2,008 research outputs found
On the Width of the K-Absorption Edge of Cobalt
Marshall McLuhan, pioneer of modern media studies, wrote his Ph.D. thesis on the Elizabethan writer Thomas Nashe and the history of the classical trivium. This essay shows how McLuhan’s early exposure to Nashe influenced his later work on speech, print, and modern media. It argues that Nashe’s use of print to re-create oral conditions and his invention of personae drawn from fairground and marketplace helped shape McLuhan’s response to media and popular culture. Rhodes goes on to argue that it was Nashe’s attack on Ramus, to which McLuhan gave particular emphasis, that was the source of the idea that print promotes linear thinking and closure at the expense of the very different qualities associated with oral culture. He ends by countering some of the charges made against McLuhan that he sentimentalizes the oral by using it to represent an ideal of human wholeness
Truncated Harmonic Osillator and Parasupersymmetric Quantum Mechanics
We discuss in detail the parasupersymmetric quantum mechanics of arbitrary
order where the parasupersymmetry is between the normal bosons and those
corresponding to the truncated harmonic oscillator. We show that even though
the parasusy algebra is different from that of the usual parasusy quantum
mechanics, still the consequences of the two are identical. We further show
that the parasupersymmetric quantum mechanics of arbitrary order p can also be
rewritten in terms of p supercharges (i.e. all of which obey ).
However, the Hamiltonian cannot be expressed in a simple form in terms of the p
supercharges except in a special case. A model of conformal parasupersymmetry
is also discussed and it is shown that in this case, the p supercharges, the p
conformal supercharges along with Hamiltonian H, conformal generator K and
dilatation generator D form a closed algebra.Comment: 9 page
Computer simulation study of the subquadratic quantum number dependence of vibrational overtone dephasing: comparison with the mode-coupling theory predictions
Experimental studies have demonstrated that the vibrational dephasing of overtones do not always follow the quadratic quantum number (n) dependence predicted by the Kubo-Oxtoby theory of vibrational line shapes. While the reason for this failure of the theory is not quite clear yet, a recent theory suggested that the pronounced Gaussian time dependence of the frequency-modulation time-correlation function (tcf) could be a possible reason [Gayathri et al., J. Chem. Phys., 107, 10381 (1997)]. The theoretical study was based on a mode coupling theory calculation of the force-force time-correlation function that is required in the calculation of the frequency-modulation tcf. In order to test this and other predictions of the above study, detailed computer simulations of two neat liquids have been carried out. The systems studied are N-N stretch in liquid N2 and the C-I stretch in CH3I. It is found that although the frequency-modulation time-correlation function is largely Gaussian in both the cases, the overtone dephasing remains largely quadratic in n for N2. For methyl iodide, on the other hand, a pronounced sub-quadratic n dependence has been observed. Both the theory and the computer simulations suggest that this nonquadratic dependence can be expected when not only the decay of the frequency time-correlation function is Gaussian but the time scale of decay of the frequency-modulation tcf is comparable to that of the normal coordinate. The latter can happen when the following conditions are satisfied. First, the frequency of the normal mode should not be too large. Second, the mean-square fluctuation of the frequency-modulation and the anharmonicity coefficient of vibration should be large. It is found that both for N2 and CH3I, the resonant energy transfer between different molecules is significant. The effect of rotational-vibrational coupling, on the other hand, is found to be negligible for the systems studied
Towards Understanding the Structure, Dynamics and Bio-activity of Diabetic Drug Metformin
Small molecules are often found to exhibit extraordinarily diverse biological
activities. Metformin is one of them. It is widely used as anti-diabetic drug
for type-two diabetes. In addition to that, metformin hydrochloride shows
anti-tumour activities and increases the survival rate of patients suffering
from certain types of cancer namely colorectal, breast, pancreas and prostate
cancer. However, theoretical studies of structure and dynamics of metformin
have not yet been fully explored. In this work, we investigate the
characteristic structural and dynamical features of three mono-protonated forms
of metformin hydrochloride with the help of experiments, quantum chemical
calculations and atomistic molecular dynamics simulations. We validate our
force field by comparing simulation results to that of the experimental
findings. Nevertheless, we discover that the non-planar tautomeric form is the
most stable. Metformin forms strong hydrogen bonds with surrounding water
molecules and its solvation dynamics show unique features. Because of an
extended positive charge distribution, metformin possesses features of being a
permanent cationic partner toward several targets. We study its interaction and
binding ability with DNA using UV spectroscopy, circular dichroism, fluorimetry
and metadynamics simulation. We find a non-intercalating mode of interaction.
Metformin feasibly forms a minor/major groove-bound state within a few tens of
nanoseconds, preferably with AT rich domains. A significant decrease in the
free-energy of binding is observed when it binds to a minor groove of DNA.Comment: 60 pages, 24 figure
Competing PT potentials and re-entrant PT symmetric phase for a particle in a box
We investigate the effects of competition between two complex,
-symmetric potentials on the -symmetric phase of a
"particle in a box". These potentials, given by and
, represent long-range and localized
gain/loss regions respectively. We obtain the -symmetric phase in
the plane, and find that for locations near the edge of the
box, the -symmetric phase is strengthened by additional losses to
the loss region. We also predict that a broken -symmetry will be
restored by increasing the strength of the localized potential. By
comparing the results for this problem and its lattice counterpart, we show
that a robust -symmetric phase in the continuum is consistent
with the fragile phase on the lattice. Our results demonstrate that systems
with multiple, -symmetric potentials show unique, unexpected
properties.Comment: 7 pages, 3 figure
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