3,751 research outputs found

    Weakly coupled two slow- two fast systems, folded node and mixed mode oscillationsM

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    We study Mixed Mode Oscillations (MMOs) in systems of two weakly coupled slow/fast oscillators. We focus on the existence and properties of a folded singularity called FSN II that allows the emergence of MMOs in the presence of a suitable global return mechanism. As FSN II corresponds to a transcritical bifurcation for a desingularized reduced system, we prove that, under certain non-degeneracy conditions, such a transcritical bifurcation exists. We then apply this result to the case of two coupled systems of FitzHugh- Nagumo type. This leads to a non trivial condition on the coupling that enables the existence of MMOs

    Urban stream management: interdisciplinary assessment of the Ship Creek fishery

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2009The Lower Ship Creek Fishery in the city of Anchorage, Alaska is one of the state's most popular sport fisheries. After years of channelization and development, this social-ecological system (SES) continues to experience the effects of urbanization and is struggling to achieve robustness. I applied a robustness framework to the management of management this fishery because of its semi-engineered nature. This framework uses interdisciplinary methods to study the interrelationships between the fishery's socio-economic and ecological components. Robustness is more appropriate than resilience as an analytical framework because of the relative insensitivity of the engineered components to ecological feedbacks. On Lower Ship Creek, the engineered hatchery fish continue to thrive despite declining stream conditions. The robustness of this fishery contributes to the resilience of the city by increasing local food and recreation options and supporting a diverse set of businesses. To study the robustness of this SES in the context of the resilience of Anchorage, I first combined historical photos and existing Ship Creek data with research conducted on other streams to create an environmental history of the creek. This history then was used to describe how eras of urban development have altered the creek's ecosystem processes and created new ecological constraints related to 1) loss of wetlands and riparian vegetation; 2) erosion, pollution, and channelization; 3) loss of fish species; and 4) flow alteration and habitat loss. Using Lovecraft's (2008) typology, I proposed four plausible management scenarios that highlight the trade-offs associated with management of this fishery: 1) Ship Creek Redesign, 2) Mitigation, Construction, and Maintenance, 3) KAPP Dam Removal, and 4) Business as Usual. The second of these scenarios is most consistent with the current ecological constraints, the characteristics preferred by most stakeholders, and current socio-economic trends. Since Scenario 2 will require a large monetary investment, I examined this SES's cost structure and compared it with previously published analyses of the economic benefits of the fishery. By quantifying the costs borne by each agency, I showed how externalities produce intra- and inter-agency tension. These data were used to construct a new cost-sharing framework that provides decision makers with an economic incentive to work more cooperatively in the future. I then explored the interrelationship of the SES's socioeconomic and ecological subsystems, using Anderies et al.'s (2004) framework. I applied Ostrom's design principles (1990) to sport fisheries to explore the reasons why agencies have not cooperated to produce a more robust fishery. This SES fails to meet three of the design principles: it lacks 1) an equal proportion of benefits and costs, 2) collective-choice arrangements, and 3) user and biophysical monitoring. I then suggest how to improve the design and increase the robustness of this SES. This study proposes that the maintenance of semi-engineered systems is important both for local users and for the resilience of states and countries. In the context of global trends toward increasing urbanization, this study provides an interdisciplinary approach to increasing the robustness of urban streams and building resilience within states and countries

    Application and use of spinal immobilization devices in zero-gravity flight

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    A KC-135 parabolic flight was performed for the purpose of evaluation of spinal immobilization techniques in microgravity. The flight followed the standard 40 parabola profile with four NASA/KRUG experimenters involved. One performed as coordinator/recorder, one as test subject, and two as the Crew Medical Officers (CMO). The flight was to evaluate the application of spinal immobilization devices and techniques in microgravity as are performed during initial stabilization or patient transport scenarios. The sequence of detail for examination of the following objectives included: attempted cervical spine immobilization with all free floating, the patient restrained to the floor, various hand positioning techniques; c-collar placement; Kendrick Extrication Device (KED) application with various restraints for patient and CMO; patient immobilization and transport using the KED; patient transported on KED and spine board. Observations for each task are included. Major conclusions and issues are also included

    SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component

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    The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a complementary tool to SN Ia. Reliable use of Mg II requires a good understanding of all the systematic effects involved in the measurement of the line properties, including the contamination by Fe II UV emission. We performed three spectroscopic observations of a quasar LBQS 2113-4538 (z = 0.956) with the SALT telescope separated in time by several months and we analyze in detail the mean spectrum and the variability in the spectral shape. We show that even in our good-quality spectra the Mg II doublet is well fit by a single Lorentzian shape. We tested several models of the Fe II pseudo-continuum and showed that one of them well represents all the data. The amplitudes of both components vary in time, but the shapes do not change significantly. The measured line width of LBQS 2113-4538 identifies this object as a class A quasar. The upper limit of 3%3\% for the contribution of the Narrow Line Region (NLR) to Mg II may suggest that the separation of the Broad Line Region (BLR) and NLR disappears in this class of objects.Comment: 10 pages, 8 figures, accepted to A&

