High-power Lamps Research Articles

Continuous Flow Photochemical Synthesis of 3-Methyl-4-arylmethylene Isoxazole-5(4H)-ones through Organic Photoredox Catalysis and Investigation of Their Larvicidal Activity

Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction might be induced by light, as described in previous works. Remarkable results were obtained using a high-power lamp, reducing reaction times compared to methodologies that used heating or catalysis. Since there are many examples of successful continuous flow heterocycle synthesis, including photochemical reactions, the study evolved to run the reaction in flow conditions and scale up the synthesis of isoxazolones using a photochemical reactor set-up. Eight different compounds were obtained, and among them, three showed larvicidal activity on immature forms of Aedes aegypti in tests that investigated its growth inhibitory character. Mechanistic investigations indicate that the reactions occur through organic photoredox catalysis.

Computational fluid dynamics–based modeling and optimization of flow rate and radiant exitance for 1,4-dioxane degradation in a vacuum ultraviolet photoreactor

1,4-Dioxane is one of the most persistent organic micropollutants in conventional drinking-water-treatment processes. Vacuum ultraviolet (VUV) treatment is a promising means of removing micropollutants such as 1,4-dioxane from source water, but this approach has not yet been implemented in a full-scale water treatment plant, partly because the operating parameters for pilot and full-scale VUV photoreactors have not been optimized. Here, we developed a computational fluid dynamics–based method for optimizing VUV photoreactor performance through energy-based analyses that take into account the effects of two important operating parameters—flow rate and radiant exitance. First, we constructed a computational fluid dynamics model and determined the sole parameter required for the model, the pseudo-first-order rate constant for the reaction of 1,4-dioxane, by simple batch experiment. Then, we validated the model by using a pilot-scale flow-through annular photoreactor. Finally, we used the validated model to examine the effects of flow rate and radiant exitance on the efficiency of 1,4-dioxane degradation in a virtual annular photoreactor. Radiation efficiency, which was defined as the ratio of the logarithmic residual ratio of 1,4-dioxane to the theoretical minimum logarithmic residual ratio (best possible performance) under the given operating conditions, was calculated as an energy-based index of cost-effectiveness. Radiation efficiency was found to increase with increasing flow rate but decreasing radiant exitance. An electrical energy per order (EEO) analysis suggested that VUV treatment under laminar flow was most economical when low-power lamps and a high flow rate were used. In contrast, VUV treatment under turbulent flow was suggested to be most economical when high-power lamps were used at a high flow rate.

Development of an electrothermal vaporizer for direct mercury determination in soil by inductively-coupled plasma mass spectrometry

The need to determine mercury in environmental samples is well known, along with its related difficulty. Most methods require samples to be decomposed, involving the use of concentrated acids; this requires considerable time and is liable to lead to analyte loss. The aim of this work is to develop a simple electrothermal vaporization (ETV) system coupled to inductively coupled plasma mass spectrometry (ICP-MS) for Hg determination by direct solid sample analysis (DSSA). The ETV system consists of a high-power lamp enclosed in glass chamber equipped with solenoid valves to control the flow of argon gas (Ar) during pyrolysis and vaporization steps. The system is controlled by a printed circuit board and software developed in the LabVIEW environment. In this system, the analyte vapour was extracted through a glass tube positioned just above the sample, avoiding the analyte deposition on the chamber wall and consequently reducing memory effect. The heating program was optimised and the pyrolysis step was not necessary since it was possible to vaporize the analyte at relatively low temperature (700 °C) without matrix interference. Soil mass between 0.500 and 5.000 mg can be analysed with the ETV system. Calibration was carried out by using a certified reference material (CRM) of soil (NIST2709) ranged from 0.1 to 1.0 ng of Hg. The relative standard deviation was lower than 20% (n = 3) and the limit of quantification (10σ) of Hg was 3.1 ng g−1. The accuracy was evaluated by comparison of results obtained for Hg in CRMs and no statistical differences were observed (paired t-test at a confidence level of 95%). To evaluate the performance of ETV system, soil samples with different concentration levels were analysed and the results were in good agreement (paired t-test at a confidence level of 95%) with those obtained by nebulization-ICP-MS (NEB-ICP-MS) after acid extraction. Therefore, the proposed method can be used for routine analysis, where the time of analysis of approximately 60 s per sample, risk of contamination, analyte losses and generation of residues are drastically reduced in comparison with techniques that require sample extraction for Hg determination by NEB-ICP-MS.

