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•Medico-economic evaluation of three malaria chemoprophylaxis reimbursement strategies.•The three strategies decrease the number of imported malaria cases in France.•The cost per prevented malaria case ranges from € 15,000 to € 34,000.•Restricting the reimbursement to travelers to West and Central Africa seems the best approach.

To establish recommendations on immunization for patients with multiple sclerosis (MS).

La prévalence de la lithiase urique augmente régulièrement puisqu’elle est plus fréquente en cas d’obésité, d’HTA, de syndrome métabolique, de diabète et chez les sujets âgés. Le traitement chirurgical des calculs n’en est pas toujours aisé, la LEC peu efficace. Aussi, le traitement médical bien prescrit par le médecin et bien suivi par le patient est aussi efficace pour la dissolution du calcul que sur la prévention de la récidive. Le pH urinaire acide qui est le facteur majeur de lithogenèse doit être corrigé par une alcalinisation des urines. Le plus efficace avec le moins d’effet secondaire est le citrate de potassium qui doit être prescrit dilué dans 1,5L/d’eau pour être actif tout au long de la journée et éviter les troubles digestifs.

We demonstrate a two-color planar laser-induced fluorescence technique for obtaining two-dimensional temperature images in water. For this method, a pulsed Nd:YAG laser at 532 nm excites a solution of temperature-sensitive rhodamine 560 and temperature-insensitive sulforhodamine 640. The resulting emissions are optically separated through filters and detected via a charged-couple device (CCD) camera system. A ratio of the two images yields temperature images independent of incident irradiance. An uncertainty in temperature of ±1.4 °C is established at the 95% confidence interval.

Quantitative two-point hydroxyl time-series measurements have been performed in a turbulent nonpremixed flame by using two-point picosecond time-resolved laser-induced fluorescence. The current diagnostic system has been improved from its preliminary version to address optical aberrations and fluorescence lifetime fluctuations. In particular, with a newly designed collection system, the aberration-limited blur spot is reduced from 6 mm to 180 μm. Additional photon-counting channels enable the recovery of absolute OH concentrations through a triple-bin integration method. The present research represents what we believe to be the first application of this two-point technique to turbulent flames. Two independent schemes have been applied to remove uncorrelated noise in the derived two-point statistics. We show that optical aberrations can have a significant effect on space-time correlations. However, the sampling rate and fluctuations in the fluorescence lifetime barely affect the spatial autocorrelation function and thus the integral length scale. Such length scales for hydroxyl are found to rise linearly with increasing axial distance at peak [OH] locations. Along the jet centerline, the integral length scale varies slightly below the flame tip but increases rapidly above the flame tip. In addition, the OH length scale demonstrates the same trend as the OH time scale along the jet centerline, but the opposite trend at peak [OH] locations.

