Search results for: ultraviolet radiations

Authors: Fedda Y. Alzoubi, Ihsan A. Aljarrah

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Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in different applications, especially in biomedical applications. Samples of different alkaline water were prepared in order to study the effect of alkalinity of water on the optical properties, size, and morphology of colloidal AgNPs prepared according to the chemical reduction method using the prepared water samples. Ultraviolet-Visible spectrophotometer, Zeta-sizer, and Scanning electron microscope (SEM) have been utilized to carry out this study. Absorption spectra AgNPs in different alkaline water show a surface Plasmon resonance (SPR) peak at the wavelength of 420 nm. The position of this peak is sensitive to the shape of the particles, and in our case, it indicates that the particles are spherical. As the alkalinity increases, the intensity of the SPR peak decreases, indicating the aggregation of particles. Zeta-sizer measurements show that the average diameter for AgNPs in pure water is found to be 53.51 nm, and this value increases as the alkalinity increases. Zeta potential values of samples show that the negatively coated particles are stable in the solution. SEM images insure the spherical shape of the prepared nanoparticles and show that as the alkalinity increases the particles aggregate into larger particles.

Keywords: aggregation, alkalinity, colloid, nanoparticle

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Authors: Akash Bera, Suraj Singh, Jacinta Dsouza, Ramakrishna V. Hosur, Pushpa Mishra

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Ultraviolet C (UVC) radiation induces apoptosis in mammalian cells and it is suggested that the mechanism by which this occurs is the mitochondrial pathway of apoptosis through the release of cytochrome c from the mitochondria into the cytosol. The Bcl-2 family of proteins pro-and anti-apoptotic is the regulators of the mitochondrial pathway of apoptosis. Upon UVC irradiation, the proliferation of apoptosis is enhanced through the downregulation of the anti-apoptotic protein Bcl-xl and up-regulation of Bax. Although the participation of the Bcl-2 family of proteins in apoptosis appears responsive to UVC radiation, to the author's best knowledge, it is unknown how the structure and, effectively, the function of these proteins are directly impacted by UVC exposure. In this background, we present here a structural rationale for the effect of UVC irradiation in restoring apoptosis using two of the relevant proteins, namely, Bid-FL and Bcl-xl ΔC, whose solution structures have been reported previously. Using a variety of biophysical tools such as circular dichroism, fluorescence and NMR spectroscopy, we show that following UVC irradiation, the structures of Bcl-xlΔC and Bid-FL are irreversibly altered. Bcl-xLΔC is found to be more sensitive to UV exposure than Bid-FL. From the NMR data, dramatic structural perturbations (α-helix to β-sheet) are seen to occur in the BH3 binding region, a crucial segment of Bcl-xlΔC which impacts the efficacy of its interactions with pro-apoptotic tBid. These results explain the regulation of apoptosis by UVC irradiation. Our results on irradiation dosage dependence of the structural changes have therapeutic potential for the treatment of cancer.

Keywords: Bid, Bcl-xl, UVC, apoptosis

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Authors: Shinhao Yang, Hsiao-Chien Huang, Chin-Hsiang Luo

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The leakage of protective clothing is an important issue in the occupational health field. There is no quantitative method for measuring the leakage of personal protective equipment. This work aims to measure the quantitative leakage of the personal protective equipment by using the fluorochrome aerosol tracer. The fluorescent aerosols were employed as airborne particulates in a controlled chamber with ultraviolet (UV) light-detectable stickers. After an exposure-and-leakage test, the protective equipment was removed and photographed with UV-scanning to evaluate areas, color depth ratio, and aerosol deposition and shielding effects of the areas where fluorescent aerosols had adhered to the body through the protective equipment. Thus, this work built a calculation software for quantitative leakage ratio of protective clothing based on fluorescent illumination depth/aerosol concentration ratio, illumination/Fa ratio, aerosol deposition and shielding effects, and the leakage area ratio on the segmentation. The results indicated that the two-repetition total leakage rate of the X, Y, and Z type protective clothing for subject T were about 3.05, 4.21, and 3.52 (mg/m2). For five-repetition, the leakage rate of T were about 4.12, 4.52, and 5.11 (mg/m2).

Keywords: fluorochrome, deposition, shielding effects, digital image processing, leakage ratio, personal protective equipment

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Authors: Z. Miao, Y. Chu, Y. Zhang

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The unique cholesteric phase liquid crystals obtained by mixing nematic liquid crystals with chiral dopants have gained valuable applications in the display field for their selective reflection and circular dichroism properties. The periodic arrangement of the helical structure of cholesteric liquid crystals makes it possible to produce Bragg reflection of circularly polarized light irradiated perpendicularly to the liquid crystals and, therefore, to acquire semi- or fully reflective surfaces or films. If the polymer-liquid crystal composites are combined with polymeric monomers, commercialized reflective broadband films can be fabricated. In this study, the polymer-liquid crystal composites reflecting visible light region (wavelength centered at 550 nm) were studied to analyze the effects of AC electric field at different voltages and frequencies on the optical texture of the composites, as well as the effects of polymerization temperature and ultraviolet (UV) intensity on the polymerization reaction and reflection bandwidth. The optimal sample was finally obtained at 100Hz, 120V, 30℃, 1.00 mW/cm², which provides a research suggestion to solve the influencing factors of visible light reflection bandwidths.

