Filter Tube Research Articles

Obtaining optimum exposure conditions for digital X-ray radiography of fresh nuclear fuel rods

X-ray radiography is widely used as a non-destructive method for defect detection and quality checks of nuclear fuel rod’s components in the fabrication process. In this paper, an approach based on Monte Carlo method is proposed to obtain optimum filter and exposure parameters such tube voltage, current and exposure for digital radiography of a nuclear fuel rod including UO2 pellets with a maximum diameter of 11.9 mm. Monte Carlo N-Particle (MCNP) code was implemented to model an digital X-ray radiography system composed of an industrial X-ray machine and a computed radiography phosphor imaging plate. Three main image quality parameters of contrast, resolution and signal to noise ratio (SNR) were evaluated in various exposure conditions. The results show that using a Cu intermediate filter with a thickness of 0.5 mm and a tube voltage in the range of 400–500kV with a minimum exposure of 20 mA min, can provide the highest quality for imaging the mentioned fuel rod. Moreover, the highest quality can be also achieved for tube voltages in the range of 500–600kV in condition that a minimum exposure of 40 mA min is provided. In addition to obtaining optimum conditions, the mentioned method can propose best exposure conditions proportional to the limitation of laboratory apparatuses. As a case study, the obtained results from simulation were implemented for the existence apparatuses in our laboratory and then an experimental work was carried out. The laboratory apparatuses included an X-ray machine with a peak voltage of 300 kV and a standard phosphor imaging plate. In the obtained experimental image, the details and components of the fuel rods including pellets, springs, Zircaloy clad and also the gap between the pellets were clearly observed. The proposed method can easily be implemented for all types of nuclear fuels with various dimensions and material types.

A study for the optimization of tube voltage and filter in digital mammography

Objective To investigate the image quality and average glandular dose from different breast compression thickness, and to provide recommendations for filtration material and tube voltage in digital mammography. Methods The CDMAM phantom of 2 to 7 cm thickness were exposed by manual exposure modes(proper mAs, 21 to 39 kVp range) using Mo/Mo and Mo/Rh anode/filer combinations at full-field digital mammography. The image quality figure (IQF), contrast to noise ratio (CNR), figure of merit (FOM) and the average glandular dose (AGD) were obtained from images. The optimum filtration and kVp for each breast thickness were found from the calculated FOMs. And the paired sample rank sum test was used to analyze the difference of AGD, CNR, IQF and FOM for Mo and Rh filters. Results For both Mo and Rh as used filter, under the compression of 2 to 7 cm thickness and the fixed mAs, with the increasing of tube voltage, AGD, CNR and IQF will gradually increase as following: AGD had the significant increasing while CNR and IQF gradually increasing to balance. Under different compression thickness, the AGD for Mo and Rh were statistically different (P 0.05).When the compression thickness was 4 cm, CNR for Mo and Rh were with no statistical significance (P 0.05) under the thickness of 5 cm and 7 cm; the IQF for Mo and Rh with no statistical significance (P>0.05). The FOM in each thickness for Mo and Rh filtration had statistical significance (P FOMMo. For different compression thickness, the suitable matching of tube voltage and filter material were Rh filtration, 2 cm and 27 kVp, 3 cm and 29 kVp, 4 cm and 29 kVp, 5 cm and 30 kVp, 6 cm and 31 kVp, 7 cm and 32 kVp. Conclusion Considering both image quality and radiation dose, Rh filtration is the optimum selection material and there is a corresponding optimal energy response in all kinds of thickness. Key words: Mammography; Image quality; Radiation dosage

Unfolding X-ray spectra using a flat panel detector. Determination of the accuracy of the method with the Monte Carlo method

The primary X-ray spectrum depends on different parameters such as high voltage, filament current, high voltage ripple, anode angle and thickness of filter material. The objective of this work is to determine whether the unfolding technique based on the Tikhonov regularization method is accurate enough to estimate the X-ray spectrum when slight changes in the operation variables are considered. In this frame, several X-ray spectra are considered (extracted from the IPEM78 Catalogue Report) varying the main operation variables of the X-ray tube (high voltage, voltage ripple, filter thickness and filter material). With those spectra, the corresponding absorbed dose curves are obtained by simulation with a MCNP5 model reproducing a flat panel detector and a PMMA wedge. Once the absorbed dose curves are simulated and applying the unfolding Tikhonov regularization method, the unfolded spectrum is obtained, which is finally compared with the theoretical one (IPEM78 Catalogue Report). Discrepancies between unfolded and primary X-ray spectra can be attributed to the fact that this is an ill-posed problem, and the unfolding of the spectrum is strongly affected by the method used to improve the conditioning of the response function (response matrix).

Accidental dual humidification in intensive care units: Repeated alerts and system changes are not enough

PurposeThe inadvertent, simultaneous use of heat and moisture exchangers (HMEs) and heated humidifiers (HHs) can result in waterlogging of the filter and sudden ventilation tube occlusion, with potentially fatal consequences. Following an NHS England Safety Alert, a near miss and educational reminders in our institution, we introduced new guidelines to solely use HHs in the intensive care unit and HMEs only for patient transfers. No further incidents have occurred, however this solution is potentially fallible. Two years later, we sought to assess staff knowledge and likelihood of recognising this error should it occur. Materials and methodsIn a simulation study, a tracheally intubated and ventilated mannequin had a breathing circuit containing both a HME and a HH. Participants were asked to assess the circuit, identify errors and undertake corrective measures. ResultsOnly 30% (6/20) recognised and undertook corrective measures. ConclusionsDespite educational efforts and system changes, recognition of this error remained poor. System changes may reduce the likelihood of the error occurring, but when it does, recognition may not occur. Substantial reductions or elimination of this error may be achieved through a safety-engineered fail-safe within the equipment, which alerts staff to improve recognition and prevent the mistake.

Monte Carlo analysis of beam blocking grid design parameters: Scatter estimation and the importance of electron backscatter

Beam blocking grids provide a simple and direct measurement of the scattered photon signal which degrades image quality in x-ray imaging systems, such as cone-beam CT (CBCT). This study evaluates the scatter estimation accuracy of the beam blocking method to optimize the design parameters of the grid system (e.g., grid thickness, source-to-grid distance (SGD), septa width, air interspace, and grid ratio) using Monte Carlo (MC) simulations. A MC model of a CBCT imaging system with a beam blocking grid in place is made using code based on EGSnrc, with the x-ray tube portion of the simulation including electron backscatter between the anode and cathode. The inclusion of the electron backscatter allowed a more complete model of the contamination signal to be estimated. The contamination signal consists of the off-focal radiation (OFR) and source component scatter (photon scatter in source components such as tube housing, filters, and collimators). The MC model was validated against measurements collected on a bench top imaging system with a grid in place. The MC model was used to simulate 11 different grid design configurations in addition to a case with no grid. For each design a simulated projection with and without a phantom in place was computed. The simulated projections were then used to estimate the scatter and contamination portion of the signal using the signal behind the grid septa. The estimated signals from the grid data were compared to the actual signals labeled during the MC simulation. Simulated results showed good agreeance with measured results with the importance of including electron backscatter resulting in off-focal radiation in the simulation being highlighted. When the source was free of contamination photons all grids performed with an error less than 8% when estimating just the scatter from the object. When the contamination photons were included in the simulation, the error in estimating both the scatter and contamination signal rose by a factor of 4 on average. In the case when both signals are present, increasing the grid thickness, changing the SGD, and reducing septa width and air interspace sizes all showed the ability to improve the grid-based estimates of the object scatter and contamination portion signal. The inclusion of the contamination signal in MC simulations of x-ray imaging systems is important in the design, validation, and evaluation of measurement-based scatter methods. Beam blocking grids show potential not only in object scatter estimation but in the estimation of the contamination signal, but appropriate interpolation functions must be used to account for higher frequencies found in contamination signal.

