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Sample records for junction proved futile

  1. Medical futility and nursing.

    PubMed

    Taylor, C

    1995-01-01

    Defining medical futility is central to the efforts of clinicians and ethicists who seek to identify the limits of patient autonomy. This article is a critique of current efforts to define and then use policies of medical futility to justify refusing requests for treatment and care that have no perceived medical benefit. After exploring the current definitions of medical futility in the bioethics and clinical literature, comparisons of the advantages and disadvantages of the following three options are provided: allowing patients to decide all but physiologic futility, allowing clinicians to decide futility, and pursuing negotiated compromise. The third option--negotiated compromise--is recommended. A role is developed for nurses in preventing and resolving conflict about futile treatment.

  2. Laying Futility to Rest

    PubMed Central

    Nair-Collins, Michael

    2015-01-01

    In this essay I examine the formal structure of the concept of futility, enabling identification of the appropriate roles played by patient, professional, and society. I argue that the concept of futility does not justify unilateral decisions to forego life-sustaining medical treatment over patient or legitimate surrogate objection, even when futility is determined by a process or subject to ethics committee review. Furthermore, I argue for a limited positive ethical obligation on the part of health care professionals to assist patients in achieving certain restricted goals, including the preservation of life, even in circumstances in which most would agree that that life is of no benefit to the patient. Finally, I address the objection that professional integrity overrides this limited obligation and find the objection unconvincing. In short, my aim in this essay is to see the concept of futility finally buried, once and for all. PMID:26232595

  3. Knowing when to stop: futility in the ICU.

    PubMed

    Wilkinson, Dominic J C; Savulescu, Julian

    2011-04-01

    Decisions to withdraw or withhold potentially life-sustaining treatment are common in intensive care and precede the majority of deaths. When families resist or oppose doctors' suggestions that it is time to stop treatment, it is often unclear what should be done. This review will summarize recent literature around futility judgements in intensive care emphasising ethical and practical questions. There has been a shift in the language of futility. Patients' families often do not believe medical assessments that further treatment would be unsuccessful. Attempts to determine through data collection which patients have a low or zero chance of survival have been largely unsuccessful, and are hampered by varying definitions of futility. A due-process model for adjudicating futility disputes has been developed, and may provide a better solution to futility disputes than previous futility statutes. Specific criteria for unilateral withdrawal of treatment have proved hard to define or defend. However, it is ethical for doctors to decline to provide treatment that is medically inappropriate or futile. Understanding the justification for a futility judgement may be relevant to deciding the most appropriate way to resolve futility disputes.

  4. Buddhism and medical futility.

    PubMed

    Chan, Tuck Wai; Hegney, Desley

    2012-12-01

    Religious faith and medicine combine harmoniously in Buddhist views, each in its own way helping Buddhists enjoy a more fruitful existence. Health care providers need to understand the spiritual needs of patients in order to provide better care, especially for the terminally ill. Using a recently reported case to guide the reader, this paper examines the issue of medical futility from a Buddhist perspective. Important concepts discussed include compassion, suffering, and the significance of the mind. Compassion from a health professional is essential, and if medical treatment can decrease suffering without altering the clarity of the mind, then a treatment should not be considered futile. Suffering from illness and death, moreover, is considered by Buddhists a normal part of life and is ever-changing. Sickness, old age, birth, and death are integral parts of human life. Suffering is experienced due to the lack of a harmonious state of body, speech, and mind. Buddhists do not believe that the mind is located in the brain, and, for Buddhists, there are ways suffering can be overcome through the control of one's mind.

  5. REVERSING THE SPIRAL TOWARD FUTILITY.

    ERIC Educational Resources Information Center

    PROCTOR, SAMUEL D.

    CONDITIONS THAT ENGENDER FUTILITY AND HOSTILITY AMONG NEGROES CAN BE REVERSED BY COMPETENT, DEDICATED TEACHERS. FACTORS LEADING TO NEGRO ATTITUDES OF DEFEAT ARE ANALYZED. EXPERIENCE OF REJECTION AND AWARENESS OF BEING DIFFERENT AND INFERIOR ARE AMONG THE FIRST REALIZATIONS OF THE NEGRO. FROM REJECTION GROWS FEAR OF WHITE INSTITUTIONS AND OF…

  6. Futile care and the neonate.

    PubMed

    Romesberg, Tricia L

    2003-10-01

    The concept of futile care is controversial and difficult to define. Efforts to prolong life, once considered an outcome of healing, may now be viewed by some as harmful acts of prolonging suffering. This article reviews a number of cases representing this challenging ethical dilemma, such as Baby K and MacDonald v. Milleville. The Baby Doe regulations, the Emergency Medical Treatment and Labor Act (EMTALA), and the Born-Alive Protection Act of 2001, also are discussed to provide an improved understanding of the legal framework that impacts ethical decision making. Nurses at the bedside must be equipped with the ethical knowledge and communication skills necessary to care for patients and families facing the ethical dilemma of futile care. An increased focus on neonatal palliative care is suggested to provide infants, families, and staff with the necessary tools to work through this painful process.

  7. Futility has no utility in resuscitation medicine.

    PubMed

    Ardagh, M

    2000-10-01

    "Futility" is a word which means the absence of benefit. It has been used to describe an absence of utility in resuscitation endeavours but it fails to do this. Futility does not consider the harms of resuscitation and we should consider the balance of benefit and harm that results from our resuscitation endeavours. If a resuscitation is futile then any harm that ensues will bring about an unfavourable benefit/harm balance. However, even if the endeavour is not futile, by any definition, the benefit/harm balance may still be unfavourable if the harms that ensue are great. It is unlikely that we will ever achieve a consensus definition of futility and certainly not one that is applicable to every patient undergoing resuscitation. In the meantime our use of the term "futile", in the mistaken belief that it tells us whether it is worth resuscitating or not, has no utility as it will never succeed in telling us this. Furthermore we risk causing offence by use of the term and we risk harming the patient's autonomy by using futility as an overriding force. Instead we should consider the utility of our endeavours, for which an assessment of the harms of resuscitation should be added to our considerations of its benefit. This balance of benefit and harm should then be evaluated as best it can be from the patient's perspective. The words futile and futility should be abandoned by resuscitationists.

  8. Does professional autonomy protect medical futility judgments?

    PubMed

    Gampel, Eric

    2006-04-01

    Despite substantial controversy, the use of futility judgments in medicine is quite common, and has been backed by the implementation of hospital policies and professional guidelines on medical futility. The controversy arises when health care professionals (HCPs) consider a treatment futile which patients or families believe to be worthwhile: should HCPs be free to refuse treatments in such a case, or be required to provide them? Most physicians seem convinced that professional autonomy protects them from being forced to provide treatments they judge mentally futile, given the lack of patient benefit as well as the waste of medical resources involved. The argument from professional autonomy has been presented in a number of articles, but it has not been subjected to much critical scrutiny. In this paper I distinguish three versions of the argument: 1) that each physician should be free to exercise his or her own medical judgment; 2) that the medical profession as a whole may provide futility standards to govern the practice of its members; and 3) that the moral integrity of each physician serves as a limit to treatment demands. I maintain that none of these versions succeeds in overcoming the standard objection that futility determinations involve value judgments best left to the patients, their designated surrogates, or their families. Nor do resource considerations change this fact, since they should not influence the properly patient-centered judgment about futility.

  9. The Conscientious Practice Policy: a futility policy for acute care hospitals.

    PubMed

    Mercurio, Mark R

    2005-08-01

    Much attention has been paid in recent years to the conflict that may occur when patients or their families insist on a therapy that the physician feels would be futile. In 1999 the Council on Ethical and Judicial Affairs of the American Medical Association recommended that all health-care institutions adopt a policy on medical futility that follows a fair process. Development of such a policy has proved problematic for many hospitals. The Conscientious Practice Policy at Lawrence & Memorial Hospital was developed as a response to the AMA recommendation. It outlines a specific process to be followed in the event that a physician wishes to refuse to provide a requested therapy, whether that refusal is based on perceived futility or other concerns. The policy was subsequently modified slightly and adopted by two other Connecticut acute care hospitals.

  10. Fruitful or futile: intensive care nurses' experiences and perceptions of medical futility.

    PubMed

    Heland, Melodie

    2006-02-01

    The study sought to investigate the perceptions and experiences of nurses practising in adult intensive care units (ICUs) with regard to medical futility. A qualitative exploratory descriptive design was used, providing a framework which enabled information to be gathered on a relatively undefined phenomena. Data were gathered via semi-structured interviews with seven intensive care nurses. Findings concluded that there is no 'one size fits all' definition of medical futility. To arrive at the decision whether treatment is futile, participants want to understand patients' views on treatment limitation. In some ICUs, 'the decision' about whether to cease or continue treatment is unilaterally made by medical staff, raising concerns about value laden judgement. Nurses experience frustration with having to administer treatment with which they do not agree and may actually leave intensive care nursing because of their moral conflict. There are opportunities for nurses to have input into 'the decision', but they must have a cogent and articulate approach to be heard. Once treatment is deemed to be futile, nurses play a key role in treatment withdrawal and can have a significant impact on the patient and family experience if they manage the situation well; this nursing role in medically futile situations and treatment withdrawal is detailed. 'Medical futility' is not easily defined. Understanding patients' views about treatment limitation is important in deciding whether treatment is medically futile. To do this, an inclusive decision making process should be developed by ICUs which incorporates nursing and family input. Experienced ICU nurses can have a significant impact on the management of futile cases; they need to share their understanding of the processes surrounding medical futility and assist junior nurses in negotiating the difficult challenges encountered in decision making and treatment withdrawal.

  11. Futility and the care of surgical patients: ethical dilemmas.

    PubMed

    Grant, Scott B; Modi, Parth K; Singer, Eric A

    2014-07-01

    Futility has been a contentious topic in medicine for several decades. Surgery in critical or end-of-life situations often raises difficult questions about futility. In this article, we discuss the definition of futility, methods for resolving futility disputes, and some ways to reframe the futility debate to a more fruitful discussion about the goals of care, better communication between surgeon and patient/surrogate, and palliative surgical care. Many definitions of futile therapy have been discussed. The most controversial of these is "qualitative futility" which describes a situation in which the treatment provided is likely to result in an unacceptable quality of life. This is an area of continued controversy because it has been impossible to identify universally held beliefs about acceptable quality of life. Many authors have described methods for resolving futility disputes, including community standards and legalistic multi-step due process protocols. Others, however, have abandoned the concept of futility altogether as an unhelpful term. Reframing the issue of futility as one of inadequate physician-patient communication, these authors have advocated for methods of improving communication and strengthening the patient-physician relationship. Finally, we discuss the utilization of consultants who may be of use in resolving futility disputes: ethics committees, palliative care specialists, pastoral care teams, and dedicated patient advocates. Involving these specialists in a futility conflict can help improve communication and provide invaluable assistance in arriving at the appropriate treatment decision.

  12. Futility and the Care of Surgical Patients: Ethical Dilemmas

    PubMed Central

    Grant, Scott B.; Modi, Parth K.

    2016-01-01

    Futility has been a contentious topic in medicine for several decades. Surgery in critical or end-of-life situations often raises difficult questions about futility. In this article, we discuss the definition of futility, methods for resolving futility disputes, and some ways to reframe the futility debate to a more fruitful discussion about the goals of care, better communication between surgeon and patient/surrogate, and palliative surgical care. Many definitions of futile therapy have been discussed. The most controversial of these is “qualitative futility” which describes a situation in which the treatment provided is likely to result in an unacceptable quality of life. This is an area of continued controversy because it has been impossible to identify universally held beliefs about acceptable quality of life. Many authors have described methods for resolving futility disputes, including community standards and legalistic multi-step due process protocols. Others, however, have abandoned the concept of futility altogether as an unhelpful term. Reframing the issue of futility as one of inadequate physician–patient communication, these authors have advocated for methods of improving communication and strengthening the patient–physician relationship. Finally, we discuss the utilization of consultants who may be of use in resolving futility disputes: ethics committees, palliative care specialists, pastoral care teams, and dedicated patient advocates. Involving these specialists in a futility conflict can help improve communication and provide invaluable assistance in arriving at the appropriate treatment decision. PMID:24849199

  13. Medical futility and the social context.

    PubMed Central

    Halliday, R

    1997-01-01

    The concept of medical futility has come to be seen in some quarters as a value-neutral trump card when dealing with issues of power and conflicting values in medicine. I argue that this concept is potentially useful, but only in a social context that provides a normative framework for its use. This social context needs to include a broad consensus about the purpose of medicine and the nature of the physician-patient relationship. PMID:9220326

  14. Futile xylitol cycle in Lactobacillus casei.

    PubMed Central

    Hausman, S Z; Thompson, J; London, J

    1984-01-01

    A futile xylitol cycle appears to be responsible for xylitol-mediated inhibition of growth of Lactobacillus casei Cl-16 at the expense of ribitol. The gratuitously induced xylitol-specific phosphoenolpyruvate-dependent phosphotransferase accumulates the pentitol as xylitol-5-phosphate, a phosphatase cleaves the latter, and an export system expels the xylitol. Operation of the cycle rapidly dissipates the ribitol-5-phosphate pool (and ultimately the energy supply of the cell), thereby producing bacteriostasis. Images PMID:6090413

  15. Determination of "futility" in emergency medicine.

    PubMed

    Marco, C A; Larkin, G L; Moskop, J C; Derse, A R

    2000-06-01

    The practice of emergency medicine routinely requires rapid decisionmaking regarding various interventions and therapies. Such decisions should be based on the expected risks and benefits to the patient, family, and society. At times, certain interventions and therapies may be considered "futile," or of low expected likelihood of benefit to the patient. Various interpretations of the term "futility" and its practical application to the practice of emergency medicine are explored, as well as background information and potential application of various legal, ethical, and organizational policies regarding the determination of "futility. "Decisions regarding potential benefit of interventions should be based on scientific evidence, societal consensus, and professional standards, not on individual bias regarding quality of life or other subjective matters. Physicians are under no ethical obligation to provide treatments they judge to have no realistic likelihood of benefit to the patient. Decisions to withhold treatment should be made with careful consideration of scientific evidence of likelihood of medical benefit, other benefits (including intangible benefits), potential risks of the proposed intervention, patient preferences, and family wishes. When certain interventions are withheld, special efforts should be made to maintain effective communication, comfort, support, and counseling for the patient, family, and friends.

  16. Perceptions of "futile care" among caregivers in intensive care units.

    PubMed

    Sibbald, Robert; Downar, James; Hawryluck, Laura

    2007-11-06

    Many caregivers in intensive care units (ICUs) feel that they sometimes provide inappropriate or excessive care, but little is known about their definition of "futile care" or how they attempt to limit its impact. We sought to explore how ICU staff define medically futile care, why they provide it and what strategies might promote a more effective use of ICU resources. Using semi-structured interviews, we surveyed 14 physician directors, 16 nurse managers and 14 respiratory therapists from 16 ICUs across Ontario. We analyzed the transcripts using a modified grounded-theory approach. From the interviews, we generated a working definition of medically futile care to mean the use of considerable resources without a reasonable hope that the patient would recover to a state of relative independence or be interactive with his or her environment. Respondents felt that futile care was provided because of family demands, a lack of timely or skilled communication, or a lack of consensus among the treating team. Respondents said they were able to resolve cases of futile care most effectively by improving communication and by allowing time for families to accept the reality of the situation. Respondents felt that further efforts to limit futile care should focus on educating the public and health care professionals about the role of the ICU and about alternatives such as palliative care; mandating early and skilled discussion of resuscitation status; establishing guidelines for admission to the ICU; and providing legal and ethical support for physicians who encounter difficulties. There was a broad consistency in responses among all disciplines. ICU physicians, nurses and respiratory therapists have similar and well-formed opinions about how to define and resolve medically futile care and where to focus future efforts to limit the impact of futile care in the ICU.

  17. The utility of futility: the construction of bioethical problems.

    PubMed

    Carnevale, F A

    1998-11-01

    The aim of this article is to analyse the contemporary 'futility discourse' from a constructivist perspective. I will argue that bioethics discourse typically disregards the context from which controversies emerge and the processes that inform and constrain such discourse. Constructivists have argued that scientific knowledge is expressive of the dominant paradigm within which a scientific community is working. I will outline an analysis of 'medical futility' as a construction of biomedical and bioethical communities (and their respective paradigms). I will trace the emergence and utilization of futility in the literature. My analysis of the context (i.e. the historical circumstances, the particular actors involved) within which the futility discourse emerged suggests that medical futility was constructed, in part, as a means of enhancing physician domination of a context wherein medical authority was threatened. The actors in this debate express widely divergent frameworks of 'the good', arguing from distinctive representations of moral agency. At times, this controversy has been argued from incommensurate moral horizons wherein the discussants debate incomparable problems. This discussion is related to a study of the 'practice' of futility in the clinical context. Further studies on the construction of bioethical problems are a necessary condition for supporting the truth claims of bioethical arguments.

  18. Is tube feeding futile in advanced dementia?

    PubMed Central

    Lynch, Matthew C.

    2016-01-01

    It is controversial whether tube feeding in people with dementia improves nutritional status or prolongs survival. Guidelines published by several professional societies cite observational studies that have shown no benefit and conclude that tube feeding in patients with advanced dementia should be avoided. However, all studies on tube feeding in dementia have major methodological flaws that invalidate their findings. The present evidence is not sufficient to justify general guidelines. Patients with advanced dementia represent a very heterogeneous group, and evidence demonstrates that some patients with dementia benefit from tube feeding. However, presently available guidelines make a single recommendation against tube feeding for all patients. Clinicians, patients, and surrogates should be aware that the guidelines and prior commentary on this topic tend both to overestimate the strength of evidence for futility and to exaggerate the burdens of tube feeding. Shared decision making requires accurate information tailored to the individual patient's particular situation, not blanket guidelines based on flawed data. Lay Summary: Many doctors believe that tube feeding does not help people with advanced dementia. Scientific studies suggest that people with dementia who have feeding tubes do not live longer or gain weight compared with those who are carefully hand fed. However, these studies are not very helpful because of flaws in design, which are discussed in this article. Guidelines from professional societies make a blanket recommendation against feeding tubes for anyone with dementia, but an individual approach that takes each person's situation into account seems more appropriate. Patients and surrogates should be aware that the guidelines on this topic tend both to underestimate the benefit and exaggerate the burdens of tube feeding. PMID:27833208

  19. Medical futility and its challenges: a review study.

    PubMed

    Aghabarary, Maryam; Dehghan Nayeri, Nahid

    2016-01-01

    Concerns over limited medical equipment and resources, particularly in intensive care units (ICUs), have raised the issue of medical futility. Medical futility draws a contrast between physician's authority and patients' autonomy and it is one of the major issues of end-of-life ethical decision-making. The aim of this study was to review medical futility and its challenges. In this systematized review study, a comprehensive search of the existing literature was performed using an internet search with broad keywords to access related articles in both Persian and English databases. Finally, 89 articles were selected and surveyed. Medical futility is a complex, ambiguous, subjective, situation-specific, value-laden, and goal-dependent concept which is almost always surrounded by some degrees of uncertainty; hence, there is no objective and valid criterion for its determination. This concept is affected by many different factors such as physicians' and patients' value systems, medical goals, and sociocultural and religious context, and individuals' emotions and personal characteristics. It is difficult to achieve a clear consensus over the concept of medical futility; hence, it should be defined and determined at an individual level and based on the unique condition of each patient.

  20. Medical futility and its challenges: a review study

    PubMed Central

    Aghabarary, Maryam; Dehghan Nayeri, Nahid

    2016-01-01

    Concerns over limited medical equipment and resources, particularly in intensive care units (ICUs), have raised the issue of medical futility. Medical futility draws a contrast between physician’s authority and patients’ autonomy and it is one of the major issues of end-of-life ethical decision-making. The aim of this study was to review medical futility and its challenges. In this systematized review study, a comprehensive search of the existing literature was performed using an internet search with broad keywords to access related articles in both Persian and English databases. Finally, 89 articles were selected and surveyed. Medical futility is a complex, ambiguous, subjective, situation-specific, value-laden, and goal-dependent concept which is almost always surrounded by some degrees of uncertainty; hence, there is no objective and valid criterion for its determination. This concept is affected by many different factors such as physicians’ and patients’ value systems, medical goals, and sociocultural and religious context, and individuals’ emotions and personal characteristics. It is difficult to achieve a clear consensus over the concept of medical futility; hence, it should be defined and determined at an individual level and based on the unique condition of each patient. PMID:28050241

  1. Futile cycling increases sensitivity toward oxidative stress in Escherichia coli

    PubMed Central

    Adolfsen, Kristin J.; Brynildsen, Mark P.

    2015-01-01

    Reactive oxygen species (ROS) are toxic molecules utilized by the immune system to combat invading pathogens. Recent evidence suggests that inefficiencies in ATP production or usage can lead to increased endogenous ROS production and sensitivity to oxidative stress in bacteria. With this as inspiration, and knowledge that ATP is required for a number of DNA repair mechanisms, we hypothesized that futile cycling would be an effective way to increase sensitivity to oxidative stress. We developed a mixed integer linear optimization framework to identify experimentally-tractable futile cycles, and confirmed metabolic modeling predictions that futile cycling depresses growth rate, and increases both O2 consumption and ROS production per biomass generated. Further, intracellular ATP was decreased and sensitivity to oxidative stress increased in all actively cycling strains compared to their catalytically inactive controls. This research establishes a fundamental connection between ATP metabolism, endogenous ROS production, and tolerance toward oxidative stress in bacteria. PMID:25732623

  2. Medically Inappropriate or Futile Treatment: Deliberation and Justification 1

    PubMed Central

    Misak, Cheryl J.; White, Douglas B.; Truog, Robert D.

    2016-01-01

    This paper reframes the futility debate, moving away from the question “Who decides when to end what is considered to be a medically inappropriate or futile treatment?” and toward the question “How can society make policy that will best account for the multitude of values and conflicts involved in such decision-making?” It offers a pragmatist moral epistemology that provides us with (1) a clear justification of why it is important to take best standards, norms, and physician judgment seriously and (2) a clear justification of why ample opportunity must be made for patients, families, and society to challenge those standards and norms. PMID:26681796

  3. Family presence during cardiopulmonary resuscitation: grief therapy or prolonged futility?

    PubMed

    Sherman, David A

    2008-01-01

    Nursing leaders are responsible in part for implementing procedures supporting family presence during cardiopulmonary resuscitation. Family presence has received broad support in nursing literature and from professional organizations. A case study suggests that, when a patient's spokesperson is struggling with the question of whether to set limits to treatments, allowing family presence may inappropriately prolong futile care.

  4. The Moderately Efficient Enzyme: Futile Encounters and Enzyme Floppiness.

    PubMed

    Bar-Even, Arren; Milo, Ron; Noor, Elad; Tawfik, Dan S

    2015-08-18

    The pioneering model of Henri, Michaelis, and Menten was based on the fast equilibrium assumption: the substrate binds its enzyme reversibly, and substrate dissociation is much faster than product formation. Here, we examine this assumption from a somewhat different point of view, asking what fraction of enzyme-substrate complexes are futile, i.e., result in dissociation rather than product formation. In Knowles' notion of a "perfect" enzyme, all encounters of the enzyme with its substrate result in conversion to product. Thus, the perfect enzyme's catalytic efficiency, kcat/KM, is constrained by only the diffusion on-rate, and the fraction of futile encounters (defined as φ) approaches zero. The available data on >1000 different enzymes suggest that for ≥90% of enzymes φ > 0.99 and for the "average enzyme" φ ≥ 0.9999; namely, <1 of 10(4) encounters is productive. Thus, the "fast equilibrium" assumption holds for the vast majority of enzymes. We discuss possible molecular origins for the dominance of futile encounters, including the coexistence of multiple sub-states of an enzyme's active site (enzyme floppiness) and/or its substrate. Floppiness relates to the inherent flexibility of proteins, but also to conflicting demands, or trade-offs, between rate acceleration (the rate-determining chemical step) and catalytic turnover, or between turnover rate and accuracy. The study of futile encounters and active-site floppiness may contribute to a better understanding of enzyme catalysis, enzyme evolution, and improved enzyme design.

  5. Futile debate on assessment of field dependence-independence.

    PubMed

    Tinajero, C; Páramo, M F; Guisande, A

    2007-10-01

    A long-standing debate on assessment has troubled research on field dependence-independence. The main arguments and a recent measurement proposal by Riding, et al., are revised to illustrate the futility of this debate and to defend the strength of the cognitive style dimension.

  6. On Mathematical Proving

    NASA Astrophysics Data System (ADS)

    Stefaneas, Petros; Vandoulakis, Ioannis M.

    2015-12-01

    This paper outlines a logical representation of certain aspects of the process of mathematical proving that are important from the point of view of Artificial Intelligence. Our starting-point is the concept of proof-event or proving, introduced by Goguen, instead of the traditional concept of mathematical proof. The reason behind this choice is that in contrast to the traditional static concept of mathematical proof, proof-events are understood as processes, which enables their use in Artificial Intelligence in such contexts, in which problem-solving procedures and strategies are studied. We represent proof-events as problem-centered spatio-temporal processes by means of the language of the calculus of events, which captures adequately certain temporal aspects of proof-events (i.e. that they have history and form sequences of proof-events evolving in time). Further, we suggest a "loose" semantics for the proof-events, by means of Kolmogorov's calculus of problems. Finally, we expose the intented interpretations for our logical model from the fields of automated theorem-proving and Web-based collective proving.

  7. On Mathematical Proving

    NASA Astrophysics Data System (ADS)

    Stefaneas, Petros; Vandoulakis, Ioannis M.

    2015-12-01

    This paper outlines a logical representation of certain aspects of the process of mathematical proving that are important from the point of view of Artificial Intelligence. Our starting-point is the concept of proof-event or proving, introduced by Goguen, instead of the traditional concept of mathematical proof. The reason behind this choice is that in contrast to the traditional static concept of mathematical proof, proof-events are understood as processes, which enables their use in Artificial Intelligence in such contexts, in which problem-solving procedures and strategies are studied. We represent proof-events as problem-centered spatio-temporal processes by means of the language of the calculus of events, which captures adequately certain temporal aspects of proof-events (i.e. that they have history and form sequences of proof-events evolving in time). Further, we suggest a "loose" semantics for the proof-events, by means of Kolmogorov's calculus of problems. Finally, we expose the intented interpretations for our logical model from the fields of automated theorem-proving and Web-based collective proving.

  8. Futility and unilateral decision making: a different view.

    PubMed

    Mahowald, Mary B

    1993-01-01

    ... Resuscitation of PVS patients is futile if the goal is to restore the patient to a cognitive or conscious state but not if the goal is restoration of respiratory function. The judgment of futility in either case is based on nonmedical (as well as medical) values or criteria, i.e., the value of cognitive life vs. the value of noncognitive life. If all of the affected parties concur that noncognitive recovery is a goal not worth achieving, a DNR order should be written. Lacking such concurrence, justification for a DNR order might be found in societal assessment of the burdens and benefits to others (besides the patient) of providing treatment in such circumstances. This is not a decision to be made unilaterally by a single physician, whose values are not necessarily reflective of those of the patient, family members, other physicians, or society at large.

  9. Legal briefing: futile or non-beneficial treatment.

    PubMed

    Pope, Thaddeus Mason

    2011-01-01

    This issue's "Legal Briefing" column covers recent legal developments involving futile or non-beneficial medical treatment. This topic has been the subject of recent articles in JCE. Indeed, it was the subject of a "Legal Briefing" in fall 2009. Accordingly, this column focuses on legal developments from the past two years. These developments are usefully grouped into the following 11 categories: 1. Texas Advance Directives Act, 2. Ontario Consent and Capacity Board, 3. Surrogate selection, 4. Ex post cases for damages, 5. Ex ante cases for injunctions, 6. Coercion and duress, 7. Assent and transparency, 8. Brain-death cases, 9. Criminal and administrative sanctions, 10. Conscientious objection, 11. Penalties for providing futile treatment.

  10. The futility study—progress over the last decade

    PubMed Central

    Levin, Bruce

    2015-01-01

    We review the futility clinical trial design (also known as the non-superiority design) with respect to its emergence and methodologic developments over the last decade, especially in regard to its application to clinical trials for neurological disorders. We discuss the design’s strengths as a programmatic screening device to weed out unpromising new treatments, its limitations and pitfalls, and a recent critique of the logic of the method. PMID:26123873

  11. Conceptualization of Idle (Laghw) and its relation to medical futility.

    PubMed

    Rezaei Aderyani, Mohsen; Javadi, Mohsen; Nazari Tavakkoli, Saeid; Kiani, Mehrzad; Abbasi, Mahmood

    2016-01-01

    A major debate in medical ethics is the request for futile treatment. The topic of medical futility requires discrete assessment in Iran for at least two reasons. First, the common principles and foundations of medical ethics have taken shape in the context of Western culture and secularism. Accordingly, the implementation of the same guidelines and codes of medical ethics as Western societies in Muslim communities does not seem rational. Second, the challenges arising in health service settings are divergent across different countries. The Quranic concept of idle (laghw) and its derivatives are used in 11 honorable verses of the Holy Quran. Among these verses, the 3rd verse of the blessed Al-Muminūn Surah was selected for its closer connection to the concept under examination. The selected verse was researched in the context of all dictionaries presented in Noor Jami` al-Tafasir 2 (The Noor Collection of Interpretations 2) software. "Idle" is known as any insignificant speech, act, or thing that is not beneficial; an action from which no benefit is gained; any falsehood (that is not stable or realized); an entertaining act; any foul, futile talk and action unworthy of attention; loss of hope; and something that is not derived from method and thought. The word has also been used to refer to anything insignificant. The notes and derived interpretations were placed in the following categories: A) Having no significant benefit (When medical care does not benefit the patient (his body and/or soul and his life in this world and/or the Hereafter), it is wrong to proceed with that medical modality; B) Falsehood (Actions that fail to provide, maintain, and improve health are clearly futile); C) Unworthy of attention (An action that neither improves health nor threatens it is wrong and impermissible).

  12. Conceptualization of Idle (Laghw) and its relation to medical futility

    PubMed Central

    Rezaei Aderyani, Mohsen; Javadi, Mohsen; Nazari Tavakkoli, Saeid; Kiani, Mehrzad; Abbasi, Mahmood

    2016-01-01

    A major debate in medical ethics is the request for futile treatment. The topic of medical futility requires discrete assessment in Iran for at least two reasons. First, the common principles and foundations of medical ethics have taken shape in the context of Western culture and secularism. Accordingly, the implementation of the same guidelines and codes of medical ethics as Western societies in Muslim communities does not seem rational. Second, the challenges arising in health service settings are divergent across different countries. The Quranic concept of idle (laghw) and its derivatives are used in 11 honorable verses of the Holy Quran. Among these verses, the 3rd verse of the blessed Al-Muminūn Surah was selected for its closer connection to the concept under examination. The selected verse was researched in the context of all dictionaries presented in Noor Jami` al-Tafasir 2 (The Noor Collection of Interpretations 2) software. "Idle" is known as any insignificant speech, act, or thing that is not beneficial; an action from which no benefit is gained; any falsehood (that is not stable or realized); an entertaining act; any foul, futile talk and action unworthy of attention; loss of hope; and something that is not derived from method and thought. The word has also been used to refer to anything insignificant. The notes and derived interpretations were placed in the following categories: A) Having no significant benefit (When medical care does not benefit the patient (his body and/or soul and his life in this world and/or the Hereafter), it is wrong to proceed with that medical modality; B) Falsehood (Actions that fail to provide, maintain, and improve health are clearly futile); C) Unworthy of attention (An action that neither improves health nor threatens it is wrong and impermissible). PMID:27390616

  13. Futility rules in bioequivalence trials with sequential designs.

    PubMed

    Fuglsang, Anders

    2014-01-01

    Health Canada, the US Food and Drug Administration, as well as the European Medicines Agency consider sequential designs acceptable for bioequivalence studies as long as the type I error is controlled at 5%. The EU guideline explicitly asks for specification of stopping rules, so the goal of this work is to investigate how stopping rules may affect type I errors and power for recently published sequential bioequivalence trial designs. Using extensive trial simulations, five different futility rules were evaluated for their effect on type I error rates and power in two-stage scenarios. Under some circumstances, notably low sample size in stage 1 and/or high variability power may be very severely affected by the stopping rules, whereas type I error rates appear less affected. Because applicants may initiate sequential studies when the variability is not known in advance, achieving sufficient power and thereby complying with certain guideline requirements may be challenging and application of optimistic futility rules could possibly be unethical. This is the first work to investigate how futility rules affect type I errors and power in sequential bioequivalence trials.

  14. Identifying futility in a paediatric critical care setting: a prospective observational study

    PubMed Central

    Goh, A; Mok, Q

    2001-01-01

    AIMS—To determine the extent of futile care provided to critically ill children admitted to a paediatric intensive care setting.
METHODS—Prospective evaluation of consecutive admissions to a 20 bedded multidisciplinary paediatric intensive care unit of a North London teaching hospital over a nine month period. Three previously defined criteria for futility were used: (1) imminent demise futility (those with a mortality risk greater than 90% using the Paediatric Risk of Mortality (PRISM II) score); (2) lethal condition futility (those with conditions incompatible with long term survival); and (3) qualitative futility (those with unacceptable quality of life and high morbidity).
RESULTS—A total of 662 children accounting for 3409 patient bed days were studied. Thirty four patients fulfilled at least one of the criteria for futility, and used a total of 104 bed days (3%). Only 33 (0.9%) bed days were used by patients with mortality risk greater than 90%, 60 (1.8%) by patients with poor long term prognosis, and 16 (0.5%) by those with poor quality of life. Nineteen of 34 patients died; withdrawal of treatment was the mode of death in 15 (79%).
CONCLUSIONS—Cost containment initiatives focusing on futility in the paediatric intensive care unit setting are unlikely to be successful as only relatively small amounts of resources were used in providing futile care. Paediatricians are recognising futility early and may have taken ethically appropriate measures to limit care that is futile.

 PMID:11207181

  15. Is futile care in the injured elderly an important target for cost savings?

    PubMed

    Fleischman, Ross J; Mullins, Richard J; McConnell, K John; Hedges, Jerris R; Ma, O John; Newgard, Craig D

    2012-07-01

    This study proposes a definition of futile care and quantifies its cost in injured elders. This was a retrospective study of Medicare patients with an International Classification of Diseases-9 injury diagnosis admitted to 171 Oregon and Washington facilities from January 1, 2001, through December 31, 2002, who died within 6 months of admission. Futile care was defined as death within 7 days of discharge from a hospitalization of at least 14 days. We compared health care costs in the last 6 months of life with those who did and did not meet our definition of futility. To simulate predicting and preventing futility early in the hospital course, we examined the effect of reducing spending on the futile care cohort to the level of those who survived 7 to 10 days after injury. There were 6,832 elders who died within 6 months of injury, of whom 230 (3.4%) met our definition of futility. The median cost of care in the last 6 months of life was $33,373 for those not meeting our definition of futility and $87,391 for the futile care group (p < 0.001). The 3.4% receiving futile care incurred 8.9% of total costs. Reducing expenditures in the futile care group to the level of those who died from 7 to 10 days after injury (median, $25,633) would result in an overall cost savings of 6.5%. End-of-life health care costs were significantly higher for those who received futile care. However, even aggressive reductions in futile care would result in small savings overall. Economic analysis, level III.

  16. Intensive care nurses' perception of futility: job satisfaction and burnout dimensions.

    PubMed

    Özden, Dilek; Karagözoğlu, Şerife; Yildirim, Gülay

    2013-06-01

    Suffering repeated experiences of moral distress in intensive care units due to applications of futility reflects on nurses' patient care negatively, increases their burnout, and reduces their job satisfaction. This study was carried out to investigate the levels of job satisfaction and exhaustion suffered by intensive care nurses and the relationship between them through the futility dimension of the issue. The study included 138 intensive care nurses. The data were obtained with the futility questionnaire developed by the researchers, Maslach Burnout Inventory and Minnesota Satisfaction Questionnaire. It was determined that nurses who agreed to the proposition that the application of futility demoralizes health-care professionals had low levels of job satisfaction but high levels of depersonalization. It was determined that nurses had moderate levels of job satisfaction, emotional exhaustion, and personal achievements but high levels of sensitivity. Nurses' job satisfaction and sensitivities are positively affected when they consider that futility does not contradict the purposes of medicine.

  17. Elective Inactivation of Total Artificial Heart Technology in Non-Futile Situations: Inpatients, Outpatients and Research Participants

    ERIC Educational Resources Information Center

    Bramstedt, Katrina A.

    2004-01-01

    Total artificial heart technology as a potential clinical therapy raises the issue of elective device inactivation in both futile and non-futile situations. This article explores elective device inactivation in non-futile situations. In reply to such requests for inactivation, the medical team should reflect on the individual's decision-making…

  18. Elective Inactivation of Total Artificial Heart Technology in Non-Futile Situations: Inpatients, Outpatients and Research Participants

    ERIC Educational Resources Information Center

    Bramstedt, Katrina A.

    2004-01-01

    Total artificial heart technology as a potential clinical therapy raises the issue of elective device inactivation in both futile and non-futile situations. This article explores elective device inactivation in non-futile situations. In reply to such requests for inactivation, the medical team should reflect on the individual's decision-making…

  19. Hillsborough part 2: advance decisions and futile treatment.

    PubMed

    Griffith, Richard

    In the second article on the impact of the Hillsborough football stadium disaster on healthcare law, Richard Griffith discusses the case of Tony Bland, who suffered prolonged hypoxia due to the crushing crowd surge, leaving him in a persistent vegetative state. Some 3 years after the incident, the judicial committee of the House of Lords was asked to rule on whether it would be lawful to withdraw his artificial nutrition and hydration, resulting in death. The opinions of the law lords in Airedale NHS Trust v Bland [1993] continue to inform health law 25 years after the disaster, shaping and developing the use of advance decisions to refuse treatment and setting out when it would be lawful to withdraw futile life-sustaining treatment.

  20. Negotiating futility, managing emotions: nursing the transition to palliative care.

    PubMed

    Broom, Alex; Kirby, Emma; Good, Phillip; Wootton, Julia; Yates, Patsy; Hardy, Janet

    2015-03-01

    Nurses play a pivotal role in caring for patients during the transition from life-prolonging care to palliative care. This is an area of nursing prone to emotional difficulty, interpersonal complexity, and interprofessional conflict. It is situated within complex social dynamics, including those related to establishing and accepting futility and reconciling the desire to maintain hope. Here, drawing on interviews with 20 Australian nurses, we unpack their accounts of nursing the transition to palliative care, focusing on the purpose of nursing at the point of transition; accounts of communication and strategies for representing palliative care; emotional engagement and burden; and key interprofessional challenges. We argue that in caring for patients approaching the end of life, nurses occupy precarious interpersonal and interprofessional spaces that involve a negotiated order around sentimental work, providing them with both capital (privileged access) and burden (emotional suffering) within their day-to-day work.

  1. Medical futility at the end of life: the perspectives of intensive care and palliative care clinicians.

    PubMed

    Jox, Ralf J; Schaider, Andreas; Marckmann, Georg; Borasio, Gian Domenico

    2012-09-01

    Medical futility at the end of life is a growing challenge to medicine. The goals of the authors were to elucidate how clinicians define futility, when they perceive life-sustaining treatment (LST) to be futile, how they communicate this situation and why LST is sometimes continued despite being recognised as futile. The authors reviewed ethics case consultation protocols and conducted semi-structured interviews with 18 physicians and 11 nurses from adult intensive and palliative care units at a tertiary hospital in Germany. The transcripts were subjected to qualitative content analysis. Futility was identified in the majority of case consultations. Interviewees associated futility with the failure to achieve goals of care that offer a benefit to the patient's quality of life and are proportionate to the risks, harms and costs. Prototypic examples mentioned are situations of irreversible dependence on LST, advanced metastatic malignancies and extensive brain injury. Participants agreed that futility should be assessed by physicians after consultation with the care team. Intensivists favoured an indirect and stepwise disclosure of the prognosis. Palliative care clinicians focused on a candid and empathetic information strategy. The reasons for continuing futile LST are primarily emotional, such as guilt, grief, fear of legal consequences and concerns about the family's reaction. Other obstacles are organisational routines, insufficient legal and palliative knowledge and treatment requests by patients or families. Managing futility could be improved by communication training, knowledge transfer, organisational improvements and emotional and ethical support systems. The authors propose an algorithm for end-of-life decision making focusing on goals of treatment.

  2. THE OPPORTUNITY COST OF FUTILE TREATMENT IN THE INTENSIVE CARE UNIT

    PubMed Central

    Huynh, Thanh N.; Kleerup, Eric C.; Raj, Prince P.; Wenger, Neil S.

    2014-01-01

    Objective When used to prolong life without achieving a benefit meaningful to the patient, critical care is often considered “futile.” While futile treatment is acknowledged as a misuse of resources by many, no study has evaluated its opportunity cost, that is, how it affects care for others. Our objective was to evaluate delays in care when futile treatment is provided. Design For 3 months, we surveyed critical care physicians in 5 intensive care units (ICUs) to identify patients that clinicians identified as receiving futile treatment. We identified days when an ICU was full and containedat least one patient who was receiving futile treatment. For those days, we evaluated the number of patients waiting for ICU admission more than 4 hours in the emergency department (ED) or more than 1 day at an outside hospital. Setting One health system that included a quaternary care medical center and an affiliated community hospital. Patients Critically ill patients Interventions none Measurements Boarding time in the ED and waiting time on the transfer list Main Results 36 critical care specialists made 6916 assessments on 1136 patients of whom 123 were assessed to receive futile treatment. A full ICU was less likely to contain a patient receiving futile treatment compared to an ICU with available beds (38% v 68%, p<0.001). On 72 (16%) days, an ICU was full and contained at least one patient receiving futile treatment. During these days, 33 patients boarded in the ED for >4 hours after admitted to the ICU team, 9patients waited >1 day to be transferred from an outside hospital, and 15 patients cancelled the transfer request after waiting >1 day. Two patients died while waiting to be transferred. Conclusions Futile critical care was associated with delays in care to other patients. PMID:24810527

  3. The gynecologic oncologist and futile therapy in a managed care setting.

    PubMed

    Benrubi, Guy I

    2002-06-01

    The concept of futility is basic to the provision of ethical medical care. The precise definition has been elusive for medical ethicists because of difficulties in trying to "measure" futility, either by "quality" or by "quantity." The change in health care from a fee-for-service basis to one of managed care has added to the dilemmas posed by the requests of patients for care that physicians consider futile. However, using the concept of medical indications and clinical pathways may lead to resolutions of these medical-ethical dilemmas.

  4. Clinical Trial Testing Lithium in ALS Terminates Early for Futility

    PubMed Central

    Aggarwal, Swati P.; Zinman, Lorne; Simpson, Elizabeth; McKinley, Jane; Jackson, Katherine E.; Pinto, Hanika; Conwit, Robin A.; Schoenfeld, David; Shefner, Jeremy; Cudkowicz, Merit

    2011-01-01

    Background We studied the safety and efficacy of lithium in combination with riluzole in ALS. Recently, a pilot study demonstrated a dramatic effect of lithium in slowing ALS progression. To confirm or refute these findings, United States and Canadian funding organizations and investigators collaborated to design and execute a multicenter, double-blind placebo controlled trial in a rapid and efficient manner. Methods Eligible participants had familial or sporadic ALS diagnosed as clinically possible, laboratory supported probable, probable, or definite ALS according to El Escorial criteria and were taking a stable dose of riluzole for at least 30 days. Subjects were equally randomized by a centralized computer to receive either lithium (serum levels maintained between 0.4-0.8 mEq/L) or placebo. Subjects, caregivers and investigators were blinded to treatment assignment throughout the study. The study used a ‘time to an event’ design, novel to ALS trials. An event was defined as ≥ 6 points drop in the ALS Functional Rating Scale-Revised (ALSFRS-R) score or death. The primary efficacy analysis used a log-rank test to compare the distributions of the time to an event between the lithium and placebo groups. The first interim analysis occurred after 84 of 250 participants were randomized. The stopping boundary for futility at first interim analysis was a p-value ≥ 0.68. Findings The study was terminated early at the first intent-to-treat interim analysis as criterion for futility was met. A log-rank statistical analysis testing the superiority of lithium favored placebo (p-value = 0.78). In the final dataset, 22/40 subjects experienced an event in the lithium group compared to 20/44 subjects in the placebo group (p= 0.51). The point estimate (95% CI) for the hazard ratio of reaching the primary endpoint was 1.126 (0.6116 to 2.073). There were no major safety concerns. Fall (p=0.04) and back pain (p=0.05) were significantly more common in the lithium group

  5. Combined Multimodal Computed Tomography Score Correlates With Futile Recanalization After Thrombectomy in Patients With Acute Stroke.

    PubMed

    Espinosa de Rueda, Mariano; Parrilla, Guillermo; Manzano-Fernández, Sergio; García-Villalba, Blanca; Zamarro, Joaquín; Hernández-Fernández, Francisco; Sánchez-Vizcaino, Cristina; Carreón, Ester; Morales, Ana; Moreno, Antonio

    2015-09-01

    Futile recanalization after acute ischemic stroke occurs in almost half of the patients despite optimal angiographic results. Multimodal neuroimaging may help to improve patient's selection but is still dismissed by many interventionalists. Our aim was to evaluate the accuracy of each parameter of multimodal computed tomography (CT) and their combination for predicting futile recanalization after successful thrombectomy. We retrospectively reviewed a cohort of consecutive patients with anterior circulation stroke, fully assessable multimodal CT, and successful recanalization. Nonenhanced CT, CT angiography source images, cerebral blood volume (CBV), cerebral blood flow (CBF), and mismatch CBV-CBF maps were studied by Alberta Stroke Program Early CT Score (ASPECTS); collaterals on CT angiography were graded as poor or good (≤50% or >50% of the middle cerebral artery territory). Futile recanalization was defined as modified Rankin Scale score >2 at 3 months despite successful recanalization. One hundred fifty patients were included and 57% of them had futile recanalization. They had lower ASPECTS on nonenhanced CT, CT angiography source images, CBV, CBF, and mismatch CBV-CBF and presented more frequently poor collaterals (all P<0.001). Among them, CBV showed the highest area under the curve (0.83; 95% confidence interval, 0.76-0.88). In multivariate analyses, CT angiography source images ≤5 (odds ratio, 5.1; 95% confidence interval, 1.2-21.9), CBV≤6 (odds ratio, 3.5; 95% confidence interval, 1.2-9.7), and poor collaterals (odds ratio, 8.6; 95% confidence interval, 1.8-41.7) were independent predictors of futile recanalization. A combined score of these 3 parameters added complementary information: 57% of the patients with score-1, 89% with score-2, and 100% with score-3 had futile recanalization. Reclassification analyses indicated that this score improved prediction of futile recanalization. In this population, a combined multimodal CT score predicted futile

  6. Nurses’ Experiences of Futile Care at Intensive Care Units: A Phenomenological Study

    PubMed Central

    Yekefallah, Leili; Ashktorab, Tahereh; Manoochehri, Houman; Hamid, Alavi Majd

    2015-01-01

    The concept and meaning of futile care depends on the existing culture, values, religion, beliefs, medical achievements and emotional status of a country. We aimed to define the concept of futile care in the viewpoints of nurses working in intensive care units (ICUs). In this phenomenological study, the experiences of 25 nurses were explored in 11 teaching hospitals affiliated to Social Security Organization in Ghazvin province in the northwest of Iran. Personal interviews and observations were used for data collection. All interviews were recorded as well as transcribed and codes, subthemes and themes were extracted using Van Manen’s analysis method. Initially, 191 codes were extracted. During data analysis and comparison, the codes were reduced to 178. Ultimately, 9 sub-themes and four themes emerged: uselessness, waste of resources, torment, and aspects of futility. Nurses defined futile care as “useless, ineffective care giving with wastage of resources and torment of both patients and nurses having nursing and medical aspects” As nurses play a key role in managing futile care, being aware of their experiences in this regard could be the initial operational step for providing useful care as well as educational programs in ICUs. Moreover, the results of this study could help nursing managers adopt supportive approaches to reduce the amount of futile care which could in turn resolve some of the complications nurses face at these wards such as burnout, ethical conflicts, and leave. PMID:25946928

  7. Medical futility, treatment withdrawal and the persistent vegetative state.

    PubMed

    Mitchell, K R; Kerridge, I H; Lovat, T J

    1993-06-01

    Why do we persist in the relentless pursuit of artificial nourishment and other treatments to maintain a permanently unconscious existence? In facing the future, if not the present world-wide reality of a huge number of persistent vegetative state (PVS) patients, will they be treated because of our ethical commitment to their humanity, or because of an ethical paralysis in the face of biotechnical progress? The PVS patient is cut off from the normal patterns of human connection and communication, with a life unlike other forms of human existence. Why the struggle to justify ending a life which, it is said, has suffered an irreversible loss of the content of consciousness? Elsewhere, the authors have addressed the ethical controversies and confusion engendered by ambiguous terminology, misuse of medical facts and the differing interpretations of what constitutes 'effective' treatment: in particular, the issue of whether in fact artificial nutrition and hydration is a medical treatment, or simply part of the obligatory care owed to all patients, permanently unconscious or not. In this paper, we intend to argue that recent analyses of medical futility, its meaning and ethical implications, despite an absence of public consensus, permit some tentative re-evaluation of our ethical obligations to the PVS patient.

  8. Medical futility, treatment withdrawal and the persistent vegetative state.

    PubMed Central

    Mitchell, K R; Kerridge, I H; Lovat, T J

    1993-01-01

    Why do we persist in the relentless pursuit of artificial nourishment and other treatments to maintain a permanently unconscious existence? In facing the future, if not the present world-wide reality of a huge number of persistent vegetative state (PVS) patients, will they be treated because of our ethical commitment to their humanity, or because of an ethical paralysis in the face of biotechnical progress? The PVS patient is cut off from the normal patterns of human connection and communication, with a life unlike other forms of human existence. Why the struggle to justify ending a life which, it is said, has suffered an irreversible loss of the content of consciousness? Elsewhere, the authors have addressed the ethical controversies and confusion engendered by ambiguous terminology, misuse of medical facts and the differing interpretations of what constitutes 'effective' treatment: in particular, the issue of whether in fact artificial nutrition and hydration is a medical treatment, or simply part of the obligatory care owed to all patients, permanently unconscious or not. In this paper, we intend to argue that recent analyses of medical futility, its meaning and ethical implications, despite an absence of public consensus, permit some tentative re-evaluation of our ethical obligations to the PVS patient. PMID:8331640

  9. Comparison of futility monitoring guidelines using completed phase III oncology trials.

    PubMed

    Zhang, Qiang; Freidlin, Boris; Korn, Edward L; Halabi, Susan; Mandrekar, Sumithra; Dignam, James J

    2017-02-01

    Futility (inefficacy) interim monitoring is an important component in the conduct of phase III clinical trials, especially in life-threatening diseases. Desirable futility monitoring guidelines allow timely stopping if the new therapy is harmful or if it is unlikely to demonstrate to be sufficiently effective if the trial were to continue to its final analysis. There are a number of analytical approaches that are used to construct futility monitoring boundaries. The most common approaches are based on conditional power, sequential testing of the alternative hypothesis, or sequential confidence intervals. The resulting futility boundaries vary considerably with respect to the level of evidence required for recommending stopping the study. We evaluate the performance of commonly used methods using event histories from completed phase III clinical trials of the Radiation Therapy Oncology Group, Cancer and Leukemia Group B, and North Central Cancer Treatment Group. We considered published superiority phase III trials with survival endpoints initiated after 1990. There are 52 studies available for this analysis from different disease sites. Total sample size and maximum number of events (statistical information) for each study were calculated using protocol-specified effect size, type I and type II error rates. In addition to the common futility approaches, we considered a recently proposed linear inefficacy boundary approach with an early harm look followed by several lack-of-efficacy analyses. For each futility approach, interim test statistics were generated for three schedules with different analysis frequency, and early stopping was recommended if the interim result crossed a futility stopping boundary. For trials not demonstrating superiority, the impact of each rule is summarized as savings on sample size, study duration, and information time scales. For negative studies, our results show that the futility approaches based on testing the alternative hypothesis

  10. Yeast adaptation to weak acids prevents futile energy expenditure

    PubMed Central

    Ullah, Azmat; Chandrasekaran, Gayathri; Brul, Stanley; Smits, Gertien J.