Keywords: cholesteric liquid crystal, reflection bandwidths, negative dielectric anisotropy, planar texture

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Authors: Sanam Pudasaini, A. T. K. Perera, Ahmed Syed Shaheer Uddin, Sum Huan Ng, Chun Yang

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Development of high-efficiency and environment friendly bacterial inactivation methods is of great importance for preventing waterborne diseases which are one of the leading causes of death in the world. Traditional bacterial inactivation methods (e.g., ultraviolet radiation and chlorination) have several limitations such as longer treatment time, formation of toxic byproducts, bacterial regrowth, etc. Recently, an electroporation-based inactivation method was introduced as a substitute. Here, an electroporation-based continuous flow microfluidic device equipped with an array of micropillars is developed, and the device achieved high bacterial inactivation performance ( > 99.9%) within a short exposure time ( < 1 s). More than 99.9% reduction of Escherichia coli bacteria was obtained for the flow rate of 1 mL/hr, and no regrowth of bacteria was observed. Images from scanning electron microscope confirmed the formation of electroporation-induced nano-pore within the cell membrane. Through numerical simulation, it has been shown that sufficiently large electric field strength (3 kV/cm), required for bacterial electroporation, were generated using PDMS micropillars for an applied voltage of 300 V. Further, in this method of inactivation, there is no involvement of chemicals and the formation of harmful by-products is also minimum.

Keywords: electroporation, high-efficiency, inactivation, microfluidics, micropillar

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Authors: Adesoji Sodeinde

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Analytical derivatives has recently undergone an explosive growth in areas of separation techniques, likewise in detectability of certain compound/concentrated ions. The gloomy and depressing scenario which charaterized the application of analytical derivatives in areas of water analysis, water cycle and the environment should not be allowed to continue unabated. Due to technological advancement in various chemical/biochemical analysis separation techniques is widely used in areas of medical, forensic and to measure and assesses environment and social-economic impact of alternative control strategies. This technological improvement was dully established in the area of comparison between certain separation/detection techniques to bring about vital result in forensic[as Gas liquid chromatography reveals the evidence given in court of law during prosecution of drunk drivers]. The water quality analysis,pH and water temperature analysis can be performed in the field, the concentration of dissolved free amino-acid [DFAA] can also be detected through separation techniques. Some important derivatives/ions used in separation technique. Water analysis : Total water hardness [EDTA to determine ca and mg ions]. Gas liquid chromatography : innovative gas such as helium [He] or nitrogen [N] Water cycle : Animal bone charcoal,activated carbon and ultraviolet light [U.V light].

Keywords: analytical derivative, environment, water analysis, chemical/biochemical analysis

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Authors: Xiangxu Chai, Bin Feng, Ping Li, Deyan Zhu, Liquan Wang, Guanzhong Wang, Yukun Jing

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In high power large-aperture laser systems, such as the inertial confinement fusion project, the Nd: glass laser (1053nm) is usually needed to be converted to ultraviolet (UV) light and the fourth harmonic generation (FHG) is one of the most favorite candidates to achieve UV light. Deuterated potassium dihydrogen phosphate (DKDP) crystal is an optimal choice for converting the Nd: glass radiation to the fourth harmonic laser by noncritical phase matching (NCPM). To reduce the damage probability of focusing lens, the DKDP crystal is suggested to be set before the focusing lens. And a converging beam enters the FHG crystal consequently. In this paper, we simulate the process of FHG in the scheme and the dependence of FHG efficiency on the lens’ F is derived. Besides, DKDP crystal with gradient deuterium is proposed to realize the NCPM FHG of the converging beam. At every position, the phase matching is achieved by adjusting the deuterium level, and the FHG efficiency increases as a result. The relation of the lens’ F with the deuterium gradient is investigated as well.

Keywords: fourth harmonic generation, laser induced damage, converging beam, DKDP crystal

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Authors: M.F. Elkady, Sahar Zaki, Desouky Abd-El-Haleem

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Silver nanoparticles (AgNPs) are already widely prepared using different technologies. However, there are limited data on the effects of hydrogen ion concentration on nano-silver production. In this investigation, the impact of the pH reaction medium toward the particle size, agglomeration and the yield of the produced bio-synthesized silver were established. Quasi-spherical silver nanoparticles were synthesized through the biosynthesis green production process using the Egyptian E. coli bacterial strain 23N at different pH values. The formation of AgNPs has been confirmed with ultraviolet–visible spectra through identification of their characteristic peak at 410 nm. The quantitative production yield and the orientation planes of the produced nano-silver were examined using X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Quantitative analyses indicated that the silver production yield was promoted at elevated pH regarded to increase the reduction rate of silver precursor through both chemical and biological processes. As a result, number of the nucleus and thus the size of the silver nanoparticles were tunable through changing pH of the reaction system. Accordingly, the morphological structure and size of the produced silver and its aggregates were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. It was considered that the increment in pH value of the reaction media progress the aggregation of silver clusters. However, the presence of stain 23N biomass decreases the possibility of silver aggregation at the pH 7.

