Approximating multiple class queueing models with loss models

Multiple class queueing models arise in situations where some flexibility is sought through pooling of demands for different services. Earlier research has shown that most of the benefits of flexibility can be obtained with only a small proportion of cross-trained operators. Predicting the performance of a system with different types of demands and operator pools with different skills is very difficult. We present an approximation method that is based on equivalent loss systems. We successively develop approximations for the waiting probability, The average waiting time and the service level. Our approximations are validated using a series of simulations. Along the way we present some interesting insights into some similarities between queueing systems and equivalent loss systems that have to our knowledge never been reported in the literature.

The Orbital Light Curve of Aquila X-1

We obtained R- and I-band CCD photometry of the soft X-ray transient/neutron- star binary Aql X-1 in 1998 June while it was at quiescence. We find that its light curve is dominated by ellipsoidal variations, although the ellipsoidal variations are severely distorted and have unequal maxima. After we correct for the contaminating flux from a field star located only 0.46" away, the peak-to-peak amplitude of the modulation is ~0.25 mag in the R band, which requires the orbital inclination to be greater than 36 degrees. The orbital period we measure is consistent with the 18.95 h period measured by Chevalier & Ilovaisky (1998). During its outbursts the light curve of Aql X-1 becomes single humped. The outburst light curve observed by Garcia et al. (1999) agrees in phase with our quiescent light curve. We show that the single humped variation is caused by a ``reflection effect,'' that is, by heating of the side of the secondary star facing towards the neutron star.Comment: 18 manuscript pages, 7 figures; accepted by A

EVALUATION OF BORON SUPPLEMENTATION IN SWINE AND POULTRY

The objectives of this dissertation were to evaluate dietary boron (B) supplementation as sodium borate in various swine models and broiler chicks through a series of experiments. The initial experiment evaluated supplemental B (0, 25, 50, and 100 ppm B) on serum insulin, glucose, and clinical chemistry panel of growing pigs. Serum insulin/glucose ratio tended to decrease linearly with increasing supplemental B in a fasting state (P = 0.08). These findings were more noticeable (linear effect, P = 0.02) in a postprandial state (~ 50 minutes following a meal). A series of follow-up studies further evaluating B supplementation (0, 5, and 25 ppm B) in sows, piglets, and grower and market pigs were conducted. In multiparous sows, B supplementation tended to result in sows farrowing fewer piglets (quadratic, P = 0.08) yet piglet birth weight was increased quadratically (P ≤ 0.05) with increasing B supplementation. Furthermore, B supplementation to multiparous sows resulted in a quadratic decrease in late gestation (d 80-90 of gestation) fasting serum insulin/glucose ratio (P = 0.02) whereas, in a postprandial state, serum insulin/glucose ratio was linearly increased (P = 0.02) with increasing B supplementation. In the second study, piglets from sows supplemented with dietary B exhibited an increase in the Mg content of the femur (quadratic effect, P = 0.02) at weaning. In the third study, both grower (70 kg BW) and market pigs supplemented with B had a greater kidney ash percentage (linear effect, P = 0.03; linear tendency, P = 0.08, respectively) compared to that of the control. Furthermore, grower pigs exhibited a linear increase in Mg concentration for the 3rd and 4th metacarpals (P = 0.05) with increasing B supplementation. In the final swine study, evaluating B supplementation on the apparent total tract digestibility (ATTD) and retention of nutrients in growing pigs resulted in a linear increase in both Mg absorption and digestibility regarding increasing B supplementation (P = 0.01 and P = 0.04, respectively). Lastly, an experiment evaluating B supplementation (0, 1, 2, 5, 10, 25, and 50 ppm B) to a semi-purified diet fed to broiler chicks resulted in a linear tendency for increasing tibia ash percentage (P = 0.08) with increasing supplemental B. Additionally, there was a greater tibia Mg concentration of birds supplemented B compared to control birds (P \u3c 0.01). In summation, B supplementation appeared to affect insulin concentration in both grower pigs and sows. Furthermore, B improved Mg absorption and digestibility in growing barrows while also affecting Mg concentrations in the bones of broilers, weaning pigs, and grower pigs, all suggesting B may play a key role in Mg metabolism

