2,958 research outputs found
Luminescent Naphthalene Diimide-Based Peptide in Aqueous Medium and in Solid State: Rewritable Fluorescent Color Code
No full textThis study convincingly demonstrates a unique example of the self-assembly of a naphthalene diimide (NDI)-appended peptide into a fluorescent J-aggregate in aqueous media. Moreover, this aggregated species shows a remarkable yellow fluorescence in solid state, an unusual phenomenon for NDI-based compounds. The aggregated species has been characterized using transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, X-ray diffraction, time-correlated single proton counting (TCSPC), UV-vis, and photoluminescence studies. TEM images reveal cross-linked nanofibrillar morphology of this aggregated species in water (pH 7.4). TCSPC study clearly indicates that the aggregated species in water has a higher average lifetime compared to that of the non-aggregated species. Interestingly, this NDI-based peptide shows H+ ion concentration-dependent change in the emission property in water. The fluorescence output is erased completely in the presence of an alkali, and it reappears in the presence of an acid, indicating its erasing and rewritable property. This indicates its probable use in authentication tools for security purposes as a rewritable fluorescence color code. This NDI-appended peptide-based molecule can be used for encryption of information due to erasing and rewritable property of the molecule in the aggregated state in aqueous medium
Complications and management in Descemet′s stripping endothelial keratoplasty: Analysis of consecutive 430 cases
No full textPurpose: To analyze the complications and their managements in Descemet′s stripping endothelial keratoplasty (DSEK) in consecutive 430 cases by single surgeon in a tertiary eye hospital. Materials and Methods: 430 eyes of 366 patients with endothelial dysfunctions scheduled for DSEK, were analyzed retrospectively. In all cases donor dissection was performed manually, and ′Taco′ insertion and unfolding technique was used. Intra-operative and postoperative complications with their managements and outcomes were reviewed retrospectively. Periodic endothelial cell density was analyzed for each patient till the last visit. Follow-up period was between 3 to 60 months (mean 18.7 months). Results: 13 (3.0%) eyes had operative complications during donor dissection and 16 (3.7%) had during recipient procedure. In 7 (1.6%) eyes, donor lenticule was replaced with a new one during the surgery. In early postoperative period, 21 (4.9%) eyes had donor dislocation and 12 (2.8%) eyes had air-induced pupillary block; and they were managed immediately. 2 cases had primary graft failure and in 1 case had postoperative bacterial endophthalmitis requiring evisceration. In late postoperative period, 48 (11.3%) eyes had secondary glaucoma and 14 (3.3%) eyes had late secondary graft failure. Endothelial rejection occurred in 5 (1.2%) cases. Mean endothelial cell loss was 19.7% after 3 months and 54.2% after 5 years. Total graft failure in this series was 31 (7.2%) and in 17 cases re-DSEK was performed successfully. Conclusions: Both operative and postoperative complications do occur in DSEK. Most of these complications can be managed by medical or appropriate surgical means. Some of the complications can be avoided and reduced with experience
Benzene fused monocyclic enediynyl amides: synthesis, reactivity and DNA-Cleavage activity in comparison to the corresponding sulfonamides
No full textMonocyclic enediynyl amides 2a-2c have been synthesized via the corresponding free amine 5. Kinetic studies in chloroform revealed the reactivity of these amides towards Bergman cyclization to be less than that of the corresponding sulfonamides. However, differential scanning calorimetry (DSC) measurements in the solid state and DNA-cleavage studies in aqueous buffer showed higher reactivity for the amides than the sulphonamides
Brain activation during dual-task processing is associated with cardiorespiratory fitness and performance in older adults
No full textCitation: Wong, C. N., Chaddock-Heyman, L., Voss, M. W., Burzynska, A. Z., Basak, C., Erickson, K. I., . . . Kramer, A. F. (2015). Brain activation during dual-task processing is associated with cardiorespiratory fitness and performance in older adults. Frontiers in Aging Neuroscience, 7, 10. doi:10.3389/fnagi.2015.00154Higher cardiorespiratory fitness is associated with better cognitive performance and enhanced brain activation. Yet, the extent to which cardiorespiratory fitness-related brain activation is associated with better cognitive performance is not well understood. In this cross-sectional study, we examined whether the association between cardiorespiratory fitness and executive function was mediated by greater prefrontal cortex activation in healthy older adults. Brain activation was measured during dual-task performance with functional magnetic resonance imaging in a sample of 128 healthy older adults (59-80 years). Higher cardiorespiratory fitness was associated with greater activation during dual-task processing in several brain areas including the anterior cingulate and supplementary motor cortex (ACC/SMA), thalamus and basal ganglia, right motor/somatosensory cortex and middle frontal gyrus, and left somatosensory cortex, controlling for age, sex, education, and gray matter volume. Of these regions, greater ACC/SMA activation mediated the association between cardiorespiratory fitness and dual-task performance. We provide novel evidence that cardiorespiratory fitness may support cognitive performance by facilitating brain activation in a core region critical for executive function
