Displaying publications 101 - 120 of 147 in total

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  1. Fulltext Prevalence of hand-arm vibration syndrome among tyre shop workers in Kelantan, Malaysia
    Qamruddin AA, Nik Husain NR, Sidek MY, Hanafi MH, Ripin ZM, Ali N
    J Occup Health, 2019 Nov;61(6):498-507.
    PMID: 31364246 DOI: 10.1002/1348-9585.12078
    BACKGROUND: Prolonged exposure to hand-arm vibration is associated with a disorder of the vascular, neurological, and musculoskeletal systems of the upper limb known as hand-arm vibration syndrome (HAVS). Currently, the evidence of HAVS in tropical environments is limited.

    OBJECTIVES: To determine the prevalence and severity of HAVS among tyre shop workers in Kelantan, Malaysia.

    METHODS: A cross-sectional study involving 200 tyre shop workers from two districts in Kelantan was performed. Part one data were collected at the field using questionnaire, and hand-arm vibration was measured. Part two involved a set of hand clinical examinations. The workers were divided into high (≥5 m s-2 ) and low/moderate (<5 m s-2 ) exposure group according to their 8-hr time weighted average [A(8)] of vibration exposure. The differences between the two exposure group were then compared.

    RESULTS: The prevalence of the vascular, neurological, and musculoskeletal symptoms was 12.5% (95% CI 10.16 to 14.84), 37.0% (95% CI 30.31 to 43.69), and 44.5% (95% CI 37.61 to 51.38) respectively. When divided according to their exposure statuses, there was a significant difference in the prevalence of HAVS for all three components of vascular, neurological, and musculoskeletal (22.68% vs 2.91%, 62.89% vs 12.62% and 50.52% and 38.83%) respectively. All the clinical examinations findings also significantly differed between the two groups with the high exposure group having a higher abnormal result.

    CONCLUSION: Exposure to high A(8) of vibration exposure was associated with a higher prevalence of all three component of HAVS. There is a need for better control of vibration exposure in Malaysia.

    Matched MeSH terms: Hand-Arm Vibration Syndrome/etiology*
  2. Transmission of vibration through glove materials: effects of contact force
    Md Rezali KA, Griffin MJ
    Ergonomics, 2018 Sep;61(9):1246-1258.
    PMID: 29628001 DOI: 10.1080/00140139.2018.1462407
    This study investigated effects of applied force on the apparent mass of the hand, the dynamic stiffness of glove materials and the transmission of vibration through gloves to the hand. For 10 subjects, 3 glove materials and 3 contact forces, apparent masses and glove transmissibilities were measured at the palm and at a finger at frequencies in the range 5-300 Hz. The dynamic stiffnesses of the materials were also measured. With increasing force, the dynamic stiffnesses of the materials increased, the apparent mass at the palm increased at frequencies greater than the resonance and the apparent mass at the finger increased at low frequencies. The effects of force on transmissibilities therefore differed between materials and depended on vibration frequency, but changes in apparent mass and dynamic stiffness had predictable effects on material transmissibility. Depending on the glove material, the transmission of vibration through a glove can be increased or decreased when increasing the applied force. Practitioner summary: Increasing the contact force (i.e. push force or grip force) can increase or decrease the transmission of vibration through a glove. The vibration transmissibilities of gloves should be assessed with a range of contact forces to understand their likely influence on the exposure of the hand and fingers to vibration.
    Matched MeSH terms: Vibration*
  3. Lower back pain and its association with whole-body vibration and manual materials handling among commercial drivers in Sabah
    Awang Lukman K, Jeffree MS, Rampal KG
    Int J Occup Saf Ergon, 2019 Mar;25(1):8-16.
