19672 research outputs found
Sort by
Titanium dioxide fiber saturable absorber for Q-switched fiber laser generation in the 1-micrometer region
No full textA passively Q-switched ytterbium-doped fiber laser (YDFL) operating at 1062 nm was demonstrated by using a segment of 20 cm titanium dioxide-doped fiber saturable absorber (TiO 2 DF SA). The Q-switched YDFL emerged stably with tunable repetition rates ranging from 32 kHz to 53 kHz as the pump power rose from 109 mW to 233 mW. Within this range of pump power, a maximum output power of 10.1 mW, maximum peak power of 75 mW, and maximum pulse energy of 191 nJ were obtained. The narrowest pulse width of 2.55 μs was attained at the maximum pump power of 233 mW, while the signal-to-noise ratio of the fundamental frequency was 47 dB. This demonstration reveals that the proposed TiO 2 DF SA is feasible for constructing a flexible and reliably stable Q-switched pulsed fiber laser in the 1-micrometer region. © 2019 Optical Society of America
Simultaneous enhanced antibacterial and osteoblast cytocompatibility performance of Ti6Al7Nb implant by nano-silver/graphene oxide decorated mixed oxide nanotube composite
No full textThe self-ordered architecture allows for the exact design and control of geometrical features, to achieve materials with unique properties. For this reason, mixed oxide nanotube arrays have been highly regarded by the scientific community in recent years. In the present study, a hybrid approach of an optimized physical vapor deposition magnetron sputtering (PVDMS), electrochemical anodization as well as spin coating is proposed to improve the mechanical properties, corrosion resistance, antibacterial and osteoblast cytocompatibility performance of Ti6Al7Nb implant (Ti67IMP). Accordingly, controlled decorations of mixed oxide nanotube with silver nanoparticles/graphene oxide (AgNPs/GO) were designed to assess the biofunctionality of the modified Ti6Al7Nb implant. The results show that the surface modification has dramatically reduced the viability of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) cells. Besides, the AgNPs/GO loaded mixed oxide nanotube has significantly promoted cell adhesion and spreading, compared to the bare substrate. The proposed hybrid approach can also be extended to fabricate highly complex nanoarchitectures with controlled shape and biofunctionality for various orthopedic applications. © 2019 Elsevier B.V
Novel helical screw-fluidized bed reactor for bio-oil production in slow-pyrolysis mode: A preliminary study
No full textSlow pyrolysis has been generally recognized as an improper mode of bio-oil production because it produces a low liquid yield of ˜30 wt.%. This research introduces a type of innovation in which the designed helical screw-fluidized bed reactor can operate in the slow-pyrolysis mode to obtain high-yielding liquids. The concept of the reactor was designed to develop the fluidization condition by using a mechanical device. Experiments were performed at the heating rate of 10 °C/min to achieve 500 °C without using any inert gases. The focus of the preliminary study was on reactor performance, particularly for a setting with helical rotation (50 rpm) and another one without rotation (0 rpm). For the setting without the influence of helical screw rotation, the obtained liquid yield was 38.4 wt.%. Then, the liquid yield was remarkably increased to 51.6 wt.% when the 50-rpm condition was applied. The liquid obtained from the 50-rpm condition contained a higher proportion of organic phase than aqueous phase. The presence of oxygen compound in the organic phase in the 50-rpm condition was lower than that in the 0-rpm condition. Apart from the ability to obtain high-yielding liquids in the slow-pyrolysis condition, the reactor also has other good features, such as low pyrolysis time, fast vapor production, non-agglomeration of particles, non-occurrence of pressure drop during process implementation, and production of good-quality byproduct char. © 2019 Elsevier B.V
The influence of economic, technical, and social aspects on energy-associated CO2 emissions in Malaysia: An extended Kaya identity approach
