VUV PROPERTIES OF Eu3+- DOPED YBO3 PHOSPHOR PREPARED VIA ALDO-KETO AND SOLID-STATE PROCESS

The Eu3+ doped YBO3 was prepared by the novel aldo-keto method. The structure and VUV luminescence properties of the title compound were studied and compared to the corresponding properties of the materials prepared by a conventional solid state reaction. The use of novel aldo-keto method in preparation lowered the reaction threshold temperature by c.a. 300oC. The YBO3 phosphor from the aldo-keto method look like evenly sized spherical structures, whereas those from the solid-state process look like some agglomerates of little spheres. The Eu3+-doped YBO3 phosphors prepared by both methods showed the red emission with peak around 592, 611 and 627 nm at excitations wavelengths 147 and172 nm, which corresponds to the transitions from the excited 5D0 level to the 7FJ (J = 1, 2, 3, 4) levels of Eu3+ activators. However, the emission intensity of the Eu3+ doped YBO3 from the aldo-keto system is about 2 times as much as that from the sold-state process

EVALUATION OF BIOLOGICAL ACTIVITIES OF NANOCRYSTALLINE TETRAGONAL ZIRCONIA SYNTHESIZED VIA SOL-GEL METHOD

Objective: The objective of the following study was a synthesis of nanocrystalline tetragonal zirconia (ZrO2) using simple sol–gel method and evaluation of its structural and biological properties.Methods: The sample was characterized by X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and evaluated for cell growth study using 3T3 mouse fibroblast cells and for degradation using Phosphate Buffered Saline (PBS) solution. The synthesized materials were also evaluated for their antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacterial strains.Results: The XRD pattern shows that the tetragonal phase of nanocrystalline zirconia was obtained at relatively low temperature i.e. 300 °C. The FESEM images showed that the prepared sample consists of particles in the range of 35-69 nm and homogenous particle size distribution. The TEM images confirmed the results shown by FESEM images. The sample of zirconia has excellent tissue biocompatibility, higher cell growth and does not show the toxicity towards normal 3T3 mouse fibroblast cells. The result of qualitative antibacterial tests revealed that the nanocrystalline zirconia had an important inhibitory activity on E. coli and S. aureus. The sample shows stability at the physiological condition and does not show degradation.Conclusion: Nanocrystalline tetragonal zirconia shows higher cell growth and efficient antibacterial activity against E. coli and S. aureus bacterial pathogen and also it is stable at the physiological condition. Hence, it can be used for various biomedical applications.Keywords: Nanocrystalline zirconia, Sol-gel route, Antimicrobial action, Biomedical applicatio

Categorizing and comparing psychophysical detection strategies based on biomechanical responses to short postural perturbations

<p>Abstract</p> <p>Background</p> <p>A fundamental unsolved problem in psychophysical detection experiments is in discriminating guesses from the correct responses. This paper proposes a coherent solution to this problem by presenting a novel classification method that compares biomechanical and psychological responses.</p> <p>Methods</p> <p>Subjects (13) stood on a platform that was translated anteriorly 16 mm to find psychophysical detection thresholds through a Adaptive 2-Alternative-Forced-Choice (2AFC) task repeated over 30 separate sequential trials. Anterior-posterior center-of-pressure (APCoP) changes (i.e., the biomechanical response R_B) were analyzed to determine whether sufficient biomechanical information was available to support a subject's psychophysical selection (R_Ψ) of interval 1 or 2 as the stimulus interval. A time-series-bitmap approach was used to identify anomalies in interval 1 (a₁) and interval 2 (a₂) that were present in the resultant APCoP signal. If a₁> a₂then R_B= Interval 1. If a₁< a₂, then R_B= Interval 2. If a₂- a₁< 0.1, R_Bwas set to 0 (no significant difference present in the anomaly scores of interval 1 and 2).</p> <p>Results</p> <p>By considering both biomechanical (R_B) and psychophysical (R_Ψ) responses, each trial run could be classified as a: 1) HIT (and True Negative), if R_Band R_Ψboth matched the stimulus interval (SI); 2) MISS, if R_Bmatched SI but the subject's reported response did not; 3) PSUEDO HIT, if the subject signalled the correct SI, but R_Bwas linked to the non-SI; 4) FALSE POSITIVE, if R_B= R_Ψ, and both associated to non-SI; and 5) GUESS, if R_B= 0, if insufficient APCoP differences existed to distinguish SI. Ensemble averaging the data for each of the above categories amplified the anomalous behavior of the APCoP response.</p> <p>Conclusions</p> <p>The major contributions of this novel classification scheme were to define and verify by logistic models a 'GUESS' category in these psychophysical threshold detection experiments, and to add an additional descriptor, "PSEUDO HIT". This improved classification methodology potentially could be applied to psychophysical detection experiments of other sensory modalities.</p

Individual rules for trail pattern formation in Argentine ants (Linepithema humile)