Failure mechanisms in lithium silicon batteries
No full textLithium silicon (Li-Si) batteries offer more than ten times the theoretical specific capacity compared to current lithium ion battery technologies, by using a silicon anode. In practice however, the cycle life of Li-Si batteries is very limited. The large volume change of the silicon anode is known to be the main reason for this. Research on the volume changes during varying cell cycles and voltages is presented in this thesis and an experimental set up for a quasi in situ study of the SEI layer is suggested. Cycling tests with an amorphous silicon thin film of 220 nm deposited using magnetron sputtering on a copper foil current collector confirmed that the major cause of capacity loss is swelling of the silicon during lithiation, causing the silicon to detach from the current collector and resulting in significant capacity loss. Increasing the lower cut off voltage from 0 V to 0.2 V resulted in a slight improvement of cycle life. Silicon detachment also decreased as determined by SEM images. EFTEM and EDX mapping showed a clear split between a partially lithiated silicon layer on the surface and a pure silicon layer on the current collector side. It can be concluded that discharging Li-Si batteries to 0.2 V instead of 0 V is a promising method to reduce the swelling of silicon during lithiation.HREMQuantum NanoscienceApplied Science
Hydrolysis of homocysteine thiolactone results in the formation of Protein‐Cys‐S‐S‐homocysteinylation
No full textAn increased level of homocysteine, a reactive thiol amino acid, is associated with several complex disorders and is an independent risk factor for cardiovascular disease. A majority (>80%) of circulating homocysteine is protein bound. Homocysteine exclusively binds to protein cysteine residues via thiol disulfide exchange reaction, the mechanism of which has been reported. In contrast, homocysteine thiolactone, the cyclic thioester of homocysteine, is believed to exclusively bind to the primary amine group of lysine residue leading to N-homocysteinylation of proteins and hence studies on binding of homocysteine thiolactone to proteins thus far have only focused on N-homocysteinylation. Although it is known that homocysteine thiolactone can hydrolyze to homocysteine at physiological pH, surprisingly the extent of S-homocysteinylation during the exposure of homocysteine thiolactone with proteins has never been looked into. In this study, we clearly show that the hydrolysis of homocysteine thiolactone is pH dependent, and at physiological pH, 1 mM homocysteine thiolactone is hydrolysed to ~0.71 mM homocysteine within 24 h. Using albumin, we also show that incubation of HTL with albumin leads to a greater proportion of S-homocysteinylation (0.41 mol/mol of albumin) than N-homocysteinylation (0.14 mol/mol of albumin). S-homocysteinylation at Cys34 of HSA on treatment with homocysteine thiolactone was confirmed using LC-MS. Further, contrary to earlier reports, our results indicate that there is no cross talk between the cysteine attached to Cys34 of albumin and homocysteine attached to lysine residues
Laboratory bioassay of six pesticides, an entomopathogenic fungus, and a botanical pesticide on two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)
No full textBasak, Rumpa, Akter, Mahbuba, Tumpa, Toufica A., Sharmin, Dilruba, Ullah, Mohammad S. (2021): Laboratory bioassay of six pesticides, an entomopathogenic fungus, and a botanical pesticide on two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Persian Journal of Acarology 10 (23): 269-280, DOI: 10.22073/pja.v10i3.6509
Stress in the interfaces of metal matrix composites (MMCs) in thermal and tensile loading
No full textThe influence of contents, sizes and shapes of reinforcements on the matrix-particle interfaces in terms of (a) von-Mises stress, (b) directions as well as spreading of principal stresses during cooling and under tension were analysed in this investigation through numerical simulation for SiC particle reinforced Al6061 matrix MMCs. The result shows that the rapid variation of von-Mises stress in the interfaces depends on the shape of reinforced particles. The interfaces in MMCs with triangular reinforcements experienced the slimiest stress variation. Nevertheless, the uppermost stress was intensified in the corners of the triangle shaped reinforcements. The shape of the reinforcements affects the stress vectors directions. The range of the von-Mises stress rises through the rise of particle amount and decrease of particles size at a constant number of particles. For nearly all the cases, excluding the MMCs with triangle reinforcements, when the stress rises, with the rise of the applied positive elongation, the stress scatterings are unaffected.A. Pramanik, A. K. Basak, G. Littlefair, A. R. Dixit, S. Chattopadhyay
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