    PMID: 28978270 DOI: 10.1080/10803548.2017.1388571
    A cross-sectional study was undertaken to determine the prevalence of lower back pain (LBP) and its association with whole-body vibration (WBV) and manual materials handling (MMH). We studied 110 commercial vehicle drivers using a self-administered questionnaire and the VI-400Pro human vibration monitor. Prevalence of LBP was 66.4%. The percentage of drivers who had frequent manual handling of heavy loads was 45.5% and those who handled heavy loads in awkward postures accounted for 86.4%. Daily vibration A(8) averaged on the z axis was 0.25 (0.06) m·s-2 and at vector sum was 0.29 (0.07) m·s-2. Daily vibration exposures on the z axis, frequent manual handling of heavy loads and awkward posture during MMH were significantly associated with LBP. Drivers who are exposed to WBV and frequently handle heavy loads manually and with awkward postures probably have more LBP than drivers who are exposed to only one of these risk factors.
    Matched MeSH terms: Vibration/adverse effects*
  4. Effects of vibration on occupant driving performance under simulated driving conditions
    Azizan A, Fard M, Azari MF, Jazar R
    Appl Ergon, 2017 Apr;60:348-355.
    PMID: 28166895 DOI: 10.1016/j.apergo.2016.12.020
    Although much research has been devoted to the characterization of the effects of whole-body vibration on seated occupants' comfort, drowsiness induced by vibration has received less attention to date. There are also little validated measurement methods available to quantify whole body vibration-induced drowsiness. Here, the effects of vibration on drowsiness were investigated. Twenty male volunteers were recruited for this experiment. Drowsiness was measured in a driving simulator, before and after 30-min exposure to vibration. Gaussian random vibration, with 1-15 Hz frequency bandwidth was used for excitation. During the driving session, volunteers were required to obey the speed limit of 100 kph and maintain a steady position on the left-hand lane. A deviation in lane position, steering angle variability, and speed deviation were recorded and analysed. Alternatively, volunteers rated their subjective drowsiness by Karolinska Sleepiness Scale (KSS) scores every 5-min. Following 30-min of exposure to vibration, a significant increase of lane deviation, steering angle variability, and KSS scores were observed in all volunteers suggesting the adverse effects of vibration on human alertness level.
    Matched MeSH terms: Vibration/adverse effects*
  5. Fulltext Improvement of adaptive GAs and back propagation ANNs performance in condition diagnosis of multiple bearing system using grey relational analysis
    Wulandhari LA, Wibowo A, Desa MI
    Comput Intell Neurosci, 2014;2014:419743.
    PMID: 25587265 DOI: 10.1155/2014/419743
    Condition diagnosis of multiple bearings system is one of the requirements in industry field, because bearings are used in many equipment and their failure can result in total breakdown. Conditions of bearings commonly are reflected by vibration signals data. In multiple bearing condition diagnosis, it will involve many types of vibration signals data; thus, consequently, it will involve many features extraction to obtain precise condition diagnosis. However, large number of features extraction will increase the complexity of the diagnosis system. Therefore, in this paper, we presented a diagnosis method which is hybridization of adaptive genetic algorithms (AGAs), back propagation neural networks (BPNNs), and grey relational analysis (GRA) to diagnose the condition of multiple bearings system. AGAs are used in the diagnosis algorithm to determine the best initial weights of BPNNs in order to improve the diagnosis accuracy. In addition, GRA is applied to determine and select the dominant features from the vibration signal data which will provide good diagnosis of multiple bearings system in less features extraction. The experiments results show that AGAs-BPNNs with GRA approaches can increase the accuracy of diagnosis in shorter processing time, compared with the AGAs-BPNNs without the GRA.
    Matched MeSH terms: Vibration
  6. Vocal fold vibratory characteristics in normal female speakers from high-speed digital imaging
    Ahmad K, Yan Y, Bless DM
    J Voice, 2012 Mar;26(2):239-53.
