Fabrication of highly efficient grating band-pass filters and their applications in soliton propagation system

We report here fabrication of highly efficient in-fiber grating bandpass filters using the established UV-side- exposure technique. Various combinations of passband/stopband and transmission/rejection of single- and multi-channel filters have been produced in hydrogenated standard telecom, high Ge-doped and B/Ge-codoped fibers. Up to > 60 dB rejection stopbands ranging from -2 nm to 55 nm, and passbands with 0.02 nm - 3 nm linewidths and transmissivity up to > 90% have been achieved with these devices. By concatenating several structures, a bandpass filter has been demonstrated with a combination of a 0.16 nm passband centered in a approximately 35 nm stopband, representing the highest reported finesse of 220 for any multi-nanometer stopband filter. We also report the first application of a grating bandpass filter for suppressing timing jitter in soliton propagation system, enabling transmission of 10 ps solitons over a distance of 2700 km

Generation Of 20 Mw Of Blue Laser-Radiation From A Diode-Pumped Sum-Frequency Laser

Resonant intracavity sum-frequency mixing of a diode-pumped Nd:yAG laser and a 100 mW single stripe laser diode, has been used to generate a measured output power of 20 mW of blue laser radiation at 459 nm. This represents a total conversion efficiency of approximately 68% of the single stripe laser diode power incident on the cavity. The laser was also demonstrated to operate over a tuning range of 12 nm via angle tuning of the nonlinear crystal

General duality for abelian-group-valued statistical-mechanics models

We introduce a general class of statistical-mechanics models, taking values in an abelian group, which includes examples of both spin and gauge models, both ordered and disordered. The model is described by a set of ``variables'' and a set of ``interactions''. A Gibbs factor is associated to each variable and to each interaction. We introduce a duality transformation for systems in this class. The duality exchanges the abelian group with its dual, the Gibbs factors with their Fourier transforms, and the interactions with the variables. High (low) couplings in the interaction terms are mapped into low (high) couplings in the one-body terms. The idea is that our class of systems extends the one for which the classical procedure 'a la Kramers and Wannier holds, up to include randomness into the pattern of interaction. We introduce and study some physical examples: a random Gaussian Model, a random Potts-like model, and a random variant of discrete scalar QED. We shortly describe the consequence of duality for each example.Comment: 26 pages, 2 Postscript figure

The effects of changes in the order of verbal labels and numerical values on children's scores on attitude and rating scales

Research with adults has shown that variations in verbal labels and numerical scale values on rating scales can affect the responses given. However, few studies have been conducted with children. The study aimed to examine potential differences in children’s responses to Likert-type rating scales according to their anchor points and scale direction, and to see whether or not such differences were stable over time. 130 British children, aged 9 to 11, completed six sets of Likert-type rating scales, presented in four different ways varying the position of positive labels and numerical values. The results showed, both initially and 8-12 weeks later, that presenting a positive label or a high score on the left of a scale led to significantly higher mean scores than did the other variations. These findings indicate that different arrangements of rating scales can produce different results which has clear implications for the administration of scales with children

Differences in Major Histocompatibility Complex Frequencies after Multitrait, Divergent Selection for Immunocompetence

White Leghorn chickens from lines selected for four immune-response traits (IR lines) were serotyped for B system alloantigens characterizing the haplotypes and genotypes to examine the effect of divergent selection for multitrait immunocompetence on MHC haplotype and genotype frequencies. The selected lines were derived from the Ottawa Strain 7. The selection index included four immunocompetence traits: antibody production against Mycoplasma gallisepticum (MG) and Pasteurella multocida, inflammatory response to phytohemagglutinin, and reticuloendothelial carbon clearance. The four lines include two replicates of high and low multitrait-immunocompetence lines. After four cycles of selection, significant differences (P \u3c .05) in several B system haplotype frequencies were observed, both among IR lines and between the IR lines and the Ottawa Strain 7. The B2 haplotype frequency was greater in all IR lines than in the Ottawa Strain 7. The B21 frequency was less in both high lines than in the Ottawa Strain 7. In comparisons among lines, frequencies of B21 were greater in both replicates of the low lines and the B12 and B19 frequencies were significantly greater (P \u3c .05) in the high lines. A gene substitution model showed effects (P \u3c .10) of specific haplotypes on MG and on the index. The B2 haplotype had a positive effect associated with MG. Haplotype B21 was positively associated with the multitrait index. Haplotype B13 had a negative effect on both MG and the index. Significant differences (P \u3c .01) in genotype frequencies were also noted among the IR lines. Associations between specific MHC haplotypes or genotypes and immune-response traits may offer insight into MHC-mediated mechanisms of disease resistance

