Showing papers by "Carleton University published in 1999"

Routing with guaranteed delivery in ad hoc wireless networks

Abstract: We consider routing problems in ad hoc wireless networks modeled as unit graphs in which nodes are points in the plane and two nodes can communicate if the distance between them is less than some fixed unit. We describe the first distributed algorithms for routing that do not require duplication of packets or memory at the nodes and yet guarantee that a packet is delivered to its destination. These algorithms can be extended to yield algorithms for broadcasting and geocasting that do not require packet duplication. A byproduct of our results is a simple distributed protocol for extracting a planar subgraph of a unit graph. We also present simulation results on the performance of our algorithms.

Confidence level computation for combining searches with small statistics

Abstract: This article describes an efficient procedure for computing approximate confidence levels for searches for new particles where the expected signal and background levels are small enough to require the use of Poisson statistics. The results of many independent searches for the same particle may be combined easily, regardless of the discriminating variables which may be measured for the candidate events. The effects of systematic uncertainty in the signal and background models are incorporated in the confidence levels. The procedure described allows efficient computation of expected confidence levels.

Independent effects of forest cover and fragmentation on the distribution of forest breeding birds

Abstract: The aims of this study were (1) to determine the relative importance of the independent effects of forest cover and fragmentation on the distribution of forest breeding birds, and (2) to test the hypothesis that the negative effect of forest fragmentation on species distribution increases with decreasing forest cover, i.e., the negative interaction effect of forest cover and fragmentation on distribution. The independent effects of forest cover and forest fragmentation on the distribution of forest breeding birds were studied in 94 landscapes, 10 × 10 km each, ranging in forest cover from 2.5% to 55.8%. For each landscape, percent forest cover was measured, and a fragmentation index (independent of forest cover) was generated using PCA from the measures of mean forest patch size, number of forest patches, and total forest edge. Presence of 31 forest breeding bird species in each landscape was determined using Breeding Bird Atlas data. The effects of forest cover and forest fragmentation on species presenc...

Analytic Pro-P Groups

Abstract: Prelude Part I. Pro-p Groups: 1. Profinite groups and pro-p groups 2. Powerful p-groups 3. Pro-p groups of finite rank 4. Uniformly powerful groups 5. Automorphism groups Interlude A. Fascicule de resultats: pro-p groups of finite rank Part II. Analytic Groups: 6. Normed algebras 7. The group algebra Interlude B. Linearity criteria 8. P-adic analytic groups Interlude C. Finitely generated groups, p-adic analytic groups and Poincare series 9. Lie theory Part III. Further Topics: 10. Pro-p groups of finite co-class 11. Dimension subgroup methods 12. Some graded algebras Interlude D. The Golod Shafarevic inequality Interlude E. Groups of sub-exponential growth 13. Analytic groups over pro-p rings.

What Works for Female Offenders: A Meta-Analytic Review

Abstract: Although the question of what works for general offender populations has received considerable attention within the rehabilitation literature, very little research has examined female offenders. The present investigation examined the principles of effective correctional treatment for female offenders through a meta-analytic review. The results indicated that the clinically relevant and psychologically informed principles of human service, risk, need, and responsivity identified in past meta-analytic reviews were associated with enhanced reductions in reoffending.

ROOTS IN SOIL: Unearthing the Complexities of Roots and Their Rhizospheres

Abstract: ▪ Abstract The root system of a plant is as complicated as the shoot in its diversity, in its reactions with the matrix of substances, and with the myriad organisms that surround it. Laboratory studies blind us to the complexity found by careful study of roots in soil. This complexity is illustrated in the much-studied corn root system, covering the changes along the framework roots: the surface tissues and their interactions with the soil, the water-conducting xylem, whose gradual elaboration dictates the water status of the root. A conspicuous manifestation of the changes is the rhizosheath, whose microflora differs from that on the mature bare zones. The multitude of fine roots is the most active part of the system in acquiring water and nutrients, with its own multitude of root tips, sites of intense chemical activity, that strongly modify the soil they contact, mobilize reluctant ions, immobilize toxic ions, coat the soil particles with mucilage, and select the microflora.

Predicting Invasiveness of Plant Species Based on Biological Information

Abstract: Previous studies suggest that, within particular groups of plant species, biological attributes can be used to predict the potential invasiveness of species that are intentionally introduced for horticultural or agri- cultural purposes. We examined the broad question of whether commonly available biological information can predict the invasiveness of a wide range of intentionally and accidentally introduced species. We collected information from published floras on 165 pairs of plant species. In each pair, one species originated in Eu- rope and successfully invaded New Brunswick, Canada, and the other was a congeneric species that has not invaded North America. Only three biological characters—lifeform, stem height, and flowering period—and European geographic range were known for all species. We conducted multiple logistic regression analyses us- ing two-thirds (110) of the species pairs and tested the predictive ability of resulting models using the remain- ing 55 pairs. Although a significant logistic regression model was obtained using the biological attributes, the model could not predict invasiveness of the test species pairs. In contrast, a model using only European range successfully predicted invasiveness in 70% of the test species. The importance of geographic range suggests that prediction of invasiveness on a species-by-species basis is not likely to help stem the flow of accidentally introduced invasive species. Species that are inadvertently picked up and moved to a new location due to their wide distribution are the same species that are likely to succeed in a new environment due to their wide environmental tolerances.

WWW-based negotiation support: design, implementation, and use

Abstract: Support for international negotiations requires integration of decision-theoretic approaches with communication facilities, and different visualization modes. In addition, negotiation support systems (NSS) should also be tailored to different cultural and educational backgrounds of their users. While there have been studies on cross-cultural negotiations involving simple game or economic models, there have been no experiments with NSS in international and cross-cultural contexts. At the same time the emergence and quickly spreading use of the World Wide Web (WWW) and electronic commerce indicates the potential of NSS supporting commercial transactions across borders. This paper presents INSPIRE, the first Web-based NSS that has been tested and used in teaching and training in several countries. Developed in the context of a cross-cultural study of decision making and negotiation, it has been primarily used to conduct and study negotiation via WWW as well as in teaching and training. The architecture of INSPIRE, which relies heavily on the net-centric computing paradigm and object oriented design, is also discussed.

Excess loop delay in continuous-time delta-sigma modulators

Abstract: Continuous-time (CT) delta-sigma modulators (/spl Delta//spl Sigma/M's) suffer from a problem not seen in discrete-time (DT) designs, that of excess loop delay: nonzero delay between the quantizer clock edge and the time when a change in output bit is seen at the feedback point in the modulator. This paper analytically shows how such delay affects the equivalence between the CT modulator loop filter and its DT counterpart. The effect of this delay on modulator dynamic range is studied through simulation for the standard double-integration (low pass) CT modulator and its equivalent fourth-order f/sub s//4 band pass circuit. For the first time, the results are extended to higher order low-pass and bandpass designs, as well as multibit designs. Methods for alleviating the performance loss caused by excess loop delay are also discussed.

Endocrine and cytokine correlates of major depression and dysthymia with typical or atypical features

Abstract: Depression has been associated with both suppression and enhancement of various aspects of immune functioning. It was of interest to determine whether cytokine alterations associated with depression, including interleukin-1 (IL-1β) and interleukin-2 (IL-2), were related to the neurovegetative symptom profile or to the chronicity of the illness. Circulating ACTH, cortisol, norepinephrine (NE) and epinephrine levels, and production of IL-1β and IL-2 from mitogen-stimulated lymphocytes were assessed in classical major depression, atypical depression (ie, with reversed neurovegetative features), and dysthymia (chronic depression without comorbid major depression) with either typical or atypical profiles, as well as nondepressed control subjects. Among atypical depressives, plasma ACTH levels were elevated while cortisol was reduced relative to controls. Irrespective of neurovegetative profile, IL-1β production was increased in dysthymic patients, and was highly correlated with age-of-onset and duration of illness. In contrast, IL-2 production was reduced in each of the groups, although less so among atypical major depressives. Moreover, IL-2 production in the depressive groups was directly related to plasma NE levels. While neither depressed mood per se nor neurovegetative features accounted for this effect, it seemed likely that chronicity of illness or age-of-onset were associated with cytokine alterations. Given that circulating cytokines influence neuroendocrine functioning, and may affect neurovegetative features, a role for interleukins may exist with respect to the pathophysiology of certain subtypes of depression.

