cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Contributions to the Design of Asynchronous Macromodular Systems
Creators: name: Plana, Luis A.
Publisher: name: Columbia University
Year: 1999
Subjects: Computer science

description: In this thesis, I advocate the use of macromodules to design and build robust and performance-competitive asynchronous systems. The contributions of the work relate to different aspects of the design of asynchronous macromodular systems. First, an architectural optimization for 4-phase systems is introduced. The goal of the optimization is to increase the performance of a system by increasing the level of concurrent activity in the sequencing of data processing stages. In particular, three new asynchronous sequencers are designed, which increase the throughput of the system. Existing asynchronous data paths do not operate correctly at this increased level of concurrency: data hazards may result. Interlock mechanisms are introduced to insure correct operation. The technique can also be regarded as a low-power optimization: The increased throughput can be traded for a significant reduction in the power consumption of the entire system. SPICE simulation results show that the new sequencers allow roughly twice the throughput of non-concurrent sequencers. The simulations also show that, after voltage scaling, energy dissipation is reduced by a factor of 2.5. Second, the use of pulses for efficient inter-module synchronization is introduced. The idea is complemented with the definition of a pulse-mode handshake protocol and the characterization of Pulse-Burst Operation (PBO), an important extension to traditional pulse-mode operation. Also, a basic set of macromodules, that efficiently implement control operations such as sequencing, selection, iteration, concurrency control, resource sharing, and arbitration is presented. Modules for interfacing pulse-mode circuits with traditional 2-phase and 4-phase circuits are also included in the set. Finally, the design of a packet switch is used to demonstrate the viability of pulse-mode macromodules to implement complex, high performance systems. The switch organization, its asynchronous operation, and the low control overhead introduced by pulse-mode macromodules result in a design that can handle 2.4 times the target throughput of 155 Mbits/Sec. Also, the switch is characterized by very low input-to-output latency. These results suggest that pulse-mode macromodules can keep control overhead low without introducing complex, unsafe timing considerations, two necessary conditions to achieve robust, performance-competitive systems.
On supersymmetric Einstein-Weyl spaces
Creators: name: Meessen, P.
name: Ortín, T.
name: Palomo-Lozano, A.
Publisher: name: arXiv
Year: 2011
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: Differential Geometry (math.DG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We consider weighted parallel spinors in Lorentzian Weyl geometry in arbitrary dimensions, choosing the weight such that the integrability condition for the existence of such a spinor, implies the geometry to be Einstein-Weyl. We then use techniques developed for the classification of supersymmetric solutions to supergravity theories to characterise those Lorentzian EW geometries that allow for a weighted parallel spinor, calling the resulting geometries supersymmetric. The overall result is that they are either conformally related to ordinary geometries admitting parallel spinors (w.r.t. the Levi-Civita connection) or are conformally related to certain Kundt spacetimes. A full characterisation is obtained for the 4 and 6 dimensional cases.
description: 17 pages, version to be published in JGP
Implementing Intelligent Network Services with the Session Initiation Protocol
Creators: name: Lennox, Jonathan
name: Schulzrinne, Henning G.
name: La Porta, Thomas F.
Publisher: name: Columbia University
Year: 1999
Subjects: Computer science

description: Internet telephony is receiving increasing interest as an alternative to traditional telephone networks. This article shows how the IETF's Session Initiation Protocol (SIP) can be used to perform the services of traditional Intelligent Network protocols, as well as additional services.
Automated Solar Feature Detection for Space Weather Applications
Creators: name: Pérez-Suárez, David
name: Higgins, Paul A.
name: Bloomfield, D. Shaun
name: McAteer, R. T. James
name: Krista, Larisza D.
name: Byrne, Jason P.
name: Gallagher, Peter. T.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The solar surface and atmosphere are highly dynamic plasma environments, which evolve over a wide range of temporal and spatial scales. Large-scale eruptions, such as coronal mass ejections, can be accelerated to millions of kilometres per hour in a matter of minutes, making their automated detection and characterisation challenging. Additionally, there are numerous faint solar features, such as coronal holes and coronal dimmings, which are important for space weather monitoring and forecasting, but their low intensity and sometimes transient nature makes them problematic to detect using traditional image processing techniques. These difficulties are compounded by advances in ground- and space- based instrumentation, which have increased the volume of data that solar physicists are confronted with on a minute-by-minute basis; NASA's Solar Dynamics Observatory for example is returning many thousands of images per hour (~1.5 TB/day). This chapter reviews recent advances in the application of images processing techniques to the automated detection of active regions, coronal holes, filaments, CMEs, and coronal dimmings for the purposes of space weather monitoring and prediction.
description: 20 pages, 6 figures, Book chapter in "Applied Signal and Image Processing: Multidisciplinary Advancements" (ed. Rami Qahwaji, Roger Green and Evor L. Hines) pp. 207-225
Distribution of Treponema species and antimicrobial resistance genes in digital dermatitis lesions
Creators: name: Beninger, Caroline
Publisher: name: Graduate Studies
Year: 2018
Subjects: subject: Digital dermatitis
subject: Treponema
subject: qPCR
subject: Antibiotic resistance
subject: polymicrobial
subject: Lameness
subject: Genetics
subject: FOS: Biological sciences
subject: Microbiology
subject: Veterinary Science

