Testing quantum electrodynamics in extreme fields using helium-like uranium.

Quantum electrodynamics (QED), the quantum field theory that describes the interaction between light and matter, is commonly regarded as the best-tested quantum theory in modern physics. However, this claim is mostly based on extremely precise studies performed in the domain of relatively low field strengths and light atoms and ions1-6. In the realm of very strong electromagnetic fields such as in the heaviest highly charged ions (with nuclear charge Z ≫ 1), QED calculations enter a qualitatively different, non-perturbative regime. Yet, the corresponding experimental studies are very challenging, and theoretical predictions are only partially tested. Here we present an experiment sensitive to higher-order QED effects and electron-electron interactions in the high-Z regime. This is achieved by using a multi-reference method based on Doppler-tuned X-ray emission from stored relativistic uranium ions with different charge states. The energy of the 1s1/22p3/2 J = 2 → 1s1/22s1/2 J = 1 intrashell transition in the heaviest two-electron ion (U90+) is obtained with an accuracy of 37 ppm. Furthermore, a comparison of uranium ions with different numbers of bound electrons enables us to disentangle and to test separately the one-electron higher-order QED effects and the bound electron-electron interaction terms without the uncertainty related to the nuclear radius. Moreover, our experimental result can discriminate between several state-of-the-art theoretical approaches and provides an important benchmark for calculations in the strong-field domain.

Properties of polycapillary optics dedicated to low-energy parallel-beam wavelength-dispersive spectrometers for synchrotron-based X-ray fluorescence study.

The main advantage of wavelength-dispersive spectrometers applied in X-ray study is their high energy resolution. The design and construction of spectrometer, usually dedicated to the specific experimental systems, for example synchrotron based setups, need information about the characteristics of the main elements of the spectrometer such as X-ray optics elements, crystals and detectors. Such information can be obtained using Monte-Carlo simulations. In this paper, the Monte-Carlo simulations of X-ray tracing in parallel-beam wavelength-dispersive spectrometer (PBWDS), equipped with polycapillary optics, are presented and discussed. The study concentrates on the description of the polycapillary model, simulations of the properties of X-ray polycapillary optics and, finally, on the simulations of X-ray track in the spectrometer designed and installed at the ID21 beamline at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). The results of simulations were compared with experimental data obtained for different registered X-ray energies and spectrometer crystals, showing good agreement. The obtained results showed that the X-ray transmission in the tested polycapillary optics is at the level of 15%, while the divergence of the outgoing beam changes from 8 mrad to 3 mrad with an increase of photon energy from 2 keV to 10 keV. The spectrometer provides an energy resolution of 5 eV and 33 eV in the energy range of 1.4 keV - 6.5 keV. The developed simulation program can be successfully used for the construction of spectrometers dedicated to the different experimental conditions.

A DuMond-type crystal spectrometer for synchrotron-based X-ray emission studies in the energy range of 15-26 keV.

The design and performance of a high-resolution transmission-type X-ray spectrometer for use in the 15-26 keV energy range at synchrotron light sources is reported. Monte Carlo X-ray-tracing simulations were performed to optimize the performance of the transmission-type spectrometer, based on the DuMond geometry, for use at the Super X-ray absorption beamline of the Swiss Light Source at the Paul Scherrer Institute. This spectrometer provides an instrumental energy resolution of 3.5 eV for X-ray emission lines around 16 keV and 12.5 eV for emission lines at 26 keV, which is comparable to the natural linewidths of the K and L X-ray transitions in the covered energy range. First experimental data are presented and compared with results of the Monte Carlo X-ray simulations.

Multielemental Analysis of Tobacco Plant and Tobacco Products by TXRF.

