Biomedical subjects

R Hema

Publications and source records attributed to R Hema.

4 recordsLinked to original sources

PubMed2006

Polarization-rich continuous wave direct imaging: modeling and visualization.

We report a study and comparison of continuous-wave, optical polarization difference imaging (PDI) and polarization modulation imaging (PMI) for imaging through scattering media. The problem is cast in the framework of a theoretical estimation, and the comparison is based on three visualization parameters, namely, the magnitude, the degree, and the orientation of the polarization. We show that PDI is superior in estimating the first two parameters in active imaging under specific conditions, while the PMI is suitable for passive imaging and is the only way to estimate polarization orientation. We also propose new schemes for rendering polarization information as a color image and for applying the newly introduced polarization-orientation imaging for segmentation. Simulation and experimental results verify the theoretical conclusions.

Algorithms↗

PubMed2003

3-(4-Chlorobenzoyl)-7-(N,N-dimethylamino)-1-phenylindolizine and 3-(2,4-dichlorobenzoyl)-7-(N,N-dimethylamino)-1-phenylindolizine.

In both of the title compounds, C(23)H(19)ClN(2)O, (I), and C(23)H(18)Cl(2)N(2)O, (II), the molecular packing is influenced by weak intermolecular C-H.O and C-H.pi interactions, but despite the chemical similarity of the compounds, the packing in (II) is entirely different from that observed in (I).

Journal Article↗

PubMed2003

16-(4-Cyanobenzylidene)-17-oxoandrost-5-en-3beta-ol.

In the title compound, 4-(3beta-hydroxy-17-oxoandrost-5-en-16-ylidenemethyl)benzonitrile, C(27)H(31)NO(2), rings A and C of the steroid nucleus are in chair conformations. The central six-membered ring B is in an 8beta,9alpha-half-chair conformation, while the five-membered ring D adopts a 13beta,14alpha-half-chair conformation. The cyanobenzylidene moiety has an E configuration with respect to the carbonyl group at position C17. The dihedral angle between the planes of the steroid nucleus and the cyanobenzylidene moiety is 22.61 (15) degrees. Intermolecular O-H.N hydrogen bonds formed between the hydroxyl group of the steroid and the N atom of the cyanobenzylidene moiety of symmetry-related molecules link the steroid molecules into chains which run parallel to the b axis.

Androstenols↗

PubMed2002

16-(4-Cyanobenzylidene)-3 beta-pyrrolidinoandrost-5-en-17 beta-ol monohydrate.

In the title compound, C(31)H(40)N(2)O x H(2)O, the outer two six-membered rings are in chair conformations, while the central ring is in an 8 beta,9 alpha-half-chair conformation. The five-membered ring adopts a 13 beta-envelope conformation and the cyanobenzylidene moiety has an E configuration with respect to the hydroxyl group at position 17. The steroid nuclei are linked by intermolecular O[bond]H...O and O[bond]H...N hydrogen bonds to form a molecular network. The molecular packing has an interesting feature, with the steroids aligned parallel to the b axis, forming a closed loop through hydrogen bonds linked via water molecules.

Journal Article↗