Performance of Optimum Combining in a Poisson Field of Interferers and Rayleigh Fading Channels

This paper studies the performance of antenna array processing in distributed multiple access networks without power control. The interference is represented as a Poisson point process. Desired and interfering signals are subject to both path-loss fading (with an exponent greater than 2) and to independent Rayleigh fading. Using these assumptions, we derive the exact closed form expression for the cumulative distribution function of the output signal-to-interference-plus-noise ratio when optimum combining is applied. This results in a pertinent measure of the network performance in terms of the outage probability, which in turn provides insights into the network capacity gain that could be achieved with antenna array processing. We present and discuss examples of applications, as well as some numerical results.Comment: Submitted to IEEE Trans. on Wireless Communication (Jan. 2009

Décodage à seuil itératif sans entrelacement des codes convolutionnels doublement orthogonaux

Décodage à seuil en quantification ferme pour les codes convolutionnels -- Décodeur à seuil à sortie pondérée (ou à sortie non-quantifiée) -- Processus itératif de décodage à seuil à sortie pondérée sans entrelacement -- Décodage à seuil itératif à sortie non-quantifiée -- Définition des codes convolutionnels doublement orthogonaux -- Décodage itératif des code CSO2C-WS -- Amélioration de l'algorithme de décodage à seuil itératif pour des CSO2C-WS -- Définition au sens strict des codes convolutionnels doublement orthogonaux -- Décodage à seui itératif des CSO2-SS -- Analyse des performances d'erreur du décodage à seuil itératif sans entrelacement -- Probabilités d'erreur par bit du décodage à seuil à sortie non-quantifiée pour des CSOC -- Extension : évaluation de la probabilité d'erreur pour M itérations de décodage -- Codes convolutionnels doublement orthogonaux récursifs (R-CSO2C) -- Equivalence entre les codes à faible densité et les codes doublement orthogonaux -- Définition et décodage des codes R-CSO2C -- Analyse de la complexité et de la latence du décodage itératif sans entrelacement -- Calculs de la complexité det de la latence du décodage itératif des CSO2 sans entrelacement -- Comparaisons avec d'autres techniques de décodage itératif avec entrelacement -- Recommandations pour recherches futures

Rethinking John Dewey’s Instrumentalism Vis a Vis the Igbo Notion of “Akonucheism”

This work examines John Dewey’s instrumentalism postulate against the Igbo notion of “Akonucheism”. Dewey proposes instrumentalization of man, morality and knowledge in order to pragmatically solve human problems. He prescribes the experimental method for all disciplines and insists that science be allowed to operate without a moral umpire. This overemphasis on the scientific method constitutes one of the problematics of his pragmatism and engenders the receptivity of the sciento-technological rationality among strictly cultural societies such as the Igbo. On the other hand, the term “Akonucheism” is a coinage, which derives from Igbo words for intelligence (Ako or Izu) and thought (Uche). It describes the employment of intelligent thought, which entails the pragmatic integration of the positive elements found in the moral charter (culture) of the Igbo people of Nigeria, with acquired learning, knowledge or technical skill (amumamu and nka-na-uzu) to produce problem-resolving or relevant knowledge (now styled wisdom). This wisdom, contextually solves existential problems and the process of its extraction is what is called “Akonucheism”. Our aim in this paper, therefore, is to propose a balanced and rational integration, which makes it possible for the positive moral elements locatable in cultures to readily and complementarily fuse with the sciento-technological rationality in order to produce problem solving wisdom (Amamihe). However, we observe that among the Igbo, the circuit of knowing gets only completed when humane solutions are achieved without loss of human dignity, personhood and moral values hence, our rethinking Dewey’s instrumentalism. The analytical and comparative methods of enquiry are adopted for this research.Key Words: Instrumentalism, “Akonucheism”, Experimentalism, Wisdom, Knowledg

A Fatal Overdose of Cocaine Associated with Coingestion of Marijuana, Buprenorphine, and Fluoxetine. Body Fluid and Tissue Distribution of Cocaine and Its Metabolites Determined by Hydrophilic Interaction Chromatography-Mass Spectrometry (HILIC-MS)