The aim of this research is to develop a fast analytical method for multielemental analysis of the tobacco plant Virginia tobacco (cultivated in Poland) and tobacco products (cigarettes, cigars, cigarillos, snuff and two kinds of properly crafted tobacco such as a shisha and cigarette tobacco) distributed in Polish markets by means of a low-power benchtop total reflection X-ray fluorescence (TXRF) system. For this purpose, a set of certified tobacco materials and real samples was employed. In leaves and stalks of V. tobacco and tobacco products, a concentration of 18 elements (P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr and Pb) was determined. Analyzing elemental composition of tobacco plants, one can see that concentrations of S, Ca, Ti, Mn, Zn, Sr and Pb are higher in leaves, whereas the concentrations of P, Cl, K, Fe Cu and Br are higher in stalks; the levels of Cr, Ni, As and Rb are comparable in both these parts of the tobacco plant. All of the parameters affecting sample preparation and TXRF measurements conditions were carefully evaluated. The accuracy and precision of the TXRF measurements were verified using an internal standardization approach for quantification.

Observation of coherence in the time-reversed relativistic photoelectric effect.

The photoelectric effect has been studied in the regime of hard x rays and strong Coulomb fields via its time-reversed process of radiative recombination (RR). In the experiment, the relativistic electrons recombined into the 2p_{3/2} excited state of hydrogenlike uranium ions, and both the RR x rays and the subsequently emitted characteristic x rays were detected in coincidence. This allowed us to observe the coherence between the magnetic substates in a highly charged ion and to identify the contribution of the spin-orbit interaction to the RR process.

Electron- and proton-impact excitation of hydrogenlike uranium in relativistic collisions.

The K shell excitation of H-like uranium (U(91+)) in relativistic collisions with different gaseous targets has been studied at the experimental storage ring at GSI Darmstadt. By performing measurements with different targets as well as with different collision energies, we were able to observe for the first time the effect of electron-impact excitation (EIE) process in the heaviest hydrogenlike ion. The large fine-structure splitting in H-like uranium allowed us to unambiguously resolve excitation into different L shell levels. State-of-the-art calculations performed within the relativistic framework which include excitation mechanisms due to both protons (nucleus) and electrons are in good agreement with the experimental findings. Moreover, our experimental data clearly demonstrate the importance of including the generalized Breit interaction in the treatment of the EIE process.

Spectral shape of the two-photon decay of the 2 1S0 state in he-like tin.

The spectral distribution of the 1s2s {1}S{0}-->1s{2} 1S0 two-photon decay of He-like tin was measured using a novel approach at the gas-jet target of the ESR storage ring. Relativistic collisions of Li-like projectiles with low-density gaseous matter have been exploited to selectively populate the desired 1s2s state. Compared to conventional techniques, this approach results in a substantial gain in statistical and systematic accuracy, which allowed us to achieve for the first time a sensitivity to relativistic effects on the two-photon decay spectral shape as well as to discriminate the measured spectrum for Sn from theoretical shapes for different elements along the He-isoelectronic sequence.

Comparison of clinical evaluation of genitourinary symptoms in female adolescents among primary care versus emergency department physicians.

OBJECTIVE: To compare clinical approaches to assessment and treatment of female adolescents with genitourinary symptoms among primary care and emergency department (ED) physicians. DESIGN: A chart review was performed of the evaluation and treatment of 472 patients presenting between July 1, 2005, and June 30, 2006. SETTING: Suburban and tertiary care EDs and primary care settings. PARTICIPANTS: Female patients age 13-21 years with genitourinary symptoms. INTERVENTIONS: None. OUTCOME MEASURES: Physician assessment of sexual history, performance of pelvic exam and sexually transmitted infection (STI) tests, empiric treatment of suspected STIs. RESULTS: Patients seen in primary care settings were more likely to be asked about sexual history, including contraceptive use, than patients in the ED (P<0.001). After adjustment for age and race, there was no statistically significant difference between the ED and primary care sites in performance of pelvic exams or gonorrhea and chlamydia tests. However, there was a higher likelihood that older adolescents would undergo pelvic exams (P=0.001), and STI testing (P=0.002) than younger patients. There was no significant difference in empiric treatment of patients with positive STI tests between ED and primary care sites or across the age spectrum. CONCLUSIONS: ED physicians should obtain sexual histories on patients with genitourinary symptoms. Both primary care and ED clinicians should consistently test for STIs in sexually active patients who have genitourinary symptoms. Physicians in both settings should have a low threshold for testing and empirically treating adolescents with symptoms or physical exam findings consistent with STIs.

