Certification Report of EQRAIN Plutonium - Program N° 10

The EQRAIN Plutonium N° 10 is an evaluation program set up by CEA/CETAMA in order to evaluate the quality of results from nuclear measurement laboratories. The objective of this programme is to determine the plutonium concentration of a plutonium nitrate solution. Three ampoules were sent to each participant. At the IM/nuclear group, it was decided to analyse both of the EQRAIN N° 10 samples, H53 and H91. The results of this exercise would possibly enable us to identify problems occuring during the handling and measurements by mass spectrometric isotope dilution analysis (IDMS) of Pu. The evaluation of the mass-spectrometry analysis as part of this program could indicate unexplained processes such as the behaviour of the fractionation factor and outlier results not identified during measurements.JRC.D.4-Isotope measurement

Exploring covalently bonded diamondoid particles with valence photoelectron spectroscopy

We investigated the valence electronic structure of diamondoid particles in the gas phase, utilizing valence photoelectron spectroscopy. The samples were singly or doubly covalently bonded dimers or trimers of the lower diamondoids. Both the bond type and the combination of bonding partners are shown to affect the overall electronic structure. For singly bonded particles, we observe a small impact of the bond on the electronic structure, whereas for doubly bonded particles, the connecting bond determines the electronic structure of the highest occupied orbitals. In the singly bonded particles a superposition of the bonding partner orbitals determines the overall electronic structure. The experimental findings are supported by density functional theory computations at the M06-2X/cc-pVDZ level of theory.Comment: 7 pages, 7 figure

The awareness of the scared - context dependent influence of oxytocin on brain function

Oxytocin is both a hormone and a neurotransmitter and has been originally recognized for its role in childbirth and lactation. Later, it became widely known as a "cuddle hormone" that induces trusting behavior towards strangers and reduces social stress and anxiety. Several studies showed that oxytocin influences empathic behavior and has prosocial effects. The anterior cingulate cortex and the anterior insula are brain regions that are active when humans observe fear in others. Therefore, the aim of this study was to investigate whether oxytocin administration affects activity in these regions depending on whether a threat is directed at another person (empathy) compared to when the threat is directed at the subject itself (fear). Our findings demonstrate increased anterior cingulate cortex activation after oxytocin administration in the fear, but not in the empathy condition. Furthermore, oxytocin administration was associated with deceased anterior insula activity in the empathy condition. However, our findings do not support the idea that oxytocin generally augments activity in brain regions associated with empathy. Thereby this study supports current research questioning that oxytocin has exclusively prosocial effects on human behavior. Rather, the effect of oxytocin depends on various contextual (e.g. presence of a familiar person) and interindividual (e.g. sex, mental disorder) factors. Therefore, to consider oxytocin an empathy inducing hormone is an oversimplification and future research should focus on factors moderating oxytocin effects

Efficient visible laser emission of GaN laser diode pumped Pr-doped fluoride scheelite crystals.

In the present work we report on the growth, spectroscopy and laser results of diode pumped Pr-doped LiYF4, LiLuF4 and LiGdF4 fluoride, scheelite-type structure crystals. We measured the polarisation dependent absorption and emission properties as well as the decay time of the P-3(0) level. Exploiting the P-3(2) absorption around 444 nm, we obtained efficient laser emission under GaN laser diode pumping on several transitions from the green to the near infrared wavelength range. (C) 2008 Optical Society of Americ

Update on REIMEP-15: Isotopic Ratios of uranium in UF6

The REIMEP (Regular European Interlaboratory Measurement Evaluation Programme) campaign 15 for isotopic ratios of uranium in UF6 samples has been completed in 2002. The participants received 4 samples of low-enriched or slightly depleted uranium in the form of UF6 in standard monel capsules. The samples were prepared at IRMM by mixing uranium reference materials certified by gas mass-spectrometry in the form of UF6. The minor isotopes, 234U and 236U were certified at IRMM by Thermal Isotope Mass-spectrometry (TIMS) using a MAT262-RPQ mass spectrometer in ion counting mode. Certified values were sent to the participating laboratories immediately after receiving their measured results. The measured results and their comparison with the certified values allowed an overall view of the analytical capability in the nuclear field to measure uranium isotopic ratios in UF6 samples. However, for the so-called minor ratio 234U.238U the comparison of IRMM¿s certified values with all the participants results showed a significant relative deviation of about 2%, which is by far larger than the typical uncertainties expected for this kind of measurements. This significant deviation was considered disappointing for IRMM as the leading European nuclear safeguards metrology institute. This problem has now overcome first by measurements using the new TRITON TIMS at IRMM and second by a thorough investigation on the reasons for the deviation observed in the past.JRC.D.4-Isotope measurement

Preparation and Certification of the Isotopic Reference Material IRMM-049d

A highly enriched 242Pu Isotopic Reference Material (IRMM-049d) has been prepared and certified for the 242Pu isotope amount content. The certified value of 3.666 8(18) x 10-7 mol 242Pu per g of solution was established by Isotope Dilution Mass Spectrometry (IDMS). The plutonium isotopic composition was determined by Thermal Ionization Mass Spectrometry (TIMS) and calibration of these measurements by means of synthetic mixtures. The IRMM-049d Isotopic Reference Material is supplied in a glass ampoule with a screw cap seals containing about 10 mL of 5 mol x L-1 nitric acid with plutonium. The content of each vial is approximately 1 mg 242Pu. This Isotopic Reference Material is the product of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations.JRC.D.2-Reference material

Performance of Drift-Tube Detectors at High Counting Rates for High-Luminosity LHC Upgrades

The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drifttube (MDT) chambers with 30 mm tube diameter have been designed to cope with and neutron background hit rates of up to 500 Hz/square cm. Background rates of up to 14 kHz/square cm are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates