Polarized optical scattering signatures from biological materials

Original article can be found at: http://www.sciencedirect.com/science/journal/00224073 Copyright Elsevier B.V.The polarization of laser light backscattered from biological samples has been measured over the wavelength range 350-850. nm. Incident circular, linearly polarized, and unpolarized light produces significant spectral features in the case of samples containing chlorophyll such as leaves and cyanobacteria. Polarization scattering signatures are observed around the chlorophyll 'red edge' that may have diagnostic value in the search for life signatures from extrasolar planets. © 2010 Elsevier Ltd.Peer reviewe

Circular polarization in scattered light as a possible biomarker

Original article can be found at : http://www.sciencedirect.com/ Copyright ElsevierBiological molecules exhibit homochirality and are optically active. Therefore, it is possible that the scattering of light by biological molecules might result in a macroscopic signature in the form of circular polarization. If this is the case, then circular polarization spectroscopy, which may be utilized in remote sensing, can offer a powerful indicator of the presence of a universal biosignature, namely homochirality. Here, we describe laboratory experiments designed to investigate this idea. We focus on photosynthetic microorganisms, and also show results from macroscopic vegetation and control minerals. In the microorganisms, we find unambiguous circular polarization associated with electronic absorption bands of the photosynthetic apparatus. Macroscopic vegetation yields a stronger and more complex signature while the control minerals produce low-levels of circular polarization unrelated to their spectra. We propose a heuristic explanation of our results, which is that the polarization is produced by circular dichroism in the material after the light has undergone its last scattering event. The results are encouraging for the use of circular polarization spectroscopy in remote sensing of a generic biomarker from space or the ground.Peer reviewe

Correction for Sparks et al., Detection of circular polarization in light scattered from photosynthetic microbes [fig 1]

Peer reviewe

Heat blocking gallium arsenide solar cells

The solar cell industry is witnessing an era of unprecedented growth and this trend is set to continue for the foreseeable future. Here we describe a heat reflection pigment-coated single-junction gallium arsenide solar cell that is capable of reflecting heat-inducing near-infrared radiation. The cell maintains its performance better than non-coated cells when exposed to infrared-rich radiant flux. In situations where solar cells get heated mainly from incident infrared radiation, these cells exhibit superior performance. The heat reflecting pigment, cell structure, coating process and cell performance have been describe

Enterotoxemia em caprinos no Rio Grande do Sul Caprine enterotoxaemia in Rio Grande do Sul, Brazil

São descritos surtos de enterotoxemia em caprinos em cinco propriedades no Estado do Rio Grande do Sul. Os animais afetados eram, normalmente, encontrados mortos ou apresentavam evolução aguda de 2 a 3 horas com acentuada depressão, cólicas abdominais e diarréia profusa com fibrina. Em duas propriedades relataram-se casos com a evolução de até 12 horas. Em treze animais necropsiados observaram-se aumento de líquidos nas cavidades abdominal, torácica e pericárdica, congestão e hiperemia da serosa e mucosa do intestino, conteúdo do cólon líquido com fibrina além de hemorragias de serosa e fibrina. Em um animal constatou-se microangiopatia cerebral caracterizada por acúmulo de material homogêneo e eosinofílico no espaço perivascular. No conteúdo intestinal, colônias com bastonetes morfológica e bioquimicamente sugestivos de Clostridium perfringens foram caracterizadas no estudo bacteriológico. A soroneutralização em camundongos com conteúdo intestinal dos animais afetados, revelou a presença da toxina épsilon. Estes achados evidenciam a enterotoxemia como doença de importância para criação de caprinos no Rio Grande do Sul.<br>Five outbreaks of caprine enterotoxaemia in Rio Grande do Sul, Brazil, were studied. The animals were found dead or had a clinical course that usually lasted 2-3 hours. From two farms a clinical manifestation period of 12 hours was reported. Clinical signs were characterized by depression, marked abdominal discomfort, profuse watery diarrhea with fibrin clots, and death. Thirteen necropsies were performed and hydropericardium, hydrothorax and hydroperitoneum were commonly found. The mucosa and serosa of the colon were congested, and its contents was watery with multiple fibrin clots. Serosal hemorrhages and fibrin clots in the gallbladder were also seen. Fibrinous colitis and thyphilitis were the most frequent histological changes. Cerebral microangiopathy was observed in one case, which was characterized by acute perivascular proteinaceous edema around arterioles of the nucleus caudatus and thalamus. Large numbers of Gram-positive rods, often in clumps and with morphology consistent with Clostridium perfringens, were seen in intestinal smears. The intestinal contents of six goats were positive for epsilon toxin by mouse neutralization test. These findings suggest that enterotoxaemia is an important disease of goat flocks in southern Brazil