description: Digital dermatitis lesions are ulcerative or proliferative masses between the heel bulbs. The most significant clinical outcome of digital dermatitis (DD) is lameness, leading to animal welfare concerns and economic loss for dairy producers worldwide due to premature culling, milk loss, and decreased fertility. While there is insufficient evidence to determine the etiological agent(s) responsible for DD, it is widely accepted that DD is a polymicrobial disease significantly associated with anaerobic bacteria, Treponema. Difficulties in obtaining pure cultures and the nearly exclusive presence of Treponema in diseases as members of a polytreponemal or polymicrobial communities has led to insufficient species identification within lesions and incomparable prevalence estimates based on phylotype. Our primary research objectives were to develop a diagnostic tool to identify Treponema spp. within DD lesions to associate presence and abundance with DD lesion grades. Further, we examined the distribution of antimicrobial resistance genes (AMGs) within sequenced isolates of DD-associated Treponema and designed targeted PCR for Treponema AMGs (AMGsTrep) within lesions. We provide significant evidence that the absolute quantities of Treponema and AMGsTrep are lower in chronic and early, active DD lesions suggesting Treponema spp. within these lesions may be more susceptible to antimicrobials (AMs) compared to species in advanced, active lesions. We have identified potential interactions among Treponema spp. that may facilitate DD progression and enhance pathogenicity and may affect AM susceptibility and lesion chronicity. With the novel diagnostic tool developed here, future research should elucidate interactions among Treponema spp. and in vitro susceptibility profiles and the efficacy of treating early and chronic lesions compared to advanced, active lesions on infection resolution.
aMC@NLO predictions for Wjj production at the Tevatron
Creators: name: Frederix, Rikkert
name: Frixione, Stefano
name: Hirschi, Valentin
name: Maltoni, Fabio
name: Pittau, Roberto
name: Torrielli, Paolo
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We use aMC@NLO to predict the lv+ 2-jet cross section at the NLO accuracy in QCD matched to parton shower simulations. We find that the perturbative expansion is well behaved for all the observables we study, and in particular for those relevant to the experimental analyses. We therefore conclude that NLO corrections to this process cannot be responsible for the excess of events in the dijet invariant mass observed by the CDF collaboration.
description: 14 pages, 3 figures
The implicit knowledge retention ecosystem
Creators: name: Arpita Pal
name: Alyssa Nicole
Publisher: name: Zenodo
Year: 2021
Subjects: implicit knowledge
storytelling
communities of practice
information architecture
apprenticeship
after actions review

description: The final proposal discusses implicit knowledge’s capture and transmission strategy, with efficient processes for capturing, storing, and distributing the implicit knowledge within an organization. Our proposal was selected as one of the three winners of the AECT – NATO 2021 Design and Development Competition. We named our solution “the implicit knowledge retention ecosystem.”
The implicit knowledge retention ecosystem: An information architecture analysis
Creators: name: Arpita Pal
name: Alyssa Nicole
Publisher: name: Zenodo
Year: 2021
Subjects: implicit knowledge
storytelling
communities of practice
information architecture
apprenticeship
after actions review

description: In an organizational setting, a constant stream of implicit knowledge is being created. For example, an organization may have a formal recruitment process to hire candidates - a type of explicit knowledge. However, the effectiveness of the process depends on the recruiter's skills and experience developed over time as they learn how to hire the highest quality candidates. This type of knowledge, acquired from practice and experience, is called implicit knowledge. When key talents like subject matter experts, leaders, or other high-performing individuals leave an organization for any reason, they also take away the implicit knowledge needed to operate at top efficiency and effectiveness. Simultaneously, existing employees who do similar work and desire to increase their skills and knowledge miss out on the implicit knowledge unless exchanged with each other. This is a problem for organizations since new employees, those moving into new leadership positions, or employees doing similar work might not have the ability to access or share implicit knowledge.
The final proposal discusses implicit knowledge's capture and transmission strategy, with efficient processes for capturing, storing, and distributing the implicit knowledge within an organization. Our proposal was selected as one of the three winners of the AECT – NATO 2021 Design and Development Competition. We named our solution "the implicit knowledge retention ecosystem."
TCP-Friendly Rate Control with Token Bucket for VoIP Congestion Control
Creators: name: Maldonado, Miguel
name: Baset, Salman Abdul
name: Schulzrinne, Henning G.
Publisher: name: Columbia University
Year: 2005
Subjects: Computer science