A Concept of Thermographic Method for Non-Destructive Testing of Polymeric Composite Structures Using Self-Heating Effect.

Traditional techniques of active thermography require an external source of energy used for excitation, usually in the form of high power lamps or ultrasonic devices. In this paper, the author presents an alternative approach based on the self-heating effect observable in polymer-based structures during cyclic loading. The presented approach is based on, firstly, determination of bending resonance frequencies of a tested structure, and then, on excitation of a structure with a multi-harmonic signal constructed from the harmonics with frequencies of determined resonances. Following this, heating-up of a tested structure occurs in the location of stress concentration and mechanical energy dissipation due to the viscoelastic response of a structure. By applying multi-harmonic signal, one ensures coverage of the structure by such heated regions. The concept is verified experimentally on artificially damaged composite specimens. The results demonstrate the presented approach and indicate its potential, especially when traditional methods of excitation with an external structure for thermographic inspection cannot be applied.

Pulse Width Modulation Based Decentralized Street LED Light Dimming System

<p>The high power consumption of conventional street lighting systems, and the consequences on environmental ecosystem due to continuous turning ON of light, have led researchers to seek solutions to this problem. LED light dimming system has been presented in many studies using computerized systems with or without wireless monitoring facility. The demerits of these systems include complexity, high cost and unfixed data transfer speed. This paper proposes to reduce power consumption of street lighting through a decentralized light dimming system that is based on Pulse Width Modulation (PWM). This is in addition to replacing conventional high power lamps with lower power LED lamps. The dimming control circuit of this system is fixed on each pole and controlled individually resulting in faster and more reliable response. The proposed system uses the available infrastructure and is suitable for small or main streets regardless of the number of light poles. It is also flexible in its coverage distance due to the freedom of motion detector selection. The advantages of using LED lighting on the environment as compared to conventional lighting are explained. Simulations reveal the effectiveness of the proposed system on energy saving and on the environment.</p>

3D thermography for improving temperature measurements in thermal vacuum testing

The application of thermography to thermal vacuum (TV) testing of spacecrafts is becoming a vital additional tool in the mapping of structures during thermal cycles and thermal balance (TB) testing. Many of the customers at the European Space Agency (ESA) test centre, European Space Research and Technology Centre (ESTEC), The Netherlands, now make use of a thermal camera during TB-TV campaigns. This complements the use of embedded thermocouples on the structure, providing the prospect of monitoring temperatures at high resolution and high frequency. For simple flat structures with a well-defined emissivity, it is possible to determine the surface temperatures with reasonable confidence. However, for most real spacecraft and sub-systems, the complexity of the structure’s shape and its test environment creates inter-reflections from external structures. This and the additional complication of angular and spectral variations of the spacecraft surface emissivity make the interpretation of the radiation detected by a thermal camera more difficult in terms of determining a validated temperature with high confidence and well-defined uncertainty. One solution to this problem is: to map the geometry of the test specimen and thermal test environment; to model the surface temperatures and emissivity variations of the structures and materials; and to use this model to correct the apparent temperatures recorded by the thermal camera. This approach has been used by a team from NPL (National Physical Laboratory), Psi-tran, and PhotoCore, working with ESA, to develop a 3D thermography system to provide a means to validate thermal camera temperatures, based on a combination of thermal imaging photogrammetry and ray-tracing scene modeling. The system has been tested at ESTEC in ambient conditions with a dummy spacecraft structure containing a representative set of surface temperatures, shapes, and spacecraft materials, and with hot external sources and a high power lamp as a sun simulator. The results are presented here with estimated temperature measurement uncertainties and defined confidence levels according to the internationally accepted Guide to Uncertainty of Measurement as used in the IEC/ISO17025 test and measurement standard. This work is understood to represent the first application of well-understood thermal imaging theory, commercial photogrammetry software, and open-source ray-tracing software (adapted to realize the Planck function for thermal wavebands and target emission), and to produce from these elements a complete system for determining true surface temperatures for complex spacecraft-testing applications.