Keywords: silver nanoparticles, biosynthesis, reaction media pH, nano-silver characterization

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Authors: Seyed Ali Mahdipour, Maryam Shafeei Sarvestani

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Radiation pressure acceleration (RPA) and target normal sheath acceleration (TNSA) are the most important methods of Laser-accelerated proton beams (LAP) planning systems.LAP has inspired novel applications that can benefit from proton bunch properties different from conventionally accelerated proton beams. The secondary neutron and photon produced in the collision of protons with beamline components are of the important concern in proton therapy. Various published Monte Carlo researches evaluated the beamline and shielding considerations for TNSA method, but there is no studies directly address secondary neutron and photon production from RPA method in LAP. The purpose of this study is to calculate the flux distribution of neutron and photon secondary radiations on the first area ofLAP and to determine the optimize thickness and radius of the energyselector in a LAP planning system based on RPA method. Also, we present the Monte Carlo calculations to determine the appropriate beam pipe for shielding a LAP planning system. The GEANT4 Monte Carlo toolkit has been used to simulate a secondary radiation production in LAP. A section of new multifunctional LAP beamlinehas been proposed, based on the pulsed power solenoid scheme as a GEANT4 toolkit. The results show that the energy selector is the most important source of neutron and photon secondary particles in LAP beamline. According to the calculations, the pure Tungsten energy selector not be the proper case, and using of Tungsten+Polyethylene or Tungsten+Graphitecomposite selectors will reduce the production of neutron and photon intensities by approximately ~10% and ~25%, respectively. Also the optimal radiuses of energy selectors were found to be ~4 cm and ~6 cm for a 3 degree and 5 degree proton deviation angles, respectively.

Keywords: neutron, photon, flux distribution, energy selector, GEANT4 toolkit

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Authors: Uchenna Sydney Mbamara, Bolu Olofinjana, Ezekiel Oladele B. Ajayi

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Elaborate surface metrology of undoped ZnO thin films, deposited by organometallic chemical vapour deposition (OMCVD) technique at different precursor flow rates, was carried out. Dicarbomethyl-zinc precursor was used. The films were deposited on AISI304L steel and soda-lime glass substrates. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy showed that all the thin films were over 80% transparent, with an average bandgap of 3.39 eV, X-ray diffraction (XRD) results showed that the thin films were crystalline with a hexagonal structure, while Rutherford backscattering spectroscopy (RBS) results identified the elements present in each thin film as zinc and oxygen in the ratio of 1:1. Microscope and contactless profilometer results gave images with characteristic colours. The profilometer also gave the surface roughness data in both 2D and 3D. The asperity distribution of the thin film surfaces was Gaussian, while the average fractal dimension Da was in the range of 2.5 ≤ Da. The metrology proved the surfaces good for ‘touch electronics’ and coating mechanical parts for low friction.

Keywords: undoped ZnO, precursor flow rate, OMCVD, thin films, surface texture, tribology

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Authors: Hoda Aleali, Nastran Mansour, Maryam Mirzaie

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In this paper, we study the optical nonlinearities of Silver sulfide (Ag2S) nanostructures dispersed in the Dimethyl sulfoxide (DMSO) under exposure to 532 nm, 15 nanosecond (ns) pulsed laser irradiation. Ultraviolet–visible absorption spectrometry (UV-Vis), X-ray diffraction (XRD), and transmission electron microscopy (TEM) are used to characterize the obtained nanocrystal samples. The band gap energy of colloid is determined by analyzing the UV–Vis absorption spectra of the Ag2S NPs using the band theory of semiconductors. Z-scan technique is used to characterize the optical nonlinear properties of the Ag2S nanoparticles (NPs). Large enhancement of two photon absorption effect is observed with increase in concentration of the Ag2S nanoparticles using open Z-scan measurements in the ns laser regime. The values of the nonlinear absorption coefficients are determined based on the local nonlinear responses including two photon absorption. The observed aperture dependence of the Ag2S NP limiting performance indicates that the nonlinear scattering plays an important role in the limiting action of the sample.The concentration dependence of the optical liming is also investigated. Our results demonstrate that the optical limiting threshold decreases with increasing the silver sulfide NPs in DMSO.

Keywords: nanoscale materials, silver sulfide nanoparticles, nonlinear absorption, nonlinear scattering, optical limiting

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Authors: Hussain Mustatab Wahedi, Sun You Kim

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Skin acts as a barrier against the harmful environmental factors. Integrity and timely recovery of the skin from injuries and harmful effects of radiations is thus very important. This study aimed to investigate the importance of Sirt1 in the recovery of skin from UVB-induced damage and cutaneous wounds by using natural and synthetic novel Sirt1 activators. Juglone, known as a natural Pin1 inhibitor, and NED416 a novel synthetic Sirt1 activator were checked for their ability to regulate the expression and activity of Sirt1 and hence photo-damage and wound healing in cultured skin cells (NHDF and HaCaT cells) and mouse model by using Sirt1 siRNA knockdown, cell migration assay, GST-Pulldown assay, western blot analysis, tube formation assay, and immunohistochemistry. Interestingly, Sirt1 knockdown inhibited skin cell migration in vitro. Juglone up regulated the expression of Sirt1 in both the cell lines under normal and UVB irradiated conditions, enhanced Sirt1 activity and increased the cell viability by reducing reactive oxygen species synthesis and apoptosis. Juglone promoted wound healing by increasing cell migration and angiogenesis through Cdc42/Rac1/PAK, MAPKs and Smad pathways in skin cells. NED416 upregulated Sirt1 expression in HaCaT and NHDF cells as well as increased Sirt1 activity. NED416 promoted the process of wound healing in early as well as later stages by increasing macrophage recruitment, skin cell migration, and angiogenesis through Cdc42/Rac1 and MAPKs pathways. So, both these compounds activated Sirt1 and promoted the process of wound healing thus pointing towards the possible role of Sirt1 in skin regeneration and wound healing.

