Displaying publications 1 - 20 of 623 in total

  1. Pung S, Ong C, Mohd Isha K, Othman M
    Sains Malaysiana, 2014;43:273-281.
    Cu-doped ZnO nanorods were synthesized by sol-gel method using zinc nitrate tetrahydrate, methenamine and cupric acetate monohydrate as precursors. The as-synthesized ZnO nanorods have a twin-rod structure. The polar (002) surface of ZnO nanorods, which could be either negatively charge (O-terminated) or positively charged (Zn- terminated), was responsible for the formation of twin-rod structure. The results showed that the size, aspect ratio, crystallinity and c-lattice parameter of Cu doped ZnO nanorods decreased with increasing of Cu dopant concentration. In fact, the presence of Cu retarded the growth of ZnO nanorods in its preferred growth direction, i.e. (0001). The XPS analysis indicates that Cu ions were oxidized (Cu2+) and substituted into the ZnO lattice at the Zn2+ site. The presence of Cu reduced the optical bandgap of ZnO from 3.34 eV (undoped ZnO nanorods) to 3.31 eV (20 mol% Cu doped ZnO). Besides, it induced a visible PL emission at 2.97 eV, which could be related to the transition of electrons from conduction band (Ec) to Cu acceptor energy level (Ev + 0.45 eV) radiatively.
    Matched MeSH terms: Zinc; Zinc Oxide; Zinc Compounds
  2. Daud, S.N.H., Chiu, W.S., Aspanut, Z., Khiew, P.S.
    Current study report the growth of Zinc Oxide (ZnO) nanorods (NRs) by a facile and low temperature method on Zinc (Zn) foil in deionized (DI) water. These ZnO NRs have a typical length of 500-700 nm and average diameter of 50-70 nm. By using different volume of DI water, the morphology of ZnO nanostructures are tunable from rod-like to flower-like structures. Under the presence of Zn nitrate precursor, mixture of rod/wall-like structures are formed. Both of ZnO NRs and combined nanorods/nanowalls render higher diffraction for the (002) peak reveals, which implies preferred orientation growth along c-axis take place. However, photoluminescence (PL) study indicates that ZnO NRs have strong emission located at ~380 nm if compared to that of combined ZnO nanorods/nanowalls. This shows that ZnO NRs have higher-densities of defects.
    Matched MeSH terms: Zinc; Zinc Oxide; Zinc Compounds
    Sains Malaysiana, 2013;42:1663-1670.
    Filem nipis ZnO terdop Ga (ZnO:Ga) disediakan menggunakan teknik sol-gel dan salutan berputar. Ga didopkan kepada ZnO dengan peratusan berat (wt. %) yang berbeza iaitu 0, 2, 4, 6 dan 8 wt. %. Kesan pengedopan Ga ke atas struktur dan sifat optik filem nipis ZnO dikaji. Pencirian struktur filem nipis ini dilakukan menggunakan kaedah pembelauan sinar-X (XRD), mikroskop imbasan elektron pancaran medan (FESEM) dan mikroskop daya atom (AFM). Pencirian sifat optik filem nipis pula dilakukan menggunakan spektroskopi ultraungu cahaya nampak (UV-VIS) dan fotoluminesen (PL). Ujian XRD mengesahkan kesemua sampel berstruktur wurtzit. Saiz kristalit ZnO mengecil dengan peningkatan peratusan berat Ga seterusnya mengurangkan kekasaran permukaan filem. Pengedopan Ga menunjukkan peratus transmisi cahaya pada panjang gelombang 300 - 380 nm bertambah berbanding filem nipis ZnO tanpa dop. Nilai jurang tenaga optik, Eg dan keamatan PL filem nipis ZnO meningkat apabila pengedopan Ga dilakukan. Hasil kajian ini menunjukkan saiz kristalit yang lebih kecil memberi kesan ke atas sifat optik sampel pada peratus pengedopan Ga 0-6%. Pada peratus pengedopan Ga yang lebih tinggi, kesan transformasi struktur menjadi lebih dominan dalam mempengaruhi nilai Eg.
    Matched MeSH terms: Zinc Oxide
  4. Pang WY, Ahmad AL, Zaulkiflee ND
    J Environ Manage, 2019 Nov 01;249:109358.
