-01
The main goal of this paper is an application of Bayesian model comparison, based on the posterior probabilities and posterior odds ratios, in testing the explanatory power of a set of competing GARCH (Generalized Autoregressive Conditionally Heteroscedastic) specifications, all with asymmetric and heavy tailed conditional distributions. In building competing volatility models we consider, as an initial specification, conditionally Student-t GARCH process with unknown degrees of freedom parameter. By introducing skewness into Student-t family and incorporating the resulting class as a conditional distribution we generated various GARCH models, which compete in explaining possible asymmetry of both conditional and unconditional distribution of financial data. In order to make Student-t family skewed we consider various alternative mechanisms recently proposed in the literature. In particular, we apply the hidden truncation mechanism, an approach based on the inverse scale factors in the positive and the negative orthant, order statistics concept, Beta distribution transformation and Bernstein density transformation. Additionally, we consider GARCH process with conditional alpha -Stable distribution. Based on the daily returns of hypothetical financial time series, we discuss the results of Bayesian comparison of alternative skewing mechanisms applied in the initial Student-t GARCH framework. Additionally, we present formal Bayesian inference about conditional asymmetry of the distribution of the daily returns in all competing specifications on the basis of the skewness measure defined by Arnold and Groenveld.
The Curious Anomaly of Skewed Judgment Distributions and Systematic Error in the Wisdom of Crowds
Nash, Ulrik W.
2014-01-01
Judgment distributions are often skewed and we know little about why. This paper explains the phenomenon of skewed judgment distributions by introducing the augmented quincunx (AQ) model of sequential and probabilistic cue categorization by neurons of judges. In the process of developing inferences about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can be inferred from how skewed their judgment distributions are, and in what direction they tilt. This implies not just that judgment distributions are shaped by cues, but that judgment distributions are cues themselves for the wisdom of crowds. The AQ model also predicts that judgment variance correlates positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support, and implications are discussed with reference to three central ideas on collective intelligence, these being Galton's conjecture on the distribution of judgments, Muth's rational expectations hypothesis, and Page's diversity prediction theorem. PMID:25406078
Skew-varicose instability in two-dimensional generalized Swift-Hohenberg equations.
Weliwita, J A; Rucklidge, A M; Tobias, S M
2011-09-01
We apply analytical and numerical methods to study the linear stability of stripe patterns in two generalizations of the two-dimensional Swift-Hohenberg equation that include coupling to a mean flow. A projection operator is included in our models to allow exact stripe solutions. In the generalized models, stripes become unstable to the skew-varicose, oscillatory skew-varicose, and cross-roll instabilities, in addition to the usual Eckhaus and zigzag instabilities. We analytically derive stability boundaries for the skew-varicose instability in various cases, including several asymptotic limits. We also use numerical techniques to determine eigenvalues and hence stability boundaries of other instabilities. We extend our analysis to both stress-free and no-slip boundary conditions and we note a crossover from the behavior characteristic of no-slip to that of stress-free boundaries as the coupling to the mean flow increases or as the Prandtl number decreases. Close to the critical value of the bifurcation parameter, the skew-varicose instability has the same curvature as the Eckhaus instability provided the coupling to the mean flow is greater than a critical value. The region of stable stripes is completely eliminated by the cross-roll instability for large coupling to the mean flow.
Large-scale age-dependent skewed sex ratio in a sexually dimorphic avian scavenger.
Lambertucci, Sergio A; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando
2012-01-01
Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed. PMID:23029488
NASA Technical Reports Server (NTRS)
Deissler, Robert G.
1990-01-01
The variation of the velocity-derivative skewness of a Navier-Stokes flow as the Reynolds number goes toward zero is calculated numerically. The value of the skewness, which has been somewhat controversial, is shown to become small at low Reynolds numbers.
Space charge induced nonlinear effects in quadrupole ion traps.
Guo, Dan; Wang, Yuzhuo; Xiong, Xingchuang; Zhang, Hua; Zhang, Xiaohua; Yuan, Tao; Fang, Xiang; Xu, Wei
2014-03-01
A theoretical method was proposed in this work to study space charge effects in quadrupole ion traps, including ion trapping, ion motion frequency shift, and nonlinear effects on ion trajectories. The spatial distributions of ion clouds within quadrupole ion traps were first modeled for both 3D and linear ion traps. It is found that the electric field generated by space charge can be expressed as a summation of even-order fields, such as quadrupole field, octopole field, etc. Ion trajectories were then solved using the harmonic balance method. Similar to high-order field effects, space charge will result in an "ocean wave" shape nonlinear resonance curve for an ion under a dipolar excitation. However, the nonlinear resonance curve will be totally shifted to lower frequencies and bend towards ion secular frequency as ion motion amplitude increases, which is just the opposite effect of any even-order field. Based on theoretical derivations, methods to reduce space charge effects were proposed.
Study of a micro chamber quadrupole mass spectrometer
Wang Jinchan; Zhang Xiaobing; Mao Fuming; Xiao Mei; Cui Yunkang; Engelsen, Daniel den; Lei Wei
2008-03-15
The design of a micro chamber quadrupole mass spectrometer (MCQMS) having a small total volume of only 20 cm{sup 3}, including Faraday cup ion detector and ion source, is described. This MCQMS can resist a vacuum baking temperature of 400-500 deg. C. The quadrupole elements with a hyperbolic surface are made of a ceramic material and coated with a thin metal layer. The quadrupole mass filter has a field radius of 3 mm and a length of 100 mm. Prototypes of this new MCQMS can detect a minimum partial pressure of 10{sup -8} Pa, have a peak width of {delta}M=1 at 10% peak height from mass number 1 to 60, and show an excellent long-term stability. The new MCQMS is intended to be used in residual gas analyses of electron devices during a mutual pumping and baking process.
Mechanical design of a large bore quadrupole triplet magnet
Abbott, S.; Caylor, R.; Fong, E.; Tanabe, J.
1987-03-01
The mechanical design and construction of a 1 meter bore, low gradient quadrupole triplet is described. The magnet will be used for focussing a proton beam in accelerator studies of neutral particle at the Los Alamos National Laboratory. A significant feature of this magnet design is the precision location of the coil conductors within the steel yoke tube. Each of the quadrupole coils have been fabricated from water cooled aluminum conductor, wound in a cosine 2-theta geometry. The conductor bundles have been wound to a positional accuracy within +-0.050 cm which was required to reduce the harmonic content to less than 0.04% of the quadrupole field. Important aspects of the design, construction and assembly are described.
Variable-field permanent magnet quadrupole for the SSC
Barlow, D.B.; Kraus, R.H. Jr.; Martinez, R.P.; Meyer, R.E.
1993-10-01
A set of compact variable-field permanent-magnet quadrupoles have been designed, fabricated, and tested for use In the SSC linac matching section. The quadrupoles have 24 mm-diameter apertures and 40 mm-long poles. The hybrid (permanent-magnet and iron) design, uses a fixed core of magnet material (NdFeB) and iron (C-1006) surrounded by a rotating ring of the same magnet material and iron. The quadrupole gradient-length product can be smoothly varied from a minimum of 0.7 T up to a maximum, of 4.3 T by a 90{degrees} rotation of the outer ring of iron and magnet material.
Cryogen free superconducting splittable quadrupole magnet for linear accelerators
Kashikhin, V.S.; Andreev, N.; Kerby, J.; Orlov, Y.; Solyak, N.; Tartaglia, M.; Velev, G.; /Fermilab
2011-09-01
A new superconducting quadrupole magnet for linear accelerators was fabricated at Fermilab. The magnet is designed to work inside a cryomodule in the space between SCRF cavities. SCRF cavities must be installed inside a very clean room adding issues to the magnet design, and fabrication. The designed magnet has a splittable along the vertical plane configuration and could be installed outside of the clean room around the beam pipe previously connected to neighboring cavities. For more convenient assembly and replacement a 'superferric' magnet configuration with four racetrack type coils was chosen. The magnet does not have a helium vessel and is conductively cooled from the cryomodule LHe supply pipe and a helium gas return pipe. The quadrupole generates 36 T integrated magnetic field gradient, has 600 mm effective length, and the peak gradient is 54 T/m. In this paper the quadrupole magnetic, mechanical, and thermal designs are presented, along with the magnet fabrication overview and first test results.
Reproductive skew and relatedness in social groups of European badgers, Meles meles.
Dugdale, Hannah L; Macdonald, David W; Pope, Lisa C; Johnson, Paul J; Burke, Terry
2008-04-01
Reproductive skew is a measure of the proportion of individuals of each sex that breed in a group and is a valuable measure for understanding the evolution and maintenance of sociality. Here, we provide the first quantification of reproductive skew within social groups of European badgers Meles meles, throughout an 18-year study in a high-density population. We used 22 microsatellite loci to analyse within-group relatedness and demonstrated that badger groups contained relatives. The average within-group relatedness was high (R = 0.20) and approximately one-third of within-group dyads were more likely to represent first-order kin than unrelated pairs. Adult females within groups had higher pairwise relatedness than adult males, due to the high frequency of extra-group paternities, rather than permanent physical dispersal. Spatial clustering of relatives occurred among neighbouring groups, which we suggest was due to the majority of extra-group paternities being attributable to neighbouring males. Reproductive skew was found among within-group candidate fathers (B = 0.26) and candidate mothers (B = 0.07), but not among breeding individuals; our power to detect skew in the latter was low. We use these results to evaluate reproductive skew models. Although badger society best fits the assumptions of the incomplete-control models, our results were not consistent with their predictions. We suggest that this may be due to female control of paternity, female-female reproductive suppression occurring only in years with high food availability resulting in competition over access to breeding sites, extra-group paternity masking the benefits of natal philopatry, and/or the inconsistent occurrence of hierarchies that are linear when established. PMID:18371017
Reynolds, Pamela L; Bruno, John F
2012-01-01
Widespread overharvesting of top consumers of the world's ecosystems has "skewed" food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.
Risk-sensitive foraging and the evolution of cooperative breeding and reproductive skew
Poethke, Hans J; Liebig, Jürgen
2008-01-01
Background Group formation and food sharing in animals may reduce variance in resource supply to breeding individuals. For some species it has thus been interpreted as a mechanism of risk avoidance. However, in many groups reproduction is extremely skewed. In such groups resources are not shared equally among the members and inter-individual variance in resource supply may be extreme. The potential consequences of this aspect of group living have not attained much attention in the context of risk sensitive foraging. Results We develop a model of individually foraging animals that share resources for reproduction. The model allows analyzing how mean foraging success, inter-individual variance of foraging success, and the cost of reproduction and offspring raising influence the benefit of group formation and resource sharing. Our model shows that the effects are diametrically opposed in egalitarian groups versus groups with high reproductive skew. For individuals in egalitarian groups the relative benefit of group formation increases under conditions of increasing variance in foraging success and decreasing cost of reproduction. On the other hand individuals in groups with high skew will profit from group formation under conditions of decreasing variance in individual foraging success and increasing cost of reproduction. Conclusion The model clearly demonstrates that reproductive skew qualitatively changes the influence of food sharing on the reproductive output of groups. It shows that the individual benefits of variance reduction in egalitarian groups and variance enhancement in groups with reproductive skew depend critically on ecological and life-history parameters. Our model of risk-sensitive foraging thus allows comparing animal societies as different as spiders and birds in a single framework. PMID:18366668
High and ulta-high gradient quadrupole magnets
Brunk, W.O.; Walz, D.R.
1985-05-01
Small bore conventional dc quadrupoles with apertures from 1 to 2.578cm were designed and prototypes built and measured. New fabrication techniques including the use of wire electric discharge milling (EDM) to economically generate the pole tip contours and aperture tolerances are described. Magnetic measurement data from a prototype of a 1cm aperture quadrupole with possible use in future e/sup +//e/sup -/ super colliders are presented. At a current of 400A, the lens achieved a gradient of 2.475 T/cm, and had an efficiency of 76.6%.
Conceptual design of a quadrupole magnet for eRHIC
Witte, H.; Berg, J. S.
2015-05-03
eRHIC is a proposed upgrade to the existing Relativistic Heavy Ion Collider (RHIC) hadron facility at Brookhaven National Laboratory, which would allow collisions of up to 21 GeV polarized electrons with a variety of species from the existing RHIC accelerator. eRHIC employs an Energy Recovery Linac (ERL) and an FFAG lattice for the arcs. The arcs require open-midplane quadrupole magnets of up to 30 T/m gradient of good field quality. In this paper we explore initial quadrupole magnet design concepts based on permanent magnetic material which allow to modify the gradient during operation.
Quadrupole Collective Inertia in Nuclear Fission: Cranking Approximation
Baran, A.; Sheikh, J. A.; Dobaczewski, J.; Nazarewicz, Witold
2011-01-01
Collective mass tensor derived from the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) approach is compared with that obtained in the Gaussian Overlap Approximation (GOA) to the generator coordinate method. Illustrative calculations are carried out for one-dimensional quadrupole fission pathways in ^{256}Fm. It is shown that the collective mass exhibits strong variations with the quadrupole collective coordinate. These variations are related to the changes in the intrinsic shell structure. The differences between collective inertia obtained in cranking and perturbative cranking approximations to ATDHFB, and within GOA, are discussed.
Simple loss scaling laws for quadrupoles and higher-order multipoles used in antihydrogen traps
Fajans, J.; Bertsche, W.; Burke, K.; Deutsch, A.; Chapman, S. F.; Gomberoff, K.; Wurtele, J. S.; Werf, D. P. van der
2006-10-18
Simple scaling laws strongly suggest that for antihydrogen relevant parameters, quadrupole magnetic fields will transport particles into, or near to, the trap walls. Consequently quadrupoles are a poor choice for antihydrogen trapping. Higher order multipoles lead to much less transport.
NASA Astrophysics Data System (ADS)
Onimaru, T.; Izawa, K.; Matsumoto, K. T.; Yoshida, T.; Machida, Y.; Ikeura, T.; Wakiya, K.; Umeo, K.; Kittaka, S.; Araki, K.; Sakakibara, T.; Takabatake, T.
2016-08-01
Orbital degrees of freedom in condensed matter could play important roles in forming a variety of exotic electronic states by interacting with conduction electrons. In 4 f -electron systems, because of strong intra-atomic spin-orbit coupling, an orbitally degenerate state inherently carries quadrupolar degrees of freedom. The present work has focused on a purely quadrupole-active system PrIr2Zn20 showing superconductivity in the presence of an antiferroquadrupole order at TQ=0.11 K. We observed non-Fermi-liquid (NFL) behaviors emerging in the electrical resistivity ρ and the 4 f contribution to the specific heat, C4 f, in the paramagnetic state at T > TQ. Moreover, in magnetic fields B ≤6 T, all data sets of ρ (T ) and C4 f(T ) are well scaled with characteristic temperatures T0's. This observation of the NFL state in the nonmagnetic quadrupole-active system has an origin intrinsically different from that observed in the vicinity of the conventional quantum critical point. It implies possible formation of a quadrupole Kondo lattice resulting from hybridization between the quadrupoles and the conduction electrons with an energy scale of kBT0 . At T ≤0.13 K, ρ (T ) and C4 f(T ) exhibit anomalies as B approaches 5 T. This is the manifestation of a field-induced crossover toward a Fermi-liquid ground state in the quadrupole Kondo lattice.
Tests of planar permanent magnet multipole focusing elements
Cobb, J.; Tatchyn, R.
1993-08-01
In recent work, planar configurations of permanent magnets were proposed as substitutes for conventional current-driven iron quadrupoles in applications limited by small aperture sizes and featuring small beam occupation diameters. Important examples include the configuring of focusing lattices in small-gap insertion devices, and the implementation of compact mini-beta sections on linear or circular machines. In subsequent analysis, this approach was extended to sextupoles and higher-order multipoles. In this paper we report on initial measurements conducted at the Stanford Linear Accelerator Center on recently fabricated planar permanent magnet quadrupoles and sextupoles configured out of SmCo and NdFe/B.
Cooks, Robert Graham; Baird, Zane; Peng, Wen-Ping
2015-11-10
The invention generally relates to apparatuses for focusing ions at or above ambient pressure and methods of use thereof. In certain embodiments, the invention provides an apparatus for focusing ions that includes an electrode having a cavity, at least one inlet within the electrode configured to operatively couple with an ionization source, such that discharge generated by the ionization source is injected into the cavity of the electrode, and an outlet. The cavity in the electrode is shaped such that upon application of voltage to the electrode, ions within the cavity are focused and directed to the outlet, which is positioned such that a proximal end of the outlet receives the focused ions and a distal end of the outlet is open to ambient pressure.
Measurement of an atomic quadrupole moment using dynamic decoupling
NASA Astrophysics Data System (ADS)
Akerman, Nitzan; Shaniv, Ravid; Ozeri, Roee
2016-05-01
Some of the best clocks today are ion-based optical clocks. These clocks are referenced to a narrow optical transition in a trapped ion. An example for such a narrow transition is the electric quadrupole E 2 transition between states with identical parity. An important systematic shift of such a transition is the quadrupole shift resulting from the electric field gradient inherent to the ion trap. We present a new dynamic decoupling method that rejects magnetic field noise while measuring the small quadrupole shift of the optical clock transition. Using our sequence we measured the quadrupole moment of the 4D5/2 level in a trapped 88 Sr+ ion to be 2 .973-0 . 033 + 0 . 026 ea02 , where e is the electron charge and a0 is the Bohr radius. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in 88 Sr+ based optical atomic clocks and verifies complicated many-body quantum calculations.
Magnetic field data on Fermilab Energy-Saver quadrupoles
Schmidt, E.E.; Brown, B.C.; Cooper, W.E.; Fisk, H.E.; Gross, D.A.; Hanft, R.; Ohnuma, S.; Turkot, F.T.
1983-03-01
The Fermilab Energy Saver/Doubler (Tevatron) accelerator contains 216 superconducting quadrupole magnets. Before installation in the Tevatron ring, these magnets plus an additional number of spares were extensively tested at the Fermilab Magnet Test Facility (MTF). Details on the results of the tests are presented here.
Large energy-spread beam diagnostics through quadrupole scans
Frederico, Joel; Adli, Erik; Hogan, Mark; Raubenheimer, Tor
2012-12-21
The Facility for Advanced Accelerator and Experimental Tests (FACET) is a new user facility at the SLAC National Accelerator Laboratory, servicing next-generation accelerator experiments. The 1.5% RMS energy spread of the FACET beam causes large chromatic aberrations in optics. These aberrations necessitate updated quadrupole scan fits to remain accurate.
Hybrid quadrupole excitons and polaritons in cuprous oxide
NASA Astrophysics Data System (ADS)
Roslyak, Oleksiy
In this thesis I consider novel type of materials such as hybrid organic/inorganic heteoro-structures and polystyrene micro-spheres/inorganic composites. The organic/inorganic compound is presented by DCM2:CA:PS/cuprous oxide material. Using "solid state solvent" mechanism I propose to bring the Frenkel exciton (FE) of the DCM2 into resonance with 1S quadrupole Wanier-Mott exciton (WE) in cuprous oxide. This two types of the excitons form new type of quadrupole-dipole hybrid exciton. This hybrid is characterized by long lifetime and big oscillator strength inherited from the organic FE. In the part I of the thesis I investigate the enhancement of the quadrupole properties generic to cuprous oxide exciton by means of such resonant hybridization. I consider enhancement of photo-thermal bi-stability and second harmonic generation. The second part is devoted to the problems of light-matter interaction in cuprous oxide crystals such as weak interaction with LA phonons and whispering gallery modes (WGM) in adjacent layer of polystyrene micro-spheres. While the first effect is likely to impeded BEC of the polaritons, the second mechanism provides necessary temporal coherence. It is possible by trapping the light part of the polariton into resonant WGM through big gradient of the evanescent tail which provides big lifetime of such evanescent polariton. Due to big gradient of the evanescent field it couples "naturally" to the quadrupole WE in cuprous oxide.
Driving a quadrupole mass spectrometer via an isolating stage
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Aalami, Dean (Inventor); Darrach, Murray (Inventor); Orient, Otto (Inventor)
2002-01-01
Driving a quadrupole mass spectrometer includes obtaining an air core transformer with a primary and a secondary, matching the secondary to the mass spectrometer, and driving the primary based on first and second voltage levels. Driving of the primary is via an isolating stage that minimizes low level drive signal coupling.
NASA Astrophysics Data System (ADS)
Boswell, S. M.; Zheng, L.; Gordon, R. G.; Dyment, J.