description: TCP Friendly Rate Control (TFRC) is a congestion control algorithm that provides a smooth transmission rate for real-time network applications. TFRC refrains from halving the sending rate on every packet drop, instead it is adjusted as a function of the loss rate during a single round trip time. TFRC has been proven to be fair when competing with TCP flows over congested links, but it lacks quality-of-service parameters to improve the performance of real-time traffic. A problem with TFRC is that it uses additive increase to adjust the sending rate during periods with no congestion. This leads to short term congestion that can degrade the quality of voice applications. We propose two changes to TFRC that improve the performance of VoIP applications. Our implementation, TFRC with Token Bucket (TFRC-TB), uses discrete calculated bit rates based on audio codec bandwidth usage to increase the sending rate. Also, it uses a token bucket to control the sending rate during congestion periods. We have used ns2, the network simulator, to compare our implementation to TFRC in a wide range of network conditions. Our results suggest that TFRC-TB can provide a quality of service (QoS) mechanism to voice applications while competing fairly with other traffic over congested links.
Industry perspectives on legislative efficiency of well site reclamation
Creators: name: Milne, Kathryn
Publisher: name: Environmental Design
Year: 2007

description: Bibliography: p. 115-118
description: Some pages are in colour.
description: Approval page is missing.
description: In Canada, oil and gas companies operating in multiple provinces must develop reclamation protocols to satisfy the separate provincial legislative regimes. Ava t amount of land is affected by oil and gas development, and a vast amount of resource are used to reclaim the land. Thus, a better understanding of legislative efficiencies is required to ensure that resources are used appropriately to maximize the quality of reclamation. For each province, this MDP analyze : the structure and role of pertinent regulatory agencies involved in reclamation; the reclamation legislation itself; and the process of implementing this legislation. Legislative analysis and industry interviews have identified key issues which may influence the efficiency of the legislative regime, and consequently, the degree to which reclamation is achieved. These issues include: communication and coordination between regulatory agencies; clearly defined objective and aligned legislation; and liability. British Columbia appears to have the least efficient legislative regime, as it requires a high degree of resource input, with little guarantee of timely certification. The relative efficiencies of Alberta and Saskatchewan are less clear cut. Alberta's regime require a high degree of resource input, yet produces high quality certified reclaimed sites. On the other hand, Saskatchewan's regime demands fewer resources, but compared to Alberta, produces lower quality reclaimed land. Field research assessing the quality of reclamation in each province; evaluation of other pertinent regulatory agencies , and a cross comparison between industries are all example of future research that will advance our understanding of how legislation influences reclamation.
Redistribution policy: A European model
Creators: name: Casella, Alessandra M.
Publisher: name: Columbia University
Year: 2002
Subjects: Economics
International relations
Europeans

description: Following the rationale for regional redistribution programs described in the official documents of the European Union, this paper studies a very simple multi-country model built around two regions: a core and a periphery. Technological spill-overs link firms' productivity in each of the two region, and each country's territory falls partly in the core and partly in the periphery, but the exact shares vary across countries. We find that, in line with the EU view, the efficient regional allocation requires both national and international transfers. If migration is fully free across all borders, then optimal redistribution policy results from countries' uncoordinated policies, obviating the need for a central agency. But if countries have the option of setting even imperfect border barriers, then efficiency is likely to require coordination on both barriers and international transfers (both of which will be set optimally at positive levels). The need for coordination increases as the Union increases in size.
Speculation, Embedding, and Food Prices: A Cointegration Analysis
Creators: name: Windawi, A. Jason
Publisher: name: Columbia University
Year: 2012
Subjects: Economics

description: The disparity between massive volatility in food prices and relatively slow changes in agricultural supply and demand since the beginning of the food crisis in 2007 has focused attention on the potential effects of financial speculators in food markets. The challenge of identifying the effects of such speculators has been complicated by a number of factors, key among which has been the criteria used to define speculative activity. This paper provides a more targeted analysis of one particular kind of speculator, and builds on a combination of sociological and econometric analysis to identify their presence in commodity markets during the food crisis.
Agnostically Learning Halfspaces
Creators: name: Kalai, Adam
name: Klivans, Adam
name: Mansour, Yishay
name: Servedio, Rocco Anthony
Publisher: name: Columbia University
Year: 2005
Subjects: Computer science