    PMID: 31450197 DOI: 10.1016/j.jenvman.2019.109358
    The aim of this study is to evaluate the performance and antifouling properties of polyethersulfone (PES) membrane incorporated with dual nanofiller, zinc oxide (ZnO) and multi-walled carbon nanotube (MWCNT). The synergistic effect of the these nanofillers in PES membrane is studied by blending different ratio of ZnO/MWCNT nanofiller into the PES membrane. The fabricated membranes were characterized in terms of cross-section and surface morphology, surface hydrophilicity, pore size and porosity. The filtration performance of the membranes was tested using 50 mg/L humic acid (HA) solution as model solution. SEM image and gravimetric evaluation reported that the incorporation of both MWCNT and ZnO into the PES membrane improved porosity significantly up to 46.02%. Lower water contact angle of PES membrane incorporated with equal ratio of MWCNT and ZnO (PES 3) revealed that it has neat PES membrane properties and more hydrophilic membrane surface than single filler. PES 3 outperform other membranes with excellent HA permeate flux of 40.00 L/m2.h and rejection of 88.51%. Due to hydrophilic membrane surface, PES 3 membrane demonstrate efficient antifouling properties with lower relative flux reduction (RFR) and higher flux recovery ratio (FRR). PES 3 also showed notable antibacterial properties with less bacterial attached to the membrane compared to neat PES membrane (PES 0).
    Matched MeSH terms: Zinc Oxide*
  5. Baiuitiar Ul Haq, Ahmed R, Shaari A, Afaq A, Hussain R
    Sains Malaysiana, 2014;43:813-817.
    The central theme of nanotechnology to miniaturize devices has stimulated interest in diluted magnetic semiconductors (DMS). DMS that simultaneously exhibit magnetic and semiconducting behavior are capable of parting properties of two different function devices into one. In this research we present our first principles investigations related to the structural and electronic properties of, Cr doped zinc-blende (zB) ZnO, DMS. These calculations are carried out using full potential linearized augmented plane wave plus local orbital (FP-L(APW+lo)) with generalized gradient approximations approach as implemented in WIEN2k code. In this study, the effect of Cr doping on lattice parameters, spin polarized electronic band structure, density of states (Dos) of ZnO is presented and analyzed in detail.
    Matched MeSH terms: Zinc; Zinc Oxide
  6. Haarindraprasad R, Gopinath SCB, Veeradassan P
    Biotechnol Appl Biochem, 2022 Dec;69(6):2698-2712.
    PMID: 34997977 DOI: 10.1002/bab.2316
    A "Janus particle" refers to the production of two materials in a single system and shows a difference in physical characteristics, and two surfaces participate in the formation with different chemistries. This research generated the Janus using a hybrid of zinc oxide (ZnO) and gold (Au) on the sensor surface toward making high-performance DNA sensors. The Janus ZnO/Au-textured film was synthesized via the one-step sol-gel method, which involves a suitable ratio of a mixture of ZnO sol seed solution. The synthesized Janus ZnO/Au-textured film undergoes a low-temperature aqueous hydrothermal route to synthesize quasi-one-dimensional nanowires. The average grain size in the Janus ZnO/Au nanotextured wire was 41.60 nm. The fabricated nanotextured wire was further optimized by tuning the thickness and characterized by XRD and high-resolution microscopy. Electrical characterization was conducted on the Janus ZnO/Au nanotextured wire coupled with an interdigitated electrode sensor to detect the specific leptospirosis DNA strand. The generated device is capable of detecting lower DNA concentration at 1 × 10-13 M with a sensitivity of 8.54 MΩ M-1 cm-2 . The high performance is attained on linear concentrations of 10-6 -10-13 M with the determination coefficient, "I = 135437.63C-3609.07" R2 = 0.9551. A potential strategy is proposed as a base for developing different high-performance sensors.
    Matched MeSH terms: Zinc Oxide*
  7. Mohamed Isa ED, Che Jusoh NW, Hazan R, Shameli K
    Environ Sci Pollut Res Int, 2021 Feb;28(5):5774-5785.