2010-12-01
In past work, reliable paleomagnetic poles have been determined from skewness data by solving for a single additional adjustable parameter, anomalous skewness, assumed to be independent of spreading rate [Petronotis et al. 1992, 1994; Petronotis & Gordon 1999]. Nonetheless, analysis of anomalies in several ocean basins indicate that anomalous skewness depends on spreading rate for spreading half rates less than ≈50 mm/yr [Roest et al., 1992; Dyment et al. 1994]. To facilitate investigation of the influence of spreading-rate dependent anomalous skewness on the determination of paleomagnetic poles determined from skewness, we build on the model for marine magnetic anomalies due to seafloor spreading of Dyment and Arkani-Hamed [1995]. We use this model to estimate anomalous skewness as a function of spreading rate for many anomalies. Synthetic magnetic anomaly profiles for oceanic lithosphere with sloping curving reversal boundaries were produced by forward modeling. Anomalous skewness values for chrons 25n to 33r were visually determined at various spreading rates using two approaches: balancing the shoulders of an anomaly corresponding to a single chron and best matching an anomaly corresponding to a single chron to a synthetic anomaly determined assuming vertical reversal boundaries. The new results may facilitate the determination of paleomagnetic poles from less widely distributed crossings of a magnetic anomaly than were used before. Further implications for determination of paleomagnetic poles for the Pacific plate will be discussed.
Construction engineering of steel tub-girder bridge systems for skew effects
NASA Astrophysics Data System (ADS)
Jimenez Chong, Juan Manuel
Closed structural sections, such as those having circular, rectangular or trapezoidal shape, possess high rotational rigidity when compared to open sections such as I-girders. The high torsional rigidity of closed sections makes them ideal for use in highly curved bridges. In this case, the geometry of the bridge results in large torsional forces. Because of structural efficiency and economy reasons, most of these closed-section bridges consist of a trapezoidal cross-section, with a top concrete slab and bottom and side steel plates. The slab is cast after the steel is erected and thus a system of internal diaphragms and braces is necessary to stabilize the system during erection. During the steel erection and the early stages of the concrete deck placement, the section can be considered as quasi-closed as the top concrete flange has not been cast or is not yet effective. During steel erection, undetermined and/or large torsional forces and/or displacements may result in fit-up problems requiring large stresses to overcome. During concrete deck placement, the undetermined displacements can affect the control of the deck thickness and the final deck geometry, such as the alignment of deck joints and the matching of stages in phased constructions projects. Due to the interactions between their various components, the behavior of curved and skewed tub-girder bridges is significantly more complex than that of straight bridges. When skewed supports are used in tub-girders, the interaction of the girder bending rotations and the displacement constraints induced by the skewed support diaphragms causes twisting of the girders at the supports. These twist rotations introduce additional torques into the system. Both curvature and skew can cause design and construction difficulties, especially at the supports, where the corresponding steel dead load deflections and the large torsional stiffness of the girders may lead to large fit-up forces. Currently, the general
Commutative n-ary superalgebras with an invariant skew-symmetric form
NASA Astrophysics Data System (ADS)
Vishnyakova, E. G.
2015-12-01
We study n-ary commutative superalgebras and L∞-algebras that possess a skew-symmetric invariant form, using the derived bracket formalism. This class of superalgebras includes for instance Lie algebras and their n-ary generalizations, commutative associative and Jordan algebras with an invariant form. We give a classification of anti-commutative m-dimensional (m - 3) -ary algebras with an invariant form, and a classification of real simple m-dimensional Lie (m - 3) -algebras with a positive definite invariant form up to isometry. Furthermore, we develop the Hodge Theory for L∞-algebras with a symmetric invariant form, and we describe quasi-Frobenius structures on skew-symmetric n-ary algebras.
Tang, An-Min; Tang, Nian-Sheng
2015-02-28
We propose a semiparametric multivariate skew-normal joint model for multivariate longitudinal and multivariate survival data. One main feature of the posited model is that we relax the commonly used normality assumption for random effects and within-subject error by using a centered Dirichlet process prior to specify the random effects distribution and using a multivariate skew-normal distribution to specify the within-subject error distribution and model trajectory functions of longitudinal responses semiparametrically. A Bayesian approach is proposed to simultaneously obtain Bayesian estimates of unknown parameters, random effects and nonparametric functions by combining the Gibbs sampler and the Metropolis-Hastings algorithm. Particularly, a Bayesian local influence approach is developed to assess the effect of minor perturbations to within-subject measurement error and random effects. Several simulation studies and an example are presented to illustrate the proposed methodologies. PMID:25404574
Optimization Of Mean-Semivariance-Skewness Portfolio Selection Model In Fuzzy Random Environment
NASA Astrophysics Data System (ADS)
Chatterjee, Amitava; Bhattacharyya, Rupak; Mukherjee, Supratim; Kar, Samarjit
2010-10-01
The purpose of the paper is to construct a mean-semivariance-skewness portfolio selection model in fuzzy random environment. The objective is to maximize the skewness with predefined maximum risk tolerance and minimum expected return. Here the security returns in the objectives and constraints are assumed to be fuzzy random variables in nature and then the vagueness of the fuzzy random variables in the objectives and constraints are transformed into fuzzy variables which are similar to trapezoidal numbers. The newly formed fuzzy model is then converted into a deterministic optimization model. The feasibility and effectiveness of the proposed method is verified by numerical example extracted from Bombay Stock Exchange (BSE). The exact parameters of fuzzy membership function and probability density function are obtained through fuzzy random simulating the past dates.
Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution
Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.
2013-01-01
The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351
Skewed X-chromosome inactivation in women affected by Alzheimer's disease.
Bajic, Vladan; Mandusic, Vesna; Stefanova, Elka; Bozovic, Ana; Davidovic, Radoslav; Zivkovic, Lada; Cabarkapa, Andrea; Spremo-Potparevic, Biljana
2015-01-01
X-chromosome instability has been a long established feature in Alzheimer's disease (AD). Premature centromere division and aneuploidy of the X-chromosome has been found in peripheral blood lymphocytes and neuronal tissue in female AD patients. Interestingly, only one chromosome of the X pair has been affected. These results raised a question, "Is the X-chromosome inactivation pattern altered in peripheral blood lymphocytes of women affected by AD?" To address this question, we analyzed the methylation status of androgen receptor promoter which may show us any deviation from the 50 : 50% X inactivation status in peripheral blood lymphocytes of women with AD. Our results showed skewed inactivation patterns (>90%). These findings suggest that an epigenetic alteration on the inactivation centers of the X-chromosome (or skewing) relates not only to aging, by might be a novel property that could account for the higher incidence of AD in women. PMID:25159673
Truck loading positions for maximum live load girder moment in skewed integral bridges
NASA Astrophysics Data System (ADS)
Yalcin, O. Fatih
2015-12-01
In this study, the effect of the longitudinal and transverse truck positions on the distribution of live load moment among the girders of skewed integral abutment bridges (SIBs) is investigated. For this purpose, three dimensional finite element models (FEMs) of several single-span SIBs are built and analyzed. In the analyses, bridges with various skew angles under all possible single and double truck loading positions both in longitudinal and transverse directions are considered. An automated analysis procedure managed by a visual basic program is developed to obtain the structural models and apply the wheel loads of trucks. The finite element analyses (FEA) results are then used to find the most critical loading cases of single truck and adjacent two trucks for the live load moment in the girders of SIBs. The results revealed that, the trucks should be placed nearby the midline of the bridge deck in a diagonal manner.
Bauke, W.; Clark, D.A.; Trujillo, P.B.
1985-01-01
Optical Tooling evolved from traditional surveying, and both technologies are sometimes used interchangeably in large industrial installations, since the instruments and their specialized adapters and supports complement each other well. A unique marriage of both technologies was accomplished in a novel application at LAMPF, the Los Alamos Meson Physics Facility. LAMPF consists of a linear accelerator with multiple target systems, one of which had to be altered to accommodate a new beamline for a neutrino experiment. The new line was to be installed into a crowded beam tunnel and had to be skewed and tilted in compound angles to avoid existing equipment. In this paper we describe how Optical Tooling was used in conjunction with simple alignment and reference fixtures to set fiducials on the magnets and other mechanical components of the beamline, and how theodolites and sight levels were then adapted to align these components along the calculated skew planes. Design tolerances are compared with measured alignment results.
Kinetic investigation of the extrinsic spin Hall effect induced by skew scattering
NASA Astrophysics Data System (ADS)
Cheng, J. L.; Wu, M. W.
2008-02-01
A study of the kinetics of the extrinsic spin Hall conductivity induced by skew scattering is performed using the fully microscopic kinetic spin Bloch equation approach to the (001) GaAs symmetric quantum well. In the steady state, the extrinsic spin Hall current/conductivity vanishes for the linear k dependent spin-orbit coupling and is very small for the cubic k dependent spin-orbit coupling. The spin precession induced by the Dresselhaus/Rashba spin-orbit coupling plays a very important role in the vanishing of the extrinsic spin Hall conductivity in the steady state. An in-plane spin polarization is induced by the skew scattering, with the help of the spin-orbit coupling. This spin polarization is very different from the current-induced spin polarization.
Research on the optimal structure configuration of dither RLG used in skewed redundant INS
NASA Astrophysics Data System (ADS)
Gao, Chunfeng; Wang, Qi; Wei, Guo; Long, Xingwu
2016-05-01
The actual combat effectiveness of weapon equipment is restricted by the performance of Inertial Navigation System (INS), especially in high reliability required situations such as fighter, satellite and submarine. Through the use of skewed sensor geometries, redundant technique has been applied to reduce the cost and improve the reliability of the INS. In this paper, the structure configuration and the inertial sensor characteristics of Skewed Redundant Strapdown Inertial Navigation System (SRSINS) using dithered Ring Laser Gyroscope (RLG) are analyzed. For the dither coupling effects of the dither gyro, the system measurement errors can be amplified either the individual gyro dither frequency is near one another or the structure of the SRSINS is unreasonable. Based on the characteristics of RLG, the research on coupled vibration of dithered RLG in SRSINS is carried out. On the principle of optimal navigation performance, optimal reliability and optimal cost-effectiveness, the comprehensive evaluation scheme of the inertial sensor configuration of SRINS is given.
Olfactory learning skews mushroom body output pathways to steer behavioral choice in Drosophila
Owald, David; Waddell, Scott
2015-01-01
Learning permits animals to attach meaning and context to sensory stimuli. How this information is coded in neural networks in the brain, and appropriately retrieved and utilized to guide behavior, is poorly understood. In the fruit fly olfactory memories of particular value are represented within sparse populations of odor-activated Kenyon cells (KCs) in the mushroom body ensemble. During learning reinforcing dopaminergic neurons skew the mushroom body network by driving zonally restricted plasticity at synaptic junctions between the KCs and subsets of the overall small collection of mushroom body output neurons. Reactivation of this skewed KC-output neuron network retrieves memory of odor valence and guides appropriate approach or avoidance behavior. PMID:26496148
Linac Sector 21-30 'QE' Quadrupole Magnet Excitation in LCLS Operation
Emma, P
2010-11-24
The existing SLAC linac quadrupole magnets, described as the 'QE' quadrupoles, are designed for excitation currents up to 200 A with length-integrated gradients up to 100 kG needed to focus up to 50-GeV electron or positron beams. The eight 'QE' magnets within a linac sector are powered in series on a single 200-A bulk power supply, and each magnet in sectors 21-29 also includes a 20-A booster supply (adds 0-20 A to each magnet) for gradient tapering within the sector. Sector 30 is different again with individual 200-A power supplies per magnet. The LCLS will use these same quadrupole magnets, mostly in their existing locations and with their present power supplies, but for an electron energy range of 0.25-14 GeV. This much lower beam energy will require good power supply regulation ({le} 0.05% rms for f > 0.5 Hz) [1] and accurate field excitation at much lower currents, as low as a few amperes. The present (pre-2006) gradient-to-current polynomials (IVBU) in the SLC database are based on magnetic measurements at excitation currents above 20 A, and are not accurate in extrapolation below about 10 A. For this reason the IVBU polynomials for all 'QE' quadrupoles in sectors 21-30 will be updated in 2007 for LCLS operation. Magnets beyond Q21601 will be updated with a new generic polynomial (with polarity considerations) based on magnetic measurements from zero current all the way up to 200 A, with additional data taken in the 0-20 A range for accuracy in LCLS mode (see Fig. 1). In addition, the first five LCLS 'QE' magnets (Q21201, Q21301, Q21401, Q21501, and Q21601), most of which run at the lowest currents of <3 A, have been individually measured and fitted with a specific polynomial to meet their special settings in LCLS mode. All changes will continue to fully support 30-50 GeV linac operations. This note describes these changes and the method used to arrive at this solution. Regulation tests have already been run on both the bulk and booster power supplies which
Skewness-induced asymmetric modulation of small-scale turbulence by large-scale structures
NASA Astrophysics Data System (ADS)
Agostini, Lionel; Leschziner, Michael; Gaitonde, Datta
2016-01-01
Several recent studies discuss of role of skewness of the turbulent velocity fluctuations in near-wall shear layers, in the context of quantifying the correlation between large-scale motions and amplitude variations of small-scale fluctuations—referred to as "modulation." The present study is based on the premise that the skewness of the small-scale fluctuations should be accounted for explicitly in the process of defining their envelope, which characterizes their amplitude variations. This leads to the notion of two envelopes, one for positive and the other for negative small-scale fluctuations, and hence also to two corresponding correlation coefficients. Justification for this concept is provided first by an examination of a high-frequency synthetic signal subjected to realistic skewness-inducing modulation. A new formalism is provided for deriving the two envelopes, and its fidelity is demonstrated for the synthetic test case. The method is then applied to a channel flow at a friction Reynolds number of 4200, for which direct numerical simulation (DNS) data are available. The large-scale and small-scale fields are separated by the empirical mode decomposition method, and the modulation of the small-scale fluctuations by the large scales is examined. Separate maps of the correlation coefficient and of two-point correlations, the latter linking the large-scale motions and the envelopes of the small-scale motions, are derived for the two envelopes pertaining to positive and negative small-scale fluctuations, and these demonstrate a significant sensitivity to the envelope-definition process, especially close to the wall where the skewness of the small-scale fluctuations is the dominant contributor to the total value.
Measuring skewness of red blood cell deformability distribution by laser ektacytometry
Nikitin, S Yu; Priezzhev, A V; Lugovtsov, A E; Ustinov, V D
2014-08-31
An algorithm is proposed for measuring the parameters of red blood cell deformability distribution based on laser diffractometry of red blood cells in shear flow (ektacytometry). The algorithm is tested on specially prepared samples of rat blood. In these experiments we succeeded in measuring the mean deformability, deformability variance and skewness of red blood cell deformability distribution with errors of 10%, 15% and 35%, respectively. (laser biophotonics)
Reynolds, Pamela L.; Bruno, John F.
2012-01-01
Widespread overharvesting of top consumers of the world’s ecosystems has “skewed” food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions. PMID:22693549
Detection of microscopic defects in optical fiber coatings using angle-resolved skew rays.
Chen, George Y; Monro, Tanya M; Lancaster, David G
2016-09-01
Microscopic defects in optical fiber coatings can be an impending catastrophe for high-power fiber laser and telecommunications systems and are difficult to detect with conventional methods. We demonstrate a highly sensitive interrogation technique that can readily identify faults such as microscopic nicks, scrapes, low-quality recoatings, and internal defects in fibers and their coatings, based on skew ray excitation and angle-resolved analysis.
Detection of microscopic defects in optical fiber coatings using angle-resolved skew rays.
Chen, George Y; Monro, Tanya M; Lancaster, David G
2016-09-01
Microscopic defects in optical fiber coatings can be an impending catastrophe for high-power fiber laser and telecommunications systems and are difficult to detect with conventional methods. We demonstrate a highly sensitive interrogation technique that can readily identify faults such as microscopic nicks, scrapes, low-quality recoatings, and internal defects in fibers and their coatings, based on skew ray excitation and angle-resolved analysis. PMID:27607966
Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps.
Chak, Solomon Tin Chi; Duffy, J Emmett; Rubenstein, Dustin R
2015-06-22
Sexual dimorphism is typically a result of strong sexual selection on male traits used in male-male competition and subsequent female choice. However, in social species where reproduction is monopolized by one or a few individuals in a group, selection on secondary sexual characteristics may be strong in both sexes. Indeed, sexual dimorphism is reduced in many cooperatively breeding vertebrates and eusocial insects with totipotent workers, presumably because of increased selection on female traits. Here, we examined the relationship between sexual dimorphism and sociality in eight species of Synalpheus snapping shrimps that vary in social structure and degree of reproductive skew. In species where reproduction was shared more equitably, most members of both sexes were physiologically capable of breeding. However, in species where reproduction was monopolized by a single individual, a large proportion of females--but not males--were reproductively inactive, suggesting stronger reproductive suppression and conflict among females. Moreover, as skew increased across species, proportional size of the major chela--the primary antagonistic weapon in snapping shrimps--increased among females and sexual dimorphism in major chela size declined. Thus, as reproductive skew increases among Synalpheus, female-female competition over reproduction appears to increase, resulting in decreased sexual dimorphism in weapon size.
Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps
Chak, Solomon Tin Chi; Duffy, J. Emmett; Rubenstein, Dustin R.
2015-01-01
Sexual dimorphism is typically a result of strong sexual selection on male traits used in male–male competition and subsequent female choice. However, in social species where reproduction is monopolized by one or a few individuals in a group, selection on secondary sexual characteristics may be strong in both sexes. Indeed, sexual dimorphism is reduced in many cooperatively breeding vertebrates and eusocial insects with totipotent workers, presumably because of increased selection on female traits. Here, we examined the relationship between sexual dimorphism and sociality in eight species of Synalpheus snapping shrimps that vary in social structure and degree of reproductive skew. In species where reproduction was shared more equitably, most members of both sexes were physiologically capable of breeding. However, in species where reproduction was monopolized by a single individual, a large proportion of females—but not males—were reproductively inactive, suggesting stronger reproductive suppression and conflict among females. Moreover, as skew increased across species, proportional size of the major chela—the primary antagonistic weapon in snapping shrimps—increased among females and sexual dimorphism in major chela size declined. Thus, as reproductive skew increases among Synalpheus, female–female competition over reproduction appears to increase, resulting in decreased sexual dimorphism in weapon size. PMID:26041357
A QTL Study for Regions Contributing to Arabidopsis thaliana Root Skewing on Tilted Surfaces.
Vaughn, Laura M; Masson, Patrick H
2011-07-01
Plant root systems must grow in a manner that is dictated by endogenous genetic pathways, yet sensitive to environmental input. This allows them to provide the plant with water and nutrients while navigating a heterogeneous soil environment filled with obstacles, toxins, and pests. Gravity and touch, which constitute important cues for roots growing in soil, have been shown to modulate root architecture by altering growth patterns. This is illustrated by Arabidopsis thaliana roots growing on tilted hard agar surfaces. Under these conditions, the roots are exposed to both gravity and touch stimulation. Consequently, they tend to skew their growth away from the vertical and wave along the surface. This complex growth behavior is believed to help roots avoid obstacles in nature. Interestingly, A. thaliana accessions display distinct growth patterns under these conditions, suggesting the possibility of using this variation as a tool to identify the molecular mechanisms that modulate root behavior in response to their mechanical environment. We have used the Cvi/Ler recombinant inbred line population to identify quantitative trait loci that contribute to root skewing on tilted hard agar surfaces. A combination of fine mapping for one of these QTL and microarray analysis of expression differences between Cvi and Ler root tips identifies a region on chromosome 2 as contributing to root skewing on tilted surfaces, potentially by modulating cell wall composition.
Stress Analysis of a New Disk-Type Variable Torque Slipping Clutch with Skewed Rollers
NASA Astrophysics Data System (ADS)
Feng, Ming; Ono, Kyosuke; Mimura, Kenji
In this paper a new disk type of the variable torque slipping clutch with skewed rollers (VTSCSR) is presented and investigated both theoretically and experimentally. It is comprised of two flat disks, a number of skewed cylindrical rollers, and a cage. The slipping torque is produced by the skewed rollers rolling and slipping between the two disks. Based on the integral equation of the Boussinesq solution, the contact pressures are numerically calculated under the condition that the nonlinear equilibrium equations of the clutch elements are satisfied. By considering both pressure and friction, the components of subsurface stress are calculated from the integration of the Mindlin's subsurface stress equations of concentrated force. A numerical solver is then successfully developed by which the characteristics of the disk-type VTSCSR, including the torque capacity, angular velocities of the roller and cage, contact pressure and von Mises stress, etc, are calculated and illustrated for the typical designs. The influences on the distribution of the von Mises stress by applying various types of profiled rollers to the disk-type VTSCSR are also discussed. It has been found that the full crown with two arcs profiled roller can approximately give rise to the axially uniform distribution of the von Mises stress and therefore satisfies the design principle of the average damage of materials. In addition, the preliminary experiment was done in order to show the feasibility of this design idea and to verify the theoretical torque capacity.