Design and Performance Analysis of B15 Engine Intake System

<p>In recent years, with the development of the economy, the automobile industry has also undergone ever-changing changes. At present, the design of the engine in addition to the car to achieve the dynamic, economic indicators but also need to meet their emissions and noise requirements, it is necessary for the engine into the exhaust system for in-depth study. The intake system mainly comprises two parts of the pipeline and the intake manifold before the intake manifold, in which the pipeline in front of the manifold acts to reduce the intake noise. How to design the components of the intake system reasonably and analyze its comprehensive performance is the most important topic in the project.</p><p>Firstly, this article introduces the principle of variable valve timing and variable intake manifold technology, establishes B15 engine model in GT-Power software and uses the test data to complete the calibration of the model so that the error is not more than 5% for subsequent simulation calculations. In order to design the silencer element of the intake system, the sensitivity of the parameters of the Helmholtz resonator, 1/4 wavelength tube and air filter is calculated and analyzed, and the influence of the parameter change on the muffler performance is summarized. The design flow and method of the intake muffler element are described in detail, and the concrete design scheme is put forward. The noise of the muffler element is optimized according to the problem that the noise of the individual order is higher than the target value. After the optimization of the intake system air intake noise improved significantly, the pressure loss is no higher than 2.5 kPa, in line with the target value requirements, the optimization effect is good.</p><p>Secondly, in order to analyze the performance of the intake manifold, three methods are proposed: the zero-dimensional or one-dimensional model is used to simplify the processing, and the CFD software is used to calculate the steady-state or isolated transients and the coupling analysis using one-dimensional and three-dimensional software. By comparing the advantages and disadvantages of the three methods, it is found that the coupling of software can obtain real-time boundary condition in the calculation process and have high accuracy. This paper focuses on the key issues that need to be solved by coupling with GT-Power and STAR-CCM + software and completes the calculation of the model.</p><p>Finally, in order to evaluate the advantages and disadvantages of the intake muffler element better, the maximum noise of the intake system is calculated by using the model of the vehicle acceleration in the GT-Power software, and the maximum noise of the intake system is 61.8 dB (A) which satisfies the target requirement for the individual contribution rate through noise.</p>

Investigation of major parasitic diseases and related knowledge, attitude and practice among rural residents in Liyang City

To investigate the prevalence of major parasitic diseases and related knowledge, attitude and practice among rural residents in Liyang City, so as to provide the evidence for formulating appropriate preventive strategies and measures. Three villages were selected from three towns as survey sites, and the residents who were above three years old and had been in the village for over six months were investigated. The Kato-Katz technique was applied to detect intestinal parasite eggs in residents' feces, and the cellophane anal swab was used to detect Enterobius vermicularis eggs among children aged 3-6 years. The iodine liquid smear and saline smear methods were used to examine intestinal protozoa cysts or trophozoites. Hookworm species were identified by the tube filter paper culture method. A structured questionnaire was used to collect the information on residents' knowledge, attitude and practice of the prevention and control of major parasitic diseases. Totally 759 residents were investigated and tested at the three rural survey sites, and only 2 cases were detected of parasitic infection and the total infection rate was 0.26%. Both cases were mild infections without mixed infection. The total awareness rate of knowledge on ascariasis, trichuriasis and ancylostomiasis was 37.9%, while the awareness rate of knowledge on clonorchiasis was 13.8%. The age and educational level were important factors of the knowledge on prevention and control of parasitic diseases among the residents. The formation rates of washing hands before meal and after using the toilet, and never drinking unboiled water were 83.8% and 92.1%, respectively. Totally 11.6% of the residents usually ate raw or half-cooked freshwater fishes and shrimps, and 53.0% had not the behavior to prepare raw and cooked food using the different chopping boards. The proportions of residents using fresh feces as manure and working in the field with bare feet were 13.8% and 22.8% respectively. The proportions of residents who thought they could, could not, or were not sure to change the risk behaviors and habits of parasitic infections were 40.2%, 28.5% and 31.4%, respectively. The infection rate of major parasitic diseases among the rural residents in Liyang City is low, and the awareness rate of knowledge on preventing parasitic diseases is also low. Therefore, the health education on the prevention and control of parasitic diseases should be strengthened to guide them to develop good hygiene, diet and farming habits. The environmental sanitation should be continuously improved to block the endemic of parasitic infection.

Usate of Filter Tube to Reduce Pb, Turbidity And Increase pH of Rain Water Flowing Through Zinc Rooftop House

Pb contained in rain water comes from zinc rooftop, beside that, it comes from the pollutant dissolved and comes into rain water reservoir and is used for community drinking water source. This research objective is to evaluate Pb, pH and turbidity of rain water before and after process and to analyze efectivity of shell sand filtration and activated carbon absorbtion in the filter tube to decrease Pb and turbidity and increase pH of rain water. This research is an experiment with pre and post test design with control and observational with cross sectional design. It is conducted in Pontianak and Kubu Raya West Kalimantan in 2016 with two target regions which represent urban and rural ones. The result indicated that average lead (Pb) contained in rain water and turbidity process is high with 131.7 g/l and 20 NTU and pH is low with 5.2. After process, Pb become 0.71 g/l and turbidity become 5.66 NTU while pH increases to 6.9. The effectivity of filter tube to reduce lead (Pb) contained in rain water is 99.4% and to reduce turbidity is 72%.

Effectiveness of ATP bioluminescence assay for presumptive identification of microorganisms in hospital water sources

BackgroundLaboratory analysis of organisms in water include arduous methods, such as the multiple tube and membrane filter. The ATP bioluminescence system, proposes a new way of measuring cellular material in water by measuring adenosine triphosphate (ATP) levels, which are expressed in relative light units (RLU). The ATP bioluminescence assay has been increasingly used to assess the microbiological safety of the hospital environment. However, there are few studies investigating the use of this methodology to evaluate the microbiological quality of water. The objective of the present study was to verify whether ATP, as measured by the 3 M™ Clean-Trace Water™ ATP test, can be used as an alternative tool for presumptive testing for the presence of microorganisms in hospital water.MethodsWater samples (N = 88) were collected from faucets (74) and water purifiers (14) in a university hospital. The sample were filtered by the membrane filter technique (100 mL for bacterial analysis and 100 mL for fungal analysis) and then submitted to ATP bioluminescence assay to the determine quantity of RLU in each sample. In order to compare RLU and the presence of microorganisms, a receiver operating characteristic (ROC) curve was used to calculate sensitivity and specificity (levels higher than 90% were considered significant). In addition, control tests were conducted to compare RLU to the quantities of bacterial and fungal organisms added to distilled water (ANOVA and Tukey’s tests; p ≤ 0.05). This inoculum was compared to RLU emission, and the data were analyzed by calculating the Pearson’s correlation coefficient, with a 95% confidence interval.ResultsIn the present study, 94.3% of the water samples presented bacterial growth. Of these, 15.6% showed heterotrophic bacteria above recommended levels and fungal contamination was detected in 55.6% of samples. Sensitivity and specificity of the samples were not significant (< 90%), and the correlation between ATP and the presence of these microorganisms in the samples (hospital water) was not significant, whereas, in distilled water, the results revealed a significant difference (p < 0.0001).ConclusionsThese results demonstrated that the ATP test cannot be used as an alternative tool for presumptive assessment of the presence of microorganisms in water.

Field experiment and numerical simulation of coupling non-Darcy flow caused by curtain and pumping well in foundation pit dewatering

High-velocity non-Darcy flow produced larger drawdown than Darcy flow under the same pumping rate. When the non-Darcy flow caused by curtain met non-Darcy flow caused by pumping wells, superposition and amplification effect occurred in the coupling area, the non-Darcy flow was defined as coupling non-Darcy flow. The coupling non-Darcy flow can be produced and controlled using different combination of curtain and pumping wells in foundation pit dewatering to obtain the maximum drawdown using the minimum pumping rate. The Qianjiang Century City Station foundation pit of Hangzhou subway, China, was selected as background. Field experiments were performed to observe the coupling non-Darcy flow in round gravel. A generalized conceptual model was established to study the coupling effect under different combination of curtain and pumping wells. Numerical simulations of the coupling non-Darcy flow in foundation pit dewatering were carried out based on the Forchheimer equation. The non-Darcy flow area and flow velocity were influenced by the coupling effect. Short filter tube, large pumping rate, small horizontal distance between filter tube and diaphragm wall, and small vertical distance between the filter tube and confined aquifer roof effectively strengthened the coupling effect and obtained a large drawdown. The pumping wells installed close to a curtain was an intentional choice designed to create coupling non-Darcy flow and obtain the maximize drawdown. It can be used in the dewatering of a long and narrow foundation pit, such as a subway foundation pit.

Adsorption of Cd(II) and Pb(II) by in situ oxidized Fe3O4 membrane grafted on 316L porous stainless steel filter tube and its potential application for drinking water treatment

Removing heavy metal ions from aqueous solutions is one of the most challenging separations. In situ oxidized Fe3O4 membranes using 316L porous stainless steel filter tube have shown great potential for removing anion Cr(VI). Here we report the performances of the in situ oxidized Fe3O4 membranes for removing two toxic cations Cd(II) and Pb(II) commonly existing in water and their potential applications for drinking water purification. The membranes exhibited high removal efficiency: 97% at pH 9.0 for Cd(II) of 1.0 mg/L initial concentration and 100% at pH 5.0–6.0 for Pb(II) of 5.0 mg/L initial concentration. The maximum adsorption capabilities were estimated at 0.800 mg/g and 2.251 mg/g respectively for Cd(II) and Pb(II) at 318 K by the Langmuir model. Results of batch tests revealed the existence of electrostatic attraction and chemisorption. XRD and FT-IR analyses indicated that the chemisorption might be the insertion of Cd(II) and Pb(II) into the Fe3O4 crystal faces of 311 and 511 to form mononuclear or binuclear coordination with O atoms of Fe-O6 groups. Competitive adsorption of Cd(II) and Pb(II) in binary solutions revealed a preferential adsorption for Pb(II). Na2EDTA solution was used to regenerate the membranes, and the maximum desorption ratio was 90.29% and 99.75% respectively for Cd(II) and Pb(II). The membranes were able to efficiently lower Cd(II) and Pb(II) concentrations to meet the drinking water standards recommended by the World Health Organization and are promising for engineering applications aimed at drinking water purification.

Analysis on thermal behavior of the type of filter tubes of extraction-injection wells in geothermal utilization

Groundwater heat pump (GWHP) has recently gained popularity because of its high efficiency, energy conservation, environment protection, etc. However, thermal breakthrough restricts its sustainable development. In order to delay and minimize thermal breakthrough, a new type of filter tube named as semi-circumference filter tube was proposed and numerical simulations followed. The reliability of the simulation has been validated. The extraction-injection well spacing and the degree of thermal imbalance were selected as the independent variable to study thermo-fluid difference between the semi-circumference filter tube and the traditional one. The pumping temperature evolution, the extent of thermal breakthrough and the energy loss resulting from thermal breakthrough were analyzed. Results show that the semi-circumference filter tube can delay the occurrence time of thermal breakthrough and decrease the energy loss. With a proper extraction-injection well spacing, the pumping temperature of the semi-circumference filter tube can almost keep a constant value, which is in favor of stable and long-term operation of the system.

Optimizing dual-energy x-ray parameters for the ExacTrac clinical stereoscopic imaging system to enhance soft-tissue imaging.

Stereoscopic x-ray image guided radiotherapy for lung tumors is often hindered by bone overlap and limited soft-tissue contrast. This study aims to evaluate the feasibility of dual-energy imaging techniques and to optimize parameters of the ExacTrac stereoscopic imaging system to enhance soft-tissue imaging for application to lung stereotactic body radiation therapy. Simulated spectra and a physical lung phantom were used to optimize filter material, thickness, tube potentials, and weighting factors to obtain bone subtracted dual-energy images. Spektr simulations were used to identify material in the atomic number range (3-83) based on a metric defined to separate spectra of high and low-energies. Both energies used the same filter due to time constraints of imaging in the presence of respiratory motion. The lung phantom contained bone, soft tissue, and tumor mimicking materials, and it was imaged with a filter thickness in the range of (0-0.7) mm and a kVp range of (60-80) for low energy and (120,140) for high energy. Optimal dual-energy weighting factors were obtained when the bone to soft-tissue contrast-to-noise ratio (CNR) was minimized. Optimal filter thickness and tube potential were achieved by maximizing tumor-to-background CNR. Using the optimized parameters, dual-energy images of an anthropomorphic Rando phantom with a spherical tumor mimicking material inserted in his lung were acquired and evaluated for bone subtraction and tumor contrast. Imaging dose was measured using the dual-energy technique with and without beam filtration and matched to that of a clinical conventional single energy technique. Tin was the material of choice for beam filtering providing the best energy separation, non-toxicity, and non-reactiveness. The best soft-tissue-weighted image in the lung phantom was obtained using 0.2 mm tin and (140, 60) kVp pair. Dual-energy images of the Rando phantom with the tin filter had noticeable improvement in bone elimination, tumor contrast, and noise content when compared to dual-energy imaging with no filtration. The surface dose was 0.52 mGy per each stereoscopic view for both clinical single energy technique and the dual-energy technique in both cases of with and without the tin filter. Dual-energy soft-tissue imaging is feasible without additional imaging dose using the ExacTrac stereoscopic imaging system with optimized acquisition parameters and no beam filtration. Addition of a single tin filter for both the high and low energies has noticeable improvements on dual-energy imaging with optimized parameters. Clinical implementation of a dual-energy technique on ExacTrac stereoscopic imaging could improve lung tumor visibility.