Copper mobilization affected by weather conditions in a stormwater detention system receiving runoff waters from vineyard soils (Champagne, France).

Copper, a priority substance on the EU-Water Framework Directive list, is widely used to protect grapevines against fungus diseases. Many vineyards being located on steep slopes, large amounts of Cu could be discharged in downstream systems by runoff water. The efficiency of stormwater detention basins to retain copper in a vineyard catchment was estimated. Suspended solids, dissolved (Cu(diss)) and total Cu (Cu(tot)) concentrations were monitored in runoff water, upstream, into and downstream from a detention pond. Mean Cu(tot) concentrations in entering water was 53.6 microg/L whereas it never exceeded 2.4 microg/L in seepage. Cu(tot) concentrations in basin water (>100 microg/L in 24% of the samples) exceeded LC(50) values for several aquatic animals. Copper was principally sequestered by reduced compounds in the basin sediments (2/3 of Cu(tot)). Metal sequestration was reversible since sediment resuspension resulted in Cu remobilization. Wind velocity controlled resuspension, explained 70% of Cu(diss) variability and could help predicting Cu mobilization.

Can we use stable isotopes for ecotoxicological studies? Effect of DDT on isotopic fractionation in Perca fluviatilis.

Nitrogen and carbon stable isotope analyses are frequently used to assess contaminant biomagnification in animals in the wild. Previous studies, mainly on plant but also on animal tissues, have shown that chemical stress can lead to shifts in delta(15)N. In order to assess if an exposure to DDT at realistic concentration disrupted stable isotope signature in animals, delta(15)N and delta(13)C were studied in several tissues (liver, muscle, gill) of Perca fluviatilis fed with the same commercial diet uncontaminated or contaminated with DDT. We observed no DDT effect on the delta(15)N and delta(13)C of fish tissues. Our results show that stable isotopes can remain useful for field ecotoxicological studies despite food-chain contamination. However, correlations between the delta(13)C or delta(15)N values measured in the different organs were only found in DDT treated fish, suggesting some disruption of major biochemical compound metabolism in tissues.

Organochlorines in the Vaccarès Lagoon trophic web (Biosphere Reserve of Camargue, France).

During a decade (1996-2006), ecotoxicological studies were carried out in biota of the Vaccarès Lagoon (Biosphere Reserve in Rhone Delta, France). A multicontamination was shown at all levels of the trophic web due to a direct bioconcentration of chemical from the medium combined with a food transfer. Here, the pollutants investigated were organochlorines, among which many compounds banned or in the course of prohibition (or restriction) (PCB, lindane, pp'-DDE, dieldrin, aldrin, heptachlor, endosulfan...) and some substances likely still used in the Rhone River basin (diuron, fipronil). The results confirmed the ubiquity of contamination. It proves to be chronic, variable and tends to regress; however contamination levels depend on the trophic compartment. A biomagnification process was showed. A comparison of investigation methods used in other Mediterranean wetlands provides basis of discussion, and demonstrates the urgent need of modelling to assess the ecotoxicological risk in order to improve the management of such protected areas.

Rice fields regulate organochlorine pesticides and PCBs in lagoons of the Nature Reserve of Camargue.

In order to assess pollutant transfer in Camargue ponds from bordering agrosystems, a biomonitoring assay was conducted in irrigation and drainage channels of rice fields in the Rhone Delta (France). A filter-feeding bivalve, the Asian clam, Corbicula fluminea, was used as bioindicator and caged in upstream and downstream channels of an area of conventional rice fields. After 6 weeks incubation, many lipophilic biocides were identified in Corbicula tissues, including pesticides used in rice plantations (pretilachlor, oxadiazon), pesticides presumed in use in the Rhone basin [diuron and its metabolite 3,4 dichloroaniline (3,4-DCA)] and organochlorine pesticides (OCPs) banned for several decades. In addition, PCBs were highly bioaccumulated in Corbicula. Downstream bivalves had significantly lower concentrations of OCPs, PCB and 3,4-DCA. However, the exposure biomarkers (glutathione S-transferase, catalase and propionylcholinesterase) were not correlated with the decreased concentrations. The results of this experiment raise several questions concerning the potential role of immersed plants in a retention process.