An inconvenient sea truth: spread, steepness, and skewness of surface slopes.
Munk, Walter
2009-01-01
Bréon and Henriot (BH) have collected eight million globally distributed satellite images of sunglitter, which yield a few simple, robust rules about the statistics of surface slopes: 1) constant angular spread, 2) linear steepness, and 3) sigmoid (near stepwise) skewness (all with respect to wind speed). Yet the information is sparse because it says nothing about time and space scales. The BH rules are an inconvenient sea truth, too fundamental to be ignored, too incomplete to be understood. With regard to BH rule 1 (BH:1), I suggest that the constant spread is associated with a wake-like geometry of the short gravities. Steepness linearity (BH:2) remains an enigma. Skewness (BH:3) appears to be correlated with a rather sudden onset of breaking for winds above 4 m s(-1). I do not think that skewness comes from parasitic capillaries. These are tentative conclusions; I look forward to intensive sea-going experiments over the next few years demolishing the proposed interpretations.
A Bayesian estimate of the concordance correlation coefficient with skewed data.
Feng, Dai; Baumgartner, Richard; Svetnik, Vladimir
2015-01-01
Concordance correlation coefficient (CCC) is one of the most popular scaled indices used to evaluate agreement. Most commonly, it is used under the assumption that data is normally distributed. This assumption, however, does not apply to skewed data sets. While methods for the estimation of the CCC of skewed data sets have been introduced and studied, the Bayesian approach and its comparison with the previous methods has been lacking. In this study, we propose a Bayesian method for the estimation of the CCC of skewed data sets and compare it with the best method previously investigated. The proposed method has certain advantages. It tends to outperform the best method studied before when the variation of the data is mainly from the random subject effect instead of error. Furthermore, it allows for greater flexibility in application by enabling incorporation of missing data, confounding covariates, and replications, which was not considered previously. The superiority of this new approach is demonstrated using simulation as well as real-life biomarker data sets used in an electroencephalography clinical study. The implementation of the Bayesian method is accessible through the Comprehensive R Archive Network. PMID:26033433
Aminian, Manuchehr; Bernardi, Francesca; Camassa, Roberto; McLaughlin, Richard M
2015-10-01
We study the role geometry plays in the emergence of asymmetries in diffusing passive scalars advected by pressure-driven flows in ducts and pipes of different aspect ratios. We uncover nonintuitive, multi-time-scale behavior gauged by a new statistic, which we term "geometric skewness" S^{G}, which measures instantaneously forming asymmetries at short times due to flow geometry. This signature distinguishes elliptical pipes of any aspect ratio, for which S^{G}=0, from rectangular ducts whose S^{G} is generically nonzero, and, interestingly, shows that a special duct of aspect ratio ≈0.53335 behaves like a circular pipe as its geometric skewness vanishes. Using a combination of exact solutions, novel short-time asymptotics, and Monte Carlo simulations, we establish the relevant time scales for plateaus and extrema in the evolution of the skewness and kurtosis for our class of geometries. For ducts limiting to channel geometries, we present new exact, single-series formulas for the first four moments on slices used to benchmark Monte Carlo simulations. PMID:26550727
Free vibration of composite skewed cylindrical shell panel by finite element method
NASA Astrophysics Data System (ADS)
Haldar, Salil
2008-03-01
In this paper a composite triangular shallow shell element has been used for free vibration analysis of laminated composite skewed cylindrical shell panels. In the present element first-order shear deformation theory has been incorporated by taking transverse displacement and bending rotations as independent field variables. The interpolation function used to approximate transverse displacement is one order higher than for bending rotations. This has made the element free from locking in shear. Two types of mass lumping schemes have been recommended. In one of the mass lumping scheme the effect of rotary inertia has been incorporated in the element formulations. Free vibration of skewed composite cylindrical shell panels having different thickness to radius ratios ( h/R=0.01-0.2), length to radius ratios ( L/R), number of layers and fiber orientation angles have been analyzed following the shallow shell method. The results for few examples obtained in the present analysis have compared with the published results. Some new results of composite skewed cylindrical shell panels have been presented which are expected to be useful to future research in this direction.
Study of a final focus system for high intensity beams
Henestroza, Enrique; Eylon, Shmuel; Roy, Prabir K.; Yu, Simon S.; Bieniosek, Frank M.; Shuman, Derek B.; Waldron, William L.
2004-06-01
The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high perveance heavy ion beams. The final focus scenario in an HIF driver consists of several large aperture quadrupole magnets followed by a drift section in which the beam space charge is neutralized by a plasma. This beam is required to hit a millimeter-sized target spot at the end of the drift section. The objective of the NTX experiments and associated theory and simulations is to study the various physical mechanisms that determine the final spot size (radius r{sub s}) at a given distance (f) from the end of the last quadrupole. In a fusion driver, f is the standoff distance required to keep the chamber wall and superconducting magnets properly protected. The NTX final quadrupole focusing system produces a converging beam at the entrance to the neutralized drift section where it focuses to a small spot. The final spot is determined by the conditions of the beam entering the quadrupole section, the beam dynamics in the magnetic lattice, and the plasma neutralization dynamics in the drift section. The main issues are the control of emittance growth due to high order fields from magnetic multipoles and image fields. In this paper, we will describe the theoretical and experimental aspects of the beam dynamics in the quadrupole lattice, and how these physical effects influence the final beam size. In particular, we present theoretical and experimental results on the dependence of final spot size on geometric aberrations and perveance.
New final focus system for the SLAC linear collider
Toge, N.; Ash, W.W.; Chao, Y.C.; Erickson, R.; Gray, R.; Mansour, D.; Spencer, C.M.; Ziemann, V. ); Band, H. . Dept. of Physics); Bazarko, A.O. . Dept. of Physics); Hertzbach, S.S.; Kofler, R.R. . Dept. of Physics); Turk, J. (Yale Univ., New
1991-05-01
The final focus system of the SLC has been upgraded by replacing the final quadrupole magnets with higher gradient superconducting magnets positioned closer to the interaction point. The parameters of the new system have been chosen to be compatible with the SLD detector with a minimum of changes to other final focus components. Commissioning plans for the new system are also presented. 5 refs., 1 fig.
Ng, Benjamin; Cai, Wenju; Walsh, Kevin
2014-08-12
A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming.
Using skew-logistic probability density function as a model for age-specific fertility rate pattern.
Asili, Sahar; Rezaei, Sadegh; Najjar, Lotfollah
2014-01-01
Fertility rate is one of the most important global indexes. Past researchers found models which fit to age-specific fertility rates. For example, mixture probability density functions have been proposed for situations with bi-modal fertility patterns. This model is less useful for unimodal age-specific fertility rate patterns, so a model based on skew-symmetric (skew-normal) pdf was proposed by Mazzuco and Scarpa (2011) which was flexible for unimodal and bimodal fertility patterns. In this paper, we introduce skew-logistic probability density function as a better model: its residuals are less than those of the skew-normal model and it can more precisely estimate the parameters of the model. PMID:24967404
Strong focusing influence on high gain FEL characteristics
Smirnov, A.; Varfolomeev, A.
1995-12-31
The use of intrinsic alternating focusing in a linac-driven FEL with planar undulator is considered numerically. The analysis is done on the basis of TDA code for soft X-ray FEL with FD lattice implementing focusing of quadrupole and periodic sextupole type. The influence of the focusing (type and phase advance) on FEL performance and the reasons of difference in FEL performance for focusing of two kinds are analyzed. A possibility of some kind of beam conditioning for intrinsic focusing is discussed.
Wolf, Ruth E.; Adams, Monique
2015-01-01
Typically, quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) is used to determine as many as 57 major, minor, and trace elements in aqueous geochemical samples, including natural surface water and groundwater, acid mine drainage water, and extracts or leachates from geological samples. The sample solution is aspirated into the inductively coupled plasma (ICP) which is an electrodeless discharge of ionized argon gas at a temperature of approximately 6,000 degrees Celsius. The elements in the sample solution are subsequently volatilized, atomized, and ionized by the ICP. The ions generated are then focused and introduced into a quadrupole mass filter which only allows one mass to reach the detector at a given moment in time. As the settings of the mass analyzer change, subsequent masses are allowed to impact the detector. Although the typical quadrupole ICP-MS system is a sequential scanning instrument (determining each mass separately), the scan speed of modern instruments is on the order of several thousand masses per second. Consequently, typical total sample analysis times of 2–3 minutes are readily achievable for up to 57 elements.
NASA Technical Reports Server (NTRS)
Snyder, Robert S.
2001-01-01
Electrophoretic focusing is a new method of continuous flow electrophoresis that introduces precision flow control to achieve high resolution separations. The electric field is applied perpendicular to an incoming sample lamina and buffer but also perpendicular to the broad faces of the thin rectangular chamber. A uniform fluid cross-flow then enters and exits the separation chamber through the same broad faces which are porous. A balance is achieved by adjusting either the electric field or the cross-flow so the desired sample fraction with its specific migration velocity encounters an opposing flow of the same velocity. Applying an electric field transverse to the incoming sample lamina and opposing this field with a carefully configured buffer flow, a sample constituent can be selected and focused into a narrow stream for subsequent analysis. Monotonically changing either electric field or buffer cross-flow will yield a scan of all constituents of the sample. Stopping the scan increases the collection time for minor constituents to improve their analysis. Using the high voltage gradients and/or cross-flow to rapidly deflect extraneous sample through the porous screens and into either of the side (purge) chambers, the selected sample is focused in the center plane of the separation chamber and collected without contact or interaction with the separation chamber walls. Results will be presented on the separation of a range of materials including dyes, proteins, and monodisperse polystyrene latexes. Sources of sample dispersion inherent in other electrokinetic techniques will be shown to be negligible for a variety of sample concentrations, buffer properties and operating conditions.
Electron beam final focus system for Thomson scattering at ELBE
NASA Astrophysics Data System (ADS)
Krämer, J. M.; Budde, M.; Bødker, F.; Irman, A.; Jochmann, A.; Kristensen, J. P.; Lehnert, U.; Michel, P.; Schramm, U.
2016-09-01
The design of an electron beam final focus system (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and divergences of about 10 mrad using the FFS.
Godler, David E; Inaba, Yoshimi; Schwartz, Charles E; Bui, Quang M; Shi, Elva Z; Li, Xin; Herlihy, Amy S; Skinner, Cindy; Hagerman, Randi J; Francis, David; Amor, David J; Metcalfe, Sylvia A; Hopper, John L; Slater, Howard R
2015-01-01
Methylation of the fragile X mental retardation 1 (FMR1) exon 1/intron 1 boundary positioned fragile X related epigenetic element 2 (FREE2), reveals skewed X-chromosome inactivation (XCI) in fragile X syndrome full mutation (FM: CGG > 200) females. XCI skewing has been also linked to abnormal X-linked gene expression with the broader clinical impact for sex chromosome aneuploidies (SCAs). In this study, 10 FREE2 CpG sites were targeted using methylation specific quantitative melt analysis (MS-QMA), including 3 sites that could not be analysed with previously used EpiTYPER system. The method was applied for detection of skewed XCI in FM females and in different types of SCA. We tested venous blood and saliva DNA collected from 107 controls (CGG < 40), and 148 FM and 90 SCA individuals. MS-QMA identified: (i) most SCAs if combined with a Y chromosome test; (ii) locus-specific XCI skewing towards the hypomethylated state in FM females; and (iii) skewed XCI towards the hypermethylated state in SCA with 3 or more X chromosomes, and in 5% of the 47,XXY individuals. MS-QMA output also showed significant correlation with the EpiTYPER reference method in FM males and females (P < 0.0001) and SCAs (P < 0.05). In conclusion, we demonstrate use of MS-QMA to quantify skewed XCI in two applications with diagnostic utility. PMID:26132880
Godler, David E; Inaba, Yoshimi; Schwartz, Charles E; Bui, Quang M; Shi, Elva Z; Li, Xin; Herlihy, Amy S; Skinner, Cindy; Hagerman, Randi J; Francis, David; Amor, David J; Metcalfe, Sylvia A; Hopper, John L; Slater, Howard R
2015-07-01
Methylation of the fragile X mental retardation 1 (FMR1) exon 1/intron 1 boundary positioned fragile X related epigenetic element 2 (FREE2), reveals skewed X-chromosome inactivation (XCI) in fragile X syndrome full mutation (FM: CGG > 200) females. XCI skewing has been also linked to abnormal X-linked gene expression with the broader clinical impact for sex chromosome aneuploidies (SCAs). In this study, 10 FREE2 CpG sites were targeted using methylation specific quantitative melt analysis (MS-QMA), including 3 sites that could not be analysed with previously used EpiTYPER system. The method was applied for detection of skewed XCI in FM females and in different types of SCA. We tested venous blood and saliva DNA collected from 107 controls (CGG < 40), and 148 FM and 90 SCA individuals. MS-QMA identified: (i) most SCAs if combined with a Y chromosome test; (ii) locus-specific XCI skewing towards the hypomethylated state in FM females; and (iii) skewed XCI towards the hypermethylated state in SCA with 3 or more X chromosomes, and in 5% of the 47,XXY individuals. MS-QMA output also showed significant correlation with the EpiTYPER reference method in FM males and females (P < 0.0001) and SCAs (P < 0.05). In conclusion, we demonstrate use of MS-QMA to quantify skewed XCI in two applications with diagnostic utility.
Measurement reports for the cryogenically-cooled drift tube quadrupoles
1993-12-31
This compilation contains quadrupole measurement reports for LANL type A and type E drift tube cryoquads. The cryoquad information gives s/n, vendor, field strength, phase, b3/b2, b4/b2, b5/b2, b6/b2, center wire location. The measurements for the harmonic measuring system gives time and date of measurements, magnet p/n, coil p/n, coil radii, coil turns, low and high gain, and temperature. Quadrupole information includes effective B` X L, and magnetic center. Bucked and unbucked calculations give signal in {mu}V{center_dot}sec, field in Tesla{center_dot}meter, B(n)/B(2), absolute and relative phase.
Development and test of LARP technological quadrupole (TQC) magnet
Feher, S.; Bossert, R.C.; Ambrosio, G.; Andreev, N.; Barzi, E.; Carcagno, R.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; /Fermilab /LBL, Berkeley
2006-08-01
In support of the development of a large-aperture Nb{sub 3}Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, two-layer quadrupole models (TQC and TQS) with 90-mm aperture are being constructed at Fermilab and LBNL within the framework of the US LHC Accelerator Research Program (LARP). This paper describes the construction and test of model TQC01. ANSYS calculations of the structure are compared with measurements during construction. Fabrication experience is described and in-process measurements are reported. Test results at 4.5K are presented, including magnet training, current ramp rate studies and magnet quench current . Results of magnetic measurements at helium temperature are also presented.
Development and Test of LARP Technological Quadrupole (TQC) Magnet
Feher, S.; Bossert, R.C.; Ambrosio, G.; Andreev, N.; Barzi, E.; Carcagno, R.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; Pischalnikov, Yu.; Sylvester, C.; Tartaglia, M.; Turrioni, D.; Whitson, G.; Yamada, R.; Zlobin, A.V.; Caspi, S.; Dietderich, D.; Ferracin, P.; Hannaford, R.; Hafalia, A.R.; Sabbi, G.
2007-06-01
In support of the development of a large-aperture Nb{sub 3}Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade, two-layer quadrupole models (TQC and TQS) with 90 mm aperture are being constructed at Fermilab and LBNL within the framework of the US LHC Accelerator Research Program (LARP). This paper describes the construction and test of model TQC01. ANSYS calculations of the structure are compared with measurements during construction. Fabrication experience is described and in-process measurements are reported. Test results at 4.5 K are presented, including magnet training, current ramp rate studies and magnet quench current. Results of magnetic measurements at helium temperature are also presented.
Performance of An Adjustable Strength Permanent Magnet Quadrupole
Gottschalk, S.C.; DeHart, T.E.; Kangas, K.W.; Spencer, C.M.; Volk, J.T.; /Fermilab
2006-03-01
An adjustable strength permanent magnet quadrupole suitable for use in Next Linear Collider has been built and tested. The pole length is 42cm, aperture diameter 13mm, peak pole tip strength 1.03Tesla and peak integrated gradient * length (GL) is 68.7 Tesla. This paper describes measurements of strength, magnetic CL and field quality made using an air bearing rotating coil system. The magnetic CL stability during -20% strength adjustment proposed for beam based alignment was < 0.2 microns. Strength hysteresis was negligible. Thermal expansion of quadrupole and measurement parts caused a repeatable and easily compensated change in the vertical magnetic CL. Calibration procedures as well as CL measurements made over a wider tuning range of 100% to 20% in strength useful for a wide range of applications will be described. The impact of eddy currents in the steel poles on the magnetic field during strength adjustments will be reported.
Nuclear quadrupole moment of the {sup 99}Tc ground state
Errico, Leonardo; Darriba, German; Renteria, Mario; Tang Zhengning; Emmerich, Heike; Cottenier, Stefaan
2008-05-15
By combining first-principles calculations and existing nuclear magnetic resonance (NMR) experiments, we determine the quadrupole moment of the 9/2{sup +} ground state of {sup 99}Tc to be (-)0.14(3)b. This confirms the value of -0.129(20)b, which is currently believed to be the most reliable experimental determination, and disagrees with two earlier experimental values. We supply ab initio calculated electric-field gradients for Tc in YTc{sub 2} and ZrTc{sub 2}. If this calculated information would be combined with yet to be performed Tc-NMR experiments in these compounds, the error bar on the {sup 99}Tc ground state quadrupole moment could be further reduced.
Superferric quadrupoles for FAIR Super FRS energy buncher
NASA Astrophysics Data System (ADS)
Pal, G.; Bhunia, U.; Akhter, J.; Nandi, C.; Datta, A.; Sarma, P. R.; Roy, S.; Bajirao, S.; Bhattacharyya, S.; Bhattacharyya, T. K.; Dey, M. K.; Mallik, C.; Bhandari, R. K.
2012-12-01
The quadrupole magnets for FAIR Super FRS energy buncher have large usable aperture, high magnetic pole-tip field and high gradient field quality. The iron-dominated magnets with superconducting coils have to be used in this application. The NbTi coil, laminated iron, and support structure of about 22 tons is immersed in liquid helium. The 4.5 K helium chamber is completely covered with a thermal shield cooled by helium at 50-80 K on its outer and inner surface. The helium chamber and thermal shield is enclosed in a vacuum shell. The paper presents design details of the long quadrupole. Coupled thermal, magnetic and structural analysis was carried out to design the magnet iron, magnet coil, helium vessel and support links and ensure the required gradient field quality is achieved. The paper also presents the design of support links and outer vacuum chamber.
ELECTRON TRAPPING IN WIGGLER AND QUADRUPOLE MAGNETS OF CESRTA
Wang, Lanfa; Huang, Xiaobiao; Pivi, Mauro; /SLAC
2010-08-25
The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D [1]. One of the primary goals of the CesrTA program is to investigate the interaction of the electron cloud with low emittance positron beam to explore methods to suppress the electron cloud, develop suitable advanced instrumentation required for these experimental studies and benchmark predictions by simulation codes. This paper reports the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using the 3D code CLOUDLAND. We found that electrons can be trapped with long lifetime in a quadrupole magnet due to the mirror field trapping mechanism and photoelectrons produced in the wiggler zero field zone have long lifetime due to their complicated trajectory.
Detection of the quadrupole hyperfine structure in HCNH(+)
NASA Technical Reports Server (NTRS)
Ziurys, L. M.; Apponi, A. J.; Yoder, J. T.
1992-01-01
We report the first measurement of the electric quadrupole hyperfine structure of HCNH(+). The J = 1-0 transition of this interstellar molecular ion was observed toward the cold, dark cloud TMC-1, using the NRAO 12 m telescope at 74 GHz. The three hyperfine components of this transition were clearly detected and resolved, enabling the first experimental determination of the quadrupole coupling constant eqQ of HCNH(+). The value of this constant is calculated to be eqQ = -0.49 +/- 0.07 MHz. The column density of HCNH(+) toward TMC-1 was found to be N(tot) about 2.8 x 10 exp 13/sq cm, corresponding to a fractional abundance relative to H2 of f about 3 x 10 exp -9. This abundance is at least one order of magnitude higher than the predictions of ion-molecule chemistry. Detection of the hyperfine structure clearly establishes the presence of HCNH(+) in interstellar space.
Specification of multipole tolerances for the APS quadrupole magnet
Kramer, S.L.