    PMID: 21621975 DOI: 10.1016/j.jvoice.2011.02.001
    The purpose of the study was to investigate relationships between vocal fold vibrations and voice quality. Laryngeal images obtained from high-speed digital imaging (HSDI) were examined for their open-closed timing characteristics and perturbation values. A customized software delineated the glottal edges and used the Hilbert transform-based method of analysis to provide objective quantification of glottal perturbation. Overlay tracings of the transformed glottal cycles provided visual patterns on the overall vibratory dynamics. In this paper, we described the use of this method in looking at vibratory characteristics of a group of young female speakers (N=23). We found that, females with no voice complaints and who had been perceived to have normal voices were not a homogeneous group in terms of their glottal vibratory patterns during phonation. Their vibratory patterns showed characteristics similar to exemplar voices targeted to be clear (50%), pressed (27%), breathy (15%), or a mixed quality (8%). Perturbation range in terms of cycle-to-cycle frequency and amplitude was small and did not discriminate patterns. All these patterns yielded perceptually normal voices suggesting that in normal young speakers, the level of perturbation may be more important to the judgment than the actual pattern of closure.
    Matched MeSH terms: Vibration
  7. Ab initio calculation of vibrational frequencies and Raman spectra of barium peroxide glass including comparison of tetrahedral BaO4 with GeO4 and SiO4
    Rosli AN, Zabidi NA, Kassim HA, Shrivastava KN
    Spectrochim Acta A Mol Biomol Spectrosc, 2011 Sep;79(5):1251-5.
    PMID: 21571582 DOI: 10.1016/j.saa.2011.04.051
    We have calculated the vibrational frequencies of clusters of atoms from the first principles by using the density-functional theory in the local density approximation (LDA). We are also able to calculate the electronic binding energy for all of the clusters of atoms from the optimized structure. We have made clusters of BanOm (n, m=1-6) and have determined the bond lengths, vibrational frequencies as well as intensities in each case. We find that the peroxide cluster BaO2 occurs with the O-O vibrational frequency of 836.3 cm(-1). We also find that a glass network occurs in the material which explains the vibrational frequency of 67 cm(-1). The calculated values agree with those measured from the Raman spectra of barium peroxide and Ba-B-oxide glass. We have calculated the vibrational frequencies of BaO4, GeO4 and SiO4 each in tetrahedral configuration and find that the vibrational frequencies in these systems depend on the inverse square root of the atomic mass.
    Matched MeSH terms: Vibration
  8. One pot synthesis, molecular structure and spectroscopic studies (X-ray, IR, NMR, UV-Vis) of novel 2-(4,6-dimethoxy-1,3,5-triazin-2-yl) amino acid ester derivatives
    El-Faham A, Soliman SM, Osman SM, Ghabbour HA, Siddiqui MR, Fun HK, et al.
    Spectrochim Acta A Mol Biomol Spectrosc, 2016 Apr 15;159:184-98.
    PMID: 26845586 DOI: 10.1016/j.saa.2016.01.051
    Novel series of 2-(4,6-dimethoxy,1,3,5-triazin-2-yl) amino acid ester derivatives were synthesized using simple one pot method in methanol. The products were obtained in high yields and purities as observed from their spectral data, elemental analyses, GC-MS and X-ray crystallographic analysis. The B3LYP/6-311G(d,p) calculated molecular structures are well correlated with the geometrical parameters obtained from the X-ray analyses. The spectroscopic properties such as IR vibrational modes, NMR chemical shifts and UV-Vis electronic transitions were discussed both experimentally and theoretically. The IR vibrational frequencies showed good correlations with the experimental data (R(2)=0.9961-0.9995). The electronic spectra were assigned based on the TD-DFT results. Intense electronic transition band is calculated at 198.1nm (f=0.1389), 204.2nm (f=0.2053), 205.0 (f=0.1704) and 205.7 (0.2971) for compounds 6a-i, respectively. The molecular orbital energy levels contributed in the longest wavelength transition band were explained. For all compounds, the experimental wavelengths showed red shifts compared to the calculations due to the solvent effect. The NMR chemical shifts were calculated using GIAO method. The NBO analyses were performed to predict the stabilization energies due to the electron delocalization processes occur in the studied systems.