Keywords: skin regeneration, wound healing, Sirt1, UVB light

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Authors: Irena Vuković-Kwiatkowska, Halina Kaczmarek

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Poly (lactic acid) is well known polymer, often called green material because of its origin (renewable resources) and biodegradability. This biopolymer can be used in the packaging industry very often. Poor resistance to permeation of gases is the disadvantage of poly (lactic acid). The permeability of gases and vapor through the films applied for packages and bottles generally should be very low to prolong products shelf-life. We propose innovation method of PLA gas barrier modification using electromagnetic radiation in ultraviolet range. Poly (lactic acid) (PLA) and multifunctional acrylate monomers were mixed in different composition. Final films were obtained by photochemical reaction (photocrosslinking). We tested permeability to water vapor and carbon dioxide through these films. Also their resistance to UV radiation was also studied. The samples were conditioned in the activated sludge and in the natural soil to test their biodegradability. An innovative method of PLA modification allows to expand its usage, and can reduce the future costs of waste management what is the result of consuming such materials like PET and HDPE. Implementation of our material for packaging will contribute to the protection of the environment from the harmful effects of extremely difficult to biodegrade materials made from PET or other plastic

Keywords: interpenetrating polymer network, packaging films, photocrosslinking, polyacrylates dipentaerythritol pentaacrylate DPEPA, poly (lactic acid), polymer biodegradation

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Authors: R. Ondarza-Rovira, T. J. M. Boyd

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Intense femtosecond laser light incident on over-critical density plasmas has shown to emit a prolific number of high-order harmonics of the driver frequency, with spectra characterized by power-law decays Pm ~ m-p, where m denotes the harmonic order and p the spectral decay index. When the laser pulse is p-polarized, plasma effects do modify the harmonic spectrum, weakening the so-called universal decay with p=8/3 to p=5/3, or below. In this work, appeal is made to a single particle radiation model in support of the predictions from particle-in-cell (PIC) simulations. Using this numerical technique we further show that the emission radiated by electrons -that are relativistically accelerated by the laser field inside the plasma, after being expelled into vacuum, the so-called Brunel electrons is characterized not only by the plasma line but also by ultraviolet harmonic orders described by the 5/3 decay index. Results obtained from these simulations suggest that for ultra-relativistic light intensities, the spectral decay index is further reduced, with p now in the range 2/3 ≤ p ≤ 4/3. This reduction is indicative of a transition from the regime where Brunel-induced plasma radiation influences the spectrum to one dominated by bremsstrahlung emission from the Brunel electrons.

Keywords: ultra-relativistic, laser-plasma interactions, high-order harmonic emission, radiation, spectrum

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Authors: P. Jayaram, Prasoon Prasannan, N. K. Deepak, P. P. Pradyumnan

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Indium and Zirconium co doped zinc oxide (InZrZnO) thin films are prepared by chemical spray pyrolysis method on pre-heated quartz substrates. The films are subjected to vacuum annealing at 400ᵒC for three hours in an appropriate air (10-5mbar) ambience after deposition. X-ray diffraction, Scanning electron microscopy, energy dispersive spectra and photoluminescence are used to characterize the films. Temperature dependent electrical measurements are conducted on the films and the films exhibit exceptional conductivity at higher temperatures. XRD analysis shows that all the films prepared in this work have hexagonal wurtzite structure. The average crystallite sizes of the films were calculated using Scherrer’s formula, and uniform deformation model (UDM) of Williamson-Hall method is used to establish the micro-strain values. The dislocation density is determined from the Williamson and Smallman’s formula. Intense, broad and strongly coupled multiple photoluminescence were observed from photoluminescence spectra. PL indicated relatively high concentration defective oxygen and Zn vacancies in the film composition. Strongly coupled ultraviolet near blue emissions authenticate that the dopants are capable of inducing modulated free excitonic (FX), donor accepter pair (DAP) and longitudinal optical phonon emissions in thin films.

Keywords: PL, SEM, TCOs, thin films, XRD

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Authors: Ayed S. Al-Shihri, Abul Kalam, Abdullah G. Al-Sehemi, Gaohui Du, Tokeer Ahmad, Ahmad Irfan

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We report here the synthesis of nickel oxide (NiO) nanoparticles by microwave-assisted method, using a common precipitating agent followed by calcination in air at 400°C. The effect of the microwave and pH on the crystallite size, morphology, structure, energy band gap and surface area of NiO have been investigated by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV-vis) and BET surface area studies. X-ray diffraction studies showed the formation of monophasic and highly crystalline cubic NiO. TEM analysis led to decrease the average grain size of NiO nanoparticles from 16.5 nm to 14 nm on increasing the amount of NaOH. FTIR studies also confirm the formation of NiO nanoparticles. It was observed that on increasing the volume of NaOH, the optical band gap energy (2.85 eV to 2.95 eV) and specific surface area (33.1 to 39.8 m2/g) increases, however the average particles size decreases (16.5 nm to 14 nm). This method may be extended to large scale synthesis of other metal oxides nanoparticles and the present study could be used for the potential applications in water treatment and many other fields.

Keywords: BET surface area analysis, electron microscopy, optical properties, X-ray techniques

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Authors: Abdulmohsen Alruwaili

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A partial differential system featuring momentum and energy balance is often used to describe simulations of flow initiation and thermal shifting in boundary layers. The buoyancy force in terms of temperature is factored in the momentum balance equation. Buoyancy force causes the flow quantity to fluctuate along the streamwise direction 𝑋; therefore, the problem can be, to our best knowledge, analyzed through nonsimilar modeling. In this analysis, a nonsimilar model is evolved for radiative mixed convection of a magnetized power-law nanoliquid flow on top of a vertical plate installed in a stationary fluid. The upward linear stretching initiated the flow in the vertical direction. Assuming nanofluids are composite of copper (Cu) and alumina (Al₂O₃) nanoparticles, the viscous dissipation in this case is negligible. The nonsimilar system is dealt with analytically by local nonsimilarity (LNS) via numerical algorithm bvp4c. Surface temperature and flow field are shown visually in relation to factors like mixed convection, magnetic field strength, nanoparticle volume fraction, radiation parameters, and Prandtl number. The repercussions of magnetic and mixed convection parameters on the rate of energy transfer and friction coefficient are represented in tabular forms. The results obtained are compared to the published literature. It is found that the existence of nanoparticles significantly improves the temperature profile of considered nanoliquid. It is also observed that when the estimates of the magnetic parameter increase, the velocity profile decreases. Enhancement in nanoparticle concentration and mixed convection parameter improves the velocity profile.

Keywords: nanofluid, power law model, mixed convection, thermal radiation

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Authors: Adriana Stefan, Cristina-Elisabeta Pelin, George Pelin, Maria Daniela Stelescu, Elena Manaila

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Elastomeric composites have been known for a long time, but, to our knowledge, space and the aeronautic community has been directing a special attention to them only in the last decade. The required properties of advanced elastomeric materials used in space applications (such as O-rings) are sealing, abrasion, low-temperature flexibility, the long-term compression set properties, impact resistance and low-temperature thermal stability in different environments, such as ionized radiations. Basically, the elastomeric nanocomposites are composed of a rubber matrix and a wide and varied range of nanofillers, added with the aim of improving the physico-mechanical and elasticity modulus properties of the materials as well as their stability in different environments. The paper presents a partial synthesis of the research regarding the use of silicon carbide in nanometric form and/or organophylized montmorillonite as fillers in butyl rubber matrix. The need of composite materials arose from the fact that stand-alone polymers are ineffective in providing all the superior properties required by different applications. These drawbacks can be diminished or even eliminated by incorporating a new range of additives into the organic matrix, fillers that have important roles in modifying properties of various polymers. A composite material can provide superior and unique mechanical and physical properties because it combines the most desirable properties of its constituents while suppressing their least desirable properties. The commercial importance of polymers and the continuous increase of their use results in the continuous demand for improvement in their properties to meet the necessary conditions. To study the performance of the elastomeric nanocomposites were mechanically tested, it will be tested the qualities of tensile at low temperatures and RT and the behavior at the compression at cryogenic to room temperatures and under different environments. The morphology of specimens will be investigated by optical and scanning electronic microscopy.

Keywords: elastomeric nanocomposites, O-rings, space applications, mechanical properties

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Authors: Wedad Azhar

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Vitamin D is an essential fat-soluble vitamin that is required for the maintenance of good health. It is obtained either through exposure to sunlight (ultraviolet B radiation) or through dietary sources. The role of vitamin D is beyond bone health. Indeed, it plays a critical role in the immune system and a broad range of organ functions such as the cardiovascular system. Moreover, vitamin D plays a critical role in the endothelial function, which is one of the main indicators of atherosclerosis. This study is investigating the correlation between vitamin D status and endothelial function in preventing and treating atherosclerosis especially in country that has ample of sunshine but yet, Saudis from suffering from this issue vitamin D deficiency and insufficiency. Ninety participants from both genders and aged 40 to 60will be involved. The participants will be categorised into three groups: the control group will be healthy persons, patients at risk of developing atherosclerosis, patients formally diagnosed atherosclerosis. Half of the participants in each group should already have been taking vitamin D supplementations. Fasting blood samples will be taken from the participants for biochemical assays. Endothelial function will be assist by flow-mediated dilation of the brachial artery. Participants will be asked to complete a questionnaire on their social and economic status, education level, daily exposure to sunlight, smoking status, consumption of supplements and medication, and a food frequency of vitamin D intake. The data will be analysed using SPSS.

Keywords: atherosclerosis, endothelial function, nutrition, vitamin D

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Authors: Manel Bouloudenine, Karima Djeddou, Hadjer Ben Manser, Hana Soualah Alila, Mohmed Bououdina

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This survey research involves the elaboration and characterization of silver nanoparticles for therapeutic and environmental applications. The silver nanoparticles "Ag NPs" were synthesized by reducing AgNO3 with microwaves. The characterization of nanoparticles was done by using Transmission Electron Microscopy " TEM ", Energy Dispersive Spectroscopy "EDS", Selected Area Electron Diffraction "SEAD", UV-Visible Spectroscopy and Dynamic Light Scattering "DLS". Transmission Electron Microscopy and Electron Diffraction have confirmed the nanoscale, the shape, and the crystalline quality of as synthesized silver nanoparticles. Elementary analysis has proved the purity of Ag NPs and the presence of the Surface Plasmon Resonance phenomenon "SPR". A strong absorption shift was observed in the visible range of the UV-visible spectrum of as synthesized Ag NPs, which indicates the presence of metallic silver. When the strong absorption in the ultraviolet range of the spectrum has revealed the presence of ionic Ag NPs ionic Ag aggregates species. The autocorrelation function measured by the Dynamic Light Scattering has shown a strong monodispersed character of Ag NPs, which is indicated by the presence of a single size population, with a minima and a maxima laying between 40 and 111 nm. Related to other research, our results confirm the performance properties of as synthesized Ag NPs, which allows them to be performing in many technological applications, including therapeutic and environmental ones.