Given that breast cancer is depending on multiple hormonal influences, the nuclear receptors, estrogen receptor alpha, estrogen receptor beta and androgen receptor, are candidates for cancer susceptibility markers. We conducted an association study in a case-control population (139 cases and 145 controls) by genotyping three potentially functional microsatellites (TA)n, (CA)n and (CAG)n in the ERa, ERb and AR genes respectively. For (CAG)n polymorphism, a significant difference was observed using a cut-off 15 repeats CAG between genotypes short-short/short-long/long-long in cases and control subjects (p=0.009) and also between the distribution of short/long allele in the two groups of individuals (p=0.001). Genotypes comprising one or two short (CAG)n sequences had higher risk of breast cancer compared to genotypes with two long allele (odds ratio=1,93; confidence interval=1.05–3.55; p=0.03). No significant difference was observed in allele frequency or in short/long allele percentage for (CA)n or (TA)n polymorphism (cut-off 22 CA and 19 TA repeats), neither in genotype frequencies (short-short, short-long or long-long). When the three microsatellite genotype were taken in analysis, the profile short CA-long TA-short CAG could clearly discriminate between cases and controls (p=0.006). Also, this combined genotype profile has greater predictive values for breast cancer than (CAG)n genotype alone (predictive positive value 57,1% versus 53,7% and predictive negative value 53% versus 23% respectively). Our results sustain a polygenic model of breast cancer with gene-gene interactions; combined effects of three low-risk polymorphisms conferred significant genetic predisposition. Genotyping hormonal receptor genes ERa, ERb and AR could be a useful genetic marker for defining disease risk.Given that breast cancer is depending on multiple hormonal influences, the nuclear receptors, estrogen receptor alpha, estrogen receptor beta and androgen receptor, are candidates for cancer susceptibility markers. We conducted an association study in a case-control population (139 cases and 145 controls) by genotyping three potentially functional microsatellites (TA)n, (CA)n and (CAG)n in the ERa, ERb and AR genes respectively. For (CAG)n polymorphism, a significant difference was observed using a cut-off 15 repeats CAG between genotypes short-short/short-long/long-long in cases and control subjects (p=0.009) and also between the distribution of short/long allele in the two groups of individuals (p=0.001). Genotypes comprising one or two short (CAG)n sequences had higher risk of breast cancer compared to genotypes with two long allele (odds ratio=1,93; confidence interval=1.05–3.55; p=0.03). No significant difference was observed in allele frequency or in short/long allele percentage for (CA)n or (TA)n polymorphism (cut-off 22 CA and 19 TA repeats), neither in genotype frequencies (short-short, short-long or long-long). When the three microsatellite genotype were taken in analysis, the profile short CA-long TA-short CAG could clearly discriminate between cases and controls (p=0.006). Also, this combined genotype profile has greater predictive values for breast cancer than (CAG)n genotype alone (predictive positive value 57,1% versus 53,7% and predictive negative value 53% versus 23% respectively). Our results sustain a polygenic model of breast cancer with gene-gene interactions; combined effects of three low-risk polymorphisms conferred significant genetic predisposition. Genotyping hormonal receptor genes ERa, ERb and AR could be a useful genetic marker for defining disease risk.

We report quantitative, spatially resolved measurements of methylidyne concentration ([CH]) in laminar, counterflow partially premixed and nonpremixed flames at atmospheric pressure by using both cavity ring-down spectroscopy (CRDS) and linear laser-induced fluorescence (LIF) in the A-X (0, 0) band. Three partially premixed (?_B = 1.45, 1.6, 2.0) flames plus a single nonpremixed methane-air flame are investigated at a global strain rate of 20 s^-1. These quantitative measurements are compared with predictions from an opposed-flow flame code when utilizing two GRI chemical kinetic mechanisms (versions 2.11 and 3.0). The LIF measurements of [CH] are corrected for variations in the electronic quenching rate coefficient by using predicted major species concentrations and temperatures along with quenching cross sections for CH that are available in the literature. The peak CH concentration obtained by CRDS is used to calibrate the quenching-corrected LIF measurements. Excellent agreement is obtained between CH concentration profiles measured by using the CRDS and LIF techniques. The spatial location of the CH layer is very well predicted by GRI 3.0; moreover, the measured and predicted CH concentrations are in good agreement for all the flames of this study.

The momentary rate of complex biochemical reactions and biological processes may depend not only on temperature (or an equivalent factor like pH or moisture contents) but also on the system's momentary state. Also, complex reactions and processes need not have a single ‘energy of activation’ and their ‘kinetic order’ is not always clearly defined. Thus, the progress of such a reaction or process is governed by time dependent kinetics whose description requires a departure from the traditional models, which are based on an analogy to simple chemical reactions. A general model that takes these considerations into account is demonstrated with simulated biochemical reactions under monotonic temperature increase and decrease and under regular and irregular temperature fluctuations. Its potential application to microbial growth and growth followed by decay is also demonstrated. The model is in the form of a cumbersome differential equation, which, nevertheless, can be solved by standard mathematical software. In certain cases, the same software can also be used to determine the process's basic kinetic parameters, and their temperature dependence, from experimental data obtained under non-isothermal conditions. This could simplify the study of fast reactions and processes, where shortening the come up and cooling times to insignificance, as required by the traditional isothermal analyses, is not a viable option.

