Polarization-preserving totally reflecting prisms with a single medium layer

When reflectors with layers are used at non-normal incidence, the two planes of polarization generally have different phase shifts. The difference in the shifts is known as phase retardance. For prisms with a single layer, this retardance depends on four factors: prism index, layer index, the ratio of the optical thickness of the layer to the wavelength, and angle of incidence. When the retardance is kept at zero and the reflectance for both p and s components of a polarized light are controlled at almost 100% after reflection, a polarization-preserving total reflection is realized. Polarization-preserving totally reflecting prisms (PPTRP's) have many applications in scientific research and optical engineering. Designers of the PPTRP's need references concerning the phase properties of the PPTRP's. However, few papers can be found in which the effects of the four factors on the retardance of the PPTRP's were investigated and compared thoroughly, although the theory concerned has been known and the influences from some (not all) factors have been reported. Therefore it is still necessary to study the behavior of the PPTRP's from all aspects. The effects of all four factors on the retardance are analyzed and compared from all aspects. A general method of designing PPTRP's is proposed. As an example, a special PPTRP is designed and both theoretical and experiment results are given.     

Design, implementation, and characterization of an optical power supply spot-array generator for a four-stage free-space optical backplane

The design and implementation of a robust, scalable, and modular optical power supply spot-array generator for a modulator-based free-space optical backplane demonstrator is presented. Four arrays of 8 x 4 spots with 6.47-mum radii (at 1/e(2) points) pitched at 125 mum in the vertical direction and 250 mum in the horizontal were required to provide the light for the optical interconnect. Tight system tolerances demanded careful optical design, robust optomechanics, and effective alignment techniques. Issues such as spot-array generation, polarization, power efficiency, and power uniformity are discussed. Characterization results are presented.     

Lipid and fatty acid profiles in rats consuming different high-fat ketogenic diets

High-fat ketogenic diets are used to treat intractable seizures in children, but little is known of the mechanism by which these diets work or whether fats rich in n−3 polyunsaturates might be beneficial. Tissue lipid and fatty acid profiles were determined in rats consuming very high fat (80 weight%), low-carbohydrate ketogenic diets containing either medium-chain triglyceride, flaxseed oil, butter, or an equal combination of these three fat sources. Ketogenic diets containing butter markedly raised liver triglyceride but had no effect on plasma cholesterol. Unlike the other fats, flaxseed oil in the ketogenic diet did not raise brain cholesterol. Brain total and free fatty acid profiles remained similar in all groups, but there was an increase in the proportion of arachidonate in brain total lipids in the medium-chain triglyceride group, while the two groups consuming flaxseed oil had significantly lower arachidonate in brain, liver, and plasma. The very high dietary intake of α-linolenate in the flaxseed group did not change docosahexaenoate levels in the brain. Our previous report based on these diets showed that although ketosis is higher in rats consuming a ketogenic diet based on medium-chain triglyceride oil, seizure resistance in the pentylenetetrazol model is not clearly related to the degree of ketosis achieved. In combination with our present data from the same seizure study, it appears that ketogenic diets with widely differing effects on tissue lipids and fatty acid profiles can confer a similar amount of seizure protection.     

Coating multi-walled carbon nanotubes with rare-earth complexes by an in situ synthetic method

Multi-walled carbon nanotubes (MWCNTs) were coated with rare-earth (RE) (Eu(3+), Tb(3+)) complex layers by a simple in?situ synthetic method via noncovalently functionalized MWCNTs with sodium dodecyl sulfate. Extensive characterizations of the resulting nanocomposite materials have been performed using scanning electron microscopy (SEM), FT-IR spectra, x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS). The photoluminescence properties of the RE-complex-modified MWCNTs were also investigated. Under the excitation of UV light, these samples exhibit characteristic emissions of Eu(3+) or Tb(3+) ions. The presence of the MWCNT framework does not quench the lanthanide-centered luminescence originating from the characteristic electronic transitions within the 4f shell of the RE ions. Furthermore, the existence of the nanotube framework can improve the stability of the RE complex under UV irradiation and elongate the fluorescence lifetime of the RE complex.     

Study on in vivo distribution of liver-targeting nanopaticles encapsulating thymidine kinase gene (TK gene) in mice

Nanoparticles formulated from polylactic-co-glycolic acid (PLGA) polymer loading a new recombinant plasmid pEGFP-TKAFB (TK-PLGA-NPs) were prepared by a double-emulsion evaporation technique. Both in vitro and in vivo release behaviors of TK-PLGA-NPs (with particle diameter ranged from 50 to 100 nm) were investigated, using ethidium bromide (EB) staining and gamma scintigraphy, respectively. The results indicated that the in vitro release rate of DNA (pEGFP-TKAFB plasmid) in TK-PLGA-NPs showed good fit into the Higuichi Equation and dependence in the molecular weight of PLGA polymer. 0.5 h after injection of nanoparticles containing ³²P labeled pEGFP-TKAFB plasmid (³²P-TK-PLGA-NP) via caudal vein of the mice, the ratio of radioactivity intensity in the liver to total intensity was above 70%, which showed a 1.4-fold increase over that by injection of ³²P labeled pEGFP-TKAFB plasmid (³²pEGFP-TKAFB plasmid, ³²P-TK). Similarly, 2 h after hypodermic injection of ³²P-TK-PLGA-NPs in mice, the ratio of radioactivity in the liver against total radioactivity was more than 70%, which was 1.6-fold compared with naked ³²P-TK. All these data showed that the TK-PLGA-NPs has the potential for liver-targeting and delayed drug release.     