    PMID: 32975756 DOI: 10.1007/s11356-020-10939-1
    One of mankind's biggest concerns is water pollution. Textile industry emerged as one of the main contributors with dyes as the main pollutant. Presence of dyes in water is very dangerous due to their toxicity; thus, it is important to remove them from water. In these recent years, heterogeneous advance oxidation process surfaced as a possible dyes' removal technique. This process utilizes semiconductor as photocatalyst to degrade the dyes in presence of light and zinc oxide (ZnO) appears to be a promising photocatalyst for this process. In this study, pullulan, a biopolymer, was used to produce porous ZnO microflowers (ZnO-MFs) through green synthesis via precipitation method. The effects of pullulan's amount on the properties of ZnO-MFs were investigated. The ZnO-MF particle size decreased with the increased of pullulan amount. Interestingly, formation of pores occurred in presence of pullulan. The synthesized ZnO-MFs have the surface area ranging from 6.22 to 25.65 m2 g-1 and pore volume up to 0.1123 cm3 g-1. The ZnO-MF with the highest surface area was chosen for photocatalytic degradation of methyl orange (MO). The highest degradation occurred in 300 min with 150 mg catalyst dosage, 10 ppm initial dye concentration, and pH 7 experimental conditions. However, through comparison of photodegradation of MO with all synthesized ZnO-MFs, 25PZ exhibited the highest degradation rate. This shows that photocatalytic activity is not dependent on surface area alone. Based on these results, ZnO-MF has the potential to be applied in wastewater treatment. However, further improvement is needed to increase its photocatalytic activity.
    Matched MeSH terms: Zinc Oxide*
  8. Abd Khalil AT, Shah Buddin MMH, Puasa SW, Ahmad AL
    Environ Sci Pollut Res Int, 2023 Mar;30(15):45244-45258.
    PMID: 36705837 DOI: 10.1007/s11356-023-25208-0
    Zinc (Zn) was identified as one of the most toxic heavy metals and often found contaminating the water sources as a result of inefficient treatment of industrial effluent. A green emulsion liquid membrane (GELM) was proposed in this study as a method to minimize the concentration of Zn ions in an aqueous solution. Instead of the common petroleum-based diluent, the emulsion is reformulated with untreated waste cooking oil (WCO) collected from the food industry as a sustainable and cheaper diluent. It also includes Bis(2-ethylhexyl) phosphate (D2EHPA) as a carrier, Span 80 as a surfactant, sulfuric acid (H2SO4) as an internal phase, and ZnSO4 solution as an external phase. Such formulation requires a thorough understanding of the oil characteristics as well as the interaction of the components in the membrane phase. The compatibility of WCO and D2EHPA, as well as the external phase pH, was confirmed via a liquid-liquid extraction (LLE) method. To obtain the best operating conditions for Zn extraction using GELM, the extraction time and speed, carrier, surfactant and internal phase concentrations, and W/O ratio were varied. 95.17% of Zn ions were removed under the following conditions; 0.001 M of H2SO4 in external phase, 700 rpm extraction speed for 10 min, 8 wt% of carrier and 4 wt% of surfactant concentrations, 1:4 of W/O ratio, and 1 M of internal phase concentration.
    Matched MeSH terms: Zinc*
  9. Mohamad NS, Tan LL, Ali NIM, Mazlan NF, Sage EE, Hassan NI, et al.
    Environ Sci Pollut Res Int, 2023 Mar;30(11):28422-28445.
    PMID: 36680719 DOI: 10.1007/s11356-023-25257-5
    The current study aims to provide a roadmap for future research by analyzing the research structures and trends in scholarly publications related to the status of zinc in public health. Only journal articles published between 1978 and 2022 are included in the refined bibliographical outputs retrieved from the Web of Science (WoS) database. The first section announces findings based on WoS categories, such as discipline heterogeneity, times cited and publications over time, and citation reports. The second section then employs VoSViewer software for bibliometric analysis, which includes a thorough examination of co-authorship among researchers, organizations, and countries and a count of all bibliographic databases among documents. The final section discusses the research's weaknesses and strengths in zinc status, public health, and potential future directions; 7158 authors contributed to 1730 papers (including 339 with publications, more than three times). "Keen, C.L." is a researcher with the most publications and a better understanding of zinc status in public health. Meanwhile, the USA has been the epicenter of research on the status of zinc in public health due to the highest percentage of publications with the most citations and collaboration with the rest of the world, with the top institution being the University of California, Davis. Future research can be organized collaboratively based on hot topics from co-occurrence network mapping and bibliographic couplings to improve zinc status and protect public health.