No full textThe rapid global economic development over the past two decades has been accompanied by rising energy demand and CO2 emission rates. Understanding the driving forces of CO2 emissions is necessary for future energy planning and policy formulation. This paper examines the driving factors behind the increase in CO2 emissions in Malaysia with special focus on the manufacturing, electricity and transportation sectors. The paper extends the Kaya identity by incorporating energy mix, investment efficiency, capital-labor substitution, population-to-employment, urbanization rates, and per capita CO2, along with the standard variables including economic activity, economic structure, and energy intensity. The paper also evaluates if any macroeconomic instability (economic crisis) in the country has led to reduction in emission rates. The study utilizes the latest country data, covering the period 2002–2016. The result shows that, while economic activity is always associated with CO2 emissions, more efficient energy use would help restrain the rise in emission rates without hampering economic growth regardless of economic structure. Emission reduction targets in Malaysia should be reinforced with an appropriate economic restructuring that restrains the economic structure effect. Due to the extensive energy use in the transportation and electricity generation, future emission control should focus more on these sectors. © 2019 Elsevier Lt
Malabaricone C as Natural Sphingomyelin Synthase Inhibitor against Diet-Induced Obesity and Its Lipid Metabolism in Mice
No full textThe interaction between natural occurring inhibitors and targeted membrane proteins could be an alternative medicinal strategy for the treatment of metabolic syndrome, notably, obesity. In this study, we identified malabaricones A-C and E (1-4) isolated from the fruits of Myristica cinnamomea King as natural inhibitors for sphingomyelin synthase (SMS), a membrane protein responsible for sphingolipid biosynthesis. Having the most promising inhibition, oral administration of compound 3 exhibited multiple efficacies in reducing weight gain, improving glucose tolerance, and reducing hepatic steatosis in high fat diet-induced obesity mice models. Liver lipid analysis revealed a crucial link between the SMS activities of compound 3 and its lipid metabolism in vitro and in vivo. The nontoxic nature of compound 3 makes it a suitable candidate in search of drugs which can be employed in the treatment and prevention of obesity. © 2019 American Chemical Society
Quantum plasmonics of finite-size particles with coherent anti-Stokes Raman scattering
No full textWe have developed a semianalytical theory to study a quantum plasmonic system composed of a quantum particle and a metallic particle with finite size. The quantum particle is composed of molecules driven by three laser fields and produces a coherent anti-Stokes Raman scattering (CARS) signal which is enhanced by plasmonic resonance of the metallic particle. The enhanced CARS field and the control laser form a Λ scheme that gives highly nonlinear and spatially nonlocal effects. We obtain absorption spectra that show periodic oscillations with radius of the spherical quantum particle, the whispering gallery effect. Plasmonic resonance gives very large and narrow absorption peaks as well as vanishing absorption or Fano dip at specific values of frequency and interparticle distance. The space between the two particles provides a resonant cavity effect which explains the oscillations of absorption power spectra with interparticle distance. © 2019 American Physical Society
TG : HDL-C Ratio Is a Good Marker to Identify Children Affected by Obesity with Increased Cardiometabolic Risk and Insulin Resistance
No full textMetabolic syndrome (MetS) is an important predictor of cardiovascular diseases in adulthood. This study aims to examine the clinical utility of triglyceride to high-density lipoprotein ratio (TG: HDL-C) in identifying cardiometabolic risk and insulin resistance (IR) among children with obesity, in comparison with MetS as defined by the International Diabetes Federation (IDF). Data of 232 children with obesity aged 10-16 years were obtained from our study, MyBFF@school study, conducted between January and December 2014. Children were divided into tertiles of TG: HDL-C ratio. The minimum value of the highest tertile was 1.11. Thus, elevated TG: HDL-C ratio was defined as TG: HDL-C ≥1.11. Children with MetS were categorized based on the definition established by the IDF. Out of 232 children, 23 (9.9%) had MetS, out of which 5.6% were boys. Almost twofold of boys and girls had elevated TG: HDL-C ratio compared to MetS: 13.8% vs. 5.6% and 13.8% vs. 4.3%, respectively. Children with elevated TG: HDL-C ratio had lower fasting glucose compared to children with MetS (boys = 5.15 ± 0.4 vs. 6.34 ± 2.85 mmol/l, p=0.02; girls = 5.17 ± 0.28 vs. 6.8 ± 4.3 mmol/l, p=0.03). Additionally, boys with elevated TG: HDL-C ratio had a higher HDL-C level compared to those with MetS (1.08 ± 0.18 vs. 0.96 ± 0.1 mmol/l, p=0.03). There was no significant difference across other MetS-associated risk factors. Overall, TG: HDL-C ratio demonstrated higher sensitivity (42.7% vs. 12.9%) but lower specificity (74.8% vs. 93.2%) than MetS in identifying IR, either in HOMA-IR ≥2.6 for prepubertal children or HOMA-IR ≥4 for pubertal children. TG: HDL-C ratio in children with obesity is thus as useful as the diagnosis of MetS. It should be considered an additional component to MetS, especially as a surrogate marker for IR. © 2019 Ahmad Kamil Nur Zati Iwani et al