Keywords: silvers nanoparticles, microwaves, EDS, TEM

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Authors: S. Koul, Joshua Adedamola

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Currently, the global concerning fact about electromagnetic pollution (EMP) is that it not only adversely affects human health but rather projects the malfunctioning of sensitive equipment both locally and at a global level. The market offers many incumbent technologies to solve the issues, but still, a processable sustainable material solution with acceptable limits for GHG emission is still at an exploratory stage. The present work offers a sustainable material solution with a wide range of processability in terms of a polymeric resin matrix and shielding operational efficiency across the electromagnetic spectrum, covering both ionizing and non-ionizing electromagnetic radiations. The present work offers an in-situ synthesized conducting polyaniline (PANI) in the presence of the hybrid dual dopant system with tuned conductivity and high shielding efficiency between 89 to 92 decibels, depending upon the EMI frequency range. The conductive polymer synthesized in the presence of a hybrid dual dopant system via the in-situ emulsion polymerization method offers a higher surface resistance of 1.0 ohms/cm with thermal stability up to 2450C in their powder form. This conductive polymer with a hybrid dual dopant system was used as a filler material with different polymeric thermoplastic resin systems for the preparation of conductive composites. Intrinsically Conductive polymeric (ICP) composites based on hybrid dual dopant systems were prepared using melt blending, extrusion, and finally by, compression molding processing techniques. ICP composites with hybrid dual dopant systems offered good mechanical, thermal, structural, weathering, and stable surface resistivity properties over a period of time. The preliminary shielding behavior for ICP composites between frequency levels of 10 GHz to 24GHZ offered a shielding efficiency of more than 90 dB.

Keywords: ICP, dopant, EMI, shielding

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Authors: Kanika Arora, Madhu Bala

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The small intestine epithelium is highly sensitive and major targets of ionizing radiation. Radiation causes gastrointestinal toxicity either by direct deposition of energy or indirectly (inflammation or bystander effects) generating free radicals and reactive oxygen species. Oxidative stress generated as a result of radiation causes active inflammation within the intestinal mucosa leading to structural and functional impairment of gut epithelial barrier. As a result, there is a loss of tolerance to normal dietary antigens and commensal flora together with exaggerated response to pathogens. Dysbiosis may therefore thought to play a role in radiation enteropathy and can contribute towards radiation induced bowel toxicity. Lactobacilli residing in the gut shares a long conjoined evolutionary history with their hosts and by doing so these organisms have developed an intimate and complex symbiotic relationships. The objective behind this study was to look for the strains with varying resistance to ionizing radiation and to see whether the niche of the bacteria is playing any role in radiation resistance property of bacteria. In this study, we have isolated the Lactobacillus spp. from probiotic preparation and murine gastrointestinal tract, both of which were supposed to be the important source for its isolation. Biochemical characterization did not show a significant difference in the properties, while a significant preference was observed in carbohydrate utilization capacity by the isolates. Effect of ionizing radiations induced by Co60 gamma radiation (10 Gy) on lactobacilli cells was investigated. A cellular survival curve versus absorbed doses was determined. Radiation resistance studies showed that the response of isolates towards cobalt-60 gamma radiation differs from each other and significant decrease in survival was observed in a dose-dependent manner. Thus the present study revealed that the property of radioresistance in Lactobacillus depends upon the source from where they have been isolated.

Keywords: dysbiosis, lactobacillus, mitigation, radiation

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Authors: Bouchou Aïssa, Mohamed Akbi

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Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermo dynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver-metal oxide (Ag-MeO) electrical contacts (Ag-ZnO (92/8), before and after surface heat treatments at 296 K  813 K, under UHV conditions (residual gas pressure of 1.4 x 10-7 mbar). The electron work function (EWF) of silver zinc oxide materials was measured photoelectrically, using both Fowler’s method of isothermal curves and linearized Fowler plots. In this paper, we present the development of a method for measuring photoelectric work function of contact materials. Also reported in this manuscript are the results of experimental work whose purpose has been the buildup of a reliable photoelectric system and associated monochromatic ultra-violet radiations source, and the photoelectric measurement of the electron work functions (EWF) of contact materials. In order to study the influence of annealing temperature on the EWF, a vacuum furnace was used for heating the metallic samples up to 800 K. The EWF of the silver – zinc oxide materials were investigated to study the influence of annealing temperature on the EWF. In the present study, the photoelectric measurements about Ag-ZnO(92/8) contacts have shown a linear decrease of the EWF with increasing temperature, i.e. the temperature coefficient is constant and negative: for the first annealing # 1, in the temperature range [299 K  823 K]. On the contrary, a linear increase was observed with increasing temperature (i.e. , being constant and positive), for the next annealing # 2, in the temperature range [296 K  813 K]. The EWFs obtained for silver-zinc oxide Ag-ZnO(92/8) show an obvious dependence on the annealing temperature which is strongly associated with the evolution of the arrangement on ZnO nano particles on the Ag-ZnO contact surface as well as surface charge distribution.