    Matched MeSH terms: Zinc*
  10. Isa EDM, Jusoh NWC, Rodzi AAM
    Environ Sci Pollut Res Int, 2023 Nov;30(55):116921-116933.
    PMID: 37178288 DOI: 10.1007/s11356-023-27576-z
    The scarcity of water leads to research nowadays to focus on techniques for treating wastewater. Photocatalysis emerged as a technique of interest due to its nature of friendliness. It utilizes light and catalyst to degrade the pollutants. One of the popular catalysts to be used is zinc oxide (ZnO), but its usage is limited due to the high recombination rate of electron-hole pair. Herein, in this study, ZnO is modified with graphitic carbon nitride (GCN), and the GCN loading amount was varied to study the impact on photocatalytic degradation of mixed dye solution. To the best of our knowledge, this is the first work that reports on the degradation of mixed dye solution using modified ZnO with GCN. Structural analysis showed that GCN is present in the composites which proves the success of the modification. Photocatalytic activity revealed that the composite with 5 wt% loading of GCN showed the best activity at a catalyst dosage of 1 g/L with degradation rates of 0.0285, 0.0365, 0.0869, and 0.1758 min-1 for methyl red, methyl orange, rhodamine B, and methylene blue dyes, respectively. This observation is expected due to the formation of heterojunction between ZnO and GCN which creates a synergistic effect and thus led to an improvement in the photocatalytic activity. Based on these results, ZnO modified with GCN has a good potential to be used in the treatment of textile wastewater which consists of various dye mixtures.
    Matched MeSH terms: Zinc Oxide*
  11. Garg J, Chiu MN, Krishnan S, Kumar R, Rifah M, Ahlawat P, et al.
    Appl Biochem Biotechnol, 2024 Feb;196(2):1008-1043.
    PMID: 37314636 DOI: 10.1007/s12010-023-04570-2
    Over the last few decades, the application of nanoparticles (NPs) gained immense attention towards environmental and biomedical applications. NPs are ultra-small particles having size ranges from 1 to 100 nm. NPs loaded with therapeutic or imaging compounds have proved a versatile approach towards healthcare improvements. Among various inorganic NPs, zinc ferrite (ZnFe2O4) NPs are considered as non-toxic and having an improved drug delivery characteristics . Several studies have reported broader applications of ZnFe2O4 NPs for treating carcinoma and various infectious diseases. Additionally, these NPs are beneficial for reducing organic and inorganic environmental pollutants. This review discusses about various methods to fabricate ZnFe2O4 NPs and their physicochemical properties. Further, their biomedical and environmental applications have also been explored comprehensively.
    Matched MeSH terms: Zinc*
  12. Kamaruddin SA, Chan KY, Sahdan MZ, Rusop M, Saim H
    J Nanosci Nanotechnol, 2010 Sep;10(9):5618-22.
    PMID: 21133082
    Zinc oxide (ZnO) is an emerging material in large area electronic applications such as thin-film solar cells and transistors. We report on the fabrication and characterization of ZnO microstructures and nanostructures. The ZnO microstructures and nanostructures have been synthesized using sol-gel immerse technique on oxidized silicon substrates. Different precursor's concentrations ranging from 0.0001 M to 0.01 M (M=molarity) using zinc nitrate hexahydrate [Zn(NO3)2. 6H2O] and hexamethylenetetramine [C6H12N4] were employed in the synthesis of the ZnO structures. The surface morphologies were examined using scanning electron microscope (SEM) and atomic force microscope (AFM). In order to investigate the structural properties, the ZnO microstructures and nanostructures were measured using X-ray diffractometer (XRD). The optical properties of the ZnO structures were measured using photoluminescence (PL) and ultraviolet-visible (UV-Vis) spectroscopies.
    Matched MeSH terms: Zinc; Zinc Oxide; Zinc Compounds
  13. Shariffudin SS, Mamat MH, Rusop M
    J Nanosci Nanotechnol, 2012 Oct;12(10):8165-8.
    PMID: 23421195
    Transparent nanostructured ZnO thin films were successfully deposited using sol-gel spin coating method on a quartz substrate. The 0.4 M ZnO solution gel was prepared using zinc acetate dihydrate (Zn(CH3COO)22H2O) as the precursor, 2-methoxyethanol as the solvent and monoethanolamine (MEA) as the stabilizer. The electrical and optical properties dependencies on the annealing temperature of the nanostructured ZnO thin films were investigated. It was found that as the annealing temperature increased, the particle size, conductivity and the peak of the UV emission also increased.
    Matched MeSH terms: Zinc; Zinc Oxide; Zinc Acetate
  14. Mohd Yusof H, Mohamad R, Zaidan UH, Rahman NA
    Microb Cell Fact, 2020 Jan 15;19(1):10.
    PMID: 31941498 DOI: 10.1186/s12934-020-1279-6
    BACKGROUND: The use of microorganisms in the biosynthesis of zinc oxide nanoparticles (ZnO NPs) has recently emerged as an alternative to chemical and physical methods due to its low-cost and eco-friendly method. Several lactic acid bacteria (LAB) have developed mechanisms in tolerating Zn2+ through prevention against their toxicity and the production of ZnO NPs. The LAB's main resistance mechanism to Zn2+ is highly depended on the microorganisms' ability to interact with Zn2+ either through biosorption or bioaccumulation processes. Besides the inadequate studies conducted on biosynthesis with the use of zinc-tolerant probiotics, the understanding regarding the mechanism involved in this process is not clear. Therefore, this study determines the features of probiotic LAB strain TA4 related to its resistance to Zn2+. It also attempts to illustrate its potential in creating a sustainable microbial cell nanofactory of ZnO NPs.

    RESULTS: A zinc-tolerant probiotic strain TA4, which was isolated from local fermented food, was selected based on the principal component analysis (PCA) with the highest score of probiotic attributes. Based on the 16S rRNA gene analysis, this strain was identified as Lactobacillus plantarum strain TA4, indicating its high resistance to Zn2+ at a maximum tolerable concentration (MTC) value of 500 mM and its capability of producing ZnO NPs. The UV-visible spectroscopy analysis proved the formations of ZnO NPs through the notable absorption peak at 380 nm. It was also found from the dynamic light scattering (DLS) analysis that the Z-average particle size amounted to 124.2 nm with monodisperse ZnO NPs. Studies on scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy, and Fourier-transform infrared spectroscopy (FT-IR) revealed that the main mechanisms in ZnO NPs biosynthesis were facilitated by the Zn2+ biosorption ability through the functional groups present on the cell surface of strain TA4.

    CONCLUSIONS: The strong ability of zinc-tolerant probiotic of L. plantarum strain TA4 to tolerate high Zn2+ concentration and to produce ZnO NPs highlights the unique properties of these bacteria as a natural microbial cell nanofactory for a more sustainable and eco-friendly practice of ZnO NPs biosynthesis.

    Matched MeSH terms: Zinc; Zinc Oxide*
  15. Hussein MZ, Rahman NS, Sarijo SH, Zainal Z
    Int J Mol Sci, 2012;13(6):7328-42.
    PMID: 22837696 DOI: 10.3390/ijms13067328
    Herbicides, namely 4-(2,4-dichlorophenoxy) butyrate (DPBA) and 2-(3-chlorophenoxy) propionate (CPPA), were intercalated simultaneously into the interlayers of zinc layered hydroxide (ZLH) by direct reaction of zinc oxide with both anions under aqueous environment to form a new nanohybrid containing both herbicides labeled as ZCDX. Successful intercalation of both anions simultaneously into the interlayer gallery space of ZLH was studied by PXRD, with basal spacing of 28.7 Å and supported by FTIR, TGA/DTG and UV-visible studies. Simultaneous release of both CPPA and DPBA anions into the release media was found to be governed by a pseudo second-order equation. The loading and percentage release of the DPBA is higher than the CPPA anion, which indicates that the DPBA anion was preferentially intercalated into and released from the ZLH interlayer galleries. This work shows that layered single metal hydroxide, particularly ZLH, is a suitable host for the controlled release formulation of two herbicides simultaneously.
