An adaptive corridor-wide signal timing optimization methodology for traffic network with multiple highway-rail grade crossings.

DOT National Transportation Integrated Search

2016-06-01

Highway-rail grade crossings (HRGCs) and the intersections in their proximity are areas where potential problems in terms of safety and efficiency often arise if only simple or outdated treatments, such as normal signal timing or passive railroad war...

Plastics in the Ocean: More Than a Litter Problem.

ERIC Educational Resources Information Center

Center for Environmental Education, Washington, DC.

Environmental impacts arise from entanglement of marine animals in plastic debris and from ingestion of plastics by marine organisms. Plastic debris can cause potential threats to humans when divers become entangled or vessels become fouled in debris. The depletion of fishery resources, vessel damage, and aesthetic degradation resulting in lost…

Unidimensional Interpretations for Multidimensional Test Items

ERIC Educational Resources Information Center

Kahraman, Nilufer

2013-01-01

This article considers potential problems that can arise in estimating a unidimensional item response theory (IRT) model when some test items are multidimensional (i.e., show a complex factorial structure). More specifically, this study examines (1) the consequences of model misfit on IRT item parameter estimates due to unintended minor item-level…

Triangles with Integer Dimensions

ERIC Educational Resources Information Center

Gilbertson, Nicholas J.; Rogers, Kimberly Cervello

2016-01-01

Interesting and engaging mathematics problems can come from anywhere. Sometimes great problems arise from interesting contexts. At other times, interesting problems arise from asking "what if" questions while appreciating the structure and beauty of mathematics. The intriguing problem described in this article resulted from the second…

New Old Inflation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dvali, Gia

2003-10-03

We propose a new class of inflationary solutions to the standard cosmological problems (horizon, flatness, monopole,...), based on a modification of old inflation. These models do not require a potential which satisfies the normal inflationary slow-roll conditions. Our universe arises from a single tunneling event as the inflaton leaves the false vacuum. Subsequent dynamics (arising from either the oscillations of the inflaton field or thermal effects) keep a second field trapped in a false minimum, resulting in an evanescent period of inflation (with roughly 50 e-foldings) inside the bubble. This easily allows the bubble to grow sufficiently large to containmore » our present horizon volume. Reheating is accomplished when the inflaton driving the last stage of inflation rolls down to the true vacuum, and adiabatic density perturbations arise from moduli-dependent Yukawa couplings of the inflaton to matter fields. Our scenario has several robust predictions, including virtual absence of gravity waves, a possible absence of tilt in scalar perturbations, and a higher degree of non-Gaussianity than other models. It also naturally incorporates a solution to the cosmological moduli problem.« less

Implementing Coteaching and Cogenerative Dialoguing in Urban Science Education

ERIC Educational Resources Information Center

Tobin, Kenneth; Roth, Wolff-Michael

2005-01-01

Over the past 7 years the authors have been involved in the development of a new model for the education of science teachers that has the potential to address teacher education in challenging urban settings characterized by problems such as teacher turnover and retention, low job satisfaction, and contradictions arising from cultural and ethnic…

Carbon fiber study

NASA Technical Reports Server (NTRS)

1977-01-01

A coordinated Federal Government action plan for dealing with the potential problems arising from the increasing use of graphite fiber reinforced composite materials in both military and civilian applications is presented. The required dissemination of declassified information and an outline of government actions to minimize the social and economic consequences of proliferated composite materials applications were included.

American college of gastroenterology monograph on the management of irritable bowel syndrome.

PubMed

Camilleri, Michael

2015-04-01

This editorial reviews a recently published guideline on management of irritable bowel syndrome. The guideline illustrates problems arising from the quality of clinical trials used in systematic reviews and the potential impact of the inherent weaknesses of those trials on rating the strength of evidence and the resulting recommendations.

The Problems of Diagnosis and Remediation of Dyscalculia.

ERIC Educational Resources Information Center

Price, Nigel; Youe, Simon

2000-01-01

Focuses on the problems of diagnosis and remediation of dyscalculia. Explores whether there is justification for believing that specific difficulty with mathematics arises jointly with a specific language problem, or whether a specific difficulty with mathematics can arise independently of problems with language. Uses a case study to illuminate…

'Health should not have to be a problem': talking health and accountability in an internet forum on veganism.

PubMed

Sneijder, Petra; te Molder, Hedwig F M

2004-07-01

This article draws upon insights from discursive psychology to examine how participants in an Internet forum on veganism orient to the relationship between food choice, health and accountability. First, we explore the ways in which participants ascribe responsibility for health problems like vitamin deficiency to individual recipients. By suggesting individual practices as a cause for problems, speakers undermine the notion that problems arise through veganism as a matter of principle. Second, we show how participants construct solutions to individual health problems as involving mundane and simple actions. Both discursive procedures enable speakers to resist negative assumptions about the potentially complicated nature of veganism in relation to health protection.

Non linear predictive control of a LEGO mobile robot

NASA Astrophysics Data System (ADS)

Merabti, H.; Bouchemal, B.; Belarbi, K.; Boucherma, D.; Amouri, A.

2014-10-01

Metaheuristics are general purpose heuristics which have shown a great potential for the solution of difficult optimization problems. In this work, we apply the meta heuristic, namely particle swarm optimization, PSO, for the solution of the optimization problem arising in NLMPC. This algorithm is easy to code and may be considered as alternatives for the more classical solution procedures. The PSO- NLMPC is applied to control a mobile robot for the tracking trajectory and obstacles avoidance. Experimental results show the strength of this approach.

A fast isogeometric BEM for the three dimensional Laplace- and Helmholtz problems

NASA Astrophysics Data System (ADS)

Dölz, Jürgen; Harbrecht, Helmut; Kurz, Stefan; Schöps, Sebastian; Wolf, Felix

2018-03-01

We present an indirect higher order boundary element method utilising NURBS mappings for exact geometry representation and an interpolation-based fast multipole method for compression and reduction of computational complexity, to counteract the problems arising due to the dense matrices produced by boundary element methods. By solving Laplace and Helmholtz problems via a single layer approach we show, through a series of numerical examples suitable for easy comparison with other numerical schemes, that one can indeed achieve extremely high rates of convergence of the pointwise potential through the utilisation of higher order B-spline-based ansatz functions.

Avoiding potential problems when selling accounts receivable.

PubMed

Ayers, D H; Kincaid, T J

1996-05-01

Accounts receivable financing is a potential tool for managing a provider organization's working capital needs. But before entering into a financing agreement, organizations need to consider and take steps to avoid serious problems that can arise from participation in an accounts receivable financing program. For example, the purchaser may cease purchasing the receivables, leaving the organization without funding needed for operations. Or, the financing program may be inordinately complex and unnecessarily costly to the organization. Sometimes the organization itself may fail to comply with the terms of the agreement under which the accounts receivable were sold, thus necessitating that restitution be made to the purchaser or provoking charges of fraud. These potential problems should be addressed as early as possible--before an organization enters into an accounts receivable financing program--in order to minimize time, effort, and expanse and maximize the benefits of the financing agreement.

Guidance and control strategies for aerospace vehicles

NASA Technical Reports Server (NTRS)

Naidu, Desineni S.; Hibey, Joseph L.

1989-01-01

The optimal control problem arising in coplanar orbital transfer employing aeroassist technology and the fuel-optimal control problem arising in orbital transfer vehicles employing aeroassist technology are addressed.

Blow-up behavior of ground states for a nonlinear Schrödinger system with attractive and repulsive interactions

NASA Astrophysics Data System (ADS)

Guo, Yujin; Zeng, Xiaoyu; Zhou, Huan-Song

2018-01-01

We consider a nonlinear Schrödinger system arising in a two-component Bose-Einstein condensate (BEC) with attractive intraspecies interactions and repulsive interspecies interactions in R2. We get ground states of this system by solving a constrained minimization problem. For some kinds of trapping potentials, we prove that the minimization problem has a minimizer if and only if the attractive interaction strength ai (i = 1 , 2) of each component of the BEC system is strictly less than a threshold a*. Furthermore, as (a1 ,a2) ↗ (a* ,a*), the asymptotical behavior for the minimizers of the minimization problem is discussed. Our results show that each component of the BEC system concentrates at a global minimum of the associated trapping potential.

SSME turbopump technology improvements via transient rotordynamic analysis

NASA Technical Reports Server (NTRS)

Childs, D. W.

1975-01-01

The rotordynamic behavior of the high pressure oxygen turbopump and high pressure fuel pump was analyzed for the Space Shuttle Main Engine. The identification of potential rotordynamic problem areas which might arise during operation of these units prior to their testing was accomplished. Alternative procedures for correcting potential rotordynamic problems should they occur were investigated. An adequate analytic and physical understanding of the turbopump rotordynamics was developed to improve the probability of a correct diagnosis of rotordynamic problems from test data. Transient rotordynamic models were developed for both turbopumps. The transient models model the hydrodynamic forces of the turbopump seals. A linear stability analysis was performed for the turbopump rotordynamics models, which included gyroscopic effects, seal forces, speed-dependent bearing characteristics, and internal rotor damping. Results are presented and discussed.

Applying Graph Theory to Problems in Air Traffic Management

NASA Technical Reports Server (NTRS)

Farrahi, Amir Hossein; Goldbert, Alan; Bagasol, Leonard Neil; Jung, Jaewoo

2017-01-01

Graph theory is used to investigate three different problems arising in air traffic management. First, using a polynomial reduction from a graph partitioning problem, it is shown that both the airspace sectorization problem and its incremental counterpart, the sector combination problem are NP-hard, in general, under several simple workload models. Second, using a polynomial time reduction from maximum independent set in graphs, it is shown that for any fixed e, the problem of finding a solution to the minimum delay scheduling problem in traffic flow management that is guaranteed to be within n1-e of the optimal, where n is the number of aircraft in the problem instance, is NP-hard. Finally, a problem arising in precision arrival scheduling is formulated and solved using graph reachability. These results demonstrate that graph theory provides a powerful framework for modeling, reasoning about, and devising algorithmic solutions to diverse problems arising in air traffic management.

Applying Graph Theory to Problems in Air Traffic Management

NASA Technical Reports Server (NTRS)

Farrahi, Amir H.; Goldberg, Alan T.; Bagasol, Leonard N.; Jung, Jaewoo

2017-01-01

Graph theory is used to investigate three different problems arising in air traffic management. First, using a polynomial reduction from a graph partitioning problem, it isshown that both the airspace sectorization problem and its incremental counterpart, the sector combination problem are NP-hard, in general, under several simple workload models. Second, using a polynomial time reduction from maximum independent set in graphs, it is shown that for any fixed e, the problem of finding a solution to the minimum delay scheduling problem in traffic flow management that is guaranteed to be within n1-e of the optimal, where n is the number of aircraft in the problem instance, is NP-hard. Finally, a problem arising in precision arrival scheduling is formulated and solved using graph reachability. These results demonstrate that graph theory provides a powerful framework for modeling, reasoning about, and devising algorithmic solutions to diverse problems arising in air traffic management.

Coexistence or Conflict? A European Perspective on GMOs and the Problem of Liability

ERIC Educational Resources Information Center

Rodgers, Christopher P.

2007-01-01

In March 2004, the U.K. government announced its intention to grant limited authorization for the growing of commercial genetically modified (GM) crops. This article reviews the potential liabilities that may arise from GM cropping, for environmental damage and for economic losses claimed by non-GM producers. It considers the application of the…

Ionic mechanisms subserving mechanosensory transduction and neural integration in statocyst hair cells of Hermissenda

NASA Technical Reports Server (NTRS)

Farley, Joseph

1988-01-01

The neural processing of gravitational-produced sensory stimulation of statocyst hair cells in the nudibranch mollusk Hermissenda was studied. The goal in these studies was to understand how: gravireceptor neurons sense or transduce gravitational forces, gravitational stimulation is integrated so as to produce a graded receptor potential, and ultimately the generation of an action potential, and various neural adaptation phenomena which hair cells exhibit arise. The approach to these problems was primarily electrophysical.

Inequalities, Assessment and Computer Algebra

ERIC Educational Resources Information Center

Sangwin, Christopher J.

2015-01-01

The goal of this paper is to examine single variable real inequalities that arise as tutorial problems and to examine the extent to which current computer algebra systems (CAS) can (1) automatically solve such problems and (2) determine whether students' own answers to such problems are correct. We review how inequalities arise in contemporary…

Impact of Alternative Timber Management Policies on Availability of Forest Land in the Northeast

Treesearch

Owen W. Herrick

1977-01-01

Gaging the ability of the forest resource to satisfy future timber requirements is central to solving many problems arising from competition for use of forest land. In this study, production potentials of forest acreage in the Northeastern United States under management alternatives that range from extensive to intensive are weighed against several estimates of timber...

Comment on "Out-of-plane equilibrium points in the restricted three-body problem with oblateness (Research Note)"

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Xuefeng; Zhou, Li-Yong

2018-06-01

Douskos & Markellos (2006, A&A, 446, 357) first reported the existence of the out-of-plane equilibrium points in restricted three-body problem with oblateness. This result deviates significantly from the intuitive physical point of view that there is no other force that can balance the combined gravitation in Z direction. In fact, the out-of-plane equilibrium in that model is illusory and we prove here that such equilibrium points arise from the improper application of the potential function.

Coal conversion: description of technologies and necessary biomedical and environmental research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1976-08-01

This document contains a description of the biomedical and environmental research necessary to ensure the timely attainment of coal conversion technologies amenable to man and his environment. The document is divided into three sections. The first deals with the types of processes currently being considered for development; the data currently available on composition of product, process and product streams, and their potential effects; and problems that might arise from transportation and use of products. Section II is concerned with a description of the necessary research in each of the King-Muir categories, while the third section presents the research strategies necessarymore » to assess the potential problems at the conversion plant (site specific) and those problems that might effect the general public and environment as a result of the operation of large-scale coal conversion plants.« less

Balanced program plan. Volume IV. Coal conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richmond, C. R.; Reichle, D. E.; Gehrs, C. W.

1976-05-01

This document contains a description of the biomedical and environmental research necessary to ensure the timely attainment of coal conversion technologies amenable to man and his environment. The document is divided into three sections. The first deals with the types of processes currently being considered for development; the data currently available on composition of product, process and product streams, and their potential effects; and problems that might arise from transportation and use of products. Section II is concerned with a description of the necessary research in each of the King-Muir categories, while the third section presents the research strategies necessarymore » to assess the potential problems at the conversion plant (site specific) and those problems that might effect the general public and environment as a result of the operation of large-scale coal conversion plants. (auth)« less

Balanced program plan. Volume 4. Coal conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1976-05-01

This document contains a description of the biomedical and environmental research necessary to ensure the timely attainment of coal conversion technologies amenable to man and his environment. The document is divided into three sections. The first deals with the types of processes currently being considered for development; the data currently available on composition of product, process and product streams, and their potential effects; and problems that might arise from transportation and use of products. Section II is concerned with a description of the necessary research in each of the King-Muir categories, while the third section presents the research strategies necessarymore » to assess the potential problems at the conversion plant (site specific) and those problems that might effect the general public and environment as a result of the operation of large-scale coal conversion plants.« less

Providers must plan for accrual of medical malpractice claims.

PubMed

Zatorski, R

1988-11-01

Because of the change in accounting regulations that requires accrual for certain medical malpractice claims, healthcare providers could soon be experiencing significant effects on their financial results. AICPA Statement Position 87-1, "Accounting for Asserted and Unasserted Medical Malpractice Claims of Health Care Providers and Related Issues," states that if healthcare providers have not transferred all risk for medical malpractice claims arising out of occurrences prior to the financial statement date to a third party, some accrual will be required. Providers need to prepare themselves for the financial problems that could arise from these reporting guidelines. Estimating the potential accrual amounts with advanced planning and extensive data gathering and analysis could lower a healthcare provider's financial risk.

Letters of Recommendation/Verbal References Should Not Become Endangered Communications: an Analysis of Rights, Responsibilities, and Duties of References.

ERIC Educational Resources Information Center

Bell, James D.

In view of the dramatic increase in the numbers of laws and lawsuits since the 1960s, teachers must become aware of the privacy considerations and potential legal problems that may arise when writing a letter of recommendation or giving a verbal reference. They should become familiar with present common law doctrine and recent legislation…

Young People's Health as a Challenge for Physical Education in Schools in the Twenty-First Century: The Case of Flanders (Belgium)

ERIC Educational Resources Information Center

Seghers, Jan; de Martelaer, Kristine; Cardon, Greet

2009-01-01

Background: A lack of physical activity (PA) and the occurrence of overweight and obesity among school-aged youth have become a major societal problem. Arising from the general concern about the future generations' health, schools have been found to be potentially important settings to promote positive health behaviour, since all pupils can be…

EPR-dosimetry of ionizing radiation

NASA Astrophysics Data System (ADS)

Popova, Mariia; Vakhnin, Dmitrii; Tyshchenko, Igor

2017-09-01

This article discusses the problems that arise during the radiation sterilization of medical products. It is propose the solution based on alanine EPR-dosimetry. The parameters of spectrometer and methods of absorbed dose calculation are given. In addition, the problems that arise during heavy particles irradiation are investigated.

Quantum damped oscillator II: Bateman’s Hamiltonian vs. 2D parabolic potential barrier

NASA Astrophysics Data System (ADS)

Chruściński, Dariusz

2006-04-01

We show that quantum Bateman’s system which arises in the quantization of a damped harmonic oscillator is equivalent to a quantum problem with 2D parabolic potential barrier known also as 2D inverted isotropic oscillator. It turns out that this system displays the family of complex eigenvalues corresponding to the poles of analytical continuation of the resolvent operator to the complex energy plane. It is shown that this representation is more suitable than the hyperbolic one used recently by Blasone and Jizba.

Exploring the potential energy landscape over a large parameter-space

NASA Astrophysics Data System (ADS)

He, Yang-Hui; Mehta, Dhagash; Niemerg, Matthew; Rummel, Markus; Valeanu, Alexandru

2013-07-01

Solving large polynomial systems with coefficient parameters are ubiquitous and constitute an important class of problems. We demonstrate the computational power of two methods — a symbolic one called the Comprehensive Gröbner basis and a numerical one called coefficient-parameter polynomial continuation — applied to studying both potential energy landscapes and a variety of questions arising from geometry and phenomenology. Particular attention is paid to an example in flux compactification where important physical quantities such as the gravitino and moduli masses and the string coupling can be efficiently extracted.

Kleene Algebra and Bytecode Verification

DTIC Science & Technology

2016-04-27

computing the star (Kleene closure) of a matrix of transfer functions. In this paper we show how this general framework applies to the problem of Java ...bytecode verification. We show how to specify transfer functions arising in Java bytecode verification in such a way that the Kleene algebra operations...potentially improve the performance over the standard worklist algorithm when a small cutset can be found. Key words: Java , bytecode, verification, static

Theory and practice in the electrometric determination of pH in precipitation

NASA Astrophysics Data System (ADS)

Brennan, Carla Jo; Peden, Mark E.

Basic theory and laboratory investigations have been applied to the electrometric determination of pH in precipitation samples in an effort to improve the reliability of the results obtained from these low ionic strength samples. The theoretical problems inherent in the measurement of pH in rain have been examined using natural precipitation samples with varying ionic strengths and pH values. The importance of electrode design and construction has been stressed. The proper choice of electrode can minimize or eliminate problems arising from residual liquid junction potentials, streaming potentials and temperature differences. Reliable pH measurements can be made in precipitation samples using commercially available calibration buffers providing low ionic strength quality control solutions are routinely used to verify electrode and meter performance.

Emergent cosmology revisited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bag, Satadru; Sahni, Varun; Shtanov, Yuri

We explore the possibility of emergent cosmology using the effective potential formalism. We discover new models of emergent cosmology which satisfy the constraints posed by the cosmic microwave background (CMB). We demonstrate that, within the framework of modified gravity, the emergent scenario can arise in a universe which is spatially open/closed. By contrast, in general relativity (GR) emergent cosmology arises from a spatially closed past-eternal Einstein Static Universe (ESU). In GR the ESU is unstable, which creates fine tuning problems for emergent cosmology. However, modified gravity models including Braneworld models, Loop Quantum Cosmology (LQC) and Asymptotically Free Gravity result inmore » a stable ESU. Consequently, in these models emergent cosmology arises from a larger class of initial conditions including those in which the universe eternally oscillates about the ESU fixed point. We demonstrate that such an oscillating universe is necessarily accompanied by graviton production. For a large region in parameter space graviton production is enhanced through a parametric resonance, casting serious doubts as to whether this emergent scenario can be past-eternal.« less

"This above All: To Thine Own Self Be True"--Ethical Considerations and Risks in Conducting Higher Education Learning Activities in the Virtual World "Second Life" [TM

ERIC Educational Resources Information Center

Childs, Mark; Schnieders, H. Lori; Williams, Gweno

2012-01-01

Using virtual worlds as media for learning and teaching gives rise to the potential for many unique ethical problems. Some of these arise due to the nature of the engagement with these virtual worlds, in which the students create a virtual representation, called an avatar, which may enable a sense of embodiment, and hence exposure, within the…

Constraint-Based Local Search for Constrained Optimum Paths Problems

NASA Astrophysics Data System (ADS)

Pham, Quang Dung; Deville, Yves; van Hentenryck, Pascal

Constrained Optimum Path (COP) problems arise in many real-life applications and are ubiquitous in communication networks. They have been traditionally approached by dedicated algorithms, which are often hard to extend with side constraints and to apply widely. This paper proposes a constraint-based local search (CBLS) framework for COP applications, bringing the compositionality, reuse, and extensibility at the core of CBLS and CP systems. The modeling contribution is the ability to express compositional models for various COP applications at a high level of abstraction, while cleanly separating the model and the search procedure. The main technical contribution is a connected neighborhood based on rooted spanning trees to find high-quality solutions to COP problems. The framework, implemented in COMET, is applied to Resource Constrained Shortest Path (RCSP) problems (with and without side constraints) and to the edge-disjoint paths problem (EDP). Computational results show the potential significance of the approach.

The Difficult Stoma: Challenges and Strategies

PubMed Central

Strong, Scott A.

2016-01-01

The problems that a patient experiences after the creation of a temporary or permanent stoma can result from many factors, but a carefully constructed stoma located in an ideal location is typically associated with appropriate function and an acceptable quality of life. The construction of the stoma can be confounded by many concomitant conditions that increase the distance that the bowel must traverse or shorten the bowel's capacity to reach. Stomas can be further troubled by a variety of problems that potentially arise early in the recovery period or months later. Surgeons must be familiar with these obstacles and complications to avoid their occurrence and minimize their impact. PMID:27247541

Optimizing Restriction Site Placement for Synthetic Genomes

NASA Astrophysics Data System (ADS)

Montes, Pablo; Memelli, Heraldo; Ward, Charles; Kim, Joondong; Mitchell, Joseph S. B.; Skiena, Steven

Restriction enzymes are the workhorses of molecular biology. We introduce a new problem that arises in the course of our project to design virus variants to serve as potential vaccines: we wish to modify virus-length genomes to introduce large numbers of unique restriction enzyme recognition sites while preserving wild-type function by substitution of synonymous codons. We show that the resulting problem is NP-Complete, give an exponential-time algorithm, and propose effective heuristics, which we show give excellent results for five sample viral genomes. Our resulting modified genomes have several times more unique restriction sites and reduce the maximum gap between adjacent sites by three to nine-fold.

Explore or Exploit? A Generic Model and an Exactly Solvable Case

NASA Astrophysics Data System (ADS)

Gueudré, Thomas; Dobrinevski, Alexander; Bouchaud, Jean-Philippe

2014-02-01

Finding a good compromise between the exploitation of known resources and the exploration of unknown, but potentially more profitable choices, is a general problem, which arises in many different scientific disciplines. We propose a stylized model for these exploration-exploitation situations, including population or economic growth, portfolio optimization, evolutionary dynamics, or the problem of optimal pinning of vortices or dislocations in disordered materials. We find the exact growth rate of this model for treelike geometries and prove the existence of an optimal migration rate in this case. Numerical simulations in the one-dimensional case confirm the generic existence of an optimum.

Running Injuries: The Infrapatellar Fat Pad and Plica Injuries.

PubMed

McConnell, Jenny

2016-02-01

When considering knee pain in runners, clinicians differentiate sources of symptoms and determine their cause. Knee problems arise when a runner increases the amount/frequency of the loading through the lower limb. The way the loading is distributed through the knee determines which tissues are abnormally loaded. Knee problems cannot be considered in isolation, requiring a thorough investigation of static and dynamic lower limb mechanics, and footwear and surfaces. This article examines potential sources of knee pain and explores the role of the infrapatellar fat pad and synovial plica in the mechanics of the knee and its involvement in knee symptoms. Copyright © 2016 Elsevier Inc. All rights reserved.

Explore or exploit? A generic model and an exactly solvable case.

PubMed

Gueudré, Thomas; Dobrinevski, Alexander; Bouchaud, Jean-Philippe

2014-02-07

Finding a good compromise between the exploitation of known resources and the exploration of unknown, but potentially more profitable choices, is a general problem, which arises in many different scientific disciplines. We propose a stylized model for these exploration-exploitation situations, including population or economic growth, portfolio optimization, evolutionary dynamics, or the problem of optimal pinning of vortices or dislocations in disordered materials. We find the exact growth rate of this model for treelike geometries and prove the existence of an optimal migration rate in this case. Numerical simulations in the one-dimensional case confirm the generic existence of an optimum.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trędak, Przemysław, E-mail: przemyslaw.tredak@fuw.edu.pl; Rudnicki, Witold R.; Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, ul. Pawińskiego 5a, 02-106 Warsaw

The second generation Reactive Bond Order (REBO) empirical potential is commonly used to accurately model a wide range hydrocarbon materials. It is also extensible to other atom types and interactions. REBO potential assumes complex multi-body interaction model, that is difficult to represent efficiently in the SIMD or SIMT programming model. Hence, despite its importance, no efficient GPGPU implementation has been developed for this potential. Here we present a detailed description of a highly efficient GPGPU implementation of molecular dynamics algorithm using REBO potential. The presented algorithm takes advantage of rarely used properties of the SIMT architecture of a modern GPUmore » to solve difficult synchronizations issues that arise in computations of multi-body potential. Techniques developed for this problem may be also used to achieve efficient solutions of different problems. The performance of proposed algorithm is assessed using a range of model systems. It is compared to highly optimized CPU implementation (both single core and OpenMP) available in LAMMPS package. These experiments show up to 6x improvement in forces computation time using single processor of the NVIDIA Tesla K80 compared to high end 16-core Intel Xeon processor.« less

Definition of current density in the presence of a non-local potential.

PubMed

Li, Changsheng; Wan, Langhui; Wei, Yadong; Wang, Jian

2008-04-16

In the presence of a non-local potential arising from electron-electron interaction, the conventional definition of current density J(c) = (e/2m)([(p-eA)ψ](*)ψ-ψ(*)[(p-eA)ψ]) cannot satisfy the condition of current conservation, i.e., [Formula: see text] in the steady state. In order to solve this problem, we give a new definition of current density including the contribution due to the non-local potential. We show that the current calculated based on the new definition of current density conserves the current and is the same as that obtained from the Landauer-Büttiker formula. Examples are given to demonstrate our results.

PREFACE: XXIst International Symposium on the Jahn-Teller Effect 2012

NASA Astrophysics Data System (ADS)

Koizumi, Hiroyasu

2013-04-01

(The PDF contains the full conference program, the list of sponsors and the conference poster.) The 21st International Symposium on the Jahn-Teller effect was held at the University of Tsukuba, Japan, from 26-31 August 2012. People from 23 different countries participated and the number of registered participants was 118. In this symposium, the phrase 'Jahn-Teller effect' was taken to have a rather broad meaning. We discussed the Jahn-Teller and pseudo Jahn-Teller distortions. We also discussed general vibronic problems, and the problems associated with the conical intersections of the potential energy surfaces. As is indicated in the subtitle of the present symposium, 'Physics and Chemistry of Symmetry Breaking', a number of different topics concerning symmetry breaking were also extensively discussed. In particular, we had many discussions on magnetism, ferroelectricity, and superconductivity. A subtle but important problem that was dealt with was the appearance of multi-valuedness in the use of multi-component wave functions. In the Jahn-Teller problems, we almost always use the multi-component wave functions, thus, the knowledge of the proper handling of multi-valuedness is very important. Digital computers are not good at dealing with multi-valuedness, but we need to somehow handle it in our calculations. A very well known example of successful handling is found in the problem of the molecular system with the conical intersection: we cannot obtain the solution that satisfies the single-valuedness of wave functions (SVWF) just using the potential energy surface generated by a package program, and solving the Schrödinger equation with the quantum Hamiltonian constructed from the classical counterpart by replacing the classical variables with the corresponding operators; however, if a gauge potential is included and the double-valuedness of the electronic wave functions around the conical intersections is taken into account, the solution that satisfies the SVWF is obtained. A related problem also arises when dealing with the so-called adiabatic-diabatic transformation (ADT) that removes coupling terms between different Born-Oppenheimer electronic states. It is known that an exact ADT does not exist in general, however, digital computers do this impossible task erroneously if we just plug in numbers. The results obtained may be good in practice; however, we need to be aware that such calculations may miss some important details. I asked Professor Mead to write a note on this matter since there is still confusion in the treatment of the ADT. The proper handling on the ADT may be a topic in the next Jahn-Teller symposium. Although more than a quarter of a century has passed since its discovery, the mechanism of cuprate superconductivity is still actively discussed. In the cuprate, the multi-valuedness problem arises when the conduction electrons create spin-vortices and the twisting of the spin basis occurs. Since a number of experiments and theories indicate the presence of spin-vortices in the cuprate, a proper handling of the multi-valuedness arising from the spin-degree-of-freedom will be important. It has been argued that such multi-valuedness induces a vector potential that generates the persistent current. As the papers in this proceedings indicate, the Jahn-Teller effects are ubiquitous in physics and chemistry. The ideas and methodologies developed in this community have very wide applicability. I believe that this community will continue to contribute to the advancement of science in a fundamental way. Hiroyasu Koizumi Tsukuba, February 2013 Conference photograph

Thermal issues at the SSC

NASA Technical Reports Server (NTRS)

Ranganathan, Raj P.; Dao, Bui V.

1992-01-01

A variety of heat transfer problems arise in the design of the Superconducting Super Collider (SSC). One class of problems is to minimize heat leak from the ambient to the SSC rings, since the rings contain superconducting magnets maintained at a temperature of 4 K. Another arises from the need to dump the beam of protrons (traveling around the SSC rings) on to absorbers during an abort of the collider. Yet another category of problems is the cooling of equipment to dissipate the heat generated during operation. An overview of these problems and sample heat transfer results are given in this paper.

Strategies for Limiting Engineers' Potential Liability for Indoor Air Quality Problems.

PubMed

von Oppenfeld, Rolf R; Freeze, Mark E; Sabo, Sean M

1998-10-01

Engineers face indoor air quality (IAQ) issues at the design phase of building construction as well as during the investigation and mitigation of potential indoor air pollution problems during building operation. IAQ issues that can be identified are "building-related illnesses" that may include problems of volatile organic compounds (VOCs). IAQ issues that cannot be identified are termed "sick building syndrome." Frequently, microorganism-caused illnesses are difficult to confirm. Engineers who provide professional services that directly or indirectly impact IAQ face significant potential liability to clients and third parties when performing these duties. Potential theories supporting liability claims for IAQ problems against engineers include breach of contract and various common law tort theories such as negligence and negligent misrepresentation. Furthermore, an increasing number of federal, state, and local regulations affect IAQ issues and can directly increase the potential liability of engineers. A duty to disclose potential or actual air quality concerns to third parties may apply for engineers in given circumstances. Such a duty may arise from judicial precedent, the Model Guide for Professional Conduct for Engineers, or the Code of Ethics for Engineers. Practical strategies engineers can use to protect themselves from liability include regular training and continuing education in relevant regulatory, scientific, and case law developments; detailed documentation and recordkeeping practices; adequate insurance coverage; contractual indemnity clauses; contractual provisions limiting liability to the scope of work performed; and contractual provisions limiting the extent of liability for engineers' negligence. Furthermore, through the proper use of building materials and construction techniques, an engineer or other design professional can effectively limit the potential for IAQ liability.

Invited Commentary: Explaining the Relationship Between Attending Worship Services and Mortality-A Brief Excursion Into the Contribution of Social Relationships in Religious Institutions.

PubMed

Krause, Neal

2017-04-01

In this issue of the Journal, VanderWeele et al. (Am J Epidemiol. 2017;000(00):000-000) report that more frequent attendance at worship services is associated with a lower mortality risk. However, the underlying processes that might explain this relationship were not discussed fully. A problem arises because the potentially beneficial association between attending worship services and mortality risk may be due to a number of different factors. At least part of the explanation may be found by turning to social relationships that arise in religious institutions. Within this context, there are potentially important benefits of providing social support to others. Support can be provided in several ways that involve potentially important health-related associations. In this commentary, I briefly examine the possible relationships between religious social support systems and other dimensions of congregational life and health. In-depth conceptual analyses are needed to move research in religious involvement and mortality to the next level. © The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Watermarking-based protection of remote sensing images: requirements and possible solutions

NASA Astrophysics Data System (ADS)

Barni, Mauro; Bartolini, Franco; Cappellini, Vito; Magli, Enrico; Olmo, Gabriella

2001-12-01

Earth observation missions have recently attracted ag rowing interest form the scientific and industrial communities, mainly due to the large number of possible applications capable to exploit remotely sensed data and images. Along with the increase of market potential, the need arises for the protection of the image products from non-authorized use. Such a need is a very crucial one even because the Internet and other public/private networks have become preferred means of data exchange. A crucial issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. A question that obviously arises is whether the requirements imposed by remote sensing imagery are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: i) assessment of the requirements imposed by the characteristics of remotely sensed images on watermark-based copyright protection ii) analysis of the state-of-the-art, and performance evaluation of existing algorithms in terms of the requirements at the previous point.

Point-particle effective field theory I: classical renormalization and the inverse-square potential

NASA Astrophysics Data System (ADS)

Burgess, C. P.; Hayman, Peter; Williams, M.; Zalavári, László

2017-04-01

Singular potentials (the inverse-square potential, for example) arise in many situations and their quantum treatment leads to well-known ambiguities in choosing boundary conditions for the wave-function at the position of the potential's singularity. These ambiguities are usually resolved by developing a self-adjoint extension of the original prob-lem; a non-unique procedure that leaves undetermined which extension should apply in specific physical systems. We take the guesswork out of this picture by using techniques of effective field theory to derive the required boundary conditions at the origin in terms of the effective point-particle action describing the physics of the source. In this picture ambiguities in boundary conditions boil down to the allowed choices for the source action, but casting them in terms of an action provides a physical criterion for their determination. The resulting extension is self-adjoint if the source action is real (and involves no new degrees of freedom), and not otherwise (as can also happen for reasonable systems). We show how this effective-field picture provides a simple framework for understanding well-known renormalization effects that arise in these systems, including how renormalization-group techniques can resum non-perturbative interactions that often arise, particularly for non-relativistic applications. In particular we argue why the low-energy effective theory tends to produce a universal RG flow of this type and describe how this can lead to the phenomenon of reaction catalysis, in which physical quantities (like scattering cross sections) can sometimes be surprisingly large compared to the underlying scales of the source in question. We comment in passing on the possible relevance of these observations to the phenomenon of the catalysis of baryon-number violation by scattering from magnetic monopoles.

On the Asymptotic Behavior of a Log Gas in the Bulk Scaling Limit in the Presence of a Varying External Potential I

NASA Astrophysics Data System (ADS)

Bothner, Thomas; Deift, Percy; Its, Alexander; Krasovsky, Igor

2015-08-01

We study the determinant , of the integrable Fredholm operator K s acting on the interval (-1, 1) with kernel . This determinant arises in the analysis of a log-gas of interacting particles in the bulk-scaling limit, at inverse temperature , in the presence of an external potential supported on an interval of length . We evaluate, in particular, the double scaling limit of as and , in the region , for any fixed . This problem was first considered by Dyson (Chen Ning Yang: A Great Physicist of the Twentieth Century. International Press, Cambridge, pp. 131-146, 1995).

Efficient implementation of the many-body Reactive Bond Order (REBO) potential on GPU

NASA Astrophysics Data System (ADS)

Trędak, Przemysław; Rudnicki, Witold R.; Majewski, Jacek A.

2016-09-01

The second generation Reactive Bond Order (REBO) empirical potential is commonly used to accurately model a wide range hydrocarbon materials. It is also extensible to other atom types and interactions. REBO potential assumes complex multi-body interaction model, that is difficult to represent efficiently in the SIMD or SIMT programming model. Hence, despite its importance, no efficient GPGPU implementation has been developed for this potential. Here we present a detailed description of a highly efficient GPGPU implementation of molecular dynamics algorithm using REBO potential. The presented algorithm takes advantage of rarely used properties of the SIMT architecture of a modern GPU to solve difficult synchronizations issues that arise in computations of multi-body potential. Techniques developed for this problem may be also used to achieve efficient solutions of different problems. The performance of proposed algorithm is assessed using a range of model systems. It is compared to highly optimized CPU implementation (both single core and OpenMP) available in LAMMPS package. These experiments show up to 6x improvement in forces computation time using single processor of the NVIDIA Tesla K80 compared to high end 16-core Intel Xeon processor.

Non-Boolean computing with nanomagnets for computer vision applications

NASA Astrophysics Data System (ADS)

Bhanja, Sanjukta; Karunaratne, D. K.; Panchumarthy, Ravi; Rajaram, Srinath; Sarkar, Sudeep

2016-02-01

The field of nanomagnetism has recently attracted tremendous attention as it can potentially deliver low-power, high-speed and dense non-volatile memories. It is now possible to engineer the size, shape, spacing, orientation and composition of sub-100 nm magnetic structures. This has spurred the exploration of nanomagnets for unconventional computing paradigms. Here, we harness the energy-minimization nature of nanomagnetic systems to solve the quadratic optimization problems that arise in computer vision applications, which are computationally expensive. By exploiting the magnetization states of nanomagnetic disks as state representations of a vortex and single domain, we develop a magnetic Hamiltonian and implement it in a magnetic system that can identify the salient features of a given image with more than 85% true positive rate. These results show the potential of this alternative computing method to develop a magnetic coprocessor that might solve complex problems in fewer clock cycles than traditional processors.

Searching for otherness: the view of a novel.

PubMed

Magalhães, Susana; Carvalho, Ana Sofia

2010-01-01

The ethical issues concerning the use of PGD (Preimplantation Genetic Diagnosis) to select embryos of a particular HLA (Human Leukocyte Antigen) type are numerous. They arise from the potentially conflicting interests between those of the pre-existing child, the subject of a treatment which may be curative, and those of the sibling to be created, who cannot give consent to the donation, together with the problem of the destruction of potentially healthy embryos. This essay focuses on the web of vulnerabilities affecting the parents, the sick child and the "saviour sibling," while addressing three areas: science, bioethics and literature. The novel My Sister's Keeper, by Jodi Picoult, provides the reader with an in-depth view of the conflicting interests and emotional problems that affect the Fitzgeralds, a family experiencing the pain of seeing one of their children dying while facing the tragic consequences of trying to save this child by having another offspring.

Wavelets in electronic structure calculations

NASA Astrophysics Data System (ADS)

Modisette, Jason Perry

1997-09-01

Ab initio calculations of the electronic structure of bulk materials and large clusters are not possible on today's computers using current techniques. The storage and diagonalization of the Hamiltonian matrix are the limiting factors in both memory and execution time. The scaling of both quantities with problem size can be reduced by using approximate diagonalization or direct minimization of the total energy with respect to the density matrix in conjunction with a localized basis. Wavelet basis members are much more localized than conventional bases such as Gaussians or numerical atomic orbitals. This localization leads to sparse matrices of the operators that arise in SCF multi-electron calculations. We have investigated the construction of the one-electron Hamiltonian, and also the effective one- electron Hamiltonians that appear in density-functional and Hartree-Fock theories. We develop efficient methods for the generation of the kinetic energy and potential matrices, the Hartree and exchange potentials, and the local exchange-correlation potential of the LDA. Test calculations are performed on one-electron problems with a variety of potentials in one and three dimensions.

Modeling the Acid-Base Properties of Montmorillonite Edge Surfaces.

PubMed

Tournassat, Christophe; Davis, James A; Chiaberge, Christophe; Grangeon, Sylvain; Bourg, Ian C

2016-12-20

The surface reactivity of clay minerals remains challenging to characterize because of a duality of adsorption surfaces and mechanisms that does not exist in the case of simple oxide surfaces: edge surfaces of clay minerals have a variable proton surface charge arising from hydroxyl functional groups, whereas basal surfaces have a permanent negative charge arising from isomorphic substitutions. Hence, the relationship between surface charge and surface potential on edge surfaces cannot be described using the Gouy-Chapman relation, because of a spillover of negative electrostatic potential from the basal surface onto the edge surface. While surface complexation models can be modified to account for these features, a predictive fit of experimental data was not possible until recently, because of uncertainty regarding the densities and intrinsic pK a values of edge functional groups. Here, we reexamine this problem in light of new knowledge on intrinsic pK a values obtained over the past decade using ab initio molecular dynamics simulations, and we propose a new formalism to describe edge functional groups. Our simulation results yield reasonable predictions of the best available experimental acid-base titration data.

Comment on: Accurate and fast numerical solution of Poisson s equation for arbitrary, space-filling Voronoi polyhedra: Near-field corrections revisited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonis, Antonios; Zhang, Xiaoguang

2012-01-01

This is a comment on the paper by Aftab Alam, Brian G. Wilson, and D. D. Johnson [1], proposing the solution of the near-field corrections (NFC s) problem for the Poisson equation for extended, e.g., space filling, charge densities. We point out that the problem considered by the authors can be simply avoided by means of performing certain integrals in a particular order, while their method does not address the genuine problem of NFC s that arises when the solution of the Poisson equation is attempted within multiple scattering theory. We also point out a flaw in their line ofmore » reasoning leading to the expression for the potential inside the bounding sphere of a cell that makes it inapplicable to certain geometries.« less

Comment on ``Accurate and fast numerical solution of Poisson's equation for arbitrary, space-filling Voronoi polyhedra: Near-field corrections revisited''

NASA Astrophysics Data System (ADS)

Gonis, A.; Zhang, X.-G.

2012-09-01

This is a Comment on the paper by Alam, Wilson, and Johnson [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.84.205106 84, 205106 (2011)], proposing the solution of the near-field corrections (NFCs) problem for the Poisson equation for extended, e.g., space-filling charge densities. We point out that the problem considered by the authors can be simply avoided by means of performing certain integrals in a particular order, whereas, their method does not address the genuine problem of NFCs that arises when the solution of the Poisson equation is attempted within multiple-scattering theory. We also point out a flaw in their line of reasoning, leading to the expression for the potential inside the bounding sphere of a cell that makes it inapplicable for certain geometries.

Attention problems and pathological gaming: resolving the 'chicken and egg' in a prospective analysis.

PubMed

Ferguson, Christopher J; Ceranoglu, T Atilla

2014-03-01

Pathological gaming (PG) behaviors are behaviors which interfere with other life responsibilities. Continued debate exists regarding whether symptoms of PG behaviors are a unique phenomenon or arise from other mental health problems, including attention problems. Development of attention problems and occurrence of pathological gaming in 144 adolescents were followed during a 1-year prospective analysis. Teens and their parents reported on pathological gaming behaviors, attention problems, and current grade point average, as well as several social variables. Results were analyzed using regression and path analysis. Attention problems tended to precede pathological gaming behaviors, but the inverse was not true. Attention problems but not pathological gaming predicted lower GPA 1 year later. Current results suggest that pathological gaming arises from attention problems, but not the inverse. These results suggest that pathological gaming behaviors are symptomatic of underlying attention related mental health issues, rather than a unique phenomenon.

Automated Systematic Generation and Exploration of Flat Direction Phenomenology in Free Fermionic Heterotic String Theory

NASA Astrophysics Data System (ADS)

Greenwald, Jared

Any good physical theory must resolve current experimental data as well as offer predictions for potential searches in the future. The Standard Model of particle physics, Grand Unied Theories, Minimal Supersymmetric Models and Supergravity are all attempts to provide such a framework. However, they all lack the ability to predict many of the parameters that each of the theories utilize. String theory may yield a solution to this naturalness (or self-predictiveness) problem as well as offer a unifed theory of gravity. Studies in particle physics phenomenology based on perturbative low energy analysis of various string theories can help determine the candidacy of such models. After a review of principles and problems leading up to our current understanding of the universe, we will discuss some of the best particle physics model building techniques that have been developed using string theory. This will culminate in the introduction of a novel approach to a computational, systematic analysis of the various physical phenomena that arise from these string models. We focus on the necessary assumptions, complexity and open questions that arise while making a fully-automated at direction analysis program.

A fully implicit finite element method for bidomain models of cardiac electromechanics

PubMed Central

Dal, Hüsnü; Göktepe, Serdar; Kaliske, Michael; Kuhl, Ellen

2012-01-01

We propose a novel, monolithic, and unconditionally stable finite element algorithm for the bidomain-based approach to cardiac electromechanics. We introduce the transmembrane potential, the extracellular potential, and the displacement field as independent variables, and extend the common two-field bidomain formulation of electrophysiology to a three-field formulation of electromechanics. The intrinsic coupling arises from both excitation-induced contraction of cardiac cells and the deformation-induced generation of intra-cellular currents. The coupled reaction-diffusion equations of the electrical problem and the momentum balance of the mechanical problem are recast into their weak forms through a conventional isoparametric Galerkin approach. As a novel aspect, we propose a monolithic approach to solve the governing equations of excitation-contraction coupling in a fully coupled, implicit sense. We demonstrate the consistent linearization of the resulting set of non-linear residual equations. To assess the algorithmic performance, we illustrate characteristic features by means of representative three-dimensional initial-boundary value problems. The proposed algorithm may open new avenues to patient specific therapy design by circumventing stability and convergence issues inherent to conventional staggered solution schemes. PMID:23175588

Ethical issues and addiction.