Four Cases of Pediatric Photokeratitis Present to the Emergency Department After Watching the Same Theater Show.

We report four consecutive cases of photokeratitis that presented to the emergency department, interestingly after having watched the same theatre performance in the same school. The patients’ ages (3 male, 1 female) ranged from 9 to 13 years. All patients presented with similar complaints consisting of pain, tearing, foreign body sensation, photophobia and blurred vision in both eyes. Patients reported watching a theatre performance in the same school approximately 4 hours before symptom onset. On slit-lamp examination, conjunctival injection and corneal punctate epithelial erosions were observed in the interpalpebral zone in both eyes. On fundus examination, no pathology was observed in the vitreous, posterior pole or peripheral retina. All cases were treated with topical antibiotics and lubricant eye drops. Corneas were clear two days later in the control visit. In this case report, exposure to ultraviolet light from high-power lamps used in the theatre was proposed as a possible cause of corneal epithelial cell damage and subsequent photokeratitis.

The effects of volumetric flow rate and inclination angle on the performance of a solar thermal collector

A solar collector is a device that converts solar energy into heat. This paper presents an experimental study on the influences of volumetric flow rate and inclination angle on the performance of a solar collector. The tests were conducted on a solar energy demonstration system (ET200), which consists of a solar collector, a storage tank, a control and command cabinet and a high power lamp simulating solar energy. For radiation intensity of 1.033kW/m2 and inclination angle of 0°, the results showed that the efficiency of the collector followed a linear relationship versus the flow rate; η=0.68×Qv+49.79 and presented a coefficient of correlation (R2) of 0.9898. Similarly, the increase of the inclination angle from 0° to 60° increased the effectiveness of the collector. A linear relationship; η=0.43×α+53.07 with a high coefficient of determination (R2=0.967) relates the collector efficiency to the inclination angle. It is important to operate at higher mass flow rates and take the collector angle at 0° in order to reach its meaning full efficiency (heating water).

Generation of reactive oxygen species in simulated flue gas under vacuum ultraviolet radiation

Reactive oxygen species, which are responsible for the removal of SO2 and NOx, generated under vacuum ultraviolet (VUV) radiation in simulated flue gas (N2/O2/CO2/H2O (v/v)=74%/8%/10%/8% without SO2 and NOx) were determined. Under typical experimental conditions, 26.5μmol ozone, 1.7μmol hydrogen peroxide, and 0.3μmol hydroxyl radical were detected. The effects of H2O and O2 contents, gas flow rate, and lamp power on the generation of reactive oxygen species were investigated. Results show that H2O and O2 contents as well as flow rate significantly affected O3 and H2O2 production. High content of H2O resulted in a decrease in O3 production but an increase in H2O2 production, whereas O2 content demonstrated the opposite effects owing to its varying absorption across sections. O3 and H2O2 production increased with increasing flow rate, while their concentrations changed slightly. High-power lamps had a negligible effect on O3 and H2O2 production, but O3 production decreased and H2O2 production increased under extremely low-power lamp radiation. In addition, the variations of the production of reactive oxygen species were also correlated with the oxidation processes of VUV-induced simultaneous desulfurization and denitrification.

Effect of high-intensity irradiation from dental photopolymerization on the isolated and superfused vertebrate retina

Light or electromagnetic radiation may damage the neurosensory retina during irradiation of photopolymerizing resinous materials. Direct and indirect effects of irradiation emitted from polymerisation curing light may represent a severe risk factor for the eyes and the skin of the lamp operators, as well as for the patient's oral mucosa. Bovine superfused retinas were used to record their light-evoked electroretinogram (ERG) as ex vivo ERGs. Both the a- and the b-waves were used as indicators for retinal damage on the functional level. The isolated retinas were routinely superfused with a standard nutrient solution under normoglycemic conditions (5 mM D-glucose). The change in the a- and b-wave amplitude and implicit time, caused by low and high intensity irradiation, was calculated and followed over time. From the results, it can be deduced that the irradiation from LED high-power lamps affects severely the normal physiological function of the bovine retina. Irradiations of 1,200 lx irreversibly damaged the physiological response. In part, this may be reversible at lower intensities, but curing without using the appropriate filter will bleach the retinal rhodopsin to a large extent within 20 to 40 s of standard application times. Constant exposure to intense ambient irradiation affects phototransduction (a-wave) as well as transretinal signalling. The proper use of the UV- and blue-light filtering device is highly recommended, and may prevent acute and long lasting damage of the neurosensory retina.

Development of a vaporization system for direct determination of chlorine in petroleum coke by ICP-MS

An electrothermal vaporization system (ETV) was developed for direct chlorine (Cl) determination in petroleum coke by inductively coupled plasma mass spectrometry (ICP-MS). The ETV system consists of a high power lamp enclosed in glass chamber equipped with solenoid valves. The system is controlled by a printed circuit board and software developed in LabVIEW environment. The temperature and heating time were optimized. Solenoid valves were used to control the flow of Ar (carrier gas) during pyrolysis and vaporization steps. Pyrolysis and vaporization temperatures were set at 350°C and 900°C, respectively; while the Ar flow rate was 1.20lmin−1 and the plasma power 1300W. Up to 5mg of petroleum coke sample can be analyzed. Calibration was carried out by standard addition whereas a certified reference material of coal (SARM 19) was used for that purpose. The relative standard deviation was lower than 9% (n=4) and the limit of quantification (10s) of Cl was 3.5μgg−1. Results obtained for chlorine in petroleum coke sample were in agreement with those obtained using other validated methods for Cl determination. The time of analysis (approximately 2min per sample), risk of contamination, analyte losses and waste generation are drastically reduced in comparison with techniques that require sample digestion for chlorine determination.

A portable and autonomous multichannel fluorescence detector for on-line and in situ explosive detection in aqueous phase

A multichannel fluorescence detector used to detect nitroaromatic explosives in aqueous phase has been developed, which is composed of a five-channel sample-sensor unit, a measurement and control unit, a microcontroller, and a communication unit. The characteristics of the detector as developed are mainly embedded in the sensor unit, and each sensor consists of a fluorescent sensing film, a light emitting diode (LED), a multi-pixel photon counter (MPPC), and an optical module with special bandpass optical filters. Due to the high sensitivity of the sensing film, the small size and low cost of LED and MPPC, the developed detector not only has a better detecting performance and small size, but also has a very low cost - it is an alternative to the device made with an expensive high power lamp and photomultiplier tube. The wavelengths of the five sensors covered extend from the upper UV through the visible spectrum, 370-640 nm, and thereby it possesses the potential to detect a variety of explosives and other hazardous materials in aqueous phase. An additional function of the detector is its ability to function via a wireless network, by which the data recorded by the detector can be sent to the host computer, and at the same time the instructions can be sent to the detector from the host computer. By means of the powerful computing ability of the host computer, and utilizing the classical principal component analysis (PCA) algorithm, effective classification of the analytes is achieved. Furthermore, the detector has been tested and evaluated using NB, PA, TNT and DNT as the analytes, and toluene, benzene, methanol and ethanol as interferent compounds (concentration various from 10 and 60 μM). It has been shown that the detector can detect the four nitroaromatics with high sensitivity and selectivity.

Investigation of acoustic resonances in high-power lamps

High-power, medium-pressure, mercury-containing lamps are used as UV sources for many industrial applications. Lamps investigated in this paper are driven with an electronic ballast with a non-sinusoidal current waveform at a fixed frequency of 20 kHz and a maximum power output of 35 kW. Instabilities can occur if the input power is reduced below 50%. The reason is identified as acoustic resonances in the lamp. Comparison of calculated and measured resonance frequencies shows a good agreement and explains the observed lamp behaviour. This has led to the development of a new ballast prototype which is able to avoid instabilities by changing the driving frequency dependent on the applied power.