1988-08-01
This note will address a proposed method for specifying the multipole tolerance for the design and production of APS quadrupole magnets. The tolerances for the multipole components for the quadrupole magnets will be set to that level which reduces the dynamic aperture by about 10--15% from the ideal machine dynamic aperture (as specified in CDR-87). This level may appear rather stringent, especially compared to the 50--60% reduction resulting from quad placement errors. However, when all tolerances are taken together, the residual dynamic aperture would be prohibitively small and commissioning would be difficult if these tolerances were at twice this level. The dynamic aperture was determined using the numerical tracking program RACETRACK.
Quadrupole moments of wobbling excitations in 163Lu
Gorgen, A.; Clark, R.M.; Cromaz, M.; Fallon, P.; Hagemann, G.B.; Hubel, H.; Lee, I.Y.; Macchiavelli, A.O.; Sletten, G.; Ward, D.; Bengtsson, R.
2004-01-01
Lifetimes of states in the triaxial strongly deformed bands of {sup 163}Lu have been measured in a Gammasphere experiment using the Doppler-shift attenuation method. The bands are interpreted as wobbling-phonon excitations from the characteristic electromagnetic properties of the transitions connecting the bands. Quadrupole moments were extracted for the 0-phonon yrast band and, for the first time, for the 1-phonon wobbling band. The very similar results found for both bands suggest a similar intrinsic structure confirming the wobbling interpretation. While the in-band quadrupole moments for the bands show a decreasing trend towards higher spin, the strength of the inter-band transitions remains constant. Both features can be understood by a small increase in triaxiality towards higher spin. Such a change in triaxiality is also found in cranking calculations, to which the experimental results are compared.
Improved performance of a quadrupole based glow discharge mass spectrometer
Valiga, R.E.; Duckworth, D.C.; Smith, D.H.
1995-12-31
Glow discharge mass spectrometry (GDMS) has experienced most of its commercial success in trace multi-element analysis using sector-based mass spectrometry. In most cases, the mass resolution available with these instruments allows elements of interest to be analyzed, even in the presence of polyatomic interferences (e.g., ArC+, ArN+, ArO+). Because quadrupole mass filters have little more than unit resolution, background equivalent concentrations (BEC`s) for many elements can be quite high (1-100 ppm). Because of this, many have discounted quadrupole GDMS as a useful trace analysis technique. In this work, the authors have explored methods of reducing the polyatomic interferences.
120-mm supercondcting quadrupole for interaction regions of hadron colliders
Zlobin, A.V.; Kashikhin, V.V.; Mokhov, N.V.; Novitski, I.; /Fermilab
2010-05-01
Magnetic and mechanical designs of a Nb{sub 3}Sn quadrupole magnet with 120-mm aperture suitable for interaction regions of hadron colliders are presented. The magnet is based on a two-layer shell-type coil and a cold iron yoke. Special spacers made of a low-Z material are implemented in the coil mid-planes to reduce the level of radiation heat deposition and radiation dose in the coil. The quadrupole mechanical structure is based on aluminum collars supported by an iron yoke and a stainless steel skin. Magnet parameters including maximum field gradient and field harmonics, Nb3Sn coil pre-stress and protection at the operating temperatures of 4.5 and 1.9 K are reported. The level and distribution of radiation heat deposition in the coil and other magnet components are discussed.
Quadrupole association and dissociation of hydrogen in the early Universe
NASA Astrophysics Data System (ADS)
Forrey, Robert C.
2016-10-01
Radiative association and photodissociation rates are calculated for quadrupole transitions of H2. A complete set of bound and unbound states are included in a self-consistent master equation to obtain steady-state concentrations for a dilute system of hydrogen atoms and molecules. Phenomenological rate constants computed from the steady-state concentrations satisfy detailed balance for any combination of matter and radiation temperature. Simple formulas are derived for expressing the steady-state distributions in terms of equilibrium distributions. The rate constant for radiative association is found to be generally small for all temperature combinations. The photodissociation rate constant for quadrupole transitions is found to dominate the rate constants for other H2 photodestruction mechanisms for {T}{{R}} ≤slant 3000 K. Implications for the formation and destruction of H2 in the early Universe are discussed.
Allen, L.A.
1997-02-01
The focus of this dissertation is the use of a twin quadrupole inductively coupled plasma mass spectrometer (ICP-MS) for the simultaneous detection of two m/z values. The twin quadrupole ICP-MS is used with laser ablation sample introduction in both the steady state (10 Hz) and single pulse modes. Steady state signals are highly correlated and the majority of flicker noise cancels when the ratio is calculated. Using a copper sample, the isotope ratio {sup 63}Cu{sup +}/{sup 65}Cu{sup +} is measured with a relative standard deviation (RSD) of 0.26%. Transient signals for single laser pulses are also obtained. Copper isotope ratio measurements for several laser pulses are measured with an RSD of 0.85%. Laser ablation (LA) is used with steel samples to assess the ability of the twin quadrupole ICP-MS to eliminate flicker noise of minor components of steel samples. Isotopic and internal standard ratios are measured in the first part of this work. The isotope ratio {sup 52}Cr{sup +}/{sup 53}Cr{sup +} (Cr present at 1.31 %) can be measured with an RSD of 0.06 % to 0.1 %. For internal standard elements, RSDs improve from 1.9 % in the Cr{sup +} signal to 0.12% for the ratio of {sup 51}V{sup +} to {sup 52}Cr{sup +}. In the second part of this work, one mass spectrometer is scanned while the second channel measures an individual m/z value. When the ratio of these two signals is calculated, the peak shapes in the mass spectrum are improved significantly. Pulses of analyte and matrix ions from individual drops are measured simultaneously using the twin quadrupole ICP-MS with monodisperse dried microparticulate injection (MDMI). At modest Pb concentrations (500 ppm), a shoulder on the leading edge of the Li{sup +} signal becomes apparent. Space charge effects are consistent with the disturbances seen.
Gravitational radiation quadrupole formula is valid for gravitationally interacting systems
NASA Technical Reports Server (NTRS)
Walker, M.; Will, C. M.
1980-01-01
An argument is presented for the validity of the quadrupole formula for gravitational radiation energy loss in the far field of nearly Newtonian (e.g., binary stellar) systems. This argument differs from earlier ones in that it determines beforehand the formal accuracy of approximation required to describe gravitationally self-interacting systems, uses the corresponding approximate equation of motion explicitly, and evaluates the appropriate asymptotic quantities by matching along the correct space-time light cones.
Microfabricated quadrupole ion trap for mass spectrometer applications.
Pau, S; Pai, C S; Low, Y L; Moxom, J; Reilly, P T A; Whitten, W B; Ramsey, J M
2006-03-31
An array of miniaturized cylindrical quadrupole ion traps, with a radius of 20 microm, is fabricated using silicon micromachining using phosphorus doped polysilicon and silicon dioxide for the purpose of creating a mass spectrometer on a chip. We have operated the array for mass-selective ion ejection and mass analysis using Xe ions at a pressure of 10(-4). The scaling rules for the ion trap in relation to operating pressure, voltage, and frequency are examined. PMID:16605890
Magnetic performance of new Fermilab high gradient quadrupoles
Hanft, R.; Brown, B.C.; Carson, J.A.; Gourlay, S.A.; Lamm, M.J.; McInturff, A.D.; Mokhtarani, A.; Riddiford, A.
1991-05-01
For the Fermilab Tevatron low beta insertions installed in 1990--1991 as part of a luminosity upgrade there were built approximately 35 superconducting cold iron quadrupoles utilizing a two layer cos 2{theta} coil geometry with 76 mm diameter aperature. The field harmonics and strengths of these magnets obtained by measurement at cryogenic conditions are presented. Evidence for a longitudinal periodic structure in the remnant field is shown. 6 refs., 2 figs., 3 tabs.
Analysis on linac quadrupole misalignment in FACET commissioning 2012
Sun, Yipeng; /SLAC
2012-07-05
In this note, the analysis on linac quadrupole misalignment is presented for the FACET linac section LI05-09 plus LI11-19. The effectiveness of the beam-based alignment technique is preliminarily confirmed by the measurement. Beam-based alignment technique was adopted at SLAC linac since SLC time. Here the beam-based alignment algorithms are further developed and applied in the FACET commissioning during 2012 run.
Design and Measurement of the NSLS II Quadrupole Prototypes
Rehak,M.; Jain, A. K.; Skaritka, J.; Spataro, C.
2009-05-04
The design and measurement of the NSLS-II ring quadrupoles prototypes are presented. These magnets are part of a larger prototype program described in [1]. Advances in software, hardware, and manufacturing have led to some new level of insight in the quest for the perfect magnet design. Three geometric features are used to minimize the first three allowed harmonics by way of optimization. Validations through measurement and confidence levels in calculations are established.
Quadrupole Magnetic Sorting of Porcine Islets of Langerhans
Shenkman, Rustin M.; Chalmers, Jeffrey J.; Hering, Bernhard J.; Kirchhof, Nicole
2009-01-01
Islet transplantation is emerging as a treatment option for selected patients with type 1 diabetes. Inconsistent isolation, purification, and recovery of large numbers of high-quality islets remain substantial impediments to progress in the field. Removing islets as soon as they are liberated from the pancreas during digestion and circumventing the need for density gradient purification is likely to result in substantially increased viable islet yields by minimizing exposure to proteolytic enzymes, reactive oxygen intermediates, and mechanical stress associated with centrifugation. This study capitalized on the hypervascularity of islets compared with acinar tissue to explore their preferential enrichment with magnetic beads to enable immediate separation in a magnetic field utilizing a quadrupole magnetic sorting. The results demonstrate that (1) preferential enrichment of porcine islets is achievable, but homogeneous bead distribution within the pancreas is difficult to achieve with current protocols; (2) greater than 70% of islets in the dissociated pancreatic tissue were recovered by quadrupole magnetic sorting, but their purity was low; and (3) infused islets purified by density gradients and subsequently passed through quadrupole magnetic sorting had similar potency as uninfused islets. These results demonstrate proof of concept and define the steps for implementation of this technology in pig and human islet isolation. PMID:19505179
Transverse beam emittance measurement using quadrupole variation at KIRAMS-430
NASA Astrophysics Data System (ADS)
An, Dong Hyun; Hahn, Garam; Park, Chawon
2015-02-01
In order to produce a 430 MeV/u carbon ion (12 C 6+) beam for medical therapy, the Korea Institute of Radiological & Medical Sciences (KIRAMS) has carried out the development of a superconducting isochronous cyclotron, the KIRAMS-430. At the extraction of the cyclotron, an Energy Selection System (ESS) is located to modulate the fixed beam energy and to drive the ion beam through High Energy Beam Transport (HEBT) into the treatment room. The beam emittance at the ion beamline is to be measured to provide information on designing a beam with high quality. The well-known quadrupole variation method was used to determine the feasibility of measuring the transverse beam emittance. The beam size measured at the beam profile monitor (BPM) is to be utilized and the transformation of beam by transfer matrix is to be applied being taken under various transport condition of varying quadrupole magnetic strength. Two different methods where beam optics are based on the linear matrix formalism and particle tracking with a 3-D magnetic field distribution obtained by using OPERA3D TOSCA, are applied to transport the beam. The fittings for the transformation parameters are used to estimate the transverse emittance and the twiss parameters at the entrance of the quadrupole in the ESS. Including several systematic studies, we conclude that within the uncertainty the estimated emittances are consistent with the ones calculated by using Monte Carlo simulations.
CMB quadrupole suppression. II. The early fast roll stage
Boyanovsky, D.; Vega, H. J. de; Sanchez, N. G.
2006-12-15
Within the effective field theory of inflation, an initialization of the classical dynamics of the inflaton with approximate equipartition between the kinetic and potential energy of the inflaton leads to a brief fast roll stage that precedes the slow roll regime. The fast roll stage leads to an attractive potential in the wave equations for the mode functions of curvature and tensor perturbations. The evolution of the inflationary perturbations is equivalent to the scattering by this potential and a useful dictionary between the scattering data and observables is established. Implementing methods from scattering theory we prove that this attractive potential leads to a suppression of the quadrupole moment for CMB and B-mode angular power spectra. The scale of the potential is determined by the Hubble parameter during slow roll. Within the effective field theory of inflation at the grand unification (GUT) energy scale we find that if inflation lasts a total number of e-folds N{sub tot}{approx}59, there is a 10%-20% suppression of the CMB quadrupole and about 2%-4% suppression of the tensor quadrupole. The suppression of higher multipoles is smaller, falling off as 1/l{sup 2}. The suppression is much smaller for N{sub tot}>59, therefore if the observable suppression originates in the fast roll stage, there is the upper bound N{sub tot}{approx}59.
Perfect 2-d quadrupole fields from permanent magnets
Lee, E.P.; Vella, M.
1996-04-01
Consider the 13-beam channel array shown in Figure 1. It is asserted that, under mathematically ideal assumptions, a pure quadrupole field is centered in each of the 13 beam channel boxes. An identical quadrupole field (for {bar H}, not {bar B}) is also centered in each of the 4 boxes containing 4 magnetic wedges located near the center of the system. An iron yoke ({mu} = {infinity}) with the displayed zig-zag shape provides a boundary condition (H{sub {parallel}} = 0) that makes the 13 channels equivalent to a portion of an infinite array. A similar array can be readily drawn for any number of beams. The quadrupole gradient in the beam channels is B{prime} = M{sub o}/2b, where M{sub o} is the remnant field of the magnetic wedges, and the channel diameter (wedge-to-wedge) is 2b. Note that a unit cell of the array, containing one beam, has diameter 2{radical}2 b (viewed from 45{degree} tilt) so its area is 8 b{sup 2}. A significant advantage of this design over those using dipolar blocks is the large fraction of cross section devoted to beam channels (50% vs 25%). Application to a heavy ion fusion driver is discussed.
Gallien, Sebastien; Domon, Bruno
2014-08-01
High resolution/accurate mass hybrid mass spectrometers have considerably advanced shotgun proteomics and the recent introduction of fast sequencing capabilities has expanded its use for targeted approaches. More specifically, the quadrupole-orbitrap instrument has a unique configuration and its new features enable a wide range of experiments. An overview of the analytical capabilities of this instrument is presented, with a focus on its application to quantitative analyses. The high resolution, the trapping capability and the versatility of the instrument have allowed quantitative proteomic workflows to be redefined and new data acquisition schemes to be developed. The initial proteomic applications have shown an improvement of the analytical performance. However, as quantification relies on ion trapping, instead of ion beam, further refinement of the technique can be expected.
NASA Astrophysics Data System (ADS)
Boswell, S. M.; Zheng, L.; Gordon, R. G.; Dyment, J.
2011-12-01
An improved understanding of the spreading-rate dependence of anomalous skewness from magnetic anomalies due to seafloor spreading will allow for better constraints on apparent polar wander paths, plate reconstructions, and the magnetic and thermal structure of oceanic lithosphere. Anomalous skewness, which is the difference between experimentally determined skewness and skewness expected from simple magnetization models with vertical reversal boundaries, has been observed to vary as a function of spreading rate, decreasing with increasing spreading rate and becoming negligible at spreading half-rates exceeding about 55 mm/a [Roest et al. 1992; Dyment et al. 1994]. In our analysis, we determine model-based estimates of anomalous skewness as a function of spreading rate for each anomaly. We do so by creating many synthetic profiles using the model of Dyment and Arkani-Hamed (1995), which was specifically constructed to produce anomalies with anomalous skewness consistent with observed anomalies. We experimentally determine the phase shift that causes the resulting synthetic magnetic anomaly to best match a profile produced from a "standard" model for anomalies due to seafloor spreading that assumes simple vertical reversal boundaries. We present results for those anomalies between 12r and 33r from which reliable paleomagnetic poles may potentially be determined. Differences in anomalous skewness for different anomalies determined at the same spreading rate can be attributed to the sequence effect, that is, the effect on the shape of a magnetic anomaly above seafloor of a single polarity chron of the magnetization of neighboring blocks of lithosphere magnetized during other chrons. We find that the sequence effect is smaller than we expected with the largest difference being between the results for anomaly 25r and those for anomaly 33r, for which the difference is 14 degrees at a 10 mm/a half-rate. Results for other anomalies lie between these two. We also infer a
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Astrophysics Data System (ADS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, heat transfer model with both radially inward and outward flow. Trip strips, skewed at 45 deg to the flow direction, were machined on the leading and trailing surfaces of the radial coolant passages. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation and buoyancy, decreased to as low as 40 percent of the value without rotation. However, the maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels previously obtained with the smooth wall models. It was concluded that (1) both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer in models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design information.
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
1992-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, heat transfer model with both radially inward and outward flow. Trip strips, skewed at 45 deg to the flow direction, were machined on the leading and trailing surfaces of the radial coolant passages. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation and buoyancy, decreased to as low as 40 percent of the value without rotation. However, the maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels previously obtained with the smooth wall models. It was concluded that (1) both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer in models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design information.
Measuring skew in average surface roughness as a function of surface preparation
NASA Astrophysics Data System (ADS)
Stahl, Mark T.
2015-08-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo® white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.
Eigenvalue analysis of an irreversible random walk with skew detailed balance conditions.
Sakai, Yuji; Hukushima, Koji
2016-04-01
An irreversible Markov-chain Monte Carlo (MCMC) algorithm with skew detailed balance conditions originally proposed by Turitsyn et al. is extended to general discrete systems on the basis of the Metropolis-Hastings scheme. To evaluate the efficiency of our proposed method, the relaxation dynamics of the slowest mode and the asymptotic variance are studied analytically in a random walk on one dimension. It is found that the performance in irreversible MCMC methods violating the detailed balance condition is improved by appropriately choosing parameters in the algorithm. PMID:27176439
A method for skew-free distribution of digital signals using matched variable delay lines
NASA Astrophysics Data System (ADS)
Knight, Thomas; Wu, Henry
1992-03-01
The ability to distribute signals to all parts of a circuit with precisely controlled and known delays is essential in large, high-speed digital systems. We present a technique by which a signal driver can adjust the arrival time of the signal at the end of the wire using a pair of matched variable delay lines. We show how this idea can be implemented requiring no extra wiring, and how it can be extended to distribute signals skew-free to receivers along the signal run as well as the receiving end. We demonstrate how this scheme can be implemented as part of the pad and scan logic of a VLSI chip.
Asymptotic of the Solutions of Hyperbolic Equations with a Skew-Symmetric Perturbation
NASA Astrophysics Data System (ADS)
Gallagher, Isabelle
1998-12-01
Using methods introduced by S. Schochet inJ. Differential Equations114(1994), 476-512, we compute the first term of an asymptotic expansion of the solutions of hyperbolic equations perturbated by a skew-symmetric linear operator. That result is first applied to two systems describing the motion of geophysic fluids: the rotating Euler equations and the primitive system of the quasigeostrophic equations. Finally in the last part, we study the slightly compressible Euler equations by application of that same result.
Stability of a cantilevered skew inhomogeneous plate in supersonic gas flow
NASA Astrophysics Data System (ADS)
Isaulova, T. N.; Lavit, I. M.
2011-07-01
This paper considers the vibrations of a skew inhomogeneous plate in gas flow. The plate is clamped in a certain section of one of its sides. Interaction of the flow with the plate is described using piston theory. The problem solution is based on the Hamilton's variational principle and finite element method. The calculation results are compared with known data of theoretical studies and experiments. For the inhomogeneous plate, similarity parameters were established for the problem, which, in practically important cases, appears to be self-similar for one of the similarity parameters. This allows one to reduce the solution of this problem to the solution of an algebraic eigenvalue problem.
Extrinsic spin Hall effect induced by resonant skew scattering in graphene.
Ferreira, Aires; Rappoport, Tatiana G; Cazalilla, Miguel A; Castro Neto, A H
2014-02-14
We show that the extrinsic spin Hall effect can be engineered in monolayer graphene by decoration with small doses of adatoms, molecules, or nanoparticles originating local spin-orbit perturbations. The analysis of the single impurity scattering problem shows that intrinsic and Rashba spin-orbit local couplings enhance the spin Hall effect via skew scattering of charge carriers in the resonant regime. The solution of the transport equations for a random ensemble of spin-orbit impurities reveals that giant spin Hall currents are within the reach of the current state of the art in device fabrication. The spin Hall effect is robust with respect to thermal fluctuations and disorder averaging.
Extrinsic Spin Hall Effect Induced by Resonant Skew Scattering in Graphene
NASA Astrophysics Data System (ADS)
Ferreira, Aires; Rappoport, Tatiana G.; Cazalilla, Miguel A.; Castro Neto, A. H.
2014-02-01
We show that the extrinsic spin Hall effect can be engineered in monolayer graphene by decoration with small doses of adatoms, molecules, or nanoparticles originating local spin-orbit perturbations. The analysis of the single impurity scattering problem shows that intrinsic and Rashba spin-orbit local couplings enhance the spin Hall effect via skew scattering of charge carriers in the resonant regime. The solution of the transport equations for a random ensemble of spin-orbit impurities reveals that giant spin Hall currents are within the reach of the current state of the art in device fabrication. The spin Hall effect is robust with respect to thermal fluctuations and disorder averaging.