Online Routing in Triangulations

Abstract: We consider online routing strategies for routing between the vertices of embedded planar straight line graphs. Our results include (1) two deterministic memoryless routing strategies, one that works for all Delaunay triangulations and the other that works for all regular triangulations, (2) a randomized memoryless strategy that works for all triangulations, (3) an O(1) memory strategy that works for all convex subdivisions, (4) an O(1) memory strategy that approximates the shortest path in Delaunay triangulations, and (5) theoretical and experimental results on the competitiveness of these strategies.

Measurement of the strong coupling constant αs and the vector and axial-vector spectral functions in hadronic tau decays the opal collaboration

Abstract: The spectral functions of the vector current and the axial-vector current have been measured in hadronic $\tau$ decays using the OPAL detector at LEP. Within the framework of the Operator Product Expansion a simultaneous determination of the strong coupling constant $\alpha_{\rm s}$ , the non-perturbative operators of dimension 6 and 8 and of the gluon condensate has been performed. Different perturbative descriptions have been compared to the data. The Contour Improved Fixed Order Perturbation Theory gives $\alpha_{\rm s}(m_\tau^2) = 0.348 \pm 0.009_{\rm exp} \pm 0.019_{\rm theo}$ at the $\tau$ -mass scale and $\alpha_{\rm s}(m^2_{\rm Z}) = 0.1219 \pm 0.0010_{\rm exp} \pm 0.0017_{\rm theo}$ at the ${\rm Z}^0$ -mass scale. The values obtained for $\alpha_{\rm s}(m^2_{\rm Z})$ using Fixed Order Perturbation Theory or Renormalon Chain Resummation are 2.3% and 4.1% smaller, respectively. The ‘running’ of the strong coupling between $s_0 \simeq 1.3 {\rm GeV}^2$ and $s_0 = m_\tau^2$ has been tested from direct fits to the integrated differential hadronic decay rate $R_\tau(s_0)$ . A test of the saturation of QCD sum rules at the $\tau$ -mass scale has been performed.

Clock jitter and quantizer metastability in continuous-time delta-sigma modulators

Abstract: The performance of continuous-time (CT) delta-sigma modulators (/spl Delta//spl Sigma/M's) suffers more severely from time jitter in the quantizer clock than discrete-time designs. Clock jitter adds a random phase modulation to the modulator feedback signal, which whitens the quantization noise in the band of interest and hence degrades converter resolution. Even with a perfectly uniform sampling clock, a similar whitening can be caused by metastability in the quantizer: a real quantizer has finite regeneration gain, and thus, quantizer inputs near zero take longer to resolve. This paper quantifies the performance lost due to clock jitter in a practical integrated CT /spl Delta//spl Sigma/M clocked with an on-chip voltage-controlled oscillator. It also characterizes metastability in a practical integrated quantizer using the quantizer output zero-crossing time and rise time as a function of both quantizer input voltage and the slope of the input voltage at the sampling instant, and predicts the maximum-achievable performance of a practical CT /spl Delta//spl Sigma/M given jitter and metastability constraints.

Theoretical Study of X−H Bond Energetics (X = C, N, O, S): Application to Substituent Effects, Gas Phase Acidities, and Redox Potentials

Abstract: Bond dissociation energies, electron affinities, and proton affinities are computed for a variety of molecules containing C−H, N−H, O−H, and S−H bonds using density functional theory with the B3LYP...