    2013-01-01

    Weak organic acids (WOAs) are widely used preservatives to prevent fungal spoilage of foods and beverages. Exposure of baker's yeast Saccharomyces cerevisiae to WOA leads to cellular acidification and anion accumulation. Pre-adaptation of cultures reduced the rate of acidification caused by weak acid exposure, most likely as a result of changes in plasma membrane or cell wall composition. In order to adapt to sublethal concentrations of the acids and grow, yeast cells activate ATP consuming membrane transporters to remove protons and anions. We explored to what extent ATP depletion contributes to growth inhibition in sorbic or acetic acid treated cells. Therefore, we analyzed the effect of the reduction of proton and anion pumping activity on intracellular pH (pHi), growth, and energy status upon exposure to the hydrophilic acetic acid (HA) and the lipophilic sorbic acid (HS). ATP concentrations were dependent on the severity of the stress. Unexpectedly, we observed a stronger reduction of ATP with growth reducing than with growth inhibitory concentrations of both acids. We deduce that the not the ATP reduction caused by proton pumping, but rather the cost of sorbate anion pumping contributes to growth inhibition. A reduction of proton pumping activity may reduce ATP consumption, but the resulting decrease of pHi affects growth more. ATP utilization was differentially regulated during moderate and severe stress conditions. We propose that the energy depletion alone is not the cause of growth inhibition during HA or HS stress. Rather, the cells appear to reduce ATP consumption in high stress conditions, likely to prevent futile cycling and maintain energy reserves for growth resumption in more favorable conditions. The mechanism for such decision making remains to be established. PMID:23781215

  11. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  12. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  13. Computers for liquid meter proving

    SciTech Connect

    Lurie, B.D.

    1995-12-01

    Computer evolution has leveraged the 1990`s into the {open_quotes}Information Super-Highway{close_quotes}. Computer development has enhanced communications more than ten fold in the past twenty years. Today, we have communication tools such as SCADA (supervisory control and data acquisition) and DCS (distributed control system), and communication linkage via MODBUS and FIELDBUS. This paper describes the evolution of computers as they apply to liquid meter proving. Meter proving is essential for controlling expenses and product accountability whereas prover computers have enhanced the ability for errorless precision accuracy.

  14. Is Proving a Visual Act?

    ERIC Educational Resources Information Center

    Mudaly, Vimolan

    2013-01-01

    This paper looks at the role of visualisation in the proving process. It considers the different functions of proof and then describes student responses when engaged in the process of discovering Viviani's Theorem. The findings show that learners can attain high levels of conviction when working in a dynamic geometry environment. In particular,…

  15. Proving Program Correctness. Volume V.

    DTIC Science & Technology

    1981-11-01

    td&Ot’ ’i number) Programming Sy Stems S.. - nulation Pr~ogramming Languages Sche,!%L -g Algorithm Programming Grammars Logic Programming 9roving...able to prove that programs perform as they are specified than is currently possible. Task 3. Grammars of Programming (P.I.: E.F. Storm). This group is...is "An Algorithmic Solution for a Queueing Model of a Computer System with Interactive and Batch Jobs. Volume 4. Report from the Grammars of

  16. Josephson junction

    DOEpatents

    Wendt, J.R.; Plut, T.A.; Martens, J.S.

    1995-05-02

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material. 10 figs.

  17. Josephson junction

    DOEpatents

    Wendt, Joel R.; Plut, Thomas A.; Martens, Jon S.

    1995-01-01

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material.

  18. Gap junctions.

    PubMed

    Goodenough, Daniel A; Paul, David L

    2009-07-01

    Gap junctions are aggregates of intercellular channels that permit direct cell-cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology.

  19. Gap Junctions

    PubMed Central

    Goodenough, Daniel A.; Paul, David L.

    2009-01-01

    Gap junctions are aggregates of intercellular channels that permit direct cell–cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology. PMID:20066080

  20. Gap junctions.

    PubMed

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2012-07-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1853-1872, 2012.

  1. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  2. Proving Stabilization of Biological Systems

    NASA Astrophysics Data System (ADS)

    Cook, Byron; Fisher, Jasmin; Krepska, Elzbieta; Piterman, Nir

    We describe an efficient procedure for proving stabilization of biological systems modeled as qualitative networks or genetic regulatory networks. For scalability, our procedure uses modular proof techniques, where state-space exploration is applied only locally to small pieces of the system rather than the entire system as a whole. Our procedure exploits the observation that, in practice, the form of modular proofs can be restricted to a very limited set. For completeness, our technique falls back on a non-compositional counterexample search. Using our new procedure, we have solved a number of challenging published examples, including: a 3-D model of the mammalian epidermis; a model of metabolic networks operating in type-2 diabetes; a model of fate determination of vulval precursor cells in the C. elegans worm; and a model of pair-rule regulation during segmentation in the Drosophila embryo. Our results show many orders of magnitude speedup in cases where previous stabilization proving techniques were known to succeed, and new results in cases where tools had previously failed.

  3. Leukoaraiosis is a predictor of futile recanalization in acute ischemic stroke.

    PubMed

    Gilberti, Nicola; Gamba, Massimo; Premi, Enrico; Costa, Angelo; Vergani, Veronica; Delrio, Ilenia; Spezi, Raffaella; Dikran, Mardighian; Frigerio, Michele; Gasparotti, Roberto; Pezzini, Alessandro; Padovani, Alessandro; Magoni, Mauro

    2017-03-01

    Futile recanalization occurs when successful recanalization fails to improve clinical outcome in acute ischemic stroke patients. Predictors of futile recanalization are still debated and may help in selecting patients for reperfusion strategies. We aim to determine whether leukoaraiosis may be useful in predicting futile recanalization in acute ischemic stroke patients treated by endovascular mechanical thrombectomy. We included in the analysis patients with acute ischemic stroke due to anterior circulation large vessel occlusion undergoing endovascular mechanical thrombectomy obtaining complete vessel recanalization. Demographics, vascular risk factors, baseline National Institutes of Health Stroke Scale score, time from symptoms onset to recanalization, Alberta Stroke Program Early CT Score, and leukoaraiosis graded on a 4-point van Swieten scale were collected. We dichotomized patients into those with moderate-severe leukoaraiosis (2-4) versus those with absent-slight leukoaraiosis (0, 1). Outcome measures were symptomatic intracranial hemorrhage, and modified Rankin scale score at 90 days. The relationships among radiological parameters and clinical data with outcome measures were studied with univariate and multivariable analyses. Sixty-eight patients were identified. Recanalization was futile in 32.4% of cases. On multivariable logistic regression analysis, the presence of moderate-severe LA was independent predictors of FR (P = 0.01). Furthermore, higher NIHSS score at baseline (P < 0.01) end endovascular mechanical thrombectomy alone treatment (P < 0.01) resulted associated with futile recanalization. Our results showed that the presence of moderate-severe leukoaraiosis is associated with poor outcome in recanalized patients.

  4. Gap junctions.

    PubMed

    Shimizu, Kazumichi; Stopfer, Mark

    2013-12-02

    In vertebrates and invertebrates, signaling among neurons is most commonly mediated by chemical synapses. At these synapses neurotransmitter released by presynaptic neurons is detected by receptors on the postsynaptic neurons, leading to an influx of ions through the receptors themselves or through channels activated by intracellular signaling downstream of the receptors. But neurons can communicate with each other in a more direct way, by passing signals composed of small molecules and ions through pores called gap junctions. Gap junctions that transmit electrical signals are called electrical synapses. Unlike most chemical synapses, electrical synapses interact through axon-to-axon or dendrite-to-dendrite contacts. Found throughout the nervous system, they are probably best known for linking the relatively few inhibitory, GABAergic, neurons into large, effective networks within vertebrate brains. They are particularly important early in development before the formation of most chemical synapses, but recent work shows gap junctions play important roles in the adult nervous system, too. Gap junctions are sometimes thought to be mere passageways between cells. But, as recent work shows, their properties can be complex and surprising. Gap junctions help generate, propagate, and regulate neural oscillations, can filter electrical signals, and can be modulated in a variety of ways. Here we discuss recent work highlighting the diversity and importance of gap junctions throughout the nervous system. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. A different approach to patients and loved ones who request "futile" treatments.

    PubMed

    Howe, Edmund G

    2012-01-01

    The author describes an alternative approach that care-providers may want to consider when caring for patients who request interventions that careproviders see as futile. This approach is based, in part, on findings of recent neuroimaging research. The author also provides several examples of seemingly justifiable "paternalistic omissions," taken from articles in this issue of The Journal of Clinical Ethics (JCE). The author suggests that while careproviders should always give patients and their loved ones all potentially relevant information regarding "futile" decisions, care-providers may wish to consider, paradoxically, not giving advice in these situations, when the advice is based mostly or wholly on their own moral views, based on this same, ethical rationale.

  6. [Futile medical care and euthanasia in the opinion of professional nurses].

    PubMed

    Renn-Zurek, Agnieszka

    2014-03-01

    Futile medical care and euthanasia are hard to assess unequivocally and are becoming a frequent topic of social discussion. The problem requires both ethical and moral consideration as well as legal regulations. As a medical issue it has got both its supporters and opponents. The aim of the study was to evaluate of nurses' attitudes and knowledge concerning euthanasia and persistend therapy. The survey group included 183 nurses aged 30-58. The diagnostic method poll was applied, the technique used was a questionnaire. Among the nurses participating in the survey, 83% is against providing futile medical care when it is known that it will not bring any effect, while increasing the suffering and prolonging dying. 45% of the respondents consider euthanasia unacceptable, 41% think that euthanasia could be performed in cases in which patient's suffering cannot be relieved. 49% of the surveyed think that euthanasia should remain strictly prohibited by the Polish law, while 31% think that Polish legal system should legalize euthanasia. The nurses are aware that futile medical care for terminally ill and dying patients does not lead to successful treatment but instead it prolongs dying and suffering, at the same time resulting in extremely high financial costs. In most cases they are advocates of its discontinuing. The surveyed nurses differ in their approach towards euthanasia, some of them supporting the idea, the other--opposing it. Most of them express the opinion that euthanasia should be forbidden in the Polish law and their personal approach towards euthanasia is negative.

  7. Interplay between tight junctions & adherens junctions.

    PubMed

    Campbell, Hannah K; Maiers, Jessica L; DeMali, Kris A

    2017-09-01

    Cell-cell adhesions are critical for the development and maintenance of tissues. Present at sites of cell-cell contact are the adherens junctions and tight junctions. The adherens junctions mediate cell-cell adhesion via the actions of nectins and cadherins. The tight junctions regulate passage of ions and small molecules between cells and establish cell polarity. Historically, the adherens and tight junctions have been thought of as discrete complexes. However, it is now clear that a high level of interdependency exists between the two junctional complexes. The adherens junctions and tight junctions are physically linked, by the zonula occludens proteins, and linked via signaling molecules including several polarity complexes and actin cytoskeletal modifiers. This review will first describe the individual components of both the adherens and tight junctions and then discuss the coupling of the two complexes with an emphasis on the signaling links and physical interactions between the two junctional complexes. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Proving allelopathy in crop-weed interactions

    USDA-ARS?s Scientific Manuscript database

    Allelopathy (plant/plant chemical warfare) is difficult to prove, especially when competition for resources is the dominant component of plant/plant interference (interference = allelopathy +competition). This paper describes experimental approaches for proving allelopathy and points out common pit...

  9. Optimal Futility Interim Design: A Predictive Probability of Success Approach with Time-to-Event Endpoint.

    PubMed

    Tang, Zhongwen

    2015-01-01

    An analytical way to compute predictive probability of success (PPOS) together with credible interval at interim analysis (IA) is developed for big clinical trials with time-to-event endpoints. The method takes account of the fixed data up to IA, the amount of uncertainty in future data, and uncertainty about parameters. Predictive power is a special type of PPOS. The result is confirmed by simulation. An optimal design is proposed by finding optimal combination of analysis time and futility cutoff based on some PPOS criteria.

  10. RNA Futile Cycling in Model Persisters Derived from MazF Accumulation

    PubMed Central

    Mok, Wendy W. K.; Park, Junyoung O.; Rabinowitz, Joshua D.

    2015-01-01

    ABSTRACT Metabolism plays an important role in the persister phenotype, as evidenced by the number of strategies that perturb metabolism to sabotage this troublesome subpopulation. However, the absence of techniques to isolate high-purity populations of native persisters has precluded direct measurement of persister metabolism. To address this technical challenge, we studied Escherichia coli populations whose growth had been inhibited by the accumulation of the MazF toxin, which catalyzes RNA cleavage, as a model system for persistence. Using chromosomally integrated, orthogonally inducible promoters to express MazF and its antitoxin MazE, bacterial populations that were almost entirely tolerant to fluoroquinolone and β-lactam antibiotics were obtained upon MazF accumulation, and these were subjected to direct metabolic measurements. While MazF model persisters were nonreplicative, they maintained substantial oxygen and glucose consumption. Metabolomic analysis revealed accumulation of all four ribonucleotide monophosphates (NMPs). These results are consistent with a MazF-catalyzed RNA futile cycle, where the energy derived from catabolism is dissipated through continuous transcription and MazF-mediated RNA degradation. When transcription was inhibited, oxygen consumption and glucose uptake decreased, and nucleotide triphosphates (NTPs) and NTP/NMP ratios increased. Interestingly, the MazF-inhibited cells were sensitive to aminoglycosides, and this sensitivity was blocked by inhibition of transcription. Thus, in MazF model persisters, futile cycles of RNA synthesis and degradation result in both significant metabolic demands and aminoglycoside sensitivity. PMID:26578677

  11. Defining futile life-prolonging treatments through Neo-Socratic Dialogue

    PubMed Central

    2013-01-01

    Background In Japan, people are negative towards life-prolonging treatments. Laws that regulate withholding or discontinuing life-prolonging treatments and advance directives do not exist. Physicians, however, view discontinuing life-prolonging treatments negatively due to fears of police investigations. Although ministerial guidelines were announced regarding the decision process for end-of-life care in 2007, a consensus could not be reached on the definition of end-of-life and conditions for withholding treatment. We established a forum for extended discussions and consensus building on this topic. Methods We used the Neo-Socratic Dialogue (NSD) method which promotes philosophical discussion based on a case-study to address a question and formulate a consensus and answer in a group. The question chosen for the dialogue was: “What is a life-prolonging treatment?” A series of dialogues took place over a period of one and a half days. It was carried out by three groups in 2010 and 2011. Seven participants with diverse backgrounds were recruited per group. We analyzed the content of the discussion. Results Based on three case studies concerning different opinions about treatment options for an older dementia patient, a patient demanding chemotherapy, and a severely ill neonate, conditions for futile life-prolonging treatment were elucidated through NSD. Such treatments are those carried out for the sole purpose of prolonging life and are detrimental to the patient, and should be decided based foremost on the patient’s lack of desire for treatment, the consensus of those involved, and through social acceptance. These arguments are essentially consistent with ones on medical futility in the United States. By expressing the objective of healthcare and the requirement of social acceptance, participants were also able to elucidate issues related to the awareness of those involved and the medical environment. Compared to the end-of-life guidelines in Japan, the

  12. Batch Proving and Proof Scripting in PVS

    NASA Technical Reports Server (NTRS)

    Munoz, Cesar A.

    2007-01-01

    The batch execution modes of PVS are powerful, but highly technical, features of the system that are mostly accessible to expert users. This paper presents a PVS tool, called ProofLite, that extends the theorem prover interface with a batch proving utility and a proof scripting notation. ProofLite enables a semi-literate proving style where specification and proof scripts reside in the same file. The goal of ProofLite is to provide batch proving and proof scripting capabilities to regular, non-expert, users of PVS.

  13. Proving relations between modular graph functions

    NASA Astrophysics Data System (ADS)

    Basu, Anirban

    2016-12-01

    We consider modular graph functions that arise in the low energy expansion of the four graviton amplitude in type II string theory. The vertices of these graphs are the positions of insertions of vertex operators on the toroidal worldsheet, while the links are the scalar Green functions connecting the vertices. Graphs with four and five links satisfy several non-trivial relations, which have been proved recently. We prove these relations by using elementary properties of Green functions and the details of the graphs. We also prove a relation between modular graph functions with six links.

  14. Novel Preoperative Nomogram for Prediction of Futile Resection in Patients Undergoing Exploration for Potentially Resectable Intrahepatic Cholangiocarcinoma

    PubMed Central

    Nam, Kwangwoo; Hwang, Dae Wook; Shim, Ju Hyun; Song, Tae Jun; Lee, Sang Soo; Seo, Dong-Wan; Lee, Sung Koo; Kim, Myung-Hwan; Kim, Ki-Hun; Hwang, Shin; Park, Kwang-Min; Lee, Young-Joo; Han, Minkyu; Park, Do Hyun

    2017-01-01

    Surgical resection is the treatment of choice for intrahepatic cholangiocarcinoma (IHCC). However, discrepancies between preoperative workup and intraoperative findings can occur, resulting in unexpected and unfavorable surgical outcomes. The aim of this study was to develop a feasible preoperative nomogram to predict futile resection of IHCC. A total of 718 patients who underwent curative-intent surgery for IHCC between January 2005 and December 2014 were included. The patients were divided into a training cohort (2005–2010, n = 377) and validation cohort (2011–2014, n = 341). The predictive accuracy and discriminative ability of the nomogram were determined by the concordance index and calibration curves. In multivariate analysis of the training cohort, tumor number, lymph node enlargement, presence of intrahepatic duct stones, and elevated neutrophil-to-lymphocyte ratio (NLR) (≥2.7) were independently correlated with the risk of futile resection. The predictive nomogram was established based on these factors. The concordance index of the nomogram for the training and the validation cohorts was 0.847 and 0.740, respectively. In this nomogram, the negative predictive value (128 points, probability of futile resection of 36%) in the validation cohort was 93.3%. In conclusion, our novel preoperatively applicable nomogram is a feasible method to predict futile resection of IHCC in curative-intent surgery. PMID:28211504

  15. 'Futile cycle' enzymes in the flight muscles of North American bumblebees.

    PubMed

    Staples, James F; Koen, Erin L; Laverty, Terence M

    2004-02-01

    In the flight muscles of European bumblebees, high activities of fructose-1,6-bisphosphatase (FbPase) relative to phosphofructokinase (PFK) have suggested a thermogenic 'futile cycle' important for regional endothermy. We find generally low activities of FbPase (0.7-19.7 units g(-1) thorax) in North American Bombus species, with the exception of Bombus rufocinctus, where activity (43.1 units g(-1) thorax) is comparable with that of European congeners. These data, taken with estimates of maximal rates of heat production by cycling, do not support a significant thermogenic role for the PFK/FbPase cycle. In agreement with earlier studies, both PFK and FbPase activities were found to scale allometrically with body size (allometric exponents -0.18 and -1.33, respectively). The cycle may serve to supplement thermogenesis or amplify glycolytic flux in rest-to-flight transitions, especially in smaller bees.

  16. Testing of the assumptions made in estimating the extent of futile cycling

    SciTech Connect

    Wajngot, A.; Chandramouli, V.; Schumann, W.C.; Kumaran, K.; Efendic, S.; Landau, B.R.

    1989-05-01

    In estimating glucose and fructose 6-phosphate futile cycling in vivo, complete detritiation of (2-/sup 3/H)glucose is assumed at the glucose 6-phosphate level, (3-/sup 3/H)glucose at triose phosphate formation, and (6-/sup 3/H)glucose in its conversion to glucose via pyruvate. (3-/sup 3/H)glucose detritiation via the pentose cycle is assumed to be negligible. Normal and non-insulin-dependent diabetic subjects, in the basal state and infused with glucose, were given (2-/sup 3/H,2-/sup 14/C)galactose, and /sup 3/H-to-/sup 14/C ratios in blood glucose were determined. (2-/sup 3/H,2-/sup 14/C)glucose was given with acetaminophen, and 3H/14C in urinary glucuronide was determined. Detritiation at glucose 6-phosphate was approximately 80%. (3-/sup 3/H,1-/sup 14/C)fructose was infused, and /sup 3/H//sup 14/C was determined in blood glucose and urinary glucuronide. At triose phosphate, 75-90% of the /sup 3/H was removed. The pentose cycle contribution was only a few percent. (6-/sup 3/H,6-/sup 14/C)glucose was infused, and 3H/14C in blood lactate was determined. (3-/sup 3/H,3-/sup 14/C)lactate was infused, and ratios in blood glucose were determined. Maximally, 10% of /sup 3/H from (6-/sup 3/H)glucose was retained. If glucose and galactose are metabolized in the same hepatic site(s), glucose conversion to three-carbon intermediates in the indirect pathway of glycogen formation occurs in extrahepatic tissue(s). Reported estimates of futile cycling, although qualitatively correct, quantitatively require correction.

  17. Beyond the Futility Argument: The Fair Process Approach and Time-Limited Trials for Managing Dialysis Conflict

    PubMed Central

    2013-01-01

    Summary Futility is an ancient concept arising from Greek mythology that was resurrected for its medical application in the 1980s with the proliferation of many lifesaving technologies, including dialysis and renal transplantation. By that time, the domineering medical paternalism that characterized the pre-1960s physician–patient relationship morphed into assertive patient autonomy, and some patients began to claim the right to demand aggressive, high-technology interventions, despite physician disapproval. To counter this power struggle, the establishment of a precise definition of futility offered hope for a futility policy that would allow physicians to justify withholding or withdrawing treatment, despite patient and family objections. This article reviews the various attempts made to define medical futility and describes their limited applicability to dialysis. When futility concerns arise, physicians should recognize the opportunity to address conflict, using best practice communication skills. Physicians would also benefit from understanding the ethical principles of respect for patient autonomy, beneficence, nonmaleficence, justice, and professional integrity that underlie medical decision-making. Also reviewed is the use of a fair process approach or time-limited trial when conflict resolution cannot be achieved. These topics are addressed in the Renal Physician Association’s clinical practice guideline Shared Decision-Making in the Appropriate Initiation and Withdrawal from Dialysis, with which nephrologists should be well versed. A case presentation of intractable calciphylaxis in a new dialysis patient illustrates the pitfalls of physicians not fully appreciating the ethics of medical decision-making and failing to use effective conflict management approaches in the clinical practice guideline. PMID:23868900

  18. Beyond the futility argument: the fair process approach and time-limited trials for managing dialysis conflict.

    PubMed

    Rinehart, Ann

    2013-11-01

    Futility is an ancient concept arising from Greek mythology that was resurrected for its medical application in the 1980s with the proliferation of many lifesaving technologies, including dialysis and renal transplantation. By that time, the domineering medical paternalism that characterized the pre-1960s physician-patient relationship morphed into assertive patient autonomy, and some patients began to claim the right to demand aggressive, high-technology interventions, despite physician disapproval. To counter this power struggle, the establishment of a precise definition of futility offered hope for a futility policy that would allow physicians to justify withholding or withdrawing treatment, despite patient and family objections. This article reviews the various attempts made to define medical futility and describes their limited applicability to dialysis. When futility concerns arise, physicians should recognize the opportunity to address conflict, using best practice communication skills. Physicians would also benefit from understanding the ethical principles of respect for patient autonomy, beneficence, nonmaleficence, justice, and professional integrity that underlie medical decision-making. Also reviewed is the use of a fair process approach or time-limited trial when conflict resolution cannot be achieved. These topics are addressed in the Renal Physician Association's clinical practice guideline Shared Decision-Making in the Appropriate Initiation and Withdrawal from Dialysis, with which nephrologists should be well versed. A case presentation of intractable calciphylaxis in a new dialysis patient illustrates the pitfalls of physicians not fully appreciating the ethics of medical decision-making and failing to use effective conflict management approaches in the clinical practice guideline.

  19. Protein misfolding, amyotrophic lateral sclerosis and guanabenz: protocol for a phase II RCT with futility design (ProMISe trial).

    PubMed

    Bella, Eleonora Dalla; Tramacere, Irene; Antonini, Giovanni; Borghero, Giuseppe; Capasso, Margherita; Caponnetto, Claudia; Chiò, Adriano; Corbo, Massimo; Eleopra, Roberto; Filosto, Massimiliano; Giannini, Fabio; Granieri, Enrico; Bella, Vincenzo La; Lunetta, Christian; Mandrioli, Jessica; Mazzini, Letizia; Messina, Sonia; Monsurrò, Maria Rosaria; Mora, Gabriele; Riva, Nilo; Rizzi, Romana; Siciliano, Gabriele; Silani, Vincenzo; Simone, Isabella; Sorarù, Gianni; Volanti, Paolo; Lauria, Giuseppe

    2017-08-11

    Recent studies suggest that endoplasmic reticulum stress may play a critical role in the pathogenesis of amyotrophic lateral sclerosis (ALS) through an altered regulation of the proteostasis, the cellular pathway-balancing protein synthesis and degradation. A key mechanism is thought to be the dephosphorylation of eIF2α, a factor involved in the initiation of protein translation. Guanabenz is an alpha-2-adrenergic receptor agonist safely used in past to treat mild hypertension and is now an orphan drug. A pharmacological action recently discovered is its ability to modulate the synthesis of proteins by the activation of translational factors preventing misfolded protein accumulation and endoplasmic reticulum overload. Guanabenz proved to rescue motoneurons from misfolding protein stress both in in vitro and in vivo ALS models, making it a potential disease-modifying drug in patients. It is conceivable investigating whether its neuroprotective effects based on the inhibition of eIF2α dephosphorylation can change the progression of ALS. Protocolised Management In Sepsis is a multicentre, randomised, double-blind, placebo-controlled phase II clinical trial with futility design. We will investigate clinical outcomes, safety, tolerability and biomarkers of neurodegeneration in patients with ALS treated with guanabenz or riluzole alone for 6 months. The primary aim is to test if guanabenz can reduce the proportion of patients progressed to a higher stage of disease at 6 months compared with their baseline stage as measured by the ALS Milano-Torino Staging (ALS-MITOS) system and to the placebo group. Secondary aims are safety, tolerability and change in at least one biomarker of neurodegeneration in the guanabenz arm compared with the placebo group. Findings will provide reliable data on the likelihood that guanabenz can slow the course of ALS in a phase III trial. The study protocol was approved by the Ethics Committee of IRCCS 'Carlo Besta Foundation' of Milan

  20. Regulation of Traffic Lights at Road Junctions

    NASA Astrophysics Data System (ADS)

    Cutolo, Alfredo; Manzo, Rosanna; Rarità, Luigi

    2009-08-01

    In this work, we aim to investigate the effects of traffic lights regulation at road junctions, modelled by a fluid dynamic approach. Numerical simulations prove that it is possible to plan some optimization strategies for green and red phases for networks consisting of more nodes.

  1. Generic Example Proving Criteria for All

    ERIC Educational Resources Information Center

    Yopp, David; Ely, Rob; Johnson­-Leung, Jennifer

    2015-01-01

    We review literature that discusses generic example proving and highlight ambiguities that pervade our research community's discourse about generic example arguments. We distinguish between pedagogical advice for choosing good examples that can serve as generic examples when teaching and advice for developing generic example arguments. We provide…

  2. Generic Example Proving Criteria for All

    ERIC Educational Resources Information Center

    Yopp, David; Ely, Rob; Johnson­-Leung, Jennifer

    2015-01-01

    We review literature that discusses generic example proving and highlight ambiguities that pervade our research community's discourse about generic example arguments. We distinguish between pedagogical advice for choosing good examples that can serve as generic examples when teaching and advice for developing generic example arguments. We provide…

  3. Affect, Behavioural Schemas and the Proving Process

    ERIC Educational Resources Information Center

    Selden, Annie; McKee, Kerry; Selden, John

    2010-01-01

    In this largely theoretical article, we discuss the relation between a kind of affect, behavioural schemas and aspects of the proving process. We begin with affect as described in the mathematics education literature, but soon narrow our focus to a particular kind of affect--nonemotional cognitive feelings. We then mention the position of feelings…

  4. The Role of Abduction in Proving Processes

    ERIC Educational Resources Information Center

    Pedemonte, Bettina; Reid, David

    2011-01-01

    This paper offers a typology of forms and uses of abduction that can be exploited to better analyze abduction in proving processes. Based on the work of Peirce and Eco, we describe different kinds of abductions that occur in students' mathematical activity and extend Toulmin's model of an argument as a methodological tool to describe students'…

  5. Generic Proving: Reflections on Scope and Method

    ERIC Educational Resources Information Center

    Leron, Uri; Zaslavsky, Orit

    2013-01-01

    We analyze the role of generic proofs in helping students access difficult proofs more easily and naturally. We present three examples of generic proving--an elementary one on numbers, a more advanced one on permutations, and yet more advanced one on groups--and consider the affordances and pitfalls of the method by reflecting on these examples. A…

  6. Epithelial adhesive junctions

    PubMed Central

    Capaldo, Christopher T.; Farkas, Attila E.

    2014-01-01

    Epithelial adhesive cell-to-cell contacts contain large, plasma membrane-spanning multiprotein aggregates that perform vital structural and signaling functions. Three prominent adhesive contacts are the tight junction, adherens junction, and the desmosome. Each junction type has unique cellular functions and a complex molecular composition. In this review, we comment on recent and exciting advances in our understanding of junction composition and function. PMID:24592313

  7. Theorem Proving In Higher Order Logics

    NASA Technical Reports Server (NTRS)

    Carreno, Victor A. (Editor); Munoz, Cesar A.; Tahar, Sofiene

    2002-01-01

    The TPHOLs International Conference serves as a venue for the presentation of work in theorem proving in higher-order logics and related areas in deduction, formal specification, software and hardware verification, and other applications. Fourteen papers were submitted to Track B (Work in Progress), which are included in this volume. Authors of Track B papers gave short introductory talks that were followed by an open poster session. The FCM 2002 Workshop aimed to bring together researchers working on the formalisation of continuous mathematics in theorem proving systems with those needing such libraries for their applications. Many of the major higher order theorem proving systems now have a formalisation of the real numbers and various levels of real analysis support. This work is of interest in a number of application areas, such as formal methods development for hardware and software application and computer supported mathematics. The FCM 2002 consisted of three papers, presented by their authors at the workshop venue, and one invited talk.

  8. Wideband rotating junctions

    NASA Astrophysics Data System (ADS)

    Pochernyaev, V. N.

    1993-06-01

    Rotating junctions of coaxial-waveguide and waveguide type with a traveling wave coefficient exceeding 0.8 in a wide frequency range are considered. The design of these junctions is based on a method of the theory of electrodynamic circuits. Numerical results are obtained for rotating junctions of partially filled rectangular waveguide type and their particular cases.

  9. Hepatectomy for hepatocellular carcinoma larger than 10 cm: preoperative risk stratification to prevent futile surgery

    PubMed Central

    Lim, Chetana; Compagnon, Philippe; Sebagh, Mylène; Salloum, Chady; Calderaro, Julien; Luciani, Alain; Pascal, Gérard; Laurent, Alexis; Levesque, Eric; Maggi, Umberto; Feray, Cyrille; Cherqui, Daniel; Castaing, Denis; Azoulay, Daniel

    2015-01-01

    Objectives Appropriate patient selection is important to achieving good outcomes and obviating futile surgery in patients with huge (≥10 cm) hepatocellular carcinoma (HCC). The aim of this study was to identify independent predictors of futile outcomes, defined as death within 3 months of surgery or within 1 year from early recurrence following hepatectomy for huge HCC. Methods The outcomes of 149 patients with huge HCCs who underwent resection during 1995–2012 were analysed. Multivariate logistic regression analysis was performed to identify preoperative independent predictors of futility. Results Independent predictors of 3-month mortality (18.1%) were: total bilirubin level <34 μmol/l [P = 0.0443; odds ratio (OR) 16.470]; platelet count of <150 000 cells/ml (P = 0.0098; OR 5.039), and the presence of portal vein tumour thrombosis (P = 0.0041; OR 5.138). The last of these was the sole independent predictor of 1-year recurrence-related mortality (17.2%). Rates of recurrence-related mortality at 3 months and 1 year were, respectively, 6.3% and 7.1% in patients with Barcelona Clinic Liver Cancer (BCLC) stage A disease, 12.5% and 14% in patients with BCLC stage B disease, and 37.8% (P = 0.0002) and 75% (P = 0.0002) in patients with BCLC stage C disease. Conclusions According to the present data, among patients submitted to hepatectomy for huge HCC, those with a high bilirubin level, low platelet count and portal vein thrombosis are at higher risk for futile surgery. The presence of portal vein tumour thrombosis should be regarded as a relative contraindication to surgery. PMID:25980326

  10. Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots.

    PubMed

    Coskun, Devrim; Britto, Dev T; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J

    2013-12-01

    Futile transmembrane NH3/NH4(+) cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4(+) toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4(+)) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope (13)N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4(+) ion. Influx of (13)NH3/(13)NH4(+), which exceeded 200 µmol g(-1) h(-1), was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4(+)), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g(-1) h(-1)). Efflux of (13)NH3/(13)NH4(+) responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions.

  11. The Messiha and Schiavo cases: third-party ethical and legal [corrected] interventions in futile care disputes.

    PubMed

    Faunce, Thomas A; Stewart, Cameron

    2005-09-05

    Relatives may increasingly demand that an incompetent patient's treatment be continued indefinitely, despite clinical advice that it is technically "futile" (offering no reasonable prospect of return to a meaningful quality of life). Third-party interventions may become a more frequent part of attempts to resolve such disputes where there is no formal advance directive. In the Messiha case, the Supreme Court of New South Wales upheld clinical judgement regarding the patient's best interests as most important. In the Schiavo case in the United States, clinicians' decisions on futility of treatment had received unwavering judicial support in more than 20 proceedings. Political differences between the US and Australia make it unlikely clinicians in this country will face Schiavo-type legislative challenges to individual clinical decisions and the judicial rulings upholding them. Consulting a clinical ethics committee in such scenarios is both legally recommended and clinically warranted as an important device for diffusing tensions between relatives and clinicians, as well as clarifying their respective ethical and legal responsibilities. In protracted or apparently irresolvable disputes with relatives, applying for a judicial declaration on futility of treatment has become a practical option for intensivists in Australia and should be a recognised part of their training.

  12. Detachment, futile cycling, and nucleotide pocket collapse in myosin-V stepping

    NASA Astrophysics Data System (ADS)

    Boon, Neville J.; Hoyle, Rebecca B.

    2015-02-01

    Myosin-V is a highly processive dimeric protein that walks with 36-nm steps along actin tracks, powered by coordinated adenosine triphosphate (ATP) hydrolysis reactions in the two myosin heads. No previous theoretical models of the myosin-V walk reproduce all the observed trends of velocity and run length with adenosine diphosphate (ADP), ATP and external forcing. In particular, a result that has eluded all theoretical studies based upon rigorous physical chemistry is that run length decreases with both increasing [ADP] and [ATP]. We systematically analyze which mechanisms in existing models reproduce which experimental trends and use this information to guide the development of models that can reproduce them all. We formulate models as reaction networks between distinct mechanochemical states with energetically determined transition rates. For each network architecture, we compare predictions for velocity and run length to a subset of experimentally measured values, and fit unknown parameters using a bespoke Monte Carlo simulated annealing optimization routine. Finally we determine which experimental trends are replicated by the best-fit model for each architecture. Only two models capture them all: one involving [ADP]-dependent mechanical detachment, and another including [ADP]-dependent futile cycling and nucleotide pocket collapse. Comparing model-predicted and experimentally observed kinetic transition rates favors the latter.

  13. Toward the clarification of ideas: medical futility, persistent/obstinate therapy and extra/ordinary means.

    PubMed

    Niebroj, Leslaw; Bargiel-Matusiewicz, Kamilla; Wilczynska, Agnieszka

    2013-01-01

    Despite reluctance of a part of medical society to accept the moral and/or legal permission to euthanasia, there is seemingly a common agreement on the need to resolve the problem of excessive therapy. Several ethical concepts are used to justify decisions to withhold/withdraw such treatment. Three of them are of particular value. The ordinary-extraordinary means distinction has a long tradition deeply-rooted in the Catholic medical ethics. During the last decades the concept of futile (or pointless) treatment has reached popularity within bioethical discourse. Also, slightly less common in use, the term 'obstinate therapy' and the relative concept seems to provide interesting insights into ethical debate. What is however to be emphasized is the ambiguity of meanings attached to these terms/concepts which prompt many bioethicists to reject these terms in favor of other concepts. In the present study a PubMed literature database review is done in order to recognize and then to classify the different ways of interpretation of the three concepts related to withholding/withdrawing excessive treatment. Retrieved interpretations of these concepts are evaluated in the light of an integrated model of moral justification. The undertaken analyses permit reaching the conclusion that the concepts which are the subject matter of this article can be properly defined and used only within the context of the so called holistic ethics and as an example of such i.e., a holistic approach to bioethics, the life's programs approach to bioethics is given.

  14. Mating pheromone in Cryptococcus neoformans is regulated by a transcriptional/degradative "futile" cycle.

    PubMed

    Park, Yoon-Dong; Panepinto, John; Shin, Soowan; Larsen, Peter; Giles, Steven; Williamson, Peter R

    2010-11-05

    Sexual reproduction in fungi requires induction of signaling pheromones within environments that are conducive to mating. The fungus Cryptococcus neoformans is currently the fourth greatest cause of infectious death in regions of Africa and undergoes mating in phytonutrient-rich environments to create spores with infectious potential. Here we show that under conditions where sexual development is inhibited, a ∼17-fold excess of MFα pheromone transcript is synthesized and then degraded by a DEAD box protein, Vad1, resulting in low steady state transcript levels. Transfer to mating medium or deletion of the VAD1 gene resulted in high level accumulation of MFα transcripts and enhanced mating, acting in concert with the mating-related HOG1 pathway. We then investigated whether the high metabolic cost of this apparently futile transcriptional cycle could be justified by a more rapid induction of mating. Maintenance of Vad1 activity on inductive mating medium by constitutive expression resulted in repressed levels of MFα that did not prevent but rather prolonged the time to successful mating from 5-6 h to 15 h (p < 0.0001). In sum, these data suggest that VAD1 negatively regulates the sexual cell cycle via degradation of constitutive high levels of MFα transcripts in a synthetic/degradative cycle, providing a mechanism of mRNA induction for time-critical cellular events, such as mating induction.

  15. Identification of productive and futile encounters in an electron transfer protein complex.

    PubMed

    Andrałojć, Witold; Hiruma, Yoshitaka; Liu, Wei-Min; Ravera, Enrico; Nojiri, Masaki; Parigi, Giacomo; Luchinat, Claudio; Ubbink, Marcellus

    2017-03-07

    Well-defined, stereospecific states in protein complexes are often in exchange with an ensemble of more dynamic orientations: the encounter states. The structure of the stereospecific complex between cytochrome P450cam and putidaredoxin was solved recently by X-ray diffraction as well as paramagnetic NMR spectroscopy. Other than the stereospecific complex, the NMR data clearly show the presence of additional states in the complex in solution. In these encounter states, populated for a small percentage of the time, putidaredoxin assumes multiple orientations and samples a large part of the surface of cytochrome P450cam. To characterize the nature of the encounter states, an extensive paramagnetic NMR dataset has been analyzed using the Maximum Occurrence of Regions methodology. The analysis reveals the location and maximal spatial extent of the additional states needed to fully explain the NMR data. Under the assumption of sparsity of the size of the conformational ensemble, several minor states can be located quite precisely. The distribution of these minor states correlates with the electrostatic potential map around cytochrome P450cam. Whereas some minor states are on isolated positively charged patches, others are connected to the stereospecific site via positively charged paths. The existence of electrostatically favorable pathways between the stereospecific interaction site and the different minor states or lack thereof suggests a means to discriminate between productive and futile encounter states.

  16. Early stopping in clinical trials and epidemiologic studies for "futility": conditional power versus sequential analysis.

    PubMed

    van der Tweel, Ingeborg; van Noord, Paulus A H

    2003-07-01

    Early stopping of a clinical trial is well accepted when there is enough evidence for a significant effect. However, during the course of a trial, there can be reasons to consider early termination for "futility." In epidemiologic studies, costly or destructive laboratory tests or slow case accrual can make it desirable to stop a study early for reasons of efficiency. Estimation of the conditional power (CP) is proposed as a decision tool to stop a study early or to continue it. We consider the disadvantages of this method. We propose (group) sequential continuation of the trial or study as a less arbitrary strategy. We re-analyzed two data sets from the literature to illustrate the advantages of a sequential approach. We conclude that (group) sequential analyses have several advantages over CP. More studies should consider a sequential design and analysis to enable early stopping when enough evidence has accumulated to conclude a lack of the expected effect. Such a strategy can save valuable resources for more promising hypotheses.

  17. Two-stage biomarker panel study and estimation allowing early termination for futility.

    PubMed

    Zhao, Shanshan; Zheng, Yingye; Prentice, Ross L; Feng, Ziding

    2015-10-01

    Technological advances have yielded a wealth of biomarkers that have the potential to detect chronic diseases such as cancer. However, most biomarkers considered for further validation turn out not to have strong enough performance to be used in clinical practice. Group sequential designs that allow early termination for futility may be cost-effective for biomarker studies based on biobanks of stored specimens. Previous studies proposed a group sequential design for the validation of a single biomarker. In this article, we adapt a 2-stage design to the setting where a panel of candidate biomarkers are under investigation. Conditional estimators of the clinical performance are proposed under an updated risk model that uses all accrued data, and can be computed through resampling procedures. Under a special case where a multivariate binormal distribution applies for biomarkers following a suitable transformation, these estimators have analytical forms, alleviating the computational burden while retaining statistical efficiency. Performance of the proposed 2-stage design and estimators are compared with a traditional fixed-sample design and an existing 2-stage design that allows early termination but does not update the risk model with accrued information. Our proposed design and estimators show an ability to reduce sample size when the biomarker panel is not promising, while controlling rejection rate and gaining efficiency when the panel is promising. We apply the proposed methods to a biomarker panel development for the detection of high-grade prostate cancer in a study conducted within the National Cancer Institute's Early Detection Research Network.

  18. Localized products of futile cycle/lrmp promote centrosome-nucleus attachment in the zebrafish zygote

    PubMed Central

    Lindeman, Robin Emily; Pelegri, Francisco

    2012-01-01

    SUMMARY Background The centrosome has a well-established role as a microtubule organizer during mitosis and cytokinesis. In addition, it facilitates the union of parental haploid genomes following fertilization by nucleating a microtubule aster along which the female pronucleus migrates towards the male pronucleus. Stable associations between the sperm aster and the pronuclei are essential during this directed movement. Results Our studies reveal that the zebrafish gene futile cycle (fue) is required in the zygote for male pronucleus-centrosome attachment and female pronuclear migration. We show that fue encodes a novel, maternally-provided long form of lymphoid-restricted membrane protein (lrmp), a vertebrate-specific gene of unknown function. Both maternal lrmp mRNA and protein are highly localized in the zygote, in a largely overlapping pattern at nuclear membranes, centrosomes, and spindles. Truncated Lrmp-EGFP fusion proteins identified subcellular targeting signals in the C-terminus of Lrmp, however endogenous mRNA localization is likely important to ensure strict spatial expression of the protein. Localization of both Lrmp protein and lrmp RNA is defective in fue mutant embryos, indicating that correct targeting of lrmp gene products is dependent on Lrmp function. Conclusions Lrmp is a conserved vertebrate gene whose maternally-inherited products are essential for nucleus-centrosome attachment and pronuclear congression during fertilization. Precise subcellular localization of lrmp products also suggests a requirement for strict spatiotemporal regulation of their function in the early embryo. PMID:22542100

  19. Localized products of futile cycle/lrmp promote centrosome-nucleus attachment in the zebrafish zygote.

    PubMed

    Lindeman, Robin E; Pelegri, Francisco

    2012-05-22

    The centrosome has a well-established role as a microtubule organizer during mitosis and cytokinesis. In addition, it facilitates the union of parental haploid genomes following fertilization by nucleating a microtubule aster along which the female pronucleus migrates toward the male pronucleus. Stable associations between the sperm aster and the pronuclei are essential during this directed movement. Our studies reveal that the zebrafish gene futile cycle (fue) is required in the zygote for male pronucleus-centrosome attachment and female pronuclear migration. We show that fue encodes a novel, maternally-provided long form of lymphoid-restricted membrane protein (lrmp), a vertebrate-specific gene of unknown function. Both maternal lrmp messenger RNA (mRNA) and protein are highly localized in the zygote, in a largely overlapping pattern at nuclear membranes, centrosomes, and spindles. Truncated Lrmp-EGFP fusion proteins identified subcellular targeting signals in the C terminus of Lrmp; however, endogenous mRNA localization is likely important to ensure strict spatial expression of the protein. Localization of both Lrmp protein and lrmp RNA is defective in fue mutant embryos, indicating that correct targeting of lrmp gene products is dependent on Lrmp function. Lrmp is a conserved vertebrate gene whose maternally inherited products are essential for nucleus-centrosome attachment and pronuclear congression during fertilization. Precise subcellular localization of lrmp products also suggests a requirement for strict spatiotemporal regulation of their function in the early embryo. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. When is it futile for ambulance personnel to initiate cardiopulmonary resuscitation?

    PubMed Central

    Marsden, A. K.; Ng, G. A.; Dalziel, K.; Cobbe, S. M.

    1995-01-01

    OBJECTIVE--To determine whether patients with unexpected prehospital cardiac arrest could be identified in whom ambulance resuscitation attempts would be futile. DESIGN--Review of ambulance and hospital records; detailed review of automated external defibrillator rhythm strips of patients in whom no shock was advised. SETTING--Scottish Ambulance Service; all cardiopulmonary resuscitation attempts after cardiorespiratory arrest during 1988-94 included in the Heartstart Scotland database. SUBJECT--414 cardiorespiratory arrest patients with no pulse or breathing on arrival of ambulance personnel, no bystander cardiopulmonary resuscitation performed, and more than 15 minutes from time of arrest to arrival of ambulance. Patients were stratified into those with "shockable" and "non-shockable" rhythms. MAIN OUTCOME MEASURES--Return of spontaneous circulation, or survival to reach hospital alive, or survival to discharge, or all three. RESULTS--No patient with a non-shockable rhythm who met the entry criteria for analysis survived a resuscitation attempt. Review of the defibrillator rhythm strips of these patients failed to find any case in which the tracing was deemed compatible with survival. CONCLUSION--On the basis that it would be inappropriate to initiate vigorous resuscitation in patients who can be identified as "dead" and beyond help an algorithm was prepared to guide ambulance personnel. Images p49-a PMID:7613330

  1. YBCO Josephson Junction Arrays

    DTIC Science & Technology

    1993-07-14

    Conductus 969 West Maude Avenue ř ’AEOTR. 19 4 0 0 75 Sunnyvale CA 94086 9. SPONSORING MONITORING AGENCY NAME(S) AND ADDRESS(ES) ’C 510 N’_ ; i )N !’->.G...the primary junction being investigated at Conductus (and one of the better performing junctions in the community) was the bi-epitaxial structure [4...achieved. 2.1 Junctions At the time of proposal, the primary junction being investigated at Conductus (and one of the better performing junctions in

  2. Proving refinement transformations using extended denotational semantics

    SciTech Connect

    Winter, V.L.; Boyle, J.M.

    1996-04-01

    TAMPR is a fully automatic transformation system based on syntactic rewrites. Our approach in a correctness proof is to map the transformation into an axiomatized mathematical domain where formal (and automated) reasoning can be performed. This mapping is accomplished via an extended denotational semantic paradigm. In this approach, the abstract notion of a program state is distributed between an environment function and a store function. Such a distribution introduces properties that go beyond the abstract state that is being modeled. The reasoning framework needs to be aware of these properties in order to successfully complete a correctness proof. This paper discusses some of our experiences in proving the correctness of TAMPR transformations.

  3. Futility interim monitoring with control of type I and II error probabilities using the interim Z-value or confidence limit.

    PubMed

    Lachin, John M

    2009-12-01

    It is highly desirable to terminate a clinical trial early if the emerging data suggests that the experimental treatment is ineffective, or substantially less effective than the level the study was designed to detect. Many studies have used a conditional power calculation as the basis for termination for futility. However, in order to compute conditional power one must posit an assumption about the distribution of the future data yet to be observed, such as that the original design assumptions will apply, or that the future data will have the same treatment effect as that estimated from the current 'trend' in the data. Each such assumption will yield a different conditional power value. The assessment of futility is described in terms of the observed quantities alone, specifically the interim Z-value or the interim confidence limit on the magnitude of the treatment effect, such that specified type I and II error probabilities are achieved. No assumption is required regarding the distribution of the future data yet to be observed. Lachin [1] presents a review of futility stopping based on assessment of conditional power and evaluates the statistical properties of a futility stopping rule. These methods are adapted to futility stopping using only the observed data without any assumption about the future data yet to be observed. The statistical properties of the futility monitoring plan depend specifically on the corresponding boundary value for the interim Z-value. These include the probability of interim stopping under the null or under a specific alternative hypothesis, and the resulting type I and II error probabilities. Thus, the stopping rule can be uniquely specified in terms of a boundary for the interim Z-value. Alternately, the stopping rule can be specified in terms of a boundary on the upper confidence limit for the treatment group effect (favoring treatment). Herein it is shown that this approach is equivalent to a boundary on the test Z-value, from which

  4. Theorem Proving in Intel Hardware Design

    NASA Technical Reports Server (NTRS)

    O'Leary, John

    2009-01-01

    For the past decade, a framework combining model checking (symbolic trajectory evaluation) and higher-order logic theorem proving has been in production use at Intel. Our tools and methodology have been used to formally verify execution cluster functionality (including floating-point operations) for a number of Intel products, including the Pentium(Registered TradeMark)4 and Core(TradeMark)i7 processors. Hardware verification in 2009 is much more challenging than it was in 1999 - today s CPU chip designs contain many processor cores and significant firmware content. This talk will attempt to distill the lessons learned over the past ten years, discuss how they apply to today s problems, outline some future directions.

  5. [Clinical anatomy of the esophagogastric junction].

    PubMed

    Tănase, M; Aldea, A S

    2012-01-01

    The esophagogastric junction is a controversial anatomical area, due to its sphincteric mechanism which does not show an obvious anatomical basis. The aim of this study is to investigate the anatomical components that endoscopically indicate the mucosal esophagogastric junction in hiatal hernia patients. The esophagogastric junction was investigated in 27 hiatal hernia patients undergoing surgery. Hiatal hernia is an extension of the stomach situated between the esophagogastric junction and the diaphragmatic indentation. The following types of hiatal hernia were found: sliding hiatal hernia (type I) in 4 patients (14.81%), rolling hiatal hernia (type II) in 2 (7.4%), mixed hiatal hernia (type III) in 12 (44.44%), type IV hiatal hernia in 4 (14.81%) and recurrent hiatal hernia in 5 (18.51%). Of the 27 hiatal hernia patients, 8 (29.6%) were operated using classical procedures: laparotomy--6 (75%) and laparoscopic surgery--2 (25%). The angle of His cannot be used for marking the mucosal esophagogastric junction due to the severe damage of the lower esophageal sphincter in hiatal hernia patients. The squamocolumnar junction is displaced in hiatal hernia patients and was not an option for the study group. The distal end of the esophageal longitudinal palisading vessels needs medication (proton pump inhibitors that reduce the gastric acid production), in order to enhance the visibility of these vessels. The proximal end of gastric longitudinal mucosal folds proved to be the most reliable site to identify endoscopically the mucosal esophagogastric junction. The anatomical structure of the esophagogastric junction differs in hiatal hernia patients and these peculiarities are very important in surgery.

  6. Spatio-temporal analysis of sub-hourly rainfall over Mumbai, India: Is statistical forecasting futile?

    NASA Astrophysics Data System (ADS)

    Singh, Jitendra; Sekharan, Sheeba; Karmakar, Subhankar; Ghosh, Subimal; Zope, P. E.; Eldho, T. I.

    2017-04-01

    Mumbai, the commercial and financial capital of India, experiences incessant annual rain episodes, mainly attributable to erratic rainfall pattern during monsoons and urban heat-island effect due to escalating urbanization, leading to increasing vulnerability to frequent flooding. After the infamous episode of 2005 Mumbai torrential rains when only two rain gauging stations existed, the governing civic body, the Municipal Corporation of Greater Mumbai (MCGM) came forward with an initiative to install 26 automatic weather stations (AWS) in June 2006 (MCGM 2007), which later increased to 60 AWS. A comprehensive statistical analysis to understand the spatio-temporal pattern of rainfall over Mumbai or any other coastal city in India has never been attempted earlier. In the current study, a thorough analysis of available rainfall data for 2006-2014 from these stations was performed; the 2013-2014 sub-hourly data from 26 AWS was found useful for further analyses due to their consistency and continuity. Correlogram cloud indicated no pattern of significant correlation when we considered the closest to the farthest gauging station from the base station; this impression was also supported by the semivariogram plots. Gini index values, a statistical measure of temporal non-uniformity, were found above 0.8 in visible majority showing an increasing trend in most gauging stations; this sufficiently led us to conclude that inconsistency in daily rainfall was gradually increasing with progress in monsoon. Interestingly, night rainfall was lesser compared to daytime rainfall. The pattern-less high spatio-temporal variation observed in Mumbai rainfall data signifies the futility of independently applying advanced statistical techniques, and thus calls for simultaneous inclusion of physics-centred models such as different meso-scale numerical weather prediction systems, particularly the Weather Research and Forecasting (WRF) model.

  7. Learning the futility of the thought suppression enterprise in normal experience and in obsessive compulsive disorder.