PubMed

Lambert, Binta; Scheiner, Melissa; Campbell, Deborah

2010-04-01

The epidemic of substance abuse continues to pose a significant challenge to clinicians nationwide. Although there is a tendency to simply associate drug abuse with poverty, the problem affects every social stratum gender and race; and pregnant women are no exception. Caring for pregnant, substance-using women and their infants presents complex legal and ethical issues. Debate is ongoing about whether criminal penalties should be imposed on women based solely on their use of alcohol and other drugs during pregnancy. Furthermore, controversies persist about the rights and wishes of pregnant women versus the interests of their fetuses. For health professionals, conflict arises when the pregnant woman chooses behaviors that have the potential to harm the developing fetus. The ethical dilemma arises from competing autonomy-based and beneficence-based obligations to the maternal-fetal dyad. This chapter explores the ethics-based conflicts in the delivery of health care to drug abusing pregnant women.

Surgery insight: late complications following repair of tetralogy of Fallot and related surgical strategies for management.

PubMed

Karamlou, Tara; McCrindle, Brian W; Williams, William G

2006-11-01

Biventricular correction of tetralogy of Fallot was devised more than 50 years ago. Current short-term outcomes are excellent. The potential for late complications is, however, an important concern for the growing number of postrepair survivors. Progressive pulmonary valve regurgitation leading to right heart failure and arrhythmia are centrally important problems faced by these patients. New techniques are, however, likely to change the future outcomes for postrepair survivors. These techniques include percutaneous valve replacement, arrhythmia ablation surgery, and strategies that emphasize preservation of the pulmonary valve even at the cost of leaving some residual valvular stenosis. The objectives of this Review are to outline the major complications that arise late after repair of tetralogy of Fallot, to describe the surgical approaches that have been developed to avoid and manage arising complications, and to briefly explore how novel treatment paradigms could change the future long-term outlook for patients following tetralogy repair.

Quenching rate for a nonlocal problem arising in the micro-electro mechanical system

NASA Astrophysics Data System (ADS)

Guo, Jong-Shenq; Hu, Bei

2018-03-01

In this paper, we study the quenching rate of the solution for a nonlocal parabolic problem which arises in the study of the micro-electro mechanical system. This question is equivalent to the stabilization of the solution to the transformed problem in self-similar variables. First, some a priori estimates are provided. In order to construct a Lyapunov function, due to the lack of time monotonicity property, we then derive some very useful and challenging estimates by a delicate analysis. Finally, with this Lyapunov function, we prove that the quenching rate is self-similar which is the same as the problem without the nonlocal term, except the constant limit depends on the solution itself.

Cost-effective use of minicomputers to solve structural problems

NASA Technical Reports Server (NTRS)

Storaasli, O. O.; Foster, E. P.

1978-01-01

Minicomputers are receiving increased use throughout the aerospace industry. Until recently, their use focused primarily on process control and numerically controlled tooling applications, while their exposure to and the opportunity for structural calculations has been limited. With the increased availability of this computer hardware, the question arises as to the feasibility and practicality of carrying out comprehensive structural analysis on a minicomputer. This paper presents results on the potential for using minicomputers for structural analysis by (1) selecting a comprehensive, finite-element structural analysis system in use on large mainframe computers; (2) implementing the system on a minicomputer; and (3) comparing the performance of the minicomputers with that of a large mainframe computer for the solution to a wide range of finite element structural analysis problems.

Innovative architectures for dense multi-microprocessor computers

NASA Technical Reports Server (NTRS)

Larson, Robert E.

1989-01-01

The purpose is to summarize a Phase 1 SBIR project performed for the NASA/Langley Computational Structural Mechanics Group. The project was performed from February to August 1987. The main objectives of the project were to: (1) expand upon previous research into the application of chordal ring architectures to the general problem of designing multi-microcomputer architectures, (2) attempt to identify a family of chordal rings such that each chordal ring can be simply expanded to produce the next member of the family, (3) perform a preliminary, high-level design of an expandable multi-microprocessor computer based upon chordal rings, (4) analyze the potential use of chordal ring based multi-microprocessors for sparse matrix problems and other applications arising in computational structural mechanics.

Golden Ratio in a Coupled-Oscillator Problem

ERIC Educational Resources Information Center

Moorman, Crystal M.; Goff, John Eric

2007-01-01

The golden ratio appears in a classical mechanics coupled-oscillator problem that many undergraduates may not solve. Once the symmetry is broken in a more standard problem, the golden ratio appears. Several student exercises arise from the problem considered in this paper.

Nonlocality and Short-Range Wetting Phenomena

NASA Astrophysics Data System (ADS)

Parry, A. O.; Romero-Enrique, J. M.; Lazarides, A.

2004-08-01

We propose a nonlocal interfacial model for 3D short-range wetting at planar and nonplanar walls. The model is characterized by a binding-potential functional depending only on the bulk Ornstein-Zernike correlation function, which arises from different classes of tubelike fluctuations that connect the interface and the substrate. The theory provides a physical explanation for the origin of the effective position-dependent stiffness and binding potential in approximate local theories and also obeys the necessary classical wedge covariance relationship between wetting and wedge filling. Renormalization group and computer simulation studies reveal the strong nonperturbative influence of nonlocality at critical wetting, throwing light on long-standing theoretical problems regarding the order of the phase transition.

Nonlocality and short-range wetting phenomena.

PubMed

Parry, A O; Romero-Enrique, J M; Lazarides, A

2004-08-20

We propose a nonlocal interfacial model for 3D short-range wetting at planar and nonplanar walls. The model is characterized by a binding-potential functional depending only on the bulk Ornstein-Zernike correlation function, which arises from different classes of tubelike fluctuations that connect the interface and the substrate. The theory provides a physical explanation for the origin of the effective position-dependent stiffness and binding potential in approximate local theories and also obeys the necessary classical wedge covariance relationship between wetting and wedge filling. Renormalization group and computer simulation studies reveal the strong nonperturbative influence of nonlocality at critical wetting, throwing light on long-standing theoretical problems regarding the order of the phase transition.

Calculation of Rayleigh type sums for zeros of the equation arising in spectral problem

NASA Astrophysics Data System (ADS)

Kostin, A. B.; Sherstyukov, V. B.

2017-12-01

For zeros of the equation (arising in the oblique derivative problem) μ J n ‧ ( μ ) cos α + i n J n ( μ ) sin α = 0 , μ ∈ ℂ , with parameters n ∈ ℤ, α ∈ [-π/2, π/2] and the Bessel function Jn (μ) special summation relationships are proved. The obtained results are consistent with the theory of well-known Rayleigh sums calculating by zeros of the Bessel function.

Four common herbs seen in dental practice: properties and potential adverse effects.

PubMed

Shankland, Wesley E

2009-04-01

The use of herbal supplements in North America is steadily growing and raises concerns about safety, efficacy, and how they affect safe patient care. The most notable and direct health risks associated with herbal supplements include hypertension, prolonged bleeding, and the potential for drug-herb interactions, which is of particular concern for patients undergoing anesthesia, both general and local anesthesia. In this article, four of the most commonly used herbs today in North America will be discussed: garlic, gingko, ginseng, and ginger. The pharmacology, benefits, and possible side effects of these herbs will be presented. Awareness of the rising use of herbs is important to prevent, recognize, and treat potential problems that can arise from herbal preparations taken alone or in conjunction with prescription medications.

Common Methodological Problems in Research on the Addictions.

ERIC Educational Resources Information Center

Nathan, Peter E.; Lansky, David

1978-01-01

Identifies common problems in research on the addictions and offers suggestions for remediating these methodological problems. The addictions considered include alcoholism and drug dependencies. Problems considered are those arising from inadequate, incomplete, or biased reviews of relevant literatures and methodological shortcomings of subject…

Watermarking techniques for electronic delivery of remote sensing images

NASA Astrophysics Data System (ADS)

Barni, Mauro; Bartolini, Franco; Magli, Enrico; Olmo, Gabriella

2002-09-01

Earth observation missions have recently attracted a growing interest, mainly due to the large number of possible applications capable of exploiting remotely sensed data and images. Along with the increase of market potential, the need arises for the protection of the image products. Such a need is a very crucial one, because the Internet and other public/private networks have become preferred means of data exchange. A critical issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. A question that obviously arises is whether the requirements imposed by remote sensing imagery are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: assessment of the requirements imposed by remote sensing applications on watermark-based copyright protection, and modification of two well-established digital watermarking techniques to meet such constraints. More specifically, the concept of near-lossless watermarking is introduced and two possible algorithms matching such a requirement are presented. Experimental results are shown to measure the impact of watermark introduction on a typical remote sensing application, i.e., unsupervised image classification.

Sustaining Health and Performance in the Cold: Environmental Medicine Guidance for Cold-Weather Operation.

DTIC Science & Technology

1992-07-01

or vehicle should be suspected of possible CO poisoning. 4. DO NOT APPLY OINTMENTS , SNOW OR ICE TO THE BURN , 3. Proper field sanitation is very AND DO...susceptible to cold injuries, and the use of indoor stoves may lead to burns or suffocation. Operational problems often arise in cold weather. Heavy...potential for body heat to escape. When the skin is exposed to cold, the brain signals the blood vessels in the skin to tighten, and blood flow to the skin

High order discretization techniques for real-space ab initio simulations

NASA Astrophysics Data System (ADS)

Anderson, Christopher R.

2018-03-01

In this paper, we present discretization techniques to address numerical problems that arise when constructing ab initio approximations that use real-space computational grids. We present techniques to accommodate the singular nature of idealized nuclear and idealized electronic potentials, and we demonstrate the utility of using high order accurate grid based approximations to Poisson's equation in unbounded domains. To demonstrate the accuracy of these techniques, we present results for a Full Configuration Interaction computation of the dissociation of H2 using a computed, configuration dependent, orbital basis set.

To the issue of the environmental development of housing construction in the integrated land use management

NASA Astrophysics Data System (ADS)

Politi, Violetta

2018-03-01

The paper considers environmental problems arising during the implementation of housing programs for the integrated development of territories by high-rise buildings. The need to assess the quality of the environment in the functional zoning of territories is identified and a calculation of the index of the ecological potential of the territories is proposed. The main stages of organization of construction of environmental real estate and the introduction of energy-saving and resource-saving technologies at the regional level are formulated

Low thrust propulsion system effects on communication satellites.

NASA Technical Reports Server (NTRS)

Hall, D. F.; Lyon, W. C.

1972-01-01

Choice of type and placement of thrusters on spacecraft (s/c) should include consideration of their effects on other subsystems. Models are presented of the exhaust plumes of mercury, cesium, colloid, hydrazine, ammonia, and Teflon rockets. Effects arising from plume impingement on s/c surfaces, radio frequency interference, optical interference, and earth environmental contamination are discussed. Some constraints arise in the placement of mercury, cesium, and Teflon thrusters. Few problems exist with other thruster types, nor is earth contamination a problem.

The use of Lanczos's method to solve the large generalized symmetric definite eigenvalue problem

NASA Technical Reports Server (NTRS)

Jones, Mark T.; Patrick, Merrell L.

1989-01-01

The generalized eigenvalue problem, Kx = Lambda Mx, is of significant practical importance, especially in structural enginering where it arises as the vibration and buckling problem. A new algorithm, LANZ, based on Lanczos's method is developed. LANZ uses a technique called dynamic shifting to improve the efficiency and reliability of the Lanczos algorithm. A new algorithm for solving the tridiagonal matrices that arise when using Lanczos's method is described. A modification of Parlett and Scott's selective orthogonalization algorithm is proposed. Results from an implementation of LANZ on a Convex C-220 show it to be superior to a subspace iteration code.

Support System for Mental Health Professionals*

PubMed Central

Dandekar, Ajit

2015-01-01

This paper talks of support systems for mental health professionals wherein the Bombay Psychiatric Society (BPS) should devote some meetings exclusively to problems pertaining to the profession, e.g., long and odd working hours leading to potentially hazardous practice schedules, unhealthy competitive attitudes and culture. A crash course in self-defence against potentially psychotic patients and drug addicts is advocated as also awareness of the potential hazards in dealing with the litigious paranoid patients, erotomaniacs and some of the difficult hysterical patients. Potential medicolegal problems arise in treating an uncooperative patient without his knowledge and consent on an outpatient department basis, admitting such an uncooperative patient to a nursing home or a hospital, administering electroconvulsive therapies, maintaining detailed clinical records of patients, and legal issues involving smaller psychiatric private nursing homes. This paper stresses on the use of Yoga as a recognised psycho-physiological therapy. Furthermore, it suggests on the need for BPS, as a professional body, to have a cell to guide and help aspiring young professionals in setting up private practice. It points out the need to evolve some concrete programmes that in the long run should help alleviate stresses and strains and promote positive comprehensive health amongst mental health professionals. PMID:25838730

Eigenmode computation of cavities with perturbed geometry using matrix perturbation methods applied on generalized eigenvalue problems

NASA Astrophysics Data System (ADS)

Gorgizadeh, Shahnam; Flisgen, Thomas; van Rienen, Ursula

2018-07-01

Generalized eigenvalue problems are standard problems in computational sciences. They may arise in electromagnetic fields from the discretization of the Helmholtz equation by for example the finite element method (FEM). Geometrical perturbations of the structure under concern lead to a new generalized eigenvalue problems with different system matrices. Geometrical perturbations may arise by manufacturing tolerances, harsh operating conditions or during shape optimization. Directly solving the eigenvalue problem for each perturbation is computationally costly. The perturbed eigenpairs can be approximated using eigenpair derivatives. Two common approaches for the calculation of eigenpair derivatives, namely modal superposition method and direct algebraic methods, are discussed in this paper. Based on the direct algebraic methods an iterative algorithm is developed for efficiently calculating the eigenvalues and eigenvectors of the perturbed geometry from the eigenvalues and eigenvectors of the unperturbed geometry.

The Riemann-Hilbert problem for nonsymmetric systems

NASA Astrophysics Data System (ADS)

Greenberg, W.; Zweifel, P. F.; Paveri-Fontana, S.

1991-12-01

A comparison of the Riemann-Hilbert problem and the Wiener-Hopf factorization problem arising in the solution of half-space singular integral equations is presented. Emphasis is on the factorization of functions lacking the reflection symmetry usual in transport theory.

Forks in the road: choices in procedures for designing wildland linkages.

PubMed

Beier, Paul; Majka, Daniel R; Spencer, Wayne D

2008-08-01

Models are commonly used to identify lands that will best maintain the ability of wildlife to move between wildland blocks through matrix lands after the remaining matrix has become incompatible with wildlife movement. We offer a roadmap of 16 choices and assumptions that arise in designing linkages to facilitate movement or gene flow of focal species between 2 or more predefined wildland blocks. We recommend designing linkages to serve multiple (rather than one) focal species likely to serve as a collective umbrella for all native species and ecological processes, explicitly acknowledging untested assumptions, and using uncertainty analysis to illustrate potential effects of model uncertainty. Such uncertainty is best displayed to stakeholders as maps of modeled linkages under different assumptions. We also recommend modeling corridor dwellers (species that require more than one generation to move their genes between wildland blocks) differently from passage species (for which an individual can move between wildland blocks within a few weeks). We identify a problem, which we call the subjective translation problem, that arises because the analyst must subjectively decide how to translate measurements of resource selection into resistance. This problem can be overcome by estimating resistance from observations of animal movement, genetic distances, or interpatch movements. There is room for substantial improvement in the procedures used to design linkages robust to climate change and in tools that allow stakeholders to compare an optimal linkage design to alternative designs that minimize costs or achieve other conservation goals.

An observational study of bullying as a contributing factor in youth suicide in Toronto.

PubMed

Sinyor, Mark; Schaffer, Ayal; Cheung, Amy H

2014-12-01

Bullying has been identified as a potential contributing factor in youth suicide. This issue has been highlighted in recent widely publicized media reports, worldwide, in which deceased youth were bullied. We report on an observational study conducted to determine the frequency of bullying as a contributing factor to youth suicide. Coroner records were reviewed for all suicide deaths in youth aged between 10 and 19 in the city of Toronto from 1998 to 2011. Data abstracted were recent stressors (including bullying), clinical variables, such as the presence of mental illness, demographics, and methods of suicide. Ninety-four youth suicides were included in the study. The mean age was 16.8 years, and 70.2% were male. Bullying was present in 6 deaths (6.4%), and there were no deaths where online or cyberbullying was detected. Bullying was the only identified contributing factor in fewer than 5 deaths. The most common stressors identified were conflict with parents (21.3%), romantic partner problems (17.0%), academic problems (10.6%), and criminal and (or) legal problems (10.6%). Any stressor or mental and (or) physical illness was detected in 78.7% of cases. Depression was detected in 40.4% of cases. Our study highlights the need to view suicide in youth as arising from a complex interplay of various biological, psychological, and social factors of which bullying is only one. It challenges simple cause-and-effect models that may suggest that suicide arises from anyone factor, such as bullying.

A Comparison of Solver Performance for Complex Gastric Electrophysiology Models

PubMed Central

Sathar, Shameer; Cheng, Leo K.; Trew, Mark L.

2016-01-01

Computational techniques for solving systems of equations arising in gastric electrophysiology have not been studied for efficient solution process. We present a computationally challenging problem of simulating gastric electrophysiology in anatomically realistic stomach geometries with multiple intracellular and extracellular domains. The multiscale nature of the problem and mesh resolution required to capture geometric and functional features necessitates efficient solution methods if the problem is to be tractable. In this study, we investigated and compared several parallel preconditioners for the linear systems arising from tetrahedral discretisation of electrically isotropic and anisotropic problems, with and without stimuli. The results showed that the isotropic problem was computationally less challenging than the anisotropic problem and that the application of extracellular stimuli increased workload considerably. Preconditioning based on block Jacobi and algebraic multigrid solvers were found to have the best overall solution times and least iteration counts, respectively. The algebraic multigrid preconditioner would be expected to perform better on large problems. PMID:26736543

Task-oriented situation recognition

NASA Astrophysics Data System (ADS)

Bauer, Alexander; Fischer, Yvonne

2010-04-01

From the advances in computer vision methods for the detection, tracking and recognition of objects in video streams, new opportunities for video surveillance arise: In the future, automated video surveillance systems will be able to detect critical situations early enough to enable an operator to take preventive actions, instead of using video material merely for forensic investigations. However, problems such as limited computational resources, privacy regulations and a constant change in potential threads have to be addressed by a practical automated video surveillance system. In this paper, we show how these problems can be addressed using a task-oriented approach. The system architecture of the task-oriented video surveillance system NEST and an algorithm for the detection of abnormal behavior as part of the system are presented and illustrated for the surveillance of guests inside a video-monitored building.

Problem-Solving during Shared Reading at Kindergarten

ERIC Educational Resources Information Center

Gosen, Myrte N.; Berenst, Jan; de Glopper, Kees

2015-01-01

This paper reports on a conversation analytic study of problem-solving interactions during shared reading at three kindergartens in the Netherlands. It illustrates how teachers and pupils discuss book characters' problems that arise in the events in the picture books. A close analysis of the data demonstrates that problem-solving interactions do…

Transnational Environmental Problems--The United States, Canada, Mexico.

ERIC Educational Resources Information Center

Wilcher, Marshall E.

1983-01-01

Examines problems associated with transboundary environmental pollution, focusing on problems arising between the United States and Mexico and between the United States and Canada. Also discusses new organizational forms developed to bring transboundary issues to a higher policy-making level. (JN)

Distinctions between fraud, bias, errors, misunderstanding, and incompetence.

PubMed

DeMets, D L

1997-12-01

Randomized clinical trials are challenging not only in their design and analysis, but in their conduct as well. Despite the best intentions and efforts, problems often arise in the conduct of trials, including errors, misunderstandings, and bias. In some instances, key players in a trial may discover that they are not able or competent to meet requirements of the study. In a few cases, fraudulent activity occurs. While none of these problems is desirable, randomized clinical trials are usually found sufficiently robust by many key individuals to produce valid results. Other problems are not tolerable. Confusion may arise among scientists, scientific and lay press, and the public about the distinctions between these areas and their implications. We shall try to define these problems and illustrate their impact through a series of examples.

A non-local free boundary problem arising in a theory of financial bubbles

PubMed Central

Berestycki, Henri; Monneau, Regis; Scheinkman, José A.

2014-01-01

We consider an evolution non-local free boundary problem that arises in the modelling of speculative bubbles. The solution of the model is the speculative component in the price of an asset. In the framework of viscosity solutions, we show the existence and uniqueness of the solution. We also show that the solution is convex in space, and establish several monotonicity properties of the solution and of the free boundary with respect to parameters of the problem. To study the free boundary, we use, in particular, the fact that the odd part of the solution solves a more standard obstacle problem. We show that the free boundary is and describe the asymptotics of the free boundary as c, the cost of transacting the asset, goes to zero. PMID:25288815

First principles cable braid electromagnetic penetration model

DOE PAGES

Warne, Larry Kevin; Langston, William L.; Basilio, Lorena I.; ...

2016-01-01

The model for penetration of a wire braid is rigorously formulated. Integral formulas are developed from energy principles for both self and transfer immittances in terms of potentials for the fields. The detailed boundary value problem for the wire braid is also set up in a very efficient manner; the braid wires act as sources for the potentials in the form of a sequence of line multi-poles with unknown coefficients that are determined by means of conditions arising from the wire surface boundary conditions. Approximations are introduced to relate the local properties of the braid wires to a simplified infinitemore » periodic planar geometry. Furthermore, this is used to treat nonuniform coaxial geometries including eccentric interior coaxial arrangements and an exterior ground plane.« less

A Summary of Some Discrete-Event System Control Problems

NASA Astrophysics Data System (ADS)

Rudie, Karen

A summary of the area of control of discrete-event systems is given. In this research area, automata and formal language theory is used as a tool to model physical problems that arise in technological and industrial systems. The key ingredients to discrete-event control problems are a process that can be modeled by an automaton, events in that process that cannot be disabled or prevented from occurring, and a controlling agent that manipulates the events that can be disabled to guarantee that the process under control either generates all the strings in some prescribed language or as many strings as possible in some prescribed language. When multiple controlling agents act on a process, decentralized control problems arise. In decentralized discrete-event systems, it is presumed that the agents effecting control cannot each see all event occurrences. Partial observation leads to some problems that cannot be solved in polynomial time and some others that are not even decidable.

The Visual Effects of Intraocular Colored Filters

PubMed Central

Hammond, Billy R.

2012-01-01

Modern life is associated with a myriad of visual problems, most notably refractive conditions such as myopia. Human ingenuity has addressed such problems using strategies such as spectacle lenses or surgical correction. There are other visual problems, however, that have been present throughout our evolutionary history and are not as easily solved by simply correcting refractive error. These problems include issues like glare disability and discomfort arising from intraocular scatter, photostress with the associated transient loss in vision that arises from short intense light exposures, or the ability to see objects in the distance through a veil of atmospheric haze. One likely biological solution to these more long-standing problems has been the use of colored intraocular filters. Many species, especially diurnal, incorporate chromophores from numerous sources (e.g., often plant pigments called carotenoids) into ocular tissues to improve visual performance outdoors. This review summarizes information on the utility of such filters focusing on chromatic filtering by humans. PMID:24278692

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

Several topics arising in the finite element solution of the incompressible Navier-Stokes equations are considered. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. The role of artificial viscosity in viscous flow calculations is studied, emphasizing work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some modifications are mentioned.

Multigrid Algorithms for the Solution of Linear Complementarity Problems Arising from Free Boundary Problems.

DTIC Science & Technology

1980-10-01

faster than previous algorithms. Indeed, with only minor modifications, the standard multigrid programs solve the LCP with essentially the same efficiency... Lemna 2.2. Let Uk be the solution of the LCP (2.3), and let uk > 0 be an approximate solu- tion obtained after one or more Gk projected sweeps. Let...in Figure 3.2, Ivu IIG decreased from .293 10 to .110 10 with the expenditure of (99.039-94.400) = 4.639 work units. While minor variations do arise, a

Analytical-numerical solution of a nonlinear integrodifferential equation in econometrics

NASA Astrophysics Data System (ADS)

Kakhktsyan, V. M.; Khachatryan, A. Kh.

2013-07-01

A mixed problem for a nonlinear integrodifferential equation arising in econometrics is considered. An analytical-numerical method is proposed for solving the problem. Some numerical results are presented.

An investigation into waste charges in Ireland, with emphasis on public acceptability.

PubMed

Dunne, Louise; Convery, Frank J; Gallagher, Louise

2008-12-01

There are 34 local authorities in Ireland with legal responsibility to deal with waste arising in their jurisdictions. In 2003 the National government introduced legislation that allows local authorities to recover the costs of waste collection and disposal, and to do so by 'executive function', i.e., not requiring support or agreement by the relevant local political representatives. The year 2005 was set as the date by which implementation of a pay by weight or volume was to be introduced. The local authorities were given autonomy as to how they addressed this challenge, so we have - in theory - 34 potentially different experiences from which to learn. This paper examines the pay-as-you-throw (PAYT) waste system in Ireland as it develops in line with EU and National demands, with a view to assessing economic and environmental efficiency. All local authorities were surveyed and thirteen responded. While this only represents about 38% of the total number, it includes jurisdictions that contribute in total more than 50% of waste arising. Key figures in the policy and business community were also interviewed in order to identify how the charging schemes were implemented, and to what effect. These insights and parallel investigations are used to review the potential for problems regarding public acceptability of environmental taxes and examine the evidence for economic and environmental efficiency, as well as problem areas, using data from each of the responding local authority jurisdictions. Concentrating on the incentives and drivers across households, municipalities and private waste contractors, the variations in charging system, annual charges and landfill charges are compared where information was available. The various jurisdictions are also examined in terms of relative successes and problems encountered in the transition from fixed charge or free waste collection to PAYT systems. The Irish situation is placed in the context of the international literature on PAYT, the growing waste crisis, environmental attitudes vs. behaviours, and the acceptability of environmental taxes generally.

Extension of the KLI approximation toward the exact optimized effective potential.

PubMed

Iafrate, G J; Krieger, J B

2013-03-07

The integral equation for the optimized effective potential (OEP) is utilized in a compact form from which an accurate OEP solution for the spin-unrestricted exchange-correlation potential, Vxcσ, is obtained for any assumed orbital-dependent exchange-correlation energy functional. The method extends beyond the Krieger-Li-Iafrate (KLI) approximation toward the exact OEP result. The compact nature of the OEP equation arises by replacing the integrals involving the Green's function terms in the traditional OEP equation by an equivalent first-order perturbation theory wavefunction often referred to as the "orbital shift" function. Significant progress is then obtained by solving the equation for the first order perturbation theory wavefunction by use of Dalgarno functions which are determined from well known methods of partial differential equations. The use of Dalgarno functions circumvents the need to explicitly address the Green's functions and the associated problems with "sum over states" numerics; as well, the Dalgarno functions provide ease in dealing with inherent singularities arising from the origin and the zeros of the occupied orbital wavefunctions. The Dalgarno approach for finding a solution to the OEP equation is described herein, and a detailed illustrative example is presented for the special case of a spherically symmetric exchange-correlation potential. For the case of spherical symmetry, the relevant Dalgarno function is derived by direct integration of the appropriate radial equation while utilizing a user friendly method which explicitly treats the singular behavior at the origin and at the nodal singularities arising from the zeros of the occupied states. The derived Dalgarno function is shown to be an explicit integral functional of the exact OEP Vxcσ, thus allowing for the reduction of the OEP equation to a self-consistent integral equation for the exact exchange-correlation potential; the exact solution to this integral equation can be determined by iteration with the natural zeroth order correction given by the KLI exchange-correlation potential. Explicit analytic results are provided to illustrate the first order iterative correction beyond the KLI approximation. The derived correction term to the KLI potential explicitly involves spatially weighted products of occupied orbital densities in any assumed orbital-dependent exchange-correlation energy functional; as well, the correction term is obtained with no adjustable parameters. Moreover, if the equation for the exact optimized effective potential is further iterated, one can obtain the OEP as accurately as desired.

Extension of the KLI approximation toward the exact optimized effective potential

NASA Astrophysics Data System (ADS)

Iafrate, G. J.; Krieger, J. B.

2013-03-01

The integral equation for the optimized effective potential (OEP) is utilized in a compact form from which an accurate OEP solution for the spin-unrestricted exchange-correlation potential, Vxcσ, is obtained for any assumed orbital-dependent exchange-correlation energy functional. The method extends beyond the Krieger-Li-Iafrate (KLI) approximation toward the exact OEP result. The compact nature of the OEP equation arises by replacing the integrals involving the Green's function terms in the traditional OEP equation by an equivalent first-order perturbation theory wavefunction often referred to as the "orbital shift" function. Significant progress is then obtained by solving the equation for the first order perturbation theory wavefunction by use of Dalgarno functions which are determined from well known methods of partial differential equations. The use of Dalgarno functions circumvents the need to explicitly address the Green's functions and the associated problems with "sum over states" numerics; as well, the Dalgarno functions provide ease in dealing with inherent singularities arising from the origin and the zeros of the occupied orbital wavefunctions. The Dalgarno approach for finding a solution to the OEP equation is described herein, and a detailed illustrative example is presented for the special case of a spherically symmetric exchange-correlation potential. For the case of spherical symmetry, the relevant Dalgarno function is derived by direct integration of the appropriate radial equation while utilizing a user friendly method which explicitly treats the singular behavior at the origin and at the nodal singularities arising from the zeros of the occupied states. The derived Dalgarno function is shown to be an explicit integral functional of the exact OEP Vxcσ, thus allowing for the reduction of the OEP equation to a self-consistent integral equation for the exact exchange-correlation potential; the exact solution to this integral equation can be determined by iteration with the natural zeroth order correction given by the KLI exchange-correlation potential. Explicit analytic results are provided to illustrate the first order iterative correction beyond the KLI approximation. The derived correction term to the KLI potential explicitly involves spatially weighted products of occupied orbital densities in any assumed orbital-dependent exchange-correlation energy functional; as well, the correction term is obtained with no adjustable parameters. Moreover, if the equation for the exact optimized effective potential is further iterated, one can obtain the OEP as accurately as desired.

Contextualized Mathematics Problems and Transfer of Knowledge: Establishing Problem Spaces and Boundaries

ERIC Educational Resources Information Center

McGraw, Rebecca; Patterson, Cody L.

2017-01-01

In this study, we examine how inservice secondary mathematics teachers working together on a contextualized problem negotiate issues arising from the ill-structured nature of the problem such as what assumptions one may make, what real-world considerations should be taken into account, and what constitutes a satisfactory solution. We conceptualize…

Pilots of the future - Human or computer?

NASA Technical Reports Server (NTRS)

Chambers, A. B.; Nagel, D. C.

1985-01-01

In connection with the occurrence of aircraft accidents and the evolution of the air-travel system, questions arise regarding the computer's potential for making fundamental contributions to improving the safety and reliability of air travel. An important result of an analysis of the causes of aircraft accidents is the conclusion that humans - 'pilots and other personnel' - are implicated in well over half of the accidents which occur. Over 70 percent of the incident reports contain evidence of human error. In addition, almost 75 percent show evidence of an 'information-transfer' problem. Thus, the question arises whether improvements in air safety could be achieved by removing humans from control situations. In an attempt to answer this question, it is important to take into account also certain advantages which humans have in comparison to computers. Attention is given to human error and the effects of technology, the motivation to automate, aircraft automation at the crossroads, the evolution of cockpit automation, and pilot factors.

Ethics and the psychiatry journal editor: responsibilities and dilemmas.

PubMed

Greenberg, David; D Strous, Rael

2014-01-01

An array of potential ethical stumbling blocks awaits the editors of scientific journals. There are issues of particular relevance to mental health journals, and others unique to local journals with a relatively small circulation and low impact factor. The blind review system, conflict of interests, redundant publication, fraud and plagiarism, guest and ghost authorship and ghost writing, advertising, language and stigma, patient consent, and "rigging" the Impact Factor are all issues of importance. It is critical that editors are aware and informed of these important issues, and have an accessible forum for evaluating problems as they arise.

Smile design: rules, tools and strategies to help plan aesthetic restorative dentistry.

PubMed

Holyoak, Matthew

2013-10-01

This article is intended to provide dentists with a framework to help in objectively assessing upper anterior aesthetic restorations. Not all of the areas discussed will be equally important in all cases, and a degree of subjectivity, based on clinical experience, is essential. There has been a huge increase in settlements in cases when aesthetic treatment has not led to patient satisfaction. The author hopes that this type of approach, in conjunction with good patient communication and detailed records, will minimise the potential for litigation, should problems arise. Success or failure is largely defined during the planning stage.

Monitoring the evolving land use patterns using remote sensing

NASA Technical Reports Server (NTRS)

Goehring, D. R.

1971-01-01

The urbanization of Walnut Valley from 1953-71 prompted land use change from intensive von Thunen market-oriented patterns to extensive, disinvested, production-factor-minimized patterns. Shortrun, interim land use planning, has allowed agriculture to persist but only in the form of barley farming and grazing. Aerial photography used synoptically recorded six periods of land use change that bracketed dates before and after the freeway was announced and built. Interpretations of these changes help recognize potential conversions to urban uses which allow guidelines to be established that deal with rural-urban transition problems before they arise.

Coping strategies in an ethnic minority group: the Aeta of Mount Pinatubo.

PubMed

Seitz, S

1998-03-01

The particular problems arising in the aftermath of natural disasters in indigenous societies in the Third World, especially in ethnic or cultural minorities, have until now received only little attention in social scientific research. The potential of such indigenous groups to use their traditional knowledge and behaviour patterns in coping with natural disasters has been badly neglected. The example of the Aeta in Zambales, Philippines, a marginal group who were hit directly by the eruption of Mt Pinatubo in 1991, shows how traditional economic and social behaviour can in some measure determine their various survival strategies.

From the Golden Rectangle and Fibonacci to Pedagogy and Problem Posing

ERIC Educational Resources Information Center

Brown, Stephen I.

1976-01-01

Beginning with an analysis of the golden rectangle, the author shows how a series of problems for student investigation arise from queries concerning changes in conditions and analogous situations. (SD)

Problems in Recording the Electrocardiogram.

ERIC Educational Resources Information Center

Webster, John G.

The unwanted signals that arise in electrocardiography are discussed. A technical background of electrocardiography is given, along with teaching techniques that educate students of medical instrumentation to solve the problems caused by these signals. (MJH)

An Inverse Problem for a Class of Conditional Probability Measure-Dependent Evolution Equations

PubMed Central

Mirzaev, Inom; Byrne, Erin C.; Bortz, David M.

2016-01-01

We investigate the inverse problem of identifying a conditional probability measure in measure-dependent evolution equations arising in size-structured population modeling. We formulate the inverse problem as a least squares problem for the probability measure estimation. Using the Prohorov metric framework, we prove existence and consistency of the least squares estimates and outline a discretization scheme for approximating a conditional probability measure. For this scheme, we prove general method stability. The work is motivated by Partial Differential Equation (PDE) models of flocculation for which the shape of the post-fragmentation conditional probability measure greatly impacts the solution dynamics. To illustrate our methodology, we apply the theory to a particular PDE model that arises in the study of population dynamics for flocculating bacterial aggregates in suspension, and provide numerical evidence for the utility of the approach. PMID:28316360

Exploiting Symmetry on Parallel Architectures.

NASA Astrophysics Data System (ADS)

Stiller, Lewis Benjamin

1995-01-01

This thesis describes techniques for the design of parallel programs that solve well-structured problems with inherent symmetry. Part I demonstrates the reduction of such problems to generalized matrix multiplication by a group-equivariant matrix. Fast techniques for this multiplication are described, including factorization, orbit decomposition, and Fourier transforms over finite groups. Our algorithms entail interaction between two symmetry groups: one arising at the software level from the problem's symmetry and the other arising at the hardware level from the processors' communication network. Part II illustrates the applicability of our symmetry -exploitation techniques by presenting a series of case studies of the design and implementation of parallel programs. First, a parallel program that solves chess endgames by factorization of an associated dihedral group-equivariant matrix is described. This code runs faster than previous serial programs, and discovered it a number of results. Second, parallel algorithms for Fourier transforms for finite groups are developed, and preliminary parallel implementations for group transforms of dihedral and of symmetric groups are described. Applications in learning, vision, pattern recognition, and statistics are proposed. Third, parallel implementations solving several computational science problems are described, including the direct n-body problem, convolutions arising from molecular biology, and some communication primitives such as broadcast and reduce. Some of our implementations ran orders of magnitude faster than previous techniques, and were used in the investigation of various physical phenomena.

Parallel block schemes for large scale least squares computations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golub, G.H.; Plemmons, R.J.; Sameh, A.

1986-04-01

Large scale least squares computations arise in a variety of scientific and engineering problems, including geodetic adjustments and surveys, medical image analysis, molecular structures, partial differential equations and substructuring methods in structural engineering. In each of these problems, matrices often arise which possess a block structure which reflects the local connection nature of the underlying physical problem. For example, such super-large nonlinear least squares computations arise in geodesy. Here the coordinates of positions are calculated by iteratively solving overdetermined systems of nonlinear equations by the Gauss-Newton method. The US National Geodetic Survey will complete this year (1986) the readjustment ofmore » the North American Datum, a problem which involves over 540 thousand unknowns and over 6.5 million observations (equations). The observation matrix for these least squares computations has a block angular form with 161 diagnonal blocks, each containing 3 to 4 thousand unknowns. In this paper parallel schemes are suggested for the orthogonal factorization of matrices in block angular form and for the associated backsubstitution phase of the least squares computations. In addition, a parallel scheme for the calculation of certain elements of the covariance matrix for such problems is described. It is shown that these algorithms are ideally suited for multiprocessors with three levels of parallelism such as the Cedar system at the University of Illinois. 20 refs., 7 figs.« less

Use of Picard and Newton iteration for solving nonlinear ground water flow equations

USGS Publications Warehouse

Mehl, S.

2006-01-01

This study examines the use of Picard and Newton iteration to solve the nonlinear, saturated ground water flow equation. Here, a simple three-node problem is used to demonstrate the convergence difficulties that can arise when solving the nonlinear, saturated ground water flow equation in both homogeneous and heterogeneous systems with and without nonlinear boundary conditions. For these cases, the characteristic types of convergence patterns are examined. Viewing these convergence patterns as orbits of an attractor in a dynamical system provides further insight. It is shown that the nonlinearity that arises from nonlinear head-dependent boundary conditions can cause more convergence difficulties than the nonlinearity that arises from flow in an unconfined aquifer. Furthermore, the effects of damping on both convergence and convergence rate are investigated. It is shown that no single strategy is effective for all problems and how understanding pitfalls and merits of several methods can be helpful in overcoming convergence difficulties. Results show that Picard iterations can be a simple and effective method for the solution of nonlinear, saturated ground water flow problems.

Institutional Resource Requirements, Management, and Accountability.

ERIC Educational Resources Information Center

Matlock, John; Humphries, Frederick S.

A detailed resource management study was conducted at Tennessee State University, and resource management problems at other higher education institutions were identified through the exchange of data and studies. Resource requirements and management problems unique to black institutions were examined, as were the problems that arise from regional…

Second Computational Aeroacoustics (CAA) Workshop on Benchmark Problems

NASA Technical Reports Server (NTRS)

Tam, C. K. W. (Editor); Hardin, J. C. (Editor)

1997-01-01

The proceedings of the Second Computational Aeroacoustics (CAA) Workshop on Benchmark Problems held at Florida State University are the subject of this report. For this workshop, problems arising in typical industrial applications of CAA were chosen. Comparisons between numerical solutions and exact solutions are presented where possible.

Conducting qualitative research within Clinical Trials Units: avoiding potential pitfalls.

PubMed

Cooper, Cindy; O'Cathain, Alicia; Hind, Danny; Adamson, Joy; Lawton, Julia; Baird, Wendy

2014-07-01

The value of using qualitative research within or alongside randomised controlled trials (RCTs) is becoming more widely accepted. Qualitative research may be conducted concurrently with pilot or full RCTs to understand the feasibility and acceptability of the interventions being tested, or to improve trial conduct. Clinical Trials Units (CTUs) in the United Kingdom (UK) manage large numbers of RCTs and, increasingly, manage the qualitative research or collaborate with qualitative researchers external to the CTU. CTUs are beginning to explicitly manage the process, for example, through the use of standard operating procedures for designing and implementing qualitative research with trials. We reviewed the experiences of two UK Clinical Research Collaboration (UKCRC) registered CTUs of conducting qualitative research concurrently with RCTs. Drawing on experiences gained from 15 studies, we identify the potential for the qualitative research to undermine the successful completion or scientific integrity of RCTs. We show that potential problems can arise from feedback of interim or final qualitative findings to members of the trial team or beyond, in particular reporting qualitative findings whilst the trial is on-going. The problems include: We make recommendations for improving the management of qualitative research within CTUs. Copyright © 2014. Published by Elsevier Inc.

A New Approach to Isolating External Magnetic Field Components in Spacecraft Measurements of the Earth's Magnetic Field Using Global Positioning System observables

NASA Technical Reports Server (NTRS)

Raymond, C.; Hajj, G.

1994-01-01

We review the problem of separating components of the magnetic field arising from sources in the Earth's core and lithosphere, from those contributions arising external to the Earth, namely ionospheric and magnetospheric fields, in spacecraft measurements of the Earth's magnetic field.

Solution algorithms for nonlinear transient heat conduction analysis employing element-by-element iterative strategies

NASA Technical Reports Server (NTRS)

Winget, J. M.; Hughes, T. J. R.

1985-01-01

The particular problems investigated in the present study arise from nonlinear transient heat conduction. One of two types of nonlinearities considered is related to a material temperature dependence which is frequently needed to accurately model behavior over the range of temperature of engineering interest. The second nonlinearity is introduced by radiation boundary conditions. The finite element equations arising from the solution of nonlinear transient heat conduction problems are formulated. The finite element matrix equations are temporally discretized, and a nonlinear iterative solution algorithm is proposed. Algorithms for solving the linear problem are discussed, taking into account the form of the matrix equations, Gaussian elimination, cost, and iterative techniques. Attention is also given to approximate factorization, implementational aspects, and numerical results.

Tractable Experiment Design via Mathematical Surrogates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Brian J.

This presentation summarizes the development and implementation of quantitative design criteria motivated by targeted inference objectives for identifying new, potentially expensive computational or physical experiments. The first application is concerned with estimating features of quantities of interest arising from complex computational models, such as quantiles or failure probabilities. A sequential strategy is proposed for iterative refinement of the importance distributions used to efficiently sample the uncertain inputs to the computational model. In the second application, effective use of mathematical surrogates is investigated to help alleviate the analytical and numerical intractability often associated with Bayesian experiment design. This approach allows formore » the incorporation of prior information into the design process without the need for gross simplification of the design criterion. Illustrative examples of both design problems will be presented as an argument for the relevance of these research problems.« less

On the solution of integral equations with a generalized cauchy kernal

NASA Technical Reports Server (NTRS)

Kaya, A. C.; Erdogan, F.

1986-01-01

A certain class of singular integral equations that may arise from the mixed boundary value problems in nonhonogeneous materials is considered. The distinguishing feature of these equations is that in addition to the Cauchy singularity, the kernels contain terms that are singular only at the end points. In the form of the singular integral equations adopted, the density function is a potential or a displacement and consequently the kernal has strong singularities of the form (t-x)(-2), x(n-2) (t+x)(n), (n is = or 2, 0 x, t b). The complex function theory is used to determine the fundamental function of the problem for the general case and a simple numerical technique is described to solve the integral equation. Two examples from the theory of elasticity are then considered to show the application of the technique.

A constitutive law for finite element contact problems with unclassical friction

NASA Technical Reports Server (NTRS)

Plesha, M. E.; Steinetz, B. M.

1986-01-01

Techniques for modeling complex, unclassical contact-friction problems arising in solid and structural mechanics are discussed. A constitutive modeling concept is employed whereby analytic relations between increments of contact surface stress (i.e., traction) and contact surface deformation (i.e., relative displacement) are developed. Because of the incremental form of these relations, they are valid for arbitrary load-deformation histories. The motivation for the development of such a constitutive law is that more realistic friction idealizations can be implemented in finite element analysis software in a consistent, straightforward manner. Of particular interest is modeling of two-body (i.e., unlubricated) metal-metal, ceramic-ceramic, and metal-ceramic contact. Interfaces involving ceramics are of engineering importance and are being considered for advanced turbine engines in which higher temperature materials offer potential for higher engine fuel efficiency.

Positive Discipline A to Z: 1001 Solutions to Everyday Parenting Problems.

ERIC Educational Resources Information Center

Nelsen, Jane; And Others

This book is a parenting reference work that offers background on common disciplinary problems and parenting issues, advice on how to handle problems and issues as they arise, and insight into how to avoid disciplinary problems in the future. The book is divided into three sections: Basic Positive Discipline Parenting Tools, Positive Discipline…

Cognitive Abilities Adjustment and Parenting Practices in Preschoolers with Disruption Conduct Problems

ERIC Educational Resources Information Center

Fernandez-Parra, A.; Lopez-Rubio, S.; Mata, S.; Calero, M. D.; Vives, M. C.; Carles, R.; Navarro, E.

2013-01-01

Introduction: Conduct problems arising in infancy are one of the main reasons for which parents seek psychological assistance. Although these problems usually begin when the child has started school, in recent years a group of children has been identified who begin to manifest such problems from their earliest infancy and whose prognosis seems to…

Opportunities and challenges for the application of SP measurements to monitor subsurface flow (Invited)

NASA Astrophysics Data System (ADS)

Jackson, M.; Vinogradov, J.; MacAllister, D.; Butler, A. P.; Leinov, E.; Zhang, J.

