2,560 research outputs found
Lambda hyperonic effect on the normal driplines
A generalized mass formula is used to calculate the neutron and proton drip
lines of normal and lambda hypernuclei treating non-strange and strange nuclei
on the same footing. Calculations suggest existence of several bound
hypernuclei whose normal cores are unbound. Addition of Lambda or,
Lambda-Lambda hyperon(s) to a normal nucleus is found to cause shifts of the
neutron and proton driplines from their conventional limits.Comment: 6 pages, 4 tables, 0 figur
Propagating Disturbances along fan-like coronal loops in an active region
Propagating disturbances are often observed in active region fan-like coronal
loops. They were thought to be due to slow mode MHD waves based on some of the
observed properties. But the recent studies involving spectroscopy indicate
that they could be due to high speed quasi-periodic upflows which are difficult
to distinguish from upward propagating slow waves. In this context, we have
studied a fan loop structure in the active region AR 11465 using simultaneous
spectroscopic and imaging observations from Extreme-ultraviolet Imaging
Spectrometer (EIS) on board Hinode and Atmospheric Imaging Assembly (AIA) on
board SDO. Analysis of the data shows significant oscillations at different
locations. We explore the variations in different line parameters to determine
whether the waves or flows could cause these oscillations to improve the
current understanding on the nature of these disturbances.Comment: 12 pages, 6 figures. Accepted for publication in RA
Remarks on the Noncommutative Gravitational Quantum Well
A planar phase space having both position and momentum noncommutativity is
defined in a more inclusive setting than that considered elsewhere. The
dynamics of a particle in a gravitational quantum well in this space is
studied. The use of the WKB approximation and the virial theorem enable
analytic discussions on the effect of noncommutativity. Consistent results are
obtained following either commutative space or noncommutative space
descriptions. Comparison with recent experimental data with cold neutrons at
Grenoble imposes an upper bound on the noncommutative parameter. Also, our
results are compared with a recent numerical analysis of a similar problem.Comment: Latex, 17 pages, Title changed, minor modifications, 3 new references
added, To appear in Phys. Rev.
A scaling theory of quantum breakdown in solids
We propose a new scaling theory for general quantum breakdown phenomena. We
show, taking Landau-Zener type breakdown as a particular example, that the
breakdown phenomena can be viewed as a quantum phase transition for which the
scaling theory is developed. The application of this new scaling theory to
Zener type breakdown in Anderson insulators, and quantum quenching has been
discussed.Comment: 3 page
Double-layer shocks in a magnetized quantum plasma
The formation of small but finite amplitude electrostatic shocks in the
propagation of quantum ion-acoustic waves (QIAWs) obliquely to an external
magnetic field is reported in a quantum electron-positron-ion (e-p-i) plasma.
Such shocks are seen to have double-layer (DL) structures composed of the
compressive and accompanying rarefactive slow-wave fronts. Existence of such DL
shocks depends critically on the quantum coupling parameter associated with
the Bohm potential and the positron to electron density ratio . The
profiles may, however, steepen initially and reach a steady state with a number
of solitary waves in front of the shocks. Such novel DL shocks could be a good
candidate for particle acceleration in intense laser-solid density plasma
interaction experiments as well as in compact astrophysical objects, e.g.,
magnetized white dwarfs.Comment: 4 pages, 1 figure (to appear in Physical Review E
Polypyrrole nanoparticles for tunable, pH-sensitive and sustained drug release
We report the development of a generalized pH-sensitive drug delivery system that can release any charged drug preferentially at the pH range of interest. Our system is based on polypyrrole nanoparticles (PPy NPs), synthesized via a simple one-step microemulsion technique. These nanoparticles are highly monodisperse, stable in solution over the period of a month, and have good drug loading capacity (∼15 wt%). We show that PPy NPs can be tuned to release drugs at both acidic and basic pH by varying the pH, the charge of the drug, as well as by adding small amounts of charged amphiphiles. Moreover, these NPs may be delivered locally by immobilizing them in a hydrogel. Our studies show encapsulation within a calcium alginate hydrogel results in sustained release of the incorporated drug for more than 21 days. Such a nanoparticle-hydrogel composite drug delivery system is promising for treatment of long-lasting conditions such as cancer and chronic pain which require controlled, localized, and sustained drug release.DAA
Peterodimenzijski kozmološki model struna u drugoj samotvornoj teoriji
In this paper we have constructed a five-dimensional string cosmological model in Barber\u27s (1982) second self-creation theory of gravitation. When the coupling constant becomes zero, the model degenerates into two different string cosmological models in Einstein\u27s theory corresponding to variable G and constant G. Some physical and geometrical properties of the model are discussed.U ovom smo radu razvili peterodimenzijski kozmološki model struna u okviru druge Barberove samotvorne teorije gravitacije. Kada konstanta vezanja postane jednaka nuli, model se pretvara u dva različita kozmološka modela struna u Einsteinovoj teoriji koji odgovaraju promjenljivom G i stalnom G. Raspravljaju se neka fizička i geometrijska svojstva modela
Electrical Conductance of Molecular Wires
Molecular wires (MW) are the fundamental building blocks for molecular
electronic devices. They consist of a molecular unit connected to two continuum
reservoirs of electrons (usually metallic leads). We rely on Landauer theory as
the basis for studying the conductance properties of MW systems. This relates
the lead to lead current to the transmission probability for an electron to
scatter through the molecule. Two different methods have been developed for the
study of this scattering. One is based on a solution of the Lippmann-Schwinger
equation and the other solves for the {\bf t} matrix using Schroedinger's
equation. We use our methodology to study two problems of current interest. The
first MW system consists of 1,4 benzene-dithiolate (BDT) bonded to two gold
nanocontacts. Our calculations show that the conductance is sensitive to the
chemical bonding between the molecule and the leads. The second system we study
highlights the interesting phenomenon of antiresonances in MW. We derive an
analytic formula predicting at what energies antiresonances should occur in the
transmission spectra of MW. A numerical calculation for a MW consisting of
filter molecules attached to an active molecule shows the existence of an
antiresonance at the energy predicted by our formula.Comment: 14 pages, 5 figure
Peterodimenzijski kozmološki model struna u drugoj samotvornoj teoriji
In this paper we have constructed a five-dimensional string cosmological model in Barber\u27s (1982) second self-creation theory of gravitation. When the coupling constant becomes zero, the model degenerates into two different string cosmological models in Einstein\u27s theory corresponding to variable G and constant G. Some physical and geometrical properties of the model are discussed.U ovom smo radu razvili peterodimenzijski kozmološki model struna u okviru druge Barberove samotvorne teorije gravitacije. Kada konstanta vezanja postane jednaka nuli, model se pretvara u dva različita kozmološka modela struna u Einsteinovoj teoriji koji odgovaraju promjenljivom G i stalnom G. Raspravljaju se neka fizička i geometrijska svojstva modela
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