    PubMed

    Najmi, Sadia; Reese, Hannah; Wilhelm, Sabine; Fama, Jeanne; Beck, Celeste; Wegner, Daniel M

    2010-01-01

    The belief that we can control our thoughts is not inevitably adaptive, particularly when it fuels mental control activities that have ironic unintended consequences. The conviction that the mind can and should be controlled can prompt people to suppress unwanted thoughts, and so can set the stage for the intrusive return of those very thoughts. An important question is whether or not these beliefs about the control of thoughts can be reduced experimentally. One possibility is that behavioral experiments aimed at revealing the ironic return of suppressed thoughts might create a lesson that could reduce unrealistic beliefs about the control of thoughts. The present research assessed the influence of the thought suppression demonstration on beliefs about the control of thoughts in a non-clinical sample, and among individuals with obsessive-compulsive disorder (OCD). In Study 1, we assessed the effect of the thought suppression demonstration on beliefs about the control of thoughts among low and high obsessive individuals in the non-clinical population (N = 62). In Study 2, we conducted a similar study with individuals with OCD (N = 29). Results suggest that high obsessive individuals in the non-clinical population are able to learn the futility of suppression through the thought suppression demonstration and to alter their faulty beliefs about the control of thoughts; however, for individuals with OCD, the demonstration may be insufficient for altering underlying beliefs. For individuals with OCD, the connection between suppressing a neutral thought in the suppression demonstration and suppressing a personally relevant obsession may need to be stated explicitly in order to affect their obsessive beliefs.

  8. Myosins in cell junctions

    PubMed Central

    Liu, Katy C.; Cheney, Richard E.

    2012-01-01

    The development of cell-cell junctions was a fundamental step in metazoan evolution, and human health depends on the formation and function of cell junctions. Although it has long been known that actin and conventional myosin have important roles in cell junctions, research has begun to reveal the specific functions of the different forms of conventional myosin. Exciting new data also reveals that a growing number of unconventional myosins have important roles in cell junctions. Experiments showing that cell junctions act as mechanosensors have also provided new impetus to understand the functions of myosins and the forces they exert. In this review we will summarize recent developments on the roles of myosins in cell junctions. PMID:22954512

  9. Proving Program Termination With Matrix Weighted Digraphs

    NASA Technical Reports Server (NTRS)

    Dutle, Aaron

    2015-01-01

    Program termination analysis is an important task in logic and computer science. While determining if a program terminates is known to be undecidable in general, there has been a significant amount of attention given to finding sufficient and computationally practical conditions to prove termination. One such method takes a program and builds from it a matrix weighted digraph. These are directed graphs whose edges are labeled by square matrices with entries in {-1,0,1}, equipped with a nonstandard matrix multiplication. Certain properties of this digraph are known to imply the termination of the related program. In particular, termination of the program can be determined from the weights of the circuits in the digraph. In this talk, the motivation for addressing termination and how matrix weighted digraphs arise will be briefly discussed. The remainder of the talk will describe an efficient method for bounding the weights of a finite set of the circuits in a matrix weighted digraph, which allows termination of the related program to be deduced.

  10. a Test to Prove Cloud Whitening THEORY!

    NASA Astrophysics Data System (ADS)

    Buttram, J. W.

    2011-12-01

    Climate science researchers believe our planet can possibly tolerate twice the present carbon dioxide levels with no upwards temperature change, IF we could increase the amount of energy reflected back out into space by about 2.0%. (c)Cloudtec basically alters a blend of seawater and applies heat derived from magma to it at a temperature exceeding 2,000 degrees F. The interaction of seawater and magma displaces the oxygen, causing the volume of water to vaporize and expand over 4,000 times - transforming billions of tons of seawater into thousands of cubic miles of white, maritime, stratocumulus clouds to reflect the incident Sun's rays back out into space. A 6 month test to prove Cloud Whitening Theory will cost 6 million dollars. (No profit added.) This study will enable everyone on the planet with a computer the transparency to use satellite imagery and check out for themselves - if and when Cloud Whitening is occurring. If Cloud Whitening Theory is validated, (c)Cloudtec's innovation can strategically create the clouds we need to reflect the Sun's rays back out into space and help neutralize the projected 3.6 degrees F rise in temperature. Based on reasonable calculations of anthropogenic global warming: this one move alone would be comparable to slashing global carbon dioxide emissions by over 60% over the next 40 years.

  11. PET/CT Fusion Scan prevents futile laparotomy in early pancreatic cancer

    PubMed Central

    Kim, Richard; Prithviraj, Gopi; Kothari, Nishi; Springett, Greg; Malafa, Mokenge; Hodul, Pamela; Kim, Jongphil; Yue, Binglin; Morse, Brian; Mahipal, Amit

    2016-01-01

    Background In pancreatic cancer, early detection and complete surgical resection with negative margins offers the only cure for the disease. Work up to evaluate resectability includes triple phase helical scan CT of the pancreas and endoscopic ultrasound (EUS). A paucity of data exists in using PET/CT scan as staging work up in early resectable pancreatic cancer. The objective of our study was to determine if PET/CT prevents futile laparotomy by detecting occult metastatic disease in patients with resectable/borderline pancreatic cancer. Methods We looked at our institutional PET/CT data base incorporating National Oncologic PET Registry with diagnosis of resectable or borderline resectable pancreatic cancer from 2005 to 2012. Clinical, radiographic, and pathologic follow-up was evaluated, including age, gender, evidence of metastatic disease, and initial CA 19–9 levels. The impact of PET/CT on patient management was estimated by calculating the percentage of patients whose treatment plan was altered due to PET/CT. The confidence interval was computed using the exact binomial distribution. The effect on the change was evaluated by the multiple logistic regression model. The final model was selected using the backward elimination method. Results We identified 285 patients with early stage (resectable or borderline) pancreatic cancer who received PET/CT as part of initial staging workup. Upon initial work up (CT + EUS), 62% of patients were considered resectable and 38% were borderline resectable. Addition of PET/CT scan changed the management in 10.9% (n=31) of patients (95% CI: 7.5%–15.1%). Median time from EUS to PET/CT was 5 days. Metastatic lesions were confirmed with biopsy in 19 (61%) patients. The proportion in the change in treatment plan is significantly higher in patients who were initially considered to have borderline resectable compared to resectable malignancy (16.5% vs. 7.4%). In 199 patients who were taken to surgery, 18.1% (n=36) were found to

  12. The discovery of epidermal tight junctions.

    PubMed

    Ozawa, Toshiyuki; Sugawara, Koji; Tsuruta, Daisuke

    2014-06-01

    It was previously thought that the skin barrier is composed singly by the stratum corneum. However, this concept was overturned by the report of Tsukita's group in 2002. They convinced us that tight junctions exist in the stratum granulosum of the epidermis, with the constituent proteins being occludin, claudin-1 and claudin-4. However, more than 30 years before this, Hashimoto et al. described the possible existence of tight junctions in the epidermis in 'Intercellular spaces of the human epidermis as demonstrated with lanthanum' in 1971. Dr. Hashimoto observed lanthanum nitrate-injected human skin by electron microscopy. He discovered that the injected lanthanum penetrated the intercellular spaces of the basal and spinous layers of the epidermis and then moved towards the skin surface until penetration was halted in the granular cell layer near the stratum corneum. He described the cell-to-cell adhesion structures that blocked the movement of lanthanum as 'truly tight junctions'. Thus, this was the first description of the existence of tight junctions in the epidermis. However, the presence of these structures was denied by others and was forgotten. Thanks to the discovery of claudin, the existence of tight junctions between epidermal keratinocytes was finally confirmed. It is interesting that Hashimoto's finding was eventually proved to be correct three decades later as a result of progress in molecular biology. This article encourages us to recognize the importance of careful observation in the molecular biology era. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Indian Ocean Triple Junction

    SciTech Connect

    Tapscott, C.R.; Patriat, P.; Fisher, R.L.; Sclater, J.G.; Hoskins, H.; Parsons, B.

    1980-09-10

    The boundaries of three major plates (Africa, India, and Antarctica) meet in a triple junction in the Indian Ocean near 25 /sup 0/S, 70 /sup 0/E. Using observed bathymetry and magnetic anomalies, we locate the junction to within 5 km and show that it is a ridge-ridge-ridge type. Relative plate motion is N60 /sup 0/E at 50 mm/yr (full rate) across the Central Indian Ridge, N47 /sup 0/E at 60 mm/yr across the Southeast Indian Ridge, and N3 /sup 0/W at 15 mm/yr across te Southwest Indian Ridge; the observed velocity triangle is closed. Poles of instantaneous relative plate motion are determined for all plate pairs. The data in the South Atlantic and Indian oceans are consistent with a rigid African plate without significant internal deformation. Two of the ridges at the triple junction are normal midocean spreading centers with well-defined median valleys. The Southwest Indian Ridge, however, has a peculiar morphology near the triple junction, that of an elongate triangular deep, with the triple junction at its apex. The floor of the deep represents crust formed at the Southwest Indian Ridge, and the morphology is a consequence of the evolution of the triple junction and is similar to that at the Galapagos Triple Junction. Though one cannot determine with precision the stability conditions at the triple junction, the development of the junction over the last 10 m.y. can be mapped, and the topographic expressions of the triple junction traces may be detected on the three plates.

  14. Alberta Stroke Program Early CT Score applied to CT angiography source images is a strong predictor of futile recanalization in acute ischemic stroke.

    PubMed

    Kawiorski, Michal M; Martínez-Sánchez, Patricia; García-Pastor, Andrés; Calleja, Patricia; Fuentes, Blanca; Sanz-Cuesta, Borja E; Lourido, Daniel; Marín, Begoña; Díaz-Otero, Fernando; Vicente, Agustina; Sierra-Hidalgo, Fernando; Ruiz-Ares, Gerardo; Díez-Tejedor, Exuperio; Fandiño, Eduardo; Alonso de Leciñana, María

    2016-05-01

    Reliable predictors of poor clinical outcome despite successful revascularization might help select patients with acute ischemic stroke for thrombectomy. We sought to determine whether baseline Alberta Stroke Program Early CT Score (ASPECTS) applied to CT angiography source images (CTA-SI) is useful in predicting futile recanalization. Data are from the FUN-TPA study registry (ClinicalTrials.gov; NCT02164357) including patients with acute ischemic stroke due to proximal arterial occlusion in anterior circulation, undergoing reperfusion therapies. Baseline non-contrast CT and CTA-SI-ASPECTS, time-lapse to image acquisition, occurrence, and timing of recanalization were recorded. Outcome measures were NIHSS at 24 h, symptomatic intracranial hemorrhage, modified Rankin scale score, and mortality at 90 days. Futile recanalization was defined when successful recanalization was associated with poor functional outcome (death or disability). Included were 110 patients, baseline NIHSS 17 (IQR 12; 20), treated with intravenous thrombolysis (IVT; 45 %), primary mechanical thrombectomy (MT; 16 %), or combined IVT + MT (39 %). Recanalization rate was 71 %, median delay of 287 min (225; 357). Recanalization was futile in 28 % of cases. In an adjusted model, baseline CTA-SI-ASPECTS was inversely related to the odds of futile recanalization (OR 0.5; 95 % CI 0.3-0.7), whereas NCCT-ASPECTS was not (OR 0.8; 95 % CI 0.5-1.2). A score ≤5 in CTA-SI-ASPECTS was the best cut-off to predict futile recanalization (sensitivity 35 %; specificity 97 %; positive predictive value 86 %; negative predictive value 77 %). CTA-SI-ASPECTS strongly predicts futile recanalization and could be a valuable tool for treatment decisions regarding the indication of revascularization therapies.

  15. miR-378 Activates the Pyruvate-PEP Futile Cycle and Enhances Lipolysis to Ameliorate Obesity in Mice.

    PubMed

    Zhang, Yong; Li, Changyin; Li, Hu; Song, Yipeng; Zhao, Yixia; Zhai, Lili; Wang, Haixia; Zhong, Ran; Tang, Huiru; Zhu, Dahai

    2016-03-01

    Obesity has been linked to many health problems, such as diabetes. However, there is no drug that effectively treats obesity. Here, we reveal that miR-378 transgenic mice display reduced fat mass, enhanced lipolysis, and increased energy expenditure. Notably, administering AgomiR-378 prevents and ameliorates obesity in mice. We also found that the energy deficiency seen in miR-378 transgenic mice was due to impaired glucose metabolism. This impairment was caused by an activated pyruvate-PEP futile cycle via the miR-378-Akt1-FoxO1-PEPCK pathway in skeletal muscle and enhanced lipolysis in adipose tissues mediated by miR-378-SCD1. Our findings demonstrate that activating the pyruvate-PEP futile cycle in skeletal muscle is the primary cause of elevated lipolysis in adipose tissues of miR-378 transgenic mice, and it helps orchestrate the crosstalk between muscle and fat to control energy homeostasis in mice. Thus, miR-378 may serve as a promising agent for preventing and treating obesity in humans.

  16. Potential uselessness and futility of left atrial appendage occlusion and patent foramen ovale closure in cardioembolic stroke.

    PubMed

    Nicolosi, Gian L

    2017-02-16

    International guidelines indicate that interventional closure of left atrial appendage and patent foramen ovale may be considered in selected patients for stroke prevention. These procedures appear, however, from the published literature, at high risk of uselessness and futility in the single case, if not even capable to induce harm and adverse events. In fact, all reported systematic reviews and meta-analyses have not shown in a convincing manner the superiority of these procedures in stroke prevention, taking into account the occurrence of possible complications also, as compared with alternative medical treatment. On the basis of these considerations, it becomes very difficult to define always and unequivocally how adequate and complete was the information when given to each single candidate patient before the procedure by the Heart Team, the left atrial appendage occlusion Team or patent foramen ovale closure Team, potentially involved in conflict of interest. Before indicating these procedures, a complete diagnostic work-up should then be planned for each single patient to identify and treat not only one, but all concomitant risk factors and potential different cardioembolic sources. It could also be suggested to have, for each single candidate patient, a second independent opinion from physicians not involved in the procedure and possibly not operating in the same institution. This prudential approach could reduce in each single case the risk of uselessness, futility and even potential harm and adverse events of those procedures.

  17. Futile transmembrane NH4+ cycling: A cellular hypothesis to explain ammonium toxicity in plants

    PubMed Central

    Britto, Dev T.; Siddiqi, M. Yaeesh; Glass, Anthony D. M.; Kronzucker, Herbert J.

    2001-01-01

    {mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{4}^{+}}}\\end{equation*}\\end{document}, reveal that, at elevated [NH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{4}^{+}}}\\end{equation*}\\end{document}]o, barley cells engage a high-capacity NH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{4}^{+}}}\\end{equation*}\\end{document}-efflux system that supports outward NH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{4}^{+}}}\\end{equation*}\\end{document} fluxes against a sizable gradient. Ammonium efflux is shown to constitute as much as 80% of primary influx, resulting in a never-before-documented futile cycling of nitrogen across the plasma membrane of root cells. This futile cycling carries a high energetic cost (we record a 40% increase in root respiration) that is independent of N metabolism and is accompanied by a decline in growth. In rice, by contrast, a cellular defense strategy has evolved that is characterized by an energetically neutral, near-Nernstian, equilibration of NH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{4}^{+}}}\\end{equation*}\\end{document} at high [NH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage

  18. Quantum junction solar cells.

    PubMed

    Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics.

  19. Perceived Ethnic Discrimination by Teachers and Ethnic Minority Students' Academic Futility: Can Parents Prepare Their Youth for Better or for Worse?

    PubMed

    D'hondt, Fanny; Eccles, Jacquelynne S; Van Houtte, Mieke; Stevens, Peter A J

    2016-06-01

    This study focuses on the interplay of perceived ethnic discrimination by teachers, parents' ethnic socialization practices, and ethnic minority students' sense of academic futility. Since discrimination creates barriers beyond control of the individual, the first research goal is to examine the association of perceived ethnic discrimination by teachers with ethnic minority students' sense of academic futility. The second research goal is to focus on the role of perceived parental ethnic socialization (e.g., cultural socialization and preparation for bias) to get a better understanding of the interaction between family level factors and the potentially negative consequences of ethnic teacher discrimination. A multilevel analysis on 1181 ethnic minority students (50.6 % girls; mean age = 15.5), originating from migration, in 53 secondary schools in Flanders (Belgium) shows that the frequent perception of ethnic discrimination by teachers is associated with stronger feelings of academic futility, and if these students also received high levels of parents' ethnic socialization, they perceive even stronger feelings of futility. The group of ethnic minority students, who perceive frequent ethnic teacher discrimination, is a group at risk, and parents' ethnic socialization does not seem able to change this.

  20. The dynamic organic p-n junction.

    PubMed

    Matyba, Piotr; Maturova, Klara; Kemerink, Martijn; Robinson, Nathaniel D; Edman, Ludvig

    2009-08-01

    Static p-n junctions in inorganic semiconductors are exploited in a wide range of today's electronic appliances. Here, we demonstrate the in situ formation of a dynamic p-n junction structure within an organic semiconductor through electrochemistry. Specifically, we use scanning kelvin probe microscopy and optical probing on planar light-emitting electrochemical cells (LECs) with a mixture of a conjugated polymer and an electrolyte connecting two electrodes separated by 120 microm. We find that a significant portion of the potential drop between the electrodes coincides with the location of a thin and distinct light-emission zone positioned >30 microm away from the negative electrode. These results are relevant in the context of a long-standing scientific debate, as they prove that electrochemical doping can take place in LECs. Moreover, a study on the doping formation and dissipation kinetics provides interesting detail regarding the electronic structure and stability of the dynamic organic p-n junction, which may be useful in future dynamic p-n junction-based devices.

  1. Disruption of BCATm in mice leads to increased energy expenditure associated with the activation of a futile protein turnover cycle

    PubMed Central

    She, Pengxiang; Reid, Tanya M.; Bronson, Sarah K.; Vary, Thomas C.; Hajnal, Andras; Lynch, Christopher J; Hutson, Susan M.

    2009-01-01

    Summary Leucine is recognized as a nutrient signal, however the long-term in vivo consequences of leucine signaling and the role of branched chain amino acid (BCAA) metabolism in this signaling remains unclear. To investigate these questions, the BCATm gene encoding the enzyme catalyzing the first step in peripheral BCAA metabolism was disrupted. BCATm−/− mice exhibited elevated plasma BCAAs, decreased adiposity and body weight, despite eating more food, along with increased energy expenditure, remarkable improvements in glucose and insulin tolerance, and protection from diet induced obesity. The increased energy expenditure did not seem to be due to altered locomotor activity, uncoupling proteins, sympathetic activity, and thyroid hormones but was strongly associated with food consumption and an active futile cycle of increased protein degradation and synthesis. These observations suggest that either elevated BCAAs and/or loss of BCAA catabolism in peripheral tissues play an important role in regulating insulin sensitivity and energy expenditure. PMID:17767905

  2. RIP140 represses the "brown-in-white" adipocyte program including a futile cycle of triacylglycerol breakdown and synthesis.

    PubMed

    Kiskinis, Evangelos; Chatzeli, Lemonia; Curry, Edward; Kaforou, Myrsini; Frontini, Andrea; Cinti, Saverio; Montana, Giovanni; Parker, Malcolm G; Christian, Mark

    2014-03-01

    Receptor-interacting protein 140 (RIP140) is a corepressor of nuclear receptors that is highly expressed in adipose tissues. We investigated the role of RIP140 in conditionally immortal preadipocyte cell lines prepared from white or brown fat depots. In white adipocytes, a large set of brown fat-associated genes was up-regulated in the absence of RIP140. In contrast, a relatively minor role can be ascribed to RIP140 in the control of basal gene expression in differentiated brown adipocytes because significant changes were observed only in Ptgds and Fabp3. The minor role of RIP140 in brown adipocytes correlates with the similar histology and uncoupling protein 1 and CIDEA staining in knockout compared with wild-type brown adipose tissue (BAT). In contrast, RIP140 knockout sc white adipose tissue (WAT) shows increased numbers of multilocular adipocytes with elevated staining for uncoupling protein 1 and CIDEA. Furthermore in a white adipocyte cell line, the markers of BRITE adipocytes, Tbx1, CD137, Tmem26, Cited1, and Epsti1 were repressed in the presence of RIP140 as was Prdm16. Microarray analysis of wild-type and RIP140-knockout white fat revealed elevated expression of genes associated with cold-induced expression or high expression in BAT. A set of genes associated with a futile cycle of triacylglycerol breakdown and resynthesis and functional assays revealed that glycerol kinase and glycerol-3-phosphate dehydrogenase activity as well as [(3)H]glycerol incorporation were elevated in the absence of RIP140. Thus, RIP140 blocks the BRITE program in WAT, preventing the expression of brown fat genes and inhibiting a triacylglycerol futile cycle, with important implications for energy homeostasis.

  3. 13C and 1H Nuclear Magnetic Resonance Study of Glycogen Futile Cycling in Strains of the Genus Fibrobacter

    PubMed Central

    Matheron, Christelle; Delort, Anne-Marie; Gaudet, Geneviève; Forano, Evelyne; Liptaj, Tibor

    1998-01-01

    We investigated the carbon metabolism of three strains of Fibrobacter succinogenes and one strain of Fibrobacter intestinalis. The four strains produced the same amounts of the metabolites succinate, acetate, and formate in approximately the same ratio (3.7/1/0.3). The four strains similarly stored glycogen during all growth phases, and the glycogen-to-protein ratio was close to 0.6 during the exponential growth phase. 13C nuclear magnetic resonance (NMR) analysis of [1-13C]glucose utilization by resting cells of the four strains revealed a reversal of glycolysis at the triose phosphate level and the same metabolic pathways. Glycogen futile cycling was demonstrated by 13C NMR by following the simultaneous metabolism of labeled [13C]glycogen and exogenous unlabeled glucose. The isotopic dilutions of the CH2 of succinate and the CH3 of acetate when the resting cells were metabolizing [1-13C]glucose and unlabeled glycogen were precisely quantified by using 13C-filtered spin-echo difference 1H NMR spectroscopy. The measured isotopic dilutions were not the same for succinate and acetate; in the case of succinate, the dilutions reflected only the contribution of glycogen futile cycling, while in the case of acetate, another mechanism was also involved. Results obtained in complementary experiments are consistent with reversal of the succinate synthesis pathway. Our results indicated that for all of the strains, from 12 to 16% of the glucose entering the metabolic pathway originated from prestored glycogen. Although genetically diverse, the four Fibrobacter strains studied had very similar carbon metabolism characteristics. PMID:12033219

  4. RIP140 Represses the “Brown-in-White” Adipocyte Program Including a Futile Cycle of Triacyclglycerol Breakdown and Synthesis

    PubMed Central

    Kiskinis, Evangelos; Chatzeli, Lemonia; Curry, Edward; Kaforou, Myrsini; Frontini, Andrea; Cinti, Saverio; Montana, Giovanni; Parker, Malcolm G.

    2014-01-01

    Receptor-interacting protein 140 (RIP140) is a corepressor of nuclear receptors that is highly expressed in adipose tissues. We investigated the role of RIP140 in conditionally immortal preadipocyte cell lines prepared from white or brown fat depots. In white adipocytes, a large set of brown fat-associated genes was up-regulated in the absence of RIP140. In contrast, a relatively minor role can be ascribed to RIP140 in the control of basal gene expression in differentiated brown adipocytes because significant changes were observed only in Ptgds and Fabp3. The minor role of RIP140 in brown adipocytes correlates with the similar histology and uncoupling protein 1 and CIDEA staining in knockout compared with wild-type brown adipose tissue (BAT). In contrast, RIP140 knockout sc white adipose tissue (WAT) shows increased numbers of multilocular adipocytes with elevated staining for uncoupling protein 1 and CIDEA. Furthermore in a white adipocyte cell line, the markers of BRITE adipocytes, Tbx1, CD137, Tmem26, Cited1, and Epsti1 were repressed in the presence of RIP140 as was Prdm16. Microarray analysis of wild-type and RIP140-knockout white fat revealed elevated expression of genes associated with cold-induced expression or high expression in BAT. A set of genes associated with a futile cycle of triacylglycerol breakdown and resynthesis and functional assays revealed that glycerol kinase and glycerol-3-phosphate dehydrogenase activity as well as [3H]glycerol incorporation were elevated in the absence of RIP140. Thus, RIP140 blocks the BRITE program in WAT, preventing the expression of brown fat genes and inhibiting a triacylglycerol futile cycle, with important implications for energy homeostasis. PMID:24479876

  5. Quantifying the bias in the estimated treatment effect in randomized trials having interim analyses and a rule for early stopping for futility.

    PubMed

    Walter, S D; Han, H; Briel, M; Guyatt, G H

    2017-04-30

    In this paper, we consider the potential bias in the estimated treatment effect obtained from clinical trials, the protocols of which include the possibility of interim analyses and an early termination of the study for reasons of futility. In particular, by considering the conditional power at an interim analysis, we derive analytic expressions for various parameters of interest: (i) the underestimation or overestimation of the treatment effect in studies that stop for futility; (ii) the impact of the interim analyses on the estimation of treatment effect in studies that are completed, i.e. that do not stop for futility; (iii) the overall estimation bias in the estimated treatment effect in a single study with such a stopping rule; and (iv) the probability of stopping at an interim analysis. We evaluate these general expressions numerically for typical trial scenarios. Results show that the parameters of interest depend on a number of factors, including the true underlying treatment effect, the difference that the trial is designed to detect, the study power, the number of planned interim analyses and what assumption is made about future data to be observed after an interim analysis. Because the probability of stopping early is small for many practical situations, the overall bias is often small, but a more serious issue is the potential for substantial underestimation of the treatment effect in studies that actually stop for futility. We also consider these ideas using data from an illustrative trial that did stop for futility at an interim analysis. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Overcoming the Obstacle of Poor Knowledge in Proving Geometry Tasks

    ERIC Educational Resources Information Center

    Magajna, Zlatan

    2013-01-01

    Proving in school geometry is not just about validating the truth of a claim. In the school setting, the main function of the proof is to convince someone that a claim is true by providing an explanation. Students consider proving to be difficult; in fact, they find the very concept of proof demanding. Proving a claim in planar geometry involves…

  7. Four-junction superconducting circuit

    NASA Astrophysics Data System (ADS)

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-06-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.

  8. Four-junction superconducting circuit

    PubMed Central

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  9. Dot junction solar cells

    NASA Technical Reports Server (NTRS)

    Daud, T.; Crotty, G. T.

    1986-01-01

    A design of solar cells with reduced junction area on the cell surface is investigated for reduction of saturation current and increase in open-circuit voltage. Equidiameter dot junctions distributed across the surface of the cell offer an efficient alternative, with variations in dot diameter and in the spacing between dots giving the required variations in the ratio of junction area to total surface area. A simplified analysis for short-circuit current and other cell parameters, which enables cell design optimization, is presented. Experimental solar-cell performance results, as functions of different area ratios, are presented and compared with the model. It is shown that saturation current reduction is possible for achieving efficiencies as high as 18 percent in flat-plate terrestrial applications.

  10. Victory Junction Gang Camp

    ERIC Educational Resources Information Center

    Shell, Ryan

    2007-01-01

    This article describes the Victory Junction Gang Camp, a not-for-profit, NASCAR-themed camp for children with chronic medical conditions that serves 24 different disease groups. The mission of the camp is to give children life-changing camping experiences that are exciting, fun, and empowering in a safe and medically sound environment. While doing…

  11. Brain barriers: Crosstalk between complex tight junctions and adherens junctions.

    PubMed

    Tietz, Silvia; Engelhardt, Britta

    2015-05-25

    Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood-brain barrier (BBB) and the epithelial blood-cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function. © 2015 Tietz and Engelhardt.

  12. Intercellular junctions in myriapods.

    PubMed

    Dallai, R; Bigliardi, E; Lane, N J

    1990-01-01

    Tissue from the intestinal tract of myriapods, including millipedes, centipedes and pauropods were examined in tracer-impregnated sections and freeze-fracture replicas. The foregut and hindgut of all three classes exhibit pleated septate junctions; these display undulating intercellular ribbons in thin sections. In replicas they show discrete intramembranous particle (IMP) arrays aligned in rows in parallel; with one another. The tissues of the hindgut also possess scalariform junctions, characterized by cross-striated intercellular clefts in sections and IMP-enriched membranes in replicas. Gap junctions occur in all groups, but they are atypical in replicas in that their component IMPs do not always fracture onto the E face, as is characteristic of other arthropods; some IMPs cleave to the P face and others to the E face. The midgut of these organisms exhibits smooth septate junctions with conventional straight septal ribbons and occasional interseptal columns. However the intramembranous appearance in replicas is variable, particularly in centipedes, in that the rows of IMPs in chemically-unfixed propanecryofixed tissues, are prominent and adhere preferentially to the E face, with complementary P face grooves, while in fixed tissues the IMPs are much less distinct and fracture to either P face or E face. They tend not to protrude far beyond the mid-plane of the membrane bilayer and lie in rows which commonly take on the form of a network. Individual rows of the network sometimes curve to run beside a second row, over a short distance, before bending away into another part of the network. The aligned particle rows, which are much more prominent in millipedes, where they frequently lie in close parallel appositions, do not fuse into ridges as often occurs in insect tissues. The myriapod junctions, therefore, are of the same general kind as are found in the gut tract of other arthropod groups, but differ with respect to the subtleties of their intramembranous

  13. The Earth is Flat, and I Can Prove It!

    ERIC Educational Resources Information Center

    Klinger, Art

    1998-01-01

    Describes an educational program that asks students to attempt to prove that the earth is spherical and that it rotates. Presents tips to pique student interest and charts related to sensing the spin, nonrotation notions, flat earth fallacies, evidence that the earth is spherical and rotates, and the role of watersheds in proving that the earth…

  14. Generating and Using Examples in the Proving Process

    ERIC Educational Resources Information Center

    Sandefur, J.; Mason, J.; Stylianides, G. J.; Watson, A.

    2013-01-01

    We report on our analysis of data from a dataset of 26 videotapes of university students working in groups of 2 and 3 on different proving problems. Our aim is to understand the role of example generation in the proving process, focusing on deliberate changes in representation and symbol manipulation. We suggest and illustrate four aspects of…

  15. Reasoning-and-Proving in School Mathematics Textbooks

    ERIC Educational Resources Information Center

    Stylianides, Gabriel J.

    2009-01-01

    Despite widespread agreement that the activity of "reasoning-and-proving" should be central to all students' mathematical experiences, many students face serious difficulties with this activity. Mathematics textbooks can play an important role in students' opportunities to engage in reasoning-and-proving: research suggests that many decisions that…

  16. 14 CFR 121.163 - Aircraft proving tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Aircraft proving tests. 121.163 Section 121... REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Aircraft Requirements § 121.163 Aircraft proving...) Alterations to the aircraft or its components that materially affect flight characteristics. (e)...

  17. 14 CFR 121.163 - Aircraft proving tests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Aircraft proving tests. 121.163 Section 121... REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Aircraft Requirements § 121.163 Aircraft proving...) Alterations to the aircraft or its components that materially affect flight characteristics. (e)...

  18. 14 CFR 91.1041 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Aircraft proving and validation tests. 91... Ownership Operations Program Management § 91.1041 Aircraft proving and validation tests. (a) No program manager may permit the operation of an aircraft, other than a turbojet aircraft, for which two pilots...

  19. 14 CFR 91.1041 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Aircraft proving and validation tests. 91... Ownership Operations Program Management § 91.1041 Aircraft proving and validation tests. (a) No program manager may permit the operation of an aircraft, other than a turbojet aircraft, for which two pilots...

  20. 14 CFR 121.163 - Aircraft proving tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Aircraft proving tests. 121.163 Section 121... REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Aircraft Requirements § 121.163 Aircraft proving...) Alterations to the aircraft or its components that materially affect flight characteristics. (e)...

  1. 14 CFR 121.163 - Aircraft proving tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Aircraft proving tests. 121.163 Section 121... REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Aircraft Requirements § 121.163 Aircraft proving...) Alterations to the aircraft or its components that materially affect flight characteristics. (e)...

  2. The Status of Proving among US Secondary Mathematics Teachers

    ERIC Educational Resources Information Center

    Kotelawala, Usha

    2016-01-01

    This report examines teachers' self-espoused attitudes and beliefs on proving in the secondary mathematics classroom. Conclusions were based on a questionnaire of 78 US mathematics teachers who had completed at least 2 years of teaching mathematics at the secondary level. While these teachers placed importance on proving as a general mathematical…

  3. Cabri as a "Shared Workspace" within the Proving Process

    ERIC Educational Resources Information Center

    Olivero, Federica

    2003-01-01

    This paper will discuss some findings from a study investigating the development of the proving process in a dynamic geometry environment. Through a detailed analysis of students' processes when working with open geometry problems involving conjecturing and proving in Cabri, an analytical and explanatory framework has been developed. This paper…

  4. Generating and Using Examples in the Proving Process

    ERIC Educational Resources Information Center

    Sandefur, J.; Mason, J.; Stylianides, G. J.; Watson, A.

    2013-01-01

    We report on our analysis of data from a dataset of 26 videotapes of university students working in groups of 2 and 3 on different proving problems. Our aim is to understand the role of example generation in the proving process, focusing on deliberate changes in representation and symbol manipulation. We suggest and illustrate four aspects of…

  5. The Earth is Flat, and I Can Prove It!

    ERIC Educational Resources Information Center

    Klinger, Art

    1998-01-01

    Describes an educational program that asks students to attempt to prove that the earth is spherical and that it rotates. Presents tips to pique student interest and charts related to sensing the spin, nonrotation notions, flat earth fallacies, evidence that the earth is spherical and rotates, and the role of watersheds in proving that the earth…

  6. 20 CFR 219.23 - Evidence to prove death.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Evidence to prove death. 219.23 Section 219... EVIDENCE REQUIRED FOR PAYMENT Evidence of Age and Death § 219.23 Evidence to prove death. (a) Preferred evidence of death. The best evidence of a person's death is— (1) A certified copy of or extract from the...

  7. 20 CFR 219.23 - Evidence to prove death.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true Evidence to prove death. 219.23 Section 219.23... REQUIRED FOR PAYMENT Evidence of Age and Death § 219.23 Evidence to prove death. (a) Preferred evidence of death. The best evidence of a person's death is— (1) A certified copy of or extract from the public...

  8. 20 CFR 219.23 - Evidence to prove death.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false Evidence to prove death. 219.23 Section 219... EVIDENCE REQUIRED FOR PAYMENT Evidence of Age and Death § 219.23 Evidence to prove death. (a) Preferred evidence of death. The best evidence of a person's death is— (1) A certified copy of or extract from the...

  9. 20 CFR 219.23 - Evidence to prove death.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false Evidence to prove death. 219.23 Section 219... EVIDENCE REQUIRED FOR PAYMENT Evidence of Age and Death § 219.23 Evidence to prove death. (a) Preferred evidence of death. The best evidence of a person's death is— (1) A certified copy of or extract from the...

  10. 20 CFR 219.23 - Evidence to prove death.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true Evidence to prove death. 219.23 Section 219.23... REQUIRED FOR PAYMENT Evidence of Age and Death § 219.23 Evidence to prove death. (a) Preferred evidence of death. The best evidence of a person's death is— (1) A certified copy of or extract from the public...

  11. A New Approach for Proving or Generating Combinatorial Identities

    ERIC Educational Resources Information Center

    Gonzalez, Luis

    2010-01-01

    A new method for proving, in an immediate way, many combinatorial identities is presented. The method is based on a simple recursive combinatorial formula involving n + 1 arbitrary real parameters. Moreover, this formula enables one not only to prove, but also generate many different combinatorial identities (not being required to know them "a…

  12. 34 CFR 75.51 - How to prove nonprofit status.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 1 2014-07-01 2014-07-01 false How to prove nonprofit status. 75.51 Section 75.51... Grant § 75.51 How to prove nonprofit status. (a) Under some programs, an applicant must show that it is... Revenue Service currently recognizes the applicant as an organization to which contributions are tax...

  13. 34 CFR 75.51 - How to prove nonprofit status.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false How to prove nonprofit status. 75.51 Section 75.51... Grant § 75.51 How to prove nonprofit status. (a) Under some programs, an applicant must show that it is... Revenue Service currently recognizes the applicant as an organization to which contributions are tax...

  14. 34 CFR 75.51 - How to prove nonprofit status.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 1 2012-07-01 2012-07-01 false How to prove nonprofit status. 75.51 Section 75.51... Grant § 75.51 How to prove nonprofit status. (a) Under some programs, an applicant must show that it is... Revenue Service currently recognizes the applicant as an organization to which contributions are tax...

  15. 34 CFR 75.51 - How to prove nonprofit status.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 34 Education 1 2013-07-01 2013-07-01 false How to prove nonprofit status. 75.51 Section 75.51... Grant § 75.51 How to prove nonprofit status. (a) Under some programs, an applicant must show that it is... Revenue Service currently recognizes the applicant as an organization to which contributions are tax...

  16. 34 CFR 75.51 - How to prove nonprofit status.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 1 2011-07-01 2011-07-01 false How to prove nonprofit status. 75.51 Section 75.51... Grant § 75.51 How to prove nonprofit status. (a) Under some programs, an applicant must show that it is... Revenue Service currently recognizes the applicant as an organization to which contributions are tax...

  17. The Status of Proving among US Secondary Mathematics Teachers

    ERIC Educational Resources Information Center

    Kotelawala, Usha

    2016-01-01

    This report examines teachers' self-espoused attitudes and beliefs on proving in the secondary mathematics classroom. Conclusions were based on a questionnaire of 78 US mathematics teachers who had completed at least 2 years of teaching mathematics at the secondary level. While these teachers placed importance on proving as a general mathematical…

  18. 14 CFR 121.163 - Aircraft proving tests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Aircraft proving tests. 121.163 Section 121... REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Aircraft Requirements § 121.163 Aircraft proving...) Alterations to the aircraft or its components that materially affect flight characteristics. (e) No...

  19. Preservice Mathematics Teachers' Metaphorical Perceptions towards Proof and Proving

    ERIC Educational Resources Information Center

    Ersen, Zeynep Bahar

    2016-01-01

    Since mathematical proof and proving are in the center of mathematics; preservice mathematics teachers' perceptions against these concepts have a great importance. Therefore, the study aimed to determine preservice mathematics teachers' perceptions towards proof and proving through metaphors. The participants consisted of 192 preservice…

  20. Holliday Junction Resolvases

    PubMed Central

    Wyatt, Haley D.M.; West, Stephen C.

    2014-01-01

    Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes. PMID:25183833

  1. Holliday junction resolvases.

    PubMed

    Wyatt, Haley D M; West, Stephen C

    2014-09-02

    Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

  2. Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4+ Toxicity in Plant Roots1[C][W

    PubMed Central

    Coskun, Devrim; Britto, Dev T.; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J.

    2013-01-01

    Futile transmembrane NH3/NH4+ cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4+ toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4+) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope 13N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4+ ion. Influx of 13NH3/13NH4+, which exceeded 200 µmol g–1 h–1, was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4+), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g–1 h–1). Efflux of 13NH3/13NH4+ responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions. PMID:24134887

  3. Activation of futile cycles as an approach to increase ethanol yield during glucose fermentation in Saccharomyces cerevisiae.

    PubMed

    Semkiv, Marta V; Dmytruk, Kostyantyn V; Abbas, Charles A; Sibirny, Andriy A

    2016-04-02

    An increase in ethanol yield by yeast from the fermentation of conventional sugars such as glucose and sucrose is possible by reducing the production of a key byproduct such as cellular biomass. Previously we have reported that overexpression of PHO8 gene encoding non-specific ATP-hydrolyzing alkaline phosphatase can lead to a decrease in cellular ATP content and to an increase in ethanol yield during glucose fermentation by Saccharomyces cerevisiae. In this work we further report on 2 new successful approaches to reduce cellular levels of ATP that increase ethanol yield and productivity. The first approach is based on the overexpression of the heterologous Escherichia coli apy gene encoding apyrase or SSB1 part of the chaperon that exhibit ATPase activity in yeast. In the second approach we constructed a futile cycle by the overexpression of S. cerevisiae genes encoding pyruvate carboxylase and phosphoenolpyruvate carboxykinase in S. cerevisiae. These genetically engineered strains accumulated more ethanol compared to the wild-type strain during alcoholic fermentation.

  4. Fractional order junctions

    NASA Astrophysics Data System (ADS)

    Machado, J. Tenreiro

    2015-01-01

    Gottfried Leibniz generalized the derivation and integration, extending the operators from integer up to real, or even complex, orders. It is presently recognized that the resulting models capture long term memory effects difficult to describe by classical tools. Leon Chua generalized the set of lumped electrical elements that provide the building blocks in mathematical models. His proposal of the memristor and of higher order elements broadened the scope of variables and relationships embedded in the development of models. This paper follows the two directions and proposes a new logical step, by generalizing the concept of junction. Classical junctions interconnect system elements using simple algebraic restrictions. Nevertheless, this simplistic approach may be misleading in the presence of unexpected dynamical phenomena and requires including additional "parasitic" elements. The novel γ -junction includes, as special cases, the standard series and parallel connections and allows a new degree of freedom when building models. The proposal motivates the search for experimental and real world manifestations of the abstract conjectures.

  5. Thermoelectricity in molecular junctions.

    PubMed

    Reddy, Pramod; Jang, Sung-Yeon; Segalman, Rachel A; Majumdar, Arun

    2007-03-16

    By trapping molecules between two gold electrodes with a temperature difference across them, the junction Seebeck coefficients of 1,4-benzenedithiol (BDT), 4,4'-dibenzenedithiol, and 4,4''-tribenzenedithiol in contact with gold were measured at room temperature to be +8.7 +/- 2.1 microvolts per kelvin (muV/K), +12.9 +/- 2.2 muV/K, and +14.2 +/- 3.2 muV/K, respectively (where the error is the full width half maximum of the statistical distributions). The positive sign unambiguously indicates p-type (hole) conduction in these heterojunctions, whereas the Au Fermi level position for Au-BDT-Au junctions was identified to be 1.2 eV above the highest occupied molecular orbital level of BDT. The ability to study thermoelectricity in molecular junctions provides the opportunity to address these fundamental unanswered questions about their electronic structure and to begin exploring molecular thermoelectric energy conversion.

  6. Functional ferroelectric tunnel junctions on silicon

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Wang, Zhe; Zeng, Shengwei; Han, Kun; Huang, Lisen; Schlom, Darrell G.; Venkatesan, T.; Ariando; Chen, Jingsheng

    2015-07-01

    The quest for solid state non-volatility memory devices on silicon with high storage density, high speed, low power consumption has attracted intense research on new materials and novel device architectures. Although flash memory dominates in the non-volatile memory market currently, it has drawbacks, such as low operation speed, and limited cycle endurance, which prevents it from becoming the “universal memory”. In this report, we demonstrate ferroelectric tunnel junctions (Pt/BaTiO3/La0.67Sr0.33MnO3) epitaxially grown on silicon substrates. X-ray diffraction spectra and high resolution transmission electron microscope images prove the high epitaxial quality of the single crystal perovskite films grown on silicon. Furthermore, the write speed, data retention and fatigue properties of the device compare favorably with flash memories. The results prove that the silicon-based ferroelectric tunnel junction is a very promising candidate for application in future non-volatile memories.

  7. 17 CFR 229.1203 - (Item 1203) Proved undeveloped reserves.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ENERGY POLICY AND CONSERVATION ACT OF 1975-REGULATION S-K Disclosure by Registrants Engaged in Oil and... reasons why material amounts of proved undeveloped reserves in individual fields or countries remain...

  8. 17 CFR 229.1203 - (Item 1203) Proved undeveloped reserves.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... ENERGY POLICY AND CONSERVATION ACT OF 1975-REGULATION S-K Disclosure by Registrants Engaged in Oil and... reasons why material amounts of proved undeveloped reserves in individual fields or countries remain...

  9. U.S. Crude Oil and Natural Gas Proved Reserves

    EIA Publications

    2016-01-01

    U.S. oil and natural gas proved reserves declined in 2015 due to lower prices. U.S. crude oil and lease condensate proved reserves declined 4.7 billion barrels (11.8%) from their year-end 2014 level to 35.2 billion barrels at year-end 2015, according to U.S. Crude Oil and Natural Gas Proved Reserves, Year-end 2015, released today by the U.S. Energy Information Administration. U.S natural gas proved reserves decreased 64.5 trillion cubic feet, a 16.6% decline, reducing the U.S. total to 324.3 Tcf at year-end 2015.

  10. Naval Proving Ground Indian Head, Bounded by the Mattawoman Creek ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Naval Proving Ground Indian Head, Bounded by the Mattawoman Creek to the south, the Potomac River to the west and north, and Benson Road and State Route 210 to the east, Indian Head, Charles County, MD

  11. U.S. Crude Oil and Natural Gas Proved Reserves

    EIA Publications

    2016-01-01

    U.S. oil and natural gas proved reserves declined in 2015 due to lower prices. U.S. crude oil and lease condensate proved reserves declined 4.7 billion barrels (11.8%) from their year-end 2014 level to 35.2 billion barrels at year-end 2015, according to U.S. Crude Oil and Natural Gas Proved Reserves, Year-end 2015, released today by the U.S. Energy Information Administration. U.S natural gas proved reserves decreased 64.5 trillion cubic feet, a 16.6% decline, reducing the U.S. total to 324.3 Tcf at year-end 2015.

  12. 29 CFR 18.405 - Methods of proving character.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... proving character. (a) Reputation of opinion. In all cases in which evidence of character or a trait of... conduct. (b) Specific instances of conduct. In cases in which character or a trait of character of...

  13. 29 CFR 18.405 - Methods of proving character.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... proving character. (a) Reputation of opinion. In all cases in which evidence of character or a trait of... conduct. (b) Specific instances of conduct. In cases in which character or a trait of character of...

  14. 29 CFR 18.405 - Methods of proving character.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... proving character. (a) Reputation of opinion. In all cases in which evidence of character or a trait of... conduct. (b) Specific instances of conduct. In cases in which character or a trait of character of...

  15. 29 CFR 18.405 - Methods of proving character.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... proving character. (a) Reputation of opinion. In all cases in which evidence of character or a trait of... conduct. (b) Specific instances of conduct. In cases in which character or a trait of character of...

  16. 29 CFR 18.405 - Methods of proving character.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... proving character. (a) Reputation of opinion. In all cases in which evidence of character or a trait of... conduct. (b) Specific instances of conduct. In cases in which character or a trait of character of...

  17. Signatures of topological Josephson junctions

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Pientka, Falko; Berg, Erez; Oreg, Yuval; von Oppen, Felix

    2016-08-01

    Quasiparticle poisoning and diabatic transitions may significantly narrow the window for the experimental observation of the 4 π -periodic dc Josephson effect predicted for topological Josephson junctions. Here, we show that switching-current measurements provide accessible and robust signatures for topological superconductivity which persist in the presence of quasiparticle poisoning processes. Such measurements provide access to the phase-dependent subgap spectrum and Josephson currents of the topological junction when incorporating it into an asymmetric SQUID together with a conventional Josephson junction with large critical current. We also argue that pump-probe experiments with multiple current pulses can be used to measure the quasiparticle poisoning rates of the topological junction. The proposed signatures are particularly robust, even in the presence of Zeeman fields and spin-orbit coupling, when focusing on short Josephson junctions. Finally, we also consider microwave excitations of short topological Josephson junctions which may complement switching-current measurements.

  18. Josephson junctions with delayed feedback

    NASA Astrophysics Data System (ADS)

    Grønbech-Jensen, Niels; Blackburn, James A.; Huberman, Bernardo A.; Smith, H. J. T.

    1992-12-01

    We study a simple model of an overdamped Josephson junction coupled to a transmission line, which is regarded as a delayed feedback to the junction. It is demonstrated analytically how the nonlocal time dependence can give rise to hysteresis and steps in the current-voltage characteristics of the junction and the fundamental difference between positive and negative feedback is discussed. Excellent agreement between the analytical results and the results of numerical simulations is found.

  19. An induced junction photovoltaic cell

    NASA Technical Reports Server (NTRS)

    Call, R. L.

    1974-01-01

    Silicon solar cells operating with induced junctions rather than diffused junctions have been fabricated and tested. Induced junctions were created by forming an inversion layer near the surface of the silicon by supplying a sheet of positive charge above the surface. Measurements of the response of the inversion layer cell to light of different wavelengths indicated it to be more sensitive to the shorter wavelengths of the sun's spectrum than conventional cells. The greater sensitivity occurs because of the shallow junction and the strong electric field at the surface.

  20. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  1. Manipulation of Majorana states in X-junction geometries

    NASA Astrophysics Data System (ADS)

    Aristov, D. N.; Gutman, D. B.

    2016-08-01

    We study quantum manipulation based on four Majorana bound states in X-junction geometry. The parameter space of this setup is bigger than of the previously studied Y-junction and is described by SO(4) symmetry group. In order for quantum computation to be dephasing free, two Majorana states have to stay degenerate at all times. We find a condition necessary for that and compute the Berry’s phase, 2α , accumulated during the manipulation. We construct simple protocols for the variety of values of α, including π /8 needed for the purposes of quantum computation. Although the manipulations in general X-junction geometry are not topologically protected, they may prove to be a feasible compromise for aims of quantum computation.

  2. Characterization and control of charge transfer in a tunnel junction

    NASA Astrophysics Data System (ADS)

    Gabelli, Julien; Thibault, Karl; Gasse, Gabriel; Lupien, Christian; Reulet, Bertrand

    2017-03-01

    Charge transfer in a tunnel junction is studied under dc and ac voltage bias using quantum shot noise. Under dc voltage bias $V$, spectral density of noise measured within a very large bandwidth enables to deduce the current-current correlator in the time domain by Fourier transform. This correlator exhibits regular oscillations proving that electrons try to cross the junction regularly, every $h/eV$. Using harmonic and bi-harmonic ac voltage bias, we then show that quasiparticles excitations can be transferred through the junction in a controlled way. By measuring the reduction of the excess shot noise, we are able to determine the number of electron-hole pairs surrounding the injected electrons and demonstrate that bi-harmonic voltage pulses realize an on-demand electron source with a very small admixture of electron-hole pairs.

  3. Metabolic network analysis of perfused livers under fed and fasted states: incorporating thermodynamic and futile-cycle-associated regulatory constraints.

    PubMed

    Orman, Mehmet A; Androulakis, Ioannis P; Berthiaume, Francois; Ierapetritou, Marianthi G

    2012-01-21

    Isolated liver perfusion systems have been extensively used to characterize intrinsic metabolic changes in liver under various conditions, including systemic injury, hepatotoxin exposure, and warm ischemia. Most of these studies were performed utilizing fasted animals prior to perfusion so that a simplified metabolic network could be used in order to determine intracellular fluxes. However, fasting induced metabolic alterations might interfere with disease related changes. Therefore, there is a need to develop a "unified" metabolic flux analysis approach that could be similarly applied to both fed and fasted states. In this study we explored a methodology based on elementary mode analysis in order to determine intracellular fluxes and active pathways simultaneously. In order to decrease the solution space, thermodynamic constraints, and enzymatic regulatory properties for the formation of futile cycles were further considered in the model, resulting in a mixed integer quadratic programming problem. Given the published experimental observations describing the perfused livers under fed and fasted states, the proposed approach successfully determined that gluconeogenesis, glycogenolysis and fatty acid oxidation were active in both states. However, fasting increased the fluxes in gluconeogenic reactions whereas it decreased fluxes associated with glycogenolysis, TCA cycle, fatty acid oxidation and electron transport reactions. This analysis further identified that more pathways were found to be active in fed state while their weight values were relatively lower compared to fasted state. Glucose, lactate, glutamine, glutamate and ketone bodies were also found to be important external metabolites whose extracellular fluxes should be used in the hepatic metabolic network analysis. In conclusion, the mathematical formulation explored in this study is an attractive tool to analyze the metabolic network of perfused livers under various disease conditions. This approach could

  4. Novel phosphoenolpyruvate-dependent futile cycle in Streptococcus lactis: 2-deoxy-D-glucose uncouples energy production from growth.

    PubMed Central

    Thompson, J; Chassy, B M

    1982-01-01

    The addition of 2-deoxy-D-glucose to cultures of Streptococcus lactis 133 that were growing exponentially on sucrose or lactose reduced the growth rate by ca. 95%. Inhibition did not occur with glucose or mannose as the growth sugar. The reduction in growth rate was concomitant with rapid accumulation of the analog in phosphorylated form (2-deoxy-D-glucose 6-phosphate) via the phosphoenolpyruvate-dependent mannose:phosphotransferase system. Within 5 min the intracellular 2-deoxy-D-glucose 6-phosphate concentration reached a steady-state level of greater than 100 mM. After maximum accumulation of the sugar phosphate, the rate of sucrose metabolism (glycolysis) decreased by only 30%, but the cells were depleted of fructose-1,6-diphosphate. The addition of glucose to 2-deoxy-D-glucose 6-phosphate preloaded cells caused expulsion of 2-deoxy-D-glucose and a resumption of normal growth. S. lactis 133 contained an intracellular Mg2+-dependent, fluoride-sensitive phosphatase which hydrolyzed 2-deoxy-D-glucose 6-phosphate (and glucose 6-phosphate) to free sugar and inorganic phosphate. Because of continued dephosphorylation and efflux of the non-metabolizable analog, the maintenance of the intracellular 2-deoxy-D-glucose 6-phosphate pool during growth stasis was dependent upon continued glycolysis. This steady-state condition represented a dynamic equilibrium of: (i) phosphoenolpyruvate-dependent accumulation of 2-deoxy-D-glucose 6-phosphate, (ii) intracellular dephosphorylation, and (iii) efflux of free 2-deoxy-D-glucose. This sequence of events constitutes a futile cycle which promotes the dissipation of phosphoenolpyruvate. We conclude that 2-deoxy-D-glucose functions as an uncoupler by dissociating energy production from growth in S. lactis 133. Images PMID:6286601

  5. Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

    PubMed Central

    Malagoli, Philippe; Britto, Dev T.; Schulze, Lasse M.; Kronzucker, Herbert J.