2013-12-01

Measurements of self-potential (SP) have been proposed or applied to monitor flow in the shallow subsurface in numerous settings, including volcanoes, earthquake zones, geothermal fields and hydrocarbon reservoirs, to detect leaks from dams, tanks and embankments, and to characterize groundwater flow and hydraulic properties. To interpret the measurements, it is generally assumed that the SP is dominated by the streaming potential, arising from the drag of excess electrical charge in the diffuse part of the electrical double layer at the mineral-fluid interfaces. The constitutive equation relating electrical current density j to the driving forces ▽V and ▽P is then j = -σ▽V -σC▽P=-σ▽V + Qv (1) where V is the streaming potential, P is the water pressure, σ is the saturated rock conductivity, v is the Darcy velocity, C is the streaming potential coupling coefficient, and Q is the excess charge transported by the flow. Equation (1) shows that there is a close relationship between flow properties of interest, such as the pressure gradient or Darcy velocity, and the streaming potential component of the SP. Hence SP measurements are an attractive method to monitor subsurface flow. However, the problem with interpreting the measurements is that both C and Q can vary over orders of magnitude, in response to variations in pore-water salinity, temperature, rock texture, and the presence of NAPLs in the pore-space. Moreover, additional current sources may be present if there are gradients in concentration or temperature, arising from differential rates of ion migration down gradient (diffusion potentials), and because of charge exclusion from the pore-space (exclusion potentials). In general, these additional current sources are neglected. This talk suggests a potential new opportunity for the application of SP measurements to monitor subsurface flow, in which the signal of interest arises from salinity rather than pressure gradients. Saline intrusion into freshwater aquifers is a global problem, threatening the water supply of millions of people in coastal settlements. Abstraction rates could be much more efficiently managed if encroaching saline water could be detected before it arrived at the borehole. However, current monitoring is based largely on borehole conductivity measurements, which requires a dense network of monitoring boreholes to map the saline front. Recent laboratory and field experiments suggest that the concentration gradient associated with the front generates an SP signal which can be detected at an abstraction well prior to the arrival of the front, potentially allowing monitoring using a comparatively cheap array of non-polarising borehole electrodes. Current challenges in interpreting SP measurements for subsurface flow are also discussed, particularly the use of models to predict the values of C and Q. The importance of accounting for the pore-level distribution of flow and excess charge in such models is emphasised, and a way forward is suggested in which pore-scale network models, used previously to predict relative permeability and capillary pressure, are extended to include charge transport at the pore-level.

The Line-drawing Problem in Disease Definition.

PubMed

Rogers, Wendy A; Walker, Mary Jean

2017-08-01

Biological dysfunction is regarded, in many accounts, as necessary and perhaps sufficient for disease. But although disease is conceptualized as all-or-nothing, biological functions often differ by degree. A tension is created by attempting to use a continuous variable as the basis for a categorical definition, raising questions about how we are to pinpoint the boundary between health and disease. This is the line-drawing problem. In this paper, we show how the line-drawing problem arises within "dysfunction-requiring" accounts of disease, such as those of Christopher Boorse and Jerome Wakefield. We then provide several detailed examples to establish that biological dysfunction cannot provide a boundary. We examine potential ways of resolving the line-drawing problem, either by dropping one of the claims that generates it, or by appealing to additional criteria. We argue that two of these options are plausible, and that each of these can be applied with regard to different diseases. © The Author 2017. Published by Oxford University Press, on behalf of the Journal of Medicine and Philosophy Inc. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Validation of a finite element method framework for cardiac mechanics applications

NASA Astrophysics Data System (ADS)

Danan, David; Le Rolle, Virginie; Hubert, Arnaud; Galli, Elena; Bernard, Anne; Donal, Erwan; Hernández, Alfredo I.

2017-11-01

Modeling cardiac mechanics is a particularly challenging task, mainly because of the poor understanding of the underlying physiology, the lack of observability and the complexity of the mechanical properties of myocardial tissues. The choice of cardiac mechanic solvers, especially, implies several difficulties, notably due to the potential instability arising from the nonlinearities inherent to the large deformation framework. Furthermore, the verification of the obtained simulations is a difficult task because there is no analytic solutions for these kinds of problems. Hence, the objective of this work is to provide a quantitative verification of a cardiac mechanics implementation based on two published benchmark problems. The first problem consists in deforming a bar whereas the second problem concerns the inflation of a truncated ellipsoid-shaped ventricle, both in the steady state case. Simulations were obtained by using the finite element software GETFEM++. Results were compared to the consensus solution published by 11 groups and the proposed solutions were indistinguishable. The validation of the proposed mechanical model implementation is an important step toward the proposition of a global model of cardiac electro-mechanical activity.

An Observational Study of Bullying as a Contributing Factor in Youth Suicide in Toronto

PubMed Central

Sinyor, Mark; Schaffer, Ayal; Cheung, Amy H

2014-01-01

Objective Bullying has been identified as a potential contributing factor in youth suicide. This issue has been highlighted in recent widely publicized media reports, worldwide, in which deceased youth were bullied. We report on an observational study conducted to determine the frequency of bullying as a contributing factor to youth suicide. Method: Coroner records were reviewed for all suicide deaths in youth aged between 10 and 19 in the city of Toronto from 1998 to 2011. Data abstracted were recent stressors (including bullying), clinical variables, such as the presence of mental illness, demographics, and methods of suicide. Results: Ninety-four youth suicides were included in the study. The mean age was 16.8 years, and 70.2% were male. Bullying was present in 6 deaths (6.4%), and there were no deaths where online or cyberbullying was detected. Bullying was the only identified contributing factor in fewer than 5 deaths. The most common stressors identified were conflict with parents (21.3%), romantic partner problems (17.0%), academic problems (10.6%), and criminal and (or) legal problems (10.6%). Any stressor or mental and (or) physical illness was detected in 78.7% of cases. Depression was detected in 40.4% of cases. Conclusions: Our study highlights the need to view suicide in youth as arising from a complex interplay of various biological, psychological, and social factors of which bullying is only one. It challenges simple cause-and-effect models that may suggest that suicide arises from any one factor, such as bullying. PMID:25702362

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

This paper considers several topics arising in the finite element solution of the incompressible Navier-Stokes equations. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. Following this, the role of artificial viscosity in viscous flow calculations is studied, emphasizing recent work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some recent modifications are mentioned.

The Problem with Paradigms: Bateman's Worldview as a Case Study.

PubMed

Tang-Martinez, Zuleyma; Ryder, T Brandt

2005-11-01

Bateman's principles, their corollaries and predictions constitute a paradigm for the study of sexual selection theory, evolution of mating systems, parental investment theory, and sexual dimorphism in male and female behavior. Some aspects of this paradigm have been challenged in recent years, while others have been supported by empirical and theoretical research. We re-examine Bateman's 1948 paper in detail, including some methodological problems. Additionally, we review three areas in which an over-reliance on Bateman's predictions about sexual dynamics hindered our ability to understand the potential importance of certain behaviors: 1) male mate choice and sperm allocation; 2) the role of females in initiating and soliciting extra-pair copulations and fertilizations; and 3) the role of females in lekking systems, in which recent evidence suggests that copulations with multiple males (polyandrous behavior) may be common. We conclude this introduction to the symposium by emphasizing the heuristic value of Bateman's contributions, as well as the problems that arise when Bateman's paradigm is viewed through the lens of modern behavioral ecology and evolutionary theory.

The Ethics of Doing Ethics.

PubMed

Hansson, Sven Ove

2017-02-01

Ethicists have investigated ethical problems in other disciplines, but there has not been much discussion of the ethics of their own activities. Research in ethics has many ethical problems in common with other areas of research, and it also has problems of its own. The researcher's integrity is more precarious than in most other disciplines, and therefore even stronger procedural checks are needed to protect it. The promotion of some standpoints in ethical issues may be socially harmful, and even our decisions as to which issues we label as "ethical" may have unintended and potentially harmful social consequences. It can be argued that ethicists have an obligation to make positive contributions to society, but the practical implications of such an obligation are not easily identified. This article provides an overview of ethical issues that arise in research into ethics and in the application of such research. It ends with a list of ten practical proposals for how these issues should be dealt with.

The Model of Landscape Development in Big Cities Of Central Java

NASA Astrophysics Data System (ADS)

Darmawan, E.; Murtini, T. W.

2018-05-01

The existence of urban parks as a part of urban green space is very important for the environment and the citizen of the city, and inseparable part from the urban landscape. In its development, the existence of an urban parks could create a safe, comfortable, productive, and visually aesthetical environment. The problem arising now is a view that the urban parks are often unsuitable with the surrounding. Therefore, the parks are not functional and does not have significant visual. So that, this research is aimed to reveal model of landscape development in big cities in Central Java. The method used is descriptive qualitative that can describe the detail of problem, in determining the plan to overcome the problem. The research location will focused on big cities in Central Java with potential landscape that can be improved. The results of the research will be composed in an international scientific journals and is expected to be a reference in the field of urban landscape arrangement.

Responding to Adolescent Suicide.

ERIC Educational Resources Information Center

Phi Delta Kappa Educational Foundation, Bloomington, IN.

This publication is designed to help educators deal with the problems that arise after an adolescent's suicide. It recommends that teachers should be able to detect differences in students' responses to emotional problems. Following a preface and a brief review of the extent of the problem, the first chapter discusses which adolescents are…

Introducing the Hero Complex and the Mythic Iconic Pathway of Problem Gambling

ERIC Educational Resources Information Center

Nixon, Gary; Solowoniuk, Jason

2009-01-01

Early research into the motivations behind problem gambling reflected separate paradigms of thought splitting our understanding of the gambler into divergent categories. However, over the past 25 years, problem gambling is now best understood to arise from biological, environmental, social, and psychological processes, and is now encapsulated…

Esperanto and International Language Problems: A Research Bibliography.

ERIC Educational Resources Information Center

Tonkin, Humphrey R.

This bibliography is intended both for the researcher and for the occasional student of international language problems, particularly as these relate to the international language Esperanto. The book is divided into two main sections: Part One deals with problems arising from communication across national boundaries and the search for a solution…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warne, Larry K.; Langston, William L.; Basilio, Lorena I.

The model for penetration of a wire braid is rigorously formulated. Integral formulas are developed from energy principles and reciprocity for both self and transfer immittances in terms of potentials for the fields. The detailed boundary value problem for the wire braid is also setup in a very efficient manner; the braid wires act as sources for the potentials in the form of a sequence of line multipoles with unknown coefficients that are determined by means of conditions arising from the wire surface boundary conditions. Approximations are introduced to relate the local properties of the braid wires to a simplifiedmore » infinite periodic planar geometry. This is used in a simplified application of reciprocity to be able to treat nonuniform coaxial geometries including eccentric interior coaxial arrangements and an exterior ground plane.« less

Scalar field cosmologies with inverted potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boisseau, B.; Giacomini, H.; Polarski, D., E-mail: bruno.boisseau@lmpt.univ-tours.fr, E-mail: hector.giacomini@lmpt.univ-tours.fr, E-mail: david.polarski@umontpellier.fr

Regular bouncing solutions in the framework of a scalar-tensor gravity model were found in a recent work. We reconsider the problem in the Einstein frame (EF) in the present work. Singularities arising at the limit of physical viability of the model in the Jordan frame (JF) are either of the Big Bang or of the Big Crunch type in the EF. As a result we obtain integrable scalar field cosmological models in general relativity (GR) with inverted double-well potentials unbounded from below which possess solutions regular in the future, tending to a de Sitter space, and starting with a Bigmore » Bang. The existence of the two fixed points for the field dynamics at late times found earlier in the JF becomes transparent in the EF.« less

3D Compton scattering imaging and contour reconstruction for a class of Radon transforms

NASA Astrophysics Data System (ADS)

Rigaud, Gaël; Hahn, Bernadette N.

2018-07-01

Compton scattering imaging is a nascent concept arising from the current development of high-sensitive energy detectors and is devoted to exploit the scattering radiation to image the electron density of the studied medium. Such detectors are able to collect incoming photons in terms of energy. This paper introduces potential 3D modalities in Compton scattering imaging (CSI). The associated measured data are modeled using a class of generalized Radon transforms. The study of this class of operators leads to build a filtered back-projection kind algorithm preserving the contours of the sought-for function and offering a fast approach to partially solve the associated inverse problems. Simulation results including Poisson noise demonstrate the potential of this new imaging concept as well as the proposed image reconstruction approach.

Potential Use of Antiviral Agents in Polio Eradication

PubMed Central

De Palma, Armando M.; Pürstinger, Gerhard; Wimmer, Eva; Patick, Amy K.; Andries, Koen; Rombaut, Bart; De Clercq, Erik

2008-01-01

In 1988, the World Health Assembly launched the Global Polio Eradication Initiative, which aimed to use large-scale vaccination with the oral vaccine to eradicate polio worldwide by the year 2000. Although important progress has been made, polio remains endemic in several countries. Also, the current control measures will likely be inadequate to deal with problems that may arise in the postpolio era. A panel convoked by the National Research Council concluded that the use of antiviral drugs may be essential in the polio eradication strategy. We here report on a comparative study of the antipoliovirus activity of a selection of molecules that have previously been reported to be inhibitors of picornavirus replication and discuss their potential use, alone or in combination, for the treatment or prophylaxis of poliovirus infection. PMID:18394270

Errors, Error, and Text in Multidialect Setting.

ERIC Educational Resources Information Center

Candler, W. J.

1979-01-01

This article discusses the various dialects of English spoken in Liberia and analyzes the problems of Liberian students in writing compositions in English. Errors arise mainly from differences in culture and cognition, not from superficial linguistic problems. (CFM)

An adaptive large neighborhood search heuristic for Two-Echelon Vehicle Routing Problems arising in city logistics

PubMed Central

Hemmelmayr, Vera C.; Cordeau, Jean-François; Crainic, Teodor Gabriel

2012-01-01

In this paper, we propose an adaptive large neighborhood search heuristic for the Two-Echelon Vehicle Routing Problem (2E-VRP) and the Location Routing Problem (LRP). The 2E-VRP arises in two-level transportation systems such as those encountered in the context of city logistics. In such systems, freight arrives at a major terminal and is shipped through intermediate satellite facilities to the final customers. The LRP can be seen as a special case of the 2E-VRP in which vehicle routing is performed only at the second level. We have developed new neighborhood search operators by exploiting the structure of the two problem classes considered and have also adapted existing operators from the literature. The operators are used in a hierarchical scheme reflecting the multi-level nature of the problem. Computational experiments conducted on several sets of instances from the literature show that our algorithm outperforms existing solution methods for the 2E-VRP and achieves excellent results on the LRP. PMID:23483764

An adaptive large neighborhood search heuristic for Two-Echelon Vehicle Routing Problems arising in city logistics.

PubMed

Hemmelmayr, Vera C; Cordeau, Jean-François; Crainic, Teodor Gabriel

2012-12-01

In this paper, we propose an adaptive large neighborhood search heuristic for the Two-Echelon Vehicle Routing Problem (2E-VRP) and the Location Routing Problem (LRP). The 2E-VRP arises in two-level transportation systems such as those encountered in the context of city logistics. In such systems, freight arrives at a major terminal and is shipped through intermediate satellite facilities to the final customers. The LRP can be seen as a special case of the 2E-VRP in which vehicle routing is performed only at the second level. We have developed new neighborhood search operators by exploiting the structure of the two problem classes considered and have also adapted existing operators from the literature. The operators are used in a hierarchical scheme reflecting the multi-level nature of the problem. Computational experiments conducted on several sets of instances from the literature show that our algorithm outperforms existing solution methods for the 2E-VRP and achieves excellent results on the LRP.

A cautionary note on the use of the Analysis of Covariance (ANCOVA) in classification designs with and without within-subject factors

PubMed Central

Schneider, Bruce A.; Avivi-Reich, Meital; Mozuraitis, Mindaugas

2015-01-01

A number of statistical textbooks recommend using an analysis of covariance (ANCOVA) to control for the effects of extraneous factors that might influence the dependent measure of interest. However, it is not generally recognized that serious problems of interpretation can arise when the design contains comparisons of participants sampled from different populations (classification designs). Designs that include a comparison of younger and older adults, or a comparison of musicians and non-musicians are examples of classification designs. In such cases, estimates of differences among groups can be contaminated by differences in the covariate population means across groups. A second problem of interpretation will arise if the experimenter fails to center the covariate measures (subtracting the mean covariate score from each covariate score) whenever the design contains within-subject factors. Unless the covariate measures on the participants are centered, estimates of within-subject factors are distorted, and significant increases in Type I error rates, and/or losses in power can occur when evaluating the effects of within-subject factors. This paper: (1) alerts potential users of ANCOVA of the need to center the covariate measures when the design contains within-subject factors, and (2) indicates how they can avoid biases when one cannot assume that the expected value of the covariate measure is the same for all of the groups in a classification design. PMID:25954230

Improving Teaching Quality and Problem Solving Ability through Contextual Teaching and Learning in Differential Equations: A Lesson Study Approach

ERIC Educational Resources Information Center

Khotimah, Rita Pramujiyanti; Masduki

2016-01-01

Differential equations is a branch of mathematics which is closely related to mathematical modeling that arises in real-world problems. Problem solving ability is an essential component to solve contextual problem of differential equations properly. The purposes of this study are to describe contextual teaching and learning (CTL) model in…

Chemistry and the Internal Combustion Engine II: Pollution Problems.

ERIC Educational Resources Information Center

Hunt, C. B.

1979-01-01

Discusses pollution problems which arise from the use of internal combustion (IC) engines in the United Kingdom (UK). The IC engine exhaust emissions, controlling IC engine pollution in the UK, and some future developments are also included. (HM)

"Que vienen los lobos!" (Breve nota sobre el plural de los apellidos) ("May The Wolves Come:" [A Brief Note on the Plural of Surnames])

ERIC Educational Resources Information Center

Vivaldi, Gonzalo Martin

1975-01-01

This article discusses the problems that arise with the formation of plural forms of surnames in Spanish, problems both with morphology and with ambiguity. Suggestions as to how to lessen problems are made. (Text is in Spanish.) (CLK)

Establishing a pragmatic framework to optimise health outcomes in heart failure and multimorbidity (ARISE-HF): A multidisciplinary position statement.

PubMed

Stewart, Simon; Riegel, Barbara; Boyd, Cynthia; Ahamed, Yasmin; Thompson, David R; Burrell, Louise M; Carrington, Melinda J; Coats, Andrew; Granger, Bradi B; Hides, Julie; Weintraub, William S; Moser, Debra K; Dickson, Victoria Vaughan; McDermott, Cressida J; Keates, Ashley K; Rich, Michael W

2016-06-01

Multimorbidity in heart failure (HF), defined as HF of any aetiology and multiple concurrent conditions that require active management, represents an emerging problem within the ageing HF patient population worldwide. To inform this position paper, we performed: 1) an initial review of the literature identifying the ten most common conditions, other than hypertension and ischaemic heart disease, complicating the management of HF (anaemia, arrhythmias, cognitive dysfunction, depression, diabetes, musculoskeletal disorders, renal dysfunction, respiratory disease, sleep disorders and thyroid disease) and then 2) a review of the published literature describing the association between HF with each of the ten conditions. From these data we describe a clinical framework, comprising five key steps, to potentially improve historically poor health outcomes in this patient population. We identified five key steps (ARISE-HF) that could potentially improve clinical outcomes if applied in a systematic manner: 1) Acknowledge multimorbidity as a clinical syndrome that is associated with poor health outcomes, 2) Routinely profile (using a standardised protocol - adapted to the local health care system) all patients hospitalised with HF to determine the extent of concurrent multimorbidity, 3) Identify individualised priorities and person-centred goals based on the extent and nature of multimorbidity, 4) Support individualised, home-based, multidisciplinary, case management to supplement standard HF management, and 5) Evaluate health outcomes well beyond acute hospitalisation and encompass all-cause events and a person-centred perspective in affected individuals. We propose ARISE-HF as a framework for improving typically poor health outcomes in those affected by multimorbidity in HF. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Bose–Einstein condensation temperature of finite systems

NASA Astrophysics Data System (ADS)

Xie, Mi

2018-05-01

In studies of the Bose–Einstein condensation of ideal gases in finite systems, the divergence problem usually arises in the equation of state. In this paper, we present a technique based on the heat kernel expansion and zeta function regularization to solve the divergence problem, and obtain the analytical expression of the Bose–Einstein condensation temperature for general finite systems. The result is represented by the heat kernel coefficients, where the asymptotic energy spectrum of the system is used. Besides the general case, for systems with exact spectra, e.g. ideal gases in an infinite slab or in a three-sphere, the sums of the spectra can be obtained exactly and the calculation of corrections to the critical temperatures is more direct. For a system confined in a bounded potential, the form of the heat kernel is different from the usual heat kernel expansion. We show that as long as the asymptotic form of the global heat kernel can be found, our method works. For Bose gases confined in three- and two-dimensional isotropic harmonic potentials, we obtain the higher-order corrections to the usual results of the critical temperatures. Our method can also be applied to the problem of generalized condensation, and we give the correction of the boundary on the second critical temperature in a highly anisotropic slab.

Expectations for inflationary observables: simple or natural?

NASA Astrophysics Data System (ADS)

Musoke, Nathan; Easther, Richard

2017-12-01

We describe the general inflationary dynamics that can arise with a single, canonically coupled field where the inflaton potential is a 4-th order polynomial. This scenario yields a wide range of combinations of the empirical spectral observables, ns, r and αs. However, not all combinations are possible and next-generation cosmological experiments have the ability to rule out all inflationary scenarios based on this potential. Further, we construct inflationary priors for this potential based on physically motivated choices for its free parameters. These can be used to determine the degree of tuning associated with different combinations of ns, r and αs and will facilitate treatments of the inflationary model selection problem. Finally, we comment on the implications of these results for the naturalness of the overall inflationary paradigm. We argue that ruling out all simple, renormalizable potentials would not necessarily imply that the inflationary paradigm itself was unnatural, but that this eventuality would increase the importance of building inflationary scenarios in the context of broader paradigms of ultra-high energy physics.

Common misconceptions about the dynamical theory of crystal lattices: Cauchy relations, lattice potentials and infinite crystals

NASA Astrophysics Data System (ADS)

Elcoro, Luis; Etxebarria, Jesús

2011-01-01

The requirement of rotational invariance for lattice potential energies is investigated. Starting from this condition, it is shown that the Cauchy relations for the elastic constants are fulfilled if the lattice potential is built from pair interactions or when the first-neighbour approximation is adopted. This is seldom recognized in widely used solid-state textbooks. Frequently, pair interaction is even considered to be the most general situation. In addition, it is shown that the demand of rotational invariance in an infinite crystal leads to inconsistencies in the symmetry of the elastic tensor. However, for finite crystals, no problems arise, and the Huang conditions are deduced using exclusively a microscopic approach for the elasticity theory, without making any reference to macroscopic parameters. This work may be useful in both undergraduate and graduate level courses to point out the crudeness of the pair-potential interaction and to explore the limits of the infinite-crystal approximation.

Squamous cell carcinoma arising within a maxillary odontogenic keratocyst: A rare occurrence

PubMed Central

Jalali, Elnaz; Ferneini, Elie M.; Rengasamy, Kandasamy

2017-01-01

Squamous cell carcinoma (SCC) arising within the lining of an odontogenic keratocyst (OKC) is a rare occurrence. Although potentially locally destructive, OKC is a benign odontogenic process that typically presents with clinical and radiographic features characteristic of a benign intraosseous neoplasm. We present the clinical and radiographic features of a maxillary mass that demonstrated SCC arising from the lining of an OKC. Although the initial clinical and radiographic presentation suggested an infection or malignant neoplasm, biopsies revealed an infiltrative well-differentiated SCC contiguous with and arising from the focus of a pre-existing OKC. The patient subsequently underwent a type II hemi-maxillectomy with neoadjuvant chemoradiation. This report discusses the clinical and radiographic features associated with intraosseous malignancies, especially those arising from an otherwise benign odontogenic lesion. While the majority of OKCs are benign, the current report illustrates the potential for carcinomatous transformation within the lining of an OKC. PMID:28680851

Voltera's Solution of the Wave Equation as Applied to Three-Dimensional Supersonic Airfoil Problems

NASA Technical Reports Server (NTRS)

Heslet, Max A; Lomax, Harvard; Jones, Arthur L

1947-01-01

A surface integral is developed which yields solutions of the linearized partial differential equation for supersonic flow. These solutions satisfy boundary conditions arising in wing theory. Particular applications of this general method are made, using acceleration potentials, to flat surfaces and to uniformly loaded lifting surfaces. Rectangular and trapezoidal plan forms are considered along with triangular forms adaptable to swept-forward and swept-back wings. The case of the triangular plan form in sideslip is also included. Emphasis is placed on the systematic application of the method to the lifting surfaces considered and on the possibility of further application.

Synovial sarcoma of the neck associated with previous head and neck radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mischler, N.E.; Chuprevich, T.; Tormey, D.C.

1978-08-01

Synovial sarcoma is a rare neoplasm that uncommonly arises in the neck. Fourteen years after facial and neck radiation therapy for acne, synovial sarcoma of the neck developed in a young man. Possible radiation-induced benign and malignant neoplasms that arise in the head and neck region, either of thyroid or extrathyroid origin, remain a continuing medical problem.

Obesity: a problem of darwinian proportions?

PubMed

Watnick, Suzanne

2006-10-01

Obesity has been described as an abnormality arising from the evolution of man, who becomes fat during the time of perpetual plenty. From the perspective of "Darwinian Medicine," if famine is avoided, obesity will prevail. Problems regarding obesity arise within many disciplines, including socioeconomic environments, the educational system, science, law, and government. This article will discuss various ethical aspects of several disciplines regarding obesity, with a focus on scientific inquiry. We will discuss this within the categories: (1) chronic kidney disease predialysis, (2) dialysis, and (3) renal transplantation. This article aims to help nephrologists and their patients navigate through the ethical aspects of obesity and chronic kidney disease.

Riemann–Hilbert problem approach for two-dimensional flow inverse scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agaltsov, A. D., E-mail: agalets@gmail.com; Novikov, R. G., E-mail: novikov@cmap.polytechnique.fr; IEPT RAS, 117997 Moscow

2014-10-15

We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given.

Improving monoclonal antibody selection and engineering using measurements of colloidal protein interactions

PubMed Central

Geng, Steven B.; Cheung, Jason K.; Narasimhan, Chakravarthy; Shameem, Mohammed; Tessier, Peter M.

2014-01-01

A limitation of using monoclonal antibodies as therapeutic molecules is their propensity to associate with themselves and/or with other molecules via non-affinity (colloidal) interactions. This can lead to a variety of problems ranging from low solubility and high viscosity to off-target binding and fast antibody clearance. Measuring such colloidal interactions is challenging given that they are weak and potentially involve diverse target molecules. Nevertheless, assessing these weak interactions – especially during early antibody discovery and lead candidate optimization – is critical to preventing problems that can arise later in the development process. Here we review advances in developing and implementing sensitive methods for measuring antibody colloidal interactions as well as using these measurements for guiding antibody selection and engineering. These systematic efforts to minimize non-affinity interactions are expected to yield more effective and stable monoclonal antibodies for diverse therapeutic applications. PMID:25209466

Biomarkers for the clinical evaluation of the cognitively impaired elderly: amyloid is not enough

PubMed Central

McEvoy, Linda K; Brewer, James B

2012-01-01

The number of elderly patients seeking clinical treatment for memory problems will rise sharply in coming years as our population ages. These patients present a challenge for diagnosis and prognosis since cognitive problems in older patients can arise from many etiologies, some of which are curable. With the development of clinically available biomarkers for detecting Alzheimer’s disease pathology in living patients, evaluation of cognitively impaired elderly patients is about to undergo a major paradigm shift. This article describes the two classes of biomarkers available for assessing Alzheimer’s disease risk: those that indicate presence of amyloid pathology and those that provide evidence of neuronal injury and neurodegeneration. We argue that, currently, incorporation of biomarkers of neurodegeneration can help in patient prognosis whereas tests for amyloid, if used in isolation, have potential for harm. Amyloid tests are clinically useful only when evidence suggests progressive cognitive decline or neurodegeneration. PMID:23420460

On the solution of integral equations with a generalized cauchy kernel

NASA Technical Reports Server (NTRS)

Kaya, A. C.; Erdogan, F.

1986-01-01

In this paper a certain class of singular integral equations that may arise from the mixed boundary value problems in nonhomogeneous materials is considered. The distinguishing feature of these equations is that in addition to the Cauchy singularity, the kernels contain terms that are singular only at the end points. In the form of the singular integral equations adopted, the density function is a potential or a displacement and consequently the kernel has strong singularities of the form (t-x) sup-2, x sup n-2 (t+x) sup n, (n or = 2, 0x,tb). The complex function theory is used to determine the fundamental function of the problem for the general case and a simple numerical technique is described to solve the integral equation. Two examples from the theory of elasticity are then considered to show the application of the technique.

Use of dispersion modelling for Environmental Impact Assessment of biological air pollution from composting: Progress, problems and prospects.

PubMed

Douglas, P; Hayes, E T; Williams, W B; Tyrrel, S F; Kinnersley, R P; Walsh, K; O'Driscoll, M; Longhurst, P J; Pollard, S J T; Drew, G H

2017-12-01

With the increase in composting asa sustainable waste management option, biological air pollution (bioaerosols) from composting facilities have become a cause of increasing concern due to their potential health impacts. Estimating community exposure to bioaerosols is problematic due to limitations in current monitoring methods. Atmospheric dispersion modelling can be used to estimate exposure concentrations, however several issues arise from the lack of appropriate bioaerosol data to use as inputs into models, and the complexity of the emission sources at composting facilities. This paper analyses current progress in using dispersion models for bioaerosols, examines the remaining problems and provides recommendations for future prospects in this area. A key finding is the urgent need for guidance for model users to ensure consistent bioaerosol modelling practices. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Primordial magnetic fields from a non-singular bouncing cosmology

NASA Astrophysics Data System (ADS)

Membiela, Federico Agustín

2014-08-01

Although inflation is a natural candidate to generate the lengths of coherence of magnetic fields needed to explain current observations, it needs to break conformal invariance of electromagnetism to obtain significant magnetic amplitudes. Of the simplest realizations are the kinetically-coupled theories f2(ϕ)FμνF (or IFF theories). However, these are known to suffer from electric fields backreaction or the strong coupling problem. In this work we shall confirm that such class of theories are problematic to support magnetogenesis during inflationary cosmology. On the contrary, we show that a bouncing cosmology with a contracting phase dominated by an equation of state with p>-ρ/3 can support magnetogenesis, evading the backreaction/strong-coupling problem. Finally, we study safe magnetogenesis in a particular bouncing model with an ekpyrotic-like contracting phase. In this case we found that f2(ϕ)F2-instabilities might arise during the final kinetic-driven expanding phase for steep ekpyrotic potentials.

Does the "new philosophy" in predictive, preventive and personalised medicine require new ethics?

PubMed

Gefenas, Eugenijus; Cekanauskaite, Asta; Tuzaite, Egle; Dranseika, Vilius; Characiejus, Dainius

2011-06-01

This paper maps the ethical issues that arise in the context of personalised medicine. First, it highlights the ethical problems related to increased predictive power of modern diagnostic interventions. Such problems emerge because the ability to identify individuals or groups of individuals that can potentially benefit from a particular therapeutic intervention also raises a question of personal responsibility for health-related behaviour and lifestyle. The second major area of ethical concern is related to health prevention and distributive justice. The paper discusses the ethical challenges brought by the personalised medicine in the context of the Additional Protocol to the Convention on Human Rights and Biomedicine concerning Genetic Testing for Health Purposes. Finally, it notes that the issue of consent in the context of biobanks, the need to rethink the prevalent models of research designs and to communicate relevant findings to the donors of biological materials deserve further discussion.

Inter-Fork Strand Annealing causes genomic deletions during the termination of DNA replication.

PubMed

Morrow, Carl A; Nguyen, Michael O; Fower, Andrew; Wong, Io Nam; Osman, Fekret; Bryer, Claire; Whitby, Matthew C

2017-06-06

Problems that arise during DNA replication can drive genomic alterations that are instrumental in the development of cancers and many human genetic disorders. Replication fork barriers are a commonly encountered problem, which can cause fork collapse and act as hotspots for replication termination. Collapsed forks can be rescued by homologous recombination, which restarts replication. However, replication restart is relatively slow and, therefore, replication termination may frequently occur by an active fork converging on a collapsed fork. We find that this type of non-canonical fork convergence in fission yeast is prone to trigger deletions between repetitive DNA sequences via a mechanism we call Inter-Fork Strand Annealing (IFSA) that depends on the recombination proteins Rad52, Exo1 and Mus81, and is countered by the FANCM-related DNA helicase Fml1. Based on our findings, we propose that IFSA is a potential threat to genomic stability in eukaryotes.

Chemical processing of glasses

NASA Astrophysics Data System (ADS)

Laine, Richard M.

1990-11-01

The development of chemical processing methods for the fabrication of glass and ceramic shapes for photonic applications is frequently Edisonian in nature. In part, this is because the numerous variables that must be optimized to obtain a given material with a specific shape and particular properties cannot be readily defined based on fundamental principles. In part, the problems arise because the basic chemistry of common chemical processing systems has not been fully delineated. The prupose of this paper is to provide an overview of the basic chemical problems associated with chemical processing. The emphasis will be on sol-gel processing, a major subset pf chemical processing. Two alternate approaches to chemical processing of glasses are also briefly discussed. One approach concerns the use of bimetallic alkoxide oligomers and polymers as potential precursors to mulimetallic glasses. The second approach describes the utility of metal carboxylate precursors to multimetallic glasses.

Cell culture contamination.

PubMed

Stacey, Glyn N

2011-01-01

Microbial contamination is a major issue in cell culture, but there are a range of procedures which can be adopted to prevent or eliminate contamination. Contamination may arise from the operator and the laboratory environment, from other cells used in the laboratory, and from reagents. Some infections may present a risk to laboratory workers: containment and aseptic technique are the key defence against such risks. Remedial management of suspected infection may simply mean discarding a single potentially infected culture. However, if a more widespread problem is identified, then all contaminated cultures and associated unused media that have been opened during this period should be discarded, equipment should be inspected and cleaned, cell culture operations reviewed, and isolation from other laboratories instituted until the problem is solved. Attention to training of staff, laboratory layout, appropriate use of quarantine for new cultures or cell lines, cleaning and maintenance, and quality control are important factors in preventing contamination in cell culture laboratories.

Asymptotic analysis of the local potential approximation to the Wetterich equation

NASA Astrophysics Data System (ADS)

Bender, Carl M.; Sarkar, Sarben

2018-06-01

This paper reports a study of the nonlinear partial differential equation that arises in the local potential approximation to the Wetterich formulation of the functional renormalization group equation. A cut-off-dependent shift of the potential in this partial differential equation is performed. This shift allows a perturbative asymptotic treatment of the differential equation for large values of the infrared cut-off. To leading order in perturbation theory the differential equation becomes a heat equation, where the sign of the diffusion constant changes as the space-time dimension D passes through 2. When D  <  2, one obtains a forward heat equation whose initial-value problem is well-posed. However, for D  >  2 one obtains a backward heat equation whose initial-value problem is ill-posed. For the special case D  =  1 the asymptotic series for cubic and quartic models is extrapolated to the small infrared-cut-off limit by using Padé techniques. The effective potential thus obtained from the partial differential equation is then used in a Schrödinger-equation setting to study the stability of the ground state. For cubic potentials it is found that this Padé procedure distinguishes between a -symmetric theory and a conventional Hermitian theory (g real). For an theory the effective potential is nonsingular and has a stable ground state but for a conventional theory the effective potential is singular. For a conventional Hermitian theory and a -symmetric theory (g  >  0) the results are similar; the effective potentials in both cases are nonsingular and possess stable ground states.

Closed solutions to a differential-difference equation and an associated plate solidification problem.

PubMed

Layeni, Olawanle P; Akinola, Adegbola P; Johnson, Jesse V

2016-01-01

Two distinct and novel formalisms for deriving exact closed solutions of a class of variable-coefficient differential-difference equations arising from a plate solidification problem are introduced. Thereupon, exact closed traveling wave and similarity solutions to the plate solidification problem are obtained for some special cases of time-varying plate surface temperature.

POEMS in Newton's Aerodynamic Frustum

ERIC Educational Resources Information Center

Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita

2010-01-01

The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…

How Do They Solve It? An Insight into the Learner's Approach to the Mechanism of Physics Problem Solving

ERIC Educational Resources Information Center

Hegde, Balasubrahmanya; Meera, B. N.

2012-01-01

A perceived difficulty is associated with physics problem solving from a learner's viewpoint, arising out of a multitude of reasons. In this paper, we have examined the microstructure of students' thought processes during physics problem solving by combining the analysis of responses to multiple-choice questions and semistructured student…

Corrosion control and disinfection studies in spacecraft water systems. [considering Saturn 5 orbital workshop

NASA Technical Reports Server (NTRS)

Shea, T. G.

1974-01-01

Disinfection and corrosion control in the water systems of the Saturn 5 Orbital Workshop Program are considered. Within this framework, the problem areas of concern are classified into four general areas: disinfection; corrosion; membrane-associated problems of disinfectant uptake and diffusion; and taste and odor problems arising from membrane-disinfectant interaction.

Psychotherapy with Older Dying Persons.

ERIC Educational Resources Information Center

Dye, Carol J.

Psychotherapy with older dying patients can lead to problems of countertransference for the clinician. Working with dying patients requires flexibility to adapt basic therapeutics to the institutional setting. Goals of psychotherapy must be reconceptualized for dying clients. The problems of countertransference arise because clinicians themselves…

Spelling: A Visual Skill.

ERIC Educational Resources Information Center

Hendrickson, Homer

1988-01-01

Spelling problems arise due to problems with form discrimination and inadequate visualization. A child's sequence of visual development involves learning motor control and coordination, with vision directing and monitoring the movements; learning visual comparison of size, shape, directionality, and solidity; developing visual memory or recall;…

General Boundary Conditions for a Majorana Single-Particle in a Box in (1 + 1) Dimensions

NASA Astrophysics Data System (ADS)

De Vincenzo, Salvatore; Sánchez, Carlet

2018-05-01

We consider the problem of a Majorana single-particle in a box in (1 + 1) dimensions. We show that the most general set of boundary conditions for the equation that models this particle is composed of two families of boundary conditions, each one with a real parameter. Within this set, we only have four confining boundary conditions—but infinite not confining boundary conditions. Our results are also valid when we include a Lorentz scalar potential in this equation. No other Lorentz potential can be added. We also show that the four confining boundary conditions for the Majorana particle are precisely the four boundary conditions that mathematically can arise from the general linear boundary condition used in the MIT bag model. Certainly, the four boundary conditions for the Majorana particle are also subject to the Majorana condition.

Inequalities, assessment and computer algebra

NASA Astrophysics Data System (ADS)

Sangwin, Christopher J.

2015-01-01

The goal of this paper is to examine single variable real inequalities that arise as tutorial problems and to examine the extent to which current computer algebra systems (CAS) can (1) automatically solve such problems and (2) determine whether students' own answers to such problems are correct. We review how inequalities arise in contemporary curricula. We consider the formal mathematical processes by which such inequalities are solved, and we consider the notation and syntax through which solutions are expressed. We review the extent to which current CAS can accurately solve these inequalities, and the form given to the solutions by the designers of this software. Finally, we discuss the functionality needed to deal with students' answers, i.e. to establish equivalence (or otherwise) of expressions representing unions of intervals. We find that while contemporary CAS accurately solve inequalities there is a wide variety of notation used.

An iterative Riemann solver for systems of hyperbolic conservation law s, with application to hyperelastic solid mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Gregory H.

2003-08-06

In this paper we present a general iterative method for the solution of the Riemann problem for hyperbolic systems of PDEs. The method is based on the multiple shooting method for free boundary value problems. We demonstrate the method by solving one-dimensional Riemann problems for hyperelastic solid mechanics. Even for conditions representative of routine laboratory conditions and military ballistics, dramatic differences are seen between the exact and approximate Riemann solution. The greatest discrepancy arises from misallocation of energy between compressional and thermal modes by the approximate solver, resulting in nonphysical entropy and temperature estimates. Several pathological conditions arise in commonmore » practice, and modifications to the method to handle these are discussed. These include points where genuine nonlinearity is lost, degeneracies, and eigenvector deficiencies that occur upon melting.« less

Complexity seems to open a way towards a new Aristotelian-Thomistic ontology.

PubMed

Strumia, Alberto

2007-01-01

Today's sciences seem to converge all towards very similar foundational questions. Such claims, both of epistemological and ontological nature, seem to rediscover, in a new fashion some of the most relevant topics of ancient Greek and Mediaeval philosophy of nature, logic and metaphysics, such as the problem of the relationship between the whole and its parts (non redictionism), the problems of the paradoxes arising from the attempt to conceive the entity like an univocal concept (analogy and analogia entis), the problem of the mind-body relationship and that of an adequate cognitive theory (abstraction and immaterial nature of the mind), the complexity of some physical, chemical and biological systems and global properties arising from information (matter-form theory), etc. Medicine too is involved in some of such relevant questions and cannot avoid to take them into a special account.

Ethical issues concerning New Zealand sports doctors

PubMed Central

Anderson, L; Gerrard, D

2005-01-01

Success in sport can provide a source of national pride for a society, and vast financial and personal rewards for an individual athlete. It is therefore not surprising that many athletes will go to great lengths in pursuit of success. The provision of healthcare for elite sports people has the potential to create many ethical issues for sports doctors; however there has been little discussion of them to date. This study highlights these issues. Respondents to a questionnaire identified many ethical matters, common to other areas of medicine. However they also raised problems unique to sports medicine. Some of these ethical difficulties arise out of the place of the sports doctor within the hierarchy of sport. Yet others arise out of the special relationship between sports doctors and individual players/athletes. This study raises some important questions regarding the governance of healthcare in sport, and what support and guidance is available to sports doctors. As medical and scientific intervention in sport escalates, there is a risk that demands for enhanced performance may compromise the health of the athlete, and the role the sports doctor plays remains a critical question. PMID:15681672

Joule heating effects on electromagnetohydrodynamic flow through a peristaltically induced micro-channel with different zeta potential and wall slip

NASA Astrophysics Data System (ADS)

Ranjit, N. K.; Shit, G. C.

2017-09-01

This paper aims to develop a mathematical model for magnetohydrodynamic flow of biofluids through a hydrophobic micro-channel with periodically contracting and expanding walls under the influence of an axially applied electric field. The velocity slip effects have been taken into account at the channel walls by employing different slip lengths due to hydrophobic gating. Different temperature jump factors have also been used to investigate the thermomechanical interactions at the fluid-solid interface. The electromagnetohydrodynamic flow in a microchannel is simplified under the framework of Debye-Hückel linearization approximation. We have derived the closed-form solutions for the linearized dimensionless boundary value problem under the assumptions of long wave length and low Reynolds number. The axial velocity, temperature, pressure distribution, stream function, wall shear stress and the Nusselt number have been appraised for diverse values of the parameters approaching into the problem. Our main focus is to determine the effects of different zeta potential on the axial velocity and temperature distribution under electromagnetic environment. This study puts forward an important observation that the different zeta potential plays an important role in controlling fluid velocity. The study further reveals that the temperature increases significantly with the Joule heating parameter and the Brinkman number (arises due to the dissipation of energy).

Identifying Unique Ethical Challenges of Indigenous Field-Workers: A Commentary on Alexander and Richman's "Ethical Dilemmas in Evaluations Using Indigenous Research Workers"

ERIC Educational Resources Information Center

Smith, Nick L.

2008-01-01

In contrast with nonindigenous workers, to what extent do unique ethical problems arise when indigenous field-workers participate in field studies? Three aspects of study design and operation are considered: data integrity issues, risk issues, and protection issues. Although many of the data quality issues that arise with the use of indigenous…

A Computer Program for Solving a Set of Conditional Maximum Likelihood Equations Arising in the Rasch Model for Questionnaires.

ERIC Educational Resources Information Center

Andersen, Erling B.

A computer program for solving the conditional likelihood equations arising in the Rasch model for questionnaires is described. The estimation method and the computational problems involved are described in a previous research report by Andersen, but a summary of those results are given in two sections of this paper. A working example is also…

Real-Space Multiple-Scattering Theory and Its Applications at Exascale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eisenbach, Markus; Wang, Yang

In recent decades, the ab initio methods based on density functional theory (DFT) (Hohenberg and Kohn 1964, Kohn and Sham 1965) have become a widely used tool in computational materials science, which allows theoretical prediction of physical properties of materials from the first principles and theoretical interpretation of new physical phenomena found in experiments. In the framework of DFT, the original problem that requires solving a quantum mechanical equation for a many-electron system is reduced to a one-electron problem that involves an electron moving in an effective field, while the effective field potential is made up of an electrostatic potential,more » also known as Hartree potential, arising from the electronic and ion charge distribution in space and an exchange–correlation potential, which is a function of the electron density and encapsulates the exchange and correlation effects of the many-electron system. Even though the exact functional form of the exchange-correlation potential is formally unknown, a local density approximation (LDA) or a generalized gradient approximation (GGA) is usually applied so that the calculation of the exchange–correlation potential, as well as the exchange–correlation energy, becomes tractable while a required accuracy is retained. Based on DFT, ab initio electronic structure calculations for a material generally involve a self-consistent process that iterates between two computational tasks: (1) solving an one-electron Schrödinger equation, also known as Kohn–Sham equation, to obtain the electron density and, if needed, the magnetic moment density, and (2) solving the Poisson equation to obtain the electrostatic potential corresponding to the electron density and constructing the effective potential by adding the exchange–correlation potential to the electrostatic potential. This self-consistent process proceeds until a convergence criteria is reached.« less

Solving LP Relaxations of Large-Scale Precedence Constrained Problems

NASA Astrophysics Data System (ADS)

Bienstock, Daniel; Zuckerberg, Mark

We describe new algorithms for solving linear programming relaxations of very large precedence constrained production scheduling problems. We present theory that motivates a new set of algorithmic ideas that can be employed on a wide range of problems; on data sets arising in the mining industry our algorithms prove effective on problems with many millions of variables and constraints, obtaining provably optimal solutions in a few minutes of computation.

NASA Aviation Safety Reporting System

NASA Technical Reports Server (NTRS)

1980-01-01

Problems in briefing of relief by air traffic controllers are discussed, including problems that arise when duty positions are changed by controllers. Altimeter reading and setting errors as factors in aviation safety are discussed, including problems associated with altitude-including instruments. A sample of reports from pilots and controllers is included, covering the topics of ATIS broadcasts an clearance readback problems. A selection of Alert Bulletins, with their responses, is included.

Projected regression method for solving Fredholm integral equations arising in the analytic continuation problem of quantum physics

NASA Astrophysics Data System (ADS)

Arsenault, Louis-François; Neuberg, Richard; Hannah, Lauren A.; Millis, Andrew J.

2017-11-01

We present a supervised machine learning approach to the inversion of Fredholm integrals of the first kind as they arise, for example, in the analytic continuation problem of quantum many-body physics. The approach provides a natural regularization for the ill-conditioned inverse of the Fredholm kernel, as well as an efficient and stable treatment of constraints. The key observation is that the stability of the forward problem permits the construction of a large database of outputs for physically meaningful inputs. Applying machine learning to this database generates a regression function of controlled complexity, which returns approximate solutions for previously unseen inputs; the approximate solutions are then projected onto the subspace of functions satisfying relevant constraints. Under standard error metrics the method performs as well or better than the Maximum Entropy method for low input noise and is substantially more robust to increased input noise. We suggest that the methodology will be similarly effective for other problems involving a formally ill-conditioned inversion of an integral operator, provided that the forward problem can be efficiently solved.

How Seductive Are Decorative Elements in Learning Materials?

ERIC Educational Resources Information Center

Rey, Gunter Daniel

2012-01-01

The seductive detail effect arises when people learn more deeply from a multimedia presentation when interesting but irrelevant adjuncts are excluded. However, previous studies about this effect are rather inconclusive and contained various methodical problems. The recent experiment attempted to overcome these methodical problems. Undergraduate…

Phantom Effects in Multilevel Compositional Analysis: Problems and Solutions

ERIC Educational Resources Information Center

Pokropek, Artur

2015-01-01

This article combines statistical and applied research perspective showing problems that might arise when measurement error in multilevel compositional effects analysis is ignored. This article focuses on data where independent variables are constructed measures. Simulation studies are conducted evaluating methods that could overcome the…

Essential problems in the interpretation of epidemiologic evidence for an association between mobile phone use and brain tumours

NASA Astrophysics Data System (ADS)

Kundi, Michael

2010-11-01

Due to the close proximity of a mobile phone to the head when placing a call, concerns have been raised that exposure from microwaves during mobile phone use may exert adverse health effects and, in particular, may increase the risk of brain tumours. In response to these concerns epidemiological studies have been conducted, most applying the case-control design. While epidemiology can provide decisive evidence for an association between an exposure and a disease fundamental problems arise if exposure is short compared to the natural history of the disease. For brain tumours latencies of decades have been implicated making special considerations about potential effects of exposures necessary that commence during an already growing tumour. It is shown that measures of disease risk like odds ratios and relative risks can under such circumstances not be interpreted as indicators of a long term effect on incidences in the exposed population. Besides this problem, the issues of a suitable exposure metric and the selection of endpoints are unresolved. It is shown that the solution of these problems affords knowledge about the mechanism of action by which exposure increases the risk of manifest disease.

A Unified Framework for Association Analysis with Multiple Related Phenotypes

PubMed Central

Stephens, Matthew

2013-01-01

We consider the problem of assessing associations between multiple related outcome variables, and a single explanatory variable of interest. This problem arises in many settings, including genetic association studies, where the explanatory variable is genotype at a genetic variant. We outline a framework for conducting this type of analysis, based on Bayesian model comparison and model averaging for multivariate regressions. This framework unifies several common approaches to this problem, and includes both standard univariate and standard multivariate association tests as special cases. The framework also unifies the problems of testing for associations and explaining associations – that is, identifying which outcome variables are associated with genotype. This provides an alternative to the usual, but conceptually unsatisfying, approach of resorting to univariate tests when explaining and interpreting significant multivariate findings. The method is computationally tractable genome-wide for modest numbers of phenotypes (e.g. 5–10), and can be applied to summary data, without access to raw genotype and phenotype data. We illustrate the methods on both simulated examples, and to a genome-wide association study of blood lipid traits where we identify 18 potential novel genetic associations that were not identified by univariate analyses of the same data. PMID:23861737

The Unintended Consequences of Social Media in Healthcare: New Problems and New Solutions.

PubMed

Hors-Fraile, S; Atique, S; Mayer, M A; Denecke, K; Merolli, M; Househ, M

2016-11-10

Social media is increasingly being used in conjunction with health information technology (health IT). The objective of this paper is to identify some of the undesirable outcomes that arise from this integration and to suggest solutions to these problems. After a discussion with experts to elicit the topics that should be included in the survey, we performed a narrative review based on recent literature and interviewed multidisciplinary experts from different areas. In each case, we identified and analyzed the unintended effects of social media in health IT. Each analyzed topic provided a different set of unintended consequences. Most relevant consequences include lack of privacy with ethical and legal issues, patient confusion in disease management, poor information accuracy in crowdsourcing, unclear responsibilities, misleading and biased information in the prevention and detection of epidemics, and demotivation in gamified health solutions with social components. Using social media in healthcare offers several benefits, but it is not exempt of potential problems, and not all of these problems have clear solutions. We recommend careful design of digital systems in order to minimize patient's feelings of demotivation and frustration and we recommend following specific guidelines that should be created by all stakeholders in the healthcare ecosystem.

Obstetric factors and different causes of special educational need: retrospective cohort study of 407,503 schoolchildren.

PubMed

Mackay, D F; Smith, G C S; Dobbie, R; Cooper, S-A; Pell, J P

2013-02-01

To determine whether relationships with gestational age and birthweight centile vary between specific causes of special educational need (SEN). Retrospective cohort study. Scotland. A cohort of 407,503 schoolchildren. Polytomous logistic regression was used to examine the risk of each cause of SEN across the spectrum of gestation at delivery and birthweight centile, adjusting for potential confounding factors. Crude and adjusted odds ratios and confidence intervals. Of the 19,821 children with SEN, 557 (2.8%) had sensory impairments, 812 (4.1%) had physical or motor disabilities, 876 (4.4%) had language impairments, 2823 (14.2%) had social, emotional, or behavioural problems, 7018 (35.4%) had intellectual disabilities, 4404 (22.2%) had specific learning difficulties, and 1684 (8.5%) autistic spectrum disorder (ASD). Extreme preterm delivery (at 24-27 weeks of gestation) was a strong predictor of sensory (adjusted OR 23.64, 95% CI 12.03-46.45), physical or motor (adjusted OR 29.69, 95% CI 17.49-50.40), and intellectual (adjusted OR 11.67, 95% CI 8.46-16.10) impairments, with dose relationships across the range of gestation. Similarly, birthweight below the third centile was associated with sensory (adjusted OR 2.85, 95% CI 2.04-3.99), physical or motor (adjusted OR 2.47, 95% CI 1.82-3.37), and intellectual (adjusted OR 2.67, 95% CI 2.41-2.96) impairments. Together, gestation and birthweight centile accounted for 24.0% of SEN arising from sensory impairment, 34.3% arising from physical or motor disabilities, and 26.6% arising from intellectual disabilities. Obstetric factors were less strongly associated with specific learning difficulties and social or emotional problems, and there were no significant associations with ASD. The association between gestation and birthweight centile and overall risk of SEN is largely driven by very strong associations with sensory, physical or motor impairments, and intellectual impairments. © 2012 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2012 RCOG.

Transformational leadership can improve workforce competencies.

PubMed

Thompson, Juliana

2012-03-01

Staffing problems can arise because of poor delegation skills or a failure by leaders to respond appropriately to economic factors and patient demographics. Training dilemmas, meanwhile, can arise because of managers' confusion about what constitutes 'training' and what constitutes 'education', and where responsibility of provision lies, with the consequence that they neglect these activities. This article uses Kouzes and Posner's (2009) transformational leadership model to show how managers can respond. Leaders who challenge budgets, consider new ways of working and engage effectively with the workforce can improve productivity and care, while those who invest in appropriate learning will have a highly trained workforce. The author explains how integration of leadership roles and management functions can lead to innovative problem solving.

Euthanasia from the perspective of hospice care.

PubMed

Gillett, G

1994-01-01

The hospice believes in the concept of a gentle and harmonious death. In most hospice settings there is also a rejection of active euthanasia. This set of two apparently conflicting principles can be defended on the basis of two arguments. The first is that doctors should not foster the intent to kill as part of their moral and clinical character. This allows proper sensitivity to the complex and difficult situation that arises in many of the most difficult terminal care situations. The second argument turns on the seduction of technological solutions to human problems and the slippery slope that may arise in the presence of a quick and convenient way of dealing with problems of death and dying.

Solving Integer Programs from Dependence and Synchronization Problems

DTIC Science & Technology

1993-03-01

DEFF.NSNE Solving Integer Programs from Dependence and Synchronization Problems Jaspal Subhlok March 1993 CMU-CS-93-130 School of Computer ScienceT IC...method Is an exact and efficient way of solving integer programming problems arising in dependence and synchronization analysis of parallel programs...7/;- p Keywords: Exact dependence tesing, integer programming. parallelilzng compilers, parallel program analysis, synchronization analysis Solving

The King and Prisoner Puzzle: A Way of Introducing the Components of Logical Structures

ERIC Educational Resources Information Center

Roh, Kyeong Hah; Lee, Yong Hah; Tanner, Austin

2016-01-01

The purpose of this paper is to provide issues related to student understanding of logical components that arise when solving word problems. We designed a logic problem called the King and Prisoner Puzzle--a linguistically simple, yet logically challenging problem. In this paper, we describe various student solutions to the puzzle and discuss the…

The application of NASTRAN at Sperry Univac Holland. [analysis of engineering, modelling, and use of program system

NASA Technical Reports Server (NTRS)

Koopmans, G.

1973-01-01

Very divergent problems arising with different calculations indicate that NASTRAN is not always accessible for common use. Problems with engineering, modelling, and use of the program system are analysed and a way of solution is outlined. Related to this, some supplementary modifications are made at Sperry Univac Holland to facilitate the program for the less skilled user. The implementation of a new element also gives an insight into the use of NASTRAN at Sperry Univac Holland. As the users of Univac computers are from very different kinds of industries like shipbuilders, petrochemical industries, and building industries, the variety of problems coming from these users is very large. This variety results in experience not with one special kind of calculation nor one special kind of construction, but with a wide area of problems arising in the use of NASTRAN. These problems can roughly be divided into three different groups: (1) recognition of what is to be calculated and how, (2) construction of a model, and (3) handling the NASTRAN program. These are the basic problems for every less skilled user of NASTRAN and the Application/Research Department of Sperry Univac has to give reasonable answers to these questions.

Dioxins: diagnostic and prognostic challenges arising from complex mechanisms

PubMed Central

Rysavy, Noel M.; Maaetoft-Udsen, Kristina; Turner, Helen

2013-01-01

Dioxins are ubiquitous environmental challenges to humans, with a pervasiveness that arises from two hundred years of rapid industrialization and mechanization of Western societies and which is now extending into the developing world. Despite their penetrance of the human biota, these compounds are poorly understood in terms of their true physiological potential for harm, and the mechanisms by which they impact cellular and organ level function are only recently becoming clear. Emerging awareness that chronic exposures to toxins may have generational and subtle effects on the outcomes of diseases such as cancer and diabetes, which are already multifactorial and highly complex, creates the context for the current review paper. Here, we summarize dioxin exposure paradigms and the resulting physiological effects that have been documented in animals and humans. Novel insights into potential endogenous end exogenous ligands, as well as the mechanisms by which these ligands impact acute and chronic cellular processes, are discussed. We develop the idea that the diagnosis of dioxin exposure, the subtleties of the cellular effects of the compounds and prognosis of the long term effects of exposure are problems requiring that researchers leverage the power of genomics and epigenetics. However, the continuation of longitudinal epidemiological studies and development of a firmer basis from which to extrapolate animal studies will be critical in ensuring optimal insight from these resource-intensive techniques. PMID:22610997

A temps nouveaux, solutions nouvelles: quelques propositions (New Times, New Solutions: Some Proposals).

ERIC Educational Resources Information Center

Capelle, Guy

1983-01-01

Serious problems in education in Latin America arising from political, economic, and social change periodically put in question the status, objectives, and manner of French second-language instruction. A number of solutions to general and specific pedagogical problems are proposed. (MSE)

Understanding Gender-Based Wage Discrimination: Legal Interpretation and Trends of Pay Equity in Higher Education.

ERIC Educational Resources Information Center

Luna, Gaye

1990-01-01

Traces the history of laws and litigation concerning pay equity issues, also referred to as wage equity and comparable worth. Suggests that universities and colleges identify possible problems and take voluntary corrective measures before pay-equity problems arise. (MLF)

Reflective Questions, Self-Questioning and Managing Professionally Situated Practice

ERIC Educational Resources Information Center

Malthouse, Richard; Watts, Mike; Roffey-Barentsen, Jodi

2015-01-01

Reflective self-questioning arises within the workplace when people are confronted with professional problems and situations. This paper focuses on reflective and "situated reflective" questions in terms of self-questioning and professional workplace problem solving. In our view, the situational context, entailed by the setting, social…

Expanding the scope of health information systems. Challenges and developments.

PubMed

Kuhn, K A; Wurst, S H R; Bott, O J; Giuse, D A

2006-01-01

To identify current challenges and developments in health information systems. Reports on HIS, eHealth and process support were analyzed, core problems and challenges were identified. Health information systems are extending their scope towards regional networks and health IT infrastructures. Integration, interoperability and interaction design are still today's core problems. Additional problems arise through the integration of genetic information into the health care process. There are noticeable trends towards solutions for these problems.

Can ethnography save the life of medical ethics?

PubMed

Hoffmaster, B

1992-12-01

Since its inception contemporary medical ethics has been regarded by many of its practitioners as 'applied ethics', that is, the application of philosophical theories to the moral problems that arise in health care. This 'applied ethics' model of medical ethics is, however, beset with internal and external difficulties. The internal difficulties point out that the model is intrinsically flawed. The external difficulties arise because the model does not fit work in the field. Indeed, the strengths of that work are its highly nuanced, particularized analyses of cases and issues and its appreciation of the circumstances and contexts that generate and structure these cases and issues. A shift away from a theory-driven 'applied ethics' to a more situational, contextual approach to medical ethics opens the way for ethnographic studies of moral problems in health care as well as a conception of moral theory that is more responsive to the empirical dimensions of those problems.

[Current problems arising from not having biosafety level 4 laboratories in Japan--qualitative study of infectious disease experts].

PubMed

Yamamoto, Yuko; Horiguchi, Itsuko; Marui, Eiji

2009-09-01

No public consensus exists yet on handling Biosafety Level 4 agents and no laboratory is operational at BSL4 in Japan. A discussion that includes neighboring residents and experts should be initiated to communicate risks. In this article, we present the current situation and prioritize problems we presently face. A three-stage Delphi survey was conducted. The subjects were twenty-two persons with extensive experience and knowledge of infectious diseases. Seven projections and issues were made with regard to the problems arising from the lack of an operational BSL4 laboratory. These were tabulated by the KJ method. The top seven projections were scored, such that the top received 7 points and the last received 1 point. A total of 51 projections were obtained for the first part of the survey, 39 for the second, and 29 for the last. The projection with the highest score was that it is impossible to cope with newly emerging infectious diseases. The second was that complete diagnoses are impossible without a BSL4 laboratory. All projections and issues were divided into the following four main groups: issues for researchers and laboratory staff, clinical practice and research on BSL4 agents, domestic and global security, and Japan's international position. We clarified possible problem arising from not having BSL4 laboratories in Japan. The identification of projections by the Delphi survey in this study should be considered as one of many attempts to develop effective risk communication strategies.

Observing quantum trajectories: From Mott’s problem to quantum Zeno effect and back

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gosson, Maurice de, E-mail: maurice.de.gosson@univie.ac.at; Hiley, Basil; TPRU, Birkbeck, University of London, Malet Street, London WC1E 7HX

2016-11-15

The experimental results of Kocsis et al., Mahler et al. and the proposed experiments of Morley et al. show that it is possible to construct “trajectories” in interference regions in a two-slit interferometer. These results call for a theoretical re-appraisal of the notion of a “quantum trajectory” first introduced by Dirac and in the present paper we re-examine this notion from the Bohm perspective based on Hamiltonian flows. In particular, we examine the short-time propagator and the role that the quantum potential plays in determining the form of these trajectories. These trajectories differ from those produced in a typical particlemore » tracker and the key to this difference lies in the active suppression of the quantum potential necessary to produce Mott-type trajectories. We show, using a rigorous mathematical argument, how the active suppression of this potential arises. Finally we discuss in detail how this suppression also accounts for the quantum Zeno effect.« less

Mesh-Based Entry Vehicle and Explosive Debris Re-Contact Probability Modeling

NASA Technical Reports Server (NTRS)

McPherson, Mark A.; Mendeck, Gavin F.

2011-01-01

The risk to a crewed vehicle arising from potential re-contact with fragments from an explosive breakup of any jettisoned spacecraft segments during entry has long sought to be quantified. However, great difficulty lies in efficiently capturing the potential locations of each fragment and their collective threat to the vehicle. The method presented in this paper addresses this problem by using a stochastic approach that discretizes simulated debris pieces into volumetric cells, and then assesses strike probabilities accordingly. Combining spatial debris density and relative velocity between the debris and the entry vehicle, the strike probability can be calculated from the integral of the debris flux inside each cell over time. Using this technique it is possible to assess the risk to an entry vehicle along an entire trajectory as it separates from the jettisoned segment. By decoupling the fragment trajectories from that of the entry vehicle, multiple potential separation maneuvers can then be evaluated rapidly to provide an assessment of the best strategy to mitigate the re-contact risk.

Self-organization of muscle cell structure and function.

PubMed

Grosberg, Anna; Kuo, Po-Ling; Guo, Chin-Lin; Geisse, Nicholas A; Bray, Mark-Anthony; Adams, William J; Sheehy, Sean P; Parker, Kevin Kit

2011-02-01

The organization of muscle is the product of functional adaptation over several length scales spanning from the sarcomere to the muscle bundle. One possible strategy for solving this multiscale coupling problem is to physically constrain the muscle cells in microenvironments that potentiate the organization of their intracellular space. We hypothesized that boundary conditions in the extracellular space potentiate the organization of cytoskeletal scaffolds for directed sarcomeregenesis. We developed a quantitative model of how the cytoskeleton of neonatal rat ventricular myocytes organizes with respect to geometric cues in the extracellular matrix. Numerical results and in vitro assays to control myocyte shape indicated that distinct cytoskeletal architectures arise from two temporally-ordered, organizational processes: the interaction between actin fibers, premyofibrils and focal adhesions, as well as cooperative alignment and parallel bundling of nascent myofibrils. Our results suggest that a hierarchy of mechanisms regulate the self-organization of the contractile cytoskeleton and that a positive feedback loop is responsible for initiating the break in symmetry, potentiated by extracellular boundary conditions, is required to polarize the contractile cytoskeleton.

Advertising emergency department wait times.

PubMed

Weiner, Scott G

2013-03-01

Advertising emergency department (ED) wait times has become a common practice in the United States. Proponents of this practice state that it is a powerful marketing strategy that can help steer patients to the ED. Opponents worry about the risk to the public health that arises from a patient with an emergent condition self-triaging to a further hospital, problems with inaccuracy and lack of standard definition of the reported time, and directing lower acuity patients to the higher cost ED setting instead to primary care. Three sample cases demonstrating the pitfalls of advertising ED wait times are discussed. Given the lack of rigorous evidence supporting the practice and potential adverse effects to the public health, caution about its use is advised.

Boundary violations and departments of psychiatry.

PubMed

Garfinkel, P E; Dorian, B; Sadavoy, J; Bagby, R M

1997-09-01

To explore a number of issues related to boundary violations in psychiatry, including the relationship between the individual physician and his or her patient and broader issues related to various dilemmas arising in academic departments of psychiatry. Several potentially troublesome scenarios are presented and discussed in the contexts of 1) the doctor-patient relationship, 2) sexual boundary violations, and 3) nonsexual forms of exploitation, such as finances, confidentiality, dual relationships, and relationships with industry. A number of examples of boundary problems involving psychiatrists have been explored, and although some of these behaviours are clearly forbidden and harmful, others are less clear and require careful consideration if the profession is to arrive at a thoughtful consensus.

Dynamics of the cosmological relaxation after reheating

NASA Astrophysics Data System (ADS)

Choi, Kiwoon; Kim, Hyungjin; Sekiguchi, Toyokazu

2017-04-01

We examine if the cosmological relaxation mechanism, which was proposed recently as a new solution to the hierarchy problem, can be compatible with high reheating temperature well above the weak scale. As the barrier potential disappears at high temperature, the relaxion rolls down further after the reheating, which may ruin the successful implementation of the relaxation mechanism. It is noted that if the relaxion is coupled to a dark gauge boson, the new frictional force arising from dark gauge boson production can efficiently slow down the relaxion motion, which allows the relaxion to be stabilized after the electroweak phase transition for a wide range of model parameters, while satisfying the known observational constraints.

Solar Physics - Plasma Physics Workshop

NASA Technical Reports Server (NTRS)

Baum, P. J.; Beckers, J. M.; Newman, C. E.; Priest, E. R.; Rosenberg, H.; Smith, D. F.; Sturrock, P. A.; Wentzel, D. G.

1974-01-01

A summary of the proceedings of a conference whose purpose was to explore plasma physics problems which arise in the study of solar physics is provided. Sessions were concerned with specific questions including the following: (1) whether the solar plasma is thermal or non-themal; (2) what spectroscopic data is required; (3) what types of magnetic field structures exist; (4) whether magnetohydrodynamic instabilities occur; (5) whether resistive or non-magnetohydrodynamic instabilities occur; (6) what mechanisms of particle acceleration have been proposed; and (7) what information is available concerning shock waves. Very few questions were answered categorically but, for each question, there was discussion concerning the observational evidence, theoretical analyses, and existing or potential laboratory and numerical experiments.

Parallel simulations of Grover's algorithm for closest match search in neutron monitor data

NASA Astrophysics Data System (ADS)

Kussainov, Arman; White, Yelena

We are studying the parallel implementations of Grover's closest match search algorithm for neutron monitor data analysis. This includes data formatting, and matching quantum parameters to a conventional structure of a chosen programming language and selected experimental data type. We have employed several workload distribution models based on acquired data and search parameters. As a result of these simulations, we have an understanding of potential problems that may arise during configuration of real quantum computational devices and the way they could run tasks in parallel. The work was supported by the Science Committee of the Ministry of Science and Education of the Republic of Kazakhstan Grant #2532/GF3.

Use of optical technique for inspection of warpage of IC packages

NASA Astrophysics Data System (ADS)

Toh, Siew-Lok; Chau, Fook S.; Ong, Sim Heng

2001-06-01

The packaging of IC packages has changed over the years, form dual-in-line, wire-bond, and pin-through-hole in printed wiring board technologies in the 1970s to ball grid array, chip scale and surface mount technologies in the 1990s. Reliability has been a big problem for manufacturers for some moisture-sensitive packages. One of the potential problems in plastic IC packages is moisture-induced popcorn effect which can arise during the reflow process. Shearography is a non-destructive inspection technique that may be used to detect the delamination and warpage of IC packages. It is non-contacting and permits a full-field observation of surface displacement derivatives. Another advantage of this technique is that it is able to give the real-time formation of the fringes which indicate flaws in the IC package under real-time simulation condition of Surface Mount Technology (SMT) IR reflow profile. It is extremely fast and convenient to study the true behavior of the packaging deformation during the SMT process. It can be concluded that shearography has the potential for the real- time detection, in situ and non-destructive inspection of IC packages during the surface mount process.

Addressing Cultural Diversity: Effects of a Problem-Based Intercultural Learning Unit

ERIC Educational Resources Information Center

Busse, Vera; Krause, Ulrike-Marie

2015-01-01

This article explores to what extent a problem-based learning unit in combination with cooperative learning and affectively oriented teaching methods facilitates intercultural learning. As part of the study, students reflected on critical incidents, which display misunderstandings or conflicts that arise as a result of cultural differences. In…

A Separate Reality: The Problem of Uncooperative Experiments.

ERIC Educational Resources Information Center

Lersten, Ken

The problem of the uncooperative experiment arises with the use of human subjects. Evidence shows that typical volunteer subjects have the following characteristics: better education, higher paying jobs, greater need for approval, lower authoritarianism, higher I.Q. score, and better adjustment to personal questions than nonvolunteers. Data also…

Introducing Mathematics to Information Problem-Solving Tasks: Surface or Substance?

ERIC Educational Resources Information Center

Erickson, Ander

2017-01-01

This study employs a cross-case analysis in order to explore the demands and opportunities that arise when information problem-solving tasks are introduced into college mathematics classes. Professors at three universities collaborated with me to develop statistics-related activities that required students to engage in research outside the…

Classroom Crisis Intervention through Contracting: A Moral Development Model.

ERIC Educational Resources Information Center

Smaby, Marlowe H.; Tamminen, Armas W.

1981-01-01

A counselor can arbitrate problem situations using a systematic approach to classroom intervention which includes meetings with the teacher and students. This crisis intervention model based on moral development can be more effective than reliance on guidance activities disconnected from the actual classroom settings where the problems arise.…

Lexical Frames and Reported Speech

ERIC Educational Resources Information Center

Williams, Howard

2004-01-01

This paper addresses a problem of lexical choice that arises for ESL/EFL learners in the writing of research papers, critiques, interview reports, or any other sort of discourse that requires source attribution. The problem falls naturally into two parts. One part concerns the general lack of linguistic resources typically available (for various…

RACIAL IMBALANCE AND EDUCATIONAL PLANNING.

ERIC Educational Resources Information Center

CONROY, VINCENT F.

HARVARD'S ADMINISTRATIVE CAREER PROGRAM FACED THE GROWING PROBLEM OF NEGRO ENROLLMENT IN THE PUBLIC SCHOOLS. NOTING THE FREQUENCY AND INTENSITY WITH WHICH THE PROBLEM WAS ARISING AT THE NATIONAL LEVEL, A GROUP OF LAWYERS AND EDUCATORS CONVENED TO WORK OUT THE LEGAL ASPECTS OF SCHOOL INTEGRATION. FUNDS FROM THE FORD FOUNDATION INITIATED THE…

Polyomino Problems to Confuse Computers

ERIC Educational Resources Information Center

Coffin, Stewart

2009-01-01

Computers are very good at solving certain types combinatorial problems, such as fitting sets of polyomino pieces into square or rectangular trays of a given size. However, most puzzle-solving programs now in use assume orthogonal arrangements. When one departs from the usual square grid layout, complications arise. The author--using a computer,…

Digital Maps, Matrices and Computer Algebra

ERIC Educational Resources Information Center

Knight, D. G.

2005-01-01

The way in which computer algebra systems, such as Maple, have made the study of complex problems accessible to undergraduate mathematicians with modest computational skills is illustrated by some large matrix calculations, which arise from representing the Earth's surface by digital elevation models. Such problems are often considered to lie in…

Development of a process control computer device for the adaptation of flexible wind tunnel walls

NASA Technical Reports Server (NTRS)

Barg, J.

1982-01-01

In wind tunnel tests, the problems arise of determining the wall pressure distribution, calculating the wall contour, and controlling adjustment of the walls. This report shows how these problems have been solved for the high speed wind tunnel of the Technical University of Berlin.

CONGRESS ON SCIENCE TEACHING AND ECONOMIC GROWTH.

ERIC Educational Resources Information Center

Inter-Union Commission on the Teaching of Science, Paris (France).

REPORTED ARE THE ACTIVITIES OF THE CONGRESS ORGANIZED BY THE INTER-UNION COMMISSION ON SCIENCE TEACHING (CEIS) OF THE INTERNATIONAL COUNCIL OF SCIENTIFIC UNIONS (ICSU). STUDIED WERE PROBLEMS ARISING IN SEVERAL BRANCHES OF KNOWLEDGE DUE TO BOTH INCREASED NUMBERS OF STUDENTS AND SHORTAGE OF TEACHERS. OF PARTICULAR INTEREST WERE THE PROBLEMS OF…

IMPACTS OF MATERIAL SUBSTITUTION IN AUTOMOBILE MANUFACTURE ON RESOURCE RECOVERY. VOLUME II. APPENDICES A-E

EPA Science Inventory

Probable changes in the mix of materials used to manufacture automobiles were examined to determine if economic or technical problems in recycling could arise such that the 'abandoned automobile problem' would be resurrected. Future trends in materials composition of the automobi...

On the Inclusion of Difference Equation Problems and Z Transform Methods in Sophomore Differential Equation Classes

ERIC Educational Resources Information Center

Savoye, Philippe

2009-01-01

In recent years, I started covering difference equations and z transform methods in my introductory differential equations course. This allowed my students to extend the "classical" methods for (ordinary differential equation) ODE's to discrete time problems arising in many applications.

Ethical considerations in revision rhinoplasty.

PubMed

Wayne, Ivan

2012-08-01

The problems that arise when reviewing another surgeon's work, the financial aspects of revision surgery, and the controversies that present in marketing and advertising will be explored. The technological advances of computer imaging and the Internet have introduced new problems that require our additional consideration. Copyright © 2012 by Thieme Medical Publishers, Inc.

The legacy of Charles Marlatt and efforts to limit plant pest invasions

Treesearch

Andrew M. Liebhold; Robert L. Griffin

2016-01-01

The problem of invasions by non-native plant pests has come to dominate the field of applied entomology. Most of the damaging insect pests of agriculture and forestry are non-native (Sailer 1978, Aukema et al. 2010) and this is a problem being faced around the world. This problem did not arise overnight; instead, there has been a steady accumulation of non-native...

High-Order Accurate Solutions to the Helmholtz Equation in the Presence of Boundary Singularities

NASA Astrophysics Data System (ADS)

Britt, Darrell Steven, Jr.

Problems of time-harmonic wave propagation arise in important fields of study such as geological surveying, radar detection/evasion, and aircraft design. These often involve highfrequency waves, which demand high-order methods to mitigate the dispersion error. We propose a high-order method for computing solutions to the variable-coefficient inhomogeneous Helmholtz equation in two dimensions on domains bounded by piecewise smooth curves of arbitrary shape with a finite number of boundary singularities at known locations. We utilize compact finite difference (FD) schemes on regular structured grids to achieve highorder accuracy due to their efficiency and simplicity, as well as the capability to approximate variable-coefficient differential operators. In this work, a 4th-order compact FD scheme for the variable-coefficient Helmholtz equation on a Cartesian grid in 2D is derived and tested. The well known limitation of finite differences is that they lose accuracy when the boundary curve does not coincide with the discretization grid, which is a severe restriction on the geometry of the computational domain. Therefore, the algorithm presented in this work combines high-order FD schemes with the method of difference potentials (DP), which retains the efficiency of FD while allowing for boundary shapes that are not aligned with the grid without sacrificing the accuracy of the FD scheme. Additionally, the theory of DP allows for the universal treatment of the boundary conditions. One of the significant contributions of this work is the development of an implementation that accommodates general boundary conditions (BCs). In particular, Robin BCs with discontinuous coefficients are studied, for which we introduce a piecewise parameterization of the boundary curve. Problems with discontinuities in the boundary data itself are also studied. We observe that the design convergence rate suffers whenever the solution loses regularity due to the boundary conditions. This is because the FD scheme is only consistent for classical solutions of the PDE. For this reason, we implement the method of singularity subtraction as a means for restoring the design accuracy of the scheme in the presence of singularities at the boundary. While this method is well studied for low order methods and for problems in which singularities arise from the geometry (e.g., corners), we adapt it to our high-order scheme for curved boundaries via a conformal mapping and show that it can also be used to restore accuracy when the singularity arises from the BCs rather than the geometry. Altogether, the proposed methodology for 2D boundary value problems is computationally efficient, easily handles a wide class of boundary conditions and boundary shapes that are not aligned with the discretization grid, and requires little modification for solving new problems.

Dark energy from the string axiverse.

PubMed

Kamionkowski, Marc; Pradler, Josef; Walker, Devin G E

2014-12-19

String theories suggest the existence of a plethora of axionlike fields with masses spread over a huge number of decades. Here, we show that these ideas lend themselves to a model of quintessence with no super-Planckian field excursions and in which all dimensionless numbers are order unity. The scenario addresses the "Why now?" problem-i.e., Why has accelerated expansion begun only recently?-by suggesting that the onset of dark-energy domination occurs randomly with a slowly decreasing probability per unit logarithmic interval in cosmic time. The standard axion potential requires us to postulate a rapid decay of most of the axion fields that do not become dark energy. The need for these decays is averted, though, with the introduction of a slightly modified axion potential. In either case, a universe like ours arises in roughly 1 in 100 universes. The scenario may have a host of observable consequences.

Stochastic modeling of total suspended solids (TSS) in urban areas during rain events.

PubMed

Rossi, Luca; Krejci, Vladimir; Rauch, Wolfgang; Kreikenbaum, Simon; Fankhauser, Rolf; Gujer, Willi

2005-10-01

The load of total suspended solids (TSS) is one of the most important parameters for evaluating wet-weather pollution in urban sanitation systems. In fact, pollutants such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), phosphorous and organic compounds are adsorbed onto these particles so that a high TSS load indicates the potential impact on the receiving waters. In this paper, a stochastic model is proposed to estimate the TSS load and its dynamics during rain events. Information on the various simulated processes was extracted from different studies of TSS in urban areas. The model thus predicts the probability of TSS loads arising from combined sewer overflows (CSOs) in combined sewer systems as well as from stormwater in separate sewer systems in addition to the amount of TSS retained in treatment devices in both sewer systems. The results of this TSS model illustrate the potential of the stochastic modeling approach for assessing environmental problems.

Multiple shooting algorithms for jump-discontinuous problems in optimal control and estimation

NASA Technical Reports Server (NTRS)

Mook, D. J.; Lew, Jiann-Shiun

1991-01-01

Multiple shooting algorithms are developed for jump-discontinuous two-point boundary value problems arising in optimal control and optimal estimation. Examples illustrating the origin of such problems are given to motivate the development of the solution algorithms. The algorithms convert the necessary conditions, consisting of differential equations and transversality conditions, into algebraic equations. The solution of the algebraic equations provides exact solutions for linear problems. The existence and uniqueness of the solution are proved.

Sensitivity of Force Fields on Mechanical Properties of Metals Predicted by Atomistic Simulations

NASA Astrophysics Data System (ADS)

Rassoulinejad-Mousavi, Seyed Moein; Zhang, Yuwen

Increasing number of micro/nanoscale studies for scientific and engineering applications, leads to huge deployment of atomistic simulations such as molecular dynamics and Monte-Carlo simulation. Many complains from users in the simulation community arises for obtaining wrong results notwithstanding of correct simulation procedure and conditions. Improper choice of force field, known as interatomic potential is the likely causes. For the sake of users' assurance, convenience and time saving, several interatomic potentials are evaluated by molecular dynamics. Elastic properties of multiple FCC and BCC pure metallic species are obtained by LAMMPS, using different interatomic potentials designed for pure species and their alloys at different temperatures. The potentials created based on the Embedded Atom Method (EAM), Modified EAM (MEAM) and ReaX force fields, adopted from available open databases. Independent elastic stiffness constants of cubic single crystals for different metals are obtained. The results are compared with the experimental ones available in the literature and deviations for each force field are provided at each temperature. Using current work, users of these force fields can easily judge on the one they are going to designate for their problem.

Program Aids Visualization Of Data

NASA Technical Reports Server (NTRS)

Truong, L. V.

1995-01-01

Living Color Frame System (LCFS) computer program developed to solve some problems that arise in connection with generation of real-time graphical displays of numerical data and of statuses of systems. Need for program like LCFS arises because computer graphics often applied for better understanding and interpretation of data under observation and these graphics become more complicated when animation required during run time. Eliminates need for custom graphical-display software for application programs. Written in Turbo C++.

Stochastic species abundance models involving special copulas

NASA Astrophysics Data System (ADS)

Huillet, Thierry E.

2018-01-01

Copulas offer a very general tool to describe the dependence structure of random variables supported by the hypercube. Inspired by problems of species abundances in Biology, we study three distinct toy models where copulas play a key role. In a first one, a Marshall-Olkin copula arises in a species extinction model with catastrophe. In a second one, a quasi-copula problem arises in a flagged species abundance model. In a third model, we study completely random species abundance models in the hypercube as those, not of product type, with uniform margins and singular. These can be understood from a singular copula supported by an inflated simplex. An exchangeable singular Dirichlet copula is also introduced, together with its induced completely random species abundance vector.

[Specific problems posed by carbohydrate utilization in the rainbow trout].

PubMed

Bergot, F

1979-01-01

Carbohydrate incorporation in trout diets arises problems both at digestive and metabolic levels. Digestive utilization of carbohydrate closely depends on their molecular weight. In addition, in the case of complex carbohydrates (starches), different factors such as the level of incorporation, the amount consumed and the physical state of starch influence the digestibility. The measurement of digestibility in itself is confronted with methodological difficulties. The way the feces are collected can affect the digestion coefficient. Dietary carbohydrates actually serve as a source of energy. Nevertheless, above a certain level in the diet, intolerance phenomena may appear. The question that arises now is to establish the optimal part that carbohydrates can take in the metabolizable energy of a given diet.

78 FR 42991 - Self-Regulatory Organizations; the Depository Trust Company; Order Approving Proposed Rule Change...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-18

... intraday uncertainty that may arise from reclaim transactions and any potential credit and liquidity risk... receiving Participant prior to DTC processing, thereby reducing the intraday uncertainty that may arise from...

Optimization-based mesh correction with volume and convexity constraints

DOE PAGES

D'Elia, Marta; Ridzal, Denis; Peterson, Kara J.; ...

2016-02-24

In this study, we consider the problem of finding a mesh such that 1) it is the closest, with respect to a suitable metric, to a given source mesh having the same connectivity, and 2) the volumes of its cells match a set of prescribed positive values that are not necessarily equal to the cell volumes in the source mesh. This volume correction problem arises in important simulation contexts, such as satisfying a discrete geometric conservation law and solving transport equations by incremental remapping or similar semi-Lagrangian transport schemes. In this paper we formulate volume correction as a constrained optimizationmore » problem in which the distance to the source mesh defines an optimization objective, while the prescribed cell volumes, mesh validity and/or cell convexity specify the constraints. We solve this problem numerically using a sequential quadratic programming (SQP) method whose performance scales with the mesh size. To achieve scalable performance we develop a specialized multigrid-based preconditioner for optimality systems that arise in the application of the SQP method to the volume correction problem. Numerical examples illustrate the importance of volume correction, and showcase the accuracy, robustness and scalability of our approach.« less

Bone graft complications: what can we do to prevent them?

NASA Astrophysics Data System (ADS)

Tandon, Rahul; Herford, Alan S.

2014-03-01

Introduction: Bone grafts are commonly used in oral and maxillofacial surgery, helping to restore missing bone structure and provide osseous support. In spite of their reported success, complications can and do arise. Examples include loosening and resorption of the graft, infection, and complete loss of the graft. These complications can potentially lead to larger defects, necessitating additional procedures to correct the problem. This not only causes great discomfort to the patient, but also drains considerable time and resources away from the clinician. Thus, improvements on identifying ways to identify and prevent these complications are constantly being sought. We have performed a literature review and identified several areas in the field of optics that could potentially help solve our problem. Optical Techniques: Raman spectroscopy has been shown to provide a transcutaneous measurement of bone mineral and matrix Raman bands. This could potentially provide surgeons with the ability to more accurately assess bone graft osseointegration. In-vivo near-infrared optical imaging could potentially provide accurate diagnosis of pathologic lesions such as osteosarcoma. Contrast-enhanced ultrasound could be used to detect vascular disturbances and other information related to the transplantation of osseous components. Conclusion: Bone graft complications can be one of the most devastating consequences of osseous surgery. As surgeons, we are constantly searching for ways to identify them earlier and prevent them. We hope that by presenting areas that could be used, we can gain a better insight to ways in which both fields can benefit.

Quality Problem-Based Learning Experiences for Students: Design Deliberations among Teachers from Diverse Disciplines.

ERIC Educational Resources Information Center

Butler, Susan McAleenan

This qualitative study, investigating the claims, concerns, and issues arising within the design stages of problem-based learning (PBL) curriculum units, was conducted during two masters-level classes during the summer of 1999. A hermeneutic dialectic discourse among veteran teachers (who were novice PBL curriculum designers) was facilitated by…

Peculiarities of Students of Pedagogical Specialties Training in Preventive Work with Juveniles Delinquents

ERIC Educational Resources Information Center

Moskalenko, Maxim R.; Dorozhkin, Evgenij M.; Ozhiganova, Maria V.; Murzinova, Yana A.; Syssa, Daria O.

2016-01-01

The relevance of the problem under investigation is due to the high significance of preventive work with juvenile delinquents to society. The article aims to study the problems arising while developing students' competencies in professional activities for the prevention of the infringing behavior of juvenile delinquents, as well as the…

A Solution to the Mysteries of Morality

ERIC Educational Resources Information Center

DeScioli, Peter; Kurzban, Robert

2013-01-01

We propose that moral condemnation functions to guide bystanders to choose the same side as other bystanders in disputes. Humans interact in dense social networks, and this poses a problem for bystanders when conflicts arise: which side, if any, to support. Choosing sides is a difficult strategic problem because the outcome of a conflict…

Transfer of Learning Transformed

ERIC Educational Resources Information Center

Larsen-Freeman, Diane

2013-01-01

Instruction is motivated by the assumption that students can transfer their learning, or apply what they have learned in school to another setting. A common problem arises when the expected transfer does not take place, what has been referred to as the inert knowledge problem. More than an academic inconvenience, the failure to transfer is a major…

The Plasticity of Adolescent Cognitions: Data from a Novel Cognitive Bias Modification Training Task

ERIC Educational Resources Information Center

Lau, Jennifer Y. F.; Molyneaux, Emma; Telman, Machteld D.; Belli, Stefano

2011-01-01

Many adult anxiety problems emerge in adolescence. Investigating how adolescent anxiety arises and abates is critical for understanding and preventing adult psychiatric problems. Drawing threat interpretations from ambiguous material is linked to adolescent anxiety but little research has clarified the causal nature of this relationship. Work in…

Coorientational Accuracy during Regional Development of Energy Resources: Problems in Agency-Public Communication.

ERIC Educational Resources Information Center

Bowes, John E.; Stamm, Keith R.

This paper presents a progress report from a research program aimed at elucidating communication problems which arise among citizens and government agencies during the development of regional environmental policy. The eventual objective of the program is to develop a paradigm for evaluative research in communication that will provide for the…

Anger/Frustration, Task Persistence, and Conduct Problems in Childhood: A Behavioral Genetic Analysis

ERIC Educational Resources Information Center

Deater-Deckard, Kirby; Petrill, Stephen A.; Thompson, Lee A.

2007-01-01

Background: Individual differences in conduct problems arise in part from proneness to anger/frustration and poor self-regulation of behavior. However, the genetic and environmental etiology of these connections is not known. Method: Using a twin design, we examined genetic and environmental covariation underlying the well-documented correlations…

A chance constraint estimation approach to optimizing resource management under uncertainty

Treesearch

Michael Bevers

2007-01-01

Chance-constrained optimization is an important method for managing risk arising from random variations in natural resource systems, but the probabilistic formulations often pose mathematical programming problems that cannot be solved with exact methods. A heuristic estimation method for these problems is presented that combines a formulation for order statistic...

Zones of Intervention: Teaching and Learning at All Places and at All Times

ERIC Educational Resources Information Center

Taylor, Jonathan E.; McKissac, Jonathan C.

2014-01-01

This article identifies four distinct zones in which workplace problems can be addressed through education and training. These zones enable educators to address workplace learning more widely and broadly. Very often, problems arising in the workplace are dealt with through training in the classroom, but other options exist. The theoretical…

Variational formulation for Black-Scholes equations in stochastic volatility models

NASA Astrophysics Data System (ADS)

Gyulov, Tihomir B.; Valkov, Radoslav L.

2012-11-01

In this note we prove existence and uniqueness of weak solutions to a boundary value problem arising from stochastic volatility models in financial mathematics. Our settings are variational in weighted Sobolev spaces. Nevertheless, as it will become apparent our variational formulation agrees well with the stochastic part of the problem.

Community-University Research Partnerships: Devising a Model for Ethical Engagement

ERIC Educational Resources Information Center

Silka, Linda; Renault-Caragianes, Paulette

2006-01-01

Profound changes taking place in communities and in universities are bringing researchers and community members new opportunities for joint research endeavors and new problems that must be resolved. In such partnerships, questions about shared decision making--about the ethics of collaboration--arise at every stage: Who decides which problems are…

Sparse Measurement Systems: Applications, Analysis, Algorithms and Design

ERIC Educational Resources Information Center

Narayanaswamy, Balakrishnan

2011-01-01

This thesis deals with "large-scale" detection problems that arise in many real world applications such as sensor networks, mapping with mobile robots and group testing for biological screening and drug discovery. These are problems where the values of a large number of inputs need to be inferred from noisy observations and where the…

The Changing Demographics of the Hispanic Family.

ERIC Educational Resources Information Center

McKay, Emily Gantz

Hispanics will become the largest United States minority population sometime early in the next century. A problem that arises with attempts to provide Hispanic people with better opportunities is the lack of adequate data on Hispanic socioeconomic status. Those data which do exist focus on problems of the individual, yet one of the greatest…

Projected Issues in the Practice of Educational Administration: The English Context.

ERIC Educational Resources Information Center

Browning, Peter

Current and incipient problems in educational administration in England can be grouped into two areas: those resulting from reorganization and those arising from social and political factors. Many problems faced by educational administrators result from school reorganization that is a result of an increase in the number of comprehensive schools.…

Focal-Plane Alignment Sensing

DTIC Science & Technology

1993-02-01

amplification induced by the inverse filter. The problem of noise amplification that arises in conventional image deblurring problems has often been... noise sensitivity, and strategies for selecting a regularization parameter have been developed. The probability of convergence to within a prescribed...Strategies in Image Deblurring .................. 12 2.2.2 CLS Parameter Selection ........................... 14 2.2.3 Wiener Parameter Selection

Damage Control: Closing Problematic Sequences in Hearing-Impaired Interaction

ERIC Educational Resources Information Center

Skelt, Louise

2007-01-01

When a problem of understanding arises for a hearing-impaired recipient in the course of a conversation, and is detected, repairing that problem is only one of several possible courses of action for participants. Another possibility is the collaborative closing of the part of the conversation which has proved problematic for understanding, to…

A New Homotopy Perturbation Scheme for Solving Singular Boundary Value Problems Arising in Various Physical Models

NASA Astrophysics Data System (ADS)

Roul, Pradip; Warbhe, Ujwal

2017-08-01

The classical homotopy perturbation method proposed by J. H. He, Comput. Methods Appl. Mech. Eng. 178, 257 (1999) is useful for obtaining the approximate solutions for a wide class of nonlinear problems in terms of series with easily calculable components. However, in some cases, it has been found that this method results in slowly convergent series. To overcome the shortcoming, we present a new reliable algorithm called the domain decomposition homotopy perturbation method (DDHPM) to solve a class of singular two-point boundary value problems with Neumann and Robin-type boundary conditions arising in various physical models. Five numerical examples are presented to demonstrate the accuracy and applicability of our method, including thermal explosion, oxygen-diffusion in a spherical cell and heat conduction through a solid with heat generation. A comparison is made between the proposed technique and other existing seminumerical or numerical techniques. Numerical results reveal that only two or three iterations lead to high accuracy of the solution and this newly improved technique introduces a powerful improvement for solving nonlinear singular boundary value problems (SBVPs).

