Neutron fluence rate measurement using prompt gamma rays

A gamma ray spectrometer, with a 3(') ? X 3(') NaI(Tl) detector, with a moderator sphere has been utilised to measure the neutron fluence rate, with this value the H(10) was estimated. When a neutron is captured by the hydrogen-based moderator, a 2.22 MeV prompt gamma ray is produced. In a multichannel analyser the net area under the 2.22 MeV photopeak is proportional to the total neutron fluence rate. The features of this system were determined by a Monte Carlo study that includes 3-, 5- and 10-inches diameter, water and polyethylene moderators and a (239)Pu-Be source. The prompt gamma response was extended to monoenergetic neutron sources. To verify the response, a (239)Pu-Be source in combination with a 10(') polyethylene sphere having a gamma-ray spectrometer with NaI(Tl) was utilised to estimate the neutron fluence rate and the H(10). These results were compared with neutron fluence rate and H(10) obtained using a Bonner sphere spectrometer and with the H(10) measured using a neutron remmeter.     

Artificial neural networks technology for neutron spectrometry and dosimetry

Artificial Neural Network Technology has been applied to unfold neutron spectra and to calculate 13 dosimetric quantities using seven count rates from a Bonner Sphere Spectrometer with a (6)LiI(Eu). Two different networks, one for spectrometry and another for dosimetry, were designed. To train and test both networks, 177 neutron spectra from the IAEA compilation were utilised. Spectra were re-binned into 31 energy groups, and the dosimetric quantities were calculated using the MCNP code and the fluence-to-dose conversion coefficients from ICRP 74. Neutron spectra and UTA4 response matrix were used to calculate the expected count rates in the Bonner spectrometer. Spectra and H(10) of (239)PuBe and (241)AmBe were experimentally obtained and compared with those determined with the artificial neural networks.     

Water-extended polyester neutron shield for a 252Cf neutron source

A Monte Carlo study to determine the shielding features to neutrons of water-extended polyester was carried out. During calculations, (252)Cf and shielding were modelled and the neutron spectra as well as the H(10) were calculated in four sites. The calculation was extended to include a water shielding, the source in vacuum and in air. Besides neutron shielding characteristics, the Kerma in air due to gammas emitted by (252)Cf and due to capture gamma rays in the shielding were included.     

Processing of ultrasonic array signals for characterizing defects. Part I: signal synthesis

This work presents a novel procedure to characterize damage using an array of ultrasonic measurements in a generalized model-based inversion scheme, which integrates the complete information recorded from the measurements. In the past, we proposed some idealized nondestructive evaluation test methods with emphasis on the numerical results, but it is necessary to develop the techniques in greater detail in order to apply the techniques to real conditions. Our detection principle is based on the measurement and inversion of frequency-domain data combined with a reduced set of output parameters. The approach is developed and tested for the case of an aluminum specimen with a synthetic array of point contact ultrasonic transmitters and receivers. The first part of this two-part paper is focused on numerical synthesis of the experimental measurements using the boundary element method for a general ultrasonic propagation model. This part also deals with the deconvolution by comparing the data measured from the damaged and undamaged specimens. The deconvolution technique allows us to calibrate the data by taking into account the uncertainties due to mechanical properties, input signal, and other coherent noise. The second part of the paper presents the inversion of the measurements to obtain the parameters and ultimately to predict the position and size of the real defect.     

Production and characterization of anAspergillus terteus α-l-rhamnosidase of oenological interest

Conditions for maximal batch culture production of extracellularα-L-rhamnosidase byAspergillus terreus have been investigated. Production of the enzyme appeared to be inducible by rhamnose and rutin, reaching a maximal level after an incubation period of 162 h when the fungus was grown at 37°C on either of these compounds as the carbon source and on ammonium phosphate as the nitrogen source. Nonionic surfactants did not enhanceα-L-rhamnosidase secretion. Under optimal conditions,A. terreus produced only oneα-L-rhamnosidase of approximate molecular weight 90 kDa (SDS-PAGE) and isoelectric point of 4.6. Onp-nitrophenyl-α-L-rhamnopyranoside as substrate, the enzyme showed pH and temperature optima of 6–8 and 45–50°C, respectively. Neither divalent cations nor ethylenediaminetetraacetate (EDTA) inhibited or stimulated enzyme activity. The enzyme was active at the concentrations of glucose found in must or of ethanol in wine.     

Multiplexed holographic data page storage on a polyvinyl alcohol/acrylamide photopolymer memory

Holographic data pages were multiplexed in different thickness layers of a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. A liquid crystal device was used to modify the object beam and store the data pages. A peristrophic multiplexing method is used to store a large number of data pages in the same spot in the material. The bit error rate was calculated fitting the histograms of the images to determine what parameters improve the quality of the images.     

