Quantitative analysis of directional spontaneous emission spectra from light sources in photonic crystals

We have performed angle-resolved measurements of spontaneous-emission spectra from laser dyes and quantum dots in opal and inverse opal photonic crystals. Pronounced directional dependencies of the emission spectra are observed: angular ranges of strongly reduced emission adjoin with angular ranges of enhanced emission. It appears that emission from embedded light sources is affected both by the periodicity and by the structural imperfections of the crystals: the photons are Bragg diffracted by lattice planes and scattered by unavoidable structural disorder. Using a model comprising diffuse light transport and photonic band structure, we quantitatively explain the directional emission spectra. This provides detailed understanding of the transport of spontaneously emitted light in real photonic crystals, which is essential in the interpretation of quantum-optics in photonic band-gap crystals and for applications wherein directional emission and total emission power are controlled.Comment: 10 pages, 10 figures, corrected pdf, inserted new referenc

Genetics of Hirschsprung disease:Rare variants, in vivo analysis and expression profiling

Hirschsprung disease (HSCR) is characterized by the absence of neurons in the distal region of the colon. Due to the lack of neuronal innervation, the muscles in the colon are unable to relax, causing life-threatening obstipation. HSCR is a heritable disease. Over 15 genes have been associated with the disease, but mutations in these genes are found in only a quarter of all patients. We aimed to identify new disease genes for HSCR by focusing on de novo mutations. De novo mutations are new genetic variations that are found in a child, but not in the parents. We investigated whether genes carrying de novo mutations in HSCR patients are involved in the development of the nervous system in the gut. To this end we inactivated these genes one by one in a zebrafish model in which the cells of the nervous system are fluorescently labeled. This led to the identification of four new genes for HSCR. We employed the same zebrafish model to show that overexpression of a particular gene on chromosome 21 possibly explains the high prevalence of HSCR among patients with Down syndrome. Additionally, we studied which genes are important for the development of the nervous system in the gastrointestinal tract of the mouse. We identified several genes that are critical for this developmental process, and these genes are excellent candidate genes for HSCR

Enhanced Efficiencies for High-Concentration, Multijunction PV Systems by Optimizing Grid Spacing under Nonuniform Illumination

The design of a triple junction solar cell’s front contact grid can significantly affect cell conversion efficiency under high concentration. We consider one aspect of grid design, choosing a linear grid within a distributed resistance cell model to optimize finger spacings at concentrations between 500 and 2500 suns under uniform and nonuniform illumination. Optimization for maximum efficiency under Gaussian irradiance profiles is done by SPICE analysis. Relative to the optimized uniform illumination designs, we find enhancements of 0.5% to 2% in absolute efficiencies for uniform spacing. Efficiency enhancement with nonuniform spacing under nonuniform illumination is also evaluated. Our model suggests that, at lower concentrations (<1000 suns), the penalty for using uniformly spaced fingers instead of nonuniformly spaced fingers is <0.1%. However, at a concentration of 2500 suns the penalty increases to 0.3%. Thus, relative to a uniform irradiance optimization, an absolute efficiency increase of 2.3% can be attained for an optimized nonuniform spacing given the Gaussian irradiance profile under consideration

Integration of deep transcriptome and proteome analyses reveals the components of alkaloid metabolism in opium poppy cell cultures

<p>Abstract</p> <p>Background</p> <p><it>Papaver somniferum </it>(opium poppy) is the source for several pharmaceutical benzylisoquinoline alkaloids including morphine, the codeine and sanguinarine. In response to treatment with a fungal elicitor, the biosynthesis and accumulation of sanguinarine is induced along with other plant defense responses in opium poppy cell cultures. The transcriptional induction of alkaloid metabolism in cultured cells provides an opportunity to identify components of this process via the integration of deep transcriptome and proteome databases generated using next-generation technologies.</p> <p>Results</p> <p>A cDNA library was prepared for opium poppy cell cultures treated with a fungal elicitor for 10 h. Using 454 GS-FLX Titanium pyrosequencing, 427,369 expressed sequence tags (ESTs) with an average length of 462 bp were generated. Assembly of these sequences yielded 93,723 unigenes, of which 23,753 were assigned Gene Ontology annotations. Transcripts encoding all known sanguinarine biosynthetic enzymes were identified in the EST database, 5 of which were represented among the 50 most abundant transcripts. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) of total protein extracts from cell cultures treated with a fungal elicitor for 50 h facilitated the identification of 1,004 proteins. Proteins were fractionated by one-dimensional SDS-PAGE and digested with trypsin prior to LC-MS/MS analysis. Query of an opium poppy-specific EST database substantially enhanced peptide identification. Eight out of 10 known sanguinarine biosynthetic enzymes and many relevant primary metabolic enzymes were represented in the peptide database.</p> <p>Conclusions</p> <p>The integration of deep transcriptome and proteome analyses provides an effective platform to catalogue the components of secondary metabolism, and to identify genes encoding uncharacterized enzymes. The establishment of corresponding transcript and protein databases generated by next-generation technologies in a system with a well-defined metabolite profile facilitates an improved linkage between genes, enzymes, and pathway components. The proteome database represents the most relevant alkaloid-producing enzymes, compared with the much deeper and more complete transcriptome library. The transcript database contained full-length mRNAs encoding most alkaloid biosynthetic enzymes, which is a key requirement for the functional characterization of novel gene candidates.</p

Hydra: software for tailored processing of H/D exchange data from MS or tandem MS analyses

<p>Abstract</p> <p>Background</p> <p>Hydrogen/deuterium exchange mass spectrometry (H/DX-MS) experiments implemented to characterize protein interaction and protein folding generate large quantities of data. Organizing, processing and visualizing data requires an automated solution, particularly when accommodating new tandem mass spectrometry modes for H/DX measurement. We sought to develop software that offers flexibility in defining workflows so as to support exploratory treatments of H/DX-MS data, with a particular focus on the analysis of very large protein systems and the mining of tandem mass spectrometry data.</p> <p>Results</p> <p>We present a software package ("Hydra") that supports both traditional and exploratory treatments of H/DX-MS data. Hydra's software architecture tolerates flexible data analysis procedures by allowing the addition of new algorithms without significant change to the underlying code base. Convenient user interfaces ease the organization of raw data files and input of peptide data. After executing a user-defined workflow, extracted deuterium incorporation values can be visualized in tabular and graphical formats. Hydra also automates the extraction and visualization of deuterium distribution values. Manual validation and assessment of results is aided by an interface that aligns extracted ion chromatograms and mass spectra, while providing a means of rapidly reprocessing the data following manual adjustment. A unique feature of Hydra is the automated processing of tandem mass spectrometry data, demonstrated on a large test data set in which 40,000 deuterium incorporation values were extracted from replicate analysis of approximately 1000 fragment ions in one hour using a typical PC.</p> <p>Conclusion</p> <p>The customizable workflows and user-friendly interfaces of Hydra removes a significant bottleneck in processing and visualizing H/DX-MS data and helps the researcher spend more time executing new experiments and interpreting results. This increased efficiency will encourage the analysis of larger protein systems. The ability to accommodate the tandem MS dimension supports alternative data collection and analysis strategies, as well as higher resolution localization of deuteration where permitted by the fragmentation mechanism.</p

Sustainable employability of teachers with hearing loss

Objective In many countries the retirement age is rising. Consequently, age-related hearing loss is an increasing occupational health problem. This study examined the association between hearing loss and sustainable employability of teachers. Design For this cross-sectional study a survey and an online hearing screening test were used. Sustainable employability was measured with the Capability Set for Work Questionnaire (CSWQ), examining seven work values. CSWQ-scores of teachers with poor, insufficient, and good hearing were investigated with ordinal regression analyses. Work values and discrepancies between the importance and achievement of the values were examined by chi-square tests. Study sample Dutch teachers (N = 737) of whom 146 (20%) had insufficient and 86 (12%) poor hearing. Results Teachers with insufficient (OR = 0.64; 95% CI 0.46–0.89) and poor (OR = 0.55; 95% CI 0.36–0.83) hearing had lower CSWQ-scores compared with good hearing teachers. Adjustment for covariates, in particular for self-rated health, attenuated the associations. Compared with good hearing teachers, teachers with poor hearing reported more discrepancies in using their knowledge and skills and setting their own goals at work. Conclusions Hearing loss was negatively associated with sustainable employability of teachers. This emphasises the importance of assessing the hearing status of teachers

Spectrally-resolved measurement of concentrated light distributions for Fresnel lens concentrators

A test method that measures spectrally resolved irradiance distribution for a concentrator photovoltaic (CPV) optical system is presented. In conjunction with electrical I-V curves, it is a means to visualize and characterize the effects of chromatic aberration and nonuniform flux profiles under controllable testing conditions. The indoor characterization test bench, METHOD (Measurement of Electrical, Thermal and Optical Devices), decouples the temperatures of the primary optical element (POE) and the cell allowing their respective effects on optical and electrical performance to be analysed. In varying the temperature of the POE, the effects on electrical efficiency, focal distance, spectral sensitivity, acceptance angle and multi-junction current matching profiles can be quantified. This work presents the calibration procedures to accurately image the spectral irradiance distribution of a CPV system and a study of system behavior over lens temperature