42,946 research outputs found
Biological patterns: Novel indicators for pharmacological assays
Variable gravity testing using the KC-135 demonstrated clearly that biological pattern formation was definitely shown to result from gravity alone, and not from oxygen gradients in solution. Motile pattern formation of spermatozoa are driven by alternate mechanisms, and apparently not affected by short-term changes in gravity. The chemical effects found appear to be secondary to the primary effect of gravity. Cryopreservation may be the remedy to the problem of 'spare' or 'standing order' biological samples for testing of space lab investigations, but further studies are necessary
Excitation energies, polarizabilities, multipole transition rates, and lifetimes of ions along the francium isoelectronic sequence
Relativistic many-body perturbation theory is applied to study properties of
ions of the francium isoelectronic sequence. Specifically, energies of the 7s,
7p, 6d, and 5f states of Fr-like ions with nuclear charges Z = 87 - 100 are
calculated through third order; reduced matrix elements, oscillator strengths,
transition rates, and lifetimes are determined for 7s - 7p, 7p - 6d, and 6d -
5f electric-dipole transitions; and 7s - 6d, 7s - 5f, and 5f_5/2 - 5f_7/2
multipole matrix elements are evaluated to obtain the lifetimes of low-lying
excited states. Moreover, for the ions Z = 87 - 92 calculations are also
carried out using the relativistic all-order single-double method, in which
single and double excitations of Dirac-Fock wave functions are included to all
orders in perturbation theory. With the aid of the SD wave functions, we obtain
accurate values of energies, transition rates, oscillator strengths, and the
lifetimes of these six ions. Ground state scalar polarizabilities in Fr I, Ra
II, Ac III, and Th IV are calculated using relativistic third-order and
all-order methods. Ground state scalar polarizabilities for other Fr-like ions
are calculated using a relativistic second-order method. These calculations
provide a theoretical benchmark for comparison with experiment and theory.Comment: 13 figures, 11 table
Excitation energies, polarizabilities, multipole transition rates, and lifetimes in Th IV
Excitation energies of the ns_{1/2} (n=7-10), np_j (n=7-9), nd_j (n=6-8),
nf_{j} (n=5-7), and ng_{j} (n=5-6) states in Th IV are evaluated. First-,
second-, third-, and all-order Coulomb energies and first- and second-order
Coulomb-Breit energies are calculated. Reduced matrix elements, oscillator
strengths, transition rates, and lifetimes are determined for the 96 possible
nl_j-n'l'_j' electric-dipole transitions. Multipole matrix elements
(7s_{1/2}-6d_j, 7s_{1/2}-5f_j, and 5f_{5/2}-5f_{7/2}) are evaluated to obtain
the lifetimes of the and 7s_{1/2}$ states. Matrix elements are
calculated using both relativistic many-body perturbation theory, complete
through third order, and a relativistic all-order method restricted to single
and double (SD) excitations. Scalar and tensor polarizabilities for the
5f_{5/2} ground state in Th3+ are calculated using relativistic third-order and
all-order methods. These calculations provide a theoretical benchmark for
comparison with experiment and theory.Comment: 9 pages, 9 figure
Relativistic many-body calculation of energies, lifetimes, polarizabilities, blackbody radiative shift and hyperfine constants in Lu2+
Energy levels of 30 low-lying states of Lu2+ and allowed electric-dipole
matrix elements between these states are evaluated using a relativistic
all-order method in which all single, double and partial triple excitations of
Dirac-Fock wave functions are included to all orders of perturbation theory.
Matrix elements are critically evaluated for their accuracy and recommended
values of the matrix elements are given together with uncertainty estimates.
Line strengths, transition rates and lifetimes of the metastable 5d(3/2) and
5d(5/2) states are calculated. Recommended values are given for static
polarizabilities of the 6s, 5d and 6p states and tensor polarizabilities of the
5d and 6p(3/2) states. Uncertainties of the polarizability values are estimated
in all cases. The blackbody radiation shift of the 6s(1/2)-5d(5/2) transition
frequency of the Lu2+ ion is calculated with the aid of the recommended scalar
polarizabilities of the 6s(1/2) and 5d(5/2) states. Finally, A and B hyperfine
constants are determined for states of 175Lu2+ with n <= 9. This work provides
recommended values of transition matrix elements, polarizabilities and
hyperfine constants of Lu2+, critically evaluated for accuracy, for benchmark
tests of high-precision theoretical methodology and planning of future
experiments.Comment: 9 pages, 10 table
Forbidden M1 and E2 transitions in monovalent atoms and ions
We carried out a systematic high-precision relativistic study of the
forbidden magnetic-dipole and electric-quadrupole transitions in Ca+, Rb, Sr+,
Cs, Ba+, Fr, Ra+, Ac2+, and Th3+. This work is motivated by the importance of
these transitions for tests of fundamental physics and precision measurements.