Optical Centrifuge for Molecules

Abstract: Strong infrared fields can be used for controlled spinning of molecules to very high angular momentum states. The angular momentum acquired can be sufficient to break molecular bonds. The approach is suitable for all anisotropic molecules, and we illustrate it by dissociating a homonuclear diatomic Cl2, with optical centrifuge efficiently separating Cl 35 and Cl 37 isotopes and thus demonstrating high sensitivity to the moment of inertia. [S0031-9007(99)09026-2] PACS numbers: 33.80.Rv, 82.50.Fv Optical manipulation of atoms (trapping, cooling, acceleration) has grown into a well-developed and established field. Its successful use of resonant processes is difficult to mimic for manipulation of molecules, due to the complexity of molecular energy spectra. However, intense nonresonant fields can provide forces similar to or even stronger than the resonant weak fields used in atom optics. Nonresonant forces have been long utilized in the manipulation of microscopic particles [1,2] but were only recently demonstrated for molecules, in optical deflection [3] and trapping [4] experiments. Molecular optics has a rich potential due to additional degrees of freedom offered by molecules. A range of molecular optics devices has been proposed [5] to control the external degrees of freedom using strong fields, while the field of coherent (or, more generally, active) control has been exploring ways to control the internal degrees of freedom [6]. We propose to use a nonresonant strong field to exert large optical torques on anisotropic molecules, leading to controlled molecular rotations induced with a simple pulse. This follows the work on strong field alignment [7] and complements the application of feedback control methods [8] to optimally excite specific angular momentum states. Molecular dissociation via rotations is used to demonstrate our method. The scheme distinguishes between molecules based on their moment of inertia, and thus acts as an optical centrifuge. An anisotropic molecule placed in a linearly polarized infrared laser field experiences a time-averaged (over the laser cycle) potential 2U0 cos 2 u due to the induced dipole moment interacting with the electric field. Here u is the angle between laser polarization and molecular axis, and U0 › s1y4 ds a k 2a ’ d E 2 , with E the field amplitude and ak and a’ the polarizability components parallel and perpendicular to the molecular axis [7]. Oblong molecules have ak .a ’ and align with the electric field. For most diatomics, U0 , 30 100 meV can be achieved before ionization becomes important on the nanosecond time scale [3]. Imagine now slowly rotating the polarization of the infrared field about a fixed axis —the molecule will follow and rotate with the same angular frequency. Accelerating the rotation of the polarization will increase the molecule’s angular momentum in a controlled manner. This rotation results in large centrifugal forces which can distort or even break the molecular bonds, including those in homonuclear diatomics which do not readily absorb in the infrared. The slowly rotating potential is produced by the field $ E › E0 cosvt f ˆ x cosfLstd 1 ˆ

Neuromodeling of microwave circuits exploiting space-mapping technology

Abstract: For the first time, we present modeling of microwave circuits using artificial neural networks (ANN's) based on space-mapping (SM) technology, SM-based neuromodels decrease the cost of training, improve generalization ability, and reduce the complexity of the ANN topology with respect to the classical neuromodeling approach. Five creative techniques are proposed to generate SM-based neuromodels. A frequency-sensitive neuromapping is applied to overcome the limitations of empirical models developed under quasi-static conditions, Huber optimization is used to train the ANN's. We contrast SM-based neuromodeling with the classical neuromodeling approach as well as with other state-of-the-art neuromodeling techniques. The SM-based neuromodeling techniques are illustrated by a microstrip bend and a high-temperature superconducting filter.

A novel adaptive mismatch cancellation system for quadrature IF radio receivers

Abstract: This paper investigates and resolves in-phase/quadrature phase (I/Q) imbalances between the input paths of quadrature IF receivers. These mismatches along the paths result in the image interference aliasing into the desired signal band, thus reducing the dynamic range and degrading the performance of the receivers. I/Q errors occur because of gain and phase imbalances between quadrature mixers. They are also caused by capacitor mismatches in analog-to-digital converters (A/Ds), which are designed to be identical for each input path. This paper presents a novel and feasible digital signal processing (DSP) solution for the I/Q mismatch problems. The system includes a novel complex least mean square algorithm and a modified adaptive noise canceler (signal separator) to separate the desired signal and the image noise caused by the mismatch. The noise canceler can also solve the signal leakage problem, which is that the noise reference includes signal components. This system was implemented in a Xilinx FPGA and an Analog Devices DSP chip. It was tested with a complex intermediate frequency receiver, which includes an analog front end and a complex sigma-delta modulator. Both simulation results and test results show a dramatic attenuation of the image noise. Extending applications of the system to N-path systems further indicates the robustness and feasibility of this novel adaptive mismatch cancellation system.