    2008-01-01

    Globally, over one-third of irrigated land is affected by salinity, including much of the land under lowland rice cultivation in the tropics, seriously compromising yields of this most important of crop species. However, there remains an insufficient understanding of the cellular basis of salt tolerance in rice. Here, three methods of 24Na+ tracer analysis were used to investigate primary Na+ transport at the root plasma membrane in a salt-tolerant rice cultivar (Pokkali) and a salt-sensitive cultivar (IR29). Futile cycling of Na+ at the plasma membrane of intact roots occurred at both low and elevated levels of steady-state Na+ supply ([Na+]ext=1 mM and 25 mM) in both cultivars. At 25 mM [Na+]ext, a toxic condition for IR29, unidirectional influx and efflux of Na+ in this cultivar, but not in Pokkali, became very high [>100 μmol g (root FW)−1 h−1], demonstrating an inability to restrict sodium fluxes. Current models of sodium transport energetics across the plasma membrane in root cells predict that, if the sodium efflux were mediated by Na+/H+ antiport, this toxic scenario would impose a substantial respiratory cost in IR29. This cost is calculated here, and compared with root respiration, which, however, comprised only ∼50% of what would be required to sustain efflux by the antiporter. This suggests that either the conventional ‘leak-pump’ model of Na+ transport or the energetic model of proton-linked Na+ transport may require some revision. In addition, the lack of suppression of Na+ influx by both K+ and Ca2+, and by the application of the channel inhibitors Cs+, TEA+, and Ba2+, questions the participation of potassium channels and non-selective cation channels in the observed Na+ fluxes. PMID:18854575

  6. Tight Junctions Go Viral!

    PubMed

    Torres-Flores, Jesús M; Arias, Carlos F

    2015-09-23

    Tight junctions (TJs) are highly specialized membrane domains involved in many important cellular processes such as the regulation of the passage of ions and macromolecules across the paracellular space and the establishment of cell polarity in epithelial cells. Over the past few years there has been increasing evidence that different components of the TJs can be hijacked by viruses in order to complete their infectious cycle. Viruses from at least nine different families of DNA and RNA viruses have been reported to use TJ proteins in their benefit. For example, TJ proteins such as JAM-A or some members of the claudin family of proteins are used by members of the Reoviridae family and hepatitis C virus as receptors or co-receptors during their entry into their host cells. Reovirus, in addition, takes advantage of the TJ protein Junction Adhesion Molecule-A (JAM-A) to achieve its hematogenous dissemination. Some other viruses are capable of regulating the expression or the localization of TJ proteins to induce cell transformation or to improve the efficiency of their exit process. This review encompasses the importance of TJs for viral entry, replication, dissemination, and egress, and makes a clear statement of the importance of studying these proteins to gain a better understanding of the replication strategies used by viruses that infect epithelial and/or endothelial cells.

  7. Proving Light Quanta Exist in an Undergraduate Laboratory

    NASA Astrophysics Data System (ADS)

    Neel, M. S.; Thorn, J. J.; Davies, R. E.; Beck, M.

    2003-05-01

    While well known experiments involving phenomena such as the photoelectric effect and Compton scattering strongly suggest the existence of photons, they do not prove the existence of light quanta. For example, it is possible to explain both of the aforementioned effects using a semiclassical treatment in which the electromagnetic field is not quantized, and is instead treated as a classical wave. To prove the existence of light quanta one must perform an experiment whose results cannot be explained using classical waves. Here we have performed an experiment that cannot be explained with a classical wave theory, and which demonstrates the localization of light quanta. Namely, we prove that a single photon can only go one way when it leaves a beamsplitter. (P. Grangier, G. Roger and A. Aspect, Europhys. Lett. 1, 173 (1986).) The experimental apparatus is appropriate for an undergraduate teaching laboratory.

  8. Learning-assisted theorem proving with millions of lemmas☆

    PubMed Central

    Kaliszyk, Cezary; Urban, Josef

    2015-01-01

    Large formal mathematical libraries consist of millions of atomic inference steps that give rise to a corresponding number of proved statements (lemmas). Analogously to the informal mathematical practice, only a tiny fraction of such statements is named and re-used in later proofs by formal mathematicians. In this work, we suggest and implement criteria defining the estimated usefulness of the HOL Light lemmas for proving further theorems. We use these criteria to mine the large inference graph of the lemmas in the HOL Light and Flyspeck libraries, adding up to millions of the best lemmas to the pool of statements that can be re-used in later proofs. We show that in combination with learning-based relevance filtering, such methods significantly strengthen automated theorem proving of new conjectures over large formal mathematical libraries such as Flyspeck. PMID:26525678

  9. Proving the mechanical integrity of solution mined caverns

    SciTech Connect

    Van Fossan, N.E.

    1982-01-01

    The Safe Drinking Water Act of 1974 (Public Law 93-523) specifies an Underground Injection Control (UIC) program be promulgated to satisfy certain requirements of the act. Underground storage wells are covered by the act. The most crucial item in any UIC program is the requirement of proving the mechanical integrity of a storage system. This work enumerates the individual elements of a hydrocarbon underground storage system in domal salt, addresses the nature and magnitude of the maximum forces which may be exerted on each element, and proposes tests which will prove that each element is capable of resisting these forces. Appropriate safety factors also are proposed.

  10. Proved and potential vectors of yellow fever in South Africa

    PubMed Central

    De Meillon, Botha

    1954-01-01

    This paper, based on records obtained from the Entomology Department of the South African Institute for Medical Research, Johannesburg, gives a summary of the distribution, adult habits, and breeding-places of the proved and potential vectors of yellow fever in South Africa. PMID:13209304

  11. 14 CFR 91.1041 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... manager may permit the operation of an aircraft, other than a turbojet aircraft, for which two pilots are... the Administrator. (b) No program manager may permit the operation of a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least 25 hours...

  12. 14 CFR 135.145 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... operate an aircraft, other than a turbojet aircraft, for which two pilots are required by this chapter for... route airports as determined by the Administrator. (b) No certificate holder may operate a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least...

  13. 14 CFR 135.145 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... operate an aircraft, other than a turbojet aircraft, for which two pilots are required by this chapter for... route airports as determined by the Administrator. (b) No certificate holder may operate a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least...

  14. 14 CFR 91.1041 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... manager may permit the operation of an aircraft, other than a turbojet aircraft, for which two pilots are... the Administrator. (b) No program manager may permit the operation of a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least 25 hours...

  15. 14 CFR 135.145 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... operate an aircraft, other than a turbojet aircraft, for which two pilots are required by this chapter for... route airports as determined by the Administrator. (b) No certificate holder may operate a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least...

  16. 14 CFR 91.1041 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... manager may permit the operation of an aircraft, other than a turbojet aircraft, for which two pilots are... the Administrator. (b) No program manager may permit the operation of a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least 25 hours...

  17. 14 CFR 135.145 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... operate an aircraft, other than a turbojet aircraft, for which two pilots are required by this chapter for... route airports as determined by the Administrator. (b) No certificate holder may operate a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least...

  18. 14 CFR 135.145 - Aircraft proving and validation tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... operate an aircraft, other than a turbojet aircraft, for which two pilots are required by this chapter for... route airports as determined by the Administrator. (b) No certificate holder may operate a turbojet airplane if it has not previously proved a turbojet airplane in operations under this part in at least...

  19. Learning to prove: from examples to general statements

    NASA Astrophysics Data System (ADS)

    Abramovitz, Buma; Berezina, Miryam; Berman, Abraham

    2014-11-01

    In this paper we describe a method for teaching students to prove some mathematical statements independently, by using specially designed auxiliary assignments. The assignments are designed as homework problems and can be adapted for online learning. We illustrate our method using examples from calculus and differential equations.

  20. Proof phenomenon as a function of the phenomenology of proving.

    PubMed

    Hipólito, Inês

    2015-12-01

    Kurt Gödel wrote (1964, p. 272), after he had read Husserl, that the notion of objectivity raises a question: "the question of the objective existence of the objects of mathematical intuition (which, incidentally, is an exact replica of the question of the objective existence of the outer world)". This "exact replica" brings to mind the close analogy Husserl saw between our intuition of essences in Wesensschau and of physical objects in perception. What is it like to experience a mathematical proving process? What is the ontological status of a mathematical proof? Can computer assisted provers output a proof? Taking a naturalized world account, I will assess the relationship between mathematics, the physical world and consciousness by introducing a significant conceptual distinction between proving and proof. I will propose that proving is a phenomenological conscious experience. This experience involves a combination of what Kurt Gödel called intuition, and what Husserl called intentionality. In contrast, proof is a function of that process - the mathematical phenomenon - that objectively self-presents a property in the world, and that results from a spatiotemporal unity being subject to the exact laws of nature. In this essay, I apply phenomenology to mathematical proving as a performance of consciousness, that is, a lived experience expressed and formalized in language, in which there is the possibility of formulating intersubjectively shareable meanings.

  1. Proving Invariants of I/O Automata with TAME

    DTIC Science & Technology

    2002-01-01

    Intelligence, 29(1–4):139–181. Archer, M. 2002. Proving correctness of the basic TESLA multicast stream authentication protocol with TAME. In Informal...introduction to requirements capture using PVS: Specification of a simple autopilot , NASA Technical Memorandum 110255, NASA Langley Research Center

  2. Prove It! Putting Together the Evidence-Based Practice Puzzle

    ERIC Educational Resources Information Center

    Little, Hannah Byrd

    2015-01-01

    Why is it important to prove that school libraries add value to the school program? The National Center for Education Statistics reports that 20 percent of U.S. public schools lack a full or part-time certified librarian (NCES 2013). In California the ratio of certified school librarians to students is 1:7,374 (California Department of Education…

  3. Responsibility for proving and defining in abstract algebra class

    NASA Astrophysics Data System (ADS)

    Fukawa-Connelly, Timothy

    2016-07-01

    There is considerable variety in inquiry-oriented instruction, but what is common is that students assume roles in mathematical activity that in a traditional, lecture-based class are either assumed by the teacher (or text) or are not visible at all in traditional math classrooms. This paper is a case study of the teaching of an inquiry-based undergraduate abstract algebra course. In particular, gives a theoretical account of the defining and proving processes. The study examines the intellectual responsibility for the processes of defining and proving that the professor devolved to the students. While the professor wanted the students to engage in all aspects of defining and proving, he was only successful at devolving responsibility for certain aspects and much more successful at devolving responsibility for proving than conjecturing or defining. This study suggests that even a well-intentioned instructor may not be able to devolve responsibility to students for some aspects of mathematical practice without using a research-based curriculum or further professional development.

  4. Dutch Plural Inflection: The Exception that Proves the Analogy

    ERIC Educational Resources Information Center

    Keuleers, Emmanuel; Sandra, Dominiek; Daelemans, Walter; Gillis, Steven; Durieux, Gert; Martens, Evelyn

    2007-01-01

    We develop the view that inflection is driven partly by non-phonological analogy and that non-phonological information is of particular importance to the inflection of non-canonical roots, which in the view of [Marcus, G. F., Brinkmann, U., Clahsen, H., Wiese, R., & Pinker, S. (1995). "German inflection: the exception that proves the rule."…

  5. Dutch Plural Inflection: The Exception that Proves the Analogy

    ERIC Educational Resources Information Center

    Keuleers, Emmanuel; Sandra, Dominiek; Daelemans, Walter; Gillis, Steven; Durieux, Gert; Martens, Evelyn

    2007-01-01

    We develop the view that inflection is driven partly by non-phonological analogy and that non-phonological information is of particular importance to the inflection of non-canonical roots, which in the view of [Marcus, G. F., Brinkmann, U., Clahsen, H., Wiese, R., & Pinker, S. (1995). "German inflection: the exception that proves the rule."…

  6. Three Lectures on Theorem-proving and Program Verification

    NASA Technical Reports Server (NTRS)

    Moore, J. S.

    1983-01-01

    Topics concerning theorem proving and program verification are discussed with particlar emphasis on the Boyer/Moore theorem prover, and approaches to program verification such as the functional and interpreter methods and the inductive assertion approach. A history of the discipline and specific program examples are included.

  7. 25 CFR 11.702 - Proving and admitting will.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ORDER CODE Probate Proceedings § 11.702 Proving and admitting will. (a) Upon initiating the probate of... admitted to probate by filing an affidavit of an attesting witness which identifies such will as being the... probate, any person having an interest in the decedent's estate may contest the validity of such will....

  8. 25 CFR 11.702 - Proving and admitting will.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... ORDER CODE Probate Proceedings § 11.702 Proving and admitting will. (a) Upon initiating the probate of... admitted to probate by filing an affidavit of an attesting witness which identifies such will as being the... probate, any person having an interest in the decedent's estate may contest the validity of such will....

  9. 25 CFR 11.702 - Proving and admitting will.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... ORDER CODE Probate Proceedings § 11.702 Proving and admitting will. (a) Upon initiating the probate of... admitted to probate by filing an affidavit of an attesting witness which identifies such will as being the... probate, any person having an interest in the decedent's estate may contest the validity of such will....

  10. 25 CFR 11.702 - Proving and admitting will.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... ORDER CODE Probate Proceedings § 11.702 Proving and admitting will. (a) Upon initiating the probate of... admitted to probate by filing an affidavit of an attesting witness which identifies such will as being the... probate, any person having an interest in the decedent's estate may contest the validity of such will....

  11. 25 CFR 11.702 - Proving and admitting will.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... ORDER CODE Probate Proceedings § 11.702 Proving and admitting will. (a) Upon initiating the probate of... admitted to probate by filing an affidavit of an attesting witness which identifies such will as being the... probate, any person having an interest in the decedent's estate may contest the validity of such will....

  12. Prove It! Putting Together the Evidence-Based Practice Puzzle

    ERIC Educational Resources Information Center

    Little, Hannah Byrd

    2015-01-01

    Why is it important to prove that school libraries add value to the school program? The National Center for Education Statistics reports that 20 percent of U.S. public schools lack a full or part-time certified librarian (NCES 2013). In California the ratio of certified school librarians to students is 1:7,374 (California Department of Education…

  13. Between Affect and Cognition: Proving at University Level

    ERIC Educational Resources Information Center

    Furinghetti, Fulvia; Morselli, Francesca

    2004-01-01

    In this paper we report on a case study of a university student (third year of Mathematics course). She was engaged in proving a statement of elementary number theory. We asked her to write the thoughts that accompanied her solving process. She was collaborative and her protocol is suitable to study the interrelation between affect and cognition.…

  14. Disordered graphene Josephson junctions

    NASA Astrophysics Data System (ADS)

    Muñoz, W. A.; Covaci, L.; Peeters, F. M.

    2015-02-01

    A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples, or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single-atom vacancies, we observe a strong suppression of the supercurrent, which is a consequence of strong intervalley scattering. Although lattice deformations should not induce intervalley scattering, we find that the supercurrent is still suppressed, which is due to the presence of pseudomagnetic barriers. For charged impurities, we consider two cases depending on whether the average doping is zero, i.e., existence of electron-hole puddles, or finite. In both cases, short-range impurities strongly affect the supercurrent, similar to the vacancies scenario.

  15. Ion bipolar junction transistors.

    PubMed

    Tybrandt, Klas; Larsson, Karin C; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-06-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated.

  16. Ion bipolar junction transistors

    PubMed Central

    Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-01-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  17. Gap junctions, pannexins and pain.

    PubMed

    Spray, David C; Hanani, Menachem

    2017-06-22

    Enhanced expression and function of gap junctions and pannexin (Panx) channels have been associated with both peripheral and central mechanisms of pain sensitization. At the level of the sensory ganglia, evidence includes augmented gap junction and pannexin1 expression in glial cells and neurons in inflammatory and neuropathic pain models and increased synchrony and enhanced cross-excitation among sensory neurons by gap junction-mediated coupling. In spinal cord and in suprapinal areas, evidence is largely limited to increased expression of relevant proteins, although in several rodent pain models, hypersensitivity is reduced by treatment with gap junction/Panx1 channel blocking compounds. Moreover, targeted modulation of Cx43 expression was shown to modulate pain thresholds, albeit in somewhat contradictory ways, and mice lacking Panx1 expression globally or in specific cell types show depressed hyperalgesia. We here review the evidence for involvement of gap junctions and Panx channels in a variety of animal pain studies and then discuss ways in which gap junctions and Panx channels may mediate their action in pain processing. This discussion focusses on spread of signals among satellite glial cells, in particular intercellular Ca(2+) waves, which are propagated through both gap junction and Panx1-dependent routes and have been associated with the phenomenon of spreading depression and the malady of migraine headache with aura. Copyright © 2017. Published by Elsevier B.V.

  18. Metallic Junction Thermoelectric Device Simulations

    NASA Technical Reports Server (NTRS)

    Duzik, Adam J.; Choi, Sang H.

    2017-01-01

    Thermoelectric junctions made of semiconductors have existed in radioisotope thermoelectric generators (RTG) for deep space missions, but are currently being adapted for terrestrial energy harvesting. Unfortunately, these devices are inefficient, operating at only 7% efficiency. This low efficiency has driven efforts to make high-figure-of-merit thermoelectric devices, which require a high electrical conductivity but a low thermal conductivity, a combination that is difficult to achieve. Lowered thermal conductivity has increased efficiency, but at the cost of power output. An alternative setup is to use metallic junctions rather than semiconductors as thermoelectric devices. Metals have orders of magnitude more electrons and electronic conductivities higher than semiconductors, but thermal conductivity is higher as well. To evaluate the viability of metallic junction thermoelectrics, a two dimensional heat transfer MATLAB simulation was constructed to calculate efficiency and power output. High Seebeck coefficient alloys, Chromel (90%Ni-10%Cr) and Constantan (55%Cu-45%Ni), produced efficiencies of around 20-30%. Parameters such as the number of layers of junctions, lateral junction density, and junction sizes for both series- and parallel-connected junctions were explored.

  19. Resistance Is Futile

    ERIC Educational Resources Information Center

    O'Hanlon, Charlene

    2009-01-01

    How odd it should seem that even today, with interactive whiteboards, content management systems, wireless broadband, handhelds, and every sort of sophisticated computing device penetrating and improving the classroom experience for students, David Roh, general manager for Follett Digital Resources can still say, "There are hundreds of…

  20. Unexploded ordnance issues at Aberdeen Proving Ground: Background information

    SciTech Connect

    Rosenblatt, D.H.

    1996-11-01

    This document summarizes currently available information about the presence and significance of unexploded ordnance (UXO) in the two main areas of Aberdeen Proving Ground: Aberdeen Area and Edgewood Area. Known UXO in the land ranges of the Aberdeen Area consists entirely of conventional munitions. The Edgewood Area contains, in addition to conventional munitions, a significant quantity of chemical-munition UXO, which is reflected in the presence of chemical agent decomposition products in Edgewood Area ground-water samples. It may be concluded from current information that the UXO at Aberdeen Proving Ground has not adversely affected the environment through release of toxic substances to the public domain, especially not by water pathways, and is not likely to do so in the near future. Nevertheless, modest but periodic monitoring of groundwater and nearby surface waters would be a prudent policy.

  1. Thermopower measurements in molecular junctions.

    PubMed

    Rincón-García, Laura; Evangeli, Charalambos; Rubio-Bollinger, Gabino; Agraït, Nicolás

    2016-08-07

    The measurement of thermopower in molecular junctions offers complementary information to conductance measurements and is becoming essential for the understanding of transport processes at the nanoscale. In this review, we discuss the recent advances in the study of the thermoelectric properties of molecular junctions. After presenting the theoretical background for thermoelectricity at the nanoscale, we review the experimental techniques for measuring the thermopower in these systems and discuss the main results. Finally, we consider the challenges in the application of molecular junctions in viable thermoelectric devices.

  2. Renewable Energy Opportunties at Dugway Proving Ground, Utah

    SciTech Connect

    Orrell, Alice C.; Kora, Angela R.; Russo, Bryan J.; Horner, Jacob A.; Williamson, Jennifer L.; Weimar, Mark R.; Gorrissen, Willy J.; Nesse, Ronald J.; Dixon, Douglas R.

    2010-05-31

    This document provides an overview of renewable resource potential at Dugway Proving Ground, based primarily upon analysis of secondary data sources supplemented with limited on-site evaluations. This effort focuses on grid-connected generation of electricity from renewable energy sources and ground source heat pumps (GSHPs). The effort was funded by the U.S. Army Installation Management Command (IMCOM) as follow-on to the 2005 Department of Defense (DoD) Renewables Assessment.

  3. Historic Properties Report: Yuma Proving Ground, Yuma, Arizona.

    DTIC Science & Technology

    1984-07-01

    testing a new floating bridge on the Colorado River below Imperial Dam, several miles northwest of Camp Laguna. Tests were conducted by the Engineer ...between Building Technology Incorporated, Silver Spring, Maryland and the Historic American Building Survey/Historic American Engineering Record...American Engineering Record, National Park Service U.S. Department of the Interior EXECUTIVE SUMMARY The Yuma Proving Ground, part of the U.S. Army Test and

  4. A Atomic Energy Lower Bound that Proves Scott's Correction

    NASA Astrophysics Data System (ADS)

    Hughes, Barnwell Webster

    In this paper, we will prove that the energy of an atom with nuclear charge Z is greater than -C(,TF)Z('7/3) + (q/8)Z('2) + O(Z('17/9)log Z) atomic units as Z (--->) (INFIN). q is the number of spin states (q = 2 for electrons) and C(,TF) is the Thomas-Fermi constant for such systems.

  5. Implementing Metamathematics as an Approach to Automatic Theorem Proving

    DTIC Science & Technology

    1989-01-01

    Approach to Automatic Theorem Proving* Robert L. Constable Douglas J. Howet Abstract A simple but important algorithm used to support automated...metatheory in NuprL In E Lusk and R. Overbeek , editors, 9th International Conference on Automated Deduction, pages 238-257, New York, 1988. Springer-Verlag...Wang. Toward mechanical mathematics. IBM J. Research and Development, (4):2- 22., 1960. [331 L. Wos, R. Overbeek , L. Ewing, and J. Boyle. Automated

  6. Acetaminophen Toxicity and 5-Oxoproline (Pyroglutamic Acid): A Tale of Two Cycles, One an ATP-Depleting Futile Cycle and the Other a Useful Cycle

    PubMed Central

    2014-01-01

    Summary The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes. PMID:24235282

  7. Acetaminophen toxicity and 5-oxoproline (pyroglutamic acid): a tale of two cycles, one an ATP-depleting futile cycle and the other a useful cycle.

    PubMed

    Emmett, Michael

    2014-01-01

    The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes.

  8. Preparing for Mars: The Evolvable Mars Campaign 'Proving Ground' Approach

    NASA Technical Reports Server (NTRS)

    Bobskill, Marianne R.; Lupisella, Mark L.; Mueller, Rob P.; Sibille, Laurent; Vangen, Scott; Williams-Byrd, Julie

    2015-01-01

    As the National Aeronautics and Space Administration (NASA) prepares to extend human presence beyond Low Earth Orbit, we are in the early stages of planning missions within the framework of an Evolvable Mars Campaign. Initial missions would be conducted in near-Earth cis-lunar space and would eventually culminate in extended duration crewed missions on the surface of Mars. To enable such exploration missions, critical technologies and capabilities must be identified, developed, and tested. NASA has followed a principled approach to identify critical capabilities and a "Proving Ground" approach is emerging to address testing needs. The Proving Ground is a period subsequent to current International Space Station activities wherein exploration-enabling capabilities and technologies are developed and the foundation is laid for sustained human presence in space. The Proving Ground domain essentially includes missions beyond Low Earth Orbit that will provide increasing mission capability while reducing technical risks. Proving Ground missions also provide valuable experience with deep space operations and support the transition from "Earth-dependence" to "Earth-independence" required for sustainable space exploration. A Technology Development Assessment Team identified a suite of critical technologies needed to support the cadence of exploration missions. Discussions among mission planners, vehicle developers, subject-matter-experts, and technologists were used to identify a minimum but sufficient set of required technologies and capabilities. Within System Maturation Teams, known challenges were identified and expressed as specific performance gaps in critical capabilities, which were then refined and activities required to close these critical gaps were identified. Analysis was performed to identify test and demonstration opportunities for critical technical capabilities across the Proving Ground spectrum of missions. This suite of critical capabilities is expected to

  9. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false River Junction. 9.164... River Junction. (a) Name. The name of the viticultural area described in this section is “River Junction.” (b) Approved maps. The appropriate maps for determining the boundaries of the River Junction...

  10. 27 CFR 9.164 - River Junction.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false River Junction. 9.164... River Junction. (a) Name. The name of the viticultural area described in this section is “River Junction.” (b) Approved maps. The appropriate maps for determining the boundaries of the River Junction...

  11. Thermal conductance of superlattice junctions

    SciTech Connect

    Lu, Simon; McGaughey, Alan J. H.

    2015-05-15

    We use molecular dynamics simulations and the lattice-based scattering boundary method to compute the thermal conductance of finite-length Lennard-Jones superlattice junctions confined by bulk crystalline leads. The superlattice junction thermal conductance depends on the properties of the leads. For junctions with a superlattice period of four atomic monolayers at temperatures between 5 and 20 K, those with mass-mismatched leads have a greater thermal conductance than those with mass-matched leads. We attribute this lead effect to interference between and the ballistic transport of emergent junction vibrational modes. The lead effect diminishes when the temperature is increased, when the superlattice period is increased, and when interfacial disorder is introduced, but is reversed in the harmonic limit.

  12. Josephson junction Q-spoiler

    DOEpatents

    Clarke, J.; Hilbert, C.; Hahn, E.L.; Sleator, T.

    1986-03-25

    An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

  13. Shalbatana/Simud Vallis Junction

    NASA Image and Video Library

    2003-01-11

    The sinuous channels and streamlined islands at the junction of Shalbatana and Simud Vallis, seen in this NASA Mars Odyssey image, present an erosional history of the catastrophic floods that scoured the Martian surface hundreds of millions of years ago.

  14. Josephson junction Q-spoiler

    DOEpatents

    Clarke, John; Hilbert, Claude; Hahn, Erwin L.; Sleator, Tycho

    1988-01-01

    An automatic Q-spoiler comprising at least one Josephson tunnel junction connected in an LC circuit for flow of resonant current therethrough. When in use in a system for detecting the magnetic resonance of a gyromagnetic particle system, a high energy pulse of high frequency energy irradiating the particle system will cause the critical current through the Josephson tunnel junctions to be exceeded, causing the tunnel junctions to act as resistors and thereby damp the ringing of the high-Q detection circuit after the pulse. When the current has damped to below the critical current, the Josephson tunnel junctions revert to their zero-resistance state, restoring the Q of the detection circuit and enabling the low energy magnetic resonance signals to be detected.

  15. Tunable φ Josephson junction ratchet

    NASA Astrophysics Data System (ADS)

    Menditto, R.; Sickinger, H.; Weides, M.; Kohlstedt, H.; Koelle, D.; Kleiner, R.; Goldobin, E.

    2016-10-01

    We demonstrate experimentally the operation of a deterministic Josephson ratchet with tunable asymmetry. The ratchet is based on a φ Josephson junction with a ferromagnetic barrier operating in the underdamped regime. The system is probed also under the action of an additional dc current, which acts as a counterforce trying to stop the ratchet. Under these conditions the ratchet works against the counterforce, thus producing a nonzero output power. Finally, we estimate the efficiency of the φ Josephson junction ratchet.

  16. LOW RESISTANCE JUNCTIONS IN CRAYFISH

    PubMed Central

    Peracchia, Camillo

    1973-01-01

    The ultrastructure of low resistance junctions between segments of lateral giant fibers in crayfish is studied in sections from specimens fixed either by conventional methods or by glutaraldehyde-H2O2 or by glutaraldehyde-lanthanum. Cross sections through junctions fixed by conventional glutaraldehyde display the usual trilaminar profile of two parallel membranes separated by a narrow gap. Most of the junctional regions appear covered by 500–800 Å vesicles which lie on both sides of the junction in rows adjacent to the membranes. Gross sections through junctions fixed by glutaraldehyde-H2O2 display, in regions containing vesicles, membranes with a beaded profile. The beads correspond to globules ∼125 Å in width and ∼170 Å in height arranged in a hexagonal pattern with a unit cell of ∼200 Å. The globules of one membrane match precisely with those of the adjacent membrane, and opposite globules seem to come in contact with each other at the center of the junction. The membrane of the vesicles also contains globules. Occasionally the globules of the vesicles seem to join with those of the junctional membranes, apparently forming intracellular junctions. Injunctions negatively stained by lanthanum the globules are seen organized into two arrangements. Areas containing globules in a hexagonal array with a unit cell of ∼200 Å (swollen pattern) are seen adjacent to areas in which the globules are more closely and disorderly packed (close packing), the minimum center-to-center distance between adjacent globules being ∼125 Å. At higher magnification each globule appears composed of six subunits arranged in a circle around a central region occupied by lanthanum (possibly a pit). PMID:4120610

  17. Tight junctions as regulators of tissue remodelling.

    PubMed

    Balda, Maria S; Matter, Karl

    2016-10-01

    Formation of tissue barriers by epithelial and endothelial cells requires neighbouring cells to interact via intercellular junctions, which includes tight junctions. Tight junctions form a semipermeable paracellular diffusion barrier and act as signalling hubs that guide cell behaviour and differentiation. Components of tight junctions are also expressed in cell types not forming tight junctions, such as cardiomyocytes, where they associate with facia adherens and/or gap junctions. This review will focus on tight junction proteins and their importance in tissue homeostasis and remodelling with a particular emphasis on what we have learned from animal models and human diseases. Copyright © 2016. Published by Elsevier Ltd.

  18. Electronic thermometry in tunable tunnel junction

    DOEpatents

    Maksymovych, Petro

    2016-03-15

    A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may be measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.

  19. Proving Causation With Epidemiological Evidence in Tobacco Lawsuits

    PubMed Central

    2016-01-01

    Recently, a series of lawsuits were filed in Korea claiming tort liability against tobacco companies. The Supreme Court has already issued decisions in some cases, while others are still pending. The primary issue in these cases is whether the epidemiological evidence submitted by the plaintiffs clearly proves the causal relationship between smoking and disease as required by civil law. Proving causation is difficult in tobacco lawsuits because factors other than smoking are involved in the development of a disease, and also because of the lapse of time between smoking and the manifestation of the disease. The Supreme Court (Supreme Court Decision, 2011Da22092, April 10, 2014) has imposed some limitations on using epidemiological evidence to prove causation in tobacco lawsuits filed by smokers and their family members, but these limitations should be reconsidered. First, the Court stated that a disease can be categorized as specific or non-specific, and for each disease type, causation can be proven by different types of evidence. However, the concept of specific diseases is not compatible with multifactor theory, which is generally accepted in the field of public health. Second, when the epidemiological association between the disease and the risk factor is proven to be significant, imposing additional burdens of proof on the plaintiff may considerably limit the plaintiff’s right to recovery, but the Court required the plaintiffs to provide additional information such as health condition and lifestyle. Third, the Supreme Court is not giving greater weight to the evidential value of epidemiological study results because the Court focuses on the fact that these studies were group-level, not individual-level. However, group-level studies could still offer valuable information about individual members of the group, e.g., probability of causation. PMID:27055545

  20. An entry in the 1992 Overbeek theorem-proving contest

    SciTech Connect

    Lusk, E.L.; McCune, W.W.

    1992-11-01

    The Conference on Automated Deduction (CADE) has been for nearly twenty years a meeting where both theoreticians and system implementors present their work. Feeling perhaps that the conference was becoming dominated by the theoreticians, Ross Overbeek proposed at CADE-10 in 1990 a contest to stimulate work on the implementation and use of theorem-proving systems. The challenge was to prove a set of theorems, and do so with a uniform approach. That is, it was not allowed to set parameters in the system to specialize it for individual problems. There were actually two separate contests, one represented by a set of seven problems designed to test basic inference components, and the other represented by a set of ten problems designed to test equality-based systems. This paper describes our experiences in preparing to enter the contest with OTTER and Roo, two systems developed at Argonne National Laboratory. Roo is a parallel version of OTTER, but has such different behavior in some cases that we treat them as separate entries. We entered each of them in both contests. Some of the problems are difficult ones; and although many of the problems had been done before with OTTER, in each case we had set OTTER'S many input parameters in a way customized to the problem at hand, and chosen a set of support that appeared to us to be most natural. It was a challenge to come up with a uniform set of parameter settings and a information algorithm for picking the set of support that would allow OTTER to prove each of the theorems.

  1. An entry in the 1992 Overbeek theorem-proving contest

    SciTech Connect

    Lusk, E.L.; McCune, W.W.

    1992-11-01

    The Conference on Automated Deduction (CADE) has been for nearly twenty years a meeting where both theoreticians and system implementors present their work. Feeling perhaps that the conference was becoming dominated by the theoreticians, Ross Overbeek proposed at CADE-10 in 1990 a contest to stimulate work on the implementation and use of theorem-proving systems. The challenge was to prove a set of theorems, and do so with a uniform approach. That is, it was not allowed to set parameters in the system to specialize it for individual problems. There were actually two separate contests, one represented by a set of seven problems designed to test basic inference components, and the other represented by a set of ten problems designed to test equality-based systems. This paper describes our experiences in preparing to enter the contest with OTTER and Roo, two systems developed at Argonne National Laboratory. Roo is a parallel version of OTTER, but has such different behavior in some cases that we treat them as separate entries. We entered each of them in both contests. Some of the problems are difficult ones; and although many of the problems had been done before with OTTER, in each case we had set OTTER`S many input parameters in a way customized to the problem at hand, and chosen a set of support that appeared to us to be most natural. It was a challenge to come up with a uniform set of parameter settings and a information algorithm for picking the set of support that would allow OTTER to prove each of the theorems.

  2. Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement

    NASA Astrophysics Data System (ADS)

    Ito, S.; Feng, B.; Arita, M.; Takayama, A.; Liu, R.-Y.; Someya, T.; Chen, W.-C.; Iimori, T.; Namatame, H.; Taniguchi, M.; Cheng, C.-M.; Tang, S.-J.; Komori, F.; Kobayashi, K.; Chiang, T.-C.; Matsuda, I.

    2016-12-01

    The topology of pure Bi is controversial because of its very small (˜10 meV ) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14-202 bilayer Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ˜10 meV . Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach.

  3. The Ultimate Challenge: Prove B. F. Skinner Wrong

    PubMed Central

    Chance, Paul

    2007-01-01

    For much of his career, B. F. Skinner displayed the optimism that is often attributed to behaviorists. With time, however, he became less and less sanguine about the power of behavior science to solve the major problems facing humanity. Near the end of his life he concluded that a fair consideration of principles revealed by the scientific analysis of behavior leads to pessimism about our species. In this article I discuss the case for Skinner's pessimism and suggest that the ultimate challenge for behavior analysts today is to prove Skinner wrong. PMID:22478494

  4. NASA's Space Launch System: Progress Toward the Proving Ground

    NASA Technical Reports Server (NTRS)

    Jackman, Angie; Johnson, Les

    2017-01-01

    With significant and substantial progress being accomplished toward readying the Space Launch System (SLS) rocket for its first test flight, work is already also underway on preparations for the second flight - using an upgraded version of the vehicle - and beyond. SLS is the most powerful human-rated launch vehicle the United States has ever undertaken, and together with the Orion spacecraft will support human exploration missions into the proving ground of cislunar space and ultimately to Mars. This paper will provide a description of the SLS vehicle, and an overview of the vehicle's capabilities and utilization potential.

  5. Strategy-Enhanced Interactive Proving and Arithmetic Simplification for PVS

    NASA Technical Reports Server (NTRS)

    diVito, Ben L.

    2003-01-01

    We describe an approach to strategy-based proving for improved interactive deduction in specialized domains. An experimental package of strategies (tactics) and support functions called Manip has been developed for PVS to reduce the tedium of arithmetic manipulation. Included are strategies aimed at algebraic simplification of real-valued expressions. A general deduction architecture is described in which domain-specific strategies, such as those for algebraic manipulation, are supported by more generic features, such as term-access techniques applicable in arbitrary settings. An extended expression language provides access to subterms within a sequent.

  6. Strategy-Enhanced Interactive Proving and Arithmetic Simplification for PVS

    NASA Technical Reports Server (NTRS)

    DiVito, Ben L.

    2003-01-01

    We describe an approach to strategy-based proving for improved interactive deduction in specialized domains. An experimental package of strategies (tactics) and support functions called Manip has been developed for PVS to reduce the tedium of arithmetic manipulation. Included are strategies aimed at algebraic simplification of real-valued expressions. A general deduction architecture is described in which domain-specific strategies, such as those for algebraic manipulation, are supported by more generic features, such as term-access techniques applicable in arbitrary settings. An extended expression language provides access to subterms within a sequent.

  7. The ultimate challenge: prove B. F. Skinner wrong.

    PubMed

    Chance, Paul

    2007-01-01

    For much of his career, B. F. Skinner displayed the optimism that is often attributed to behaviorists. With time, however, he became less and less sanguine about the power of behavior science to solve the major problems facing humanity. Near the end of his life he concluded that a fair consideration of principles revealed by the scientific analysis of behavior leads to pessimism about our species. In this article I discuss the case for Skinner's pessimism and suggest that the ultimate challenge for behavior analysts today is to prove Skinner wrong.

  8. Research in advanced formal theorem-proving techniques

    NASA Technical Reports Server (NTRS)

    Rulifson, J. F.

    1971-01-01

    The present status is summarized of a continuing research program aimed at the design and implementation of a language for expressing problem-solving procedures in several areas of artificial intelligence, including program synthesis, robot planning, and theorem proving. Notations, concepts, and procedures common to the representation and solution of many of these problems were abstracted and incorporated as features into the language. The areas of research covered are described, and abstracts of six papers that contain extensive description and technical detail of the work are presented.

  9. Reasoning by analogy as an aid to heuristic theorem proving.

    NASA Technical Reports Server (NTRS)

    Kling, R. E.

    1972-01-01

    When heuristic problem-solving programs are faced with large data bases that contain numbers of facts far in excess of those needed to solve any particular problem, their performance rapidly deteriorates. In this paper, the correspondence between a new unsolved problem and a previously solved analogous problem is computed and invoked to tailor large data bases to manageable sizes. This paper outlines the design of an algorithm for generating and exploiting analogies between theorems posed to a resolution-logic system. These algorithms are believed to be the first computationally feasible development of reasoning by analogy to be applied to heuristic theorem proving.

  10. Octagonal Defects at Carbon Nanotube Junctions

    PubMed Central

    Jaskólski, W.; Pelc, M.; Chico, Leonor; Ayuela, A.

    2013-01-01

    We investigate knee-shaped junctions of semiconductor zigzag carbon nanotubes. Two dissimilar octagons appear at such junctions; one of them can reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at Fermi energy (EF). The reconstructed junction has only one state near EF, indicating that these localized states are related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system. PMID:24089604

  11. Polarization : Proving ground for methods in radiative transfer.

    NASA Astrophysics Data System (ADS)

    Nagendra, K. N.; Anusha, L. S.; Sampoorna, M.

    Polarization of solar lines arises due to illumination of radiating atom by anisotropic (limb darkened/brightened) radiation. Modelling the polarized spectra of the Sun and stars requires solution of the line radiative transfer problem in which the relevant polarizing physical mechanisms are incorporated. The purpose of this paper is to describe in what different ways the polarization state of the radiation `complicates' the numerical methods originally designed for scalar radiative transfer. We present several interesting situations involving the solution of polarized line transfer to prove our point. They are (i) Comparison of the polarized approximate lambda iteration (PALI) methods with new approaches like Bi-conjugate gradient method that is faster, (ii) Polarized Hanle scattering line radiative transfer in random magnetic fields, (iii) Difficulties encountered in incorporating polarized partial frequency redistribution (PRD) matrices in line radiative transfer codes, (iv) Technical difficulties encountered in handling polarized specific intensity vector, some components of which are sign changing, (v) Proving that scattering polarization is indeed a boundary layer phenomenon. We provide credible benchmarks in each of the above studies. We show that any new numerical methods can be tested in the best possible way, when it is extended to include polarization state of the radiation field in line scattering.

  12. Proving Correctness for Pointer Programs in a Verifying Compiler

    NASA Technical Reports Server (NTRS)

    Kulczycki, Gregory; Singh, Amrinder

    2008-01-01

    This research describes a component-based approach to proving the correctness of programs involving pointer behavior. The approach supports modular reasoning and is designed to be used within the larger context of a verifying compiler. The approach consists of two parts. When a system component requires the direct manipulation of pointer operations in its implementation, we implement it using a built-in component specifically designed to capture the functional and performance behavior of pointers. When a system component requires pointer behavior via a linked data structure, we ensure that the complexities of the pointer operations are encapsulated within the data structure and are hidden to the client component. In this way, programs that rely on pointers can be verified modularly, without requiring special rules for pointers. The ultimate objective of a verifying compiler is to prove-with as little human intervention as possible-that proposed program code is correct with respect to a full behavioral specification. Full verification for software is especially important for an agency like NASA that is routinely involved in the development of mission critical systems.

  13. Predictive models for mortality after ruptured aortic aneurysm repair do not predict futility and are not useful for clinical decision making.

    PubMed

    Thompson, Patrick C; Dalman, Ronald L; Harris, E John; Chandra, Venita; Lee, Jason T; Mell, Matthew W

    2016-12-01

    The clinical decision-making utility of scoring algorithms for predicting mortality after ruptured abdominal aortic aneurysms (rAAAs) remains unknown. We sought to determine the clinical utility of the algorithms compared with our clinical decision making and outcomes for management of rAAA during a 10-year period. Patients admitted with a diagnosis rAAA at a large university hospital were identified from 2005 to 2014. The Glasgow Aneurysm Score, Hardman Index, Vancouver Score, Edinburgh Ruptured Aneurysm Score, University of Washington Ruptured Aneurysm Score, Vascular Study Group of New England rAAA Risk Score, and the Artificial Neural Network Score were analyzed for accuracy in predicting mortality. Among patients quantified into the highest-risk group (predicted mortality >80%-85%), we compared the predicted with the actual outcome to determine how well these scores predicted futility. The cohort comprised 64 patients. Of those, 24 (38%) underwent open repair, 36 (56%) underwent endovascular repair, and 4 (6%) received only comfort care. Overall mortality was 30% (open repair, 26%; endovascular repair, 24%; no repair, 100%). As assessed by the scoring systems, 5% to 35% of patients were categorized as high-mortality risk. Intersystem agreement was poor, with κ values ranging from 0.06 to 0.79. Actual mortality was lower than the predicted mortality (50%-70% vs 78%-100%) for all scoring systems, with each scoring system overestimating mortality by 10% to 50%. Mortality rates for patients not designated into the high-risk cohort were dramatically lower, ranging from 7% to 29%. Futility, defined as 100% mortality, was predicted in five of 63 patients with the Hardman Index and in two of 63 of the University of Washington score. Of these, surgery was not offered to one of five and one of two patients, respectively. If one of these two models were used to withhold operative intervention, the mortality of these patients would have been 100%. The actual mortality

  14. Geophysical study of the Building 103 Dump, Aberdeen Proving Ground

    SciTech Connect

    McGinnis, L.D.; Miller, S.F.; Thompson, M.D.; McGinnis, M.G.

    1992-12-01

    The Building 103 Dump is one of ten potentially contaminated sites in the Canal Creek and Westwood areas of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May of 1992. Noninvasive geophysical surveys, including magnetics, resistivity, ground-penetrating radar, and seismic refraction, were conducted. These surveys indicate that much of the area is free of debris. However, prominent magnetic and resistivity anomalies occur along well-defined lineaments, suggestive of a dendritic stream pattern. Prior to the onset of dumping, the site was described as a ``sand pit,`` which suggests that headward erosion of Canal Creek tributaries cut into the surficial aquifer. Contaminants dumped into the landfill would have direct access to the surficial aquifer and thus to Canal Creek. Seismic refraction profiling indicates 6--12 ft of fill material now rests on the former land surface. Only the northern third of the former landfill was geophysically surveyed.

  15. Methods for proving the equivalency of detonator performance

    SciTech Connect

    Munger, Alan C; Akinci, Adrian A; Thomas, Keith A; Clarke, Steve A; Martin, Eric S; Murphy, Michael J

    2009-01-01

    One of the challenges facing engineers is developing newer, safer detonators that are equivalent to devices currently in use. There is no clear consensus on an exact method for drawing equivalence of detonators. This paper summarizes our current efforts to develop diagnostics addressing various aspects of detonator design to better quantify and prove equivalency. We consider various optical techniques to quantify the output pressure and output wave shape. The development of a unique interpretation of streak camera breakouts, known as the apparent center of initiation, will be discussed as a metric for detonation wave shape. Specific examples apply these techniques to the comparison of a new laser-driven detonator with an existing exploding bridgewire (EBW) detonator. Successes and short-comings of the techniques will be discussed.

  16. Trusted Theorem Proving: A Case Study in SLD-Resolution

    NASA Astrophysics Data System (ADS)

    Arkoudas, Konstantine; Shivers, Olin

    Prolog's implementation of SLD-resolution furnishes an efficient theorem-proving technique for the Horn-clause subset of first-order logic, and makes for a powerful addition to any automatic or semi-automatic verification system. However, due to the complexity of SLD-resolution, a naive incorporation of a Prolog engine into such a system would inordinately increase the overall trusted base. In this paper we show how to integrate this procedure in a disciplined, trusted manner, by making the Prolog engine justify its results with very simple natural deduction reasoning. In effect, instead of taking SLD-resolution as a primitive inference rule, we express it as a derived inference rule in terms of much simpler rules such as conditional elimination.

  17. Surface Observation Climatic Summaries for Dugway Proving Grounds, Utah

    DTIC Science & Technology

    1990-08-01

    9 10-14 15-19 20-24 25-29 0-34 35-39 40-49 50-64 GE 65 TOTAL I UML (DEGREES) Z WlIND U 020-040 .5 1.2 .9 2.7 7.8 9.0 050-070 4.3 .5 .1 5.0 3A4 $J (E...OSURYVAT IO~t 1TATION NUPWU: 690110 STATION AANE: DUMMY PINNING GROLMS UT PERIOD OF RECORD: PAY &0 - Apit 90) LST TO UTC: + 7 MNOTH: JUJN H"~S: 15-17 WIND...AS•VlI,•NCTRUE IC.JLY OBSEAVATIOUS USAFETAC, AIEVLLE V MOBS SAGNETIC RUNWY HEADING: 120-300 STATION 1IM ;R: 690110 STATION M•K: DUMMY PROVING GRIOUNS

  18. Proving the Authenticity of Ancient DNA by Comparative Genomic Hybridization

    NASA Astrophysics Data System (ADS)

    Hummel, S.; Herrmann, B.; Rameckers, J.; Müller, D.; Sperling, K.; Neitzel, H.; Tönnies, H.

    In PCR-supported amplification of ancient, degraded DNA, contamination with contemporary DNA can lead to false-positive results, which frequently give rise to discussions in which the mere existence of ancient DNA is doubted. Our confirmation of ancient DNA using comparative genome hybridization (CGH) eliminates these doubts. Unlike PCR methods, CGH requires no amplification of the DNA to be analyzed if adequate amounts of specimen DNA is used. Thus, false results traceable to contaminations are practically ruled out. The examples provided here prove the authenticity of ancient DNA for a 250-year-old and a 3000-year-old sample. At the same time, the CGH of ancient DNA offers the chance to gain insight into the pattern of DNA degradation and to monitor the preservation of certain chromosomal segments.

  19. Thomas Cragg Proves to Be a Good Observer (Abstract)

    NASA Astrophysics Data System (ADS)

    Howe, R.; Clette, F.

    2015-12-01

    (Abstract only) Thomas Cragg proves to be a good observer, enough to be included in the restricted club of 21 long-duration stations without major stability problems over the interval 1945-2015. Although, his counts seem to make a slight downward jump in 1983, and there is a sharp decline in the last two years of his observing career (aging?). Cragg's observations will be used for the equivalent comparison with the new reconstructed sunspot number that is produced from the 21 stations showing the same features in the past six solar cycles. This reconstructed number is fully independent from the original Zürich sunspot number. It actually confirms the corrections being applied to the original sunspot number series (a more simple approach simply multiplying the original series by the correction factor established for the Locarno Observatory's drift), as published in the 2014 paper, by Frédéric Clette, SILSO, Royal Observatory of Belgium.

  20. Model Checking Failed Conjectures in Theorem Proving: A Case Study

    NASA Technical Reports Server (NTRS)

    Pike, Lee; Miner, Paul; Torres-Pomales, Wilfredo

    2004-01-01

    Interactive mechanical theorem proving can provide high assurance of correct design, but it can also be a slow iterative process. Much time is spent determining why a proof of a conjecture is not forthcoming. In some cases, the conjecture is false and in others, the attempted proof is insufficient. In this case study, we use the SAL family of model checkers to generate a concrete counterexample to an unproven conjecture specified in the mechanical theorem prover, PVS. The focus of our case study is the ROBUS Interactive Consistency Protocol. We combine the use of a mechanical theorem prover and a model checker to expose a subtle flaw in the protocol that occurs under a particular scenario of faults and processor states. Uncovering the flaw allows us to mend the protocol and complete its general verification in PVS.

  1. Evaluation of depleted uranium in the environment at Aberdeen Proving Grounds, Maryland and Yuma Proving Grounds, Arizona. Final report

    SciTech Connect

    Kennedy, P.L.; Clements, W.H.; Myers, O.B.; Bestgen, H.T.; Jenkins, D.G.

    1995-01-01

    This report represents an evaluation of depleted uranium (DU) introduced into the environment at the Aberdeen Proving Grounds (APG), Maryland and Yuma Proving Grounds (YPG) Arizona. This was a cooperative project between the Environmental Sciences and Statistical Analyses Groups at LANL and with the Department of Fishery and Wildlife Biology at Colorado State University. The project represents a unique approach to assessing the environmental impact of DU in two dissimilar ecosystems. Ecological exposure models were created for each ecosystem and sensitivity/uncertainty analyses were conducted to identify exposure pathways which were most influential in the fate and transport of DU in the environment. Research included field sampling, field exposure experiment, and laboratory experiments. The first section addresses DU at the APG site. Chapter topics include bioenergetics-based food web model; field exposure experiments; bioconcentration by phytoplankton and the toxicity of U to zooplankton; physical processes governing the desorption of uranium from sediment to water; transfer of uranium from sediment to benthic invertebrates; spead of adsorpion by benthic invertebrates; uptake of uranium by fish. The final section of the report addresses DU at the YPG site. Chapters include the following information: Du transport processes and pathway model; field studies of performance of exposure model; uptake and elimination rates for kangaroo rates; chemical toxicity in kangaroo rat kidneys.

  2. Suspended metal mask techniques in Josephson junction fabrication

    SciTech Connect

    Ono, R.H.; Sauvageau, J.E.; Jain, A.K.; Schwartz, D.B.; Springer, K.T.; Lukens, J.E.

    1985-01-01

    We report here two processes for in-situ, self-aligned fabrication of niobium based Josephson tunnel junctions and SNS microbridges in which multiple evaporations at varying angles are made through a suspended metal stencil fabricated by electron beam lithography (EBL). Both techniques have proved superior to earlier all-polymer suspended masks, particularly with e-gun evaporated refractory metals such as niobium. The first process uses a trilevel resist and ion milling to pattern a gold stencil suspended on PMMA. In the second process, an aluminum stencil suspended on polyimide (PI) is patterned by lift-off with an EBL mask written in a PMMA layer on top of the PI. The PI is then undercut using an oxygen plasma etch through the aluminum mask. Reproducible ( +- 20 nm) submicrometer dimensions and good junction characteristics have been achieved using these techniques without the need for difficult-to-control surface cleaning procedures.

  3. Proton radiation damage in vertical junction solar cells

    NASA Astrophysics Data System (ADS)

    Walker, D. H.; Statler, R. L.

    A comparative experimental study of proton radiation damage in silicon vertical junction (VJ) and silicon planar solar cells was performed at three energies, 1-MeV, 2-MeV, and 3.5-MeV, for a normal incidence monoenergetic proton beam. Proton fluence levels up to 3 x 10 to the 12th protons/sq cm were achieved, with solar cell I-V characterization measurements performed at incremental fluences, using a recently calibrated Spectrolab X-25L Solar Simulator. The VJ cells were made from 0.4 ohm-cm silicon, while the planar cells were made from 10 ohm-cm silicon and had a back surface reflector. The VJ cells proved to be more radiation resistant than the baseline planar cells, and the damage data from various proton energies indicate that the vertical junction concept does work effectively for maintaining high collection efficiency despite heavy radiation exposure.

  4. Induction of an abortive and futile DNA repair process in E. coli by the antitumor DNA bifunctional intercalator, ditercalinium: role in polA in death induction.

    PubMed Central

    Lambert, B; Roques, B P; Le Pecq, J B

    1988-01-01

    Ditercalinium, an antitumor bifunctional intercalator which forms a high affinity reversible complex with DNA, was found to be specifically cytotoxic for polA and lig7 E. coli strains. In the polA strain, the cytotoxic effect of ditercalinium was suppressed by the uvrA mutation. DNA single strand breaks accumulated in presence of ditercalinium at high temperature in lig7 strains but not in polA strains. Ditercalinium caused no DNA synthesis inhibition although it was able to induce SOS functions. It is proposed that the ditercalinium DNA complex because of its non covalent nature acts as a dummy lesion for the UV repair system in E. coli leading to a futile and abortive repair process. Polymerase I appears to be required to prevent the malfunctioning of a DNA repair process triggered by molecules forming non covalent complex with DNA. PMID:2830590

  5. Transport in Carbon Nanotube Junctions

    NASA Astrophysics Data System (ADS)

    Khoo, K. H.; Chelikowsky, James R.

    2008-03-01

    There is growing interest in the use of carbon nanotube thin films as transparent electrical conductors and thin-film transistors owing to their high optical transmittance, low sheet resistivity, and ease of fabrication. [1,2] A major contribution to the sheet resistivity originates at nanotube junctions, as electrical contact is typically poor between adjacent nanotubes. It is thus important to characterize carbon nanotube junctions in order to understand the conduction properties of nanotube thin films. To this end, we have performed ab initio density functional theory calculations to investigate the structural, electronic and transport properties of carbon nanotube junctions as a function of nanotube chirality and contact geometry [1] Z. Wu et al., Science 305, 1273 (2004) [2] E. S. Snow, J. P. Novak, P. M. Campbell, and D. Park, Appl. Phys. Lett. 82, 2145 (2003).

  6. A comparison of the universal TOR Guideline to the absence of prehospital ROSC and duration of resuscitation in predicting futility from out-of-hospital cardiac arrest.

    PubMed

    Drennan, Ian R; Case, Erin; Verbeek, P Richard; Reynolds, Joshua C; Goldberger, Zachary D; Jasti, Jamie; Charleston, Mark; Herren, Heather; Idris, Ahamed H; Leslie, Paul R; Austin, Michael A; Xiong, Yan; Schmicker, Robert H; Morrison, Laurie J

    2017-02-01

    The Universal Termination of Resuscitation (TOR) Guideline accurately identifies potential out-of-hospital cardiac arrest (OHCA) survivors. However, implementation is inconsistent with some Emergency Medical Service (EMS) agencies using absence of return of spontaneous circulation (ROSC) as sole criterion for termination. To compare the performance of the Universal TOR Guideline with the single criterion of no prehospital ROSC. Second, to determine factors associated with survival for patients transported without a ROSC. Lastly, to compare the impact of time to ROSC as a marker of futility to the Universal TOR Guideline. Retrospective, observational cohort study. Non-traumatic, adult (≥18 years) OHCA patients of presumed cardiac etiology treated by EMS providers. ROC-PRIMED and ROC-Epistry post ROC-PRIMED databases between 2007 and 2011. Primary outcome was survival to hospital discharge and the secondary outcome was functional survival. We used multivariable regression to evaluate factors associated with survival in patients transported without a ROSC. 36,543 treated OHCAs occurred of which 9467 (26%) were transported to hospital without a ROSC. Patients transported without a ROSC who met the Universal TOR Guideline for transport had a survival of 3.0% (95% CI 2.5-3.4%) compared to 0.7% (95% CI 0.4-0.9%) in patients who met the Universal TOR Guideline for termination. The Universal TOR Guideline identified 99% of survivors requiring continued resuscitation and transportation to hospital including early identification of survivors who sustained a ROSC after extended durations of CPR. Using absence of ROSC as a sole predictor of futility misses potential survivors. The Universal TOR Guideline remains a strong predictor of survival. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  7. Stereoselective pharmacokinetics of ketoprofen and ketoprofen glucuronide in end-stage renal disease: evidence for a ‘futile cycle’ of elimination

    PubMed Central

    Grubb, N G; Rudy, D W; Brater, D C; Hall, S D

    1999-01-01

    Aims To assess if futile cycling of ketoprofen occurs in patients with decreased renal function. Methods Ketoprofen was administered to six haemodialysis-dependent patients with end-stage renal disease as single (50 mg) or multiple doses (50 mg three times daily, for 7 days). Plasma and dialysate concentrations of the unconjugated and glucuronidated R- and S-enantiomers of ketoprofen were determined using h.p.l.c. following the single and multiple dosing. Results The oral clearance was decreased and terminal elimination half-lives of R- and S-ketoprofen and the corresponding acyl glucuronides were increased in functionally anephric patients compared with healthy subjects. In contrast with the R-isomers, S-ketoprofen and S-ketoprofen glucuronide exhibited an unexpected accumulation (2.7–3.8 fold) after repeated dosing achieving S:R ratios of 3.3±1.7 and 11.2±5.3, respectively. The plasma dialysis clearances for R- and S-ketoprofen glucuronides were 49.4±19.8 and 39.0±15.9 ml min−1, respectively, and 10.8±17.6 and 13.3±23.5 ml min−1 for unconjugated R- and S-ketoprofen. Conclusions The selective accumulation of S-ketoprofen and its acyl glucuronide are consistent with amplification of chiral inversion subsequent to futile cycling between R-ketoprofen and R-ketoprofen glucuronide. Severe renal insufficiency, and possibly more modest decrements, results in a disproportionate increase in systemic exposure to the S-enantiomer which inhibits both pathologic and homeostatic prostaglandin synthesis. PMID:10583018

  8. The GOES-R Proving Ground: 2012 Update

    NASA Astrophysics Data System (ADS)

    Gurka, J.; Goodman, S. J.; Schmit, T.; Demaria, M.; Mostek, A.; Siewert, C.; Reed, B.

    2011-12-01

    The Geostationary Operational Environmental Satellite (GOES)-R will provide a great leap forward in observing capabilities, but will also offer a significant challenge to ensure that users are ready to exploit the vast improvements in spatial, spectral, and temporal resolutions. To ensure user readiness, forecasters and other users must have access to prototype advanced products well before launch, and have the opportunity to provide feedback to product developers and computing and communications managers. The operational assessment is critical to ensure that the end products and NOAA's computing and communications systems truly meet their needs in a rapidly evolving environment. The GOES-R Proving Ground (PG) engages the National Weather Service (NWS) forecast, watch and warning community and other agency users in pre-operational demonstrations of select products with GOES-R attributes (enhanced spectral, spatial, and temporal resolution). In the PG, developers and forecasters test and apply algorithms for new GOES-R satellite data and products using proxy and simulated data sets, including observations from current and future satellite instruments (MODIS, AIRS, IASI, SEVIRI, NAST-I, NPP/VIIRS/CrIS, LIS), lightning networks, and computer simulated products. The complete list of products to be evaluated in 2012 will be determined after evaluating results from experiments in 2011 at the NWS' Storm Prediction Center, National Hurricane Center, Aviation Weather Center, Ocean Prediction Center, Hydrometeorological Prediction Center, and from the six NWS regions. In 2012 and beyond, the PG will test and validate data processing and distribution systems and the applications of these products in operational settings. Additionally developers and forecasters will test and apply display techniques and decision aid tools in operational environments. The PG is both a recipient and a source of training. Training materials are developed using various distance training tools in

  9. NASA SPoRT GOES-R Proving Ground Activities

    NASA Technical Reports Server (NTRS)

    Stano, Geoffrey T.; Fuell, Kevin K.; Jedloec, Gary J.

    2010-01-01

    The NASA Short-term Prediction Research and Transition (SPoRT) program is a partner with the GOES-R Proving Ground (PG) helping prepare forecasters understand the unique products to come from the GOES-R instrument suite. SPoRT is working collaboratively with other members of the GOES-R PG team and Algorithm Working Group (AWG) scientists to develop and disseminate a suite of proxy products that address specific forecast problems for the WFOs, Regional and National Support Centers, and other NOAA users. These products draw on SPoRT s expertise with the transition and evaluation of products into operations from the MODIS instrument and the North Alabama Lightning Mapping Array (NALMA). The MODIS instrument serves as an excellent proxy for the Advanced Baseline Imager (ABI) that will be aboard GOES-R. SPoRT has transitioned and evaluated several multi-channel MODIS products. The true and false color products are being used in natural hazard detection by several SPoRT partners to provide better observation of land features, such as fires, smoke plumes, and snow cover. Additionally, many of SPoRT s partners are coastal offices and already benefit from the MODIS sea surface temperature composite. This, along with other surface feature observations will be developed into ABI proxy products for diagnostic use in the forecast process as well as assimilation into forecast models. In addition to the MODIS instrument, the NALMA has proven very valuable to WFOs with access to these total lightning data. These data provide situational awareness and enhanced warning decision making to improve lead times for severe thunderstorm and tornado warnings. One effort by SPoRT scientists includes a lightning threat product to create short-term model forecasts of lightning activity. Additionally, SPoRT is working with the AWG to create GLM proxy data from several of the ground based total lightning networks, such as the NALMA. The evaluation will focus on the vastly improved spatial

  10. Gap junctions - guards of excitability.

    PubMed

    Stroemlund, Line Waring; Jensen, Christa Funch; Qvortrup, Klaus; Delmar, Mario; Nielsen, Morten Schak

    2015-06-01

    Cardiomyocytes are connected by mechanical and electrical junctions located at the intercalated discs (IDs). Although these structures have long been known, it is becoming increasingly clear that their components interact. This review describes the involvement of the ID in electrical disturbances of the heart and focuses on the role of the gap junctional protein connexin 43 (Cx43). Current evidence shows that Cx43 plays a crucial role in organizing microtubules at the intercalated disc and thereby regulating the trafficking of the cardiac sodium channel NaV1.5 to the membrane.

  11. Conducting polyaniline nanowire electrode junction

    NASA Astrophysics Data System (ADS)

    Gaikwad, Sumedh; Bodkhe, Gajanan; Deshmukh, Megha; Patil, Harshada; Rushi, Arti; Shirsat, Mahendra D.; Koinkar, Pankaj; Kim, Yun-Hae; Mulchandani, Ashok

    2015-03-01

    In this paper, a synthesis of conducting polyaniline nanowires electrode junction (CPNEJ) has been reported. Conducting polyaniline nanowires electrode junction on Si/SiO2 substrate (having 3 μm gap between two gold microelectrodes) is prepared. Polyaniline nanowires with diameter (ca. 140 nm to 160 nm) were synthesized by one step electrochemical polymerization using galvanostatic (constant current) technique to bridge this gap. The surface morphology of CPNEJ was studied by scanning electron microscope (SEM). The synthesized CPNEJ is an excellent platform for biosensor applications.

  12. Predicting coaxial helical stacking in RNA junctions

    PubMed Central

    Laing, Christian; Wen, Dongrong; Wang, Jason T. L.; Schlick, Tamar

    2012-01-01

    RNA junctions are important structural elements that form when three or more helices come together in space in the tertiary structures of RNA molecules. Determining their structural configuration is important for predicting RNA 3D structure. We introduce a computational method to predict, at the secondary structure level, the coaxial helical stacking arrangement in junctions, as well as classify the junction topology. Our approach uses a data mining approach known as random forests, which relies on a set of decision trees trained using length, sequence and other variables specified for any given junction. The resulting protocol predicts coaxial stacking within three- and four-way junctions with an accuracy of 81% and 77%, respectively; the accuracy increases to 83% and 87%, respectively, when knowledge from the junction family type is included. Coaxial stacking predictions for the five to ten-way junctions are less accurate (60%) due to sparse data available for training. Additionally, our application predicts the junction family with an accuracy of 85% for three-way junctions and 74% for four-way junctions. Comparisons with other methods, as well applications to unsolved RNAs, are also presented. The web server Junction-Explorer to predict junction topologies is freely available at: http://bioinformatics.njit.edu/junction. PMID:21917853

  13. Geophysics: Building E5476 decommissiong, Aberdeen Proving Ground

    SciTech Connect

    Miller, S.F.; Thompson, M.D.; McGinnis, M.G.; McGinnis, L.D.

    1992-11-01

    Building E5476 was one of ten potentially contaminated sites in the Canal Creek and Westwood areas of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May of 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar, were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. The large number of magnetic sources surrounding the building are believed to be contained in construction fill. The smaller anomalies, for the most part, were not imaged with ground radar or by electrical profiling. Large magnetic anomalies near the southwest comer of the building are due to aboveground standpipes and steel-reinforced concrete. Two high-resistivity areas, one projecting northeast from the building and another south of the original structure, may indicate the presence of organic pore fluids in the subsurface. A conductive lineament protruding from the south wall that is enclosed by the southem, high-resistivity feature is not associated with an equivalent magnetic anomaly. Magnetic and electrical anomalies south of the old landfill boundary are probably not associated with the building. The boundary is marked by a band of magnetic anomalies and a conductive zone trending northwest to southeast. The cause of high resistivities in a semicircular area in the southwest comer, within the landfill area, is unexplained.

  14. Geophysics: Building E5375 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    McGinnis, M.G.; McGinnis, L.D.; Miller, S.F.; Thompson, M.D.

    1992-08-01

    Building E5375 was one of ten potentially contaminated sites in the Canal Creek area of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar (GPR), were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. Several anomalies wear, noted: (1) An underground storage tank located 25 ft east of Building E5375 was identified with magnetic, resistivity, and GPR profiling. (2) A three-point resistivity anomaly, 12 ft east of the northeast comer of Building E5374 (which borders Building E5375) and 5 ft south of the area surveyed with the magnetometer, may be caused by another underground storage tank. (3) A 2,500-gamma magnetic anomaly near the northeast corner of the site has no equivalent resistivity anomaly, although disruption in GPR reflectors was observed. (4) A one-point magnetic anomaly was located at the northeast comer, but its source cannot be resolved. A chaotic reflective zone to the east represents the radar signature of Building E5375 construction fill.

  15. Geophysics: Building E5282 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    Thompson, M.D.; McGinnis, M.G.; McGinnis, L.D.; Miller, S.F.

    1992-08-01

    This report discusses Building E5282 which was one of 10 potentially contaminated sites in the Canal Creek area of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May of 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar (GPR), were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. Magnetic surveys identified small, complicated, multiple anomalies west, north, and northeast of the building that may be caused by construction fill. Two underground storage tanks, at the northeast and southeast corners, were identified. A large magnetic anomaly complex east of the building was caused by aboveground pipes and unexploded ordnance fragments scattered at the surface. Electrical resistivity profiling showed a broad, conductive terrain superimposed over magnetic anomalies on the north and west. A broad, high-resistivity, nonmagnetic area centered 25 ft east of the building has an unknown origin, but it may be due to nonconductive organic liquids, construction fill, or a buried concrete slab; GPR imaging showed this area as a highly reflective zone at a depth of about 5 ft. The GPR data also showed a small-diameter pipe oriented north-south located east of the building.

  16. Depleted uranium risk assessment at Aberdeen Proving Ground

    SciTech Connect

    Ebinger, M.H.; Myers, O.B.; Kennedy, P.L.; Clements, W.H.

    1993-03-01

    The Environmental Science Group at Los Alamos and the Test and Evaluation Command (TECOM) are assessing the risk of depleted uranium (DU) testing at Aberdeen Proving Ground (APG). Conceptual and mathematical models of DU transfer through the APG ecosystem have been developed in order to show the mechanisms by which DU migrates or remains unavailable to different flora and fauna and to humans. The models incorporate actual rates of DU transfer between different ecosystem components as much as possible. Availability of data on DU transport through different pathways is scarce and constrains some of the transfer rates that can be used. Estimates of transfer rates were derived from literature sources and used in the mass-transfer models when actual transfer rates were unavailable. Objectives for this risk assessment are (1) to assess if DU transports away from impact areas; (2) to estimate how much, if any, DU migrates into Chesapeake Bay; (3) to determine if there are appreciable risks to the ecosystems due to DU testing; (4) to estimate the risk to human health as a result of DU testing.

  17. Depleted uranium risk assessment at Aberdeen Proving Ground

    SciTech Connect

    Ebinger, M.H. ); Myers, O.B.; Kennedy, P.L.; Clements, W.H. . Dept. of Fishery and Wildlife Biology)

    1993-01-01

    The Environmental Science Group at Los Alamos and the Test and Evaluation Command (TECOM) are assessing the risk of depleted uranium (DU) testing at Aberdeen Proving Ground (APG). Conceptual and mathematical models of DU transfer through the APG ecosystem have been developed in order to show the mechanisms by which DU migrates or remains unavailable to different flora and fauna and to humans. The models incorporate actual rates of DU transfer between different ecosystem components as much as possible. Availability of data on DU transport through different pathways is scarce and constrains some of the transfer rates that can be used. Estimates of transfer rates were derived from literature sources and used in the mass-transfer models when actual transfer rates were unavailable. Objectives for this risk assessment are (1) to assess if DU transports away from impact areas; (2) to estimate how much, if any, DU migrates into Chesapeake Bay; (3) to determine if there are appreciable risks to the ecosystems due to DU testing; (4) to estimate the risk to human health as a result of DU testing.

  18. Geophysics: Building E5440 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    McGinnis, L.D.; Miller, S.F.; Thompson, M.D.; McGinnis, M.G.

    1992-11-01

    Building E5440 was one of ten potentially contaminated sites in the Canal Creek and Westwood areas of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar (GPR), were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. The results show several complex geophysical signatures. Isolated, one-point, magnetic anomalies surrounding the building may be associated with construction fill. A 10-ft-wide band of strongly magnetic positive anomalies bordering the north side of the building obliterates small magnetic sources that might otherwise be seen. A prominent magnetic nose'' extending northward from this band toward a standpipe at 100N,63E may be connected to an underground tank. The southeast corner of the site is underlain by a rectangular, magnetized source associated with strong radar images. A magnetic lineament extending south from the anomaly may be caused by a buried pipe; the anomaly itself may be caused by subsurface equipment associated with a manhole or utility access pit. A 2,500-gamma, positive magnetic anomaly centered at 0N,20E, which is also the location of a 12 [Omega]-m resistivity minimum, may be caused by a buried vault. It appears on radar imaging as a strong reflector.

  19. Geophysics: Building E5481 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    Thompson, M.D.; McGinnis, M.G.; McGinnis, L.D.; Miller, S.F.

    1992-11-01

    Building E5481 is one of ten potentially contaminated sites in the Canal Creek and Westwood areas of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May of 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar, were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. The building is located on the northern margin of a landfill that was sited in a wetland. The large number of magnetic sources surrounding the building are believed to be contained in construction fill that had been used to raise the grade. The smaller anomalies, for the most part, are not imaged with ground radar or by electrical profiling. A conductive zone trending northwest to southeast across the site is spatially related to an old roadbed. Higher resistivity areas in the northeast and east are probably representive of background values. Three high-amplitude, positive, rectangular magnetic anomalies have unknown sources. The features do not have equivalent electrical signatures, nor are they seen with radar imaging.

  20. Environmental geophysics at Beach Point, Aberdeen Proving Ground, Maryland

    SciTech Connect

    McGinnis, L.D.; Daudt, C.R.; Thompson, M.D.; Miller, S.F.; Mandell, W.A.; Wrobel, J.

    1994-07-01

    Geophysical studies at Beach Point Peninsula, in the Edgewood area of Aberdeen Proving Ground, Maryland, provide diagnostic signatures of the hydrogeologic framework and possible contaminant pathways. These studies permit construction of the most reasonable scenario linking dense, nonaqueous-phase liquid contaminants introduced at the surface with their pathway through the surficial aquifer. Subsurface geology and contaminant presence were identified by drilling, outcrop mapping, and groundwater sampling and analyses. Suspected sources of near-surface contaminants were defined by magnetic and conductivity measurements. Negative conductivity anomalies may be associated with unlined trenches. Positive magnetic and conductivity anomalies outline suspected tanks and pipes. The anomalies of greatest concern are those spatially associated with a concrete slab that formerly supported a mobile clothing impregnating plant. Resistivity and conductivity profiling and depth soundings were used to identify an electrical anomaly extending through the surficial aquifer to the basal pleistocene unconformity, which was mapped by using seismic reflection methods. The anomaly may be representative of a contaminant plume connected to surficial sources. Major activities in the area included liquid rocket fuel tests, rocket fuel fire suppression tests, pyrotechnic material and smoke generator tests, and the use of solvents at a mobile clothing impregnating plant.

  1. Geophysics: Building E5032 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    McGinnis, L.D.; Miller, S.F.

    1991-07-01

    integration of data from surveys using three geophysical technologies has provided information used to define the locations of buried utilities, tanks, vaults, and debris near building E5032 at the Aberdeen Proving Ground. Ground penetrating radar (GPR) profiles indicate the presence of buried pipes, tanks, reinforcement rods (rebar), and remnants of railroad tracks. A magnetic map constructed from a detailed magnetic survey on the north side of the building outlines buried iron-rich objects that are interpreted to be iron pipes, tank, and other debris of uncertain origin at relatively shallow depths. Horizontal electrical resistivity surveys and vertical electrical resistivity soundings essentially corroborated the findings obtained with the magnetometer and GPR. In addition, a highly resistance layer was observed on the east side of the building where a former railroad bed with a thick grave fill is believed to immediately underlie the lawn. The resistivity data show no evidence of a conductive leachate plume. Geophysical measurements from three techniques over a buried concrete slab approximately 130 ft north of Building E5032 give geophysical signatures interpreted to be due to the presence of a large iron tank or vault. An attempt was made to gather meaningful magnetic data on the east, west, and south sides of the building; however, the quality of subsurface interpretations in those areas was poor because of the influence of surficial iron lids, pipes, grates, and the effects of the corrugated iron building itself. 11 figs., 1 tab.

  2. Geophysics: Building E5190 decommissioning, Aberdeen Proving Ground

    SciTech Connect

    Miller, S.F.; Thompson, M.D.; McGinnis, M.G.; McGinnis, L.D.

    1992-07-01

    Building E5190 is one of ten potentially contaminated sites in the Canal Creek area of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May 1992. A noninvasive geophysical survey, including the complementary technologies of magnetics, electrical resistivity, and ground-penetrating radar, was conducted around the perimeter as a guide to developing a sampling and monitoring program prior to decommissioning and dismantling the building. The magnetics surveys indicated that multistation, positive magnetic sources are randomly distributed north and west of the building. Two linear trends were noted: one that may outline buried utility lines and another that is produced by a steel-covered trench. The resistivity profiling indicated three conductive zones: one due to increased moisture in a ditch, one associated with buried utility lines, and a third zone associated with the steel-covered trench. Ground-penetrating radar imaging detected two significant anomalies, which were correlated with small-amplitude magnetic anomalies. The objectives of the study -- to detect and locate objects and to characterize a located object were achieved.

  3. Proving refinement transformations for deriving high-assurance software

    SciTech Connect

    Winter, V.L.; Boyle, J.M.

    1996-05-01

    The construction of a high-assurance system requires some evidence, ideally a proof, that the system as implemented will behave as required. Direct proofs of implementations do not scale up well as systems become more complex and therefore are of limited value. In recent years, refinement-based approaches have been investigated as a means to manage the complexity inherent in the verification process. In a refinement-based approach, a high-level specification is converted into an implementation through a number of refinement steps. The hope is that the proofs of the individual refinement steps will be easier than a direct proof of the implementation. However, if stepwise refinement is performed manually, the number of steps is severely limited, implying that the size of each step is large. If refinement steps are large, then proofs of their correctness will not be much easier than a direct proof of the implementation. The authors describe an approach to refinement-based software development that is based on automatic application of refinements, expressed as program transformations. This automation has the desirable effect that the refinement steps can be extremely small and, thus, easy to prove correct. They give an overview of the TAMPR transformation system that the use for automated refinement. They then focus on some aspects of the semantic framework that they have been developing to enable proofs that TAMPR transformations are correctness preserving. With this framework, proofs of correctness for transformations can be obtained with the assistance of an automated reasoning system.

  4. Ecological effects of soil contamination at Aberdeen Proving Ground, Maryland

    SciTech Connect

    Kuperman, R.G.; Dunn, C.P. )

    1994-06-01

    Assessment of the ecological condition of contaminated soil was conducted in portions of the U.S. Army's Aberdeen Proving Ground, Maryland as part of an ecological risk assessment. This area is covered by open fields, woods and nontidal marshes. Chemicals disposed of in open burning pits included methylphosphonothioic acid, dichlorodiethyl sulfide, and titanium tetrachloride and sulfur trioxide/chlorosulfonic acid. Previous soil analysis showed extensive surface soil contamination with metals, nitrate, PCBs and pesticides. This assessment included characterizing soil biota, biologically-mediated processes in soil and aboveground biomass. Field surveys of the soil invertebrate communities showed significant reductions in the total abundance of animals, reductions in the abundance of several taxonomic and functional groups of soil invertebrates, and changes in the activity of epigeic arthropods in contaminated areas when compared with the local [open quotes]background[close quotes] area. Laboratory toxicity tests also demonstrated that microbial activity and success of egg hatching of ground beetle Harpalus pensylvanicus were reduced in contaminated soils. These results suggest that impacts to soil ecosystems should be explicitly considered in ecological risk assessment.

  5. Potential Cislunar and Interplanetary Proving Ground Excursion Trajectory Concepts

    NASA Technical Reports Server (NTRS)

    McGuire, Melissa L.; Strange, Nathan J.; Burke, Laura M.; MacDonald, Mark A.; McElrath, Timothy P.; Landau, Damon F.; Lantoine, Gregory; Hack, Kurt J.; Lopez, Pedro

    2016-01-01

    NASA has been investigating potential translunar excursion concepts to take place in the 2020s that would be used to test and demonstrate long duration life support and other systems needed for eventual Mars missions in the 2030s. These potential trajectory concepts could be conducted in the proving ground, a region of cislunar and near-Earth interplanetary space where international space agencies could cooperate to develop the technologies needed for interplanetary spaceflight. Enabled by high power Solar Electric Propulsion (SEP) technologies, the excursion trajectory concepts studied are grouped into three classes of increasing distance from the Earth and increasing technical difficulty: the first class of excursion trajectory concepts would represent a 90-120 day round trip trajectory with abort to Earth options throughout the entire length, the second class would be a 180-210 day round trip trajectory with periods in which aborts would not be available, and the third would be a 300-400 day round trip trajectory without aborts for most of the length of the trip. This paper provides a top-level summary of the trajectory and mission design of representative example missions of these three classes of excursion trajectory concepts.

  6. Environmental geophysics, offshore Bush River Peninsula, Aberdeen Proving Ground, Maryland

    SciTech Connect

    Miller, S.F.; Kuecher, G.J.; Davies, B.E.

    1995-11-01

    Geophysical studies in shallow waters adjacent to the Bush River Peninsula, Edgewood Area of Aberdeen Proving Ground, Maryland, have delineated the extent of waste disposal sites and established a hydrogeologic framework, which may control contaminant transport offshore. These studies indicate that during the Pleistocene Epoch, alternating stands of high and low sea levels resulted in a complex pattern of shallow channel-fill deposits around the Bush River Peninsula. Ground-penetrating radar studies reveal paleochannels greater than 50 ft deep. Some of the paleochannels are also imaged with marine seismic reflection. Conductivity highs measured with the EM-31 are also indicative of paleochannels. This paleochannel depositional system is environmentally significant because it may control the shallow groundwater flow regime beneath the peninsula. Magnetic, conductivity, and side-scan sonar anomalies outline anthropogenic anomalies in the study area. On the basis of geophysical data, underwater anthropogenic materials do exist in some isolated areas, but large-scale offshore dumping has not occurred in the area studied.

  7. Pacific Proving Grounds radioisotope imprint in the Philippine Sea sediments.

    PubMed

    Pittauer, Daniela; Roos, Per; Qiao, Jixin; Geibert, Walter; Elvert, Marcus; Fischer, Helmut W

    2017-08-23

    Radionuclide concentrations were studied in sediment cores taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial Western Pacific. High resolution deposition records of anthropogenic radionuclides were collected at this site. Excess (210)Pb together with excess (228)Th and anthropogenic radionuclides provided information about accumulation rates. Concentrations of Am and Pu isotopes were detected by gamma spectrometry, alpha spectrometry and ICP-MS. The Pu ratios indicate a high portion (minimum of 60%) of Pu from the Pacific Proving Grounds (PPG). This implies that the transport of PPG derived plutonium with the Mindanao Current southward is similarly effective as the previously known transport towards the north with the Kuroshio Current. The record is compared to other studies from northwest Pacific marginal seas and Lombok basin in the Indonesian Archipelago. The sediment core top was found to contain a 6 cm thick layer dominated by terrestrial organic matter, which was interpreted as a result of the 2012 Typhoon Pablo-related fast deposition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Simple Electronic Analog of a Josephson Junction.

    ERIC Educational Resources Information Center

    Henry, R. W.; And Others

    1981-01-01

    Demonstrates that an electronic Josephson junction analog constructed from three integrated circuits plus an external reference oscillator can exhibit many of the circuit phenomena of a real Josephson junction. Includes computer and other applications of the analog. (Author/SK)

  9. Simple Electronic Analog of a Josephson Junction.

    ERIC Educational Resources Information Center

    Henry, R. W.; And Others

    1981-01-01

    Demonstrates that an electronic Josephson junction analog constructed from three integrated circuits plus an external reference oscillator can exhibit many of the circuit phenomena of a real Josephson junction. Includes computer and other applications of the analog. (Author/SK)

  10. Yuma proving grounds automatic UXO detection using biomorphic robots

    SciTech Connect

    Tilden, M.W.

    1996-07-01

    The current variety and dispersion of Unexploded Ordnance (UXO) is a daunting technological problem for current sensory and extraction techniques. The bottom line is that the only way to insure a live UXO has been found and removed is to step on it. As this is an upsetting proposition for biological organisms like animals, farmers, or Yuma field personnel, this paper details a non-biological approach to developing inexpensive, automatic machines that will find, tag, and may eventually remove UXO from a variety of terrains by several proposed methods. The Yuma proving grounds (Arizona) has been pelted with bombs, mines, missiles, and shells since the 1940s. The idea of automatic machines that can clean up after such testing is an old one but as yet unrealized because of the daunting cost, power and complexity requirements of capable robot mechanisms. A researcher at Los Alamos National Laboratory has invented and developed a new variety of living robots that are solar powered, legged, autonomous, adaptive to massive damage, and very inexpensive. This technology, called Nervous Networks (Nv), allows for the creation of capable walking mechanisms (known as Biomorphic robots, or Biomechs for short) that rather than work from task principles use instead a survival-based design philosophy. This allows Nv based machines to continue doing work even after multiple limbs and sensors have been removed or damaged, and to dynamically negotiate complex terrains as an emergent property of their operation (fighting to proceed, as it were). They are not programmed, and indeed, the twelve transistor Nv controller keeps their electronic cost well below that of most pocket radios. It is suspected that advanced forms of these machines in huge numbers may be an interesting, capable solution to the problem of general and specific UXO identification, tagging, and removal.

  11. Automated Theorem Proving in High-Quality Software Design

    NASA Technical Reports Server (NTRS)

    Schumann, Johann; Swanson, Keith (Technical Monitor)

    2001-01-01

    The amount and complexity of software developed during the last few years has increased tremendously. In particular, programs are being used more and more in embedded systems (from car-brakes to plant-control). Many of these applications are safety-relevant, i.e. a malfunction of hardware or software can cause severe damage or loss. Tremendous risks are typically present in the area of aviation, (nuclear) power plants or (chemical) plant control. Here, even small problems can lead to thousands of casualties and huge financial losses. Large financial risks also exist when computer systems are used in the area of telecommunication (telephone, electronic commerce) or space exploration. Computer applications in this area are not only subject to safety considerations, but also security issues are important. All these systems must be designed and developed to guarantee high quality with respect to safety and security. Even in an industrial setting which is (or at least should be) aware of the high requirements in Software Engineering, many incidents occur. For example, the Warshaw Airbus crash, was caused by an incomplete requirements specification. Uncontrolled reuse of an Ariane 4 software module was the reason for the Ariane 5 disaster. Some recent incidents in the telecommunication area, like illegal "cloning" of smart-cards of D2GSM handies, or the extraction of (secret) passwords from German T-online users show that also in this area serious flaws can happen. Due to the inherent complexity of computer systems, most authors claim that only a rigorous application of formal methods in all stages of the software life cycle can ensure high quality of the software and lead to real safe and secure systems. In this paper, we will have a look, in how far automated theorem proving can contribute to a more widespread application of formal methods and their tools, and what automated theorem provers (ATPs) must provide in order to be useful.

  12. High resolution seismic reflection profiling at Aberdeen Proving Grounds, Maryland

    SciTech Connect

    Miller, R.D.; Xia, Jianghai; Swartzel, S.; Llopis, J.; Miller, P.

    1996-11-01

    The effectiveness of shallow high resolution seismic reflection (i.e., resolution potential) to image geologic interfaces between about 70 and 750 ft at the Aberdeen Proving Grounds, Maryland (APG), appears to vary locally with the geometric complexity of the unconsolidated sediments that overlay crystalline bedrock. The bedrock surface (which represents the primary geologic target of this study) was imaged at each of three test areas on walkaway noise tests and CDP (common depth point) stacked data. Proven high resolution techniques were used to design and acquire data on this survey. Feasibility of the technique and minimum acquisition requirements were determined through evaluation and correlation of walkaway noise tests, CDP survey lines, and a downhole velocity check shot survey. Data processing and analysis revealed several critical attributes of shallow seismic data from APG that need careful consideration and compensation on reflection data sets. This survey determined: (1) the feasibility of the technique, (2) the resolution potential (both horizontal and vertical) of the technique, (3) the optimum source for this site, (4) the optimum acquisition geometries, (5) general processing flow, and (6) a basic idea of the acoustic variability across this site. Source testing involved an accelerated weight drop, land air gun, downhole black powder charge, sledge hammer/plate, and high frequency vibrator. Shallow seismic reflection profiles provided for a more detailed picture of the geometric complexity and variability of the distinct clay sequences (aquatards), previously inferred from drilling to be present, based on sparse drill holes and basewide conceptual models. The seismic data also reveal a clear explanation for the difficulties previously noted in correlating individual, borehole-identified sand or clay units over even short distances.

  13. Environmental geophysics at J-Field, Aberdeen Proving Ground, Maryland

    SciTech Connect

    Daudt, C.R.; McGinnis, L.D.; Miller, S.F.; Thompson, M.D.

    1994-11-01

    Geophysical data collected at J-Field, Aberdeen Proving Ground, Maryland, were used in the characterization of the natural hydrogeologic framework of the J-Field area and in the identification of buried disturbances (trenches and other evidences of contamination). Seismic refraction and reflection data and electrical resistivity data have aided in the characterization of the leaky confining unit at the base of the surficial aquifer (designated Unit B of the Tertiary Talbot Formation). Excellent reflectors have been observed for both upper and lower surfaces of Unit B that correspond to stratigraphic units observed in boreholes and on gamma logs. Elevation maps of both surfaces and an isopach map of Unit B, created from reflection data at the toxic burning pits site, show a thickening of Unit B to the east. Abnormally low seismic compressional-wave velocities suggest that Unit B consists of gassy sediments whose gases are not being flushed by upward or downward moving groundwater. The presence of gases suggests that Unit B serves as an efficient aquitard that should not be penetrated by drilling or other activities. Electromagnetic, total-intensity magnetic, and ground-penetrating radar surveys have aided in delineating the limits of two buried trenches, the VX burning pit and the liquid smoke disposal pit, both located at the toxic burning pits site. The techniques have also aided in determining the extent of several other disturbed areas where soils and materials were pushed out of disposal pits during trenching activities. Surveys conducted from the Prototype Building west to the Gunpowder River did not reveal any buried trenches.

  14. The Yolla Bolly junction revisited

    SciTech Connect

    Blake, M.C.; Jayko, A.S. ); Jones, D.L. . Dept. of Geology and Geophysics); Engebretson, D.C. . Dept. of Geology)

    1993-04-01

    West of Red Bluff, California, rocks of the northern Coast Ranges, Klamath-Sierra Nevada, and Great Valley provinces come together at what has been called the Yolla Bolly junction. Mapping of the Red Bluff and Willows 1:100,000 quadrangles has greatly clarified the enigmatic features of this complex area. Terranes of the Klamath Mountains and their Cretaceous sedimentary cover have been thrust northwestward over the Elder Creek terrane and Franciscan rocks, north of the left-lateral Cold Fork fault zone. The Condrey Mountain window (Franciscan Pickett Peak terrane) provides a measure of the magnitude of this thrusting (ca 90 km). South of the Cold Fork fault zone, the Franciscan and Elder Creek terranes were driven southeastward as tectonic wedges onto Sierran-Klamath basement. Timing of this scissor-tectonics is not constrained near the junction, but further north in southwest Oregon, Lower Eocene strata were deformed by overthrusting of the Klamath block whereas Upper Eocene strata overlap the thrust, indicating that thrusting occurred between about 52 and 60 Ma. Plate reconstructions for this time interval indicate the close proximity of the Kula-Farallon-North America triple junction and that old (ca 100 m.y.) Farallon lithosphere was being subducted north of the junction whereas to the south, very young (ca 10 m.y.) Kula plate was presumably obducted onto North America.

  15. Improved Solar-Cell Tunnel Junction

    NASA Technical Reports Server (NTRS)

    Daud, T.; Kachare, A.

    1986-01-01

    Efficiency of multiple-junction silicon solar cells increased by inclusion of p+/n+ tunnel junctions of highly doped GaP between component cells. Relatively low recombination velocity at GaP junction principal reason for recommending this material. Relatively wide band gap also helps increase efficiency by reducing optical losses.

  16. Analytical models of on-resistance and breakdown voltage for 4H-SiC floating junction Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Yuan, Hao; Tang, Xiaoyan; Song, Qingwen; Zhang, Yimen; Zhang, Yuming; Yang, Fei; Niu, Yingxi

    2015-01-01

    The analytical models of on-resistance and reverse breakdown voltage for 4H-SiC floating junction SBD are presented with the analysis of the transport path of the carriers and electric field distribution in the drift region. The calculation results from the analytical models well agree with the simulation results. The effects of the key structure parameters on specific on-resistance and breakdown voltage are described respectively by analytical models. Moreover, the relationship between BFOM and parameters of floating junction are investigated. It is proved that the analytical models are more convenient for the design of the floating junction SBDs.

  17. Depleted uranium human health risk assessment, Jefferson Proving Ground, Indiana

    SciTech Connect

    Ebinger, M.H.; Hansen, W.R.

    1994-04-29

    The risk to human health from fragments of depleted uranium (DU) at Jefferson Proving Ground (JPG) was estimated using two types of ecosystem pathway models. A steady-state, model of the JPG area was developed to examine the effects of DU in soils, water, and vegetation on deer that were hunted and consumed by humans. The RESRAD code was also used to estimate the effects of farming the impact area and consuming the products derived from the farm. The steady-state model showed that minimal doses to humans are expected from consumption of deer that inhabit the impact area. Median values for doses to humans range from about 1 mrem ({plus_minus}2.4) to 0.04 mrem ({plus_minus}0.13) and translate to less than 1 {times} 10{sup {minus}6} detriments (excess cancers) in the population. Monte Carlo simulation of the steady-state model was used to derive the probability distributions from which the median values were drawn. Sensitivity analyses of the steady-state model showed that the amount of DU in airborne dust and, therefore, the amount of DU on the vegetation surface, controlled the amount of DU ingested by deer and by humans. Human doses from the RESRAD estimates ranged from less than 1 mrem/y to about 6.5 mrem/y in a hunting scenario and subsistence fanning scenario, respectively. The human doses exceeded the 100 mrem/y dose limit when drinking water for the farming scenario was obtained from the on-site aquifer that was presumably contaminated with DU. The two farming scenarios were unrealistic land uses because the additional risk to humans due to unexploded ordnance in the impact area was not figured into the risk estimate. The doses estimated with RESRAD translated to less than 1 {times} 10{sup {minus}6} detriments to about 1 {times} 10{sup {minus}3} detriments. The higher risks were associated only with the farming scenario in which drinking water was obtained on-site.

  18. Cannabinoids in hair: strategy to prove marijuana/hashish consumption.

    PubMed

    Uhl, Michael; Sachs, Hans

    2004-10-29

    a THC outcome. The most appropriate strategy to prove cannabis consumption is immunochemical initial test followed by a GC/MS/MS confirmation of THCA.

  19. Polyphenon E, non-futile at neuroprotection in multiple sclerosis but unpredictably hepatotoxic: Phase I single group and phase II randomized placebo-controlled studies.

    PubMed

    Lovera, Jesus; Ramos, Alexander; Devier, Deidre; Garrison, Virginia; Kovner, Blake; Reza, Tara; Koop, Dennis; Rooney, William; Foundas, Anne; Bourdette, Dennis

    2015-11-15

    Phase I (PhI): assess the safety of Polyphenon E in people with multiple sclerosis (MS) and determine the futility of Polyphenon E as a neuroprotective agent. Correlate plasma levels of EGCG with neuroprotective effects. Phase II (PhII): Further assess safety and confirm the neuroprotective effects of Polyphenon E. PhI: single group futility study. PhII: parallel group randomized double-blind placebo-controlled study. Recruitment area (both studies): LSU MS Center, New Orleans, LA and general public from surrounding areas. Inclusion criteria (both studies): 1) MS per 2005 McDonald criteria; 2) relapsing remitting or secondary progressive MS; 3) stable for six months prior to enrollment on either no therapy or glatiramer acetate (GA) for the PhI study and on either on GA or Interferon β for the PhII study. Exclusion criteria (both studies): 1) complete bone marrow ablation or alentuzumab use at any time; 2) mitoxantrone, cyclophosphamide, natalizumab or fingolimod use in the prior nine months; 3) liver problems or significant medical problems. PhI: Polyphenon E, a green tea extract containing 50% of the antioxidant Epigallocatechin-gallate (EGCG), two capsules twice daily (200mg of EGCG per capsule; total daily dose 800mg) for six months. PhII: Polyphenon E or matching placebo capsules, same dose for one year. Only the research pharmacist knew treatment assignment and she randomized participants (one-to-one, stratified by GA or Interferon β, blocks of 4 or 6). Outcome evaluators did not discuss side effects with participants. PhI: 1) adverse events (AE); 2) futility: decrease in N-acetyl aspartate (NAA) from baseline to six months of 10% or more; 3) association between EGCG plasma levels and change in NAA. PhII: 1) AEs; 2) difference in the rate of change of NAA-levels over twelve months.We measured NAA using a point resolved magnetic resonance spectroscopic imaging sequence (TE30/TR2000) on a 10cm×10cm×1cm volume of interest (VOI) located just superior to the

  20. Polyphenon E, Non-futile at Neuroprotection in Multiple Sclerosis but Unpredictably Hepatotoxic: Phase I Single Group and Phase II Randomized Placebo-Controlled Studies

    PubMed Central

    Lovera, Jesus; Ramos, Alexander; Devier, Deidre; Garrison, Virginia; Kovner, Blake; Reza, Tara; Koop, Dennis; Rooney, William; Foundas, Anne; Bourdette, Dennis

    2015-01-01

    Objectives Phase I (PhI): assess the safety of Polyphenon E in people with multiple sclerosis (MS) and determine the futility of Polyphenon E as a neuroprotective agent. Correlate plasma levels of EGCG with neuroprotective effects. Phase II (PhII): Further assess safety and confirm the neuroprotective effects of Polyphenon E. Design PhI: single group futility study. PhII: parallel group randomized double-blind placebo-controlled study. Participants Recruitment area (both studies) LSU MS Center, New Orleans, LA and general public from surrounding areas. Inclusion criteria (both studies) 1) MS per 2005 McDonald criteria; 2) relapsing remitting or secondary progressive MS; 3) stable for six months prior to enrollment on either no therapy or glatiramer acetate (GA) for the PhI study and on either on GA or Interferon β for the PhII study. Exclusion criteria (both studies) 1) complete bone marrow ablation or alentuzumab use at any time; 2) mitoxantrone, cyclophosphamide, natalizumab or fingolimod use in the prior nine months; 3) liver problems or significant medical problems. Interventions PhI: Polyphenon E, a green tea extract containing 50% of the antioxidant Epigallocatechin-gallate (EGCG), two capsules twice daily (200 mg of EGCG per capsule; total daily dose 800mg) for six months. PhII: Polyphenon E or matching placebo capsules, same dose for one year. Only the research pharmacist knew treatment assignment and she randomized participants (one-to-one, stratified by GA or Interferon β, blocks of 4 or 6). Outcome evaluators did not discuss side effects with participants. Outcome measures PhI: 1) adverse events (AE); 2) futility: decrease in N-acetyl aspartate (NAA) from baseline to six months of 10% or more; 3) association between EGCG plasma levels and change in NAA. PhII: 1) AEs; 2) difference in the rate of change of NAA-levels over twelve months. We measured NAA using a point resolved magnetic resonance spectroscopic imaging sequence (TE30/TR2000) on a 10cm × 10

  1. Tight junction proteins: from barrier to tumorigenesis.

    PubMed

    Runkle, E Aaron; Mu, David

    2013-08-28

    The tight junction is a multi-protein complex and is the apical most junctional complex in certain epithelial and endothelial cells. A great deal of attention has been devoted to the understanding of these proteins in contributing to the barrier function - that is, regulating the paracellular flux or permeability between adjacent cells. However, tight junction proteins are now recognized as having functions beyond the barrier. The focus of this review is to discuss the barrier function of the tight junction and to summarize the literature with a focus on the role of tight junction proteins in proliferation, transformation, and metastasis.

  2. Tight Junction Proteins: From Barrier to Tumorigenesis

    PubMed Central

    Runkle, E. Aaron; Mu, David

    2013-01-01

    The tight junction is a multi-protein complex and is the apical most junctional complex in certain epithelial and endothelial cells. A great deal of attention has been devoted to the understanding of these proteins in contributing to the barrier function - that is, regulating the paracellular flux or permeability between adjacent cells. However, tight junction proteins are now recognized as having functions beyond the barrier. The focus of this review is to discuss the barrier function of the tight junction and to summarize the literature with a focus on the role of tight junction proteins in proliferation, transformation, and metastasis. PMID:23743355

  3. Three Smoking Guns Prove Falsity of Green house Warming

    NASA Astrophysics Data System (ADS)

    Fong, P.

    2001-12-01

    Three observed facts: 1, the cloud coverage increased 4.1% in 50 years; 2. the precipitation increased 7.8% in 100 years; 3. the two rates are the same. {Interpretation}. 1, By the increased albedo of the clouds heat dissipation is increased 3.98 W/m2 by 2XCO2 time, canceling out greenhouse warming of 4 W/m{2}. Thus no global warming. 2, The precipitation increase show the increased release of latent heat of vaporization, which turns out to be equal to that absorbed by ocean due to increased evaporation by the greenhouse forcing. This all greenhouse heat is used up in evaporation and the warming of the earth is zero. 3, The identity of the two rates double-checked the two independent proofs. Therefore experimentally no greenhouse warming is triply proved. A new branch of science Pleistocene Climatology is developed to study the theoretical origin of no greenhouse warming. Climatology, like mechanics of a large number of particles, is of course complex and unwieldy. If totally order-less then there is no hope. However, if some regularity appears, then a systematic treatment can be done to simplify the complexity. The rigid bodies are subjected to a special simplifying condition (the distances between all particles are constant) and only 6 degrees of freedom are significant, all others are sidetracked. To study the spinning top there is no need to study the dynamics of every particle of the top by Newton's laws through super-computer. It only needs to solve the Euler equations without computer. In climate study the use of super-computer to study all degrees of freedom of the climate is as untenable as the study of the spinning top by super-computer. Yet in spite of the complexity there is strict regularity as seen in the ice ages, which works as the simplifying conditions to establish a new science Pleistocene climatology. See my book Greenhouse Warming and Nuclear Hazards just published (www.PeterFongBook.com). This time the special condition is the presence of a

  4. NASA'S Space Launch System: Progress Toward the Proving Ground

    NASA Technical Reports Server (NTRS)

    Jackman, Angie; Johnson, Les

    2017-01-01

    With significant and substantial progress being accomplished toward readying the Space Launch System (SLS) rocket for its first test flight, work is already also underway on preparations for the second flight – using an upgraded version of the vehicle – and beyond. Designed to support human missions into deep space, Space Launch System (SLS), is the most powerful human-rated launch vehicle the United States has ever undertaken, and together with the Orion spacecraft will support human exploration missions into the proving ground of cislunar space and ultimately to Mars. For its first flight, SLS will deliver a near-term heavy-lift capability for the nation with its 70-metric-ton Block 1 configuration. Each element of the vehicle now has flight hardware in production in support of the initial flight of the SLS, which will propel Orion around the moon and back. For its second flight, SLS will be upgraded to the more-capable Block 1B configuration. While the Block 1 configuration is capable of delivering more than 70 metric tons to low Earth orbit, the Block 1B vehicle will increase that capability to 105 metric tons. For that flight, the new configuration introduces two major new elements to the vehicle – an Exploration Upper Stage (EUS) that will be used for both ascent and in-space propulsion, and a Universal Stage Adapter (USA) that serves as a “payload bay” for the rocket, allowing the launch of large exploration systems along with the Orion spacecraft. Already, flight hardware is being prepared for the Block 1B vehicle. Beyond the second flight, additional upgrades will be made to the vehicle. The Block 1B vehicle will also be able to launch 8.4-meter-diameter payload fairings, larger than any previously flown, and the Spacecraft Payload Integration and Evolution (SPIE) Element will oversee development and production of those fairings. Ultimately, SLS will be evolved to a Block 2 configuration, which will replace the solid rocket boosters on the Block

  5. Tight Junction Proteins in Human Schwann Cell Autotypic Junctions

    PubMed Central

    Alanne, Maria H.; Pummi, Kati; Heape, Anthony M.; Grènman, Reidar; Peltonen, Juha; Peltonen, Sirkku

    2009-01-01

    Tight junctions (TJs) form physical barriers in various tissues and regulate paracellular transport of ions, water, and molecules. Myelinating Schwann cells form highly organized structures, including compact myelin, nodes of Ranvier, paranodal regions, Schmidt-Lanterman incisures, periaxonal cytoplasmic collars, and mesaxons. Autotypic TJs are formed in non-compacted myelin compartments between adjacent membrane lamellae of the same Schwann cell. Using indirect immunofluorescence and RT-PCR, we analyzed the expression of adherens junction (E-cadherin) and TJ [claudins, zonula occludens (ZO)-1, occludin] components in human peripheral nerve endoneurium, showing clear differences with published rodent profiles. Adult nerve paranodal regions contained E-cadherin, claudin-1, claudin-2, and ZO-1. Schmidt-Lanterman incisures contained E-cadherin, claudin-1, claudin-2, claudin-3, claudin-5, ZO-1, and occludin. Mesaxons contained E-cadherin, claudin-1, claudin-2, claudin-3, ZO-1, and occludin. None of the proteins studied were associated with nodal inter-Schwann cell junctions. Fetal nerve expression of claudin-1, claudin-3, ZO-1, and occludin was predominantly punctate, with a mesaxonal labeling pattern, but paranodal (ZO-1, claudin-3) and Schmidt-Lanterman incisure (claudins-1 and -3) expression profiles typical of compact myelin were visible by gestational week 37. The clear differences observed between human and published rodent nerve profiles emphasize the importance of human studies when translating the results of animal models to human diseases. (J Histochem Cytochem 57:523–529, 2009) PMID:19153196

  6. Molecular series-tunneling junctions.

    PubMed

    Liao, Kung-Ching; Hsu, Liang-Yan; Bowers, Carleen M; Rabitz, Herschel; Whitesides, George M

    2015-05-13

    Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure Ag(TS)/O2C-R1-R2-H//Ga2O3/EGaIn, where Ag(TS) is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units-(CH2)n and (C6H4)m-that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the Ag(TS)/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(-β1d1 - β2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β.

  7. Role of gap junctions in epilepsy.

    PubMed

    Jin, Miao-Miao; Chen, Zhong

    2011-12-01

    Epilepsy is a common neurological disorder characterized by periodic and unpredictable seizures. Gap junctions have recently been proposed to be involved in the generation, synchronization and maintenance of seizure events. The present review mainly summarizes recent reports concerning the contribution of gap junctions to the pathophysiology of epilepsy, together with the regulation of connexin after clinical and experimental seizure activity. The anticonvulsant effects of gap junction blockers both in vitro and in vivo suggest that the gap junction is a candidate target for the development of antiepileptic drugs. It is also of interest that the roles of neuronal and astrocytic gap junctions in epilepsy have been investigated independently, based on evidence from pharmacological manipulations and connexin-knockout mice. Further studies using more specific manipulations of gap junctions in different cell types and in human epileptic tissue are needed to fully uncover the role of gap junctions in epilepsy.

  8. A codimension-two point associated with coupled Josephson junctions

    NASA Astrophysics Data System (ADS)

    Aronson, D. G.; Doedel, E. J.; Terman, D. H.

