Continuous Sampling System Research Articles

Development of Automatic Continuous Soil Sampling System

Development of Automatic Continuous Soil Sampling System

定量的ＰＥＴ測定に用いる測定器の信頼性‐電離箱式放射能測定装置，ウェル型シンチレーションカウンタ，持続動脈血中放射能濃度測定器およびＰＥＴ装置の評価‐

Positron emission tomography (PET) is a powerful tool for measuring in vivo functions such as blood flow, metabolism, enzyme activity, receptors, and transporters. However, plural measuring instruments (i.e., the dose-calibrator, the auto well gamma counter, the continuous blood sampling system) are necessary for the quantitative PET measurement as well as the PET scanner. The purpose of this study was to investigate the reliability of plural measuring instruments from the maintenance data for 6 years. Four kinds of measuring instrument were evaluated: a dose-calibrator (CAPINTEC, CRC-15R), an auto well gamma counter (ALOKA, ARC-400), a continuous blood sampling system (ESPEC Techno, PH type), and a dedicated PET scanner (Siemens, ECAT EXACT HR+). We examined whether the initial performance for system sensitivity is maintained. The reliability of the PET scanner was evaluated from the value of mean time between failures (MTBF) for each part of the system obtained from the maintenance data for 6 years. The sensitivity of a dose-calibrator and an auto well gamma counter were maintained virtually constant during the 6 years, but the sensitivity of a continuous blood sampling system was 0.1+/-3.2%. The sensitivity of a PET scanner was decreased to 92.3% of the initial value. Fifty-one percent of the problems with the PET scanner were for detector block (DB) and analog processor (AP) board. The MTBF of DB and AP board module were 199 and 244 days, respectively. The MTBF of the PET scanner was 56 days. The performance of three measuring instruments, excepting the PET scanner, was relatively stable. The reliability of the PET scanner strongly depends on the MTBF of the DB and AP board. For quantitative PET measurement, it is effective to evaluate the reliability of the system and to make it known to the users.

GEM fluxes and atmospheric mercury concentrations (GEM, RGM and [formula omitted]) in the Canadian Arctic at Alert, Nunavut, Canada (February–June 2005)

Five months of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle bound mercury ( Hg p ) concentrations as well as fluxes of GEM were measured at Alert, Nunavut, Canada above the Arctic snow pack. The study spanned February to June of 2005 to capture the effects of polar night, the transition period between night and day as well as polar day on the behaviour of mercury in the near surface atmosphere. A micrometeorological approach was used to infer the flux of GEM using a continuous two-level sampling system to measure the GEM concentration gradient. The required turbulent transfer coefficients were derived from meteorological parameters measured on site. The flux of GEM was approximately zero during atmospheric mercury depletion events (AMDEs) demonstrating that mercury is not being deposited as GEM to the snow pack. Following AMDEs, there was no evidence of a net emission of GEM. The highest depositional fluxes of GEM occurred during polar night and the largest emission occurred when the tundra was first visible, followed by significant emission and deposition fluxes during the snow melt. Fluxes continued until the snow had completely melted ( ∼ JD 170) before returning to near zero. Average concentrations of RGM ( 44.4 ± 49.8 pg m - 3 ) , Hg p ( 102.6 ± 124.9 pg m - 3 ) and GEM ( 1.0 ± 0.4 ng m - 3 ) were variable throughout the study due to the dynamic nature of atmospheric mercury during AMDEs. Increases in Hg p preceded elevated levels of RGM during AMDEs by 60 days, yielding peak levels at 694 and 344 pg m - 3 , respectively. Elevated concentrations of Hg p typically occurred when the specific humidity dropped below 0.75 g kg - 1 , winds were light ( < 3 m s - 1 ) and the air temperature dropped below - 20 ∘ C . Increased levels of RGM were also noted when the winds were light ( < 3 m s - 1 ) but when the temperature increased above - 10 ∘ C and the specific humidity was in the range of 1 and 3 g kg - 1 . As different environmental conditions were observed for the elevated concentrations of Hg p versus RGM at Alert, it suggests that the formation mechanisms for each species may be different but tied to the atmospheric temperature and water content. Total mercury (TM) levels in fresh snow measured approximately 5– 10 ng l - 1 during AMDEs and reached nearly 80 ng l - 1 outside of depletion events, suggesting that wet deposition may not be a significant removal mechanism of GEM during depletion events. An unusually high concentration of TM was measured during a non-depletion event which coincided with the transitional period where atmospheric loading of RGM exceeded levels of Hg p .

