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A Vaziri

Publications and source records attributed to A Vaziri.

12 recordsLinked to original sources
PubMed2006

Quantized rotation of atoms from photons with orbital angular momentum.

We demonstrate the coherent transfer of the orbital angular momentum of a photon to an atom in quantized units of variant Planck's over 2pi, using a 2-photon stimulated Raman process with Laguerre-Gaussian beams to generate an atomic vortex state in a Bose-Einstein condensate of sodium atoms. We show that the process is coherent by creating superpositions of different vortex states, where the relative phase between the states is determined by the relative phases of the optical fields. Furthermore, we create vortices of charge 2 by transferring to each atom the orbital angular momentum of two photons.

Journal Article↗
PubMed2006

High-order quantum resonances observed in a periodically kicked Bose-Einstein condensate.

We have observed high-order quantum resonances in a realization of the quantum delta-kicked rotor, using Bose-condensed Na atoms subjected to a pulsed standing wave of laser light. These resonances occur for pulse intervals that are rational fractions of the Talbot time, and are characterized by ballistic momentum transfer to the atoms. The condensate's narrow momentum distribution not only permits the observation of the quantum resonances at 3/4 and 1/3 of the Talbot time, but also allows us to study scaling laws for the resonance width in quasimomentum and pulse interval.

Journal Article↗
PubMed2006

Superficial wrinkles in stretched, drying gelatin films.

When a thin film of initially hydrated gelatin is allowed to dry from the surface, superficial changes in the structure of the material affect the local mechanical properties of the drying region. If the film is simultaneously subjected to large strain deformation (above 20%), a periodic pattern of wrinkles appears on the surface of the gelatin along the length of the sample in the direction of the applied force. These wrinkles are uniformly distributed on the surface of the gelatin with a wavelength that is much smaller than the sample thickness, which changes with sample composition, aging time, and deformation rate. We investigate these patterns via in situ environmental scanning electron microscopy (ESEM) and provide a theory for their origin.

Chemistry, Physical↗
PubMed2005

Experimental quantum coin tossing.

In this Letter we present the first implementation of a quantum coin-tossing protocol. This protocol belongs to a class of "two-party" cryptographic problems, where the communication partners distrust each other. As with a number of such two-party protocols, the best implementation of the quantum coin tossing requires qutrits, resulting in a higher security than using qubits. In this way, we have also performed the first complete quantum communication protocol with qutrits. In our experiment the two partners succeeded to remotely toss a row of coins using photons entangled in the orbital angular momentum. We also show the experimental bounds of a possible cheater and the ways of detecting him.

Journal Article↗
PubMed2004

Triggered qutrits for quantum communication protocols.

A general protocol in quantum information and communication relies in the ability of producing, transmitting, and reconstructing, in general, qunits. In this Letter we show for the first time the experimental implementation of these three basic steps on a pure state in a three-dimensional space, by means of the orbital angular momentum of the photons. The reconstruction of the qutrit is performed with tomographic techniques and a maximum-likelihood estimation method. For the tomographic reconstruction we used more than 2400 different projections. In this way we also demonstrate that we can perform any transformation in the three-dimensional space.

Journal Article↗
PubMed2001

Entanglement of the orbital angular momentum states of photons.

Entangled quantum states are not separable, regardless of the spatial separation of their components. This is a manifestation of an aspect of quantum mechanics known as quantum non-locality. An important consequence of this is that the measurement of the state of one particle in a two-particle entangled state defines the state of the second particle instantaneously, whereas neither particle possesses its own well-defined state before the measurement. Experimental realizations of entanglement have hitherto been restricted to two-state quantum systems, involving, for example, the two orthogonal polarization states of photons. Here we demonstrate entanglement involving the spatial modes of the electromagnetic field carrying orbital angular momentum. As these modes can be used to define an infinitely dimensional discrete Hilbert space, this approach provides a practical route to entanglement that involves many orthogonal quantum states, rather than just two Multi-dimensional entangled states could be of considerable importance in the field of quantum information, enabling, for example, more efficient use of communication channels in quantum cryptography.

Journal Article↗
PubMed2000

Mitochondrial DNA and chromosomal studies of wild mice (Mus) from Turkey and Iran.

