Passive Monitor Research Articles

Determination of deployment specific chemical uptake rates for SDB-RPD Empore disk using a passive flow monitor (PFM)

The use of the adsorbent styrenedivinylbenzene-reverse phase sulfonated (SDB-RPD) Empore disk in a chemcatcher type passive sampler is routinely applied in Australia when monitoring herbicides in aquatic environments. One key challenge in the use of passive samplers is mitigating the potentially confounding effects of varying flow conditions on chemical uptake by the passive sampler. Performance reference compounds (PRCs) may be applied to correct sampling rates ( R s ) for site specific changed in flow and temperature however evidence suggests the use of PRCs is unreliable when applied to adsorbent passive samplers. The use of the passive flow monitor (PFM) has been introduced for the assessment of site-specific changes in water flow. In the presented study we have demonstrated that the R s at which both atrazine and prometryn are accumulated within the SDB-RPD-Empore disk is dependent on the flow conditions. Further, the calibration of the measured R s for chemical uptake by the SDB-RPD-Empore disk to the mass lost from the PFM has shown that the PFM provides an accurate measure of R s for flow velocities from 0 to 16 cm s −1. Notably, for flow rates >16 cm s −1, a non linear increase in the R s of both herbicides was observed which indicates that the key resistance to uptake into the SDB-RPD Empore disk is associated with the diffusion through the overlying diffusion limiting membrane. Overall the greatest uncertainty remains at very low flow conditions, which are unlikely to often occur in surface waters. Validation of the PFM use has also been undertaken in a limited field study.

A passive acoustic monitor of treatment effectiveness during extracorporeal lithotripsy

Although extracorporeal shockwave lithotripsy (ESWL) has now been in the clinic for at least three decades, there has been little advance in efforts (i) to estimate the efficacy of the treatment whilst it is in progress, or (ii) to determine the end-point of a treatment session in terms of the degree of stone fragmentation achieved. Previous in vitro experimentation and clinical trials have shown that a passive acoustic monitor has the potential to provide evidence of the effectiveness and end-point of lithotripsy. The system exploits secondary emissions generated during shock-tissue interaction, whose features depend on the quality of tissue at the beam focus. This prototype was developed into the first commercially available clinical ESWL treatment monitor (Precision Acoustic Ltd, Dorchester, UK), and a unit has been acquired and tested in the clinical routine by urologists at Guy's and St Thomas NHS Trust in March 2009. This paper critically assesses the performance of the new system for the first 25 treatments monitored. The ESWL monitor correctly predicted the treatment outcome of 15 of the 18 treatments that were followed-up clinically. In addition, it was noted that the measure of treatment effectiveness provided by the monitor after 500 shocks was predictive of the final treatment outcome (p < 0.001). This suggests that the system could be used in pre-assessment; indicating if the stone is susceptible to ESWL or if the patient should be sent for surgery.

Effectiveness of Bed Bug Monitors for Detecting and Trapping Bed Bugs in Apartments

Bed bugs, Cimex lectularius L., are now considered a serious urban pest in the United States. Because they are small and difficult to find, there has been strong interest in developing and using monitoring tools to detect bed bugs and evaluate the results of bed bug control efforts. Several bed bug monitoring devices were developed recently, but their effectiveness is unknown. We comparatively evaluated three active monitors that contain attractants: CDC3000, NightWatch, and a home-made dry ice trap. The Climbup Insect Interceptor, a passive monitor (without attractants), was used for estimating the bed bug numbers before and after placing active monitors. The results of the Interceptors also were compared with the results of the active monitors. In occupied apartments, the relative effectiveness of the active monitors was: dry ice trap > CDC3000 > NightWatch. In lightly infested apartments, the Interceptor (operated for 7 d) trapped similar number of bed bugs as the dry ice trap (operated for 1 d) and trapped more bed bugs than CDC3000 and NightWatch (operated for 1 d). The Interceptor was also more effective than visual inspections in detecting the presence of small numbers of bed bugs. CDC3000 and the dry ice trap operated for 1 d were equally as effective as the visual inspections for detecting very low level of infestations, whereas 1-d deployment of NightWatch detected significantly lower number of infestations compared with visual inspections. NightWatch was designed to be able to operate for several consecutive nights. When operated for four nights, NightWatch trapped similar number of bed bugs as the Interceptors operated for 10 d after deployment of NightWatch. We conclude these monitors are effective tools in detecting early bed bug infestations and evaluating the results of bed bug control programs.

The effects of high ambient radon on thermoluminescence dosimetry readings

The effect of a high level of ambient (222)Rn gas on thermoluminescence dosemeters (TLDs) is examined. Groups of LiF:Mg,Ti and CaF(2):Dy TLDs were exposed to (222)Rn under controlled environmental conditions over ∼7 d using a luminous (226)Ra aircraft dial. LiF:Mg,Ti TLDs were tested bare, and both types were tested mounted in cards used for environmental dosimetry and mounted in cards enclosed in plastic badges. A passive continuous radon monitor was used to measure the (222)Rn level in the small chamber during the experiments. The data were analysed to determine the relationship between the integrated (222)Rn level and the TLD response. Although both LiF:Mg,Ti and CaF(2):Dy TLDs showed a strong response to (222)Rn, the badges prevented measurable radon detection by the TLDs within. The TLDs were not used to directly measure the radon concentration; rather, a correction for its influence was desired.

Elemental Analysis of Desert Varnish Samples in the Vicinity of Coal-Fired Power Plants and the Nevada Test Site Using Laser Ablation ICPMS

Desert varnish is a thin manganese-iron rich dark coating that forms on rocks most often in arid climates. This coating may be up to a few hundred microns in thickness and is thought to grow by approximately one micron per thousand years. Recent research has shown that many elements are incorporated into this coating, and, in spite of its slow growth, it may serve as a passive environmental monitor for recent and historical air pollution. To test this hypothesis, small pieces of varnished rock were probed directly by laser ablation inductively coupled plasma mass spectrometry (LA- ICPMS). Results were obtained for 11 elements (13 isotopes: 9 Be, 107 Ag, 111 Cd, 118 Sn, 121 Sb, 138 Ba, 184 W, 205 Tl, 206 Pb, 207 Pb, 208 Pb, 232 Th, and 238 U) by magnetic sector ICPMS and for 23 elements (25 isotopes: same as before plus 51 V, 52 Cr, 59 Co, 60 Ni, 65 Cu, 66 Zn, 88 Sr, 98 Mo, 115 In, 133 Cs, 197 Au, and 209 Bi) by quadrupole ICPMS. Varnished rock samples were collected mainly in the fallout patterns of two coal-fired power plants and downwind from the Nevada Test Site (NTS). The LA-ICPMS data indicate that many of the elements commonly found in fly ash from coal-fired power plants (e.g., Cr, Co, Ni, Cu, Zn, Cd, Sn, Sb, Tl and Pb) were highly enriched in the rock coatings in relation to the upper continental crust (UCC). For one of the power plants, where tracer plume studies had been carried out, the highest concentrations in the rock varnish coincide with the peak tracer concentration locations. Thus, these elements in rock varnish hold promise for identifying those geographical regions impacted by nearby power plants. Overall, the results indicate that rock varnish can be used as a passive environmental monitor of relatively recent events, and that the trace element fingerprints held in rock varnish may also hold much potential in forensic air pollution studies.

A cost effective, highly sensitive, passive neutron fluence monitor for nuclear contraband detection

Natural gadolinium possesses a very high thermal neutron capture ( n , γ ) cross-section on the other hand, carbon-doped aluminium oxide thermoluminescence dosimeters (α-Al 2 O 3 :C), available as TLD 500 are extremely responsive to gamma rays . Hence, by combining those two unique phenomena we have developed a highly sensitive passive neutron detector . The lowest detectable (fission) neutron fluence rate was evaluated to be 7.1 neutrons cm −2 s −1 for an integration period of 1 h. This detection level is adequate enough to detect 3 g of 240 Pu from a distance of 1 m, producing spontaneous fission neutrons. Application of this neutron fluence monitor in the passive detection of nuclear contraband is suggested. Further developmental work aiming to augment the present device with instantaneous data display and alarm actuation capabilities is ongoing.