The geometry of discombinations and its applications to semi-inverse problems in anelasticity

PubMed Central

Yavari, Arash; Goriely, Alain

2014-01-01

The geometrical formulation of continuum mechanics provides us with a powerful approach to understand and solve problems in anelasticity where an elastic deformation is combined with a non-elastic component arising from defects, thermal stresses, growth effects or other effects leading to residual stresses. The central idea is to assume that the material manifold, prescribing the reference configuration for a body, has an intrinsic, non-Euclidean, geometrical structure. Residual stresses then naturally arise when this configuration is mapped into Euclidean space. Here, we consider the problem of discombinations (a new term that we introduce in this paper), that is, a combined distribution of fields of dislocations, disclinations and point defects. Given a discombination, we compute the geometrical characteristics of the material manifold (curvature, torsion, non-metricity), its Cartan's moving frames and structural equations. This identification provides a powerful algorithm to solve semi-inverse problems with non-elastic components. As an example, we calculate the residual stress field of a cylindrically symmetric distribution of discombinations in an infinite circular cylindrical bar made of an incompressible hyperelastic isotropic elastic solid. PMID:25197257

On multiple crack identification by ultrasonic scanning

NASA Astrophysics Data System (ADS)

Brigante, M.; Sumbatyan, M. A.

2018-04-01

The present work develops an approach which reduces operator equations arising in the engineering problems to the problem of minimizing the discrepancy functional. For this minimization, an algorithm of random global search is proposed, which is allied to some genetic algorithms. The efficiency of the method is demonstrated by the solving problem of simultaneous identification of several linear cracks forming an array in an elastic medium by using the circular Ultrasonic scanning.

A bicriteria heuristic for an elective surgery scheduling problem.

PubMed

Marques, Inês; Captivo, M Eugénia; Vaz Pato, Margarida

2015-09-01

Resource rationalization and reduction of waiting lists for surgery are two main guidelines for hospital units outlined in the Portuguese National Health Plan. This work is dedicated to an elective surgery scheduling problem arising in a Lisbon public hospital. In order to increase the surgical suite's efficiency and to reduce the waiting lists for surgery, two objectives are considered: maximize surgical suite occupation and maximize the number of surgeries scheduled. This elective surgery scheduling problem consists of assigning an intervention date, an operating room and a starting time for elective surgeries selected from the hospital waiting list. Accordingly, a bicriteria surgery scheduling problem arising in the hospital under study is presented. To search for efficient solutions of the bicriteria optimization problem, the minimization of a weighted Chebyshev distance to a reference point is used. A constructive and improvement heuristic procedure specially designed to address the objectives of the problem is developed and results of computational experiments obtained with empirical data from the hospital are presented. This study shows that by using the bicriteria approach presented here it is possible to build surgical plans with very good performance levels. This method can be used within an interactive approach with the decision maker. It can also be easily adapted to other hospitals with similar scheduling conditions.

A methodology for constraining power in finite element modeling of radiofrequency ablation.

PubMed

Jiang, Yansheng; Possebon, Ricardo; Mulier, Stefaan; Wang, Chong; Chen, Feng; Feng, Yuanbo; Xia, Qian; Liu, Yewei; Yin, Ting; Oyen, Raymond; Ni, Yicheng

2017-07-01

Radiofrequency ablation (RFA) is a minimally invasive thermal therapy for the treatment of cancer, hyperopia, and cardiac tachyarrhythmia. In RFA, the power delivered to the tissue is a key parameter. The objective of this study was to establish a methodology for the finite element modeling of RFA with constant power. Because of changes in the electric conductivity of tissue with temperature, a nonconventional boundary value problem arises in the mathematic modeling of RFA: neither the voltage (Dirichlet condition) nor the current (Neumann condition), but the power, that is, the product of voltage and current was prescribed on part of boundary. We solved the problem using Lagrange multiplier: the product of the voltage and current on the electrode surface is constrained to be equal to the Joule heating. We theoretically proved the equality between the product of the voltage and current on the surface of the electrode and the Joule heating in the domain. We also proved the well-posedness of the problem of solving the Laplace equation for the electric potential under a constant power constraint prescribed on the electrode surface. The Pennes bioheat transfer equation and the Laplace equation for electric potential augmented with the constraint of constant power were solved simultaneously using the Newton-Raphson algorithm. Three problems for validation were solved. Numerical results were compared either with an analytical solution deduced in this study or with results obtained by ANSYS or experiments. This work provides the finite element modeling of constant power RFA with a firm mathematical basis and opens pathway for achieving the optimal RFA power. Copyright © 2016 John Wiley & Sons, Ltd.

Integrated Hardware and Software for No-Loss Computing

NASA Technical Reports Server (NTRS)

James, Mark

2007-01-01

When an algorithm is distributed across multiple threads executing on many distinct processors, a loss of one of those threads or processors can potentially result in the total loss of all the incremental results up to that point. When implementation is massively hardware distributed, then the probability of a hardware failure during the course of a long execution is potentially high. Traditionally, this problem has been addressed by establishing checkpoints where the current state of some or part of the execution is saved. Then in the event of a failure, this state information can be used to recompute that point in the execution and resume the computation from that point. A serious problem arises when one distributes a problem across multiple threads and physical processors is that one increases the likelihood of the algorithm failing due to no fault of the scientist but as a result of hardware faults coupled with operating system problems. With good reason, scientists expect their computing tools to serve them and not the other way around. What is novel here is a unique combination of hardware and software that reformulates an application into monolithic structure that can be monitored in real-time and dynamically reconfigured in the event of a failure. This unique reformulation of hardware and software will provide advanced aeronautical technologies to meet the challenges of next-generation systems in aviation, for civilian and scientific purposes, in our atmosphere and in atmospheres of other worlds. In particular, with respect to NASA s manned flight to Mars, this technology addresses the critical requirements for improving safety and increasing reliability of manned spacecraft.

Engineering the electronic health record for safety: a multi-level video-based approach to diagnosing and preventing technology-induced error arising from usability problems.

PubMed

Borycki, Elizabeth M; Kushniruk, Andre W; Kuwata, Shigeki; Kannry, Joseph

2011-01-01

Electronic health records (EHRs) promise to improve and streamline healthcare through electronic entry and retrieval of patient data. Furthermore, based on a number of studies showing their positive benefits, they promise to reduce medical error and make healthcare safer. However, a growing body of literature has clearly documented that if EHRS are not designed properly and with usability as an important goal in their design, rather than reducing error, EHR deployment has the potential to actually increase medical error. In this paper we describe our approach to engineering (and reengineering) EHRs in order to increase their beneficial potential while at the same time improving their safety. The approach described in this paper involves an integration of the methods of usability analysis with video analysis of end users interacting with EHR systems and extends the evaluation of the usability of EHRs to include the assessment of the impact of these systems on work practices. Using clinical simulations, we analyze human-computer interaction in real healthcare settings (in a portable, low-cost and high fidelity manner) and include both artificial and naturalistic data collection to identify potential usability problems and sources of technology-induced error prior to widespread system release. Two case studies where the methods we have developed and refined have been applied at different levels of user-computer interaction are described.

Contraceptive services for adolescents in Latin America: facts, problems and perspectives.

PubMed

Pons, J E

1999-12-01

This review presents facts about sexual and contraceptive behavior of Latin American adolescents, analyzes barriers to contraception, and summarizes present perspectives. Between 13 and 30% of Latin American adolescent women live in union before their 20th birthday and between 46 and 63% have had sexual relations. The prevalence of contraceptive use among adolescents at risk of pregnancy remains very low. The pill is the best known contraceptive method. When sexual activity becomes a permanent practice, contraceptive use increases but remains low. Barriers to contraception can be identified as: (1) arising from adolescents themselves (moral objections, alleged medical reasons, lack of confidence in adults and in the health system, promiscuity; (2) arising from the sexual partner (partner's opposition, masculine irresponsibility); (3) arising from adults (moral objections, fear of sex education, adult control and power of decision-making); (4) arising from the health system (inappropriateness of services, regulatory barriers, gender inequality); (5) arising from health professionals (medical barriers to contraceptive use, discomfort with sexual matters); (6) arising from the educational system (educational failure, teachers' reluctance); and (7) arising from other social agents (religious opposition, media ambivalent messages, fund restraints). There have been improvements in recent years, including the achievements of groups working for and with adolescents, and the support from distinguished personalities.

Customer-centered problem solving.

PubMed

Samelson, Q B

1999-11-01

If there is no single best way to attract new customers and retain current customers, there is surely an easy way to lose them: fail to solve the problems that arise in nearly every buyer-supplier relationship, or solve them in an unsatisfactory manner. Yet, all too frequently, companies do just that. Either we deny that a problem exists, we exert all our efforts to pin the blame elsewhere, or we "Band-Aid" the problem instead of fixing it, almost guaranteeing that we will face it again and again.

Robust Consumption-Investment Problem on Infinite Horizon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zawisza, Dariusz, E-mail: dariusz.zawisza@im.uj.edu.pl

In our paper we consider an infinite horizon consumption-investment problem under a model misspecification in a general stochastic factor model. We formulate the problem as a stochastic game and finally characterize the saddle point and the value function of that game using an ODE of semilinear type, for which we provide a proof of an existence and uniqueness theorem for its solution. Such equation is interested on its own right, since it generalizes many other equations arising in various infinite horizon optimization problems.

Bethe-Salpeter Eigenvalue Solver Package (BSEPACK) v0.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

SHAO, MEIYEU; YANG, CHAO

2017-04-25

The BSEPACK contains a set of subroutines for solving the Bethe-Salpeter Eigenvalue (BSE) problem. This type of problem arises in this study of optical excitation of nanoscale materials. The BSE problem is a structured non-Hermitian eigenvalue problem. The BSEPACK software can be used to compute all or subset of eigenpairs of a BSE Hamiltonian. It can also be used to compute the optical absorption spectrum without computing BSE eigenvalues and eigenvectors explicitly. The package makes use of the ScaLAPACK, LAPACK and BLAS.

The Soccer-Ball Problem

NASA Astrophysics Data System (ADS)

Hossenfelder, Sabine

2014-07-01

The idea that Lorentz-symmetry in momentum space could be modified but still remain observer-independent has received quite some attention in the recent years. This modified Lorentz-symmetry, which has been argued to arise in Loop Quantum Gravity, is being used as a phenomenological model to test possibly observable effects of quantum gravity. The most pressing problem in these models is the treatment of multi-particle states, known as the 'soccer-ball problem'. This article briefly reviews the problem and the status of existing solution attempts.

Measuring Time Costs in Interventions Designed to Reduce Behavior Problems Among Children and Youth

PubMed Central

Foster, E. Michael; Johnson‐Shelton, Deborah; Taylor, Ted K.

2007-01-01

The economic evaluation of psychosocial interventions is a growing area of research. Though time costs are central to the economist’s understanding of social costs, these costs generally have been ignored by prevention scientists. This article highlights the need to measure such costs and then reviews the principles economists use in valuing time. It then considers the specific time costs that often arise in interventions designed to reduce behavior problems among children and youth. These include classroom time devoted to program activities, the time of parents or other caregivers, the time of teachers (outside of the classroom), and the time of volunteers. We consider the economic principles that govern how economists value these inputs and then apply these principles to data from an evaluation of a prominent intervention in the field, the Incredible Years Program. We find that the time costs are potentially rather large and consider the implications for public policy of ignoring them. PMID:17592769

Testing a Flexible Method to Reduce False Monsoon Onsets

PubMed Central

Stiller-Reeve, Mathew Alexander; Spengler, Thomas; Chu, Pao-Shin

2014-01-01

To generate information about the monsoon onset and withdrawal we have to choose a monsoon definition and apply it to data. One problem that arises is that false monsoon onsets can hamper our analysis, which is often alleviated by smoothing the data in time or space. Another problem is that local communities or stakeholder groups may define the monsoon differently. We therefore aim to develop a technique that reduces false onsets for high-resolution gridded data, while also being flexible for different requirements that can be tailored to particular end-users. In this study, we explain how we developed our technique and demonstrate how it successfully reduces false onsets and withdrawals. The presented results yield improved information about the monsoon length and its interannual variability. Due to this improvement, we are able to extract information from higher resolution data sets. This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations. PMID:25105900

[Possibilities of medical opinionating in cases associated with "exposure to direct danger of death or serious health damage"].

PubMed

Konopka, Tomasz; Skupień, Elzbieta

2008-01-01

In the opinion of some forensic medicine experts, assessment of potential consequences in keeping with Article 160 of the Polish Penal code, which refers to the crime of "exposure to direct danger of death or severe health damage", lies within the competence of medicolegal specialists. This view is accepted by courts and prosecution offices. However, the knowledge of physicians in the field of predicting consequences which did not occur is only somewhat better than that of lawyers. In simple cases, e.g. in trauma involving a sensitive area of the body, passing an opinion confirming a serious danger is not associated with any major problems. Similarly, no problems arise when passing an opinion on the lack of such a danger e.g. in the case of traumawithout any injuries. In complex cases, however, which include the majority of medical error cases, passing an opinion on exposure to direct danger of death or severe health damage may be not feasible.

The inverse problem of estimating the gravitational time dilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gusev, A. V., E-mail: avg@sai.msu.ru; Litvinov, D. A.; Rudenko, V. N.

2016-11-15

Precise testing of the gravitational time dilation effect suggests comparing the clocks at points with different gravitational potentials. Such a configuration arises when radio frequency standards are installed at orbital and ground stations. The ground-based standard is accessible directly, while the spaceborne one is accessible only via the electromagnetic signal exchange. Reconstructing the current frequency of the spaceborne standard is an ill-posed inverse problem whose solution depends significantly on the characteristics of the stochastic electromagnetic background. The solution for Gaussian noise is known, but the nature of the standards themselves is associated with nonstationary fluctuations of a wide class ofmore » distributions. A solution is proposed for a background of flicker fluctuations with a spectrum (1/f){sup γ}, where 1 < γ < 3, and stationary increments. The results include formulas for the error in reconstructing the frequency of the spaceborne standard and numerical estimates for the accuracy of measuring the relativistic redshift effect.« less

Spacetime encodings. II. Pictures of integrability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brink, Jeandrew

I visually explore the features of geodesic orbits in arbitrary stationary axisymmetric vacuum (SAV) spacetimes that are constructed from a complex Ernst potential. Some of the geometric features of integrable and chaotic orbits are highlighted. The geodesic problem for these SAV spacetimes is rewritten as a 2 degree of freedom problem and the connection between current ideas in dynamical systems and the study of two manifolds sought. The relationship between the Hamilton-Jacobi equations, canonical transformations, constants of motion, and Killing tensors are commented on. Wherever possible I illustrate the concepts by means of examples from general relativity. This investigation ismore » designed to build the readers' intuition about how integrability arises, and to summarize some of the known facts about 2 degree of freedom systems. Evidence is given, in the form of an orbit-crossing structure, that geodesics in SAV spacetimes might admit a fourth constant of motion that is quartic in momentum (by contrast with Kerr spacetime, where Carter's fourth constant is quadratic)« less

Reduction by symmetries in singular quantum-mechanical problems: General scheme and application to Aharonov-Bohm model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, A. G., E-mail: smirnov@lpi.ru

2015-12-15

We develop a general technique for finding self-adjoint extensions of a symmetric operator that respects a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schrödinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to themore » three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.« less

Brane with variable tension as a possible solution to the problem of the late cosmic acceleration

NASA Astrophysics Data System (ADS)

García-Aspeitia, Miguel A.; Hernandez-Almada, A.; Magaña, Juan; Amante, Mario H.; Motta, V.; Martínez-Robles, C.

2018-05-01

Braneworld models have been proposed as a possible solution to the problem of the accelerated expansion of the Universe. The idea is to dispense the dark energy (DE) and drive the late-time cosmic acceleration with a five-dimensional geometry. We investigate a brane model with variable brane tension as a function of redshift called chrono-brane. We propose the polynomial λ =(1 +z )n function inspired in tracker-scalar-field potentials. To constrain the n exponent we use the latest observational Hubble data from cosmic chronometers, Type Ia Supernovae from the full joint-light-analysis sample, baryon acoustic oscillations and the posterior distance from the cosmic microwave background of Planck 2015 measurements. A joint analysis of these data estimates n ≃6.19 ±0.12 which generates a DE-like (cosmological-constantlike at late times) term, in the Friedmann equation arising from the extra dimensions. This model is consistent with these data and can drive the Universe to an accelerated phase at late times.

Words and pictures: An electrophysiological investigation of domain specific processing in native Chinese and English speakers

PubMed Central

Yum, Yen Na; Holcomb, Phillip J.; Grainger, Jonathan

2011-01-01

Comparisons of word and picture processing using Event-Related Potentials (ERPs) are contaminated by gross physical differences between the two types of stimuli. In the present study, we tackle this problem by comparing picture processing with word processing in an alphabetic and a logographic script, that are also characterized by gross physical differences. Native Mandarin Chinese speakers viewed pictures (line drawings) and Chinese characters (Experiment 1), native English speakers viewed pictures and English words (Experiment 2), and naïve Chinese readers (native English speakers) viewed pictures and Chinese characters (Experiment 3) in a semantic categorization task. The varying pattern of differences in the ERPs elicited by pictures and words across the three experiments provided evidence for i) script-specific processing arising between 150–200 ms post-stimulus onset, ii) domain-specific but script-independent processing arising between 200–300 ms post-stimulus onset, and iii) processing that depended on stimulus meaningfulness in the N400 time window. The results are interpreted in terms of differences in the way visual features are mapped onto higher-level representations for pictures and words in alphabetic and logographic writing systems. PMID:21439991

Host population structure and treatment frequency maintain balancing selection on drug resistance

PubMed Central

Baskerville, Edward B.; Colijn, Caroline; Hanage, William; Fraser, Christophe; Lipsitch, Marc

2017-01-01

It is a truism that antimicrobial drugs select for resistance, but explaining pathogen- and population-specific variation in patterns of resistance remains an open problem. Like other common commensals, Streptococcus pneumoniae has demonstrated persistent coexistence of drug-sensitive and drug-resistant strains. Theoretically, this outcome is unlikely. We modelled the dynamics of competing strains of S. pneumoniae to investigate the impact of transmission dynamics and treatment-induced selective pressures on the probability of stable coexistence. We find that the outcome of competition is extremely sensitive to structure in the host population, although coexistence can arise from age-assortative transmission models with age-varying rates of antibiotic use. Moreover, we find that the selective pressure from antibiotics arises not so much from the rate of antibiotic use per se but from the frequency of treatment: frequent antibiotic therapy disproportionately impacts the fitness of sensitive strains. This same phenomenon explains why serotypes with longer durations of carriage tend to be more resistant. These dynamics may apply to other potentially pathogenic, microbial commensals and highlight how population structure, which is often omitted from models, can have a large impact. PMID:28835542

Copyright protection of remote sensing imagery by means of digital watermarking

NASA Astrophysics Data System (ADS)

Barni, Mauro; Bartolini, Franco; Cappellini, Vito; Magli, Enrico; Olmo, Gabriella; Zanini, R.

2001-12-01

The demand for remote sensing data has increased dramatically mainly due to the large number of possible applications capable to exploit remotely sensed data and images. As in many other fields, along with the increase of market potential and product diffusion, the need arises for some sort of protection of the image products from unauthorized use. Such a need is a very crucial one even because the Internet and other public/private networks have become preferred and effective means of data exchange. An important issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. Before applying watermarking techniques developed for multimedia applications to remote sensing applications, it is important that the requirements imposed by remote sensing imagery are carefully analyzed to investigate whether they are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: (1) assessment of the requirements imposed by the characteristics of remotely sensed images on watermark-based copyright protection; (2) discussion of a case study where the performance of two popular, state-of-the-art watermarking techniques are evaluated by the light of the requirements at the previous point.

[Chemical hazards arising from shale gas extraction].

PubMed

Pakulska, Daria

2015-01-01

The development of the shale industry is gaining momentum and hence the analysis of chemical hazards to the environment and health of the local population is extreiely timely and important. Chemical hazards are created during the exploitation of all minerals, but in the case of shale gas production, there is much more uncertainty as regards to the effects of new technologies application. American experience suggests the increasing risk of environmental contamination, mainly groundwater. The greatest, concern is the incomplete knowledge of the composition of fluids used for fracturing shale rock and unpredictability of long-term effects of hydraulic fracturing for the environment and health of residents. High population density in the old continent causes the problem of chemical hazards which is much larger than in the USA. Despite the growing public discontent data on this subject are limited. First of all, there is no epidemiological studies to assess the relationship between risk factors, such as air and water pollution, and health effects in populations living in close proximity to gas wells. The aim of this article is to identify and discuss existing concepts on the sources of environmental contamination, an indication of the environment elements under pressure and potential health risks arising from shale gas extraction.

A simple analytical method for determining the atmospheric dispersion of upward-directed high velocity releases

NASA Astrophysics Data System (ADS)

Palazzi, E.

The evaluation of atmospheric dispersion of a cloud, arising from a sudden release of flammable or toxic materials, is an essential tool for properly designing flares, vents and other safety devices and to quantify the potential risk related to the existing ones or arising from the various kinds of accidents which can occur in chemical plants. Among the methods developed to treat the important case of upward-directed jets, Hoehne's procedure for determining the behaviour and extent of flammability zone is extensively utilized, particularly concerning petrochemical plants. In a previous study, a substantial simplification of the aforesaid procedure was achieved, by correlating the experimental data with an empirical formula, allowing to obtain a mathematical description of the boundaries of the flammable cloud. Following a theoretical approach, a most general model is developed in the present work, applicable to the various kinds of design problems and/or risk evaluation regarding upward-directed releases from high velocity sources. It is also demonstrated that the model gives conservative results, if applied outside the range of the Hoehne's experimental conditions. Moreover, with simple modifications, the same approach could be easily applied to deal with the atmospheric dispersion of anyhow directed releases.

Cardiac emergencies and problems of the critical care patient.

PubMed

Marr, Celia M

2004-04-01

Cardiac disease and dysfunction can occur as a primary disorder(ie, with pathology situated in one or more of the cardiac structures) or can be classified as a secondary problem when it occurs in patients with another primary problem that has affected the heart either directly or indirectly. Primary cardiac problems are encountered in horses presented to emergency clinics; however,this occurs much less frequently in equine critical patients than cardiac problems arising secondary to other conditions. Nevertheless,if primary or secondary cardiac problems are not identified and addressed, they certainly contribute to the morbidity and mortality of critical care patients.

Low frequency acoustic and electromagnetic scattering

NASA Technical Reports Server (NTRS)

Hariharan, S. I.; Maccamy, R. C.

1986-01-01

This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k/2/ log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.

The Unintended Consequences of Social Media in Healthcare: New Problems and New Solutions

PubMed Central

Atique, S.; Mayer, M. A.; Denecke, K.; Merolli, M.; Househ, M.

2016-01-01

Summary Objectives Social media is increasingly being used in conjunction with health information technology (health IT). The objective of this paper is to identify some of the undesirable outcomes that arise from this integration and to suggest solutions to these problems. Methodology After a discussion with experts to elicit the topics that should be included in the survey, we performed a narrative review based on recent literature and interviewed multidisciplinary experts from different areas. In each case, we identified and analyzed the unintended effects of social media in health IT. Results Each analyzed topic provided a different set of unintended consequences. Most relevant consequences include lack of privacy with ethical and legal issues, patient confusion in disease management, poor information accuracy in crowdsourcing, unclear responsibilities, misleading and biased information in the prevention and detection of epidemics, and demotivation in gamified health solutions with social components. Conclusions Using social media in healthcare offers several benefits, but it is not exempt of potential problems, and not all of these problems have clear solutions. We recommend careful design of digital systems in order to minimize patient’s feelings of demotivation and frustration and we recommend following specific guidelines that should be created by all stakeholders in the healthcare ecosystem. PMID:27830230

Problems for biomedical research at the academia-industrial interface.

PubMed

Weatherall, David

2003-01-01

Throughout much of the world, universities have driven towards industrial partnerships. This collaboration, which, in the biochemical field at least, has to continue if potential benefits for patients are to be realised, has brought with it a number of problems. These include the neglect of long-term research in favour of short-term projects, the curtailing of free dissemination of research information within university departments and the biasing of results of clinical trials by the financial interests of the investigators. It is very important that governments, universities, and industry itself address these problems. Universities should monitor the amount of basic, curiosity-driven research that is being carried on, compared with that which is more short-term goal orientated. PhD students and post-doctoral fellows should be exposed to the principles of bioethics early on in their careers. Further work is necessary on the terms of research contracts to protect, on the one hand, the rights of individual scientists and, on the other, industry from rogue scientists. Where problems arise, procedures should be in place for independent reviews to be conducted by bodies such as the Medical Research Council in the UK or the National Institutes of Health in the USA. The conflict-of-interest rules recently introduced for publication in medical journals should be extended to all branches of science.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses.

PubMed

Eberhard, Monika J B; Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-09-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. Copyright © 2015 the American Physiological Society.

A temperature rise reduces trial-to-trial variability of locust auditory neuron responses

PubMed Central

Schleimer, Jan-Hendrik; Schreiber, Susanne; Ronacher, Bernhard

2015-01-01

The neurophysiology of ectothermic animals, such as insects, is affected by environmental temperature, as their body temperature fluctuates with ambient conditions. Changes in temperature alter properties of neurons and, consequently, have an impact on the processing of information. Nevertheless, nervous system function is often maintained over a broad temperature range, exhibiting a surprising robustness to variations in temperature. A special problem arises for acoustically communicating insects, as in these animals mate recognition and mate localization typically rely on the decoding of fast amplitude modulations in calling and courtship songs. In the auditory periphery, however, temporal resolution is constrained by intrinsic neuronal noise. Such noise predominantly arises from the stochasticity of ion channel gating and potentially impairs the processing of sensory signals. On the basis of intracellular recordings of locust auditory neurons, we show that intrinsic neuronal variability on the level of spikes is reduced with increasing temperature. We use a detailed mathematical model including stochastic ion channel gating to shed light on the underlying biophysical mechanisms in auditory receptor neurons: because of a redistribution of channel-induced current noise toward higher frequencies and specifics of the temperature dependence of the membrane impedance, membrane potential noise is indeed reduced at higher temperatures. This finding holds under generic conditions and physiologically plausible assumptions on the temperature dependence of the channels' kinetics and peak conductances. We demonstrate that the identified mechanism also can explain the experimentally observed reduction of spike timing variability at higher temperatures. PMID:26041833

Transformations between Jordan and Einstein frames: Bounces, antigravity, and crossing singularities

NASA Astrophysics Data System (ADS)

Kamenshchik, Alexander Yu.; Pozdeeva, Ekaterina O.; Vernov, Sergey Yu.; Tronconi, Alessandro; Venturi, Giovanni

2016-09-01

We study the relation between the Jordan-Einstein frame transition and the possible description of the crossing of singularities in flat Friedmann universes, using the fact that the regular evolution in one frame can correspond to crossing singularities in the other frame. We show that some interesting effects arise in simple models such as one with a massless scalar field or another wherein the potential is constant in the Einstein frame. The dynamics in these models and in their conformally coupled counterparts are described in detail, and a method for the continuation of such cosmological evolutions beyond the singularity is developed. We compare our approach with some other, recently developed, approaches to the problem of the crossing of singularities.

Envisioning migration: Mathematics in both experimental analysis and modeling of cell behavior

PubMed Central

Zhang, Elizabeth R.; Wu, Lani F.; Altschuler, Steven J.

2013-01-01

The complex nature of cell migration highlights the power and challenges of applying mathematics to biological studies. Mathematics may be used to create model equations that recapitulate migration, which can predict phenomena not easily uncovered by experiments or intuition alone. Alternatively, mathematics may be applied to interpreting complex data sets with better resolution—potentially empowering scientists to discern subtle patterns amid the noise and heterogeneity typical of migrating cells. Iteration between these two methods is necessary in order to reveal connections within the cell migration signaling network, as well as to understand the behavior that arises from those connections. Here, we review recent quantitative analysis and mathematical modeling approaches to the cell migration problem. PMID:23660413

Advertising Emergency Department Wait Times

PubMed Central

Weiner, Scott G.

2013-01-01

Advertising emergency department (ED) wait times has become a common practice in the United States. Proponents of this practice state that it is a powerful marketing strategy that can help steer patients to the ED. Opponents worry about the risk to the public health that arises from a patient with an emergent condition self-triaging to a further hospital, problems with inaccuracy and lack of standard definition of the reported time, and directing lower acuity patients to the higher cost ED setting instead to primary care. Three sample cases demonstrating the pitfalls of advertising ED wait times are discussed. Given the lack of rigorous evidence supporting the practice and potential adverse effects to the public health, caution about its use is advised. PMID:23599836

Envisioning migration: mathematics in both experimental analysis and modeling of cell behavior.

PubMed

Zhang, Elizabeth R; Wu, Lani F; Altschuler, Steven J

2013-10-01

The complex nature of cell migration highlights the power and challenges of applying mathematics to biological studies. Mathematics may be used to create model equations that recapitulate migration, which can predict phenomena not easily uncovered by experiments or intuition alone. Alternatively, mathematics may be applied to interpreting complex data sets with better resolution--potentially empowering scientists to discern subtle patterns amid the noise and heterogeneity typical of migrating cells. Iteration between these two methods is necessary in order to reveal connections within the cell migration signaling network, as well as to understand the behavior that arises from those connections. Here, we review recent quantitative analysis and mathematical modeling approaches to the cell migration problem. Copyright © 2013 Elsevier Ltd. All rights reserved.

Advanced Ultrasonic Tomograph of Children's Bones

NASA Astrophysics Data System (ADS)

Lasaygues, Philippe; Lefebvre, Jean-Pierre; Guillermin, Régine; Kaftandjian, Valérie; Berteau, Jean-Philippe; Pithioux, Martine; Petit, Philippe

This study deals with the development of an experimental device for performing ultrasonic computed tomography (UCT) on bone in pediatric degrees. The children's bone tomographs obtained in this study, were based on the use of a multiplexed 2-D ring antenna (1 MHz and 3 MHz) designed for performing electronic and mechanical scanning. Although this approach is known to be a potentially valuable means of imaging objects with similar acoustical impedances, problems arise when quantitative images of more highly contrasted media such as bones are required. Various strategies and various mathematical procedures for modeling the wave propagation based on Born approximations have been developed at our laboratory, which are suitable for use with pediatric cases. Inversions of the experimental data obtained are presented.

Working Mothers

MedlinePlus

... valued and supported by family, friends, and coworkers. Conflicts Problems can arise if a woman does not ... is earning more money than the other. Such conflicts can strain the marriage and may make the ...

Development of a coupled expert system for the spacecraft attitude control problem

NASA Technical Reports Server (NTRS)

Kawamura, K.; Beale, G.; Schaffer, J.; Hsieh, B.-J.; Padalkar, S.; Rodriguezmoscoso, J.; Vinz, F.; Fernandez, K.

1987-01-01

A majority of the current expert systems focus on the symbolic-oriented logic and inference mechanisms of artificial intelligence (AI). Common rule-based systems employ empirical associations and are not well suited to deal with problems often arising in engineering. Described is a prototype expert system which combines both symbolic and numeric computing. The expert system's configuration is presented and its application to a spacecraft attitude control problem is discussed.

Evaluation of emerging factors blocking filtration of high-adjunct-ratio wort.

PubMed

Ma, Ting; Zhu, Linjiang; Zheng, Feiyun; Li, Yongxian; Li, Qi

2014-08-20

Corn starch has become a common adjunct for beer brewing in Chinese breweries. However, with increasing ratio of corn starch, problems like poor wort filtration performance arise, which will decrease production capacity of breweries. To solve this problem, factors affecting wort filtration were evaluated, such as the size of corn starch particle, special yellow floats formed during liquefaction of corn starch, and residual substance after liquefaction. The effects of different enzyme preparations including β-amylase and β-glucanase on filtration rate were also evaluated. The results indicate that the emerging yellow floats do not severely block filtration, while the fine and uniform-shape corn starch particle and its incompletely hydrolyzed residue after liquefaction are responsible for filtration blocking. Application of β-amylase preparation increased the filtration rate of liquefied corn starch. This study is useful for our insight into the filtration blocking problem arising in the process of high-adjunct-ratio beer brewing and also provides a feasible solution using enzyme preparations.

Eigenvalue problems for Beltrami fields arising in a three-dimensional toroidal magnetohydrodynamic equilibrium problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hudson, S. R.; Hole, M. J.; Dewar, R. L.

2007-05-15

A generalized energy principle for finite-pressure, toroidal magnetohydrodynamic (MHD) equilibria in general three-dimensional configurations is proposed. The full set of ideal-MHD constraints is applied only on a discrete set of toroidal magnetic surfaces (invariant tori), which act as barriers against leakage of magnetic flux, helicity, and pressure through chaotic field-line transport. It is argued that a necessary condition for such invariant tori to exist is that they have fixed, irrational rotational transforms. In the toroidal domains bounded by these surfaces, full Taylor relaxation is assumed, thus leading to Beltrami fields {nabla}xB={lambda}B, where {lambda} is constant within each domain. Two distinctmore » eigenvalue problems for {lambda} arise in this formulation, depending on whether fluxes and helicity are fixed, or boundary rotational transforms. These are studied in cylindrical geometry and in a three-dimensional toroidal region of annular cross section. In the latter case, an application of a residue criterion is used to determine the threshold for connected chaos.« less

A stabilized element-based finite volume method for poroelastic problems

NASA Astrophysics Data System (ADS)

Honório, Hermínio T.; Maliska, Clovis R.; Ferronato, Massimiliano; Janna, Carlo

2018-07-01

The coupled equations of Biot's poroelasticity, consisting of stress equilibrium and fluid mass balance in deforming porous media, are numerically solved. The governing partial differential equations are discretized by an Element-based Finite Volume Method (EbFVM), which can be used in three dimensional unstructured grids composed of elements of different types. One of the difficulties for solving these equations is the numerical pressure instability that can arise when undrained conditions take place. In this paper, a stabilization technique is developed to overcome this problem by employing an interpolation function for displacements that considers also the pressure gradient effect. The interpolation function is obtained by the so-called Physical Influence Scheme (PIS), typically employed for solving incompressible fluid flows governed by the Navier-Stokes equations. Classical problems with analytical solutions, as well as three-dimensional realistic cases are addressed. The results reveal that the proposed stabilization technique is able to eliminate the spurious pressure instabilities arising under undrained conditions at a low computational cost.

αAMG based on Weighted Matching for Systems of Elliptic PDEs Arising From Displacement and Mixed Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Ambra, P.; Vassilevski, P. S.

2014-05-30

Adaptive Algebraic Multigrid (or Multilevel) Methods (αAMG) are introduced to improve robustness and efficiency of classical algebraic multigrid methods in dealing with problems where no a-priori knowledge or assumptions on the near-null kernel of the underlined matrix are available. Recently we proposed an adaptive (bootstrap) AMG method, αAMG, aimed to obtain a composite solver with a desired convergence rate. Each new multigrid component relies on a current (general) smooth vector and exploits pairwise aggregation based on weighted matching in a matrix graph to define a new automatic, general-purpose coarsening process, which we refer to as “the compatible weighted matching”. Inmore » this work, we present results that broaden the applicability of our method to different finite element discretizations of elliptic PDEs. In particular, we consider systems arising from displacement methods in linear elasticity problems and saddle-point systems that appear in the application of the mixed method to Darcy problems.« less

Theory of signs and statistical approach to big data in assessing the relevance of clinical biomarkers of inflammation and oxidative stress.

PubMed

Ghezzi, Pietro; Davies, Kevin; Delaney, Aidan; Floridi, Luciano

2018-03-06

Biomarkers are widely used not only as prognostic or diagnostic indicators, or as surrogate markers of disease in clinical trials, but also to formulate theories of pathogenesis. We identify two problems in the use of biomarkers in mechanistic studies. The first problem arises in the case of multifactorial diseases, where different combinations of multiple causes result in patient heterogeneity. The second problem arises when a pathogenic mediator is difficult to measure. This is the case of the oxidative stress (OS) theory of disease, where the causal components are reactive oxygen species (ROS) that have very short half-lives. In this case, it is usual to measure the traces left by the reaction of ROS with biological molecules, rather than the ROS themselves. Borrowing from the philosophical theories of signs, we look at the different facets of biomarkers and discuss their different value and meaning in multifactorial diseases and system medicine to inform their use in patient stratification in personalized medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Zhaojun; Yang, Chao

What is common among electronic structure calculation, design of MEMS devices, vibrational analysis of high speed railways, and simulation of the electromagnetic field of a particle accelerator? The answer: they all require solving large scale nonlinear eigenvalue problems. In fact, these are just a handful of examples in which solving nonlinear eigenvalue problems accurately and efficiently is becoming increasingly important. Recognizing the importance of this class of problems, an invited minisymposium dedicated to nonlinear eigenvalue problems was held at the 2005 SIAM Annual Meeting. The purpose of the minisymposium was to bring together numerical analysts and application scientists to showcasemore » some of the cutting edge results from both communities and to discuss the challenges they are still facing. The minisymposium consisted of eight talks divided into two sessions. The first three talks focused on a type of nonlinear eigenvalue problem arising from electronic structure calculations. In this type of problem, the matrix Hamiltonian H depends, in a non-trivial way, on the set of eigenvectors X to be computed. The invariant subspace spanned by these eigenvectors also minimizes a total energy function that is highly nonlinear with respect to X on a manifold defined by a set of orthonormality constraints. In other applications, the nonlinearity of the matrix eigenvalue problem is restricted to the dependency of the matrix on the eigenvalues to be computed. These problems are often called polynomial or rational eigenvalue problems In the second session, Christian Mehl from Technical University of Berlin described numerical techniques for solving a special type of polynomial eigenvalue problem arising from vibration analysis of rail tracks excited by high-speed trains.« less

A genetic algorithm used for solving one optimization problem

NASA Astrophysics Data System (ADS)

Shipacheva, E. N.; Petunin, A. A.; Berezin, I. M.

2017-12-01

A problem of minimizing the length of the blank run for a cutting tool during cutting of sheet materials into shaped blanks is discussed. This problem arises during the preparation of control programs for computerized numerical control (CNC) machines. A discrete model of the problem is analogous in setting to the generalized travelling salesman problem with limitations in the form of precursor conditions determined by the technological features of cutting. A certain variant of a genetic algorithm for solving this problem is described. The effect of the parameters of the developed algorithm on the solution result for the problem with limitations is investigated.

Development and Evaluation of an Interactive Mobile Learning Environment with Shared Display Groupware

ERIC Educational Resources Information Center

Yang, Jie Chi; Lin, Yi Lung

2010-01-01

When using mobile devices in support of learning activities, students gain mobility, but problems arise when group members share information. The small size of the mobile device screen becomes problematic when it is being used by two or more students to share and exchange information. This problem affects interactions among group members. To…

Administrative Problem-Solving for Writing Programs and Writing Centers: Scenarios in Effective Program Management.

ERIC Educational Resources Information Center

Myers-Breslin, Linda

Addressing the issues and problems faced by writing program administrators (WPAs) and writing center directors (WCDs), and how they can most effectively resolve the political, pedagogical, and financial questions that arise, this book presents essays from experienced WPAs and WCDs at a wide variety of institutions that offer scenarios and case…

Succession Planning in England: New Leaders and New Forms of Leadership

ERIC Educational Resources Information Center

Bush, Tony

2011-01-01

There are concerns about the supply of head teachers in many countries. In England, this problem arises from demographic changes and the perceived difficulty of the job. The National College responded to this problem by initiating a Succession Planning programme. This article reports the main findings from the external evaluation of the programme…

Effects of Inequality and Poverty vs. Teachers and Schooling on America's Youth

ERIC Educational Resources Information Center

Berliner, David C.

2013-01-01

Background/Context: This paper arises out of frustration with the results of school reforms carried out over the past few decades. These efforts have failed. They need to be abandoned. In their place must come recognition that income inequality causes many social problems, including problems associated with education. Sadly, compared to all other…

Practical Solutions to Practically Every Problem: The Early Childhood Teacher's Manual. Revised Edition.

ERIC Educational Resources Information Center

Saifer, Steffen

Based on sound developmentally appropriate theory, this revised guide is designed to help early childhood teachers deal with common problems that arise in all aspects of their work. Following an introduction and a list of the 20 most important principles for successful preschool teaching, the guide is divided into nine parts. Part 1 addresses…

An evolution infinity Laplace equation modelling dynamic elasto-plastic torsion

NASA Astrophysics Data System (ADS)

Messelmi, Farid

2017-12-01

We consider in this paper a parabolic partial differential equation involving the infinity Laplace operator and a Leray-Lions operator with no coercitive assumption. We prove the existence and uniqueness of the corresponding approached problem and we show that at the limit the solution solves the parabolic variational inequality arising in the elasto-plastic torsion problem.

Co-Rumination Cultivates Anxiety: A Genetically Informed Study of Friend Influence during Early Adolescence

ERIC Educational Resources Information Center

Dirghangi, Shrija; Kahn, Gilly; Laursen, Brett; Brendgen, Mara; Vitaro, Frank; Dionne, Ginette; Boivin, Michel

2015-01-01

This study tested 2 related hypotheses. The first holds that high co-rumination anticipates heightened internalizing problems. The second holds that positive relationships with friends exacerbate the risk for internalizing problems arising from co-rumination. A sample of MZ twins followed from birth (194 girls and 170 boys) completed (a)…

Symmetry of the Adiabatic Condition in the Piston Problem

ERIC Educational Resources Information Center

Anacleto, Joaquim; Ferreira, J. M.

2011-01-01

This study addresses a controversial issue in the adiabatic piston problem, namely that of the piston being adiabatic when it is fixed but no longer so when it can move freely. It is shown that this apparent contradiction arises from the usual definition of adiabatic condition. The issue is addressed here by requiring the adiabatic condition to be…

The Perceived Benefits and Problems Associated with Teaching Activities Undertaken by Doctoral Students

ERIC Educational Resources Information Center

Jordan, Katy; Howe, Christine

2018-01-01

Postgraduate students involved in delivering undergraduate teaching while working toward a research degree are known as graduate teaching assistants (GTAs). This study focused upon the problems and benefits arising from this dual role as researchers and teachers, as perceived by GTAs at the University of Cambridge. To this end, GTAs at Cambridge…

Practical Solutions to Practically Every Problem: The Early Childhood Teacher's Manual.

ERIC Educational Resources Information Center

Saifer, Steffen

This book is designed to help early childhood teachers deal with common problems that arise in all aspects of their work. Part one addresses daily dilemmas such as schedule planning, meal and nap times, art, and outdoor play. Part two covers classroom concerns such as the physical environment, curriculum, individual student needs, field trips,…

Measuring forest evapotranspiration--theory and problems

Treesearch

Anthony C. Federer; Anthony C. Federer

1970-01-01

A satisfactory general method of measuring forest evapotranspiration has yet to be developed. Many procedures have been tried, but only the soil-water budget method and the micrometeorological methods offer any degree of success. This paper is a discussion of these procedures and the problems that arise in applying them. It is designed as a reference for scientists and...

Reflections on the surface energy imbalance problem

Treesearch

Ray Leuning; Eva van Gorsela; William J. Massman; Peter R. Isaac

2012-01-01

The 'energy imbalance problem' in micrometeorology arises because at most flux measurement sites the sum of eddy fluxes of sensible and latent heat (H + λE) is less than the available energy (A). Either eddy fluxes are underestimated or A is overestimated. Reasons for the imbalance are: (1) a failure to satisfy the fundamental assumption of one-...

Who Is Listening? An Examination of Gender Effects and Employment Choice in Sustainability Education in an Undergraduate Business School

ERIC Educational Resources Information Center

Weaven, Scott; Griffin, Deborah; McPhail, Ruth; Smith, Calvin

2013-01-01

Whilst universities acknowledge the importance of sustainability education, numerous problems exist in relation to the nature, delivery and outcomes of sustainability instruction. Many of these problems arise due to a lack of understanding about students' perception towards, and knowledge about business sustainability. This article examines…

Estimation of coefficients and boundary parameters in hyperbolic systems

NASA Technical Reports Server (NTRS)

Banks, H. T.; Murphy, K. A.

1984-01-01

Semi-discrete Galerkin approximation schemes are considered in connection with inverse problems for the estimation of spatially varying coefficients and boundary condition parameters in second order hyperbolic systems typical of those arising in 1-D surface seismic problems. Spline based algorithms are proposed for which theoretical convergence results along with a representative sample of numerical findings are given.

Selection bias in population-based cancer case-control studies due to incomplete sampling frame coverage.

PubMed

Walsh, Matthew C; Trentham-Dietz, Amy; Gangnon, Ronald E; Nieto, F Javier; Newcomb, Polly A; Palta, Mari

2012-06-01

Increasing numbers of individuals are choosing to opt out of population-based sampling frames due to privacy concerns. This is especially a problem in the selection of controls for case-control studies, as the cases often arise from relatively complete population-based registries, whereas control selection requires a sampling frame. If opt out is also related to risk factors, bias can arise. We linked breast cancer cases who reported having a valid driver's license from the 2004-2008 Wisconsin women's health study (N = 2,988) with a master list of licensed drivers from the Wisconsin Department of Transportation (WDOT). This master list excludes Wisconsin drivers that requested their information not be sold by the state. Multivariate-adjusted selection probability ratios (SPR) were calculated to estimate potential bias when using this driver's license sampling frame to select controls. A total of 962 cases (32%) had opted out of the WDOT sampling frame. Cases age <40 (SPR = 0.90), income either unreported (SPR = 0.89) or greater than $50,000 (SPR = 0.94), lower parity (SPR = 0.96 per one-child decrease), and hormone use (SPR = 0.93) were significantly less likely to be covered by the WDOT sampling frame (α = 0.05 level). Our results indicate the potential for selection bias due to differential opt out between various demographic and behavioral subgroups of controls. As selection bias may differ by exposure and study base, the assessment of potential bias needs to be ongoing. SPRs can be used to predict the direction of bias when cases and controls stem from different sampling frames in population-based case-control studies.

