5,472 research outputs found
N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei
We examine the effects of the additional term of the type on the recently proposed empirical formula for the lowest excitation
energy of the states in even-even nuclei. This study is motivated by the
fact that this term carries the favorable dependence of the valence nucleon
numbers dictated by the scheme. We show explicitly that there is not
any improvement in reproducing by including the extra
term. However, our study also reveals that the excitation energies
, when calculated by the term alone (with the mass number
dependent term), are quite comparable to those calculated by the original
empirical formula.Comment: 14 pages, 5 figure
Formation of Warped Disks by Galactic Fly-by Encounters. I. Stellar Disks
Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and
test the `fly-by scenario' of warp formation, in which impulsive encounters
between galaxies are responsible for warped disks. Based on N-body simulations,
we investigate the morphological and kinematical evolution of the stellar
component of disks when galaxies undergo fly-by interactions with adjacent dark
matter halos. We find that the so-called `S'-shaped warps can be excited by
fly-bys and sustained for even up to a few billion years, and that this
scenario provides a cohesive explanation for several key observations. We show
that disk warp properties are governed primarily by the following three
parameters; (1) the impact parameter, i.e., the minimum distance between two
halos, (2) the mass ratio between two halos, and (3) the incident angle of the
fly-by perturber. The warp angle is tied up with all three parameters, yet the
warp lifetime is particularly sensitive to the incident angle of the perturber.
Interestingly, the modeled S-shaped warps are often non-symmetric depending on
the incident angle. We speculate that the puzzling U- and L-shaped warps are
geometrically superimposed S-types produced by successive fly-bys with
different incident angles, including multiple interactions with a satellite on
a highly elongated orbit.Comment: 16 pages, 13 figures, 3 tables. Accepted for publication in Ap
Exploiting Higher Kinematic Performance - Using a 4-Legged Redundant PM Rather than Gough-Stewart Platforms
Emergence of H3N2 Subtype Swine Influenza Viruses in Midwest Swine
A prospective study was conducted to monitor the pig population in Iowa for the emergence of new subtype(s) of swine influenza virus (SIV) other than classic H1N1 subtype. During the study, an apparently new subtype of SIV, H3N2, was isolated in association with severe reproductive and respiratory clinical disease in swine operations in Iowa and southern Minnesota. At the same time, influenza outbreaks of this subtype also were reported in other states such as North Carolina, Illinois, and Texas. To date, the new subtype of SIV has been determined to be widely spread in swine operations throughout Iowa and is expected to coexist with H1N1 subtype in swine populations in the United States. A serological survey on 6-month-old finishing pigs (N=1064) from 129 herds throughout 29 counties in Iowa demonstrated that 64% of the pigs and 92.2% of the herds had serological evidence of exposure to H3N2 SIV as of June, 1999. The isolation of H3N2 subtype SIV in association with severe clinical disease brings a new perspective to the diagnosis and control of swine influenza in this country. New vaccines will be needed for effective control of H3N2 because field reports have indicated no cross protection against H3N2 subtype SIV by vaccines currently available for H1N1 strains. Consequently it is critical for diagnosticians to have rapid and accurate methods for the diagnosis and differentiation of SIV subtypes so that effective control measure can be suggested in timely manner
Singularity Structures in Coulomb-Type Potentials in Two Body Dirac Equations of Constraint Dynamics
Two Body Dirac Equations (TBDE) of Dirac's relativistic constraint dynamics
have been successfully applied to obtain a covariant nonperturbative
description of QED and QCD bound states. Coulomb-type potentials in these
applications lead naively in other approaches to singular relativistic
corrections at short distances that require the introduction of either
perturbative treatments or smoothing parameters. We examine the corresponding
singular structures in the effective potentials of the relativistic
Schroedinger equation obtained from the Pauli reduction of the TBDE. We find
that the relativistic Schroedinger equation lead in fact to well-behaved wave
function solutions when the full potential and couplings of the system are
taken into account. The most unusual case is the coupled triplet system with
S=1 and L={(J-1),(J+1)}. Without the inclusion of the tensor coupling, the
effective S-state potential would become attractively singular. We show how
including the tensor coupling is essential in order that the wave functions be
well-behaved at short distances. For example, the S-state wave function becomes
simply proportional to the D-state wave function and dips sharply to zero at
