Order Multiplets Research Articles

Asteroseismology of hot subdwarf B stars observed with TESS: discovery of two new gravity mode pulsating stars

TIC 033834484 and TIC 309658435 are long-period pulsating subdwarf B stars, which were observed extensively (675 and 621 days, respectively) by the Transiting Exoplanet Survey Satellite (TESS). The high-precision photometric light curve reveals the presence of more than 40 pulsation modes including both stars. All the oscillation frequencies that we found are associated with gravity (g)-mode pulsations, with frequencies spanning from ∼80 µHz (2 500 s) to ∼400 µHz (12 000 s). We utilize the asteroseismic tools including asymptotic period spacings and rotational frequency multiplets in order to identify the pulsational modes. We found dipole (l = 1) mode sequences for both targets and calculate the mean period spacing of dipole modes (ΔPl=1), which allows us to identify the modes. Frequency multiplets provide a rotation period of ∼64 d for TIC 033834484. From follow-up ground-based spectroscopy, we find that TIC 033834484 has an effective temperature of 24 210 K (140), a surface gravity of log g/cms-2 = 5.28 (03) and TIC 309658435 has an effective temperature of 25 910 K (150), a surface gravity of log g/cms-2 = 5.48 (03).

Analytic gradients for spin multiplets in natural orbital functional theory.

Analytic energy gradients with respect to nuclear motion are derived for non-singlet compounds in the natural orbital functional theory. We exploit the formulation for multiplets in order to obtain a simple formula valid for any many-electron system in its ground mixed state with a total spin S and all possible spin projection Sz values. We demonstrate that the analytic gradients can be obtained without resorting to linear response theory or involving iterative procedures. A single evaluation is required, so integral derivatives can be computed on-the-fly along the calculation, thus improving the effectiveness of screening by the Schwarz inequality. The results for small- and medium-sized molecules with many spin multiplicities are shown. Our results are compared with the experimental data and accurate theoretical equilibrium geometries.

Going beyond base-pairs: topology-based characterization of base-multiplets in RNA.

Identification and characterization of base-multiplets, which are essentially mediated by base-pairing interactions, can provide insights into the diversity in the structure and dynamics of complex functional RNAs, and thus facilitate hypothesis driven biological research. The necessary nomenclature scheme, an extension of the geometric classification scheme for base-pairs by Leontis and Westhof, is however available only for base-triplets. In the absence of information on topology, this scheme is not applicable to quartets and higher order multiplets. Here we propose a topology-based classification scheme which, in conjunction with a graph-based algorithm, can be used for the automated identification and characterization of higher order base-multiplets in RNA structures. Here, the RNA structure is represented as a graph, where nodes represent nucleotides and edges represent base-pairing connectivity. Sets of connected components (of n nodes) within these graphs constitute subgraphs representing multiplets of “n” nucleotides. The different topological variants of the RNA multiplets thus correspond to different nonisomorphic forms of these subgraphs. To annotate RNA base-multiplets unambiguously, we propose a set of topology-based nomenclature rules for quartets, which are extendable to higher multiplets. We also demonstrate the utility of our approach toward the identification and annotation of higher order RNA multiplets, by investigating the occurrence contexts of selected examples in order to gain insights regarding their probable functional roles.

Baryon fields withUL(3)×UR(3)chiral symmetry. V. Pion-nucleon and kaon-nucleonΣterms

