Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe.

Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 µBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network.

Direct air activation measurements at a 15-MV medical linear accelerator.

Direct radiometric determination of (14)N (γ, n) (13)N air activation was achieved at a 15-MV medical linear accelerator operating in a high-energy photon mode. (13)N was identified by irradiating a gas-tight Marinelli beaker filled with nitrogen gas and later observing the 10-min half-life of the 511-keV positron-electron annihilation line using high-resolution gamma spectroscopy. Quantitative evaluation of the spectral signal yielded a (13)N production rate of 836.8 ± 32 Bq Gy(-1) in air per 40 × 40 cm(2) field cross section at 100 cm source-surface distance.

Rapid 20th-century increase in coastal upwelling off northwest Africa.

Near-shore waters along the northwest African margin are characterized by coastal upwelling and represent one of the world's major upwelling regions. Sea surface temperature (SST) records from Moroccan sediment cores, extending back 2500 years, reveal anomalous and unprecedented cooling during the 20th century, which is consistent with increased upwelling. Upwelling-driven SSTs also vary out of phase with millennial-scale changes in Northern Hemisphere temperature anomalies (NHTAs) and show relatively warm conditions during the Little Ice Age and relatively cool conditions during the Medieval Warm Period. Together, these results suggest that coastal upwelling varies with NHTAs and that upwelling off northwest Africa may continue to intensify as global warming and atmospheric CO2 levels increase.

Concentration and vertical distribution of 137Cs in the undisturbed soil of southwestern Nigeria.

The results of measurements of 137Cs in soil profiles that were sampled in undisturbed soil in Ondo, Ekiti, and Oyo states in the southwestern area of Nigeria are presented in this paper. Samples were collected from nine soil profiles. The vertical distributions of 137Cs in the soil profiles have been determined. Cesium concentration ranged from 0.31 +/- 0.10 Bq kg(-1) in the 0-2 cm depth to a maximum of 1.25 +/- 0.21 Bq kg(-1) in the 6-8 cm depth at some sites and from 3.16 +/- 0.16 Bq kg(-1) in 0-5 cm depth to below detection limit (BDL) at 20-25 cm at another site. 137Cs total deposition in 0-10 cm depth was found to be greatest at Ikogosi site with a value of 90.30 Bq m(-2). The results generally showed that more than 40 y after the first nuclear weapon tests, 137Cs still remains within the 25 cm upper layer of soil in the region with a migration velocity of 0.17-0.18 cm y(-1). The mean value of effective dose commitment due to the presence of cesium in soil in the entire region was found to be 10.77 microSv.

The role of education in disaster mitigation adjustment

A representative national (USA) sample of local emergency management agency (LEMA) coordinators (N=178) completed a mail-questionnaire which sought to indentify their mitigation actrivities and to determine if mitigation strategies vary by eight experience variable: education, training background, major emergency experiencedisaster, year worked as LEMA coordinador, years of EMS esperience.In descending order of reference, the co-odinators utilise the following mitigation strategies: disseminate response information throught the schools and the media seek zoning law changes, urge citizens to purchase insure, attempt building code change. The only variable observed to be associated with mitigation strategy decisions was education, college graduates being more likely to adopt any of the seven activities than non-graduates. Chi-square tests utilised. The response rate was 53 per cent (AU)

Nuclear relaxation of human brain gray and white matter: analysis of field dependence and implications for MRI.

The dependence of 1/T1 on the magnetic field strength (the relaxation dispersion) has been measured at 37 degrees C on autopsy samples of human brain gray and white matter at field strengths corresponding to proton Larmor frequencies between 10 kHz and 50 MHz (0.0002-1.2 T). Additional measurements of 1/T1 and 1/T2 have been performed at 200 MHz (4.7 T) and 20 MHz (0.47 T), respectively. Absolute signal amplitudes are found to be proportional to the sample water content, not to the "proton density," and it is concluded that the myelin lipids do not contribute to the signal. Transverse magnetization decay data can be fitted with a triple exponential function, giving characteristic results for each tissue type, and are insensitive to variations of the pulse spacing interval. The longitudinal relaxation dispersion curves show characteristic shapes for each tissue type. The most striking difference is a large dispersion for white matter at very high fields. As a consequence, the relative difference in 1/T1 between gray and white matter shows a marked maximum around 10 MHz. Possible implications for MRI are discussed. A weighted least-squares fit of the dispersions has been performed using a four-parameter function of the form 1/T1 = 1/T1,w + D + A/(1 + (f/fc)beta'). The quality of the fit is superior to that of other functions proposed previously. The results of these fits are used to predict image contrast between gray and white matter at different field strengths.

The effect of aging and storage conditions on excised tissues as monitored by longitudinal relaxation dispersion profiles.

Knowledge about the dependence of NMR parameters of excised tissues on time and storage conditions is important for correct interpretation of in vivo clinical results based upon in vitro measurements which in many cases are easier to perform. Literature data on this topic are scarce and sometimes contradictory. In this study, we investigated the change of the proton longitudinal relaxation rate (1/T1) of freshly excised rat tissues with storage conditions over a wide range of proton Larmor frequencies (0.01-50 MHz). Special interest was paid to long-term storage in the deep frozen state. After deep freezing of tissue samples on dry ice, no significant changes in 1/T1 over the whole frequency range could be observed for brain tissue, whereas for muscle and liver tissue characteristic alterations were detected. We conclude that for normal brain tissue this storage procedure is suitable for the prediction of in vivo 1/T1 results from in vitro studies.

