6,389 research outputs found
Wavelength tunable 10-GHz 3-ps pulse source using a dispersion decreasing fiber-based nonlinear optical loop mirror
No full textWe experimentally demonstrate the use of a dispersion decreasing fiber (DDF)-based nonlinear optical loop mirror (NOLM) for the generation of wavelength tunable soliton-like pulses at a repetition rate of 10 GHz. We compress ~12 ps Gaussian pulses from an electro-absorption modulator (EAM) (followed by 125 m of DCF for preliminary linear dispersion compensation) into 3 ps pedestal-free pulses using both high-order soliton compression and nonlinear switching effects within an 8.5 km DDF-based loop mirror. The output pulses from the DDF-based NOLM show considerable pedestal reduction compared to those obtained by directly compressing the EAM seed pulses via a single passage through the DDF. Wavelength tuning of the compressed pulses over a ~15 nm bandwidth (from 1541 to 1556 nm) is demonstrated without a significant increase in pulse duration or degradation in pulse quality
A genetic analysis of the introgression process from cultivated lettuce (Lactuca sativa L.) to wild prickly lettuce (L. serriola L.)
No full text Many plant species can hybridise and produce fertile offspring. Hybridization between cultivated species and their wild relatives has raised concerns with regard to GM crops, as it constitutes a possible route along which the transgene could disperse from crops into related wild species, establish itself in the natural population, and persist under natural conditions. This may cause unintended ecological consequences such as the formation of more invasive weeds and genetic erosion. After crop-wild hybridization, the persistence of the hybrids and of the crop genes (including the transgenes) in later generations depends on their genetic make-up, which consists of specific combinations of wild and crop genomic segments, and on the environmental conditions. Therefore, knowledge on the dynamics of crop-wild hybridization and introgression using conventional crop varieties is needed as it constitutes the baseline for putting into perspective the effects of transgene introgression under natural conditions. This study focused on understanding the genetic process of hybridization and introgression from cultivated to wild relative species using cultivated lettuce (Lactuca sativa L.) and its closest wild relative, prickly lettuce (L. serriola L.) as a crop-wild complex model. Natural populations of prickly lettuce in Europe were tested for the occurrence of crop-wild hybrids using Bayesian-based programmes (Structure, InStruct and NewHybrids) which returned a crop-wild hybrid occurrence of 7%. However, the geographical location of the hybrids led to the conclusion that crop-wild hybridization is not the cause of the recent northward spread of L. serriola in Europe. To test for the importance of the crop genomic segments to the performance of lettuce crop-wild hybrids, three hybrid generations were created (F2 as a selfing generation, and BC1 and BC2, backcrossed to the wild genotype to mimick the introgression process) by crossing L. sativa (cv. Dynamite) with L. serriola collected from Eys (the Netherlands). The three populations were genotyped with Single Nucleotide Polymorphism markers for genetic analysis. Because of the importance of the abiotic stresses as selection factors under natural conditions and the prospective of generating GM crop varieties with enhanced abiotic stress tolerance, the three populations were evaluated for vigour at the rosette stage under greenhouse conditions of non-stress, drought, salinity and nutrient deficiency. The BC1 population was also evaluated under field conditions at two locations (Wageningen and Sijbekarspel, the Netherlands) for hybrid germination, vigour, survival and reproduction. Based on the location and allelic effect of the QTLs for germination, vigour, survival and reproductive traits in the current lettuce crop-wild cross, genomic regions were suggested where transgenes could be or could not be located in order to mitigate their persistence in crop-wild hybrids through genetic hitchhiking and background selection. </p
Player agency in interactive narrative: audience, actor & author
No full textThe question motivating this review paper is, how can
computer-based interactive narrative be used as a constructivist learn-
ing activity? The paper proposes that player agency can be used to
link interactive narrative to learner agency in constructivist theory,
and to classify approaches to interactive narrative. The traditional
question driving research in interactive narrative is, ‘how can an in-
teractive narrative deal with a high degree of player agency, while
maintaining a coherent and well-formed narrative?’ This question
derives from an Aristotelian approach to interactive narrative that,
as the question shows, is inherently antagonistic to player agency.