description: We consider the problem of learning a halfspace in the agnostic framework of Kearns et al., where a learner is given access to a distribution on labelled examples but the labelling may be arbitrary. The learner's goal is to output a hypothesis which performs almost as well as the optimal halfspace with respect to future draws from this distribution. Although the agnostic learning framework does not explicitly deal with noise, it is closely related to learning in worst-case noise models such as malicious noise. We give the first polynomial-time algorithm for agnostically learning halfspaces with respect to several distributions, such as the uniform distribution over the $n$-dimensional Boolean cube {0,1}^n or unit sphere in n-dimensional Euclidean space, as well as any log-concave distribution in n-dimensional Euclidean space. Given any constant additive factor eps>0, our algorithm runs in poly(n) time and constructs a hypothesis whose error rate is within an additive eps of the optimal halfspace. We also show this algorithm agnostically learns Boolean disjunctions in time roughly 2^{\sqrt{n}} with respect to any distribution; this is the first subexponential-time algorithm for this problem. Finally, we obtain a new algorithm for PAC learning halfspaces under the uniform distribution on the unit sphere which can tolerate the highest level of malicious noise of any algorithm to date. Our main tool is a polynomial regression algorithm which finds a polynomial that best fits a set of points with respect to a particular metric. We show that, in fact, this algorithm is an arbitrary-distribution generalization of the well known "low-degree" Fourier algorithm of Linial, Mansour, and Nisan and has excellent noise tolerance properties when minimizing with respect to the L_1 norm. We apply this algorithm in conjunction with a non-standard Fourier transform (which does not use the traditional parity basis) for learning halfspaces over the uniform distribution on the unit sphere; we believe this technique is of independent interest.
Effect of transition-metal substitution in iron-based superconductors
Creators: name: Liu, S. L.
name: Zhou, Tao
Publisher: name: arXiv
Year: 2012
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We study theoretically the current debatable issue about the effect of transition-metal (TM) substitution in iron-based superconductors through treating all of the TM ions as randomly distributed impurities. The extra electrons from TM elements are localized at the impurity sites. In the mean time the chemical potential shifts upon substitution. The phase diagram is mapped out and it seems that the TM elements can act as effective dopants. The local density of states (LDOS) is calculated and the bottom becomes V-shaped as the impurity concentration increases. The LDOS at the Fermi energy $ρ(ω=0)$ is finite and reaches the minimum at the optimal doping level. Our results are in good agreement with the scanning tunneling microscopy experiments.
description: 5 pages, 4 figures
Service Interface and Replica Management Algorithm for Mobile File System Clients
Creators: name: Tait, Carl D.
name: Duchamp, Dan
Publisher: name: Columbia University
Year: 1991
Subjects: Computer science

description: Portable computers are now common, a fact that raises the possibility that file service clients might move on a regular basis. This new development requires rethinking some features of distributed file system design. We argue that existing approaches to file replica management would not cope well with the likely behavior of mobile clients, and we present our solution: a lazy "server-based" update operation. This operation facilitates fast, scalable, and highly fault-tolerant implementations of both read and write operations in the usual case. To cope with the weak semantics of the update operation, we propose a new file system service interface that allows applications to opt for "UNIX semantics" by use of a slower, less fault-tolerant read operation.
Neutron star atmosphere composition: the quiescent, low-mass X-ray binary in the globular cluster M28
Creators: name: Servillat, Mathieu
name: Heinke, C. O.
name: Ho, W. C. G.
name: Grindlay, J. E.
name: Hong, J.
name: Berg, M. van den
name: Bogdanov, S.
Publisher: name: arXiv
Year: 2012
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Using deep Chandra observations of the globular cluster M28, we study the quiescent X-ray emission of a neutron star in a low-mass X-ray binary in order to constrain the chemical composition of the neutron star atmosphere and the equation of state of dense matter. We fit the spectrum with different neutron star atmosphere models composed of hydrogen, helium or carbon. The parameter values obtained with the carbon model are unphysical and such a model can be ruled out. Hydrogen and helium models give realistic parameter values for a neutron star, and the derived mass and radius are clearly distinct depending on the composition of the atmosphere. The hydrogen model gives masses/radii consistent with the canonical values of 1.4 Msun and 10 km, and would allow for the presence of exotic matter inside neutron stars. On the other hand, the helium model provides solutions with higher masses/radii, consistent with the stiffest equations of state. Measurements of neutron star masses/radii by spectral fitting should consider the possibility of heavier element atmospheres, which produce larger masses/radii for the same data, unless the composition of the accretor is known independently.
description: accepted for publication in MNRAS, 6 pages, 3 figures, 1 table
The implicit knowledge retention ecosystem
Creators: name: Pal, Arpita
name: Nicole, Alyssa
Publisher: name: Zenodo
Year: 2021
Subjects: implicit knowledge
storytelling
communities of practice
information architecture
apprenticeship
after actions review

description: The final proposal discusses implicit knowledge’s capture and transmission strategy, with efficient processes for capturing, storing, and distributing the implicit knowledge within an organization. Our proposal was selected as one of the three winners of the AECT – NATO 2021 Design and Development Competition. We named our solution “the implicit knowledge retention ecosystem.”
The role of filopodia in the formation of spine synapses
Creators: name: Arstikaitis, Pamela
Publisher: name: University of British Columbia
Year: 2011

