Ultrafast Thermal Melting in Nonequilibrium Warm Dense Copper.

The ultrafast dynamics of the loss of crystalline periodicity is investigated in femtosecond laser heated warm dense copper, by the original use of x-ray absorption near-edge specific structures just above the L3 edge. The characteristic time is observed near 1 ps, for specific energy density ranging from 1 to 5 MJ/kg, using ps-resolution x-ray absorption spectroscopy. The overall experimental data are well reproduced with two-temperature hydrodynamic simulations, supporting a thermal phase transition.

Femtosecond Resolution of the Nonballistic Electron Energy Transport in Warm Dense Copper.

The ultrafast electron energy transport is investigated in laser-heated warm dense copper in a high flux regime (2.5±0.7×10^{13} W/cm^{2} absorbed). The dynamics of the electron temperature is retrieved from femtosecond time-resolved x-ray absorption near-edge spectroscopy near the Cu L3 edge. A characteristic time of ∼1 ps is observed for the increase in the average temperature in a 100 nm thick sample. Data are well reproduced by two-temperature hydrodynamic simulations, which support energy transport dominated by thermal conduction rather than ballistic electrons.

Two-channel high-resolution quasi-monochromatic X-ray imager for Al and Ti plasma.

High-resolution, high-sensitivity X-ray imaging is a real challenge in high-energy density plasma experiments. We present an improved design of the Fresnel ultra high-resolution imager instrument. Using an Ultra-High-Intensity (UHI) laser to generate hot and dense plasma in a small volume of an Al-Ti mixed target provides simultaneous imaging of both Al and Ti X-ray emission. Specifically, the Al Heß (or Lyß) and the Ti Heα lines are imaged with a resolution of (2.7 ± 0.3) µm and (5.5 ± 0.3) µm, respectively. It features two transmission Fresnel phase zone plates fabricated on the same substrate, each associated with a multilayer mirror for spectral selection. Their spatial resolution has been measured on the PTB synchrotron radiation facility laboratory at BESSY II and on the EQUINOX laser facility. Results obtained on an UHI experiment highlight the difference of emission zone sizes between Al and Ti lines and the versatility of this instrument.

Probing warm dense matter using femtosecond X-ray absorption spectroscopy with a laser-produced betatron source.

Exploring and understanding ultrafast processes at the atomic level is a scientific challenge. Femtosecond X-ray absorption spectroscopy (XAS) arises as an essential experimental probing method, as it can simultaneously reveal both electronic and atomic structures, and thus potentially unravel their nonequilibrium dynamic interplay which is at the origin of most of the ultrafast mechanisms. However, despite considerable efforts, there is still no femtosecond X-ray source suitable for routine experiments. Here we show that betatron radiation from relativistic laser-plasma interaction combines ideal features for femtosecond XAS. It has been used to investigate the nonequilibrium dynamics of a copper sample brought at extreme conditions of temperature and pressure by a femtosecond laser pulse. We measured a rise-time of the electron temperature below 100 fs. This experiment demonstrates the great potential of the table-top betatron source which makes possible the investigation of unexplored ultrafast processes in manifold fields of research.

High-resolution quasi-monochromatic X-ray imaging using a Fresnel phase zone plate and a multilayer mirror.

High-resolution, high-sensitivity X-ray imaging is a real challenge in laser plasma diagnostic to attain reliable data in high-energy density plasma experiments. In this context, ultra-high-intensity lasers generate hot and dense plasma but only in a small volume. An experiment has been performed at the LULI2000 laser facility to diagnose such plasma conditions from thermal spectroscopic data. To image the emission zone plasma's Al Heß, a Fresnel-lens-based X-ray imager has been developed. It features a 846 µm-diameter Fresnel Phase Zone Plate (FPZP) and a Pd/B4C multilayer mirror (thickness d = 5.1 nm). This association can be used between 1500 eV and 2100 eV. The FPZP's efficiency was measured on a synchrotron facility (SOLEIL) and its spatial resolution in a laser facility (EQUINOX). The mirror reflectivity was measured on the synchrotron facility BESSY II. With experimental conditions, the system resolution reaches 3.8 ± 0.6 µm with an adequate efficiency in the 1800 eV-1900 eV energy range with a solid angle of 9 × 10-6 sr. Consequently, a FPZP is an excellent optics setup for high-resolution quasi-monochromatic X-ray imaging and provides a good collection angle. Bragg-Fresnel lenses, based on the principle of FPZP and mirrors, are currently designed for an X-ray imager at the Laser MégaJoule facility.