We have previously calculated the pion-nucleon $\Sigma_{\pi N}$ term in the chiral mixing approach with $u,d$ flavors only, and found the lower bound $\Sigma_{\pi N} \geq \left(1 + \frac{16}{3} \sin^2 \theta \right){3 \over 2} \left(m_{u}^{0} + m_{d}^{0}\right)$. The mixing angle $\theta$ can be calculated as $\sin^2\theta = \frac{3}{8}\left(g_A^{(0)} + g_A^{(3)}\right)$. With presently accepted values of current quark masses, this leads to $\Sigma_{\pi N} \geq 58.0 \pm 4.5 \begin{array}{l} +11.4 \\ -6.5 \end{array}$ MeV, which is in agreement with the values extracted from experiments, and substantially higher than most previous two-flavour calculations. The causes of this enhancement are: 1) the large, ($\frac{16}{3}\simeq 5.3$), purely $SU_L(2) \times SU_R(2)$ algebraic factor, 2) the admixture of the $[(\mathbf{1},\mathbf{\frac12})\oplus (\mathbf{\frac12},\mathbf{1})]$ chiral multiplet component in the nucleon, whose presence has been known for some time, but that had not been properly taken into account, yet. We have now extended these calculations of $\Sigma_{\pi N}$ to three light flavours, i.e., to $SU_L(3) \times SU_R(3)$ multiplet mixing. Phenomenology of chiral $SU_L(3) \times SU_R(3)$ multiplet mixing demands the presence of three chiral $SU_L(3) \times SU_R(3)$ multiplets in order to successfully reproduce the baryons' flavor-octet and flavor-singlet axial currents, as well as the baryon anomalous magnetic moments. The physical significance of these results lies in the fact that they show no need for $q^4 {\bar q}$ components, and in particular, no need for an $s \bar s$ component in the nucleon, in order to explain the large "observed" $\Sigma_{\pi N}$ value. We also predict the experimentally unknown kaon-nucleon sigma term $\Sigma_{K N}$.

The impact of gate width setting and gate utilization factors on plutonium assay in passive correlated neutron counting

In the field of nuclear safeguards, passive neutron multiplicity counting (PNMC) is a method typically employed in non-destructive assay (NDA) of special nuclear material (SNM) for nonproliferation, verification and accountability purposes. PNMC is generally performed using a well-type thermal neutron counter and relies on the detection of correlated pairs or higher order multiplets of neutrons emitted by an assayed item. To assay SNM, a set of parameters for a given well-counter is required to link the measured multiplicity rates to the assayed item properties. Detection efficiency, die-away time, gate utilization factors (tightly connected to die-away time) as well as optimum gate width setting are among the key parameters. These parameters along with the underlying model assumptions directly affect the accuracy of the SNM assay. In this paper we examine the role of gate utilization factors and the single exponential die-away time assumption and their impact on the measurements for a range of plutonium materials. In addition, we examine the importance of item-optimized coincidence gate width setting as opposed to using a universal gate width value. Finally, the traditional PNMC based on multiplicity shift register electronics is extended to Feynman-type analysis and application of this approach to Pu mass assay is demonstrated.

Point model equations for neutron correlation counting: Extension of Böhnel׳s equations to any order

Various methods of autocorrelation neutron analysis may be used to extract information about a measurement item containing spontaneously fissioning material. The two predominant approaches being the time correlation analysis (that make use of a coincidence gate) methods of multiplicity shift register logic and Feynman sampling. The common feature is that the correlated nature of the pulse train can be described by a vector of reduced factorial multiplet rates. We call these singlets, doublets, triplets etc. Within the point reactor model the multiplet rates may be related to the properties of the item, the parameters of the detector, and basic nuclear data constants by a series of coupled algebraic equations – the so called point model equations. Solving, or inverting, the point model equations using experimental calibration model parameters is how assays of unknown items is performed. Currently only the first three multiplets are routinely used. In this work we develop the point model equations to higher order multiplets using the probability generating functions approach combined with the general derivative chain rule, the so called Faà di Bruno Formula. Explicit expression up to 5th order are provided, as well the general iterative formula to calculate any order. This work represents the first necessary step towards determining if higher order multiplets can add value to nondestructive measurement practice for nuclear materials control and accountancy.

Vector-like Multiplets, Mixings and the LHC

Vector-like quarks are an essential ingredient of many extensions of the Standard Model of particle physics. Moreover the presence of more than one vector-like multiplet is a common situation in many models. The interplay of these vector-like multiplet with precision electroweak bounds, flavour and collider phenomenology, especially at the Large Hadron Collider is a important point for the discovery of physics beyond the standard model. I consider the presence of two vector-like multiplets in order to show the constraints on such scenarios from tree-level data and oblique corrections in the case of a completely general flavour mixings with all the three standard model families of quarks. I also describe a framework for studying the interplay of any number of vector-like multiplets.