description: In the mammalian brain, excitatory (glutamatergic) synapses are mainly located on dendritic spines; bulbous protrusions enriched with F-actin. Dendritic filopodia are thin protrusions thought to be involved in the development of spines. However, limited evidence illustrating the emergence of spines from filopodia has been found. In addition, the molecular machinery required for filopodia induction and transformation to spines is not well understood. Paralemmin-1 has been shown to induce cell expansion and process formation and is concentrated at the plasma membrane, in part through a lipid modification known as palmitoylation. Palmitoylation of paralemmin-1 may also serve as a signal for its delivery to subcellular lipid microdomains to induce changes in cell morphology and membrane dynamics making it a candidate synapse-inducing molecule. Using live imaging as well as loss and gain-of-function approaches, our analysis identifies paralemmin-1 as a regulator of filopodia induction, synapse formation, and spine maturation. We show neuronal activity-driven translocation of paralemmin-1 to membranes induces rapid protrusion expansion, emphasizing the importance of paralemmin-1 in paradigms that control structural changes associated with synaptic plasticity and learning. Finally, we show that knockdown of paralemmin-1 results in loss of filopodia and compromises spine maturation induced by Shank1b, a protein that facilitates rapid transformation of newly formed filopodia to spines. To investigate the role of filopodia in synapse formation, we contrasted the roles of molecules that affect filopodia elaboration and motility, versus those that impact synapse induction and maturation. Expression of the palmitoylated protein motifs found in growth associated protein 43kDa, enhanced filopodia number and motility, but reduced the probability of forming a stable axon-dendrite contact. Conversely, expression of neuroligin-1 (NLG-1), a synapse inducing cell adhesion molecule, resulted in a decrease in filopodia motility, but an increase in the number of stable axonal contacts. Moreover, siRNA knockdown of NLG-1, reduced the number of presynaptic contacts formed. Postsynaptic scaffolding proteins such as Shank1b, a protein that induces the maturation of spine synapses, reduced filopodia number, but increased the stabilization of the initial contact with axons. These results suggest that increased filopodia stability and not density may be the rate-limiting step for synapse formation.
Distributed Denial of Service Attack Detection Using a Machine Learning Approach
Creators: name: Gupta, Animesh
Publisher: name: Graduate Studies
Year: 2018
Subjects: subject: Computer Science

description: A distributed denial of service (DDoS) attack is a type of cyber-attack in which the perpetrator aims to deny the services on a network/server by inundating the traffic on the network/server by superfluous requests which renders it incapable to serve requests from legitimate users. According to Corero Network Security (A DDoS protection and mitigation provider), in Q3 2017, organizations around the world experienced an average of 237 DDoS attack attempts per month, which averages to 8 DDoS attacks every day. This was a 35% increase over Q2 that year and a staggering 91% increase over Q1. According to another research by Incapsula, a DDoS attack costs an average of $40,000 per hour to businesses. There are commercially available software which detect and mitigate a DDoS attack, but the high cost of these software makes them hard to afford for small and mid-scale businesses. The proposed work aims to fill this gap by providing real time open-source robust web application for DDoS attack prediction which can be used by small to mid-scale industries to keep their networks and servers secure from malicious DDoS attacks. A Machine Learning approach is used to employ a window-based technique to predict a DDoS attack in a network with a maximum accuracy of 99.83%, if the recommended combination of feature selection and classification algorithm is chosen. The choice of both feature selection and classification algorithm is left to the user. One of the feature selection algorithms is the novel Weighted Ranked Feature Selection(WRFS) algorithm which performs better than other baseline approaches in terms of accuracy of detection and the overhead to build the model. Once the selection is made, the web application connects to the socket and starts capturing and classifying real-time network traffic. After the capture is stopped, information about attack instances (if any), number of attack packets, confusion matrix is rendered to the client using dynamic charts. The trained model used for classifying real-time packets is optimized and uses only enough attributes from the incoming packet which are necessary to successfully predict the class of that packet with high accuracy.
Recursion in Text and Its Use in Language Generation
Creators: name: McKeown, Kathleen
Publisher: name: Columbia University
Year: 1983
Subjects: Computer science
Language and languages

description: In this paper, I show how textual structure is recursive in nature: that is, the same rhetorical strategies that are available to constructing the text's macro-structure are available for constructing its sub-sequences as well, resulting in a hierarchically structured text. The recursive formalism presented can be used by a generation system to vary the amount of detail it presents for the same discourse goal in different situations.
Electricity Cost and Firm Performance: Evidence from India
Creators: name: Abeberese, Ama Baafra
Publisher: name: Columbia University
Year: 2013
Subjects: Economics