RésuméLa prématurité induit des facteurs de risques de retard cognitif, particulièrement de retard dans le langage oral et écrit. Ces facteurs de risques peuvent être liés aux variables physiologiques et/ou environnementales. Cette étude a deux objectifs: (1) repérer quels sont les enfants prématurés les plus à risque de retard cognitif et de langage oral et écrit et (2) estimer l’intérêt d’un bilan précoce de langage oral proposé dès 3½ ans à ces enfants en mesurant sa prédictivité sur l’apprentissage de la lecture. Une cohorte de 50 enfants (23 garçons et 27 filles) nés prématurément ont été suivis de 2 ans à 7½ ans. Les résultats montrent que: a) 28% des enfants présentent un retard de production du langage à 3½ ans; b) 34% des enfants présentent un retard de la lecture à 7½ ans; c) la production du langage oral à 3½ ans est prédictif des capacités de lecture à 7½ et d) les enfants nés prématurément les plus à risques sont ceux qui évoluent dans un milieu défavorisé.

Axial metal complexation was used in the organization of the cobalt(II) meso-tetra(trimethylsilylethynyl)porphyrin, CoPTMS, by the Langmuir−Blodgett (LB) technique or by self-assembly (SA). The axial ligand is a para-substituted pyridine that carries a long aliphatic chain, C18NHPy, in the case of the LB technique or a triethoxysilane group, SiPy, in the case of SA. In both cases, monomolecular films of nonaggregated porphyrins have been obtained and characterized by IR and UV spectroscopies, linear dichroism, and X-ray diffraction. A 1/1/5 mixture of CoPTMS, C18NHPy, and methyl eicosanoate spread on a silver nitrate subphase led to the formation of a silver acetylide polychelate of porphyrins. After transfer onto a solid substrate, the macrocycles displayed a flat-on orientation. The polychelate monolayers are robust enough to allow easy dissolution of the methyl eicosanoate filling molecule without disturbing the macrocycle orientation inside the LB film.

The purpose of this paper is to present the methodology set up to derive catchment soil moisture from Earth Observation (EO) data using microwave spaceborne Synthetic Aperture Radar (SAR) images from ERS satellites and to study the improvements brought about by an assimilation of this information into hydrological models. The methodology used to derive EO data is based on the appropriate selection of land cover types for which the radar signal is mainly sensitive to soil moisture variations. Then a hydrological model is chosen, which can take advantage of the new information brought by remote sensing. The assimilation of soil moisture deduced from EO data into hydrological models is based principally on model parameter updating. The main assumption of this method is that the better the model simulates the current hydrological system, the better the following forecast will be. Another methodology used is a sequential one based on Kalman filtering. These methods have been put forward for use in the European AIMWATER project on the Seine catchment upstream of Paris (France) where dams are operated to alleviate floods in the Paris area.

Quantitative hydroxyl concentration time-series measurements have been obtained by picosecond time-resolved laser-induced fluorescence in a series of methane–air and hydrogen–argon–air nonpremixed flames. The recovery of a quantitative time series is complicated by the need to account for fluctuations in the fluorescence lifetime. We have recently developed instrumentation that enables the simultaneous measurement of fluorescence signal and lifetime. The present research represents the first application of this technique to turbulent flames. The correction for hydroxyl lifetime fluctuations is shown to be significant for mean concentrations and thus probability density functions but negligible for power spectral densities (PSD’s). The hydroxyl PSD’s were found to vary slightly with radial and axial location in the flames and to vary significantly with Reynolds number. However, the PSD’s in the H_2–Ar–air flames are nearly identical to those in the CH_4–air flames.

Group therapy was the method chosen for working with PKU girls and their mothers in improving their knowledge of maternal PKU and the prevention of unplanned pregnancies. It was found effective in relieving anxiety, and the importance of including the mothers in the group was critical.

