19672 research outputs found
Sort by
Photophysical and Electroluminescence Characteristics of Polyfluorene Derivatives with Triphenylamine
No full textIn this work, polymers of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-triphenylamine] with side chains containing: pyrene (C1), diphenyl (C2), naphthalene (C3), and isopropyl (C6) structures were synthesized via a Suzuki coupling reaction. The structures were verified using NMR and cyclic voltammetry measurements provide the HOMO and LUMO of the polymers. The polymer with pyrene (C1) and naphthalene (C3) produced photoluminescence in the green while the polymer with the side chain containing diphenyl (C2) and isopropyl (C6) produce dual emission peaks of blue-green photoluminescence (PL). In order to examine the electroluminescence properties of the polymers, the solutions were spin-coated onto patterned ITO anode, dried, and subsequently coated with an Al cathode layer to form pristine single layer polymer LEDs. The results are compared to a standard PFO sample. The electroluminescence spectra resemble the PL spectra for C1 and C3. The devices of C2, C3, and C6 exhibit voltage-dependent EL. An additional red emission peak was detected for C2 and C6, resulting in spectra with peaks at 435 nm, 490 nm, and 625 nm. The effects of the side chains on the spectral characteristics of the polymer are discussed
Self‐Healing Polyester Urethane Supramolecular Elastomers Reinforced with Cellulose Nanocrystals for Biomedical Applications
No full textStretchable self-healing urethane-based biomaterials have always been crucial for biomedical applications; however, the strength is the main constraint of utilization of these healable materials. Here, a series of novel, healable, elastomeric, supramolecular polyester urethane nanocomposites of poly(1,8-octanediol citrate) and hexamethylene diisocyanate reinforced with cellulose nanocrystals (CNCs) are introduced. Nanocomposites with various amounts of CNCs from 10 to 50 wt% are prepared using solvent casting technique followed by the evaluation of their microstructural features, mechanical properties, healability, and biocompatibility. The synthesized nanocomposites indicate significantly higher tensile modulus (approximately 36–500-fold) in comparison to the supramolecular polymer alone. Upon exposure to heat, the materials can reheal, but nevertheless when the amount of CNC is greater than 10 wt%, the self-healing ability of nanocomposites is deteriorated. These materials are capable of rebonding ruptured parts and fully restoring their mechanical properties. In vitro cytotoxicity test of the nanocomposites using human dermal fibroblasts confirms their good cytocompatibility. The optimized structure, self-healing attributes, and noncytotoxicity make these nanocomposites highly promising for tissue engineering and other biomedical applications
A Community-Based Fault Isolation Approach for Effective Simultaneous Localization of Faults
No full textDuring program testing, software programs may be discovered to contain multiple faults. Multiple faults in a program may reduce the effectiveness of the existing fault localization techniques due to the complex relationship between faults and failures in the presence of multiple faults. In an ideal case, faults are isolated into fault-focused clusters, each targeting a single fault for developers to localize them simultaneously in parallel. However, the relationship between faults and failures is not easily identified and depends solely on the accuracy of clustering, such as existing clustering algorithms are not able to isolate failed tests to their causative faults effectively which hinder localization effectiveness. This paper proposes a new approach that makes use of a divisive network community clustering algorithm to isolate faults into separate fault-focused communities that target a single fault each. A community weighting and a selection mechanism that aids in prioritizing highly important fault-focused communities to the available developers to debug the faults simultaneously in parallel is also proposed. The approach is evaluated on eight subject programs ranging from medium-sized to large-sized programs (tcas, replace, gzip, sed, flex, grep, make, and ant). Overall, 540 multiple-fault versions of these programs were generated with 2-5 faulty versions. The experimental results have demonstrated that the proposed approach performs significantly better in terms of localization effectiveness in comparison with two other parallel debugging approaches for locating multiple faults in parallel
Synthesis and characterization of Ti-doped MgMn2O4 cathode material for magnesium ion batteries