Measurements of GEM fluxes and atmospheric mercury concentrations (GEM, RGM and Hg p) from an agricultural field amended with biosolids in Southern Ont., Canada (October 2004–November 2004)

Five weeks of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle bound mercury (Hg p) concentrations as well as fluxes of GEM were measured at Maryhill, Ontario, Canada above a biosolids amended field. The study occurred during the autumn of 2004 (October–November) to capture the effects of cool weather conditions on the behaviour of mercury in the atmosphere. The initial concentration of total mercury (Hg) in the amended soil was relatively low (0.4 μg g −1±10%). A micrometeorological approach was used to infer the flux of GEM using a continuous two-level sampling system with inlets at 0.40 and 1.25 m above the soil surface to measure the GEM concentration gradient. The required turbulent transfer coefficients were derived from meteorological parameters measured on site. The average GEM flux over the study was 0.1±0.2 ng m −2 h −1(±one standard deviation). The highest averaged hourly GEM fluxes occurred when the averaged net radiation was highest, although the slight diurnal patterns observed were not statistically significant for the complete flux data series. GEM emission fluxes responded to various local events including the passage of a cold front when the flux increased to 2 ng m −2 h −1 and during a biosolids application event at an adjacent field when depositional fluxes peaked at −3 ng m −2 h −1. Three substantial rain events during the study kept the surface soil moisture near field capacity and only slightly increased the GEM flux. Average concentrations of RGM (2.3±3.0 pg m −3), Hg p (3.0±6.2 pg m −3) and GEM (1.8±0.2 ng m −3) remained relatively constant throughout the study except when specific local events resulted in elevated concentrations. The application of biosolids to an adjacent field produced large increases in Hg p (25.8 pg m −3) and RGM (21.7 pg m −3) concentrations only when the wind aligned to impact the experimental equipment. Harvest events (corn) in adjacent fields also corresponded to higher concentrations of GEM and Hg p but with no elevated peaks in RGM concentrations. Diurnal patterns were not statistically significant for RGM and Hg p at Maryhill.

Continuous shipboard sampling system for determination of triple oxygen isotopes and O2/Ar ratio by dual‐inlet mass spectrometry

A continuous shipboard sampling system was developed for the determination of the isotopic composition of the triple oxygen isotopes and oxygen to argon (O(2)/Ar) ratios in dissolved air. In this system, dissolved air is separated by a hollow fiber membrane degassing module. This system collects dissolved air quantitatively and rapidly. The sample flow rate through the membrane is critical for the fractionation of the oxygen isotopes and the O(2)/Ar ratio and should be < 2 mL/min. Fractionation of oxygen between the liquid and gas phase of the air-saturated water was found to be similar to that of earlier reports. The advantages of this method over existing techniques include rapid collection of samples (30 min/sample), high efficiency in extraction of gases from the liquid phase, and the lack of a sample preparation step (e.g. degassing).

Development of a GSO detector assembly for a continuous blood sampling system

A new input function monitoring system has been developed using the GSO detector assembly for both PET and SPELT quantitative studies. Due to the rapid rise time of the pulse (about 10nsec), the coincidence time window can be reduced < 1nsec, reducing contribution of randoms associated with the high background activity surrounding the detector. Large light output improved the energy resolution of approximately 11% for 511keV photons, and 20% at 140 keV, as compared with the BGO detector, enabling the use of this system also in SPELT studies. The paired assembly of crystals provided the absolute sensitivity of approximately 7% for PET and 75% for PET tracers. Multiple arrangement of the paired detectors provided possibility of correcting for the transit time of radioactivity through the catheter tube. This study demonstrated that the present system can be of use in both clinical and small animal studies using SPECT and PET tracers.

Automatic continuous sampling system of surface plankton during cruise

Automatic continuous sampling system of surface plankton during cruise

Performance evaluation of the portable MiniVOL particulate matter sampler

The MiniVOL sampler is a popular choice for use in air quality assessments because it is portable and inexpensive relative to fixed site monitors. However, little data exist on the performance characteristics of the sampler. The reliability, precision, and comparability of the portable MiniVOL PM 10 and PM 2.5 sampler under typical ambient conditions are described in this paper. Results indicate that the MiniVOL (a) operated reliably and (b) yielded statistically similar concentration measurements when co-located with another MiniVOL ( r 2=0.96 for PM 10 measurements and r 2=0.95 for PM 2.5 measurements). Thus, the characterization of spatial distributions of PM 10 and PM 2.5 mass concentrations with the MiniVOL can be accomplished with a high level of confidence. The MiniVOL also produced statistically comparable results when co-located with a Dichotomous Sampler ( r 2=0.83 for PM 10 measurements and r 2=0.85 for PM 2.5 measurements) and a continuous mass sampling system ( r 2=0.90 for PM 10 measurements). Environmental factors such as ambient concentration, wind speed, temperature, and humidity may influence the relative measurement comparability between these sampling systems.

