Displaying publications 1 - 20 of 331 in total

  1. Ahmad H, Zulkifli MZ, Hassan NA, Harun SW
    Appl Opt, 2012 Apr 10;51(11):1811-5.
    PMID: 22505174 DOI: 10.1364/AO.51.001811
    We propose and demonstrate a tunable S-band multiwavelength Brillouin/Raman fiber laser (MBRFL) with a tuning range of between 1490 to 1530 nm. The proposed MBRFL is designed around a 7.7 km long dispersion compensating fiber in a simple ring configuration, acting as a nonlinear medium for the generation of multiple wavelengths from stimulated Brillouin scattering (SBS) and also as a nonlinear gain medium for stimulated Raman scattering (SRS) amplification. A laser source with a maximum power of 12 dBm acts as the Brillouin pump (BP), while two 1420 nm laser diodes with a total power of 26 dBm act as the Raman pumps (RPs). The MBRFL can generate a multiwavelength comb consisting of even and odd Stokes at an average power of -12 dBm and -14 dBm respectively, and by separating the even and odd Stokes outputs, a 20 GHz channel spacing is obtained between two consecutive wavelengths. Due to the four-wave mixing (FWM) effect, anti-Stokes lines are also observed. The multiwavelength comb generated is not dependent on the BP, thus providing high stability and repeatability and making it a highly potential source for many real-world applications. This is the first time, to the knowledge of the authors, that a tunable MBRFL has been developed using SRS to obtain gain in the S-band region.
    Matched MeSH terms: Spectrum Analysis, Raman
  2. Permana D, Lajis NH, Othman AG, Ali AM, Aimi N, Kitajima M, et al.
    J Nat Prod, 1999 Oct;62(10):1430-1.
    PMID: 10543909
    A new anthraquinone, 2-hydroxymethyl-10-hydroxy-1,4-anthraquinone (1), was isolated from Hedyotis herbacea along with three other known derivatives: 1,4-dihydroxy-2-hydroxymethylanthraquinone (2); 2, 3-dimethoxy-9-hydroxy-1,4-anthraquinone; and 1,4-dihydroxy-2, 3-dimethoxyanthraquinone. The structure of 1 was determined based on analysis of its spectroscopic data.
    Matched MeSH terms: Spectrum Analysis
  3. Sulandari W, Subanar S, Lee MH, Rodrigues PC
    MethodsX, 2020;7:101015.
    PMID: 32793431 DOI: 10.1016/j.mex.2020.101015
    Hybrid methodologies have become popular in many fields of research as they allow researchers to explore various methods, understand their strengths and weaknesses and combine them into new frameworks. Thus, the combination of different methods into a hybrid methodology allows to overcome the shortcomings of each singular method. This paper presents the methodology for two hybrid methods that can be used for time series forecasting. The first combines singular spectrum analysis with linear recurrent formula (SSA-LRF) and neural networks (NN), while the second combines the SSA-LRF and weighted fuzzy time series (WFTS). Some of the highlights of these proposed methodologies are:•The two hybrid methods proposed here are applicable to load data series and other time series data.•The two hybrid methods handle the deterministic and the nonlinear stochastic pattern in the data.•The two hybrid methods show a significant improvement to the single methods used separately and to other hybrid methods.
    Matched MeSH terms: Spectrum Analysis
  4. Zainuri DA, Razak IA, Arshad S
    Acta Crystallogr E Crystallogr Commun, 2018 Oct 01;74(Pt 10):1491-1496.
    PMID: 30319808 DOI: 10.1107/S2056989018013087
    The crystal structures of (E)-1-(anthracen-9-yl)-3-(3H-indol-2-yl)prop-2-en-1-one, C25H17NO, and (E)-1-(anthracen-9-yl)-3-[4-(di-methyl-amino)-naphthalen-1-yl]prop-2-en-1-one, C29H23NO, are reported. In each case the anthracene ring system and pendant ring system are almost perpendicular to each other [dihedral angles = 75.57 (7)° and 70.26 (10)°, respectively]. In the extended structures, weak N-H⋯O, C-H⋯O and C-H⋯π inter-actions influence the centrosymmetric crystal packing. Density functional theory calculations were carried out using a 6-311 G++(d,p) basis set and the calculated structures are in good agreement with the crystal structures. The compounds were also characterized by UV-Vis absorption spectroscopy and the smallest (HOMO-LUMO) energy gaps of 2.89 and 2.54 eV indicate the enhanced non-linear responses (inter-molecular charge transfers) of these systems.