No full textMagnesium batteries demonstrate potential candidate for next-generation energy storage devices because of their high energy density and low raw-materials costs. In comparison with lithium, magnesium is inherently much safer due to its air stable and environmental friendly. In the present work, magnesium manganese oxide (MgMn 2 O 4 ) with Ti-doped was synthesized by a self-propagating combustion method using citric acid as a reducing agent. The precursors of MgMn 2 O 4 and MgMn (2-x) Ti x O 4 , (x = 0.1) were annealed at 700 °C for 24 h. The prepared samples were further characterized by using Simultaneous Thermal Analysis (STA), X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). Then, the optimized sample was used as cathode in magnesium ion battery using polymer-based electrolyte. The charge-discharge profile of the fabricated battery was discussed
Effects of palbociclib on oral squamous cell carcinoma and the role of PIK3CA in conferring resistance
No full textObjective: Lack of effective therapies remains a problem in the treatment of oral squamous cell carcinoma (OSCC), especially in patients with advanced tumors. OSCC development is driven by multiple aberrancies within the cell cycle pathway, including amplification of cyclin D1 and loss of p16. Hence, cell cycle inhibitors of the CDK4/6-cyclin D axis are appealing targets for OSCC treatment. Here, we determined the potency of palbociclib and identified genetic features that are associated with the response of palbociclib in OSCC. Methods: The effect of palbociclib was evaluated in a panel of well-characterized OSCC cell lines by cell proliferation assays and further confirmed by in vivo evaluation in xenograft models. PIK3CA-mutant isogenic cell lines were used to investigate the effect of PIK3CA mutation towards palbociclib response. Results: We demonstrated that 80% of OSCC cell lines are sensitive to palbociclib at sub-micromolar concentrations. Consistently, palbociclib was effective in controlling tumor growth in mice. We identified that palbociclib-resistant cells harbored mutations in PIK3CA. Using isogenic cell lines, we showed that PIK3CA mutant cells are less responsive to palbociclib as compared to wild-type cells with concurrent upregulation of CDK2 and cyclin E1 protein levels. We further demonstrated that the combination of a PI3K/mTOR inhibitor (PF-04691502) and palbociclib completely controlled tumor growth in mice. Conclusions: This study demonstrated the potency of palbociclib in OSCC models and provides a rationale for the inclusion of PIK3CA testing in the clinical evaluation of CDK4/6 inhibitors and suggests combination approaches for further clinical studies
Evidence of Increased Hydrophobicity and Dynamics inside the Tail Region of Glycolipid Self-Assemblies Using 2-n-Alkyl-Pyrene Derivatives to Probe Different Locations
No full textNew designer biofluorophores are being increasingly used in the investigation of complex cellular processes. In this study, we utilized new derivatives of pyrene (Py), i.e., 2-n-alkyl-pyrenes (Py-C4 and Py-C8), in order to probe different regions inside the hydrophobic tail of n-dodecyl β-d-maltoside (βMal-C12) in two different phases (cubic ↔ lamellar). Although the sensitivity to the local environment is reduced compared to that of Py, attaching C4 and C8 at the 2-position of Py can provide a possible means to probe the local hydrophobicity in different parts of the tail region. The absence of excimer fluorescence and the ratio of the vibronic fluorescence peak intensities (I1/I3) in a lipid environment indicate the existence of Py as monomers in the hydrophobic region, similar to hydrophobic solvation, yet close to the headgroup region. When Py is replaced by Py-C4 and Py-C8, there is a small increase in hydrophobicity (reduction in I1/I3) as the Py moiety is pulled deeper inside the tail region of both cubic and lamellar phases. The larger space of the tail region in the lamellar phase is reflected as more local hydrophobicity measured by the probes which can penetrate deep inside, whereas the curved structure of the cubic phase limits the available space for the probes. Three fluorescence lifetime components were measured in lipid, indicating the heterogeneous nature of the hydrophobic region. In the lamellar phase, a large reduction in the average lifetime value, led by the long decay component, was measured for Py-C4 (reduction by 25%) and Py-C8 (45%) compared to that of the parent Py. This observation suggests the presence of a mechanism of interaction more collisional than static between the Py moiety and the tail region of the bilayer unit due to the ample space provided by the lamellar phase as the probe is buried deeper inside the hydrophobic region. A much smaller effect was observed in the cubic phase and was correlated with the tight environment around the probes, which stems from the increased curvature of the cubic phase. The current results provide a deeper understanding of the hydrophobic region during phase transition of lipid self-assembly which is important for better control during the process of membrane-protein crystallization