Design and simulation of a pulsed positron beam at ELI-NP

The design of the pulsing system for the slow e+ beam at ELI-NP is presented. It will deliver narrow time width e+ pulses, achieved by a combination of prebuncher, chopper and buncher. The effect of the different components on the pulse compression is simulated by a Matlab program. The results show that the best compression of the e+ pulses, which can be achieved by the proposed pulsing system, is limited to about 100 ps (FWHM). The most effective solution, applied up to now, for minimizing the influence of the backscattered e+ on the PALS spectra by using a bent tube filter is simulated by Comsol Multiphysics.

A method for water well regeneration based on shock waves and ultrasound

The regeneration of water wells is an urgent problem nowadays, when drilling of new wells becomes more and more expensive. Formation damage leads to a reduction of the formation's permeability and/or pore volume which in turn inhibits the ability of the water to flow from the reservoir formation into the wellbore. A new technology that uses high-power ultrasound to remove formation damage of water wells has been developed. The effectiveness of regeneration of wells can be enhanced if ultrasound and shockwaves are used during the same treatment. It was shown by computer modelling, that the two methods have different depths of impact. Whereas the ultrasonic method has a strong impact on the area of the filter tube, the impact of the shock waves is focused on the gavel pack, the wall of the well and the adjacent aquifer. A shockwave treatment, which is normally more effective due to larger impact zone, needs to be followed by ultrasonic treatment in order to facilitate the removal of the detached deposits. These theoretical assumptions were confirmed by field tests on two wells. The use of the method leaded to an increase of the production by 40% and 109% respectively.

First fast-ion D-alpha (FIDA) measurements and simulations on C-2U.

The first measurements of fast-ion D-alpha (FIDA) radiation have been acquired on C-2U, Tri Alpha Energy's advanced, beam-driven field-reversed configuration (FRC). These measurements are also forward modeled by FIDASIM. This is the first measurement and simulation of FIDA carried out on an FRC topology. FIDA measurements are made of Doppler-shifted Balmer-alpha light from neutralized fast ions using a bandpass filter and photomultiplier tube. One adjustable line-of-sight measured signals at eight locations and eight times during the FRC lifetime over 26 discharges. Filtered signals include only the highest energy ions (>6 keV) and share some salient features with the FIDASIM result. Highly Doppler-shifted beam radiation is also measured with a high-speed camera and is spatially well-correlated with FIDASIM.

버스 정비 작업자에 대한 석면 및 디젤 엔진 배출물질 노출 평가

Objectives: Lung cancer occurred with worker working in an urban bus garage. A survey was conducted to investigate whether lung cancer had causal relationship with work. Exposure to asbestos and diesel engine exhaust were suspected. Methods: Airborne asbestos was sampled on membrane filter and analyzed using phase-contrast microscopy. Airborne diesel exhaust was sampled using quartz filter and analyzed with thermal-optical analyzer. Polynuclear aromatic hydrocarbons was sampled using PTFE filter and XAD-2 tube and analyzed with gas chromatography-mass selective detector. Results: Airborne asbestos concentration was under 0.01 fiber/cc. Worker who warmed up an engine of urban bus for 2 hours was exposed to elemental carbon concentration, <TEX>$15.5{\mu}g/m^3$</TEX>. Only naphtalene among polynuclear aromatic hydrocarbons was detected. Conclusions: It was difficult to conclude about worker exposure to asbestos because working hour related asbestos was too short. In reviewing papers, the exposure to asbestos over 0.01 fiber/cc during exchange brake lining was found. It was identified that worker's occupational exposure to diesel exhaust based on elemental carbon was higher than the other occupational exposure to diesel exhaust.