A homotopy analysis method for the nonlinear partial differential equations arising in engineering

NASA Astrophysics Data System (ADS)

Hariharan, G.

2017-05-01

In this article, we have established the homotopy analysis method (HAM) for solving a few partial differential equations arising in engineering. This technique provides the solutions in rapid convergence series with computable terms for the problems with high degree of nonlinear terms appearing in the governing differential equations. The convergence analysis of the proposed method is also discussed. Finally, we have given some illustrative examples to demonstrate the validity and applicability of the proposed method.

An Electromagnetically-Controlled Precision Orbital Tracking Vehicle (POTV)

DTIC Science & Technology

1992-12-01

assume that C > B > A. Then 0 1(t) is purely sinusoidal. tk2 (t) is also sinusoidal because the forcing function z(t) is sinusoidal. 03 (t) is more...an unpredictable -manner. The problem arises from the rank deficiency of the G input matrix as shown below. Remember we have shown already that its...rank can never exceed five because rows two, four, and six are linearly dependent. The rank deficiency arises from the "translational part" of the input

Hausdorff dimension of certain sets arising in Engel expansions

NASA Astrophysics Data System (ADS)

Fang, Lulu; Wu, Min

2018-05-01

The present paper is concerned with the Hausdorff dimension of certain sets arising in Engel expansions. In particular, the Hausdorff dimension of the set is completely determined, where A n (x) can stand for the digit, gap and ratio between two consecutive digits in the Engel expansion of x and ϕ is a positive function defined on natural numbers. These results significantly extend the existing results of Galambos’ open problems on the Hausdorff dimension of sets related to the growth rate of digits.

Poisson image reconstruction with Hessian Schatten-norm regularization.

PubMed

Lefkimmiatis, Stamatios; Unser, Michael

2013-11-01

Poisson inverse problems arise in many modern imaging applications, including biomedical and astronomical ones. The main challenge is to obtain an estimate of the underlying image from a set of measurements degraded by a linear operator and further corrupted by Poisson noise. In this paper, we propose an efficient framework for Poisson image reconstruction, under a regularization approach, which depends on matrix-valued regularization operators. In particular, the employed regularizers involve the Hessian as the regularization operator and Schatten matrix norms as the potential functions. For the solution of the problem, we propose two optimization algorithms that are specifically tailored to the Poisson nature of the noise. These algorithms are based on an augmented-Lagrangian formulation of the problem and correspond to two variants of the alternating direction method of multipliers. Further, we derive a link that relates the proximal map of an l(p) norm with the proximal map of a Schatten matrix norm of order p. This link plays a key role in the development of one of the proposed algorithms. Finally, we provide experimental results on natural and biological images for the task of Poisson image deblurring and demonstrate the practical relevance and effectiveness of the proposed framework.

Burn disasters--an audit of the literature.

PubMed

Broeze, Carsten L; Falder, Sian; Rea, Suzanne; Wood, Fiona

2010-01-01

All events that result in disasters are unique, and it is impossible to become fully prepared. However, through thorough planning and preparedness, it is possible to gain a better understanding of the typical injury patterns and problems that arise from a variety of hazards. Such events have the potential to claim many lives and overwhelm local medical resources. Burn disasters vary in scope of injury and procedures required, and are much more labor and resource intensive than non-burn disasters. This review of the literature should help determine whether, despite each event having its own unique features, there still are common problems disaster responders face in the prehospital and hospital phases, what recommendations were made from these disasters, and whether these recommendations have been implemented into practice and the current disaster planning processes. The objective of this review was to assess: (1) prehospital and hospital responses used during past burn disasters; (2) problems faced during those disaster responses; (3) recommendations made following those disasters; (4) whether these recommendations were integrated into practice; and (5) the key characteristics of burn disasters and how they differ from other disasters. This review is important to determine why, despite having disaster plans, things still go wrong.

"Everybody knows psychology is not a real science": Public perceptions of psychology and how we can improve our relationship with policymakers, the scientific community, and the general public.

PubMed

Ferguson, Christopher J

2015-09-01

In a recent seminal article, Lilienfeld (2012) argued that psychological science is experiencing a public perception problem that has been caused by both public misconceptions about psychology, as well as the psychological science community's failure to distinguish itself from pop psychology and questionable therapeutic practices. Lilienfeld's analysis is an important and cogent synopsis of external problems that have limited psychological science's penetration into public knowledge. The current article expands upon this by examining internal problems, or problems within psychological science that have potentially limited its impact with policymakers, other scientists, and the public. These problems range from the replication crisis and defensive reactions to it, overuse of politicized policy statements by professional advocacy groups such as the American Psychological Association (APA), and continued overreliance on mechanistic models of human behavior. It is concluded that considerable problems arise from psychological science's tendency to overcommunicate mechanistic concepts based on weak and often unreplicated (or unreplicable) data that do not resonate with the everyday experiences of the general public or the rigor of other scholarly fields. It is argued that a way forward can be seen by, on one hand, improving the rigor and transparency of psychological science, and making theoretical innovations that better acknowledge the complexities of the human experience. (PsycINFO Database Record (PsycINFO Database Record (c) 2015 APA, all rights reserved).

Numerical solutions of acoustic wave propagation problems using Euler computations

NASA Technical Reports Server (NTRS)

Hariharan, S. I.

1984-01-01

This paper reports solution procedures for problems arising from the study of engine inlet wave propagation. The first problem is the study of sound waves radiated from cylindrical inlets. The second one is a quasi-one-dimensional problem to study the effect of nonlinearities and the third one is the study of nonlinearities in two dimensions. In all three problems Euler computations are done with a fourth-order explicit scheme. For the first problem results are shown in agreement with experimental data and for the second problem comparisons are made with an existing asymptotic theory. The third problem is part of an ongoing work and preliminary results are presented for this case.

Challenges created by data dissemination and access restrictions when attempting to address community concerns: individual privacy versus public wellbeing.

PubMed

Colquhoun, Amy; Aplin, Laura; Geary, Janis; Goodman, Karen J; Hatcher, Juanita

2012-05-08

Population health data are vital for the identification of public health problems and the development of public health strategies. Challenges arise when attempts are made to disseminate or access anonymised data that are deemed to be potentially identifiable. In these situations, there is debate about whether the protection of an individual's privacy outweighs potentially beneficial public health initiatives developed using potentially identifiable information. While these issues have an impact at planning and policy levels, they pose a particular dilemma when attempting to examine and address community concerns about a specific health problem. Research currently underway in northern Canadian communities on the frequency of Helicobacter pylori infection and associated diseases, such as stomach cancer, is used in this article to illustrate the challenges that data controls create on the ability of researchers and health officials to address community concerns. Barriers are faced by public health professionals and researchers when endeavouring to address community concerns; specifically, provincial cancer surveillance departments and community-driven participatory research groups face challenges related to data release or access that inhibit their ability to effectively address community enquiries. The resulting consequences include a limited ability to address misinformation or to alleviate concerns when dealing with health problems in small communities. The development of communication tools and building of trusting relationships are essential components of a successful investigation into community health concerns. It may also be important to consider that public wellbeing may outweigh the value of individual privacy in these situations. As such, a re-evaluation of data disclosure policies that are applicable in these circumstances should be considered.

Optimal control of a harmonic oscillator: Economic interpretations

NASA Astrophysics Data System (ADS)

Janová, Jitka; Hampel, David

2013-10-01

Optimal control is a popular technique for modelling and solving the dynamic decision problems in economics. A standard interpretation of the criteria function and Lagrange multipliers in the profit maximization problem is well known. On a particular example, we aim to a deeper understanding of the possible economic interpretations of further mathematical and solution features of the optimal control problem: we focus on the solution of the optimal control problem for harmonic oscillator serving as a model for Phillips business cycle. We discuss the economic interpretations of arising mathematical objects with respect to well known reasoning for these in other problems.

Space shuttle safety - A hybrid vehicle breeds new problems.

NASA Technical Reports Server (NTRS)

Pinkel, I. I.

1971-01-01

Discussion of a few novel problems raised by the design and flight plan of the space shuttle and by the dangerous cargos it might carry. Among the problems cited are those connected with the inspection of the bearings of the propellant turbopumps, particularly those of the hydrogen pump, for evidence of spalling, as well as problems arising in the inspection of the high-temperature parts of the combustor and turbine section of the airbreathing turbofan for shuttle booster and orbiter, and problems resulting from the possibility of fire hazard due to spontaneous ignition of fuel vapor in the fuel tank vapor space.

Applied mathematical problems in modern electromagnetics

NASA Astrophysics Data System (ADS)

Kriegsman, Gregory

1994-05-01

We have primarily investigated two classes of electromagnetic problems. The first contains the quantitative description of microwave heating of dispersive and conductive materials. Such problems arise, for example, when biological tissue are exposed, accidentally or purposefully, to microwave radiation. Other instances occur in ceramic processing, such as sintering and microwave assisted chemical vapor infiltration and other industrial drying processes, such as the curing of paints and concrete. The second class characterizes the scattering of microwaves by complex targets which possess two or more disparate length and/or time scales. Spatially complex scatterers arise in a variety of applications, such as large gratings and slowly changing guiding structures. The former are useful in developing microstrip energy couplers while the later can be used to model anatomical subsystems (e.g., the open guiding structure composed of two legs and the adjoining lower torso). Temporally complex targets occur in applications involving dispersive media whose relaxation times differ by orders of magnitude from thermal and/or electromagnetic time scales. For both cases the mathematical description of the problems gives rise to complicated ill-conditioned boundary value problems, whose accurate solutions require a blend of both asymptotic techniques, such as multiscale methods and matched asymptotic expansions, and numerical methods incorporating radiation boundary conditions, such as finite differences and finite elements.

Abnormal Neural Connectivity in Schizophrenia and fMRI-Brain-Computer Interface as a Potential Therapeutic Approach

PubMed Central

Ruiz, Sergio; Birbaumer, Niels; Sitaram, Ranganatha

2012-01-01

Considering that single locations of structural and functional abnormalities are insufficient to explain the diverse psychopathology of schizophrenia, new models have postulated that the impairments associated with the disease arise from a failure to integrate the activity of local and distributed neural circuits: the “abnormal neural connectivity hypothesis.” In the last years, new evidence coming from neuroimaging have supported and expanded this theory. However, despite the increasing evidence that schizophrenia is a disorder of neural connectivity, so far there are no treatments that have shown to produce a significant change in brain connectivity, or that have been specifically designed to alleviate this problem. Brain-Computer Interfaces based on real-time functional Magnetic Resonance Imaging (fMRI-BCI) are novel techniques that have allowed subjects to achieve self-regulation of circumscribed brain regions. In recent studies, experiments with this technology have resulted in new findings suggesting that this methodology could be used to train subjects to enhance brain connectivity, and therefore could potentially be used as a therapeutic tool in mental disorders including schizophrenia. The present article summarizes the findings coming from hemodynamics-based neuroimaging that support the abnormal connectivity hypothesis in schizophrenia, and discusses a new approach that could address this problem. PMID:23525496

Podometrics as a Potential Clinical Tool for Glomerular Disease Management.

PubMed

Kikuchi, Masao; Wickman, Larysa; Hodgin, Jeffrey B; Wiggins, Roger C

2015-05-01

Chronic kidney disease culminating in end-stage kidney disease is a major public health problem costing in excess of $40 billion per year with high morbidity and mortality. Current tools for glomerular disease monitoring lack precision and contribute to poor outcome. The podocyte depletion hypothesis describes the major mechanisms underlying the progression of glomerular diseases, which are responsible for more than 80% of cases of end-stage kidney disease. The question arises of whether this new knowledge can be used to improve outcomes and reduce costs. Podocytes have unique characteristics that make them an attractive monitoring tool. Methodologies for estimating podocyte number, size, density, glomerular volume and other parameters in routine kidney biopsies, and the rate of podocyte detachment from glomeruli into urine (podometrics) now have been developed and validated. They potentially fill important gaps in the glomerular disease monitoring toolbox. The application of these tools to glomerular disease groups shows good correlation with outcome, although data validating their use for individual decision making is not yet available. Given the urgency of the clinical problem, we argue that the time has come to focus on testing these tools for application to individualized clinical decision making toward more effective progression prevention. Copyright © 2015 Elsevier Inc. All rights reserved.

Guidelines to classification and nomenclature of Arabian felsic plutonic rocks

USGS Publications Warehouse

Ramsay, C.R.; Stoeser, D.B.; Drysdall, A.R.

1986-01-01

Well-defined procedures for classifying the felsic plutonic rocks of the Arabian Shield on the basis of petrographic, chemical and lithostratigraphic criteria and mineral-resource potential have been adopted and developed in the Saudi Arabian Deputy Ministry for Mineral Resources over the past decade. A number of problems with conventional classification schemes have been identified and resolved; others, notably those arising from difficulties in identifying precise mineral compositions, continue to present difficulties. The petrographic nomenclature used is essentially that recommended by the International Union of Geological Sciences. Problems that have arisen include the definition of: (1) rocks with sodic, zoned or perthitic feldspar, (2) trondhjemites, and (3) alkali granites. Chemical classification has been largely based on relative molar amounts of alumina, lime and alkalis, and the use of conventional variation diagrams, but pilot studies utilizing univariate and multivariate statistical techniques have been made. The classification used in Saudi Arabia for stratigraphic purposes is a hierarchy of formation-rank units, suites and super-suites as defined in the Saudi Arabian stratigraphic code. For genetic and petrological studies, a grouping as 'associations' of similar and genetically related lithologies is commonly used. In order to indicate mineral-resource potential, the felsic plutons are classed as common, precursor, specialized or mineralized, in order of increasing exploration significance. ?? 1986.

Solar array stepping problems in satellites and solutions

NASA Astrophysics Data System (ADS)

Maharana, P. K.; Goel, P. S.

1992-01-01

The dynamics problems arising due to stepping motion of the solar arrays of spacecraft are studied. To overcome these problems, design improvements in the drive logic based on the phase plane analysis are suggested. The improved designs are applied to the Solar Array Drive Assembly (SADA) of IRS-1B and INSAT-2A satellites. In addition, an alternate torquing strategy for very successful slewing of the arrays, and with minimum excitation of flexible modes, is proposed.

Efficient Preconditioning for the p-Version Finite Element Method in Two Dimensions

DTIC Science & Technology

1989-10-01

paper, we study fast parallel preconditioners for systems of equations arising from the p-version finite element method. The p-version finite element...computations and the solution of a relatively small global auxiliary problem. We study two different methods. In the first (Section 3), the global...20], will be studied in the next section. Problem (3.12) is obviously much more easily solved than the original problem ,nd the procedure is highly

Multiobjective optimization approach: thermal food processing.

PubMed

Abakarov, A; Sushkov, Y; Almonacid, S; Simpson, R

2009-01-01

The objective of this study was to utilize a multiobjective optimization technique for the thermal sterilization of packaged foods. The multiobjective optimization approach used in this study is based on the optimization of well-known aggregating functions by an adaptive random search algorithm. The applicability of the proposed approach was illustrated by solving widely used multiobjective test problems taken from the literature. The numerical results obtained for the multiobjective test problems and for the thermal processing problem show that the proposed approach can be effectively used for solving multiobjective optimization problems arising in the food engineering field.

Steiner trees and spanning trees in six-pin soap films

NASA Astrophysics Data System (ADS)

Dutta, Prasun; Khastgir, S. Pratik; Roy, Anushree

2010-02-01

The problem of finding minimum (local as well as absolute) path lengths joining given points (or terminals) on a plane is known as the Steiner problem. The Steiner problem arises in finding the minimum total road length joining several towns and cities. We study the Steiner tree problem using six-pin soap films. Experimentally, we observe spanning trees as well as Steiner trees partly by varying the pin diameter. We propose a possibly exact expression for the length of a spanning tree or a Steiner tree, which fails mysteriously in certain cases.

Algorithms for bilevel optimization

NASA Technical Reports Server (NTRS)

Alexandrov, Natalia; Dennis, J. E., Jr.

1994-01-01

General multilevel nonlinear optimization problems arise in design of complex systems and can be used as a means of regularization for multi-criteria optimization problems. Here, for clarity in displaying our ideas, we restrict ourselves to general bi-level optimization problems, and we present two solution approaches. Both approaches use a trust-region globalization strategy, and they can be easily extended to handle the general multilevel problem. We make no convexity assumptions, but we do assume that the problem has a nondegenerate feasible set. We consider necessary optimality conditions for the bi-level problem formulations and discuss results that can be extended to obtain multilevel optimization formulations with constraints at each level.

Managing auricular haematoma to prevent 'cauliflower ear'.

PubMed

Summers, Anthony

2012-09-01

This article describes the typical signs of auricular haematoma, how people who have the condition should be treated in emergency departments and the problems that can arise if they are managed inappropriately.

A new approach to instability theory in porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bentsen, R.G.

Early work in the area of instability theory is limited in that it is based on first-order perturbation theory and the concept of a velocity potential. Thus, while it can deal with an incipient finger, it cannot deal with the subsequent growth of a finger. This paper develops a new approach to the instability theory that overcomes this limitation. The new approach, like earlier work, is based on the assumption that the immiscible displacement of one fluid by another can be treated as a moving-boundary problem. Therefore, two solutions arise, one for each side of the plane interface that initiallymore » separates the two fluids. Because the new approach makes use of a force potential rather than a velocity potential, it is possible to impose several new conditions on these two solutions. As a consequence, further extensions to the stability theory have been obtained. In particular, it is now possible to predict the steady-state velocity at which a finger propagates and, consequently, the breakthrough recovery obtained not only when the displacement is stable, but also when it is pseudostable.« less

Building Language Through Conflict Resolution: Discussing Problems Enriches Language While Leading to Solutions

ERIC Educational Resources Information Center

Church, Ellen Booth

2005-01-01

This brief article describes how classroom group time can be "talk central" for children to discuss problems, imagine solutions, even role-play hypothetical situations. It is often in the safety and support of the large group that children develop the tools they need to learn how to resolve the inevitable conflicts that arise throughout life.…

An Improved Memetic Algorithm for Break Scheduling

NASA Astrophysics Data System (ADS)

Widl, Magdalena; Musliu, Nysret

In this paper we consider solving a complex real life break scheduling problem. This problem of high practical relevance arises in many working areas, e.g. in air traffic control and other fields where supervision personnel is working. The objective is to assign breaks to employees such that various constraints reflecting legal demands or ergonomic criteria are satisfied and staffing requirement violations are minimised.

A New Method for Calibrating Perceptual Salience across Dimensions in Infants: The Case of Color vs. Luminance

ERIC Educational Resources Information Center

Kaldy, Zsuzsa; Blaser, Erik A.; Leslie, Alan M.

2006-01-01

We report a new method for calibrating differences in perceptual salience across feature dimensions, in infants. The problem of inter-dimensional salience arises in many areas of infant studies, but a general method for addressing the problem has not previously been described. Our method is based on a preferential looking paradigm, adapted to…

Improving Productivity in the Work Force: Implications for Research and Development in Vocational Education. Occasional Paper No. 72.

ERIC Educational Resources Information Center

Sullivan, Dennis J.

Declining productivity is a major problem in the American economy. Gains in productivity, and finally, actual rates of productivity, have been declining since the late 1960s. Specific problems arising as a result of this decline in productivity are the inflationary pressures that we face as a nation, the increased regulatory environment under…

Collection and curation of IDPs in the stratosphere and below. Part 2: The Greenland and Antarctic ice sheets

NASA Technical Reports Server (NTRS)

Maurette, Michel; Hammer, C.; Harvey, R.; Immel, G.; Kurat, G.; Taylor, S.

1994-01-01

In a companion paper, Zolensky discusses interplanetary dust particles (IDP's) collected in the stratosphere. Here, we describe the recovery of much larger unmelted to partially melted IDP's from the Greenland and Antarctica ice sheet, and discuss problems arising in their collection and curation, as well as future prospects for tackling these problems.

A Jubilant Connection: General Jubal Early's Troops and the Golden Ratio

ERIC Educational Resources Information Center

Bolte, Linda A.; Noon, Tim R., Jr.

2012-01-01

The golden ratio, one of the most beautiful numbers in all of mathematics, arises in some surprising places. At first glance, we might expect that a General checking his troops' progress would be nothing more than a basic distance-rate-time problem. However, further exploration reveals a multi-faceted problem, one in which the ratio of rates…

An Investigation of Starting Point Preferences in Human Performance on Traveling Salesman Problems

ERIC Educational Resources Information Center

MacGregor, James N.

2014-01-01

Previous studies have shown that people start traveling sales problem tours significantly more often from boundary than from interior nodes. There are a number of possible reasons for such a tendency: first, it may arise as a direct result of the processes involved in tour construction; second, boundary points may be perceptually more salient than…

Problem-based learning: Using students' questions to drive knowledge construction

NASA Astrophysics Data System (ADS)

Chin, Christine; Chia, Li-Gek

2004-09-01

This study employed problem-based learning for project work in a year 9 biology class. The purpose of the study was to investigate (a) students' inspirations for their self-generated problems and questions, (b) the kinds of questions that students asked individually and collaboratively, and (c) how students' questions guided them in knowledge construction. Data sources included observation and field notes, students' written documents, audiotapes and videotapes of students working in groups, and student interviews. Sources of inspiration for students' problems and questions included cultural beliefs and folklore; wonderment about information propagated by advertisements and the media; curiosity arising from personal encounters, family members' concerns, or observations of others; and issues arising from previous lessons in the school curriculum. Questions asked individually pertained to validation of common beliefs and misconceptions, basic information, explanations, and imagined scenarios. The findings regarding questions asked collaboratively are presented as two assertions. Assertion 1 maintained that students' course of learning were driven by their questions. Assertion 2 was that the ability to ask the right'' questions and the extent to which these could be answered, were important in sustaining students' interest in the project. Implications of the findings for instructional practice are discussed.

The Doubting System 1: Evidence for automatic substitution sensitivity.

PubMed

Johnson, Eric D; Tubau, Elisabet; De Neys, Wim

2016-02-01

A long prevailing view of human reasoning suggests severe limits on our ability to adhere to simple logical or mathematical prescriptions. A key position assumes these failures arise from insufficient monitoring of rapidly produced intuitions. These faulty intuitions are thought to arise from a proposed substitution process, by which reasoners unknowingly interpret more difficult questions as easier ones. Recent work, however, suggests that reasoners are not blind to this substitution process, but in fact detect that their erroneous responses are not warranted. Using the popular bat-and-ball problem, we investigated whether this substitution sensitivity arises out of an automatic System 1 process or whether it depends on the operation of an executive resource demanding System 2 process. Results showed that accuracy on the bat-and-ball problem clearly declined under cognitive load. However, both reduced response confidence and increased response latencies indicated that biased reasoners remained sensitive to their faulty responses under load. Results suggest that a crucial substitution monitoring process is not only successfully engaged, but that it automatically operates as an autonomous System 1 process. By signaling its doubt along with a biased intuition, it appears System 1 is "smarter" than traditionally assumed.

Distraction during learning with hypermedia: difficult tasks help to keep task goals on track

PubMed Central

Scheiter, Katharina; Gerjets, Peter; Heise, Elke

2014-01-01

In educational hypermedia environments, students are often confronted with potential sources of distraction arising from additional information that, albeit interesting, is unrelated to their current task goal. The paper investigates the conditions under which distraction occurs and hampers performance. Based on theories of volitional action control it was hypothesized that interesting information, especially if related to a pending goal, would interfere with task performance only when working on easy, but not on difficult tasks. In Experiment 1, 66 students learned about probability theory using worked examples and solved corresponding test problems, whose task difficulty was manipulated. As a second factor, the presence of interesting information unrelated to the primary task was varied. Results showed that students solved more easy than difficult probability problems correctly. However, the presence of interesting, but task-irrelevant information did not interfere with performance. In Experiment 2, 68 students again engaged in example-based learning and problem solving in the presence of task-irrelevant information. Problem-solving difficulty was varied as a first factor. Additionally, the presence of a pending goal related to the task-irrelevant information was manipulated. As expected, problem-solving performance declined when a pending goal was present during working on easy problems, whereas no interference was observed for difficult problems. Moreover, the presence of a pending goal reduced the time on task-relevant information and increased the time on task-irrelevant information while working on easy tasks. However, as revealed by mediation analyses these changes in overt information processing behavior did not explain the decline in problem-solving performance. As an alternative explanation it is suggested that goal conflicts resulting from pending goals claim cognitive resources, which are then no longer available for learning and problem solving. PMID:24723907

A Case of Squamous Cell Carcinoma Developing Within a Red-Ink Tattoo.

PubMed

Sherif, Sara; Blakeway, Elizabeth; Fenn, Chris; German, Alyn; Laws, Philip

Cutaneous reactions to tattoos are well reported and include allergic reactions, infections, and foreign body granuloma or may be a presenting sign of sarcoidosis. There have been very few reported cases of squamous cell carcinoma (SCC) arising in tattoo-treated skin. We report a case of SCC arising within a red-ink tattoo and discuss the potential the role of chronic low-grade inflammation in pathogenesis. This should serve to raise awareness of potential tattoo-related serious adverse effects.

Understanding Forces: What's the Problem?

ERIC Educational Resources Information Center

Kibble, Bob

2006-01-01

Misconceptions about forces are very common and seem to arise from everyday experience and use of words. Ways to improve students' understanding of forces, as used in recent a IOP CD-Rom, are discussed here.

A Hidden Surface Algorithm for Computer Generated Halftone Pictures

DTIC Science & Technology

converting data describing three-dimensional objects into data that can be used to generate two-dimensional halftone images. It deals with some problems that arise in black and white, and color shading.

Semicompeting risks in aging research: methods, issues and needs

PubMed Central

Varadhan, Ravi; Xue, Qian-Li; Bandeen-Roche, Karen

2015-01-01

A semicompeting risks problem involves two-types of events: a nonterminal and a terminal event (death). Typically, the nonterminal event is the focus of the study, but the terminal event can preclude the occurrence of the nonterminal event. Semicompeting risks are ubiquitous in studies of aging. Examples of semicompeting risk dyads include: dementia and death, frailty syndrome and death, disability and death, and nursing home placement and death. Semicompeting risk models can be divided into two broad classes: models based only on observables quantities (class O) and those based on potential (latent) failure times (class L). The classical illness-death model belongs to class O. This model is a special case of the multistate models, which has been an active area of methodology development. During the past decade and a half, there has also been a flurry of methodological activity on semicompeting risks based on latent failure times (L models). These advances notwithstanding, the semi-competing risks methodology has not penetrated biomedical research, in general, and gerontological research, in particular. Some possible reasons for this lack of uptake are: the methods are relatively new and sophisticated, conceptual problems associated with potential failure time models are difficult to overcome, paucity of expository articles aimed at educating practitioners, and non-availability of readily usable software. The main goals of this review article are: (i) to describe the major types of semicompeting risks problems arising in aging research, (ii) to provide a brief survey of the semicompeting risks methods, (iii) to suggest appropriate methods for addressing the problems in aging research, (iv) to highlight areas where more work is needed, and (v) to suggest ways to facilitate the uptake of the semicompeting risks methodology by the broader biomedical research community. PMID:24729136

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotula, Paul Gabriel; Brozik, Susan Marie; Achyuthan, Komandoor E.

Engineered nanomaterials (ENMs) are increasingly being used in commercial products, particularly in the biomedical, cosmetic, and clothing industries. For example, pants and shirts are routinely manufactured with silver nanoparticles to render them 'wrinkle-free.' Despite the growing applications, the associated environmental health and safety (EHS) impacts are completely unknown. The significance of this problem became pervasive within the general public when Prince Charles authored an article in 2004 warning of the potential social, ethical, health, and environmental issues connected to nanotechnology. The EHS concerns, however, continued to receive relatively little consideration from federal agencies as compared with large investments in basicmore » nanoscience R&D. The mounting literature regarding the toxicology of ENMs (e.g., the ability of inhaled nanoparticles to cross the blood-brain barrier; Kwon et al., 2008, J. Occup. Health 50, 1) has spurred a recent realization within the NNI and other federal agencies that the EHS impacts related to nanotechnology must be addressed now. In our study we proposed to address critical aspects of this problem by developing primary correlations between nanoparticle properties and their effects on cell health and toxicity. A critical challenge embodied within this problem arises from the ability to synthesize nanoparticles with a wide array of physical properties (e.g., size, shape, composition, surface chemistry, etc.), which in turn creates an immense, multidimensional problem in assessing toxicological effects. In this work we first investigated varying sizes of quantum dots (Qdots) and their ability to cross cell membranes based on their aspect ratio utilizing hyperspectral confocal fluorescence microscopy. We then studied toxicity of epithelial cell lines that were exposed to different sized gold and silver nanoparticles using advanced imaging techniques, biochemical analyses, and optical and mass spectrometry methods. Finally we evaluated a new assay to measure transglutaminase (TG) activity; a potential marker for cell toxicity.« less

Ethical challenges in conducting clinical research in lung cancer

PubMed Central

Tod, Angela M.

2016-01-01

The article examines ethical challenges that arise with clinical lung cancer research focusing on design, recruitment, conduct and dissemination. Design: problems related to equipoise can arise in lung cancer studies. Equipoise is an ethics precondition for RCTs and exists where there is insufficient evidence to decide which of two or more treatments is best. Difficulties arise in deciding what level of uncertainty constitutes equipoise and who should be in equipoise, for example, patients might not be even where clinicians are. Patient and public involvement (PPI) can reduce but not remove the problems. Recruitment: (I) lung cancer studies can be complex, making it difficult to obtain good quality consent. Some techniques can help, such as continuous consent. But researchers should not expect consent to be the sole protection for participants’ welfare. This protection is primarily done elsewhere in the research process, for example, in ethics review; (II) the problem of desperate volunteers: some patients only consent to a trial because it gives them a 50/50 option of the treatment they want and can be disappointed or upset if randomised to the other arm. This is not necessarily unfair, given clinical equipoise. However, it should be avoided where possible, for example, by using alternative trial designs; (III) the so-called problem of therapeutic misconception: this is the idea that patients are mistaken if they enter trials believing this to be in their clinical best interest. We argue the problem is misconceived and relates only to certain health systems. Conduct: lung cancer trials face standard ethical challenges with regard to trial conduct. PPI could be used in decisions about criteria for stopping rules. Dissemination: as in other trial areas, it is important that all results, including negative ones, are reported. We argue also that the role of PPI with regard to dissemination is currently under-developed. PMID:27413698

Tracking Hierarchical Processing in Morphological Decomposition with Brain Potentials

ERIC Educational Resources Information Center

Lavric, Aureliu; Elchlepp, Heike; Rastle, Kathleen

2012-01-01

One important debate in psycholinguistics concerns the nature of morphological decomposition processes in visual word recognition (e.g., darkness = {dark} + {-ness}). One theory claims that these processes arise during orthographic analysis and prior to accessing meaning (Rastle & Davis, 2008), and another argues that these processes arise through…

Radioactive waste disposal implications of extending Part IIA of the Environmental Protection Act to cover radioactively contaminated land.

PubMed

Nancarrow, D J; White, M M

2004-03-01

A short study has been carried out of the potential radioactive waste disposal issues associated with the proposed extension of Part IIA of the Environmental Protection Act 1990 to include radioactively contaminated land, where there is no other suitable existing legislation. It was found that there is likely to be an availability problem with respect to disposal at landfills of the radioactive wastes arising from remediation. This is expected to be principally wastes of high volume and low activity (categorised as low level waste (LLW) and very low level waste (VLLW)). The availability problem results from a lack of applications by landfill operators for authorisation to accept LLW wastes for disposal. This is apparently due to perceived adverse publicity associated with the consultation process for authorisation coupled with uncertainty over future liabilities. Disposal of waste as VLLW is limited both by questions over volumes that may be acceptable and, more fundamentally, by the likely alpha activity of wastes (originating from radium and thorium operations). Authorised on-site disposal has had little attention in policy and guidance in recent years, but may have a part to play, especially if considered commercially attractive. Disposal at BNFL's near surface disposal facility for LLW at Drigg is limited to wastes for which there are no practical alternative disposal options (and preference has been given to operational type wastes). Therefore, wastes from the radioactively contaminated land (RCL) regime are not obviously attractive for disposal to Drigg. Illustrative calculations have been performed based on possible volumes and activities of RCL arisings (and assuming Drigg's future volumetric disposal capacity is 950,000 m3). These suggest that wastes arising from implementing the RCL regime, if all disposed to Drigg, would not represent a significant fraction of the volumetric capacity of Drigg, but could have a significant impact on the radiological capacity with respect to 226Ra plus 232Th. The government's decision-making programme for managing solid radioactive wastes in the UK may possibly achieve a general consensus that the use of landfill for LLW from the RCL regime has a fundamental role to play. However, this is unlikely to change the situation within the next few years. No new national facility arising from this programme is likely to be available during the first decade of the operation of a new RCL regime. Hence it appears that Drigg will need to play an important role for some years to come.

Neuroprediction, Violence, and the Law: Setting the Stage.

PubMed

Nadelhoffer, Thomas; Bibas, Stephanos; Grafton, Scott; Kiehl, Kent A; Mansfield, Andrew; Sinnott-Armstrong, Walter; Gazzaniga, Michael

2012-04-01

In this paper, our goal is to (a) survey some of the legal contexts within which violence risk assessment already plays a prominent role, (b) explore whether developments in neuroscience could potentially be used to improve our ability to predict violence, and (c) discuss whether neuropredictive models of violence create any unique legal or moral problems above and beyond the well worn problems already associated with prediction more generally. In "Violence Risk Assessment and the Law", we briefly examine the role currently played by predictions of violence in three high stakes legal contexts: capital sentencing ("Violence Risk Assessment and Capital Sentencing"), civil commitment hearings ("Violence Risk Assessment and Civil Commitment"), and "sexual predator" statutes ("Violence Risk Assessment and Sexual Predator Statutes"). In "Clinical vs. Actuarial Violence Risk Assessment", we briefly examine the distinction between traditional clinical methods of predicting violence and more recently developed actuarial methods, exemplified by the Classification of Violence Risk (COVR) software created by John Monahan and colleagues as part of the MacArthur Study of Mental Disorder and Violence [1]. In "The Neural Correlates of Psychopathy", we explore what neuroscience currently tells us about the neural correlates of violence, using the recent neuroscientific research on psychopathy as our focus. We also discuss some recent advances in both data collection ("Cutting-Edge Data Collection: Genetically Informed Neuroimaging") and data analysis ("Cutting-Edge Data Analysis: Pattern Classification") that we believe will play an important role when it comes to future neuroscientific research on violence. In "The Potential Promise of Neuroprediction", we discuss whether neuroscience could potentially be used to improve our ability to predict future violence. Finally, in "The Potential Perils of Neuroprediction", we explore some potential evidentiary ("Evidentiary Issues"), constitutional ("Constitutional Issues"), and moral ("Moral Issues") issues that may arise in the context of the neuroprediction of violence.

Using process groups to implement failure detection in asynchronous environments

NASA Technical Reports Server (NTRS)

Ricciardi, Aleta M.; Birman, Kenneth P.

1991-01-01

Agreement on the membership of a group of processes in a distributed system is a basic problem that arises in a wide range of applications. Such groups occur when a set of processes cooperate to perform some task, share memory, monitor one another, subdivide a computation, and so forth. The group membership problems is discussed as it relates to failure detection in asynchronous, distributed systems. A rigorous, formal specification for group membership is presented under this interpretation. A solution is then presented for this problem.

Compact scheme for systems of equations applied to fundamental problems of mechanics of continua

NASA Technical Reports Server (NTRS)

Klimkowski, Jerzy Z.

1990-01-01

Compact scheme formulation was used in the treatment of boundary conditions for a system of coupled diffusion and Poisson equations. Models and practical solutions of specific engineering problems arising in solid mechanics, chemical engineering, heat transfer and fuid mechanics are described and analyzed for efficiency and accuracy. Only 2-D cases are discussed and a new method of numerical treatment of boundary conditions common in the fundamental problems of mechanics of continua is presented.

Method of Reproduction of the Luminous Flux of the LED Light Sources by a Spherical Photometer

NASA Astrophysics Data System (ADS)

Huriev, M.; Neyezhmakov, P.

2018-02-01

In connection with transition to energy-efficient temporally stable light-emitting diodes (LEDs) lighting, a problem of ensuring the traceability of results of measurement of characteristics of light sources arises. The problem is related to existing measurement standards of luminous flux based on spherical photometers optimized for the reference incandescent lamps with a relative spectral characteristic different from the spectrum of the LEDs. We propose a method for reproduction of the luminous flux, which solves this problem.

A Preliminary Study of Building a Transmission Overlay for Regional US Power Grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Yin; Li, Yalong; Liu, Yilu

2015-01-01

Many European countries have taken steps toward a Supergrid in order to transmit large amount of intermittent and remote renewable energy over long distance to load centers. In the US, as the expected increase in renewable generation and electricity demand, similar problem arises. A potential solution is to upgrade the transmission system at a higher voltage by constructing a new overlay grid. This paper will first address basic requirements for such an overlay grid. Potential transmission technologies will also be discussed. A multi-terminal VSC HVDC model is developed in DSATools to implement the overlay grid and a test case onmore » a regional NPCC system will be simulated. Another test system of entire US power grid, with three different interconnections tied together using back-to-back HVDC, is also introduced in this paper. Building an overlay system on top of this test case is ongoing, and will be discussed in future work.« less

The contribution of molecular genetics to the understanding and management of cancer: potential future applications and implications for nurses.

PubMed

Bradley, A N

1999-06-01

Cancer is an immense medical problem and as a cause of mortality it is second only to cardiovascular disease. Much of the current understanding of cancer is owed to epidemiologists who have discovered a number of causative factors implicated in its development. These causative factors can be divided into genetic, chemical, physical, viral, radiation, immune and hormonal factors. Further advances in understanding have been made over the past decade from contributions made by the field of molecular biology. From investigation and examination of the molecular processes involved in the development of cancer it is becoming increasingly clear that changes in the genetic material of the cell nuclei are the final common pathway to cancer, whatever the initial aetiology. This article will attempt to elucidate the contribution of molecular genetics to the understanding of the likely mechanisms of carcinogenesis, the management of cancer, potential future applications and directions and the implications for nurses arising from this relatively new and evolving field of knowledge.

Optimal Solar PV Arrays Integration for Distributed Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omitaomu, Olufemi A; Li, Xueping

2012-01-01

Solar photovoltaic (PV) systems hold great potential for distributed energy generation by installing PV panels on rooftops of residential and commercial buildings. Yet challenges arise along with the variability and non-dispatchability of the PV systems that affect the stability of the grid and the economics of the PV system. This paper investigates the integration of PV arrays for distributed generation applications by identifying a combination of buildings that will maximize solar energy output and minimize system variability. Particularly, we propose mean-variance optimization models to choose suitable rooftops for PV integration based on Markowitz mean-variance portfolio selection model. We further introducemore » quantity and cardinality constraints to result in a mixed integer quadratic programming problem. Case studies based on real data are presented. An efficient frontier is obtained for sample data that allows decision makers to choose a desired solar energy generation level with a comfortable variability tolerance level. Sensitivity analysis is conducted to show the tradeoffs between solar PV energy generation potential and variability.« less

Geophysical survey for groundwater potential investigation in peat land area, Riau, Indonesia

NASA Astrophysics Data System (ADS)

Islami, N.; Irianti, M.; Azhar; Nor, M.; Fakhrudin

2018-04-01

Tropical forests, especially peat lands, are particularly vulnerable to forest fires. Fires are the most common disasters in peat lands in the dry season, especially in Riau Province, Indonesia. In the process of extinguishing the peat fire, several substantial problems arise to stop peat fires during this period. This study aims to determine the possibility of using ground water as a source of water to anticipate the early mitigation of peat land fires disaster. The geoelectrical resistivity surveys were used to predict the subsurface geological data including peat thickness and depth of aquifers. The geometry of peat lands was determined using geostatistics based on geoelectrical resistivity interpretation data. Peat Land thickness varies up to 4 m in the north and is thinner to the south. A shallower and deeper aquifer is available at a depth of 13 m to 18 m and 70 m to 90 m respectively. In general, the potential of groundwater in the shallow aquifer is predicted to be sufficient for peat land watering anytime.

Bibliography for acid-rock drainage and selected acid-mine drainage issues related to acid-rock drainage from transportation activities

USGS Publications Warehouse

Bradley, Michael W.; Worland, Scott C.

2015-01-01

Acid-rock drainage occurs through the interaction of rainfall on pyrite-bearing formations. When pyrite (FeS2) is exposed to oxygen and water in mine workings or roadcuts, the mineral decomposes and sulfur may react to form sulfuric acid, which often results in environmental problems and potential damage to the transportation infrastructure. The accelerated oxidation of pyrite and other sulfidic minerals generates low pH water with potentially high concentrations of trace metals. Much attention has been given to contamination arising from acid mine drainage, but studies related to acid-rock drainage from road construction are relatively limited. The U.S. Geological Survey, in cooperation with the Tennessee Department of Transportation, is conducting an investigation to evaluate the occurrence and processes controlling acid-rock drainage and contaminant transport from roadcuts in Tennessee. The basic components of acid-rock drainage resulting from transportation activities are described and a bibliography, organized by relevant categories (remediation, geochemical, microbial, biological impact, and secondary mineralization) is presented.

Illustrative assessment of human health issues arising from the potential release of chemotoxic substances from a generic geological disposal facility for radioactive waste.

PubMed

Wilson, James C; Thorne, Michael C; Towler, George; Norris, Simon

2011-12-01

Many countries have a programme for developing an underground geological disposal facility for radioactive waste. A case study is provided herein on the illustrative assessment of human health issues arising from the potential release of chemotoxic and radioactive substances from a generic geological disposal facility (GDF) for radioactive waste. The illustrative assessment uses a source-pathway-receptor methodology and considers a number of human exposure pathways. Estimated exposures are compared with authoritative toxicological assessment criteria. The possibility of additive and synergistic effects resulting from exposures to mixtures of chemical contaminants or a combination of radiotoxic and chemotoxic substances is considered. The case study provides an illustration of how to assess human health issues arising from chemotoxic species released from a GDF for radioactive waste and highlights potential difficulties associated with a lack of data being available with which to assess synergistic effects. It also highlights how such difficulties can be addressed.

Using satellite fire detection to calibrate components of the fire weather index system in Malaysia and Indonesia.

PubMed

Dymond, Caren C; Field, Robert D; Roswintiarti, Orbita; Guswanto

2005-04-01

Vegetation fires have become an increasing problem in tropical environments as a consequence of socioeconomic pressures and subsequent land-use change. In response, fire management systems are being developed. This study set out to determine the relationships between two aspects of the fire problems in western Indonesia and Malaysia, and two components of the Canadian Forest Fire Weather Index System. The study resulted in a new method for calibrating components of fire danger rating systems based on satellite fire detection (hotspot) data. Once the climate was accounted for, a problematic number of fires were related to high levels of the Fine Fuel Moisture Code. The relationship between climate, Fine Fuel Moisture Code, and hotspot occurrence was used to calibrate Fire Occurrence Potential classes where low accounted for 3% of the fires from 1994 to 2000, moderate accounted for 25%, high 26%, and extreme 38%. Further problems arise when there are large clusters of fires burning that may consume valuable land or produce local smoke pollution. Once the climate was taken into account, the hotspot load (number and size of clusters of hotspots) was related to the Fire Weather Index. The relationship between climate, Fire Weather Index, and hotspot load was used to calibrate Fire Load Potential classes. Low Fire Load Potential conditions (75% of an average year) corresponded with 24% of the hotspot clusters, which had an average size of 30% of the largest cluster. In contrast, extreme Fire Load Potential conditions (1% of an average year) corresponded with 30% of the hotspot clusters, which had an average size of 58% of the maximum. Both Fire Occurrence Potential and Fire Load Potential calibrations were successfully validated with data from 2001. This study showed that when ground measurements are not available, fire statistics derived from satellite fire detection archives can be reliably used for calibration. More importantly, as a result of this work, Malaysia and Indonesia have two new sources of information to initiate fire prevention and suppression activities.

The Mohawkian Chronostratigraphic Problem: building a reliable timescale by combining biostratigraphy, chemostratigraphy, and tephrochronology

NASA Astrophysics Data System (ADS)

Sell, B. K.; Sadler, P.; Leslie, S.; Mitchell, C.; Samson, S. D.

2011-12-01

The abundant exposures of Mohawkian (late Sandbian to early Katian) sedimentary rocks in eastern North America have been well-studied for insights into the Taconic orogeny and potential petroleum sources. Considerable information has been published toward establishing the sequence stratigraphic architecture, biozones for conodonts, graptolites and chitinozoans, chemostratigraphic correlations and a tephrochronologic framework. And yet, correlation remains difficult. Problems arise from complex sedimentary facies changes across the Laurentian margin and associated provincalism of the faunas. The difficulties are exacerbated by some imprecise usage of bentonite names, the short time spans of key stratigraphic sections, and a paucity of sections with muliple kinds of information. Also, linking so many taxon range end, ash-fall, and stable isotope excursion events into a coherent stratigraphic sequence is a daunting numerical problem. It falls into the notorious "NP-Complete" category because the number of possible solutions grows so fast as the number of events increases. "Simulated annealing" is one of the algorithms developed for such problems. We adopt it to solve the stratigraphic sequencing problem as a constrained optimization (CONOP). Nevertheless, to realize the full potential, more bentonite charactization and dating is needed in sections with detailed range charts for fossil species. CONOP works best with the individual taxon ranges, not the derived biozone boundaries. We examine the potential resolving power of CONOP in the context of a re-evaluation of bentonite correlations and newly acquired CA-TIMS U-Pb zircon dates from sections with rich biostratigraphic data. In particular we use 206Pb/238U zircon dates from two bentonites in the Womble Shale at the Katian Global Stratotype Section and Point (452.8 ± 0.2 and 453.5 ± 0.3 Ma, weighted mean with 2σ internal error) to compare various correlations with other dated bentonites in eastern North America. Preliminary dates for five long-range (>1000 km) bentonite correlations made on the basis of single-crystal apatite trace-element analyses (Mg, Cl, Mn, Fe, Ce, Y) help resolve previous conflicts among various biostratgraphic data, but raise new questions about the interpretation of stratigraphic sequences and chemostratigraphic data.