    1997-09-01

    The dynamics of a pair of identical Josephson junctions coupled through a shared purely capacitive load are governed by a two-parameter system of two second-order nonlinear ordinary differential equations. Numerical simulations have shown that this system possesses many different running and periodic solutions. Continuation studies using AUTO indicate that many of these solution branches are generated by a codimension-2 connection which occurs at a particular parameter point. In this paper, we first describe these calculations in detail. We then study a general two-parameter system whose properties reflect some of those found in our numerical studies of the Josephson junction system. In particular, our model system is assumed to possess an appropriate codimension-2 connection, and we prove that its unfolding generates a large variety of codimension-1 connection curves. These results, combined with the particular symmetry and periodicity properties of the junction equations, account for all of the numerically observed solution branches. Indeed, the theoretical analysis predicted the existence of branches which were not initially observed, but which were subsequently found.

  9. Seebeck effect in molecular junctions

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya A.

    2016-05-01

    Advances in the fabrication and characterization of nanoscale systems presently allow for a better understanding of their thermoelectric properties. As is known, the building blocks of thermoelectricity are the Peltier and Seebeck effects. In the present work we review results of theoretical studies of the Seebeck effect in single-molecule junctions and similar systems. The behavior of thermovoltage and thermopower in these systems is controlled by several factors including the geometry of molecular bridges, the characteristics of contacts between the bridge and the electrodes, the strength of the Coulomb interactions between electrons on the bridge, and of electron-phonon interactions. We describe the impact of these factors on the thermopower. Also, we discuss a nonlinear Seebeck effect in molecular junctions.

  10. Thermocouple, multiple junction reference oven

    NASA Technical Reports Server (NTRS)

    Leblanc, L. P. (Inventor)

    1981-01-01

    An improved oven for maintaining the junctions of a plurality of reference thermocouples at a common and constant temperature is described. The oven is characterized by a cylindrical body defining a heat sink with axially extended-cylindrical cavity a singularized heating element which comprises a unitary cylindrical heating element consisting of a resistance heating coil wound about the surface of metallic spool with an axial bore defined and seated in the cavity. Other features of the oven include an annular array of radially extended bores defined in the cylindrical body and a plurality of reference thermocouple junctions seated in the bores in uniformly spaced relation with the heating element, and a temperature sensing device seated in the axial bore for detecting temperature changes as they occur in the spool and circuit to apply a voltage across the coil in response to detected drops in temperatures of the spool.

  11. Seebeck effect in molecular junctions.

    PubMed

    Zimbovskaya, Natalya A

    2016-05-11

    Advances in the fabrication and characterization of nanoscale systems presently allow for a better understanding of their thermoelectric properties. As is known, the building blocks of thermoelectricity are the Peltier and Seebeck effects. In the present work we review results of theoretical studies of the Seebeck effect in single-molecule junctions and similar systems. The behavior of thermovoltage and thermopower in these systems is controlled by several factors including the geometry of molecular bridges, the characteristics of contacts between the bridge and the electrodes, the strength of the Coulomb interactions between electrons on the bridge, and of electron-phonon interactions. We describe the impact of these factors on the thermopower. Also, we discuss a nonlinear Seebeck effect in molecular junctions.

  12. Morphogenesis of rat myotendinous junction.

    PubMed

    Curzi, Davide; Ambrogini, Patrizia; Falcieri, Elisabetta; Burattini, Sabrina

    2013-10-01

    Myotendinous junction (MTJ) is the highly specialized complex which connects the skeletal muscle to the tendon for transmitting the contractile force between the two tissues. The purpose of this study was to investigate the MTJ development and rat EDL was chosen as a model. 1, 15, 30 day animals were considered and the junctions were analyzed by light and electron microscopy. The MTJ interface architecture increased during the development, extending the interaction between muscle and tendon. 1-day-old rats showed disorganized myofibril bundles, spread cytosol and incomplete rough endoplasmic reticulum, features partially improved in 15-day-old rats, and completely developed in 30-day-old animals. These findings indicate that muscle-tendon interface displays, during rat lifetime, numerically increased and longer tendon interdigitations, correlated with an improved organization of both tissues and with a progressive acquirement of full functionality.

  13. Morphogenesis of rat myotendinous junction

    PubMed Central

    Curzi, Davide; Ambrogini, Patrizia; Falcieri, Elisabetta; Burattini, Sabrina

    2013-01-01

    Summary Myotendinous junction (MTJ) is the highly specialized complex which connects the skeletal muscle to the tendon for transmitting the contractile force between the two tissues. The purpose of this study was to investigate the MTJ development and rat EDL was chosen as a model. 1, 15, 30 day animals were considered and the junctions were analyzed by light and electron microscopy. The MTJ interface architecture increased during the development, extending the interaction between muscle and tendon. 1-day-old rats showed disorganized myofibril bundles, spread cytosol and incomplete rough endoplasmic reticulum, features partially improved in 15-day-old rats, and completely developed in 30-day-old animals. These findings indicate that muscle-tendon interface displays, during rat lifetime, numerically increased and longer tendon interdigitations, correlated with an improved organization of both tissues and with a progressive acquirement of full functionality. PMID:24596690

  14. Bronchoscopic diagnostic procedures and microbiological examinations in proving endobronchial tuberculosis.

    PubMed

    Şimşek, Abdullah; Yapıcı, İlhami; Babalık, Mesiha; Şimşek, Zekiye; Kolsuz, Mustafa

    2016-01-01

    To determine the proportional distribution of endobronchial tuberculosis (EBTB) subtypes and to evaluate the types of bronchoscopic diagnostic procedures that can prove granulomatous inflammation. This was a retrospective study of 18 HIV-negative patients with biopsy-proven EBTB treated between 2010 and 2014. The most common EBTB subtypes, as classified by the bronchoscopic features, were tumorous and granular (in 22.2% for both). Sputum smear microscopy was performed in 11 patients and was positive for AFB in 4 (36.3%). Sputum culture was also performed in 11 patients and was positive for Mycobacterium tuberculosis in 10 (90.9%). Smear microscopy of BAL fluid (BALF) was performed in 16 patients and was positive for AFB in 10 (62.5%). Culture of BALF was also performed in 16 patients and was positive for M. tuberculosis in 15 (93.7%). Culture of BALF was positive for M. tuberculosis in 93.7% of the 16 patients tested. Among the 18 patients with EBTB, granulomatous inflammation was proven by the following bronchoscopic diagnostic procedures: bronchial mucosal biopsy, in 8 (44.4%); bronchial brushing, in 7 (38.8%); fine-needle aspiration biopsy, in 2 (11.1%); and BAL, in 2 (11.1%). Bronchial anthracofibrosis was observed in 5 (27.7%) of the 18 cases evaluated. In our sample of EBTB patients, the most common subtypes were the tumorous and granular subtypes. We recommend that sputum samples and BALF samples be evaluated by smear microscopy for AFB and by culture for M. tuberculosis, which could increase the rates of early diagnosis of EBTB. We also recommend that bronchial brushing be employed together with other bronchoscopic diagnostic procedures in patients suspected of having EBTB. Determinar a distribuição proporcional dos subtipos de tuberculose endobrônquica (TBEB) e avaliar os tipos de procedimentos diagnósticos broncoscópicos que podem revelar inflamação granulomatosa. Este foi um estudo retrospectivo com 18 pacientes HIV negativos com TBEB comprovada

  15. Inelastic effects of Josephson junctions

    NASA Astrophysics Data System (ADS)

    Ranjan, Samir

    We have investigated the effects of the inelastic interaction of electrons with phonons in the barrier region of S-I-S and S-N-S Josephson junctions. We find that under suitable conditions this mechanism can cause substantial modifications of the temperature dependence of the critical current jsb{c} as the inevitable loss of coherence can be more than compensated by the enhancement of the tunneling probability resulting from the phonon absorption. The effect depends strongly on the ratio qsb{TF}a of the junction width a to the screening length in the barrier region. For a S-I-S junction, a monotonic decrease in the critical current with temperature is found for qsb{TF}a ≫ 1 whereas for qsb{TF}a ≪ 1, the appearance of a peak in jsb{c}(T) near Tsb{c} is predicted. This new interesting effect is the consequence of the competition between the decrease of the superconducting gap function and the increase in the number of phonons with temperature. A wide range of parameter values has been explored and contact with relevant experimental results has been made. For an S-N-S junction, there is a large increase in the coherence length in the non-superconducting region leading to a substantial enhancement of the critical current over a wide range of temperature. It turns out that the entire temperature range can be divided broadly into two regimes. At low temperatures, the electron predominantly exchanges energy with just one phonon and it is this process that mainly determines the critical current. At higher temperatures the critical current is determined by processes in which the electrons exchange energy with many phonons during their under barrier motion.

  16. Early postoperative assessment of the functional patency of ureterovesical junction following ureteroneocystostomy

    SciTech Connect

    Koff, S.A.; Kogan, B.; Kass, E.J.; Thrall, J.H.

    1981-04-01

    We studied 37 children soon after ureteroneocystostomy using diuretic radionuclide urography to assess the patency of the ureterovesical junction. Postoperative obstruction was excluded correctly in 90 per cent of the patients. Transient ureterovesical obstruction occurred in 5 patients, identification of which was useful in assigning risk and in guiding followup studies. Because it is a safe, noninvasive and relatively low radiation test the diuretic radionuclide urogram proves to be an attractive alternative to the excretory urogram in the early and late followup of patients undergoing a ureterovesical junction operation.

  17. The Electrostatic Breakdown on Metal-Dielectric Junction Immersed in a Plasma

    NASA Technical Reports Server (NTRS)

    Vayner, Boris V.; Galofaro, Joel T.; Ferguson, Dale C.; Lyons, Valerie J. (Technical Monitor)

    2002-01-01

    New results are presented of an experimental study and theoretical analysis of arcing on metal-dielectric junctions immersed in low-density plasmas. Two samples of conventional solar arrays and four different metal-quartz junctions have been used to investigate the effects of arcing within a wide range of neutral gas pressures, ion currents, and electron number densities. The effect of surface conditioning (decrease of arc rate due to outgassing) was clearly demonstrated. Moreover, a considerable increase in arc rate due to absorption of molecules from atmospheric air has been confirmed. It has been proved that the are inception mechanism in plasma is different from one in vacuum.

  18. Steiner minimal trees—the final destinations for lipid nanotube networks with three-way junctions

    NASA Astrophysics Data System (ADS)

    Yin, YaJun; Wu, JiYe; Yin, Jie; Fan, QinShan

    2011-04-01

    Through the combination of the minimum energy principle in physics and the Steiner minimal tree (SMT) theory in geometry, this paper proves a universal law for lipid nanotube networks (LNNs): at stable equilibrium state, the network of three-way lipid nanotube junctions is equivalent to a SMT. Besides, an arbitrary (usually non-equilibrium) network of lipid nanotube junctions may fission into a SMT through diffusions and dynamic self-organizations of lipid molecules. Potential applications of the law to the micromanipulations of LNNs are presented.

  19. Superconducting tunnel-junction refrigerator

    NASA Astrophysics Data System (ADS)

    Melton, Robert G.; Paterson, James L.; Kaplan, S. B.

    1980-03-01

    The dc current through an S1-S2 tunnel junction, with Δ2 greater than Δ1, when biased with eV<Δ1+Δ2, will lower the energy in S1. This energy reduction will be shared by the phonons and electrons. This device is shown to be analogous to a thermoelectric refrigerator with an effective Peltier coefficient π*~Δ1e. Tunneling calculations yield the cooling power Pc, the electrical power Pe supplied by the bias supply, and the cooling efficiency η=PcPe. The maximum cooling power is obtained for eV=+/-(Δ2-Δ1) and t1=T1Tc1~0.9. Estimates are made of the temperature difference T2-T1 achievable in Al-Pb and Sn-Pb junctions with an Al2O3 tunneling barrier. The performance of this device is shown to yield a maximum cooling efficiency η~=Δ1(Δ2-Δ1) which can be compared with that available in an ideal Carnot refrigerator of η=T1(T2-T1). The development of a useful tunnel-junction refrigerator requires a tunneling barrier with an effective thermal conductance per unit area several orders of magnitude less than that provided by the Al2O3 barrier in the Al-Pb and Sn-Pb systems.

  20. Thermoelectric efficiency of molecular junctions.

    PubMed

    Perroni, C A; Ninno, D; Cataudella, V

    2016-09-21

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron-vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions.

  1. Squeezed States in Josephson Junctions.

    NASA Astrophysics Data System (ADS)

    Hu, X.; Nori, F.

    1996-03-01

    We have studied quantum fluctuation properties of Josephson junctions in the limit of large Josephson coupling energy and small charging energy, when the eigenstates of the system can be treated as being nearly localized. We have considered(X. Hu and F. Nori, preprints.) a Josephson junction in a variety of situations, e.g., coupled to one or several of the following elements: a capacitor, an inductor (in a superconducting ring), and an applied current source. By solving an effective Shrödinger equation, we have obtained squeezed vacuum (coherent) states as the ground states of a ``free-oscillating'' (linearly-driven) Josephson junction, and calculated the uncertainties of its canonical momentum, charge, and coordinate, phase. We have also shown that the excited states of the various systems we consider are similar to the number states of a simple harmonic oscillator but with different fluctuation properties. Furthermore, we have obtained the time-evolution operators for these systems. These operators can make it easier to calculate the time-dependence of the expectation values and fluctuations of various quantities starting from an arbitrary initial state.

  2. Large voltage modulation in superconducting quantum interference devices with submicron-scale step-edge junctions

    NASA Astrophysics Data System (ADS)

    Lam, Simon K. H.

    2017-09-01

    A promising direction to improve the sensitivity of a SQUID is to increase its junction's normal resistance value, Rn, as the SQUID modulation voltage scales linearly with Rn. As a first step to develop highly sensitive single layer SQUID, submicron scale YBCO grain boundary step edge junctions and SQUIDs with large Rn were fabricated and studied. The step-edge junctions were reduced to submicron scale to increase their Rn values using focus ion beam, FIB and the measurement of transport properties were performed from 4.3 to 77 K. The FIB induced deposition layer proves to be effective to minimize the Ga ion contamination during the FIB milling process. The critical current-normal resistance value of submicron junction at 4.3 K was found to be 1-3 mV, comparable to the value of the same type of junction in micron scale. The submicron junction Rn value is in the range of 35-100 Ω, resulting a large SQUID modulation voltage in a wide temperature range. This performance promotes further investigation of cryogen-free, high field sensitivity SQUID applications at medium low temperature, e.g. at 40-60 K.

  3. Synchronization in Disordered Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Dissanayake, S. T. M.; Trees, B. R.

    2001-10-01

    There is considerable scientific and technological interest in the time-dependent behavior of arrays of non-identical Josephson junctions, whose voltages oscillate with individual bare frequencies that can be made, through interactions, to renormalize their frequencies to a common value. We have studied the degree of synchronization of a subset of overdamped junctions in a ladder geometry, in which the voltages across the ``rung'' junctions of the ladder oscillate with the same, renormalized frequency and a fixed phase difference. We measure the degree of synchronization of the junctions with an order parameter, r (0<= r<= 1), as a function of the nearest-neighbor junction coupling strength. We also determined that a time-averaged version of the resistively-shunted junction (RSJ) equations could be used as an accurate description of the dynamics of the junctions. The solutions to the averaged equations exhibit phase slips between pairs of junctions for certain ranges of the junction coupling strength and also demonstrated that the relationship between the array size N and the critical coupling strength for all junctions to oscillate with the same frequency scales as N^2. This research was partially funded by a grant to Ohio Wesleyan University from the McGregor Foundation to support student research.

  4. Decreased Expression of Multidrug Resistance-Associated Protein 4 (MRP4/ABCC4) Leads to Reduced Glucuronidation of Flavonoids in UGT1A1-Overexpressing HeLa Cells: The Role of Futile Recycling.

    PubMed

    Sun, Hua; Zhou, Xiaotong; Zhang, Xingwang; Wu, Baojian

    2015-07-08

    In this study, the role of futile recycling (or deglucuronidation) in the disposition of two flavonoids (i.e., genistein and apigenin) was explored using UGT1A1-overexpressing HeLa cells (or HeLa1A1 cells). Glucuronidation of the flavonoids by HeLa1A1 cell lysate followed the substrate inhibition kinetics (Vmax = 0.10 nmol/min/mg, Km = 0.54 μM, and Ksi = 2.0 μM for genistein; Vmax = 0.19 nmol/min/mg, Km = 0.56 μM, and Ksi = 3.7 μM for apigenin). Glucuronide was efficiently generated and excreted after incubation of the cells with the aglycone (at doses of 1.25-20 nmol). The excretion rates were 0.40-0.69 and 0.84-1.1 nmol/min/mg protein for genistein glucuronide (GG) and apigenin glucuronide (AG), respectively. Furthermore, glucuronide excretion and total glucuronidation were significantly reduced in MRP4 knocked-down as compared to control cells. The alterations were well characterized by a two-compartment pharmacokinetic model incorporating the process of futile recycling (defined by a first-order rate constant, Kde). The derived Kde values were 15 and 25 h(-1) for GG and AG, respectively. This was well consistent with the in vitro observation that AG was subjected to more efficient futile recycling compared to GG. In conclusion, futile recycling was involved in cellular glucuronidation, accounting for transporter-dependent glucuronidation of flavonoids.

  5. The structure of 4-way DNA junctions: specific binding of bis-intercalators with rigid linkers.

    PubMed Central

    Carpenter, M L; Lowe, G; Cook, P R

    1996-01-01

    During replication and recombination, two DNA duplexes lie side by side. We have developed reagents that might be used to probe structure during these critical processes; they contain two intercalating groups connected by a rigid linker that forces those groups to point in opposite directions. If their stereochemistry proves appropriate, such structure-specific agents should intercalate specifically into adjacent duplexes in the Y- and X-shaped structures (i.e. 3- and 4-way junctions, now known as 3H and 4H junctions) found at replication and recombination sites. We prepared DNA structures in which four duplexes were arranged in all possible combinations around 2- and 4-way junctions and then probed the accessibility to DNase I of all their phosphodiester bonds. In the absence of any bis-intercalators, 7-9 nucleotides (nt) in each of the strands in 4-way junctions were protected from attack; protected regions were significantly offset to the 3' side of the junction in continuous strands, but only slightly offset, if at all, in exchanging strands. All the intercalators decreased accessibility throughout the structure, but none did so at specific points in the two adjacent arms of 4-way junctions. However, one bis-intercalator--but not its sister with a shorter linker--strikingly increased access to a particular CpT bond that lay 9 nt away from the centre of some 4-way junctions without reducing access to neighbouring bonds. Binding was both sequence and structure specific, and depended on complementary stereochemistry between bis-intercalator and junction. PMID:8649974

  6. In vitro formation of gap junction vesicles.

    PubMed

    Goodenough, D A

    1976-02-01

    A method is described that uses trypsin digestion combined with collagenase-hyaluronidase which produces a population of gap junction vesicles. The hexagonal lattice of subunits ("connexons") comprising the gapjunctions appears unaltered by various structural criteria and by buoyant density measurements. The gap junction vesciles are closed by either a single or a double profile of nonjunctional "membrane," which presents a smooth, particle-free fracture face. Horseradish peroxidase and cytochrome c studies have revealed that about 20% of the gap junction vesicles are impermeable to proteins 12,000 daltons or larger. The increased purity of the trypsinized junction preparation suggests that one of the disulfide reduction products of the gap-junction principal protein may be a nonjunctional contaminating peptide. The gap junction appears to be composed of a single 18,000-dalton protein, connexin, which may be reduced to a single 9,000-dalton peak. The number of peptides in this reduced peak are still unknown.

  7. Physics and Applications of NIS Junctions

    SciTech Connect

    Ullom, J N

    2001-08-24

    This paper reviews the physics and applications of Normal-Insulator-Superconductor (NIS) tunnel junctions. The current-voltage properties of NIS junctions are diode-like with a strong temperature dependence. Hence, these structures can be used as sensitive thermometers at temperatures well below the energy gap, {Delta}, of the superconducting electrode. For junction voltages comparable to {Delta}/q, current flow removes energy from the normal electrode. This property has been exploited to build refrigerators capable of cooling thin-film circuits from 0.3 K to 0.1 K. Calorimeters and bolometers for the detection of X-rays and millimeter-wave radiation, respectively, have successfully been built from NIS junctions. NIS junctions have also been used to probe the superconducting state. Finally, recent ideas for the use of NIS junctions as simple circuit elements are described.

  8. The Dissolution of Double Holliday Junctions

    PubMed Central

    Bizard, Anna H.; Hickson, Ian D.

    2014-01-01

    Double Holliday junctions (dHJS) are important intermediates of homologous recombination. The separate junctions can each be cleaved by DNA structure-selective endonucleases known as Holliday junction resolvases. Alternatively, double Holliday junctions can be processed by a reaction known as “double Holliday junction dissolution.” This reaction requires the cooperative action of a so-called “dissolvasome” comprising a Holliday junction branch migration enzyme (Sgs1/BLM RecQ helicase) and a type IA topoisomerase (Top3/TopoIIIα) in complex with its OB (oligonucleotide/oligosaccharide binding) fold containing accessory factor (Rmi1). This review details our current knowledge of the dissolution process and the players involved in catalyzing this mechanistically complex means of completing homologous recombination reactions. PMID:24984776

  9. [Gap junctions and cancer: implications and perspectives].

    PubMed

    Mesnil, Marc

    2004-02-01

    Gap junctions are made of intercellular channels which permit the diffusion from cytoplasm to cytoplasm of small hydrophilic molecules (<1,200 Da) such as ions, sugars, amino acids, nucleotides, second messengers (calcium, inositol triphosphate, etc.). Since their discovery in the early sixties, several groups have described the loss of their function in cancer cells. The accumulation of such data led to the hypothesis that gap junctions are involved in the carcinogenesis process. This assumption has been confirmed by data establishing that gap junctional intercellular communication is inhibited by most of the tumor promoters and that the restoration of such a communication, by transfection of cDNAs encoding gap junction proteins (connexins), inhibits the aberrant growth rates of tumorigenic cells. Despite these important informations, several fundamental questions remain still open. First, we do not know how gap junctions mediate such a tumor suppressor effect and whether it may depend either on the cell type or on the connexin type. Moreover, most of the data concerning a possible involvement of gap junctions in carcinogenesis have been obtained from in vitro and animal models. The very few results which have been currently collected from human tumors are not sufficient to have a clear idea concerning the real involvement of gap junctions in sporadic human cancers. These points as well as other unresolved questions about the role of gap junctional intercellular communication in carcinogenesis are mentioned. To bring some answers, some prospects are proposed with the objective to use gap junctions for increasing the effect of anticancer therapies.

  10. Ventral surgical approaches to craniovertebral junction chordomas.

    PubMed

    Singh, Harminder; Harrop, James; Schiffmacher, Paul; Rosen, Marc; Evans, James

    2010-03-01

    Chordomas are primarily malignant tumors encountered at either end of the neural axis; the craniovertebral junction and the sacrococcygeal junction. In this article, we discuss the surgical management of craniovertebral junction chordomas. In this paper, we discuss the surgical management of craniovertebral junction chordomas. The following approaches are illustrated: transoral-transpalatopharyngeal approach, high anterior cervical retropharyngeal approach, endoscopic transoral approach, and endoscopic transnasal approach. No single operative approach can be used for all craniovertebral chordomas. Therefore, the location of the tumor dictates which approach or approaches should be used.

  11. Gap Junctions Couple Astrocytes and Oligodendrocytes

    PubMed Central

    Orthmann-Murphy, Jennifer L.; Abrams, Charles K.; Scherer, Steven S.

    2009-01-01

    In vertebrates, a family of related proteins called connexins form gap junctions (GJs), which are intercellular channels. In the central nervous system (CNS), GJs couple oligodendrocytes and astrocytes (O/A junctions) and adjacent astrocytes (A/A junctions), but not adjacent oligodendrocytes, forming a “glial syncytium.” Oligodendrocytes and astrocytes each express different connexins. Mutations of these connexin genes demonstrate that the proper functioning of myelin and oligodendrocytes requires the expression of these connexins. The physiological function of O/A and A/A junctions, however, remains to be illuminated. PMID:18236012

  12. Thermoelectric effects in nanoscale junctions.

    PubMed

    Dubi, Yonatan; Di Ventra, Massimiliano

    2009-01-01

    Despite its intrinsic nonequilibrium origin, thermoelectricity in nanoscale systems is usually described within a static scattering approach which disregards the dynamical interaction with the thermal baths that maintain energy flow. Using the theory of open quantum systems, we show instead that unexpected properties, such as a resonant structure and large sign sensitivity, emerge if the nonequilibrium nature of this problem is considered. Our approach also allows us to define and study a local temperature, which shows hot spots and oscillations along the system according to the coupling of the latter to the electrodes. This demonstrates that Fourier's lawa paradigm of statistical mechanicsis generally violated in nanoscale junctions.

  13. Magnetic tunnel junction pattern technique

    NASA Astrophysics Data System (ADS)

    Chen, Eugene; Schwarz, Benjamin; Choi, Chang Ju; Kula, Witold; Wolfman, Jerome; Ounadjela, Kamel; Geha, Sam

    2003-05-01

    We have developed a magnetic tunnel junction (MTJ) pattern technique that involves transforming the magnetic layer above the tunnel barrier in unwanted areas into an insulator, thus providing insulation between different MTJ devices without suffering common tunnel barrier shorting problems. With this technique, 90%-100% yielding MTJ devices have been observed. MTJ results using this process are superior to an etching based process. Switching distribution of patterned magnetic bits is also narrower using this novel technique. Process control and the ability to stop on the tunnel barrier have been demonstrated.

  14. Operation Junction City, Vietnam, 1967

    DTIC Science & Technology

    1983-06-03

    a standard infantry rifle , the Soviet-made AK-47. They possessed some 7.62 machine guns in each battalion and very few .51 caliber machine guns, if... rifles , and Chinese-manufactured antitank mines. Fire support was provided by 6 0-mm, 82-mm, and for the first time in the war, 120-mm mortars. The...MINIHTHAN) ’ ~ 9j~ REPLACED BY ON I APRIL OL DAli TIENG AP’ GAU BANG’ OPERATION JUNCTION CITY TASK ORGANIZATION PHASE I II FIELD FORCE 1st Inf Div 25th

  15. Method for shallow junction formation

    DOEpatents

    Weiner, K.H.

    1996-10-29

    A doping sequence is disclosed that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated. 8 figs.

  16. Method for shallow junction formation

    DOEpatents

    Weiner, Kurt H.

    1996-01-01

    A doping sequence that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated.

  17. Electrodeposited, Transverse Nanowire Electroluminescent Junctions.

    PubMed

    Qiao, Shaopeng; Xu, Qiang; Dutta, Rajen K; Le Thai, Mya; Li, Xiaowei; Penner, Reginald M

    2016-09-27

    The preparation by electrodeposition of transverse nanowire electroluminescent junctions (tn-ELJs) is described, and the electroluminescence (EL) properties of these devices are characterized. The lithographically patterned nanowire electrodeposition process is first used to prepare long (millimeters), linear, nanocrystalline CdSe nanowires on glass. The thickness of these nanowires along the emission axis is 60 nm, and the width, wCdSe, along the electrical axis is adjustable from 100 to 450 nm. Ten pairs of nickel-gold electrical contacts are then positioned along the axis of this nanowire using lithographically directed electrodeposition. The resulting linear array of nickel-CdSe-gold junctions produces EL with an external quantum efficiency, EQE, and threshold voltage, Vth, that depend sensitively on wCdSe. EQE increases with increasing electric field and also with increasing wCdSe, and Vth also increases with wCdSe and, therefore, the electrical resistance of the tn-ELJs. Vth down to 1.8(±0.2) V (for wCdSe ≈ 100 nm) and EQE of 5.5(±0.5) × 10(-5) (for wCdSe ≈ 450 nm) are obtained. tn-ELJs produce a broad EL emission envelope, spanning the wavelength range from 600 to 960 nm.

  18. θ0 thermal Josephson junction

    NASA Astrophysics Data System (ADS)

    Silaev, M. A.

    2017-08-01

    We predict the thermal counterpart of the anomalous Josephson effect in superconductor/ferromagnet/superconductor junctions with noncoplanar magnetic texture. The heat current through the junction is shown to have the phase-sensitive interference component proportional to cos(θ -θ0) , where θ is the Josephson phase difference and θ0 is the texture-dependent phase shift. In the generic trilayer magnetic structure with the spin-filtering tunnel barrier θ0 is determined by the spin chirality of magnetic configuration and can be considered as the direct manifestation of the energy transport with participation of spin-triplet Cooper pairs. In case of the ideal spin filter the phase shift is shown to be robust against spin relaxation caused by the spin-orbital scattering. Possible applications of the coupling between heat flow and magnetic precession are discussed. For the nonideal spin filters with practically relevant parameters we show that θ0 is much larger than the phase shift of the equilibrium Josephson current.

  19. Down to 2 nm Ultra Shallow Junctions : Fabrication by IBS Plasma Immersion Ion Implantation Prototype PULSION registered

    SciTech Connect

    Torregrosa, Frank; Etienne, Hasnaa; Mathieu, Gilles; Roux, Laurent

    2006-11-13

    Classical beam line implantation is limited in low energies and cannot achieve P+/N junctions requirements for <45nm node. Compared to conventional beam line ion implantation, limited to a minimum of about 200 eV, the efficiency of Plasma Immersion Ion Implantation (PIII) is no more to prove for the realization of Ultra Shallow Junctions (USJ) in semiconductor applications: this technique allows to get ultimate shallow profiles (as implanted) thanks to no lower limitation of energy and offers high dose rate. In the field of the European consortium NANOCMOS, Ultra Shallow Junctions implanted on a semi-industrial PIII prototype (PULSION registered ) designed by the French company IBS, have been studied. Ultra shallow junctions implanted with BF3 at acceleration voltages down to 20V were realized. Contamination level, homogeneity and depth profile are studied. The SIMS profiles obtained show the capability to make ultra shallow profiles (as implanted) down to 2nm.

  20. Effect of penicillin on the increase in membrane conductance induced by γ-aminobutyric acid at the crab neuromuscular junction

    PubMed Central

    Earl, Janet; Large, W. A.

    1973-01-01

    The effects of penicillin and picrotoxin on the increase in membrane conductance produced by γ-aminobutyric acid (GABA) at the hermit crab neuromuscular junction were investigated. Penicillin failed to block the effects of GABA, while picrotoxin proved to be a potent antagonist. PMID:4733733

  1. [Shen cha zheng ji yan fang (Inspection of the Collection of TCM Proved Prescriptions) , the first official collection of proved prescriptions in Modern China].

    PubMed

    Liu, Y; Zhang, P F; Chen, X J

    2017-01-28

    Yan Xishan, the local ruler of Shanxi Province in modern period, claiming that the folk TCM prescriptions should be collected, inspected and maintained because of its definite effect. The government of Shanxi Province provided a lot of resources in collecting TCM proved prescriptions since 1929. The TCM Improving Society of Shanxi made more effort on the inspecting process, with a reasonable incentive system and standardized methods established. As a result, the Shen cha zheng ji yan fang (Inspection of the Collection of TCM Proved Prescriptions) was published, characterized by the principles of "cheap, convenient and effective" . It was the beginning of official collection and collation of TCM proved prescriptions in modern China.

  2. The Mathematical Nature of Reasoning-and-Proving Opportunities in Geometry Textbooks

    ERIC Educational Resources Information Center

    Otten, Samuel; Gilbertson, Nicholas J.; Males, Lorraine M.; Clark, D. Lee

    2014-01-01

    International calls have been made for reasoning-and-proving to permeate school mathematics. It is important that efforts to heed this call are grounded in an understanding of the opportunities to reason-and-prove that already exist, especially in secondary-level geometry where reasoning-and-proving opportunities are prevalent but not thoroughly…

  3. Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes

    NASA Astrophysics Data System (ADS)

    Borzenets, I. V.; Amet, F.; Ke, C. T.; Draelos, A. W.; Wei, M. T.; Seredinski, A.; Watanabe, K.; Taniguchi, T.; Bomze, Y.; Yamamoto, M.; Tarucha, S.; Finkelstein, G.

    2016-12-01

    We investigate the critical current IC of ballistic Josephson junctions made of encapsulated graphene-boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, IC is found to scale as ∝exp (-kBT /δ E ). The extracted energies δ E are independent of the carrier density and proportional to the level spacing of the ballistic cavity. As T →0 the critical current of a long (or short) junction saturates at a level determined by the product of δ E (or Δ ) and the number of the junction's transversal modes.

  4. Some properties of Cosmic String Junctions

    NASA Astrophysics Data System (ADS)

    Karouby, Johanna

    2011-07-01

    Cosmic strings are linear concentrations of energy of macroscopic size. Since cosmic superstrings can form junctions, observing them would give some support to string theory. In the following, we study the lensing cosmic string junctions create, the shift in photons' wavelength passing through (leading to the Kaiser-Stebbins effect), and the gravitational radiation they emit.

  5. Dressed fluxon in a Josephson window junction

    NASA Astrophysics Data System (ADS)

    Caputo, Jean Guy; Flytzanis, Nikos; Devoret, Michel

    1994-09-01

    The static fluxon solutions of a Josephson window junction have been studied numerically. We show that the effect of the idle region surrounding the junction is to ``dress'' the fluxon causing its energy to increase. This effect can be predicted accurately by a simple model.

  6. Slit Diaphragms Contain Tight Junction Proteins

    PubMed Central

    Fukasawa, Hirotaka; Bornheimer, Scott; Kudlicka, Krystyna; Farquhar, Marilyn G.

    2009-01-01

    Slit diaphragms are essential components of the glomerular filtration apparatus, as changes in these junctions are the hallmark of proteinuric diseases. Slit diaphragms, considered specialized adherens junctions, contain both unique membrane proteins (e.g., nephrin, podocin, and Neph1) and typical adherens junction proteins (e.g., P-cadherin, FAT, and catenins). Whether slit diaphragms also contain tight junction proteins is unknown. Here, immunofluorescence, immunogold labeling, and cell fractionation demonstrated that rat slit diaphragms contain the tight junction proteins JAM-A (junctional adhesion molecule A), occludin, and cingulin. We found these proteins in the same protein complexes as nephrin, podocin, CD2AP, ZO-1, and Neph1 by cosedimentation, coimmunoprecipitation, and pull-down assays. PAN nephrosis increased the protein levels of JAM-A, occludin, cingulin, and ZO-1 several-fold in glomeruli and loosened their attachment to the actin cytoskeleton. These data extend current information about the molecular composition of slit diaphragms by demonstrating the presence of tight junction proteins, although slit diaphragms lack the characteristic morphologic features of tight junctions. The contribution of these proteins to the assembly of slit diaphragms and potential signaling cascades requires further investigation. PMID:19478094

  7. The tight junction: a multifunctional complex.

    PubMed

    Schneeberger, Eveline E; Lynch, Robert D

    2004-06-01

    Multicellular organisms are separated from the external environment by a layer of epithelial cells whose integrity is maintained by intercellular junctional complexes composed of tight junctions, adherens junctions, and desmosomes, whereas gap junctions provide for intercellular communication. The aim of this review is to present an updated overview of recent developments in the area of tight junction biology. In a relatively short time, our knowledge of the tight junction has evolved from a relatively simple view of it being a permeability barrier in the paracellular space and a fence in the plane of the plasma membrane to one of it acting as a multicomponent, multifunctional complex that is involved in regulating numerous and diverse cell functions. A group of integral membrane proteins-occludin, claudins, and junction adhesion molecules-interact with an increasingly complex array of tight junction plaque proteins not only to regulate paracellular solute and water flux but also to integrate such diverse processes as gene transcription, tumor suppression, cell proliferation, and cell polarity.

  8. Analysis of Tight Junction Formation and Integrity

    SciTech Connect

    Karakaya, Mahmut; Kerekes, Ryan A; Morrell-Falvey, Jennifer L; Foster, Carmen M; Retterer, Scott T

    2012-01-01

    In this paper, we study segmentation of tight junctions and analyze the formation and integrity of tight junctions in large-scale confocal image stacks, a challenging biological problem because of the low spatial resolution images and the presence of breaks in tight junction structure. We present an automated, three-step processing approach for tight junction analysis. In our approach, we first localize each individual nucleus in the image by using thresholding, morphological filters and active contours. By using each nucleus position as a seed point, we automatically segment the cell body based on the active contour. We then use an intensity-based skeletonization algorithm to generate the boundary regions for each cell, and features are extracted from tight junctions associated with each cell to assess tight junction continuity. Based on qualitative results and quantitative comparisons, we show that we are able to automatically segment tight junctions and compute relevant features that provide a quantitative measure of tight junction formation to which the permeability of the cell monolayer can ultimately be correlated.

  9. Zipper and freeway shear zone junctions

    NASA Astrophysics Data System (ADS)

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  10. Overlap junctions for high coherence superconducting qubits

    NASA Astrophysics Data System (ADS)

    Wu, X.; Long, J. L.; Ku, H. S.; Lake, R. E.; Bal, M.; Pappas, D. P.

    2017-07-01

    Fabrication of sub-micron Josephson junctions is demonstrated using standard processing techniques for high-coherence, superconducting qubits. These junctions are made in two separate lithography steps with normal-angle evaporation. Most significantly, this work demonstrates that it is possible to achieve high coherence with junctions formed on aluminum surfaces cleaned in situ by Ar plasma before junction oxidation. This method eliminates the angle-dependent shadow masks typically used for small junctions. Therefore, this is conducive to the implementation of typical methods for improving margins and yield using conventional CMOS processing. The current method uses electron-beam lithography and an additive process to define the top and bottom electrodes. Extension of this work to optical lithography and subtractive processes is discussed.

  11. Holliday junction affinity of the base excision repair factor Endo III contributes to cholera toxin phage integration.

    PubMed

    Bischerour, Julien; Spangenberg, Claudia; Barre, François-Xavier

    2012-09-12

    Toxigenic conversion of Vibrio cholerae bacteria results from the integration of a filamentous phage, CTX phage. Integration is driven by the bacterial Xer recombinases, which catalyse the exchange of a single pair of strands between the phage single-stranded DNA and the host double-stranded DNA genomes; replication is thought to convert the resulting pseudo-Holliday junction (HJ) intermediate into the final recombination product. The natural tendency of the Xer recombinases to recycle HJ intermediates back into substrate should thwart this integration strategy, which prompted a search for additional co-factors aiding directionality of the process. Here, we show that Endo III, a ubiquitous base excision repair enzyme, facilitates CTX phage-integration in vivo. In vitro, we show that it prevents futile Xer recombination cycles by impeding new rounds of strand exchanges once the pseudo-HJ is formed. We further demonstrate that this activity relies on the unexpected ability of Endo III to bind to HJs even in the absence of the recombinases. These results explain how tandem copies of the phage genome can be created, which is crucial for subsequent virion production.

  12. Holliday junction affinity of the base excision repair factor Endo III contributes to cholera toxin phage integration

    PubMed Central

    Bischerour, Julien; Spangenberg, Claudia; Barre, François-Xavier

    2012-01-01

    Toxigenic conversion of Vibrio cholerae bacteria results from the integration of a filamentous phage, CTXϕ. Integration is driven by the bacterial Xer recombinases, which catalyse the exchange of a single pair of strands between the phage single-stranded DNA and the host double-stranded DNA genomes; replication is thought to convert the resulting pseudo-Holliday junction (HJ) intermediate into the final recombination product. The natural tendency of the Xer recombinases to recycle HJ intermediates back into substrate should thwart this integration strategy, which prompted a search for additional co-factors aiding directionality of the process. Here, we show that Endo III, a ubiquitous base excision repair enzyme, facilitates CTXϕ-integration in vivo. In vitro, we show that it prevents futile Xer recombination cycles by impeding new rounds of strand exchanges once the pseudo-HJ is formed. We further demonstrate that this activity relies on the unexpected ability of Endo III to bind to HJs even in the absence of the recombinases. These results explain how tandem copies of the phage genome can be created, which is crucial for subsequent virion production. PMID:22863778

  13. Shear zone junctions: Of zippers and freeways

    NASA Astrophysics Data System (ADS)

    Passchier, Cees W.; Platt, John P.

    2017-02-01

    Ductile shear zones are commonly treated as straight high-strain domains with uniform shear sense and characteristic curved foliation trails, bounded by non-deforming wall rock. Many shear zones, however, are branched, and if movement on such branches is contemporaneous, the resulting shape can be complicated and lead to unusual shear sense arrangement and foliation geometries in the wall rock. For Y-shaped shear zone triple junctions with three joining branches and transport direction at a high angle to the branchline, only eight basic types of junction are thought to be stable and to produce significant displacement. The simplest type, called freeway junctions, have similar shear sense in all three branches. The other types show joining or separating behaviour of shear zone branches similar to the action of a zipper. Such junctions may have shear zone branches that join to form a single branch (closing zipper junction), or a single shear zone that splits to form two branches, (opening zipper junction). All categories of shear zone junctions show characteristic foliation patterns and deflection of markers in the wall rock. Closing zipper junctions are unusual, since they form a non-active zone with opposite deflection of foliations in the wall rock known as an extraction fault or wake. Shear zipper junctions can form domains of overprinting shear sense along their flanks. A small and large field example are given from NE Spain and Eastern Anatolia. The geometry of more complex, 3D shear zone junctions with slip parallel and oblique to the branchline is briefly discussed.

  14. Macroscopic quantum tunneling in Josephson tunnel junctions and Coulomb blockade in single small tunnel junctions

    SciTech Connect

    Cleland, A.N.

    1991-04-01

    Experiments investigating the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very small capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters; the tunneling rate in the moderately damped (Q {approx} 1) junction is seen to be reduced by a factor of 300 from that predicted for an undamped junction. The phase is seen to be a good quantum-mechanical variable. The experiments on small capacitance tunnel junctions extend the measurements on the larger-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wavefunction has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias. I present the first clear observation of the Coulomb blockade in single junctions. The electrical environment of the tunnel junction, however, strongly affects the behavior of the junction: higher resistance leads are observed to greatly sharpen the Coulomb blockade over that seen with lower resistance leads. I present theoretical descriptions of how the environment influences the junctions; comparisons with the experimental results are in reasonable agreement.

  15. LOW RESISTANCE JUNCTIONS IN CRAYFISH

    PubMed Central

    Peracchia, Camillo

    1973-01-01

    Low resistance junctions between axons of crayfish ganglia are studied by freeze-fracture and negative staining. In freeze-fracture, fracture planes that go through a junctional membrane expose two faces, both internal, called face A and face B. Face A belongs to the internal membrane leaflet and faces the gap. Face B belongs to the external membrane leaflet and faces the axoplasm. Face A displays pits, 60–100 Å in diameter, arranged in a hexagonal array with a unit cell of ∼200 Å. An ∼25 Å bump is frequently seen at the center of each pit. Some pits are occupied by a globule ∼125 Å in diameter, which displays a central depression ∼25 Å in size. Face B contains globules also arranged in a fairly regular hexagonal pattern. The center-to-center distance between adjacent globules is most frequently ∼200 Å; however, occasionally certain globules are seen separated by a distance as short as ∼125 Å. The top surface of the globules occasionally displays a starlike profile and seems to contain a central depression ∼25 Å in diameter. In negatively stained preparations of membranes from the nerve cord, two types of membranes are seen containing a fairly regular pattern. In one, globules ∼95 Å in diameter form a hexagonal close packing with a unit cell of ∼95 Å. In the other, globules of the same size are organized in a larger hexagonal array with a unit cell of ∼155 Å (swollen arrangement). Some of the globules forming the swollen arrangement are seen containing six subunits. The six subunits form a hexagon which is skewed with respect to the main rows of hexagons in such a way that the subunits lie on rows which make an angle of ∼37° with the main rows. PMID:4120611

  16. Electrostatic control of thermoelectricity in molecular junctions.

    PubMed

    Kim, Youngsang; Jeong, Wonho; Kim, Kyeongtae; Lee, Woochul; Reddy, Pramod

    2014-11-01

    Molecular junctions hold significant promise for efficient and high-power-output thermoelectric energy conversion. Recent experiments have probed the thermoelectric properties of molecular junctions. However, electrostatic control of thermoelectric properties via a gate electrode has not been possible due to technical challenges in creating temperature differentials in three-terminal devices. Here, we show that extremely large temperature gradients (exceeding 1 × 10(9) K m(-1)) can be established in nanoscale gaps bridged by molecules, while simultaneously controlling their electronic structure via a gate electrode. Using this platform, we study prototypical Au-biphenyl-4,4'-dithiol-Au and Au-fullerene-Au junctions to demonstrate that the Seebeck coefficient and the electrical conductance of molecular junctions can be simultaneously increased by electrostatic control. Moreover, from our studies of fullerene junctions, we show that thermoelectric properties can be significantly enhanced when the dominant transport orbital is located close to the chemical potential (Fermi level) of the electrodes. These results illustrate the intimate relationship between the thermoelectric properties and charge transmission characteristics of molecular junctions and should enable systematic exploration of the recent computational predictions that promise extremely efficient thermoelectric energy conversion in molecular junctions.

  17. Microtubules regulate disassembly of epithelial apical junctions

    PubMed Central

    Ivanov, Andrei I; McCall, Ingrid C; Babbin, Brian; Samarin, Stanislav N; Nusrat, Asma; Parkos, Charles A

    2006-01-01

    Background Epithelial tight junction (TJ) and adherens junction (AJ) form the apical junctional complex (AJC) which regulates cell-cell adhesion, paracellular permeability and cell polarity. The AJC is anchored on cytoskeletal structures including actin microfilaments and microtubules. Such cytoskeletal interactions are thought to be important for the assembly and remodeling of apical junctions. In the present study, we investigated the role of microtubules in disassembly of the AJC in intestinal epithelial cells using a model of extracellular calcium depletion. Results Calcium depletion resulted in disruption and internalization of epithelial TJs and AJs along with reorganization of perijunctional F-actin into contractile rings. Microtubules reorganized into dense plaques positioned inside such F-actin rings. Depolymerization of microtubules with nocodazole prevented junctional disassembly and F-actin ring formation. Stabilization of microtubules with either docetaxel or pacitaxel blocked contraction of F-actin rings and attenuated internalization of junctional proteins into a subapical cytosolic compartment. Likewise, pharmacological inhibition of microtubule motors, kinesins, prevented contraction of F-actin rings and attenuated disassembly of apical junctions. Kinesin-1 was enriched at the AJC in cultured epithelial cells and it also accumulated at epithelial cell-cell contacts in normal human colonic mucosa. Furthermore, immunoprecipitation experiments demonstrated association of kinesin-1 with the E-cadherin-catenin complex. Conclusion Our data suggest that microtubules play a role in disassembly of the AJC during calcium depletion by regulating formation of contractile F-actin rings and internalization of AJ/TJ proteins. PMID:16509970

  18. Atomically Abrupt Topological p-n Junction.

    PubMed

    Kim, Sung Hwan; Jin, Kyung-Hwan; Kho, Byung Woo; Park, Byeong-Gyu; Liu, Feng; Kim, Jun Sung; Yeom, Han Woong

    2017-08-24

    Topological insulators (TI's) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p-n junctions. Interesting electronic properties of a 'topological' p-n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p-n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p-n junction of topological surface states (TSS's) of a three-dimensional (3D) topological insulator (TI) with an atomically abrupt interface. When a ultrathin Sb film is grown on a 3D TI of Bi2Se3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi2Se3 surface. Thus, the Bi2Se3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS's as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p-n junctions with the scalability down to atomic dimensions.

  19. The futile cycling of hexose phosphates could account for the fact that hexokinase exerts a high control on glucose phosphorylation but not on glycolytic rate in transgenic potato (Solanum tuberosum) roots.

    PubMed

    Claeyssen, Eric; Dorion, Sonia; Clendenning, Audrey; He, Jiang Zhou; Wally, Owen; Chen, Jingkui; Auslender, Evgenia L; Moisan, Marie-Claude; Jolicoeur, Mario; Rivoal, Jean

    2013-01-01

    The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined. An 11-fold variation in HK activity resulted in altered root growth, with antisense roots growing better than sense roots. Quantification of sugars, organic acids and amino acids in transgenic roots demonstrated that the manipulation of HK activity had very little effect on the intracellular pools of these metabolites. However, adenylate and free Pi levels were negatively affected by an increase in HK activity. The flux control coefficient of HK over the phosphorylation of glucose was measured for the first time in plants. Its value varied with HK level. It reached 1.71 at or below normal HK activity value and was much lower (0.32) at very high HK levels. Measurements of glycolytic flux and O(2) uptake rates demonstrated that the differences in glucose phosphorylation did not affect significantly glycolytic and respiratory metabolism. We hypothesized that these results could be explained by the existence of a futile cycle between the pools of hexose-Ps and carbohydrates. This view is supported by several lines of evidence. Firstly, activities of enzymes capable of catalyzing these reactions were detected in roots, including a hexose-P phosphatase. Secondly, metabolic tracer experiments using (14)C-glucose as precursor showed the formation of (14)C-fructose and (14)C-sucrose. We conclude that futile cycling of hexose-P could be partially responsible for the differences in energetic status in roots with high and low HK activity and possibly cause the observed alterations in growth in transgenic roots. The involvement of HK and futile cycles in the control of glucose-6P metabolism is discussed.

  20. The Futile Cycling of Hexose Phosphates Could Account for the Fact That Hexokinase Exerts a High Control on Glucose Phosphorylation but Not on Glycolytic Rate in Transgenic Potato (Solanum tuberosum) Roots

    PubMed Central

    Clendenning, Audrey; He, Jiang Zhou; Wally, Owen; Chen, Jingkui; Auslender, Evgenia L.; Moisan, Marie-Claude; Jolicoeur, Mario; Rivoal, Jean

    2013-01-01

    The metabolism of potato (Solanum tuberosum) roots constitutively over- and underexpressing hexokinase (HK, EC 2.7.1.1) was examined. An 11-fold variation in HK activity resulted in altered root growth, with antisense roots growing better than sense roots. Quantification of sugars, organic acids and amino acids in transgenic roots demonstrated that the manipulation of HK activity had very little effect on the intracellular pools of these metabolites. However, adenylate and free Pi levels were negatively affected by an increase in HK activity. The flux control coefficient of HK over the phosphorylation of glucose was measured for the first time in plants. Its value varied with HK level. It reached 1.71 at or below normal HK activity value and was much lower (0.32) at very high HK levels. Measurements of glycolytic flux and O2 uptake rates demonstrated that the differences in glucose phosphorylation did not affect significantly glycolytic and respiratory metabolism. We hypothesized that these results could be explained by the existence of a futile cycle between the pools of hexose-Ps and carbohydrates. This view is supported by several lines of evidence. Firstly, activities of enzymes capable of catalyzing these reactions were detected in roots, including a hexose-P phosphatase. Secondly, metabolic tracer experiments using 14C-glucose as precursor showed the formation of 14C-fructose and 14C-sucrose. We conclude that futile cycling of hexose-P could be partially responsible for the differences in energetic status in roots with high and low HK activity and possibly cause the observed alterations in growth in transgenic roots. The involvement of HK and futile cycles in the control of glucose-6P metabolism is discussed. PMID:23382859

  1. Constraints on string networks with junctions

    SciTech Connect

    Copeland, E. J.; Kibble, T. W. B.; Steer, D. A.

    2007-03-15

    We consider the constraints on string networks with junctions in which the strings may all be different, as may be found, for example, in a network of (p,q) cosmic superstrings. We concentrate on three aspects of junction dynamics. First we consider the propagation of small-amplitude waves across a static three-string junction. Then, generalizing our earlier work, we determine the kinematic constraints on two colliding strings with different tensions. As before, the important conclusion is that strings do not always reconnect with a third string; they can pass straight through one another (or in the case of non-Abelian strings become stuck in an X configuration), the constraint depending on the angle at which the strings meet, on their relative velocity, and on the ratios of the string tensions. For example, if the two colliding strings have equal tensions, then for ultrarelativistic initial velocities they pass through one another. However, if their tensions are sufficiently different they can reconnect. Finally, we consider the global properties of junctions and strings in a network. Assuming that, in a network, the incoming waves at a junction are independently randomly distributed, we determine the root-mean-square (r.m.s.) velocities of strings and calculate the average speed at which a junction moves along each of the three strings from which it is formed. Our findings suggest that junction dynamics may be such as to preferentially remove the heavy strings from the network leaving a network of predominantly light strings. Furthermore the r.m.s. velocity of strings in a network with junctions is smaller than 1/{radical}(2), the result for conventional Nambu-Goto strings without junctions in Minkowski space-time.

  2. Temperature dependence of thermopower in molecular junctions

    NASA Astrophysics Data System (ADS)

    Kim, Youngsang; Lenert, Andrej; Meyhofer, Edgar; Reddy, Pramod

    2016-07-01

    The thermoelectric properties of molecular junctions are of considerable interest due to their promise for efficient energy conversion. While the dependence of thermoelectric properties of junctions on molecular structure has been recently studied, their temperature dependence remains unexplored. Using a custom built variable temperature scanning tunneling microscope, we measured the thermopower and electrical conductance of individual benzenedithiol junctions over a range of temperatures (100 K-300 K). We find that while the electrical conductance is independent of temperature, the thermopower increases linearly with temperature, confirming the predictions of the Landauer theory.

  3. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

    Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

    2007-01-01

    A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (SiC) make this wide band gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

  4. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

    Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

    2006-01-01

    A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (SiC) make this wide band gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

  5. Circuit Theory of Unconventional Superconductor Junctions

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Nazarov, Yu. V.; Kashiwaya, S.