Phytoassessment of Vetiver grass enhanced with EDTA soil amendment grown in single and mixed heavy metal–contaminated soil
No full textOver the years, ethylene-diamine-tetra-acetate (EDTA) has been widely used for many purposes. However, there are inadequate phytoassessment studies conducted using EDTA in Vetiver grass. Hence, this study evaluates the phytoassessment (growth performance, accumulation trends, and proficiency of metal uptake) of Vetiver grass, Vetiveria zizanioides (Linn.) Nash in both single and mixed heavy metal (Cd, Pb, Cu, and Zn)—disodium EDTA-enhanced contaminated soil. The plant growth, metal accumulation, and overall efficiency of metal uptake by different plant parts (lower root, upper root, lower tiller, and upper tiller) were thoroughly examined. The relative growth performance, metal tolerance, and phytoassessment of heavy metal in roots and tillers of Vetiver grass were examined. Metals in plants were measured using the flame atomic absorption spectrometry (F-AAS) after acid digestion. The root-tiller (R/T) ratio, biological concentration factor (BCF), biological accumulation coefficient (BAC), tolerance index (TI), translocation factor (TF), and metal uptake efficacy were used to estimate the potential of metal accumulation and translocation in Vetiver grass. All accumulation of heavy metals were significantly higher (p >> Cu > Pb >> Cd for all treatments. Furthermore, both upper roots and tillers of Vetiver grass recorded high tendency of accumulation for appreciably greater amounts of all heavy metals, regardless of single and/or mixed metal treatments. Thus, Vetiver grass can be recommended as a potential phytoextractor for all types of heavy metals, whereby its tillers will act as the sink for heavy metal accumulation in the presence of EDTA for all treatments. © 2019, Springer Nature Switzerland AG
The Role of Transient Receptor Potential (TRP) Channels in the Transduction of Dental Pain
Get PDFDental pain is a common health problem that negatively impacts the activities of daily living. Dentine hypersensitivity and pulpitis-associated pain are among the most common types of dental pain. Patients with these conditions feel pain upon exposure of the affected tooth to various external stimuli. However, the molecular mechanisms underlying dental pain, especially the transduction of external stimuli to electrical signals in the nerve, remain unclear. Numerous ion channels and receptors localized in the dental primary afferent neurons (DPAs) and odontoblasts have been implicated in the transduction of dental pain, and functional expression of various polymodal transient receptor potential (TRP) channels has been detected in DPAs and odontoblasts. External stimuli-induced dentinal tubular fluid movement can activate TRP channels on DPAs and odontoblasts. The odontoblasts can in turn activate the DPAs by paracrine signaling through ATP and glutamate release. In pulpitis, inflammatory mediators may sensitize the DPAs. They could also induce post-translational modifications of TRP channels, increase trafficking of these channels to nerve terminals, and increase the sensitivity of these channels to stimuli. Additionally, in caries-induced pulpitis, bacterial products can directly activate TRP channels on DPAs. In this review, we provide an overview of the TRP channels expressed in the various tooth structures, and we discuss their involvement in the development of dental pain
In-situ tuning of Sn doped In2O3 (ITO) films properties by controlling deposition Argon/Oxygen flow
No full textIn this work, we report that the properties of Sn-doped In 2 O 3 (ITO) can be properly tuned by varying Argon/ Oxygen (Ar/O 2 ) percentage during the sputtering process from 7% O 2 to 93% O 2 . The characteristics of the ITO grown in oxygen deficient to the oxygen-rich condition are properly studied. It is found that there is a strong correlation between the concentration incorporation of oxygen with the properties of ITO films. ITO films were grown in oxygen deficient condition (7% O 2 ) resulted in a rougher surface, wider band gap, and lower resistivity compared to the other films grown with 33%, 67%, and 93%. Blue shifts in absorbance edge and band gap widening indicate that the number of carrier concentration was also changed linearly with the presence of oxygen in the film. These findings provide a simple way to effectively tune the properties of ITO films for ITO to be applied in optoelectronics, power device as well as sensor applications. © 2019 Elsevier B.V