We studied the formation of trail patterns by Argentine ants exploring an empty arena. Using a novel imaging and analysis technique we estimated pheromone concentrations at all spatial positions in the experimental arena and at different times. Then we derived the response function of individual ants to pheromone concentrations by looking at correlations between concentrations and changes in speed or direction of the ants. Ants were found to turn in response to local pheromone concentrations, while their speed was largely unaffected by these concentrations. Ants did not integrate pheromone concentrations over time, with the concentration of pheromone in a 1 cm radius in front of the ant determining the turning angle. The response to pheromone was found to follow a Weber's Law, such that the difference between quantities of pheromone on the two sides of the ant divided by their sum determines the magnitude of the turning angle. This proportional response is in apparent contradiction with the well-established non-linear choice function used in the literature to model the results of binary bridge experiments in ant colonies (Deneubourg et al. 1990). However, agent based simulations implementing the Weber's Law response function led to the formation of trails and reproduced results reported in the literature. We show analytically that a sigmoidal response, analogous to that in the classical Deneubourg model for collective decision making, can be derived from the individual Weber-type response to pheromone concentrations that we have established in our experiments when directional noise around the preferred direction of movement of the ants is assumed.Comment: final version, 9 figures, submitted to Plos Computational Biology (accepted

Nutritional upgrading for omnivorous carpenter ants by the endosymbiont Blochmannia

<p>Abstract</p> <p>Background</p> <p>Carpenter ants (genus <it>Camponotus</it>) are considered to be omnivores. Nonetheless, the genome sequence of <it>Blochmannia floridanus</it>, the obligate intracellular endosymbiont of <it>Camponotus floridanus</it>, suggests a function in nutritional upgrading of host resources by the bacterium. Thus, the strongly reduced genome of the endosymbiont retains genes for all subunits of a functional urease, as well as those for biosynthetic pathways for all but one (arginine) of the amino acids essential to the host.</p> <p>Results</p> <p>Nutritional upgrading by <it>Blochmannia </it>was tested in 90-day feeding experiments with brood-raising in worker-groups on chemically defined diets with and without essential amino acids and treated or not with antibiotics. Control groups were fed with cockroaches, honey water and Bhatkar agar. Worker-groups were provided with brood collected from the queenright mother-colonies (45 eggs and 45 first instar larvae each). Brood production did not differ significantly between groups of symbiotic workers on diets with and without essential amino acids. However, aposymbiotic worker groups raised significantly less brood on a diet lacking essential amino acids. Reduced brood production by aposymbiotic workers was compensated when those groups were provided with essential amino acids in their diet. Decrease of endosymbionts due to treatment with antibiotic was monitored by qRT-PCR and FISH after the 90-day experimental period. Urease function was confirmed by feeding experiments using ¹⁵N-labelled urea. GC-MS analysis of ¹⁵N-enrichment of free amino acids in workers revealed significant labelling of the non-essential amino acids alanine, glycine, aspartic acid, and glutamic acid, as well as of the essential amino acids methionine and phenylalanine.</p> <p>Conclusion</p> <p>Our results show that endosymbiotic <it>Blochmannia </it>nutritionally upgrade the diet of <it>C. floridanus </it>hosts to provide essential amino acids, and that it may also play a role in nitrogen recycling via its functional urease. <it>Blochmannia </it>may confer a significant fitness advantage via nutritional upgrading by enhancing competitive ability of <it>Camponotus </it>with other ant species lacking such an endosymbiont. Domestication of the endosymbiont may have facilitated the evolutionary success of the genus <it>Camponotus</it>.</p

Friends and Foes from an Ant Brain's Point of View – Neuronal Correlates of Colony Odors in a Social Insect

Background: Successful cooperation depends on reliable identification of friends and foes. Social insects discriminate colony members (nestmates/friends) from foreign workers (non-nestmates/foes) by colony-specific, multi-component colony odors. Traditionally, complex processing in the brain has been regarded as crucial for colony recognition. Odor information is represented as spatial patterns of activity and processed in the primary olfactory neuropile, the antennal lobe (AL) of insects, which is analogous to the vertebrate olfactory bulb. Correlative evidence indicates that the spatial activity patterns reflect odor-quality, i.e., how an odor is perceived. For colony odors, alternatively, a sensory filter in the peripheral nervous system was suggested, causing specific anosmia to nestmate colony odors. Here, we investigate neuronal correlates of colony odors in the brain of a social insect to directly test whether they are anosmic to nestmate colony odors and whether spatial activity patterns in the AL can predict how odor qualities like ‘‘friend’’ and ‘‘foe’’ are attributed to colony odors. Methodology/Principal Findings: Using ant dummies that mimic natural conditions, we presented colony odors and investigated their neuronal representation in the ant Camponotus floridanus. Nestmate and non-nestmate colony odors elicited neuronal activity: In the periphery, we recorded sensory responses of olfactory receptor neurons (electroantennography), and in the brain, we measured colony odor specific spatial activity patterns in the AL (calcium imaging). Surprisingly, upon repeated stimulation with the same colony odor, spatial activity patterns were variable, and as variable as activity patterns elicited by different colony odors. Conclusions: Ants are not anosmic to nestmate colony odors. However, spatial activity patterns in the AL alone do not provide sufficient information for colony odor discrimination and this finding challenges the current notion of how odor quality is coded. Our result illustrates the enormous challenge for the nervous system to classify multi-component odors and indicates that other neuronal parameters, e.g., precise timing of neuronal activity, are likely necessary for attribution of odor quality to multi-component odors