Attenuation of Ischemia-Induced Cellular and Behavioral Deficits by X Chromosome-Linked Inhibitor of Apoptosis Protein Overexpression in the Rat Hippocampus

Abstract: Transient forebrain ischemia produced by four-vessel occlusion (4-VO) triggers the delayed death of CA1 neurons in the hippocampus, resulting in behavioral deficits of spatial learning performance. We demonstrate that CA1 neuronal loss induced by 4-VO (12 min) is preceded by a selective and marked elevation of catalytically active caspase-3 in these neurons, indicative of apoptosis. Virally mediated overexpression of the anti-apoptotic gene X chromosome-linked inhibitor of apoptosis protein (XIAP) prevented both the production of catalytically active caspase-3 and degeneration of CA1 neurons after transient forebrain ischemia. CA1 neurons protected in this manner appeared to function normally, as assessed by immunohistochemical detection of the neuronal activity marker nerve growth factor inducible-A and by spatial learning performance in the Morris water maze. These findings indicate that caspase-3 activation is a key event in ischemic neuronal death and that blockade of this event by XIAP overexpression permits CA1 neurons to survive and operate properly after an ischemic insult.

Calibration of the speleothem delta function: an absolute temperature record for the Holocene in northern Norway

Abstract: The speleothem delta function (SDF) provides a new transfer function between the d18O signal of speleothem calcite and surface ground temperature. The function is based on physical principles, relating d18O of the calcite to thermodynamic fractionation, and to the dripwater function, which in turn relates d18O of dripwaters to that of the local precipitation and thus to the modification of source water in relationship to the geographical position of the site. The SDF must be calibrated against at least two reliable and well-dated palaeotemperature points. The end product is a reconstruction of absolute cave and surface temperatures. The technique is tested using a Holocene speleothem from north Norway, SG93, dated by 12 TIMS U-Th dates. The reconstructed temperature curve is presented and compared with the GISP2 ice-core record and with the historic record. In both cases the correlation with SG93 is impressive, indicating the validity of the technique.

Anhedonic and Anxiogenic Effects of Cytokine Exposure

Abstract: It is abundantly clear that interactions occur between the immune, endocrine, central, and autonomic nervous systems. Immunologic manipulations (or products of an activated immune system, e.g., cytokines) affect neuroendocrine and central neurotransmitter processes, and conversely, neuroendocrine and central neurotransmitter alterations may impact on immune activity (Anisman, Zalcman, & Zacharko, 1993; Blalock, 1994; Dunn, 1990; Rivier, 1993; Rothwell & Hopkins, 1995). It has been posited that, among other things, the immune system acts like a sensory organ informing the brain of antigenic challenge (Blalock, 1984, 1994). Furthermore, given the nature of the neurochemical changes elicited by antigens and cytokines, it was suggested that immune activation may be interpreted by the CNS as a stressor (Anisman et al., 1993; Dunn, 1990; Dunn, Powell, Meitin, & Small, 1989). To be sure, the effects of systemic Stressors (e.g., those associated with viral insults, bacterial endotoxins, cytokines) are not entirely congruous with those elicited by processive stressors (i.e., those involving higher-order sensory processing, e.g., fear conditioning, exposure to a predator or novel environment) (Herman & Cullinan, 1997). Nevertheless, cytokines may be part of a regulatory loop that, by virtue of effects on CNS functioning, might influence behavioral outputs and may even contribute to the symptoms of behavioral pathologies, including mood and anxiety-related disorders (Anisman et al., 1993; Crnic, 1991). It is curious that while cytokines have found an increasingly greater role in immunotherapy, and may contribute to neurodegenerative processes (Rothwell, Luheshi, & Toulmond, 1996), limited attention has been devoted to behavioral analyses of these cytokines in animal studies.

