4,335 research outputs found
Southway Park subdivision
No full textThis is a plat of Southway subdivision for the B.M. Johnson Real Estate Investment and Development Company to the west of Church Street (10th Avenue Drive today), in J.K. Singletary's subdivision in Bradenton. Benton M. Johnson was a prominent real estate agent during the Florida land boom of the 1920s. Johnson came to Bradenton in 1924, and the company was dissolved in 1928. He appears to have subsequently left the area
Better management of Sonchus oleraceus L. (common sowthistle) based on the weed's ecology
No full textSonchus oleraceus (common sowthistle) was recently identified in a survey as the most common weed of the sub-tropical grain region of Australia. In addition, the weed was identified as having a moderate risk of developing resistance to glyphosate, while populations already have resistance to Group B herbicides. Hence, S. oleraceus is a weed that not only requires better management but also strategies that reduce the risk of resistance to herbicides. Weed ecology was investigated closely to assist devising management strategies. In particular, seed germination, emergence, persistence, dormancy, and production, as well as plant morphology, competition in crop, and response to tillage were studied. The characteristics that are important for better management of this weed are the weed's prolific seed production, the ability of this seed to germinate all year round and the ability of the weed to grow and produce seed across diverse environments. An integrated and sustainable approach to management of S. oleraceus should include growing competitive crops, strategic tillage, follow up herbicide applications, and rotation of herbicide groups especially for Group B and M herbicides
A conditional full frontier approach for investigating the Averch-Johnson effect
No full textThis paper applies a probabilistic approach in order to develop conditional and unconditional Data Envelopment Analysis (DEA) models for the measurement of sectors’ input oriented technical and scale efficiency levels for a sample of 23 Greek manufacturing sectors. In order to capture the Averch and Johnson effect (A-J effect), we measure sectors’ efficiency levels conditioned on the number of companies competing within the sectors. Particularly, various DEA models have been applied alongside with bootstrap techniques in order to determine the effect of competition conditions on sectors’ inefficiency levels. Additionally, this study illustrates how the recent developments in efficiency analysis and statistical inference can be applied when evaluating the effect of regulations in an industry. The results reveal that sectors with fewer numbers of companies appear to have greater scale and technical inefficiencies due to the existence of the A-J effect.Averch-Johnson effect; Industry regulations; Manufacturing sectors; Nonparametric analysis
Optimizing quantum error correction for superconducting qubit processors
No full textThe theory of quantum mechanics describes many phenomena that may initially seem to be counter-intuitive and, in some cases, impossible, given the understanding of classical mechanics that most of us are more intimately familiar with. Following its initial introduction, there was a great deal of debate among scientists regarding the predictions made by this theory. The strange nature of quantum mechanics has led to many memorable quotes and the use of “spooky” to describe some of these predictions. Since its initial introduction, quantum mechanics has been rigorously tested and has proven to be quite a successful theory. Quantum mechanics has found many different applications and has led to the existence of devices and technologies we use daily. Another potential application of quantum mechanics is quantum computation, which Richard Feynman first put forward as an idea in 1982. Quantum computers have the potential to solve specific problems that can be infeasible for even the most powerful (classical) supercomputers and have potential applications in many different areas, such as quantum chemistry, cryptography, and optimization. However, performing a quantum computation is challenging and requires overcoming the inherent fragility of quantum systems. Storing information in a quantum system requires it to be well isolated from the environment to avoid any unwanted interactions that can corrupt the stored data. Unfortunately, at the same time, we need the ability to control this system, make it interact with other such systems, and ultimately measure it for us to perform an actual computation. This is a universal issue and all of the systems we have so far developed to be used as quantum bits (qubits) have been plagued by noise. Each operation applied to the qubit or even the act of leaving the qubit idling for some time generally leads to an error with a non-negligible probability. The impact of this noise has so far prevented quantum computers from performing any practical computation. While substantial