Keywords: Photoemission, Electron work function, Fowler methods, Ag-ZnO contact materials, Vacuum heat treatment

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Authors: A. O. Oluwajobi, O. A. Falusi, N. A. Zubbair, T. Owoeye, F. Ladejobi, M. C. Dangana, A. Abubakar

Abstract:

The technology of mobile telephony has positively enhanced human life and reports on the bio safety of the radiation from their antennae have been contradictory, leading to serious litigations and violent protests by residents in several parts of the world. The crave for more information, as requested by WHO in order to resolve this issue, formed the basis for this study on the effect of the radiation from 900 MHz GSM antenna on the DNA of Hibiscus sabdariffa. Seeds of H. sabdariffa were raised in pots placed in three replicates at 100, 200, 300 and 400 metres from the GSM antennae in three selected test locations and a control where there was no GSM signal. Temperature (˚C) and the relative humidity (%) of study sites were measured for the period of study (24 weeks). Fresh young leaves were harvested from each plant at two, eight and twenty-four weeks after sowing and the DNA extracts were subjected to RAPD-PCR analyses. There were no significant differences between the weather conditions (temperature and relative humidity) in all the study locations. However, significant differences were observed in the intensities of radiations between the control (less than 0.02 V/m) and the test (0.40-1.01 V/m) locations. Data obtained showed that DNA of samples exposed to rays from GSM antenna had various levels of distortions, estimated at 91.67%. Distortions occurred in 58.33% of the samples between 2-8 weeks of exposure while 33.33% of the samples were distorted between 8-24 weeks exposure. Approximately 8.33% of the samples did not show distortions in DNA while 33.33% of the samples had their DNA damaged twice, both at 8 and at 24 weeks of exposure. The study showed that radiation from the 900 MHz GSM antenna is potent enough to cause distortions to DNA of H. sabdariffa even within 2-8 weeks of exposure. DNA damage was also independent of the distance from the antenna. These observations would qualify emissions from GSM mast as environmental hazard to the existence of plant biodiversities and all life forms in general. These results will trigger efforts to prevent further erosion of plant genetic resources which have been threatening food security and also the risks posed to living organisms, thereby making our environment very safe for our existence while we still continue to enjoy the benefits of the GSM technology.

Keywords: damage, DNA, GSM antenna, radiation

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Authors: Veronique Jubera, Guillaume Salek, Manuel Gaudon, Alain Garcia, Alain Demourgues

Abstract:

Luminescence of transition metal and rare earth elements cover ultraviolet to far infrared wavelengths. Applications of phosphors are numerous. One can cite lighting, sensing, laser, energy, medical or military applications. But regarding each domain, specific criteria are required and they can be achieved with a strong control of the chemical composition. Emission of doped materials can be tailored with modifications of the local environment of the cations. For instance, the increase of the crystal field effect shifts the divalent manganese radiative transitions from the green to the red color. External factor as heat-treatment can induce changes of the doping element location or modify the unit cell crystalline symmetry. By controlling carefully the synthesis route, it is possible to initiate emission shift and to establish the thermal history of a compound. We propose to demonstrate through the luminescence of divalent manganese and trivalent rare earth doped oxide, that it is possible to follow the thermal history of a material. After optimization of the synthesis route, structural and optical properties are discussed. Finally, thermal calibration graphs are successfully established on these doped compounds. This makes these materials promising probe for thermal sensing.

Keywords: emission, thermal sensing, transition metal, rare eath element

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Authors: Ayesha Asma, Aqsa Arooj

Abstract:

It is an essential need in this era of Science and Technology to investigate some unique and appropriate materials for optoelectronic applications. Here, we deliberated, for the first time, the structural, optoelectronic, mechanical, vibrational, and thermo dynamical properties of hexagonal structure selenium-based ternary chalcogenides AScSe₂ (A= K, Cs) by using Perdew-Burke-Ernzerhof Generalized-Gradient-Approximation (PBE-GGA). The lattice angles for these materials are found as α=β=90o and γ=120o. KScSe₂ optimized with lattice parameters a=b=4.3 (Å), c=7.81 (Å) whereas CsScSe₂ got relaxed at a=b=4.43 (Å) and c=8.51 (Å). However, HSE06 functional has overestimated the lattice parameters to the extent that for KScSe₂ a=b=4.92 (Å), c=7.10 (Å), and CsScSe₂ a=b=5.15 (Å), c=7.09 (Å). The energy band gap of these materials calculated via PBE-GGA and HSE06 functionals confirms their semiconducting nature. Concerning Born’s criteria, these materials are mechanically stable ones. Moreover, the temperature dependence of thermodynamic potentials and specific heat at constant volume are also determined while using the harmonic approximation. The negative values of free energy ensure their thermodynamic stability. The vibrational modes are calculated by plotting the phonon dispersion and the vibrational density of states (VDOS), where infrared (IR) and Raman spectroscopy are used to characterize the vibrational modes. The various optical parameters are examined at a smearing value of 0.5eV. These parameters unveil that these materials are good absorbers of incident light in ultra-violet (UV) regions and may be utilized in photovoltaic applications.

Keywords: structural, optimized, vibrational, ultraviolet

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Authors: Koyar Rane

Abstract:

