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Inactivation efficiency of Bacillus endospores via modified flow-through PUV treatment with comparison to conventional LPUV treatment
摘要： Water is a fragile resource, consequently there is a pressing need to develop sustainable environmental-friendly disinfection technologies. This constitutes the first study to compare efficacy of continuous low-pressure UV (LPUV) to that of pulsed UV light (PUV) for UV disinfection performance in flow-through water systems. Bacillus endospores were used as these are frequently deployed as biodosimeters for drinking water UV reactor validation protocols. Results showed a PUV system output of 2,052 mJ/cm2 (energy below 300 nm) was required for a 2 log inactivation of B.pumilus endospores, whereas a lower LPUV system output of 12 mJ/cm2 produced a similar level of disinfection. Measurements of dose incident to the samples (which were 10.75 cm from the PUV light source) showed supplementation of cultivation media with manganese sulphate monohydrate (MnSO4.H2O) employed to enhance the rate of endospore formation for propagation was shown to increase the UV resistance of different Bacillus spp. to both irradiation approaches (P < 0.05). Conventional LPUV light that is commonly-used by the drinking water industry is a reliable and superior approach to PUV which requires substantial modification for effective disinfection of continuous flow-through water. Caution must also be exercised when manipulating media formulation to propagate endospores as this may lead to inconsistencies in reporting efficacy of intervention treatments with implications for validation and environmental evaluation.
关键词： Bacillus endospores,Pulsed UV,Low-pressure UV,Disinfection,Media formulation
更新于2025-09-23 15:23:52
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Enhancement of THz Generation by Two-Color TW Laser Pulses in a Low-Pressure Gas
摘要： We identify experimental conditions for efficient generation of THz pulses by high power near IR laser radiation: 2 TW, 30 fs, 800-nm laser pulses with their second harmonic were slightly focused in a low-pressure gas cell in such a way to avoid multiple filamentation and excessive ionization. This two-color scheme yields a microjoule level of THz pulses which is two orders of magnitude higher than the signal generated in the atmosphere of ambient air.
关键词： THz,Two-color,Plasma absorption,Terawatt,Chirp,Filament,Low pressure,Saturation
更新于2025-09-23 15:21:01
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Electron dynamics in low pressure capacitively coupled radio frequency discharges
摘要： In low temperature plasmas, the interaction of the electrons with the electric field is an important current research topic that is relevant for many applications. Particularly, in the low pressure regime ((cid:1)10 Pa), electrons can traverse a distance that may be comparable to the reactor dimensions without any collisions. This causes “nonlocal,” dynamics which results in a complicated space- and time-dependence and a strong anisotropy of the distribution function. Capacitively coupled radio frequency (CCRF) discharges, which operate in this regime, exhibit extremely complex electron dynamics. This is because the electrons interact with the space- and time-dependent electric field, which arises in the plasma boundary sheaths and oscillates at the applied radio frequency. In this tutorial paper, the fundamental physics of electron dynamics in a low pressure electropositive argon discharge is investigated by means of particle-in-cell/Monte Carlo collisions simulations. The interplay between the fundamental plasma parameters (densities, fields, currents, and temperatures) is explained by analysis (aided by animations) with respect to the spatial and temporal dynamics. Finally, the rendered picture provides an overview of how electrons gain and lose their energy in CCRF discharges.
关键词： low pressure,particle-in-cell/Monte Carlo collisions simulations,electron dynamics,plasma parameters,capacitively coupled radio frequency discharges
更新于2025-09-23 15:21:01
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Laser machined ultralow water adhesion surface by low pressure processing
摘要： Ultralow water adhesion aluminum surface has been fabricated by eco friendly low pressure processing technique. The laser patterned surface shows interconnected spongy porous nanostructures with micro packets at regular intervals. The micro volume of air present inside the interconnected porous surface structure together with the adsorbed hydrocarbons by low pressure processing leads to ultralow water adhesion surface. Application of bigger droplet volumes to the patterned surface showed a decrease in static contact angle measurement due to larger radius of curvature and axisymmetrical compared to the smaller droplets.
关键词： Sliding angle,Ultrafast laser,Low pressure,Wetting,Adhesion
更新于2025-09-23 15:21:01
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Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas
摘要： A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The in?uence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.
关键词： Monte Carlo simulation,instantaneous mean-free-path,ablated particles,transport dynamic,low pressure
更新于2025-09-23 15:19:57
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Absolute density measurement of hydrogen atom in inductively coupled Ar/H2 plasmas using vacuum ultraviolet absorption spectroscopy
摘要： The absolute density measurement of atomic species such as hydrogen is crucial for plasma processing because of their strong chemical reactivity. In this work, to measure the hydrogen atom density in Ar/H2 inductively coupled plasmas (ICP), the self-absorption-applied vacuum ultraviolet absorption spectroscopy (VUVAS) is studied with a micro-hollow cathode H2/He discharge lamp (MHCL) emitting VUV light (Lyman alpha line; Lα 121.56 nm). The absolute density of hydrogen atoms in the ICP is investigated for various powers (50 W–850 W) in the low pressure region (30 mTorr–50 mTorr). The hydrogen density in remote plasma region is shown to vary from 2.1 × 1011 cm?3 to 1.25 × 1012 cm?3 with respect to plasma power.