efforts have been made to reduce these physical error rates over the past several years, we are still far from the universal fault-tolerant quantum computers we ultimately strive for. Fortunately, quantum error correction can help us reach the low error rates necessary for quantum computers to realize their potential applications in the future. This can be achieved by storing the quantum information in a logical qubit instead of a noisy physical one. When using a stabilizer code, which will be the focus of this dissertation, this logical information is distributed over many (noisy) physical qubits, referred to as data qubits. Another set of qubits, the so-called ancilla qubits, is used to perform indirect parity measurements, which do not destroy the stored information but give some information about whether an error has occurred. We then try to interpret this information to identify what errors have happened and correct them, which is done by a classical algorithm referred to as the decoder. Increasing the number of physical qubits used to encode the logical qubits allows more physical errors to be detected and corrected. The number of correctable errors is captured by the distance of the code, defined as the minimum number of physical single-qubit errors that constitute a logical error. One of the critical properties of error correction is the ability to reduce the logical error rate by increasing the code distance, which requires the physical error rates to be below some threshold value. The valiant experimental effort over the years has led to several recent experiments that implement various error-correcting codes and demonstrate the reduction of the error rates promised by error correction. In particular, these experiments (and the experiments leading up to them) identified several noise sources that had not been explored in sufficient detail and could significantly impact the logical performance of the code. In this dissertation, we explore the impact of the noise encountered in transmon-qubit devices on the performance of error-correcting codes, namely the surface code. Transmon qubits are, in practice, multi-level systems, and only the lowest two energy levels are used for computation. Unfortunately, they are also weakly anharmonic, leading to the applied operations having some probability of exciting the qubit outside of this computational subspace, referred to as a leakage error. We explore the impact of leakage in both simulations and experiments and develop schemes to mitigate it. We also consider other approaches to improve the logical performance or to reduce unwanted interactions. In Chapter 2, we develop a realistic model of leakage induced by the two-qubit gates between flux-tunable transmon qubits. We show that leaked qubits effectively spread errors on their neighboring qubits, which are then detected by the parity measurements. We show that a Hidden Markov model can detect the increased error rate due to leakage. This enables us to post-select out runs during which any qubit has leaked to restore the code performance. Unfortunately, post-selection is ultimately not scalable. Instead, it is desirable to have operations that return leaked qubits to the computational subspace. These operations are called leakage-reduction units and convert leakage into a regular error. In Chapter 3, we propose a leakage-reduction scheme, which does not require any overhead in the time needed to perform the parity measurements or an overhead in the quantum hardware. For data qubits, we propose an operation that transfers the leakage to a dedicated readout resonator, where it can quickly decay. This operation is designed to not disturb the computational states, allowing it to be applied unconditionally. For the ancilla qubit, we use the fact that measurements can determine if a qubit is in the leaked state. We then apply a conditional operation to return the qubit to the computational subspace whenever it is measured to be leaked. Using detailed density-matrix simulation, we show that this scheme can be easily implemented to remove qubit leakage from the system, mitigating its impact on the logical performance of the code. In Chapter 4, we realize the data-qubit leakage reduction unit in an experiment and show it can also be used to remove ancilla-qubit leakage, removing the need for fast conditional operations and readout that distinguishes the leaked states. We show that these operations can remove most of the leaked population in about a hundred nanoseconds while having a negligible impact on the computational subspace. We also demonstrate that these operations decrease the number of observed errors by a two-qubit parity check, showing that the effect of leakage can be mitigated. Chapter 5 considers an architecture employing two types of superconducting qubits, the transmon qubit and the fluxonium qubit. These qubits have very different frequencies, making it unclear whether these qubits can even interact with each other in the first place. We show that the