392 research outputs found
MS/MS studies on the selective on-line detection of sesquiterpenes using a Flowing Afterglow-Tandem Mass Spectrometer (FA-TMS)
A Flowing Afterglow-Tandem Mass Spectrometer (FA-TMS) was used to investigate the feasibility of selective on-line detection of a series of seven sesquiterpenes (SQTs). These SQTs were chemically ionized by either H3O+ or NO+ reagent ions in the FA, resulting among others in protonated SQT and SQT molecular ions, respectively. These and other Chemical Ionization (CI) product ions were subsequently subjected to dissociation by collisions with Ar atoms in the collision cell of the tandem mass spectrometer. The fragmentation spectra show similarities with mass spectra obtained for these compounds with other instruments such as a Proton Transfer Reaction-Linear Ion Trap (PTR-LIT), a Proton Transfer Reaction-Mass Spectrometer (PTR-MS), a Triple Quadrupole-Mass Spectrometer (QqQ-MS) and a Selected Ion Flow Tube-Mass Spectrometer (SIFT-MS). Fragmentation of protonated SQT is characterized by fragment ions at the same masses but with different intensities for the individual SQT. Distinction of SQTs is based on well-chosen intensity ratios and collision energies. The fragmentation patterns of SQT molecular ions show specific fragment ion tracers at m/z 119, m/z 162, m/z 137 and m/z 131 for alpha-cedrene, delta-neoclovene, isolongifolene and alpha-humulene, respectively. Consequently, chemical ionization of SQT by NO+, followed by MS/MS of SQT(+) seems to open a way for selective quantification of SQTs in mixtures
A family of integrable maps associated with the Volterra lattice
Recently Gubbiotti, Joshi, Tran and Viallet classified birational maps in
four dimensions admitting two invariants (first integrals) with a particular
degree structure, by considering recurrences of fourth order with a certain
symmetry. The last three of the maps so obtained were shown to be Liouville
integrable, in the sense of admitting a non-degenerate Poisson bracket with two
first integrals in involution. Here we show how the first of these three
Liouville integrable maps corresponds to genus 2 solutions of the infinite
Volterra lattice, being the case of a family of maps associated with the
Stieltjes continued fraction expansion of a certain function on a hyperelliptic
curve of genus . The continued fraction method provides explicit
Hankel determinant formulae for tau functions of the solutions, together with
an algebro-geometric description via a Lax representation for each member of
the family, associating it with an algebraic completely integrable system. In
particular, in the elliptic case (), as a byproduct we obtain Hankel
determinant expressions for the solutions of the Somos-5 recurrence, but
different to those previously derived by Chang, Hu and Xin. By applying
contraction to the Stieltjes fraction, we recover integrable maps associated
with Jacobi continued fractions on hyperelliptic curves, that one of us
considered previously, as well as the Miura-type transformation between the
Volterra and Toda lattices
Photoassociation inside an optical dipole trap: absolute rate coefficients and Franck-Condon factors
We present quantitative measurements of the photoassociation of cesium
molecules inside a far-detuned optical dipole trap. A model of the trap
depletion dynamics is derived which allows to extract absolute photoassociation
rate coefficients for the initial single-photon photoassociation step from
measured trap-loss spectra. The sensitivity of this approach is demonstrated by
measuring the Franck-Condon modulation of the weak photoassociation transitions
into the low vibrational levels of the outer well of the 0g- state that
correlates to the 6s+6p3/2 asymptote. The measurements are compared to
theoretical predictions. In a magneto-optical trap these transitions have
previously only been observed indirectly through ionization of ground state
molecules
Precision measurements with polar molecules: the role of the black body radiation
In the perspective of the outstanding developments of high-precision
measurements of fundamental constants using polar molecules related to ultimate
checks of fundamental theories, we investigate the possibly counterproductive
role of black-body radiation on a series of diatomic molecules which would be
trapped and observed for long durations. We show that the absorption of
black-body radiation at room temperature may indeed limit the lifetime of
trapped molecules prepared in a well-defined quantum state. Several examples
are treated, corresponding to pure rotational absorption, pure vibrational
absorption or both. We also investigate the role of a black-body
radiation-induced energy shift on molecular levels and how it could affect
high-precision frequency measurements
Integrable maps in 4D and modified Volterra lattices
In recent work, we presented the construction of a family of difference
equations associated with the Stieltjes continued fraction expansion of a
certain function on a hyperelliptic curve of genus . As well as proving that
each such discrete system is an integrable map in the Liouville sense, we also
showed it to be an algebraic completely integrable system. In the discrete
setting, the latter means that the generic level set of the invariants is an
affine part of an abelian variety, in this case the Jacobian of the
hyperelliptic curve, and each iteration of the map corresponds to a translation
by a fixed vector on the Jacobian. In addition, we demonstrated that, by
combining the discrete integrable dynamics with the flow of one of the
commuting Hamiltonian vector fields, these maps provide genus
algebro-geometric solutions of the infinite Volterra lattice, which justified
naming them Volterra maps, denoted .
