Potential-flow models for channelled two-dimensional premixed flames around near-circular obstacles

International audienceThe dynamics of two-dimensional thin premixed flames is addressed in the framework of mathematical models where the flow field on either side of the front is piecewise incompressible and vorticity free. Flames confined in channels with asymptotically straight impenetrable walls are considered. Besides a few free propagations along straight channels, attention is focused on flames propagating against high-speed flows and positioned near a round central obstacle or near two symmetric bumps protruding inward. Combining conformal maps and Green's functions, a regularized generalization of Frankel's integro-differential equation for the instantaneous front shape in each configuration is derived and solved numerically. This produces a variety of real looking phenomena: steady fronts symmetric or not, noise-induced subwrinkles, flashback events, and breathing fronts in pulsating flows. Perspectives and open mathematical and physical problems are finally evoked

Optimal Robot Arm Movement using Tabu Search Algorithm

Abstract: This study presents an optimum approach to calculate the optimal robot arm movement for processing a considerable commitment of tasks using Tabu Search (TS) algorithm. In the scheduling problem, the objective is to minimize the total processing time related to tasks distances from each other. In the first step, the TS method is reviewed and we employ the proposed method in order to assign efficiently the optimal robot arm movement. In our proposed algorithm, the crossover rate is large at first and gradually it is decreased based on convergence improvement in next generations. We define an objective function including the operation times. Then, by minimizing this function using discrete TS algorithm, the optimal robot arm movement trajectory is assigned efficiently and quickly. If the resulted best cost converges to global minima, the crossover rate will be decreased in next generation. This method is studied in terms of operation time, convergence speed and quality of the results. Superior features of this algorithm are fast tuning, rapid convergence, less computational burden and capability to avoid from local minima. High promising results demonstrate that our proposed method is very efficient and can obtain higher quality solutions with better computational capability

Estimate of the Cosmological Bispectrum from the MAXIMA-1 Cosmic Microwave Background Map

We use the measurement of the cosmic microwave background taken during the MAXIMA-1 flight to estimate the bispectrum of cosmological perturbations. We propose an estimator for the bispectrum that is appropriate in the flat sky approximation, apply it to the MAXIMA-1 data and evaluate errors using bootstrap methods. We compare the estimated value with what would be expected if the sky signal were Gaussian and find that it is indeed consistent, with a $\chi^2$ per degree of freedom of approximately unity. This measurement places constraints on models of inflation.Comment: 5 pages, 2 figures. New version to match paper accepted for publication in Phys. Rev. Lett. Non-diagonal terms included leading to new limits on f_N

MAXIMA: an experiment to measure temperature anisotropy in the cosmic microwave background

We describe the MAXIMA experiment, a balloon-borne measurement designed to map temperature anisotropy in the Cosmic Microwave Background (CMB) over a wide range of angular scales (multipole range 80 < l < 800). The experiment consists of a 1.3 m diameter off-axis Gregorian telescope and a receiver with a 16 element array of bolometers cooled to 100 mK. The frequency bands are centered at 150, 240, and 410 GHz. The 10' FWHM beam sizes are well matched to the scale of acoustic peaks expected in the angular power spectrum of the CMB. The first flight of the experiment in its full configuration was launched in August 1998. A 122 sq-deg map of the sky was made near the Draco constellation during the 7 hour flight in a region of extremely low galactic dust contamination. This map covers 0.3% of the sky and has 3200 independent beamsize pixels. We describe the MAXIMA instrument and its performance during the recent flight.Comment: To appear in proceedings of `3K Cosmology', ed. F Melchiorri, Conference held Oct 5-10 1998, Rome, 13 pages LaTeX (using aipproc2.sty & aipproc2.cls), Postscript with higher resolution graphics available at http://cfpa.berkeley.edu/group/cmb/gen.htm

Determining Foreground Contamination in CMB Observations: Diffuse Galactic Emission in the MAXIMA-I Field

Observations of the CMB can be contaminated by diffuse foreground emission from sources such as Galactic dust and synchrotron radiation. In these cases, the morphology of the contaminating source is known from observations at different frequencies, but not its amplitude at the frequency of interest for the CMB. We develop a technique for accounting for the effects of such emission in this case, and for simultaneously estimating the foreground amplitude in the CMB observations. We apply the technique to CMB data from the MAXIMA-1 experiment, using maps of Galactic dust emission from combinations of IRAS and DIRBE observations, as well as compilations of Galactic synchrotron emission observations. The spectrum of the dust emission over the 150--450 GHz observed by MAXIMA is consistent with preferred models but the effect on CMB power spectrum observations is negligible.Comment: 19 pages, 8 figures, accepted for publication in the Astrophysical Journal. Monor changes to match the published versio

Determination of six chemotherapeutic agents in municipal wastewater using online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry

• We analyzed six chemotherapy agents in wastewaters. • We used 1 ml injections and an 11 min SPE-LC-MS/MS. • Limits of detection ranged from 4 to 20 ng L − 1 . • Cyclophosphamide and methotrexate were found in wastewater at 17-60 ng L Due to the increased consumption of chemotherapeutic agents, their high toxicity, carcinogenicity, their occurrence in the aquatic environment must be properly evaluated. An analytical method based on online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry was developed and validated. A 1 mL injection volume was used to quantify six of the most widely used cytotoxic drugs (cyclophosphamide, gemcitabine, ifosfamide, methotrexate, irinotecan and epirubicin) in municipal wastewater. The method was validated using standard additions. The validation results in wastewater influent had coefficients of determination (R 2 ) between 0.983 and 0.998 and intra-day precision ranging from 7 to 13% (expressed as relative standard deviation %RSD), and from 9 to 23% for inter-day precision. Limits of detection ranged from 4 to 20 ng L −1 while recovery values were greater than 70% except for gemcitabine, which is the most hydrophilic compound in the selected group and had a recovery of 47%. Matrix effects were interpreted by signal suppression and ranged from 55 to 118% with cyclophosphamide having the highest value. Two of the target anticancer drugs (cyclophosphamide and methotrexate) were detected and quantified in wastewater (effluent and influent) and ranged from 13 to 60 ng L −1 . The proposed method thus allows proper monitoring of potential environmental releases of chemotherapy agents