    Matched MeSH terms: Vibration
  9. Observations of acoustic streaming fields around an oscillating ultrasonic file
    Ahmad M, Roy RA, Kamarudin AG
    Endod Dent Traumatol, 1992 Oct;8(5):189-94.
    PMID: 1302678
    The steady acoustic streaming generated around straight and precurved oscillating ultrasonic files driven by the Piezon-Master 400 unit was examined in the free field and in small channels using a stereomicroscope. In addition, the effect of file-wall contact on streaming production was also investigated. The results indicated that the ultrasonic files can generate acoustic streaming both in the free field and in the small channel. Higher velocity streaming was observed when smaller size files were employed and when the file was precurved. Light file-wall contact did not totally inhibit streaming while severe file-wall contact inhibited movement of the file and, as a result, no streaming was observed. The positions and length scales of the streaming vortices appeared to be influenced by the presence of boundaries. In the free field, two rows of vortices were situated along the sides of the file while in the small channel, the vortices were positioned above the surface of the file. These results indicated that it is possible for acoustic streaming to occur in a confined space as in a root canal provided that severe file-wall contact is avoided. It is therefore recommended that light filing or allowing the file to freely vibrate during some stage of treatment should be carried out in order to generate streaming in the root canal.
    Matched MeSH terms: Vibration
  10. Some observations on the mechanics of oscillation of ultrasonic files
    Ahmad M
    Endod Dent Traumatol, 1990 Feb;6(1):12-5.
    PMID: 2202589
    The resonant characteristics of ultrasonic files driven by the Cavi-Endo unit were examined. The investigation was carried out by evaluating the pattern of oscillation and the power emitted by the ultrasonic files. It was observed that the files oscillated in a sinusoidal fashion, exhibiting a standing wave pattern along the file. The power emitted was found to be directly proportional to the flexibility of the file. Such behaviour is typical of a system that exhibits resonance.
    Matched MeSH terms: Vibration
  11. Measurements of temperature generated by ultrasonic file in vitro
    Ahmad M
    Endod Dent Traumatol, 1990 Oct;6(5):230-1.
    PMID: 2133315
    The temperature rise of the irrigant in the root canal during free vibration of the ultrasonic file was studied in vitro in 10 human teeth. The mean temperature rise was found to be 0.6 degrees C. The minimal temperature increase may not significantly contribute to the effectiveness of ultrasonic root canal instrumentation.
    Matched MeSH terms: Vibration
  12. Fulltext Smart Walk Stick for Visually Impaired People: Design and Implementation
    Saud, Safaa Najah, Manivannan, Dasarataan, Adzliza Binti Salmi, Lilysuriazna Raya
    Journal of Management & Science, 2018;16(2):19-28.
    MyJurnal
    Nowadays, the scientific knowledge is developing frequently in numerous characteristics to be able to offer versatile and also safe and sound tendency for the users. At this time many of prevalent together with employed indicate by the visually impaired people are using the ivory stick, nonetheless it possesses constraints. With the recent technological innovation, it is easy to prolong the assistance acquire for people who have visual disability throughout their movability; this design endorses a cost-effective ultrasonic stick for visually encountered people today, to be able to achieve an exclusive self-reliance and even exempt from the additional assist. A portable convenient to use technology is designed which could recognize the obstructions in the way working with ultrasonic sensors in addition to vibrator. Ultrasonic sensors will be able to inspect three types of distinct heights. Vibrator is frequently used as a substitute gadget in the areas that surrounds with the minimal signal coverage also nosy environment. The buzzer and vibration motor are initialized while any kind of hindrance is identified. Global positioning system device presents the details about to the proceeding approach both work or even home, that has been supplied considering that control keys together with a contingency switch. Text message unit is utilized by the blind to send out SMS info to the saved phone numbers in the Arduino in the event of unexpected emergency.