Ultrafast short-range disordering of femtosecond-laser-heated warm dense aluminum.

We have probed, with time-resolved x-ray absorption near-edge spectroscopy (XANES), a femtosecond-laser-heated aluminum foil with fluences up to 1 J/cm2. The spectra reveal a loss of the short-range order in a few picoseconds. This time scale is compared with the electron-ion equilibration time, calculated with a two-temperature model. Hydrodynamic simulations shed light on complex features that affect the foil dynamics, including progressive density change from solid to liquid (∼10 ps). In this density range, quantum molecular dynamics simulations indicate that XANES is a relevant probe of the ionic temperature.

Picosecond short-range disordering in isochorically heated aluminum at solid density.

Using ultrafast x-ray probing, we experimentally observed a progressive loss of ordering within solid-density aluminum as the temperature raises from 300 K to >10{4} K. The Al sample was isochorically heated by a short ( approximately ps), laser-accelerated proton beam and probed by a short broadband x-ray source around the Al K edge. The loss of short-range ordering is detected through the progressive smoothing of the time-resolved x-ray absorption near-edge spectroscopy (XANES) structure. The results are compared with two different theoretical models of warm dense matter and allow us to put an upper bound on the onset of ion lattice disorder within the heated solid-density medium of approximately 10 ps.

Ensuring financial access to emergency obstetric care: three years of experience with Obstetric Risk Insurance in Nouakchott, Mauritania.

INTRODUCTION: The high cost of emergency obstetric care (EmOC) is a catastrophic health expenditure for households, causing delay in seeking and providing care in poor countries. METHODS: In Nouakchott, the Ministry of Health instituted Obstetric Risk Insurance to allow obstetric risk sharing among all pregnant women on a voluntary basis. The fixed premium (US$21.60) entitles women to an obstetric package including EmOC and hospital care as well as post-natal care. The poorest are enrolled at no charge, addressing the problem of equity. RESULTS: 95% of pregnant women in the catchment area (48.3% of the city's deliveries) enrolled. Utilization rates increased over the 3-year period of implementation causing quality of care to decline. Basic and comprehensive EmOC are now provided 24/7. The program has generated US$382,320 in revenues, more than twice as much as current user fees. All recurrent costs other than salaries are covered. CONCLUSION: This innovative sustainable financing scheme guarantees access to obstetric care to all women at an affordable cost.

Electronic structure and equation of state data of warm dense gold.

Equation of state data and electrical resistivity of warm dense gold were measured in the internal energy range 8 - 12 MJ/kg. Experimental results were compared with quantum molecular dynamics simulations. The theoretical results match well the experimental data, allowing a detailed interpretation of the theoretical thermodynamic properties and frequency-dependent conductivities.

Picosecond time-resolved X-ray absorption spectroscopy of ultrafast aluminum plasmas.

We have used point-projection K-shell absorption spectroscopy to infer the ionization and recombination dynamics of transient aluminum plasmas. Two femtosecond beams of the 100 TW laser at the LULI facility were used to produce an aluminum plasma on a thin aluminum foil (83 or 50 nm), and a picosecond x-ray backlighter source. The short-pulse backlighter probed the aluminum plasma at different times by adjusting the delay between the two femtosecond driving beams. Absorption x-ray spectra at early times are characteristic of a dense and rather homogeneous plasma. Collisional-radiative atomic physics coupled with hydrodynamic simulations reproduce fairly well the measured average ionization as a function of time.

Aluminum equation-of-state data in the warm dense matter regime.

Isochore measurements were performed in the warm dense matter regime. Pressure and internal energy variation of aluminum plasma (density 0.1 g/cm(3) and 0.3 g/cm(3)) are measured using a homogeneous and thermally equilibrated media produced inside an isochoric plasma closed vessel in the internal energy range 20-50 MJ/kg. These data are compared to detailed calculations obtained from ab initio quantum molecular dynamics, average atom model within the framework of the density functional theory, and standard theories. A dispersion between theoretical isochore equation of state is found in the studied experimental thermodynamic regime.

Combined pressure and electrical-resistivity measurements of warm dense aluminum and titanium plasmas.