Within this approach, player agency must be restricted and manip-
ulated to maintain the narrative. Two alternative approaches based
on Brecht’s Epic Theatre and Boal’s Theatre of the Oppressed are
reviewed. If a Boalian approach to interactive narrative is taken the
conflict between narrative and player agency dissolves. The question
that emerges from this approach is quite different from the traditional
question above, and presents a more useful approach to applying in-
teractive narrative as a constructivist learning activity
The Sensations of the 1920s: Martha Ostenso's Wild Geese and Mazo de la Roche's Jalna
No full textMartha Ostenso's Wild Geese and Mazo de la Roche's Jalna were both prize-winning, wildly successful novels, in the United States as well as in Canada, but each received a rather different critical response in this country. Jalna's suggestive anti-Americanism and its explicit British loyalism was evidently to be preferred over Wild Geese's more ambiguously North American (as opposed to what was then considered distinctly Canadian) aesthetic. This is despite its easy fit into T.D. Maclulich's classification as a Canadian 'Northern' fiction (a tradition which includes Frederick Philip Grove, Ernest Buckler, Sinclair Ross, and others). As well, the intense and often violent eroticism of Ostenso's novel was more difficult for critics of the 1920s to tolerate than was the coy sexiness of Jalna. Although little critical attention has been paid to either author in recent years, Ostenso's literary reputation appears to have surpassed de la Roche's
A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms
No full textWe describe a genetic variation map for the chicken genome containing 2.8 million single-nucleotide polymorphisms (SNPs). This map is based on a comparison of the sequences of three domestic chicken breeds (a broiler, a layer and a Chinese silkie) with that of their wild ancestor, red jungle fowl. Subsequent experiments indicate that at least 90% of the variant sites are true SNPs, and at least 70% are common SNPs that segregate in many domestic breeds. Mean nucleotide diversity is about five SNPs per kilobase for almost every possible comparison between red jungle fowl and domestic lines, between two different domestic lines, and within domestic lines--in contrast to the notion that domestic animals are highly inbred relative to their wild ancestors. In fact, most of the SNPs originated before domestication, and there is little evidence of selective sweeps for adaptive alleles on length scales greater than 100 kilobases
Investigation of the S-1/ICT -> S-0 internal conversion lifetime of 4 '-apo-beta-caroten-4 '-al and 8 '-apo-beta-caroten-8 '-al: Dependence on conjugation length and solvent polarity
No full textThe ultrafast internal conversion (IC) dynamics of aldehyde-substituted apocarotenoids (n'-apo-beta-caroten-n'-als with n = 4, 8 and 12) have been investigated in a systematic variation of conjugation length and solvent polarity using time-resolved femtosecond transient absorption spectroscopy. After excitation to the S-2 state with different excess energies, the subsequent intramolecular dynamics were investigated at several probe wavelengths covering the S-0 -> S-2 and S-1/ICT -> S-n absorption bands. Time constants tau(1) for the internal conversion process S-1/ICT -> S-0 of 4'-apo-beta-caroten-4'-al and 8'-apo-beta-caroten-8'-al have been newly measured. We compared these results with our earlier measurements for 12'-apo-beta-caroten-12'-al (D.A. Wild, K. Winkler, S. Stalke, K. Oum, T. Lenzer Phys. Chem. Chem. Phys. 2006, 8, 2499). In the case of the aldehyde with the longest conjugation (4'-apo-beta-caroten-4'-al), tau(1) is almost independent of solvent polarity (4-5 ps), whereas a significant reduction of tau(1) from 22.7 to 8.6 ps for the shorter 8'-apo-beta-caroten-8'-al and an even more pronounced reduction from 220 to 8.0 ps for 12'-apo-beta-caroten-12'-al were observed when the solvent medium was changed from n-hexane to methanol, respectively. In n-hexane, tau(1) of the apocarotenals is strongly dependent on the conjugation length and this can be well understood in terms of an energy gap law description where the S-1-S-0 energy differences were estimated from their steady-state fluorescence spectra. In highly polar solvents, the IC to S-0 is very fast, irrespective of the conjugation length. This is probably due to the stabilization of an intramolecular charge transfer (ICT) state in 12'-apo-beta-caroten-12'-al and 8'-apo-beta-caroten-8'-al. In the case of 4'-apo-beta-caroten-4'-al, such an influence of an ICT state is presumably less important than for the other two apocarotenals
Pathobiology of avian influenza in wild bird species
No full textAvian influenza viruses, especially highly pathogenic avian influenza viruses (HPAIV), affect a wide range of species, including humans and have thus become a major concern for veterinary medicine and public health. A HPAIV-H5N1 belonging to clade 2.2, originally from South East Asia, spread across Eurasia and reached Sweden in 2006. Currently the most commonly isolated HPAIV-H5N1 from wild birds belong to clade 2.3.2. There is a growing concern that the H5N1 virus has evolved in such a way that it can be maintained in the wild bird population without causing severe disease. At the same time the role of natural hosts, such as mallards (Anas platyrhynchos), in the epidemiology of avian influenza is an ongoing concern. In order to characterize the natural disease in free ranging birds in Sweden and to assess the pathogenicity of clade 2.3.2 viruses, histopathology, polymerase chain reaction, virus isolation and immunohistochemistry (IHC) were used to