    2003-04-01

    We extend the circuit theory of superconductivity to cover transport and proximity effect in mesoscopic systems that contain unconventional superconductor junctions. The approach fully accounts for zero-energy Andreev bound states forming at the surface of unconventional superconductors. As a simple application, we investigate the transport properties of a diffusive normal metal in series with a d-wave superconductor junction. We reveal the competition between the formation of Andreev bound states and proximity effect that depends on the crystal orientation of the junction interface.

  6. Efficient photonic crystal Y-junctions

    NASA Astrophysics Data System (ADS)

    Wilson, Rab; Karle, Tim J.; Moerman, I.; Krauss, Thomas F.

    2003-07-01

    A highly efficient Y-junction based on a planar photonic crystal (PhC) platform is presented. The PhC consists of a triangular array of holes etched into a GaAs/AlGaAs heterostructure, with a typical period of 322 nm and ~35% fill factor. The Y-junction has smaller holes positioned at the centre of the junction, giving rise to very uniform splitting and high transmission. The performance is very encouraging, with experimental transmission of approximately 40% for each arm of the Y-splitter relative to a comparable single-defect PhC waveguide.

  7. Molecular mechanism of double Holliday junction dissolution

    PubMed Central

    2014-01-01

    Processing of homologous recombination intermediates is tightly coordinated to ensure that chromosomal integrity is maintained and tumorigenesis avoided. Decatenation of double Holliday junctions, for example, is catalysed by two enzymes that work in tight coordination and belong to the same ‘dissolvasome’ complex. Within the dissolvasome, the RecQ-like BLM helicase provides the translocase function for Holliday junction migration, while the topoisomerase III alpha-RMI1 subcomplex works as a proficient DNA decatenase, together resulting in double-Holliday-junction unlinking. Here, we review the available architectural and biochemical knowledge on the dissolvasome machinery, with a focus on the structural interplay between its components. PMID:25061510

  8. Structure-Property Relationships in Atomic-Scale Junctions: Histograms and Beyond.

    PubMed

    Hybertsen, Mark S; Venkataraman, Latha

    2016-03-15

    are pulled apart has given complementary information such as the stiffness and rupture force of the molecule-metal link bond. Overall, while the BJ technique does not produce a single molecule circuit for practical applications, it has proved remarkably versatile for fundamental studies. Measured data and analysis have been combined with atomic-scale theory and calculations, typically performed for representative junction structures, to provide fundamental physical understanding of structure-function relationships. This Account integrates across an extensive series of our specific nanoscale junction studies which were carried out with the STM- and AFM-BJ techniques and supported by theoretical analysis and density functional theory based calculations, with emphasis on the physical characteristics of the measurement process and the rich data sets that emerge. Several examples illustrate the impact of measured trends based on the most probable values for key characteristics (obtained from ensembles of order 1000-10 000 individual junctions) to build a solid picture of conductance phenomena as well as attributes of the link bond chemistry. The key forward-looking question posed here is the extent to which the full data sets represented by the individual trajectories can be analyzed to address structure-function questions at the level of individual junctions. Initial progress toward physical modeling of conductance of individual junctions indicates trends consistent with physical junction structures. Analysis of junction mechanics reveals a scaling procedure that collapses existing data onto a universal force-extension curve. This research directed to understanding the distribution of structures and physical characteristics addresses fundamental questions concerning the interplay between chemical control and stochastically driven diversity.

  9. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

    Olson, Jerry M.; Kurtz, Sarah R.

    1992-01-01

    A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect.

  10. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

    Olson, J.M.; Kurtz, S.R.

    1992-11-24

    A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect. 5 figs.

  11. Current trends in salivary gland tight junctions

    PubMed Central

    Baker, Olga J.

    2016-01-01

    ABSTRACT Tight junctions form a continuous intercellular barrier between epithelial cells that is required to separate tissue spaces and regulate selective movement of solutes across the epithelium. They are composed of strands containing integral membrane proteins (e.g., claudins, occludin and tricellulin, junctional adhesion molecules and the coxsackie adenovirus receptor). These proteins are anchored to the cytoskeleton via scaffolding proteins such as ZO-1 and ZO-2. In salivary glands, tight junctions are involved in polarized saliva secretion and barrier maintenance between the extracellular environment and the glandular lumen. This review seeks to provide an overview of what is currently known, as well as the major questions and future research directions, regarding tight junction expression, organization and function within salivary glands. PMID:27583188

  12. Enhancement at the junction of silver nanorods.

    PubMed

    Gu, Geun Hoi; Suh, Jung Sang

    2008-08-19

    The enhancement of surface enhanced Raman scattering (SERS) at the junction of linearly joined silver nanorods (31 nm in diameter) deposited in the pores of anodic aluminum oxide templates was studied systematically by excitation with a 632.8 nm laser line. The single and joined silver nanorod arrays showed a similar extinction spectrum when their length was the same. Maximum enhancement was observed from the junction system of two nanorods of the same size with a total length of 62 nm. This length also corresponded to the optimum length of single nanorods for SERS by excitation with a 632.8 nm laser line. The enhancement at the junction was approximately 40 times higher than that of the 31 nm single nanorod, while it was 4 times higher than that of the 62 nm single nanorod. The enhancement factor at the junction after oxide removal was approximately 3.9 x 10 (9).

  13. Presynaptic spike broadening reduces junctional potential amplitude.

    PubMed

    Spencer, A N; Przysiezniak, J; Acosta-Urquidi, J; Basarsky, T A

    1989-08-24

    Presynaptic modulation of action potential duration may regulate synaptic transmission in both vertebrates and invertebrates. Such synaptic plasticity is brought about by modifications to membrane currents at presynaptic release sites, which, in turn, lead to changes in the concentration of cytosolic calcium available for mediating transmitter release. The 'primitive' neuromuscular junction of the jellyfish Polyorchis penicillatus is a useful model of presynaptic modulation. In this study, we show that the durations of action potentials in the motor neurons of this jellyfish are negatively correlated with the amplitude of excitatory junctional potentials. We present data from in vitro voltage-clamp experiments showing that short duration voltage spikes, which elicit large excitatory junctional potentials in vivo, produce larger and briefer calcium currents than do long duration action potentials, which elicit small excitatory junctional potentials.

  14. UTE MRI of the Osteochondral Junction

    PubMed Central

    Biswas, Reni; Chen, Karen; Chang, Eric Y.; Chung, Christine B.

    2014-01-01

    The osteochondral junction is composed of numerous tissue components and serves important functions relating to structural stability and proper nutrition in joints such as the knee and spine. Conventional MR techniques have been inadequate at imaging the tissues of the osteochondral junction primarily because of the intrinsically short T2 nature of these tissues, rendering them “invisible” with the standard acquisitions. Ultrashort time to echo (UTE) MR techniques acquire sufficient MR signal of osteochondral tissues, thereby allowing direct evaluation. This article reviews the anatomy of the osteochondral junction of the knee and the spine, technical aspects of UTE MRI, and the application of UTE MRI for evaluation of the osteochondral junction. PMID:25061547

  15. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

  16. Adrenocortical Gap Junctions and Their Functions

    PubMed Central

    Bell, Cheryl L.; Murray, Sandra A.

    2016-01-01

    Adrenal cortical steroidogenesis and proliferation are thought to be modulated by gap junction-mediated direct cell–cell communication of regulatory molecules between cells. Such communication is regulated by the number of gap junction channels between contacting cells, the rate at which information flows between these channels, and the rate of channel turnover. Knowledge of the factors regulating gap junction-mediated communication and the turnover process are critical to an understanding of adrenal cortical cell functions, including development, hormonal response to adrenocorticotropin, and neoplastic dedifferentiation. Here, we review what is known about gap junctions in the adrenal gland, with particular attention to their role in adrenocortical cell steroidogenesis and proliferation. Information and insight gained from electrophysiological, molecular biological, and imaging (immunocytochemical, freeze fracture, transmission electron microscopic, and live cell) techniques will be provided. PMID:27445985

  17. Tight junctions in skin inflammation.

    PubMed

    Bäsler, Katja; Brandner, Johanna M

    2017-01-01

    Inflammation of the skin is found after various external stimuli, e.g., UV radiation, allergen uptake, microbial challenge, or contact with irritants, as well as due to intrinsic, not always well-defined, stimuli, e.g., in autoimmune responses. Often, it is also triggered by a combination of both. The specific processes, which mean the kind of cytokines and immune cells involved and the extent of the reaction, depend not only on the trigger but also on the predisposition of the individual. Tight junctions (TJs) in the skin have been shown to form a barrier in the granular cell layer of the epidermis. Furthermore, TJ proteins were found in several additional epidermal layers. Besides barrier function, TJ proteins have been shown to be involved in proliferation, differentiation, cell-cell adhesion, and apoptosis in keratinocytes. In inflamed skin, TJ proteins are often affected. We summarize here the impact of skin inflammation on TJs, e.g., in various forms of dermatitis including atopic dermatitis, in skin infection, and in UV-irradiated skin, and discuss the role of TJs in these inflammatory processes.

  18. Tunnel junctions with multiferroic barriers.

    PubMed

    Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

    2007-04-01

    Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La(0.1)Bi(0.9)MnO(3) (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2 nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

  19. Gap junctions, homeostasis, and injury.

    PubMed

    De Maio, Antonio; Vega, Virginia L; Contreras, Jorge E

    2002-06-01

    Gap junctions (Gj) play an important role in the communication between cells of many tissues. They are composed of channels that permit the passage of ions and low molecular weight metabolites between adjacent cells, without exposure to the extracellular environment. These pathways are formed by the interaction between two hemichannels on the surface of opposing cells. These hemichannels are formed by the association of six identical subunits, named connexins (Cx), which are integral membrane proteins. Cell coupling via Gj is dependent on the specific pattern of Cx gene expression. This pattern of gene expression is altered during several pathological conditions resulting in changes of cell coupling. The regulation of Cx gene expression is affected at different levels from transcription to post translational processes during injury. In addition, Gj cellular communication is regulated by gating mechanisms. The alteration of Gj communication during injury could be rationalized by two opposite theories. One hypothesis proposes that the alteration of Gj communication attenuates the spread of toxic metabolites from the injured area to healthy organ regions. The alternative proposition is that a reduction of cellular communication reduces the loss of important cellular metabolisms, such as ATP and glucose. Copyright 2002 Wiley-Liss, Inc.

  20. The Futility of PLC Lite

    ERIC Educational Resources Information Center

    DuFour, Rick; Reeves, Douglas

    2016-01-01

    Although many schools around the world have claimed to embrace the Professional Learning Community process, it would be more accurate to describe the current state of affairs in many schools as PLC Lite. Educators rename their traditional faculty or department meetings as PLC meetings, engage in book studies that result in no action, or devote…

  1. The Futility of PLC Lite

    ERIC Educational Resources Information Center

    DuFour, Rick; Reeves, Douglas

    2016-01-01

    Although many schools around the world have claimed to embrace the Professional Learning Community process, it would be more accurate to describe the current state of affairs in many schools as PLC Lite. Educators rename their traditional faculty or department meetings as PLC meetings, engage in book studies that result in no action, or devote…

  2. Noise and Chaos in Driven Josephson Junctions

    DTIC Science & Technology

    1987-03-01

    induced step ( n = integer), the corresponding Fokker - Planck equation is essentially the same as that for a purely dc biased junction in the zero... Planck equation which governs the two-dimensional distribution function P((j), d(t)/dt, t) will reduce to the one-dimensional Smoluchowski equation ...Junction). Its equation of motion turns out exacdy the same as a damped driven pendulum, except its characteristic frequency is about 10^-10^^ times

  3. Degradation of connexins and gap junctions

    PubMed Central

    Falk, Matthias M.; Kells, Rachael M.; Berthoud, Viviana M.

    2014-01-01

    Connexin proteins are short-lived within the cell, whether present in the secretory pathway or in gap junction plaques. Their levels can be modulated by their rate of degradation. Connexins, at different stages of assembly, are degraded through the proteasomal, endo-/lysosomal, and phago-/lysosomal pathways. In this review, we summarize the current knowledge about connexin and gap junction degradation including the signals and protein-protein interactions that participate in their targeting for degradation. PMID:24486527

  4. Anaesthesia management in craniovertebral junctional anomalies

    PubMed Central

    Mascarenhas, Oswald

    2016-01-01

    Craniovertebral Junctional (CVJ) anomalies are developmental disorders that affect the skeleton and enclosed neuraxis at the junction of cranium and cervical spine. The high prevalence of airway obstruction and restrictive pulmonary disease in combination with cardiovascular manifestations poses a high anaesthetic risk to these patients. This article provides a discussion of management of anaesthesia in patients with craniovertebral anomalies, the evaluation of risk factors in these patients and their management, including emergency airway issues. PMID:27891026

  5. Heat dissipation in atomic-scale junctions.

    PubMed

    Lee, Woochul; Kim, Kyeongtae; Jeong, Wonho; Zotti, Linda Angela; Pauly, Fabian; Cuevas, Juan Carlos; Reddy, Pramod

    2013-06-13

    Atomic and single-molecule junctions represent the ultimate limit to the miniaturization of electrical circuits. They are also ideal platforms for testing quantum transport theories that are required to describe charge and energy transfer in novel functional nanometre-scale devices. Recent work has successfully probed electric and thermoelectric phenomena in atomic-scale junctions. However, heat dissipation and transport in atomic-scale devices remain poorly characterized owing to experimental challenges. Here we use custom-fabricated scanning probes with integrated nanoscale thermocouples to investigate heat dissipation in the electrodes of single-molecule ('molecular') junctions. We find that if the junctions have transmission characteristics that are strongly energy dependent, this heat dissipation is asymmetric--that is, unequal between the electrodes--and also dependent on both the bias polarity and the identity of the majority charge carriers (electrons versus holes). In contrast, junctions consisting of only a few gold atoms ('atomic junctions') whose transmission characteristics show weak energy dependence do not exhibit appreciable asymmetry. Our results unambiguously relate the electronic transmission characteristics of atomic-scale junctions to their heat dissipation properties, establishing a framework for understanding heat dissipation in a range of mesoscopic systems where transport is elastic--that is, without exchange of energy in the contact region. We anticipate that the techniques established here will enable the study of Peltier effects at the atomic scale, a field that has been barely explored experimentally despite interesting theoretical predictions. Furthermore, the experimental advances described here are also expected to enable the study of heat transport in atomic and molecular junctions--an important and challenging scientific and technological goal that has remained elusive.

  6. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, John F.; Zolper, John C.

    1997-01-01

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

  7. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, J.F.; Zolper, J.C.

    1997-10-21

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

  8. Gravitational wave bursts from cosmic superstrings with Y-junctions

    SciTech Connect

    Binetruy, P.; Bohe, A.; Hertog, T.; Steer, D. A.

    2009-12-15

    Cosmic superstring loops generically contain strings of different tensions that meet at Y-junctions. These loops evolve nonperiodically in time, and have cusps and kinks that interact with the junctions. We study the effect of junctions on the gravitational wave signal emanating from cosmic string cusps and kinks. We find that earlier results on the strength of individual bursts from cusps and kinks on strings without junctions remain largely unchanged, but junctions give rise to additional contributions to the gravitational wave signal coming from strings expanding at the speed of light at a junction and kinks passing through a junction.

  9. Cell junctions in the gut of Protura.

    PubMed

    Xué, L; Romano, D

    1992-01-01

    The main cell junctions in the intestinal tract of a small group of apterygotan insects, Protura, were examined in conventional thin sections, tracer-infiltrated sections and freeze-fracture replicas. The smooth septate junctions in the midgut of collembolan Tomocerus minor were also studied for comparison. Pleated septate junctions are found in foregut, hindgut and Malpighian papillae. They exhibit regular septa crossing the intercellular clefts in thin sections; and the septa with a pronounced zig-zag appearance run parallel to form a honeycomb structure in tracer-impregnated sections. After freeze-fracture undulating rows of intramembranous particles (IMPs) are visible on the P face. Smooth septate junctions are observed in the midgut. The intercellular septa often run in pairs for long tracts and exhibit a wavy course in lanthanum impregnated sections. The IMPs exhibited on the E face are usually separated one from another. Twin arrangement of particle rows is also apparent on the replicas. Gap junctions are frequent in both the midgut and hindgut and possess the conventional characteristics of 'inverted gap junction' with E face connexons. These results provide further evidence relating Protura closely to Collembola as well as to primitive arthropods.

  10. Epidermal tight junctions in health and disease.

    PubMed

    Brandner, J M; Zorn-Kruppa, M; Yoshida, T; Moll, I; Beck, L A; De Benedetto, A

    2015-01-01

    The skin, the largest organ of the body, is an essential barrier that under homeostatic conditions efficiently protects and/or minimizes damage from both environmental (e.g. microorganisms, physical trauma, ultraviolet radiation) and endogenous (e.g., cancers, inflammation) factors. This formidable barrier function resides mainly in the epidermis, a dynamic, highly-stratified epithelium. The epidermis has 2 major barrier structures: stratum corneum, the outmost layer and tight junctions, intercellular junctions that seal adjacent keratinocytes in the stratum granulosum, found below the stratum corneum. In recent years there have been significant advances in our understanding of tight junction function, composition and regulation. Herein we review what is known about tight junctions in healthy skin and keratinocyte culture systems and highlight the dynamic crosstalk observed between tight junctions and the cutaneous immune system. Finally we discuss the preliminary observations suggesting that tight junction function or protein expression may be relevant for the pathogenesis of a number of common cutaneous inflammatory and neoplastic conditions.

  11. Predictive modelling of ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Velev, Julian P.; Burton, John D.; Zhuravlev, Mikhail Ye; Tsymbal, Evgeny Y.

    2016-05-01

    Ferroelectric tunnel junctions combine the phenomena of quantum-mechanical tunnelling and switchable spontaneous polarisation of a nanometre-thick ferroelectric film into novel device functionality. Switching the ferroelectric barrier polarisation direction produces a sizable change in resistance of the junction—a phenomenon known as the tunnelling electroresistance effect. From a fundamental perspective, ferroelectric tunnel junctions and their version with ferromagnetic electrodes, i.e., multiferroic tunnel junctions, are testbeds for studying the underlying mechanisms of tunnelling electroresistance as well as the interplay between electric and magnetic degrees of freedom and their effect on transport. From a practical perspective, ferroelectric tunnel junctions hold promise for disruptive device applications. In a very short time, they have traversed the path from basic model predictions to prototypes for novel non-volatile ferroelectric random access memories with non-destructive readout. This remarkable progress is to a large extent driven by a productive cycle of predictive modelling and innovative experimental effort. In this review article, we outline the development of the ferroelectric tunnel junction concept and the role of theoretical modelling in guiding experimental work. We discuss a wide range of physical phenomena that control the functional properties of ferroelectric tunnel junctions and summarise the state-of-the-art achievements in the field.

  12. Multi-junction solar cell device

    DOEpatents

    Friedman, Daniel J.; Geisz, John F.

    2007-12-18

    A multi-junction solar cell device (10) is provided. The multi-junction solar cell device (10) comprises either two or three active solar cells connected in series in a monolithic structure. The multi-junction device (10) comprises a bottom active cell (20) having a single-crystal silicon substrate base and an emitter layer (23). The multi-junction device (10) further comprises one or two subsequent active cells each having a base layer (32) and an emitter layer (23) with interconnecting tunnel junctions between each active cell. At least one layer that forms each of the top and middle active cells is composed of a single-crystal III-V semiconductor alloy that is substantially lattice-matched to the silicon substrate (22). The polarity of the active p-n junction cells is either p-on-n or n-on-p. The present invention further includes a method for substantially lattice matching single-crystal III-V semiconductor layers with the silicon substrate (22) by including boron and/or nitrogen in the chemical structure of these layers.

  13. Gap junctions: structure and function (Review).

    PubMed

    Evans, W Howard; Martin, Patricia E M

    2002-01-01

    Gap junctions are plasma membrane spatial microdomains constructed of assemblies of channel proteins called connexins in vertebrates and innexins in invertebrates. The channels provide direct intercellular communication pathways allowing rapid exchange of ions and metabolites up to approximately 1 kD in size. Approximately 20 connexins are identified in the human or mouse genome, and orthologues are increasingly characterized in other vertebrates. Most cell types express multiple connexin isoforms, making likely the construction of a spectrum of heteromeric hemichannels and heterotypic gap junctions that could provide a structural basis for the charge and size selectivity of these intercellular channels. The precise nature of the potential signalling information traversing junctions in physiologically defined situations remains elusive, but extensive progress has been made in elucidating how connexins are assembled into gap junctions. Also, participation of gap junction hemichannels in the propagation of calcium waves via an extracellular purinergic pathway is emerging. Connexin mutations have been identified in a number of genetically inherited channel communication-opathies. These are detected in connexin 32 in Charcot Marie Tooth-X linked disease, in connexins 26 and 30 in deafness and skin diseases, and in connexins 46 and 50 in hereditary cataracts. Biochemical approaches indicate that many of the mutated connexins are mistargeted to gap junctions and/or fail to oligomerize correctly into hemichannels. Genetic ablation approaches are helping to map out a connexin code and point to specific connexins being required for cell growth and differentiation as well as underwriting basic intercellular communication.

  14. Exercise regulation of intestinal tight junction proteins.

    PubMed

    Zuhl, Micah; Schneider, Suzanne; Lanphere, Katherine; Conn, Carole; Dokladny, Karol; Moseley, Pope

    2014-06-01

    Gastrointestinal distress, such as diarrhoea, cramping, vomiting, nausea and gastric pain are common among athletes during training and competition. The mechanisms that cause these symptoms are not fully understood. The stress of heat and oxidative damage during exercise causes disruption to intestinal epithelial cell tight junction proteins resulting in increased permeability to luminal endotoxins. The endotoxin moves into the blood stream leading to a systemic immune response. Tight junction integrity is altered by the phosphoylation state of the proteins occludin and claudins, and may be regulated by the type of exercise performed. Prolonged exercise and high-intensity exercise lead to an increase in key phosphorylation enzymes that ultimately cause tight junction dysfunction, but the mechanisms are different. The purpose of this review is to (1) explain the function and physiology of tight junction regulation, (2) discuss the effects of prolonged and high-intensity exercise on tight junction permeability leading to gastrointestinal distress and (3) review agents that may increase or decrease tight junction integrity during exercise.

  15. Gap junctions and blood-tissue barriers.

    PubMed

    Li, Michelle W M; Mruk, Dolores D; Cheng, C Yan

    2012-01-01

    Gap junction is a cell-cell communication junction type found in virtually all mammalian epithelia and endothelia and provides the necessary "signals" to coordinate physiological events to maintain the homeostasis of an epithelium and/or endothelium under normal physiological condition and following changes in the cellular environment (e.g., stimuli from stress, growth, development, inflammation, infection). Recent studies have illustrated the significance of this junction type in the maintenance of different blood-tissue barriers, most notably the blood-brain barrier and blood-testis barrier, which are dynamic ultrastructures, undergoing restructuring in response to stimuli from the environment. In this chapter, we highlight and summarize the latest findings in the field regarding how changes at the gap junction, such as the result of a knock-out, knock-down, knock-in, or gap junction inhibition and/or its activation via the use of inhibitors and/or activators, would affect the integrity or permeability of the blood-tissue barriers. These findings illustrate that much research is needed to delineate the role of gap junction in the blood-tissue barriers, most notably its likely physiological role in mediating or regulating the transport of therapeutic drugs across the blood-tissue barriers.

  16. GAP JUNCTIONS AND BLOOD-TISSUE BARRIERS

    PubMed Central

    Li, Michelle W.M.; Mruk, Dolores D.; Cheng, C. Yan

    2014-01-01

    Gap junction is a cell-cell communication junction type found in virtually all mammalian epithelia and endothelia and provides the necessary “signals” to coordinate physiological events to maintain the homeostasis of an epithelium and/or endothelium under normal physiological condition and following changes in the cellular environment (e.g., stimuli from stress, growth, development, inflammation, infection). Recent studies have illustrated the significance of this junction type in the maintenance of different blood-tissue barriers, most notably the blood-brain barrier and blood-testis barrier, which are dynamic ultrastructures, undergoing restructuring in response to stimuli from the environment. In this chapter, we highlight and summarize the latest findings in the field regarding how changes at the gap junction, such as the result of a knock-out, knock-down, knock-in, or gap junction inhibition and/or its activation via the use of inhibitors and/or activators, would affect the integrity or permeability of the blood-tissue barriers. These findings illustrate that much research is needed to delineate the role of gap junction in the blood-tissue barriers, most notably its likely physiological role in mediating or regulating the transport of therapeutic drugs across the blood-tissue barriers. PMID:23397629

  17. Graphene tunnel junctions with aluminum oxide barrier

    NASA Astrophysics Data System (ADS)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2016-10-01

    We report a development of graphene tunnel junctions made by chemical vapor deposition grown graphene and sputtered aluminum insulating by an in-situ grown aluminum oxide. The thin oxide layer formed in between the metal layer and the two-dimensional material is a crucial part of a tunnel junction. We characterized surface morphology of oxide layers and studied tunneling spectra of lead and silver tunnel junctions to estimate the quality of the aluminum oxide. The Brinkman-Rowell-Dynes model was applied to fit the conductance-voltage plots to calculate the thickness of oxide layers. Junctions with graphene both on bottom and on top were fabricated and their tunneling properties were characterized after exposure to air for weeks to test time stability. Furthermore, the resistances of graphene tunnel junctions with aluminum oxide formed naturally and in an oxygen atmosphere were studied. Our results demonstrate that in-situ aluminum oxide is an effective barrier for graphene tunnel junctions. The methods of barrier formation enable the realization of more tunnel devices and circuits based on graphene.

  18. Synchronization in Disordered Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Trees, B. R.; Dissanayake, S. T. M.

    2002-03-01

    We have studied the dynamics of a ladder array of overdamped Josephson junctions with periodic boundary conditions. The junctions have critical current and resistive disorder, are current biased above the critical current, and their voltages oscillate with nonidentical bare frequencies. We have been interested in the onset of synchronization in the rung junctions of the ladder, in which nearest neighbor interactions of strength α renormalize the bare frequencies to a common value. The degree of synchronization of the array is measured by an order parameter, r (0<= r<= 1), as a function of α and the spread of bare frequencies. For a given frequency spread, a synchronization phase transition is clearly visible with an increase in α. We have also determined that a time-averaged version of the resistively-shunted junction equations can be used as an accurate description of the dynamics of the junctions. The solutions to the averaged equations exhibit phase slips between pairs of junctions for certain ranges of values of α and also demonstrate that the relationship between the array size, N, and the critical coupling strength for the onset of synchronization scales as N^2. This research was partially funded by a grant to Ohio Wesleyan University from the McGregor Foundation to support student research.

  19. Epidermal tight junctions in health and disease

    PubMed Central

    Brandner, JM; Zorn-Kruppa, M; Yoshida, T; Moll, I; Beck, LA; De Benedetto, A

    2014-01-01

    The skin, the largest organ of the body, is an essential barrier that under homeostatic conditions efficiently protects and/or minimizes damage from both environmental (e.g. microorganisms, physical trauma, ultraviolet radiation) and endogenous (e.g., cancers, inflammation) factors. This formidable barrier function resides mainly in the epidermis, a dynamic, highly-stratified epithelium. The epidermis has 2 major barrier structures: stratum corneum, the outmost layer and tight junctions, intercellular junctions that seal adjacent keratinocytes in the stratum granulosum, found below the stratum corneum. In recent years there have been significant advances in our understanding of tight junction function, composition and regulation. Herein we review what is known about tight junctions in healthy skin and keratinocyte culture systems and highlight the dynamic crosstalk observed between tight junctions and the cutaneous immune system. Finally we discuss the preliminary observations suggesting that tight junction function or protein expression may be relevant for the pathogenesis of a number of common cutaneous inflammatory and neoplastic conditions. PMID:25838981

  20. Learning to Prove in Geometry: Learning from Heuristic Examples and How It Can Be Supported

    ERIC Educational Resources Information Center

    Hilbert, Tatjana S.; Renkl, Alexander; Kessler, Stephan; Reiss, Kristina

    2008-01-01

    This field experiment tested whether a special type of worked-out examples (i.e., heuristic examples) helps learners develop better conceptual knowledge about mathematical proving and proving skills than a control condition focussing on mathematical contents. Additionally, we analysed the benefits of self-explanation prompts and completion…

  1. Commognitive Analysis of Undergraduate Mathematics Students' Responses in Proving Subgroup's Non-Emptiness

    ERIC Educational Resources Information Center

    Ioannou, Marios

    2016-01-01

    Proving that a given set is indeed a subgroup, one needs to show that it is non-empty, and closed under operation and inverses. This study focuses on the first condition, analysing students' responses to this task. Results suggest that there are three distinct problematic responses: the total absence of proving this condition, the problematic…

  2. Junction conditions in quadratic gravity: thin shells and double layers

    NASA Astrophysics Data System (ADS)

    Reina, Borja; Senovilla, José M. M.; Vera, Raül

    2016-05-01

    The junction conditions for the most general gravitational theory with a Lagrangian containing terms quadratic in the curvature are derived. We include the cases with a possible concentration of matter on the joining hypersurface—termed as thin shells, domain walls or braneworlds in the literature—as well as the proper matching conditions where only finite jumps of the energy-momentum tensor are allowed. In the latter case we prove that the matching conditions are more demanding than in general relativity. In the former case, we show that generically the shells/domain walls are of a new kind because they possess, in addition to the standard energy-momentum tensor, a double layer energy-momentum contribution which actually induces an external energy flux vector and an external scalar pressure/tension on the shell. We prove that all these contributions are necessary to make the entire energy-momentum tensor divergence-free, and we present the field equations satisfied by these energy-momentum quantities. The consequences of all these results are briefly analyzed.

  3. Charge transport in nanoscale junctions.

    PubMed

    Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

    2008-09-03

    many particle excitations, new surface states in semiconductor electrodes, various mechanisms for single molecule rectification of the current, inelastic electron spectra and SERS spectroscopy. Three terminal architectures allowing (electrochemical) gating and transistor effects. Electrochemical nanojunctions and gating: intermolecular electron transfer in multi-redox metalloproteins, contact force modulation, characteristic current-noise patterns due to conformational fluctuations, resonance effects and electrocatalysis. Novel architectures: linear coupled quantum-dot-bridged junctions, electrochemical redox mediated transfer in two center systems leading to double maxima current-voltage plots and negative differential resistance, molecular-nanoparticle hybrid junctions and unexpected mesoscopic effects in polymeric wires. Device integration: techniques for creating stable metal/molecule/metal junctions using 'nano-alligator clips' and integration with 'traditional' silicon-based technology. The Guest Editors would like to thank all of the authors and referees of this special issue for their meticulous work in making each paper a valuable contribution to this research area, the early-bird authors for their patience, and Journal of Physics: Condensed Matter editorial staff in Bristol for their continuous support.

  4. Junction formation and current transport mechanisms in hybrid n-Si/PEDOT:PSS solar cells

    NASA Astrophysics Data System (ADS)

    Jäckle, Sara; Mattiza, Matthias; Liebhaber, Martin; Brönstrup, Gerald; Rommel, Mathias; Lips, Klaus; Christiansen, Silke

    2015-08-01

    We investigated hybrid inorganic-organic solar cells combining monocrystalline n-type silicon (n-Si) and a highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The build-in potential, photo- and dark saturation current at this hybrid interface are monitored for varying n-Si doping concentrations. We corroborate that a high build-in potential forms at the hybrid junction leading to strong inversion of the n-Si surface. By extracting work function and valence band edge of the polymer from ultraviolet photoelectron spectroscopy, a band diagram of the hybrid n-Si/PEDOT:PSS heterojunction is presented. The current-voltage characteristics were analyzed using Schottky and abrupt pn-junction models. The magnitude as well as the dependence of dark saturation current on n-Si doping concentration proves that the transport is governed by diffusion of minority charge carriers in the n-Si and not by thermionic emission of majorities over a Schottky barrier. This leads to a comprehensive explanation of the high observed open-circuit voltages of up to 634 mV connected to high conversion efficiency of almost 14%, even for simple planar device structures without antireflection coating or optimized contacts. The presented work clearly shows that PEDOT:PSS forms a hybrid heterojunction with n-Si behaving similar to a conventional pn-junction and not, like commonly assumed, a Schottky junction.

  5. Junction formation and current transport mechanisms in hybrid n-Si/PEDOT:PSS solar cells

    PubMed Central

    Jäckle, Sara; Mattiza, Matthias; Liebhaber, Martin; Brönstrup, Gerald; Rommel, Mathias; Lips, Klaus; Christiansen, Silke

    2015-01-01

    We investigated hybrid inorganic-organic solar cells combining monocrystalline n-type silicon (n-Si) and a highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The build-in potential, photo- and dark saturation current at this hybrid interface are monitored for varying n-Si doping concentrations. We corroborate that a high build-in potential forms at the hybrid junction leading to strong inversion of the n-Si surface. By extracting work function and valence band edge of the polymer from ultraviolet photoelectron spectroscopy, a band diagram of the hybrid n-Si/PEDOT:PSS heterojunction is presented. The current-voltage characteristics were analyzed using Schottky and abrupt pn-junction models. The magnitude as well as the dependence of dark saturation current on n-Si doping concentration proves that the transport is governed by diffusion of minority charge carriers in the n-Si and not by thermionic emission of majorities over a Schottky barrier. This leads to a comprehensive explanation of the high observed open-circuit voltages of up to 634 mV connected to high conversion efficiency of almost 14%, even for simple planar device structures without antireflection coating or optimized contacts. The presented work clearly shows that PEDOT:PSS forms a hybrid heterojunction with n-Si behaving similar to a conventional pn-junction and not, like commonly assumed, a Schottky junction. PMID:26278010

  6. The energy barrier at noble metal/TiO{sub 2} junctions

    SciTech Connect

    Hossein-Babaei, F. E-mail: fhbabaei@yahoo.com; Lajvardi, Mehdi M. Alaei-Sheini, Navid

    2015-02-23

    Nobel metal/TiO{sub 2} structures are used as catalysts in chemical reactors, active components in TiO{sub 2}-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO{sub 2} layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO{sub 2} behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 10{sup 6} times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO{sub 2} contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

  7. Model Building to Facilitate Understanding of Holliday Junction and Heteroduplex Formation, and Holliday Junction Resolution

    ERIC Educational Resources Information Center

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and…

  8. Model Building to Facilitate Understanding of Holliday Junction and Heteroduplex Formation, and Holliday Junction Resolution

    ERIC Educational Resources Information Center

    Selvarajah, Geeta; Selvarajah, Susila

    2016-01-01

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and…

  9. Geodetic Survey Coordinates to Support Global Positioning System Tests at Yuma Proving Grounds Arizona

    DTIC Science & Technology

    1975-10-01

    The additional GEOCEIVER survey provided a means by which the local survey can be accurately related to WGS 72. The accepted accuracy for...Washington, D.C; May 1974. [Presented by Thomas 0. Seppelln at the International Symposium of Problems Related to the Redefinition of North...gravel road right (Cibola West Access Road); turn right and go northeast for 0.75 mile to the junction with Water Tank Road; bear left and

  10. Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes.

    PubMed

    Borzenets, I V; Amet, F; Ke, C T; Draelos, A W; Wei, M T; Seredinski, A; Watanabe, K; Taniguchi, T; Bomze, Y; Yamamoto, M; Tarucha, S; Finkelstein, G

    2016-12-02

    We investigate the critical current I_{C} of ballistic Josephson junctions made of encapsulated graphene-boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, I_{C} is found to scale as ∝exp(-k_{B}T/δE). The extracted energies δE are independent of the carrier density and proportional to the level spacing of the ballistic cavity. As T→0 the critical current of a long (or short) junction saturates at a level determined by the product of δE (or Δ) and the number of the junction's transversal modes.

  11. Presentiment or entanglement? An alternative explanation for apparent entanglement in provings.

    PubMed

    Lewith, G T; Brien, Sarah; Hyland, Michael E

    2005-04-01

    A number of authors have recently discussed the possible role entanglement in homeopathy. Walach et al have published a homeopathic proving which they interpreted as demonstrating entanglement between placebo and verum groups in a proving. The lack of a 'run-in' period was a weakness of this trial. We present further results of our proving of Belladonna which show that subjects who reported symptoms during the placebo run-in period ('presentiment provers') were more likely to report symptoms during the treatment period. This data suggests and the observations of Walach et al may be explicable by conventional mechanisms including differential reporting and constitutional type.

  12. A single-gradient junction technique to replace multiple-junction shifts for craniospinal irradiation treatment

    SciTech Connect

    Hadley, Austin; Ding, George X.

    2014-01-01

    Craniospinal irradiation (CSI) requires abutting fields at the cervical spine. Junction shifts are conventionally used to prevent setup error–induced overdosage/underdosage from occurring at the same location. This study compared the dosimetric differences at the cranial-spinal junction between a single-gradient junction technique and conventional multiple-junction shifts and evaluated the effect of setup errors on the dose distributions between both techniques for a treatment course and single fraction. Conventionally, 2 lateral brain fields and a posterior spine field(s) are used for CSI with weekly 1-cm junction shifts. We retrospectively replanned 4 CSI patients using a single-gradient junction between the lateral brain fields and the posterior spine field. The fields were extended to allow a minimum 3-cm field overlap. The dose gradient at the junction was achieved using dose painting and intensity-modulated radiation therapy planning. The effect of positioning setup errors on the dose distributions for both techniques was simulated by applying shifts of ± 3 and 5 mm. The resulting cervical spine doses across the field junction for both techniques were calculated and compared. Dose profiles were obtained for both a single fraction and entire treatment course to include the effects of the conventional weekly junction shifts. Compared with the conventional technique, the gradient-dose technique resulted in higher dose uniformity and conformity to the target volumes, lower organ at risk (OAR) mean and maximum doses, and diminished hot spots from systematic positioning errors over the course of treatment. Single-fraction hot and cold spots were improved for the gradient-dose technique. The single-gradient junction technique provides improved conformity, dose uniformity, diminished hot spots, lower OAR mean and maximum dose, and one plan for the entire treatment course, which reduces the potential human error associated with conventional 4-shifted plans.

  13. Clathrin and Cx43 gap junction plaque endoexocytosis

    SciTech Connect

    Nickel, Beth M.; DeFranco, B. Hewa; Gay, Vernon L.; Murray, Sandra A.

    2008-10-03

    In earlier transmission electron microscopic studies, we have described pentilaminar gap junctional membrane invaginations and annular gap junction vesicles coated with short, electron-dense bristles. The similarity between these electron-dense bristles and the material surrounding clathrin-coated pits led us to suggest that the dense bristles associated with gap junction structures might be clathrin. To confirm that clathrin is indeed associated with annular gap junction vesicles and gap junction plaques, quantum dot immuno-electron microscopic techniques were used. We report here that clathrin associates with both connexin 43 (Cx43) gap junction plaques and pentilaminar gap junction vesicles. An important finding was the preferential localization of clathrin to the cytoplasmic surface of the annular or of the gap junction plaque membrane of one of the two contacting cells. This is consistent with the possibility that the direction of gap junction plaque internalization into one of two contacting cells is regulated by clathrin.

  14. Tunnel junctions, cantilevers, and potentials

    NASA Astrophysics Data System (ADS)

    Tanner, Shawn

    We have developed a process for making sub-micrometer dimensional cantilevers, clamped beams, and more complicate electro-mechanical structures that carry integrated electrical leads. Such objects are perhaps useful as test structures for connecting to and measuring the electrical properties of molecular sized objects, as high frequency electromechanical components for radio and microwave frequency applications, and as sensor components for studying the fluctuation physics of small machines. Our process uses two realigned electron-beam lithography steps, a thin film angled deposition system, and differential removal of sacrificial aluminum layers to produce freely suspended sub-micron electromechanical components. We have produced cantilevers and beams on a variety of substrates (silica, silicon, and poly-imide) and have produced insulating, conductive, and multi-layer mechanical structures. We have measured mechanical resonances in the 10 MHz range by electrostatically actuating the cantilevers while in a magnetic field (3500 gauss) and measuring the voltage that results across the front edge of the cantilever. Two structures are fabricated sharing a common ground so that a balanced detection technique can be used to eliminate background signals. Due to the square dependence of the electrostatic force on the voltage, they can be resonated by a drive voltage of 1/2 the natural frequency or at the natural frequency. Two separate attempts have been made to apply these resonators. First, a process was developed to integrate a tunnel junction with the cantilever. These devices can possibly be used for probing small-scale systems such as molecules. We have verified the exponential variation of the tunneling resistance with both substrate flex and electrostatic gating. Second, a novel gate structure was developed to create a double potential well for resonator motion. This is accomplished by placing a multilayer structure in front of the hairpin cantilever consisting two

  15. YBCO step-edge junctions with high IcRn

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Foley, C. P.

    2010-06-01

    Step-edge junctions represent one type of grain boundary Josephson junction employed in high-temperature superconducting junction technology. To date, the majority of results published in the literature focus on [001]-tilt grain boundary junctions (GBJs) produced using bicrystal substrates. We investigate the step morphology and YBCO (yttrium barium copper oxide) film structure of YBCO-based step-edge junctions on MgO [001] substrates which structurally resemble [100]-tilt junctions. High-resolution electron microscopy reveals a clean GBJ interface of width ~ 1 nm and a single junction at the top edge. The dependence of the transport properties on the MgO step-edge and junction morphology is examined at 4.2 K, to enable direct comparison with results for other junction studies such as [001]-tilt and [100]-tilt junctions and building on previously published 77 K data. MgO step-edge junctions show a slower reduction in critical current density with step angle compared with [001]-tilt junctions. For optimized step parameters, transport measurements revealed large critical current and normal resistance (IcRN) products (~3-5 mV), comparable with the best results obtained in other kinds of [100]-tilt GBJs in YBCO at 4.2 K. Junction-based devices such as SQUIDs (superconducting quantum interference devices) and THz imagers show excellent performance when MgO-based step-edge junctions are used.

  16. Dislocation Multi-junctions and Strain Hardening

    SciTech Connect

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  17. Dislocation multi-junctions and strain hardening.

    PubMed

    Bulatov, Vasily V; Hsiung, Luke L; Tang, Meijie; Arsenlis, Athanasios; Bartelt, Maria C; Cai, Wei; Florando, Jeff N; Hiratani, Masato; Rhee, Moon; Hommes, Gregg; Pierce, Tim G; de la Rubia, Tomas Diaz

    2006-04-27

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects called dislocations. First proposed theoretically in 1934 (refs 1-3) to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening, a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions that tie the dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed 'multi-junctions'. We first predict the existence of multi-junctions using dislocation dynamics and atomistic simulations and then confirm their existence by transmission electron microscopy experiments in single-crystal molybdenum. In large-scale dislocation dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication, thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in body-centred cubic crystals.

  18. Semiconductor Lasers Containing Quantum Wells in Junctions

    NASA Technical Reports Server (NTRS)

    Yang, Rui Q.; Qiu, Yueming

    2004-01-01

    In a recent improvement upon In(x)Ga(1-x)As/InP semiconductor lasers of the bipolar cascade type, quantum wells are added to Esaki tunnel junctions, which are standard parts of such lasers. The energy depths and the geometric locations and thicknesses of the wells are tailored to exploit quantum tunneling such that, as described below, electrical resistances of junctions and concentrations of dopants can be reduced while laser performances can be improved. In(x)Ga(1-x)As/InP bipolar cascade lasers have been investigated as sources of near-infrared radiation (specifically, at wavelengths of about 980 and 1,550 nm) for photonic communication systems. The Esaki tunnel junctions in these lasers have been used to connect adjacent cascade stages and to enable transport of charge carriers between them. Typically, large concentrations of both n (electron-donor) and p (electron-acceptor) dopants have been necessary to impart low electrical resistances to Esaki tunnel junctions. Unfortunately, high doping contributes free-carrier absorption, thereby contributing to optical loss and thereby, further, degrading laser performance. In accordance with the present innovation, quantum wells are incorporated into the Esaki tunnel junctions so that the effective heights of barriers to quantum tunneling are reduced (see figure).

  19. Spontaneous calcium signals induced by gap junctions in a network model of astrocytes

    NASA Astrophysics Data System (ADS)

    Kazantsev, V. B.

    2009-01-01

    The dynamics of a network model of astrocytes coupled by gap junctions is investigated. Calcium dynamics of the single cell is described by the biophysical model comprising the set of three nonlinear differential equations. Intercellular dynamics is provided by the diffusion of inositol 1,4,5-trisphosphate (IP3) through gap junctions between neighboring astrocytes. It is found that the diffusion induces the appearance of spontaneous activity patterns in the network. Stability of the network steady state is analyzed. It is proved that the increase of the diffusion coefficient above a certain critical value yields the generation of low-amplitude subthreshold oscillatory signals in a certain frequency range. It is shown that such spontaneous oscillations can facilitate calcium pulse generation and provide a certain time scale in astrocyte signaling.

  20. Study on the pressure self-adaptive water-tight junction box in underwater vehicle

    NASA Astrophysics Data System (ADS)

    Huang, Haocai; Ye, Yanying; Leng, Jianxing; Yuan, Zhuoli; Chen, Ying

    2012-09-01

    Underwater vehicles play a very important role in underwater engineering. Water-tight junction box (WJB) is one of the key components in underwater vehicle. This paper puts forward a pressure self-adaptive water-tight junction box (PSAWJB) which improves the reliability of the WJB significantly by solving the sealing and pressure problems in conventional WJB design. By redundancy design method, the pressure self-adaptive equalizer (PSAE) is designed in such a way that it consists of a piston pressure-adaptive compensator (PPAC) and a titanium film pressureadaptive compensator (TFPAC). According to hydro-mechanical simulations, the operating volume of the PSAE is more than or equal to 11.6 % of the volume of WJB liquid system. Furthermore, the required operating volume of the PSAE also increases as the gas content of oil, hydrostatic pressure or temperature difference increases. The reliability of the PSAWJB is proved by hyperbaric chamber tests

  1. Methods for the fabrication of thermally stable magnetic tunnel junctions

    DOEpatents

    Chang, Y. Austin; Yang, Jianhua J.; Ladwig, Peter F.

    2009-08-25

    Magnetic tunnel junctions and method for making the magnetic tunnel junctions are provided. The magnetic tunnel junctions are characterized by a tunnel barrier oxide layer sandwiched between two ferromagnetic layers. The methods used to fabricate the magnetic tunnel junctions are capable of completely and selectively oxidizing a tunnel junction precursor material using an oxidizing gas containing a mixture of gases to provide a tunnel junction oxide without oxidizing the adjacent ferromagnetic materials. In some embodiments the gas mixture is a mixture of CO and CO.sub.2 or a mixture of H.sub.2 and H.sub.2O.

  2. Molecular organization of tricellular tight junctions.

    PubMed

    Furuse, Mikio; Izumi, Yasushi; Oda, Yukako; Higashi, Tomohito; Iwamoto, Noriko

    2014-01-01

    When the apicolateral border of epithelial cells is compared with a polygon, its sides correspond to the apical junctional complex, where cell adhesion molecules assemble from the plasma membranes of two adjacent cells. On the other hand, its vertices correspond to tricellular contacts, where the corners of three cells meet. Vertebrate tricellular contacts have specialized structures of tight junctions, termed tricellular tight junctions (tTJs). tTJs were identified by electron microscopic observations more than 40 years ago, but have been largely forgotten in epithelial cell biology since then. The identification of tricellulin and angulin family proteins as tTJ-associated membrane proteins has enabled us to study tTJs in terms of not only the paracellular barrier function but also unknown characteristics of epithelial cell corners via molecular biological approaches.

  3. Brownian refrigeration by hybrid tunnel junctions

    NASA Astrophysics Data System (ADS)

    Peltonen, J. T.; Helle, M.; Timofeev, A. V.; Solinas, P.; Hekking, F. W. J.; Pekola, J. P.

    2011-10-01

    Voltage fluctuations generated in a hot resistor can cause extraction of heat from a colder normal metal electrode of a hybrid tunnel junction between a normal metal and a superconductor. We extend the analysis presented in Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.98.210604 98, 210604 (2007) of this heat rectifying system, bearing resemblance to a Maxwell’s demon. Explicit analytic calculations show that the entropy of the total system is always increasing. We then consider a single-electron transistor configuration with two hybrid junctions in series, and show how the cooling is influenced by charging effects. We analyze also the cooling effect from nonequilibrium fluctuations instead of thermal noise, focusing on the shot noise generated in another tunnel junction. We conclude by discussing limitations for an experimental observation of the effect.

  4. Electrostatic Modeling of Vacuum Insulator Triple Junctions

    SciTech Connect

    Tully, L K; Goerz, D A; Houck, T L; Javedani, J B

    2006-10-25

    Triple junctions are often initiation points for insulator flashover in pulsed power devices. The two-dimensional finite-element TriComp [1] modeling software suite was utilized for its electrostatic field modeling package to investigate electric field behavior in the anode and cathode triple junctions of a high voltage vacuum-insulator interface. TriComp enables simple extraction of values from a macroscopic solution for use as boundary conditions in a subset solution. Electric fields computed with this zoom capability correlate with theoretical analysis of the anode and cathode triple junctions within submicron distances for nominal electrode spacing of 1.0 cm. This paper will discuss the iterative zoom process with TriComp finite-element software and the corresponding theoretical verification of the results.

  5. Tunnel junction based memristors as artificial synapses

    PubMed Central

    Thomas, Andy; Niehörster, Stefan; Fabretti, Savio; Shepheard, Norman; Kuschel, Olga; Küpper, Karsten; Wollschläger, Joachim; Krzysteczko, Patryk; Chicca, Elisabetta

    2015-01-01

    We prepared magnesia, tantalum oxide, and barium titanate based tunnel junction structures and investigated their memristive properties. The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use. Here, we increased the amplitude of the resistance change from 10% up to 100%. Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses. We observed analogs of long-term potentiation, long-term depression and spike-time dependent plasticity in these simple two terminal devices. Finally, we suggest a possible pathway of these devices toward their integration in neuromorphic systems for storing analog synaptic weights and supporting the implementation of biologically plausible learning mechanisms. PMID:26217173

  6. Photocurrent Measurements of Carbon Nanotube PN Junctions

    NASA Astrophysics Data System (ADS)

    Gabor, Nathaniel; Zhong, Zhaohui; Bosnick, Ken; Park, Jiwoong; McEuen, Paul

    2007-03-01

    Gated p-n junctions in semiconducting nanotubes have recently drawn much attention for their electronic and optoelectronic characteristics [1,2,3]. We investigate the photocurrent response at a nanotube gated p-n junction using a focused laser illumination source. We find that the photocurrent at zero source-drain bias increases linearly with optical power for the component of light along the length of the nanotube. Scanned photocurrent imaging demonstrates that carrier generation occurs primarily between the p- and n- type segments of the device. Measurements in an optical cryostat down to 4K reveal large photoresponse and step-like structure in the reverse bias photocurrent. These results show that nanotube p-n junctions are highly sensitive, nanoscale photodetectors. [1] J.U. Lee et al, App. Phys. Lett. 85, 145 (2004). [2] J.U. Lee, App. Phys. Lett. 87, 073101 (2005). [3] K. Bosnick et al, App. Phys. Lett. 89, 163121 (2006).

  7. Junction-side illuminated silicon detector arrays

    DOEpatents

    Iwanczyk, Jan S.; Patt, Bradley E.; Tull, Carolyn

    2004-03-30

    A junction-side illuminated detector array of pixelated detectors is constructed on a silicon wafer. A junction contact on the front-side may cover the whole detector array, and may be used as an entrance window for light, x-ray, gamma ray and/or other particles. The back-side has an array of individual ohmic contact pixels. Each of the ohmic contact pixels on the back-side may be surrounded by a grid or a ring of junction separation implants. Effective pixel size may be changed by separately biasing different sections of the grid. A scintillator may be coupled directly to the entrance window while readout electronics may be coupled directly to the ohmic contact pixels. The detector array may be used as a radiation hardened detector for high-energy physics research or as avalanche imaging arrays.

  8. Ferromagnetic resonance with long Josephson junction

    NASA Astrophysics Data System (ADS)

    Golovchanskiy, I. A.; Abramov, N. N.; Stolyarov, V. S.; Emelyanova, O. V.; Golubov, A. A.; Ustinov, A. V.; Ryazanov, V. V.

    2017-05-01

    In this work we propose a hybrid device based on a long Josephson junction (JJ) coupled inductively to an external ferromagnetic (FM) layer. The long JJ in a zero-field operation mode induces a localized AC magnetic field in the FM layer and enables a synchronized magnetostatic standing wave. The magnetostatic wave induces additional dissipation for soliton propagation in the junction and also enables a phase locking (resonant soliton synchronization) at a frequency of natural ferromagnetic resonance. The later manifests itself as an additional constant voltage step on the current-voltage characteristics at the corresponding voltage. The proposed device allows to study magnetization dynamics of individual micro-scaled FM samples using just DC technique, and also it provides additional phase locking frequency in the junction, determined exclusively by characteristics of the ferromagnet.

  9. Thermionic refrigeration at CNT-CNT junctions

    NASA Astrophysics Data System (ADS)

    Li, C.; Pipe, K. P.

