5,984 research outputs found
Use of non-ionic substrates for determination of cellulase
Use of non-ionic substrates for determination of cellulas
The method of Gaussian weighted trajectories. V. On the 1GB procedure for polyatomic processes
In recent years, many chemical reactions have been studied by means of the
quasi-classical trajectory (QCT) method within the Gaussian binning (GB)
procedure. The latter consists in "quantizing" the final vibrational actions in
Bohr spirit by putting strong emphasis on the trajectories reaching the
products with vibrational actions close to integer values. A major drawback of
this procedure is that if N is the number of product vibrational modes, the
amount of trajectories necessary to converge the calculations is ~ 10^N larger
than with the standard QCT method. Applying it to polyatomic processes is thus
problematic. In a recent paper, however, Czako and Bowman propose to quantize
the total vibrational energy instead of the vibrational actions [G. Czako and
J. M. Bowman, J. Chem. Phys., 131, 244302 (2009)], a procedure called 1GB here.
The calculations are then only ~ 10 times more time-consuming than with the
standard QCT method, allowing thereby for considerable numerical saving. In
this paper, we propose some theoretical arguments supporting the 1GB procedure
and check its validity on model test cases as well as the prototype four-atom
reaction OH+D_2 -> HOD+D
Gravitational Radiation from First-Order Phase Transitions
It is believed that first-order phase transitions at or around the GUT scale
will produce high-frequency gravitational radiation. This radiation is a
consequence of the collisions and coalescence of multiple bubbles during the
transition. We employ high-resolution lattice simulations to numerically evolve
a system of bubbles using only scalar fields, track the anisotropic stress
during the process and evolve the metric perturbations associated with
gravitational radiation. Although the radiation produced during the bubble
collisions has previously been estimated, we find that the coalescence phase
enhances this radiation even in the absence of a coupled fluid or turbulence.
We comment on how these simulations scale and propose that the same enhancement
should be found at the Electroweak scale; this modification should make direct
detection of a first-order electroweak phase transition easier.Comment: 7 pages, 7 figure
Coherent Control and Entanglement in the Attosecond Electron Recollision Dissociation of D2+
We examine the attosecond electron recollision dissociation of D2+ recently
demonstrated experimentally [H. Niikura et al., Nature (London) 421, 826
(2003)] from a coherent control perspective. In this process, a strong laser
field incident on D2 ionizes an electron, accelerates the electron in the laser
field to eV energies, and then drives the electron to recollide with the parent
ion, causing D2+ dissociation. A number of results are demonstrated. First, a
full dimensional Strong Field Approximation (SFA) model is constructed and
shown to be in agreement with the original experiment. This is then used to
rigorously demonstrate that the experiment is an example of coherent pump-dump
control. Second, extensions to bichromatic coherent control are proposed by
considering dissociative recollision of molecules prepared in a coherent
superposition of vibrational states. Third, by comparing the results to similar
scenarios involving field-free attosecond scattering of independently prepared
D2+ and electron wave packets, recollision dissociation is shown to provide an
example of wave-packet coherent control of reactive scattering. Fourth, this
analysis makes clear that it is the temporal correlations between the continuum
electron and D2+ wave packet, and not entanglement, that are crucial for the
sub-femtosecond probing resolution demonstrated in the experiment. This result
clarifies some misconceptions regarding the importance of entanglement in the
recollision probing of D2+. Finally, signatures of entanglement between the
recollision electron and the atomic fragments, detectable via coincidence
measurements, are identified
The quality of different types of child care at 10 and 18 months. A comparison between types and factors related to quality.