Electrical resistivity, pressure, and internal energy variation of warm dense correlated titanium (density 0.2 g/cm(3)) and aluminum (density 0.1 g/cm(3)) plasmas are measured using a homogeneous and thermally equilibrated media produced inside an isochoric closed-vessel plasma. These data are compared to detailed calculations based on the density functional theory. In the studied temperature range (15,000-30,000 K), it appears that both exchange-correlation and ion-ion interaction treatments are of great importance to calculate accurate theoretical values.

Study of the ion-distribution dynamics of an aluminum laser-produced plasma with picosecond resolution.

The ion-distribution dynamics of an expanding aluminum plasma produced by a nanosecond laser pulse at moderate intensity (10(13) W cm(-2)) is studied by point-projection x-ray absorption spectroscopy with unprecedented, picosecond, time resolution. We show that the ionic populations measured as a function of distance to the target and at different probing times differ markedly from those predicted by widely accepted collisional radiative models coupled to hydrodynamic simulations. We discuss the effects of radiation, conduction, and expansion cooling on the spatiotemporal ionic distribution evolution.

[The delivery record: a help to make the right decision]. / La dossier d'accouchement: une aide à la décision.

The delivery record is a key document for risk assessment and proper decision making at the right time during delivery. If it is exhaustive or badly presented, health workers see it as an administrative constraint, not as a help. The authors recall some principles regarding its form and contents. Its different parts are reviewed: administrative data, medical history, antenatal care, admission clinical examination, partograph, delivery, newborn, recent post-partum and exit examinations. An example of a delivery record used in Nouakchott is presented.

[Evaluation of the nutritional status of children less than 5 years of age in Moundou, Chad: correlations with morbidity and hospital mortality]. / Evaluation de l'état nutritionnel de l'enfant de moins de 5 ans à Moundou, Tchad: relations avec la morbidité et la mortalité hospitalières.

The purpose of this study carried out in the pediatric ward of the regional hospital in Moundou, Chad, between June 1992 and May 1993 was to assess the prevalence of protein-energy malnutrition in children under 5 years of age and its relationship with various diseases and in-hospital mortality. A total of 1050 children ranging in age from 1 to 59 months were hospitalized in the ward during the study period and included in the study. Nutritional status was assessed using weight-for-height (W/H) and height-for-age (H/A) charts. Diarrhea, dehydratation, malaria, anemia, acute respiratory infection, and meningitis accounted for 85.5% of the underlying diseases and for 76% of deaths. At entry into study the prevalence of malnutrition was 63.1% (W/H < -2 Z-score) including 37% with severe malnutrition (W/H < -3 Z-score) and 16.1% with stunted growth (H/A < -2 Z-score). Malnutrition was more prevalent in children under than over 2 years of age (80% vs. 42.7% respectively). The same trend was observed with regard to severe malnutrition. The prevalence of malnutrition was highest in children with acute respiratory infections or diarrhea (61.3% and 89.8% respectively). Mortality was significantly higher in severely malnourished children and malnourished children with respiratory infection especially at ages under 1 year. Death was attributed to malnutrition in 30% of cases. Better low cost nutritional care is currently feasible. The most cost efficient methods of fighting against this problem are prevention and education especially concerning breast feeding.

[Anemia in infants less than 1 year old in Moundou, Chad: prevalence and etiology]. / L'anémie de l'enfant de moins de un an à Moundou, Tchad: prévalence et étiologies.

In order to evaluate the prevalence of anemia in infants under one year of age and ascertain the main etiologic factors, a survey was conducted in Moundou, Chad at the end of the rainy season. Tests were performed in 144 infants to determine hemoglobin levels, mean erythrocyte volume, transferrin saturation coefficient, serum iron level, Plasmodium positivity on blood smears, and nutritional status according to GOMEZ. Using the criteria defined by the World Health Organization, 139 infants were diagnosed as anemic including 19 cases classified as severe (hemoglobin level less than 5 g/dl). In addition, 32 of the 141 infants studied (22.7%) presented iron deficiency confirmed by two positive indicators. Serology demonstrated malaria in 45% of infants. Mean hemoglobin levels were significantly lower in infants with positive blood smears and this lowering increased the higher serum parasite levels. Nutritional status was directly correlated with hemoglobin level. This data suggests that malaria plays a major etiologic role in anemia in infants particularly severe anemia. This finding justifies use of antimalarial chemoprophylaxis in infants and the Centers for the Extended Vaccination Program provide the framework.