    Matched MeSH terms: Spectrum Analysis
  5. Fasihuddin B.A., Laily B. Din, Zuriati Zakaria
    Three compounds were isolated and characterized from the roots of Goniothalamus woodii. Based on their spectroscopic data, the compounds were identified as goniothalamin, 5-acetoxygoniothalamin and goniotriol.
    Tiga sebatian telah dipisahkan dan dicamkan daripada akar Goniothalamus woodii. Berdasarkan dari data spektroskopi, sebatian telah dikenalpasti sebagai goniotalamin, 5-asetoksigoniotalamin dan goniotriol.
    Matched MeSH terms: Spectrum Analysis
  6. Muthudoss P, Kumar S, Ann EYC, Young KJ, Chi RLR, Allada R, et al.
    J Pharm Biomed Anal, 2022 Feb 20;210:114581.
    PMID: 35026592 DOI: 10.1016/j.jpba.2022.114581
    Particle size distribution (PSD), spatial location and particle cluster size of ingredients, polymorphism, compositional distribution of a pharmaceutical product are few of the most important attributes in establishing the drug release-controlling microstructural and solid state properties that would be used to (re)design or reproduce similar products. There are numerous solid-state techniques available for PSD analysis. Laser diffraction (LD) is mostly used to study PSD of raw materials. However, a constraint of LD is the interference between the active pharmaceutical ingredients (API) and excipients, where it is very challenging to measure API size in a tablet. X-ray powder diffraction (XRPD) is widely employed in establishing the polymorphism of API and excipients. This research examined a commercial osmotic tablet in terms of extracting solid state properties of API and functional excipient by Raman Imaging. Establishing repeatability, reproducibility, and sample representativeness when the samples are non-uniform and inhomogeneous necessitates multiple measurements. In such scenarios, when employing imaging-based techniques, it can be time-consuming and tedious. Advanced statistical methodologies are used to overcome these disadvantages and expedite the characterization process. Overall, this study demonstrates that Raman imaging can be employed as a non-invasive and effective offline method for assessing the solid-state characteristics of API and functional excipients in complex dosage forms like osmotic tablets.
    Matched MeSH terms: Spectrum Analysis, Raman*
  7. Yusof NA, Ahmad M
    PMID: 17531526
    A flow-through optical fibre chemical sensor for the determination of Co(II) at trace level using immobilised 2-(4-pyridylazo)resorcinol (PAR) as the reagent phase is proposed. PAR is physically adsorbed onto XAD-7. This method provided a great sensitivity and simplicity with wide linear response range from 1x10(-2) to 1x10(3)ppm and detection limit of 20ppb. This method also showed a reproducible result with relative standard deviation (R.S.D.) of 1.78% and response time of approximately 5min. The response towards Co(II) was also reversible using acidified KCl as the regenerating solution. Interference studies showed that Cr(III) significantly interfered during the determination. Excellent agreement with reference to inductively coupled plasma optical emission spectroscopy (ICPOES) method was achieved when the developed sensor was applied for determination of Co(II) in aqueous samples.
    Matched MeSH terms: Spectrum Analysis/instrumentation*; Spectrum Analysis/methods*
  8. Parhoodeh P, Rahmani M, Hashim NM, Sukari MA, Lian GE
    Molecules, 2011 Mar 07;16(3):2268-73.
    PMID: 21383663 DOI: 10.3390/molecules16032268
    During our phytochemical investigation of Haplophyllum villosum (Rutaceae), a perennial herb from Iran, a new 4,8-diaryl-3,7-dioxobicyclo-(3,3,0)-octane type lignan, eudesmin A (1), together with four known compounds--eudesmin (2), haplamine (3), umbelliferone (4) and scopoletin (5)--were isolated from aerial parts of the plant. The structures of the compounds were elucidated using NMR spectral analysis (¹H-NMR, ¹³C-NMR, HSQC, COSY and HMBC) as well as UV, IR and MS spectra and comparison with previously reported data.
    Matched MeSH terms: Spectrum Analysis/methods
  9. Rajudin E, Ahmad F, Sirat HM, Arbain D, Aboul-Enein HY
    Nat Prod Res, 2010 Mar;24(4):387-90.