Building Technological Capability Through Importing Technology: The Case of Indonesian Manufacturing Industry

Abstract: This research investigates the critical elements affecting the ability of firms in developing countries to cultivate their technological capability through imported technology. The information obtained from forty-five technology recipient Indonesian manufacturing firms indicate that the cultivation of technological capability is affected by several factors such as a firm's technological absorption capacity in terms of RD transfer channels; government's involvement; and a firm's learning culture. Also, the acquisition of mature technology just to boost production capacity or improve product quality contributes very little to the development of technological capability.

Light meson spectroscopy

Abstract: The authors survey the current status of light-meson spectroscopy, beginning with a general introduction to meson spectroscopy and its importance in understanding the physical states of quantum chromodynamics. Phenomenological models of hadron spectroscopy are described with particular emphasis on the constituent-quark model and the qualitative features it predicts for the meson spectrum. The authors next discuss expectations for hadrons lying outside the quark model, such as hadron states with excited gluonic degrees of freedom. These states include so-called hybrids and glueballs, as well as multiquark states. The established meson states are compared to the quark-model predictions and most meson states are found to be well described by the quark model. However, a number of states in the light-quark sector do not fit in well, suggesting the existence of hadronic states with additional degrees of freedom. The review ends with a brief description of future directions in meson spectroscopy.

Sensitization to the effects of tumor necrosis factor-alpha: neuroendocrine, central monoamine, and behavioral variations.

Abstract: Consistent with the proposition that cytokines act as immunotransmitters between the immune system and the brain, systemic administration of the proinflammatory cytokine tumor necrosis factor-α (TNF-α; 1.0–4.0 μg) induced mild illness in CD-1 mice, increased plasma corticosterone concentrations, and altered central norepinephrine, dopamine, and serotonin turnover. The actions of TNF-α were subject to a time-dependent sensitization effect. After reexposure to a subeffective dose of the cytokine (1.0 μg) 14–28 d after initial treatment, marked illness was evident (reduced consumption of a palatable substance and diminished activity and social exploration), coupled with an elevation of plasma corticosterone levels. In contrast, cytokine reexposure 1–7 d after initial treatment did not elicit illness, and at the 1 d interval the corticosterone response to the cytokine was reduced. The increase of norepinephrine release within the paraventricular nucleus of the hypothalamus, as reflected by elevated accumulation of 3-methoxy-4-hydroxyphenylglycol, was augmented at the longer reexposure intervals. In contrast, within the central amygdala and the prefrontal cortex TNF-α reexposure at the 1 d interval was associated with a pronounced sensitization-like effect, which was not apparent at longer intervals. Evidently, systemic TNF-α proactively influences the response to subsequent treatment; however, the nature of the effects (i.e., the behavioral, neuroendocrine, and central transmitter alterations) vary over time after initial cytokine treatment. It is suggested that the sensitization may have important repercussions with respect to cognitive effects of TNF-α and may also be relevant to analyses of the neuroprotective or neurodestructive actions of cytokines.

Hard Tasks for Weak Robots: The Role of Common Knowledge in Pattern Formation by Autonomous Mobile Robots

Abstract: In this paper we aim at an understanding of the fundamental algorithmic limitations on what a set of autonomous mobile robots can or cannot achieve. We study a hard task for a set of weak robots. The task is for the robots in the plane to form any arbitrary pattern that is given in advance. The robots are weak in several aspects. They are anonymous; they cannot explicitly communicate with each other, but only observe the positions of the others; they cannot remember the past; they operate in a very strong form of asynchronicity. We show that the tasks that such a system of robots can perform depend strongly on their common knowledge about their environment, i.e., the readings of their environment sensors.