Strong, weak and flavor scalar triplets for the CDF Wjj anomaly

A model describing the 4.1\sigma\ Wjj anomaly observed by the CDF experiment at the Tevatron collider is introduced. It features new scalar particles which are charged both under the SU(3)_C and the SU(2)_L gauge groups and which couple to pairs of quarks. We introduce several identical replicas of the scalar multiplets in order to leave an unbroken U(3)_Q x U(3)_U x U(3)_D flavor symmetry to satisfy the constraints coming from flavor physics. We discuss the LHC reach on the new scalar resonances both in the resonant production channel (with the Wjj final state) and in the QCD pair production channel (with the 4j final state).

Blazhko RR Lyrae light curves as modulated signals

We present an analytical formalism for the description of Blazhko RR Lyrae light curves. In this formalism the amplitude and frequency modulations are treated in a manner similar to the theory of electronic signal transmission. We consider monoperiodic RR Lyrae light curves to be carrier waves, and modulate their amplitude (AM), frequency (FM) and phase (PM); as a general case we discuss simultaneous AM and FM. The main advantages of this method are the following: (i) the mathematical formalism naturally explains numerous light-curve characteristics found in the Blazhko RR Lyrae stars such as mean brightness variations, complicated envelope curves and non-sinusoidal frequency variations; (ii) our elucidation also explains the properties of the Fourier spectra such as apparent higher order multiplets, amplitude distribution of the sidepeaks, the appearance of the modulation frequency itself and its harmonics. In addition, compared to the traditional methods, our light-curve solutions reduce the number of necessary parameters. This formalism can be applied to any type of modulated light curves, not just to Blazhko RR Lyrae star light curves.

Multiple gestation and infertility treatment: registration, reflection and reaction—the Belgian project

Multiple pregnancies associated with infertility treatment are recognized as an adverse outcome and are responsible for morbidity and mortality related to prematurity and very low birthweight population. Due to the epidemic of iatrogenic multiple births, the incidence of maternal, perinatal and childhood morbidity and mortality has increased. This results in a hidden healthcare cost of infertility therapy and this may lead to social and political concern. Reducing the number of embryos transferred and the use of natural cycle IVF will surely decrease the number of multiple gestations. Consequently, optimized cryopreservation programmes will be essential. For non-IVF hormonal stimulation, responsible for more than one-third of all multiple pregnancies after infertility treatment, a strict ovarian stimulation protocol aiming at mono-ovulation is crucial. Multifetal pregnancy reduction is an effective method to reduce high order multiplets but carries its own risk of medical and emotional complications. Excellent data collection of all infertility treatments is needed in our discussion with policy makers. The Belgian project, in which reimbursement of assisted reproduction technology-related laboratory activities is linked to a transfer policy aiming at substantial multiple pregnancy reduction, is a good example of cost-efficient health care through responsible, well considered clinical practice.

New guide for first order multiplet analysis by modified J doubling in the frequency domain

Pattern recognition is extremely important for both structure elucidation and stereochemical studies as a means for the measurement of spin-spin coupling constants. Many treatises deal with the formation of splitting trees to create a pattern for a given set of spin-spin coupling constants. We present here a general systematic procedure to easily analyze first order multiplets in NMR spectroscopy. This method has the advantage of measuring coupling constants while deconvolving the signals at the same time using an extension of the modified J doubling in the frequency domain.

Ion optical study of a transmission ion microscope

This paper describes new imaging methods which use a nuclear microprobe lens system placed after the sample to focus the transmitted ions. Recent experimental work has demonstrated how a quadrupole lens multiplet can be used to magnify the angular distribution of unfocused proton beams passing through thin silicon crystals, and also the spatial distribution of unfocused beams of MeV protons passing through free-standing grids. It has also been shown how a highly convergent, focused MeV proton beam which passed through a thin silicon crystal could be used to directly image the defects present. Such experimental work has highlighted the need for new ion optical studies on how MeV ion beams can be manipulated by quadrupole lens multiplets in order to fully understand this previous work, and also to show how the attainable spatial and angular magnification can be further increased. This paper presents such calculations in the form of ion optical trajectory plots using the matrix ray-tracing program PRAM, which takes chromatic and spherical aberrations into account.