Photochemical Removal of N2O in N2 or Air Using 172 nm Excimer Lamps

N2O removal was investigated in N2 or air using 172 nm Xe2 excimer lamps (50 or 300 mW/cm2) without using any expensive catalysts. The residual amount of N2O and the formation ratios of products were measured as functions of photoirradiation time, N2O concentration, and O2 concentration. N2O (100 ppm) was completely converted to N2 and O2 without NOx emission in N2 at atmospheric pressure after 30 min photoirradiation using a high-power Xe2 excimer lamp (300 mW/cm2). 76% of N2O (100 ppm) was also converted to N2, O2, and HNO3 in air (20% O2) after 30 min photoirradiation using the high-power lamp. We concluded that N2O is dominantly decomposed by 172 nm photolysis in N2 and by the O(1D) + N2O reaction in air, where O(1D) atoms dominantly arise from the 172 nm photolysis of O2. The conversion of N2O in air increased more than twofold by decreasing the total pressure from atmospheric pressure to 20 kPa by suppressing the collisional quenching of O(1D) by N2 and O2 buffer gases. In a flow experiment, the conversion of N2O in N2 was only 6–18% in the total flow rate range of 0.1–1 L/min owing to the short residence time of N2O in the photolysis chamber.

Photochemical removal of NO 2 by using 172-nm Xe 2 excimer lamp in N 2 or air at atmospheric pressure

Photochemical removal of NO 2 in N 2 or air (5–20% O 2) mixtures was studied by using 172-nm Xe 2 excimer lamps to develop a new simple photochemical aftertreatment technique of NO 2 in air at atmospheric pressure without using any catalysts. When a high power lamp (300 mW/cm 2) was used, the conversion of NO 2 (200–1000 ppm) to N 2 and O 2 in N 2 was >93% after 1 min irradiation, whereas that to N 2O 5, HNO 3, N 2, and O 2 in air (10% O 2) was 100% after 5 s irradiation in a batch system. In a flow system, about 92% of NO 2 (200 ppm) in N 2 was converted to N 2 and O 2, whereas NO 2 (200–400 ppm) in air (20% O 2) could be completely converted to N 2O 5, HNO 3, N 2, and O 2 at a flow rate of 1 l/min. It was found that NO could also be decomposed to N 2 and O 2 under 172-nm irradiation, though the removal rate is slower than that of NO 2 by a factor of 3.8. A simple model analysis assuming a consecutive reaction NO 2 → NO → N + O indicated that 86% of NO 2 is decomposed directly into N + O 2 and the rest is dissociated into NO + O under 172-nm irradiation. These results led us to conclude that the present technique is a new promising catalyst-free photochemical aftertreatment method of NO 2 in N 2 and air in a flow system.

A highly efficient 5 kW peak power Nd:YAG laser with time-shared fiber optic beam delivery

Here, we report on the development of an efficient, high peak power lamp pumped Nd:YAG laser with time-shared fiber optic beam delivery. A maximum average output power of 270 W with 100 J maximum pulse energy and 5 kW peak power has been achieved with an electrical to laser conversion efficiency of 5.4%, which is on higher side for typical lamp pumped solid-state lasers. We have improved efficiency by spectral conversion and water flow optimization in the pump cavity, with a resulting beam quality comparable to commercial systems of similar power level. The resonator has been designed for stable operation from single-shot to 200 Hz repetition rate. A study of pulse-to-pulse laser energy stability for different resonator configurations has also been performed. The resonator was designed to achieve a good beam quality for the whole range of operation with a maximum beam parameter product of 15 mm mrad ( M 2∼45). A simple mechanism for time-shared fiber optic port selection has also been devised. Material processing applications such as cutting of stainless steel sheets up to 14 mm thickness and welding of metals such as carbon steel with weld depths up to 2 mm using the developed laser system has also been reported.