关键词： VUV absorption spectroscopy,Low-pressure,Self-absorption,Hydrogen atom density,inductively coupled plasma
更新于2025-09-23 15:19:57
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Laser Technology to Guide Rainfall to a Particular Region
摘要： Rain bearing clouds can be effectively guided to a specific region during monsoon or other seasons so that rainfall shall be equitably distributed without creating drought situations. Lasers sent into the lower troposphere region with intensities sufficient to create a temperature gradient and thereby creating a low pressure area in a specific region can invite rain bearing clouds to a region opposite to where heat is generated by laser effect, so as to bring convective rainfall during a season.
关键词： Troposphere,Laser effect,Low pressure,Convective rainfall,Equitably,Temperature gradient
更新于2025-09-23 15:19:57
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H-D analysis employing energy transfer from He metastable excited state in double pulse LIBS at low pressure He gas
摘要： The laser induced breakdown spectroscopy (LIBS) experiment with a unique double pulse setup and operational procedure in low pressure (3 kPa) He ambient gas is performed for the study on the detection of light elements such as hydrogen (H) and deuterium (D) as well as elements of high excitation energies such as fluorine (F) and chlorine (Cl) which are usually difficult to be detected using ordinary LIBS technique. A nanosecond (ns) Nd:YAG laser operated in its fundamental wavelength with energy of 54 mJ is focused onto the Al target to generate the He plasma. Another picosecond (ps) Nd:YAG laser operated in its fundamental wavelength with energy of 2 mJ is focused onto the sample surface and activated 2 μs before the operation of ns laser. The application to polyvinylchloride (PVC) and polytetrafluoroethylene (PTFE) samples produces sharp and high intensity Cl and F emission lines. Meanwhile the sharp and well resolved H-D emission lines with merely 0.18 nm wavelength separation are also clearly detected from zircaloy sample. Further measurement of a set of zircaloy samples containing different concentrations of D yields a linear calibration curve with zero intercept. The detection limit of D is found to be about 10 ppm.
关键词： F analysis,Cl analysis,H-D analysis,double pulse low pressure LIBS,He metastable excited state
更新于2025-09-23 15:19:57
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Thermometry in a Gas Discharge Cell of an Optical Wavelength Calibrator
摘要： Temperature and pressure in a sealed Ar cell of an optical wavelength calibrator are measured using diode laser spectroscopy. The values of the thermodynamic parameters allowed determination of the fluctuations of the shift of the argon line at 811.5 nm. The expected fluctuation amplitude appears lower than ±15 MHz. The result obtained indicates the applicability of the studied calibrator as an optical reference and the correctness of previous measurements of pressure shift coefficients of the 811.5 nm argon line.
关键词： thermometry,diode-laser spectroscopy,optical calibrator,low pressure RF discharge,spectral line pressure shift,argon
更新于2025-09-19 17:15:36
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Low pressure chemical vapor deposition of In <sub/>2</sub> O <sub/>3</sub> films on off-axis c-sapphire substrates
摘要： Heteroepitaxial In2O3 films were grown on transparent c-sapphire substrates with 0°, 3.5°, 6° and 8° off-axis angles via low pressure chemical vapor deposition (LPCVD). Metallic solid indium and oxygen gas were used as the precursors. X-ray diffraction (XRD) spectroscopy and cross-sectional scanning transmission electron microscopy (STEM) were used to study the effects of substrate off-axis on the crystalline quality of the as-grown films. The XRD 2θ-ω spectra confirmed the growth of body centered cubic bixbyite In2O3 films with (111) out-of-plane orientation. STEM images revealed the suppressed dislocation density in the films grown on substrates with off-axis angles. The crystal structure was further confirmed by Raman spectroscopy. Fifteen peaks corresponding to bcc-In2O3 Raman modes were observed at room temperature (RT). XRD ω-rocking curves, XRD Φ-scan profiles and STEM images indicate improved crystalline quality in films grown on substrates with, particularly, 3.5° and 6° off-cut angles. Growth rates in a wide range of ~ 0.5 - 30 μm/hr were achieved. RT photoluminescence peak at ~2.15 eV is attributed to the deep level defect transitions. RT photoluminescence excitation peak at ~3.38 eV corresponds to the optical bandgap of bcc-In2O3. RT electron Hall mobilities of ~ 88 - 116 cm2/V.s were measured with background carrier concentrations of ~ 6 - 9x1017 cm-3.
关键词： low pressure chemical vapor deposition,Indium oxide,off-axis substrate,c-sapphire
更新于2025-09-19 17:15:36