Two-photon-excited fluorescence (TPF) has been used to determine the OH concentration profile in an atmospheric-pressure hydrogen–oxygen flame. Individual rovibronic transitions within the A^2Σ^+−X^2Π (0,0) system of OH were identified by comparing calculated wavelengths to emission spectra obtained by laser excitation from 604 to 638 nm. Relative OH concentrations were determined by individually exciting the O_1(5), O_2(5), and P_2(5) transitions and monitoring the resulting fluorescence with a filtered photomultiplier and a gated integrator system. The expected quadratic dependence of the fluorescence signal on laser power was verified indicating the probable lack of photochemical effects. The OH profile determined by the TPF method was found to be in good agreement with that determined by absorption spectroscopy. The estimated OH detection limit using TPF is ∼10^14 molecules/cm^3 at atmospheric pressure.

Cold resistance of male Sprague Dawley rats (300 g) fed a laboratory chow (P) or a semi-purified diet (T4F or H) for 14 days was evaluated by the degree of hypothermia developed under unrestrained conditions at -18°C or under restraint at +6°C or +1°C. Cold tests were started either at 09:00 h, 14:00 h or 23:00 h. Rats fed a semi-purified diet were more resistant to cold than P-fed rats in winter and summer but not in spring or fall. Cold resistance followed a circadian cycle, being very high at 23:00 h, very low at 14:00 h and in between at 09:00 h. The higher resistance to cold of rats on semi-purified diets coincided with a higher liver glycogen reserve throughout the day and a higher production of corticosterone in stressful conditons than in rats on P diet. However, unrelated diurnal cycles of cold resistance and liver glycogen, absence of hypoglycemia and maintenance of a high level of blood corticosterone in hypothermic rats fed P or semi-purified diets indicate that cold resistance is not limited by glycogen availability in liver or glucose and corticosterone in blood respectively. The lower fecal lactobacilli content found in rats fed a semi-purified diet supports the hypothesis that heat producing organs of these animals may have to compete with a smaller bacterial population in their small intestine for essential nutrients than the P-fed rats which could be a factor in their greater degree of cold resistance.

In June and July 1988, the European Space Agency organized in five European countries the Agriscatt '88 campaign. For this campaign two airborne scatterometers were used, including the French dual-frequency (C and X band) dual-polarization (HH and W) forward-looking radar ERASME. For the French site, the Orgeval hydrological basin, one of the aims of the experiment was to develop a soil moisture retrieval algorithm from radar data. It is shown, from comparison with the ground-truth data, that the use of a multiconfiguration radar improves the capacity of imaging radar for soil moisture mapping. In particular, an algorithm based on a vegetation absorption index and a soil moisture one is tested over wheat fields.

Published creep equations, derived from the Kelvin-Voigt model with a discrete retardation time spectrum were used to generate data for linear presentation of the creep function. It is shown that 2–3 term creep functions, containing 4–6 constants, could be reduced to an algebraic expression having two constants only. Consequently, entire creep curves of a variety of biological and food materials could be described by a single type of equation in the form of:P (t) = k0 + k1 t + t/(k2 + k3t) whereP (t) is the creep parameter (compliance, strain or deformation),k0 a constant representing the instantaneous compliance,k1 a constant representing the steady-state flow, andk2 andk3 the characteristic constants of the creep function? (t) obtained by regression from the linear relationship oft/? (t) vst.

We report the application of quasi-continuous wave (cw) inverse stimulated Raman spectroscopy (SRS) to the quantitative measurement of methane concentrations in atmospheric mixtures near room temperature. The quasi-cw SRS signal, with the use of the v1, fundamental of methane (2916 cm−1), is shown to be proportional to the powers of both the pump and probe lasers as well as to the methane concentration. The current minimum detectable signal corresponds to ∼200 ppm (v/v).

Obtaining quantitative measurements of NO concentration via laser-induced flourescence (LIF) at high pressure requires application of a suitable calibration. While it is best to calibrate as close to the measurement condition as possible, this is not always feasible. To assess the transportability of a calibration factor at high pressure, we have calculated ratios between linear LIF signals corresponding to a constant NO concentration at different measurement and calibration conditions for high-pressure ethane flames. We find that pressure broadening limits the utility of calibrating at a pressure different from that of the measurement, although a calibration performed at a higher pressure is applicable over a wider range of pressures than one performed at atmospheric pressure. If one calibrates at the same pressure, it is best to calibrate at a temperature within 500 K of the measurement temperature. In general, the calculations indicate that a judicious choice of a calibration condition will guarantee a measured NO concentration within a factor of two of the actual NO concentration.