description: Despite the widely acknowledged importance of infrastructure for economic growth, there has been relatively little research on how infrastructure affects the decisions of firms. Using data on Indian manufacturing firms, this paper provides evidence on how electricity prices affect a firm's industry choice and productivity growth. I construct an instrument for electricity price as the interaction between the price of coal paid by power utilities, which is arguably exogenous to firm characteristics, and the initial share of thermal generation in a state's total electricity generation capacity. I find that, in response to an exogenous increase in electricity price, firms reduce their electricity consumption and switch to industries with less electricity-intensive production processes. I also find that firm output, machine intensity and labor productivity decline with an increase in electricity price. In addition to these level effects, I show that firm output and productivity growth rates are negatively affected by high electricity prices. These results suggest that electricity constraints faced by firms may limit a country's growth by leading firms to operate in industries with fewer productivity-enhancing opportunities.
Multi-Layer Utilization Maximal Fairness for Multi-Rate Multimedia Sessions
Creators: name: Mendes, Paulo
name: Schulzrinne, Henning G.
name: Monteiro, Edmundo
Publisher: name: Columbia University
Year: 2001
Subjects: Computer science

description: We present a fairness model, called Multi-Layer Utilization Maximal Fairness (MLUM). The motivation of the MLUM model is to accomplish intra-session and inter-session fairness in the presence of multi-rate (multi-layer) multimedia sessions, distributing bandwidth between multicast trees of different sessions, considering the number of receivers in each session, and improving bandwidth efficiency. To accomplish this goal, the model is divided in three components: a fairness definition,a policy and a protocol. The MLUM definition guarantees fairness between receivers in a session and fairness between different sessions, considering the number of receivers in each session. The MLUM policy implements the MLUM definition in multicast aware border routers of Autonomous Systems (AS). It's functionality is divided in the control plane and the data plane. In the control plane, sessions fair rates are estimated based upon the MLUM fairness definition. In the data plane, a queueing discipline will fairly distribute bandwidth between sessions, considering their fair rates. The MLUM protocol allows the exchange of control information (sessions number of receivers and fair rates) between MLUM policy routers in order to accomplish a fair distribution of bandwidth between concurrent sessions. This paper aim to present the MLUM fairness definition, to describe the MLUM fairness policy control and data plane functionality and to evaluate how the policy data plane can fairly distribute bandwidth. We present some simulations that evaluate the performance of the MLUM policy data plane in different scenarios and that compare its performance to other queueing disciplines. We also briefly describe the MLUM protocol, due to its close relation with of the MLUM policy functionality.
American coot collective on-water dynamics
Creators: name: Trenchard, Hugh
Publisher: name: arXiv
Year: 2012
Subjects: subject: Adaptation and Self-Organizing Systems (nlin.AO)
subject: Biological Physics (physics.bio-ph)
subject: FOS: Physical sciences

description: American coot (Fulica americana) flocks exhibit water surface (two-dimensional) collective dynamics that oscillate between two primary phases: a disordered phase of low density and non-uniform coot body orientations; a synchronized phase characterized by high density, uniform body orientations and speed. For this small-scale study, data was obtained for flocks of 10 to ~250 members for these phases. Approximate durations of phase occurrences were recorded for different flock sizes and for both relatively calm and severe weather conditions. Results indicate that for timed durations of up to ~ 2 hours, small flocks (10 coots) exhibit a comparatively high disordered/synchronized phase ratio (PR) in relatively warm and well-sheltered conditions (substantially >1); large flocks (~100 or more) generally exhibit a PR near 1, while large flocks spend comparatively more time in a disordered phase in relatively calm conditions (PR somewhat >1), and spend more time in a synchronized phase during severe conditions (PR <1). Data suggests a correlation between flock size and PR; and weather conditions and PR, whereby coupling principles driving on-water collective behavior include energy-savings and thermoregulation. Secondary phases occur, including expanding circle and sequential short distance flight, near-single-file lines, convex and concave arcs, among others.
description: 24 pages, 14 figure, 2 tables; Nonlinear Dynamics, Psychology, and Life Sciences IN PRESS
Phonon-mediated coupling between quantum dots through an off-resonant microcavity
Creators: name: Majumdar, Arka
name: Bajcsy, Michal
name: Rundquist, Armand
name: Kim, Erik
name: Vuckovic, Jelena
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We present experimental results showing phonon-mediated coupling between two quantum dots embedded inside a photonic crystal microcavity. With only one of the dots being spectrally close to the cavity, we observe both frequency up-conversion and down-conversion of the pump light via a $\sim1.2$ THz phonon. We demonstrate this process for both weak and strong regimes of dot-cavity coupling, and provide a simple theoretical model explaining our observations.
Amplification of non-Markovian decay due to bound state absorption into continuum
Creators: name: Garmon, Savannah
name: Petrosky, Tomio
name: Simine, Lena
name: Segal, Dvira
Publisher: name: arXiv
Year: 2012
Subjects: subject: Quantum Physics (quant-ph)
subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: It is known that quantum systems yield non-exponential (power law) decay on long time scales, associated with continuum threshold effects contributing to the survival probability for a prepared initial state. For an open quantum system consisting of a discrete state coupled to continuum, we study the case in which a discrete bound state of the full Hamiltonian approaches the energy continuum as the system parameters are varied. We find in this case that at least two regions exist yielding qualitatively different power law decay behaviors; we term these the long time `near zone' and long time `far zone.' In the near zone the survival probability falls off according to a $t^{-1}$ power law, and in the far zone it falls off as $t^{-3}$. We show that the timescale $T_Q$ separating these two regions is inversely related to the gap between the discrete bound state energy and the continuum threshold. In the case that the bound state is absorbed into the continuum and vanishes, then the time scale $T_Q$ diverges and the survival probability follows the $t^{-1}$ power law even on asymptotic scales. Conversely, one could study the case of an anti-bound state approaching the threshold before being ejected from the continuum to form a bound state. Again the $t^{-1}$ power law dominates precisely at the point of ejection.
description: 15 pages, 9 figures
Isotropic extensions of the vacuum solutions in general relativity
Creators: name: Molina, C.
name: Martín-Moruno, Prado
name: González-Díaz, Pedro F.
Publisher: name: arXiv
Year: 2011
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this work, we obtain isotropic extensions of the usual spherically symmetric vacuum geometries in general relativity. Exact and perturbative solutions are derived. The classes of geometries obtained include black holes in compact and noncompact universes, wormholes in the interior region of cosmological horizons, and anti-de Sitter geometries with excess/deficit solid angle. The tools developed here are applicable in more general contexts.
description: 12 pages, 6 figures. Version to be published in Physical Review D
Role of autophagy in porcine spermatogonia
Creators: name: Valenzuela-Leon, Paula
Publisher: name: Graduate Studies
Year: 2018
Subjects: subject: spermatogonial stem cells
subject: autophagy
subject: phthalates
subject: germ cells
subject: Testis
subject: Biology--Cell
subject: Veterinary Science