investigate lesions and viral tissue targeting of HPAIV-H5N1 in naturally infected tufted ducks (Aythya fuligula) and in tufted ducks experimentally infected with a clade 2.3.2 virus. Since neurotropism is a key feature of HPAIV-H5N1 infection, the encephalitis in 9 wild bird species from the Swedish outbreak was characterized in more detail. Results were compared to mallards infected with a low pathogenic avian influenza virus H1N1. The studies highlight the range and variation of the presentation of the natural disease in wild birds. Experimentally infected ducks were highly susceptible to the current HPAIV-H5N1 clade and showed similar lesions and viral antigen distribution as the naturally infected ducks. The studies suggest that there are several routes of infection and dissemination of the virus including, respiratory, hematogenous and olfactory routes. The respiratory tract is probably the main route of excretion of HPAIV-H5N1 since no viral antigen was found in the intestine. This was in contrast to the experimentally infected mallards which had primarily intestinal replication with minimal lesions. The results highlight the importance of continued investigation of the pathobiology of both low- and HPAIV infections in wild birds which is essential in the understanding of their epidemiology and, in turn, can contribute to the design and implementation of preventive and control measures to protect the health of humans and animals
Tryptophan-Tryptophan energy migration as a tool to follow apoflavodoxin folding
No full textSubmolecular details of Azotobacter vinelandii apoflavodoxin (apoFD) (un)folding are revealed by time-resolved fluorescence anisotropy using wild-type protein and variants lacking one or two of apoFD's three tryptophans. ApoFD equilibrium (un)folding by guanidine hydrochloride follows a three-state model: native unfolded intermediate. In native protein, W128 is a sink for Förster resonance energy transfer (FRET). Consequently, unidirectional FRET with a 50-ps transfer correlation time occurs from W167 to W128. FRET from W74 to W167 is much slower (6.9 ns). In the intermediate, W128 and W167 have native-like geometry because the 50-ps transfer time is observed. However, non-native structure exists between W74 and W167 because instead of 6.9 ns the transfer correlation time is 2.0 ns. In unfolded apoFD this 2.0-ns transfer correlation time is also detected. This decrease in transfer correlation time is a result of W74 and W167 becoming solvent accessible and randomly oriented toward one another. Apparently W74 and W167 are near-natively separated in the folding intermediate and in unfolded apoFD. Both tryptophans may actually be slightly closer in space than in the native state, even though apoFD's radius increases substantially upon unfolding. In unfolded apoFD the 50-ps transfer time observed for native and intermediate folding states becomes 200 ps as W128 and W167 are marginally further separated than in the native state. Apparently, apoFD's unfolded state is not a featureless statistical coil but contains well-defined substructures. The approach presented is a powerful tool to study protein folding
The efficacy of emamectin benzoate against infestations of Lepeophtheirus salmonis on farmed Atlantic salmon (Salmo salar L) in Scotland, 2002-2006
No full textInfestations of the parasitic copepod Lepeophtheirus salmonis, commonly referred to as sea lice, represent a major challenge to commercial salmon aquaculture. Dependence on a limited number of theraputants to control such infestations has led to concerns of reduced sensitivity in some sea lice populations. This study investigates trends in the efficacy of the in-feed treatment emamectin benzoate in Scotland, the active ingredient most widely used across all salmon producing regions. Study data were drawn from over 50 commercial Atlantic salmon farms on the west coast of Scotland between 2002 and 2006. An epi-informatics approach was adopted whereby available farm records, descriptive epidemiological summaries and statistical linear modelling methods were used to identify factors that significantly affect sea lice abundance following treatment with emamectin benzoate (SLICEH, Schering Plough Animal Health). The results show that although sea lice infestations are reduced following the application of emamectin benzoate, not all treatments are effective. Specifically there is evidence of variation across geographical regions and a reduction in efficacy over time. Reduced sensitivity and potential resistance to currently available medicines are constant threats to maintaining control of sea lice populations on Atlantic salmon farms. There is a need for on-going monitoring of emamectin benzoate treatment efficacy together with reasons for any apparent reduction in performance. In addition, strategic rotation of medicines should be encouraged and empirical evidence for the benefit of such strategies more fully evaluated
PS-dependent decryption of TF mutant lacking the PS-interactive residues.
No full textTHP-1 cells expressing equal amounts of wild-type TF (TF WT) or TF mutant of the lipid binding region (TFLBR) were treated with a control vehicle or HgCl2 (100 μM for 5 min) in the presence or absence of annexin V (400 nM). TF-FVIIa activation of FX was measured by adding FVIIa (10 nM) and FX (175 nM) to the cells. In parallel wells, cells were incubated with 125I-labeled TF mAb 9C3 to measure TF protein expression levels on the cell surface. The data obtained in these two assays were used to calculate the specific activity of wild-type and mutant TF. The data shown in the figure represents the mean ± SEM from 3 independent experiments performed in duplicate.</p
- …
