Charge delocalization in self-assembled mixed-valence aromatic cation radicals

The spontaneous assembly of aromatic cation radicals (D(+•)) with their neutral counterpart (D) affords dimer cation radicals (D(2)(+•)). The intermolecular dimeric cation radicals are readily characterized by the appearance of an intervalence charge-resonance transition in the NIR region of their electronic spectra and by ESR spectroscopy. The X-ray crystal structure analysis and DFT calculations of a representative dimer cation radical (i.e., the octamethylbiphenylene dimer cation radical) have established that a hole (or single positive charge) is completely delocalized over both aromatic moieties. The energetics and the geometrical considerations for the formation of dimer cation radicals is deliberated with the aid of a series of cyclophane-like bichromophoric donors with drastically varied interplanar angles between the cofacially arranged aryl moieties. X-ray crystallography of a number of mixed-valence cation radicals derived from monochromophoric benzenoid donors established that they generally assemble in 1D stacks in the solid state. However, the use of polychromophoric intervalence cation radicals, where a single charge is effectively delocalized among all of the chromophores, can lead to higher-order assemblies with potential applications in long-range charge transport. As a proof of concept, we show that a single charge in the cation radical of a triptycene derivative is evenly distributed on all three benzenoid rings and this triptycene cation radical forms a 2D electronically coupled assembly, as established by X-ray crystallography.

Direct observation of electron-transfer-induced conformational transformation (molecular actuation) in a bichromophoric electron donor

With the aid of laser-flash photolysis, the one-electron oxidation of conformationally mobile tetramethoxydibenzobicyclo[4.4.1]undecane (1), using photoexcited chloranil as an oxidant, allows us to show that extended 1(+•) undergoes a conformational transformation to π-stacked folded 1(+•) on a microsecond time scale (τ ≈ 1 μs), which is at least six times longer than that found for the conformationally locked model compound.

Meningitis caused by Rhodotorula rubra in an human immunodeficiency virus infected patient

Rhodotorula spp. are common saprophytes but may be responsible for systemic infections in immunocompromised patients. Meningitis caused by Rhodotorula spp. in human immunodeficiency virus (HIV) infected patients has been reported only rarely. We present a case of meningitis caused by Rhodotorula rubra in HIV infected patient. The presumptive diagnosis of cryptococcal meningitis was made on the basis of India ink preparation, Gram staining and latex agglutination test (LAT) for cryptococcal antigen. The final diagnosis was confirmed by isolation of Rhodotorula rubra from cerebrospinal fluid on culture. LAT was considered false positive. Amphotericin B and 5-fluorocytosine were administered but the patient succumbed to his illness.

Cranial vault Salmonella osteomyelitis leading to extradural abscess - a case report

A case of rarely encountered Salmonella typhi osteomyelitis of left occipital bone leading to extradural abscess, is reported. The causative organism was not suspected until the culture report was obtained. The patient responded promptly to surgical drainage and antibiotic therapy.

Bacterial indices of drinking water from natural sources

Two hundred forty samples of water from twenty natural sources were subjected to the study for the detection of four bacterial indicators of faecal pollution. The samples were subjected to the detection of coliform, faecal coliform, E. coli, S. faecalis, Cl. welchii and plate count at 37 degrees C and 22 degrees C. All these samples were found unfit for human consumption. MPN for coliforms, E. coli and S. faecalis varied from 3 to 1800 per 100 ml of water, sero to 1800 per 100 ml water and zero to 540 per 100 ml of water respectively. Plate count at 37 degrees C and 22 degrees C varied from 2.5 x 10(3) to > 150 x 10(3) per ml of water. Cl. welchii was detected in 30.4% samples in rainy season and high plate count at 37 degrees C and 22 degrees C was observed during the same period.

Shima drinking water--a bacteriological analysis

300 water samples, 60 from piped supply and 240 from 20 natural sources were analyzed bacteriologically for four important bacterial indicators every month over a period of one year. The MPN of total coliforms, Escherichia coli, Streptococcus faecalis were detected by multiple tube method and Clostridium perfringens was isolated using litmus milk medium. From piped water supply, only one sample was found unfit for human consumption. The plate count at 37 degrees C and 22 degrees C varied from 0.5 x 10(3) to 15 x 10(3) per ml. of water. From natural sources, MPN indices for coliforms, Esch. coli and S. faecalis varied from 3 to > 1800, 0 to > 1800 and 0 to 540 per 100 ml. of water respectively. About 1/3rd of samples showed presence of Cl. perfringens. The plate count varied from 1.0 x 10(3) to > 150 x 10(3) per ml. of water. Salmonella typhi was isolated in 1.25% samples by membrane filtration technique. The water from all the natural sources was unfit for human consumption whereas piped water supply was of good quality in general.