In vivo tibial lead measurement to assess the health hazard of Venezuelan workers

Gamma-ray induced X-ray emission (GIXE) technique for elemental lead in-vivo tibial measurement using a large volume hyper pure germanium detector is presented with the most convenient source-sample-detector geometry. The system operates advantageously when several parameters are considered for a lower dead time operation. The detection limit (DL) is better that 3.5 μg/g of Ca. Results of in-vivo average tibial lead concentration for some of the monitored groups are: control 7 μg of lead per g of Ca; gasoline filling attendants 6 μg/g of Ca; custom office workers near the DL; industrial workers range from DL up to 84±3 μg/g of Ca, suggesting that lead accumulation in the bone does not represent a major health risk This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of metal-ligand stoichiometries for inorganic complexes using total reflection X-ray fluorescence

The methods usually used to determine the ratio metal-ligand in inorganic complexes require a set of solutions with different concentrations for both the ligand and metal. We propose a new method using the total reflection X-ray fluorescence technique, in which the ratio between metal and ligand is determined precisely, easily, and quickly. Experimental results provide evidence that for different chemical complexes, the ligand-metal ratio determined by this technique deviates at most from stoichiometric values by 6%. The technique is restricted usually to elements with Z above 14, and its detection limit is on the order of 10(-8) g/g.     

Energy and line width in the induced emission of Mössbauer radiation

Summary Some promising schemes proposed for extending the range of lasers to the X-ray and gamma-ray regions are those involving a transition from a long-lived nuclear excited state. While metastable states allow the creation of conditions for population inversion, they also give rise to problems due to the narrowness of the expected line width. We discuss the line width of the radiation due to gamma transitions between excited states and derive a corrected relation for the cross-section in this case. Criteria for choosing an appropriate isotope are deduced from the corrected crosssection, showing that the problems derived from the narrowness of the line width can be avoided in a transition from an isomeric state to a lower short-lived excited state in which case the line width of the radiation is totally determined by the breadth of the lower excited state.

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Riassunto Alcuni schemi promettenti proposti per estendere il campo dei laser alle regioni dei raggi X e dei raggi gamma sono quelli che coinvolgono una transizione da uno stato eccitato nucleare a vita lunga. Mentre gli stati metastabili permettono la creazione delle condizioni per l’inversione della popolazione, essi danno luogo anche ai problemi dovuti alla ristrettezza dell’ampiezza della linea attesa. Si discute l’ampiezza di linea della radiazione dovuta alle transizioni gamma tra gli stati eccitati e si deduce una relazione corretta per la sezione d’urto in questo caso. Si deducono i criteri per scegliere un isotopo appropriato dalla sezione d’urto corretta, mostrando che i problemi che derivano dalla ristrettezza dell’ampiezza di linea si possono evitare in una transizione da uno stato isomerico a uno stato eccitato piú basso a vita breve, nel qual caso l’ampiezza di linea della radiazione si determina totalmente dalla larghezza dello stato eccitato piú basso.

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Резюме Были предложены обнадеживающие схемы для расширения области лазеров в рентгеновскую и гамма-области. Эти схемы вкяючают переход из долгоживущего ядерного возбужденного состояния. Так как метастабильные состояния допускают создание условий для инверсной заселенности, то они также приводят к проблемам, обусловленным узостью ожидаемой ширины линии. Мы обсуждаем ширину линии излучения, обусловленную гамма-переходами между возбужденными состояниями и выводим соотношение для поперечного сечения в этом случае. Выводятся критерии для выбора соответствующего изотопа из полученного поперечного сечения. Показывается, что проблемы, связанные с узостью ширины линии, можно обойти в случае перехода из изомерного состояния в низшее короткоживущее возбужденное состояние, причем в этом случае ширина линии излучения полностью определяется шириной низшего возбужденного состояния.

     

Sulphur content estimation of Venezuelan heavy oil by fast neutron and gamma transmission technique

A compact and modern equipment for implementing the fast neutron and γ-ray transmission technique (FNGT) has been developed in order to estimate the sulphur content of crude oil. FNGT is employed for non- destructive analysis of different kinds of samples. The compact system presented in this work represents an improvement of our previous experimental set-up [1, 2]. It makes use of a ²⁵²Cf source, an EJ-301 liquid scintillator detector (2″ × 2″) with excellent n/γ discrimination capabilities, and modern nuclear electronics based on fast digitizers. The fast neutron and gamma transmission technique was employed to study a system for on-line sulphur concentration measurement in Venezuelan heavy sour oil. The range of sulphur concentrations investigated is between 0.1 and 6.5 wt%. The equipment performances and limitations are compared with those predicted by a Monte Carlo model built in GEANT4 v10.01. The results show the possibility to implement a compact unit for on-line determination of sulphur concentration in crude oil.

     

Nuclear track detector response to energetic heavy ions: study case

Journal of Radioanalytical and Nuclear Chemistry - Nuclear track methodology (NTM), is employed to analyze PADC detectors response to different energetic ion beams. Due to the passive device...     

Methods of Fourier optics in digital holographic microscopy

In this paper, processing methods of Fourier optics implemented in a digital holographic microscopy system are presented. The proposed methodology is based on the possibility of the digital holography in carrying out the whole reconstruction of the recorded wave front and consequently, the determination of the phase and intensity distribution in any arbitrary plane located between the object and the recording plane. In this way, in digital holographic microscopy the field produced by the objective lens can be reconstructed along its propagation, allowing the reconstruction of the back focal plane of the lens, so that the complex amplitudes of the Fraunhofer diffraction, or equivalently the Fourier transform, of the light distribution across the object can be known. The manipulation of Fourier transform plane makes possible the design of digital methods of optical processing and image analysis. The proposed method has a great practical utility and represents a powerful tool in image analysis and data processing. The theoretical aspects of the method are presented, and its validity has been demonstrated using computer generated holograms and images simulations of microscopic objects.     

Environmental radioactivity near the central coast of Venezuela and its radiological impact

The concentrations of⁴⁰K,²²⁶Ra,²³²Th and¹³⁷Cs were determined in the upper layers of soils in the central coastal region of Venezuela. The activities of¹³⁷Cs are higher in the areas where the forest is well developed, oriented towards the wind and at higher elevations. The origin of the¹³⁷Cs deposition is from water input from the clouds directly in the cloudforest and rainfall from the northeast trade winds. Even though the values of¹³⁷Cs are much higher in these areas, there is little or no significant increase in the health risk. The natural radioactivity is correlated with the geology in the region except in the area of Urama. The values for the natural radiation background are as follows: for potassium between 1–3%, for radium between 1–3 ppm and for thorium the range was 6–39 ppm. The corresponding amounts of absorbed dose rates in air, the exposure rates and the annual effective dose equivalents are in the following ranges respectively: 11–39 pGy/s, 4–16 uR/h and 0.25–0.86 mSv/y. The annual effective dose equivalents include the contribution of the global average (2.57 mSv/y) of the rest of the natural sources of radiation. Finally, the largest natural radioactivity background, was found near Chichiriviche as a result of the massive granite deposits in this area, but again there is no significant health risk.