MAXIPOL: Cosmic Microwave Background Polarimetry Using a Rotating Half-Wave Plate

We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization of the cosmic microwave background radiation (CMB). MAXIPOL is the first bolometric CMB experiment to observe the sky using rapid polarization modulation. To build MAXIPOL, the CMB temperature anisotropy experiment MAXIMA was retrofitted with a rotating half-wave plate and a stationary analyzer. We describe the instrument, the observations, the calibration and the reduction of data collected with twelve polarimeters operating at 140 GHz and with a FWHM beam size of 10 arcmin. We present maps of the Q and U Stokes parameters of an 8 deg^2 region of the sky near the star Beta Ursae Minoris. The power spectra computed from these maps give weak evidence for an EE signal. The maximum-likelihood amplitude of l(l+1)C^{EE}_{l}/(2 pi) is 55_{-45}^{+51} uK^2 (68%), and the likelihood function is asymmetric and skewed positive such that with a uniform prior the probability that the amplitude is positive is 96%. This result is consistent with the expected concordance LCDM amplitude of 14 uK^2. The maximum likelihood amplitudes for l(l+1)C^{BB}_{l}/(2 pi) and $\ell(\ell+1)C^{EB}_{\ell}/2\pi$ are -31_{-19}^{+31} and 18_{-34}^{+27} uK^2 (68%), respectively, which are consistent with zero. All of the results are for one bin in the range 151 < l < 693. Tests revealed no residual systematic errors in the time or map domain. A comprehensive discussion of the analysis of the data is presented in a companion paper.Comment: 19 pages, 11 figures, 2 tables, submitted to Ap

The MAXIMA Experiment: Latest Results and Consistency Tests

The MAXIMA cosmic microwave background anisotropy experiment had a significant impact on cosmology. Results from the program have played a significant role in determining the geometry of the universe, given strong supporting evidence to inflation, and, in combination with other astrophysical data, showed that the universe is filled with dark matter and energy. We present a subset of the internal consistency checks that were carried out on the MAXIMA-1 data prior to their release, which demonstrate that systematics errors were much smaller than statistical errors. We also discuss the MAXIMA-2 flight and data, compare the maps of MAXIMA-1 and -2 in areas where they overlap and show that the two independent experiments confirm each other. All of these results demonstrate that MAXIMA mapped the cosmic microwave background anisotropy with high accuracyComment: to be published in C.R. Physique, 2003, (Academie des Science), 14 pages, figures embedded, a version with high quality figures is available from http://cosmology.berkeley.edu/maxima/comp_publications.htm

From the time-ordered data to the Maximum-Likelihood temperature maps of the Cosmic Microwave Backgorund anisotropy

We review selected methods of the Cosmic Microwave Background data analysis appropriate for the analysis of the largest currently available data sets. We focus on techniques of the time-ordered data manipulation and map making algorithms based on the maximum-likelihood approach. The presented methods have been applied to the MAXIMA data analysis (Hanany et al 2000) and the description of the algorithms is illustrated with the examples drawn from that experience. The more extensive presentation of the here-mentioned issues will be given in the forthcoming paper (Stompor et al 2001)

The Quintessential CMB, Past & Future

The past, present and future of cosmic microwave background (CMB) anisotropy research is discussed, with emphasis on the Boomerang and Maxima balloon experiments. These data are combined with large scale structure (LSS) information and high redshift supernova (SN1) observations to explore the inflation-based cosmic structure formation paradigm. Here we primarily focus on a simplified inflation parameter set, {omega_b,omega_{cdm},Omega_{tot}, Omega_Q,w_Q, n_s,tau_C, sigma_8}. After marginalizing over the other cosmic and experimental variables, we find the current CMB+LSS+SN1 data gives Omega_{tot}=1.04\pm 0.05, consistent with (non-baroque) inflation theory. Restricting to Omega_{tot}=1, we find a nearly scale invariant spectrum, n_s =1.03 \pm 0.07. The CDM density, omega_{cdm}=0.17\pm 0.02, is in the expected range, but the baryon density, omega_b=0.030\pm 0.004, is slightly larger than the current nucleosynthesis estimate. Substantial dark energy is inferred, Omega_Q\approx 0.68\pm 0.05, and CMB+LSS Omega_Q values are compatible with the independent SN1 estimates. The dark energy equation of state, parameterized by a quintessence-field pressure-to-density ratio w_Q, is not well determined by CMB+LSS (w_Q<-0.3 at 95%CL), but when combined with SN1 the resulting w_Q<-0.7 limit is quite consistent with the w_Q=-1 cosmological constant case. Though forecasts of statistical errors on parameters for current and future experiments are rosy, rooting out systematic errors will define the true progress.Comment: 14 pages, 3 figs., in Proc. CAPP-2000 (AIP), CITA-2000-6