Optimization of an enclosed gas analyzer sampling system for measuring eddy covariance fluxes of H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;

Abstract. Several initiatives are currently emerging to observe the exchange of energy and matter between the earth's surface and atmosphere standardized over larger space and time domains. For example, the National Ecological Observatory Network (NEON) and the Integrated Carbon Observing System (ICOS) are set to provide the ability of unbiased ecological inference across ecoclimatic zones and decades by deploying highly scalable and robust instruments and data processing. In the construction of these observatories, enclosed infrared gas analyzers are widely employed for eddy covariance applications. While these sensors represent a substantial improvement compared to their open- and closed-path predecessors, remaining high-frequency attenuation varies with site properties and gas sampling systems, and requires correction. Here, we show that components of the gas sampling system can substantially contribute to such high-frequency attenuation, but their effects can be significantly reduced by careful system design. From laboratory tests we determine the frequency at which signal attenuation reaches 50 % for individual parts of the gas sampling system. For different models of rain caps and particulate filters, this frequency falls into ranges of 2.5–16.5 Hz for CO2, 2.4–14.3 Hz for H2O, and 8.3–21.8 Hz for CO2, 1.4–19.9 Hz for H2O, respectively. A short and thin stainless steel intake tube was found to not limit frequency response, with 50 % attenuation occurring at frequencies well above 10 Hz for both H2O and CO2. From field tests we found that heating the intake tube and particulate filter continuously with 4 W was effective, and reduced the occurrence of problematic relative humidity levels (RH &gt; 60 %) by 50 % in the infrared gas analyzer cell. No further improvement of H2O frequency response was found for heating in excess of 4 W. These laboratory and field tests were reconciled using resistor–capacitor theory, and NEON's final gas sampling system was developed on this basis. The design consists of the stainless steel intake tube, a pleated mesh particulate filter and a low-volume rain cap in combination with 4 W of heating and insulation. In comparison to the original design, this reduced the high-frequency attenuation for H2O by ≈ 3∕4, and the remaining cospectral correction did not exceed 3 %, even at high relative humidity (95 %). The standardized design can be used across a wide range of ecoclimates and site layouts, and maximizes practicability due to minimal flow resistance and maintenance needs. Furthermore, due to minimal high-frequency spectral loss, it supports the routine application of adaptive correction procedures, and enables largely automated data processing across sites.

Potential continuous removal of toluene by ZnO nanorods grown on permeable alumina tube filters

Vertical ZnO nanorods were successfully grown on the crystalline surface of an Al2O3 microfilter by the simple technique of evaporation of prepared solution at atmospheric pressure (ESAP) for photocatalytic degradation of toluene.

Mean glandular dose coefficients (DgN) for x-ray spectra used in contemporary breast imaging systems

To develop tables of normalized glandular dose coefficients for a range of anode–filter combinations and tube voltages used in contemporary breast imaging systems.Previously published mono-energetic values were used with various spectra to mathematically compute coefficients. The tungsten anode spectra from TASMICS were used; molybdenum and rhodium anode-spectra were generated using MCNPX Monte Carlo code. The spectra were filtered with various thicknesses of Al, Rh, Mo or Cu. An initial half value layer (HVL) calculation was made using the anode and filter material. A range of the HVL values was produced with the addition of small thicknesses of polymethyl methacrylate (PMMA) as a surrogate for the breast compression paddle, to produce a range of HVL values at each tube voltage. Using a spectral weighting method, coefficients for the generated spectra were calculated for breast glandular densities of 0%, 12.5%, 25%, 37.5%, 50% and 100% for a range of compressed breast thicknesses from 3 to 8 cm.Eleven tables of normalized glandular dose () coefficients were produced for the following anode/filter combinations: W + 50 μm Ag, W + 500 μm Al, W + 700 μm Al, W + 200 μm Cu, W + 300 μm Cu, W + 50 μm Rh, Mo + 400 μm Cu, Mo + 30 μm Mo, Mo + 25 μm Rh, Rh + 400 μm Cu and Rh + 25 μm Rh. Where possible, these results were compared to previously published values and were found to be on average less than 2% different than previously reported values.Over 200 pages of coefficients were computed for modeled x-ray system spectra that are used in a number of new breast imaging applications. The reported values were found to be in excellent agreement when compared to published values.