An Artificial Neural Network Controller for Intelligent Transportation Systems Applications

DOT National Transportation Integrated Search

1996-01-01

An Autonomous Intelligent Cruise Control (AICC) has been designed using a feedforward artificial neural network, as an example for utilizing artificial neural networks for nonlinear control problems arising in intelligent transportation systems appli...

Humane Ethics in Veterinary Education

ERIC Educational Resources Information Center

Fox, M. W.

1978-01-01

This discussion focuses on the problem faced by biomedical students who are learning objective, factual information and techniques without being given the opportunity to consider the many ethical dilemmas and moral questions that will arise after graduation. (LBH)

Spin reorientation of a nonsymmetric body with energy dissipation

NASA Technical Reports Server (NTRS)

Cenker, R. J.

1973-01-01

Stable rotating semi-rigid bodies were demonstrated analytically, and verified in flights such as Explorer 1 and ATS-5 satellites. The problem arises from the two potential orientations which the final spin vector can take after large angle reorientation from minor to major axis, i.e., along the positive or negative axis of the maximum inertia. Reorientation of a satellite initially spinning about the minor axis using an energy dissipation device may require that the final spin orientation be controlled. Examples of possible applications are the Apogee Motor Assembly with Paired Satellites (AMAPS) configuration, where proper orientation of the thruster is required; and reorientation of ATS-5, where the spin sensitive nature of the despin device (yo-yo mechanism) requires that the final spin vector point is a specified direction.

Extracting Depth From Motion Parallax in Real-World and Synthetic Displays

NASA Technical Reports Server (NTRS)

Hecht, Heiko; Kaiser, Mary K.; Aiken, William; Null, Cynthia H. (Technical Monitor)

1994-01-01

In psychophysical studies on human sensitivity to visual motion parallax (MP), the use of computer displays is pervasive. However, a number of potential problems are associated with such displays: cue conflicts arise when observers accommodate to the screen surface, and observer head and body movements are often not reflected in the displays. We investigated observers' sensitivity to depth information in MP (slant, depth order, relative depth) using various real-world displays and their computer-generated analogs. Angle judgments of real-world stimuli were consistently superior to judgments that were based on computer-generated stimuli. Similar results were found for perceived depth order and relative depth. Perceptual competence of observers tends to be underestimated in research that is based on computer generated displays. Such findings cannot be generalized to more realistic viewing situations.

Security and Privacy Grand Challenges for the Internet of Things

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fink, Glenn A.; Zarzhitsky, Dimitri V.; Carroll, Thomas E.

Abstract— The growth of the Internet of Things (IoT) is driven by market pressures, and while security is being considered, the relationship between the unintended consequences of billions of such devices connecting to the Internet cannot be described with existing mathematical methods. The possibilities for illicit surveillance through lifestyle analysis, unauthorized access to information, and new attack vectors will continue to increase by 2020, when up-to 50 billion devices may be connected. This paper discusses various kinds of vulnerabilities that can be expected to arise, and presents a research agenda for mitigating the worst of the impacts. We hope tomore » draw research attention to the potential dangers of IoT so that many of these problems can be avoided.« less

Perspectives on Social Network Analysis for Observational Scientific Data

NASA Astrophysics Data System (ADS)

Singh, Lisa; Bienenstock, Elisa Jayne; Mann, Janet

This chapter is a conceptual look at data quality issues that arise during scientific observations and their impact on social network analysis. We provide examples of the many types of incompleteness, bias and uncertainty that impact the quality of social network data. Our approach is to leverage the insights and experience of observational behavioral scientists familiar with the challenges of making inference when data are not complete, and suggest avenues for extending these to relational data questions. The focus of our discussion is on network data collection using observational methods because they contain high dimensionality, incomplete data, varying degrees of observational certainty, and potential observer bias. However, the problems and recommendations identified here exist in many other domains, including online social networks, cell phone networks, covert networks, and disease transmission networks.

Palo Alto Research Center - Smart Embedded Network of Sensors with an Optical Readout

ScienceCinema

Raghavan, Ajay; Sahu, Saroj; Bringans, Ross; Johnson, Noble; Kiesel, Peter; Saha, Bhaskar

2018-05-18

PARC is developing new fiber optic sensors that would be embedded into batteries to monitor and measure key internal parameters during charge and discharge cycles. Two significant problems with today's best batteries are their lack of internal monitoring capabilities and their design oversizing. The lack of monitoring interferes with the ability to identify and manage performance or safety issues as they arise, which are presently managed by very conservative design oversizing and protection approaches that result in cost inefficiencies. PARC's design combines low-cost, embedded optical battery sensors and smart algorithms to overcome challenges faced by today's best battery management systems. These advanced fiber optic sensing technologies have the potential to dramatically improve the safety, performance, and life-time of energy storage systems.

Differentiability of energy functionals in spin-density-functional theory

NASA Astrophysics Data System (ADS)

Gál, Tamás

2007-06-01

Recently, nonuniqueness of external electrostatic and magnetic fields yielding a given many-electron ground state has been pointed out [K. Capelle and G. Vignale, Phys. Rev. Lett. 86, 5546 (2001); H. Eschrig and W. E. Pickett, Solid State Commun. 118, 123 (2001)], implying the nondifferentiability of the ground-state energy functional of spin-density-functional theory (SDFT), on the basis of which the applicability of widely used DFT methods in SDFT has been put into question and the need for a critical reexamination of those applications has been concluded. Here it is shown, for collinear magnetic fields, that the nonuniqueness of the external potentials in SDFT does not imply the nonexistence of number-conserving functional derivatives as well, with the use of which therefore problems arising from the nondifferentiability are avoided.

Patient dumping, COBRA, and the public psychiatric hospital.

PubMed

Elliott, R L

1993-02-01

Serious clinical and risk management problems arise when indigent patients with acute medical conditions are transferred from general medical hospitals or emergency departments to public psychiatric hospitals that are ill equipped to provide medical care. To combat such practices, referred to as dumping, Congress included measures in the Consolidated Omnibus Budget Reconciliation Act of 1985 (COBRA) prohibiting such transfers. Because physicians and administrators in public psychiatric hospitals are generally not aware of the potential usefulness of COBRA in reducing dumping, this paper describes its important provisions. The key to preventing dumping is to educate referral sources to limitations on the medical care available at the receiving hospital and to discourage negligent patient transfers by enforcing COBRA. Public hospital staff and legal counsel who become familiar with COBRA's provisions can develop an antidumping strategy.

Radiative transfer in a polluted urban planetary boundary layer

NASA Technical Reports Server (NTRS)

Viskanta, R.; Johnson, R. O.; Bergstrom, R. W.

1977-01-01

Radiative transfer in a polluted urban atmosphere is studied using a dynamic model. The diurnal nature of radiative transfer for summer conditions is simulated for an urban area 40 km in extent and the effects of various parameters arising in the problem are investigated. The results of numerical computations show that air pollution has the potential of playing a major role in the radiative regime of the urban area. Absorption of solar energy by aerosols in realistic models of urban atmosphere are of the same order of magnitude as that due to water vapor. The predicted effect of the air pollution aerosol in the city is to warm the earth-atmosphere system, and the net effect of gaseous pollutant is to warm the surface and cool the planetary boundary layer, particularly near the top.

[Assisted reproductive technologies and ethics].

PubMed

Belaisch-Allart, Joëlle

2014-01-01

Since the first birth after in vitro fertilization more than 5 million of IVF babies are born in the world. Assisted reproductive technologies captivate the public, they allow maternity without ovary (oocyte donation), without uterus (surrogate mother), paternity without spermatozoids (sperm donation), parentality without limits of age, parentality after death and homoparentality. These technologies arise a lot of ethics questions, the problem is that the answers are not the same all-round the world, laws are based on morals, beliefs, faiths, and convictions. Theses variations arise themselves questions on the value of these non-universal answers.

Reflections on psychoanalytic treatment of Lubavitch Chassidim couples: working with a culturally divergent population.

PubMed

Schulman, Martin A; Kaplan, Ricki S

2014-08-01

Chassidic Jews create separate developmental lines for males and females beginning at three years of age. Since early marriages are encouraged and there is minimal contact between the sexes prior to marriage, problems inevitably arise in relationships. This article discusses both newlywed and long-term married Lubavitch Chassidim in couples treatment with secular analysts, parameters necessary for successful treatment, and countertransferences that arise. It is part of an ongoing series of publications based on the authors' decade-long psychoanalytic work with this population.

Interest Subsidies on Student Loans: A Better Class of Drain. CEE DP 114

ERIC Educational Resources Information Center

Barr, Nicholas; Johnston, Alison

2010-01-01

The British system of student loans has a zero real rate of interest, less than it costs the government to borrow the money. This paper discusses the problems that arise from interest subsidies in the UK system of student loans; systems in other countries, for example Australia and New Zealand, face similar problems. The topic appears to be narrow…

Two Problems with Table Saws

ERIC Educational Resources Information Center

Vautaw, William R.

2008-01-01

We solve two problems that arise when constructing picture frames using only a table saw. First, to cut a cove running the length of a board (given the width of the cove and the angle the cove makes with the face of the board) we calculate the height of the blade and the angle the board should be turned as it is passed over the blade. Second, to…

Elucidation of Heterogeneous Processes Controlling Boost Phase Signatures

DTIC Science & Technology

1990-09-12

three year research program to develop efficient theoretical methods to study collisional processes involved in radiative signature modeling . The...Marlboro, MD 20772 I. Statement of Problem For strategic defense, it is important to be able to effectively model radiative signaturesl arising from...Thus our computational work was on problems or models for which exact results for making comparisons were available. Our key validations were

The forest ecosystem of southeast Alaska: 6. Forest diseases.

Treesearch

Thomas H. Laurent

1974-01-01

The disease problems of old growth are largely being taken care of by cutting. This same cutting is rapidly converting large areas of old growth to reproduction and young growth. It is in these areas of young growth that our disease problems will most probably arise. With a few exceptions the reproduction and young-growth stands appear quite healthy at this time with...

A numerical solution of a singular boundary value problem arising in boundary layer theory.

PubMed

Hu, Jiancheng

2016-01-01

In this paper, a second-order nonlinear singular boundary value problem is presented, which is equivalent to the well-known Falkner-Skan equation. And the one-dimensional third-order boundary value problem on interval [Formula: see text] is equivalently transformed into a second-order boundary value problem on finite interval [Formula: see text]. The finite difference method is utilized to solve the singular boundary value problem, in which the amount of computational effort is significantly less than the other numerical methods. The numerical solutions obtained by the finite difference method are in agreement with those obtained by previous authors.

Crack problems involving nonhomogeneous interfacial regions in bonded materials

NASA Technical Reports Server (NTRS)

Erdogan, F.

1990-01-01

Consideration is given to two classes of fracture-related solid mechanics problems in which the model leads to some physically anomalous results. The first is the interface crack problem associated with the debonding process in which the corresponding elasticity solution predicts severe oscillations of stresses and the crack surface displacements vary near the crack tip. The second deals with crack intersecting the interface. The nature of the solutions around the crack tips arising from these problems is reviewed. The rationale for introducing a new interfacial zone model is discussed, its analytical consequences within the context of the two crack-problem classes are described, and some examples are presented.

Semiconductor crystal growth and segregation problems on earth and in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.

1982-01-01

Semiconductor crystal growth and segregation problems are examined in the context of their relationship to material properties, and some of the problems are illustrated with specific experimental results. The compositional and structural defects encountered in semiconductors are largely associated with gravity-induced convective currents in the melt; additional problems are introduced by variations in stoichiometry. It is demonstrated that in near-zero gravity environment, crystal growth and segregation takes place under ideal steady-state conditions with minimum convective interference. A discussion of the advantages of zero-gravity crystal growth is followed by a summary of problems arising from the absence of gravitational forces.

Conflict of Interest in the Evaluation and Dissemination of “Model” School-based Drug and Violence Prevention Programs

PubMed Central

Gorman, Dennis M.; Conde, Eugenia

2010-01-01

Conflict of interest refers to a set of conditions in which professional judgment concerning the validity of research might be influenced by a secondary competing interest. The competing interest that has received most attention in the literature addressing the prevalence and effects of such conflicts on the practice of empirical research has been that of financial relationships between investigators and research sponsors. The potential for conflicts of interest to arise in the evaluation of drug prevention programs was raised by Moskowitz in this journal in 1993, but to date there has been no attempt made to estimate the scope of this problem. The present study addressed this issue using a sample of “model” school-based drug and violence prevention interventions by first, identifying the types or relationships that exist between program developers and program distributors, and, second, by assessing how many of the evaluations of these programs published in peer-reviewed journals had been conducted by the developers of the programs compared to independent evaluation teams. The data presented indicate that there are relatively few published evaluations that do not involve program developers and that there are few instances in which there is complete separation between the program developer and program distributor. Using the open systems model of the Institute of Medicine Committee on Research Integrity as a framework, it is argued that the culture and norms of the program developer and those of the program evaluator are fundamentally distinct and therefore failure to separate these roles produces high potential for conflict of interest to arise. PMID:17945143

Polymeric Carriers for Gene Delivery: Chitosan and Poly(amidoamine) Dendrimers

PubMed Central

Xu, Qingxing; Wang, Chi-Hwa; Pack, Daniel Wayne

2012-01-01

Gene therapy is a potential medical solution that promises new treatments and may hold the cure for many different types of diseases and disorders of the human race. However, gene therapy is still a growing medical field and the technology is still in its infancy. The main challenge for gene therapy is to find safe and effective vectors that are able to deliver genes to the specific cells and get them to express inside the cells. Due to safety concerns, synthetic delivery systems, rather than viral vectors, are preferred for gene delivery and significant efforts have been focused on the development of this field. However, we are faced with problems like low gene transfer efficiency, cytotoxicity and lack of cell-targeting capability for these synthetic delivery systems. Over the years, we have seen a variety of new and effective polymers which have been designed and synthesized specifically for gene delivery. Moreover, various strategies that aimed at enhancing their physicochemical properties, improving transfection efficiency, reducing cytotoxicity as well as incorporating functional groups that offer better targetability and higher cellular uptake are established. Here, we look at two potential polymeric carriers, chitosan and poly(amidoamine) dendrimers, which have been widely reported for gene delivery. For chitosan, the interest arises from their availability, excellent non-cytotoxicity profile, biodegradability and ease of modification. For poly(amidoamine) dendrimers, the interest arises from their ease of synthesis with controlled structure and size, minimal cytotoxicity, biodegradability and high transfection efficiencies. The latest developments on these polymers for gene delivery will be the main focus of this article. PMID:20618156

Vibration due to non-circularity of a rotating ring having discrete radial supports - With application to thin-walled rotor/magnetic bearing systems

NASA Astrophysics Data System (ADS)

Fakkaew, Wichaphon; Cole, Matthew O. T.

2018-06-01

This paper investigates the vibration arising in a thin-walled cylindrical rotor subject to small non-circularity and coupled to discrete space-fixed radial bearing supports. A Fourier series description of rotor non-circularity is incorporated within a mathematical model for vibration of a rotating annulus. This model predicts the multi-harmonic excitation of the rotor wall due to bearing interactions. For each non-circularity harmonic there is a set of distinct critical speeds at which resonance can potentially arise due to flexural mode excitation within the rotor wall. It is shown that whether each potential resonance occurs depends on the multiplicity and symmetry of the bearing supports. Also, a sufficient number of evenly spaced identical supports will eliminate low order resonances. The considered problem is pertinent to the design and operation of thin-walled rotors with active magnetic bearing (AMB) supports, for which small clearances exist between the rotor and bearing and so vibration excitation must be limited to avoid contacts. With this motivation, the mathematical model is further developed for the case of a distributed array of electromagnetic actuators controlled by feedback of measured rotor wall displacements. A case study involving an experimental system with short cylindrical rotor and a single radial AMB support is presented. The results show that flexural mode resonance is largely avoided for the considered design topology. Moreover, numerical predictions based on measured non-circularity show good agreement with measurements of rotor wall vibration, thereby confirming the validity and utility of the theoretical model.

On a numerical method for solving integro-differential equations with variable coefficients with applications in finance

NASA Astrophysics Data System (ADS)

Kudryavtsev, O.; Rodochenko, V.

2018-03-01

We propose a new general numerical method aimed to solve integro-differential equations with variable coefficients. The problem under consideration arises in finance where in the context of pricing barrier options in a wide class of stochastic volatility models with jumps. To handle the effect of the correlation between the price and the variance, we use a suitable substitution for processes. Then we construct a Markov-chain approximation for the variation process on small time intervals and apply a maturity randomization technique. The result is a system of boundary problems for integro-differential equations with constant coefficients on the line in each vertex of the chain. We solve the arising problems using a numerical Wiener-Hopf factorization method. The approximate formulae for the factors are efficiently implemented by means of the Fast Fourier Transform. Finally, we use a recurrent procedure that moves backwards in time on the variance tree. We demonstrate the convergence of the method using Monte-Carlo simulations and compare our results with the results obtained by the Wiener-Hopf method with closed-form expressions of the factors.

Solving multi-leader-common-follower games.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leyffer, S.; Munson, T.; Mathematics and Computer Science

Multi-leader-common-follower games arise when modelling two or more competitive firms, the leaders, that commit to their decisions prior to another group of competitive firms, the followers, that react to the decisions made by the leaders. These problems lead in a natural way to equilibrium problems with equilibrium constraints (EPECs). We develop a characterization of the solution sets for these problems and examine a variety of nonlinear optimization and nonlinear complementarity formulations of EPECs. We distinguish two broad cases: problems where the leaders can cost-differentiate and problems with price-consistent followers. We demonstrate the practical viability of our approach by solving amore » range of medium-sized test problems.« less

Overview of Krylov subspace methods with applications to control problems

NASA Technical Reports Server (NTRS)

Saad, Youcef

1989-01-01

An overview of projection methods based on Krylov subspaces are given with emphasis on their application to solving matrix equations that arise in control problems. The main idea of Krylov subspace methods is to generate a basis of the Krylov subspace Span and seek an approximate solution the the original problem from this subspace. Thus, the original matrix problem of size N is approximated by one of dimension m typically much smaller than N. Krylov subspace methods have been very successful in solving linear systems and eigenvalue problems and are now just becoming popular for solving nonlinear equations. It is shown how they can be used to solve partial pole placement problems, Sylvester's equation, and Lyapunov's equation.

About some types of constraints in problems of routing

NASA Astrophysics Data System (ADS)

Petunin, A. A.; Polishuk, E. G.; Chentsov, A. G.; Chentsov, P. A.; Ukolov, S. S.

2016-12-01

Many routing problems arising in different applications can be interpreted as a discrete optimization problem with additional constraints. The latter include generalized travelling salesman problem (GTSP), to which task of tool routing for CNC thermal cutting machines is sometimes reduced. Technological requirements bound to thermal fields distribution during cutting process are of great importance when developing algorithms for this task solution. These requirements give rise to some specific constraints for GTSP. This paper provides a mathematical formulation for the problem of thermal fields calculating during metal sheet thermal cutting. Corresponding algorithm with its programmatic implementation is considered. The mathematical model allowing taking such constraints into account considering other routing problems is discussed either.

The Lumbar Artery Perforator Flap: 3-Dimensional Anatomical Study and Clinical Applications.

PubMed

Bissell, Mary Beth; Greenspun, David T; Levine, Josh; Rahal, William; Al-Dhamin, Ammar; AlKhawaji, Ali; Morris, Steven F

2016-10-01

The lumbar region is a potential donor site for perforator-based rotational or free flaps or as a recipient site for free flaps to obtain coverage for deficits in the sacral region. Because of the lack of consensus regarding the microvascular anatomy of this potential flap site, a robust investigation of the anatomy of this region is required. Three-dimensional reconstructions (n = 6) of the microvasculature of the lumbar region were generated using MIMICS software (Materialise, Belgium) for each of the four paired lumbar vessels. Diameter, course, and pedicle length were recorded for all lumbar artery (LA) perforators. Statistical analysis was performed using SigmaStat 4.0 and graphs were generated using GraphPad Prism 6 Software. Perforators arising from the first pair of LAs are reliably detected along the inferior margin of the 12th rib, extending inferiorly and laterally from the midline while perforators arising from the fourth pair of LA perforate the fascia along a horizontal plane connecting the posterior iliac crests. There are significantly more cutaneous perforators arising from the first (L1) and fourth (L4) pairs of LA than from the second (L2) and third (L3) (mean ± SD: L1, 5.5 ± 1.2; L2, 1.4 ± 0.7; L3, 1.3 ± 0.7; L4, 4.8 ± 1.0; P < 0.05). The average perforator diameter arising from L1 is greater than those arising from L4 (diameter ± SD: L1, 1.2 mm ± 0.2 >L4, 0.8 mm ± 0.2; P < 0.0001). L1 and L4 perforators have longer pedicle lengths than those arising from L2 and L3 (length ± SD: L1, 98.2 mm ± 57.8; L4, 106.1 mm ± 23.3 >L2, 67.5 mm ± 27.4; L3, 78.5 mm ± 30.3; P < 0.05). Perforators arising from the first and fourth LAs arise in a predictable fashion, have adequate pedicle lengths, and are of suitable diameter to support a perforator flap. We present a case to support the potential use of this flap for microvascular breast reconstruction.

The Cauchy problem for the Pavlov equation

NASA Astrophysics Data System (ADS)

Grinevich, P. G.; Santini, P. M.; Wu, D.

2015-10-01

Commutation of multidimensional vector fields leads to integrable nonlinear dispersionless PDEs that arise in various problems of mathematical physics and have been intensively studied in recent literature. This report aims to solve the scattering and inverse scattering problem for integrable dispersionless PDEs, recently introduced just at a formal level, concentrating on the prototypical example of the Pavlov equation, and to justify an existence theorem for global bounded solutions of the associated Cauchy problem with small data. An essential part of this work was made during the visit of the three authors to the Centro Internacional de Ciencias in Cuernavaca, Mexico in November-December 2012.

Decentralized control

NASA Technical Reports Server (NTRS)

Steffen, Chris

1990-01-01

An overview of the time-delay problem and the reliability problem which arise in trying to perform robotic construction operations at a remote space location are presented. The effects of the time-delay upon the control system design will be itemized. A high level overview of a decentralized method of control which is expected to perform better than the centralized approach in solving the time-delay problem is given. The lower level, decentralized, autonomous, Troter Move-Bar algorithm is also presented (Troters are coordinated independent robots). The solution of the reliability problem is connected to adding redundancy to the system. One method of adding redundancy is given.

Photovoltaic module hot spot durability design and test methods

NASA Technical Reports Server (NTRS)

Arnett, J. C.; Gonzalez, C. C.

1981-01-01

As part of the Jet Propulsion Laboratory's Low-Cost Solar Array Project, the susceptibility of fat-plate modules to hot-spot problems is investigated. Hot-spot problems arise in modules when the cells become back-biased and operate in the negative-voltage quadrant, as a result of short-circuit current mismatch, cell cracking or shadowing. The details of a qualification test for determining the capability of modules of surviving field hot-spot problems and typical results of this test are presented. In addition, recommended circuit-design techniques for improving the module and array reliability with respect to hot-spot problems are presented.

The EEOC's New Equal Pay Act Guidelines.

ERIC Educational Resources Information Center

Greenlaw, Paul S.; Kohl, John P.

1982-01-01

Analyzes the new guidelines for enforcement of the Equal Pay Act and their implications for personnel management. Argues that there are key problem areas in the new regulations arising from considerable ambiguity and uncertainty about their interpretation. (SK)

Remain in Your Seats: Crisis Management for the Alumni Travel Director.

ERIC Educational Resources Information Center

Bonenberger, Lynne M.

1991-01-01

Three alumni travel directors offer advice on taking control when tour crises arise. The cases cited involved irresponsible tour agents, problem travelers, and on-location disasters. Both precautions and creative solutions are emphasized. (MSE)

The case of the missing third.

PubMed

Robertson, Robin

2005-01-01

How is it that form arises out of chaos? In attempting to deal with this primary question, time and again a "Missing Third" is posited that lies between extremes. The problem of the "Missing Third" can be traced through nearly the entire history of thought. The form it takes, the problems that arise from it, the solutions suggested for resolving it, are each representative of an age. This paper traces the issue from Plato and Parmenides in the 4th--5th centuries, B.C.; to Neoplatonism in the 3rd--5th centuries; to Locke and Descartes in the 17th century; on to Berkeley and Kant in the 18th century; Fechner and Wundt in the 19th century; to behaviorism and Gestalt psychology, Jung, early in the 20th century, ethology and cybernetics later in the 20th century, then culminates late in the 20th century, with chaos theory.

Is CT angiography of the pulmonary arteries indicated in patients with high clinical probability of pulmonary embolism?

PubMed

Martínez Montesinos, L; Plasencia Martínez, J M; García Santos, J M

When a diagnostic test confirms clinical suspicion, the indicated treatment can be administered. A problem arises when the diagnostic test does not confirm the initially suspected diagnosis; when the suspicion is grounded in clinically validated predictive rules and is high, the problem is even worse. This situation arises in up to 40% of patients with high suspicion for acute pulmonary embolism, raising the question of whether CT angiography of the pulmonary arteries should be done systematically. This paper reviews the literature about this issue and lays out the best evidence about the relevant recommendations for patients with high clinical suspicion of acute pulmonary embolism and negative findings on CT angiography. It also explains the probabilistic concepts derived from Bayes' theorem that can be useful for ascertaining the most appropriate approach in these patients. Copyright © 2017 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

Relative locality and the soccer ball problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amelino-Camelia, Giovanni; Freidel, Laurent; Smolin, Lee

We consider the behavior of macroscopic bodies within the framework of relative locality [G. Amelino-Camelia, L. Freidel, J. Kowalski-Glikman, and L. Smolin, arXiv:1101.0931]. This is a recent proposal for Planck scale modifications of the relativistic dynamics of particles which are described as arising from deformations in the geometry of momentum space. We consider and resolve a common objection against such proposals, which is that, even if the corrections are small for elementary particles in current experiments, they are huge when applied to composite systems such as soccer balls, planets, and stars, with energies E{sub macro} much larger than M{sub P}.more » We show that this soccer ball problem does not arise within the framework of relative locality because the nonlinear effects for the dynamics of a composite system with N elementary particles appear at most of order E{sub macro}/N{center_dot}M{sub P}.« less

Survival probability of diffusion with trapping in cellular neurobiology

NASA Astrophysics Data System (ADS)

Holcman, David; Marchewka, Avi; Schuss, Zeev

2005-09-01

The problem of diffusion with absorption and trapping sites arises in the theory of molecular signaling inside and on the membranes of biological cells. In particular, this problem arises in the case of spine-dendrite communication, where the number of calcium ions, modeled as random particles, is regulated across the spine microstructure by pumps, which play the role of killing sites, while the end of the dendritic shaft is an absorbing boundary. We develop a general mathematical framework for diffusion in the presence of absorption and killing sites and apply it to the computation of the time-dependent survival probability of ions. We also compute the ratio of the number of absorbed particles at a specific location to the number of killed particles. We show that the ratio depends on the distribution of killing sites. The biological consequence is that the position of the pumps regulates the fraction of calcium ions that reach the dendrite.

Gelfand-type problem for two-phase porous media

PubMed Central

Gordon, Peter V.; Moroz, Vitaly

2014-01-01

We consider a generalization of the Gelfand problem arising in Frank-Kamenetskii theory of thermal explosion. This generalization is a natural extension of the Gelfand problem to two-phase materials, where, in contrast to the classical Gelfand problem which uses a single temperature approach, the state of the system is described by two different temperatures. We show that similar to the classical Gelfand problem the thermal explosion occurs exclusively owing to the absence of stationary temperature distribution. We also show that the presence of interphase heat exchange delays a thermal explosion. Moreover, we prove that in the limit of infinite heat exchange between phases the problem of thermal explosion in two-phase porous media reduces to the classical Gelfand problem with renormalized constants. PMID:24611025

Gambling harms and gambling help-seeking amongst indigenous Australians.

PubMed

Hing, Nerilee; Breen, Helen; Gordon, Ashley; Russell, Alex

2014-09-01

This paper aimed to analyze the harms arising from gambling and gambling-related help-seeking behaviour within a large sample of Indigenous Australians. A self-selected sample of 1,259 Indigenous Australian adults completed a gambling survey at three Indigenous sports and cultural events, in several communities and online. Based on responses to the problem gambling severity index (PGSI), the proportions of the sample in the moderate risk and problem gambler groups were higher than those for the population of New South Wales. Many in our sample appeared to face higher risks with their gambling and experience severe gambling harms. From PGSI responses, notable harms include financial difficulties and feelings of guilt and regret about gambling. Further harms, including personal, relationship, family, community, legal and housing impacts, were shown to be significantly higher for problem gamblers than for the other PGSI groups. Most problem gamblers relied on family, extended family and friends for financial help or went without due to gambling losses. Nearly half the sample did not think they had a problem with gambling but the results show that the majority (57.7 %) faced some risk with their gambling. Of those who sought gambling help, family, extended family, friends and respected community members were consulted, demonstrating the reciprocal obligations underpinning traditional Aboriginal culture. The strength of this finding is that these people are potentially the greatest source of gambling help, but need knowledge and resources to provide that help effectively. Local Aboriginal services were preferred as the main sources of professional help for gambling-related problems.

Thermal transport in the Falicov-Kimball model

NASA Astrophysics Data System (ADS)

Freericks, J. K.; Zlatić, V.

2001-12-01

We prove the Jonson-Mahan theorem for the thermopower of the Falicov-Kimball model by solving explicitly for correlation functions in the large dimensional limit. We prove a similar result for the thermal conductivity. We separate the results for thermal transport into the pieces of the heat current that arise from the kinetic energy and those that arise from the potential energy. Our method of proof is specific to the Falicov-Kimball model, but illustrates the near cancellations between the kinetic- and potential-energy pieces of the heat current implied by the Jonson-Mahan theorem.

Ionic effects on the temperature-force phase diagram of DNA.

PubMed

Amnuanpol, Sitichoke

2017-12-01

Double-stranded DNA (dsDNA) undergoes a structural transition to single-stranded DNA (ssDNA) in many biologically important processes such as replication and transcription. This strand separation arises in response either to thermal fluctuations or to external forces. The roles of ions are twofold, shortening the range of the interstrand potential and renormalizing the DNA elastic modulus. The dsDNA-to-ssDNA transition is studied on the basis that dsDNA is regarded as a bound state while ssDNA is regarded as an unbound state. The ground state energy of DNA is obtained by mapping the statistical mechanics problem to the imaginary time quantum mechanics problem. In the temperature-force phase diagram the critical force F c (T) increases logarithmically with the Na + concentration in the range from 32 to 110 mM. Discussing this logarithmic dependence of F c (T) within the framework of polyelectrolyte theory, it inevitably suggests a constraint on the difference between the interstrand separation and the length per unit charge during the dsDNA-to-ssDNA transition.

A rare case report of squamous-cell carcinoma arising from mature cystic teratoma of ovary.

PubMed

Kalampokas, E; Boutas, I; Kairi-Vasilatou, E; Salakos, N; Panoulis, K; Aravantinos, L; Damaskos, C; Kalampokas, T; Deligeoroglou, E

2014-01-01

The most frequent ovarian germ cell tumors are mature cystic teratomas (MCTs), composing 10-25% of all ovarian neoplasms. MCTs have the potential of undergoing malignant transformation, typically in postmenopausal women, with a frequency of 0.17-3%, with squamous cell carcinoma being the most common malignant tumor arising from MCT. We present the rare clinical entity of a squamous cell carcinoma arising from a mature cystic teratoma in a 56-year-old premenopausal woman as well as diagnostic and therapeutic route followed.

Small dark energy and stable vacuum from Dilaton-Gauss-Bonnet coupling in TMT

NASA Astrophysics Data System (ADS)

Guendelman, Eduardo I.; Nishino, Hitoshi; Rajpoot, Subhash

2017-04-01

In two measures theories (TMT), in addition to the Riemannian measure of integration, being the square root of the determinant of the metric, we introduce a metric-independent density Φ in four dimensions defined in terms of scalars \\varphi _a by Φ =\\varepsilon ^{μ ν ρ σ } \\varepsilon _{abcd} (partial _{μ }\\varphi _a)(partial _{ν }\\varphi _b) (partial _{ρ }\\varphi _c) (partial _{σ }\\varphi _d). With the help of a dilaton field φ we construct theories that are globally scale invariant. In particular, by introducing couplings of the dilaton φ to the Gauss-Bonnet (GB) topological density {√{-g}} φ ( R_{μ ν ρ σ }^2 - 4 R_{μ ν }^2 + R^2 ) we obtain a theory that is scale invariant up to a total divergence. Integration of the \\varphi _a field equation leads to an integration constant that breaks the global scale symmetry. We discuss the stabilizing effects of the coupling of the dilaton to the GB-topological density on the vacua with a very small cosmological constant and the resolution of the `TMT Vacuum-Manifold Problem' which exists in the zero cosmological-constant vacuum limit. This problem generically arises from an effective potential that is a perfect square, and it gives rise to a vacuum manifold instead of a unique vacuum solution in the presence of many different scalars, like the dilaton, the Higgs, etc. In the non-zero cosmological-constant case this problem disappears. Furthermore, the GB coupling to the dilaton eliminates flat directions in the effective potential, and it totally lifts the vacuum-manifold degeneracy.

Hydrodynamics of the Capture Zone of a Partially Penetrating Well in a Confined Aquifer

NASA Astrophysics Data System (ADS)

Faybishenko, Boris A.; Javandel, Iraj; Witherspoon, Paul A.

1995-04-01

In the pump and treat approach to the problem of managing a contaminated aquifer, a key problem is to design an effective capture system that collects only the polluted groundwater without allowing any of it to escape. At present, it is customary to design a capture system using fully penetrating withdrawal wells. Very often, however, only part of the vertical thickness of the aquifer is contaminated, so the question may arise whether a more efficient capture system can be achieved using partially penetrating wells. Very little work has been done on the application of partially penetrating wells to this problem. A new semianalytic method that can be used in determining the geometry of the capture zone for steady state flow to a partially penetrating well that is screened from the top (or from the bottom) of a confined aquifer has been developed. By combining the velocity potentials for flow to the well with that for the regional flow field, a three-dimensional velocity potential that can be used in determining the complete geometry of the capture surface has been developed. The results have shown that with a constant pumping rate the maximum horizontal extent of the capture surface at the top (or bottom) of the aquifer increases as the degree of penetration decreases. As one would expect, the maximum vertical extent increases as the depth of penetration increases. Thus, if one knows the actual location of the contaminant plume, an appropriate combination of the degree of penetration and pumping rate can be selected to create an effective capture zone.

Recognizing the professionals who help to solve "the population problem".

PubMed

Miro, C A

1984-12-01

It is the population professionals who belong to the "developing" world who have helped to create and expand the basic information which makes it possible to describe the demographic situation of countries and social groups more adequately. These professionals have developed, promoted, and applied analytical techniques which have enriched understanding of the components of demographic change. It is these professionals who have managed to make major contributions towards explaining the relationship between demographic and socioeconomic factors. The professionals are insisting on developing applied, theoretical, and methodological population research, the results of which will serve essentially to propose alternatives for action. This group of professionals participates daily in the training of technical staff and professionals and academics, specialists who will continue to promote the development of demography as a discipline. Finally, these professionals, through various publications, keep population topics at the center of the attention of those who are concerned with studying them. Groups of countries in Africa, Asia, and Latin America suffer, although to a different extent and in different ways, from the problems created by the rapid growth of certain cities, particularly capital cities. In addition to the problems which may arise from the operation of the specific population dynamics in different countries and between different social groups within those countries, there are those arising from the unequal distribution of agricultural land, foodstuffs, and wealth in general, those arising from the unjust organization of the international economy and from the obsolete international financial structure, and those deriving from the irrational use of resources for military spending and the manufacture and stockpiling of vast nuclear arsenals.

Reducing Teacher Turnover by Utilizing a National List of Reasons for Teacher Dissatisfaction or How to Keep Teachers from Declaring "Dear Folks, I Quit"

ERIC Educational Resources Information Center

Lopez, Angela J.

2010-01-01

Background: Teacher turnover is a national problem and has been investigated on the national level since the 1920's. This study compares the reasons teachers give for leaving teaching positions from data collected nationwide with local data. Purpose: To examine whether the same problems that arise on the local level have been identified in the…

[Problems in implementing a pain management program for rheumatoid patients and studies of its effectiveness].

PubMed

Cziske, R; Jäckel, W; Jacobi, E

1987-01-01

A pain management program is presented which enables patients to reduce pain by means of relaxation and attention-diversion, etc. The problems arising from applying a psychological training to organic diseases, and the most favourable therapist's behaviour in facing these difficulties are elucidated. Finally, controlled studies are cited showing that pain can be reduced and the emotional state improved by pain management techniques.

Error Correcting Codes I. Applications of Elementary Algebra to Information Theory. Modules and Monographs in Undergraduate Mathematics and Its Applications Project. UMAP Unit 346.

ERIC Educational Resources Information Center

Rice, Bart F.; Wilde, Carroll O.

It is noted that with the prominence of computers in today's technological society, digital communication systems have become widely used in a variety of applications. Some of the problems that arise in digital communications systems are described. This unit presents the problem of correcting errors in such systems. Error correcting codes are…

The Social Implications of Light at Night

NASA Astrophysics Data System (ADS)

Henshaw, Colin

2015-08-01

Summary: It has been shown that Light at Night (LAN) has serious implications for both the environment and human health. What is considered here are the social implications that arise from these problems, and what needs to be done to redress these issues.Introduction: Light at Night is a serious environmental problem whose environmental and medical implications have been seriously underestimated. If no action is taken the problem will become progressively worse and may reach a point where nothing can be done about it. The issues arising from it need to be identified andappropriate action taken to mitigate these issues as far as possible. Hopefully this can be done amicably by self regulation within communities, but if this fails then stringent anti-light pollution legislation will have to be enacted. Some countries and local authorities have already begun to make faltering steps in this direction1, but so far the measures taken have been minimal and largely ineffective. Light at Night (and the light pollution resulting from it) therefore remains a problem and continues to get worse despite the measures already taken to reduce it. Domes of scattered light continue to hang above our cities, killing off our wildlife and endangering public health. Attitudes need to change and urgent measures need to be taken in order to reduce or eliminate its impact.

Combining nutrient intake from food/beverages and vitamin/mineral supplements.

PubMed

Garriguet, Didier

2010-12-01

To calculate total intake of a nutrient and estimate inadequate intake for a population, the amounts derived from food/beverages and from vitamin/mineral supplements must be combined. The two methods Statistics Canada has suggested present problems of interpretation. Data collected from 34,386 respondents to the 2004 Canadian Community Health Survey-Nutrition were used to compare four methods of combining nutrient intake from food/beverages and vitamin/mineral supplements: adding average intake from supplements to the 24-hour food/beverage recall and estimating the usual distribution in the population (Method 1); estimating usual individual intake from food? beverages and adding intake from supplements (Method 2); and dividing the population into supplement users and non-users and applying Method 1 or Method 2 and combining the estimates based on the percentages of users and non-users (Methods 3 and 4). Interpretation problems arise with Methods 1 and 2; for example, the percentage of the population with inadequate intake of vitamin C and folate equivalents falls outside the expected minimum-maximum range. These interpretation problems are not observed with Methods 3 and 4. Interpretation problems that may arise in combining food and supplement intake of a given nutrient are overcome if the population is divided into supplement users and non-users before Method 1 or Method 2 is applied.

A process for Decision-making after Pilot and feasibility Trials (ADePT): development following a feasibility study of a complex intervention for pelvic organ prolapse

PubMed Central

2013-01-01

Background Current Medical Research Council (MRC) guidance on complex interventions advocates pilot trials and feasibility studies as part of a phased approach to the development, testing, and evaluation of healthcare interventions. In this paper we discuss the results of a recent feasibility study and pilot trial for a randomized controlled trial (RCT) of pelvic floor muscle training for prolapse (ClinicalTrials.gov: NCT01136889). The ways in which researchers decide to respond to the results of feasibility work may have significant repercussions for both the nature and degree of tension between internal and external validity in a definitive trial. Methods We used methodological issues to classify and analyze the problems that arose in the feasibility study. Four centers participated with the aim of randomizing 50 women. Women were eligible if they had prolapse of any type, of stage I to IV, and had a pessary successfully fitted. Postal questionnaires were administered at baseline, 6 months, and 7 months post-randomization. After identifying problems arising within the pilot study we then sought to locate potential solutions that might minimize the trade-off between a subsequent explanatory versus pragmatic trial. Results The feasibility study pointed to significant potential problems in relation to participant recruitment, features of the intervention, acceptability of the intervention to participants, and outcome measurement. Finding minimal evidence to support our decision-making regarding the transition from feasibility work to a trial, we developed a systematic process (A process for Decision-making after Pilot and feasibility Trials (ADePT)) which we subsequently used as a guide. The process sought to: 1) encourage the systematic identification and appraisal of problems and potential solutions; 2) improve the transparency of decision-making processes; and 3) reveal the tensions that exist between pragmatic and explanatory choices. Conclusions We have developed a process that may aid researchers in their attempt to identify the most appropriate solutions to problems identified within future pilot and feasibility RCTs. The process includes three key steps: a decision about the type of problem, the identification of all solutions (whether addressed within the intervention, trial design or clinical context), and a systematic appraisal of these solutions. PMID:24160371

Optimal design of groundwater remediation system using a probabilistic multi-objective fast harmony search algorithm under uncertainty

NASA Astrophysics Data System (ADS)

Luo, Qiankun; Wu, Jianfeng; Yang, Yun; Qian, Jiazhong; Wu, Jichun

2014-11-01

This study develops a new probabilistic multi-objective fast harmony search algorithm (PMOFHS) for optimal design of groundwater remediation systems under uncertainty associated with the hydraulic conductivity (K) of aquifers. The PMOFHS integrates the previously developed deterministic multi-objective optimization method, namely multi-objective fast harmony search algorithm (MOFHS) with a probabilistic sorting technique to search for Pareto-optimal solutions to multi-objective optimization problems in a noisy hydrogeological environment arising from insufficient K data. The PMOFHS is then coupled with the commonly used flow and transport codes, MODFLOW and MT3DMS, to identify the optimal design of groundwater remediation systems for a two-dimensional hypothetical test problem and a three-dimensional Indiana field application involving two objectives: (i) minimization of the total remediation cost through the engineering planning horizon, and (ii) minimization of the mass remaining in the aquifer at the end of the operational period, whereby the pump-and-treat (PAT) technology is used to clean up contaminated groundwater. Also, Monte Carlo (MC) analysis is employed to evaluate the effectiveness of the proposed methodology. Comprehensive analysis indicates that the proposed PMOFHS can find Pareto-optimal solutions with low variability and high reliability and is a potentially effective tool for optimizing multi-objective groundwater remediation problems under uncertainty.

The Persistent Issue of Simulator Sickness in Naval Aviation Training.

PubMed

Geyer, Daniel J; Biggs, Adam T

2018-04-01

Virtual simulations offer nearly unlimited training potential for naval aviation due to the wide array of scenarios that can be simulated in a safe, reliable, and cost-effective environment. This versatility has created substantial interest in using existing and emerging virtual technology to enhance training scenarios. However, the virtual simulations themselves may hinder training initiatives by inducing simulator sickness among the trainees, which is a series of symptoms similar to motion sickness that can arise from simulator use. Simulator sickness has been a problem for military aviation since the first simulators were introduced. The problem has also persisted despite the increasing fidelity and sense of immersion offered by new generations of simulators. As such, it is essential to understand the various problems so that trainers can ensure the best possible use of the simulators. This review will examine simulator sickness as it pertains to naval aviation training. Topics include: the prevailing theories on why symptoms develop, methods of measurement, contributing factors, effects on training, effects when used shipboard, aftereffects, countermeasures, and recommendations for future research involving virtual simulations in an aviation training environment.Geyer DJ, Biggs AT. The persistent issue of simulator sickness in naval aviation training. Aerosp Med Hum Perform. 2018; 89(4):396-405.

Combining EEG and eye movement recording in free viewing: Pitfalls and possibilities.

PubMed

Nikolaev, Andrey R; Meghanathan, Radha Nila; van Leeuwen, Cees

2016-08-01

Co-registration of EEG and eye movement has promise for investigating perceptual processes in free viewing conditions, provided certain methodological challenges can be addressed. Most of these arise from the self-paced character of eye movements in free viewing conditions. Successive eye movements occur within short time intervals. Their evoked activity is likely to distort the EEG signal during fixation. Due to the non-uniform distribution of fixation durations, these distortions are systematic, survive across-trials averaging, and can become a source of confounding. We illustrate this problem with effects of sequential eye movements on the evoked potentials and time-frequency components of EEG and propose a solution based on matching of eye movement characteristics between experimental conditions. The proposal leads to a discussion of which eye movement characteristics are to be matched, depending on the EEG activity of interest. We also compare segmentation of EEG into saccade-related epochs relative to saccade and fixation onsets and discuss the problem of baseline selection and its solution. Further recommendations are given for implementing EEG-eye movement co-registration in free viewing conditions. By resolving some of the methodological problems involved, we aim to facilitate the transition from the traditional stimulus-response paradigm to the study of visual perception in more naturalistic conditions. Copyright © 2016 Elsevier Inc. All rights reserved.

Zeta potential control for electrophoresis cells

NASA Technical Reports Server (NTRS)

Fogal, G. L.

1973-01-01

Zeta potential arises from fact that ions tend to be adsorbed on surface of cell walls. This potential interfaces with electric field sensed by migrating particles and degrades resolution of separation. By regulating sign and magnitude of applied potential induced charge can be used to increase or decrease effective wall zeta potential.

Acaricide resistance mechanisms in Rhipicephalus microplus

USDA-ARS?s Scientific Manuscript database

Acaricide resistance has become widespread in countries where cattle ticks, Rhipicephalus (Boophilus) microplus, are a problem. Resistance arises through genetic changes in a cattle tick population that causes modifications to the target site, increased metabolism or sequestration of the acaricide, ...

Sixth-Graders Learning on "Spaceship Earth"

ERIC Educational Resources Information Center

Journal of Aerospace Education, 1974

1974-01-01

Describes a classroom organized as a self-contained closed spaceship which provides an opportunity for individualized learning based on student interests and a chance to wrestle with the problems that would arise on an interstellar journey in a spaceship. (BR)

Application of the Bootstrap Methods in Factor Analysis.