Detection of Formaldehyde Vapor Using Glass Substrate Coated With Zinc Oxide Nanorods
No full textA glass substrate coated with ZnO nanorods via a hydrothermal method for formaldehyde vapor sensing is reported. The proposed sensor device was characterized against formaldehyde vapor concentrations varying from 1% to 5% with a reference point as 0% (pure water) at room temperature. A significant sensing response was observed where the output voltage reduced by 0.0856 V via scattering effect by ZnO nanorods upon exposure to the maximum tested concentration (5%). The sensitivity and linearity of the sensing response were recorded to be approximate values of -0.0168 V/% and 98.06% correspondingly. The sensor device was found to have good measurement stability in measuring as low as 1% of concentration for a prolonged time of 600 s. This proposed sensor has potential applications in monitoring air pollution caused not only by formaldehyde vapor but also by other harmful and toxic vapors or gases
Observed Trends in Extreme Temperature over the Klang Valley, Malaysia
No full textThis study investigates the recent extreme temperature trends across 19 stations in the Klang Valley, Malaysia, over the period 2006–16. Fourteen extreme index trends were analyzed using the Mann-Kendall non-parametric test, with Sen’s slope as a magnitude estimator. Generally, the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature in the Klang Valley increased significantly, by 0.07°C yr−1, 0.07°C yr−1 and 0.08°C yr−1, respectively. For the warm temperature indices, the results indicated a significant upward trend for the annual maximum of maximum temperature, by 0.09°C yr−1, and the annual maximum of minimum temperature, by 0.11°C yr−1. The results for the total number of warm days and warm nights showed significant increasing trends of 5.02 d yr−1 and 6.92 d yr−1, respectively. For the cold temperature indices, there were upward trends for the annual minimum of maximum temperature, by 0.09°C yr−1, and the annual minimum of minimum temperature, by 0.03°C yr−1, concurrent with the decreases in the total number cold days (TX10P), with −3.80 d yr−1, and cold nights (TN10P), with −4.33 d yr−1. The 34°C and 37°C summer days results showed significant upward trends of 4.10 d yr−1 and 0.25 d yr−1, respectively. Overall, these findings showed upward warming trends in the Klang Valley, with the minimum temperature rate increasing more than that of the maximum temperature, especially in urban areas. © 2019, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature
Regenerated grating produced in a multimaterial glass-based photosensitive fiber with an ultrahigh thermal regeneration ratio
No full textThis work demonstrates thermal regeneration of gratings inscribed in a new type of multi-material glass-based photosensitive fiber. And isothermal annealing procedure has been carried out on a type-I seed grating (SG) imprinted in erbium-doped zirconia-yttria-aluminagermanium (Er-ZYAG) silica glass-based fiber, which is initiated from room temperature of 25°C up to 900°C. The findings show that the created regenerated grating (RG) has an ultrahigh thermal regeneration ratio with a value of 0.72. © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Decision to adopt online collaborative learning tools in higher education: A case of top Malaysian universities
No full textRecently cloud computing has received significant attention, but its adoption is still far from reaching its full potential, especially in educational contexts. Only a few studies have considered the students’ behavior toward adoption of cloud technology in particular for online collaborative learning purposes. Therefore, this research seeks to develop an adoption model for online collaborative learning tools in cloud environment. To this end, Technology Acceptance Model (TAM) is extended by adding mobility, collaboration, and personalization as external variables. A sample of 209 respondents is collected from four top Malaysian universities and Structural Equation Modelling (SEM) is utilized to assess the research model. The findings show that intention to adopt is significantly affected by perceived usefulness. Although, perceived ease of use does not perform a direct impact on intention to adopt, its indirect influence through perceived usefulness is supported. Mobility and personalization significantly influence perceived ease of use, but they have insignificant impacts on perceived usefulness. Furthermore, perceived usefulness and perceived ease of use are significantly influenced by collaboration. This study rounds off with discussion and conclusions, highlighting implications. The findings provide a baseline for cloud service providers and education institutions in providing effective online collaborative learning tools. © 2018, Springer Science+Business Media, LLC, part of Springer Nature