19672 research outputs found
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Enhanced Optical Delay Line in Few-Mode Fiber Based on Mode Conversion Using Few-Mode Fiber Bragg Gratings
No full textIn this paper, we proposed an optical delay system based on a segment of few-mode fiber (FMF) and two FMF Bragg gratings (FMFBGs). The FMFBGs at both the ends of the FMF segment that serve as selective mode converters enable the pulse stream to double pass the FMF segment twice via access to the optical path length on LP11 mode in the FMF. The induced time delay by the proposed system is approximately four times the time delay of a single pass in the FMF segment. The proposed system has opened up a new horizon in the optical buffering technology for an optical communication system
Spectral studies of silver nanoparticles biosynthesized by Origanum majorana
No full textSilver nanoparticles (AgNPs) were biologically synthesized in an eco-friendly manner using aqueous leaf extract of Origanum majorana plant and silver nitrate (AgNO3) solution. Size, shape, and crystallinity of the biosynthesized AgNPs were determined by using a transmission electron microscope (TEM). Zeta potential analyzer was used to prove the stability of the metallic nanoparticles, while Fourier transform infrared spectroscopy was used to identify the bioreducing and capping agents. AgNPs were electrochemically investigated using cyclic voltammetry (CV), while the optical properties of the metallic nanoparticles were studied using UV-Vis and fluorescence spectroscopies. According to TEM images, AgNPs are spherical with an average size of 35 nm. TEM also refers to the presence of mono and polycrystalline AgNPs. The value of zeta potential (-39 mV) proved the stability of AgNPs caused by capping molecules of O. majorana plant. CV studies showed that AgNPs were electrochemically investigated at 0.39 mV. AgNPs showed a surface plasmon resonance peak at 440 nm, while the emission peak was detected at 466 nm. These nanoparticles are promising for many industrial and medical applications
Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system
No full textPurpose: There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives. Design/methodology/approach: In this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior. Findings: In additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil. Originality/value: In this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version
Properties of a certain subclass of starlike functions defined by a generalized operator
No full textIn this paper, we introduce the class Sα,λ n,s (β), consisting of analytic functions defined by a generalized operator. We derive coefficient inequalities, growth and distortion theorem, extreme points and Fekete-Szegö problem for functions in this class
Hyper-Expression of PD-1 Is Associated with the Levels of Exhausted and Dysfunctional Phenotypes of Circulating CD161++TCR iVα7.2+ Mucosal-Associated Invariant T Cells in Chronic Hepatitis B Virus Infection
No full textMucosal-associated invariant T (MAIT) cells, defined as CD161++TCR iVα7.2+ T cells, play an important role in the innate defense against bacterial infections, and their functionality is impaired in chronic viral infections. Here, we investigated the frequency and functional role of MAIT cells in chronic hepatitis B virus (HBV) infection. The peripheral CD3+CD161++TCR iVα7.2+ MAIT cells in chronic HBV-infected patients and healthy controls were phenotypically characterized based on CD57, PD-1, TIM-3, and CTLA-4, as well as HLA-DR and CD38 expression. The frequency of MAIT cells was significantly decreased among chronic HBV-infected individuals as compared to controls. Expression of CD57, PD-1, CTLA-4, as well as HLA-DR and CD38 on MAIT cells was significantly elevated in chronic HBV-infected individuals relative to controls. The percentage of T cell receptor (TCR) iVα7.2+ CD161+ MAIT cells did not correlate with HBV viral load but inversely with HLA-DR on CD4+ T cells and MAIT cells and with CD57 on CD8+ T cells suggesting that decrease of MAIT cells may not be attributed to direct infection by HBV but driven by HBV-induced chronic immune activation. The percentage and expression levels of PD-1 as well as CTLA-4 on MAIT cells inversely correlated with plasma HBV-DNA levels, which may suggest either a role for MAIT cells in the control of HBV infection or the effect of HBV replication in the liver on MAIT cell phenotype. We report that decrease of TCR iVα7.2+ MAIT cells in the peripheral blood and their functions were seemingly impaired in chronic HBV-infected patients likely because of the increased expression of PD-1
Interactive effects of temperature and copper toxicity on photosynthetic efficiency and metabolic plasticity in Scenedesmus quadricauda (Chlorophyceae)
No full textWarming and copper (Cu) toxicity are two key abiotic stressors that strongly affect cell growth, photosynthetic rate, and metabolism in microalgae. In this study, a freshwater chlorophyte, Scenedesmus quadricauda, was exposed to various concentrations of copper sulfate (300, 600, and 1000 μM nominal concentrations of CuSO4·5H2O) at 25 and 35 °C. The changes in cell density, photosynthetic parameters, in vivo absorption spectra, reactive oxygen species (ROS) levels, and metabolic profile were analyzed. The effects of copper toxicity on the physiology and biochemistry of microalgae were highly dependent on water temperature. The interactive effects of both stressors induced significant impact on the photosynthetic parameters such as maximum quantum yield (Fv/Fm), saturation irradiance (Ek), and non-photochemical quenching (NPQ). Temperature induced significant impact on cell density, Ek and NPQ, while the Cu toxicity significantly affected the Fv/Fm and NPQ. Changes in the in vivo absorption spectra and high levels of reactive oxygen species (ROS) were observed across different treatments. Overall, S. quadricauda adapted to the two abiotic stresses via NPQ and metabolic restructuring. Key metabolites including glycine, proline, hexadecanoic acid, propanoic acid, octadecanoic acid, galactose, lactose, and sucrose were involved in the microalgal response. The synergistic effects of temperature and Cu stresses on microalgae might affect community tolerance and species distribution in the long run