Air nicotine monitoring study at Chennai, Tamil Nadu to assess the level of exposure to second hand smoke in public places

Air nicotine monitoring study at Chennai, Tamil Nadu to assess the level of exposure to second hand smoke in public places

A novel method for the in situ calibration of flow effects on a phosphate passive sampler

Monitoring of nutrients including phosphate in the aquatic environment remains a challenge. In the last decade passive sampling techniques have been developed that facilitates the time integrated monitoring of phosphate (P) through the use of an iron hydroxide (ferrihydrite) to sequester dissolved phosphate from solution. These methods rely on established techniques to negate the effects of flow (and associated turbulence) and control the rate at which chemicals accumulate within passive samplers. In this study we present a phosphate sampler within which a suspension of ferrihydrite is contained behind a commercially available membrane. Accumulation of dissolved phosphates into the P-sampler is governed by the rate at which ions are diffusing through the membrane and the water boundary layer (WBL). As the WBL changes subject to flow we have adopted an in situ calibration technique based on the dissolution of gypsum to predict the change in the rate of uptake dependent on flow. Here we demonstrate that the loss of gypsum from the passive flow monitor (PFM) can be used to predict the sampling rate (the volume of water extracted per day) for phosphate as a function of water velocity. The outcome of this study presents a new in-field tool for more accurate prediction of the effect of flow/turbulence on the uptake kinetics into passive samplers that is controlled by the diffusion of the chemical of interest through the stagnant water boundary layer.

Influence of the presence of humidity, ambient aerosols and thoron on the detection responses of electret radon monitors

This paper describes how the presence of humidity, ambient aerosols and thoron influences the detection responses of an electret passive environmental radon monitor (commercially E-PERM ®) using radon and thoron chambers of National Institute of Radiological Sciences (NIRS). From the initial experiments, the linear correlation between the conversion factor for radon and the midpoint voltage for the short-term and long-term electrets was determined. As a result, it was observed that the conversion factors were approximately 10% lower for the short-term electrets and 3% higher for the long-term electrets than those reported by the manufacturer. The evaluation of different magnitudes of radon concentration showed that the presence of humidity and ambient aerosols had little influence on the detection response for radon, with less than 10% relative standard deviation. In the case of thoron detection response, net voltage drop values increased linearly with time-integrated concentrations for both short-term and long-term electrets, as was the case with radon. The thoron responses to radon were less than 5% for both the electrets from the results of experiments and calculations.

Application of low-cost Gallium Arsenide light-emitting-diodes as kerma dosemeter and fluence monitor for high-energy neutrons

Displacement damage (DD) caused by fast neutrons in unbiased Gallium Arsenide (GaAs) light emitting diodes (LED) resulted in a reduction of the light output. On the other hand, a similar type of LED irradiated with gamma rays from a (60)Co source up to a dose level in excess of 1.0 kGy (1.0 x 10(5) rad) was found to show no significant drop of the light emission. This phenomenon was used to develop a low cost passive fluence monitor and kinetic energy released per unit mass dosemeter for accelerator-produced neutrons. These LED-dosemeters were used to assess the integrated fluence of photoneutrons, which were contaminated with a strong bremsstrahlung gamma-background generated by the 730 MeV superconducting electron linac driving the free electron laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron. The applications of GaAs LED as a routine neutron fluence monitor and DD precursor for the electronic components located in high-energy accelerator environment are highlighted.

Evaluation of imaging plate technique coupled with activation detector as the passive neutron monitor

The spatial distribution of neutrons was measured at the muon science laboratory of KEK by the activation detector method using an imaging plate for the radioactivity measurement. It was confirmed that this method is highly sensitive to detect the average neutron dose of 10 µSv/h. The distribution of thermal and epithermal neutrons was also measured in the experimental room. The cadmium ratio inside the experimental room is one except for the neutron leakage point. The spatial distribution of neutrons inside the concrete shield of KENS was measured by the same method. Aluminum and gold foils were used for the measurement of fast and thermal neutrons, respectively. Two dimensional change of the reaction rate of the 27Al(n,α)24Na reaction shows a good agreement with the results calculated by the Monte Carlo simulation using MARS14 code. Thermal and epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method. The flux ratios were about 30 and almost constant for every slot except for the surface of the shield, because the cadmium ratio is 2. This method was very useful to measure the activity of many pieces of detector simultaneously without any efficiency and decay correction. Wide dynamic range and high sensitivity are also the merit of this method.