Development of a phoswich detector for a continuous blood-sampling system

We have developed a phoswich detector composed of a plastic scintillator and a BGO, for a continuous blood sampling system. The beta particle (positron) from the tube is detected by the plastic scintillator and emits 511 keV gamma photons. The BGO scintillator that is optically coupled to the plastic scintillator detects one of the gamma photons. Since the decay time of the plastic scintillator and the BGO are very different, it is possible to discriminate true (beta+gamma) events from background gamma events. First, the pulse height and pulse shape of plastic scintillator for beta particles and BGO for 511 keV gamma photons were measured and compared to estimate the possibility of the proposed method. Then proposed phoswich detector was fabricated and tested. Absolute sensitivity for Ga-68 (maximum energy of 1.90 MeV) and F-18 (maximum energy of 633 keV) positrons were measured and compared with conventional beta detector in similar size. The absolute sensitivity of the developed detector was O.15 counts/Bq for Ga-68 positrons; at the center of the detector that was approximately 5 times higher sensitivity than the conventional beta detector. The absolute sensitivity of the developed detector for F-18 positrons was 0.017 counts/Bq while that of the conventional beta detector was zero. The count rate of the developed detector was linear up to 10 kcps. The background count rate was small. These results indicate that the developed detector is useful not only for higher energy positrons such as 0-15 but also lower energy positrons such as F-18 or C-11.

Fluxes of ammonia over oilseed rape: Overview of the EXAMINE experiment

An integrated field experiment was organized as part of the EC EXAMINE project to quantify surface–atmosphere fluxes of ammonia (NH 3). Fluxes of NH 3, NH 4 + aerosol, HNO 3 and HCl were measured using the gradient method with several continuous and batch sampling systems. Within-canopy NH 3 was determined to quantify the contribution of leaf cuticles, sub-stomatal apoplastic (intercellular) fluids and other sources and sinks to net fluxes. The campaign included the first field measurements of apoplastic pH and [NH 4 +], providing independent estimates of the stomatal compensation point ( χ s) for comparison with micrometeorological results. The latter also compared fluxes before and after cutting. Under the clean conditions of the experiment, [NH 3][HNO 3] and [NH 3][HCl] were much less than values required for aerosol formation, while the NH 4 + aerosol size distribution indicated that aerosol evaporation would be much slower than the time-scale of turbulent exchange. Nevertheless, the measurements suggest that aerosol production/growth as well as formation of HCl may have occurred within the canopy. Apoplastic [NH 4 +] and pH of leaves showed no diurnal patterns, with the main control on χ s being the temperature dependence of the solubility equilibria. Fluxes of NH 3 were bi-directional (−200 to 620 ng m −2 s −1), with deposition generally occurring when the canopy was wet and emission when it was dry, particularly during the day. Nocturnal emissions indicated a non-stomatal NH 3 source, while daytime emissions were larger than indicated by the apoplastic estimates of χ s. The within-canopy data, together with an inverse Lagrangian source–sink analysis, showed decomposing litter to be a significant NH 3 source, explaining nocturnal NH 3 emissions and larger emissions following cutting. Daytime net fluxes were controlled by the top part of the canopy, due to χ s for siliques apparently being larger than for leaves. The measurements have been used to develop multi-layer resistance models of NH 3 exchange. A 3-layer ‘foliage–litter–silique model’ provides a detailed mechanistic treatment of the component fluxes, while a 2-layer ‘foliage–litter model’ is better suited to generalization in atmospheric transport models. Application of the new models should help improve estimates of regional atmospheric ammonia budgets.

Long term measurements of the land–atmosphere exchange of ammonia over moorland

Measurements of the exchange of ammonia between the atmosphere and moorland vegetation using micrometeorological methods at a site in southern Scotland are reported. The median concentration of continuous measurements over seven months of the log-normally distributed ammonia data at the site is 0.45 μg NH 3 m -3 with a geometric standard deviation of 3.4. The measurements made using a continuous wet annular denuder sampling system with a separate denuder at three heights above the surface provided satisfactory fluxes by the aerodynamic flux-gradient method for over 70% of the time between January and August 1995. The site which consists of unimproved moorland vegetation represented an efficient sink for ammonia during the winter months with deposition velocities ( V d) in the range 15 to 30 mm s -1 and canopy resistances ( R c) close to zero. The monthly median V d declined with time from 25 mm s -1 in February to 5 mm s -1 in August as the result of a steady increase of the canopy resistance in the dry, warmer, summer conditions to typically 100 s m -1 during the daytime. The canopy compensation point increased from zero during winter months to about 0.2 μg m -3 in August and short periods of NH 3 emission were observed whenever ambient concentration fell below 0.2 μg m -3 during the summer. The annual input of gaseous NH 3 to this moorland surface is approximately 2 kg N ha -1, and is similar to the input of NH + 4-N in wet deposition.