The uncommon longitudinal relaxation dispersion of human brain white matter.

Human brain white matter exhibits an uncommonly strong dispersion of 1/T1 at high fields. An additional relaxation pathway via the myelin lipids, which are not directly visible to medical NMR due to their fast T2 decay, is proposed. Relaxation dispersion data are successfully analyzed on the basis of this model.

Particulate suspensions as ultrasonic contrast agents for liver and spleen.

Ultrasonic backscatter and attenuation coefficients of a medium can be increased by the addition of solid, micron-size inhomogeneities. A potentially useful agent for ultrasonic contrast of liver images has been identified. Iodipamide ethyl ester (IDE) particles can be produced in the form of dense, relatively incompressible solids with high impedance mismatch to water. The chemical, biochemical, and pharmacologic properties of the small, uniform diameter IDE particles permit safe intravenous injection followed by rapid accumulation of reticuloendothelial (RE) cells of the liver and spleen, and later elimination from these organs. Since the particles are phagocytized by RE cells, present in normal liver but not in tumors and many lesions, the selective enhancement of ultrasonic backscatter should improve detectability of lesions that are hypoechoic or isoechoic compared with surrounding tissue. The mechanisms of particle-ultrasound interaction may be described by relative motion attenuation, and scattering from a cloud of dense, incompressible spheres for the case of IDE particles in agar. Thus, values of attenuation and backscatter can be controlled by choice of ultrasound frequency and particle concentration and size. When the particles are accumulated in rat and rabbit livers, additional mechanisms induce attenuation and backscatter in excess of that predicted by IDE in agar. This preliminary work demonstrates that solid, biocompatible particles may be useful as an ultrasonic contrast agent.

Field-cycling relaxometry: medical applications.

Relaxometry between 10 kHz and 200 MHz (0.2 mT and 4.7 T) with a field-cycling device and a high-field-strength magnetic resonance (MR) unit permitted the determination of longitudinal relaxation rates of tissues and chemical compounds at numerous field strengths. The resulting nuclear magnetic relaxation dispersion profiles allowed the prediction of tissue contrast and efficacy of contrast agents at any field strength. Pure T1 contrast of normal brain tissue and pathologic lesions (multiple sclerosis, astrocytoma) increased from low field strengths to a maximum between 10 and 20 MHz and decreased afterward. Quadripolar dips reflecting the interaction between water and nitrogen atoms of the protein backbone appeared at 2.15 and 2.8 MHz, reducing T1 and opening the possibility of shorter imaging times and better tissue discrimination at these field strengths. Furthermore, it was shown that zero T1 contrast between normal and pathologic tissue samples may exist at certain field strengths. Gadolinium diethylenetriaminepentaacetic acid and gadolinium tetraazacyclododecanetetraacetic acid provided different contrast enhancement depending on the field strength.

Effect of multiple intravenous injections of diatrizoate on iodine concentrations and osmolality. An experimental study in rabbits.

Multiple intravenous injections of contrast media are used in radiology, but information regarding corresponding changes in the serum iodine concentrations and osmolality is lacking. We measured the changes in serum iodine concentration and serum osmolality in rabbits after a series of intravenous injections of contrast media. Hypaque-76 (1 cc/kg) was injected intravenously in awake rabbits at 10-minute intervals for 1 hour and arterial blood sampled at midpoint times between injections. During the 1-hour period of seven serial injections, mean serum iodine concentration at 5 minutes was 2.3 mg I/cc (+/- 0.1 SEM, n = 14); at 35 minutes, 5.1 mg I/cc (+/- 0.2); and at 65 minutes, 6.7 mg I/cc (+/- 0.4). The mean peak concentration was 6.8 mg I/cc (+/- 0.4). Serum osmolality underwent a mean increase of 16 mosm/kg during the injection period. Hypertonic mannitol injections produced a smaller increase in osmolality (10 mosm/kg). Isotonic saline injections in control animals produced no change in osmolality.

High-dose clinical urography with the low-osmolality contrast agent Hexabrix: comparison with a conventional contrast agent.

A double-blind clinical trial was performed in 60 patients to compare Hexabrix (ioxaglate meglumine and ioxaglate sodium) and Renografin-60 (diatrizoate meglumine and diatrizoate sodium). Use of Hexabrix produced higher urinary iodine concentrations, lower urine volumes at 30 minutes, and excretory urograms significantly better in diagnostic quality, as rated by four independent observers. There was no difference in nephrogram quality between contrast agents. Patients receiving Hexabrix had less of an increase in heart rate and demonstrated a slight rise in mean arterial blood pressure, rather than the biphasic rise then fall seen with Renografin-60. There was no significant change for up to 96 hours after urography in results of hematology, clinical chemistry, or urinalysis, except for an increase of 0.005 in urine specific gravity with Renografin-60. Patients reported significantly less body heat, heat in the injection arm, and overall discomfort with Hexabrix. There was a similar amount of nausea and vomiting in the two groups. Hexabrix also caused histaminic-type reactions in three patients.