    Matched MeSH terms: Vibration
  13. Fulltext Prevalence and its associated factors of low back pain among foggers in a District Health Office in Malaysia
    Muhamad Farhan Ab Razak, Titi Rahmawati Hamedon, Haidar Rizal Toha
    Malaysian Journal of Medicine and Health Sciences, 2019;15(104):109-109.
    MyJurnal
    Introduction: Low back pain (LBP) is a common symptom among working population worldwide. Foggers prone to have LBP because there are exposed to physical factors such as lifting heavy object, awkward body posture and vibration. However, LBP had never been studied among the fogger. The objective of this study was to determine the prevalence and the factors associated with LBP. Methods: A cross-sectional study was carried out in all District Health Office in Johor, Malaysia by using a validated self-administered questionnaire and anthropometric measure-ments. Chi-square or Fisher’s exact test was used for inferential statistic and multiple logistic regression was used to determine the associated factors. The significance level was determined at p < 0.05. Results: The response rate was 83.9%. Majority of them are male (99.6%), Malay (95.8%), married (85.8%) and educated up to secondary school (53.5%). Majority of respondents do not have part time job (89.6%) but they work overtime everyday (62.7%). Most of them do four hours overtime daily (77.3%). The prevalence of LBP was 68.5% among respondents. There was a significant association between doing part time job, duration of doing overtime per week, body mass index (BMI) and duration of fogging activities. Finally, the associated factors of LBP were doing overtime for more than 20 hours per week (adjusted OR=1.914, 95% CI [1.102, 3.324], p = 0.021), BMI of more than 23.00 kg/m2 (adjusted OR=2.066, 95% CI [1.090, 3.916], p = 0.026) and having no part time job (adjusted OR=0.135, 95% CI [0.031, 0.599], p = 0.021). Conclusion: Prevention needs to be initiated to change the modifiable factors of LBP in order to reduce the prevalence of LBP among them.
    Matched MeSH terms: Vibration
  14. Fulltext Enhancing the Permeate Flux of Direct Contact Membrane Distillation Modules with Inserting 3D Printing Turbulence Promoters
    Chang H, Ho CD, Chen YH, Chen L, Hsu TH, Lim JW, et al.
    Membranes (Basel), 2021 Apr 07;11(4).
    PMID: 33916991 DOI: 10.3390/membranes11040266
    Two geometric shape turbulence promoters (circular and square of same areas) of different array patterns using three-dimensional (3D) printing technology were designed for direct contact membrane distillation (DCMD) modules in the present study. The DCMD device was performed at middle temperature operation (about 45 °C to 60 °C) of hot inlet saline water associated with a constant temperature of inlet cold stream. Attempts to reduce the disadvantageous temperature polarization effect were made inserting the 3D turbulence promoters to promote both the mass and heat transfer characteristics in improving pure water productivity. The additive manufacturing 3D turbulence promoters acting as eddy promoters could not only strengthen the membrane stability by preventing vibration but also enhance the permeate flux with lessening temperature polarization effect. Therefore, the 3D turbulence promoters were individually inserted into the flow channel of the DCMD device to create vortices in the flow stream and increase turbulent intensity. The modeling equations for predicting the permeate flux in DCMD modules by inserting the manufacturing 3D turbulence promoter were investigated theoretically and experimentally. The effects of the operating conditions under various geometric shapes and array patterns of turbulence promoters on the permeate flux with hot inlet saline temperatures and flow rates as parameters were studied. The distributions of the fluid velocities were examined using computational fluid dynamics (CFD). Experimental study has demonstrated a great potential to significantly accomplish permeate flux enhancement in such new design of the DCMD system. The permeate flux enhancement for the DCMD module by inserting 3D turbulence promoters in the flow channel could provide a maximum relative increment of up to 61.7% as compared to that in the empty channel device. The temperature polarization coefficient (τtemp) was found in this study for various geometric shapes and flow patterns. A larger τtemp value (the less thermal resistance) was achieved in the countercurrent-flow operation than that in the concurrent-flow operation. An optimal design of the module with inserting turbulence promoters was also delineated when considering both permeate flux enhancement and energy utilization effectiveness.
    Matched MeSH terms: Vibration
  15. Fulltext The Study of Plasticized Sodium Ion Conducting Polymer Blend Electrolyte Membranes Based on Chitosan/Dextran Biopolymers: Ion Transport, Structural, Morphological and Potential Stability
    Asnawi ASFM, Aziz SB, Brevik I, Brza MA, Yusof YM, Alshehri SM, et al.
    Polymers (Basel), 2021 Jan 26;13(3).
    PMID: 33530553 DOI: 10.3390/polym13030383
    The polymer electrolyte system of chitosan/dextran-NaTf with various glycerol concentrations is prepared in this study. The electrical impedance spectroscopy (EIS) study shows that the addition of glycerol increases the ionic conductivity of the electrolyte at room temperature. The highest conducting plasticized electrolyte shows the maximum DC ionic conductivity of 6.10 × 10-5 S/cm. Field emission scanning electron microscopy (FESEM) is used to investigate the effect of plasticizer on film morphology. The interaction between the electrolyte components is confirmed from the existence of the O-H, C-H, carboxamide, and amine groups. The XRD study is used to determine the degree of crystallinity. The transport parameters of number density (n), ionic mobility (µ), and diffusion coefficient (D) of ions are determined using the percentage of free ions, due to the asymmetric vibration (υas(SO3)) and symmetric vibration (υs(SO3)) bands. The dielectric property and relaxation time are proved the non-Debye behavior of the electrolyte system. This behavior model is further verified by the existence of the incomplete semicircle arc from the Argand plot. Transference numbers of ion (tion) and electron (te) for the highest conducting plasticized electrolyte are identified to be 0.988 and 0.012, respectively, confirming that the ions are the dominant charge carriers. The tion value are used to further examine the contribution of ions in the values of the diffusion coefficient and mobility of ions. Linear sweep voltammetry (LSV) shows the potential window for the electrolyte is 2.55 V, indicating it to be a promising electrolyte for application in electrochemical energy storage devices.
    Matched MeSH terms: Vibration
  16. Effect of Sintering on Di-Electric Characteristics of Al-Cu Doped Cobalt Ferrite Nanoparticles
    Dabagh S, Chaudhary K, Haider Z, Ali J
    J Nanosci Nanotechnol, 2019 Jul 01;19(7):4142-4146.
    PMID: 30764983 DOI: 10.1166/jnn.2019.16331
    Aluminium substituted cobalt-copper Co1-xCuxFe2-xAlxO₄, (x ═ 0.8) nanoparticles are grown and sintered at different temperature in the range 600 to 900 °C. XRD analysis on nanoparticles prepared at sintered temperatures of 700 °C and 800 °C confirms the spinel structure and presence of hematite phase (alpha ferrite) in them. The dielectric behaviour of the prepared nano-particles is investigated. Although crystallinity improved with increase in sintering temperature and there was a dielectric loss at higher probe analyser frequency. The synthesized nanoparticles an average particle size of 20-24 nm while the FTIR absorption in regions of 586-595 cm-1 and 450-460 cm-1 indicated the presence of intrinsic vibrations of the tetrahedral and octahedral complexes respectively. Electrical resistivity as a function of temperature confirms the semiconducting nature of the Cu-Al substituted cobalt ferrite, and is attributed to the hopping mechanism between Fe2+ Fe3+ ions and Co2+ Cu2+, Co2+ Al3+. The lower values of dielectric constants and dielectric losses make Al-Cu doped cobalt ferrite, a potential material for microwave and radio wave absorber applications.