description: Spermatogonial stem cells (SSCs) sustain spermatogenesis through tightly controlled self renewal and differentiation processes. A long-term culture for porcine spermatogonia has not been established yet. To thrive in culture conditions, a cell requires to adapt to the environment. One of the tools that cells have developed to manage stress is autophagy. Autophagy is induced by cellular stress, which results in lysosomal degradation and recycling of the degradation product to generate energy for cellular homeostasis. Therefore, the main objective of this thesis is to elucidate the role autophagy plays in porcine germ cells. Initially, we identified that autophagy is active at basal levels in situ; upon isolation from the testis, the levels of autophagy increase significantly. Autophagic levels were then analyzed in testis tissue formed de novo. After 6 weeks, autophagic levels were at basal levels, which indicated that re-introduction to the microenvironment decreases germ cell stress. Considering that in vitro conditions upregulate autophagy, germ cells were cultured in two different media, and found that levels of autophagy are lower in nutrient rich medium. Levels of reactive oxygen species (ROS) were measured and were found to decrease germ cell viability; upon autophagy stimulation, viability increased. Conversely, upon autophagic inhibition, ROS increased, and germ cell viability decreased. These results suggested that autophagy is a cytoprotective mechanism for germ cells and can be used as an indicator for stress in vitro. To investigate the role of autophagy in germ cells in the presence of toxicants, we evaluated the levels of autophagy in primate testis tissue xenografted to mice exposed to phthalates. It was found that germ cells exposed to this toxicant had higher levels of autophagy than the controls. To evaluate the effects of toxicants in vitro, germ cells were treated with another phthalate, which caused germ cell viability to decrease. Upon autophagy induction, germ cell viability increased accordingly. These results show that autophagy is a cell protective mechanism for germ cells exposed to a toxicant. Overall, the work in this thesis identifies autophagy as an essential process for germ cell homeostasis.
Vertical integration, exclusive dealing, and ex post cartelization
Creators: name: Chen, Yongmin
name: Riordan, Michael H.
Publisher: name: Columbia University
Year: 2003
Subjects: Economics
Business

description: A vertically integrated firm has the incentive and ability to use exclusive contracts to foreclose an equally efficient upstream competitor and to effect a cartelization of the downstream industry. Its ability to do so may be limited when downstream firms are heterogeneous and supply contracts are not contingent on uncertain market conditions. The extent of cartelization depends on the degree of downstream market concentration and on the degree to which downstream competition is localized.
Multi-Robot Organisms: State of the Art
Creators: name: Kernbach, Serge
name: Scholz, Oliver
name: Harada, Kanako
name: Popesku, Sergej
name: Liedke, Jens
name: Raja, Humza
name: Liu, Wenguo
name: Caparrelli, Fabio
name: Jemai, Jaouhar
name: Havlik, Jiri
name: Meister, Eugen
name: Levi, Paul
Publisher: name: arXiv
Year: 2011
Subjects: subject: Robotics (cs.RO)
subject: Neural and Evolutionary Computing (cs.NE)
subject: Systems and Control (eess.SY)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: This paper represents the state of the art development on the field of artificial multi-robot organisms. It briefly considers mechatronic development, sensor and computational equipment, software framework and introduces one of the Grand Challenges for swarm and reconfigurable robotics.
Perceived Quality of Packet Audio under Bursty Losses
Creators: name: Jiang, Wenyu
name: Schulzrinne, Henning G.
Publisher: name: Columbia University
Year: 2001
Subjects: Computer science