Forecasting the inundation of postfire debris flows

In the semi-arid regions of the western United States, postfire debris flows are typically runoff generated. The U.S. Geological Survey has been studying the mechanisms of postfire debris-flow initiation for multiple decades to generate operational models for forecasting the timing, location, and magnitude of postfire debris flows. Here we discuss challenges and progress for extending operational capabilities to include modeling postfire debris-flow inundation extent. Analysis of volume and impacted area scaling relationships indicated that postfire debris flows do not conform to assumptions of geometric self-similarity. We documented sensitivity of impacted areas to rainfall intensity using a candidate methodology for generating inundation hazard assessments. Our results emphasize the importance of direct measurements of debris-flow volume, inundated area, and high temporal resolution rainfall intensity

High-resolution studies of hydride transfer in the ferredoxin:NADP+ reductase superfamily

Ferredoxin: NADP+ reductase (FNR) is an FAD-containing enzyme best known for catalysing the transfer of electrons from ferredoxin (Fd) to NADP+ to make NADPH during photosynthesis. It is also the prototype for a broad enzyme superfamily, including the NADPH oxidases (NOXs) that all catalyse similar FAD-enabled electron transfers between NAD(P)H and one-electron carriers. Here, we define further mechanistic details of the NAD(P)H \u21cc FAD hydride-transfer step of the reaction based on spectroscopic studies and high-resolution (~ 1.5 \uc5) crystallographic views of the nicotinamide-flavin interaction in crystals of corn root FNR Tyr316Ser and Tyr316Ala variants soaked with either nicotinamide, NADP+ , or NADPH. The spectra obtained from FNR crystal complexes match those seen in solution and the complexes reveal active site packing interactions and patterns of covalent distortion of the FAD that imply significant active site compression that would favour catalysis. Furthermore, anisotropic B-factors show that the mobility of the C4 atom of the nicotinamide in the FNR:NADP+ complex has a directionality matching that expected for boat-like excursions of the nicotinamide ring thought to enhance hydride transfer. Arguments are made for the relevance of this binding mode to catalysis, and specific consideration is given to how the results extrapolate to provide insight to structure-function relations for the membrane-bound NOX enzymes for which little structural information has been available

Diarrhoea in a large prospective cohort of European travellers to resource-limited destinations

BACKGROUND: Incidence rates of travellers' diarrhoea (TD) need to be updated and risk factors are insufficiently known. METHODS: Between July 2006 and January 2008 adult customers of our Centre for Travel Health travelling to a resource-limited country for the duration of 1 to 8 weeks were invited to participate in a prospective cohort study. They received one questionnaire pre-travel and a second one immediately post-travel. First two-week incidence rates were calculated for TD episodes and a risk assessment was made including demographic and travel-related variables, medical history and behavioural factors. RESULTS: Among the 3100 persons recruited, 2800 could be investigated, resulting in a participation rate of 89.2%. The first two-weeks incidence for classic TD was 26.2% (95%CI 24.5-27.8). The highest rates were found for Central Africa (29.6%, 95% CI 12.4-46.8), the Indian subcontinent (26.3%, 95%CI 2.3-30.2) and West Africa (21.5%, 95%CI 14.9-28.1). Median TD duration was 2 days (range 1-90). The majority treated TD with loperamide (57.6%), while a small proportion used probiotics (23.0%) and antibiotics (6.8%). Multiple logistic regression analysis on any TD to determine risk factors showed that a resolved diarrhoeal episode experienced in the 4 months pre-travel (OR 2.03, 95%CI 1.59-2.54), antidepressive comedication (OR 2.11, 95%CI 1.17-3.80), allergic asthma (OR 1.67, 95%CI 1.10-2.54), and reporting TD-independent fever (OR 6.56, 95%CI 3.06-14.04) were the most prominent risk factors of TD. CONCLUSIONS: TD remains a frequent travel disease, but there is a decreasing trend in the incidence rate. Patients with a history of allergic asthma, pre-travel diarrhoea, or of TD-independent fever were more likely to develop TD while abroad