Validation of image segmentation by estimating rater bias and variance

The accuracy and precision of segmentations of medical images has been difficult to quantify in the absence of a 'ground truth' or reference standard segmentation for clinical data. Although physical or digital phantoms can help by providing a reference standard, they do not allow the reproduction of the full range of imaging and anatomical characteristics observed in clinical data.An alternative assessment approach is to compare with segmentations generated by domain experts. Segmentations may be generated by raters who are trained experts or by automated image analysis algorithms. Typically, these segmentations differ due to intra-rater and inter-rater variability. The most appropriate way to compare such segmentations has been unclear.We present here a new algorithm to enable the estimation of performance characteristics, and a true labelling, from observations of segmentations of imaging data where segmentation labels may be ordered or continuous measures. This approach may be used with, among others, surface, distance transform or level-set representations of segmentations, and can be used to assess whether or not a rater consistently overestimates or underestimates the position of a boundary.     

Pupil-plane imager for scintillometry over long horizontal paths

A pupil plane imaging (PPI) system has been designed and implemented to measure scintillation induced by atmospheric turbulence and to estimate key parameters of atmospheric turbulence. A high-speed, high-resolution camera images the pupil of a telescope. The process of estimating normalized intensity variance and the underlying rationale is discussed. Experimental results are presented for data taken at North Oscura Peak in southern New Mexico from light originating at Salinas Peak or an aircraft, over near-horizontal paths of approximately 50 km. Strong scintillation is often observed. The results are compared to those of other instruments operating in parallel, and systematic and random errors are discussed. The primary goal is to accurately estimate scintillation strength using PPI in order to assess adaptive optics performance as a function of such scintillation.     

Determination of the particulate extinction-coefficient profile and the column-integrated lidar ratios using the backscatter-coefficient and optical-depth profiles

A new method is considered that can be used for inverting data obtained from a combined elastic-inelastic lidar or a high spectral resolution lidar operating in a one-directional mode, or an elastic lidar operating in a multiangle mode. The particulate extinction coefficient is retrieved from the simultaneously measured profiles of the particulate backscatter coefficient and the particulate optical depth. The stepwise profile of the column-integrated lidar ratio is found that provides best matching of the initial (inverted) profile of the optical depth to that obtained by the inversion of the backscatter-coefficient profile. The retrieval of the extinction coefficient is made without using numerical differentiation. The method reduces the level of random noise in the retrieved extinction coefficient to the level of noise in the inverted backscatter coefficient. Examples of simulated and experimental data are presented.     

Scalar diffraction modeling in optical disk recording using wave function assembling

A new scalar diffraction modeling method for simulating the readout signal of optical disks is described. The information layer is discretized into pixels that are grouped in specific ways to form written and unwritten areas. A set of 2D wave functions resulting from these pixels at the detection aperture is established. A readout signal is obtained via the assembly of wave functions from this set according to the content under the scanning spot. The method allows efficient simulation of jitter noise due to edge deformation of recorded marks, which is important at high densities. It is also capable of simulating a physically irregular mark, thereby helping to understand and optimize the recording process.     

Optimal biostimulation strategy for phenol degradation with indigenous rhizobium Ralstonia taiwanensis

This study provides a first attempt from a perspective of Gaden's classification of fermentation and phase-plane to put forward phenol degradation using various augmented nutrient media for biostimulation. It aimed to identify the most promising nutrient source(s) to attenuate synergistic interactions with phenol for optimal phenol degradation. Therefore, the growth association of phenol degradation using various nutrient media in place of combined toxic interactions was established via Gaden's classification scheme of fermentation and phase-plane analysis. In cultures grown on medium bearing dual carbon sources (glycerol and phenol) or phenol alone, phenol was found to be firstly biodegraded for microbial growth (i.e., growth-associated degradation). In contrast, when yeast extract or acetate was supplemented, a diauxic growth behavior was observed as the augmented nutrient was primarily utilized while phenol degradation was repressed. Moreover, using glycerol as the nutrient source, phenol degradation seemed to be enhanced simultaneously during the consumption of glycerol for cellular growth after ca. 2h response lag in growth. Although gluconic acid could enhance cell growth as well as phenol degradation, the phenol degradation performance was still not as good as that of glycerol. Thus, biostimulation with glycerol appeared to show the most favorable metabolic characteristics against phenol toxicity on Ralstonia taiwanensis, leading to better degradation efficiency of the toxic pollutant. Phase-plane trajectories also clearly confirmed that glycerol was the optimal biostimulating nutrient source for phenol degradation.