    Maternal and perinatal outcome in cardiac disease complicating pregnancy

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    Background: Maternal cardiac disease associated with pregnancy is considered as a high-risk pregnancy. Various physiological and hemodynamic alterations during the course of pregnancy make these women prone for various complications and related morbidity and mortality.Methods: A prospective cross-sectional study of 105 cases of pregnancy complicated by cardiac disease, reporting to tertiary care hospital for delivery, was carried out to find out the maternal and perinatal outcome.Results: The incidence of cardiac disease in pregnancy in the present study was 0.54%. Most of the women (91%) belonged to low socioeconomic class. Rheumatic heart lesions constituted 87% of the cases. Mitral stenosis alone or in combination, was the commonest (57%) valvular lesion. Incidence of spontaneous vaginal delivery was 53 percent and for ventose or outlet forceps was 12 percent. Incidence of caesarean section was 35%. There were 2 maternal deaths, one each due to complication like pulmonary oedema and atrial fibrillation. The perinatal mortality was 36 per 1000 live births, mainly due to combination of factors like prematurity, low birth weight, neonatal sepsis and birth asphyxia.Conclusions: Early diagnosis of heart disease, regular antenatal checkup, institutional delivery, limiting family size can reduce the maternal and perinatal mortality and morbidity associated with heart disease

    The mass of the black hole in RE J1034+396

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    The black hole mass measurement in active galaxies is a challenge, particularly in sources where the reverberation method cannot be applied. We aim to determine the black hole mass in a very special object, RE J1034+396, one of the two AGN with QPO oscillations detected in X-rays, and a single bright AGN with optical band totally dominated by starlight. We fit the stellar content using the code starlight, and the broad band disk contribution to optical/UV/X-ray emission is modeled with optxagnf. We also determine the black hole mass using several other independent methods. Various methods give contradictory results. Most measurements of the blacc hole mass are in the range 1.e6-1.e7 Msun, and the measurements based on dynamics give higher values than measurements based on Hbeta and Mg II emission lines.Comment: A&A, in pres

    Role of Protein Kinase C in TBT-Induced Inhibition of Lytic Function and MAPK Activation in Human Natural Killer Cells

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    Human natural killer (NK) cells are lymphocytes that destroy tumor and virally infected cells. Previous studies have shown that exposure of NK cells to tributyltin (TBT) greatly diminishes their ability to destroy tumor cells (lytic function) while activating mitogen-activated protein kinases (MAPK) (p44/42, p38, and JNK) in NK cells. The signaling pathway that regulates NK lytic function appears to include activation of protein kinase C (PKC) as well as MAPK activity. TBT-induced activation of MAPKs would trigger a portion of the NK lytic signaling pathway, which would then leave the NK cell unable to trigger this pathway in response to a subsequent encounter with a target cell. In the present study we evaluated the involvement of PKC in inhibition of NK lysis of tumor cells and activation of MAPKs caused by TBT exposure. TBT caused a 2–3-fold activation of PKC at concentrations ranging from 50 to 300 nM (16–98 ng/ml), indicating that activation of PKC occurs in response to TBT exposure. This would then leave the NK cell unable to respond to targets. Treatment with the PKC inhibitor, bisindolylmaleimide I, caused an 85% decrease in the ability of NK cells to lyse tumor cells, validating the involvement of PKC in the lytic signaling pathway. The role of PKC in the activation of MAPKs by TBT was also investigated using bisindolylmaleimide I. The results indicated that, in NK cells where PKC activation was blocked, there was no activation of the MAPK, p44/42 in response to TBT. However, TBT-induced activation of the MAPKs, p38 and JNK did not require PKC activation. These results indicate the pivotal role of PKC in the TBT-induced loss of NK lytic function including activation of p44/42 by TBT in NK cells

    Pramlintide, the synthetic analogue of amylin: physiology, pathophysiology, and effects on glycemic control, body weight, and selected biomarkers of vascular risk

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    Pramlintide is a synthetic version of the naturally occurring pancreatic peptide called amylin. Amylin and pramlintide have similar effects on lowering postprandial glucose, lowering postprandial glucagon and delaying gastric emptying. Pramlintide use in type 1 and insulin requiring type 2 diabetes mellitus (DM) is associated with modest reductions in HbA1c often accompanied by weight loss. Limited data show a neutral effect on blood pressure. Small studies suggest small reductions in LDL-cholesterol in type 2 DM and modest reductions in triglycerides in type 1 DM. Markers of oxidation are also reduced in conjunction with reductions in postprandial glucose. Nausea is the most common side effect. These data indicate that pramlintide has a role in glycemic control of both type 1 and type 2 DM. Pramlintide use is associated with favorable effects on weight, lipids and other biomarkers for atherosclerotic disease