    Matched MeSH terms: Vibration
  17. Temperature dependence of the Raman spectrum of 1-(4-chlorophenyl)-3-(2-thienyl)prop-2-en-1-one
    de Toledo TA, da Costa RC, Al-Maqtari HM, Jamalis J, Pizani PS
    Spectrochim Acta A Mol Biomol Spectrosc, 2017 Jun 05;180:9-17.
    PMID: 28259100 DOI: 10.1016/j.saa.2017.02.051
    The heterocyclic chalcone containing thiophene ring 1-(4-chlorophenyl)-3-(2-thienyl)prop-2-en-1-one, C13H9ClOS was synthesized and investigated using experimental techniques such as nuclear magnetic resonance (1H and 13C NMR), Fourier transform infrared spectroscopy (FTIR) at room temperature, differential scanning calorimeter (DSC) from room temperature to 500K and Raman scattering at the temperature range 10-413K in order to study its structure and vibrational properties as well as stability and possible phase transition. Density functional theory (DFT) calculations were performed to determine the vibrational spectrum viewing to improve the knowledge of the material properties. A reasonable agreement was observed between theoretical and experimental Raman spectrum taken at 10K since anharmonic effects of the molecular motion is reduced at low temperatures, leading to a more comprehensive assignment of the vibrational modes. Increasing the temperature up to 393K, was observed the typical phonon anharmonicity behavior associated to changes in the Raman line intensities, line-widths and red-shift, in special in the external mode region, whereas the internal modes region remains almost unchanged due its strong chemical bonds. Furthermore, C13H9ClOS goes to melting phase transition in the temperature range 393-403K and then sublimates in the temperature range 403-413K. This is denounced by the disappearance of the external modes and the absence of internal modes in the Raman spectra, in accordance with DSC curve. The enthalpy (ΔH) obtained from the integration of the endothermic peak in DSC curve centered at 397K is founded to be 121.5J/g.
    Matched MeSH terms: Vibration
  18. Fulltext FEM Analysis of Sezawa Mode SAW Sensor for VOC Based on CMOS Compatible AlN/SiO₂/Si Multilayer Structure
    Aslam MZ, Jeoti V, Karuppanan S, Malik AF, Iqbal A
    Sensors (Basel), 2018 May 24;18(6).
    PMID: 29882929 DOI: 10.3390/s18061687
    A Finite Element Method (FEM) simulation study is conducted, aiming to scrutinize the sensitivity of Sezawa wave mode in a multilayer AlN/SiO₂/Si Surface Acoustic Wave (SAW) sensor to low concentrations of Volatile Organic Compounds (VOCs), that is, trichloromethane, trichloroethylene, carbon tetrachloride and tetrachloroethene. A Complimentary Metal-Oxide Semiconductor (CMOS) compatible AlN/SiO₂/Si based multilayer SAW resonator structure is taken into account for this purpose. In this study, first, the influence of AlN and SiO₂ layers’ thicknesses over phase velocities and electromechanical coupling coefficients (k²) of two SAW modes (i.e., Rayleigh and Sezawa) is analyzed and the optimal thicknesses of AlN and SiO₂ layers are opted for best propagation characteristics. Next, the study is further extended to analyze the mass loading effect on resonance frequencies of SAW modes by coating a thin Polyisobutylene (PIB) polymer film over the AlN surface. Finally, the sensitivity of the two SAW modes is examined for VOCs. This study concluded that the sensitivity of Sezawa wave mode for 1 ppm of selected volatile organic gases is twice that of the Rayleigh wave mode.
    Matched MeSH terms: Vibration
  19. Fulltext Influence of Ispaghula and Zein Coating on Ibuprofen-Loaded Alginate Beads Prepared by Vibration Technology: Physicochemical Characterization and Release Studies
    Lyn Heng JJ, Teng JH, Saravanan M, Pushpamalar J
    Sci Pharm, 2018 Jun 05;86(2).