    2016-10-01

    Monte Carlo (MC) simulation is used to study carrier energy relaxation following thermionic emission at the junction of two van der Waals bonded single-walled carbon nanotubes (SWCNTs). An energy-dependent transmission probability gives rise to energy filtering at the junction, which is predicted to increase the average electron transport energy by as much as 0.115 eV, leading to an effective Seebeck coefficient of 386 μV/K. MC results predict a long energy relaxation length (˜8 μm) for hot electrons crossing the junction into the barrier SWCNT. For SWCNTs of optimal length, an analytical transport model is used to show that thermionic cooling can outweigh parasitic heat conduction due to high SWCNT thermal conductivity, leading to a significant cooling capacity (2.4 × 106 W/cm2).

  10. Numerical Investigation of Josephson Junction Structures

    SciTech Connect

    Hristov, I.; Dimova, S.; Boyadjiev, T.

    2009-10-29

    Multilayered long Josephson Junction Structures form an interesting physical system where both nonlinearity and interaction between subsystems play an important role. Such systems allow to study physical effects that do not occur in single Josephson junction.The Sakai-Bodin-Pedersen model--a system of perturbed sine-Gordon equations--is used to study the dynamic states of stacks of inductively coupled long Josephson Junctions (LJJs). The corresponding static problem is numerically investigated as well. In order to study the stability of possible static solutions a Sturm-Liouville problem is generated and solved.The transitions from static to dynamic state and the scenario of these transitions are analyzed depending on the model parameters. Different physical characteristics--current-voltage characteristics, individual instant voltages and internal magnetic fields, are calculated and interpreted.

  11. Silicon fiber with p-n junction

    SciTech Connect

    Homa, D.; Cito, A.; Pickrell, G.; Hill, C.; Scott, B.

    2014-09-22

    In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900 μm and core diameters of 20–800 μm. The p-n junction was formed by doping the fiber with boron and confirmed via the current-voltage characteristic. The demonstration of a p-n junction in a melt-drawn silicon core fiber paves the way for the seamless integration of optical and electronic devices in fibers.

  12. Holographic Josephson junction from massive gravity

    NASA Astrophysics Data System (ADS)

    Hu, Ya-Peng; Li, Huai-Fan; Zeng, Hua-Bi; Zhang, Hai-Qing

    2016-05-01

    We study the holographic superconductor-normal metal-superconductor (SNS) Josephson junction in de Rham-Gabadadze-Tolley massive gravity. If the boundary theory is independent of spatial directions, i.e., if the chemical potential is homogeneous in spatial directions, we find that the graviton mass parameter will make it more difficult for the normal metal-superconductor phase transition to take place. In the holographic model of the Josephson junction, it is found that the maximal tunneling current will decrease according to the graviton mass parameter. Besides, the coherence length of the junction decreases as well with respect to the graviton mass parameter. If one interprets the graviton mass parameter as the effect of momentum dissipation in the boundary field theory, this indicates that the stronger the momentum dissipation is, the smaller the coherence length is.

  13. Studies of silicon PN junction solar cells

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1975-01-01

    Silicon pn junction solar cells made with low-resistivity substrates show poorer performance than traditional theory predicts. The purpose of this research was to identify and characterize the physical mechanisms responsible for the discrepancy. Attention was concentrated on the open circuit voltage in shallow junction cells of 0.1 ohm-cm substrate resistivity. A number of possible mechanisms that can occur in silicon devices were considered. Two mechanisms which are likely to be of main importance in explaining the observed low values of open-circuit voltage were found: (1) recombination losses associated with defects introduced during junction formation, and (2) inhomogeneity of defects and impurities across the area of the cell. To explore these theoretical anticipations, various diode test structures were designed and fabricated and measurement configurations for characterizing the defect properties and the areal inhomogeneity were constructed.

  14. Non-invasive microfluidic gap junction assay.

    PubMed

    Chen, Sisi; Lee, Luke P

    2010-03-01

    Gap junctions are protein channels between cells that allow direct electrical and metabolic coupling via the exchange of biomolecules and ions. Their expression, though ubiquitous in most mammalian cell types, is especially important for the proper functioning of cardiac and neuronal systems. Many existing methods for studying gap junction communication suffer from either unquantifiable data or difficulty of use. Here, we measure the extent of dye spread and effective diffusivities through gap junction connected cells using a quantitative microfluidic cell biology platform. After loading dye by hydrodynamic focusing of calcein/AM, dye transfer dynamics into neighboring, unexposed cells can be monitored via timelapse fluorescent microscopy. By using a selective microfluidic dye loading over a confluent layer of cells, we found that high expression of gap junctions in C6 cells transmits calcein across the monolayer with an effective diffusivity of 3.4 x 10(-13) m(2)/s, which are highly coupled by Cx43. We also found that the gap junction blocker 18alpha-GA works poorly in the presence of serum even at high concentrations (50 microM); however, it is highly effective down to 2.5 microM in the absence of serum. Furthermore, when the drug is washed out, dye spread resumes rapidly within 1 min for all doses, indicating the drug does not affect transcriptional regulation of connexins in these Cx43+ cells, in contrast to previous studies. This integrated microfluidic platform enables the in situ monitoring of gap junction communication, yielding dynamic information about intercellular molecular transfer and pharmacological inhibition and recovery.

  15. Electronic Properties of Carbon Nanotubes and Junctions

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Han, Jie; Yang, Liu; Govindan, T. R.; Jaffe, R.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make the prospect of using CNT as molecular wires and possibly as electronic devices an even more interesting one. We have been modeling various electronic properties such as the density of states and the transmission coefficient of CNT wires and junctions. These studies involve first calculating the stability of junctions using molecular dynamics simulations and then calculating the electronic properties using a pi-electron tight binding Hamiltonian. We have developed the expertise to calculate the electronic properties of both finite-sized CNT and CNT systems with semi-infinite boundary conditions. In this poster, we will present an overview of some of our results. The electronic application of CNT that is most promising at this time is their use as molecular wires. The conductance can however be greatly reduced because of reflection due to defects and contacts. We have modeled the transmission through CNT in the presence of two types of defects: weak uniform disorder and strong isolated scatterers. We find that the conductance is affected in significantly different manners due to these defects Junctions of CNT have also been imaged using STM. This makes it essential to derive rules for the formation of junctions between tubes of different chirality, study their relative energies and electronic properties. We have generalized the rules for connecting two different CNT and have calculated the transmission and density of states through CNT junctions. Metallic and semiconducting CNT can be joined to form a stable junction and their current versus voltage characteristics are asymmetric. CNT are deformed by the application of external forces including interactions with a substrate or other CNT. In many experiments, these deformation are expected to

  16. Electronic Properties of Carbon Nanotubes and Junctions

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Han, Jie; Yang, Liu; Govindan, T. R.; Jaffe, R.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make the prospect of using CNT as molecular wires and possibly as electronic devices an even more interesting one. We have been modeling various electronic properties such as the density of states and the transmission coefficient of CNT wires and junctions. These studies involve first calculating the stability of junctions using molecular dynamics simulations and then calculating the electronic properties using a pi-electron tight binding Hamiltonian. We have developed the expertise to calculate the electronic properties of both finite-sized CNT and CNT systems with semi-infinite boundary conditions. In this poster, we will present an overview of some of our results. The electronic application of CNT that is most promising at this time is their use as molecular wires. The conductance can however be greatly reduced because of reflection due to defects and contacts. We have modeled the transmission through CNT in the presence of two types of defects: weak uniform disorder and strong isolated scatterers. We find that the conductance is affected in significantly different manners due to these defects Junctions of CNT have also been imaged using STM. This makes it essential to derive rules for the formation of junctions between tubes of different chirality, study their relative energies and electronic properties. We have generalized the rules for connecting two different CNT and have calculated the transmission and density of states through CNT junctions. Metallic and semiconducting CNT can be joined to form a stable junction and their current versus voltage characteristics are asymmetric. CNT are deformed by the application of external forces including interactions with a substrate or other CNT. In many experiments, these deformation are expected to

  17. Structure and function of gap junction proteins: role of gap junction proteins in embryonic heart development.

    PubMed

    Ahir, Bhavesh K; Pratten, Margaret K

    2014-01-01

    Intercellular (cell-to-cell) communication is a crucial and complex mechanism during embryonic heart development. In the cardiovascular system, the beating of the heart is a dynamic and key regulatory process, which is functionally regulated by the coordinated spread of electrical activity through heart muscle cells. Heart tissues are composed of individual cells, each bearing specialized cell surface membrane structures called gap junctions that permit the intercellular exchange of ions and low molecular weight molecules. Gap junction channels are essential in normal heart function and they assist in the mediated spread of electrical impulses that stimulate synchronized contraction (via an electrical syncytium) of cardiac tissues. This present review describes the current knowledge of gap junction biology. In the first part, we summarise some relevant biochemical and physiological properties of gap junction proteins, including their structure and function. In the second part, we review the current evidence demonstrating the role of gap junction proteins in embryonic development with particular reference to those involved in embryonic heart development. Genetics and transgenic animal studies of gap junction protein function in embryonic heart development are considered and the alteration/disruption of gap junction intercellular communication which may lead to abnormal heart development is also discussed.

  18. Conductance Spectra in Graphene-Superconductor Junctions

    NASA Astrophysics Data System (ADS)

    Tian, Jie; Zhou, Shi-Ping; Deng, Zhen-Yan

    2015-01-01

    The conductance spectra of a graphene ribbon and graphene-superconductor (G-S) junctions are investigated, using the tight-binding model and non-equilibrium Green' function formalism. It is found that the quantized conductance related to graphene' edge-states is robust against perturbations in the model parameters for a graphene monolayer ribbon with the zigzag boundary. With appropriate model parameter of the spin-orbit interaction strength, a new bound state with odd-frequency symmetry is found in the G-S junction. An enhancement in the zero-energy conductance amplitude is followed.

  19. Fluctuation of heat current in Josephson junctions

    SciTech Connect

    Virtanen, P.; Giazotto, F.

    2015-02-15

    We discuss the statistics of heat current between two superconductors at different temperatures connected by a generic weak link. As the electronic heat in superconductors is carried by Bogoliubov quasiparticles, the heat transport fluctuations follow the Levitov–Lesovik relation. We identify the energy-dependent quasiparticle transmission probabilities and discuss the resulting probability density and fluctuation relations of the heat current. We consider multichannel junctions, and find that heat transport in diffusive junctions is unique in that its statistics is independent of the phase difference between the superconductors.

  20. Resolving Atomic Connectivity in Graphene Nanostructure Junctions.

    PubMed

    Dienel, Thomas; Kawai, Shigeki; Söde, Hajo; Feng, Xinliang; Müllen, Klaus; Ruffieux, Pascal; Fasel, Roman; Gröning, Oliver

    2015-08-12

    We report on the structural characterization of junctions between atomically well-defined graphene nanoribbons (GNRs) by means of low-temperature, noncontact scanning probe microscopy. We show that the combination of simultaneously acquired frequency shift and tunneling current maps with tight binding (TB) simulations allows a comprehensive characterization of the atomic connectivity in the GNR junctions. The proposed approach can be generally applied to the investigation of graphene nanomaterials and their interconnections and is thus expected to become an important tool in the development of graphene-based circuitry.

  1. Josephson junctions with alternating critical current density

    SciTech Connect

    Mints, R.G.; Kogan, V.G.

    1997-04-01

    The magnetic-field dependence of the critical current I{sub c}(H) is considered for a short Josephson junction with the critical current density j{sub c} alternating along the tunnel contact. Two model cases, periodic and randomly alternating j{sub c}, are treated in detail. Recent experimental data on I{sub c}(H) for grain-boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub x} are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  2. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, Albert G.; Drummond, Timothy J.; Robertson, Perry J.; Zipperian, Thomas E.

    1995-01-01

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits.

  3. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, A.G.; Drummond, T.J.; Robertson, P.J.; Zipperian, T.E.

    1995-12-26

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits. 10 figs.

  4. A proposed route to independent measurements of tight junction conductance at discrete cell junctions

    PubMed Central

    Zhou, Lushan; Zeng, Yuhan; Baker, Lane A; Hou, Jianghui

    2015-01-01

    Direct recording of tight junction permeability is of pivotal importance to many biologic fields. Previous approaches bear an intrinsic disadvantage due to the difficulty of separating tight junction conductance from nearby membrane conductance. Here, we propose the design of Double whole-cell Voltage Clamp - Ion Conductance Microscopy (DVC-ICM) based on previously demonstrated potentiometric scanning of local conductive pathways. As proposed, DVC-ICM utilizes two coordinated whole-cell patch-clamps to neutralize the apical membrane current during potentiometric scanning, which in models described here will profoundly enhance the specificity of tight junction recording. Several potential pitfalls are considered, evaluated and addressed with alternative countermeasures. PMID:26716077

  5. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping.

    PubMed

    Dong, Gangqiang; Liu, Fengzhen; Liu, Jing; Zhang, Hailong; Zhu, Meifang

    2013-12-27

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm-3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells.

  6. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping

    PubMed Central

    2013-01-01

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm−3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells. PMID:24369781

  7. Too Hot for Photon-Assisted Transport: Hot-Electrons Dominate Conductance Enhancement in Illuminated Single-Molecule Junctions.

    PubMed

    Fung, E-Dean; Adak, Olgun; Lovat, Giacomo; Scarabelli, Diego; Venkataraman, Latha

    2017-02-08

    We investigate light-induced conductance enhancement in single-molecule junctions via photon-assisted transport and hot-electron transport. Using 4,4'-bipyridine bound to Au electrodes as a prototypical single-molecule junction, we report a 20-40% enhancement in conductance under illumination with 980 nm wavelength radiation. We probe the effects of subtle changes in the transmission function on light-enhanced current and show that discrete variations in the binding geometry result in a 10% change in enhancement. Importantly, we prove theoretically that the steady-state behavior of photon-assisted transport and hot-electron transport is identical but that hot-electron transport is the dominant mechanism for optically induced conductance enhancement in single-molecule junctions when the wavelength used is absorbed by the electrodes and the hot-electron relaxation time is long. We confirm this experimentally by performing polarization-dependent conductance measurements of illuminated 4,4'-bipyridine junctions. Finally, we perform lock-in type measurements of optical current and conclude that currents due to laser-induced thermal expansion mask optical currents. This work provides a robust experimental framework for studying mechanisms of light-enhanced transport in single-molecule junctions and offers tools for tuning the performance of organic optoelectronic devices by analyzing detailed transport properties of the molecules involved.

  8. Realization of radial p-n junction silicon nanowire solar cell based on low-temperature and shallow phosphorus doping

    NASA Astrophysics Data System (ADS)

    Dong, Gangqiang; Liu, Fengzhen; Liu, Jing; Zhang, Hailong; Zhu, Meifang

    2013-12-01

    A radial p-n junction solar cell based on vertically free-standing silicon nanowire (SiNW) array is realized using a novel low-temperature and shallow phosphorus doping technique. The SiNW arrays with excellent light trapping property were fabricated by metal-assisted chemical etching technique. The shallow phosphorus doping process was carried out in a hot wire chemical vapor disposition chamber with a low substrate temperature of 250°C and H2-diluted PH3 as the doping gas. Auger electron spectroscopy and Hall effect measurements prove the formation of a shallow p-n junction with P atom surface concentration of above 1020 cm-3 and a junction depth of less than 10 nm. A short circuit current density of 37.13 mA/cm2 is achieved for the radial p-n junction SiNW solar cell, which is enhanced by 7.75% compared with the axial p-n junction SiNW solar cell. The quantum efficiency spectra show that radial transport based on the shallow phosphorus doping of SiNW array improves the carrier collection property and then enhances the blue wavelength region response. The novel shallow doping technique provides great potential in the fabrication of high-efficiency SiNW solar cells.

  9. 6. View northeast, junction of SR 141 and Rockland Road, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. View northeast, junction of SR 141 and Rockland Road, western estate wall and tree lines to right - A. I. Du Pont Estate, Junction of State Route 141 & Rockland Road, Wilmington, New Castle County, DE

  10. 8. Vidw southwest, junction of SR 141 and Rockland Road, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Vidw southwest, junction of SR 141 and Rockland Road, northern estate wall and tree lines to left - A. I. Du Pont Estate, Junction of State Route 141 & Rockland Road, Wilmington, New Castle County, DE

  11. Ballistic bipolar junctions in chemically gated graphene ribbons

    PubMed Central

    Baringhaus, Jens; Stöhr, Alexander; Forti, Stiven; Starke, Ulrich; Tegenkamp, Christoph

    2015-01-01

    The realization of ballistic graphene pn-junctions is an essential task in order to study Klein tunneling phenomena. Here we show that intercalation of Ge under the buffer layer of pre-structured SiC-samples succeeds to make truly nano-scaled pn-junctions. By means of local tunneling spectroscopy the junction width is found to be as narrow as 5 nm which is a hundred times smaller compared to electrically gated structures. The ballistic transmission across the junction is directly proven by systematic transport measurements with a 4-tip STM. Various npn- and pnp-junctions are studied with respect to the barrier length. The pn-junctions are shown to act as polarizer and analyzer with the second junction becoming transparent in case of a fully ballistic barrier. This can be attributed to the almost full suppression of electron transmission through the junction away from normal incidence. PMID:25898259

  12. 3. View of junction from the west, looking east along ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. View of junction from the west, looking east along Trunk Highway 55 toward the western side of bridge no. 5820. - Cloverleaf Interchange, Junction of Trunk Highways 52, 3, & 55, Inver Grove Heights, Dakota County, MN

  13. Research Objectives for Human Missions in the Proving Ground of Cis-Lunar Space

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Eppler, D. B.; Kennedy, K. J.; Lewis, R.; Spann, J. F.; Sullivan, T. A.

    2016-01-01

    Beginning in as early as 2023, crewed missions beyond low Earth orbit will begin enabled by the new capabilities of the SLS and Orion vehicles. This will initiate the "Proving Ground" phase of human exploration with Mars as an ultimate destination. The primary goal of the Proving Ground is to demonstrate the capability of suitably long duration spaceflight without need of continuous support from Earth, i.e. become Earth Independent. A major component of the Proving Ground phase is to conduct research activities aimed at accomplishing major objectives selected from a wide variety of disciplines including but not limited to: Astronomy, Heliophysics, Fundamental Physics, Planetary Science, Earth Science, Human Systems, Fundamental Space Biology, Microgravity, and In A major component of the Proving Ground phase is to conduct research activities aimed at accomplishing major objectives selected from a wide variety of disciplines including but not limited to: Astronomy, Heliophysics, Fundamental Physics, Planetary Science, Earth Science, Human Systems, Fundamental Space Biology, Microgravity, and In Situ Resource Utilization. Mapping and prioritizing the most important objectives from these disciplines will provide a strong foundation for establishing the architecture to be utilized in the Proving Ground.

  14. Challenge problems focusing on equality and combinatory logic: Evaluating automated theorem-proving programs

    SciTech Connect

    Wos, L.; McCune, W.

    1988-01-01

    In this paper, we offer a set of problems for evaluating the power of automated theorem-proving programs and the potential of new ideas. Since the problems published in the proceedings of the first CADE conference proved to be so useful, and since researchers are now far more disposed to implementing and testing their ideas, a new set of problems to complement those that have been widely studied is in order. In general, the new problems provide a far greater challenge for an automated theorem-proving program than those in the first set do. Indeed, to our knowledge, five of the six problems we propose for study have never been proved with a theorem-proving program. For each problem, we give a set of statements that can easily be translated into a standard set of clauses. We also state each problem in its mathematical and logical form. In many cases, we also provide a proof of the theorem from which a problem is taken so that one can measure a program's progress in its attempt to solve the problem. Two of the theorems we discuss are of especial interest in that they answer questions that had been open concerning the constructibility of two types of combinator. We also include a brief description of a new strategy for restricting the application of paramodulation. All of the problems we propose for study emphasize the role of equality. This paper is tutorial in nature.

  15. Ballistic transport in InSb Josephson junctions

    NASA Astrophysics Data System (ADS)

    Damasco, John Jeffrey; Gill, Stephen; Car, Diana; Bakkers, Erik; Mason, Nadya

    We present transport measurements on Josephson junctions consisting of InSb nanowires contacted by Al at various junction lengths. Junction behavior as a function of gate voltage, electric field, and magnetic field is discussed. We show that short junctions behave as 1D quantum wires, exhibiting quantized conductance steps. In addition, we show how Josephson behavior changes as transport evolves from ballistic to diffusive as a function of contact spacing.

  16. High voltage series connected tandem junction solar battery

    DOEpatents

    Hanak, Joseph J.

    1982-01-01

    A high voltage series connected tandem junction solar battery which comprises a plurality of strips of tandem junction solar cells of hydrogenated amorphous silicon having one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon, arranged in a tandem configuration, can have the same bandgap or differing bandgaps. The tandem junction strip solar cells are series connected to produce a solar battery of any desired voltage.

  17. Costochondral junction osteomyelitis in 3 septic foals

    PubMed Central

    Cesarini, Carla; Macieira, Susana; Girard, Christiane; Drolet, Richard; d’Anjou, Marc-André; Jean, Daniel

    2011-01-01

    The costochondral junction constitutes a potential site of infection in septic foals and it could be favored by thoracic trauma. Standard radiographs and ultrasonography are useful tools for diagnosis of this condition and ultrasound-guided needle aspiration could permit the definitive confirmation of infection. PMID:22210943

  18. Intrinsically shunted Josephson junctions for electronics applications

    NASA Astrophysics Data System (ADS)

    Belogolovskii, M.; Zhitlukhina, E.; Lacquaniti, V.; De Leo, N.; Fretto, M.; Sosso, A.

    2017-07-01

    Conventional Josephson metal-insulator-metal devices are inherently underdamped and exhibit hysteretic current-voltage response due to a very high subgap resistance compared to that in the normal state. At the same time, overdamped junctions with single-valued characteristics are needed for most superconducting digital applications. The usual way to overcome the hysteretic behavior is to place an external low-resistance normal-metal shunt in parallel with each junction. Unfortunately, such solution results in a considerable complication of the circuitry design and introduces parasitic inductance through the junction. This paper provides a concise overview of some generic approaches that have been proposed in order to realize internal shunting in Josephson heterostructures with a barrier that itself contains the desired resistive component. The main attention is paid to self-shunted devices with local weak-link transmission probabilities that are so strongly disordered in the interface plane that transmission probabilities are tiny for the main part of the transition region between two super-conducting electrodes, while a small part of the interface is well transparent. We discuss the possibility of realizing a universal bimodal distribution function and emphasize advantages of such junctions that can be considered as a new class of self-shunted Josephson devices promising for practical applications in superconducting electronics operating at 4.2 K.

  19. Gap junctional communication during limb cartilage differentiation.

    PubMed

    Coelho, C N; Kosher, R A

    1991-03-01

    The onset of cartilage differentiation in the developing limb bud is characterized by a transient cellular condensation process in which prechondrogenic mesenchymal cells become closely apposed to one another prior to initiating cartilage matrix deposition. During this condensation process intimate cell-cell interactions occur which are necessary to trigger chondrogenic differentiation. In the present study, we demonstrate that extensive cell-cell communication via gap junctions as assayed by the intercellular transfer of lucifer yellow dye occurs during condensation and the onset of overt chondrogenesis in high density micromass cultures prepared from the homogeneous population of chondrogenic precursor cells comprising the distal subridge region of stage 25 embryonic chick wing buds. Furthermore, in heterogeneous micromass cultures prepared from the mesodermal cells of whole stage 23/24 limb buds, extensive gap junctional communication is limited to differentiating cartilage cells, while the nonchondrogenic cells of the cultures that are differentiating into the connective tissue lineage exhibit little or no intercellular communication via gap junctions. These results provide a strong incentive for considering and further investigating the possible involvement of cell-cell communication via gap junctions in the regulation of limb cartilage differentiation.

  20. Ureteropelvic junction obstruction presenting after antireflux surgery

    PubMed Central

    Alizadeh, Farshid; Izadpanahi, Mohammad Hossein; Khorrami, Mohammad Hatef; Nouri-Mahdavi, Kia

    2012-01-01

    Ureteropelvic junction obstruction (UPJO) and vesicoureteral reflux (VUR) are two of the most common urologic problems in children that sometimes coexist simultaneously in a patient. However, presentation of UPJO after VUR treatment is rare. We will present two cases and discuss diagnostic and therapeutic aspects of the condition. PMID:23210079

  1. Axion mass estimates from resonant Josephson junctions

    NASA Astrophysics Data System (ADS)

    Beck, Christian

    2015-03-01

    Recently it has been proposed that dark matter axions from the galactic halo can produce a small Shapiro step-like signal in Josephson junctions whose Josephson frequency resonates with the axion mass (Beck, 2013). Here we show that the axion field equations in a voltage-driven Josephson junction environment allow for a nontrivial solution where the axion-induced electrical current manifests itself as an oscillating supercurrent. The linear change of phase associated with this nontrivial solution implies the formal existence of a large magnetic field in a tiny surface area of the weak link region of the junction which makes incoming axions decay into microwave photons. We derive a condition for the design of Josephson junction experiments so that they can act as optimum axion detectors. Four independent recent experiments are discussed in this context. The observed Shapiro step anomalies of all four experiments consistently point towards an axion mass of (110±2) μeV. This mass value is compatible with the recent BICEP2 results and implies that Peccei-Quinn symmetry breaking was taking place after inflation.

  2. Limiting process in shallow junction solar cells

    NASA Technical Reports Server (NTRS)

    Meulenberg, A.; Rittner, E.

    1979-01-01

    In extending the violet and nonreflective cell technology to lower resistivities, several processes limiting output power were encountered. The most important was the dark diffusion current due to recombination at the front grid contacts. After removal of this problem by reduction of the silicon metal contact area (to 0.14 percent of the total area), the electric field enhanced junction recombination current J sub r was the main limitation. Alteration of the diffusion profile to reduce the junction field is shown to be an effective means of influencing J sub r. The remaining problems are the bulk recombination in the n+ layer and the surface recombination at the oxide-silicon interface; both of these problems are aggravated by band-narrowing resulting from heavy doping in the diffused layer. Experimental evidence for the main limitations is shown, where increased diffusion temperature is seen to reduce both the influence of the front grid contacts and the junction electric field by increasing the junction depth. The potential for further significant improvement in efficiency appears to be high.

  3. Tight junction, selective permeability, and related diseases.

    PubMed

    Krug, Susanne M; Schulzke, Jörg D; Fromm, Michael

    2014-12-01

    The tight junction forms a barrier against unlimited paracellular passage but some of the tight junction proteins just do the opposite, they form extracellular channels zigzagging between lateral membranes of neighboring cells. All of these channel-forming proteins and even some of the barrier formers exhibit selectivity, which means that they prefer certain substances over others. All channel formers exhibit at least one of the three types of selectivity: for cations (claudin-2, -10b, -15), for anions (claudin-10a, -17) or for water (claudin-2). Also some, but not all, barrier-forming claudins are charge-selective (claudin-4, -8, -14). Moreover, occludin and tricellulin turned out to be relevant for barrier formation against macromolecule passage. Tight junction proteins are dysregulated or can be genetically defective in numerous diseases, which may lead to three effects: (i) impaired paracellular transport e.g. causing magnesium loss in the kidney, (ii) increased paracellular transport of solutes and water e.g. causing leak-flux diarrhea in the intestine, and (iii) increased permeability to large molecules e.g. unwanted intestinal pathogen uptake fueling inflammatory processes. This review gives an overview on the properties of tight junction proteins featuring selective permeability, and in this context explains how these proteins induce or aggravate diseases. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Polyphosphonium-based ion bipolar junction transistors.

    PubMed

    Gabrielsson, Erik O; Tybrandt, Klas; Berggren, Magnus

    2014-11-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices.

  5. Two-dimensional bipolar junction transistors

    NASA Astrophysics Data System (ADS)

    Gharekhanlou, Behnaz; Khorasani, Sina; Sarvari, Reza

    2014-03-01

    Recent development in fabrication technology of planar two-dimensional (2D) materials has introduced the possibility of numerous novel applications. Our recent analysis has revealed that by definition of p-n junctions through appropriate patterned doping of 2D semiconductors, ideal exponential I-V characteristics may be expected. However, the theory of 2D junctions turns out to be very different to that of standard bulk junctions. Based on this theory of 2D diodes, we construct for the first time a model to describe 2D bipolar junction transistors (2D-BJTs). We derive the small-signal equivalent model, and estimate the performance of a 2D-BJT device based on graphone as the example material. A current gain of about 138 and maximum threshold frequency of 77 GHz, together with a power-delay product of only 4 fJ per 1 μm lateral width is expected at an operating voltage of 5 V. In addition, we derive the necessary formulae and a new approximate solution for the continuity equation in the 2D configuration, which have been verified against numerical solutions.

  6. All-carbon molecular tunnel junctions.

    PubMed

    Yan, Haijun; Bergren, Adam Johan; McCreery, Richard L

    2011-11-30

    This Article explores the idea of using nonmetallic contacts for molecular electronics. Metal-free, all-carbon molecular electronic junctions were fabricated by orienting a layer of organic molecules between two carbon conductors with high yield (>90%) and good reproducibility (rsd of current density at 0.5 V <30%). These all-carbon devices exhibit current density-voltage (J-V) behavior similar to those with metallic Cu top contacts. However, the all-carbon devices display enhanced stability to bias extremes and greatly improved thermal stability. Completed carbon/nitroazobenzene(NAB)/carbon junctions can sustain temperatures up to 300 °C in vacuum for 30 min and can be scanned at ±1 V for at least 1.2 × 10(9) cycles in air at 100 °C without a significant change in J-V characteristics. Furthermore, these all-carbon devices can withstand much higher voltages and current densities than can Cu-containing junctions, which fail upon oxidation and/or electromigration of the copper. The advantages of carbon contacts stem mainly from the strong covalent bonding in the disordered carbon materials, which resists electromigration or penetration into the molecular layer, and provides enhanced stability. These results highlight the significance of nonmetallic contacts for molecular electronics and the potential for integration of all-carbon molecular junctions with conventional microelectronics.

  7. Radiation comb generation with extended Josephson junctions

    SciTech Connect

    Solinas, P.; Bosisio, R.; Giazotto, F.

    2015-09-21

    We propose the implementation of a Josephson radiation comb generator based on an extended Josephson junction subject to a time dependent magnetic field. The junction critical current shows known diffraction patterns and determines the position of the critical nodes when it vanishes. When the magnetic flux passes through one of such critical nodes, the superconducting phase must undergo a π-jump to minimize the Josephson energy. Correspondingly, a voltage pulse is generated at the extremes of the junction. Under periodic driving, this allows us to produce a comb-like voltage pulses sequence. In the frequency domain, it is possible to generate up to hundreds of harmonics of the fundamental driving frequency, thus mimicking the frequency comb used in optics and metrology. We discuss several implementations through a rectangular, cylindrical, and annular junction geometries, allowing us to generate different radiation spectra and to produce an output power up to 10 pW at 50 GHz for a driving frequency of 100 MHz.

  8. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  9. Polyphosphonium-based ion bipolar junction transistors

    PubMed Central

    Gabrielsson, Erik O.; Berggren, Magnus

    2014-01-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  10. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  11. Tuberculous Spondylitis of the Craniovertebral Junction.

    PubMed

    Megaloikonomos, Panayiotis D; Igoumenou, Vasilios; Antoniadou, Thekla; Mavrogenis, Andreas F; Soultanis, Konstantinos

    2016-01-01

    Craniovertebral junction tuberculosis is rare, accounting for 0.3 to 1% of all tuberculous spondylitis cases. MR imaging is the modality of choice to detect bone involvement, abscess formation and subligamentous spreading of the pus, to differentiate from other lesions affecting the craniovertebral junction, and to determine the efficacy of treatment. Given the fact that surgical treatment of patients with craniovertebral junction tuberculosis has been associated with a high mortality rate ranging up to 10% and recurrence rate ranging up to 20%, conservative is the standard of treatment for most patients. This article presents a patient with craniovertebral junction Mycobacterium tuberculosis infection diagnosed with CT-guided biopsy. A halo vest was applied and antituberculous treatment with rifampicin, isoniazid and ethambutol was initiated. At 6-month follow-up, the patient was asymptomatic; CT of the cervical spine showed healing of the bony lesions. The halo vest was removed and physical therapy was recommended. Antituberculous treatment was continued for a total of 18 months, without any evidence of infection recurrence.

  12. Identification of Junctionally-Transmitted Growth Inhibitors

    DTIC Science & Technology

    2002-08-01

    Fig 2b. Fig 2a.. Note junctional plaques (arrows). Fig 2b Western blott of induced (left) and non- induced (right) MDA cells. Arrow indicates 43KD MW...plaques in regions of cell/cell contact (Fig 2a ) and is of the correct molecular size as shown by Western blotting (Fig 2b). We had demonstrated that

  13. Ureterocalycostomy - final resort in the management of secondary pelvi-ureteric junction obstruction: our experience.

    PubMed

    Gite, Venkat A; Siddiqui, Ayub Karam Nabi; Bote, Sachin M; Patil, Saurabh Ramesh; Kandi, Anita J; Nikose, Jayant V

    2016-01-01

    Ureterocalycostomy can be performed in patients in whom desired methods of treating secondary PUJ (Pelvi-Ureteric Junction) obstructions either failed or could not be used. In our study, one child and two adults in whom one redo-ureterocalycostomy and two ureterocalycostomies were performed for severely scarred PUJ. The causes for secondary PUJ obstruction were post-pyelolithotomy in one case, post-pyeloplasty and ureterocalycostomy for PUJ obstruction in the second patient and the third patient had long upper ureteric stricture post-ureteropyeloplasty due to tuberculosis. In all these cases ureterocalycostomy proved to be salvage/final resort for preserving functional renal unit.

  14. Measurements of the nonradiative states of optically illuminated semiconductors by a superconducting tunnel junction

    SciTech Connect

    Iguchi, I.; Kasai, Y.

    1986-08-18

    A novel technique which utilizes a superconducting tunnel junction as a phonon detector is introduced to detect nonequilibrium phonons from the nonradiative states in optically illuminated semiconductors such as Si or GaAs. The method proved to have very high sensitivity for phonon detection with a large S-italic/N-italic ratio. The detected phonon signal as a function of wavelength of the light for GaAs exhibited modulated structures below the band-gap energy consistent with the presence of an EL2 level.

  15. Observation of Thermoelectric Currents in High-Field Superconductor-Ferromagnet Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Kolenda, S.; Wolf, M. J.; Beckmann, D.

    2016-03-01

    We report on the experimental observation of spin-dependent thermoelectric currents in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of the particle-hole symmetry, and are found to be in excellent agreement with recent theoretical predictions. The maximum Seebeck coefficient inferred from the data is about -100 μ V /K , much larger than commonly found in metallic structures. Our results directly prove the coupling of spin and heat transport in high-field superconductors.

  16. Tricellular junctions: how to build junctions at the TRICkiest points of epithelial cells

    PubMed Central

    Higashi, Tomohito; Miller, Ann L.

    2017-01-01

    Tricellular contacts are the places where three cells meet. In vertebrate epithelial cells, specialized structures called tricellular tight junctions (tTJs) and tricellular adherens junctions (tAJs) have been identified. tTJs are important for the maintenance of barrier function, and disruption of tTJ proteins contributes to familial deafness. tAJs have recently been attracting the attention of mechanobiologists because these sites are hot spots of epithelial tension. Although the molecular components, regulation, and function of tTJs and tAJs, as well as of invertebrate tricellular junctions, are beginning to be characterized, many questions remain. Here we broadly cover what is known about tricellular junctions, propose a new model for tension transmission at tAJs, and discuss key open questions. PMID:28705832

  17. Single molecule junction conductance and binding geometry

    NASA Astrophysics Data System (ADS)

    Kamenetska, Maria

    This Thesis addresses the fundamental problem of controlling transport through a metal-organic interface by studying electronic and mechanical properties of single organic molecule-metal junctions. Using a Scanning Tunneling Microscope (STM) we image, probe energy-level alignment and perform STM-based break junction (BJ) measurements on molecules bound to a gold surface. Using Scanning Tunneling Microscope-based break-junction (STM-BJ) techniques, we explore the effect of binding geometry on single-molecule conductance by varying the structure of the molecules, metal-molecule binding chemistry and by applying sub-nanometer manipulation control to the junction. These experiments are performed both in ambient conditions and in ultra high vacuum (UHV) at cryogenic temperatures. First, using STM imaging and scanning tunneling spectroscopy (STS) measurements we explore binding configurations and electronic properties of an amine-terminated benzene derivative on gold. We find that details of metal-molecule binding affect energy-level alignment at the interface. Next, using the STM-BJ technique, we form and rupture metal-molecule-metal junctions ˜104 times to obtain conductance-vs-extension curves and extract most likely conductance values for each molecule. With these measurements, we demonstrated that the control of junction conductance is possible through a choice of metal-molecule binding chemistry and sub-nanometer positioning. First, we show that molecules terminated with amines, sulfides and phosphines bind selectively on gold and therefore demonstrate constant conductance levels even as the junction is elongated and the metal-molecule attachment point is modified. Such well-defined conductance is also obtained with paracyclophane molecules which bind to gold directly through the pi system. Next, we are able to create metal-molecule-metal junctions with more than one reproducible conductance signatures that can be accessed by changing junction geometry. In the

  18. Overview of the Grand Junction Office from Bluff east of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of the Grand Junction Office from Bluff east of facility. Note Buildings #35. #33 and #31A in lower left of photograph. VIEW WEST - Department of Energy, Grand Junction Office, 2597 B3/4 Road, Grand Junction, Mesa County, CO

  19. Variety of horizontal cell gap junctions in the rabbit retina.

    PubMed

    Cha, Jiook; Kim, Hong-Lim; Pan, Feng; Chun, Myung-Hoon; Massey, Stephen C; Kim, In-Beom

    2012-02-29

    In the rabbit retina, there are two types of horizontal cell (HC). The axonless A-type HCs form a coupled network via connexin 50 (Cx50) gap junctions in the outer plexiform layer (OPL). The axon-bearing B-type HCs form two independently coupled networks; the dendritic network via gap junctions consisted of unknown Cx and the axon terminal network via Cx57. The present study was conducted to examine the localization and morphological features of Cx50 and Cx57 gap junctions in rabbit HCs at cellular and subcellular levels. The results showed that each gap junction composed of Cx50 or Cx57 showed distinct features. The larger Cx50 gap junctions were located more proximally than the smaller Cx50 gap junctions. Both Cx50 plaques formed symmetrical homotypic gap junctions, but some small ones had an asymmetrical appearance, suggesting the presence of heterotypic gap junctions or hemichannels. In contrast, Cx57 gap junctions were found in the more distal part of the OPL but never on the axon terminal endings entering the rod spherules, and they were exclusively homotypic. Interestingly, about half of the Cx57 gap junctions appeared to be invaginated. These distinct features of Cx50 and Cx57 gap junctions show the variety of HC gap junctions and may provide insights into the function of different types of HCs. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  20. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided to...

  1. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided to...

  2. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided to...

  3. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided to...

  4. 30 CFR 75.602 - Trailing cable junctions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Trailing cable junctions. 75.602 Section 75.602... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Trailing Cables § 75.602 Trailing cable junctions. When two or more trailing cables junction to the same distribution center, means shall be provided to...

  5. 30 CFR 57.12007 - Junction box connection procedures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Junction box connection procedures. 57.12007... Electricity Surface and Underground § 57.12007 Junction box connection procedures. Trailing cable and power-cable connections to junction boxes shall not be made or broken under load....

  6. COEXISTENCE OF GAP AND SEPTATE JUNCTIONS IN AN INVERTEBRATE EPITHELIUM

    PubMed Central

    Hudspeth, A. J.; Revel, J. P.

    1971-01-01

    The intercellular junctions of the epithelium lining the hepatic caecum of Daphnia were examined. Electron microscope investigations involved both conventionally fixed material and tissue exposed to a lanthanum tracer of the extracellular space. Both septate junctions and gap junctions occur between the cells studied. The septate junctions lie apically and resemble those commonly discerned between cells of other invertebrates. They are atypical in that the high electron opacity of the extracellular space obscures septa in routine preparations. The gap junctions are characterized by a uniform 30 A space between apposed cell membranes. Lanthanum treatment of gap junctions reveals an array of particles of 95 A diameter and 120 A separation lying in the plane of the junction. As this pattern closely resembles that described previously in vertebrates, it appears that the gap junction is phylogenetically widespread. In view of evidence that the gap junction mediates intercellular electrotonic coupling, the assignment of a coupling role to other junctions, notably the septate junction, must be questioned wherever these junctions coexist. PMID:5563454

  7. Hormonal regulation of hepatocyte tight junctional permeability

    SciTech Connect

    Lowe, P.J.; Miyai, K.; Steinbach, J.H.; Hardison, W.G.M. Univ. of California, San Diego )

    1988-10-01

    The authors have investigated the effects of hormones on the permeability of the hepatocyte tight junction to two probes, ({sup 14}C)sucrose and horseradish peroxidase, using one-pass perfused rat livers. Using a single injection of horseradish peroxidase the authors have demonstrated that this probe can enter bile by two pathways that are kinetically distinct, a fast pathway, which corresponds to the passage of the probe through the hepatocyte tight junctions, and a slow pathway, which corresponds to the transcytotic entry into bile. The passage of horseradish peroxidase through the hepatocyte tight junctions was confirmed by electron microscopic histochemistry. Vasopressin, epinephrine, and angiotensin II, hormones that act in the hepatocyte through the intracellular mediators calcium, the inositol polyphosphates, and diacylglycerol, increased the bile-to-perfusion fluid ratio of ({sup 14}C)sucrose and the rapid entry of horseradish peroxidase into bile, indicating that the permeability of the tight junctions to these probes was increased. The effect of these hormones was dose dependent and in the cases of angiotensin II and epinephrine was inhibited by the specific inhibitors (Sar{sup 1},Thr{sup 8})angiotensin II and prazosin, respectively. Dibutyryl adenosine 3{prime},5{prime}-cyclic monophosphate did not affect the ({sup 14}C)sucrose bile-to-perfusion fluid ratio or the fast entry of horseradish peroxidase into bile. These results suggest that the hepatocyte tight junction can no longer be considered a static system of pores separating blood from bile. It is rather a dynamic barrier potentially capable of influencing the composition of the bile.

  8. Inverted Three-Junction Tandem Thermophotovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven

    2012-01-01

    An InGaAs-based three-junction (3J) tandem thermophotovoltaic (TPV) cell has been investigated to utilize more of the blackbody spectrum (from a 1,100 C general purpose heat source GPHS) efficiently. The tandem consists of three vertically stacked subcells, a 0.74-eV InGaAs cell, a 0.6- eV InGaAs cell, and a 0.55-eV InGaAs cell, as well as two interconnecting tunnel junctions. A greater than 20% TPV system efficiency was achieved by another group with a 1,040 C blackbody using a single-bandgap 0.6- eV InGaAs cell MIM (monolithic interconnected module) (30 lateral junctions) that delivered about 12 V/30 or 0.4 V/junction. It is expected that a three-bandgap tandem MIM will eventually have about 3 this voltage (1.15 V) and about half the current. A 4 A/cm2 would be generated by a single-bandgap 0.6-V InGaAs MIM, as opposed to the 2 A/cm2 available from the same spectrum when split among the three series-connected junctions in the tandem stack. This would then be about a 50% increase (3xVoc, 0.5xIsc) in output power if the proposed tandem replaced the single- bandgap MIM. The advantage of the innovation, if successful, would be a 50% increase in power conversion efficiency from radioisotope heat sources using existing thermophotovoltaics. Up to 50% more power would be generated for radioisotope GPHS deep space missions. This type of InGaAs multijunction stack could be used with terrestrial concentrator solar cells to increase efficiency from 41 to 45% or more.

  9. Graphene junction field-effect transistor

    NASA Astrophysics Data System (ADS)

    Ou, Tzu-Min; Borsa, Tomoko; van Zeghbroeck, Bart

    2014-03-01

    We have demonstrated for the first time a novel graphene transistor gated by a graphene/semiconductor junction rather than an insulating gate. The transistor operates much like a semiconductor junction Field Effect Transistor (jFET) where the depletion layer charge in the semiconductor modulates the mobile charge in the channel. The channel in our case is the graphene rather than another semiconductor layer. An increased reverse bias of the graphene/n-silicon junction increases the positive charge in the depletion region and thereby reduces the total charge in the graphene. We fabricated individual graphene/silicon junctions as well as graphene jFETs (GjFETs) on n-type (4.5x1015 cm-3) silicon with Cr/Au electrodes and 3 μm gate length. As a control device, we also fabricated back-gated graphene MOSFETs using a 90nm SiO2 on a p-type silicon substrate (1019 cm-3) . The graphene was grown by APCVD on copper foil and transferred with PMMA onto the silicon substrate. The GjFET exhibited an on-off ratio of 3.75, an intrinsic graphene doping of 1.75x1012 cm-2, compared to 1.17x1013 cm-2 in the MOSFET, and reached the Dirac point at 13.5V. Characteristics of the junctions and transistors were measured as a function of temperature and in response to light. Experimental data and a comparison with simulations will be presented.

  10. OTTER (Organized Techniques for Theorem-proving and Effective Research) 2. 0 users guide

    SciTech Connect

    McCune, W.W.

    1990-03-01

    OTTER (Organized Techniques for Theorem-proving and Effective Research) is a resolution-style theorem-proving program for first- order logic with equality. OTTER includes the inference rules binary resolution, hyperresolution, UR-resolution, and binary paramodulation. Some of its other abilities are conversion from first-order formulas to clauses, forward and back subsumption, factoring, weighting, answer literals, term ordering, forward and back demodulation, evaluable functions and predicates, and Knuth-Bendix completion. OTTER is coded in C, it is free, and it is portable to many different kinds of company. 16 refs., 2 tabs.

  11. Model building to facilitate understanding of holliday junction and heteroduplex formation, and holliday junction resolution.

    PubMed

    Selvarajah, Geeta; Selvarajah, Susila

    2016-07-08

    Students frequently expressed difficulty in understanding the molecular mechanisms involved in chromosomal recombination. Therefore, we explored alternative methods for presenting the two concepts of the double-strand break model: Holliday junction and heteroduplex formation, and Holliday junction resolution. In addition to a lecture and computer-animated video, we included a model building activity using pipe cleaners. Biotechnology undergraduates (n = 108) used the model to simulate Holliday junction and heteroduplex formation, and Holliday junction resolution. Based on student perception, an average of 12.85 and 78.35% students claimed that they completely and partially understood the two concepts, respectively. A test conducted to ascertain their understanding about the two concepts showed that 66.1% of the students provided the correct response to the three multiple choice questions. A majority of the 108 students attributed the inclusion of model building to their better understanding of Holliday junction and heteroduplex formation, and Holliday junction resolution. This underlines the importance of incorporating model building, particularly in concepts that require spatial visualization. © 2016 by The International Union of Biochemistry and Molecular Biology, 44(4):381-390, 2016.

  12. Simulations of chaos generation from Josephson junctions with various junction parameters

    NASA Astrophysics Data System (ADS)

    Hiwatashi, R.; Tamura, Y.; Shimakage, H.

    2017-07-01

    It is well known that voltage waveforms between electrodes of Josephson junctions under irradiation of a microwave behave chaos characteristics under appropriate conditions. In order to apply the chaos to a random number generator, we have been studying Josephson chaos by simulations. In the simulation, the Josephson junction is assumed to fabricate with YBCO materials. We used a RCSJ model in order to present an equivalent circuit of the Josephson junction, and derived a derivative equation. Lyapunov exponents, which determined if the state of the Josephson junction was chaotic or not, were calculated from time evolutions of voltages obtained from the equation. In the simulation, junction parameters were assigned feasible values for an actual YBCO Josephson junctions. As a result, we found that chaos can be generated by adjusting element parameters. Moreover, we found that there were lower limits in the resistance values for generation of chaos. In addition, we found that frequency margins, at which the chaos was obtained, were broadened by decrease of the resistance and increase of capacitance.

  13. Myosin-dependent remodeling of adherens junctions protects junctions from Snail-dependent disassembly

    PubMed Central

    Weng, Mo

    2016-01-01

    Although Snail is essential for disassembly of adherens junctions during epithelial–mesenchymal transitions (EMTs), loss of adherens junctions in Drosophila melanogaster gastrula is delayed until mesoderm is internalized, despite the early expression of Snail in that primordium. By combining live imaging and quantitative image analysis, we track the behavior of E-cadherin–rich junction clusters, demonstrating that in the early stages of gastrulation most subapical clusters in mesoderm not only persist, but move apically and enhance in density and total intensity. All three phenomena depend on myosin II and are temporally correlated with the pulses of actomyosin accumulation that drive initial cell shape changes during gastrulation. When contractile myosin is absent, the normal Snail expression in mesoderm, or ectopic Snail expression in ectoderm, is sufficient to drive early disassembly of junctions. In both cases, junctional disassembly can be blocked by simultaneous induction of myosin contractility. Our findings provide in vivo evidence for mechanosensitivity of cell–cell junctions and imply that myosin-mediated tension can prevent Snail-driven EMT. PMID:26754645

  14. SU-E-T-815: In Vivo Dosimetry and Daily Arc Junction Verification Using EBT3 Gafchromic Film for Pediatric Cranio-Spinal Irradiation

    SciTech Connect

    Saleh, H; Ferjani, S; Masssey, V; Howlin, T; Pokhrel, D

    2015-06-15

    Purpose: Perform dosimetric comparison between planned and delivered dose in the junction area, measure daily dose variation in the arc junction area for pediatric patients treated for medulloblastoma using Craniospinal axis irradiation(CSI) Material and methods Dose comparison in the junction area, daily dose variation in the arc junction area for a Rando Phantom and 5 pediatric patients treated using CSI technique were analyzed. Plans were created using the Eclipse treatment planning system. Two arcs for cranium and 1 arc for spine region were used. Planar dose matrix was created by projecting phantom and patient plan into the ArcCheck phantom. EBT3 film was placed in the middle of ArcCheck plug to measure dose distribution in the junction areaDuring patient treatment, strip of EBT3 film was placed daily at each junction area for verification. EBT3 films were scanned using a flatbed scanner, Epson Expression 10000 XL. Film QA pro software was used to analyze film. Scanning and analysis was performed according to vendor recommendations and AAPM TG-55 report. Films were scanned and analyzed daily after each treatment and at the end of treatment course. Planar dose distributions from films were compared with planar dose distribution from treatment planning system. Results: Comparison of planned vs. measured dose distributions for patients have passing rates of 90%–100% with 3% and 3 mm gamma analysis. In some of the treatment fractions, daily setup film showed variation in dose distribution in the junction area. Conclusion: It is critical to measure dose distribution in the arc junction area and use additional quality assurance measures to verify daily setup for CSI patient where one or more junctions are present. EBT3 film prove to be a good tool to achieve this task considering flexibility associated with the film such as symmetry, self-developing and ease of use.

  15. Enhancing an Intellectual Need for Defining and Proving: A Case of Impossible Objects

    ERIC Educational Resources Information Center

    Koichu, Boris

    2012-01-01

    Identifying mathematical and didactical conditions under which mathematics learners can encounter an intellectual need for defining and proving is recognized as a challenging research enterprise. This paper presents a particular configuration of conditions under which a group of pre-service mathematics teachers successfully constructed a…

  16. 20 CFR 219.21 - Types of evidence to prove age.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Preferred evidence. The best type of evidence to prove a claimant's age is— (1) A birth certificate recorded before age 5; (2) A church record of birth or baptism recorded before age 5; or (3) Notification of registration of birth made before age 5. (b) Other evidence of age. If an individual cannot obtain preferred...

  17. 20 CFR 219.21 - Types of evidence to prove age.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...) Preferred evidence. The best type of evidence to prove a claimant's age is— (1) A birth certificate recorded before age 5; (2) A church record of birth or baptism recorded before age 5; or (3) Notification of registration of birth made before age 5. (b) Other evidence of age. If an individual cannot obtain preferred...

  18. Proof and Proving: Logic, Impasses, and the Relationship to Problem Solving

    ERIC Educational Resources Information Center

    Savic, Milos

    2012-01-01

    Becoming a skillful prover is critical for success in advanced undergraduate and graduate mathematics courses. In this dissertation, I report my investigations of proof and the proving process in three separate studies. In the first study, I examined the amount of logic used in student-constructed proofs to help in the design of…

  19. Mathematical Understanding and Proving Abilities: Experiment with Undergraduate Student by Using Modified Moore Learning Approach

    ERIC Educational Resources Information Center

    Maya, Rippi; Sumarmo, Utari

    2011-01-01

    This paper reports findings of a post test experimental control group design conducted to investigate the role of modified Moore learning approach on improving students' mathematical understanding and proving abilities. Subjects of study were 56 undergraduate students of one state university in Bandung, who took advanced abstract algebra course.…

  20. 33 CFR 334.140 - Chesapeake Bay; U.S. Army Proving Ground Reservation, Aberdeen, Md.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., the patrol boat may operate a distinctive rotating blue and red light, public address system, sound a..., eel pot, crab pot, and all other types of nets fastened by means of poles, stakes, weights, or anchors. Permits to fish and crab within the restricted waters of Aberdeen Proving Ground may be obtained...