New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer

Stable Pb isotope ratios were measured and compared to U distributions in three soil cores located in a wetland highly impacted by water discharge of a former U-mine. Pb isotope ratios showed notable alignments in binary mixing plots, demonstrating the dissemination of radioactive-enriched material from the U-mine. Thanks to these alignments and to the measurement of the ²⁰⁴Pb isotope, a precise characterization of the Pb isotope composition of the U-ore was performed without the use of U-ore samples. The well-defined end-members with the help of a reevaluated isotope mixing model allowed the accurate determination of the radiogenic Pb percentages in the cores that were overall found to be >50%. Noncorrelated distributions of radiogenic ²⁰⁶Pb and U are observed in several of the wetland soil samples. They reveal postdepositional U redistribution explained by major U speciation changes due to redox cycling in the wetland. On the contrary, the radiogenic ²⁰⁶Pb showed no or little postdepositional mobility and thus can be considered to be a memory tracer of the dissemination of U-rich radioactive material: even after an important U loss, the radiogenic ²⁰⁶Pb is able to reveal past contamination by U-rich materials.

Transient signal isotope analysis: validation of the method for isotope signal synchronization with the determination of amplifier first-order time constants

RATIONALE

During transient signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier signal synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier signal synchronization for isotope ratio drift correction.

METHODS

Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient signals and the signal decay curves of the amplifiers were investigated.

RESULTS

Our results show that the first part of the amplifier signal decay curve is characterized by a pure exponential decay. This part of the signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope signal synchronization and were found to be in good agreement.

CONCLUSIONS

This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier signal synchronization for isotope ratio drift correction is validated.

[Profiles of people who return unused medicine to pharmacies in Puy-de-Dôme, and their motivations for doing so]

An unused drug (U.D.) is described as a drug which is purchased, whether according to a prescription or not, but which is not taken. In the past few years, French people have acquired the habit of returning U.D.s to pharmacies. Nevertheless, few studies have been performed to define their typical features and the motivations of these individuals. A descriptive study was carried out in 1/5 of the pharmacies in Puy de Dôme (France) over three 1 week periods between February and June 1998. 377 people (that is, 82% of those who bring U.D. back to the pharmacies) accepted to participate in this study. The main results are as follows: 1. the U.D. are primarily brought back by women (of all ages); 2. these women mainly return U.D. from the family medicine cabinet; 3. the donations result essentially from "the force of habit", "cleaning out the family medicine cabinet" and also, although in lesser proportion, for "humanitarian reasons". This behaviour is contradictory with the communication messages of Cyclamed, the official French association whose mission is to collect drug waste and unused drugs in order to preserve the environment and to promote energy development and valorisation.

MEP (Mars Environment Package): toward a package for studying environmental conditions at the surface of Mars from future lander/rover missions

In view to prepare Mars human exploration, it is necessary to promote and lead, at the international level, a highly interdisciplinary program, involving specialists of geochemistry, geophysics, atmospheric science, space weather, and biology. The goal of this program will be to elaborate concepts of individual instruments, then of integrated instrumental packages, able to collect exhaustive data sets of environmental parameters from future landers and rovers of Mars, and to favour the conditions of their implementation. Such a program is one of the most urgent need for preparing human exploration, in order to develop mitigation strategies aimed at ensuring the safety of human explorers, and minimizing risk for surface operations. A few main areas of investigation may be listed: particle and radiation environment, chemical composition of atmosphere, meteorology, chemical composition of dust, surface and subsurface material, water in the subsurface, physical properties of the soil, search for an hypothesized microbial activity, characterization of radio-electric properties of the Martian ionosphere. Scientists at the origin of the present paper, already involved at a high degree of responsibility in several Mars missions, and actively preparing in situ instrumentation for future landed platforms (Netlander--now cancelled, MSL-09), express their readiness to participate in both ESA/AURORA and NASA programs of Mars human exploration. They think that the formation of a Mars Environment working group at ESA, in the course of the AURORA definition phase, could act positively in favour of the program, by increasing its scientific cross-section and making it still more focused on human exploration.

[Knowledge and attitude to sexually transmitted diseases and condoms in students and undergraduate students]

Since sexually transmitted diseases (STDs) are a serious health problem among youth, proper understanding of knowledge about STDs, beliefs about condom use and associated factors are public health necessities. A self-administered questionnaire was sent to 2,920 randomly selected students and was returned by 59.3% of the sample. We observed a lack of knowledge in one third of students, negative beliefs on condom use for at least 20% of students and a low perceived risk to contract STDs. With multivariate analyses, we observed that male students, youths between 18-21 years of age and those who didn't have any sexual partner since their admission to the university should be the target of intervention programs.

Combination therapy with castration and flutamide: today's treatment of choice for prostate cancer

In order to achieve a more complete blockade of androgens of both testicular and adrenal origins, 223 patients with advanced prostate cancer (stage D2 with bone metastases) received the combination therapy with the antiandrogen Flutamide and the LH-RH agonist [D-Trp6,des-Gly-HN10(2)] LH-RH ethylamide as first treatment. As assessed by the objective criteria of the US NPCP, a positive response was obtained in 94% of patients, thus leaving only 6% of patients with no response at the start of treatment while, following standard therapy, 20-40% of patients do not respond to treatment. The duration of response was increased while longer survival (an advantage of approximately 14 months compared to standard therapy, 38.5 vs approximately 24 months) was achieved with no or minimal side effects. Highly positive results were also obtained using the combination therapy in stage C prostate cancer patients while temporary treatment with the combination therapy in stages A and B prostate cancer facilitated radical prostatectomy. The present data supported by the results of independent studies indicate that combination therapy should be the treatment for all patients with advanced disease and possibly also at earlier stages of prostate cancer in combination with surgery.