We report quantitative, spatially resolved laser-saturated fluorescence (LSF), linear laser-induced fluorescence (LIF), and planar laser-induced fluorescence (PLIF) measurements of nitric oxide (NO) concentration in a preheated, lean direct-injection spray flame at atmospheric pressure. The spray is produced by a hollow-cone, pressure-atomized nozzle supplied with liquid heptane, and the overall equivalence ratio is unity. NO is excited by means of the Q_2(26.5) transition of the γ(0, 0) band. LSF and LIF detection are performed in a 2-nm region centered on the γ(0, 1) band. PLIF detection is performed in a broad ∼70-nm region with a peak transmission at 270 nm. Quantitative radial NO profiles obtained by LSF are presented and analyzed so as to correct similar LIF and PLIF profiles. Excellent agreement is achieved among the three fluorescence methodologies.

Asynchronous Optical Sampling (ASOPS) is a pump/probe method that utilizes a dual timebase scheme to determine number densities and decay rates. In the ASOPS technique, two lasers are mode-locked at slightly different frequencies, causing a relative phase walkout between the pump and probe lasers. This allows the dynamic measurement of subnanosecond excitation processes in a time scale on the order of milliseconds. The current ASOPS instrument consists of two dye lasers synchronously pumped by two frequency-doubled Nd:YAG lasers at a repetition rate of ∼82 MHz. The ASOPS signal is obtained by AC amplification of the probe beam voltage, which is measured by a single photodiode at a beat frequency of 10 kHz.

An experimental protocol, using photoionization controlled-loss spectroscopy (PICLS), has been developed for obtaining absolute number densities of atomic hydrogen from laser-induced fluorescence measurements in flames. Two laser beams are employed, the first to excite hydrogen atoms from the ground state to the second excited state via two-photon absorption and the second to strongly photoionize the excited atoms. The resulting fluorescence measurements are independent of quenching. A model is presented that assures the viability of PICLS as long as the photoionization rate is greater than or equal to the quenching rate. The model is verified in fuel-lean, stoichiometric, and fuel-rich flat premixed H_2/O_2/N_2 flames at pressures of 20 and 72 Torr. Over this range in pressure, the ratio of number densities obtained from PICLS to those calculated from partial equilibrium is constant to within 20%. Most of the error arises from the sensitivity of the partial equilibrium calculations to small uncertainties in both the fuel-oxidizer ratio and the measured OH concentration. Because of the quenching-independent nature of PICLS, quantitative fluorescence measurements can be made by calibrating at a single favorable flame condition.

Possible use of synthetic aperture radars (SAR) for monitoring agricultural canopies is investigated in this paper. Data have been acquired on the Orgcval watershed during the AGRISCATT'88 campaign. Four radar experiments were carried out with the airborne scattcrometer ERASME (C and X bands, HH and VV polarizations, multi-incidence angles). Simultaneous ground measurements (soil moisture, leaf area index, water content of the canopy) were conducted on 11 wheat fields. Backscattering coefficients of the canopies arc interpreted in the framework of semi-empirical 'water-cloud' models. A simple paramctrization of the angular effect of soil roughness is introduced, allowing the simultaneous use of multi-incidence angle radar data. With a unique set of parameters for each radar configuration ' frequency and polarization' the water-cloud model appears to describe adequately the backscattering of all the fields, over the range of incidence angles. It is shown that in this case, attenuation is the dominant effect of the vegetation and an inversion algorithm is proposed for estimating the water content of vegetation. This algorithm requires measurements at two different incidence angles and various combinations of radar configurations are then tested.