Facilitated diffusion of proteins on chromatin

We present a theoretical model of facilitated diffusion of proteins in the cell nucleus. This model, which takes into account the successive binding/unbinding events of proteins to DNA, relies on a fractal description of the chromatin which has been recently evidenced experimentally. Facilitated diffusion is shown quantitatively to be favorable for a fast localization of a target locus by a transcription factor, and even to enable the minimization of the search time by tuning the affinity of the transcription factor with DNA. This study shows the robustness of the facilitated diffusion mechanism, invoked so far only for linear conformations of DNA.Comment: 4 pages, 4 figures, accepted versio

Picoliter-volume inkjet printing into planar microdevice reservoirs for low-waste, high-capacity drug loading.

Oral delivery of therapeutics is the preferred route for systemic drug administration due to ease of access and improved patient compliance. However, many therapeutics suffer from low oral bioavailability due to low pH and enzymatic conditions, poor cellular permeability, and low residence time. Microfabrication techniques have been used to create planar, asymmetric microdevices for oral drug delivery to address these limitations. The geometry of these microdevices facilitates prolonged drug exposure with unidirectional release of drug toward gastrointestinal epithelium. While these devices have significantly enhanced drug permeability in vitro and in vivo, loading drug into the micron-scale reservoirs of the devices in a low-waste, high-capacity manner remains challenging. Here, we use picoliter-volume inkjet printing to load topotecan and insulin into planar microdevices efficiently. Following a simple surface functionalization step, drug solution can be spotted into the microdevice reservoir. We show that relatively high capacities of both topotecan and insulin can be loaded into microdevices in a rapid, automated process with little to no drug waste

Scheduling Networks of Queues: Heavy Traffic Analysis of a Multistation Closed Network

We consider the problem of finding an optimal dynamic priority sequencing policy to maximize the mean throughput rate in a multistation, multiclass closed queueing network with general service time distributions and a general routing structure. Under balanced heavy loading conditions, this scheduling problem can be approximated by a control problem involving Brownian motion. Although a unique, closed form solution to the Brownian control problem is not derived, an analysis of the problem leads to an effective static sequencing policy, and to an approximate means of comparing the relative performance of arbitrary static policies. Three examples are given that illustrate the effectiveness of our procedure

The orthogonal fitting procedure for determination of the empirical {\Sigma} - D relations for supernova remnants: application to starburst galaxy M82

The radio surface brightness-to-diameter ({\Sigma} - D) relation for supernova remnants (SNRs) in the starburst galaxy M82 is analyzed in a statistically more robust manner than in the previous studies that mainly discussed sample quality and related selection effects. The statistics of data fits in log {\Sigma} - log D plane are analyzed by using vertical (standard) and orthogonal regressions. As the parameter values of D - {\Sigma} and {\Sigma} - D fits are invariant within the estimated uncertainties for orthogonal regressions, slopes of the empirical {\Sigma} - D relations should be determined by using the orthogonal regression fitting procedure. Thus obtained {\Sigma} - D relations for samples which are not under severe influence of the selection effects could be used for estimating SNR distances. Using the orthogonal regression fitting procedure {\Sigma} - D slope {\beta} \approx 3.9 is obtained for the sample of 31 SNRs in M82. The results of implemented Monte Carlo simulations show that the sensitivity selection effect does not significantly influence the slope of M82 relation. This relation could be used for estimation of distances to SNRs that evolve in denser interstellar environment, with number denisty up to 1000 particles per cm3 .Comment: 14 pages, 3 figures, no changes, previous version had a typo in publication related comment, accepted for publication in Ap

La mondialisation, facteur d’homogénéité ou d’hétérogénéité dans le rapport tourisme et nature ? (France/Chine)

National audienc

Processus de patrimonialisation de la nature et dynamiques touristiques : un phénomène de co-constitution mondial ? Comparaison entre la France et la Chine

International audienc