Point Spread Function Characterization of a Radially Displaced Scatterer Using Circular Synthetic Aperture Radar

This research effort investigated characterizing the point spread function (PSF) behavior of radially displaced point scatterers using circular synthetic aperture radar (CSAR). Thus far, research has been conducted to understand PSF of a scatterer located at the imaging scene center. An analytic closed-form solution has been derived assuming the scatterer is located at the origin of the CSAR imaging geometry. However, it is difficult to derive an analytic PSF solution for a scatterer that is radially displaced from the imaging scene center. Using the back projection image formation algorithm, PSF responses are generated at various point target locations. Consistent with previous studies, the three dimensional PSF for a point target located at the image center is cone shaped and serves as the basis for comparing and characterizing the PSFs of radially displaced scatterers. Simulated results show the impulse response of a radially displaced point scatterer is asymmetric and tends to exhibit increased ellipticity as it moves further from the scene center

Influence of correlation effects on the magnetic dipole hyperfine interaction in the low-lying states of Ca<SUP>+</SUP>

The relativistic coupled cluster theory is employed to calculate the hyperfine structure of the 2S &#189;, 2P &#189;, 2P 3/2, 2D 3/2 and 2D 5/2 states of singly ionized calcium. The importance of correlation effects is highlighted. Our results are compared with other theoretical calculations and experiments

Ionization potential and excitation energy calculations for Ba<SUP>+</SUP> using relativistic coupled-cluster method

We report the results of our relativistic coupled cluster singles, doubles, and partial triples calculations of the ionization potentials (IP) and excitation energies (EE) for different low-lying levels of Ba+. The accuracies of the IP's and EE's are approximately 0.2% and 1%, respectively. The inclusion of the triple excitations were crucial to achieve this degree of precision

A novel spirooxindole derivative inhibits the growth of Leishmania donovani parasite both in vitro and in vivo by targeting type IB topoisomerase

Visceral Leishmaniasis is a fatal parasitic disease and there is an emergent need for development of effective drugs against this neglected tropical disease. We report here development of a novel spirooxindole derivative N-benzyl 2, 2’ α 3, 3’, 5’, 6’, 7’, 7α,α'-octahydro-2methoxycarbonyl-spiro [indole-3, 3’ -pyrrolizidine]-2 one (Compound 4c) which inhibits Leishmania donovani topoisomerase IB (LdTopIB) and kills the wild type as well as drug-resistant parasite strains. This compound inhibits catalytic activity of LdTopIB in competitive manner. Unlike Camptothecin, the compound does not stabilize the DNA-topoisomerase IB cleavage complex; rather, they hinder drug-DNA-enzyme covalent complex formation. Fluorescence studies show stoichiometry of this compound binding to LdTopIB is 2:1 (mole/mole) with a dissociation constant of 6.65 μM. Molecular docking with LdTopIB using the stereoisomers of Compound 4c produced two probable hits for binding site: one in small subunit and the other in the hinge region of the large subunit of LdTopIB. This spirooxindole is highly cytotoxic to promastogotes of L. donovani and also induces apoptosis-like cell death in parasite. Treatment with compound 4c causes depolarization of mitochondrial membrane potential, formation of reactive oxygen species inside parasites and ultimately fragmentation of nuclear DNA. Compound 4c also effectively clears amastigote forms of wild type and drug-resistant parasites from infected mouse peritoneal macrophages but has less effect on host macrophages. Moreover compound 4c showed strong antileishmanial efficacies in BALB/c mice model of leishmaniasis. Potentially this compound can be used as a lead for developing excellent anileishmanial agent against emerging drug resistant strains of the parasite