An experimental technique is presented that both minimizes and accounts for the interference background when laser-induced-fluorescence (LIF) measurements are made of NO in lean, high-pressure, premixed, CH_4/O_2/N_2 flames. Measurement interferences such as fluorescence and Raman scattering from secondary species become increasingly important for high-pressure LIF studies. O_2 fluorescence interferences are particularly troublesome in lean premixed flames. An excitation–detection scheme that minimizes the effects of these interferences is identified. A procedure that corrects the resulting LIF signal so as to account for any remaining interference signal is then developed. This correction is found to vary from less than 10% of the overall NO signal at atmospheric pressure to over 40% of the overall signal at 14.6 atm for LIF measurements of NO in a series of worst-case flames (? = 0.6, dilution ratio 2.2). The correction technique is further demonstrated to be portable over a useful range of flame conditions at each pressure.

We experimentally investigate the influence of O_2 interferences on laser-induced fluorescence measurements of NO in lean methane-fueled flames at a range of pressures for both narrow-band and broadband fluorescence detection. We identify NO excitation schemes that minimize O_2 interferences. From detection scans we obtain interference spectra for the different NO excitation schemes. We then identify optimum excitation–detection schemes for narrow-band detection measurements of NO. To simulate broadband detection experiments, we numerically apply five different filter combinations to the experimentally obtained detection scans. We develop filter-assessment parameters to judge the effectiveness of the different filtering schemes, and we establish a methodology for evaluating broadband excitation–detection strategies. From this research we identify optimum excitation–detection schemes for broadband detection measurements of NO.

Picosecond time-resolved laser-induced fluorescence (PITLIF) can potentially be used to obtain measurements of minor species concentrations in rapidly fluctuating flames. Previous studies demonstrated this potential for atomic sodium by monitoring the temporal fluorescence signal with both an equivalent-time and a real-time sampling method. In this developmental study, PITLIF is used to determine hydroxyl concentrations in laminar CH_4–O_2–N_2 flames by the measurement of both the integrated fluorescence signal and the fluorescence lifetime. The quenching environment can be monitored with real-time sampling, and thus the necessary quenching rate coefficient is obtained in 348 μs, which is fast enough for use in many turbulent flows. Fluorescence lifetimes of OH are also measured at different equivalence ratios in laminar flames by the use of the equivalent-time sampling technique. These results compare favorably with predicted lifetimes based on relevant quenching cross sections and calculated species concentrations.

To the best of our knowledge we report the first demonstration of surface thermometry using laser-induced second-harmonic generation (SHG) on a realistic metallic surface at atmospheric pressure. The surface is probed with a pulsed infrared laser beam and the SHG signal is monitored in reflection. For metallic silver, the SHG signal is found to be temperature dependent in the 25–120 °C range. The current accuracy of the method is ±5 °C. Future work with platinum should permit the application of SHG thermometry to much higher surface temperatures.

Asynchronous optical sampling (ASOPS) is a pump–probe method for the measurement of species concentrations in turbulent high-pressure flames. We show that rapid measurement of species number density can be achieved in a highly quenched environment by maintaining a constant beat frequency between the mode-locking frequencies of the pump and the probe lasers. A model for the ASOPS method based on rate equation theory for three- and four-level atoms is presented. A number of improvements are made to the basic ASOPS instrument, which result in a greatly enhanced signal-to-noise ratio. Atomic sodium is aspirated into an atmospheric pressure C_2H_4/O_2/N_2 flame and detected with the ASOPS instrument. When excited-state lifetimes are fitted by using the ASOPS theory, a 3P_1/2,3/2 ? 3S_1/2 quenching-rate coefficient of 1.72 × 10^9 s^−1 and a 3P_3/2 ? 3P_1/2 doublet-mixing rate coefficient of 3.66 × 10^9 s^−1 are obtained, in excellent agreement with literature values. ASOPS signals obtained over a wide range of pump and probe beam powers validate the rate equation theory. Improvements are suggested to improve the signal-to-noise ratio, since the present results are limited to laminar flows.

We have evaluated the anomalous fluorescence of pyrene as a method for determining flame temperature. Vapor-phase pyrene was injected into four premixed hydrogen/oxygen flames at equivalence ratios of 1.0 and 1.5 and pressures of 22 and 72 Torr. For each flame, the relative laser-induced (S_2 ? S_0)/(S_1 ? S_0) emission was monitored as a function of height above the burner and compared to the temperature profile as measured by miniature thermocouples. The thermal behavior of pyrene is discussed in terms of a modified intermediate strong-coupling model. A theoretical calculation of the temperature dependence of the S_2/S_1 emission ratio agrees well with the experimental flame-temperature data. Based on this agreement, conditions are delineated for the most suitable use of pyrene as a molecular temperature probe.

