1,497 research outputs found
Influence of excipients on spray-dried powders for inhalation
Two areas attracting considerable attention when developing effective pulmonary drug delivery systems include the improvement of aerosolisation efficiency of the inhaled formulation and the controlled release of drug from the formulation following deposition within the lung. In this study, four saccharides were employed as excipients in the preparation of spray-dried powder formulations for the pulmonary drug delivery. Beta-cyclodextrin-, starch-, and sodium carboxymethylcellulose (NaCMC)-based spray-dried powders showed a significant (one-way ANOVA, Duncan's test, p < 0.05) increase in lower stage drug deposition in the Next Generation Impactor (NGI) when compared to lactose-based spray-dried powders. Furthermore, NaCMC-based spray-dried powder formulations exhibited a sustained drug release profile in dissolution testing; approximately 80% of salbutamol sulphate was released after an hour, whereas drug from the lactose-based spray-dried powder formulation was released within 5 min. Our results clearly demonstrate that the inclusion of NaCMC in spray-dried powder formulations increases the aerosolisation efficiency of the powder and also offers the potential for sustained drug release, which may be of benefit in the treatment of local and systemic conditions
Trapping cold atoms near carbon nanotubes: thermal spin flips and Casimir-Polder potential
We investigate the possibility to trap ultracold atoms near the outside of a
metallic carbon nanotube (CN) which we imagine to use as a miniaturized
current-carrying wire. We calculate atomic spin flip lifetimes and compare the
strength of the Casimir-Polder potential with the magnetic trapping potential.
Our analysis indicates that the Casimir-Polder force is the dominant loss
mechanism and we compute the minimum distance to the carbon nanotube at which
an atom can be trapped.Comment: 8 pages, 3 figure
An Unified Approach To Pseudo Scalar Meson Photoproductions Off Nucleons In The Quark Model
An unified approach to the pseudo scalar meson (, and )
photoproduction off nucleons are presented. It begins with the low energy QCD
Lagrangian, and the resonances in the s- and u- channels are treated in the
framework of the quark model
The duality hypothesis is imposed to limit the number of the t-channel
exchanges. The CGLN amplitudes for each reaction are evaluated, which include
both proton and neutron targets. The important role by the S-wave resonances in
the second resonance region is discussed, it is particularly important for the
and photoproductions.Comment: 31 pages in Latex fil
Hyperon-Nucleon Final State Interaction in Kaon Photoproduction of the Deuteron
Final state hyperon-nucleon interaction in strangeness photoproduction of the
deuteron is investigated making use of the covariant reaction formalism and the
P-matrix approach to the YN system. Remarkably simple analytical expression for
the amplitude is obtained. Pronounced effects due to final state interaction
are predicted including the manifestation of the 2.13 GeV resonance.Comment: LaTeX, 13 page
Quasifree kaon-photoproduction from nuclei in a relativistic approach
We compute the recoil polarization of the lambda-hyperon and the photon
asymmetry for the quasifree photoproduction of kaons in a relativistic
impulse-approximation approach. Our motivation for studying polarization
observables is threefold. First, polarization observables are more effective
discriminators of subtle dynamics than the unpolarized cross section. Second,
earlier nonrelativistic calculations suggest an almost complete insensitivity
of polarization observables to distortions effects. Finally, this insensitivity
entails an enormous simplification in the theoretical treatment. Indeed, by
introducing the notion of a ``bound-nucleon propagator'' we exploit Feynman's
trace techniques to develop closed-form, analytic expressions for all
photoproduction observables. Moreover, our results indicate that polarization
observables are also insensitive to relativistic effects and to the nuclear
target. Yet, they are sensitive to the model parameters, making them ideal
tools for the study of modifications to the elementary amplitude --- such as in
the production, propagation, and decay of nucleon resonances --- in the nuclear
medium.Comment: 15 pages and 6 figures - submitted to PR
The Kaon-Photoproduction Of Nucleons In The Quark Model
In this paper, we develop a general framework to study the
meson-photoproductions of nucleons in the chiral quark model. The S and U
channel resonance contributions are expressed in terms of the
Chew-Goldberger-Low-Nambu (CGLN) amplitudes. The kaon-photoproduction
processes, , , and , are calculated. The initial results show that the quark
model provides a much improved description of the reaction mechanism for the
kaon-photoproductions of the nucleon with less parameters than the traditional
phenomenological approaches.Comment: 25 pages, 9 postscript figures can be obtained from the author
Why Nature has made a choice of one time and three space coordinates?
We propose a possible answer to one of the most exciting open questions in
physics and cosmology, that is the question why we seem to experience four-
dimensional space-time with three ordinary and one time dimensions. We have
known for more than 70 years that (elementary) particles have spin degrees of
freedom, we also know that besides spin they also have charge degrees of
freedom, both degrees of freedom in addition to the position and momentum
degrees of freedom. We may call these ''internal degrees of freedom '' the
''internal space'' and we can think of all the different particles, like quarks
and leptons, as being different internal states of the same particle. The
question then naturally arises: Is the choice of the Minkowski metric and the
four-dimensional space-time influenced by the ''internal space''?
Making assumptions (such as particles being in first approximation massless)
about the equations of motion, we argue for restrictions on the number of space
and time dimensions. (Actually the Standard model predicts and experiments
confirm that elementary particles are massless until interactions switch on
masses.)
Accepting our explanation of the space-time signature and the number of
dimensions would be a point supporting (further) the importance of the
''internal space''.Comment: 13 pages, LaTe
Quasifree eta photoproduction from nuclei and medium modifications of resonances
We investigate the sensitivity of the differential cross section, recoil
nucleon polarization and the photon asymmetry to changes in the elementary
amplitude, medium modifications of the resonance masses, as
well as nuclear target effects. All calculations are performed within a
relativistic plane wave impulse approximation formalism resulting in analytical
expressions for all observables. The spin observables are shown to be unique
tools to study subtle effects that are not accessible by only looking at the
unpolarized differential cross section.Comment: 27 pages, 8 figures, Revtex, To be published in Phys. Rev.
Review of multi-scale electromagnetic modeling
This paper reviews various methods to solve multiscale problems ranging from low-frequency methods to very high-frequency methods. ©2010 IEEE.published_or_final_versionThe 2010 International Conference on Electromagnetics in Advanced Applications (ICEAA), Sydney, N.S.W., 20-24 September 2010. In Proceedings of ICEAA'10, 2010, p. 641-64
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