[en] In March 2001, the Los Alamos National Laboratory (LANL) completed the replacement of 720 radioactively contaminated HEPA filters for $5.7M. This project was completed five months ahead of schedule and $6.0M under budget with no worker injuries or contaminations. Numerous health and safety, environmental, and waste disposal problems were overcome, including having to perform work in a radioactively contaminated work environment, that was also contaminated with perchlorates (potential explosive). High waste disposal costs were also an issue. A project risk analysis and government cost estimate determined that the cost of performing the work would be $11.8M. To reduce risk, a $1.2M comprehensive condition assessment was performed to determine the degree of toxic and radioactive contamination trapped on the HEPA filters; and to determine whether explosive concentrations of perchlorates were present. Workers from LANL and personnel from Waldheim International of Knoxville, TN collected hundreds of samples wearing personnel protective gear against radioactive, toxic, and explosive hazards. LANL also funded research at the New Mexico Institute of Mining and Technology to determine the explosivity of perchlorates. The data acquired from the condition assessment showed that toxic metals, toxic organic compounds, and explosive concentrations of perchlorates were absent. The data also showed that the extent of actinide metal contamination was less than expected, reducing the potential of transuranic waste generation by 50%. Consequently, $4.2M in cost savings and $1.8M in risk reduction were realized by increased worker productivity and waste segregation

[en] Cefixime, a potent, broad spectrum oral cephalosporin, is currently undergoing clinical trials. To determine the extent of transfer of cefixime across the placenta to the fetus, a single dose of 17.8 mg/kg ¹⁴C-cefixime was administered to rats on day 18 of gestation via the caudal vein. Maternal serum and urine, fetal plasma and tissues, and placentae were sampled at appropriate times after dosing. Separate rats were subjected to whole body autoradiography. The half-life for elimination of radioactivity from both maternal serum and placentae was 6.9 hours. Elimination from fetal plasma and tissues was somewhat longer, 12.5 and 13.7 hours, respectively. However, based on a comparison of area under the curve, relative to maternal dose, exposure of the fetuses to cefixime was far less than that of placentae. Peak radioactivity in fetal plasma occurred at 2 hours and was less than 2% of the maternal peak at 0.5 hours after dosing. Whole body autoradiography showed the greatest radioactivity in maternal liver, kidney and intestines. Somewhat less radioactivity appeared in placentae and virtually none could be visualized within the amniotic sac. Overall, the data indicate that exposure of the rat fetus to cefixime after a single maternal dose is limited by the placenta

[en] A solid-phase radioimmunoassay has been developed as a screening technique for tetanus antibodies in blood plasma. It is based on the principle of a commercial test for Hepatitis B antibody. Compared to previous screening techniques, the radioimmunoassay showed better stability with no apparent loss of sensitivity over a 2 month period. This technique has proved useful in determining tetanus immunity and in monitoring free antibody level in treated cases of clinical tetanus. (U.K.)

[en] High count rate detectors are of particular interest in nuclear medicine as they permit lower radiation doses to be received by the patient and allow dynamic images of high statistical quality to be obtained. We have developed a high-speed gamma camera based on a multi-wire proportional chamber. The chamber is filled with a xenon gas mixture and has been operated at pressures ranging from 5 to 10 bar. With an active imaging area of 25 cmx25 cm, the chamber has been equipped with an advanced, high rate, digital, electronic read-out system which carries out pulse shaping, energy discrimination, XY coincidence and cluster selection at speeds of up to a few megahertz. In order to ensure stable, long-term operation of the camera without degradation in performance, a gas purification system was designed and integrated into the camera. Measurements have been carried out to determine the properties and applicability of the camera using photon sources in the 20-120 keV energy range. We present some design features of the camera and selected results obtained from preliminary measurements carried out to measure its performance characteristics. Initial images obtained from the camera will also be presented

[en] Late accretion of a ''veneer'' of compositionally diverse planetesimals may introduce chemical heterogeneity in the mantles of the terrestrial planets. The size of the late veneer objects is an important control on the angular momenta, eccentricities, and inclinations of the terrestrial planets, but current estimates range from meter-scale bodies to objects with diameters of thousands of kilometers. We use a three-dimensional global Monte Carlo model of impact cratering, excavation, and ejecta blanket formation to show that evidence of mantle heterogeneity can be preserved within ejecta blankets of mantle-exhuming impacts on terrestrial planets. Compositionally distinct provinces implanted at the time of the late veneer are most likely to be preserved in bodies whose subsequent geodynamical evolution is limited. Mercury may have avoided intensive mixing by solid-state convection during much of its history. Its subsequent bombardment may have then excavated evidence of primordial mantle heterogeneity introduced by the late veneer. Simple geometric arguments can predict the amount of mantle material in the ejecta blanket of mantle-exhuming impacts, and deviations in composition relative to geometric predictions can constrain the length-scale of chemical heterogeneities in the subsurface. A marked change in the relationship between mantle and ejecta composition occurs when chemically distinct provinces are ∼250 km in diameter; thus, evidence of bombardment by thousand-kilometer-sized objects should be readily apparent from the variation in compositions of ejecta blankets in Mercury's ancient cratered terrains