    PMID: 29874858 DOI: 10.3390/scipharm86020024
    The purpose behind the work was to fabricate alginate beads with better drug loading and extended drug release. Ispaghula was used to enhance the drug loading while zein was employed to extend the drug release. Ibuprofen was employed as a model drug in this study. Ibuprofen-loaded alginate beads with and without ispaghula were prepared using vibration technology and coated with zein. The beads prepared with alginate alone were shown to have loading and entrapment efficiencies of 35% and 70% w/w, respectively. Addition of ispaghula in alginate showed a significant increase (p < 0.05) in the drug loading (42% w/w) and entrapment efficiency (84% w/w). Fourier-transform infrared spectroscopy confirmed the presence of ispaghula and zein coating in the alginate beads as well as the ibuprofen loading. Scanning electron microscopy revealed better spherical geometry in the beads with ispaghula. The surface morphology of the uncoated beads was rough due to crystalline and surface drug. The zein coating has produced a smoother surface and particle adhesion. Differential scanning calorimetry has shown a reduction in drug crystallinity. Alginate beads extended the drug release for 4 h and the presence of zein extended the release for 6 h.
    Matched MeSH terms: Vibration
  20. Molecular structure, second- and third-order nonlinear optical properties and DFT studies of a novel non-centrosymmetric chalcone derivative: (2E)-3-(4-fluorophenyl)-1-(4-{[(1E)-(4-fluorophenyl)methylene]amino}phenyl)prop-2-en-1-one
    Maidur SR, Patil PS, Ekbote A, Chia TS, Quah CK
    Spectrochim Acta A Mol Biomol Spectrosc, 2017 Sep 05;184:342-354.
    PMID: 28528255 DOI: 10.1016/j.saa.2017.05.015
    In the present work, the title chalcone, (2E)-3-(4-fluorophenyl)-1-(4-{[(1E)-(4-fluorophenyl) methylene]amino}phenyl)prop-2-en-1-one (abbreviated as FAMFC), was synthesized and structurally characterized by single-crystal X-ray diffraction. The compound is crystallized in the monoclinic system with non-centrosymmetric space group P21 and hence it satisfies the essential condition for materials to exhibit second-order nonlinear optical properties. The molecular structure was further confirmed by using FT-IR and 1H NMR spectroscopic techniques. The title crystal is transparent in the Vis-NIR region and has a direct band gap. The third-order nonlinear optical properties were investigated in solution (0.01M) by Z-scan technique using a continuous wave (CW) DPSS laser at the wavelength of 532nm. The title chalcone exhibited significant two-photon absorption (β=35.8×10-5cmW-1), negative nonlinear refraction (n2=-0.18×10-8cm2W-1) and optical limiting (OL threshold=2.73kJcm-2) under the CW regime. In support of the experimental results, a comprehensive theoretical study was carried out on the molecule of FAMFC using density functional theory (DFT). The optimized geometries and frontier molecular orbitals were calculated by employing B3LYP/6-31+G level of theory. The optimized molecular structure was confirmed computationally by IR vibrational and 1H NMR spectral analysis. The experimental UV-Vis-NIR spectrum was interpreted using computational chemistry under time-dependent DFT. The static and dynamic NLO properties such as dipole moments (μ), polarizability (α), and first hyperpolarizabilities (β) were computed by using finite field method. The obtained dynamic first hyperpolarizability β(-2ω;ω,ω) at input frequency ω=0.04282a.u. is predicted to be 161 times higher than urea standard. The electronic excitation energies and HOMO-LUMO band gap for FAMFC were also evaluated by DFT. The experimental and theoretical results are in good agreement, and the NLO study suggests that FAMFC molecule can be a potential candidate in the nonlinear optical applications.
    Matched MeSH terms: Vibration
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