The original motivation behind our work was the fact that, in the particular
case , we could recover an example of an integrable symplectic map in four
dimensions found by Gubbiotti, Joshi, Tran and Viallet, who classified
birational maps in 4D admitting two invariants (first integrals) with a
particular degree structure, by considering recurrences of fourth order with a
certain symmetry. Hence, in this particular case, the map yields
genus two solutions of the Volterra lattice. The purpose of this note is to
point out how two of the other 4D integrable maps obtained in the
classification of Gubbiotti et al. correspond to genus two solutions of two
different forms of the modified Volterra lattice, being related via a
Miura-type transformation to the Volterra map .
We dedicate this work to a dear friend and colleague, Decio Levi
A traveling wave Zeeman decelerator
We developed a new-concept Zeeman decelerator which produces a traveling magnetic trap. Atoms and molecules possessing a magnetic dipole moment, in so-called low field seeking states, are trapped around a node of a propagating wave provided that the initial velocity of the wave matches a velocity populated in the supersonic beam. In addition, three dimensional confinement is achieved by controlling the radial orientation of the trap, which can be done fully independently from its longitudinal motion
Towards magnetic slowing of atoms and molecules
We outline a method to slow paramagnetic atoms or molecules using pulsed
magnetic fields. We also discuss the possibility of producing trapped particles
by adiabatic deceleration of a magnetic trap. We present numerical simulation
results for the slowing and trapping of molecular oxygen
Application of liquid chromatography coupled to high-resolution mass spectrometry to measure urinary cortisol in loose housed sows
Cortisol is the most common physiological parameter used to measure welfare in pigs. In field studies evaluating stress in individual pigs which are group housed, the collection of spontaneously voided urine is practical. The purpose of the study was to apply a liquid chromatography coupled to high-resolution mass spectrometry approach to observe the patterns of diurnal urinary cortisol excretion among loose sows of three herds. We applied the analytical method in spontaneously voided urine of thirty, repeatedly sampled within a day, multiparous sows of three Greek herds. We found the level of urinary cortisol being highest before morning feeding [geometric mean of urinary cortisol to creatinine ratio being 2.72 (95% confidence interval: 1.17, 6.30), 5.65 (3.15, 10.14) and 2.60 (1.50, 4.50) in sows of herds A, B, and C, respectively] and lowest at 19: 00 h [0.56 (0.27, 1.18), 1.24 (0.74, 2.07), 0.88 (0.55, 1.44)]. However, the patterns of diurnal urinary cortisol excretion appeared different among herds
Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas
We describe a hybrid molecular dynamics approach for the description of
ultracold neutral plasmas, based on an adiabatic treatment of the electron gas
and a full molecular dynamics simulation of the ions, which allows us to follow
the long-time evolution of the plasma including the effect of the strongly
coupled ion motion. The plasma shows a rather complex relaxation behavior,
connected with temporal as well as spatial oscillations of the ion temperature.
Furthermore, additional laser cooling of the ions during the plasma evolution
drastically modifies the expansion dynamics, so that crystallization of the ion
component can occur in this nonequilibrium system, leading to lattice-like
structures or even long-range order resulting in concentric shells
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