Quantitative risk assessment of sunbeds: impact of new high power lamps

A survey of all sunbeds in a local authority area was carried out in 1998. Since then, there have been technological developments leading to new 'fast-tan' sunlamps which have become increasingly popular, along with unmanned sun parlours. In addition, new British and European sunbed standards have been set. To discover the commercial uptake of new high power sunlamps and to determine the impact on carcinogenic risk from sunbeds. Onsite spectral measurements, traceable to national standards, were conducted at all commercial sunbed premises within two local authorities and a quantitative risk assessment applied to the findings using a skin cancer model. Sunbed users were asked to complete a questionnaire regarding their reasons for using a sunbed and the risk associated with its use. We found a 30% increase in the number of privately operated sunbeds since our 1998 survey. The median cancer-weighted exposure of all 133 sunbeds was comparable to that of Mediterranean sunlight. This was a significant increase compared to 1998. Moreover, 83% of sunbeds produced ultraviolet (UV) B radiation levels that exceeded the European standard. Fifteen per cent of respondents thought that there were no risks from use of sunbeds. Sunbeds in current use carry a cancer risk comparable to Mediterranean sunlight. This is due to the use of new high power lamps. New British and European standards are being largely ignored with more than four out of five sunbeds exceeding the limit specified in the standard. There is a strong case for regulation of sunbed operators coupled to improved public education.

Phase-Controlled Quadruple ${LC}_{p}$ Resonant Inverter to Drive 600-W HPS Lamps

This paper presents the analysis and design method of a new configuration of resonant inverter suitable for high-intensity discharge (HID) lamp ballast applications. The proposed inverter results from the parallel connection of four class D LC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> resonant inverters, sharing the total load current. In this way, the conduction losses are reduced and high frequency operation is achieved for high power lamps. The power control is implemented at constant frequency, modifying the phase displacement among the output voltages of each inverter section. Considering that the deviation of the operation point caused by the control action deteriorates the converter efficiency, this design guarantees minimum control action to correct the lamp power deviation caused by the lamp aging. A 600-W prototype has been built to validate the design proposal

Energy distribution of runaway and fast electrons upon nanosecond volume discharge in atmospheric-pressure air

Nanosecond space discharge in a gas-filled diode is promising for pumping of lasers and high-power lamps. The space charge formed in the absence of an additional preionization source has a few advantages. The energy distributions of the beam electrons and the X-ray spectrum are determined. It is demonstrated that several high-energy electron bunches are formed in such a discharge. The main contribution to the beam current measured behind the foil is related to the runaway electrons, which have energies of tens or hundreds of kiloelectronvolts (supershort avalanche electron beam (SAEB)). Fast electrons with energies of several or tens of kiloelectronvolts are responsible for the generation of the soft X rays in the discharge gap. Anomalous electrons whose energy is higher than the voltage across the gap provide for a minor (less than 5%) contribution to the beam current. The generation time of these electrons is equal to the SAEB generation time accurate to 0.1 ns. It is demonstrated that the anomalous electrons can be generated owing to the acceleration in the presence of the field in front of the moving background-electron multiplication wave. The spectra of the X-ray radiation generated by the fast electrons in the volume are calculated.

Design guidelines for fixed-bed photocatalytic reactors

This paper summarizes the results of a work aimed at the design of pilot and industrial size photocatalytic reactors for wastewaters treatment. The work is based on the findings of previous lab-scale experiments and model development. The physical reactor model was used to simulate the performance of the photocatalytic system in various configurations and different operating conditions. The cost of the water treatment was determined by considering both the energy consumption and the periodic renewal of commercial UV lamps. The results of this work show that the optimal conditions for a photocatalytic purification unit remarkably depend on the kinetics of the pollutants degradation. In the case of fast degradation reactions low-power UV sources and low absorption catalysts are preferable. On the contrary the use of high-power lamps and dense catalysts can reduce sensibly the treatment cost when the degradation processes is slow.