the origin, unlike the usual S-state wave functions. Furthermore, this behavior
is similar in both QED and QCD, independent of the asymptotic freedom behavior
of the assumed QCD vector potential. Light- and heavy-quark meson states can be
described well by using a simplified linear-plus-Coulomb-type QCD potential
apportioned appropriately between world scalar and vector potentials. We use
this potential to exhibit explicitly the origin of the large pi-rho splitting
and effective chiral symmetry breaking. The TBDE formalism developed here may
be used to study quarkonia in quark-gluon plasma environments.Comment: 23 pages, 4 figure
The effect of high-speed power training on physical frailty in older adults: Effect of a visual-guided exercise program in South Korean rural areas
Objective. Exercise has been shown to be an effective intervention; the difficulty still lies in providing exercise programs to the older adults in rural areas. Therefore, this study aimed to examine the effects of a 12-week exercise program provided with visual guidelines (prerecorded video) on frailty among older adults in rural areas. Methods. Fifty participants (71.7 ± 4.9 years) from 5 different rural areas were recruited and divided into two groups: the exercise group (EX, n = 24 (male: 8, female: 18)) and the control group (CON, n = 26 (male: 7, female: 17)). With the commencement of the exercise intervention, a prerecorded high-speed power training program for frail older adults was distributed to the EX group. A new prerecorded exercise program was delivered to the EX group every 4 weeks. Frailty status was diagnosed with Fried’s criteria before and after the intervention. Muscle strength was measured in the upper and lower limb strength (hand-grip strength and leg extension and flexion), and physical function was measured using a short physical performance battery and gait speed. Fasting blood was collected before and after the intervention and analyzed for blood lipid profile. Results. After 12 weeks of the intervention period, a significant difference in frailty status () and score () favoring the EX group was observed. Physical functions (gait speed () and time for sit to stand ()) were significantly improved in the EX group with a significant increase in knee extensor strength (). A significant difference in serum high-density lipoprotein levels favoring the EX group () was also observed. Conclusions. This study confirmed the positive effect of a visual-guided exercise program on older adults’ residents in rural areas and provided alternative methods to effectively provide exercise program for the older adults with limited resources
Relativistic Generalization of the Gamow Factor for Fermion Pair Production or Annihilation
In the production or annihilation of a pair of fermions, the initial-state or
final-state interactions often lead to significant effects on the reaction
cross sections. For Coulomb-type interactions, the Gamow factor has been
traditionally used to take into account these effects. However the Gamow factor
needs to be modified when the magnitude of the coupling constant or the
relative velocity of two particles increases. We obtain the relativistic
generalization of the Gamow factor in terms of the overlap of the Feynman
amplitude with the relativistic wave function of two fermions with an
attractive Coulomb-type interaction. An explicit form of the corrective factor
is presented for the spin-singlet S-wave state. While the corrective factor
approaches the Gamow factor in the non-relativistic limit, we found that the
Gamow factor significantly over-estimates the effects when the coupling
constant or the velocity is large.Comment: 16 pages, 4 figures in LaTe
A micropatterned multielectrode shell for 3D spatiotemporal recording from live cells
Microelectrode arrays (MEAs) have proved to be useful tools for characterizing electrically active cells such as cardiomyocytes and neurons. While there exist a number of integrated electronic chips for recording from small populations or even single cells, they rely primarily on the interface between the cells and 2D flat electrodes. Here, an approach that utilizes residual stress‐based self‐folding to create individually addressable multielectrode interfaces that wrap around the cell in 3D and function as an electrical shell‐like recording device is described. These devices are optically transparent, allowing for simultaneous fluorescence imaging. Cell viability is maintained during and after electrode wrapping around the cel and chemicals can diffuse into and out of the self‐folding devices. It is further shown that 3D spatiotemporal recordings are possible and that the action potentials recorded from cultured neonatal rat ventricular cardiomyocytes display significantly higher signal‐to‐noise ratios in comparison with signals recorded with planar extracellular electrodes. It is anticipated that this device can provide the foundation for the development of new‐generation MEAs where dynamic electrode–cell interfacing and recording substitutes the traditional method using static electrodes
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