    PMID: 20221945 DOI: 10.1080/14786410903421826
    Seven flavonoid compounds have been isolated from the aerial parts of tiger's betel (Piper porphyrophyllum), which were identified as 5,7-dimethoxyflavone, 4',5,7-trimethoxy-flavone, 3',4',5,7-tetramethoxyflavone, 4'-hydroxy-3',5,7-trimethoxyflavone, 5-hydroxy-3',4',7-trimethoxyflavone, 4',5-dihydroxy-3',7-dimethoxyflavone and 5-hydroxy-7-methoxyflavanone. The identification of all compounds was achieved by physical properties and spectroscopically. These data were also confirmed by comparison with previously reported spectral data. Flavonoid compounds with high content in P. porphyrophyllum can probably be used as a chemical marker for this Piper species.
    Matched MeSH terms: Spectrum Analysis/methods
  10. Bongalov B, Burslem DFRP, Jucker T, Thompson SED, Rosindell J, Swinfield T, et al.
    Ecol Lett, 2019 Oct;22(10):1608-1619.
    PMID: 31347263 DOI: 10.1111/ele.13357
    Both niche and stochastic dispersal processes structure the extraordinary diversity of tropical plants, but determining their relative contributions has proven challenging. We address this question using airborne imaging spectroscopy to estimate canopy β-diversity for an extensive region of a Bornean rainforest and challenge these data with models incorporating niches and dispersal. We show that remotely sensed and field-derived estimates of pairwise dissimilarity in community composition are closely matched, proving the applicability of imaging spectroscopy to provide β-diversity data for entire landscapes of over 1000 ha containing contrasting forest types. Our model reproduces the empirical data well and shows that the ecological processes maintaining tropical forest diversity are scale dependent. Patterns of β-diversity are shaped by stochastic dispersal processes acting locally whilst environmental processes act over a wider range of scales.
    Matched MeSH terms: Spectrum Analysis*
  11. Swinfield T, Both S, Riutta T, Bongalov B, Elias D, Majalap-Lee N, et al.
    Glob Chang Biol, 2020 02;26(2):989-1002.
    PMID: 31845482 DOI: 10.1111/gcb.14903
    Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences phosphorus (P) cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterized by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here, we use airborne light detection and ranging-guided hyperspectral imagery to map foliar nutrient (i.e. P, nitrogen [N]) concentrations, calibrated using field measured traits, over 400 km2 of northeastern Borneo, including a landscape-level disturbance gradient spanning old-growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrients. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old-growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old-growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as forests recover.
    Matched MeSH terms: Spectrum Analysis
  12. Che Aziz Ali, Kamal Roslan Mohamed, Nurul Afifah Mohd Radzir
    Sains Malaysiana, 2018;47:1387-1392.
    Analisis geokimia menggunakan kaedah ICP-MS menunjukkan taburan geokimia unsur di kawasan kajian dipengaruhi
    oleh dua asalan sedimen berbeza iaitu daripada marin dan daratan. Unsur Ca dan Mg dikenal pasti sebagai unsur
    marin, manakala unsur Al, Fe, Mn, Na, Cu, Cr, Zn dan Ni dikenal pasti sebagai unsur daratan. Unsur Ca dan Mg dikenal
    pasti terhasil daripada proses penyahkapuran rangka dan hidupan marin seperti cengkerang moluska dan foraminifera.
    Unsur benua berasal daripada granit dari Gunung Korbu dan Gunung Stong yang disaliri oleh Sungai Nenggiri dan
    Sungai Galas, serta batuan argilit arenit yang berasal dari bahagian selatan dan tenggara Negeri Kelantan dari
    Gunung Cintawangsa dan Gunung Stong dan disaliri oleh Sungai Lebir dan Sungai Galas. Unsur daripada batuan
    induk membebaskan unsur kimia semasa luluhawa kimia dan telah dijerap oleh cas-cas negatif pada permukaan sedimen
    halus seperti lempung dan lodak sebelum dimendapkan bersama di dalam kawasan kajian.
    Matched MeSH terms: Spectrum Analysis
  13. Rohman A, Windarsih A
    Int J Mol Sci, 2020 Jul 21;21(14).