The relative importance of the relativistic, correlation, Breit correction, and
contributions of negative-energy states is investigated. Recommended values of
reduced matrix elements are presented together with their uncertainties. The
matrix elements and resulting lifetimes are compared with other theoretical
values and with experiment where available.Comment: 9 pages, 6 table
Universal characteristics of resonant-tunneling field emission from nanostructured surfaces
We have performed theoretical and experimental studies of field emission from
nanostructured semiconductor cathodes. Resonant tunneling through
electric-field-induced interface bound states is found to strongly affect the
field-emission characteristics. Our analytical theory predicts power-law and
Lorentzian-shaped current-voltage curves for resonant-tunneling field emission
from three-dimensional substrates and two-dimensional accumulation layers,
respectively. These predicted line shapes are observed in field emission
characteristics from self-assembled silicon nanostructures. A simple model
describes formation of an accumulation layer and of the resonant level in these
systems.Comment: 5 pages, 4 figures, RevTex, to appear in J. Appl. Phy
Small-angle x-ray-scattering study of phase separation and crystallization in the bulk amorphous Mg62Cu25Y10Li3 alloy
We report on a small-angle x-ray-scattering (SAXS) and differential scanning calorimetry study of phase separation and crystallization in rapidly quenched amorphous Mg62Cu25Y10Li3 alloy samples. Differential scanning calorimetry demonstrates the occurrence of crystallization and grain growth upon isothermal annealing of these samples at 135 °C. The SAXS studies show the presence of large inhomogeneities even in the rapidly quenched as-prepared Mg62Cu25Y10Li3 alloy that is attributed to phase separation in the undercooled liquid during the cooling process. After isothermal annealing at 135 °C for longer than 30 min the samples exhibit a strong SAXS intensity that monotonically increases with increasing annealing time. During heat treatment, crystallization and growth of a nanocrystalline bcc-Mg7Li3 phase occurs in the Y-poor and MgLi-rich domains. The initially rough boundaries of the nanocrystals become sharper with increasing annealing time. Anomalous small-angle x-ray-scattering investigations near the Cu K edge indicate that while Cu is distributed homogeneously in the as-prepared sample, a Cu composition gradient develops between the matrix and the bcc-Mg7Li3 nanocrystals in the annealed sample
Wrong Repackaging and Reconstituted Drug Bank: A Potential cause of Serial Medication Errors: A Case Report
Background: Medication error is common in anaesthetic practice. Such errors could result in serial medication errors if reconstituted into a multi-dose bank. This is a report of potential serial medication errors in which suxamethonium could have been administered as vitamin K. Objective: To highlight the potential risk of medication errors from wrong repackaging and the risk of serial medication errors from reconstitution of drugs into a multi-dose drug bank. Method: A 3.5kg male baby delivered by Caesarean section (CS)at term, with Apgar scores 8 and 10 developed apnoea following administration of suxamethonium which was reconstituted and labelled as vitamin K by the attending midwife. Full recovery was achieved after manual ventilation using Ambu bag. Conclusion: A combination of wrong repackaging and reconstitution of drugs into a multi-dose bank is a potential source of serial medication error. Such errors could be averted if appropriate formulations that do not require reconstitution are manufactured by pharmaceutical companies. Same safety regulations before administration of drugs should also apply during repackaging of drugs. Key words: Wrong repackaging, Reconstituted drug bank, Serial medication error
Factors Limiting Cell Penetration in Manufacturing Plants
Despite the potential advantages of cellular manufacturing, most plants with cells have only partially converted their systems. This study examines factors that limit cell penetration within plants using a mail survey of cell users. The existence of service processes, lack of a strong champion who would push the design and implementation of more cells, and low cost of tracking non-cell parts/ products on the plant floor were found to be significant predictors of cell penetration for plants with cells and no plans for further cells. Factors limiting penetration in plants planning to implement further cells could not be determined
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