[en] We describe recent developments on diamond-like carbon (DLC) over-coated microstrip gas chambers made on boro-silicate drawn glass substrates. MSGC surface coating with thin DLC layer of stable and controlled resistivity was proposed to overcome the limitation of detector operation due to surface charging-up under avalanches. This brings also advantages for the detector manufacturing technology. The thin layer, deposited on top of a manufactured MSGC (over-coating), demonstrates excellent mechanical properties and very good stability. We report on recent measurements with DLC over-coated MSGCs of various surface resistivities (ranging from 10¹³ Ω/□ to 10¹⁶ Ω/□) on D-263 and AF45 glass substrates. Over-coated MSGCs with resistivity of the surface around 10¹⁵ Ω/□ exhibit a stable charge gain up to radiation rates in excess of 10⁶ Hz/mm². Stable long-term operation up to 50 mC/cm of accumulated charge from avalanches has been demonstrated. (orig.)

[en] We describe the construction, test and installation procedures, and the experience gained with the operation of a small but complete system of high-rate micro-strip gas chambers, made on thin borosilicate glass with a diamond-like coating with chromium or gold strips. A set of detectors, fully equipped with read-out electronics and each with an active area of 100 x 100 mm², was exposed during six months to a high-intensity muon beam at CERN with a peak intensity of ∝10⁴ mm^-2s^-1. Continuous monitoring of the performance of the chambers during the beam runs allowed the evaluation of detection efficiency and the monitoring of accidental rates, as well as the study of ambient induced variations and aging in realistic beam conditions. No significant difference has been found in the operation of under- and over-coated plates. Efficiencies could reach ∝98% in best operating conditions, although local lower values were often observed due to missing channels (open strips, broken bonds and dead electronic channels). The long-term operation of the chambers has been more difficult than expected, with the appearance of break-downs and loss of efficiency in some detectors, possibly induced by the presence of small gas leaks, to water permeation or to residual reactivity of the quencher gas (dimethylether). (orig.)

[en] We describe recent measurements carried out in well controlled and reproducible conditions to help understanding the factors affecting the short-and long-term behaviour of microstrip gas chambers. Special care has been taken concerning the gas purity and choice of materials used in the system and for the detectors construction. Detectors built on glasses with surface resistivity in the range 10¹³-10¹⁵ Ω/□ have shown satisfactory performance as they do not show charging-up process at high rate and stand the large doses required for the future high luminosity experiments (∝10 mC.cm^-1.yr^-1). Concerning the lifetime measurements, it has been observed that chambers manufactured on high-resistivity glass are far more susceptible of suffering ageing than detectors made on low resistivity, electron-conducting supports, independently of the metal used for the artwork (chromium or gold) at least in clean gas conditions. The successful operation in the laboratory of detectors manufactured on diamond-coated glass with a surface resistivity around 10¹⁵ Ω/□ confirms the last statement. Results from a long-term, high rate beam test are also reported. (orig.)

[en] We present a comment on the kinematic variable m_CT2 recently proposed in Won Sang Cho, Jihn E. Kim, and Ji-Hun Kim, Phys. Rev. D 81, 095010 (2010). The variable is designed to be applied to models such as R-parity conserving supersymmetry (SUSY) when there is pair production of new heavy particles each of which decays to a single massless visible and a massive invisible component. It was proposed by Cho, Kim, and Kim that a measurement of the peak of the m_CT2 distribution could be used to precisely constrain the masses of the SUSY particles. We show that, for the an example characterized by direct squark decays, when standard model backgrounds are included in simulations, the sensitivity of the m_CT2 variable to the SUSY particle masses is more seriously impacted for m_CT2 than for other previously proposed variables.

[en] We describe the assembly procedure and the operation in a high-intensity beam of a small but representative system of microstrip gas chambers (MSGC) fully equipped with readout electronics. The chambers, with an active area of 100 x 100 mm², are made on 300 μm diamond-like coated D-263 glass with 200 μm pitch gold or chromium strips. The readout electronics (PreMux 128) allows the recording of charge on individual anode strips. The monitoring task includes a complete control and characterization of each device before installation in the beam, such as measurement of surface resistivity, finding shorts, pulse height analysis, gas gain calibration, rate capability and testing of the final electronics. Preliminary results of the beam test are described. (orig.)