interactions with the higher-excited states can be utilized to perform operations between them, and we propose two types of gates. In practice, qubit frequencies are targeted with only a certain precision in fabrication. In certain cases, this can lead to unwanted interaction between qubits that increase the physical error rates, referred to as frequency collisions. We show that the large detuning between these qubits reduces the frequency of frequency collision, thereby increasing the expected fabrication yield. In Chapter 6, we realize a distance-two surface code experiment and perform repeated parity measurements to detect and post-select errors, given that it’s impossible to correct them when using such a small code. We implement a suite of logical operations for this code, including initialization, measurement, and several single-qubit gates. In the context of error detection, a logical operation is said to be fault-tolerant if the errors produced by each operation are detectable. We show that fault-tolerant variants of operations perform better than non-fault-tolerant ones. We also characterize the impact of various noise sources on the code performance. In Chapter 7, we look at another small-distance code, in this case, the distance-seven repetition code. We show that increasing the distance weakly suppresses the logical error rate of the code. We investigate the limiting factors behind the observed logical performance by analyzing the correlation between the observed parity measurements and performing simulations using noise models parameterized by the measured physical error rates. Chapter 8 considers a decoder that can perform the error inference more accurately. In particular, we implement a neural network decoder and investigate how it performs on experimental data from surface code experiments. We show that the accuracy of this decoder approaches what can be achieved by an optimal and computationally inefficient tensor network decoder. Transmon measurement produces analog outcomes. These are then typically converted to binary ones, leading to some information loss. We show how a neural network can also use this analog information to improve the achieved logical performance further. We have investigated the impact of non-conventional errors in simulation and in several experiments, demonstrating the importance of characterizing and mitigating these errors. We expect the methods introduced in this dissertation to lead to lower logical error rates. In the short term, this can aid in demonstrations of the usefulness of error correction. In the long term, addressing such errors is important to ensure the ability to suppress logical error rates to sufficiently low levels. We finish this dissertation with a brief conclusion of each chapter. We also outline several potential challenges that can impact future error-correction experiments, namely how to reduce the larger qubit overhead needed for fault-tolerant computation and several error sources that might become a limiting factor for future error-correction experiments.QCD/Terhal Grou
Teacher education and development
No full textpublished_or_final_versionAcknowledgements vForeword Cooke, Brian Cooke, Brian viiIntroduction Tsui, Amy B.M. Tsui, Amy B.M. Johnson, Ivor Johnson, Ivor ixNotes on the contributors 174Introduction of beginning teachers: a teacher education perspective Pang, K.C. Pang, K.C. Cooke, Brian Cooke, Brian 1Challenges in education and continuous teacher development Tsui, Amy B.M. Tsui, Amy B.M. 13Student suicide and home-school co-operation Hui, Eadaoin K.P. Hui, Eadaoin K.P. 29School-based management, school effectiveness and the school management initiative: different? how different? Wong, Andrew K.C. Wong, Andrew K.C. 45Through a glass - darkly! The computer's late entry into Hong Kong's teaching profession Day, Jeffrey Day, Jeffrey 59ECR5 and primary education in Hong Kong Cheung, K.W. Cheng, K.W. 71Kindergarten education: cinderella of the Hong Kong education system Opper, Sylvia Opper, Sylvia 80Special education and the teaching profession Crawford, Nick Crawford, Nick Yung, K.K. Yung, K.K. 90Teacher education, professional development and resources: ECR5 and considerations for the field of physical and sport education Speak, M.A. Speak, M.A. 104Developing teacher professionalism - but what kind of professionalism? Lee, W.O. Lee, W.O. 118The cat, pigeons, hawks, and headless chicks: ECR5 and aspects of teacher professionalism Sze, W.T. Sze, W.T. 134A matter of professional legitimacy: ECR5 recommendations and confusions about the general teaching council Cheng, K.M. Cheng, K.M. 148A response to ECR5 16
Classification of the Johnson Space Center stratospheric dust collection
No full textA review of 291 catalogued particles on the bases of particle size, shape, bulk chemistry, and texture is used to establish a reliable taxonomy. Extraterrestrial materials occur in three defined categories: spheres, aggregates and fragments. Approximately 76% of aggregates are of probable extraterrestrial origin, whereas spheres contain the smallest amount of extraterrestrial material (approx 43%). -B.M
Molecular Dynamics Simulation Of Solvation Dynamics In Methanol-water Mixtures
No full textThe solvation dynamics following charge-transfer electronic excitation of diatomic solutes immersed in methanol-water mixtures is investigated through molecular dynamics simulations. The solvation response functions associated with an instantaneous reversal of the solute's dipole moment for two different solute sizes in mixtures with methanol mole fractions, xm = 0.2, 0.5, and 0.8, are calculated and compared to the corresponding ones in the pure liquids. The solvation response of the mixtures is separated into methanol and water contributions in order to elucidate the role played by each molecular species on the solvation dynamics. We find significantly different responses for the two solutes and relate them to the fact that the solute with the smaller site diameters is a much better hydrogen (H)-bond acceptor than the larger diameter solute. For the small solute in methanol and in the mixed solvents, we have also calculated H-bond response functions, which measure the rate of solute-solvent H-bond formation after the solute's excitation and find that, at longer times, the solvation and H-bond formation response functions decay at similar rates. The implications of this finding for solvation dynamics of H-bonding solutes in H-bonding solvents are discussed and related to recent experimental results for such systems. © 1996 American Chemical Society.100461825818268Heitele, H., (1993) Angew. Chem., Int. Ed. Engl., 32, p. 359Hynes, J.T., (1993) Ultrafast Dynamics of Chemical Systems, , Simon, J. D., Ed.Kluwer: Dordrecht, Chapter 13Rossky, P.J., Simon, J.D., (1994) Nature (London), 370, p. 263Refs 5-8 contain reviews of various aspects of solvation dynamicsMaroncelli, M., (1993) J. Mol. 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Monitoring biodegradation capacity of organic pollutants in the environment
No full textMicro-organismen zijn in staat om organische verbindingen om te zetten in minder schadelijke stoffen en spelen daarom een belangrijke rol bij het opruimen van milieuvervuiling. Voor beleidsmakers, landgebruikers en landeigenaren is het belangrijk dat er bij milieuverontreiniging goed toezicht wordt gehouden op de biologische afbraakprocessen en dat deze goed worden beheerst. Aangezien microbiële activiteit in het milieu wordt beïnvloed door diverse fysische, geochemische en biologische factoren, is nauwkeurige kennis van het afbraakproces hierbij noodzakelijk. In dit promotieonderzoek wordt de relatie tussen geochemische condities en de biologische afbraakcapaciteit van micro-organismen in het milieu beschreven, inclusief methoden om de activiteit en metabole functies van deze micro-organismen in het milieu te mete
Building Simplification using Offset Curves obtained from the Straight Skeleton
No full textWe propose a conceptual simple algorithm based on offset curves obtained from the straight skeleton to simplify building outlines. We present initial results with some real world data and show that the approach can be used to simplify and amalgamate building outlines. We discuss how this approach can be extended to generate smooth transitions for continuous zoom.Accepted Author ManuscriptOLD Department of GIS Technolog
Distinct promoters mediate constitutive and inducible Bcl-X-L expression in malignant lymphocytes
No full textBcl-X-L is a Bcl-2-related survival protein that is essential for normal development. Bcl-X-L expression is rapidly induced by a wide range of survival signals and many cancer cells constitutively express high levels. The Bcl-X gene has a complex organization with multiple promoters giving rise to RNAs with alternate 5' non-codingexons. Here we have investigated the mechanisms that control basal and induced expression of Bcl-X-L in B-lymphoma cells. Antisense experiments demonstrated that Bcl-X-L was essential for survival of Akata6 B-lymphoma cells. The levels of RNAs containing the IB Bcl-X non-coding exon, derived from the distal 1B promoter, correlated with basal expression of Bcl-X-L in primary malignant B cells and this promoter was highly active in B-cell lines. The activity of this promoter was largely dependent on a single Ets binding site and Ets family proteins were bound at this promoter in intact cells. CD40 ligand (CD40L)-induced cell survival was associated with increased Bcl-X-L expression and accumulation of exon IA-containing RNAs, derived from the proximal 1A promoter. Nuclear factor-kappaB (NF-kappa B) inhibition prevented induction of Bcl-X-L protein and exon IA-containingRNAs by CD40L. Therefore, the distal Bcl-X 1B promoter plays a critical role in driving constitutive expression-mediated via Ets family proteins in malignant B cells, whereas NF-kappa B plays a central role in the induction of Bcl-X-L in response to CD40 signalling via the proximal 1A promoter
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