Complete D-loop sequences of 20 Mus from three localities in Turkey and seven in Iran were characterized. These countries are thought to be close to the place of origin of the subspecies Mus musculus domesticus. Five new M. m. domesticus haplotypes were added to the nine already known for the region. Four of these 14 haplotypes were very similar to the consensus D-loop sequence for western Europe defined by Nachman et al. (1994), which may represent the ancestral condition for M. m. domesticus. A divergent mtDNA lineage is found in various parts of Turkey and northern Iran; it has spread into western Europe, but other European lineages were not found in either Turkey or Iran. The other Mus D-loop sequences were of M. m. castaneus and Mus macedonicus and confirmed M. macedonicus as a monotypic species with low nucleotide diversity. The prevalence of the standard 40-chromosome complement in this region is particularly interesting with regards M. m. domesticus, as it is consistent with the in situ origin of Robertsonian karyotypic races (2n < 40) in western Europe.

Animals↗
PubMedDate not supplied

Slow release of chloroquine phosphate from multiple taste-masked W/O/W multiple emulsions.

The efficacy and safety of chloroquine as an antimalarial has contributed to the survival of millions in the past 50 years. Chloroquine is widely available, cheap, well tolerated and orally well absorbed. Therefore, it remains an important antimalarial drug. However, on oral administration, particularly to children, the unpleasant taste is a problem. This could be avoided by 'taste-masked and controlled release' formulations such as multiple emulsions. Although Plasmodium falciparum has developed resistance to many antimalarial drugs, including chloroquine, resistance may be attributed, among other factors, to subclinical dosage of chloroquine from administered pharmaceutical forms. This could also be relevant in the treatment of rheumatoid arthritis. Multiple W/O/W emulsions of chloroquine phosphate were prepared. Assessment of emulsion stability showed no significant change in the system. Prolonged storage (four months) of the emulsion resulted in negligible loss of chloroquine phosphate. The results suggest, therefore, that chloroquine phosphate releases due to diffusion of the drug from the internal globules and not as a consequence of instability of the W/O/W emulsion. These characteristics are in accordance with the requirements for controlled release pharmaceuticals. Stability of multiple emulsions could have resulted from interfacial polymerization or complexion between molecules. Release assessments showed faster rates for W/O/W emulsions which had smaller internal aqueous globules and, therefore, an increased interfacial area. Furthermore, transport of high-diffusion coefficient micelles could have given a greater solute flux in these systems.

Chemistry, Pharmaceutical↗
PubMedDate not supplied

Some preparative variables influencing the properties of W/O/W multiple emulsions.

Water-in-oil-in-water multiple emulsions of chloroquine diphosphate were prepared, using olive oil, arachis oil, Span 80, gelatin, acacia and Tween 80. Emulsifiers were employed individually or in combination. An attempt was made to correlate preparative variables with stability and drug release of multiple emulsions of roughly comparative particle size. When the emulsions were satisfactorily stabilized by the optimum blend of surfactants the rate of release varied with the nature and/or combination of emulsifiers employed. The possible effects of phase-inversion temperature, spontaneous emulsification and liquid crystal stabilization on the systems have been discussed. The mechanism probably involved complex interfacial adsorption and hydrodynamic phenomena in the presence of natural oils, co-surfactants and natural stabilizers of individual HLB number, particularly when acacia is present in the system. This could be attributed to the existence of protein in some species of acacia, since there are about 130 species of acacia, the gummy exudations of which are considered official in compendia. The protein content could be a reasonable additional specification for acacia as an emulsifier.

Acacia↗
PubMedDate not supplied

Improved stability of w/o/w multiple emulsions by addition of hydrophilic colloid components in the aqueous phases.

To improve the stability of w/o/w multiple emulsions of arachis and olive oil the stabilizing effect of cherry gum, in combination with acacia and gelatin, was examined. The outstanding film-forming properties of this gum having already been noted; the effect of its addition to the aqueous phases was measured by the coalescence of emulsion globules. The enhanced stability, as compared to controls, was achieved at a minimum concentration which liquid crystal-bearing interfacial films seem to appear. Creation of more coherent interfaces, inhibiting transfer of phases, could be the basis of the improved stability of the emulsion.

Acacia↗