Diurnal rhythm in nitrate absorption by roots of soybeans (Glycine max)

The diurnal rhythm in NO3 - absorption by the intact soybean roots was investigated by using a continuous sampling system of the culture solution. During the day and night period, the soybean absorbed NO3 - almost linearly irrespective of the time or NO3 - concentration in the medium. The NO3 - absorption rate was found to be different between the day and night period, and the level in the night was about 60-75% of that in the daytime. The temporary interruption of NO3 - absorption was observed twice a day at dawn and dusk. It was suggested that this rhythmic pattern of NO3 - absorption was not directly controlled by the shoots, based on the fact that the rhythm appeared under on extended dark period or by the cutting of the shoots. The diurnal rhythm was also observed in the N concentration of the xylem exudate collected from decapitated roots. The NO3 - absorption was completely inhibited by the addition of a metabolic inhibitor such as CCCP or KCN, but the rate was not affected by DNP. Concomitant K+ e...

The contribution of rainwater to variability in surface ocean hydrogen peroxide

Hydrogen peroxide concentrations have been determined in marine rain from the Gulf of Mexico , the western Atlantic Ocean , and one rain event off the Florida Keys . In several cases, simultaneous measurements of the concentration of H2O2 in the surface ocean were also determined. These measurements were made with the ship under way using a continuous flow sampling system with the intake at the bow. In shallow stratified layers, rain events can increase the existing hydrogen peroxide concentration by a factor greater than 10 and dramatically increase the mean H2O2 concentration of mixed depth layers of 50 m or more. Rain is a significant transient source of H2O2 in the surface ocean.

Error analysis of a quantitative cerebral blood flow measurement using H2(15)O autoradiography and positron emission tomography, with respect to the dispersion of the input function.

The effect of the inaccuracy of the input function on CBF measured by the H2(15)O autoradiographic method was investigated. In H2(15)O autoradiography the measured input function usually includes a larger dispersion than the true input function, as well as the absolute time axis having been already lost. The time constant of the external dispersion that occurred in our continuous sampling system was evaluated as 10-12 s when the dispersion function was approximated by a monoexponential function. The internal dispersion occurring in arterial lines in a human body was evaluated as 4-6 s. Such dispersion, indispensable in a patient study, was found to produce large errors in calculating CBF, e.g., 5(10) s of the dispersion caused +15(33) and +10(20)% systematic overestimations for the 40- and 60-s accumulation time respectively. An analytical correction employing an inverse Laplace transform was applied to clinical CBF studies, and the results were compared with those from the C15O2 steady-state inhalation method. Correction by 10 s in time constant, corresponding to the external dispersion, reduced the overestimation significantly from 70-100% to approximately 20%. Further correction by 5 s, corresponding to the internal dispersion, resulted in a negligible difference (less than a few percent) from the steady-state method.

Distribution of cholorophylls and phaeopigments in the Northwestern Atlantic Ocean

During a cruise in the Northwestern Atlantic the distributions of chlorophylls and phaeopigments were investigated in relation to mesoscale features by high-performance liquid chromatography. Samples were collected from hydrographic Stations and from two Continuous underway sampling systems fished simultaneously at the surface (2 m) and at deeper (30–90 m) depths. Highest pigment concentrations were associated with the transitional zones between Slope Water, the Gulf Stream and Northern Sargasso Sea. Chlorophyll b occurred in 47% of the samples analyzed and the dominant chlorophyll a degradation product was phaeophorbide a. Chlorophyllide a was usually found at low concentrations and phaeophytin a levels were undetectable. Concentrations of the various chlorophylls and their degradation products were used to infer Changes in taxonomic composition, phytoplankton biomass and zooplankton grazing pressure across several frontal zones.