description: We examine the impact of bursty losses on the perceived quality of packet audio, and investigate the effectiveness various approaches to improve the quality. Because the degree of burstiness depends on the packet interval, we first derive a formula to re-compute the conditional loss probability of a Gilbert loss model when the packet interval changes. We find that FEC works better at a larger packet interval under bursty losses. In our MOS-based (Mean Opinion Score) listening tests, we did not find a consistent trend in MOS when burstiness increases if FEC is not used. That is, In some occasions MOS can be higher with a higher burstiness. With FEC, our results confirms the analytical results that quality is better with a larger packet interval, but T should not be too large to avoid severe penalty on a single packet loss. We also find that low bit-rate redundancy generally produces lower perceived quality than FEC, if the main codec is already a low bit-rate codec. Finally, we compare our MOS results with objective quality estimation algorithms (PESQ, PSQM/PSQM+, MNB and EMBSD). We find PESQ has the best linear correlation with MOS, but the value is still less than commonly cited, implying they cannot be used in isolation to predict MOS.
Minorities and storable votes
Creators: name: Casella, Alessandra M.
name: Palfrey, Thomas R.
name: Riezman, Raymond
Publisher: name: Columbia University
Year: 2005
Subjects: subject: Political science
subject: FOS: Political science

description: The paper studies a simple voting system that has the potential to increase the power of minorities without sacrificing aggregate efficiency. Storable votes grant each voter a stock of votes to spend as desired over a series of binary decisions. By accumulating votes on issues that it deems most important, the minority can win occasionally. But because the majority typically can outvote it, the minority wins only if its strength of preference is high and the majority's strength of preference is low. The result is that with storable votes, aggregate efficiency either falls little or in fact rises. The theoretical predictions of our model are confirmed by a series of experiments: the frequency of minority victories, the relative payoff of the minority versus the majority, and the aggregate payoffs all match the theory.
Monitoring of skeletal muscle ischemia using near infrared spectroscopy
Creators: name: Shadgan, Babak
Publisher: name: University of British Columbia
Year: 2011

description: Early diagnosis of acute limb muscle ischemia (LMI) is essential in order to avoid serious, irreversible local and systemic complications resulting in loss of the limb or even death. To date, techniques for monitoring LMI are limited by lack of a feasible and reliable monitoring method. Purpose: The main purposes of this thesis were to examine the feasibility and convergent validity of conventional and wireless near infrared spectroscopy (NIRS) for continuous monitoring of skeletal muscle oxygenation and hemodynamics during transient and long-term LMI and to investigate the predictive value of NIRS-derived data for evaluation of limb muscle oxidative changes during tourniquet-induced LMI. Methods: Following a complete literature review (Chapter 2), forearm muscle oxygenation and hemodynamics were studied in 10 healthy subjects using wireless NIRS instrumentation during isometric muscle contraction and tourniquet-induced LMI (Chapter 3). In Chapter 4, changes in NIRS-derived leg muscle oxygenation and hemodynamics, in conjunction with muscle oxidative changes, following tourniquet-induced LMI were investigated in 17 patients undergoing surgery for ankle fracture. In Chapter 5, the effect of electromagnetic interference (EMI) from 3 commonly used surgical instruments on NIRS signals were investigated using a mathematical method of signal analysis. Results: Chapter 2: No validated monitoring method for early detection of acute LMI was revealed. Chapters 3-4: Wireless and conventional NIRS data were consistent with muscle ischemia and reperfusion. Chapter 4: An average of 43.2±14.6 minutes of tourniquet-induced ischemia led to a 172.3±145.7% (range: 10.7-363.3%) increase in muscle protein oxidation (P<0.0005). Changes in NIRS-derived muscle oxygenated and total-hemoglobin were both negatively correlated, while reoxygenation-rate was positively correlated (P<0.05) to muscle protein oxidation. Chapter 5: EMI from 3 OR instruments was found to have no effect on NIRS signals (P<0.01). Conclusions: NIRS is a feasible method for continuous monitoring of limb muscle oxygenation and hemodynamics during transient and long-term tourniquet-induced ischemia. Tourniquet-induced LMI of 21-74 minutes leads to oxidative muscle damage. A significant negative association between the extent of tourniquet-induced oxidative damage and changes in NIRS-derived local muscle oxygenated blood volume was found. EMI of commonly used orthopedic surgical instruments does not affect NIRS signals.