ERIC Educational Resources Information Center

Ichikawa, Masanori; Konishi, Sadanori

1995-01-01

A Monte Carlo experiment was conducted to investigate the performance of bootstrap methods in normal theory maximum likelihood factor analysis when the distributional assumption was satisfied or unsatisfied. Problems arising with the use of bootstrap methods are highlighted. (SLD)

The problem with multiple robots

NASA Technical Reports Server (NTRS)

Huber, Marcus J.; Kenny, Patrick G.

1994-01-01

The issues that can arise in research associated with multiple, robotic agents are discussed. Two particular multi-robot projects are presented as examples. This paper was written in the hope that it might ease the transition from single to multiple robot research.

Shelter as Workplace: A Review of Home-Based Enterprise in Developing Countries.

ERIC Educational Resources Information Center

Tipple, A. Graham

1993-01-01

Describes the most common types of home-based employment activities and looks at advantages and disadvantages of such small enterprises, their profitability, and measures that could be taken to solve problems that arise. (Author/JOW)

Working To Learn: A Holistic Approach to Young People's Education and Training.

ERIC Educational Resources Information Center

Senker, Peter; Rainbird, Helen; Evans, Karen; Hodkinson, Phil; Keep, Ewart; Maguire, Malcolm; Raffe, David; Unwin, Lorna

2000-01-01

Highlights deficiencies in current British policies on work-based learning for 16-19 year-olds. Discusses problems arising from employers' voluntary participation. Outlines a holistic approach based on the community of practice model. (SK)

Improving travel information products via robust estimation techniques : final report, March 2009.

DOT National Transportation Integrated Search

2009-03-01

Traffic-monitoring systems, such as those using loop detectors, are prone to coverage gaps, arising from sensor noise, processing errors and : transmission problems. Such gaps adversely affect the accuracy of Advanced Traveler Information Systems. Th...

Information retrieval algorithms: A survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghavan, P.

We give an overview of some algorithmic problems arising in the representation of text/image/multimedia objects in a form amenable to automated searching, and in conducting these searches efficiently. These operations are central to information retrieval and digital library systems.

Risk factors for readmission after neonatal cardiac surgery.

PubMed

Mackie, Andrew S; Gauvreau, Kimberlee; Newburger, Jane W; Mayer, John E; Erickson, Lars C

2004-12-01

Repeat hospitalizations place a significant burden on health care resources. Factors predisposing infants to unplanned hospital readmission after congenital heart surgery are unknown. This is a single-center, case-control study. Cases were rehospitalized or died within 30 days of discharge following an arterial switch operation (ASO) or Norwood procedure (NP) between 1992 and 2002. Controls underwent an ASO or NP between 1992 and 2002, and were neither readmitted nor died within 30 days of discharge. Patients and controls were matched by gender, year of birth, and procedure. Potential risk factors examined included indices of medical status at the time of discharge, determinants of access to health care, and provider characteristics. Forty-eight patients were readmitted; 19 of 498 (3.8%) following an ASO and 29 of 254 (11.4%) after a NP (p < 0.001). Six infants died within 30 days of discharge; 1 after an ASO and 5 after a NP. In multivariate analysis, predictors of readmission or death were: residual hemodynamic problem(s) (odds ratio [OR] 4.10 [1.18, 14.3], p = 0.026); an intensive care unit stay greater than 7 days (OR 5.17 [1.12, 23.9] p = 0.035) (ASO); residual hemodynamic problem(s) (OR 5.84 [1.98, 17.2], p = 0.001); and establishment of full oral intake less than 2 days before discharge (OR 5.83 [1.83, 18.6], p = 0.003) (NP). Combining both groups, living in a low income Zip Code (< 30,000 dollars/annum) was associated with a lower likelihood of readmission (OR 0.25 [0.07, 0.85], p = 0.027). Residual hemodynamic problem(s) predispose to hospital readmission after the ASO and NP. Low socioeconomic status may reduce the likelihood of readmission even when problems arise.

Effect of Students' Term and Educational Institution on the Arising of Indonesian Morphology-Syntactical Interference in ELLT

ERIC Educational Resources Information Center

Nurhayati, Dwi Astuti Wahyu; Djatmika; Santosa, Riyadi; Wiratno, Tri

2017-01-01

This research examines the two factors which effect on the raising of Indonesian morphology-syntactical interference. It aimed at delineating the potential effect of these two factors on the arising of Indonesian morphology-syntactical interference of undergraduate students majoring in English department of State Islamic Institute of Tulungagung…

Recent developments in the theory of protein folding: searching for the global energy minimum.

PubMed

Scheraga, H A

1996-04-16

Statistical mechanical theories and computer simulation are being used to gain an understanding of the fundamental features of protein folding. A major obstacle in the computation of protein structures is the multiple-minima problem arising from the existence of many local minima in the multidimensional energy landscape of the protein. This problem has been surmounted for small open-chain and cyclic peptides, and for regular-repeating sequences of models of fibrous proteins. Progress is being made in resolving this problem for globular proteins.

Training effectiveness assessment: Methodological problems and issues

NASA Technical Reports Server (NTRS)

Cross, Kenneth D.

1992-01-01

The U.S. military uses a large number of simulators to train and sustain the flying skills of helicopter pilots. Despite the enormous resources required to purchase, maintain, and use those simulators, little effort has been expended in assessing their training effectiveness. One reason for this is the lack of an evaluation methodology that yields comprehensive and valid data at a practical cost. Some of these methodological problems and issues that arise in assessing simulator training effectiveness, as well as problems with the classical transfer-of-learning paradigm were discussed.

Phase retrieval by constrained power inflation and signum flipping

NASA Astrophysics Data System (ADS)

Laganà, A. R.; Morabito, A. F.; Isernia, T.

2016-12-01

In this paper we consider the problem of retrieving a signal from the modulus of its Fourier transform (or other suitable transformations) and some additional information, which is also known as "Phase Retrieval" problem. The problem arises in many areas of applied Sciences such as optics, electron microscopy, antennas, and crystallography. In particular, we introduce a new approach, based on power inflation and tunneling, allowing an increased robustness with respect to the possible occurrence of false solutions. Preliminary results are presented for the simple yet relevant case of one-dimensional arrays and noisy data.

[Problems in the admission to in-hospital oral surgical care from the patient's viewpoint--results of patient interviews in the hospital for dental and maxillo-facial surgery of the Karl Marx University, Leipzig].

PubMed

Erpenbeck, F; Birnbaum, K; Langanke, B; Niemand, B; Thomzyk, I

1979-06-01

The author deals with the results from the interviewing of oral surgery patients on their problems concerning the sending and the admission to the hospital, with special attention to the problems of waiting for admission, the familiarization with the clinical environment and the improvement suggestions of the patients. The conclusions concern tasks arising from the medical and dental care for inpatients as well as for outpatients.

Numerical solution of inverse scattering for near-field optics.

PubMed

Bao, Gang; Li, Peijun

2007-06-01

A novel regularized recursive linearization method is developed for a two-dimensional inverse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium located on a substrate from data accessible through photon scanning tunneling microscopy experiments. Based on multiple frequency scattering data, the method starts from the Born approximation corresponding to weak scattering at a low frequency, and each update is obtained by continuation on the wavenumber from solutions of one forward problem and one adjoint problem of the Helmholtz equation.

A shape prior-based MRF model for 3D masseter muscle segmentation

NASA Astrophysics Data System (ADS)

Majeed, Tahir; Fundana, Ketut; Lüthi, Marcel; Beinemann, Jörg; Cattin, Philippe

2012-02-01

Medical image segmentation is generally an ill-posed problem that can only be solved by incorporating prior knowledge. The ambiguities arise due to the presence of noise, weak edges, imaging artifacts, inhomogeneous interior and adjacent anatomical structures having similar intensity profile as the target structure. In this paper we propose a novel approach to segment the masseter muscle using the graph-cut incorporating additional 3D shape priors in CT datasets, which is robust to noise; artifacts; and shape deformations. The main contribution of this paper is in translating the 3D shape knowledge into both unary and pairwise potentials of the Markov Random Field (MRF). The segmentation task is casted as a Maximum-A-Posteriori (MAP) estimation of the MRF. Graph-cut is then used to obtain the global minimum which results in the segmentation of the masseter muscle. The method is tested on 21 CT datasets of the masseter muscle, which are noisy with almost all possessing mild to severe imaging artifacts such as high-density artifacts caused by e.g. the very common dental fillings and dental implants. We show that the proposed technique produces clinically acceptable results to the challenging problem of muscle segmentation, and further provide a quantitative and qualitative comparison with other methods. We statistically show that adding additional shape prior into both unary and pairwise potentials can increase the robustness of the proposed method in noisy datasets.

The role of potential agents in making spatial perspective taking social

PubMed Central

Clements-Stephens, Amy M.; Vasiljevic, Katarina; Murray, Alexandra J.; Shelton, Amy L.

2013-01-01

A striking relationship between visual spatial perspective taking (VSPT) and social skills has been demonstrated for perspective-taking tasks in which the target of the imagined or inferred perspective is a potential agent, suggesting that the presence of a potential agent may create a social context for the seemingly spatial task of imagining a novel visual perspective. In a series of studies, we set out to investigate how and when a target might be viewed as sufficiently agent-like to incur a social influence on VSPT performance. By varying the perceptual and conceptual features that defined the targets as potential agents, we find that even something as simple as suggesting animacy for a simple wooden block may be sufficient. More critically, we found that experience with one potential agent influenced the performance with subsequent targets, either by inducing or eliminating the influence of social skills on VSPT performance. These carryover effects suggest that the relationship between social skills and VSPT performance is mediated by a complex relationship that includes the task, the target, and the context in which that target is perceived. These findings highlight potential problems that arise when identifying a task as belonging exclusively to a single cognitive domain and stress instead the highly interactive nature of cognitive domains and their susceptibility to cross-domain individual differences. PMID:24046735

The problems inherent in teaching technical writing and report writing to native Americans

NASA Technical Reports Server (NTRS)

Zukowski/faust, J.

1981-01-01

Teaching technical writing to Native Americans contending with a second language and culture is addressed. Learning difficulties arising from differences between native and acquired language and cultural systems are examined. Compartmentalized teaching, which presents the ideals of technical writing in minimal units, and skills development are considered. Rhetorical problems treated include logic of arrangement, selection of support and scope of detail, and time and space. Specific problems selected include the concept of promptness, the contextualization of purpose, interpersonal relationships, wordiness, mixture of registers, and the problem of abstracting. Four inductive procedures for students having writing and perception problems are included. Four sample exercises and a bibliography of 13 references are also included.

Estimation of Magnetic Field Growth and Construction of Adaptive Mesh in Corner Domain for the Magnetostatic Problem in Three-Dimensional Space

NASA Astrophysics Data System (ADS)

Perepelkin, Eugene; Tarelkin, Aleksandr

2018-02-01

A magnetostatics problem arises when searching for the distribution of the magnetic field generated by magnet systems of many physics research facilities, e.g., accelerators. The domain in which the boundary-value problem is solved often has a piecewise smooth boundary. In this case, numerical calculations of the problem require consideration of the solution behavior in the corner domain. In this work we obtained an upper estimation of the magnetic field growth using integral formulation of the magnetostatic problem and propose a method for condensing the differential mesh near the corner domain of the vacuum in the three-dimensional space based on this estimation.

Statistical mechanics of budget-constrained auctions

NASA Astrophysics Data System (ADS)

Altarelli, F.; Braunstein, A.; Realpe-Gomez, J.; Zecchina, R.

2009-07-01

Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise.

Mind over matter? I: philosophical aspects of the mind-brain problem.

PubMed

Schimmel, P

2001-08-01

To conceptualize the essence of the mind-body or mind-brain problem as one of metaphysics rather than science, and to propose a formulation of the problem in the context of current scientific knowledge and its limitations. The background and conceptual parameters of the mind-body problem are delineated, and the limitations of brain research in formulating a solution identified. The problem is reformulated and stated in terms of two propositions. These constitute a 'double aspect theory'. The problem appears to arise as a consequence of the conceptual limitations of the human mind, and hence remains essentially a metaphysical one. A 'double aspect theory' recognizes the essential unity of mind and brain, while remaining consistent with the dualism inherent in human experience.

Guaranteed estimation of solutions to Helmholtz transmission problems with uncertain data from their indirect noisy observations

NASA Astrophysics Data System (ADS)

Podlipenko, Yu. K.; Shestopalov, Yu. V.

2017-09-01

We investigate the guaranteed estimation problem of linear functionals from solutions to transmission problems for the Helmholtz equation with inexact data. The right-hand sides of equations entering the statements of transmission problems and the statistical characteristics of observation errors are supposed to be unknown and belonging to certain sets. It is shown that the optimal linear mean square estimates of the above mentioned functionals and estimation errors are expressed via solutions to the systems of transmission problems of the special type. The results and techniques can be applied in the analysis and estimation of solution to forward and inverse electromagnetic and acoustic problems with uncertain data that arise in mathematical models of the wave diffraction on transparent bodies.

On sampling biases arising from insufficient bottle flushing

NASA Astrophysics Data System (ADS)

Codispoti, L. A.; Paver, C. R.

2016-02-01

Collection of representative water samples using carousel bottles is important for accurately determining biological and chemical gradients. The development of more technologically advanced instrumentation and sampling apparatus causes sampling packages to increase and "soak times" to decrease, increasing the probability that insufficient bottle flushing will produce biased results. Qualitative evidence from various expeditions suggest that insufficient flushing may be a problem. Here we report on multiple field experiments that were conducted to better quantify the errors that can arise from insufficient bottle flushing. Our experiments suggest that soak times of more than 2 minutes are sometimes required to collect a representative sample.

Impact of Coulomb potential on peak structures arising in momentum and low-energy photoelectron spectra produced in strong-field ionization of laser-irradiated atoms

NASA Astrophysics Data System (ADS)

Pyak, P. E.; Usachenko, V. I.

2018-03-01

The phenomenon of pronounced peak structure(s) of longitudinal momentum distributions as well as a spike-like structure of low-energy spectra of photoelectrons emitted from laser-irradiated Ar and Ne atoms in a single ionization process is theoretically studied in the tunneling and multiphoton regimes of ionization. The problem is addressed assuming only the direct above-threshold ionization (ATI) as a physical mechanism underlying the phenomenon under consideration (viz. solely contributing to observed photoelectron momentum distributions (PMD)) and using the Coulomb-Volkov (CV) ansatz within the frame of conventional strong-field approximation (SFA) applied in the length-gauge formulation. The developed CV-SFA approach also incorporates the density functional theory essentially exploited for numerical composition of initial (laser-free) atomic state(s) constructed from atomic orbitals of Gaussian type. Our presented CV-SFA based (and laser focal-volume averaged) calculation results proved to be well reproducing both the pronounced double-peak and/or ATI-like multi-peak structure(s) experimentally observed in longitudinal PMD under conditions of tunneling and/or multiphoton regime, respectively. In addition, our CV-SFA results presented for tunneling regime also suggest and remarkably reproduce a pronounced structure observed in relevant experiments as a ‘spike-like’ enhanced maximum arising in low-energy region (around the value of about 1 eV) of photoelectron spectra. The latter consistency allows to identify and interpret these results as the so-called low-energy structure (LES) since the phenomenon proved to appear as the most prominent if the influence of Coulomb potential on photoelectron continuum states is maximally taken into account under calculations (viz. if the parameter Z in CV’s functions is put equal to 1). Moreover, the calculated LES proved to correspond (viz., established as closely related) to the mentioned double-peak structure arising in the low-momentum region ({p}| | ≤slant | 0.2| a.u.) of longitudinal PMDs calculated under condition of the tunneling regime. Thus, the phenomena under consideration can be well understood and adequately interpreted beyond the terms and/or concepts of various different alternative strong-field approaches and models (such as e.g., extensively invoked and exploited nowadays though, more sophisticated SFA-based ‘rescattering’ mechanism) compared to which, the currently applied CV-SFA model (through the same underlying physical mechanism of solely direct ATI suggested) is additionally able to provide and reveal an intimate and transparent interrelation between the phenomena of LES and double-peak structure arising in PMDs observed in the tunneling regime.

Digital Discourses in Early Childhood Educator Online Learning

ERIC Educational Resources Information Center

Hoffman, Emily Brown

2017-01-01

Active, dialogic participation is a necessary component of high quality teacher professional learning (Dunst, Bruder, & Hamby, 2015). However, logistical problems arise when implementing cooperative learning opportunities for early childhood educators, as preschool teachers are habitually separated from peers both institutionally and…

West Indians and Afro-Americans: A Partnership

ERIC Educational Resources Information Center

Best, Tony

1975-01-01

In addition to the difficulties connected with their status as immigrants, West Indians must contend with the problems arising because of their blackness. The ties that bind Afro-Americans and West Indians together are said to consist in survival processes. (Author/AM)

Cold Confusion.

ERIC Educational Resources Information Center

Fogle, Pamela W.

1991-01-01

Public relations issues arising from the University of Utah's controversial announcement of research claiming achievement of nuclear fusion at room temperature are discussed. They include problems occurring before and after the initial press conference, secrecy vs. openness, research ethics, and effects lasting past the original incident and…

Algebraic methods in system theory

NASA Technical Reports Server (NTRS)

Brockett, R. W.; Willems, J. C.; Willsky, A. S.

1975-01-01

Investigations on problems of the type which arise in the control of switched electrical networks are reported. The main results concern the algebraic structure and stochastic aspects of these systems. Future reports will contain more detailed applications of these results to engineering studies.

Modelling skin penetration using the Laplace transform technique.

PubMed

Anissimov, Y G; Watkinson, A

2013-01-01

The Laplace transform is a convenient mathematical tool for solving ordinary and partial differential equations. The application of this technique to problems arising in drug penetration through the skin is reviewed in this paper. © 2013 S. Karger AG, Basel.

48 CFR 252.228-7006 - Compliance with Spanish laws and insurance.

Code of Federal Regulations, 2010 CFR

2010-10-01

... damages as a result of death or injury to personnel or damage to real or personal property related to the... submission to Spanish law and jurisdiction of any problem that may arise with regard to the interpretation or...

48 CFR 252.228-7006 - Compliance with Spanish laws and insurance.

Code of Federal Regulations, 2011 CFR

2011-10-01

... damages as a result of death or injury to personnel or damage to real or personal property related to the... submission to Spanish law and jurisdiction of any problem that may arise with regard to the interpretation or...

The Design of Archives Buildings.

ERIC Educational Resources Information Center

Faye, Bernard

1982-01-01

Studies specific problems arising from design of archives buildings and examines three main purposes of this type of building, namely conservation, classification and restoration of archives, and the provision of access to them by administrators and research workers. Three references are listed. (Author/EJS)

Planning for Power.

ERIC Educational Resources Information Center

Failla, Victor A.; Birk, Thomas A.

1999-01-01

Discusses the electrical power problems that can arise when schools try to integrate educational technology components into an existing facility, and how to plan the electrical power design to avoid power failures. Examines setting objectives, evaluating current electrical conditions, and developing the technology power design. (GR)

Military Instructor Training in Transition

DTIC Science & Technology

1975-05-01

RNSETT 51 supervision at a training establishment; they finally return to the school for a further two weeks of consolidation. The embryo Instructor...seriously the ideal concept of individualization, severe problems could arise over the question of who controls the destinies of learners. Institutions

Interplanetary Trajectories, Encke Method (ITEM)

NASA Technical Reports Server (NTRS)

Whitlock, F. H.; Wolfe, H.; Lefton, L.; Levine, N.

1972-01-01

Modified program has been developed using improved variation of Encke method which avoids accumulation of round-off errors and avoids numerical ambiguities arising from near-circular orbits of low inclination. Variety of interplanetary trajectory problems can be computed with maximum accuracy and efficiency.

A note on the regularity of solutions of infinite dimensional Riccati equations

NASA Technical Reports Server (NTRS)

Burns, John A.; King, Belinda B.

1994-01-01

This note is concerned with the regularity of solutions of algebraic Riccati equations arising from infinite dimensional LQR and LQG control problems. We show that distributed parameter systems described by certain parabolic partial differential equations often have a special structure that smoothes solutions of the corresponding Riccati equation. This analysis is motivated by the need to find specific representations for Riccati operators that can be used in the development of computational schemes for problems where the input and output operators are not Hilbert-Schmidt. This situation occurs in many boundary control problems and in certain distributed control problems associated with optimal sensor/actuator placement.

Geometrically derived difference formulae for the numerical integration of trajectory problems

NASA Technical Reports Server (NTRS)

Mcleod, R. J. Y.; Sanz-Serna, J. M.

1981-01-01

The term 'trajectory problem' is taken to include problems that can arise, for instance, in connection with contour plotting, or in the application of continuation methods, or during phase-plane analysis. Geometrical techniques are used to construct difference methods for these problems to produce in turn explicit and implicit circularly exact formulae. Based on these formulae, a predictor-corrector method is derived which, when compared with a closely related standard method, shows improved performance. It is found that this latter method produces spurious limit cycles, and this behavior is partly analyzed. Finally, a simple variable-step algorithm is constructed and tested.

Finite element methods on supercomputers - The scatter-problem

NASA Technical Reports Server (NTRS)

Loehner, R.; Morgan, K.

1985-01-01

Certain problems arise in connection with the use of supercomputers for the implementation of finite-element methods. These problems are related to the desirability of utilizing the power of the supercomputer as fully as possible for the rapid execution of the required computations, taking into account the gain in speed possible with the aid of pipelining operations. For the finite-element method, the time-consuming operations may be divided into three categories. The first two present no problems, while the third type of operation can be a reason for the inefficient performance of finite-element programs. Two possibilities for overcoming certain difficulties are proposed, giving attention to a scatter-process.

Additive schemes for certain operator-differential equations

NASA Astrophysics Data System (ADS)

Vabishchevich, P. N.

2010-12-01

Unconditionally stable finite difference schemes for the time approximation of first-order operator-differential systems with self-adjoint operators are constructed. Such systems arise in many applied problems, for example, in connection with nonstationary problems for the system of Stokes (Navier-Stokes) equations. Stability conditions in the corresponding Hilbert spaces for two-level weighted operator-difference schemes are obtained. Additive (splitting) schemes are proposed that involve the solution of simple problems at each time step. The results are used to construct splitting schemes with respect to spatial variables for nonstationary Navier-Stokes equations for incompressible fluid. The capabilities of additive schemes are illustrated using a two-dimensional model problem as an example.

Radial Artery Coursing Behind the Biceps Brachii Tendon: Significance for the Transradial Catheterization and a Clinically Oriented Classification of the Radial Artery Variations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jelev, L., E-mail: ljelev@abv.bg; Surchev, L.

2008-09-15

In routine clinical practice the variations of the radial artery are the main reason for technical failure during transradial catheterization. If these variations are well documented, however, they do not represent a problem in the transradial approach. Therefore, we report here a rare case of the radial artery which is very strange but potentially valuable for the clinical practice: it arises at a right angle from the brachial artery and passes behind the biceps brachii tendon. Based on our findings and on an extensive literature review, we propose for the first time a clinically oriented classification of the variations ofmore » the radial artery. This classification is related to the catheterization success at the usual access site of the radial artery at the wrist.« less

Naturalness from a composite top?

DOE PAGES

Pierce, Aaron; Zhao, Yue

2017-01-12

Here, we consider a theory with composite top quarks but an elementary Higgs boson. The hierarchy problem can be solved by supplementing TeV scale top compositeness with either supersymmetry or Higgs compositeness appearing at the multi-TeV scale. Furthermore, the Higgs boson couples to uncolored partons within the top quark. We also study how this approach can give rise to a novel screening effect that suppresses production of the colored top partners at the LHC. Strong constraints arise from Z tomore » $$\\bar{b}$$b, as well potentially from avor physics. Independent of flavor considerations, current constraints imply a compositeness scale &TeV; this implies that the model is likely tuned at the percent level. Four top quark production at the LHC is a smoking-gun probe of this scenario. New CP violation in D meson mixing is also possible.« less

Sparse learning of stochastic dynamical equations

NASA Astrophysics Data System (ADS)

Boninsegna, Lorenzo; Nüske, Feliks; Clementi, Cecilia

2018-06-01

With the rapid increase of available data for complex systems, there is great interest in the extraction of physically relevant information from massive datasets. Recently, a framework called Sparse Identification of Nonlinear Dynamics (SINDy) has been introduced to identify the governing equations of dynamical systems from simulation data. In this study, we extend SINDy to stochastic dynamical systems which are frequently used to model biophysical processes. We prove the asymptotic correctness of stochastic SINDy in the infinite data limit, both in the original and projected variables. We discuss algorithms to solve the sparse regression problem arising from the practical implementation of SINDy and show that cross validation is an essential tool to determine the right level of sparsity. We demonstrate the proposed methodology on two test systems, namely, the diffusion in a one-dimensional potential and the projected dynamics of a two-dimensional diffusion process.

Recent advances in the molecular design of synthetic vaccines

NASA Astrophysics Data System (ADS)

Jones, Lyn H.

2015-12-01

Vaccines have typically been prepared using whole organisms. These are normally either attenuated bacteria or viruses that are live but have been altered to reduce their virulence, or pathogens that have been inactivated and effectively killed through exposure to heat or formaldehyde. However, using whole organisms to elicit an immune response introduces the potential for infections arising from a reversion to a virulent form in live pathogens, unproductive reactions to vaccine components or batch-to-batch variability. Synthetic vaccines, in which a molecular antigen is conjugated to a carrier protein, offer the opportunity to circumvent these problems. This Perspective will highlight the progress that has been achieved in developing synthetic vaccines using a variety of molecular antigens. In particular, the different approaches used to develop conjugate vaccines using peptide/proteins, carbohydrates and other small molecule haptens as antigens are compared.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Aaron; Zhao, Yue

Here, we consider a theory with composite top quarks but an elementary Higgs boson. The hierarchy problem can be solved by supplementing TeV scale top compositeness with either supersymmetry or Higgs compositeness appearing at the multi-TeV scale. Furthermore, the Higgs boson couples to uncolored partons within the top quark. We also study how this approach can give rise to a novel screening effect that suppresses production of the colored top partners at the LHC. Strong constraints arise from Z tomore » $$\\bar{b}$$b, as well potentially from avor physics. Independent of flavor considerations, current constraints imply a compositeness scale &TeV; this implies that the model is likely tuned at the percent level. Four top quark production at the LHC is a smoking-gun probe of this scenario. New CP violation in D meson mixing is also possible.« less

The adolescence of a thirteenth-century visionary nun.

PubMed

Kroll, J; De Ganck, R

1986-11-01

Among the most notable features of the religious revival in western Europe in the early thirteenth century was the development of mysticism among the nuns and religious women of the lowlands. As scholarly attention becomes increasingly focused on this group of remarkable women, the question arises whether a psychiatric viewpoint has something of value to offer to the understanding of such individuals and the culture in which they struggled. The methodological and intellectual problems inherent in examining the life of a thirteenth-century mystic with a twentieth-century empirical frame of reference are illustrated in this study of the adolescence of Beatrice of Nazareth. Beatrice's stormy asceticism, ecstatic states and mood swings lend themselves to potentially competing hypotheses regarding the spiritual and psychopathological significance of her adolescent development and eventual life-course. Common grounds for reconciling these alternative models are discussed.

Quantization of the nonlinear sigma model revisited

NASA Astrophysics Data System (ADS)

Nguyen, Timothy

2016-08-01

We revisit the subject of perturbatively quantizing the nonlinear sigma model in two dimensions from a rigorous, mathematical point of view. Our main contribution is to make precise the cohomological problem of eliminating potential anomalies that may arise when trying to preserve symmetries under quantization. The symmetries we consider are twofold: (i) diffeomorphism covariance for a general target manifold; (ii) a transitive group of isometries when the target manifold is a homogeneous space. We show that there are no anomalies in case (i) and that (ii) is also anomaly-free under additional assumptions on the target homogeneous space, in agreement with the work of Friedan. We carry out some explicit computations for the O(N)-model. Finally, we show how a suitable notion of the renormalization group establishes the Ricci flow as the one loop renormalization group flow of the nonlinear sigma model.

Complications of Bariatric Surgery: What You Can Expect to See in Your GI Practice.

PubMed

Schulman, Allison R; Thompson, Christopher C

2017-11-01

Obesity is one of the most significant health problems worldwide. Bariatric surgery has become one of the fastest growing operative procedures and has gained acceptance as the leading option for weight-loss. Despite improvement in the performance of bariatric surgical procedures, complications are not uncommon. There are a number of unique complications that arise in this patient population and require specific knowledge for proper management. Furthermore, conditions unrelated to the altered anatomy typically require a different management strategy. As such, a basic understanding of surgical anatomy, potential complications, and endoscopic tools and techniques for optimal management is essential for the practicing gastroenterologist. Gastroenterologists should be familiar with these procedures and complication management strategies. This review will cover these topics and focus on major complications that gastroenterologists will be most likely to see in their practice.

Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

DOE PAGES

Baczewski, Andrew David; Dault, Daniel L.; Shanker, Balasubramaniam

2012-07-03

We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within themore » context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.« less

Value gaps in dental practice: understanding how differences in core values can adversely affect the practice.

PubMed

Newsome, Philip; Wolfe, Ira S

2003-11-01

The authors explore the importance of human values in dental practice, an area often overlooked as we struggle to deal with the everyday demands of treating patients and managing staff members. Such values are, however, fundamental to the success of any practice; therefore, it is important to understand their significance. Problems arise in dental practices when gaps develop between the values held by the various players involved (that is, between the entire dental team and patients, the dentist/owner's personal values and business goals, the dentist/owner and staff members, and the dental practice and any third-party funding organizations). By understanding the potentially damaging consequences of value gaps for practice viability, dental practice owners and managers can take steps to create a more harmonious workplace in which all parties strive to reach common goals.

Crystallization in Two Dimensions and a Discrete Gauss-Bonnet Theorem

NASA Astrophysics Data System (ADS)

De Luca, L.; Friesecke, G.

2018-02-01

We show that the emerging field of discrete differential geometry can be usefully brought to bear on crystallization problems. In particular, we give a simplified proof of the Heitmann-Radin crystallization theorem (Heitmann and Radin in J Stat Phys 22(3):281-287, 1980), which concerns a system of N identical atoms in two dimensions interacting via the idealized pair potential V(r)=+∞ if r<1, -1 if r=1, 0 if r>1. This is done by endowing the bond graph of a general particle configuration with a suitable notion of discrete curvature, and appealing to a discrete Gauss-Bonnet theorem (Knill in Elem Math 67:1-7, 2012) which, as its continuous cousins, relates the sum/integral of the curvature to topological invariants. This leads to an exact geometric decomposition of the Heitmann-Radin energy into (i) a combinatorial bulk term, (ii) a combinatorial perimeter, (iii) a multiple of the Euler characteristic, and (iv) a natural topological energy contribution due to defects. An analogous exact geometric decomposition is also established for soft potentials such as the Lennard-Jones potential V(r)=r^{-6}-2r^{-12}, where two additional contributions arise, (v) elastic energy and (vi) energy due to non-bonded interactions.

Investigating the Wicked Problems of (Un)sustainability Through Three Case Studies Around the Water-Energy-Food Nexus

NASA Astrophysics Data System (ADS)

Metzger, E. P.; Curren, R. R.

2016-12-01

Effective engagement with the problems of sustainability begins with an understanding of the nature of the challenges. The entanglement of interacting human and Earth systems produces solution-resistant dilemmas that are often portrayed as wicked problems. As introduced by urban planners Rittel and Webber (1973), wicked problems are "dynamically complex, ill-structured, public problems" arising from complexity in both biophysical and socio-economic systems. The wicked problem construct is still in wide use across diverse contexts, disciplines, and sectors. Discourse about wicked problems as related to sustainability is often connected to discussion of complexity or complex systems. In preparation for life and work in an uncertain, dynamic and hyperconnected world, students need opportunities to investigate real problems that cross social, political and disciplinary divides. They need to grapple with diverse perspectives and values, and collaborate with others to devise potential solutions. Such problems are typically multi-casual and so intertangled with other problems that they cannot be resolved using the expertise and analytical tools of any single discipline, individual, or organization. We have developed a trio of illustrative case studies that focus on energy, water and food, because these resources are foundational, interacting, and causally connected in a variety of ways with climate destabilization. The three interrelated case studies progress in scale from the local and regional, to the national and international and include: 1) the 2010 Gulf of Mexico oil spill with examination of the multiple immediate and root causes of the disaster, its ecological, social, and economic impacts, and the increasing risk and declining energy return on investment associated with the relentless quest for fossil fuels; 2) development of Australia's innovative National Water Management System; and 3) changing patterns of food production and the intertwined challenge of managing transnational water resources in the rapidly growing Mekong Region of Southeast Asia. .

A numerical scheme for singularly perturbed reaction-diffusion problems with a negative shift via numerov method

NASA Astrophysics Data System (ADS)

Dinesh Kumar, S.; Nageshwar Rao, R.; Pramod Chakravarthy, P.

2017-11-01

In this paper, we consider a boundary value problem for a singularly perturbed delay differential equation of reaction-diffusion type. We construct an exponentially fitted numerical method using Numerov finite difference scheme, which resolves not only the boundary layers but also the interior layers arising from the delay term. An extensive amount of computational work has been carried out to demonstrate the applicability of the proposed method.

In-Toeing and Out-Toeing in Children

PubMed Central

Wiley, James J.

1987-01-01

In-toeing and out-toeing problems are generally physiologic variants that arise from in utero posturing, and that gradually correct spontaneously during the active growing years of the child. Few torsional deformities result in genuine problems. Most residual effects are cosmetic, compounded by the anguish of concerned relatives and friends. Rarely is operative correction warranted. If corrective surgery comes under consideration, it is usually deferred until the patient reaches the age of 10. PMID:21263851

A Joint Multitarget Estimator for the Joint Target Detection and Tracking Filter

DTIC Science & Technology

2015-06-27

function is the information theoretic part of the problem and aims for entropy maximization, while the second one arises from the constraint in the...objective functions in conflict. The first objective function is the information theo- retic part of the problem and aims for entropy maximization...theory. For the sake of completeness and clarity, we also summarize how each concept is utilized later. Entropy : A random variable is statistically

Cockpit resource management training

NASA Technical Reports Server (NTRS)

Yocum, M.; Foushee, C.

1984-01-01

Cockpit resource management which is a multifaceted concept is outlined. The system involves the effective coordination of many resources: aircraft systems, company, air traffic control, equipment, navigational aids, documents, and manuals. The main concept, however, is group interaction. Problems which arise from lack of coordination, decision making, and lack of communication are pointed out. Implementation by the regional airline industry of cockpit resource management, designed to deal with human interactions problems in the most cost effective manner, is discussed.

A Comparative Investigation of the Previous and New Secondary History Curriculum: The Issues of the Definition of the Aims and Objectives and the Selection of Curriculum Content

ERIC Educational Resources Information Center

Dinc, Erkan

2011-01-01

Discussions on history teaching in Turkey indicate that the previous versions of the history curriculum and the pedagogy of history in the country bear many problems and deficiencies. The problems of Turkish history curriculum mainly arise from the perspectives it takes and the selection of its content. Since 2003, there have been extensive…

The International Index of Erectile Function: a methodological critique and suggestions for improvement.

PubMed

Yule, Morag; Davison, Joyce; Brotto, Lori

2011-01-01

The International Index of Erectile Function is a well-worded and psychometrically valid self-report questionnaire widely used as the standard for the evaluation of male sexual function. However, some conceptual and statistical problems arise when using the measure with men who are not sexually active. These problems are illustrated using 2 empirical examples, and the authors provide recommended solutions to further strengthen the efficacy and validity of this measure.

Advance decision.

PubMed

Samuels, Alec; Barrister, J P

2007-10-01

In the UK, patients have a statutory right to refuse treatment. Parliament has authorised 'advance decision' whereby a person can specify his or her wishes regarding further medical treatment. Although the advance decision may give a person peace of mind, it could create real problems for doctors and other healthcare professionals. This article will examine the conditions and procedures surrounding the drawing up of an advance decision as well as some of the problems that could arise such as layman's language.

Development of a Parachute System for Deceleration of Flying Vehicles in Supersonic Regimes

NASA Astrophysics Data System (ADS)

Pilyugin, N. N.; Khlebnikov, V. S.

2010-09-01

Aerodynamic problems arising during design and development of braking systems for re-entry vehicles are analyzed. Aerodynamic phenomena and laws valid in a supersonic flow around a pair of bodies having different shapes are studied. Results of this research can be used in solving application problems (arrangement and optimization of experiments; design and development of various braking systems for re-entry vehicles moving with supersonic speeds in the atmosphere).

First-Order Hyperbolic System Method for Time-Dependent Advection-Diffusion Problems

DTIC Science & Technology

2014-03-01

accuracy, with rapid convergence over each physical time step, typically less than five Newton iter - ations. 1 Contents 1 Introduction 3 2 Hyperbolic...however, we employ the Gauss - Seidel (GS) relaxation, which is also an O(N) method for the discretization arising from hyperbolic advection-diffusion system...advection-diffusion scheme. The linear dependency of the iterations on Table 1: Boundary layer problem ( Convergence criteria: Residuals < 10−8.) log10Re

New Nonlinear Multigrid Analysis

NASA Technical Reports Server (NTRS)

Xie, Dexuan

1996-01-01

The nonlinear multigrid is an efficient algorithm for solving the system of nonlinear equations arising from the numerical discretization of nonlinear elliptic boundary problems. In this paper, we present a new nonlinear multigrid analysis as an extension of the linear multigrid theory presented by Bramble. In particular, we prove the convergence of the nonlinear V-cycle method for a class of mildly nonlinear second order elliptic boundary value problems which do not have full elliptic regularity.

Iterative Methods for Solving Nonlinear Parabolic Problem in Pension Saving Management

NASA Astrophysics Data System (ADS)

Koleva, M. N.

2011-11-01

In this work we consider a nonlinear parabolic equation, obtained from Riccati like transformation of the Hamilton-Jacobi-Bellman equation, arising in pension saving management. We discuss two numerical iterative methods for solving the model problem—fully implicit Picard method and mixed Picard-Newton method, which preserves the parabolic characteristics of the differential problem. Numerical experiments for comparison the accuracy and effectiveness of the algorithms are discussed. Finally, observations are given.

A unified framework for addiction: Vulnerabilities in the decision process

PubMed Central

Redish, A. David; Jensen, Steve; Johnson, Adam

2013-01-01

The understanding of decision-making systems has come together in recent years to form a unified theory of decision-making in the mammalian brain as arising from multiple, interacting systems (a planning system, a habit system, and a situation-recognition system). This unified decision-making system has multiple potential access points through which it can be driven to make maladaptive choices, particularly choices that entail seeking of certain drugs or behaviors. We identify 10 key vulnerabilities in the system: (1) moving away from homeostasis, (2) changing allostatic set points, (3) euphorigenic “reward-like” signals, (4) overvaluation in the planning system, (5) incorrect search of situation-action-outcome relationships, (6) misclassification of situations, (7) overvaluation in the habit system, (8) a mismatch in the balance of the two decision systems, (9) over-fast discounting processes, and (10) changed learning rates. These vulnerabilities provide a taxonomy of potential problems with decision-making systems. Although each vulnerability can drive an agent to return to the addictive choice, each vulnerability also implies a characteristic symptomology. Different drugs, different behaviors, and different individuals are likely to access different vulnerabilities. This has implications for an individual’s susceptibility to addiction and the transition to addiction, for the potential for relapse, and for the potential for treatment. PMID:18662461

A conservative scheme for electromagnetic simulation of magnetized plasmas with kinetic electrons

NASA Astrophysics Data System (ADS)

Bao, J.; Lin, Z.; Lu, Z. X.

2018-02-01

A conservative scheme has been formulated and verified for gyrokinetic particle simulations of electromagnetic waves and instabilities in magnetized plasmas. An electron continuity equation derived from the drift kinetic equation is used to time advance the electron density perturbation by using the perturbed mechanical flow calculated from the parallel vector potential, and the parallel vector potential is solved by using the perturbed canonical flow from the perturbed distribution function. In gyrokinetic particle simulations using this new scheme, the shear Alfvén wave dispersion relation in the shearless slab and continuum damping in the sheared cylinder have been recovered. The new scheme overcomes the stringent requirement in the conventional perturbative simulation method that perpendicular grid size needs to be as small as electron collisionless skin depth even for the long wavelength Alfvén waves. The new scheme also avoids the problem in the conventional method that an unphysically large parallel electric field arises due to the inconsistency between electrostatic potential calculated from the perturbed density and vector potential calculated from the perturbed canonical flow. Finally, the gyrokinetic particle simulations of the Alfvén waves in sheared cylinder have superior numerical properties compared with the fluid simulations, which suffer from numerical difficulties associated with singular mode structures.

Assessing the Effect of an Old and New Methodology for Scale Conversion on Examinee Scores

ERIC Educational Resources Information Center

Rizavi, Saba; Smith, Robert; Carey, Jill

2002-01-01

Research has been done to look at the benefits of BILOG over LOGIST as well as the potential issues that can arise if transition from LOGIST to BILOG is desired. A serious concern arises when comparability is required between previously calibrated LOGIST parameter estimates and currently calibrated BILOG estimates. It is imperative to obtain an…

Counting in Lattices: Combinatorial Problems from Statistical Mechanics.

NASA Astrophysics Data System (ADS)

Randall, Dana Jill

In this thesis we consider two classical combinatorial problems arising in statistical mechanics: counting matchings and self-avoiding walks in lattice graphs. The first problem arises in the study of the thermodynamical properties of monomers and dimers (diatomic molecules) in crystals. Fisher, Kasteleyn and Temperley discovered an elegant technique to exactly count the number of perfect matchings in two dimensional lattices, but it is not applicable for matchings of arbitrary size, or in higher dimensional lattices. We present the first efficient approximation algorithm for computing the number of matchings of any size in any periodic lattice in arbitrary dimension. The algorithm is based on Monte Carlo simulation of a suitable Markov chain and has rigorously derived performance guarantees that do not rely on any assumptions. In addition, we show that these results generalize to counting matchings in any graph which is the Cayley graph of a finite group. The second problem is counting self-avoiding walks in lattices. This problem arises in the study of the thermodynamics of long polymer chains in dilute solution. While there are a number of Monte Carlo algorithms used to count self -avoiding walks in practice, these are heuristic and their correctness relies on unproven conjectures. In contrast, we present an efficient algorithm which relies on a single, widely-believed conjecture that is simpler than preceding assumptions and, more importantly, is one which the algorithm itself can test. Thus our algorithm is reliable, in the sense that it either outputs answers that are guaranteed, with high probability, to be correct, or finds a counterexample to the conjecture. In either case we know we can trust our results and the algorithm is guaranteed to run in polynomial time. This is the first algorithm for counting self-avoiding walks in which the error bounds are rigorously controlled. This work was supported in part by an AT&T graduate fellowship, a University of California dissertation year fellowship and Esprit working group "RAND". Part of this work was done while visiting ICSI and the University of Edinburgh.

A taxonomy of inductive problems.

PubMed

Kemp, Charles; Jern, Alan

2014-02-01

Inductive inferences about objects, features, categories, and relations have been studied for many years, but there are few attempts to chart the range of inductive problems that humans are able to solve. We present a taxonomy of inductive problems that helps to clarify the relationships between familiar inductive problems such as generalization, categorization, and identification, and that introduces new inductive problems for psychological investigation. Our taxonomy is founded on the idea that semantic knowledge is organized into systems of objects, features, categories, and relations, and we attempt to characterize all of the inductive problems that can arise when these systems are partially observed. Recent studies have begun to address some of the new problems in our taxonomy, and future work should aim to develop unified theories of inductive reasoning that explain how people solve all of the problems in the taxonomy.

Two variants of minimum discarded fill ordering

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Azevedo, E.F.; Forsyth, P.A.; Tang, Wei-Pai

1991-01-01

It is well known that the ordering of the unknowns can have a significant effect on the convergence of Preconditioned Conjugate Gradient (PCG) methods. There has been considerable experimental work on the effects of ordering for regular finite difference problems. In many cases, good results have been obtained with preconditioners based on diagonal, spiral or natural row orderings. However, for finite element problems having unstructured grids or grids generated by a local refinement approach, it is difficult to define many of the orderings for more regular problems. A recently proposed Minimum Discarded Fill (MDF) ordering technique is effective in findingmore » high quality Incomplete LU (ILU) preconditioners, especially for problems arising from unstructured finite element grids. Testing indicates this algorithm can identify a rather complicated physical structure in an anisotropic problem and orders the unknowns in the preferred'' direction. The MDF technique may be viewed as the numerical analogue of the minimum deficiency algorithm in sparse matrix technology. At any stage of the partial elimination, the MDF technique chooses the next pivot node so as to minimize the amount of discarded fill. In this work, two efficient variants of the MDF technique are explored to produce cost-effective high-order ILU preconditioners. The Threshold MDF orderings combine MDF ideas with drop tolerance techniques to identify the sparsity pattern in the ILU preconditioners. These techniques identify an ordering that encourages fast decay of the entries in the ILU factorization. The Minimum Update Matrix (MUM) ordering technique is a simplification of the MDF ordering and is closely related to the minimum degree algorithm. The MUM ordering is especially for large problems arising from Navier-Stokes problems. Some interesting pictures of the orderings are presented using a visualization tool. 22 refs., 4 figs., 7 tabs.« less

Extensions of the standard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramond, P.

1983-01-01

In these lectures we focus on several issues that arise in theoretical extensions of the standard model. First we describe the kinds of fermions that can be added to the standard model without affecting known phenomenology. We focus in particular on three types: the vector-like completion of the existing fermions as would be predicted by a Kaluza-Klein type theory, which we find cannot be realistically achieved without some chiral symmetry; fermions which are vector-like by themselves, such as do appear in supersymmetric extensions, and finally anomaly-free chiral sets of fermions. We note that a chiral symmetry, such as the Peccei-Quinnmore » symmetry can be used to produce a vector-like theory which, at scales less than M/sub W/, appears to be chiral. Next, we turn to the analysis of the second hierarchy problem which arises in Grand Unified extensions of the standard model, and plays a crucial role in proton decay of supersymmetric extensions. We review the known mechanisms for avoiding this problem and present a new one which seems to lead to the (family) triplication of the gauge group. Finally, this being a summer school, we present a list of homework problems. 44 references.« less