Measuring Skew in Average Surface Roughness as a Function of Surface Preparation
NASA Technical Reports Server (NTRS)
Stahl, Mark
2015-01-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.
Measuring Skew in Average Surface Roughness as a Function of Surface Preparation
NASA Technical Reports Server (NTRS)
Stahl, Mark T.
2015-01-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces grinding saving both time and money and allows the science requirements to be better defined. In this study various materials are polished from a fine grind to a fine polish. Each sample's RMS surface roughness is measured at 81 locations in a 9x9 square grid using a Zygo white light interferometer at regular intervals during the polishing process. Each data set is fit with various standard distributions and tested for goodness of fit. We show that the skew in the RMS data changes as a function of polishing time.
A variational Bayesian approach for inverse problems with skew-t error distributions
NASA Astrophysics Data System (ADS)
Guha, Nilabja; Wu, Xiaoqing; Efendiev, Yalchin; Jin, Bangti; Mallick, Bani K.
2015-11-01
In this work, we develop a novel robust Bayesian approach to inverse problems with data errors following a skew-t distribution. A hierarchical Bayesian model is developed in the inverse problem setup. The Bayesian approach contains a natural mechanism for regularization in the form of a prior distribution, and a LASSO type prior distribution is used to strongly induce sparseness. We propose a variational type algorithm by minimizing the Kullback-Leibler divergence between the true posterior distribution and a separable approximation. The proposed method is illustrated on several two-dimensional linear and nonlinear inverse problems, e.g. Cauchy problem and permeability estimation problem.
Testing of Nb3Sn quadrupole coils using magnetic mirror structure
Zlobin, A.V.; Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; Tartaglia, M.; Tompkins, J.C.; /Fermilab
2009-07-01
This paper describes the design and parameters of a quadrupole mirror structure for testing the mechanical, thermal and quench performance of single shell-type superconducting quadrupole coils at field, current and force levels similar to that of real magnet. The concept was experimentally verified by testing two quadrupole coils, previously used in quadrupole models, in the developed mirror structure in the temperature range from 4.5 to 1.9 K. The coils were instrumented with voltage taps, heaters, and strain gauges to monitor their mechanical and thermal properties and quench performance. A new quadrupole coil made of improved Nb{sub 3}Sn RRP-108/127 strand and cable insulation based on E-glass tape was also tested using this structure. The fabrication and test results of the quadrupole mirror models are reported and discussed.
Testing of NB3SN Quadrupole Coils Using Magnetic Mirror Structure
NASA Astrophysics Data System (ADS)
Zlobin, A. V.; Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V. S.; Kashikhin, V. V.; Lamm, M. J.; Novitski, I.; Tartaglia, M.; Tompkins, J. C.; Turrioni, D.; Yamada, R.
2010-04-01
This paper describes the design and parameters of a quadrupole mirror structure for testing the mechanical, thermal and quench performance of single shell-type superconducting quadrupole coils at field, current and force levels similar to that of real magnet. The concept was experimentally verified by testing two quadrupole coils, previously used in quadrupole models, in the developed mirror structure in the temperature range from 4.5 to 1.9 K. The coils were instrumented with voltage taps, heaters, and strain gauges to monitor their mechanical and thermal properties and quench performance. A new quadrupole coil made of improved Nb3Sn RRP-108/127 strand and cable insulation based on E-glass tape was also tested using this structure. The fabrication and test results of the quadrupole mirror models are reported and discussed.
Sensitivity of nuclear-quadrupole double-resonance detection of half-integer spin nuclei
NASA Astrophysics Data System (ADS)
Seliger, J.; Žagar, V.
2008-10-01
The sensitivity of the Slusher and Hahn's nuclear quadrupole double resonance technique is calculated in general for an arbitrary nuclear spin S of the quadrupole nuclei and for an arbitrary asymmetry parameter η of the electric field gradient tensor. The nuclear spin S = 5/2 ( 17O, 25Mg, …) is treated in details. The influence of the cross-relaxation rate between the quadrupole nuclei and the abundant spin system on the sensitivity of double resonance is discussed. The results of the theoretical analysis are applied in the analysis of the 1H- 17O nuclear quadrupole double resonance spectra in p-toluenesulfonamide and 2-nitrobenzoic acid. The 17O nuclear quadrupole resonance frequencies from a sulfonamide group are determined for the first time. The proton-oxygen cross-relaxation rates and the proton local frequency in zero external magnetic field are experimentally determined from the nuclear quadrupole double resonance spectra.
Design and construction of a radiation resistant quadrupole using metal oxide insulated CICC
Albert F. Zeller
2012-12-28
The construction of a engineering test model of a radiation resistant quadrupole is described. The cold-iron quadrupole uses coils fabricated from metal-oixide (synthetic spinel) insulated Cable-In-Conduit-Conductor (CICC). The superconductor is NbTi in a copper matrix. The quadrupole is designed to produce a pole-tip field of 2 T with an operating current of 7,000 A.
Maximum Parsimony and the Skewness Test: A Simulation Study of the Limits of Applicability
Määttä, Jussi; Roos, Teemu
2016-01-01
The maximum parsimony (MP) method for inferring phylogenies is widely used, but little is known about its limitations in non-asymptotic situations. This study employs large-scale computations with simulated phylogenetic data to estimate the probability that MP succeeds in finding the true phylogeny for up to twelve taxa and 256 characters. The set of candidate phylogenies are taken to be unrooted binary trees; for each simulated data set, the tree lengths of all (2n − 5)!! candidates are computed to evaluate quantities related to the performance of MP, such as the probability of finding the true phylogeny, the probability that the tree with the shortest length is unique, the probability that the true phylogeny has the shortest tree length, and the expected inverse of the number of trees sharing the shortest length. The tree length distributions are also used to evaluate and extend the skewness test of Hillis for distinguishing between random and phylogenetic data. The results indicate, for example, that the critical point after which MP achieves a success probability of at least 0.9 is roughly around 128 characters. The skewness test is found to perform well on simulated data and the study extends its scope to up to twelve taxa. PMID:27035667
Using Skewness and the First-Digit Phenomenon to Identify Dynamical Transitions in Cardiac Models
Seenivasan, Pavithraa; Easwaran, Soumya; Sridhar, Seshan; Sinha, Sitabhra
2016-01-01
Disruptions in the normal rhythmic functioning of the heart, termed as arrhythmia, often result from qualitative changes in the excitation dynamics of the organ. The transitions between different types of arrhythmia are accompanied by alterations in the spatiotemporal pattern of electrical activity that can be measured by observing the time-intervals between successive excitations of different regions of the cardiac tissue. Using biophysically detailed models of cardiac activity we show that the distribution of these time-intervals exhibit a systematic change in their skewness during such dynamical transitions. Further, the leading digits of the normalized intervals appear to fit Benford's law better at these transition points. This raises the possibility of using these observations to design a clinical indicator for identifying changes in the nature of arrhythmia. More importantly, our results reveal an intriguing relation between the changing skewness of a distribution and its agreement with Benford's law, both of which have been independently proposed earlier as indicators of regime shift in dynamical systems. PMID:26793114
Changes of skewness and sharpness of partially coherent decentered annular beams on propagation
NASA Astrophysics Data System (ADS)
Yang, Ting; Ji, Xiaoling; Li, Xiaoqing; Zhang, Hao; Wang, Tao
2016-01-01
Changes of skewness and sharpness of partially coherent decentered annular beams (PCDA beams) on propagation both in free space and in oceanic turbulence are studied. Based on the Wigner distribution function, the analytical expressions for the skewness parameter A and the kurtosis parameter K of PCDA beams are derived. The analytical expression for the oceanic turbulence parameter T‧ related to K is also derived, and characteristics of T‧ are examined. It is found that the behaviors of A and K in oceanic turbulence are quite different from those in free space. In free space, the mass of the intensity distribution may move from one side of the centroid position axis yc to another side at a certain propagation distance z0, and z0 is independent of the correlation parameter τ. The mass of the intensity distribution is concentrated on one side of yc on propagation only for a poorly coherent beam in free space, but it is always this situation for different value of τ when oceanic turbulence is not weak. In free space, it takes a leptokurtic profile in the far field, and a Gaussian profile appears only for a poorly coherent beam. However, in oceanic turbulence it always reaches a Gaussian profile for different value of τ in the far field.
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Astrophysics Data System (ADS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
1992-06-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. It was concluded that (1) both Coriolis and buoyancy must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design.
Chen, Jichun; Bryant, Mark A; Dent, James J; Sun, Yu; Desierto, Marie J; Young, Neal S
2015-12-01
A deletion of a telomerase RNA component (Terc(-/-)) in C57BL/6 (B6) mice resulted in hematopoietic lineage skewing with increased neutrophils and CD11b(+) myeloid cells and decreased red blood cells and CD45R(+) B lymphocytes when animals reach ages older than 12 months. There was no decline in bone marrow (BM) c-Kit(+)Sca-1(+)Lin(-) (KSL) cells in old Terc(-/-) mice, and the lineage skewing phenomenon was not transferred when BM cells from old Terc(-/-) donors were transplanted into young B6 recipients. Necropsy and histological examinations found minimal to no change in the lung, spleen and liver but detected severe epithelia degeneration, ulceration and infection in small and large intestines, leading to enteritis, typhlitis and colitis in old Terc(-/-) mice. In a mouse model of dextran-sulfate-sodium-induced typhlitis and colitis, development of intestinal pathology was associated with increases in neutrophils and CD11b(+) myeloid cells and a decrease in CD45R(+) B cells, similar to those observed in old Terc(-/-) mice. Treatment of 11-13 month old Terc(-/-) mice with antibiotic trimethoprim-sulfa water reduced neutrophils and myeloid cells and increased B lymphocytes in the blood, indicating that mitigation of intestinal infection and inflammation could alleviate hematological abnormalities in old Terc(-/-) animals. PMID:26523501
Chen, Jichun; Bryant, Mark A; Dent, James J; Sun, Yu; Desierto, Marie J; Young, Neal S
2015-12-01
A deletion of a telomerase RNA component (Terc(-/-)) in C57BL/6 (B6) mice resulted in hematopoietic lineage skewing with increased neutrophils and CD11b(+) myeloid cells and decreased red blood cells and CD45R(+) B lymphocytes when animals reach ages older than 12 months. There was no decline in bone marrow (BM) c-Kit(+)Sca-1(+)Lin(-) (KSL) cells in old Terc(-/-) mice, and the lineage skewing phenomenon was not transferred when BM cells from old Terc(-/-) donors were transplanted into young B6 recipients. Necropsy and histological examinations found minimal to no change in the lung, spleen and liver but detected severe epithelia degeneration, ulceration and infection in small and large intestines, leading to enteritis, typhlitis and colitis in old Terc(-/-) mice. In a mouse model of dextran-sulfate-sodium-induced typhlitis and colitis, development of intestinal pathology was associated with increases in neutrophils and CD11b(+) myeloid cells and a decrease in CD45R(+) B cells, similar to those observed in old Terc(-/-) mice. Treatment of 11-13 month old Terc(-/-) mice with antibiotic trimethoprim-sulfa water reduced neutrophils and myeloid cells and increased B lymphocytes in the blood, indicating that mitigation of intestinal infection and inflammation could alleviate hematological abnormalities in old Terc(-/-) animals.
Analyzing Fish Condition Factor Index Through Skew-Gaussian Information Theory Quantifiers
NASA Astrophysics Data System (ADS)
Contreras-Reyes, Javier E.
2016-06-01
Biological-fishery indicators have been widely studied. As such the condition factor (CF) index, which interprets the fatness level of a certain species based on length and weight, has been investigated, too. However, CF has been studied without considering its temporal features and distribution. In this paper, we analyze the CF time series via skew-gaussian distributions that consider the asymmetry produced by extreme events. This index is characterized by a threshold autoregressive model and corresponds to a stationary process depending on the shape parameter of the skew-gaussian distribution. Then we use the Jensen-Shannon (JS) distance to compare CF by length classes. This distance has mathematical advantages over other divergences such as Kullback-Leibler and Jeffrey’s, and the triangular inequality property. Our results are applied to a biological catalogue of anchovy (Engraulis ringens) from the northern coast of Chile, for the period 1990-2010 that consider monthly CF time series by length classes and sex. We find that for high values of shape parameter, JS distance tends to be more sensible to detect discrepancies than Jeffrey’s divergence. In addition, the body condition of male anchovies with higher lengths coincides with the ending of the moderate-strong El Niño event 91-92 and for both males and females, the smaller lengths coincide with the beginning of the strong El Niño event 97-98.
Homoclinic snaking in plane Couette flow: bending, skewing and finite-size effects
NASA Astrophysics Data System (ADS)
Gibson, J. F.; Schneider, T. M.
2016-05-01
Invariant solutions of shear flows have recently been extended from spatially periodic solutions in minimal flow units to spatially localized solutions on extended domains. One set of spanwise-localized solutions of plane Couette flow exhibits homoclinic snaking, a process by which steady-state solutions grow additional structure smoothly at their fronts when continued parametrically. Homoclinic snaking is well understood mathematically in the context of the one-dimensional Swift-Hohenberg equation. Consequently, the snaking solutions of plane Couette flow form a promising connection between the largely phenomenological study of laminar-turbulent patterns in viscous shear flows and the mathematically well-developed field of pattern-formation theory. In this paper we present a numerical study of the snaking solutions, generalizing beyond the fixed streamwise wavelength of previous studies. We find a number of new solution features, including bending, skewing, and finite-size effects. We show that the finite-size effects result from the shift-reflect symmetry of the traveling wave and establish the parameter regions over which snaking occurs. A new winding solution of plane Couette flow is derived from a strongly skewed localized equilibrium.
Hasstrom, J.S.; Ermak, D.L.
1997-10-01
Vertical dispersion of material in the convective boundary layer, CBL, is dramatically different than in natural or stable boundary layers, as has been shown by field and laboratory experiments. Lagrangian stochastic modeling based on the Langevin equation has been shown to be useful for simulating vertical dispersion in the CBL. This modeling approach can account for the effects of the long Lagrangian time scales (associated with large-scale turbulent structures), skewed vertical velocity distributions, and vertically inhomogeneous turbulent properties found in the CBL. It has been recognized that simplified Langevin equation models that assume skewed but homogeneous velocity statistics can capture the important aspects of dispersion from sources the the CBL. The assumption of homogeneous turbulence has a significant practical advantage, specifically, longer time steps can be used in numerical simulations. In this paper, we compare two Langevin equations models that use the homogeneous turbulence assumption. We also compare and evaluate three reflection boundary conditions, the method for determining a new velocity for a particle that encounters a boundary. Model results are evaluated using data from Willis and Deardorff`s laboratory experiments for three different source heights.
Sardeshmukh, Prashant D.
2015-03-15
The probability distributions of large-scale atmospheric and oceanic variables are generally skewed and heavy-tailed. We argue that their distinctive departures from Gaussianity arise fundamentally from the fact that in a quadratically nonlinear system with a quadratic invariant, the coupling coefficients between system components are not constant but depend linearly on the system state in a distinctive way. In particular, the skewness arises from a tendency of the system trajectory to linger near states of weak coupling. We show that the salient features of the observed non-Gaussianity can be captured in the simplest such nonlinear 2-component system. If the system is stochastically forced and linearly damped, with one component damped much more strongly than the other, then the strongly damped fast component becomes effectively decoupled from the weakly damped slow component, and its impact on the slow component can be approximated as a stochastic noise forcing plus an augmented nonlinear damping. In the limit of large time-scale separation, the nonlinear augmentation of the damping becomes small, and the noise forcing can be approximated as an additive noise plus a correlated additive and multiplicative noise (CAM noise) forcing. Much of the diversity of observed large-scale atmospheric and oceanic probability distributions can be interpreted in this minimal framework.
Comment on "Universal relation between skewness and kurtosis in complex dynamics"
NASA Astrophysics Data System (ADS)
Celikoglu, Ahmet; Tirnakli, Ugur
2015-12-01
In a recent paper [M. Cristelli, A. Zaccaria, and L. Pietronero, Phys. Rev. E 85, 066108 (2012), 10.1103/PhysRevE.85.066108], the authors analyzed the relation between skewness and kurtosis for complex dynamical systems, and they identified two power-law regimes of non-Gaussianity, one of which scales with an exponent of 2 and the other with 4 /3 . They concluded that the observed relation is a universal fact in complex dynamical systems. In this Comment, we test the proposed universal relation between skewness and kurtosis with a large number of synthetic data, and we show that in fact it is not a universal relation and originates only due to the small number of data points in the datasets considered. The proposed relation is tested using a family of non-Gaussian distribution known as q -Gaussians. We show that this relation disappears for sufficiently large datasets provided that the fourth moment of the distribution is finite. We find that kurtosis saturates to a single value, which is of course different from the Gaussian case (K =3 ), as the number of data is increased, and this indicates that the kurtosis will converge to a finite single value if all moments of the distribution up to fourth are finite. The converged kurtosis value for the finite fourth-moment distributions and the number of data points needed to reach this value depend on the deviation of the original distribution from the Gaussian case.
Random sampling of skewed distributions implies Taylor's power law of fluctuation scaling.
Cohen, Joel E; Xu, Meng
2015-06-23
Taylor's law (TL), a widely verified quantitative pattern in ecology and other sciences, describes the variance in a species' population density (or other nonnegative quantity) as a power-law function of the mean density (or other nonnegative quantity): Approximately, variance = a(mean)(b), a > 0. Multiple mechanisms have been proposed to explain and interpret TL. Here, we show analytically that observations randomly sampled in blocks from any skewed frequency distribution with four finite moments give rise to TL. We do not claim this is the only way TL arises. We give approximate formulae for the TL parameters and their uncertainty. In computer simulations and an empirical example using basal area densities of red oak trees from Black Rock Forest, our formulae agree with the estimates obtained by least-squares regression. Our results show that the correlated sampling variation of the mean and variance of skewed distributions is statistically sufficient to explain TL under random sampling, without the intervention of any biological or behavioral mechanisms. This finding connects TL with the underlying distribution of population density (or other nonnegative quantity) and provides a baseline against which more complex mechanisms of TL can be compared. PMID:25852144
Diffuse holographic interferometric observation of shock wave reflection from a skewed wedge
NASA Astrophysics Data System (ADS)
Numata, D.; Ohtani, K.; Takayama, K.
2009-06-01
The pattern of shock wave reflection over a wedge is, in general, either a regular reflection or a Mach reflection, depending on wedge angles, shock wave Mach numbers, and specific heat ratios of gases. However, regular and Mach reflections can coexist, in particular, over a three-dimensional wedge surface, whose inclination angles locally vary normal to the direction of shock propagation. This paper reports a result of diffuse double exposure holographic interferometric observations of shock wave reflections over a skewed wedge surface placed in a 100 × 180 mm shock tube. The wedge consists of a straight generating line whose local inclination angle varies continuously from 30° to 60°. Painting its surface with fluorescent spray paint and irradiating its surface with a collimated object beam at a time interval of a few microseconds, we succeeded in visualizing three-dimensional shock reflection over the skewed wedge surface. Experiments were performed at shock Mach numbers, 1.55, 2.02, and 2.53 in air. From reconstructed holographic images, we estimated critical transition angles at these shock wave Mach numbers and found that these were very close to those over straight wedges. This is attributable to the flow three-dimensionality.
Fuel cell plates with skewed process channels for uniform distribution of stack compression load
Granata, Jr., Samuel J.; Woodle, Boyd M.
1989-01-01
An electrochemical fuel cell includes an anode electrode, a cathode electrode, an electrolyte matrix sandwiched between electrodes, and a pair of plates above and below the electrodes. The plate above the electrodes has a lower surface with a first group of process gas flow channels formed thereon and the plate below the electrodes has an upper surface with a second group of process gas flow channels formed thereon. The channels of each group extend generally parallel to one another. The improvement comprises the process gas flow channels on the lower surface of the plate above the anode electrode and the process gas flow channels on the upper surface of the plate below the cathode electrode being skewed in opposite directions such that contact areas of the surfaces of the plates through the electrodes are formed in crisscross arrangements. Also, the plates have at least one groove in areas of the surfaces thereof where the channels are absent for holding process gas and increasing electrochemical activity of the fuel cell. The groove in each plate surface intersects with the process channels therein. Also, the opposite surfaces of a bipolar plate for a fuel cell contain first and second arrangements of process gas flow channels in the respective surfaces which are skewed the same amount in opposite directions relative to the longitudinal centerline of the plate.