The quality of care offered in four different types of non-parental child care to 307 infants at 10 months old and 331 infants at 18 months old was compared and factors associated with higher quality were identified. Observed quality was lowest in nurseries at each age point, except that at 18 months they offered more learning activities. There were few differences in the observed quality of care by child-minders, grandparents and nannies, although grandparents had somewhat lower safety and health scores and offered children fewer activities. Cost was largely unrelated to quality of care except in child-minding, where higher cost was associated with higher quality. Observed ratios of children to adults had a significant impact on quality of nursery care; the more infants or toddlers each adult had to care for, the lower the quality of the care she gave them. Mothers' overall satisfaction with their child's care was positively associated with its quality for home-based care but not for nursery settings
State-to-state rotational transitions in H+H collisions at low temperatures
We present quantum mechanical close-coupling calculations of collisions
between two hydrogen molecules over a wide range of energies, extending from
the ultracold limit to the super-thermal region. The two most recently
published potential energy surfaces for the H-H complex, the so-called
DJ (Diep and Johnson, 2000) and BMKP (Boothroyd et al., 2002) surfaces, are
quantitatively evaluated and compared through the investigation of rotational
transitions in H+H collisions within rigid rotor approximation. The
BMKP surface is expected to be an improvement, approaching chemical accuracy,
over all conformations of the potential energy surface compared to previous
calculations of H-H interaction. We found significant differences in
rotational excitation/de-excitation cross sections computed on the two surfaces
in collisions between two para-H molecules. The discrepancy persists over a
large range of energies from the ultracold regime to thermal energies and
occurs for several low-lying initial rotational levels. Good agreement is found
with experiment (Mat\'e et al., 2005) for the lowest rotational excitation
process, but only with the use of the DJ potential. Rate coefficients computed
with the BMKP potential are an order of magnitude smaller.Comment: Accepted by J. Chem. Phy
Problematizing Strategic Alliance Research: Challenges, Issues and Paradoxes in the New Era
Strategic alliances have attracted substantial attention from industry and academia over the past three decades. However, due to rapid technological evolution, saturated marketplaces, globalisation of businesses on the one hand and de-globalisation of the market on the other (as marked by Brexit and the trade war between US and China, COVID-19 pandemic and the Ukraine war), the strategic environment of businesses is changing quickly. Fundamental and rapid changes in the wider environment necessitate the review of theoretical and practical insights of earlier and emerging studies – to examine the new challenges, issues and paradoxes of strategic alliances. This special issue attempts to provide a forum to allow researchers to question the assumptions underlying existing theory a little further beyond just “gap-spotting” or “gap-filling”. This special issue includes four very interesting literature review pieces, which venture deeper into the phenomenon, and explore the opportunities, issues and paradoxes of strategic alliances while adopting alternative theoretical perspectives, methodological approaches and interpretations to address issues of managing strategic alliances and maximising returns from them in the new strategic context
Differential and integral cross sections for the rotationally inelastic scattering of methyl radicals with H-2 and D-2
Space Charge Limited 2-d Electron Flow between Two Flat Electrodes in a Strong Magnetic Field
An approximate analytic solution is constructed for the 2-d space charge
limited emission by a cathode surrounded by non emitting conducting ledges of
width Lambda. An essentially exact solution (via conformal mapping) of the
electrostatic problem in vacuum is matched to the solution of a linearized
problem in the space charge region whose boundaries are sharp due to the
presence of a strong magnetic field. The current density growth in a narrow
interval near the edges of the cathode depends strongly on Lambda. We obtain an
empirical formula for the total current as a function of Lambda which extends
to more general cathode geometries.Comment: 4 pages, LaTex, e-mail addresses: [email protected],
[email protected]
State-to-State Differential and Relative Integral Cross Sections for Rotationally Inelastic Scattering of H2O by Hydrogen
State-to-state differential cross sections (DCSs) for rotationally inelastic
scattering of H2O by H2 have been measured at 71.2 meV (574 cm-1) and 44.8 meV
(361 cm-1) collision energy using crossed molecular beams combined with
velocity map imaging. A molecular beam containing variable compositions of the
(J = 0, 1, 2) rotational states of hydrogen collides with a molecular beam of
argon seeded with water vapor that is cooled by supersonic expansion to its
lowest para or ortho rotational levels (JKaKc= 000 and 101, respectively).
Angular speed distributions of fully specified rotationally excited final
states are obtained using velocity map imaging. Relative integral cross
sections are obtained by integrating the DCSs taken with the same experimental
conditions. Experimental state-specific DCSs are compared with predictions from
fully quantum scattering calculations on the most complete H2O-H2 potential
energy surface. Comparison of relative total cross sections and state-specific
DCSs show excellent agreement with theory in almost all detailsComment: 46 page
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