    PMID: 32708254 DOI: 10.3390/ijms21145155
    Halal is an Arabic term used to describe any components allowed to be used in any products by Muslim communities. Halal food and halal pharmaceuticals are any food and pharmaceuticals which are safe and allowed to be consumed according to Islamic law (Shariah). Currently, in line with halal awareness, some Muslim countries such as Indonesia, Malaysia, and Middle East regions have developed some standards and regulations on halal products and halal certification. Among non-halal components, the presence of pig derivatives (lard, pork, and porcine gelatin) along with other non-halal meats (rat meat, wild boar meat, and dog meat) is typically found in food and pharmaceutical products. This review updates the recent application of molecular spectroscopy, including ultraviolet-visible, infrared, Raman, and nuclear magnetic resonance (NMR) spectroscopies, in combination with chemometrics of multivariate analysis, for analysis of non-halal components in food and pharmaceutical products. The combination of molecular spectroscopic-based techniques and chemometrics offers fast and reliable methods for screening the presence of non-halal components of pig derivatives and non-halal meats in food and pharmaceutical products.
    Matched MeSH terms: Spectrum Analysis/methods*; Spectrum Analysis, Raman/methods*
  14. Sinin Hamdan, Iran Amri Musoddiq, Ahmad Fauzi Musib, Marini Sawawi
    The tone of peking 1, 2, 3, 5, 6, 1’ was investigated using time-frequency analysis (TFA). The frequencies were measured using PicoScope oscilloscope, Melda analyzer in Cubase version 9 and Adobe version 3. Three different approaches for time-frequency analysis were used: Fourier spectra (using PicoScope), spectromorphology (using Melda analyzer) and spectrograms (using Adobe). Fourier spectra only identify intensity-frequency within entire signals, while spectromorphology identify the changes of intensity-frequency spectrum at fixed time and Adobe spectrograms identify the frequency with time. PicoScope reading produces the spectra of the fundamental and overtone frequencies in the entire sound. These overtones are non-harmonic since they are non-integral multiples of the fundamental. The fundamental frequencies of peking 1, 2, 3, 5, 6 were 1066Hz (C6), 1178Hz (D6), 1342Hz (E6), 1599Hz (G6) and 1793Hz (A6) respectively while peking 1’was 2123Hz (C7) i.e. one octave higher than peking 1. Melda analyzer reading proved that all peking sustained the initial fundamental frequency and overtone at t=0 until 2s. TFA from Adobe reading provides a description of the sound in the time-frequency plane. From TFA, peking 1, 2 and 6 exhibited a much gentler attack and more rapid decay than peking 3, 5 and 1’.
    Matched MeSH terms: Spectrum Analysis
  15. Zainuri DA, Razak IA, Arshad S
    Acta Crystallogr E Crystallogr Commun, 2018 Aug 01;74(Pt 8):1087-1092.
    PMID: 30116568 DOI: 10.1107/S205698901800974X
    The title compounds, C24H18O2 and C24H17FO2, were synthesized using the Claisen-Schmidt condensation method and characterized by UV-Vis spectroscopy. Weak inter-molecular C-H⋯O, C-H⋯π and π-π hydrogen-bonding inter-actions help to stabilize the crystal structures of both compounds. The geometrical parameters obtained from the mol-ecular structure were optimized using density functional theory (DFT) calculations at the B3LYP/6-311++G(d,p) level, showing a good correlation with the experimental results. The small HOMO-LUMO energy gaps of 3.11 and 3.07 eV enhances the non-linear responses of these mol-ecular systems.
    Matched MeSH terms: Spectrum Analysis
  16. Shaharudin SM, Ismail S, Hassan NA, Tan ML, Sulaiman NAF
    Front Public Health, 2021;9:604093.