Application-Coexistent Wire-Rate Network Monitor for 10 Gigabit-per-Second Network

To apply network monitoring functions to emerging high-quality video streaming services, we proposed an application-coexistent monitor (APCM). In APCM, a streaming server can works as an active monitor and a passive monitor. In addition, IP packets sent from the server carry monitoring information together with application's data such as video signals. To achieve APCM on a 10-Gbps network, we developed a network interface card for an application-coexistent wire-rate network monitor (AWING NIC). It provides (1) a function to append GPS-based accurate timestamps to every packet that streaming applications send and receive, which can be used for real-time monitoring of delays and inter-packet gap, and (2) functions to capture and generate 10-Gbps wire-rate traffic without depending on packets' size, achieved by our highly-efficient DMA-transfer mechanisms. Such monitoring capability are unprecedented in existing PC-based systems because of the limitation in PC system's architecture. As an evaluation of APCM in an actual network, we conducted an experiment to transmit a 6-Gbps high-quality video stream over an IP network with the system in which we installed the AWING NIC. The results revealed that the video stream became highly bursty by passing through the network, and the observed smallest inter-packet gap corresponds to the value of 10-Gbps wire-rate traffic, which supports the effectiveness of our development.

Comparison of Pilots' and Controllers' Conflict Resolution Maneuver Preferences

The role of the air traffic controller in future air traffic management systems is that of a passive monitor, who intervenes in potential conflict situations only if pilots, aided by onboard traffic displays, fail to implement safe and timely conflict resolutions. Yet, such scenarios are entirely plausible and even likely, particularly in busy airspaces. However, it is also likely that an a controller will seek to implement a resolution that is different from what the pilots had planned, resulting in confusion, delays, and safety risks. This paper examines pilots' and controllers' maneuver preferences and potential sources for dissonance in conflict resolution situations. Data on pilots' maneuver tendencies were gathered from an extensive review of past literature; controllers' preferences were obtained from an experiment that systematically manipulated simulated ATC scenario difficulty and conflict geometries. Results indicate largely similar maneuver choices between controllers and pilots, but suggest a need for further research.

Leaves of Pittosporum tobira as indicators of airborne trace element and PM 10 distribution in central Italy

Leaves of the evergreen ornamental shrub species Pittosporum tobira were used as a passive monitor to describe the distribution of selected elements in three coastal cities of central Italy (namely Livorno, Rosignano Marittimo and Piombino) differing for number of inhabitants and economical activities. Unwashed healthy mature leaves collected in June 2004 from 88 sampling sites covering the whole municipalities according to a systematic stratified unallineated sampling design were analysed by ICP-MS for Al, Ba, Be, Bi, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Ti, V and Zn. Values were normalised by subtracting baseline concentrations of biologically essential elements. Enrichment factors were calculated taking Al as crustal reference element. Factor analysis allowed to identify three main source groups of elements, namely crustal components, sea-salt spray and anthropogenic sources (vehicular traffic, industrial activities). SEM–EDX analyses were performed on 556 PM 10 samples collected from the 88 sampling sites. High contributions of geological elements and marine aerosols were detected. Pb is no longer of environmental concern in the area. Results are discussed with emphasis on the potential role of vegetation for the removal of particulate pollution.

Use of GIS and ancillary variables to predict volatile organic compound and nitrogen dioxide levels at unmonitored locations

In late 1999, passive air sampling of nitrogen dioxide (NO 2) and volatile organic compounds was conducted at 22 school locations and two intensive sites in El Paso, Texas. Our goal was to predict concentrations of NO 2 and benzene, toluene, ethylbenzene, o-xylene, and m, p-xylene at a total of 55 schools. The predictive equations were developed by regressing the passive monitor measurements at the 22 monitored schools on land-use variables derived from a geographic information system (GIS). These GIS-based ancillary variables included distance to the nearest border crossing, elevation, population density, distance to roads with specified traffic volumes, traffic intensity around the schools, and distance to the nearest petroleum facility. The reliability of the predictive equations was assessed at the two intensive monitoring sites. For all pollutants, the most useful predictive ancillary variables were elevation, population density, distance to a border crossing, and distance to a petroleum facility. For estimating NO 2, traffic intensity was also important.