A feasibility study has been performed on the application of laser-saturated fluoresence (LSF) to the measurement of OH concentration in high-pressure flames. Using a numerical model for the collisional dynamics of the OH molecule under nonuniform laser excitation, we have investigated the effect of pressure on the balanced cross-rate model and determined the sensitivity of the depopulation of the laser-coupled levels to the ratio of rate coefficients describing (1) electronic quenching of the vibrational levels for which υ″ > 0 and (2) vibrational relaxation from υ″ > 0 to υ″ = 0. At sufficiently high pressures in near-saturated conditions, the total population of the laser-coupled levels reaches an asymptotic value, which is insensitive to the degree of saturation. When the ratio of electronic quenching is vibrational relaxation is small and the rate coefficients for rotational transfer in the ground and excited electronic states are nearly the same, the balanced cross-rate model remains a good approximation for all pressures. When the above ratio is large, depopulation of the laser-coupled levels becomes significant at high pressures, and thus the balanced cross-rate model no longer holds. In these conditions, however, knowledge of the asymptotic value achieved by the laser-coupled levels could be used to correct the balanced cross-rate model and thus allow LSF measurements at sufficiently high pressures.

We report the results from a new pump/probe spectrometer for potential use in combustion diagnostics that employs asynchronous optical sampling. The instrument consists of two frequency-doubled mode-locked Nd:YAG lasers operating at slightly different repetition rates, synchronously pumping two dye lasers (rhodamine 6G) to generate the pump and probe beams. The spectral and temporal capabilities of the instrument are examined by obtaining a spectrum and an excited state decay of rhodamine B. The instrument response is shown to be proportional to pump power, probe power, and sample absorptance. Different frequency synthesizers and different modes of triggering are used to study their effect on signal stability.

Rotational transfer cross sections for the OH A^2∑^+ (v = 0) rovibronic levels were determined for collisions with water vapor at flame temperatures. OH fluorescence was induced by a 10-ns pulse from a Nd:YAG pumped dye laser, and the resulting fluorescence spectrum was recorded at selected times during the laser pulse. The measurements were performed in the postflame region of 30-Torr stoichiometric hydrogen/oxygen/nitrogen flames. Four different upper rotational levels were excited. State-to-state and total rotational transfer rates were calculated by optimizing the agreement between experimental spectra and synthetic spectra generated by a time-dependent numerical code. For the F_1(1), F_1(4), F_2(5), and F_1(10) upper rotational levels in the A^2∑^+ (v = 0) manifold, total rotational transfer cross sections were found to be (110 ± 30), (170 ± 60), (190 ± 60), and (110 ± 30) × 10^−16 cm^2, respectively, for collisions of OH with water vapor.

Time-dependent and steady-state lateral fluorescence intensities are obtained analytically as a function of the saturation parameter along the laser axis for Gaussian and quasi-Lorentzian irradiance profiles. The sensitivity of these fluorescence intensities to quenching is compared with the sensitivity of the center-line fluorescence emission. Experimental saturation curves are analyzed similarly and compared to the steady-state predictions. The results show that the desired insensitivity of laser-saturated fluorescence (LSF) measurements to quenching is adversely affected by the fractional laser power in the wings of the transverse irradiance distribution. Ambiguities in the analysis of LSF measurements arising from these effects can be essentially eliminated by conducting the analysis with respect to the center-line fluorescence emission as opposed to the fluorescence intensity.

Calibration of laser-saturated fluorescence measurements using Rayleigh scattering is presented as an alternative to absorption. This new procedure is advantageous when measuring radical species at concentrations well below the corresponding detection limit for absorption. The calibration accounts for nonuniform laser irradiation by extracting the local fluorescence emission along the laser axis and works equally well for both saturated and near-saturated center-line conditions. The predicted error due to misfocusing of the collection optics is nearly negligible when the measured fluorescence is within 10% of its peak value. Number densities obtained using this method are within 15% of those obtained from absorption measurements.