    Matched MeSH terms: Zinc/chemistry; Zinc Compounds/chemistry*
    Kebahagiaan adalah rasa kesejahteraan, kegembiraan atau kepuasan yang boleh membawa kepada satu bentuk emosi yang positif dalam diri seseorang pekerja. Namun kebahagiaan akan merosot akibat daripada tekanan kerja dan masalah yang berkaitan dengan kesihatan. Kebanyakan pekerja tidak menyedari akan bahaya tekanan kerja yang pada akhirnya akan mengakibatkan kemerosotan kesihatan. Kajian ini dijalankan adalah bertujuan untuk mengenal pasti status kebahagiaan dan tekanan yang dihadapi oleh staf Universiti Malaysia Terengganu (UMT) serta mengukur kos kesihatan yang terpaksa ditanggung oleh mereka. Seramai 100 orang staf UMT, di mana 50 orang staf daripada bahagian akademik dan 50 orang staf daripada bukan akademik telah terlibat dalam kajian ini. Satu set soal selidik digunakan sebagai instrumen kajian. Data dianalisis dengan menggunakan perisian SPSS versi 20.0. Secara keseluruhannya, dapatan kajian menunjukkan bahawa terdapat hubungan yang signifikan antara faktor tekanan kerja dan kebahagiaan. Majoriti staf UMT menyatakan bahawa mereka bahagia ketika berada di tempat kerja iaitu sebanyak 78 peratus. Jumlah kos langsung perbelanjaan kesihatan yang terpaksa ditanggung oleh responden adalah RM2,220, manakala jumlah kos tidak langsung pula adalah RM1,4376.41. Antara kes tertinggi yang dirujuk ke pusat rawatan adalah berkaitan dengan tekanan darah tinggi. Oleh itu, kesedaran dalam kalangan pekerja dari segi cara mengawal tekanan mereka adalah penting untuk mencapai kesihatan yang baik seterusnya merasa bahagia apabila membuat kerja.
    Matched MeSH terms: Zinc Fingers
  17. Luqman Chuah Abdullah, Saidatul Shima, J., Choong, Thomas S.Y., Muhammad
    A series of batch laboratory studies were conducted to investigate the suitability of activated carbon SA2 for the removal of cadmium ions and zinc ions from their aqueous solutions. The single component equilibrium data were analyzed using the Langmuir and Freundlich isotherms. Overall, the Langmuir isotherm showed a better fitting for all adsorptions under investigation in terms of correlation coefficient and error analysis (SSE only 18.2 for Cd2+ and 47.95 for Zn2+). As the binary adsorption is competitive, extended Langmuir models could not predict the binary component isotherm well. The modified extended Langmuir models were used to fit the binary system equilibrium data. The binary isotherm data could be described reasonably well by the modified
    extended Langmuir model, as indicated in the error analysis.
    Matched MeSH terms: Zinc
  18. Mayappan, Ramani, Ahmad Badri Ismail, Zainal Arifin Ahmad, Hussain, Luay Bakir, Ariga, Tadashi
    In this study the intermetallic (IMC) thickness of Sn-Pb, Sn-Zn and Sn-Zn-Bi solders on copper (Cu) substrate were measured at different temperatures using reflow methods. Cu6Sn5 intermetallic phase was detected between Sn-Pb solder and Cu substrate. The J-Cu5Zn8 phase was detected between Sn-Zn and Sn-Zn-Bi lead-free solders with Cu substrate. The thickness of the intermetallics increases with temperature. The IMC thickness for Sn-8Zn-3Bi solder is lower than Sn-9Zn solder for all the soldering temperatures, indicating that Bi has suppressed the initial IMC formation.
    Matched MeSH terms: Zinc
    Sains Malaysiana, 2013;42:1811-1814.
    We studied the clusters of GaAs by using the density functional theory simulation to optimize the structure. We determined the binding energy, bond lengths, Fermi energy and vibrational frequencies for all of the clusters. We use the Raman data of nanowires of GaAs to compare our calculated values with the experimental values of the vibrational frequencies. The nanowire of GaAs gives a Raman line at 256 cm-1 whereas in the bipyramidal Ga2As3 the calculated value is 256.33 cm-1. Similarly 285 cm-1 found in the experimental Raman data agrees with 286.21 cm-1 found in the values calculated for Ga2As2 (linear) showing that linear bonds occur in the nanowire. The GaAs is found in two structures zinc-blend as well as wurtzite structures. In the nanowire mixed structures as well as clusters are formed.
    Matched MeSH terms: Zinc
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links