Chromatographic separation of highly polar basic drugs with ideal ionspray mass spectrometry volatile mobile phases is a difficult challenge. A new quantification procedure was developed using hydrophilic interaction chromatography-mass spectrometry with turbo-ionspray ionization in the positive mode. After addition of deuterated internal standards and simple clean-up liquid extraction, the dried extracts were reconstituted in 500 μL pure acetonitrile and 5 μL was directly injected onto a Waters Atlantis™ HILIC 150- × 2.1-mm, 3-μm column. Chromatographic separations of cocaine, seven metabolites, and anhydroecgonine were obtained by linear gradient-elution with decreasing high concentrations of acetonitrile (80-56% in 18 min). This high proportion of organic solvent makes it easier to be coupled with MS. The eluent was buffered with 2mM ammonium acetate at pH 4.5. Except for m-hydroxy-benzoylecgonine, the within-day and between-day precisions at 20, 100, and 500 ng/mL were below 7 and 19.1%, respectively. Accuracy was also below ± 13.5% at all tested concentrations. The limit of quantification was 5 ng/mL (%Diff < 16.1, %RSD < 4.3) and the limit of detection below 0.5 ng/mL. This method was successfully applied to a fatal overdose. In Switzerland, cocaine abuse has dramatically increased in the last few years. A 45-year-old man, a known HIV-positive drug user, was found dead at home. According to relatives, cocaine was self-injected about 10 times during the evening before death. A low amount of cocaine (0.45 mg) was detected in the bloody fluid taken from a syringe discovered near the corpse. Besides injection marks, no significant lesions were detected during the forensic autopsy. Toxicological investigations showed high cocaine concentrations in all body fluids and tissues. The peripheral blood concentrations of cocaine, benzoylecgonine, and methylecgonine were 5.0, 10.4, and 4.1 mg/L, respectively. The brain concentrations of cocaine, benzoylecgonine, and methylecgonine were 21.2, 3.8, and 3.3 mg/kg, respectively. The highest concentrations of norcocaine (about 1 mg/L) were measured in bile and urine. Very high levels of cocaine were determined in hair (160 ng/mg), indicating chronic cocaine use. A low concentration of anhydroecgonine methylester was also found in urine (0.65 mg/L) suggesting recent cocaine inhalation. Therapeutic blood concentrations of fluoxetine (0.15 mg/L) and buprenorphine (0.1 μg/L) were also discovered. A relatively high concentration of Δ9-THC was measured both in peripheral blood (8.2 μg/L) and brain cortex (13.5 μg/kg), suggesting that the victim was under the influence of cannabis at the time of death. In addition, fluoxetine might have enhanced the toxic effects of cocaine because of its weak pro-arrhythmogenic properties. Likewise, combination of cannabinoids and cocaine might have increase detrimental cardiovascular effects. Altogether, these results indicate a lethal cocaine overdose with a minor contribution of fluoxetine and cannabinoid

Species indicators of ecosystem recovery after reducing large herbivore density: Comparing taxa and testing species combinations

Indicator species have been used successfully for estimating ecosystem integrity, but comparative studies for defining optimal taxonomic group remain scarce. Furthermore, species combinations may constitute more integrative tools than single species indicators, but case studies are needed to test their efficiency. We used Indicator Species Analysis, which statistically determines the association of species to one or several groups of sites, to obtain indicators of ecosystem recovery after various deer density reductions. We used five taxonomic groups: plants, carabid beetles, bees, moths and songbirds. To test whether species combinations could complement single indicator species, we used plants as a model taxon and examined the indicator value of joint occurrence of two or three plant species. Our study relies on experimental controlled browsing enclosures established for six years on Anticosti Island (Quebec). Four levels of deer density (0, 7.5 and 15 deer km−2 and natural densities between 27 and 56 deer km−2) were studied in two vegetation cover types (uncut forests and cut-over areas), in a full factorial design for a total of eight experimental treatments. For all taxa but bees, we tested 54 treatment groups consisting in one specific density or in a sequence of two or more consecutive deer densities in one or both cover types (ten groups for bees, sampled only in cut-over areas). We found 12 plants, 11 moths and one songbird to be single species indicators of ecosystem conditions obtained under 12 different treatment groups. Six treatment groups were indicated by plants and six different ones by moths, of which one group was also identified by a songbird species. Moths were thus worth the extra sampling effort, especially since the groups they indicated were more treatment-specific (mainly one or two deer density treatments). We tested the same 54 treatment groups for plant species combinations represented by two or three co-occurring species. Plant combinations efficiently complemented plant singletons for detecting ecosystem conditions obtained under various deer densities. In fact, although singletons were highly predictive, 17 additional treatment groups were identified exclusively with two- and three-species combinations, some being more treatment-specific. Our findings show that plants and moths provide complementary indicators of ecosystem conditions under various deer densities, and that computing species combinations increases our capacity to monitor ecosystem recovery after reducing herbivore densities.Funding was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC)-Produits forestiers Anticosti Industrial Chair to SDC, the Ministère des Ressources Naturelles et de la Faune du Québec, the Canadian Forest Service of Natural Resources Canada and an NSERC scholarship to MB and NSERC DG to MP and SP. We are grateful to the Centre de la Science de la Biodiversité du Québec and Centre d’études nordiques for scholarships

Permutationally invariant state reconstruction

Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, also an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a non-linear large-scale optimization problem, this is a major challenge in the design of scalable tomography schemes. Here we present an efficient state reconstruction scheme for permutationally invariant quantum state tomography. It works for all common state-of-the-art reconstruction principles, including, in particular, maximum likelihood and least squares methods, which are the preferred choices in today's experiments. This high efficiency is achieved by greatly reducing the dimensionality of the problem employing a particular representation of permutationally invariant states known from spin coupling combined with convex optimization, which has clear advantages regarding speed, control and accuracy in comparison to commonly employed numerical routines. First prototype implementations easily allow reconstruction of a state of 20 qubits in a few minutes on a standard computer.Comment: 25 pages, 4 figues, 2 table