Nano- to submicron size particles of narrow particle size distribution of semi-conducting TiO₂, ZnO, NiO, CuO, Fe₂O₃ have been synthesized by novel hydrazine method and tested for their gas sensing, photocatalytic and bactericidal activities and the behavior found to be enhanced when the oxides in the thin film forms, that obtained in a specially built spray pyrolysis reactor. Hydrazine method is novel in the sense, say, the UV absorption edge of the white pigment grade wide band gap (~3.2eV) TiO₂ and ZnO shifted to the visible region turning into yellowish particles, indicating modification occurring the band structure. The absorption in the visible region makes these oxides visible light sensitive photocatalysis in degrading pollutants, especially the organic dyes which otherwise increase the chemical oxygen demand of the drinking water, enabling the process feasible not under the harsh energetic UV radiation regime. The electromagnetic radiations on irradiation produce electron-hole pairs Semiconductor + hν → e⁻ + h⁺ The electron-hole pairs thus produced form Reactive Oxygen Species, ROS, on the surface of the semiconductors, O₂(adsorbed)+e⁻ → O₂• - superoxide ion OH-(surface)+h⁺ →•OH - Hydroxyl radical The ROS attack the organic material and micro-organisms. Our antibacterial studies indicate the metal oxides control the Biological Oxygen Demand (BOD) of drinking water which had beyond the safe level normally found in the municipal supply. Metal oxides in the thin film form show overall enhanced properties and the films are reusable. The results of the photodegradation and antibactericidal studies are discussed. Gas sensing studies too have been done to find the versatility of the multifunctional metal oxides.

Keywords: hydrazine method, visible light sensitive, photo-degradation of dyes, water/airborne pollutant

Procedia PDF Downloads 163

Authors: Atena Naeimi, Mehri-Sadat Ekrami-Kakhki

Abstract:

Fe3O4 is one of the important magnetic oxides with spinel structure; it has exhibited unique electric and magnetic properties based on the electron transfer between Fe2+ and Fe3+ in the octahedral sites. Fe3O4 have received considerable attention in various areas such as cancer therapy, drug targeting, enzyme immobilization catalysis, magnetic cell separation, magnetic refrigeration systems and super-paramagnetic materials. Fe3O4–ZnO nanostructures were synthesized via a surfactant-free ultrasonic reaction at room temperatures. The effect of various parameters such as temperature, time, and power on the size and morphology of the product was investigated. Alternating gradient force magnetometer shows that Fe3O4 nanoparticles exhibit super-paramagnetic behaviour at room temperature. For preparation of nanocomposite 1 g of Fe3O4 nanostructures were dispersed in 100 mL of distilled water. 0.25 g of Zn (NO3)2 and 20 mL of NH3 solution 1 M were then slowly added to the solution under ultrasonic irradiation. The product was centrifuged, washed with distilled water and dried in the air. The photocatalytic behaviour of Fe3O4–ZnO nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. As time increased, more and more methyl orange was adsorbed on the nanoparticles catalyst, until the absorption peak vanish. The methyl orange concentration decreased rapidly with increasing UV-irradiation time.

Keywords: nanocomposite, ultrasonic, paramagnetic, photocatalytic

Procedia PDF Downloads 302

Authors: D. Tassalit, N. Chekir, O. Benhabiles, N. A. Laoufi, F. Bentahar

Abstract:

In the setting of the waters purification, some molecules appear recalcitrant to the traditional treatments. The exploitation of the properties of some catalysts permits to amplify the oxidization performances with ultraviolet radiance and to remove this pollution by a non biological way. This study was conducted to investigate the effect of a photocatalysis oxidation system for organic pollutants treatment using a new reactor design and ZnO/TiO2 as a catalyst under UV light. Oxidative degradation of tylosin by hydroxyl radicals (OH°) was studied in aqueous medium using suspended forms of ZnO and TiO2. The results improve that the treatment was affected by many factors such as flow-rate of solution, initial pollutant concentration and catalyst concentration. The rate equation for the tylosin degradation followed first order kinetics and the rate-constants were determined. The reaction rate fitted well with Langmuir–Hinshelwood model and the removed ratio of tylosin was 97 % in less than 60 minutes. To determine the optimum catalyst loading, a series of experiments were carried out by varying the amount of catalyst from 0.05 to 0.5 g/L. The results demonstrate that the rate of photodegradation is optimum with catalyst loading of 0.1 g/L, reaction flow rate of 3.79 mL/s and solution natural pH. The rate was found to increase with the decrease in tylosin concentration from 30 to 5 mg/L. Therefore, this simple photoreactor design for the removal of organic pollutants has the potential to be used in wastewater treatment.

Keywords: advanced oxidation, photocatalysis, TiO2, ZnO, UV light, pharmaceuticals pollutants, Spiramycin, tylosin, wastewater treatment

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Authors: James Sinclair, Katy Soapi, Brad Carte

Abstract:

The marine environment has continuously demonstrated to be a rich source of secondary metabolites and bioactive compounds that can address the many pharmaceutical problems facing mankind. The emergence of multidrug resistant pathogens has caused scientists to explore contemporary ways of combating these super bugs. A red-pigmented bacterial strain isolated from a marine alga collected in Fiji was identified to be Pseudoalteromonas rubra from 16s rRNA sequencing. This bacterial strain was cultured using a yeast-peptone media and incubated for five days. The ethyl acetate extract of this bacterium was subjected to chromatographic separation techniques such as vacuum liquid chromatography, flash chromatography, size exclusion chromatography and high-pressure liquid chromatography to yield the pure compound and a number of semi-pure fractions. The crude extract and subsequent purified fractions were analyzed by ultraviolet/visible spectroscopy and mass spectroscopy and was found to contain the compounds ivermectin, stenothricin, cyclo-L-pro-L-val, prodigiosin, mycophenolic acid, phenazine-1-carboxylic acid, eplerenone, staurosporine and pseudoalteromone A. The structure of the pure compound, pseudoalteromone A, was elucidated using NMR 1H, 13C, 1H-1H COSY, HSQC and HMBC spectroscopic data.

Keywords: Pseudoalteromonas rubra, Pseudoalteromone A, secondary metabolites, structure elucidation

Procedia PDF Downloads 213