Chlorophylls and Bacteriochlorophylls: Biochemistry, Biophysics, Functions and Applications

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The Relative Effects of General versus Descriptive Praise on a Card Sorting Task

It has frequently been postulated that descriptive praise, which labels the behavior being praised, is superior to general praise, which delivers an accolade without specifying the behavior being praised. Research investigating this postulate is meager. The purpose of this study was to investigate whether in fact descriptive praise is superior to general praise. Fifty fifth- and sixth-grade students from the Lida Lee Tall Center in Towson, Maryland were randomly selected to serve as subjects. Twelve boys and eight girls were randomly assigned to each of two praise conditions (i.e. descriptive praise and general praise) and six boys and four girls were randomly assigned to a control condition. Subjects were seen individually and pretested to ensure they could perform the experimental task. The assigned task was to sort 108 cards by one of three possible sorting methods. The first 54 card sorts served as a baseline to determine the preferred sorting method for each subject. During the final 54 card sorts, subjects in the two praise conditions received either general praise (e.g. "Great") or descriptive praise (e.g. "Great. I like the way you are sorting by shape") on a FR3 schedule for sorting cards by a randomly selected sorting method. Baseline data were collected for the entire 108 card sorts in the control condition. Multivariate analyses of variance were carried out on the extent to which the three groups changed their sorting method from their baseline method and on the extent to which the two praise groups sorted by the method they were reinforced for. The results indicated that the descriptive praise group performed significantly better than both the general praise and control groups. No significant difference emerged between the general praise and control groups. The male and female subjects did not significantly differ in their response to the two praise conditions. These results support the position that descriptive praise is more effective than general praise. It was suggested that the labeling of the behavior being reinforced in descriptive praise increased the informative value of the reinforcer thereby giving subjects in this condition an advantage over the subjects receiving general praise who had to, in effect, guess what response on their part elicited the praise

Arterial spin labelling MRI for assessment of cerebral perfusion in children with moyamoya disease: comparison with dynamic susceptibility contrast MRI

Introduction: This study seeks to evaluate the diagnostic accuracy of cerebral perfusion imaging with arterial spin labelling (ASL) MR imaging in children with moyamoya disease compared to dynamic susceptibility contrast (DSC) imaging. Methods: Ten children (7 females; age, 9.2 ± 5.4years) with moyamoya disease underwent cerebral perfusion imaging with ASL and DSC on a 3-T MRI scanner in the same session. Cerebral perfusion images were acquired with ASL (pulsed continuous 3D ASL sequence, 32 axial slices, TR = 5.5s, TE = 25ms, FOV = 24cm, matrix = 128 × 128) and DSC (gradient echo EPI sequence, 35 volumes of 28 axial slices, TR = 2,000ms, TE = 36ms, FOV = 24cm, matrix = 96 × 96, 0.2ml/kg Gd-DOTA). Cerebral blood flow maps were generated. ASL and DSC images were qualitatively assessed regarding perfusion of left and right ACA, MCA, and PCA territories by two independent readers using a 3-point-Likert scale and quantitative relative cerebral blood flow (rCBF) was calculated. Correlation between ASL and DSC for qualitative and quantitative assessment and the accuracy of ASL for the detection of reduced perfusion per territory with DSC serving as the standard of reference were calculated. Results: With a good interreader agreement (κ = 0.62) qualitative perfusion assessment with ASL and DSC showed a strong and significant correlation (ρ = 0.77; p < 0.001), as did quantitative rCBF (r = 0.79; p < 0.001). ASL showed a sensitivity, specificity and accuracy of 94%, 93%, and 93% for the detection of reduced perfusion per territory. Conclusion: In children with moyamoya disease, unenhanced ASL enables the detection of reduced perfusion per vascular territory with a good accuracy compared to contrast-enhanced DS

Radiation emitted by transverse-gradient undulators

Conventional undulators are used in synchrotron light sources to produce radiation with a narrow relative spectral width as compared to bending magnets or wigglers. The spectral width of the radiation produced by conventional undulators is determined by the number of undulator periods and by the energy spread and emittance of the electron beam. In more compact electron sources like for instance laser plasma accelerators the energy spread becomes the dominating factor. Due to this effect these electron sources cannot in general be used for high-gain free electron lasers (FELs). In order to overcome this limitation, modified undulator schemes, so-called transverse gradient undulators (TGUs), were proposed and a first superconducting TGU was built at Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany. In this paper simulations of the expected synchrotron radiation spectral distribution are presented. An experimental test with that device is under preparation at the laser wakefield accelerator at the JETI laser at the University of Jena, Germany

Identification of intramembrane hydrogen bonding between 131 keto group of bacteriochlorophyll and serine residue α27 in the LH2 light-harvesting complex

AbstractIntramembrane hydrogen bonding and its effect on the structural integrity of purple bacterial light-harvesting complex 2, LH2, have been assessed in the native membrane environment. A novel hydrogen bond has been identified by Raman resonance spectroscopy between a serine residue of the membrane-spanning region of LH2 α-subunit, and the C-131 keto carbonyl of bacteriochlorophyll (BChl) B850 bound to the β-subunit. Replacement of the serine by alanine disrupts this strong hydrogen bond, but this neither alters the strongly red-shifted absorption nor the structural arrangement of the BChls, as judged from circular dichroism. It also decreases only slightly the thermal stability of the mutated LH2 in the native membrane environment. The possibility is discussed that weak H-bonding between the C-131 keto carbonyl and a methyl hydrogen of the alanine replacing serine(−4) or the imidazole group of the nearby histidine maintains structural integrity in this very stable bacterial light-harvesting complex. A more widespread occurrence of H-bonding to C-131 not only in BChl, but also in chlorophyll proteins, is indicated by a theoretical analysis of chlorophyll/polypeptide contacts at <3.5 Å in the high-resolution structure of Photosystem I. Nearly half of the 96 chlorophylls have aa residues suitable as hydrogen bond donors to their keto groups

BIOSORPTION EVALUATION OF SYNTHETICDYE FROM FOOD INDUSTRY WASTEWATER ONTO SILKWORMCOCOONS: PRELIMINARY STUDIES

The aim of this study was to evaluate thesynthetic azo dye (tartrazine) biosorption onto second line silkworm cocoons. Batch adsorption system was used to investigate the effect of pH and initial tartrazine concentration in theliquid phase. Also, the kinetic mechanismwas investigated at 20°C and pH 2.0.The highest adsorption was obtained at the lowest pH evaluated, while the assays with pH above 3.0 did not show significant adsorption at the first hour of theprocess, indicating that biosorption is more favorable at lower values ofpH.The adsorption kinetic was studied at pH 2.0andcompared withthe kinetic mechanism ofconvective mass transfer and diffusion models.The kinetic behavior of biosorption process showed a high amount of dye adsorbedat the beginning of the process, however, after saturation of the functional groups, the adsorption rate decreased over time until saturation. After 24 hours of batch operation, the uptake of tartrazine onto silkworm cocoons was 40.39 mg g-1,and the rate of adsorption reduces from 3.430 to 0.003 mg min-1g-1, suggesting that the process approaches the equilibrium. The Crank model provided the best fit. The results revealed that silkworm cocoons have the potential to be used as a biosorbent for wastewater treatment containing tartrazin