Cell survival and chromosomal aberrations in CHO-K1 cells irradiated by carbon ions.

Chinese hamster ovary CHO-K1 cells were exposed to high LET (12)C-beam (LET: 830 keV/microm) in the dose range of 0-6 Gy and to (60)Co irradiation and the RBE value was obtained. Effects of (12)C-beam exposure on cell survival and chromosomal aberrations were calculated. The chromosomal aberration data were fitted with linear equation. The distribution of aberration in cells was examined with a standard u-test and used to evaluate the data according to Poisson probabilities. The variance to the mean ratio sigma(2)/Y and the dispersion index (u) were determined. Overdispersion was significant (p<0.05) when the value of u exceeded 1.96.

Assessment of sediment concentration and nutrient loads in effluents drained from extensively managed fishponds in France.

Expansion of aquaculture has increased concern over its environmental impact. The composition of effluents from intensive aquaculture is well documented, but few data on extensive aquaculture are available. During 12 draining operations, 523 water samples were collected downstream from six extensively-managed fishponds in northeastern France. Study ponds had surface areas of 2-620 ha and were managed for production of Cyprinids and Percids. Concentrations of total suspended solids, total phosphorus, and Kjeldahl nitrogen in effluents from the ponds were greatest during the final stage of draining. Loads of phosphorus were higher than those reported for effluents of more intensive aquaculture ponds in the USA, but the source of the potential pollutants was catchments and sediment rather than feeds and fertilizer. It will be necessary to reduce the water drawdown rate during the fishing stage and possibly implement other best management practices to prevent the TSS concentration from exceeding 1 g/L.

Radiative electron capture to the continuum and the short-wavelength limit of electron-nucleus bremsstrahlung in 90A MeV U88 + ((1s2)(2s2))+N2 Collisions.

We have measured the continuum momentum distribution for radiative electron capture to the continuum (RECC) cusp electrons in 90A MeV U88+ + N2-->U88+ + N2 +* + ecusp(0 degrees ) + hnu (RECC) collisions. We demonstrate that x rays coincident with RECC cusp electrons originate from the short-wavelength limit of the electron-nucleus bremsstrahlung and explain the asymmetric cusp shape by comparison with theory within the relativistic impulse approximation.

An irradiation facility with a horizontal beam for radiobiological studies.

A facility with a horizontal beam for radiobiological experiments with heavy ions has been designed and constructed at the Heavy Ion Laboratory in Warsaw University. The facility is optimal to investigate the radiobiological effects of charged heavy particles on a cellular or molecular level as in the region of the Bragg peak.

First measurement of the linear polarization of radiative electron capture transitions.

For radiative electron capture into the K shell of bare uranium ions, a study of the polarization properties has been performed. For this purpose a position sensitive germanium detector has been used as an efficient Compton polarimeter. This enabled us to measure the degree of linear polarization by analyzing Compton scattering inside the detector and to determine the orientation of the polarization plane. Depending on the observation angle and the beam energy used, the radiation is found to be linearly polarized by up to 80%. In all cases studied, the plane of polarization coincides with the collision plane. The results will be discussed in the context of rigorous relativistic calculations, showing that relativistic effects tend to lead to a depolarization of the radiation emitted.

Quantum electrodynamics in strong electric fields: the ground-state Lamb shift in hydrogenlike uranium.

X-ray spectra following radiative recombination of free electrons with bare uranium ions (U92+) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 degree observation geometry, allowed us to determine the ground-state Lamb shift in hydrogenlike uranium (U91+) from the observed x-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime.