Longwing butterflies, Heliconius sp., also called heliconians, are striking examples of diversity and mimicry in butterflies. Heliconians feature strongly colored patterns on their wings, arising ...from wing scales colored by pigments and/or nanostructures, which serve as an aposematic signal.
Here, we investigate the coloration mechanisms among several species of Heliconius by applying scanning electron microscopy, (micro)spectrophotometry, and imaging scatterometry. We identify seven kinds of colored scales within Heliconius whose coloration is derived from pigments, nanostructures or both. In yellow-, orange- and red-colored wing patches, both cover and ground scales contain wavelength-selective absorbing pigments, 3-OH-kynurenine, xanthommatin and/or dihydroxanthommatin. In blue wing patches, the cover scales are blue either due to interference of light in the thin-film lower lamina (e.g., H. doris) or in the multilayered lamellae in the scale ridges (so-called ridge reflectors, e.g., H. sara and H. erato); the underlying ground scales are black. In the white wing patches, both cover and ground scales are blue due to their thin-film lower lamina, but because they are stacked upon each other and at the wing substrate, a faint bluish to white color results. Lastly, green wing patches (H. doris) have cover scales with blue-reflecting thin films and short-wavelength absorbing 3-OH-kynurenine, together causing a green color.
The pigmentary and structural traits are discussed in relation to their phylogenetic distribution and the evolution of vision in this highly interesting clade of butterflies.
Background and AimsSpatial (herkogamy) and temporal (dichogamy) separation of pollen presentation and stigma receptivity have been interpreted as reducing interference between male and female ...functions in hermaphroditic flowers. However, spatial separation leads to a potential conflict: reduced pollination accuracy, where pollen may be placed in a location on the pollinator different from the point of stigma contact.MethodsTo understand better how herkogamous flowers resolve this conflict, a study was made of a subalpine herb, Parnassia epunctulata, the nectariferous flowers of which exhibit sequential anther dehiscence (staggered pollen presentation) and stamen movements; usually one newly dehisced anther is positioned each day over the central gynoecium, while the older stamens bend away from the central position.Key ResultsThe open flowers were visited by a variety of pollinators, most of which were flies. Seed set was pollinator-dependent (bagged flowers set almost no seeds) and pollen-limited (manual pollination increased seed set over open pollination). Analyses of adaptive accuracy showed that coordinated stamen movements and style elongation (movement herkogamy) dramatically increased pollination accuracy. Specifically, dehiscing anthers and receptive stigmas were positioned accurately in the vertical and horizontal planes in relation to the opposite sexual structure and pollinator position. By contrast, the spatial correspondence between anthers and stigma was dramatically lower before the anthers dehisced and after stamens bent outwards, as well as before and after the period of stigmatic receptivity.ConclusionsIt is shown for the first time that a combination of movement herkogamy and dichogamy can maintain high pollination accuracy in flowers with generalized pollination. Staggered pollen and stigma presentation with spatial correspondence can both reduce sexual interference and improve pollination accuracy.
Abstract
Background
The value of virtual reality (VR) simulators for robot-assisted surgery (RAS) for skill assessment and training of surgeons has not been established. This systematic review and ...meta-analysis aimed to identify evidence on transferability of surgical skills acquired on robotic VR simulators to the operating room and the predictive value of robotic VR simulator performance for intraoperative performance.
Methods
MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science were searched systematically. Risk of bias was assessed using the Medical Education Research Study Quality Instrument and the Newcastle–Ottawa Scale for Education. Correlation coefficients were chosen as effect measure and pooled using the inverse-variance weighting approach. A random-effects model was applied to estimate the summary effect.
Results
A total of 14 131 potential articles were identified; there were eight studies eligible for qualitative and three for quantitative analysis. Three of four studies demonstrated transfer of surgical skills from robotic VR simulators to the operating room measured by time and technical surgical performance. Two of three studies found significant positive correlations between robotic VR simulator performance and intraoperative technical surgical performance; quantitative analysis revealed a positive combined correlation (r = 0.67, 95 per cent c.i. 0.22 to 0.88).
Conclusion
Technical surgical skills acquired through robotic VR simulator training can be transferred to the operating room, and operating room performance seems to be predictable by robotic VR simulator performance. VR training can therefore be justified before operating on patients.
Graphical Abstract
Graphical Abstract
This systematic review and meta-analysis presents current evidence on transferability of surgical skills acquired on robotic VR simulators to the real operating room, and on the predictability of intraoperative performance by robotic VR simulator performances. The limited data currently available support the use of robotic VR simulators for surgical skill acquisition and assessment.
This systematic review and meta-analysis presents current evidence on transferability of surgical skills acquired on robotic VR simulators to the real operating room, and on the predictability of intraoperative performance by robotic VR simulator performances. The limited data currently available support the use of robotic VR simulators for surgical skill acquisition and assessment.
Inconsistency handling is one of the central problems in many areas of AI. There are different approaches to dealing with contradictions and other types of inconsistency. In this paper, we develop an ...approach based on logical varieties and prevarieties, which are complex structures constructed from logical calculi. Being locally isomorphic to a logical calculus, globally logical varieties form a logical structure, which allows representation of inconsistent knowledge in a consistent way and provides much more flexibility and efficacy for AI than standard logical methods. Problems of logical variety immersion into a logical calculus are studied. Such immersions extend the local structure of a logical calculus to the global structure of a logical variety. The obtained results demonstrate when it is possible to use standard logical tools, such as logical calculi, and when it is necessary to go beyond this traditional technique. Finally a particular logical variety, the Logic of Reasonable Inferences, applied to the design of legal knowledge based systems is described.
Cysteine desulfurases, designated NifS, IscS, and SufS, cleave l-cysteine to form alanine and an enzyme cysteinyl persulfide intermediate. Genetic studies on the photosynthetic cyanobacterium ...Synechocystis sp. PCC 6803 have shown that of the three Nif/Isc/SufS-like proteins encoded in its genome only the sequence group II protein, Slr0077/SufS, is essential. This protein has been overexpressed in Escherichia coli, purified to homogeneity, shown to bind pyridoxal-5‘-phosphate (PLP) and to catalyze cysteine desulfuration, and characterized in terms of its structure and kinetics. The results suggest that catalysis in the absence of accessory factors has two constituent pathways, one involving nucleophilic attack by C372 to form the Slr0077/SufS-bound cysteinyl persulfide intermediate and the second involving intermolecular attack by the sulfur of a second molecule of the substrate on the initial l-cysteine−PLP complex to form free l-cysteine persulfide. The second pathway is operant in the C372A variant protein, explaining why it retains significant activity, which is proportional to the concentration of l-cysteine (i.e., does not saturate). C−S bond cleavage by the first (normal) pathway is considerably less efficient than the equivalent step in a group I desulfurase (Slr0387) from the same organism (characterized in the accompanying paper). The 1.8 Å crystal structure of the protein, which is very similar to that previously reported for E. coli SufS, shows that the loop on which C372 resides is well-ordered and shorter by 11 residues than the corresponding disordered loop of the group I NifS-like protein from Thermotoga maritima. Sequence comparisons establish that the T. maritima and Slr0387 proteins have loops of similar length. The combined structural and kinetic data imply that the modest activity of Slr0077/SufS and other SufS proteins in comparison to their sequence group I (NifS/IscS-like) paralogues results from inefficiency in the nucleophilic attack step associated with differences in the structure or dynamics of this loop. The recent reports that SufS proteins can be activated manyfold by binding to SufE thus implies that the accessory protein either accelerates nucleophilic attack by the conserved cysteine residue of SufS by a conformational mechanism or itself contributes a nucleophilic cysteine for more efficient intermolecular attack.
A marked difference in the cellular response of Spodoptera exigua was observed when larvae were challenged with the insect mycopathogen Beauveria bassiana versus the yeast Candida albicans. Both ...fungi were rapidly phagocytized by circulating hemocytes. The relative growth rate of C. albicans as measured by daughter cell formation was partially suppressed, whereas B. bassiana blastospores produced germ tubes at rates equivalent to those under in vitro conditions. Limited growth by C. albicans within the phagocytic cells stimulated nodulation by hemocytes resulting in the protection of challenged larvae to C. albicans. Alternatively, B. bassiana suppressed the spreading ability of S. exigua hemocytes. These suppressed larvae, while capable of phagocytizing C. albicans, were unable to produce multicellular nodules. Circulating vegetative cells of both C. albicans and B. bassiana were observed to proliferate within these immunosuppressed host larvae
Vertical Cavity Surface Emitting Lasers (VCSELs) are interesting lasers for engineering applications as well as for the study of quantum phenomena. Their quantum noise properties are still under ...discussion. We present calculations of the performances of VCSELs as squeezed states generator using a semiclassical model for the noise properties of semiconductor lasers. The existence of two polarisation modes P and S is considered using a two‐mode model. The ratio S/P of the power in each polarisation mode is found to be the appropriate parameter to account for the strong influence of polarisation properties on the amplitude noise spectra as well as the correlation between the amplitude fluctuations of the two modes. Either a ratio S/P close to 1 or close to 0 is necessary to get the best squeezing performances. Experimental investigations support these conclusions, showing a strong link between amplitude noise and polarisation properties.
For pt.I see ibid., vol.33, no.11, p.2097-2104 (1997). We present noise studies of distributed feedback (DFB) laser structures, where spatial hole burning (SHB) plays a key role performed using the ...model described in part I of this paper with particular emphasis on the influence of SHB, on the coupling coefficient /spl kappa/L, and on the laser facet reflectivities. These structures exhibit high amplitude noise and the possible noise reduction is strongly reduced compared to Fabry-Perot structures. Distributed Bragg reflector (DBR) lasers are better candidates even if their performances are also strictly determined by SHB and the loss in the Bragg reflector. Finally, limitations due to gain suppression are demonstrated for such complex lasers structures. We conclude on the optimum laser structure for amplitude squeezed states generation.
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