Synthesis and characterizations of magnetic bio-material sporopollenin for the removal of oil from aqueous environment
No full textThere is an increasing global need for a simple and effective method to remove oil from water. This study details the synthesis of magnetic bio-polymer sporopollenin (MSp) and explores its use as an adsorbent for oil removal from water. The MSp was characterized using FT-IR, SEM, EDX, BET, VSM, TGA and water contact angle (WCA) measurements. The oil adsorption experiments were carried out in batch mode. The influence of adsorbent dosage, contact time and pH on oil adsorption efficiency was studied and then optimized for analysis. The optimized MSp was found to be an effective oil adsorbent, with a sorption capacity of 3.24 mg/mg. The effectiveness of MSp as an oil adsorbent is attributed to its hydrophobic surface that can be selectively adsorb oil while repelling water. The MSp is also reusable and able to maintain its sorption capacity even after five usage-regeneration cycles
VR-embedded BIM immersive system for QS engineering education
No full textInformation communications technology (ICT) has been implemented in the construction sector but there is not yet any immersive system to integrate virtual reality (VR) and building information modeling (BIM) for quantity surveying (QS) practice and education. Aiming to develop a VR-embedded BIM immersive system for quantity surveying practice and education, experiments using Autodesk Revit 2016, Autodesk 3ds Max Design 2015, and Unity were conducted in this study. The developed VR-embedded BIM immersive system for quantity surveying practice and education consists of two main components, namely: Immersive System (Head-mounted display/360-degree display) and Non-immersive systems (Desktop VR). The virtual reality application could help improving QS practitioners' and QS students' understanding on the architectural design using VR walkthrough to navigate the virtual 3D building model, thus to improve the efficiency of decision making and the precision in quantity surveying work
Prevention practices of vaginitis among Malaysian women and its associated factors
No full textInformation on vaginal-related issues among Malaysian women is very limited. This study aimed to explore factors associated with preventive practices of vaginitis among Malaysian women. A cross-sectional computer-assisted telephone interview survey of a representative sample of multi-racial Malaysian women aged 18–50 years old was conducted from January to April 2014. Women from 1446 households responded to the survey and nearly one-third (32.1%) reported to have experienced vaginitis. In multivariate analyses, respondents in the urban locality were more likely to practice vaginitis prevention (OR = 1.40, 95% CI = 1.06–1.84) compared with those in the rural areas. Respondents who perceived low susceptibility to vaginitis were less likely to practice vaginitis prevention (OR = 0.72, 95% CI = 0.57–0.91) compared with responders who highly perceive susceptibility. Respondents who had no formal education were less likely to practice vaginitis prevention (OR = 0.16, 95% CI = 0.05–0.48) compared with those with tertiary education. This study showed that comprehensive education and health programmes need to focus on women with a low educational level, living in rural areas and women with low perceived susceptibility to vaginitis.Impact statementWhat is already known on this subject? Little is known about vaginitis issues among women in Malaysia. This study provides information regarding vaginitis among Malaysian women by looking at the factors associated with prevention practices. What do the results of this study add? From our study, factors associated with prevention practices were found to be educational level, locality, and perceived susceptibility of vaginitis. Those who perform fewer vaginitis prevention practices were women with a low educational level and those who live in rural areas. From the Health Belief Model, women with a low perceived susceptibility of vaginitis were less likely to carry out vaginitis prevention practices. What are the implications of these findings for clinical practice and/or further research? The findings may provide additional insights for policy makers and healthcare providers to deliver effective approaches in order to improve prevention practices of vaginitis among women in multi-ethnic communities. This study has identified points of interest which need to be put in attention for women’s health section which has been overlooked in Malaysia
Flow pattern analysis in type B aortic dissection patients after stent-grafting repair: Comparison between complete and incomplete false lumen thrombosis
No full textEndovascular stent graft repair has become a common treatment for complicated Stanford type B aortic dissection to restore true lumen flow and induce false lumen thrombosis. Using computational fluid dynamics, this study reports the differences in flow patterns and wall shear stress distribution in complicated Stanford type B aortic dissection patients after endovascular stent graft repair. Five patients were included in this study: 2 have more than 80% false lumen thrombosis (group 1), while 3 others had less than 80% false lumen thrombosis (group 2) within 1 year following endovascular repair. Group 1 patients had concentrated re-entry tears around the abdominal branches only, while group 2 patients had re-entry tears that spread along the dissection line. Blood flow inside the false lumen which affected thrombus formation increased with the number of re-entry tears and when only small amounts of blood that entered the false lumen exited through the branches. In those cases where dissection extended below the abdominal branches (group 2), patients with fewer re-entry tears and longer distance between the tears had low wall shear stress contributing to thrombosis. This work provides an insight into predicting the development of complete or incomplete false lumen thrombosis and has implications for patient selection for treatment