Deconstructing risk: Separable encoding of variance and skewness in the brain
Symmonds, Mkael; Wright, Nicholas D.; Bach, Dominik R.; Dolan, Raymond J.
2011-01-01
Risky choice entails a need to appraise all possible outcomes and integrate this information with individual risk preference. Risk is frequently quantified solely by statistical variance of outcomes, but here we provide evidence that individuals’ choice behaviour is sensitive to both dispersion (variance) and asymmetry (skewness) of outcomes. Using a novel behavioural paradigm in humans, we independently manipulated these ‘summary statistics’ while scanning subjects with fMRI. We show that a behavioural sensitivity to variance and skewness is mirrored in neuroanatomically dissociable representations of these quantities, with parietal cortex showing sensitivity to the former and prefrontal cortex and ventral striatum to the latter. Furthermore, integration of these objective risk metrics with subjective risk preference is expressed in a subject-specific coupling between neural activity and choice behaviour in anterior insula. Our findings show that risk is neither monolithic from a behavioural nor neural perspective and its decomposition is evident both in distinct behavioural preferences and in segregated underlying brain representations. PMID:21763444
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
1992-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. It was concluded that (1) both Coriolis and buoyancy must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design.
Maximum Parsimony and the Skewness Test: A Simulation Study of the Limits of Applicability.
Määttä, Jussi; Roos, Teemu
2016-01-01
The maximum parsimony (MP) method for inferring phylogenies is widely used, but little is known about its limitations in non-asymptotic situations. This study employs large-scale computations with simulated phylogenetic data to estimate the probability that MP succeeds in finding the true phylogeny for up to twelve taxa and 256 characters. The set of candidate phylogenies are taken to be unrooted binary trees; for each simulated data set, the tree lengths of all (2n - 5)!! candidates are computed to evaluate quantities related to the performance of MP, such as the probability of finding the true phylogeny, the probability that the tree with the shortest length is unique, the probability that the true phylogeny has the shortest tree length, and the expected inverse of the number of trees sharing the shortest length. The tree length distributions are also used to evaluate and extend the skewness test of Hillis for distinguishing between random and phylogenetic data. The results indicate, for example, that the critical point after which MP achieves a success probability of at least 0.9 is roughly around 128 characters. The skewness test is found to perform well on simulated data and the study extends its scope to up to twelve taxa. PMID:27035667
Jaffé, Rodolfo; Garcia-Gonzalez, Francisco; den Boer, Susanne P A; Simmons, Leigh W; Baer, Boris
2012-12-01
Monogamy results in high genetic relatedness among offspring and thus it is generally assumed to be favored by kin selection. Female multiple mating (polyandry) has nevertheless evolved several times in the social Hymenoptera (ants, bees, and wasps), and a substantial amount of work has been conducted to understand its costs and benefits. Relatedness and inclusive fitness benefits are, however, not only influenced by queen mating frequency but also by paternity skew, which is a quantitative measure of paternity biases among the offspring of polyandrous females. We performed a large-scale phylogenetic analysis of paternity skew across polyandrous social Hymenoptera. We found a general and significant negative association between paternity frequency and paternity skew. High paternity skew, which increases relatedness among colony members and thus maximizes inclusive fitness gains, characterized species with low paternity frequency. However, species with highly polyandrous queens had low paternity skew, with paternity equalized among potential sires. Equal paternity shares among fathers are expected to maximize fitness benefits derived from genetic diversity among offspring. We discuss the potential for postcopulatory sexual selection to influence patterns of paternity in social insects, and suggest that sexual selection may have played a key, yet overlooked role in social evolution.
James, Patrick M A; Janes, Jasmine K; Roe, Amanda D; Cooke, Barry J
2016-08-01
Through their influence on effective population sizes, sex ratio skew affects population dynamics. We examined spatial variation in female-biased sex ratios in the mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in western Canada to better understand how environmental context affects sex ratio skew. Our specific objectives were to: 1) characterize spatial variation in mountain pine beetle sex ratio; 2) test previously asserted hypotheses that beetle sex ratio varies with tree diameter and year in outbreak; and 3) develop predictive models of sex ratio skew for larval and adult populations. Using logistic regression, we modeled the probability that an individual beetle (n = 2,369) was female as a function of multiple environmental variables across 34 stands in British Columbia and Alberta, Canada. We identified a consistent female-biased sex ratio with significantly greater skew in adults (2:1, n = 713) than in larvae (1.76:1, n = 1,643). We found that the proportion of larval females increased with decreasing tree size and with outbreak age. However, adults did not respond to tree size and larvae did not respond to outbreak age. Predictive models differed between larvae and adults. All identified models perform well and included predictors related to weather, tree diameter, and year in outbreak. Female-biased sex ratios appear to originate from differential male mortality during development rather than from sex-biased oviposition, suggesting sex ratio skew is not the cause of outbreaks, but rather a consequence. PMID:27209334
Gentilini, Davide; Garagnani, Paolo; Pisoni, Serena; Bacalini, Maria Giulia; Calzari, Luciano; Mari, Daniela; Vitale, Giovanni; Franceschi, Claudio; Di Blasio, Anna Maria
2015-08-01
In this study we applied a new analytical strategy to investigate the relations between stochastic epigenetic mutations (SEMs) and aging. We analysed methylation levels through the Infinium HumanMethylation27 and HumanMethylation450 BeadChips in a population of 178 subjects ranging from 3 to 106 years. For each CpG probe, epimutated subjects were identified as the extreme outliers with methylation level exceeding three times interquartile ranges the first quartile (Q1-(3 x IQR)) or the third quartile (Q3+(3 x IQR)). We demonstrated that the number of SEMs was low in childhood and increased exponentially during aging. Using the HUMARA method, skewing of X chromosome inactivation (XCI) was evaluated in heterozygotes women. Multivariate analysis indicated a significant correlation between log(SEMs) and degree of XCI skewing after adjustment for age (β = 0.41; confidence interval: 0.14, 0.68; p-value = 0.0053). The PATH analysis tested the complete model containing the variables: skewing of XCI, age, log(SEMs) and overall CpG methylation. After adjusting for the number of epimutations we failed to confirm the well reported correlation between skewing of XCI and aging. This evidence might suggest that the known correlation between XCI skewing and aging could not be a direct association but mediated by the number of SEMs.
James, Patrick M A; Janes, Jasmine K; Roe, Amanda D; Cooke, Barry J
2016-08-01
Through their influence on effective population sizes, sex ratio skew affects population dynamics. We examined spatial variation in female-biased sex ratios in the mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in western Canada to better understand how environmental context affects sex ratio skew. Our specific objectives were to: 1) characterize spatial variation in mountain pine beetle sex ratio; 2) test previously asserted hypotheses that beetle sex ratio varies with tree diameter and year in outbreak; and 3) develop predictive models of sex ratio skew for larval and adult populations. Using logistic regression, we modeled the probability that an individual beetle (n = 2,369) was female as a function of multiple environmental variables across 34 stands in British Columbia and Alberta, Canada. We identified a consistent female-biased sex ratio with significantly greater skew in adults (2:1, n = 713) than in larvae (1.76:1, n = 1,643). We found that the proportion of larval females increased with decreasing tree size and with outbreak age. However, adults did not respond to tree size and larvae did not respond to outbreak age. Predictive models differed between larvae and adults. All identified models perform well and included predictors related to weather, tree diameter, and year in outbreak. Female-biased sex ratios appear to originate from differential male mortality during development rather than from sex-biased oviposition, suggesting sex ratio skew is not the cause of outbreaks, but rather a consequence.
Progress in the Development of Superconducting Quadrupoles forHeavy-ion Fusion
Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, R.; Martovetsky, N.; Gung, C.; Minervini, J.; Schultz, J.; Myatt, L.; Meinke, R.
2002-08-19
The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Progress in the development of superconducting quadrupoles for heavy ion fusion
Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, B.; Martovetsky, N.; Gung, C.; Minervini, J.; Schultz, J.; Myatt, L.; Meinke, R.
2002-05-24
The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Comparison of conventional and novel quadrupole drift tube magnets inspired by Klaus Halbach
Feinberg, B.
1995-02-01
Quadrupole drift tube magnets for a heavy-ion linac provide a demanding application of magnet technology. A comparison is made of three different solutions to the problem of providing an adjustable high-field-strength quadrupole magnet in a small volume. A conventional tape-wound electromagnet quadrupole magnet (conventional) is compared with an adjustable permanent-magnet/iron quadrupole magnet (hybrid) and a laced permanent-magnet/iron/electromagnet (laced). Data is presented from magnets constructed for the SuperHILAC heavy-ion linear accelerator, and conclusions are drawn for various applications.
Quadrupole-induced resonant-particle transport in a pure electron plasma.
Gilson, E P; Fajans, J
2003-01-10
Small transverse magnetic quadrupole fields sharply degrade the confinement of non-neutral plasmas held in Malmberg-Penning traps. For example, a quadrupole magnetic field of only 0.02 G/cm doubles the diffusion rate in a trap with a 100 G axial magnetic field. Larger quadrupole fields noticeably change the shape of the plasma. The transport is greatest at an orbital resonance. These results cast doubt on plans to use magnetic quadrupole neutral atom traps to confine antihydrogen atoms created in double-well positron/antiproton Malmberg-Penning traps.
CMB quadrupole suppression. I. Initial conditions of inflationary perturbations
Boyanovsky, D.; Vega, H. J. de; Sanchez, N. G.
2006-12-15
We investigate the issue of initial conditions of curvature and tensor perturbations at the beginning of slow roll inflation and their effect on the power spectra. Renormalizability and small backreaction constrain the high k behavior of the Bogoliubov coefficients that define these initial conditions. We introduce a transfer function D(k) which encodes the effect of generic initial conditions on the power spectra. The constraint from renormalizability and small backreaction entails that D(k)(less-or-similar sign){mu}{sup 2}/k{sup 2} for large k, implying that observable effects from initial conditions are more prominent in the low multipoles. This behavior affects the CMB quadrupole by the observed amount {approx}10%-20% when {mu} is of the order of the energy scale of inflation. The effects on high l-multipoles are suppressed by a factor {approx}1/l{sup 2} due to the falloff of D(k) for large wave vectors k. We show that the determination of generic initial conditions for the fluctuations is equivalent to the scattering problem by a potential V({eta}) localized just prior to the slow roll stage. Such potential leads to a transfer function D(k) which automatically obeys the renormalizability and small backreaction constraints. We find that an attractive potential V({eta}) yields a suppression of the lower CMB multipoles. Both for curvature and tensor modes, the quadrupole suppression depends only on the energy scale of V({eta}), and on the time interval where V({eta}) is nonzero. A suppression of the quadrupole for curvature perturbations consistent with the data is obtained when the scale of the potential is of the order of k{sub Q}{sup 2} where k{sub Q} is the wave vector whose physical wavelength is the Hubble radius today.
Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport
Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.
2005-09-20
This research project advanced the development of reliable, cost-effective arrays of superconducting quadrupole magnets for use in multi-beam inertial fusion accelerators. The field in each array cell must be identical and meet stringent requirements for field quality and strength. An optimized compact array design using flat double-layer pancake coils was developed. Analytical studies of edge termination methods showed that it is feasible to meet the requirements for field uniformity in all cells and elimination of stray external field in several ways: active methods that involve placement of field compensating coils on the periphery of the array or a passive method that involves use of iron shielding.
Beam acceleration through proton radio frequency quadrupole accelerator in BARC
NASA Astrophysics Data System (ADS)
Bhagwat, P. V.; Krishnagopal, S.; Mathew, J. V.; Singh, S. K.; Jain, P.; Rao, S. V. L. S.; Pande, M.; Kumar, R.; Roychowdhury, P.; Kelwani, H.; Rama Rao, B. V.; Gupta, S. K.; Agarwal, A.; Kukreti, B. M.; Singh, P.
2016-05-01
A 3 MeV proton Radio Frequency Quadrupole (RFQ) accelerator has been designed at the Bhabha Atomic Research Centre, Mumbai, India, for the Low Energy High Intensity Proton Accelerator (LEHIPA) programme. The 352 MHz RFQ is built in 4 segments and in the first phase two segments of the LEHIPA RFQ were commissioned, accelerating a 50 keV, 1 mA pulsed proton beam from the ion source, to an energy of 1.24 MeV. The successful operation of the RFQ gave confidence in the physics understanding and technology development that have been achieved, and indicate that the road forward can now be traversed rather more quickly.
Nuclear quadrupole resonance studies project. [spectrometer design and spectrum analysis
NASA Technical Reports Server (NTRS)
Murty, A. N.
1978-01-01
The participation of undergraduates in nuclear quadrupole resonance research at Grambling University was made possible by NASA grants. Expanded laboratory capabilities include (1) facilities for high and low temperature generation and measurement; (2) facilities for radio frequency generation and measurement with the modern spectrum analyzers, precision frequency counters and standard signal generators; (3) vacuum and glass blowing facilities; and (4) miscellaneous electronic and machine shop facilities. Experiments carried out over a five year period are described and their results analyzed. Theoretical studies on solid state crystalline electrostatic fields, field gradients, and antishielding factors are included.
Cool Down Analysis of a Cryocooler Based Quadrupole Magnet Cryostat
NASA Astrophysics Data System (ADS)
Choudhury, A.; Kar, S.; Chacko, J.; Kumar, M.; Babu, S.; Sahu, S.; Kumar, R.; Antony, J.; Datta, T. S.
A superconducting quadrupole doublet magnet with cold superferric iron cover for the Hybrid Recoil Mass Analyzer (HYRA) beam line has been commissioned. The total cold mass of the helium vessel with iron yoke and pole is 2 ton. A set of two Sumitomo cryocoolers take care of various heat loads to the cryostat. The first successful cool down of the cryostat has been completed recently, magnets have been powered and magnetic field profiling has been done inside theroom temperature beam tube. This paper will highlight the cryostat details along with the cool down and operational test results obtained from the first cool down.
Miniature quadrupole mass spectrometer having a cold cathode ionization source
Felter, Thomas E.
2002-01-01
An improved quadrupole mass spectrometer is described. The improvement lies in the substitution of the conventional hot filament electron source with a cold cathode field emitter array which in turn allows operating a small QMS at much high internal pressures then are currently achievable. By eliminating of the hot filament such problems as thermally "cracking" delicate analyte molecules, outgassing a "hot" filament, high power requirements, filament contamination by outgas species, and spurious em fields are avoid all together. In addition, the ability of produce FEAs using well-known and well developed photolithographic techniques, permits building a QMS having multiple redundancies of the ionization source at very low additional cost.
Lumia, Richard; Baevsky, Yvonne H.
2000-01-01
Flood-frequency relations that are developed by fitting the logarithms of annual peak discharges to a Pearson Type-III distribution are sensitive to skew coefficients. Estimates of population skew for a site are improved when computed from the weighted average of (1) the sample (station) skew, and (2) an unbiased, generalized skew estimate. A weighting technique based on the number of years of record at each of 226 sites was used to develop a contour map of unbiased, generalized skew coefficients for New York. An attempt was made to group (regionalize) the station skew coefficients into five hydrologically similar areas of New York, but the statewide version proved to be as accurate as the regionalized version and therefore was adopted as the final generalized skew-coefficient map for New York. An error analysis showed the statewide contour map to have lower MSE?s (mean square errors) than those computed from (1) the five regional skewcoefficient contour maps, (2) a previously used (1982) nationwide skew coefficient map, and (3) the weighted mean of skew coefficients for sites within each of five hydrologically uniform, but distinct areas of New York.
Heavy ion plasma confinement in an RF quadrupole trap
NASA Technical Reports Server (NTRS)
Schermann, J.; Major, F. G.
1971-01-01
The confinement of an electron free plasma in a pure quadrupole RF electric trap was considered. The ultimate goal was to produce a large density of mercury ions, in order to realize a trapped ion frequency standard using the hyperfine resonance of 199 Hg(+) at 40.7 GHz. An attempt was made to obtain an iodine plasma consisting of equal numbers of positive and negative ions of atomic iodine, the positive iodine ions, being susceptible to charge-exchange with mercury atoms, will produce the desired mercury ions. The experiment showed that the photoproduction of ions pairs in iodine using the necessary UV radiation occurs with a small cross-section, making it difficult to demonstrate the feasibility of space charge neutralization in a quadrupole trap. For this reason it was considered expedient to choose thallium iodide, which has a more favorable absorption spectrum (in the region of 2000 to 2100 A). The results indicate that, although the ionic recombination is a serious limiting factor, a considerable improvement can be obtained in practice for the density of trapped ions, with a considerable advantage in lifetimes for spectroscopic purposes. The ion pair formation by photoionization is briefly reviewed.
Adjustable permanent quadrupoles for the next linear collider
James T. Volk et al.
2001-06-22
The proposed Next Linear Collider (NLC) will require over 1400 adjustable quadrupoles between the main linacs' accelerator structures. These 12.7 mm bore quadrupoles will have a range of integrated strength from 0.6 to 138 Tesla, with a maximum gradient of 141 Tesla per meter, an adjustment range of +0 to {minus}20% and effective lengths from 324 mm to 972 mm. The magnetic center must remain stable to within 1 micron during the 20% adjustment. In an effort to reduce costs and increase reliability, several designs using hybrid permanent magnets have been developed. Four different prototypes have been built. All magnets have iron poles and use Samarium Cobalt to provide the magnetic fields. Two use rotating permanent magnetic material to vary the gradient, one uses a sliding shunt to vary the gradient and the fourth uses counter rotating magnets. Preliminary data on gradient strength, temperature stability, and magnetic center position stability are presented. These data are compared to an equivalent electromagnetic prototype.
Low-frequency nuclear quadrupole resonance with a dc SQUID
Chang, J.W.
1991-07-01
Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.
Precision Magnet Measurements for X-Band Accelerator Quadrupole Triplets
Marsh, R A; Anderson, S G; Armstrong, J P
2012-05-16
An X-band test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray (MEGa-Ray) technology at LLNL. Beamline magnets will include an emittance compensation solenoid, windowpane steering dipoles, and quadrupole magnets. Demanding tolerances have been placed on the alignment of these magnets, which directly affects the electron bunch beam quality. A magnet mapping system has been established at LLNL in order to ensure the delivered magnets match their field specification, and the mountings are aligned and capable of reaching the specified alignment tolerances. The magnet measurement system will be described which uses a 3-axis Lakeshore gauss probe mounted on a 3-axis translation stage. Alignment accuracy and precision will be discussed, as well as centering measurements and analysis. The dependence on data analysis over direct multi-pole measurement allows a significant improvement in useful alignment information. Detailed analysis of measurements on the beamline quadrupoles will be discussed, including multi-pole content both from alignment of the magnets, and the intrinsic level of multi-pole magnetic field.
NASA Astrophysics Data System (ADS)
Obaya, Rafael; Sanz, Ana M.
2016-10-01
We determine sufficient conditions for uniform and strict persistence in the case of skew-product semiflows generated by solutions of non-autonomous families of cooperative systems of ODEs or delay FDEs in terms of the principal spectrums of some associated linear skew-product semiflows which admit a continuous separation. Our conditions are also necessary in the linear case. We apply our results to a noncooperative almost periodic Nicholson system with a patch structure, whose persistence turns out to be equivalent to the persistence of the linearized system along the null solution.
Sigma matrix reconstruction in the SLC final focus
Raimaondi, P.; Emma, P.J.; Toge, N.; Walker, N.J.; Ziemann, V.
1993-05-01
The knowledge of the Beam Parameters at the entrance of the SLC final focus is important for modeling the final focus optics and predicting spot sizes and angular divergences at the interaction point (IP). It is also an important diagnostic for measuring possible anomalous emittance growth in the SLC Arcs. Reported here is a technique for measuring all the independent beam parameters at the beginning of the final focus. Use is made of the spot size measurements at wire scanners as a function of quadrupole strengths. Results for the SLC 1993 run are presented.
Random X-chromosome inactivation: skewing lessons for mice and men.
Clerc, Philippe; Avner, Philip
2006-06-01
The mammalian X-chromosome exists in two flavors, active and inactive, in each cell of the adult female. This phenomenon originates from the process of random choice occurring early in development in a small number of progenitor cells in which the decision is made to inactivate either one or the other X chromosome on a cell-autonomous basis. Once made, this initial decision is irreversible, although exceptions exist in specific chromosomal territories and cell lineages. Recent findings implicate various factors, including non-coding RNAs and chromatin modification complexes, as effectors in the initiation and maintenance of X-chromosome inactivation. The functional redundancy of such factors almost certainly plays an important role in the stability of the inactive X. Studying skewing or bias opens an important opportunity for understanding facets of the random choice process.