An empirical investigation of the prevalence of spyware in internet shareware and freeware distributions

PurposeSpyware is a controversial software technology that allows the surreptitious collection of personal information from computers linked to the internet. The purpose of this study was to determine the prevalence of spyware in internet shareware and freeware and to investigate the personal information collected.Design/methodology/approachThe methodology was a two‐phase, multi‐case study. The first phase determined that five of the 50 most popular pieces of Windows®‐based freeware and shareware available to internet users from CNETDownload.com were suspected of containing spyware: these were included as data sources for phase two. The purpose of phase two was to confirm the existence of spyware and to identify the types and frequencies of any personal data transmissions. For this phase, data were collected and analyzed utilizing a passive network monitor program to examine packets of data transmitted from a personal computer to external destinations on the internet.FindingsThe findings confirmed the existence and use of spyware in three of five suspected cases. However, the data indicated that there was a low occurrence of spyware and that these programs have the capability to collect numerous types of personal data. The main limitation is that these results are based on a snapshot of data obtained during five days.Practical implicationsThe study has practical implications for internet users, who should be aware that spyware exists and understand its potential threat. Spyware developers should provide the user with an effective removal tool. Finally, marketers are cautioned that spyware might alienate customers.Originality/valueThis paper confirms the potential for misuse of these programs.

Indoor radon and thoron concentrations in the pyramides of Teotihuacan

This paper presents radon and thoron concentrations measured in the prehispanic tunnel of the Sun Pyramid and in the archeological tunnel 1 in the Moon Pyramid. Radon and thoron concentrations were measured using several electret passive environmental radon monitor (E-PERM) configurations and detection systems. Results were in good agreement with no significant difference ( P H E ) calculated for the highest concentration was much lower than the action level (3-10 mSv . y -1 ). A quality assurance program was improved.

A Field Comparison of Volatile Organic Compound Measurements Using Passive Organic Vapor Monitors and Stainless Steel Canisters

Concurrent field measurements of 10 volatile organic compounds (VOCs) were made using passive diffusion-based organic vapor monitors (OVMs) and the U.S. Federal Reference Method, which comprises active monitoring with stainless steel canisters (CANs). Measurements were obtained throughout a range of weather conditions, repeatedly over the course of three seasons, and at three different locations in the Minneapolis/St. Paul metropolitan area. Ambient concentrations of most VOCs as measured by both methods were low compared to those of other large metropolitan areas. For some VOCs a considerable fraction of measurements was below the detection limit of one or both methods. The observed differences between the two methods were similar across measurement sites, seasons, and meteorological variables. A Bayesian analysis with uniform priors on the differences was applied, with accommodation of sometimes heavy censoring (nondetection) in either device. The resulting estimates of bias and standard deviation of the OVM relative to the CAN were computed by tertile of the canister-measured concentration. In general, OVM and CAN measurements were in the best agreement for benzene and other aromatic compounds with hydrocarbon additions (ethylbenzene, toluene, and xylenes). The two methods were not in such good agreement for styrene and halogenated compounds (carbon tetrachloride, p-dichlorobenzene, methylene chloride, and trichloroethylene). OVMs slightly overestimated benzene concentrations and carbon tetrachloride at low concentrations, but in all other cases where significant differences were found, OVMs underestimated relative to canisters. Our study indicates that the two methods are in agreement for some compounds, but not all. We provide data and interpretation on the relative performance of the two VOC measurement methods, which facilitates intercomparisons among studies.

Field comparison of two different passive radon detectors

The present paper describes field performance of two different passive radon monitor devices formed, respectively, by a CR-39 track detector enclosed in a diffusion chamber and a cellulose nitrate detector (LR-115) in a heat-sealed polyethylene bag. The most important scope of these investigations was to study the performance of these detectors directly in the field. To this end, two different types of radon monitors mentioned above have been exposed simultaneously in 100 school rooms within the Italian region Friuli Venezia Giulia. Finally, the accuracy of their responses has been evaluated by exposing them under extreme humidity conditions and/or together with other radon measurement instruments.

Laboratory and field validations of a solid-phase microextraction device for the determination of ethylene oxide

Laboratory and field evaluations were performed to validate a solid-phase microextraction (SPME) device that was used as a diffusive sampler. Hydrogen bromide (HBr) was loaded onto the carboxen–polydimethylsiloxane (CAR–PDMS) fiber for the determination of ethylene oxide (EtO) with on-fiber derivatization. For laboratory evaluations, known concentrations of ethylene oxide around the threshold limit values (TLV)/time-weighted average and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. The SPME diffusive samplers and the commercially available 3M 3551 passive monitors were placed side-by-side in an exposure chamber which was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Field validations with both SPME diffusive sampler and 3M 3551 passive monitors were also performed. The correlations between the results from both SPME device and 3M 3551 passive monitor were found to be linear ( r>0.9699) and consistent (slope≅1.12±0.07). However, the variations of diffusion coefficients at different temperatures needs to be considered and the adjustment of sampling constant was a must when sampling at temperatures different from 25 °C.