Collective-flow correlations in 197Au-emulsion interactions at 10.6 A GeV

We have studied the azimuthal angle correlations in pairs of alpha particles, in Intermediate Mass Fragments (IMFs), and in higher order multiplets observed in 197Au-emulsion interactions at 10.6 A GeV. The correlation functions for higher fragment multiplets (greater than three or more fragments) exhibit characteristic signatures which are enhanced compared to those of two-fragment correlation functions. The pure multiplet contribution is extracted from the observed higher-order correlation functions. The measurements of collective flow correlations in heavy-ion collisions are best obtained by studying several fragments with mixed charges including He fragments.

LEED study of the stepped surface of vicinal Si(100)

Abstract Periodic stepped surfaces prepared on vicinal silicon (100) by ion bombardment and annealing have been studied by LEED. An unusual aspect of the diffraction patterns from [011] zone samples was the presence of fractional order multiplets with half the splitting of the integral order doublets. An explanation is given, based on the superposition of diffraction from three distinct domain types. These differ in the orientations of their dangling bonds and the arrangements of successive terraces. The simpler patterns from [001] zone samples evidenced just two reconstruction domains. All non-integral order beams disappeared when samples were exposed to ionized hydrogen. This facilitated both the identification of certain lattice distortions, and the determination of step heights, which were found to be two atomic layers in all cases.

LEED study of the stepped surface of vicinal Si (100)

Periodic stepped surfaces prepared on vicinal silicon (100) by ion bombardment and annealing have been studied by LEED. An unusual aspect of the diffraction patterns from [01̄1] zone samples was the presence of fractional order multiplets with half the splitting of the integral order doublets. An explanation is given, based on the superposition of diffraction from three distinct domain types. These differ in the orientations of their dangling bonds and the arrangements of successive terraces. The simpler patterns from [001] zone samples evidenced just two reconstruction domains. All non-integral order beams disappeared when samples were exposed to ionized hydrogen. This facilitated both the identification of certain lattice distortions, and the determination of step heights, which were found to be two atomic layers in all cases.

T1 Spin decoupling effects on the lineshapes of NMR spin—spin multiplets

T 1 relaxation of one set of nuclei causes an extra-broadening and an apparent reduction of the spin—spin splitting in the NMR spectrum of another set of nuclei coupled to it. These effects are demonstrated by line-shape calculations for first order multiplets of spin 1 2 nuclei. It is shown that in a well-resolved multiplet of nuclei A in A m X n spectra the extra-broadening of each component is given by n/2 T 1X.

The kinetics of flowing dispersions: I. Concentrated suspensions of rigid particles

In the viscous flow regime the velocity profiles of dilute suspensions of rigid spheres in Newtonian liquids undergoing Couette or Poiseuille flow were found to be identical with those predicted by the theory with no particles present. At concentrations low enough so that the formation of triplets and higher order multiplets could be neglected, a given sphere exhibited fluctuations about a fixed mean radial position. The measured distribution of lateral displacements agreed with a theory based on rectilinear approach and recession of colliding pairs, whereas the time average radial displacements were twice the predicted values. On increasing the concentration partial plug flow developed in the tube with a central core in which the particles traveled with identical velocities without rotating and at fixed radial positions. Outside this central core the particles described irregular paths which, however, were reversible with respect to translation and rotation when the direction of flow was reversed. The concentration profiles were found to be uniform over prolonged periods of flow, and the suspensions showed Newtonian behavior. The phenomena, many of which were similar in suspensions of rods and discs, were shown to result from a wall effect predicted by Vand and were not manifestations of non-Newtonian behavior.