Foldnes, Njål; Olsson, Ulf Henning
2016-01-01
We present and investigate a simple way to generate nonnormal data using linear combinations of independent generator (IG) variables. The simulated data have prespecified univariate skewness and kurtosis and a given covariance matrix. In contrast to the widely used Vale-Maurelli (VM) transform, the obtained data are shown to have a non-Gaussian copula. We analytically obtain asymptotic robustness conditions for the IG distribution. We show empirically that popular test statistics in covariance analysis tend to reject true models more often under the IG transform than under the VM transform. This implies that overly optimistic evaluations of estimators and fit statistics in covariance structure analysis may be tempered by including the IG transform for nonnormal data generation. We provide an implementation of the IG transform in the R environment.
Extrinsic Spin Hall Effect Induced by Resonant Skew Scattering in Graphene
NASA Astrophysics Data System (ADS)
Ferreira, Aires; Rappoport, Tatiana G.; Cazalilla, Miguel A.; Castro Neto, A. H.
2015-03-01
We show that the extrinsic spin Hall effect can be engineered in monolayer graphene by decoration with small doses of adatoms, molecules, or nanoparticles originating local spin-orbit perturbations. The analysis of the single impurity scattering problem shows that intrinsic and Rashba spin-orbit local couplings enhance the spin Hall effect via skew scattering of charge carriers in the resonant regime. The solution of the transport equations for a random ensemble of spin-orbit impurities reveals that giant spin Hall currents are within the reach of the current state of the art in device fabrication. The spin Hall effect is robust with respect to thermal fluctuations and disorder averaging. The author acknowledges support from the National Research Foundation-Competitive Research Programme through Grant No. R-144-000-295-281.
The Modified Concorde Position with an Intraoperative Skew Head Rotation: Technical Note
TAKASUNA, Hiroshi; TANAKA, Yuichiro
2015-01-01
The Concorde position was developed to approach pineal and cerebellar lesions with a midline suboccipital craniotomy. The neutral head position is needed to divide the occipital muscles symmetrically. The patient’s head is tilted to the right and the face is turned to the right for the microscopic procedure to keep the midline of the patient’s head axis straight in the surgical field for comfortable and accurate surgical manipulation. However, intraoperative repositioning of the patient’s head is somewhat difficult to release the holding arm of the Sugita head holder in the original method. We found that a skew head rotation by fixing the head asymmetrically in the Sugita head holder is very quick and convenient to obtain the optimal head position both for a craniotomy and a microscopic procedure. PMID:26226983
The Modified Concorde Position with an Intraoperative Skew Head Rotation: Technical Note.
Takasuna, Hiroshi; Tanaka, Yuichiro
2015-01-01
The Concorde position was developed to approach pineal and cerebellar lesions with a midline suboccipital craniotomy. The neutral head position is needed to divide the occipital muscles symmetrically. The patient's head is tilted to the right and the face is turned to the right for the microscopic procedure to keep the midline of the patient's head axis straight in the surgical field for comfortable and accurate surgical manipulation. However, intraoperative repositioning of the patient's head is somewhat difficult to release the holding arm of the Sugita head holder in the original method. We found that a skew head rotation by fixing the head asymmetrically in the Sugita head holder is very quick and convenient to obtain the optimal head position both for a craniotomy and a microscopic procedure.
Two generalized Wigner-Yanase skew information and their uncertainty relations
NASA Astrophysics Data System (ADS)
Chen, Zheng-Li; Liang, Li-Li; Li, Hao-Jing; Wang, Wen-Hua
2016-09-01
In this paper, we first define two generalized Wigner-Yanase skew information |K_{ρ ,α }|(A) and |L_{ρ ,α }|(A) for any non-Hermitian Hilbert-Schmidt operator A and a density operator ρ on a Hilbert space H and discuss some properties of them, respectively. We also introduce two related quantities |S_{ρ ,α }|(A) and |T_{ρ ,α }|(A) . Then, we establish two uncertainty relations in terms of |W_{ρ ,α }|(A) and |widetilde{W}_{ρ ,α }|(A) , which read |W_{ρ ,α }|(A)|W_{ρ ,α }|(B)≥ 1/4| {tr}( [ ρ ^{α }+ρ ^{1-α }/2 ] 2[A,B]0) | 2, √{|widetilde{W}_{ρ ,α }|(A)| widetilde{W}_{ρ ,α }|(B)}≥ 1/4 | {tr}( ρ ^{2α }[A,B]0) {tr} ( ρ ^{2(1-α )}[A,B]0) | .
Fajans, J; Bertsche, W; Burke, K; Chapman, S F; van der Werf, D P
2005-10-01
Measurements on electrons confined in a Penning trap show that extreme quadrupole fields destroy particle confinement. Much of the particle loss comes from the hitherto unrecognized ballistic transport of particles directly into the wall. The measurements scale to the parameter regime used by ATHENA and ATRAP to create antihydrogen, and suggest that quadrupoles cannot be used to trap antihydrogen.
Fajans, J.; Bertsche, W.; Burke, K.; Chapman, S.F.; Werf, D.P. van der
2005-10-07
Measurements on electrons confined in a Penning trap show that extreme quadrupole fields destroy particle confinement. Much of the particle loss comes from the hitherto unrecognized ballistic transport of particles directly into the wall. The measurements scale to the parameter regime used by ATHENA and ATRAP to create antihydrogen, and suggest that quadrupoles cannot be used to trap antihydrogen.
Measuring the Magnetic Center Behavior of an ILC Superconducting Quadrupole Prototype
Spencer, Cherrill M.; Adolphsen, Chris; Berndt, Martin; Jensen, David R.; Rogers, Ron; Sheppard, John C.; Lorant, Steve St; Weber, Thomas B.; Weisend, John, II; Brueck, Heinrich; Toral, Fernando; /Madrid, CIEMAT
2011-02-07
The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2{theta}) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.
Low paternity skew and the influence of maternal kin in an egalitarian, patrilocal primate
Strier, Karen B.; Chaves, Paulo B.; Mendes, Sérgio L.; Fagundes, Valéria; Di Fiore, Anthony
2011-01-01
Levels of reproductive skew vary in wild primates living in multimale groups depending on the degree to which high-ranking males monopolize access to females. Still, the factors affecting paternity in egalitarian societies remain unexplored. We combine unique behavioral, life history, and genetic data to evaluate the distribution of paternity in the northern muriqui (Brachyteles hypoxanthus), a species known for its affiliative, nonhierarchical relationships. We genotyped 67 individuals (22 infants born over a 3-y period, their 21 mothers, and all 24 possible sires) at 17 microsatellite marker loci and assigned paternity to all infants. None of the 13 fathers were close maternal relatives of females with which they sired infants, and the most successful male sired a much lower percentage of infants (18%) than reported for the most successful males in other species. Our findings of inbreeding avoidance and low male reproductive skew are consistent with the muriqui's observed social and sexual behavior, but the long delay (≥2.08 y) between the onset of male sexual behavior and the age at which males first sire young is unexpected. The allocation of paternity implicates individual male life histories and access to maternal kin as key factors influencing variation in paternal—and grandmaternal—fitness. The apparent importance of lifelong maternal investment in coresident sons resonates with other recent examinations of maternal influences on offspring reproduction. This importance also extends the implications of the “grandmother hypothesis” in human evolution to include the possible influence of mothers and other maternal kin on male reproductive success in patrilocal societies. PMID:22065786
A missing model in reproductive skew theory: the bordered tug-of-war.
Reeve, Hudson Kern; Shen, Sheng-Feng
2006-05-30
Models of reproductive skew can be classified into two groups: transactional models, in which group members yield shares of reproduction to each other in return for cooperation, and tug-of-war models, in which group members invest group resources in a tug-of-war over their respective reproductive shares. We synthesize these two models to yield a "bordered tug-of-war" model in which the internal tug-of-war is limited ("bordered") by the requirement that group members must achieve a certain amount of reproduction lest they pursue a noncooperative option leading to group breakup. Previous attempts to synthesize these two models did not allow for the fact that the tug-of-war will affect group output, which in turn feeds back on the reproductive payments required by group members to remain cooperative. The bordered tug-of-war model, which does not assume complete reproductive control by any individual and allows for conflict within groups, predicts that the degree of within-group selfishness will increase as the noncooperative options become less attractive, e.g., as ecological constraints on solitary breeding increase. When the noncooperative option involves fighting for the group resource (e.g., territory) and leaving if the fight is lost, the subordinate's overall share of reproduction is predicted to be independent of its relatedness to the dominant and to increase the greater its probability of winning the fight, the less the value of the territory, and the greater its personal payoff for leaving. The unique predictions of the bordered tug-of-war model may fit skew data from a number of species, including meerkats, lions, and wood mice.
Th1-skewed tissue responses to a mycolyl glycolipid in mycobacteria-infected rhesus macaques
Morita, Daisuke; Miyamoto, Ayumi; Hattori, Yuki; Komori, Takaya; Nakamura, Takashi; Igarashi, Tatsuhiko; Harashima, Hideyoshi; Sugita, Masahiko
2013-11-08
Highlights: •Glucose monomycolate (GMM) is a marker glycolipid for active tuberculosis. •Tissue responses to GMM involved up-regulation of Th1-attracting chemokines. •Th1-skewed local responses were mounted at the GMM-injected tissue. -- Abstract: Trehalose 6,6′-dimycolate (TDM) is a major glycolipid of the cell wall of mycobacteria with remarkable adjuvant functions. To avoid detection by the host innate immune system, invading mycobacteria down-regulate the expression of TDM by utilizing host-derived glucose as a competitive substrate for their mycolyltransferases; however, this enzymatic reaction results in the concomitant biosynthesis of glucose monomycolate (GMM) which is recognized by the acquired immune system. GMM-specific, CD1-restricted T cell responses have been detected in the peripheral blood of infected human subjects and monkeys as well as in secondary lymphoid organs of small animals, such as guinea pigs and human CD1-transgenic mice. Nevertheless, it remains to be determined how tissues respond at the site where GMM is produced. Here we found that rhesus macaques vaccinated with Mycobacterium bovis bacillus Calmette–Guerin mounted a chemokine response in GMM-challenged skin that was favorable for recruiting T helper (Th)1 T cells. Indeed, the expression of interferon-γ, but not Th2 or Th17 cytokines, was prominent in the GMM-injected tissue. The GMM-elicited tissue response was also associated with the expression of monocyte/macrophage-attracting CC chemokines, such as CCL2, CCL4 and CCL8. Furthermore, the skin response to GMM involved the up-regulated expression of granulysin and perforin. Given that GMM is produced primarily by pathogenic mycobacteria proliferating within the host, the Th1-skewed tissue response to GMM may function efficiently at the site of infection.
A missing model in reproductive skew theory: the bordered tug-of-war.
Reeve, Hudson Kern; Shen, Sheng-Feng
2006-05-30
Models of reproductive skew can be classified into two groups: transactional models, in which group members yield shares of reproduction to each other in return for cooperation, and tug-of-war models, in which group members invest group resources in a tug-of-war over their respective reproductive shares. We synthesize these two models to yield a "bordered tug-of-war" model in which the internal tug-of-war is limited ("bordered") by the requirement that group members must achieve a certain amount of reproduction lest they pursue a noncooperative option leading to group breakup. Previous attempts to synthesize these two models did not allow for the fact that the tug-of-war will affect group output, which in turn feeds back on the reproductive payments required by group members to remain cooperative. The bordered tug-of-war model, which does not assume complete reproductive control by any individual and allows for conflict within groups, predicts that the degree of within-group selfishness will increase as the noncooperative options become less attractive, e.g., as ecological constraints on solitary breeding increase. When the noncooperative option involves fighting for the group resource (e.g., territory) and leaving if the fight is lost, the subordinate's overall share of reproduction is predicted to be independent of its relatedness to the dominant and to increase the greater its probability of winning the fight, the less the value of the territory, and the greater its personal payoff for leaving. The unique predictions of the bordered tug-of-war model may fit skew data from a number of species, including meerkats, lions, and wood mice. PMID:16717185
Kellö, Vladimir
2015-01-22
Highly correlated scalar relativistic calculations of electric field gradients at nuclei in diatomic molecules in combination with accurate nuclear quadrupole coupling constants obtained from microwave spectroscopy are used for determination of nuclear quadrupole moments.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Hecht, Michael (Inventor); Orient, Otto (Inventor); Wiberg, Dean (Inventor); Brennen, Reid A. (Inventor)
2001-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Fuerstenau, Stephen D. (Inventor); Orient, Otto J. (Inventor); Yee, Karl Y. (Inventor); Rice, John T. (Inventor)
2000-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Hecht, Michael (Inventor); Orient, Otto (Inventor); Wiberg, Dean (Inventor); Brennen, Reid A. (Inventor)
2001-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and aligrnent for use in a final quadrupole mass spectrometer device.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Fuerstenau, Stephen D. (Inventor); Orient, Otto J. (Inventor); Yee, Karl Y. (Inventor); Rice, John T. (Inventor)
2001-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Hecht, Michael (Inventor); Orient, Otto (Inventor); Wiberg, Dean (Inventor); Brennen, Reid A. (Inventor)
2000-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.
Miniature micromachined quadrupole mass spectrometer array and method of making the same
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Fuerstenau, Stephen D. (Inventor); Orient, Otto J. (Inventor); Yee, Karl Y. (Inventor); Rice, John T. (Inventor)
2002-01-01
The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device.
NASA Astrophysics Data System (ADS)
Mejia-Ospino, E.; García, G.; Guerrero, A.; Alvarez, I.; Cisneros, C.
2005-01-01
The three-photon resonance four-photon ionization and dissociation spectra of dimethyl ether (DME) are presented in the wavelength range 450-550 nm at 1 nm intervals. The (3+1) REMPI spectra show three prominent bands corresponding to the \\tildeB \\leftarrow \\skew1\\tildeX, {\\skew1\\tildeC} \\leftarrow \\skew1\\tildeX and {\\skew1\\tildeC^{\\prime}} \\leftarrow \\skew1\\tildeX transitions with origins at 61 457 cm-1 (7.615 eV), 59 055 cm-1 (7.322 eV) and 58 010 cm-1 (7.194 eV), respectively. Several ionized species, CH3+, CHnO+ (n = 1-3) and CH3OCH3+, are observed in the region of wavelengths studied here. In order to compare the results, a shorter wavelength multiphoton dissociation and ionization of DME at 355 nm is also presented. At this wavelength, DME undergoes neutral dissociation to CH3 and CH3O and each fragment is then ionized by multiphoton absorption. The fragmentation at 355 nm is very intense and only small fragments such as CH3+, CHO+, CH2+, CH+ and C+ ions are observed. The measurement of photoelectron energy allows us to establish that the DME ionization potential is at least 9.55 ± 0.15 eV. The experiments were performed using a Nd:YAG-OPO (optical parametric oscillator) tunable laser system coupled to a time-of-flight mass spectrometer and a hemispherical electron energy analyser.
Verkuil, Yvonne I; Juillet, Cedric; Lank, David B; Widemo, Fredrik; Piersma, Theunis
2014-01-01
Sex differences in skews of vertebrate lifetime reproductive success are difficult to measure directly. Evolutionary histories of differential skew should be detectable in the genome. For example, male-biased skew should reduce variation in the biparentally inherited genome relative to the maternally inherited genome. We tested this approach in lek-breeding ruff (Class Aves, Philomachus pugnax) by comparing genetic variation of nuclear microsatellites (θn; biparental) versus mitochondrial D-loop sequences (θm; maternal), and conversion to comparable nuclear (Ne) and female (Nef) effective population size using published ranges of mutation rates for each marker (μ). We provide a Bayesian method to calculate Ne (θn = 4Neμn) and Nef (θm = 2Nefμm) using 95% credible intervals (CI) of θn and θm as informative priors, and accounting for uncertainty in μ. In 96 male ruffs from one population, Ne was 97% (79–100%) lower than expected under random mating in an ideal population, where Ne:Nef = 2. This substantially lower autosomal variation represents the first genomic support of strong male reproductive skew in a lekking species. PMID:25478153
ERIC Educational Resources Information Center
Cooper, David
2015-01-01
The paper looks closely at student enrolment trends through a case study of South African "race" enrolment data, including some hypotheses about how student social class has influenced these trends. First, data on 1988-1998 enrolments showing a "skewed revolution" in student africanisation are summarised. Then, using 2000-2012…
Viggiano, Emanuela; Ergoli, Manuela; Picillo, Esther; Politano, Luisa
2016-07-01
Duchenne and Becker dystrophinopathies (DMD and BMD) are X-linked recessive disorders caused by mutations in the dystrophin gene that lead to absent or reduced expression of dystrophin in both skeletal and heart muscles. DMD/BMD female carriers are usually asymptomatic, although about 8 % may exhibit muscle or cardiac symptoms. Several mechanisms leading to a reduced dystrophin have been hypothesized to explain the clinical manifestations and, in particular, the role of the skewed XCI is questioned. In this review, the mechanism of XCI and its involvement in the phenotype of BMD/DMD carriers with both a normal karyotype or with X;autosome translocations with breakpoints at Xp21 (locus of the DMD gene) will be analyzed. We have previously observed that DMD carriers with moderate/severe muscle involvement, exhibit a moderate or extremely skewed XCI, in particular if presenting with an early onset of symptoms, while DMD carriers with mild muscle involvement present a random XCI. Moreover, we found that among 87.1 % of the carriers with X;autosome translocations involving the locus Xp21 who developed signs and symptoms of dystrophinopathy such as proximal muscle weakness, difficulty to run, jump and climb stairs, 95.2 % had a skewed XCI pattern in lymphocytes. These data support the hypothesis that skewed XCI is involved in the onset of phenotype in DMD carriers, the X chromosome carrying the normal DMD gene being preferentially inactivated and leading to a moderate-severe muscle involvement. PMID:27098336
Ibbotson, Paul
2013-01-01
We use the Google Ngram database, a corpus of 5,195,769 digitized books containing ~4% of all books ever published, to test three ideas that are hypothesized to account for linguistic generalizations: verbal semantics, pre-emption and skew. Using 828,813 tokens of un-forms as a test case for these mechanisms, we found verbal semantics was a good predictor of the frequency of un-forms in the English language over the past 200 years—both in terms of how the frequency changed over time and their frequency rank. We did not find strong evidence for the direct competition of un-forms and their top pre-emptors, however the skew of the un-construction competitors was inversely correlated with the acceptability of the un-form. We suggest a cognitive explanation for this, namely, that the more the set of relevant pre-emptors is skewed then the more easily it is retrieved from memory. This suggests that it is not just the frequency of pre-emptive forms that must be taken into account when trying to explain usage patterns but their skew as well. PMID:24399991
Myers, E M; Zamudio, K R
2004-07-01
Aggregate, or explosive, breeding is widespread among vertebrates and likely increases the probability of multiple paternity. We assessed paternity in seven field-collected clutches of the explosively breeding spotted salamander (Ambystoma maculatum) using 10 microsatellite loci to determine the frequency of multiple paternity and the number of males contributing to a female's clutch. Using the Minimum Method of allele counts, multiple paternity was evident in 70% of these egg masses. Simple allele counts underestimate the number of contributing males because this method cannot distinguish multiple fathers with common or similar alleles. Therefore, we used computer simulations to estimate from the offspring genotypes the most likely number of contributing fathers given the distributions of allele frequencies in this population. We determined that two to eight males may contribute to A. maculatum clutches; therefore, multiple paternity is a common strategy in this aggregate breeding species. In aggregate mating systems competition for mates can be intense, thus differential reproductive success (reproductive skew) among males contributing to a female's clutch could be a probable outcome. We use our data to evaluate the potential effect of reproductive skew on estimates of the number of contributing males. We simulated varying scenarios of differential male reproductive success, ranging from equal contribution to high reproductive skew among contributing sires in multiply sired clutches. Our data suggest that even intermediate levels of reproductive skew decrease confidence substantially in estimates of the number of contributing sires when parental genotypes are unknown. PMID:15189216
NASA Astrophysics Data System (ADS)
Pipień, M.
2008-09-01
We present the results of an application of Bayesian inference in testing the relation between risk and return on the financial instruments. On the basis of the Intertemporal Capital Asset Pricing Model, proposed by Merton we built a general sampling distribution suitable in analysing this relationship. The most important feature of our assumptions is that the skewness of the conditional distribution of returns is used as an alternative source of relation between risk and return. This general specification relates to Skewed Generalized Autoregressive Conditionally Heteroscedastic-in-Mean model. In order to make conditional distribution of financial returns skewed we considered the unified approach based on the inverse probability integral transformation. In particular, we applied hidden truncation mechanism, inverse scale factors, order statistics concept, Beta and Bernstein distribution transformations and also a constructive method. Based on the daily excess returns on the Warsaw Stock Exchange Index we checked the empirical importance of the conditional skewness assumption on the relation between risk and return on the Warsaw Stock Market. We present posterior probabilities of all competing specifications as well as the posterior analysis of the positive sign of the tested relationship.