Some practical remarks on the i n s i t u calibration of the sensitivity factor S of a quadrupole mass spectrometer for hydrogen and argon during rf sputtering for the growth of thin a-Si:H layers

Calibration curves for the sensitivity factor S in a quadrupole mass spectrometer for Ar and H2 are presented. The data are gathered in a sputtering system for which the partial pressures of Ar and H2 (10−2–10−3 Torr and 10−3–10−4 Torr, respectively) are appropriate for sputtering of hydrogenated amorphous silicon (a-Si:H). A continuous sampling system added to the sputtering system enables in situ mass spectrometry before and during sputtering. The method can be used for different vacuum systems, mass spectrometers, and residual gases. It enables identification of contaminants which may have a considerable effect on the semiconductor properties. This can serve to obtain both a better quality material and to bring about more reproducible results. The relationship between the mass spectrometer ion current and the partial pressure of Ar is found to be nonlinear. However, it is possible to approximate the curve by two straight line segments, with a break point at 1.6×10−5 Torr. The pressure reduction ratios of the sampling aperture is not constant for Ar, but is a slightly decreasing function of pressure at a rate of 8.6×105 Torr−1 for an aperture with a diameter of 1.5 mm. These effects were not observed for hydrogen over the range of pressures investigated. With more than one gas present, it was observed that the introduction of argon into the vacuum system influences the ion current reading of the mass spectrometer for the other gases. This phenomenon is thought to occur as a result of a charge exchange interaction.

Temporal and spatial resolution of pump sampling systems

A simple empirical method is described for determining the fine-scale resolution of continuous flow-through sampling systems. An input delta function is provided by injection of fluorescent dye into the sampler intake. The output fluorescent signal provides time-domain estimates of delay and signal spread; Fourier transformation of the output provides the frequency domain transfer function of the system. Systems with direct intakes (hose or through-hull fitting) can resolve features of 30-s duration or less; however, sea chest intakes cause substantial blurring of the input signal. Attempts to increase vertical spatial resolution by slow lowering rates can result in profiles characterized by appearent micropatchiness and multiple layering, artifacts of the procedure.

Analyse quantitative du plomb et du soufre des aerosols urbains par spectrometrie de photoelectrons induits par rayons X

Abstract XPS ANALYSIS OF LEAD AND SULPHUR IN URBAN AEROSOLS X‐Ray Photoelectron Spectroscopy (XPS, ESCA) has been used in order to analyse lead and sulphur in atmospheric particles by coupl'ing with a continuous sampling system (streaker). The lead is detected as Pb2+ and sulphur as SO4 −− with traces of elementary sulphur and sulphite. For quantitative measurements, the spectrometer has been calibrated with an accuracy of 20%. The results of the lead analysis are in good agreement with the X‐ray fluorescence and PIXEA determinations, whereas the comparison of the sulphur anlysis show an enrichment of the external layers of the particles.

Characterization of cephalic arteriovenous LH differences by continuous sampling in ovariectomized sheep.

Blood from the external carotid artery and from the external jugular vein were collected simultaneously, and luteinizing hormone (LH) concentrations were measured in order to determine the temporal pattern of the large episodic pulses of LH secretion which are characteristic of ovariectomized sheep. Collection of paired arterial and venous samples at 5-min intervals did not provide adequate resolution of arteriovenous LH changes which accompany these pulses. Therefore, a continuous blood sampling system was developed which permitted collection of paired and venous samples over 20-second intervals throughout a sampling period of approximately 45 min. One large pulse of LH secretion was detected in 6 of 9 trials, and each pulse was characterized by a brief period (2-6 min) when venous concentrations of LH were much higher than corresponding arterial concentrations. Periods of considerable release of LH from the head were usually followed by a period when arterial LH levels were greater than the venous levels, indicating that LH was being removed from the circulation by the tissues of the head. Administration of synthetic GnRH pulses (17.5-35 ng) through the arterial cannulae of halothane-anesthetized ewes produced in different trials arteriovenous LH concentration differences ranging from no discharge of LH to discharges much larger and more prolonged than those occurring spontaneously in conscious ewes. These results suggest that individual episodes of spontaneous pulsatile discharge of LH in ovariectomized sheep last 2-6 min and probably result from episodic secretion of LH-releasing hormone by the hypothalamus. Profiles of circulating LH also appear to be modified by extravascular sequestration of LH.

A Continuous Sampling System for Room Temperature Phosphorimetric Analysis

An experimental system for the continuous sampling of organic phosphors by the room temperature phosphorimetric technique has been constructed. Phosphorimetric time resolution was achieved by the use of an analog switch phosphoroscope. The results obtained show that this system is fairly sensitive and will allow extremely rapid analyses of small amounts of samples, thereby making it quite suitable for routine analysis of molecules exhibiting phosphorescence at room temperature.