Toughening of PA6/mEPDM Blends by two Methods of Compounding,Extruder and Internal Mixer: Rheological,Morphological and Mechanical Characterization

Blends of polyamide 6 with metallocene rubber as dispersed phase and grafted rubber as compatibilizer were prepared by two methods of compounding, extruder and internal mixer. Rheological measurements and morphological analysis were made in order to study the influence of compounding. The ternary blends with the same maleic anhydride content displayed similar rheological behaviour. On the other hand, the developed morphology is related to the compounding process and blend formulation. The better particle size distribution is achieved in both methods of compounding for blends with 20 wt% of EPDM-g-MA. The addition of EPDM-g-MA improves the mechanical properties compared to blends without compatibilizer. The results confirm that the mechanical properties are more influenced by the compounding process than by the blend composition.     

Study of phenolic composition and sensory properties of red grape varieties in danger of extinction from the Spanish region of Castilla-La Mancha

This paper reports on a study of the profiles of different phenolic compounds (anthocyanins, flavonols, hydroxycinnamic acids and stilbenes) of five minor red grape varieties from the Spanish region of Castilla-La Mancha (Bobal, Moravia Agria, Moravia Dulce, Rojal and Tortosí) and a traditional variety from this growing region (Cencibel) as reference. Grape skin extracts of each variety were analysed by High Performance Liquid Chromatography coupled to Diode Array Detector (HPLC–DAD). The content of grape skins in anthocyanins (21.1–453 mg kg⁻¹), flavonols (26.9–288 mg kg⁻¹) and hydroxycinnamic acids (6.80–18.2 mg kg⁻¹) showed differences according to mainly varietal origin, although other important factors have to be taken into account such as the degree of ripeness, berry size or vintage year. In all the studied varieties, the major anthocyanin was malvidin 3-glucoside (>40%) with the exception of Rojal variety, which major one was peonidin 3-glucoside together with cyanidin 3-glucoside. Moravia Dulce and Rojal varieties contained more than 46% of quercetin 3-glucuronide; the rest of them contained less than 27%. No relation was found between profiles of hydroxycinnamic acids in the studied samples and their variety or year of vintage. All the studied grapes presented high concentrations of stilbenes that could be interesting due to the health benefits.     

Occurrence of aromatic amines and N-nitrosamines in the different steps of a drinking water treatment plant

The occurrence of 24 amines within a full scale drinking water treatment plant that used chlorinated agents as disinfectants was evaluated for the first time in this research. Prior to any treatment (raw water), aniline, 3-chloroaniline, 3,4-dichloroaniline and N-nitrosodimethylamine were detected at low levels (up to 18 ng/L) but their concentration increased ∼10 times after chloramination while 9 new amines were produced (4 aromatic amines and 5 N-nitrosamines). Within subsequent treatments, there were no significant changes in the amine levels, although the concentrations of 2-nitroaniline, N-nitrosodimethylamine and N-nitrosodiethylamine increased slightly within the distribution system. Eleven of the 24 amines studied were undetected either in the raw and in the treatment plant samples analysed. There is an important difference in the behaviour of the aromatic amines and N-nitrosamines with respect to water temperature and rainfall events. Amine concentrations were higher in winter due to low water temperatures, this effect being more noticeable for N-nitrosamines. Aromatic amines were detected at their highest concentrations (especially 3,4-dichloroaniline and 2-nitroaniline) in treated water after rainfall events. These results may be explained by the increase in the levels of amine precursors (pesticides and their degradation products) in raw water since the rainfall facilitated the transport of these compounds from soil which was previously contaminated as a result of intensive agricultural practices.     

PRECISE MEASUREMENTS OF PARTICLE ENTRAINMENT IN A STANDING-WAVE ACOUSTIC FIELD BETWEEN 20 AND 3500 Hz

An experimental study is presented to investigate entrainment coefficients of aerosol particles in a sonic wave. The experimental results are contrasted with a well-established analytical expressions for the entrainment coefficient derived from the Brandt–Freund–Hiedemann (BFH) equation. The measurements are carried out in a standing-wave field with an extremely homogeneous and well-determined acoustic velocity field. A CCD-camera with a microscope lens attachment is used to visualize the displacement amplitude of 7.9 μm glass beads in the frequency range from 20 Hz to 3.5 kHz. The particle entrainment coefficients obtained with this visualization method are in good agreement with the theoretical predictions of the BFH equation and with earlier experimental data by Gucker and Doyle. While this prior study revealed some apparent experimental limitations, the present data is derived with an accurate and repeatable measurement technique. The large number of measurements in the current study helps to draw a detailed representation of the acoustic entrainment coefficient.