Sui, Yilun; Chen, Qianqian; Sun, Xiaoxi
2015-08-01
Evidence of an association between skewed X chromosome inactivation (SXCI) and idiopathic recurrent spontaneous abortion (RSA) is conflicting. No consensus has been reached on the degree of SXCI and the number of pregnancy losses in patients who have experienced RSA. In this systematic review and meta-analysis, different degrees of skewing and definitions of RSA are used to establish an association between SXCI and idiopathic RSA. Twelve studies comprising 1594 women who had experienced RSA and 1924 controls were included. No significant association was found between SXCI and RSA when 80 or 90% was used as cut-off value of skewing; more stringent 95% or greater SXCI was significantly higher in women who had experienced RSA than in controls (odds ratio [OR] = 4.27, 95% confidence interval [CI] 1.46 to 12.46). A significantly higher incidence of SXCI when defined as greater than 90% (or ≥90%) was found in women who had experienced RSA with three or more pregnancy losses (OR = 2.31, 95% CI 1.41, 3.78); significance diminished when RSA was defined as two or more losses. Extreme skewing of SXCI is associated with idiopathic RSA with three or more losses. More studies are needed to validate the potential genetic mechanism.
NASA Technical Reports Server (NTRS)
Deissler, Robert G.
1991-01-01
The variation of the velocity-derivative skewness of a Navier-Stokes flow as the Reynolds number goes toward zero is calculated numerically. The value of the skewness, which has been somewhat controversial, is shown to become small at low Reynolds numbers.
Tranchida, Peter Q; Maimone, Mariarosa; Franchina, Flavio A; Bjerk, Thiago Rodrigues; Zini, Cláudia Alcaraz; Purcaro, Giorgia; Mondello, Luigi
2016-03-25
The present research is based on the development and use of a flow-modulation (FM) comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC×GC-qMS) method for the determination of recently-highlighted (by the Scientific Committee on Consumer Safety) fragrance allergens (54) in cosmetics. FM GC×GC-qMS conditions were finely tuned to generate flow conditions (≈7 mL min(-1)) compatible with the qMS system used. Six-point calibration curves, over the range 1, 5, 10, 20, 50, 100 mg L(-1), were constructed for the 54 target allergens, with satisfactory linearity observed in all cases. Absolute quantification was performed by using extracted ions; target analyte identification was performed through measurement of ion ratios (qualifier/quantifier), full-scan MS database matching and the use of linear retention indices. Additional analytical figures of merit subjected to measurement were intra-day repeatability, accuracy at the 25 and 5 mg L(-1) levels, and limits of detection and quantification. The number of data points per peak, along with mass spectral skewing, was also subjected to evaluation. Finally, the FM GC×GC-qMS method was used not only for the quantification of target allergens in five commercial perfumes, but also for general qualitative profiling. PMID:26718184
Covariant spectator theory of np scattering: Deuteron quadrupole moment
Gross, Franz
2015-01-26
The deuteron quadrupole moment is calculated using two CST model wave functions obtained from the 2007 high precision fits to np scattering data. Included in the calculation are a new class of isoscalar np interaction currents automatically generated by the nuclear force model used in these fits. The prediction for model WJC-1, with larger relativistic P-state components, is 2.5% smaller that the experiential result, in common with the inability of models prior to 2014 to predict this important quantity. However, model WJC-2, with very small P-state components, gives agreement to better than 1%, similar to the results obtained recently from _{X}EFT predictions to order N^{3}LO.
Covariant spectator theory of np scattering: Deuteron quadrupole moment
Gross, Franz
2015-01-26
The deuteron quadrupole moment is calculated using two CST model wave functions obtained from the 2007 high precision fits to np scattering data. Included in the calculation are a new class of isoscalar np interaction currents automatically generated by the nuclear force model used in these fits. The prediction for model WJC-1, with larger relativistic P-state components, is 2.5% smaller that the experiential result, in common with the inability of models prior to 2014 to predict this important quantity. However, model WJC-2, with very small P-state components, gives agreement to better than 1%, similar to the results obtained recently frommore » XEFT predictions to order N3LO.« less
Jentschura, U. D.; Milstein, A. I.; Terekhov, I. S.; Boie, H.; Scheit, H.; Schwalm, D.
2008-01-15
We present a quasiclassical theory of {alpha} decay accompanied by bremsstrahlung with a special emphasis on the case of {sup 210}Po, with the aim of finding a unified description that incorporates both the radiation during the tunneling through the Coulomb wall and the finite energy E{sub {gamma}} of the radiated photon up to E{sub {gamma}}{approx}Q{sub {alpha}}/{radical}({eta}), where Q{sub {alpha}} is the {alpha}-decay Q-value and {eta} is the Sommerfeld parameter. The corrections with respect to previous quasiclassical investigations are found to be substantial, and excellent agreement with a full quantum mechanical treatment is achieved. Furthermore, we find that a dipole-quadrupole interference significantly changes the {alpha}-{gamma} angular correlation. We obtain good agreement between our theoretical predictions and experimental results.
Plasma-beam traps and radiofrequency quadrupole beam coolers
Maggiore, M. Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S.; Caruso, A.; Longhitano, A.; Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M.
2014-02-15
Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.
Uranus' (3-0) H2 quadrupole line profiles
NASA Astrophysics Data System (ADS)
Trafton, L.
1987-04-01
Spectra of Uranus' S3(0) and S3(1) H2 quadrupole lines, obtained during the 1978-1980 apparitions, are analyzed, and are found to require the presence of a deep cloud. Modifications of the Baines and Bergstralh (1986) standard model, including an additional haze layer above the 16-km-am H2 level which contains strongly absorbing particles, are needed to fit the observations. For a Rayleigh phase function, such a haze (uniformly mixed with the gas above this level) would have an absorption optical depth of 0.16 and a single scattering particle albedo of 0.30. This modification would imply a fraction of normal H2 equal to 0.25 + or - 0.10, in agreement with the Baines and Bergstralh standard model.
Nb3Sn Quadrupole Magnets for the LHC IR
Sabbi, G.; Caspi, S.; Chiesa, L.; Coccoli, M.; Dietderich, D.r.; Ferracin, P.; Gourlay, S.A.; Hafalia, R.R.; Lietzke, A.F.; McInturff, A.D.; Scanlan, R.M.
2001-08-01
The development of insertion quadrupoles with 205 T/m gradient and 90 mm bore represents a promising strategy to achieve the ultimate luminosity goal of 2.5 x 10{sup 34} cm{sup -2}s{sup -1} at the Large Hadron Collider (LHC). At present, Nb{sub 3}Sn is the only practical conductor which can meet these requirements. Since Nb{sub 3}Sn is brittle, and considerably more strain sensitive than NbTi, the design concepts and fabrication techniques developed for NbTi magnets need to be modified appropriately. In addition, IR magnets must provide high field quality and operate reliably under severe radiation loads. The results of conceptual design studies addressing these issues are presented.
High gradient quadrupoles for low emittance storage rings
NASA Astrophysics Data System (ADS)
Le Bec, G.; Chavanne, J.; Benabderrahmane, C.; Farvacque, L.; Goirand, L.; Liuzzo, S.; Raimondi, P.; Villar, F.
2016-05-01
High gradient quadrupoles are key components for the coming generation of storage ring based light sources. The typical specifications of these magnets are: almost 100 T /m gradient, half a meter long, and a vertical aperture for the extraction of the x-ray beam. This paper presents the preparation work done at the European Synchrotron Radiation Facility, from the design to the manufacture and measurements of a prototype. It demonstrates the feasibility of such magnets. Different aspects of magnet engineering are discussed, including the study of the main scale factors and the preliminary design, the pole shaping, the impact of mechanical errors, and the magnetic measurements of a prototype with a stretched-wire system.
Revision of Spin Echoes in Pure Nuclear Quadrupole Resonance
NASA Astrophysics Data System (ADS)
Meriles, C. A.
2001-04-01
Goldman's spin-1/2 formalism has been used for describing the response of an I=3/2 spin system to a two-pulse sequence in a pure nuclear quadrupole resonance experiment. A detailed analysis of the polarization evolution and quadrupolar echo generation is carried out through the use of explicit expressions for secular homo- and heteronuclear dipolar interactions. In striking contrast with previous studies, it is predicted that Van Vleck's second moments governing a classical solid-echo or Hahn sequence differ from those obtained by equivalent means in magnetic resonance. In fact, it is shown that, although measured moments still complement each other, the combined use of standard sequences does not allow the separate determination of homo- and heteronuclear dipolar contributions to the linewidth, not even in an indirect manner. In this context, the importance and potential usefulness of a crossed coil probe are also briefly discussed.
Investigation of a quadrupole ultra-high vacuum ion pump
NASA Technical Reports Server (NTRS)
Schwarz, H. J.
1974-01-01
The new nonmagnetic ion pump resembles the quadrupole ionization gage. The dimensions are larger, and hyperbolically shaped electrodes replace the four rods. Their surfaces follow y sq. = 36 + x sq. (x, y in centimeters). The electrodes, 55 cm long, are positioned lengthwise in a tube. At one end a cathode emits electrons; at the other end a narrowly wound flat spiral of tungsten clad with titanium on cathode potential can be heated for titanium evaporation. Electrons accelerated by a dc potential of the surface electrodes oscillate between the ends on rotational trajectories, if a high frequency potential superimposed on the dc potential is properly adjusted. Pumping speeds (4-100 liter/sec) for different gases at different peak voltages (1000-3000V) at corresponding frequencies (57-100 MHz), and at different pressures 0.00001 to the minus 9 power Torr were observed. The lowest pressure reached was below 10 to the minus 10 power Torr.
Veilleux, Andrea G.; Stedinger, Jery R.; Eash, David A.
2012-01-01
This paper summarizes methodological advances in regional log-space skewness analyses that support flood-frequency analysis with the log Pearson Type III (LP3) distribution. A Bayesian Weighted Least Squares/Generalized Least Squares (B-WLS/B-GLS) methodology that relates observed skewness coefficient estimators to basin characteristics in conjunction with diagnostic statistics represents an extension of the previously developed B-GLS methodology. B-WLS/B-GLS has been shown to be effective in two California studies. B-WLS/B-GLS uses B-WLS to generate stable estimators of model parameters and B-GLS to estimate the precision of those B-WLS regression parameters, as well as the precision of the model. The study described here employs this methodology to develop a regional skewness model for the State of Iowa. To provide cost effective peak-flow data for smaller drainage basins in Iowa, the U.S. Geological Survey operates a large network of crest stage gages (CSGs) that only record flow values above an identified recording threshold (thus producing a censored data record). CSGs are different from continuous-record gages, which record almost all flow values and have been used in previous B-GLS and B-WLS/B-GLS regional skewness studies. The complexity of analyzing a large CSG network is addressed by using the B-WLS/B-GLS framework along with the Expected Moments Algorithm (EMA). Because EMA allows for the censoring of low outliers, as well as the use of estimated interval discharges for missing, censored, and historic data, it complicates the calculations of effective record length (and effective concurrent record length) used to describe the precision of sample estimators because the peak discharges are no longer solely represented by single values. Thus new record length calculations were developed. The regional skewness analysis for the State of Iowa illustrates the value of the new B-WLS/BGLS methodology with these new extensions.
Mynard, Jonathan P; Steinman, David A
2013-05-01
Given evidence that fully developed axisymmetric flow may be the exception rather than the rule, even in nominally straight arteries, maximum velocity (V(max)) can lie outside the Doppler sample volume (SV). The link between V(max) and derived quantities, such as volume flow (Q), may therefore be more complex than commonly thought. We performed idealized virtual Doppler ultrasound on data from image-based computational fluid dynamics (CFD) models of the normal human carotid artery and investigated how velocity profile skewing and choice of sample volume affected V(max) waveforms and derived Q variables, considering common assumptions about velocity profile shape (i.e., Poiseuille or Womersley). Severe velocity profile skewing caused substantial errors in V(max) waveforms when using a small, centered SV, although peak V(max) was reliably detected; errors with a long SV covering the vessel diameter were orientation dependent but lower overall. Cycle-averaged Q calculated from V(max) was typically within ±15%, although substantial skewing and use of a small SV caused 10%-25% underestimation. Peak Q derived from Womersley's theory was generally accurate to within ±10%. V(max) pulsatility and resistance indexes differed from Q-based values, although the Q-based resistance index could be predicted reliably. Skewing introduced significant error into V(max)-derived Q waveforms, particularly during mid-to-late systole. Our findings suggest that errors in the V(max) and Q waveforms related to velocity profile skewing and use of a small SV, or orientation-dependent errors for a long SV, could limit their use in wave analysis or for constructing characteristic or patient-specific flow boundary conditions for model studies.
First Observation of a Quadrupole Cooper Minimum in the Photoionization of Xe 5p
NASA Astrophysics Data System (ADS)
Deshmukh, P. C.; Hemmers, O.; Guillemin, R.; Wolska, A.; Lindle, D. W.; Rolles, D.; Yu, S. W.; Manson, S. T.
2006-05-01
The nondipole photoelectron angular distribution parameter ξ (= 3δ+γ) for xenon 5p1/2 and 5p3/2 has been studied experimentally in the 80 - 200 eV range. In addition, calculations have been performed using the relativistic-random-phase approximation (RRPA) methodology with all relativistic single excitation/ionization channels down to 4s coupled in both the dipole and quadrupole manifolds. The results show significant disagreement between theory and experiment above about 130 eV photon energy, in contradistinction to the Xe 5s case where rather good agreement is found. Since it is known that the dipole amplitudes are well-represented by RRPA, the difficulty must be in the quadrupole channels. It was expected that the quadrupole channels should be accurate as well since the f-wave is resonant in Xe and the main quadrupole transitions, the 5p->kf, are included in the calculation. However, we have found that these transitions each have a quadrupole Cooper minimum in the energy region of interest, so that quadrupole satellites, which are not included in the RRPA calculation, become important. This might be the first experimental indication of a quadrupole Cooper minimum.
Development of MQXF: The Nb3Sn low-β quadrupole for the HiLumi LHC
Ferracin, P.; G. Ambrosio; Anerella, M.; Ballarino, A.; Bajas, H.; Bajko, M.; Bordini, B.; Bossert, R.; Cheng, D. W.; Dietderich, D. R.; et al
2015-12-18
The High Luminosity (HiLumi) Large Hadron Collider (LHC) project has, as the main objective, to increase the LHC peak luminosity by a factor five and the integrated luminosity by a factor ten. This goal will be achieved mainly with a new interaction region layout, which will allow a stronger focusing of the colliding beams. The target will be to reduce the beam size in the interaction points by a factor of two, which requires doubling the aperture of the low-β (or inner triplet) quadrupole magnets. The use of Nb3Sn superconducting material and, as a result, the possibility of operating atmore » magnetic field levels in the windings higher than 11 T will limit the increase in length of these quadrupoles, called MQXF, to acceptable levels. After the initial design phase, where the key parameters were chosen and the magnet's conceptual design finalized, the MQXF project, a joint effort between the U.S. LHC Accelerator Research Program and the Conseil Europeen pour la Recherche Nucleaire (CERN), has now entered the construction and test phase of the short models. Concurrently, the preparation for the development of the full-length prototypes has been initiated. Lastly, this paper will provide an overview of the project status, describing and reporting on the performance of the superconducting material, the lessons learnt during the fabrication of superconducting coils and support structure, and the fine tuning of the magnet design in view of the start of the prototyping phase.« less
NPIP: A skew line needle configuration optimization system for HDR brachytherapy
Siauw, Timmy; Cunha, Adam; Berenson, Dmitry; Atamtuerk, Alper; Hsu, I-Chow; Goldberg, Ken; Pouliot, Jean
2012-07-15
Purpose: In this study, the authors introduce skew line needle configurations for high dose rate (HDR) brachytherapy and needle planning by integer program (NPIP), a computational method for generating these configurations. NPIP generates needle configurations that are specific to the anatomy of the patient, avoid critical structures near the penile bulb and other healthy structures, and avoid needle collisions inside the body. Methods: NPIP consisted of three major components: a method for generating a set of candidate needles, a needle selection component that chose a candidate needle subset to be inserted, and a dose planner for verifying that the final needle configuration could meet dose objectives. NPIP was used to compute needle configurations for prostate cancer data sets from patients previously treated at our clinic. NPIP took two user-parameters: a number of candidate needles, and needle coverage radius, {delta}. The candidate needle set consisted of 5000 needles, and a range of {delta} values was used to compute different needle configurations for each patient. Dose plans were computed for each needle configuration. The number of needles generated and dosimetry were analyzed and compared to the physician implant. Results: NPIP computed at least one needle configuration for every patient that met dose objectives, avoided healthy structures and needle collisions, and used as many or fewer needles than standard practice. These needle configurations corresponded to a narrow range of {delta} values, which could be used as default values if this system is used in practice. The average end-to-end runtime for this implementation of NPIP was 286 s, but there was a wide variation from case to case. Conclusions: The authors have shown that NPIP can automatically generate skew line needle configurations with the aforementioned properties, and that given the correct input parameters, NPIP can generate needle configurations which meet dose objectives and use as many
Wireless power transfer based on magnetic quadrupole coupling in dielectric resonators
NASA Astrophysics Data System (ADS)
Song, Mingzhao; Iorsh, Ivan; Kapitanova, Polina; Nenasheva, Elizaveta; Belov, Pavel
2016-01-01
We numerically investigate a magnetic resonant wireless power transfer system based on high refractive index dielectric resonators. We propose to operate at magnetic quadrupole mode of the resonators to enlarge the efficiency due to minimization of ohmic and radiation losses. Numerical estimation predicts the 80% efficiency of the wireless power transfer (WPT) system operating at quadrupole mode at 300 MHz. Moreover, the system operating at magnetic quadrupole mode is capable of transferring power with 70% efficiency when the receiver rotates 90°. We verify the simulated results by experimental investigation of the WPT system based on microwave ceramic resonators (ɛ = 80 and tanδ = 10-4).
Production techniques for the Superconducting Super Collider Low Energy Booster quadrupole magnet
Morrison, M.E.; Behrsing, G.U.; Fulton, R.L.
1994-07-01
The manufacturing techniques used for a prototype quadrupole magnet, developed at Lawrence Berkeley Laboratory (LBL) for the Superconducting Super Collider (SSC) Low Energy Booster (LEB), are described. The SSC LEB Ring employs 96 dipoles and 90 quadrupoles connected in series to form the magnetic lattice, requiring the use of a 21.9 mm x 23.0 mm hollow conductor for the quadrupoles. Due to the large conductor size and small bend radii required, development of special fixtures was necessary. A unique coil-forming method with close attention paid to tooling design and special assembly procedures was required to manufacture this prototype to stringent specifications.
Electric quadrupole transition probabilities and line strengths of Ti{sup 11+}
Gökçe, Yasin; Çelik, Gültekin; Yıldız, Murat
2014-07-15
Electric quadrupole transition probabilities and line strengths have been calculated using the weakest bound electron potential model for sodium-like titanium, considering many transition arrays. We employed numerical Coulomb approximation and non-relativistic Hartree–Fock wavefunctions for the expectation values of radii in determination of parameters of the model. The necessary energy values have been taken from experimental data in the literature. The calculated electric quadrupole line strengths have been compared with available data in the literature and good agreement has been obtained. Moreover, some electric quadrupole transition probability and line strength values not existing in the literature for some highly excited levels have been obtained using this method.
Reconstruction of the number and positions of dipoles and quadrupoles using an algebraic method
NASA Astrophysics Data System (ADS)
Nara, Takaaki
2008-11-01
Localization of dipoles and quadrupoles is important in inverse potential analysis, since they can effectively express spatially extended sources with a small number of parmeters. This paper proposes an algebraic method for reconstruction of pole positions as well as the number of dipole-quadrupoles without providing an initial parameter guess or iterative computing forward solutions. It is also shown that a magnetoencephalography inverse problem with a source model of dipole-quadrupoles in 3D space is reduced into the same problem as in 2D space.
De Bernardis, P.; Epifani, M.; Guarini, G.; Masi, S.; Melchiorri, F. )
1990-04-01
This paper studies the dipole and quadrupole anisotropy brightness arising from the motion of the observer in the presence of a pure Planckian spectrum and in the case of a submillimeter excess. It is found that the dipole anisotropy is enhanced in the case of the excess measured by the Japanese-U.S. groups, while it is decreased in the case of the excess found by the Canadian group. The quadrupole term is absent in the radio region, while it acquires detectable values in the IR. Comparisons are made with the observational values, and the possibility of observing the quadrupole pattern in the presence of galactic dust contamination is discussed. 15 refs.