    PMID: 34195166 DOI: 10.3389/fpubh.2021.604093
    Novel coronavirus (COVID-19) was discovered in Wuhan, China in December 2019, and has affected millions of lives worldwide. On 29th April 2020, Malaysia reported more than 5,000 COVID-19 cases; the second highest in the Southeast Asian region after Singapore. Recently, a forecasting model was developed to measure and predict COVID-19 cases in Malaysia on daily basis for the next 10 days using previously-confirmed cases. A Recurrent Forecasting-Singular Spectrum Analysis (RF-SSA) is proposed by establishing L and ET parameters via several tests. The advantage of using this forecasting model is it would discriminate noise in a time series trend and produce significant forecasting results. The RF-SSA model assessment was based on the official COVID-19 data released by the World Health Organization (WHO) to predict daily confirmed cases between 30th April and 31st May, 2020. These results revealed that parameter L = 5 (T/20) for the RF-SSA model was indeed suitable for short-time series outbreak data, while the appropriate number of eigentriples was integral as it influenced the forecasting results. Evidently, the RF-SSA had over-forecasted the cases by 0.36%. This signifies the competence of RF-SSA in predicting the impending number of COVID-19 cases. Nonetheless, an enhanced RF-SSA algorithm should be developed for higher effectivity of capturing any extreme data changes.
    Matched MeSH terms: Spectrum Analysis
  17. Afishah Alias, Siti Rahayu Mohd Hashim, Wajir, Julynnie, Fauziah Abdul Aziz, Mihaly, Judith
    Unaffected, affected and heavily affected teeth enamel were studied by using FT-Raman spectroscopy. The 14 permanent teeth’s enamel surface were measured randomly, resulting in total n=43 FT-Raman spectra. The results obtained from FT-Raman spectra of heavily affected, affected and unaffected tooth’s enamel surfaces did not show any significant difference. In this study, Kruskal-Wallis and Wilcoxon rank sum tests were used to compare the intensity between the categories of enamel as well as the surfaces of teeth samples.
    Matched MeSH terms: Spectrum Analysis, Raman
  18. Wo, Yii Mei, Hidayah Shahar, Zaharudin Ahmad
    Present of 241Am in the environment is being determined as part of surveillance and research
    programs related to nuclear activities. The separation of 241Am from environmental samples was
    carried out against the IAEA’s reference material by using an improved in-house radiochemical
    separation method through anion exchange column, followed by the electro-deposition on a
    stainless steel disc, and finally assayed on alpha spectrometry counting system. The resulting
    spectra showed good isolated peak, indicating a good separation of the radionuclide of interest.
    The analytical results were in good agreement with the certified value for IAEA-326 and IAEA-368
    with the calculated U-score was 0.36 and 0.82, respectively, showing no significant difference
    between the experimental and certified value. Using this method, distributions of 241Am in seabed
    surface sediment in the Exclusive Economic Zone of East Coast Peninsular Malaysia were studied.
    Samples were collected during June 2008 where the concentrations of 241Am were found to be
    ranged from < 0.08 to 0.36 Bq/kg, dry weight.
    Matched MeSH terms: Spectrum Analysis
  19. Lombigit, Lojius, Maslina Ibrahim, Nolida Yusup, Nur Aira Abdul Rahman, Yong, Chong Fong
    Pulse Shaping Amplifier (PSA) is an essential component in nuclear spectroscopy system. This
    amplifier has two functions; to shape the output pulse and performs noise filtering. In this paper,
    we describe the procedure for the design and development of a pulse shaping amplifier which can
    be used in a nuclear spectroscopy system. This prototype was developed using high performance
    electronics devices and assembled on a FR4 type printed circuit board. Performance of this
    prototype was tested by comparing it with an equivalent commercial spectroscopy amplifier (Model
    Silena 7611). The test results showed that the performance of this prototype was comparable
    to the commercial spectroscopic amplifier.
    Matched MeSH terms: Spectrum Analysis
  20. He MQ, Shen JY, Petrović AP, He QL, Liu HC, Zheng Y, et al.
    Sci Rep, 2016 09 02;6:32508.
    PMID: 27587000 DOI: 10.1038/srep32508
    In the interfacial superconductor Bi2Te3/Fe1+yTe, two dimensional superconductivity occurs in direct vicinity to the surface state of a topological insulator. If this state were to become involved in superconductivity, under certain conditions a topological superconducting state could be formed, which is of high interest due to the possibility of creating Majorana fermionic states. We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show highly unconventional superconductivity, which appears as complex as in the cuprate high temperature superconductors. A very large superconducting twin-gap structure is replaced by a pseudogap above ~12 K which persists up to 40 K. While the larger gap shows unconventional order parameter symmetry and is attributed to a thin FeTe layer in proximity to the interface, the smaller gap is associated with superconductivity induced via the proximity effect in the topological insulator Bi2Te3.
    Matched MeSH terms: Spectrum Analysis
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