Overall kinetic parameters describing the combustion of an irregularly-shaped carbon char are obtained based on optical measurements of the temperature, size, and velocity of individual particles observed in an entrained-flow reactor. In addition, for one set of conditions, the mass loss profile is measured by quantitatively collecting samples of partially burned char at four different heights in the reactor. The combustion conditions investigated in this study range from 12 to 36 mole-% O2with bulk gas temperatures from 1400 to 1800 K, resulting in particle temperatures from 1400 to 2100 K and overall burning rates from 8.9×10−3to 1.3×10−1gC/s·cm2(based on the external surface of the particle). The kinetic mass loss profile. Good agreement between the measured and calculated profiles is achieved when CO2formation near the particles is accounted for in the single-particle energy balance. Despite the uncertainty in the particle temperatures caused by the irregular shape of the particles, the kinetic paramters are relatively insensitive, to the simplifying assumption of a spherical particle. The measurements support an apparent reaction order of 0.7±0.2 and an apparent activation energy of 23±2 kcal/mol.

It is well known that the acquisition of consonants can be a more difficult developmental process than of vowels. In this study the authors describe a case of 'transitory developmental apraxia of speech' (TDAS) in which a French-speaking child, although he acquired the whole vowel system, showed a significant delay in consonant acquisition and usage. The results of systematic observations and assessments of general cognitive and specific language functioning cover a period of 4 years (age 3:8 to 7:1l), from first clinical assessment to evidence of a good academic achievement. It is argued that this case demonstrates an unusual example of TDAS. The language deficits observed could not be attributed to oromotor, neurological, cognitive or intellectual deficits. The findings here also raise crucial questions concerning the origins of such a speech disorder and why it is transient in nature.

We introduce an inexpensive application of a Fabry–Perot etalon to control long-term UV-laser line drift in atmospheric NO laser-induced fluorescence (LIF) measurements by monitoring the visible fundamental of a pulsed dye laser. A linear image sensor captures the interference pattern, and the dye grating can be adjusted to maintain a fixed wavelength through an interface with labview software. Results indicate that the laser wavelength can be fixed to an accuracy of ±0.0001 nm in the dye fundamental and ±0.00003 nm in the UV beam. Hence the average error in the LIF signal owing to fluctuations in spectral overlap between the laser and the NO absorption transition decreases from ∼5 to ∼0.05%, which results in improved measurement accuracy.

Picosecond time-resolved laser-induced fluorescence (PITLIF) has the potential to provide rapid measurements of minor-species concentrations by correction for local quenching conditions on the time scale of turbulence. Previous studies demonstrated that this technique could provide laser-induced fluorescence data and local quenching rates in flames but used equivalent-time sampling to obtain the required fluorescence decays. This precludes the use of PITLIF in turbulent systems. Fluorescence decays of sodium seeded into a laminar H_2–O_2–Ar diffusion flame are obtained from real-time data with an acquisition rate on the time scale of turbulence. The results obtained with this method are shown to be similar to those obtained from equivalent-time sampling.

Measurement of radical concentrations is important in understanding the chemical kinetics involved in combustion. Application of optical techniques allows for the nonintrusive determination of specific radical concentrations. One of the most challenging problems for investigators is to obtain flame data that are independent of the collisional environment. We seek to obviate this difficulty by the use of picosecond pump–probe absorption spectroscopy. A picosecond pump–probe absorption model is developed by rate-equation analysis. Implications are discussed for a laser-pulse width that is much smaller than the excited-state lifetime of the absorbing atom or molecule. The possibility of quantitative, quenching-independent concentration measurements is discussed, and detection limits for atomic sodium and the hydroxyl radical are estimated. For a three-level absorber–emitter, the model leads to a novel pump–probe strategy, called dual-beam asynchronous optical sampling, that can be used to obtain both the electronic quenching-rate coefficient and the doublet mixing-rate coefficient during a single measurement. We discuss the successful demonstration of the technique in a companion paper [Appl. Opt. 34, XXX (1995)].