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Sample records for plasma thrombin generation

  1. Inhibition of thrombin generation in plasma by fibrin formation (Antithrombin I).

    PubMed

    de Bosch, N B; Mosesson, M W; Ruiz-Sáez, A; Echenagucia, M; Rodriguez-Lemoin, A

    2002-08-01

    The adsorption of thrombin to fibrin during clotting defines "Antithrombin I" activity. We confirmed that thrombin generation in afibrinogenemic or in Reptilase defibrinated normal plasma was higher than in normal plasma. Repletion of these fibrinogen-deficient plasmas with fibrinogen 1 (gamma A/gamma A), whose fibrin has two "low affinity" non-substrate thrombin binding sites, resulted in moderately reduced thrombin generation by 29-37%. Repletion with fibrinogen 2 (gamma'/gamma A), which in addition to low affinity thrombin-binding sites in fibrin, has a "high affinity" non-substrate thrombin binding site in the carboxy-terminal region of its gamma' chain, was even more effective and reduced thrombin generation by 57-67%. Adding peptides that compete for thrombin binding to fibrin [S-Hir53-64 (hirugen) or gamma'414-427] caused a transient delay in the onset of otherwise robust thrombin generation, indicating that fibrin formation is necessary for full expression of Antithrombin I activity. Considered together, 1) the increased thrombin generation in afibrinogenemic or fibrinogen-depleted normal plasma that is mitigated by fibrinogen replacement; 2) evidence that prothrombin activation is increased in afibrinogenemia and normalized by fibrinogen replacement; 3) the severe thrombophilia that is associated with defective thrombin-binding in dysfibrinogenemias Naples I and New York I, and 4) the association of afibrinogenemia or hypofibrinogenemia with venous or arterial thromboembolism, indicate that Antithrombin I (fibrin) modulates thromboembolic potential by inhibiting thrombin generation in blood.

  2. Clotting factor VIII (FVIII) and thrombin generation in camel plasma: A comparative study with humans

    PubMed Central

    Abdel Gader, Abdel Galil M.; Al Momen, Abdul Karim M.; Alhaider, Abdulqader; Brooks, Marjory B.; Catalfamo, James L.; Al Haidary, Ahmed A.; Hussain, Mansour F.

    2013-01-01

    The objective of this study was to characterize the highly elevated levels of clotting factor VIII (FVIII) in camel plasma. Whole blood was collected from healthy camels and factor VIII clotting activity (FVIII:C) assays were conducted using both the clotting and the chromogenic techniques. The anticoagulant citrate phosphate dextrose adenine (CPDA) produced the highest harvest of FVIII:C, the level of plasma factor VIII, compared to heparin:saline and heparin:CPDA anticoagulants. Camel FVIII can be concentrated 2 to 3 times in cryoprecipitate. There was a significant loss of camel FVIII when comparing levels of FVIII in camel plasma after 1 h of incubation at 37°C (533%), 40°C (364%), and 50°C (223%). Thrombin generation of camel plasma is comparable to that of human plasma. It was concluded that camel plasma contains very elevated levels of FVIII:C, approaching 8 times the levels in human plasma, and that these elevated levels could not be attributed to excessive thrombin generation. Unlike human FVIII:C, camel FVIII:C is remarkably heat stable. Taken together, these unique features of camel FVIII could be part of the physiological adaptation of hemostasis of the Arabian camel in order to survive in the hot desert environment. PMID:24082408

  3. Plasma factor and inhibitor composition contributes to thrombin generation dynamics in patients with acute or previous cerebrovascular events

    PubMed Central

    Gissel, Matthew; Undas, Anetta; Slowik, Agnieszka; Mann, Kenneth G.; Brummel-Ziedins, Kathleen E.

    2010-01-01

    Introduction More than 80% of cerebrovascular events are ischemic and largely thromboembolic by nature. We evaluated whether plasma factor composition and thrombin generation dynamics might be a contributor to the thrombotic phenotype of ischemic cerebrovascular events. Materials and Methods We studied (1) 100 patients with acute ischemic stroke (n=50) or transient ischemic attack (TIA) (n=50) within the first 24 hours from symptom onset, and (2) 100 individuals 1 to 4 years following ischemic stroke (n=50) or TIA (n=50). The tissue factor pathway to thrombin generation was simulated with a mathematical model using plasma levels of clotting factors (F)II, V, VII, VIII, IX, X, antithrombin and free tissue factor pathway inhibitor (TFPI). Results The plasma levels of free TFPI, FII, FVIII, and FX were higher, while antithrombin was lower, in the acute patients compared to the previous event group (all p≤0.02). Thrombin generation during acute events was enhanced, with an 11% faster maximum rate, a 15% higher maximum level and a 26% larger total production (all p<0.01). The increased thrombin generation in acute patients was determined by higher FII and lower antithrombin, while increased free TFPI mediated this effect. When the groups are classified by etiology, all stroke sub-types except cardioembolic have increased TFPI and decreased AT and total thrombin produced. Conclusion Augmented thrombin generation in acute stroke/TIA is to some extent determined by altered plasma levels of coagulation factors. PMID:20709367

  4. Plasma Thrombin Generation and Sensitivity to Activated Protein C Among Patients With Myeloma and Monoclonal Gammopathy of Undetermined Significance.

    PubMed

    Crowley, Maeve P; Kevane, Barry; O'Shea, Susan I; Quinn, Shane; Egan, Karl; Gilligan, Oonagh M; Ní Áinle, Fionnuala

    2016-09-01

    The etiology of the prothrombotic state in myeloma has yet to be definitively characterized. Similarly, while recent evidence suggests that patients with monoclonal gammopathy of undetermined significance (MGUS) may also be at increased risk of thrombosis, the magnitude and the etiology of this risk have also yet to be defined. The present study aims to characterize patterns of plasma thrombin generation and sensitivity to the anticoagulant activity of activated protein C (APC) at the time of initial diagnosis of myeloma and in response to therapy in comparison to that observed among patients with MGUS and matched, healthy volunteers. Patients presenting with newly diagnosed/newly relapsed myeloma (n = 8), MGUS (n = 8), and matched healthy volunteers (n = 8) were recruited. Plasma thrombin generation was determined by calibrated automated thrombography. Peak thrombin generation was significantly higher in patients with myeloma (383.4 ± 33.4 nmol/L) and MGUS (353.4 ± 16.5 nmol/L) compared to healthy volunteers (276.7 ± 20.8 nmol/L; P < .05). In the presence of APC, endogenous thrombin potential was significantly lower in control plasma (228.6 ± 44.5 nmol/L × min) than in either myeloma (866.2 ± 241.3 nmol/L × min, P = .01) or MGUS plasma (627 ± 91.5 nmol/L × min, P = .003). Within the myeloma cohort, peak thrombin generation was significantly higher at diagnosis (353.2 ± 15.9 nmol/L) than following completion of the third cycle of therapy (282.1 ± 15.2 nmol/L; P < .005). Moreover, sensitivity to APC increased progressively with each cycle of chemotherapy. Further study of the etiology and evolving patterns of hypercoagulability among patients with these conditions is warranted and may have future implications for thromboprophylaxis strategies.

  5. Thrombin Generation in Acute Ischaemic Stroke

    PubMed Central

    Roberts, Lara N.; Patel, Raj; Pathansali, Rohan; Kalra, Lalit; Arya, Roopen

    2016-01-01

    Introduction. Stroke remains a global leading cause of death and disability. Traditional description of plasma biology in the aftermath of acute ischaemic stroke favours development of hypercoagulability, resulting from complex interplay between plasma and endothelial factors. However, no single assay measures the overall global coagulation process. We postulate that thrombin generation would assist in identifying coagulation abnormalities after acute stroke. Aim. To investigate the coagulation abnormalities after acute ischaemic stroke using thrombin generation. Methods. We evaluated thrombin generation, measured with calibrated automated thrombography in stroke of different aetiological types (n = 170) within 48 hours of symptoms onset (baseline) and in the second week (time 2) and in normal healthy volunteers (n = 71). Results. Two-point thrombin generation assays showed prolonged lag time and time to peak at baseline (3.3 (2.9, 4.0) versus 3.6 (3.2, 4.7); p = 0.005) and (3.3 (2.9, 4.0) versus 3.6 (3.2, 4.7); p = 0.002), respectively, and at time 2 (3.5 (2.9, 4.2) versus 4.0 (3.1, 4.9); p = 0.004) and (5.9 (5.3, 6.6) versus 6.8 (5.8, 7.7) p = 0.05), respectively, in cardioembolic stroke (n = 39), when compared to noncardioembolic stroke (n = 117). The result was reproduced in multiple comparisons between acute ischaemic stroke subgroups and normal healthy volunteers. Endogenous thrombin potential and peak thrombin did not indicate hypercoagulability after acute ischaemic stroke, and thrombolytic therapy did not affect thrombin generation assays. Conclusion. Our findings suggest that thrombin generation in platelet poor plasma is not useful in defining hypercoagulability in acute ischaemic stroke. This is similar to observed trend in coronary artery disease and contrary to other hypercoagulable states. PMID:28116215

  6. Thrombin generation in clinical conditions.

    PubMed

    Ten Cate, Hugo

    2012-03-01

    Commercial assays for determining thrombin generation in plasma are being tested in clinical conditions associated with thrombosis or bleeding. While pre-analytical conditions remain a source of inter laboratory variation, demanding for further standardization, clinical research proceeds. In patients at risk of venous thrombosis thrombin generation (TG) analysis may be utilized to detect underlying thrombophilia and this has been achieved both with addition of thrombomodulin or activated protein C, to test the contribution of the protein C system. In patients with documented venous thromboembolism, increased TG values are seen in those patients at greatest risk for recurrence, although the data are not consistent yet. In patients with arterial vascular disease, effects on TG patterns are seen that both reflect atherosclerosis (and its risk factors) and link to risk of recurrent atherothrombosis (coronary or stroke), but the data are limited. In patients with a bleeding diathesis, like hemophilia, the main importance of TG assays lies in the application for monitoring replacement therapy, either with factor concentrate or rFVIIa. An interesting application is in conjunction with thromboelastography, for monitoring peri-operative transfusion policy. Finally, TG analysis may contribute to monitoring anticoagulant drug treatment, but these and other applications would greatly benefit from whole blood, point of care applications of TG testing.

  7. Thrombin Generation in Zebrafish Blood

    PubMed Central

    Hemker, Coenraad; Lindhout, Theo; Kelchtermans, Hilde; de Laat, Bas

    2016-01-01

    To better understand hypercoagulability as an underlying cause for thrombosis, the leading cause of death in the Western world, new assays to study ex vivo coagulation are essential. The zebrafish is generally accepted as a good model for human hemostasis and thrombosis, as the hemostatic system proved to be similar to that in man. Their small size however, has been a hurdle for more widespread use in hemostasis related research. In this study we developed a method that enables the measurement of thrombin generation in a single drop of non-anticoagulated zebrafish blood. Pre-treatment of the fish with inhibitors of FXa and thrombin, resulted in a dose dependent diminishing of thrombin generation, demonstrating the validity of the assay. In order to establish the relationship between whole blood thrombin generation and fibrin formation, we visualized the resulting fibrin network by scanning electron microscopy. Taken together, in this study we developed a fast and reliable method to measure thrombin generation in whole blood collected from a single zebrafish. Given the similarities between coagulation pathways of zebrafish and mammals, zebrafish may be an ideal animal model to determine the effect of novel therapeutics on thrombin generation. Additionally, because of the ease with which gene functions can be silenced, zebrafish may serve as a model organism for mechanistical research in thrombosis and hemostasis. PMID:26872266

  8. [Thrombin generation assays and their clinical application].

    PubMed

    Kern, Anita; Várnai, Katalin; Vásárhelyi, Barna

    2014-06-01

    Thrombin is a key enzyme of the coagulation system, having both pro- and anticoagulant functions. Thus, the generation of thrombin is one of the most important steps in coagulation. Global haemostasis assay, the so-called thrombin generation test is appropriate for its assessment. Since thrombin generation is sensible for both pro- and anticoagulant processes it can be applied for the general characterisation of the risk of thrombosis and bleeding, too. Clinical studies confirmed augmented thrombin generation in patients with high risk of venous or arterial thrombosis. Anticoagulant therapy (also novel oral anticoagulant treatment) can be monitored by thrombin generation. In case of haemophilia thrombin generation assays reflect bleeding severity. It is applicable for monitoring of both conventional haemophilia treatment and inhibitor-bypassing therapy, which is needed when inhibitors develop in patients. Standardization of thrombin generation methods and determination of cut off values are required before its application in clinical practice.

  9. Differential Contributions of Intrinsic and Extrinsic Pathways to Thrombin Generation in Adult, Maternal and Cord Plasma Samples

    PubMed Central

    Rice, Nicklaus T.; Szlam, Fania; Varner, Jeffrey D.; Bernstein, Peter S.; Szlam, Arthur D.; Tanaka, Kenichi A.

    2016-01-01

    Background Thrombin generation (TG) is a pivotal process in achieving hemostasis. Coagulation profiles during pregnancy and early neonatal period are different from that of normal (non-pregnant) adults. In this ex vivo study, the differences in TG in maternal and cord plasma relative to normal adult plasma were studied. Methods Twenty consented pregnant women and ten consented healthy adults were included in the study. Maternal and cord blood samples were collected at the time of delivery. Platelet-poor plasma was isolated for the measurement of TG. In some samples, anti-FIXa aptamer, RB006, or a TFPI inhibitor, BAX499 were added to elucidate the contribution of intrinsic and extrinsic pathway to TG. Additionally, procoagulant and inhibitor levels were measured in maternal and cord plasma, and these values were used to mathematically simulate TG. Results Peak TG was increased in maternal plasma (393.6±57.9 nM) compared to adult and cord samples (323.2±38.9 nM and 209.9±29.5 nM, respectively). Inhibitory effects of RB006 on TG were less robust in maternal or cord plasma (52% vs. 12% respectively) than in adult plasma (81%). Likewise the effectiveness of BAX499 as represented by the increase in peak TG was much greater in adult (21%) than in maternal (10%) or cord plasma (12%). Further, BAX499 was more effective in reversing RB006 in adult plasma than in maternal or cord plasma. Ex vivo data were reproducible with the results of the mathematical simulation of TG. Conclusion Normal parturient plasma shows a large intrinsic pathway reserve for TG compared to adult and cord plasma, while TG in cord plasma is sustained by extrinsic pathway, and low levels of TFPI and AT. PMID:27196067

  10. Comparison of the effect of fondaparinux and enoxaparin on thrombin generation during in-vitro clotting of whole blood and platelet-rich plasma.

    PubMed

    Gerotziafas, Grigoris T; Depasse, François; Chakroun, Tahar; Van Dreden, Patrick; Samama, Meyer M; Elalamy, Ismail

    2004-03-01

    Fondaparinux, a selective antithrombin-dependent inhibitor of activated factor X (FXa), is effective in the prevention and treatment of deep vein thrombosis and seems to be superior to enoxaparin. However, the exact mechanism of fondaparinux antithrombotic action is still unclear. We compared the effect of clinically relevant concentrations of fondaparinux and enoxaparin on the initiation and propagation phase of prothrombin activation and on the endogenous thrombin potential (ETP). Coagulation was triggered either in whole blood or in platelet-rich plasma (PRP) by recalcification in the presence of diluted thromboplastin. Prothrombin activation in whole blood was assessed with an original method by measuring the kinetics of prothrombin F1+2 formation using an enzyme-linked immunosorbent assay. We also assessed the maximum concentration of thrombin (Cmax) and the ETP in PRP using the Thrombogram-Thrombinoscope assay. Concentrations of fondaparinux achieved in prophylaxis (0.11-0.28 anti-FXa IU/ml) prolonged the initiation phase and reduced the velocity of the propagation phase of F1+2 formation. Concentrations of enoxaparin achieved in prophylaxis (0.1-0.25 anti-FXa IU/ml) did not significantly modify these parameters. Concentrations of fondaparinux equal to or higher than 0.57 anti-FXa IU/ml significantly reduced the Cmax of F1+2 or thrombin as well as the ETP. At fondaparinux concentrations equal to or higher than 0.91 anti-FXa IU/ml, a maximum 60% inhibition of thrombin generation was observed. In the presence of enoxaparin concentrations equal to or higher than 0.8 anti-FXa IU/ml, the inhibition of thrombin generation was higher than 80%. Fondaparinux prolonged the initiation phase, decreased the velocity of the propagation phase of thrombin generation and partially reduced the total amount of generated thrombin. The inhibitory effect of fondaparinux on the initiation and propagation phase of thrombin generation seems to be responsible for its antithrombotic

  11. Thrombin Generation in the Glasgow Myocardial Infarction Study

    PubMed Central

    Smid, Machiel; Dielis, Arne W. J. H.; Spronk, Henri M. H.; Rumley, Ann; van Oerle, Rene; Woodward, Mark; ten Cate, Hugo; Lowe, Gordon

    2013-01-01

    Background Thrombin is a key protease in coagulation also implicated in complex pathology including atherosclerosis. To address the role of thrombin in relation to myocardial infarction (MI) we explored thrombin generation analysis in plasma from patients and controls that had participated in the Glasgow MI Study (GLAMIS). Methods Thrombin generation at 1 and 2 pM TF and with and without thrombomodulin (TM) was performed on plasmas from 356 subjects (171 cases, 185 age and sex matched controls) from GLAMIS collected between 3 and 9 months after the MI event. Results Although thrombin generation was slightly delayed in cases (lag time increased from 3.3 to 3.6 min) at the highest trigger, the overall potential to generate thrombin was increased by 7% for the ETP and by 15% for the peak height (both at the 1 pM TF trigger) in cases. Addition of TM did not reveal differences. Furthermore, an increased thrombin generation was associated with MI [normalized ETP: adjusted OR for the highest percentile = 2.4 (95% CI 1.3–4.5) and normalized peak height: adjusted OR = 2.6 (1.3–5.0)] at the lowest trigger; normalized ETP and peak height being 2.1 (1.1–3.8) and 2.0 (1.0–4.1) at the higher 2 pM trigger. Conclusion In GLAMIS, patients with a previous MI had an increased thrombin generation compared to controls. The absence of a clear difference in TM reduction suggests an unaltered anticoagulant activity in these patients. Further research is needed in order to unravel the underlying mechanisms of enhanced thrombin generation after MI. PMID:23826181

  12. Thrombin generation in patients after acute deep-vein thrombosis.

    PubMed

    ten Cate-Hoek, Arina J; Dielis, Arne W J H; Spronk, Henri M H; van Oerle, René; Hamulyák, Karly; Prins, Martin H; ten Cate, Hugo

    2008-08-01

    Thrombin generation measurement may be of value for assessing the risk of venous thromboembolism, but its long term profile has not been assessed in patients. We evaluated thrombin generation by Calibrated Automated Thrombogram (CAT) in plasma during follow up of 104 consecutive patients after an acute episode of deep venous thrombosis. Blood was drawn three times over the course of 24 months. Thrombin generation was measured in absence and presence of thrombomodulin and compared to a reference range derived from thrombin generation curves in 137 healthy volunteers. Thrombin generation of patients showed significantly higher endogenous thrombin potential (ETP) and peak height compared to the reference population. Differences were more pronounced in assays triggered with 1 pM TF. Inhibition by thrombomodulin was attenuated in patients off anticoagulants as compared to the reference population (21% vs. 42.2%, p < 0.0001); inhibition in patients on anticoagulant treatment was less pronounced (9.7%, p < 0.0001). Protein C activity, protein S antigen as well as free protein S showed highly negative correlation with ETP in all patients. A significant negative relation was found between FVIII levels and thrombomodulin induced reduction of ETP and peak height. In conclusion, thrombin generation by CAT reflects changes in coagulation status in patients following a thromboembolic event and is most sensitive at CAT analysis triggered with 1 pM TF. A role for factor VIII as an important attributable cause of hypercoagulability is reflected by the reduced inhibitory effect of thrombomodulin at high factor VIII levels.

  13. Thrombin generation testing for monitoring hemophilia treatment: a clinical perspective.

    PubMed

    Salvagno, Gian Luca; Berntorp, Erik

    2010-10-01

    Thrombin generation is a key process that determines the extent of a hemostatic plug or a thrombotic process. The ensuing thrombin burst is crucial for the formation of a stable fibrin clot. During its active life, thrombin exerts a multitude of highly regulated actions on the blood and the vessel wall, among which is the clotting of fibrinogen. The inappropriate generation of thrombin may lead to pathological processes, foremost of which are hemorrhagic or thrombotic diseases. The coagulation system is usually investigated by means of two in vitro classical clotting tests, the activated partial thromboplastin time and prothrombin time. These assays assess only the time taken to form a clot and do not entirely reflect global hemostatic balance. They permit identification of connectivity between the component activities identified as required for plasma coagulation and define the concept of intrinsic and extrinsic coagulation pathways, which converge at the step of formation of the prothrombinase complex. However, the mechanisms established by in vitro tests are not always mirrored in the human pathologies associated with bleeding or thrombosis. The recent development of newer tests based on the continuous registration of thrombin generation (TG) under in vitro conditions that mimic more closely what occurs in vivo prompted us to reinvestigate the balance between procoagulants and anticoagulants in patients. Thrombin generation assays (TGA) not only provide an overall assessment of hemostasis, but they also target potential extrahemostatic effects of the generated thrombin, a potent agonist of a multitude of cellular activation pathways. Moreover, estimation of an individual's thrombin generation potential may correlate more closely with a hyper- or hypocoagulable phenotype, compared with traditional coagulation tests. In this review, we discuss to what extent TG can be expected to reflect the clotting function of blood, the development and use of different TGA

  14. Mechanistic Modeling of the Effects of Acidosis on Thrombin Generation

    PubMed Central

    Mitrophanov, Alexander Y.; Rosendaal, Frits R.

    2015-01-01

    BACKGROUND: Acidosis, a frequent complication of trauma and complex surgery, results from tissue hypoperfusion and IV resuscitation with acidic fluids. While acidosis is known to inhibit the function of distinct enzymatic reactions, its cumulative effect on the blood coagulation system is not fully understood. Here, we use computational modeling to test the hypothesis that acidosis delays and reduces the amount of thrombin generation in human blood plasma. Moreover, we investigate the sensitivity of different thrombin generation parameters to acidosis, both at the individual and population level. METHODS: We used a kinetic model to simulate and analyze the generation of thrombin and thrombin–antithrombin complexes (TAT), which were the end points of this study. Large groups of temporal thrombin and TAT trajectories were simulated and used to calculate quantitative parameters, such as clotting time (CT), thrombin peak time, maximum slope of the thrombin curve, thrombin peak height, area under the thrombin trajectory (AUC), and prothrombin time. The resulting samples of parameter values at different pH levels were compared to assess the acidosis-induced effects. To investigate intersubject variability, we parameterized the computational model using the data on clotting factor composition for 472 subjects from the Leiden Thrombophilia Study. To compare acidosis-induced relative parameter changes in individual (“virtual”) subjects, we estimated the probabilities of relative change patterns by counting the pattern occurrences in our virtual subjects. Distribution overlaps for thrombin generation parameters at distinct pH levels were quantified using the Bhattacharyya coefficient. RESULTS: Acidosis in the range of pH 6.9 to 7.3 progressively increased CT, thrombin peak time, AUC, and prothrombin time, while decreasing maximum slope of the thrombin curve and thrombin peak height (P < 10–5). Acidosis delayed the onset and decreased the amount of TAT generation (P

  15. Red blood cells and thrombin generation in sickle cell disease.

    PubMed

    Whelihan, Matthew F; Lim, Ming Y; Key, Nigel S

    2014-05-01

    The prothrombotic nature of sickle cell disease (SCD) is evidenced by the chronically elevated levels of almost all coagulation activation biomarkers, and an increased incidence of certain thrombotic events, including venous thromboembolism. Numerous studies have attempted to define the extent and elucidate the mechanism of the observed increase in thrombin generation in SCD patients in vivo. In general, these studies were performed using thrombin generation assays in platelet poor or platelet rich plasma and showed little difference in endogenous thrombin potential between the SCD cohort and healthy matched controls. In SCD, erythrocytes and monocytes have been demonstrated to exhibit procoagulant characteristics. Thus, the absence of these cellular components in standard thrombin generation assays may fail to reflect global hypercoagulability in the whole blood of patients with SCD. We were therefore surprised to see no difference in net thrombin generation in tissue factor-initiated initiated clotting of whole blood from patients with SCD. However, we are continuing to reconcile these seemingly disparate observations by slight modifications of the whole blood model that include alternative coagulation triggers and a re-examination of the net thrombin generation when the protein/protein S system is simultaneously interrogated.

  16. Hypercoagulability in splenectomized thalassemic patients detected by whole-blood thromboelastometry, but not by thrombin generation in platelet-poor plasma

    PubMed Central

    Tripodi, Armando; Cappellini, Maria Domenica; Chantarangkul, Veena; Padovan, Lidia; Fasulo, Maria Rosaria; Marcon, Alessia; Mannucci, Pier Mannuccio

    2009-01-01

    Background The mechanisms responsible for the increased thrombotic risk associated with thalassemia are still unclear. They might be related to the effects of red blood cell or endothelial cell derangements, increased numbers of platelets as well as abnormal plasma coagulation. Design and Methods To evaluate the relative role played by cells and plasma we investigated 169 patients with thalassemia by means of thromboelastometry and thrombin generation tests. Thromboelastometry measures indices of the viscoelastic properties of whole blood after activation of coagulation and is characterized by the clotting time, which may be considered as a conventional coagulation time, clot formation time, defined as the time needed for the clot to reach a fixed firmness, and the maximum clot firmness, defined as the maximal amplitude of the tracing. Results All the thromboelastometry parameters determined in whole blood (including shortened clotting time and clot formation time, and increased maximum clot firmness), were consistent with hypercoagulability, especially in splenectomized patients. Conversely, thrombin generation as determined in platelet-poor plasma was not. Conclusions These findings point to blood cells and/or platelets rather than to plasma abnormalities as the most important determinants of the thrombotic risk observed in thalassemic patients who had been splenectomized. These results might have important diagnostic and therapeutic implications. PMID:19648162

  17. Thrombin generation and low-molecular-weight heparin prophylaxis in pregnant women with thrombophilia.

    PubMed

    Selmeczi, Anna; Roach, Rachel E J; Móré, Csaba; Batta, Zoltán; Hársfalvi, Jolán; van der Bom, Johanna G; Boda, Zoltán; Oláh, Zsolt

    2015-02-01

    Pregnancy is associated with increased risk of venous thromboembolism, especially in the presence of thrombophilia. However, there is no consensus on the optimal approach for thromboprophylaxis in this population. Recent evidence suggests that thrombin generation correlates with the overall procoagulant state of the plasma. Our aim was to evaluate thrombin generation in a prospective cohort of thrombophilic pregnant women, and investigate the effectiveness of low-molecular-weight heparin (LMWH) prophylaxis in pregnancy. Women with severe (n=8), mild (n=47) and no (n=15) thrombophilia were followed throughout their pregnancies. Thrombin generation was evaluated in each trimester as well as five days and eight weeks postpartum (as a reference category). In women undergoing LMWH prophylaxis, thrombin generation and anti-Factor-Xa activity were measured just before and 4 hours after administration (peak effect). Thrombin generation was determined using Technothrombin TGA assay system. For the analysis, median peak thrombin and endogenous thrombin potential were used. Peak thrombin and endogenous thrombin potential were increased during pregnancy compared to the non-pregnant state with the highest results in the severe thrombophilia group. In women receiving LMWH prophylaxis a decrease was observed in thrombin generation at peak effect but over the progression of pregnancy the extent of this decrease reduced in a stepwise fashion. Our results show that thrombin generation demonstrates the hypercoagulable state in thrombophilic pregnancies. In addition, we found the effect of LMWH prophylaxis to progressively decrease with advancing stages of pregnancy.

  18. Abciximab does not inhibit the increase of thrombin generation produced in platelet-rich plasma in vitro by sodium arachidonate or tissue factor.

    PubMed

    Altman, Raul; Scazziota, Alejandra; Santoro, Silvina; Gonzalez, Claudio

    2005-07-01

    Aspirin and platelet membrane glycoprotein (GP) IIb/IIIa blockers are currently used for acute coronary events, and in percutaneous coronary intervention for preventing further coronary outcomes, because they inhibit platelet function. Aspirin also inhibits thrombin generation (TG) in platelet-rich plasma (PRP) activated by sodium arachidonate (AA). The effect of the platelet membrane GP IIb-IIIa (integrin alpha(IIb)beta(3)) blocker abciximab on thrombin generation was studied in vitro using PRP. Thirty healthy volunteers taking no medication, and 28 volunteers who had taken aspirin (160 mg/day for 3-4 days), were included in the protocol. Control or in vivo aspirinated PRP, stimulated or not by AA or tissue factor (TF), was investigated for the inhibitory effect of abciximab pre-incubated for 3 minutes. AA and TF added in vitro activated non-aspirinated PRP: lag-time (LT) and time to peak (TTP) were significantly shortened. Peak TG (PTG) and endogenous thrombin potential (ETG) were increased by AA but not TF; thus, AA seems to be more efficient than TF for TG in this system. Abciximab added in vitro to non-activated, non-aspirinated PRP had no effect on LT, TTP, or ETP, but caused a decrease in PTG that was not statistically significant. Abciximab (3 or 4 microg/mL) added in vitro to AA or TF-activated, non-aspirinated PRP produced no effect on TG, although in aspirinated platelets both LT and time to peak were prolonged. AA as well as TF added in vitro to PRP or in vivo aspirinated PRP increased TG, although AA seems to be more efficient in our assay system. Abciximab, which affects non-aspirinated, nonactivated PRP weakly, has no effect on AA or TF in activated control PRP or in vivo aspirinated PRP.

  19. Alpha-1 proteinase inhibitor M358R reduces thrombin generation when displayed on the surface of cells expressing tissue factor.

    PubMed

    Gierczak, Richard F; Pepler, Laura; Bhagirath, Vinai; Liaw, Patricia C; Sheffield, William P

    2014-11-01

    The M358R variant of alpha-1-proteinase inhibitor (API) is a potent soluble inhibitor of thrombin. Previously we engineered AR-API M358R, a membrane-bound form of this protein and showed that it inhibited exogenous thrombin when expressed on transfected cells lacking tissue factor (TF). To determine the suitability of AR-API M358R for gene transfer to vascular cells to limit thrombogenicity, we tested the ability of AR-API M358R to inhibit endogenous thrombin generated in plasma via co-expression co-expressing it on the surface of cells expressing TF. Transfected AR-API M358R formed inhibitory complexes with thrombin following exposure of recalcified, defibrinated plasma to TF on T24/83 cells, but discontinuously monitored thrombin generation was unaffected. Similarly, AR-API M358R expression did not reduce continuously monitored thrombin generation by T24/83 cell suspensions exposed to recalcified normal plasma in a Thrombogram-Thrombinoscope-type thrombin generation assay (TGA); in contrast, 1 μM hirudin variant 3 or soluble API M358R abolished thrombin generation. Gene transfer of TF to HEK 293 conferred the ability to support TF-dependent thrombin generation on HEK 293 cells. Co-transfection of HEK 293 cells with a 9:1 excess of DNA encoding AR-API M358R to that encoding TF reduced peak thrombin generation approximately 3-fold compared to controls. These in vitro results suggest that surface display of API M358R inhibits thrombin generation when the tethered serpin is expressed in excess of TF, and suggest its potential to limit thrombosis in appropriate vascular beds in animal models.

  20. Dynamics of Thrombin Generation and Flux from Clots during Whole Human Blood Flow over Collagen/Tissue Factor Surfaces.

    PubMed

    Zhu, Shu; Lu, Yichen; Sinno, Talid; Diamond, Scott L

    2016-10-28

    Coagulation kinetics are well established for purified blood proteases or human plasma clotting isotropically. However, less is known about thrombin generation kinetics and transport within blood clots formed under hemodynamic flow. Using microfluidic perfusion (wall shear rate, 200 s(-1)) of corn trypsin inhibitor-treated whole blood over a 250-μm long patch of type I fibrillar collagen/lipidated tissue factor (TF; ∼1 TF molecule/μm(2)), we measured thrombin released from clots using thrombin-antithrombin immunoassay. The majority (>85%) of generated thrombin was captured by intrathrombus fibrin as thrombin-antithrombin was largely undetectable in the effluent unless Gly-Pro-Arg-Pro (GPRP) was added to block fibrin polymerization. With GPRP present, the flux of thrombin increased to ∼0.5 × 10(-12) nmol/μm(2)-s over the first 500 s of perfusion and then further increased by ∼2-3-fold over the next 300 s. The increased thrombin flux after 500 s was blocked by anti-FXIa antibody (O1A6), consistent with thrombin-feedback activation of FXI. Over the first 500 s, ∼92,000 molecules of thrombin were generated per surface TF molecule for the 250-μm-long coating. A single layer of platelets (obtained with αIIbβ3 antagonism preventing continued platelet deposition) was largely sufficient for thrombin production. Also, the overall thrombin-generating potential of a 1000-μm-long coating became less efficient on a per μm(2) basis, likely due to distal boundary layer depletion of platelets. Overall, thrombin is robustly generated within clots by the extrinsic pathway followed by late-stage FXIa contributions, with fibrin localizing thrombin via its antithrombin-I activity as a potentially self-limiting hemostatic mechanism.

  1. Protein disulfide isomerase inhibition blocks thrombin generation in humans by interfering with platelet factor V activation

    PubMed Central

    Stopa, Jack D.; Neuberg, Donna; Puligandla, Maneka; Furie, Bruce; Zwicker, Jeffrey I.

    2017-01-01

    BACKGROUND: Protein disulfide isomerase (PDI) is required for thrombus formation. We previously demonstrated that glycosylated quercetin flavonoids such as isoquercetin inhibit PDI activity and thrombus formation in animal models, but whether extracellular PDI represents a viable anticoagulant target in humans and how its inhibition affects blood coagulation remain unknown. METHODS: We evaluated effects of oral administration of isoquercetin on platelet-dependent thrombin generation in healthy subjects and patients with persistently elevated anti-phospholipid antibodies. RESULTS: Following oral administration of 1,000 mg isoquercetin to healthy adults, the measured peak plasma quercetin concentration (9.2 μM) exceeded its IC50 for inhibition of PDI by isoquercetin in vitro (2.5 ± 0.4 μM). Platelet-dependent thrombin generation decreased by 51% in the healthy volunteers compared with baseline (P = 0.0004) and by 64% in the anti-phospholipid antibody cohort (P = 0.015) following isoquercetin ingestion. To understand how PDI affects thrombin generation, we evaluated substrates of PDI identified using an unbiased mechanistic-based substrate trapping approach. These studies identified platelet factor V as a PDI substrate. Isoquercetin blocked both platelet factor Va and thrombin generation with an IC50 of ~5 μM. Inhibition of PDI by isoquercetin ingestion resulted in a 53% decrease in the generation of platelet factor Va (P = 0.001). Isoquercetin-mediated inhibition was reversed with addition of exogenous factor Va. CONCLUSION: These studies show that oral administration of isoquercetin inhibits PDI activity in plasma and diminishes platelet-dependent thrombin generation predominantly by blocking the generation of platelet factor Va. These pharmacodynamic and mechanistic observations represent an important step in the development of a novel class of antithrombotic agents targeting PDI. TRIAL REGISTRATION: Clinicaltrials.gov (NCT01722669) FUNDING: National Heart

  2. Systems Biology of Coagulation Initiation: Kinetics of Thrombin Generation in Resting and Activated Human Blood

    PubMed Central

    Chatterjee, Manash S.; Denney, William S.; Jing, Huiyan; Diamond, Scott L.

    2010-01-01

    Blood function defines bleeding and clotting risks and dictates approaches for clinical intervention. Independent of adding exogenous tissue factor (TF), human blood treated in vitro with corn trypsin inhibitor (CTI, to block Factor XIIa) will generate thrombin after an initiation time (Ti) of 1 to 2 hours (depending on donor), while activation of platelets with the GPVI-activator convulxin reduces Ti to ∼20 minutes. Since current kinetic models fail to generate thrombin in the absence of added TF, we implemented a Platelet-Plasma ODE model accounting for: the Hockin-Mann protease reaction network, thrombin-dependent display of platelet phosphatidylserine, VIIa function on activated platelets, XIIa and XIa generation and function, competitive thrombin substrates (fluorogenic detector and fibrinogen), and thrombin consumption during fibrin polymerization. The kinetic model consisting of 76 ordinary differential equations (76 species, 57 reactions, 105 kinetic parameters) predicted the clotting of resting and convulxin-activated human blood as well as predicted Ti of human blood under 50 different initial conditions that titrated increasing levels of TF, Xa, Va, XIa, IXa, and VIIa. Experiments with combined anti-XI and anti-XII antibodies prevented thrombin production, demonstrating that a leak of XIIa past saturating amounts of CTI (and not “blood-borne TF” alone) was responsible for in vitro initiation without added TF. Clotting was not blocked by antibodies used individually against TF, VII/VIIa, P-selectin, GPIb, protein disulfide isomerase, cathepsin G, nor blocked by the ribosome inhibitor puromycin, the Clk1 kinase inhibitor Tg003, or inhibited VIIa (VIIai). This is the first model to predict the observed behavior of CTI-treated human blood, either resting or stimulated with platelet activators. CTI-treated human blood will clot in vitro due to the combined activity of XIIa and XIa, a process enhanced by platelet activators and which proceeds in the

  3. Thrombin Generation Capacity of Prothrombin Complex Concentrate in an In Vitro Dilutional Model

    PubMed Central

    Grottke, Oliver; Rossaint, Rolf; Henskens, Yvonne; van Oerle, Rene; ten Cate, Hugo; Spronk, Henri M. H.

    2013-01-01

    Background The use of PCC for the treatment of trauma-induced coagulopathy potentially increase the risk of thromboembolism and disseminated intravascular coagulation, which is addressed to an imbalance of both pro- and anticoagulants. As PCCs differ in composition, we used an in vitro dilutional approach to assess the overall thrombin generation of five different PCCs through various laboratory assays. Methods The vitamin K-dependent coagulation factors, heparin, and antithrombin were assessed in five commercially available PCCs. The procoagulant potential of the PCCs was assessed in plasma and whole blood from 4 healthy donors by means of classical coagulation assays, thrombin generation assay and thromboelastometry. In order to reflect coagulopathy, whole blood was diluted to 80, 60, 40, and 20% with Ringer’s lactate solution. Results The five different PCCs were characterised by comparable levels of factors II, VII, IX and X (all around 20–30 IU/mL), whereas the heparin (0 to 17.6 IU/mL) and antithrombin (0.06 to 1.29 IU/mL) levels were remarkably different between manufactures. In vitro dilution of blood induced a prolongation of the PT and aPTT, and attenuation of thrombin generation and ExTem induced thromboelastometry. Overall, non- or low-heparin containing PCCs restored the in vitro dilutional coagulopathy, whereas PCCs containing heparin have an anticoagulant effect. The thrombin generation assay showed to be the most sensitive method for assessment of PCC effects. Conclusions This study shows that most available PCCs are not balanced regarding their pro- and anticoagulants. The effect of measured differences in thrombin generation among different PCCs requires further investigations to elaborate the clinical meaning of this finding in the treatment of trauma induced coagulopathy. PMID:23696866

  4. Tissue factor-driven thrombin generation and inflammation in atherosclerosis.

    PubMed

    ten Cate, Hugo

    2012-05-01

    The transmembrane receptor tissue factor is a prominent protein expressed at macrophages and smooth muscle cells within human atherosclerotic lesions. While many coagulation proteins are detectable in atherosclerosis, a locally active thrombin and fibrin generating molecular machinery may be instrumental in manipulating cellular functions involved in atherogenesis. These include inflammation, angiogenesis and cell proliferation. Indeed, many experimental studies in mice show a correlation between hypercoagulability and increased atherosclerosis. In mice, the amount of atherosclerosis and/or the plaque phenotype, appear to be modifiable by specific anticoagulant interventions. While attempts to vary tissue factor level in the vasculature does not directly reduce plaque burden, the overexpression of tissue factor pathway inhibitor attenuates thrombogenicity and neo intima formation in mice. Moreover, inhibition of factor Xa or thrombin with novel selective agents, including rivaroxaban and dabigatran, inhibits inflammation associated with atherosclerosis in apoE(-/-) mice. The potential to modify a complex chronic disease like atherosclerosis with novel selective anticoagulants merits further clinical study.

  5. Evaluation of Thrombin Generation Assay in Patients With Hemophilia.

    PubMed

    Haghpanah, Sezaneh; Bazrafshan, Asghar; Silavizadeh, Samir; Dehghani, Javad; Afrasiabi, Abdolreza; Karimi, Mehran

    2016-05-01

    We evaluated the correlation between thrombin generation (TG) parameters with bleeding symptoms and disease severity in patients with hemophilia. In this cross-sectional study, 59 patients with hemophilia without inhibitors and regardless of their severity were randomly selected from southern Iran and TG assays were conducted. Bleeding score (BS) was calculated by performing a clinical evaluation using Tosetto questionnaire. Only lag time showed a statistically significant correlation with BS (rs = .316,P= .016). All TG parameters except peak showed association with disease severity (P< .05). Endogenous thrombin potential showed a significant correlation with factor activity level (rs = .459,P< .001). Both lag time and start tail showed significant negative correlations with factor activity level (rs = -0.488,P< .001 andrs = - .289,P< .026, respectively). Although most of the TG parameters evaluated were not significantly correlated with the BS of patients with hemophilia, the majority of TG parameters were significantly associated with factor activity level and disease severity.

  6. Contact system activation and high thrombin generation in hyperthyroidism.

    PubMed

    Kim, Namhee; Gu, Ja-Yoon; Yoo, Hyun Ju; Han, Se Eun; Kim, Young Il; Nam-Goong, Il Seong; Kim, Eun Sook; Kim, Hyun Kyung

    2017-01-30

    Background Hyperthyroidism is associated with increased thrombotic risk. Since contact system activation through formation of neutrophil extracellular traps (NET) has emerged as an important trigger of thrombosis, we hypothesized that the contact system is activated along with active NET formation in hyperthyroidism and that their markers correlate with disease severity. Materials and Methods In 61 patients with hyperthyroidism and 40 normal controls, the levels of coagulation factors (fibrinogen, and factor VII, VIII, IX, XI, and XII), D-dimer, thrombin generation assay (TGA) markers, NET formation markers (histone-DNA complex, double-stranded DNA, neutrophil elastase), and contact system markers (activated factor XII [XIIa], high-molecular-weight kininogen [HMWK], prekallikrein, and bradykinin) were measured. Results Patients with hyperthyroidism showed higher levels of fibrinogen [median (interquartile range), 315 (280-344) versus 262 (223-300), P=0.001], D-dimer [103.8 (64.8-151.5) versus 50.7 (37.4-76.0), P<0.001], peak thrombin [131.9 (102.2-159.4) versus 31.6 (14.8-83.7), P<0.001] and endogenous thrombin potential [649 (538-736) versus 367 (197-1147), P=0.021] in TGA with 1 pM tissue factor, neutrophil elastase [1.10 (0.39-2.18) versus 0.23 (0.20-0.35), P<0.001], factor XIIa [66.9 (52.8-87.0) versus 73.0 (57.1-86.6), P<0.001], HMWK [6.11 (4.95-7.98) versus 3.83 (2.60-5.68), P<0.001], prekallikrein [2.15 (1.00-6.36) versus 1.41 (0.63-2.22), P=0.026], and bradykinin [152.4 (137.6-180.4) versus 118.3 (97.1-137.9), P<0.001] than did normal controls. In age- and sex-adjusted logistic regression analysis, fibrinogen, factor VIII, IX, and XIIa, D-dimer, peak thrombin, neutrophil elastase, HMWK, and bradykinin showed significant odds ratios representing hyperthyroidism's contribution to coagulation and contact system activation. Free T4 was significantly correlated with factors VIII and IX, D-dimer, double-stranded DNA, and bradykinin. Conclusion This study

  7. Argatroban-coupled Affi-Gel matrix for the purification of thrombin from plasma.

    PubMed

    Lefkowitz, Jerry B

    2005-10-01

    Sometimes it is necessary to obtain thrombin from limited amounts of human plasma for laboratory assay. None of the available purification methods easily deals with this subject. The procedure described in the present paper uses a readily available pharmaceutical agent, argatroban, to construct an affinity matrix. Argatroban has a high affinity for thrombin and its thrombin binding is reversible. Prothrombin derived from a Ba(2+) precipitate of human plasma is used as the starting material. The crude prothrombin can be bulk activated to thrombin using taipan-snake (Oxyuranus scutellatus) venom and bound to the argatroban-coupled matrix without further processing steps. The thrombin product eluted from the argatroban matrix is very pure as judged by high specific activity and by electrophoresis. This purification scheme is rapid, yielding purified thrombin within 2 days.

  8. PLASMA GENERATOR

    DOEpatents

    Foster, J.S. Jr.

    1958-03-11

    This patent describes apparatus for producing an electricity neutral ionized gas discharge, termed a plasma, substantially free from contamination with neutral gas particles. The plasma generator of the present invention comprises a plasma chamber wherein gas introduced into the chamber is ionized by a radiofrequency source. A magnetic field is used to focus the plasma in line with an exit. This magnetic field cooperates with a differential pressure created across the exit to draw a uniform and uncontaminated plasma from the plasma chamber.

  9. Thrombin generation test for evaluation of antiplatelet treatment in patients with coronary artery disease after percutaneous coronary intervention.

    PubMed

    Berezovskaya, Gelena; Smirnova, Olga; Malev, Eduard; Khromov-Borisov, Nikita; Klokova, Elena; Karpenko, Mikhail; Papayan, Lyudmila; Petrishchev, Nikolay

    2017-04-04

    To study the possibility of using thrombin generation tests in platelet-rich and platelet-poor plasma for evaluation of dual antiplatelet therapy efficacy in patients with coronary artery disease (CAD), following percutaneous coronary intervention. Venous blood was analyzed from CAD patients aged 53-75 years who had undergone percutaneous coronary intervention with stenting within one year and had been receiving standard doses of clopidogrel and aspirin (75 and 75-100 mg per day, respectively). The control group comprised age- and sex-matched subjects without clinical signs of CAD who were not receiving these drugs. Thrombin generation tests were performed in platelet-rich and platelet-poor plasma. Intravascular platelet activation, induced platelet aggregation, and routine coagulation were evaluated. Antiplatelet treatment did not influence results of routine coagulation tests or intravascular platelet activation. The dual antiplatelet therapy affects collagen-induced platelet aggregation (44 ± 2.5 vs. 7.9 ± 2.6%, р = 10(-7)) and leads to decreases in endogenous thrombin potential (1900 ± 85 vs. 1740 ± 95 nM∙min, p = 0.0045), maximum thrombin concentration (134 ± 9.5 vs. 106 ± 6.5 nM, p = 4∙10(-6)), and increases in time to peak thrombin (27 ± 1.5 vs. 31 ± 2 min, p = 0.0012). Decreases in thrombin generation rate showed the highest statistical significance (13 ± 2 vs. 7.9 ± 0.8 nM/min, p = 10(-8)). Antiplatelet treatment did not alter thrombogram parameters for platelet-poor plasma.

  10. Factor XIa and Thrombin Generation Are Elevated in Patients with Acute Coronary Syndrome and Predict Recurrent Cardiovascular Events

    PubMed Central

    Loeffen, Rinske; van Oerle, René; Leers, Mathie P. G.; Kragten, Johannes A.; Crijns, Harry; Spronk, Henri M. H.; ten Cate, Hugo

    2016-01-01

    Objective In acute coronary syndrome (ACS) cardiac cell damage is preceded by thrombosis. Therefore, plasma coagulation markers may have additional diagnostic relevance in ACS. By using novel coagulation assays this study aims to gain more insight into the relationship between the coagulation system and ACS. Methods We measured plasma thrombin generation, factor XIa and D-dimer levels in plasma from ACS (n = 104) and non-ACS patients (n = 42). Follow-up measurements (n = 73) were performed at 1 and 6 months. Associations between coagulation markers and recurrent cardiovascular events were calculated by logistic regression analysis. Results Thrombin generation was significantly enhanced in ACS compared to non-ACS patients: peak height 148±53 vs. 122±42 nM. There was a significantly diminished ETP reduction (32 vs. 41%) and increased intrinsic coagulation activation (25 vs. 7%) in ACS compared to non-ACS patients. Furthermore, compared to non-ACS patients factor XIa and D-dimer levels were significantly elevated in ACS patients: 1.9±1.1 vs. 1.4±0.7 pM and 495(310–885) vs. 380(235–540) μg/L. Within the ACS spectrum, ST-elevated myocardial infarction patients had the highest prothrombotic profile. During the acute event, thrombin generation was significantly increased compared to 1 and 6 months afterwards: peak height 145±52 vs. 100±44 vs. 98±33 nM. Both peak height and factor XIa levels on admission predicted recurrent cardiovascular events (OR: 4.9 [95%CI 1.2–20.9] and 4.5 [1.1–18.9]). Conclusion ACS patients had an enhanced prothrombotic profile, demonstrated by an increased thrombin generation potential, factor XIa and D-dimer levels. This study is the first to demonstrate the positive association between factor XIa, thrombin generation and recurrent cardiovascular events. PMID:27419389

  11. Reduced peak, but no diurnal variation, in thrombin generation upon melatonin supplementation in tetraplegia. A randomised, placebo-controlled study.

    PubMed

    Iversen, Per Ole; Dahm, Anders; Skretting, Grethe; Mowinckel, Marie-Christine; Stranda, Annicke; Østerud, Bjarne; Sandset, Per Morten; Kostovski, Emil

    2015-11-01

    Tetraplegic patients have increased risk of venous thrombosis despite anti-thrombotic prophylaxis. Moreover, they have blunted plasma variations in melatonin and altered diurnal variation of several haemostatic markers, compared with able-bodied. However, whether healthy individuals and tetraplegic patients, with or without melatonin, display abnormalities in thrombin generation during a 24-hour (h) cycle, is unknown. We therefore used the Calibrated Automated Thrombogram (CAT) assay to examine diurnal variations and the possible role of melatonin in thrombin generation. Six men with long-standing complete tetraplegia were included in a randomised placebo-controlled cross-over study with melatonin supplementation (2 mg, 4 consecutive nights), whereas six healthy, able-bodied men served as controls. Ten plasma samples were collected frequently during a 24-h awake/sleep cycle. No significant diurnal variation of any of the measured CAT indices was detected in the three study groups. Whereas endogenous thrombin potential (ETP) was independent (p > 0.05) of whether the tetraplegic men received melatonin or placebo, melatonin decreased (p = 0.005) peak values in tetraplegia compared with those given placebo. Able-bodied men had lower (p = 0.019) ETP and Lag-Time (p = 0.018) compared with tetraplegics receiving placebo. Neither the Time-to-Peak nor the Start-Tail was affected (p > 0.05) by melatonin in tetraplegia. In conclusion, indices of thrombin generation are not subjected to diurnal variation in healthy able-bodied or tetraplegia, but peak thrombin generation is reduced in tetraplegic men receiving oral melatonin.

  12. Therapeutic Correction of Thrombin Generation in Dilution-Induced Coagulopathy: Computational Analysis Based on a Data Set of Healthy Subjects

    DTIC Science & Technology

    2012-01-01

    Thrombophilia Study. For every simulated thrombin curve, we calculated and analyzed five standard thrombin generation parameters. RESULTS: The three...model of in vitro thrombin accumulation to generate and analyze thrombin curves for the 472 control subjects in the Leiden Thrombophilia Study (LETS).15... Thrombophilia Study (LETS). Thromb Haemost. 1997;78: 631Y635. 16. Brummel-Ziedins KE, Orfeo T, Rosendaal FR, Undas A, Rivard GE, Butenas S, Mann KG

  13. THROMBIN GENERATION AND PROCOAGULANT MICROPARTICLE (MP) PROFILES AFTER ACUTE TRAUMA: A PROSPECTIVE COHORT STUDY

    PubMed Central

    Park, Myung S.; Xue, Ailing; Spears, Grant M.; Halling, Timothy M.; Ferrara, Michael J.; Kuntz, Melissa M.; Dhillon, Sabtir K.; Jenkins, Donald H.; Harmsen, William S.; Ballman, Karla V.; Heit, John A.

    2015-01-01

    Objective The two sides of Trauma Induced Coagulopathy (TIC), the hypo- and the hyper- coagulable states, are poorly understood. To identify potential mechanisms for venous thromboembolism and bleeding after acute trauma, we estimated changes in circulating procoagulant MPs and thrombin activity during hospitalization for trauma. Methods Whole blood was collected by venipuncture into 3.2% trisodium citrate at 0, 6, 12, 24 and 72 hours after injury, and discharge. Platelet poor plasma was harvested and stored at −80°C until analysis. Thrombin generation was determined using the calibrated automated thrombogram (CAT), reported as lagtime (minutes), peak height (nM thrombin) and time to reach peak height (ttPeak - minutes). The concentration of total procoagulant MPs (number/uL]) was measured by flow cytometry. Data are presented as median [interquartile range]. Results Among 443 trauma patients (1734 samples; ISS=13.0 [6.0, 22.0], hospital LOS=4.0 [2.0, 10.0] days, age=48 [28, 65] years, 70.7% male, 95% with blunt mechanism, mortality 3.2%), no discernable patterns in thrombin generation or MP concentration were observed over time. The peak height and MPs were significantly different from healthy volunteers and were 337 [285, 395] nM and 400 [211, 772] per uL plasma, respectively. Extreme (defined as highest or lowest 5%) values reflecting a possible “hypercoagulable state” (lagtime ≤ 1.98, peak height ≥ 486.2, ttPeak ≤ 3.61, and total procoagulant MP ≥ 2278) were reached within 12 hours after acute trauma, while extreme values representing a possible “hypocoagulable state” (lagtime ≥ 18.6, peak height ≤ 17.8 and ttPeak ≥ 29.45) were not reached until 1-3 days. Conclusion Although there was no predictable pattern of coagulopathy observed in each patient after trauma, those who reached extreme values did so relatively early after injury. These findings should be taken into account when designing risk model tools involving coagulation

  14. Relationship between short activated partial thromboplastin times, thrombin generation, procoagulant factors and procoagulant phospholipid activity.

    PubMed

    Mina, Ashraf; Favaloro, Emmanuel J; Koutts, Jerry

    2012-04-01

    Short activated partial thromboplastin times (APTTs) are associated with thrombosis. However, what short APTTs actually represent in terms of possible mechanistic pathways is not well characterized. We have assessed thrombin generation as compared with levels of procoagulant factor (fibrinogen, V, VIII, IX, XI and XII) activities, von Willebrand factor level and activity using collagen binding, as well as procoagulant phospholipid activity, in 113 consecutive samples exhibiting a short APTT compared with an equal number of age-matched and sex-matched samples yielding a normal APTT. We found a significant difference in peak thrombin generation, velocity index and area under the curve between the two groups, and that thrombin generation markers correlated with the APTT, procoagulant phospholipid activity and several procoagulant clotting factors. We conclude that short APTTs represent a procoagulant milieu, as represented by heightened thrombin generation and several other heightened procoagulant activities, which may help explain the association with thrombosis.

  15. Phospholipid-esterified eicosanoids are generated in agonist-activated human platelets and enhance tissue factor-dependent thrombin generation.

    PubMed

    Thomas, Christopher P; Morgan, Lloyd T; Maskrey, Benjamin H; Murphy, Robert C; Kühn, Hartmut; Hazen, Stanley L; Goodall, Alison H; Hamali, Hassan A; Collins, Peter W; O'Donnell, Valerie B

    2010-03-05

    Here, a group of specific lipids, comprising phosphatidylethanolamine (PE)- or phosphatidylcholine (PC)-esterified 12S-hydroxyeicosatetraenoic acid (12S-HETE), generated by 12-lipoxygenase was identified and characterized. 12S-HETE-PE/PCs were formed within 5 min of activation by thrombin, ionophore, or collagen. Esterified HETE levels generated in response to thrombin were 5.85 +/- 1.42 (PE) or 18.35 +/- 4.61 (PC), whereas free was 65.5 +/- 17.6 ng/4 x 10(7) cells (n = 5 separate donors, mean +/- S.E.). Their generation was stimulated by triggering protease-activated receptors-1 and -4 and signaling via Ca(2+) mobilization secretory phospholipase A2, platelet-activating factor-acetylhydrolase, src tyrosine kinases, and protein kinase C. Stable isotope labeling showed that they form predominantly by esterification that occurs on the same time scale as free acid generation. Unlike free 12S-HETE that is secreted, esterified HETEs remain cell-associated, with HETE-PEs migrating to the outside of the plasma membrane. 12-Lipoxygenase inhibition attenuated externalization of native PE and phosphatidylserine and HETE-PEs. Platelets from a patient with the bleeding disorder, Scott syndrome, did not externalize HETE-PEs, and liposomes supplemented with HETE-PC dose-dependently enhanced tissue factor-dependent thrombin generation in vitro. This suggests a role for these novel lipids in promoting coagulation. Thus, oxidized phospholipids form by receptor/agonist mechanisms, not merely as an undesirable consequence of vascular and inflammatory disease.

  16. Computational Analysis of Intersubject Variability and Thrombin Generation in Dilutional Coagulopathy

    DTIC Science & Technology

    2012-11-01

    healthy subjects in the Leiden Thrombophilia Study. Individual thrombin curves were calculated for undiluted blood and for different dilution...performing computa- tional thrombin generation analyses on a data set obtained as a part of the Leiden Thrombophilia Study (LETS).24 Computer modeling...the results. Thromb Res 2007; 119:663-5. 24. van der Meer FJ, Koster T, Vandenbroucke JP, Briët E, Rosendaal FR. The Leiden thrombophilia study (LETS

  17. Endogenous platelet factor 4 stimulates activated protein C generation in vivo and improves survival after thrombin or lipopolysaccharide challenge

    PubMed Central

    Mahmud, Shawn A.; Lambert, Michele P.; Poncz, Mortimer; Slungaard, Arne

    2007-01-01

    Pharmacologic infusion of activated protein C (APC) improves survival in severe sepsis, and platelet factor 4 (PF4) accelerates APC generation in a primate thrombin-infusion model. We now tested whether endogenous platelet PF4 content affects APC generation. Mice completely deficient in PF4 (mPF4−/−) had impaired APC generation and survival after thrombin infusion, similar to the impairment seen in heterozygote protein C–deficient (PC+/−) mice. Transgenic mice overexpressing human PF4 (hPF4+) had increased plasma APC generation. Overexpression of platelet PF4 compensated for the defect seen in PC+/− mice. In both a thrombin and a lipopolysaccharide (LPS) survival model, hPF4+ and PC+/−/hPF4+ mice had improved survival. Further, infusion of hPF4+ platelets improved survival of wild-type mice after an LPS challenge. These studies suggest that endogenous PF4 release may have biologic consequences for APC generation and survival in clinical sepsis. Infusions of PF4-rich platelets may be an effective strategy to improve outcome in this setting. PMID:17540840

  18. Endogenous platelet factor 4 stimulates activated protein C generation in vivo and improves survival after thrombin or lipopolysaccharide challenge.

    PubMed

    Kowalska, M Anna; Mahmud, Shawn A; Lambert, Michele P; Poncz, Mortimer; Slungaard, Arne

    2007-09-15

    Pharmacologic infusion of activated protein C (APC) improves survival in severe sepsis, and platelet factor 4 (PF4) accelerates APC generation in a primate thrombin-infusion model. We now tested whether endogenous platelet PF4 content affects APC generation. Mice completely deficient in PF4 (mPF4(-/-)) had impaired APC generation and survival after thrombin infusion, similar to the impairment seen in heterozygote protein C-deficient (PC(+/-)) mice. Transgenic mice overexpressing human PF4 (hPF4(+)) had increased plasma APC generation. Overexpression of platelet PF4 compensated for the defect seen in PC(+/-) mice. In both a thrombin and a lipopolysaccharide (LPS) survival model, hPF4(+) and PC(+/-)/hPF4(+) mice had improved survival. Further, infusion of hPF4(+) platelets improved survival of wild-type mice after an LPS challenge. These studies suggest that endogenous PF4 release may have biologic consequences for APC generation and survival in clinical sepsis. Infusions of PF4-rich platelets may be an effective strategy to improve outcome in this setting.

  19. PLASMA GENERATOR

    DOEpatents

    Wilcox, J.M.; Baker, W.R.

    1963-09-17

    This invention is a magnetohydrodynamic device for generating a highly ionized ion-electron plasma at a region remote from electrodes and structural members, thus avoiding contamination of the plasma. The apparatus utilizes a closed, gas-filled, cylindrical housing in which an axially directed magnetic field is provided. At one end of the housing, a short cylindrical electrode is disposed coaxially around a short axial inner electrode. A radial electrical discharge is caused to occur between the inner and outer electrodes, creating a rotating hydromagnetic ionization wave that propagates aiong the magnetic field lines toward the opposite end of the housing. A shorting switch connected between the electrodes prevents the wave from striking the opposite end of the housing. (AEC)

  20. Effects of tranexamic acid on platelet function and thrombin generation (ETAPlaT): WOMAN trial sub-study

    PubMed Central

    2016-01-01

    Background. Postpartum haemorrhage (PPH) is a leading cause of maternal death. Tranexamic acid (TXA) has the potential to reduce bleeding and a large randomized placebo controlled trial of its effect in women with PPH (The WOMAN trial) is underway. TXA might also affect coagulation factors and platelets.  Objectives. To examine the effect of TXA on thrombin generation, platelet function, fibrinogen, D-dimer and coagulation factors in women with PPH.  Methods. We will conduct a sub-study within the WOMAN trial. Women with clinically diagnosed primary PPH after vaginal or caesarean delivery are eligible for inclusion. Blood samples will be collected at baseline and 30 minutes after the first dose of study treatment. Using platelet poor plasma we will measure thrombin generation, fibrinogen, D-dimer, factor V and VIII, and Von Willebrand factor. Platelet function will be evaluated in whole blood using Multiplate® tests. Outcomes. The primary outcome is the effect of TXA on thrombin generation. Secondary outcomes include the effect of TXA on platelet function, fibrinogen, D-dimer and coagulation factors. PMID:28090594

  1. Statistical analysis plan for the WOMAN-ETAPlaT study: Effect of tranexamic acid on platelet function and thrombin generation

    PubMed Central

    2016-01-01

    Background. Postpartum haemorrhage (PPH) is a potentially life-threatening complication for women, and the leading cause of maternal mortality. Tranexamic acid (TXA) is an antifibrinolytic used worldwide to treat uterine haemorrhage and to reduce blood loss in general surgery. TXA may have effects on thrombin generation, platelet function and coagulation factors as a result of its inhibition on the plasmin. Methods. WOMAN ETAPlaT is a sub-study of the World Maternal Antifibrinolitic trial (WOMAN trial). All adult women clinically diagnosed with PPH after a vaginal delivery or caesarean section, are eligible for inclusion in the study. Blood samples will be collected at the baseline and 30 minutes after the first dose of study treatment is given. Platelet function will be evaluated in whole blood immediately after sampling with Multiplate® tests (ADPtest and TRAPtest). Thrombin generation, fibrinogen, D-dimer, and coagulation factors vW, V and VIII will be analysed using platelet poor plasma. Results. Recruitment to WOMAN ETAPlaT started on 04 November 2013 and closed on 13 January 2015, during this time  188 patients were recruited. The final participant follow-up was completed on 04 March 2015. This article introduces the statistical analysis plan for the study, without reference to unblinded data.   Conclusion. The data from this study will provide evidence for the effect of TXA on thrombin generation, platelet function and coagulation factors in women with PPH. Trial registration: ClinicalTrials.gov Identifier: NCT00872469; ISRCTN76912190

  2. Profile of thrombin generation in children with acute lymphoblastic leukemia treated by Berlin-Frankfurt-Münster (BFM) protocols.

    PubMed

    Lejhancova-Tousovska, Katerina; Zapletal, Ondrej; Vytiskova, Sona; Strbackova, Petra; Sterba, Jaroslav

    2012-03-01

    Treatment with L-asparaginase is associated with coagulation disturbances with deep venous thrombosis being the most common clinical consequence. Use of the calibrated automated thrombogram allows precise estimation of thrombin generated in vitro. We show the first data on thrombin generation, measured by calibrated automated thrombography (CAT), in children with acute lymphoblastic leukemia treated with L-asparaginase. Thrombin generation was measured by means of CAT in 23 children treated for acute lymphoblastic leukemia. Samples were obtained at predefined time points during the induction and reinduction phase of acute lymphoblastic leukemia-intercontinental Berlin-Frankfurt-Münster (BFM) 2000 or Associazione Italiana Ematologica Oncologia Pedaitrica Interim BFM 2000 protocols. Antihrombin and fibrinogen were measured on the same sample. Twenty-eight sets of thrombin generation measurements were collected from 23 patients. We observed no significant effect of antithrombin deficiency and/or hypofibrinogenemia on thrombin generation. Endogenous thrombin generation and peak thrombin were significantly higher during induction than in the reinduction phase (P < 0.001). Four patients with severe infection experienced an increase in thrombin generation, reaching maximum in a median of 7.5 days after the onset of infection. Two of those patients developed deep venous thrombosis at the time of peaked endogenous thrombin generation. Thrombin generation in children with acute lymphoblastic leukemia treated according to BFM protocols is significantly higher during the induction phase compared with reinduction and is not substantially affected by hypofibrinogenemia and/or antithrombin deficiency. Severe infection during the induction phase enhances thrombin generation with subsequent risk of thrombosis.

  3. Thrombin detection in murine plasma using engineered fluorescence resonance energy transfer aptadimers

    NASA Astrophysics Data System (ADS)

    Trapaidze, Ana; Brut, Marie; Mazères, Serge; Estève, Daniel; Gué, Anne-Marie; Bancaud, Aurélien

    2015-12-01

    Biodetection strategies, in which two sides of one target protein are targeted simultaneously, have been shown to increase specificity, selectivity, and affinity, and it has been suggested that they constitute excellent candidates for protein sensing in complex media. In this study we propose a method to engineer the sequence of a DNA construct dedicated to reversible thrombin detection. This construct, called Fluorescence Resonance Energy Transfer (FRET) aptadimer, is assembled with two aptamers, which target different epitopes of thrombin, interconnected with a DNA linker that contains a FRET couple and a reversible double helix stem. In the absence of target, the stem is stable maintaining a FRET couple in close proximity, and fluorescence is unquenched upon thrombin addition due to the dehybridization of the stem. We define design rules for the conception of FRET aptadimers, and develop a software to optimize their functionality. One engineered FRET aptadimer sequence is subsequently characterized experimentally by temperature scanning fluorimetry, demonstrating the relevance of our technology for thrombin sensing in bulk and diluted murine plasma.

  4. Ex vivo reversal of effects of rivaroxaban evaluated using thromboelastometry and thrombin generation assay

    PubMed Central

    Schenk, B.; Würtinger, P.; Streif, W.; Sturm, W.; Fries, D.; Bachler, M.

    2016-01-01

    Background In major bleeding events, the new direct oral anticoagulants pose a great challenge for physicians. The aim of the study was to test for ex vivo reversal of the direct oral anticoagulant rivaroxaban with various non-specific reversal agents: prothrombin complex concentrate (PCC), activated prothrombin complex concentrate (aPCC), recombinant activated factor VII (rFVIIa), and fibrinogen concentrate (FI). Methods Blood was obtained from healthy volunteers and from patients treated with rivaroxaban. Blood samples from healthy volunteers were spiked with rivaroxaban to test the correlation between rivaroxaban concentration and coagulation tests. Patient blood samples were spiked with various concentrations of the above-mentioned agents and analysed using thromboelastometry and thrombin generation. Results When added in vitro, rivaroxaban was significantly (P<0.05) correlated with ROTEM® thromboelastometry EXTEM (extrinsic coagulation pathway) clotting time (CT), time to maximal velocity (MaxV−t), and with all measured thrombin generation parameters. In vivo, CT, MaxV−t, lag time, and peak thrombin generation (Cmax) were significantly correlated with rivaroxaban concentrations. Regarding reversal of rivaroxaban, all tested agents significantly (P<0.05) reduced EXTEM CT, but to different extents: rFVIIa by 68%, aPCC by 47%, PCC by 17%, and FI by 9%. Only rFVIIa reversed EXTEM CT to baseline values. Both PCC (+102%) and aPCC (+232%) altered overall thrombin generation (area under the curve) and increased Cmax (+461% for PCC, +87.5% for aPCC). Conclusions Thromboelastometry and thrombin generation assays do not favour the same reversal agents for rivaroxaban anticoagulation. Controlled clinical trials are urgently needed to establish doses and clinical efficacy of potential reversal agents. Clinical trial registration EudracCT trial no. 213-00474-30. PMID:27623677

  5. Efficient thrombin generation requires molecular phosphatidylserine, not a membrane surface.

    PubMed

    Majumder, Rinku; Weinreb, Gabriel; Lentz, Barry R

    2005-12-27

    Activation of prothrombin to thrombin is catalyzed by a "prothrombinase" complex, traditionally viewed as factor X(a) (FX(a)) in complex with factor V(a) (FV(a)) on a phosphatidylserine (PS)-containing membrane surface, which is widely regarded as required for efficient activation. Activation involves cleavage of two peptide bonds and proceeds via one of two released intermediates or through "channeling" (activation without the release of an intermediate). We ask here whether the PS molecule itself and not the membrane surface is sufficient to produce the fully active human "prothrombinase" complex in solution. Both FX(a) and FV(a) bind soluble dicaproyl-phosphatidylserine (C6PS). In the presence of sufficient C6PS to saturate both FX(a) and FV(a2) (light isoform of FV(a)), these proteins form a tight (Kd = 0.6 +/- 0.09 nM at 37 degrees C) soluble complex. Complex assembly occurs well below the critical micelle concentration of C6PS, as established in the presence of the proteins by quasi-elastic light scattering and pyrene fluorescence. Ferguson analysis of native gels shows that the complex migrates with an apparent molecular mass only slightly larger than that expected for one FX(a) and one FV(a2), further ruling out complex assembly on C6PS micelles. Human prothrombin activation by this complex occurs at nearly the same overall rate (2.2 x 10(8) M(-1) s(-1)) and via the same reaction pathway (50-60% channeling, with the rest via the meizothrombin intermediate) as the activation catalyzed by a complex assembled on PS-containing membranes (4.4 x 10(8) M(-1) s(-1)). These results question the accepted role of PS membranes as providing "dimensionality reduction" and favor a regulatory role for platelet-membrane-exposed PS.

  6. Comparison of thrombin generation assay with conventional coagulation tests in evaluation of bleeding risk in patients with rare bleeding disorders.

    PubMed

    Zekavat, Omid R; Haghpanah, Sezaneh; Dehghani, Javad; Afrasiabi, Abdolreza; Peyvandi, Flora; Karimi, Mehran

    2014-09-01

    Based on the premise that the capacity of plasma to generate thrombin in vitro is a comprehensive and precise functional test of the clotting system, we designed a cross-sectional, single-center study involving 83 patients with rare bleeding disorders (RBDs) to compare the usefulness of the thrombin generation (TG) assay versus conventional tests including prothrombin time (PT) and activated partial thromboplastin time (aPTT) in predicting bleeding risk in patients with RBD in southern Iran. The TG parameters consisted of endogenous thrombin potential, lag time, peak, time to peak (ttPeak), and start tail. The area under the receiver-operating characteristic (ROC) curve showed statistically significant associations between bleeding risk and lag time, ttPeak, and start tail. We determined cutoff values for these 3 TG parameters and obtained a negative predictive value of 86% to 90% in patients with RBD who had a bleeding score (BS) ≤13. The ROC curves for the association of PT and aPTT with BS did not indicate any significant association. Correlation analysis supported the results of ROC curve analysis, only lag time, ttPeak, and start tail showed significant positive correlations with BS (P < .05). Disease severity based on plasma factor activity was significantly associated with prolonged lag time and ttPeak and with prolonged PT (P <.05). We suggest that TG assay is a potentially more useful tool for predicting the bleeding risk in patients with RBD. However, the small sample size in different RBD subgroups precluded subgroup analysis. Prospective multicenter studies with larger numbers of patients are therefore advisable.

  7. Association between Stable Coronary Artery Disease and In Vivo Thrombin Generation

    PubMed Central

    Baños-González, Manuel Alfonso; Peña-Duque, Marco Antonio; Martínez-Ríos, Marco Antonio; Quintanar-Trejo, Leslie; Aptilon-Duque, Gad; Flores-García, Mirthala; Cruz-Robles, David; Cardoso-Saldaña, Guillermo

    2016-01-01

    Background. Thrombin has been implicated as a key molecule in atherosclerotic progression. Clinical evidence shows that thrombin generation is enhanced in atherosclerosis, but its role as a risk factor for coronary atherosclerotic burden has not been proven in coronary artery disease (CAD) stable patients. Objectives. To evaluate the association between TAT levels and homocysteine levels and the presence of coronary artery disease diagnosed by coronary angiography in patients with stable CAD. Methods and Results. We included 95 stable patients admitted to the Haemodynamics Department, including 63 patients with significant CAD and 32 patients without. We measured the thrombin-antithrombin complex (TAT) and homocysteine concentrations in all the patients. The CAD patients exhibited higher concentrations of TAT (40.76 μg/L versus 20.81 μg/L, p = 0.002) and homocysteine (11.36 μmol/L versus 8.81 μmol/L, p < 0.01) compared to the patients without significant CAD. Specifically, in patients with CAD+ the level of TAT level was associated with the severity of CAD being 36.17 ± 24.48 μg/L in the patients with bivascular obstruction and 42.77 ± 31.81 μg/L in trivascular coronary obstruction, p = 0.002. Conclusions. The level of in vivo thrombin generation, quantified as TAT complexes, is associated with the presence and severity of CAD assessed by coronary angiography in stable CAD patients. PMID:27597926

  8. The impact of thrombin generation and rotation thromboelastometry on assessment of severity of factor XI deficiency.

    PubMed

    Livnat, Tami; Shenkman, Boris; Martinowitz, Uri; Zivelin, Ariella; Dardik, Rima; Tamarin, Ilia; Mansharov, Rachel; Budnik, Ivan; Salomon, Ophira

    2015-08-01

    The phenotype of bleeding in patients with severe FXI deficiency is unpredictable and unlike other bleeding disorders, it is not directly correlated with levels of FXI. In this study we analyzed whether the global coagulation assays can serve as a clinical tool in predicting bleeding tendency in patients with severe FXI deficiency undergoing surgery, taking into account the large inter-individual variability of FXI levels and genotypes. Thrombin generation (TG) was measured in 39 platelet-poor plasma with or without tissue factor (TF) and in the presence or absence of corn trypsin inhibitor (CTI). Rotation thromboelastometry (ROTEM) was performed with fresh whole blood of 26 patients applying NATEM and INTEM tests. TG induced by recalcification can distinguish between bleeding and non-bleeding patients with severe FXI deficiency particularly among those with FXI activity of 2-20IU/dl. The addition of TF or TF and CTI to the TG assay masked the ability to differentiate between XI activity, genotype as well as bleeding and non-bleeding patients. ROTEM assays failed to distinguish bleeding from non-bleeding patients but could do so between different FXI activity levels and genotypes. In conclusion, in the current study we found a sensitive tool to distinguish between bleeding and non-bleeding patients. In order to recommend TG as a predictive tool for treatment tailoring, a larger patient group is required.

  9. Monitoring Low Molecular Weight Heparins at Therapeutic Levels: Dose-Responses of, and Correlations and Differences between aPTT, Anti-Factor Xa and Thrombin Generation Assays

    PubMed Central

    Thomas, Owain; Lybeck, Emanuel; Strandberg, Karin; Tynngård, Nahreen; Schött, Ulf

    2015-01-01

    Background Low molecular weight heparins (LMWH’s) are used to prevent and treat thrombosis. Tests for monitoring LMWH’s include anti-factor Xa (anti-FXa), activated partial thromboplastin time (aPTT) and thrombin generation. Anti-FXa is the current gold standard despite LMWH’s varying affinities for FXa and thrombin. Aim To examine the effects of two different LMWH’s on the results of 4 different aPTT-tests, anti-FXa activity and thrombin generation and to assess the tests’ concordance. Method Enoxaparin and tinzaparin were added ex-vivo in concentrations of 0.0, 0.5, 1.0 and 1.5 anti-FXa international units (IU)/mL, to blood from 10 volunteers. aPTT was measured using two whole blood methods (Free oscillation rheometry (FOR) and Hemochron Jr (HCJ)) and an optical plasma method using two different reagents (ActinFSL and PTT-Automat). Anti-FXa activity was quantified using a chromogenic assay. Thrombin generation (Endogenous Thrombin Potential, ETP) was measured on a Ceveron Alpha instrument using the TGA RB and more tissue-factor rich TGA RC reagents. Results Methods’ mean aPTT at 1.0 IU/mL LMWH varied between 54s (SD 11) and 69s (SD 14) for enoxaparin and between 101s (SD 21) and 140s (SD 28) for tinzaparin. ActinFSL gave significantly shorter aPTT results. aPTT and anti-FXa generally correlated well. ETP as measured with the TGA RC reagent but not the TGA RB reagent showed an inverse exponential relationship to the concentration of LMWH. The HCJ-aPTT results had the weakest correlation to anti-FXa and thrombin generation (Rs0.62–0.87), whereas the other aPTT methods had similar correlation coefficients (Rs0.80–0.92). Conclusions aPTT displays a linear dose-respone to LMWH. There is variation between aPTT assays. Tinzaparin increases aPTT and decreases thrombin generation more than enoxaparin at any given level of anti-FXa activity, casting doubt on anti-FXa’s present gold standard status. Thrombin generation with tissue factor-rich activator is

  10. [Renal function and plasma dabigatran level measured at trough by diluted thrombin time assay].

    PubMed

    Martinuzzo, Marta E; Duboscq, Cristina; Viñuales, Estela S; Girardi, Beatriz; Penchasky, Diana; Ceresetto, José; Stemmelin, Germán; Otero, Victoria; Barrera, Luis H; López, Marina S; Otaso, Juan C; Hoyhamburu, José

    2017-01-01

    Dabigatran etexilate (direct thrombin inhibitor) is effective in preventing embolic stroke in patients with atrial fibrillation. It does not require laboratory control, but given the high renal elimination, its measurement in plasma is important in renal failure. The objectives of the study were to verify the analytical quality of the diluted thrombin time assay for measurement of dabigatran plasma concentration (cc), correlate cc with classic coagulation assays, prothrombin time (PT) and activated partial thromboplastin time (APTT), and evaluate them according to the creatinine clearance (CLCr). Forty plasma samples of patients (34 consecutive and 6 suspected of drug accumulation) receiving dabigatran at 150 (n = 19) or 110 (n = 21) mg/12 hours were collected. Blood samples were drawn at 10-14 hours of the last intake. Dabigatran concentration was determined by diluted thrombin time (HemosIl DTI, Instrumentation Laboratory (IL). PT and APTT (IL) were performed on two fotooptical coagulometers, ACL TOP 300 and 500 (IL). DTI presented intra-assay coefficient of variation < 5.4% and inter-assay < 6%, linearity range 0-493 ng/ml. Patients' cc: median 83 (4-945) ng/ml. Individuals with CLCr in the lowest tertile (22.6-46.1 ml/min) showed significantly higher median cc: 308 (49-945), compared to the average 72 (12-190) and highest tertile, 60 (4-118) ng/ml. Correlation between cc and APTT or PT were moderate, r2 = 0.59 and -0.66, p < 0.0001, respectively. DTI test allowed us to quantify plasma dabigatran levels, both in patients with normal or altered renal function, representing a useful tool in clinical situations such as renal failure, pre surgery or emergencies.

  11. Thrombin generation by activated factor VII on platelet activated by different agonists. Extending the cell-based model of hemostasis

    PubMed Central

    Altman, Raul; Scazziota, Alejandra Silvia; Herrera, Maria de Lourdes; Gonzalez, Claudio

    2006-01-01

    Background Platelet activation is crucial in normal hemostasis. Using a clotting system free of external tissue factor, we investigated whether activated Factor VII in combination with platelet agonists increased thrombin generation (TG) in vitro. Methods and results TG was quantified by time parameters: lag time (LT) and time to peak (TTP), and by amount of TG: peak of TG (PTG) and area under thrombin formation curve after 35 minutes (AUC→35min) in plasma from 29 healthy volunteers using the calibrated automated thrombography (CAT) technique. TG parameters were measured at basal conditions and after platelet stimulation by sodium arachidonate (AA), ADP, and collagen (Col). In addition, the effects of recombinant activated FVII (rFVIIa) alone or combined with the other platelet agonists on TG parameters were investigated. We found that LT and TTP were significantly decreased (p < 0.05) and PTG and AUC→35min were significantly increased (p < 0.05) in platelet rich plasma activated with AA, ADP, Col, and rFVIIa compared to non-activated platelet rich plasma from normal subjects (p = 0.01). Furthermore platelet rich plasma activated by the combined effects of rFVIIa plus AA, ADP or Col had significantly reduced LT and TTP and increased AUC→35min (but not PTG) when compared to platelet rich plasma activated with agonists in the absence of rFVIIa. Conclusion Platelets activated by AA, ADP, Col or rFVIIa triggered TG. This effect was increased by combining rFVIIa with other agonists. Our intrinsic coagulation system produced a burst in TG independent of external tissue factor activity an apparent hemostatic effect with little thrombotic capacity. Thus we suggest a modification in the cell-based model of hemostasis. PMID:16630353

  12. Different Recovery Profiles of Coagulation Factors, Thrombin Generation, and Coagulation Function After Hemorrhagic Shock in Pigs

    DTIC Science & Technology

    2012-06-06

    Different recovery profiles of coagulation factors, thrombin generation, and coagulation function after hemorrhagic shock in pigs Wenjun Z. Martini ...Defense. Address for reprints: Wenjun Z. Martini , PhD, The US Army Institute of Surgical Research, 3698 Chambers Pass, Ft. Sam Houston, San Antonio, TX...ELEMENT NUMBER 6. AUTHOR(S) Martini W. Z., Cortez D. S., Dubick M. A., Blackbourne L. H., 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7

  13. Free Fatty Acids Modulate Thrombin Mediated Fibrin Generation Resulting in Less Stable Clots

    PubMed Central

    Tanka-Salamon, Anna; Komorowicz, Erzsébet; Szabó, László; Tenekedjiev, Kiril

    2016-01-01

    Upon platelet activation, free fatty acids are released at the stage of thrombus formation, but their effects on fibrin formation are largely unexplored. Our objective was to characterize the kinetic effects of fatty acids on thrombin activity, as well as the structural and mechanical properties of the resultant fibrin clots. Thrombin activity on fibrinogen was followed by turbidimetry and detailed kinetic characterization was performed using a fluorogenic short peptide substrate. The viscoelastic properties of fibrin were measured with rotatory oscillation rheometer, whereas its structure was analyzed with scanning electron microscopy (SEM). In turbidimetric assays of fibrin generation, oleate and stearate at physiologically relevant concentrations (60–600 μM) produced a bell-shaped inhibitory dose response, increasing 10- to 30-fold the time to half-maximal clotting. Oleate inhibited thrombin activity on a short peptide substrate according to a mixed-type inhibitor pattern (a 9-fold increase of the Michaelis constant, Km and a 20% decrease of the catalytic constant), whereas stearate resulted in only a minor (15%) drop in the catalytic constant without any change in the Km. Morphometric analysis of SEM images showed a 73% increase in the median fiber diameter in the presence of stearate and a 20% decrease in the presence of oleate. Concerning the viscoelastic parameters of the clots, storage and loss moduli, maximal viscosity and critical shear stress decreased by 32–65% in the presence of oleate or stearate, but loss tangent did not change indicating decreased rigidity, higher deformability and decreased internal resistance to shear stress. Our study provides evidence that free fatty acids (at concentrations comparable to those reported in thrombi) reduce the mechanical stability of fibrin through modulation of thrombin activity and the pattern of fibrin assembly. PMID:27942000

  14. The effect of dabigatran on the activated partial thromboplastin time and thrombin time as determined by the Hemoclot thrombin inhibitor assay in patient plasma samples.

    PubMed

    Hapgood, Greg; Butler, Jenny; Malan, Erica; Chunilal, Sanjeev; Tran, Huyen

    2013-08-01

    Dabigatran is an oral direct thrombin inhibitor that does not require routine laboratory monitoring. However, an assessment of its anticoagulant effect in certain clinical settings is desirable. We examined the relationship between dabigatran levels, as determined by the Hemoclot thrombin inhibitor assay (HTI), the thrombin time (TT) and the activated partial thromboplastin time (aPTT) using different reagents. We describe these parameters with the clinical outcomes of patients receiving dabigatran. Seventy-five plasma samples from 47 patients were analysed. The HTI assay was established to measure dabigatran level. aPTTs were performed using TriniCLOT aPTT S reagent (TC) and three additional aPTT reagents. From linear regression lines, we established the aPTT ranges corresponding to the therapeutic drug levels for dabigatran (90-180 ng/ml). The aPTT demonstrated a modest correlation with the dabigatran level (r= 0.80) but the correlation became less reliable at higher dabigatran levels. The therapeutic aPTT ranges for reagents were clinically and statistically different compared with our reference reagent (46-54 s (TC) vs 51-60 s (SP), 54-64 s (SS) and 61-71 s (Actin FS) (p<0.05)). The TT was sensitive to the presence of dabigatran with a level of 60 ng/ml resulting in a TT > 300 s. In conclusion, the aPTT demonstrated a modest correlation with the dabigatran level and was less responsive with supra-therapeutic levels. aPTT reagents differed in their responsiveness, suggesting individual laboratories must determine their own therapeutic range for their aPTT reagent. The TT is too sensitive to quantify dabigatran levels, but a normal TT suggests minimal or no plasma dabigatran.

  15. Thrombin-activated human platelets acutely generate oxidized docosahexaenoic-acid-containing phospholipids via 12-lipoxygenase.

    PubMed

    Morgan, Lloyd T; Thomas, Christopher P; Kühn, Hartmut; O'Donnell, Valerie B

    2010-10-01

    Arachidonate-containing oxidized phospholipids are acutely generated by 12-LOX (12-lipoxygenase) in agonist-activated platelets. In the present study, formation of structurally related lipids by oxidation of DHA (docosahexaenoic acid)-containing phospholipids is demonstrated using lipidomic approaches. Precursor scanning reverse-phase LC (liquid chromatography)-MS/MS (tandem MS) identified a new family of lipids that comprise phospholipid-esterified HDOHE (hydroxydocosahexaenoic acid). Two diacyl and two plasmalogen PEs (phosphatidylethanolamines) containing predominantly the 14-HDOHE positional isomer (18:0p/14-HDOHE-PE, 18:0a/14-HDOHE-PE, 16:0a/14-HDOHE-PE and 16:0p/14-HDOHE-PE) were structurally characterized using MS/MS and by comparison with biogenic standards. An involvement of 12-LOX was indicated as purified recombinant human 12-LOX also generated the 14-HDOHE isomer from DHA. Pharmacological studies using inhibitors and recombinant platelet 12-LOX indicate that they form via esterification of newly formed non-esterified HDOHE. HDOHE-PEs formed at significant rates (2-4 ng/4×10(7) cells) within 2-180 min of thrombin stimulation, and their formation was blocked by calcium chelation. In summary, a new family of oxidized phospholipid was identified in thrombin-activated human platelets.

  16. Thrombin generation in Cushing's Syndrome: do the conventional clotting indices tell the whole truth?

    PubMed

    Koutroumpi, S; Spiezia, L; Albiger, N; Barbot, M; Bon, M; Maggiolo, S; Gavasso, S; Simioni, P; Frigo, A; Mantero, F; Scaroni, C

    2014-02-01

    Cushing's Syndrome (CS) is associated with an increased mortality, where hypercoagulability seems to have a crucial role in both arterial and venous thrombosis. Parameters of in vitro thrombin generation (TG) such as lag time, peak thrombin and endogenous thrombin potential (ETP), that describe the time until thrombin burst, the peak amount of TG and the total amount of thrombin generated, respectively as well as classical clotting markers were evaluated in 33 CS patients compared to both a group of 28 patients matched for the features of Metabolic Syndrome (MetS) and 31 healthy individuals. CS and MetS patients had shorter lag time (p < 0.0001), higher peak and ETP (p < 0.0001) than healthy controls, though lag time was less shortened in CS (p < 0.0001) respect to MetS group. Prothrombin time (PT) was increased (p < 0.0001) in both CS and MetS patients, while partial thromboplastin time (PTT) was shorter (p < 0.0001) in CS compared to both MetS and healthy group (p < 0.0001). Factor VIII (FVIII), Antithrombin (AT), protein C and S were increased only in CS patients (p < 0.0001). lag time, AT and FVIII correlated to night salivary cortisol (r = + 0.59; p = 0.0005, r = + 0.40; p = 0.003, r = + 0.40; p = 0.04, respectively); PTT correlated inversely to urinary free cortisol (r = -0.45; p = 0.009). BMI correlated negatively to lag time (r = -0.40; p = 0.0001) and positively to peak and ETP (r = + 0.34; p = 0.001, r = + 0.28; p = 0.008, respectively). Obese and diabetic patients had shorter lag time (p = 0.0005; p = 0.0002, respectively), higher ETP (p = 0.0006; p = 0.007, respectively) and peak (p = 0.0003; p = 0.0005, respectively) as well as a more prolonged PT (p = 0.04; p = 0.009, respectively). Hypertensive individuals had higher ETP (p = 0.004), peak (p = 0.0008) and FVIII (p = 0.001). Our findings confirm a prothrombotic state in both CS and MetS patients, though lag time was less shortened in

  17. Solid expellant plasma generator

    NASA Technical Reports Server (NTRS)

    Stone, Nobie H. (Inventor); Poe, Garrett D. (Inventor); Rood, Robert (Inventor)

    2010-01-01

    An improved solid expellant plasma generator has been developed. The plasma generator includes a support housing, an electrode rod located in the central portion of the housing, and a mass of solid expellant material that surrounds the electrode rod within the support housing. The electrode rod and the solid expellant material are made of separate materials that are selected so that the electrode and the solid expellant material decompose at the same rate when the plasma generator is ignited. This maintains a point of discharge of the plasma at the interface between the electrode and the solid expellant material.

  18. Thrombin generation and whole blood viscoelastic assays in the management of hemophilia: current state of art and future perspectives.

    PubMed

    Young, Guy; Sørensen, Benny; Dargaud, Yesim; Negrier, Claude; Brummel-Ziedins, Kathleen; Key, Nigel S

    2013-03-14

    Hemophilia is a bleeding disorder that afflicts about 1 in 5000 males. Treatment relies upon replacement of the deficient factor, and response to treatment both in clinical research and practice is based upon subjective parameters such as pain and joint mobility. Existing laboratory assays quantify the amount of factor in plasma, which is useful diagnostically and prognostically. However, these assays are limited in their ability to fully evaluate the patient's clot-forming capability. Newer assays, known as global assays, provide a far more detailed view of thrombin generation and clot formation and have been studied in hemophilia for about 10 years. They have the potential to offer a more objective measure of both the hemophilic phenotype as well as the response to treatment. In particular, in patients who develop inhibitors to deficient clotting factors and in whom bypassing agents are required for hemostasis, these assays offer the opportunity to determine the laboratory response to these interventions where traditional coagulation assays cannot. In this article we review the existing literature and discuss several controversial issues surrounding the assays. Last, a vision of future clinical uses of these assays is briefly described.

  19. A novel antidote-controlled anticoagulant reduces thrombin generation and inflammation and improves cardiac function in cardiopulmonary bypass surgery.

    PubMed

    Nimjee, Shahid M; Keys, J R; Pitoc, G A; Quick, G; Rusconi, C P; Sullenger, Bruce A

    2006-09-01

    Heparin and protamine are the standard anticoagulant-antidote regimen used in almost every cardiopulmonary bypass (CPB) procedure even though both are associated with an array of complications and toxicities. Here we demonstrate that an anticoagulant aptamer-antidote pair targeting factor IXa can replace heparin and protamine in a porcine CPB model and also limit the adverse effects on thrombin generation, inflammation, and cardiac physiology associated with heparin and protamine use. These results demonstrate that targeting clotting factors upstream of thrombin in the coagulation cascade can potentially reduce the perioperative pathologies associated with CPB and suggest that the aptamer-antidote pair to FIXa may improve the outcome of patients undergoing CPB. In particular, this novel anticoagulant-antidote pair may prove to be useful in patients diagnosed with heparin-induced thrombocytopenia or those who have been sensitized to protamine, particularly patients who have insulin-dependent diabetes.

  20. Plasma thrombin-cleaved osteopontin as a potential biomarker of acute atherothrombotic ischemic stroke.

    PubMed

    Ozaki, Saya; Kurata, Mie; Kumon, Yoshiaki; Matsumoto, Shirabe; Tagawa, Masahiko; Watanabe, Hideaki; Ohue, Shiro; Higaki, Jitsuo; Ohnishi, Takanori

    2017-01-01

    We investigated whether thrombin-cleaved osteopontin N-terminal is useful as a blood biomarker of acute atherothrombotic ischemic stroke. Acute ischemic stroke patients were prospectively evaluated with brain magnetic resonance imaging and cardiac evaluations for etiological diagnosis according to the Trial of Org 10172 in Acute Stroke Treatment classification. They were divided into the atherothrombotic and non-atherothrombotic groups. Thrombin-cleaved osteopontin N-terminal, osteopontin, matrix metalloproteinase-9, S100B, C-reactive protein and D-dimer levels were measured from blood samples collected at admission. After excluding patients who met the exclusion criteria or had stroke of other/undetermined etiology, 60 of the 100 patients initially enrolled were included in the final analysis. The ischemic stroke subtypes were atherothrombotic (n=28, 46.7%), cardioembolic (n=19, 31.7%) and lacunar (n=13, 21.7%). Thrombin-cleaved osteopontin N-terminal and matrix metalloproteinase-9 levels were significantly higher in the atherothrombotic than in the non-atherothrombotic group (median (interquartile range): 5.83  (0.0-8.6 ) vs. 0.0  (0.0-3.3) pmol l(-1), P=0.03 and 544   (322-749 ) vs. 343   (254-485) ng ml(-1), P=0.01, respectively). After adjustment for the prevalence of hypertension, diabetes and dyslipidemia, thrombin-cleaved osteopontin N-terminal levels of >5.47 pmol l(-1) (odds ratio, 16.81; 95% confidence interval, 3.53-80.10) and matrix metalloproteinase-9 levels of >605.5 ng ml(-1) (6.59; 1.77-24.60) were identified as independent predictors of atherothrombosis. Within 3 h from stroke onset, only thrombin-cleaved osteopontin N-terminal independently predicted atherothrombosis and thus may add valuable, time-sensitive diagnostic information in the early evaluation of ischemic stroke, especially the atherothrombotic subtype.

  1. The effect of omega-3 polyunsaturated fatty acids on fibrin and thrombin generation in healthy subjects and subjects with cardiovascular disease.

    PubMed

    McEwen, Bradley J; Morel-Kopp, Marie-Christine; Tofler, Geoffrey H; Ward, Christopher M

    2015-04-01

    Hypercoagulability plays a key role in the progression of cardiovascular disease (CVD). Although omega-3 polyunsaturated fatty acid (PUFA) intake has been inversely related to the risk of cardiovascular events, the mechanisms are not fully understood. The aim of this study was to investigate the effects of omega-3 on novel markers of global coagulation. The generation of fibrin and thrombin, measured via overall hemostasis potential (OHP) assay and calibrated automated thrombography, respectively, was determined in 40 healthy subjects and 16 patients with CVD at baseline and after 4 weeks of 640 mg/day omega-3 PUFA. In healthy subjects, fibrin generation was significantly reduced, as measured by overall coagulation potential (p = 0.013), OHP (p < 0.001), velocity of fibrin polymerization (p = 0.002), and significant increase in delay to fibrin generation (p = 0.002). The peak of generated thrombin was significantly reduced (p = 0.043). In subjects with CVD, omega-3 PUFA significantly reduced OHP and significantly increased the lag time to thrombin generation (both p < 0.001). Treatment with omega-3 PUFA had no effect on other fibrin and thrombin generation parameters in CVD patients. Four-week omega-3 PUFA supplementation reduced thrombotic potential in healthy subjects, as shown by reduced fibrin generation and peak thrombin. There was a greater effect on fibrin generation in healthy subjects compared with those with CVD.

  2. Plasma motor generator system

    NASA Technical Reports Server (NTRS)

    Hite, Gerald E.

    1987-01-01

    The significant potential advantages of a plasma motor generator system over conventional systems for the generation of electrical power and propulsion for spacecraft in low Earth orbits warrants its further investigation. The two main components of such a system are a long insulated wire and the plasma generating hollow cathodes needed to maintain electrical contact with the ionosphere. Results of preliminary theoretical and experimental investigations of this system are presented. The theoretical work involved the equilibrium configurations of the wire and the nature of small oscillation about these equilibrium positions. A particularly interesting result was that two different configurations are allowed when the current is above a critical value. Experimental investigations were made of the optimal starting and running conditions for the proposed, low current hollow cathodes. Although optimal ranges of temperature, argon pressure and discharge voltage were identified, start up became progressively more difficult. This supposed depletion or contamination of the emissive surface could be countered by the addition of new emissive material.

  3. G-Quadruplex Aptamers to Human Thrombin Versus Other Direct Thrombin Inhibitors: The Focus on Mechanism of Action and Drug Efficiency as Anticoagulants.

    PubMed

    Zavyalova, Elena; Ustinov, Nikita; Golovin, Andrey; Pavlova, Galina; Kopylov, Alexey

    2016-01-01

    Thrombin is a key enzyme of blood coagulation system which has multiple functions including pro- and anticoagulant, platelet aggregating and inflammatory activities. Unsurprisingly, this enzyme has been a target for anticoagulant drug development for decades. Among the most interesting direct thrombin inhibitors with intravenous administration route are the following ones: 1) hirudins, proteins with bivalent binding mode to the thrombin, 2) bivalirudin, the peptide with bivalent binding mode to the thrombin, 3) argatroban, the chemical that binds to the thrombin active site, and 4) G-quadruplex DNA aptamers, structured oligonucleotides with an affinity to protein-binding site of the thrombin. Efficiency of all these inhibitors has been studied in vivo in preclinical and clinical trials, as well as in vitro with various tests, allowing to compare them thoroughly. In the review three levels of comparison were used to highlight the features of each inhibitor: 1) thrombin inhibition constants as a characteristic of inhibitor potency in simple enzymatic system; 2) inhibition of fibrin fiber formation and thrombin generation in coagulation cascade as a characteristic of anticoagulant potency in human blood plasma; and 3) therapeutic doses used and therapeutic profiles obtained after intravenous administration into animals and humans. The data clearly demonstrate weak and strong aspects of thrombin binding aptamers providing a solid background for further novel anticoagulant development.

  4. Influenza virus H1N1 activates platelets through FcγRIIA signaling and thrombin generation.

    PubMed

    Boilard, Eric; Paré, Guillaume; Rousseau, Matthieu; Cloutier, Nathalie; Dubuc, Isabelle; Lévesque, Tania; Borgeat, Pierre; Flamand, Louis

    2014-05-01

    Platelets play crucial functions in hemostasis and the prevention of bleeding. During H1N1 influenza A virus infection, platelets display activation markers. The platelet activation triggers during H1N1 infection remain elusive. We observed that H1N1 induces surface receptor activation, lipid mediator synthesis, and release of microparticles from platelets. These activation processes require the presence of serum/plasma, pointing to the contribution of soluble factor(s). Considering that immune complexes in the H1N1 pandemic were reported to play a pathogenic role, we assessed their contribution in H1N1-induced platelet activation. In influenza-immunized subjects, we observed that the virus scaffolds with immunoglobulin G (IgG) to form immune complexes that promote platelet activation. Mechanistically, this activation occurs through stimulation of low-affinity type 2 receptor for Fc portion of IgG (FcγRIIA), a receptor for immune complexes, independently of thrombin. Using a combination of in vitro and in vivo approaches, we found that the antibodies from H3N2-immunized mice activate transgenic mouse platelets that express FcγRIIA when put in the presence of H1N1, suggesting that cross-reacting influenza antibodies suffice. Alternatively, H1N1 can activate platelets via thrombin formation, independently of complement and FcγRIIA. These observations identify both the adaptive immune response and the innate response against pathogens as 2 intertwined processes that activate platelets during influenza infections.

  5. Effects of Fibrinogen Concentrate on Thrombin Generation, Thromboelastometry Parameters, and Laboratory Coagulation Testing in a 24-Hour Porcine Trauma Model

    PubMed Central

    Zentai, Christian; Solomon, Cristina; van der Meijden, Paola E. J.; Spronk, Henri M. H.; Schnabel, Jonas; Rossaint, Rolf

    2015-01-01

    Introduction: In a 24-hour porcine model of liver injury, we showed that fibrinogen supplementation does not downregulate endogenous fibrinogen synthesis. Here we report data from the same study showing the impact of fibrinogen on coagulation variables. Materials and Methods: Coagulopathy was induced in 20 German land race pigs by hemodilution and blunt liver injury. Animals randomly received fibrinogen concentrate (100 mg/kg) or saline. Coagulation parameters were assessed and thromboelastometry (ROTEM) was performed. Results: Fibrinogen concentrate significantly reduced the prolongations of EXTEM clotting time, EXTEM clot formation time, and prothrombin time induced by hemodilution and liver injury. A decrease in clot strength was also ameliorated. Endogenous thrombin potential was significantly higher in the fibrinogen group than in the control group, 20 minutes (353 ± 24 vs 289 ± 22 nmol/L·min; P < .05) and 100 minutes (315 ± 40 vs 263 ± 38 nmol/L·min; P < .05) after the start of infusion. However, no significant between-group differences were seen in other thrombin generation parameters or in d-dimer or thrombin–antithrombin levels. Fibrinogen–platelet binding was reduced following liver injury, with no significant differences between groups. No significant between-group differences were observed in any parameter at ∼12 and ∼24 hours. Conclusion: This study suggests that, in trauma, fibrinogen supplementation may shorten some measurements of the speed of coagulation initiation and produce a short-lived increase in endogenous thrombin potential, potentially through increased clotting substrate availability. Approximately 12 and 24 hours after starting fibrinogen concentrate/saline infusion, all parameters measured in this study were comparable in the 2 study groups. PMID:25948634

  6. Differential inhibitory action of apixaban on platelet and fibrin components of forming thrombi: Studies with circulating blood and in a platelet-based model of thrombin generation

    PubMed Central

    Arellano-Rodrigo, Eduardo; Reverter, Joan Carles; Lopez-Farre, Antonio; Diaz-Ricart, Maribel; Badimon, Juan Jose; Escolar, Gines

    2017-01-01

    Introduction Mechanisms of action of direct oral anticoagulants (DOAC) suggest a potential therapeutic use in the prevention of thrombotic complications in arterial territories. However, effects of DOACs on platelet activation and aggregation have not been explored in detail. We have investigated the effects of apixaban on platelet and fibrin components of thrombus formation under static and flow conditions. Methods We assessed the effects of apixaban (10, 40 and 160 ng/mL) on: 1) platelet deposition and fibrin formation onto a thrombogenic surface, with blood circulating at arterial shear-rates; 2) viscoelastic properties of forming clots, and 3) thrombin generation in a cell-model of coagulation primed by platelets. Results In studies with flowing blood, only the highest concentration of apixaban, equivalent to the therapeutic Cmax, was capable to significantly reduce thrombus formation, fibrin association and platelet-aggregate formation. Apixaban significantly prolonged thromboelastometry parameters, but did not affect clot firmness. Interestingly, results in a platelet-based model of thrombin generation under more static conditions, revealed a dose dependent persistent inhibitory action by apixaban, with concentrations 4 to 16 times below the therapeutic Cmax significantly prolonging kinetic parameters and reducing the total amount of thrombin generated. Conclusions Our studies demonstrate the critical impact of rheological conditions on the antithrombotic effects of apixaban. Studies under flow conditions combined with modified thrombin generation assays could help discriminating concentrations of apixaban that prevent excessive platelet accumulation, from those that deeply impair fibrin formation and may unnecessarily compromise hemostasis. PMID:28192448

  7. Predictive role of gene polymorphisms affecting thrombin-generation pathway in variable efficacy of photodynamic therapy for neovascular age-related macular degeneration.

    PubMed

    Parmeggiani, Francesco; Gemmati, Donato; Costagliola, Ciro; Sebastiani, Adolfo; Incorvaia, Carlo

    2009-01-01

    Age-related macular degeneration (AMD) represents the leading cause of central blindness in developed countries. The majority of severe vision loss occurs in the neovascular form of AMD, generally characterized by the presence of choroidal neovascularization (CNV) beneath the fovea. Photodynamic therapy with verteporfin (PDT-V) and drugs acting against vascular endothelial growth factor are the most commonly employed treatments for AMD-related subfoveal CNV. The combined use of both these strategies is the most promising therapeutic approach towards this harmful disease. The therapeutic action of PDT-V depends to a photochemical perturbation of thrombo-coagulative processes within CNV. Predictive correlations between peculiar coagulation-balance gene polymorphisms and different levels of post-PDT-V benefit have been recently documented in Caucasian patients with neovascular AMD. Particularly, heterozygous A-allele carriers of factor V Leiden 1691 or prothrombin 20210 gene are characterized by a greater possibility to exhibit clinical benefit after PDT-V. Both mutations induce thrombophilia increasing the thrombin generation in plasma and, thus, they can consistently intensify the photothrombotic phase of the therapeutic CNV occlusion. In prospect, considering the different individual susceptibility to PDT-V, a preoperative assessment of the genotypic thrombophilic background could optimize the eligibility criteria of this intriguing treatment. This review summarizes some of the recent published patents on treatment of neovascular AMD, with a particular attention to PDT-V application in combined therapeutic modalities.

  8. Plasma Generated Spherules

    NASA Astrophysics Data System (ADS)

    Ransom, C. J.

    2005-04-01

    Z-pinch plasma simulations have been performed that indicate the production of spherules under certain experimental parameters. (A. L. Peratt, private communication) While performing experiments dealing with the impact of plasma discharges on various materials, we observed that spherules were created at the surface of some of the materials. For specific materials and conditions, spherules were always produced. Both individual spherules and joined spherules were created. The size and shapes were nearly identical to items found by the Mars rover, Opportunity, and called ``blueberries.'' Sky & Telescope, June 2004, p. 20, among other sources indicated the blueberries were gray spherules composed of hematite. The experiments produced hematite spherules identical in appearance to those found on Mars. These experiments suggest how the newly discovered blueberries were formed on Mars while providing an explanation that does not depend on the presence of water.

  9. Plasma Generator Using Spiral Conductors

    NASA Technical Reports Server (NTRS)

    Szatkowski, George N. (Inventor); Dudley, Kenneth L. (Inventor); Ticatch, Larry A. (Inventor); Smith, Laura J. (Inventor); Koppen, Sandra V. (Inventor); Nguyen, Truong X. (Inventor); Ely, Jay J. (Inventor)

    2016-01-01

    A plasma generator includes a pair of identical spiraled electrical conductors separated by dielectric material. Both spiraled conductors have inductance and capacitance wherein, in the presence of a time-varying electromagnetic field, the spiraled conductors resonate to generate a harmonic electromagnetic field response. The spiraled conductors lie in parallel planes and partially overlap one another in a direction perpendicular to the parallel planes. The geometric centers of the spiraled conductors define endpoints of a line that is non-perpendicular with respect to the parallel planes. A voltage source coupled across the spiraled conductors applies a voltage sufficient to generate a plasma in at least a portion of the dielectric material.

  10. Platelet-induced thrombin generation by the calibrated automated thrombogram assay is increased in patients with essential thrombocythemia and polycythemia vera.

    PubMed

    Panova-Noeva, Marina; Marchetti, Marina; Spronk, Henri Maria; Russo, Laura; Diani, Erika; Finazzi, Guido; Finazzi, Good; Salmoiraghi, Silvia; Rambaldi, Alessandro; Rambaldi, Aueesandrd; Barbui, Tiziano; Barbui, Titiano; Ten Cate, Hugo; Ten Cate, Huao; Falanga, Anna

    2011-04-01

    The platelet contribution to the thrombophilic state of patients with myeloproliferative neoplasms (MPNs), i.e., essential thrombocythemia (ET) and polycythemia vera (PV), remains uncertain. In this study we aimed to characterize the thrombin generation (TG) potential expressed by platelets from these subjects, compare it to normal platelets, and identify what factors might be responsible for platelet TG. In a group of 140 MPN patients (80 ET and 60 PV) and 72 healthy subjects, we measured the global procoagulant potential of platelet-rich plasma (PRP) utilizing the TG assay by the calibrated automated thrombogram (CAT). To characterize the procoagulant contribution of platelets in PRP, the TG of both isolated platelets and platelet-poor plasma was measured, and the platelet surface expression of TF was determined. Finally, the activation status of platelets was assessed by the levels of P-selectin expressed on platelet surface. MPN patients had significantly increased PRP and isolated platelet TG potential compared to controls. This was associated to the occurrence of platelet activation. Patients carriers of the JAK2V617F mutation showed the highest values of TG and platelet surface TF and P-selectin. Platelet TG potential was significantly lower in hydroxyurea(HU) compared to non-HU-treated patients and was lowest in HU-treated JAK2V617F carriers. In subjects not receiving HU, platelet TG significantly increased by JAK2V617F allele burden increment (P < 0.05).This study demonstrates a platelet-dependent form of hypercoagulability in MPN patients, particularly in those carriers of the JAK2V617F mutation. The cytoreductive therapy with HU significantly affects this prothrombotic phenotype.

  11. Evaluation of the bone healing process utilizing platelet-rich plasma activated by thrombin and calcium chloride: a histologic study in rabbit calvaria.

    PubMed

    Betoni-Junior, Walter; Dechichi, Paula; Esteves, Jônatas Caldeira; Zanetta-Barbosa, Darceny; Magalhães, Aparecido Eurípedes Onório

    2013-02-01

    To evaluate the bone healing of defects filled with particulate bone graft in combination with platelet-rich plasma (PRP), added with a mixture of calcium chloride and thrombin or just calcium chloride. Two 5-mm bone defects were created in the calvaria of 24 rabbits. Each defect was filled with particulate bone graft and PRP. In one defect the PRP was activated by a mixture of calcium chloride and thrombin; in the other, PRP was activated by calcium chloride only. The animals were euthanized 1, 2, 4, and 8 weeks after the surgeries, and the calvaria was submitted to histologic processing for histomorphometric analysis. The qualitative analysis has shown that both defects presented the same histologic characteristics so that a better organized, more mature, and well-vascularized bone tissue was noticed in the eighth week. A good bone repair was achieved using either the mixture of calcium chloride and thrombin or the calcium chloride alone as a restarting agent of the coagulation process.

  12. Effect of two oral doses of 17beta-estradiol associated with dydrogesterone on thrombin generation in healthy menopausal women: a randomized double-blind placebo-controlled study.

    PubMed

    Rousseau, Alexandra; Robert, Annie; Gerotziafas, Grigoris; Torchin, Dahlia; Zannad, Faiez; Lacut, Karine; Libersa, Christian; Dasque, Eric; Démolis, Jean-Louis; Elalamy, Ismail; Simon, Tabassome

    2010-04-01

    Oral hormone therapy is associated with an increased risk of venous thrombosis. Drug agencies recommend the use of the lowest efficient dose to treat menopausal symptoms for a better risk/ratio profile, although this profile has not been totally investigated yet. The aim of the study was to compare the effect of the standard dose of 17beta-estradiol to a lower one on thrombin generation (TG). In a 2-month study, healthy menopausal women were randomized to receive daily 1mg or 2 mg of 17beta-estradiol (E1, n = 24 and E2, n = 26; respectively) with 10 mg dydrogesterone or placebo (PL, n = 22). Plasma levels factors VII, X, VIII and II were assessed before and after treatment as well as Tissue factor triggered TG, which allows the investigation of the different phases of coagulation process. The peak of thrombin was higher in hormone therapy groups (E1: 42.39 +/- 50.23 nm, E2: 31.08 +/- 85.86 nm vs. 10.52 +/- 40.63 nm in PL, P = 0.002 and P = 0.01). Time to reach the peak was also shortened (PL: 0.26 +/- 0.69 min vs. E1: -0.26 +/- 0.80 min, E2: -0.55 +/- 0.79 min, P <10(-3) for both comparisons) and mean rate index of the propagation phase of TG was significantly increased. Among the studied clotting factors, only the levels of FVII were significantly increased after treatment administration. The two doses of 17beta-estradiol induced in a similar degree an acceleration of the initiation and propagation phase of tissue factor triggered thrombin generation and a significant increase of FVII coagulant activity.

  13. An evaluation of platelet-rich plasma without thrombin activation with or without anorganic bone mineral in the treatment of human periodontal intrabony defects.

    PubMed

    Rodrigues, Silvia V; Acharya, Anirudh B; Thakur, Srinath L

    2011-01-01

    The efficacy of platelet-rich plasma (PRP) in periodontal regeneration is not well understood and the definite clinical viability of blood derived platelets lacks clarity. Also, the use of thrombin for platelet activation is disputed. Hence, the purpose of this study was to evaluate the efficacy of blood derived platelets without thrombin activation, alone or in combination with bovine anorganic bone mineral (ABM), in the treatment of human periodontal intrabony defects. PRP was prepared using a simple tabletop centrifuge and activated using calcium chloride without the addition of thrombin. This PRP was used alone (in Group A) and in combination with bovine ABM (in Group B) in the treatment of human periodontal angular defects. Both the control and the test groups showed definite improvement in clinical parameters. On comparison, however, there was a statistically significant improvement in the probing pocket depths and relative attachment level in Group B over Group A at 3 and 6 months intervals, whereas at the end of 9 months this difference was not statistically significant. There was no statistically significant difference between the groups with respect to the relative defect depth. Within the limitations of this study and the type of PRP used, i.e. without thrombin mediated activation, it can be concluded that both PRP and PRP combined with bovine ABM results in significant clinical improvement. Albeit statistically insignificant, there is a preponderance of better clinical results with the addition of ABM to PRP. Further studies need to be carried out on a larger sample size to confirm the results of the present study.

  14. Two distinct forms of Factor VIII coagulant protein in human plasma. Cleavage by thrombin, and differences in coagulant activity and association with von Willebrand factor.

    PubMed Central

    Weinstein, M J; Chute, L E

    1984-01-01

    We have characterized Factor VIII coagulant protein, present in normal human plasma, that reacts with a specific human 125I-labeled anti-human VIII:C antigen Fab antibody fragment. Two major Factor VIII coagulant antigen populations were present. The first, approximately 85% of the total antigen, was bound to von Willebrand factor and when tested in a standard one-stage assay had Factor VIII coagulant activity. The second antigenic population, eluting near fibrinogen when plasma was gel filtered, was not bound to von Willebrand protein, did not have Factor VIII coagulant activity unless activated, but did block anti-VIII:C Fab neutralization of clotting activity. The two antigenic populations were separable by cryoprecipitation and agarose gel electrophoresis. Although the two antigenic populations differed in their Factor VIII coagulant activity and in their binding to von Willebrand factor, the principal member of both populations is of mol wt 2.4 X 10(5). Both antigens, when proteolyzed by thrombin, were quickly converted to a 1 X 10(5)-mol wt form in association with the appearance of VIII:C activity. The 1 X 10(5)-mol wt antigen was further slowly degraded to an 8 X 10(4)-mol wt form while Factor VIII coagulant activity declined. These results demonstrate the presence of an inactive Factor VIII coagulant protein in plasma, not associated with von Willebrand factor, that can react with thrombin to yield Factor VIII coagulant activity. Images PMID:6421875

  15. Kinetic Modeling Sheds Light on the Mode of Action of Recombinant Factor VIIa on Thrombin Generation

    DTIC Science & Technology

    2011-01-01

    numerical model to generate activated factor VII (FVIIa) titration curves in the cases of normal blood composition, hemophilia A and B blood, blood...as a hemostatic agent for patients with hemophilia , congenital FVII deficiency, and Glanzmann’s thrombocytopenia [3]. Following its initial approval...normal blood composition, hemophilia A and B blood, blood lacking factor VII, blood lacking tissue factor pathway inhibitor, and diluted blood. We

  16. Thalidomide-prednisone maintenance following autologous stem cell transplant for multiple myeloma: effect on thrombin generation and procoagulant markers in NCIC CTG MY.10.

    PubMed

    Kovacs, Michael J; Davies, Gwynivere A; Chapman, Judy-Anne W; Bahlis, Nizar; Voralia, Michael; Roy, Jean; Kouroukis, C Tom; Chen, Christine; Belch, Andrew; Reece, Donna; Zhu, Liting; Meyer, Ralph M; Shepherd, Lois; Stewart, Keith A

    2015-02-01

    Venous thromboembolism (VTE) has an increased incidence in patients with multiple myeloma (MM), especially during chemotherapy. Mechanisms including upregulation of procoagulant factors, such as factor VIII, have been postulated. The National Cancer Institute of Canada Clinical Trials Group MY.10 phase III clinical trial compared thalidomide-prednisone to observation for 332 patients with MM post-autologous stem cell transplantation (ASCT), with a primary endpoint of overall survival and various secondary endpoints including the incidence of VTE. One hundred and fifty-three patients had biomarker data, including D-dimer, factor VIII and thrombin anti-thrombin (TAT) levels collected post-ASCT at baseline and 2 months after intervention investigating in-vivo thrombin generation. Differences between the time-points included a significant reduction over time in D-dimer, factor VIII and TAT levels in the observation group and sustained elevation of D-dimer, significant increase in factor VIII and reduction in TAT levels in the thalidomide-prednisone group. Eight VTE events were reported in this subset of study patients, all in the thalidomide-prednisone arm, with a trend to increase in D-dimer levels over time in those patients with VTE. This study provides physiological and clinical evidence for an increased risk of VTE associated with thalidomide-prednisone maintenance therapy post-ASCT for MM.

  17. Coagulation factor XII genetic variation, ex vivo thrombin generation, and stroke risk in the elderly: results from the Cardiovascular Health Study

    PubMed Central

    Olson, N. C.; Butenas, S.; Lange, L. A.; Lange, E. M.; Cushman, M.; Jenny, N. S.; Walston, J.; Souto, J. C.; Soria, J. M.; Chauhan, G.; Debette, S.; Longstreth, W.T.; Seshadri, S.; Reiner, A.P.; Tracy, R. P.

    2016-01-01

    Background Relationships of thrombin generation (TG) with cardiovascular disease risk are under-evaluated in population-based cohorts. Objectives Evaluate the relationships of TG influenced by the contact and tissue factor coagulation pathways ex vivo with common SNPs and incident cardiovascular disease and stroke. Patients/Methods We measured peak TG (pTG) in baseline plasma samples of Cardiovascular Health Study participants (n=5,411), both with and without inhibitory anti-FXIa antibody (pTG/FXIa−). We evaluated their associations with ~50K SNPs using the IBCv2 genotyping array, and with incident cardiovascular disease and stroke events over a median follow-up of 13.2-years. Results The minor allele for a SNP in the coagulation factor XII gene (F12), rs1801020, was associated with lower pTG in European-Americans (β=−34.2 nM ± 3.5 nM; p=3.3×10−22; minor allele frequency (MAF) =0.23) and African-Americans (β=−31.1 nM ± 7.9 nM; p=9.0×10−5; MAF=0.42). Lower FXIa-independent pTG (pTG/FXIa−) was associated with the F12 rs1801020 minor allele, and higher pTG/FXIa− was associated with the ABO SNP rs657152 minor allele (β=16.3 nM; p=4.3×10−9; MAF=0.37). The risk factor-adjusted ischemic stroke hazard ratio (95% confidence interval) was 1.09 (1.01, 1.17; p=0.03) for pTG, 1.06 (0.98, 1.15; p=0.17) for pTG/FXIa−, and 1.11 (1.02, 1.21; p=0.02) for FXIa-dependent pTG (pTG/FXIa+), per 1-SD increment (n=834 ischemic strokes). In a multi-cohort candidate gene analysis, rs1801020 was not associated with incident ischemic stroke (β= −0.02; (SE=0.08); p=0.81). Conclusions These results support the importance of contact activation pathway-dependent TG as a risk factor for ischemic stroke and indicate the importance of F12 SNPs on TG ex vivo and in vivo. PMID:26286125

  18. [New anticoagulants - direct thrombin inhibitors].

    PubMed

    Brand, B; Graf, L

    2012-11-01

    Direct thrombin-inhibitors inactivate not only free but also fibrin-bound thrombin. The group of parenteral direct thrombin-inhibitors includes the recombinant hirudins lepirudin and desirudin, the synthetic hirudin bivalirudin, and the small molecule argatroban. All these compounds do not interact with PF4/heparin-antibodies. Therefore, argatroban as well as bivalirudin are currently used to treat heparin-induced thrombocytopenia (HIT). The oral direct thrombin-inhibitor dabigatran etexilate is already licensed in many countries for the treatment of non-valvular atrial fibrillation. Dabigatran etexilate reveals a stable and predictable effect that allows a medication without dose adjustment or monitoring. The substance shows only few interactions with other drugs but strong inhibitors of p-glycoprotein can increase plasma levels of dabigatran substantially. After oral intake, the prodrug dabigatran etexilate is cleaved by esterase-mediated hydrolyses to the active compound dabigatran. Elimination of dabigatran is predominantly renal. Safety and efficacy of dabigatran etexilate were tested in an extensive clinical study program. Non-inferiority compared to current standard treatments was shown for prophylaxis of venous thromboembolic events after total knee and hip replacement, for stroke prevention in atrial fibrillation, and for treatment of acute venous thromboembolism. In daily practice, Dabigatran etexilate competes against the new direct factor Xa-inhibitors. In the absence of direct comparative clinical trials, it is not yet clear if one class of substances has distinct advantages over the other.

  19. Thrombin inhibition with dabigatran protects against high-fat diet-induced fatty liver disease in mice.

    PubMed

    Kopec, Anna K; Joshi, Nikita; Towery, Keara L; Kassel, Karen M; Sullivan, Bradley P; Flick, Matthew J; Luyendyk, James P

    2014-11-01

    Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of obesity and metabolic syndrome. Robust coagulation cascade activation is common in obese patients with NAFLD. We identified a critical temporal relationship between thrombin generation and the manifestation of hepatic steatosis, inflammation, and injury in C57BL/6J mice fed a high-fat diet (HFD) for 1, 2, and 3 months. Mice fed a HFD exhibited dramatic increases in hepatocellular injury and inflammation over time. Hepatic fibrin deposition preceded an increase in serum alanine aminotransferase, and the most dramatic changes in liver histopathology occurred in conjunction with a detectable increase in plasma thrombin-antithrombin levels at 3 months. To directly determine whether thrombin activity promotes NAFLD pathogenesis, mice were fed a HFD and simultaneously treated with the direct thrombin inhibitor dabigatran etexilate for 3 months. Notably, dabigatran treatment significantly reduced hepatic fibrin deposition, hepatic inflammation, hepatocellular injury, and steatosis in mice fed a HFD. Of interest, dabigatran treatment also significantly attenuated HFD-induced body weight gain. Gene expression analysis suggested that thrombin potentially drives NAFLD pathogenesis by altering the expression of genes associated with lipid metabolism and bile acid synthesis. Collectively, the results suggest that thrombin activity is central to HFD-induced body weight gain, liver injury, and inflammation and provide the proof-of-principle evidence that pharmacological thrombin inhibition could be effective in limiting NAFLD and associated pathologies.

  20. Presence of plasma proteins facilitates the uptake of /sup 125/I-thrombin by the rabbit thoracic aorta endothelium in vitro

    SciTech Connect

    Hatton, M.W.; Moar, S.L.

    1986-07-01

    Various purified proteins, protein derivatives and two polysaccharides were added individually to a physiological medium in order to effect uptake of /sup 125/I-thrombin by the rabbit aorta endothelium. Over a wide range of concentration (0.004-40 mg/ml), the presence of either purified rabbit or bovine albumin during thrombin uptake encouraged an increase (70-110%) in /sup 125/I-thrombin binding by the endothelium and subendothelium compared to uptake by aorta segments in the absence of added protein. Pretreatment of aorta segments with albumin before incubation with /sup 125/I-thrombin in the absence of albumin did not encourage thrombin uptake to the same extent as having /sup 125/I-thrombin and albumin together. Purified human transferrin, rabbit IgG, chicken ovalbumin or denatured bovine casein could replace albumin to produce a similar enhancement of thrombin uptake. Replacing active concentrations of albumin by either reduced-carboxymethylated albumin, defatted albumin, plasmin-treated or thermolysin-treated albumin also caused an increase (50-130%) in thrombin binding, whereas replacement by acid-hydrolysed albumin or with polyglutamic acid was either ineffective or even inhibitory. Lysine-modified or arginine-modified albumins caused a small enhancement (14-32%) and no enhancement of thrombin uptake, respectively. Dextran, at low concentration (0.04-0.4 mg/ml) did not influence thrombin uptake, and at higher concentration (4-40 mg/ml) caused a decrease in uptake by both the endothelium and subendothelial layers. Low concentration of dextran sulphate inhibited thrombin uptake to 20-30% of control values. These data express the importance of accompanying protein in the response of the vascular endothelium during binding of thrombin. The possibility that other protein-cell interactions may be similarly influenced by macromolecular solutes is also discussed.

  1. Thrombin bound to a fibrin clot confers angiogenic and haemostatic properties on endothelial progenitor cells.

    PubMed

    Smadja, David M; Basire, Agnès; Amelot, Aymeric; Conte, Aurélie; Bièche, Ivan; Le Bonniec, Bernard F; Aiach, Martine; Gaussem, Pascale

    2008-06-01

    Recent data suggest that endothelial progenitor cells (EPCs) are involved in recanalizing venous thrombi. We examined the impact of a fibrin network, and particularly of adsorbed thrombin, on EPCs derived from cord blood CD34(+) cells. Fibrin networks generated in microplates by adding CaCl(2) to platelet-depleted plasma retained adsorbed thrombin at the average concentration of 4.2 nM per well. EPCs expressed high levels of endothelial cell protein C receptor and thrombomodulin, allowing the generation of activated protein C on the fibrin matrix in the presence of exogenous human protein C. The fibrin matrix induced significant EPC proliferation and, when placed in the lower chamber of a Boyden device, strongly enhanced EPC migration. These effects were partly inhibited by hirudin by 41% and 66%, respectively), which suggests that fibrin-adsorbed thrombin interacts with EPCs via the thrombin receptor PAR-1. Finally, spontaneous lysis of the fibrin network, studied by measuring D-dimer release into the supernatant, was inhibited by EPCs but not by control mononuclear cells. Such an effect was associated with a 10-fold increase in plasminogen activator inhibitor-1 (PAI-1) secretion by EPCs cultivated in fibrin matrix. Overall, our data show that EPCs, in addition to their angiogenic potential, have both anticoagulant and antifibrinolytic properties. Thrombin may modulate these properties and contribute to thrombus recanalization by EPCs.

  2. Thrombin bound to a fibrin clot confers angiogenic and haemostatic properties on endothelial progenitor cells

    PubMed Central

    Smadja, David M; Basire, Agnès; Amelot, Aymeric; Conte, Aurélie; Bièche, Ivan; Le Bonniec, Bernard F; Aiach, Martine; Gaussem, Pascale

    2008-01-01

    Abstract Recent data suggest that endothelial progenitor cells (EPCs) are involved in recanalizing venous thrombi. We examined the impact of a fibrin network, and particularly of adsorbed thrombin, on EPCs derived from cord blood CD34+ cells. Fibrin networks generated in microplates by adding CaCl2 to platelet-depleted plasma retained adsorbed thrombin at the average concentration of 4.2 nM per well. EPCs expressed high levels of endothelial cell protein C receptor and thrombomodulin, allowing the generation of activated protein C on the fibrin matrix in the presence of exogenous human protein C. The fibrin matrix induced significant EPC proliferation and, when placed in the lower chamber of a Boyden device, strongly enhanced EPC migration. These effects were partly inhibited by hirudin by 41% and 66%, respectively), which suggests that fibrin-adsorbed thrombin interacts with EPCs via the thrombin receptor PAR-1. Finally, spontaneous lysis of the fibrin network, studied by measuring D-dimer release into the supernatant, was inhibited by EPCs but not by control mononuclear cells. Such an effect was associated with a 10-fold increase in plasminogen activator inhibitor-1 (PAI-1) secretion by EPCs cultivated in fibrin matrix. Overall, our data show that EPCs, in addition to their angiogenic potential, have both anticoagulant and antifibrinolytic properties. Thrombin may modulate these properties and contribute to thrombus recanalization by EPCs. PMID:18494938

  3. Proton driven plasma wakefield generation in a parabolic plasma channel

    NASA Astrophysics Data System (ADS)

    Golian, Y.; Dorranian, D.

    2016-11-01

    An analytical model for the interaction of charged particle beams and plasma for a wakefield generation in a parabolic plasma channel is presented. In the suggested model, the plasma density profile has a minimum value on the propagation axis. A Gaussian proton beam is employed to excite the plasma wakefield in the channel. While previous works investigated on the simulation results and on the perturbation techniques in case of laser wakefield accelerations for a parabolic channel, we have carried out an analytical model and solved the accelerating field equation for proton beam in a parabolic plasma channel. The solution is expressed by Whittaker (hypergeometric) functions. Effects of plasma channel radius, proton bunch parameters and plasma parameters on the accelerating processes of proton driven plasma wakefield acceleration are studied. Results show that the higher accelerating fields could be generated in the PWFA scheme with modest reductions in the bunch size. Also, the modest increment in plasma channel radius is needed to obtain maximum accelerating gradient. In addition, the simulations of longitudinal and total radial wakefield in parabolic plasma channel are presented using LCODE. It is observed that the longitudinal wakefield generated by the bunch decreases with the distance behind the bunch while total radial wakefield increases with the distance behind the bunch.

  4. Plasma plume MHD power generator and method

    DOEpatents

    Hammer, James H.

    1993-01-01

    Highly-conducting plasma plumes are ejected across the interplanetary magnetic field from a situs that is moving relative to the solar wind, such as a spacecraft or an astral body, such as the moon, having no magnetosphere that excludes the solar wind. Discrete plasma plumes are generated by plasma guns at the situs extending in opposite directions to one another and at an angle, preferably orthogonal, to the magnetic field direction of the solar wind plasma. The opposed plumes are separately electrically connected to their source by a low impedance connection. The relative movement between the plasma plumes and the solar wind plasma creates a voltage drop across the plumes which is tapped by placing the desired electrical load between the electrical connections of the plumes to their sources. A portion of the energy produced may be used in generating the plasma plumes for sustained operation.

  5. Low-dose menaquinone-7 supplementation improved extra-hepatic vitamin K status, but had no effect on thrombin generation in healthy subjects.

    PubMed

    Theuwissen, Elke; Cranenburg, Ellen C; Knapen, Marjo H; Magdeleyns, Elke J; Teunissen, Kirsten J; Schurgers, Leon J; Smit, Egbert; Vermeer, Cees

    2012-11-14

    Vitamin K is required for the carboxylation of Gla-proteins in the liver (coagulation factors) and extra-hepatic tissues, such as bone (osteocalcin, OC), and arterial wall (matrix Gla-protein, MGP). Although the coagulation factors are essentially fully carboxylated under normal conditions, 10-40 % of OC and MGP remains undercarboxylated. We were therefore interested to study the dose-response effects of extra intake of menaquinones on the carboxylation of the extra-hepatic Gla-proteins. A total of forty-two healthy Dutch men and women aged between 18 and 45 years were randomised into seven groups to receive: placebo capsules or menaquinone-7 (MK-7) capsules at a daily dose of 10, 20, 45, 90, 180 or 360 μg. Circulating uncarboxylated OC (ucOC), carboxylated OC (cOC) and desphospho-uncarboxylated MGP were measured by ELISA. The ucOC:cOC ratio was calculated from circulating ucOC and cOC values. Endogenous thrombin potential and peak height were determined by calibrated automated thrombography. To increase the statistical power, we collapsed the treatment groups into three dosage groups: placebo, low-dose supplementation (doses below RDA, Commission Directive 2008/100/EC), and high-dose supplementation (doses around RDA, Commission Directive 2008/100/EC). MK-7 supplementation at doses in the order of the RDA (Commission Directive 2008/100/EC) increased the carboxylation of circulating OC and MGP. No adverse effects on thrombin generation were observed. Extra MK-7 intake at nutritional doses around the RDA (Commission Directive 2008/100/EC) improved the carboxylation of the extra-hepatic vitamin K-dependent proteins. Whether this improvement contributes to public health, i.e. increasing the protection against age-related diseases needs further investigation in specifically designed intervention trials.

  6. Hydrogen ionic plasma generated using Al plasma grid

    NASA Astrophysics Data System (ADS)

    Oohara, W.; Anegawa, N.; Egawa, M.; Kawata, K.; Kamikawa, T.

    2016-08-01

    Negative hydrogen ions are produced in the apertures of a plasma grid made of aluminum under the irradiation of positive ions, generating an ionic plasma consisting of positive and negative ions. The saturation current ratio obtained using a Langmuir probe reflects the existence ratio of electrons and is found to increase in connection with the diffusion of the ionic plasma. The local increment of the current ratio suggests the collapse of negative ions and the replacement of detached electrons.

  7. Plasma generating apparatus for large area plasma processing

    DOEpatents

    Tsai, Chin-Chi; Gorbatkin, Steven M.; Berry, Lee A.

    1991-01-01

    A plasma generating apparatus for plasma processing applications is based on a permanent magnet line-cusp plasma confinement chamber coupled to a compact single-coil microwave waveguide launcher. The device creates an electron cyclotron resonance (ECR) plasma in the launcher and a second ECR plasma is created in the line cusps due to a 0.0875 tesla magnetic field in that region. Additional special magnetic field configuring reduces the magnetic field at the substrate to below 0.001 tesla. The resulting plasma source is capable of producing large-area (20-cm diam), highly uniform (.+-.5%) ion beams with current densities above 5 mA/cm.sup.2. The source has been used to etch photoresist on 5-inch diam silicon wafers with good uniformity.

  8. Plasma generating apparatus for large area plasma processing

    DOEpatents

    Tsai, C.C.; Gorbatkin, S.M.; Berry, L.A.

    1991-07-16

    A plasma generating apparatus for plasma processing applications is based on a permanent magnet line-cusp plasma confinement chamber coupled to a compact single-coil microwave waveguide launcher. The device creates an electron cyclotron resonance (ECR) plasma in the launcher and a second ECR plasma is created in the line cusps due to a 0.0875 tesla magnetic field in that region. Additional special magnetic field configuring reduces the magnetic field at the substrate to below 0.001 tesla. The resulting plasma source is capable of producing large-area (20-cm diam), highly uniform (.+-.5%) ion beams with current densities above 5 mA/cm[sup 2]. The source has been used to etch photoresist on 5-inch diam silicon wafers with good uniformity. 3 figures.

  9. High frequency plasma generator for ion thrusters

    NASA Technical Reports Server (NTRS)

    Goede, H.; Divergilio, W. F.; Fosnight, V. V.; Komatsu, G.

    1984-01-01

    The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.

  10. Electrodynamic plasma motor/generator experiment

    NASA Technical Reports Server (NTRS)

    Mccoy, James E.

    1987-01-01

    The Plasma Motor/Generator Proof of Function (PMG/POF) experiment, a low-cost payload for flight aboard the Shuttle Orbiter using the Hitchhiker G carrier, is discussed. The primary objective of this experiment is to verify that hollow cathode plasma sources can couple electric currents from either end of a long wire moving through the space plasma in LEO into and through that plasma to produce a PMG circuit. The support structure and the electrical components of the experiment are described. The experimental operation is discussed, including the calibration, experimental measurements, and follow-on missions.

  11. Ion beams from laser-generated plasmas

    NASA Technical Reports Server (NTRS)

    Hughes, R. H.; Anderson, R. J.; Gray, L. G.; Rosenfeld, J. P.; Manka, C. K.; Carruth, M. R.

    1980-01-01

    The paper describes the space-charge-limited beams produced by the plasma blowoffs generated by 20-MW bursts of 1.06-micron radiation from an active Q-switched Nd:YAG laser. Laser power densities near 10 to the 11th/sq cm on solid targets generate thermalized plasma plumes which drift to a 15-kV gridded extraction gap where the ions are extracted, accelerated, and electrostatically focused; the spatially defined ion beams are then magnetically analyzed to determine the charge state content in the beams formed from carbon, aluminum, copper, and lead targets. This technique preserves time-of-flight (TOF) information in the plasma drift region, which permits plasma ion temperatures and mass flow velocities to be determined from the Maxwellian ion curve TOF shapes for the individual charge species.

  12. Highly enhanced electrochemiluminescence based on pseudo triple-enzyme cascade catalysis and in situ generation of co-reactant for thrombin detection.

    PubMed

    Xiao, Lijuan; Chai, Yaqin; Yuan, Ruo; Wang, Haijun; Bai, Lijuan

    2014-03-07

    In this work, a novel pseudo triple-enzyme cascade catalysis amplification strategy was employed to fabricate a highly sensitive electrochemiluminescence (ECL) aptasensor for thrombin (TB) detection. The signal amplification of the proposed aptasensor was based on the synergistic catalysis of glucose dehydrogenase (GDH) and hemin/G-quadruplex to generate a co-reactant in situ for the ECL of peroxydisulfate. Gold nanorods (AuNRs) conjugated with GDH and hemin/G-quadruplex were used as the secondary aptamer bioconjugate (TBA II) in this aptasensor. TB was sandwiched between TBA II and a thiol-terminated TB aptamer which self-assembled on the AuNRs-modified electrode. The pseudo triple-enzyme cascade catalysis was completed as follows: firstly, GDH could effectively catalyze the oxidation of glucose to gluconolactone, coupling with the reduction of β-nicotinamide adenine dinucleotide hydrate (NAD(+)) into β-nicotinamide adenine dinucleotide hydrogen (NADH). Then, the hemin/G-quadruplex acted as NADH oxidase, could rapidly oxidize NADH into NAD(+) accompanied with the generation of H2O2. Simultaneously, the hemin/G-quadruplex served as the horseradish peroxidase (HRP)-mimicking DNAzyme that further catalyzed the reduction of H2O2 to generate O2in situ. Then the O2 produced acted as the co-reactant of peroxydisulfate, resulting in significant ECL signal amplification and highly sensitive ECL detection. The proposed aptasensor showed a wide linear range of 0.0001-50 nM with a low detection limit of 33 fM (S/N = 3) for TB determination. The present work demonstrated that the novel strategy has great advantages of sensitivity, selectivity and reproducibility, which hold new promise for highly sensitive bioassays applied in clinical detection.

  13. Surface plasma source with saddle antenna radio frequency plasma generator

    SciTech Connect

    Dudnikov, V.; Johnson, R. P.; Murray, S.; Pennisi, T.; Piller, C.; Santana, M.; Stockli, M.; Welton, R.

    2012-02-15

    A prototype RF H{sup -} surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA/kW. Control experiments with H{sup -} beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

  14. Surface plasma source with saddle antenna radio frequency plasma generator.

    PubMed

    Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

    2012-02-01

    A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

  15. Cold plasma brush generated at atmospheric pressure

    SciTech Connect

    Duan Yixiang; Huang, C.; Yu, Q. S.

    2007-01-15

    A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 deg. C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.

  16. Extreme hydrogen plasma densities achieved in a linear plasma generator

    SciTech Connect

    Rooij, G. J. van; Veremiyenko, V. P.; Goedheer, W. J.; de Groot, B.; Kleyn, A. W.; Smeets, P. H. M.; Versloot, T. W.; Whyte, D. G.; Engeln, R.; Schram, D. C.; Cardozo, N. J. Lopes

    2007-03-19

    A magnetized hydrogen plasma beam was generated with a cascaded arc, expanding in a vacuum vessel at an axial magnetic field of up to 1.6 T. Its characteristics were measured at a distance of 4 cm from the nozzle: up to a 2 cm beam diameter, 7.5x10{sup 20} m{sup -3} electron density, {approx}2 eV electron and ion temperatures, and 3.5 km/s axial plasma velocity. This gives a 2.6x10{sup 24} H{sup +} m{sup -2} s{sup -1} peak ion flux density, which is unprecedented in linear plasma generators. The high efficiency of the source is obtained by the combined action of the magnetic field and an optimized nozzle geometry. This is interpreted as a cross-field return current that leads to power dissipation in the beam just outside the source.

  17. Nonlinear subharmonic generation in nonuniform plasmas

    NASA Astrophysics Data System (ADS)

    Gradov, O. M.; Stenflo, L.

    1980-07-01

    Direct subharmonic wave generation in a nonuniform plasma is considered. That mechanism exists only when leaking surface waves can be parametrically excited. An expression for the instability growth rate, which includes collisions, resonance absorption and leaking losses, is derived. A possibility of generating subharmonics at omega(0)/4, 3-omega(0)/4, and 5-omega(0)/4, where omega(0) is the pump wave frequency, is pointed out, and the corresponding field intensities are estimated. The conditions for total energy absorption are discussed, and the pump wave intensity, which produces complete absorption, is obtained for a plasma with a steep density gradient.

  18. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Fosnight, V. V.

    1981-01-01

    The results of a one year program to experimentally adapt two new types of high frequency plasma generators to Argon ion thrusters and to analytically study a third high frequency source concept are presented. Conventional 30 cm two grid ion extraction was utilized or proposed for all three sources. The two plasma generating methods selected for experimental study were a radio frequency induction (RFI) source, operating at about 1 MHz, and an electron cyclotron heated (ECH) plasma source operating at about 5 GHz. Both sources utilize multi-linecusp permanent magnet configurations for plasma confinement. The plasma characteristics, plasma loading of the rf antenna, and the rf frequency dependence of source efficiency and antenna circuit efficiency are described for the RFI Multi-cusp source. In a series of tests of this source at Lewis Research Center, minimum discharge losses of 220+/-10 eV/ion were obtained with propellant utilization of .45 at a beam current of 3 amperes. Possible improvement modifications are discussed.

  19. Plasma generators, reactor systems and related methods

    SciTech Connect

    Kong, Peter C.; Pink, Robert J.; Lee, James E.

    2007-06-19

    A plasma generator, reactor and associated systems and methods are provided in accordance with the present invention. A plasma reactor may include multiple sections or modules which are removably coupled together to form a chamber. Associated with each section is an electrode set including three electrodes with each electrode being coupled to a single phase of a three-phase alternating current (AC) power supply. The electrodes are disposed about a longitudinal centerline of the chamber and are arranged to provide and extended arc and generate an extended body of plasma. The electrodes are displaceable relative to the longitudinal centerline of the chamber. A control system may be utilized so as to automatically displace the electrodes and define an electrode gap responsive to measure voltage or current levels of the associated power supply.

  20. Plasma focus experiments powered by explosive generators

    NASA Astrophysics Data System (ADS)

    Freeman, B. L.; Caird, R. S.; Erickson, D. J.; Fowler, C. M.; Garn, W. B.; Kruse, H. W.; King, J. C.; Bartram, D. E.; Kruse, P. J.

    1983-03-01

    The plasma focus project began as an effort to develop an intense, pulsed, expendable neutron radiographic source. Since previous efforts to power a plasma focus with explosive generators were successful, we proposed to couple plate generators to a coaxial-geometry plasma focus to achieve this goal. Utilizing a small capacitor bank and a selected set of diagnostics, the explosive experiments were successfully conducted with maximum currents of 1.5 MA to 2.4 MA. A maximum neutron yield of approx. 3 x 10 (11) (DD) neutrons was achieved at the 2.4 MA level. Since the neutron yield did scale as a power of the maximum delivered current, and the neutron-producing source region was small, this approach is an attractive option to achieve a neutron radiographic source. The need for a reliable open-circuiting switch at several megamperes has resulted in postponement of the project.

  1. Joint health scores in a haemophilia A cohort from Pakistan with minimal or no access to factor VIII concentrate: correlation with thrombin generation and underlying mutation.

    PubMed

    Khanum, F; Bowen, D J; Kerr, B C; Collins, P W

    2014-05-01

    Haemophilia A is associated with recurrent joint bleeding which leads to synovitis and debilitating arthropathy. Coagulation factor VIII level is an important determinant of bleed number and development of arthropathy . The aim of this study was to compare the haemophilia joint health score (HJHS) and Gilbert score with severity, age, thrombin generation (TG) and underlying mutation in a haemophilia A cohort which had minimal access to haemostatic replacement therapy. Ninety-two haemophilia A individuals were recruited from Pakistan. Age, age at first bleed, target joints, haemophilic arthropathy joints, HJHS and Gilbert score were recorded. A strong correlation was found between HJHS and Gilbert score (r = 0.98), both were significantly higher in severe (n = 59) compared with non-severe (n = 29) individuals before the age of 12 years (P ≤ 0.01) but not thereafter. When individuals were divided according to developmental age (<12 years, 12-16 years and >16 years), both HJHS and Gilbert score were significantly lower in the youngest group (P ≤ 0.001), there was no difference between 12-16 years and >16 years. In severe individuals there was no correlation between in vitro TG and joint score, whereas in non-severe individuals there was a weak negative correlation. In the severe group, no significant difference was observed for either joint score according to the underlying mutation type (inversion, missense, nonsense, frameshift). In this cohort of haemophilia A individuals with minimal access to haemostatic treatment, haemophilic arthropathy correlated with severity and age; among severe individuals, joint health scores did not relate to either the underlying mutation or in vitro TG.

  2. Plasma driven neutron/gamma generator

    DOEpatents

    Leung, Ka-Ngo; Antolak, Arlyn

    2015-03-03

    An apparatus for the generation of neutron/gamma rays is described including a chamber which defines an ion source, said apparatus including an RF antenna positioned outside of or within the chamber. Positioned within the chamber is a target material. One or more sets of confining magnets are also provided to create a cross B magnetic field directly above the target. To generate neutrons/gamma rays, the appropriate source gas is first introduced into the chamber, the RF antenna energized and a plasma formed. A series of high voltage pulses are then applied to the target. A plasma sheath, which serves as an accelerating gap, is formed upon application of the high voltage pulse to the target. Depending upon the selected combination of source gas and target material, either neutrons or gamma rays are generated, which may be used for cargo inspection, and the like.

  3. Disparate temporal expression of the prothrombin and thrombin receptor genes during mouse development.

    PubMed Central

    Soifer, S. J.; Peters, K. G.; O'Keefe, J.; Coughlin, S. R.

    1994-01-01

    The protease thrombin is a potent agonist for platelet aggregation, mesenchymal cell proliferation, and endothelial production of growth factors and adhesion molecules. Thrombin also modulates neurite outgrowth in neuronal cultures. These apparently disparate responses to thrombin appear to be largely mediated by the recently cloned thrombin receptor. In the adult, thrombin is generated from its zymogen prothrombin at sites of vascular injury when circulating coagulation factors meet extravascular tissue factor. In this context thrombin's varied actions may mediate responses to wounding. Whether thrombin's actions on cells may also play a role in development is unknown. We examined the expression of thrombin receptor, prothrombin, and tissue factor by in situ hybridization in mouse development. Thrombin receptor mRNA was expressed widely in mesenchymal cell populations during early organogenesis (E9.5) and was particularly abundant in developing heart and blood vessels. Robust receptor expression was also noted in the germinal epithelium of the hindbrain. Thrombin receptor expression became more restricted with time and by the fetal growth stage (E16.5) was most readily detected in certain neurons, endocardial and endothelial cells, and within lung and liver. In contrast to the thrombin receptor, prothrombin mRNA was limited to the embryonic liver and was not detected until E12.5, well after the onset of receptor expression. mRNA for tissue factor, one important trigger for thrombin generation in the adult, was detected in embryonic epithelia from E9.5-12.5. In several instances, tissue factor-expressing epithelia were surrounded by thrombin receptor-expressing mesenchyme. These data suggest a possible role for the thrombin receptor in development. The finding of robust thrombin receptor expression before prothrombin mRNA was detected raises the question of whether other proteases or peptide ligands can activate the thrombin receptor. Images Figure 1 Figure 2

  4. Terahertz twisted beams generation in plasma

    NASA Astrophysics Data System (ADS)

    Sobhani, Hassan; Vaziri (Khamedi), Mohammad; Rooholamininejad, Hossien; Bahrampour, Alireza

    2016-08-01

    The resonant vortex terahertz beam generation by the cross-focusing of two twisted coaxial laser beams is investigated. For the resonant excitation of terahertz radiation, the rippled density in plasma and the ripple wave number is suitably chosen to satisfy the phase matching condition. The nonlinear current density at terahertz frequency arises due to the spatial variation of two Laguerre-Gaussian coupled field. The terahertz intensity scales as the ponderomotive force of laser beams which imparts an oscillatory velocity to the electrons and, in fact, input Laguerre-Gaussian laser beams properties such as vortex charge number and beam waist. Various laser and plasma parameters are employed to yield vortex terahertz radiation with higher efficiency. Also, it is shown that when the beating frequency approaches plasma frequency, the amplitude of THz radiation increases.

  5. Runaway electron generation in a cooling plasma

    SciTech Connect

    Smith, H.; Helander, P.; Eriksson, L.-G.; Fueloep, T.

    2005-12-15

    The usual calculation of Dreicer [Phys. Rev. 115, 238 (1959); 117, 329 (1960)] generation of runaway electrons assumes that the plasma is in a steady state. In a tokamak disruption this is not necessarily true since the plasma cools down quickly and the collision time for electrons at the runaway threshold energy can be comparable to the cooling time. The electron distribution function then acquires a high-energy tail which can easily be converted to a burst of runaways by the rising electric field. This process is investigated and simple criteria for its importance are derived. If no rapid losses of fast electrons occur, this can be a more important source of runaway electrons than ordinary Dreicer generation in tokamak disruptions.

  6. Pulsed Energy Systems for Generating Plasmas

    NASA Technical Reports Server (NTRS)

    Rose, M. Franklin; Shotts, Z.

    2005-01-01

    This paper will describe the techniques needed to electrically generate highly ionized dense plasmas for a variety of applications. The components needed in pulsed circuits are described in terms of general performance parameters currently available from commercial vendors. Examples of pulsed systems using these components are described and technical data from laboratory experiments presented. Experimental data are given for point designs, capable of multi-megawatt power levels.

  7. Plasma membrane associated phospholipase C from human platelets: Synergistic stimulation of phosphatidylinositol 4,5-bisphosphate hydrolysis by thrombin and guanosine 5 prime -O-(3-thiotriphosphate)

    SciTech Connect

    Baldassare, J.J.; Henderson, P.A.; Fisher, G.J. )

    1989-01-10

    The effects of thrombin and GTP{gamma}S on the hydrolysis of phosphoinositides by membrane-associated phospholipase C (PLC) from human platelets were examined with endogenous ({sup 3}H)inositol-labeled membranes or with lipid vesicles containing either ({sup 3}H)phosphatidylinositol or ({sup 3}H)phosphatidylinositol 4,5-bisphosphate. GTP{gamma}S (1 {mu}M) or thrombin (1 unit/mL) did not stimulate release of inositol trisphosphate (IP{sub 3}), inositol bisphosphate (IP{sub 2}), or inositol phosphate (IP) from ({sup 3}H)inositol-labeled membranes. IP{sub 2} and IP{sub 3}, but not IP, from ({sup 3}H)inositol-labeled membranes were, however, stimulated 3-fold by GTP{gamma}S (1 {mu}M) plus thrombin (1 unit/mL). A higher concentration of GTP{gamma}S (100 {mu}M) alone also stimulated IP{sub 2} and IP{sub 3}, but not IP, release. In the presence of 1 mM calcium, release of IP{sub 2} and IP{sub 3} was increased 6-fold over basal levels; however, formation of IP was not observed. At submicromolar calcium concentration, hydrolysis of exogenous phosphatidylinositol 4,5-bisphosphate (PIP{sub 2}) by platelet membrane associated PLC was also markedly enhanced by GTP{gamma}S (100 {mu}M) or GTP{gamma}S (1 {mu}M) plus thrombin (1 unit/mL). Under identical conditions, exogenous phosphatidylinositol (PI) was not hydrolyzed. The same substrate specificity was observed when the membrane-associated PLC was activated with 1 mM calcium. Thrombin-induced hydrolysis of PIP{sub 2} was inhibited by treatment of the membranes with pertussis toxin or pretreatment of intact platelets with 12-O-tetradecanoyl-13-acetate (TPA) prior to preparation of membranes. Pertussis toxin did not inhibit GTP{gamma}S (100 {mu}M) or calcium (1 mM) dependent PIP{sub 2} breakdown, while TPA inhibited GTP{gamma}S-dependent but not calcium-dependent phospholipase C activity.

  8. Rational Design of Potent, Small, Synthetic Allosteric Inhibitors of Thrombin

    PubMed Central

    Sidhu, Preetpal Singh; Liang, Aiye; Mehta, Akul Y.; Abdel Aziz, May H.; Zhou, Qibing; Desai, Umesh R.

    2011-01-01

    Thrombin is a key enzyme targeted by the majority of current anticoagulants that are direct inhibitors. Allosteric inhibition of thrombin may offer a major advantage of finely tuned regulation. We present here sulfated benzofurans as the first examples of potent, small allosteric inhibitors of thrombin. A sulfated benzofuran library of 15 sulfated monomers and 13 sulfated dimers with different charged, polar and hydrophobic substituents was studied in this work. Synthesis of the sulfated benzofurans was achieved through a multiple step, highly branched strategy, which culminated with microwave-assisted chemical sulfation. Of the 28 potential inhibitors, eleven exhibited reasonable inhibition of human α-thrombin at pH 7.4. Structure activity relationship analysis indicated that sulfation at the 5-position of the benzofuran scaffold was essential for targeting thrombin. A t-butyl 5-sulfated benzofuran derivative was found to be the most potent thrombin inhibitor with an IC50 of 7.3 μM under physiologically relevant conditions. Michaelis-Menten studies showed an allosteric inhibition phenomenon. Plasma clotting assays indicate that the sulfated benzofurans prolong both the activated partial thromboplastin time and prothrombin time. Overall, this work puts forward sulfated benzofurans as the first small, synthetic molecules as powerful lead compounds for the design of a new class of allosteric inhibitors of thrombin. PMID:21714536

  9. Effect of thrombin on maturing human megakaryocytes.

    PubMed Central

    Cramer, E. M.; Massé, J. M.; Caen, J. P.; Garcia, I.; Breton-Gorius, J.; Debili, N.; Vainchenker, W.

    1993-01-01

    Thrombin causes platelet activation and secretion. In some nucleated cells, it is mitogenic. In this study, we have investigated how human megakaryocytes (MKs) respond to this agonist and whether the response depends on the maturation stage. MKs were cultured from bone marrow precursors in liquid culture in the presence of normal plasma. To determine whether thrombin can activate MKs, 14-day MK cultures were incubated with thrombin for 5 minutes, and cells were studied by electron microscopy, either by standard techniques or after embedding in glycol-methacrylate for immunoelectron microscopy. Ultrastructural examination of thrombin-treated MKs revealed dramatic morphological changes reminiscent of those found in platelets, including shape change and organelle centralization that involved immature as well as mature cells. MKs were also able to secrete alpha-granule proteins in the dilated cisternae of the demarcation membrane system, as shown by immunogold staining for thrombospondin and glycoprotein Ib. These changes were rapid (less than 5 minutes) but despite them, MKs remained viable for more than 24 hours. To determine whether thrombin has a mitogenic activity, it was added to the culture of MKs from day 3 to day 10 of culture at concentrations varying from 0.1 to 10 U/ml. Cells were subsequently studied by a double staining technique using flow cytometry to determine MK number and ploidy. No changes were observed in these two parameters, showing that thrombin is not mitogenic for MKs at the concentrations used. In conclusion, this study confirms for human MKs previous observations made about guinea pig MKs (Fedorko et al, Lab Invest 1977, 36:32). In addition, it demonstrates that immature MKs are able to respond to thrombin and that more mature cells can secrete alpha-granule proteins into the demarcation membrane system, which is in continuity with the extracellular space. This phenomenon may have implications for pathological states such as myelofibrosis

  10. Microwave generated plasma light source apparatus

    SciTech Connect

    Yoshizawa, K.; Ito, H.; Kodama, H.; Komura, H.; Minowa, Y.

    1985-02-05

    A microwave generated plasma light source including a microwave generator, a microwave cavity having a light reflecting member forming at least a portion of the cavity, and a member transparent to light and opaque to microwaves disposed across an opening of the cavity opposite the feeding opening through which the microwave generator is coupled. An electrodeless discharge bulb is disposed at a position in the cavity such that the cavity operates as a resonant cavity at least when the bulb is emitting light. In the bulb is encapsulated at least one discharge light emissive substance. The bulb has a shape and is sufficiently small that the bulb acts substantially as a point light source.

  11. Thyristor stack for pulsed inductive plasma generation

    SciTech Connect

    Teske, C.; Jacoby, J.; Schweizer, W.; Wiechula, J.

    2009-03-15

    A thyristor stack for pulsed inductive plasma generation has been developed and tested. The stack design includes a free wheeling diode assembly for current reversal. Triggering of the device is achieved by a high side biased, self supplied gate driver unit using gating energy derived from a local snubber network. The structure guarantees a hard firing gate pulse for the required high dI/dt application. A single fiber optic command is needed to achieve a simultaneous turn on of the thyristors. The stack assembly is used for switching a series resonant circuit with a ringing frequency of 30 kHz. In the prototype pulsed power system described here an inductive discharge has been generated with a pulse duration of 120 {mu}s and a pulse energy of 50 J. A maximum power transfer efficiency of 84% and a peak power of 480 kW inside the discharge were achieved. System tests were performed with a purely inductive load and an inductively generated plasma acting as a load through transformer action at a voltage level of 4.1 kV, a peak current of 5 kA, and a current switching rate of 1 kA/{mu}s.

  12. Thyristor stack for pulsed inductive plasma generation.

    PubMed

    Teske, C; Jacoby, J; Schweizer, W; Wiechula, J

    2009-03-01

    A thyristor stack for pulsed inductive plasma generation has been developed and tested. The stack design includes a free wheeling diode assembly for current reversal. Triggering of the device is achieved by a high side biased, self supplied gate driver unit using gating energy derived from a local snubber network. The structure guarantees a hard firing gate pulse for the required high dI/dt application. A single fiber optic command is needed to achieve a simultaneous turn on of the thyristors. The stack assembly is used for switching a series resonant circuit with a ringing frequency of 30 kHz. In the prototype pulsed power system described here an inductive discharge has been generated with a pulse duration of 120 micros and a pulse energy of 50 J. A maximum power transfer efficiency of 84% and a peak power of 480 kW inside the discharge were achieved. System tests were performed with a purely inductive load and an inductively generated plasma acting as a load through transformer action at a voltage level of 4.1 kV, a peak current of 5 kA, and a current switching rate of 1 kA/micros.

  13. Volumetric Near-Field Microwave Plasma Generation

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Balla, R. Jeffrey; Herring, G. C.; Popovic, S.; Vuskovic, L.

    2003-01-01

    A periodic series of microwave-induced plasmoids is generated using the outgoing wave from a microwave horn and the reflected wave from a nearby on-axis concave reflector. The plasmoids are spaced at half-wavelength separations according to a standing-wave pattern. The plasmoids are enhanced by an effective focusing in the near field of the horn (Fresnel region) as a result of a diffractive narrowing. Optical imaging, electron density, and rotational temperature measurements characterize the near field plasma region. Volumetric microwave discharges may have application to combustion ignition in scramjet engines.

  14. Power consumption analysis DBD plasma ozone generator

    NASA Astrophysics Data System (ADS)

    Nur, M.; Restiwijaya, M.; Muchlisin, Z.; Susan, I. A.; Arianto, F.; Widyanto, S. A.

    2016-11-01

    Studies on the consumption of energy by an ozone generator with various constructions electrodes of dielectric barrier discharge plasma (DBDP) reactor has been carried out. This research was done to get the configuration of the reactor, that is capable to produce high ozone concentrations with low energy consumption. BDBP reactors were constructed by spiral- cylindrical configuration, plasma ozone was generated by high voltage AC voltage up to 25 kV and maximum frequency of 23 kHz. The reactor consists of an active electrode in the form of a spiral-shaped with variation diameter Dc, and it was made by using copper wire with diameter Dw. In this research, we variated number of loops coil windings N as well as Dc and Dw. Ozone concentrations greater when the wire's diameter Dw and the diameter of the coil windings applied was greater. We found that impedance greater will minimize the concentration of ozone, in contrary to the greater capacitance will increase the concentration of ozone. The ozone concentrations increase with augmenting of power. Maximum power is effective at DBD reactor spiral-cylinder is on the Dc = 20 mm, Dw = 1.2 mm, and the number of coil windings N = 10 loops with the resulting concentration is greater than 20 ppm and it consumes energy of 177.60 watts

  15. Thrombin inhibitor design.

    PubMed

    Sanderson, P E; Naylor-Olsen, A M

    1998-08-01

    Recently, iv formulated direct thrombin inhibitors have been shown to be safe and efficacious alternatives to heparin. These results have fueled the hopes for an orally active compound. Such a compound could be a significant advance over warfarin if it had predictable pharmacokinetics and a duration of action sufficient for once or twice a day dosing. In order to develop an orally active compound which meets these criteria, the deficiencies of the prototype inhibitor efegatran have had to be addressed. First, using a combination of structure based design and empirical structure optimization, more selective compounds have been identified by modifying the P1 group or by incorporating different peptidomimetic P2/P3 scaffolds. Secondly, this optimization has resulted in the development of potent and selective non-covalent inhibitors, thus bypassing the liabilities of the serine trap. Thirdly, oral bioavailability has been achieved while maintaining selectivity and efficacy through the incorporation of progressively less basic P1 groups. The duration of action of these compounds remains to be optimized. Other advances in thrombin inhibitor design have included the development of uncharged P1 groups and the discovery of two non-peptide templates.

  16. Evidence for a hyperglycaemia-dependent decrease of antithrombin III-thrombin complex formation in humans.

    PubMed

    Ceriello, A; Giugliano, D; Quatraro, A; Marchi, E; Barbanti, M; Lefèbvre, P

    1990-03-01

    In the presence of increased levels of fibrinopeptide A, decreased antithrombin III biological activity, and thrombin-antithrombin III complex levels are seen in diabetic patients. Induced-hyperglycaemia in diabetic and normal subjects decreased antithrombin III activity and thrombin-antithrombin III levels, and increased fibrinopeptide A plasma levels, while antithrombin III concentration did not change; heparin was shown to reduced these phenomena. In diabetic patients, euglycaemia induced by insulin infusion restored antithrombin III activity, thrombin-antithrombin III complex and fibrinopeptide A concentrations; heparin administration had the same effects. These data stress the role of a hyperglycaemia-dependent decrease of antithrombin III activity in precipitating thrombin hyperactivity in diabetes mellitus.

  17. RF generated atmospheric pressure plasmas and applications

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Herrmann, Hans W.; Henins, Ivars; Gautier, Donald C.

    2001-10-01

    RF generated atmospheric pressure plasma sources have been developed for various materials applications. They operate with rf power and produce a α-mode capacitive discharge that is stable, steady-state, non-thermal, and volumetric. The plasma parameters of this source have been measured: electron densities of 10^11 cm-3 and electron temperatures of 2 eV by using neutral bremsstrahlung emission. Localized electron heating near the sheath boundary has been observed and is related to the discharge stability and α to γ mode (or arcing) transition using 1D fluid model. The discharge stability improves with increase in rf frequency. The electrode surface property such as the secondary electron emission coefficient also plays a significant role in determining α to γ mode transition. For example, a stable α-mode air discharge is produced using 100 MHz rf power with the use of a boron nitride cover on one of the electrodes. In comparison, an air discharge becomes unstable at a lower rf frequency (e.g. 13.56 MHz) or with an alumina cover. Similar results were obtained with various feedgas such as steam, CO_2, and hydrocarbon containing gases. Further characterization of this high frequency source is under progress. For its applications, we have successfully demonstrated the effective neutralization of actual chemical warfare agents such as VX, GD and HD. In addition, significant progresses have been made in the area of etching of organic and metal film etching, and production of novel materials.

  18. Plasma Motor Generator (PMG) electrodynamic tether experiment

    NASA Technical Reports Server (NTRS)

    Grossi, Mario D.

    1995-01-01

    The Plasma Motor Generator (PMG) flight of June 26, 1993 has been the most sophisticated and most successful mission that has been carried out thus far with an electrodynamic tether. Three papers from the Smithsonian Astrophysical Observatory, Washington, DC concerned with the PMG, submitted at the Fourth International Space Conference on Tethers in Space, in Washington, DC, in April 1995, are contained in this document. The three papers are (1) Electromagnetic interactions between the PMG tether and the magneto-ionic medium of the Ionosphere; (2) Tether-current-voltage characteristics, as determined by the Hollow Cathode Operation Modes; and (3) Hawaii-Hilo ground observations on the occasion for the PMG flight of June 23, 1993.

  19. Generation And Applications Of Electron-Beam Plasma Flows

    NASA Astrophysics Data System (ADS)

    Vasiliev, M. N.; Tun Win, Aung

    2015-03-01

    Plasma flows generated by continuous or interrupted injection of an electron beam into subsonic or supersonic gaseous streams are considered. Liquid and powder spraying by the electron-beam plasma (EBP) flows is studied as a technique of the aerosol plasma generation. A number of experimental setups generating both free plasma jets and plasma flows in channels are described. Examples of the EBP flows applications for industrial and aerospace technologies are given. The applications are shown to be based on unique properties of the EBP and its stability within very wide ranges of the plasma generation conditions. Some applications of the Hybrid Plasma (HP) generated by combined action of the electron beam (EB) and intermittent gas discharge on flows of gaseous mixtures and aerosols are presented as well.

  20. Plasmas generated in bubbles immersed in liquids: direct current streamers versus microwave plasma

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Sharma, Ashish; Raja, Laxminarayan L.

    2016-07-01

    Two approaches to generate non-equilibrium atmospheric-pressure plasma in bubbles immersed in liquids are compared using high-fidelity 2D fluid simulations. In the first approach, corona/streamer like plasma is generated using high-voltage negative and positive pulses applied between two electrodes (pin-to-plane geometry) immersed in liquid. In the second, the plasma is generated using a remote microwave source (frequency 2.45 GHz). We find that the microwave approach requires less energy, while generating a denser, more chemically reactive and more uniform plasma within the bubble volume, as compared to the plasma generated using high-voltage pulsing.

  1. EMF generation in low-temperature plasma

    NASA Astrophysics Data System (ADS)

    Pal, Alexander; Babichev, Valery; Dyatko, Nikolay; Filippov, Anatoly; Starostin, Andrey

    2016-09-01

    EMF generation in plasma created by an e-beam in electropositive gases at atmospheric pressure was investigated experimentally and numerically. It was found that propagation of 120 keV e-beam with cross-section 1 . 2 × 2 cm2 and current of 240 μA through argon at 105 Pa gas pressure between an aluminum exit window and an iron collector was followed by 360 μA current of opposite direction. A numerical modeling of the current flux was performed in an one-dimensional approximation along the axis z in the direction of e-beam propagation. It is seen, that the current density grows with increasing the ionization rate and the largest effect takes place in argon. The discovered effect of the current flux is determined by nonuniform gas ionization resulting in different diffusion electron fluxes near different electrodes and, therefore, in different near-electrodes potential falls. This difference creates a steady current flux in the inter-electrode gap. The mechanism of EMF generation is analogous to the Dember effect at the nonuniform photoexcitation of semiconductors. The work was supported by the Russian Science Foundation, Project No. 16-12-10511.

  2. Plasma cell treatment device Plasma-on-Chip: Monitoring plasma-generated reactive species in microwells.

    PubMed

    Oh, Jun-Seok; Kojima, Shinya; Sasaki, Minoru; Hatta, Akimitsu; Kumagai, Shinya

    2017-02-08

    We have developed a plasma cell treatment device called Plasma-on-Chip that enables the real-time monitoring of a single cell culture during plasma treatment. The device consists of three parts: 1) microwells for cell culture, 2) a microplasma device for generating reactive oxygen and nitrogen species (RONS) for use in cell treatment, and 3) through-holes (microchannels) that connect each microwell with the microplasma region for RONS delivery. Here, we analysed the delivery of the RONS to the liquid culture medium stored in the microwells. We developed a simple experimental set-up using a microdevice and applied in situ ultraviolet absorption spectroscopy with high sensitivity for detecting RONS in liquid. The plasma-generated RONS were delivered into the liquid culture medium via the through-holes fabricated into the microdevice. The RONS concentrations were on the order of 10-100 μM depending on the size of the through-holes. In contrast, we found that the amount of dissolved oxygen was almost constant. To investigate the process of RONS generation, we numerically analysed the gas flow in the through-holes. We suggest that the circulating gas flow in the through-holes promotes the interaction between the plasma (ionised gas) and the liquid, resulting in enhanced RONS concentrations.

  3. Plasma cell treatment device Plasma-on-Chip: Monitoring plasma-generated reactive species in microwells

    NASA Astrophysics Data System (ADS)

    Oh, Jun-Seok; Kojima, Shinya; Sasaki, Minoru; Hatta, Akimitsu; Kumagai, Shinya

    2017-02-01

    We have developed a plasma cell treatment device called Plasma-on-Chip that enables the real-time monitoring of a single cell culture during plasma treatment. The device consists of three parts: 1) microwells for cell culture, 2) a microplasma device for generating reactive oxygen and nitrogen species (RONS) for use in cell treatment, and 3) through-holes (microchannels) that connect each microwell with the microplasma region for RONS delivery. Here, we analysed the delivery of the RONS to the liquid culture medium stored in the microwells. We developed a simple experimental set-up using a microdevice and applied in situ ultraviolet absorption spectroscopy with high sensitivity for detecting RONS in liquid. The plasma-generated RONS were delivered into the liquid culture medium via the through-holes fabricated into the microdevice. The RONS concentrations were on the order of 10–100 μM depending on the size of the through-holes. In contrast, we found that the amount of dissolved oxygen was almost constant. To investigate the process of RONS generation, we numerically analysed the gas flow in the through-holes. We suggest that the circulating gas flow in the through-holes promotes the interaction between the plasma (ionised gas) and the liquid, resulting in enhanced RONS concentrations.

  4. Plasma cell treatment device Plasma-on-Chip: Monitoring plasma-generated reactive species in microwells

    PubMed Central

    Oh, Jun-Seok; Kojima, Shinya; Sasaki, Minoru; Hatta, Akimitsu; Kumagai, Shinya

    2017-01-01

    We have developed a plasma cell treatment device called Plasma-on-Chip that enables the real-time monitoring of a single cell culture during plasma treatment. The device consists of three parts: 1) microwells for cell culture, 2) a microplasma device for generating reactive oxygen and nitrogen species (RONS) for use in cell treatment, and 3) through-holes (microchannels) that connect each microwell with the microplasma region for RONS delivery. Here, we analysed the delivery of the RONS to the liquid culture medium stored in the microwells. We developed a simple experimental set-up using a microdevice and applied in situ ultraviolet absorption spectroscopy with high sensitivity for detecting RONS in liquid. The plasma-generated RONS were delivered into the liquid culture medium via the through-holes fabricated into the microdevice. The RONS concentrations were on the order of 10–100 μM depending on the size of the through-holes. In contrast, we found that the amount of dissolved oxygen was almost constant. To investigate the process of RONS generation, we numerically analysed the gas flow in the through-holes. We suggest that the circulating gas flow in the through-holes promotes the interaction between the plasma (ionised gas) and the liquid, resulting in enhanced RONS concentrations. PMID:28176800

  5. Dense Plasma Heating and Radiation Generation.

    DTIC Science & Technology

    1979-01-02

    34 Computor Investi- ations of Laser-Plasma Interactions", to be submitted to the 1979 IEEE International Conference on Plasma Science, Montreal, Canada...Identify by block number) carbon dioxide laser, beat heating, computor code, laser-plasma interactions. A pulsed power 20,ABSTRACT (Cntinue on reverse side

  6. Plasma structures for quasiphase matched high harmonic generation

    SciTech Connect

    Sheinfux, A. H.; Henis, Z.; Levin, M.; Zigler, A.

    2011-04-04

    A scheme for creation of periodic plasma structures by ablating a lithographic pattern is demonstrated. A proof of principle experiment was conducted, and plasma parameters were measured as a function of time with spatial resolution <10 and 100 {mu}m periodicity. Several possible applications, in particular, quasiphase matching for high harmonic generation in plasma are considered.

  7. Enhancement of terahertz wave generation from laser induced plasma

    SciTech Connect

    Xie Xu; Xu Jingzhou; Dai Jianming; Zhang, X.-C.

    2007-04-02

    It is well known that air plasma induced by ultrashort laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the laser induced plasma where there is a preexisting plasma background. When a laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another laser beam creating a plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.

  8. Effects of the glycoprotein IIb/IIIa receptor antagonist c7E3 Fab and anticoagulants on platelet aggregation and thrombin potential under high coagulant challenge in vitro.

    PubMed

    Koestenberger, M; Gallistl, S; Cvirn, G; Roschitz, B; Muntean, W

    2000-07-01

    The present study was performed to investigate the combined effects of the platelet glycoprotein IIb/IIIa receptor antagonist c7E3 Fab (abciximab) and the anticoagulants unfractionated heparin (UH), low molecular weight heparin (LMWH), and recombinant hirudin (rH) on platelet aggregation and thrombin generation under high coagulant challenge by extrinsic activation of platelet-rich plasma. Platelet aggregation and thrombin generation were assessed simultaneously in the presence of different concentrations of abciximab and anticoagulants. Increasing concentrations of abciximab resulted in a dose-dependent anti-aggregating effect with a maximum at 20 microg/ml. Doses of 5, 10, and 20 microg/ml abciximab prolonged the lag phase until the onset of platelet aggregation, but this effect was independent of the dosage used. Abciximab had no influence on the thrombin potential under our high coagulant challenge. UH, LMWH, and rH showed a dose-dependent prolongation of the lag phase until the onset of platelet aggregation and decreased the thrombin potential. Addition of anticoagulants did not contribute to further inhibition of platelet aggregation in the presence of abciximab, but the combination of abciximab and anticoagulants exhibited an additive effect on prolongation of the lag phase until the onset of platelet aggregation. Addition of abciximab to anticoagulants did not result in further decrease of the thrombin potential. Our study demonstrates the respective specific effects of abciximab and anticoagulants on platelet aggregation and thrombin potential under high coagulant challenge, and also an additive effect of abciximab and the anticoagulants UH, LMWH, and rH on the lag phase until the onset of platelet aggregation.

  9. Generation of quasistationary magnetic fields in a turbulent laser plasma

    NASA Astrophysics Data System (ADS)

    Bychenkov, V. Iu.; Gradov, O. M.; Chokparova, G. A.

    1984-07-01

    A theory is derived for the generation of quasi-stationary magnetic fields in a laser plasma with well developed ion-acoustic turbulence. Qualitative changes are caused in the nature of the magnetic-field generation by an anomalous anisotropic transport in the turbulent plasma. The role played by turbulent diffusion and thermodiffusive transport in the magnetic-field saturation is discussed.

  10. Evaluation of Potential Thrombin Inhibitors from the White Mangrove (Laguncularia racemosa (L.) C.F. Gaertn.)

    PubMed Central

    Rodrigues, Caroline Fabri Bittencourt; Gaeta, Henrique Hessel; Belchor, Mariana Novo; Ferreira, Marcelo José Pena; Pinho, Marcus Vinícius Terashima; de Oliveira Toyama, Daniela; Toyama, Marcos Hikari

    2015-01-01

    The aim of this work was to verify the effects of methanol (MeOH) and hydroalcoholic (HA) extracts and their respective partition phases obtained from white mangrove (Laguncularia racemosa (L.) C.F. Gaertn.) leaves on human thrombin activity. Among the extracts and phases tested, only the ethyl acetate and butanolic partitions significantly inhibited human thrombin activity and the coagulation of plasma in the presence of this enzyme. Chromatographic analyses of the thrombin samples incubated with these phases revealed that different compounds were able to interact with thrombin. The butanolic phase of the MeOH extract had the most potent inhibitory effects, reducing enzymatic activity and thrombin-induced plasma coagulation. Two glycosylated flavonoids in this partition were identified as the most potent inhibitors of human thrombin activity, namely quercetin-3-O-arabinoside (QAra) and quercetin-3-O-rhamnoside (Qn). Chromatographic analyses of thrombin samples incubated with these flavonoids demonstrated the chemical modification of this enzyme, suggesting that the MeOH extract contained other compounds that both induced structural changes in thrombin and diminished its activity. In this article, we show that despite the near absence of the medical use of mangrove compounds, this plant contains natural compounds with potential therapeutic applications. PMID:26197325

  11. Thrombin Increases Expression of Fibronectin Antigen on the Platelet Surface

    NASA Astrophysics Data System (ADS)

    Ginsberg, Mark H.; Painter, Richard G.; Forsyth, Jane; Birdwell, Charles; Plow, Edward F.

    1980-02-01

    Fibronectins (fn) are adhesive glycoproteins which bind to collagen and to fibrin and appear to be important in cellular adhesion to other cells or surfaces. Fn-related antigen is present in human platelets, suggesting a possible role for fn in the adhesive properties of platelets. We have studied the localization of fn in resting and thrombin-stimulated platelets by immunofluorescence and quantitative binding of radiolabeled antibody. In resting fixed platelets, variable light surface staining for fn was observed. When these cells were made permeable to antibody with detergent, staining for fn was markedly enhanced and was present in a punctate distribution, suggesting intracellular localization. Stimulation with thrombin, which is associated with increased platelet adhesiveness, resulted in increased staining for fn antigen on intact platelets. These stimulated cells did not leak 51Cr nor did they stain for F-actin, thus documenting that the increased fn staining was not due to loss of plasma membrane integrity. The thrombin-induced increase in accessible platelet fn antigen was confirmed by quantitative antibody binding studies in which thrombin-stimulated platelets specifically bound 15 times as much radiolabeled F(ab')2 anti-fn as did resting cells. Thus, thrombin stimulation results in increased expression of fn antigen on the platelet surface. Here it may participate in interactions with fibrin, connective tissue, or other cells.

  12. Coupling of the thrombin receptor to G12 may account for selective effects of thrombin on gene expression and DNA synthesis in 1321N1 astrocytoma cells.

    PubMed Central

    Post, G R; Collins, L R; Kennedy, E D; Moskowitz, S A; Aragay, A M; Goldstein, D; Brown, J H

    1996-01-01

    In 1321N1 astrocytoma cells, thrombin, but not carbachol, induces AP-1-mediated gene expression and DNA synthesis. To understand the divergent effects of these G protein-coupled receptor agonists on cellular responses, we examined Gq-dependent signaling events induced by thrombin receptor and muscarinic acetylcholine receptor stimulation. Thrombin and carbachol induce comparable changes in phosphoinositide and phosphatidylcholine hydrolysis, mobilization of intracellular Ca2+, diglyceride generation, and redistribution of protein kinase C; thus, activation of these Gq-signaling pathways appears to be insufficient for gene expression and mitogenesis. Thrombin increases Ras and mitogen-activated protein kinase activation to a greater extent than carbachol in 1321N1 cells. The effects of thrombin are not mediated through Gi, since ribosylation of Gi/Go proteins by pertussis toxin does not prevent thrombin-induced gene expression or thrombin-stimulated DNA synthesis. We recently reported that the pertussis toxin-insensitive G12 protein is required for thrombin-induced DNA synthesis. We demonstrate here, using transfection of receptors and G proteins in COS-7 cells, that G alpha 12 selectively couples the thrombin receptor to AP-1-mediated gene expression. This does not appear to result from increased mitogen-activated protein kinase activity but may reflect activation of a tyrosine kinase pathway. We suggest that preferential coupling of the thrombin receptor to G12 accounts for the selective ability of thrombin to stimulate Ras, mitogen-activated protein kinase, gene expression, and mitogenesis in 1321N1 cells. Images PMID:8930892

  13. Generator of chemically active low-temperature plasma

    NASA Astrophysics Data System (ADS)

    Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Demirov, N. A.; Spector, N. O.

    2016-11-01

    A new generator of high enthalpy (H 0 > 40 kJ/g), chemically active nitrogen and air plasmas was designed and constructed. Main feature of the generator is an expanding channel of an output electrode; the generator belongs to the class of DC plasma torches with thermionic cathode with an efficiency of 80%. The generator ensures the formation of a slightly divergent plasma jet (2α = 12°) with a diameter of D = 10-12 mm, an electric arc maximum power of 20-50 kW, plasma forming gas flow rate 1.0-2.0 g/s, and the average plasma temperature at an outlet of 8000-11000 K.

  14. Plasma-Based Studies on 4th Generation Light Sources

    SciTech Connect

    Lee, R W; Baldis, H A; Cauble, R C; Landen, O L; Wark, J S; Ng, A; Rose, S J; Lewis, C; Riley, D; Gauthier, J-C; Audebert, P

    2000-11-28

    The construction of a short pulse tunable x-ray laser source will be a watershed for plasma-based and warm dense matter research. The areas we will discuss below can be separated broadly into warn dense matter (WDM) research, laser probing of near solid density plasmas, and laser-plasma spectroscopy of ions in plasmas. The area of WDM refers to that part of the density-temperature phase space where the standard theories of condensed matter physics and/or plasma statistical physics are invalid. Warm dense matter, therefore, defines a region between solids and plasmas, a regime that is found in planetary interiors, cool dense stars, and in every plasma device where one starts from a solid, e.g., laser-solid matter produced plasma as well as all inertial fusion schemes. The study of dense plasmas has been severely hampered by the fact that laser-based methods have been unavailable. The single most useful diagnostic of local plasma conditions, e.g., the temperature (T{sub e}), the density (n{sub e}), and the ionization (Z), has been Thomson scattering. However, due to the fact that visible light will not propagate at electron densities, n{sub e}, {ge} 10{sup 22} cm{sup -3} implies dense plasmas can not be probed. The 4th generation sources, LCLS and Tesla will remove these restrictions. Laser-based plasma spectroscopic techniques have been used with great success to determine the line shapes of atomic transitions in plasmas, study the population kinetics of atomic systems embedded in plasmas, and look at redistribution of radiation. However. the possibilities end for plasmas with n{sub e} {ge} 10{sup 22} since light propagation through the medium is severely altered by the plasma. The entire field of high Z plasma kinetics from laser produced plasma will then be available to study with the tunable source.

  15. Intracellular Ascorbate Prevents Endothelial Barrier Permeabilization by Thrombin.

    PubMed

    Parker, William H; Qu, Zhi-chao; May, James M

    2015-08-28

    Intracellular ascorbate (vitamin C) has previously been shown to tighten the endothelial barrier and maintain barrier integrity during acute inflammation in vitro. However, the downstream effectors of ascorbate in the regulation of endothelial permeability remain unclear. In this study, we evaluated ascorbate as a mediator of thrombin-induced barrier permeabilization in human umbilical vein endothelial cells and their immortalized hybridoma line, EA.hy926. We found that the vitamin fully prevented increased permeability to the polysaccharide inulin by thrombin in a dose-dependent manner, and it took effect both before and after subjection to thrombin. Thrombin exposure consumed intracellular ascorbate but not the endogenous antioxidant GSH. Likewise, the antioxidants dithiothreitol and tempol did not reverse permeabilization. We identified a novel role for ascorbate in preserving cAMP during thrombin stimulation, resulting in two downstream effects. First, ascorbate maintained the cortical actin cytoskeleton in a Rap1- and Rac1-dependent manner, thus preserving stable adherens junctions between adjacent cells. Second, ascorbate prevented actin polymerization and formation of stress fibers by reducing the activation of RhoA and phosphorylation of myosin light chain. Although ascorbate and thrombin both required calcium for their respective effects, ascorbate did not prevent thrombin permeabilization by obstructing calcium influx. However, preservation of cAMP by ascorbate was found to depend on both the production of nitric oxide by endothelial nitric-oxide synthase, which ascorbate is known to activate, and the subsequent generation cGMP by guanylate cyclase. Together, these data implicate ascorbate in the prevention of inflammatory endothelial barrier permeabilization and explain the underlying signaling mechanism.

  16. Intracellular Ascorbate Prevents Endothelial Barrier Permeabilization by Thrombin*

    PubMed Central

    Parker, William H.; Qu, Zhi-chao; May, James M.

    2015-01-01

    Intracellular ascorbate (vitamin C) has previously been shown to tighten the endothelial barrier and maintain barrier integrity during acute inflammation in vitro. However, the downstream effectors of ascorbate in the regulation of endothelial permeability remain unclear. In this study, we evaluated ascorbate as a mediator of thrombin-induced barrier permeabilization in human umbilical vein endothelial cells and their immortalized hybridoma line, EA.hy926. We found that the vitamin fully prevented increased permeability to the polysaccharide inulin by thrombin in a dose-dependent manner, and it took effect both before and after subjection to thrombin. Thrombin exposure consumed intracellular ascorbate but not the endogenous antioxidant GSH. Likewise, the antioxidants dithiothreitol and tempol did not reverse permeabilization. We identified a novel role for ascorbate in preserving cAMP during thrombin stimulation, resulting in two downstream effects. First, ascorbate maintained the cortical actin cytoskeleton in a Rap1- and Rac1-dependent manner, thus preserving stable adherens junctions between adjacent cells. Second, ascorbate prevented actin polymerization and formation of stress fibers by reducing the activation of RhoA and phosphorylation of myosin light chain. Although ascorbate and thrombin both required calcium for their respective effects, ascorbate did not prevent thrombin permeabilization by obstructing calcium influx. However, preservation of cAMP by ascorbate was found to depend on both the production of nitric oxide by endothelial nitric-oxide synthase, which ascorbate is known to activate, and the subsequent generation cGMP by guanylate cyclase. Together, these data implicate ascorbate in the prevention of inflammatory endothelial barrier permeabilization and explain the underlying signaling mechanism. PMID:26152729

  17. The influence of plasma motion on disruption generated runaway electrons

    SciTech Connect

    Russo, A.J.

    1991-01-01

    One of the possible consequences of disruptions is the generation of runaway electrons which can impact plasma facing components and cause damage due to high local energy deposition. This problem becomes more serious as the machine size and plasma current increases. Since large size and high currents are characteristics of proposed future machines, control of runaway generation is an important design consideration. A lumped circuit model for disruption runaway electron generation indicates that control circuitry on strongly influence runaway behavior. A comparison of disruption data from several shots on JET and D3-D with model results, demonstrate the effects of plasma motion on runaway number density and energy. 6 refs., 12 figs.

  18. Kerf generation during the plasma cutting process

    NASA Astrophysics Data System (ADS)

    Dodun, Oana; Bangu, Sanda Ilii; Slǎtineanu, LaurenÅ£iu; Vasile, Merticaru; Beşliu, Irina; CoteaÅ£ǎ, Margareta

    2016-10-01

    The plasma beam cutting is a machining method applied in order to detach parts or workpieces from plate type workpiece. Essentially, a plasma jet is sent to workpiece, determining melting, vaporizing and removing of the material from the workpiece. If there is a relative movement between the plasma jet and the workpiece, a kerf gradually appears. Many factors exert influence on the kerf characteristics. A full factorial experiment with three independent variables at two levels was designed, in order to highlight the influence exerted by the cutting speed, workpiece thickness and arc current on the kerf width in the superior and inferior zones and on the kerf taper angle, respectively. Power type empirical mathematical models were determined by mathematical processing of the experimental results.

  19. Slot-Antenna/Permanent-Magnet Device for Generating Plasma

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2007-01-01

    A device that includes a rectangular-waveguide/slot-antenna structure and permanent magnets has been devised as a means of generating a substantially uniform plasma over a relatively large area, using relatively low input power and a low gas flow rate. The device utilizes electron cyclotron resonance (ECR) excited by microwave power to efficiently generate plasma in a manner that is completely electrodeless in the sense that, in principle, there is no electrical contact between the plasma and the antenna. Plasmas generated by devices like this one are suitable for use as sources of ions and/or electrons for diverse material-processing applications (e.g., etching or deposition) and for ion thrusters. The absence of plasma/electrode contact essentially prevents plasma-induced erosion of the antenna, thereby also helping to minimize contamination of the plasma and of objects exposed to the plasma. Consequently, the operational lifetime of the rectangular-waveguide/ slot-antenna structure is long and the lifetime of the plasma source is limited by the lifetime of the associated charged-particle-extraction grid (if used) or the lifetime of the microwave power source. The device includes a series of matched radiating slot pairs that are distributed along the length of a plasma-source discharge chamber (see figure). This arrangement enables the production of plasma in a distributed fashion, thereby giving rise to a uniform plasma profile. A uniform plasma profile is necessary for uniformity in any electron- or ion-extraction electrostatic optics. The slotted configuration of the waveguide/ antenna structure makes the device scalable to larger areas and higher powers. All that is needed for scaling up is the attachment of additional matched radiating slots along the length of the discharge chamber. If it is desired to make the power per slot remain constant in scaling up, then the input microwave power must be increased accordingly. Unlike in prior ECR microwave plasma-generating

  20. Induction therapy alters plasma fibrin clot properties in multiple myeloma patients: association with thromboembolic complications.

    PubMed

    Undas, Anetta; Zubkiewicz-Usnarska, Lidia; Helbig, Grzegorz; Woszczyk, Dariusz; Kozińska, Justyna; Dmoszyńska, Anna; Dębski, Jakub; Podolak-Dawidziak, Maria; Kuliczkowski, Kazimierz

    2015-09-01

    Induction therapy in patients with multiple myeloma increases the risk of thromboembolism. We have recently shown that multiple myeloma patients tend to form denser fibrin clots displaying poor lysability. We investigated the effect of induction therapy on fibrin clot properties in multiple myeloma patients. Ex-vivo plasma fibrin clot permeability, turbidity, susceptibility to lysis, thrombin generation, factor VIII and fibrinolytic proteins were compared in 48 multiple myeloma patients prior to and following 3 months of induction therapy, mainly with cyclophosphamide-thalidomide-dexamethasone regimen. Patients on thromboprophylaxis with aspirin or heparins were eligible. A 3-month induction therapy resulted in improved clot properties, that is higher clot permeability, compaction, shorter lag phase and higher final turbidity, along with shorter clot lysis time and higher rate of D-dimer release from fibrin clots than the baseline values. The therapy also resulted in lower thrombin generation, antiplasmin and thrombin-activatable fibrinolysis inhibitor (TAFI), but elevated factor VIII. Progressive disease was associated with lower posttreatment clot permeability and lysability. Despite thromboprophylaxis, two patients developed ischemic stroke and 10 had venous thromboembolism. They were characterized by pretreatment lower clot permeability, prolonged clot lysis time, longer lag phase, higher peak thrombin generation, TAFI and plasminogen activator inhibitor -1. Formation of denser plasma fibrin clots with reduced lysability and increased thrombin generation at baseline could predispose to thrombotic complications during induction treatment in multiple myeloma patients. We observed improved fibrin clot properties and thrombin generation in multiple myeloma patients except those with progressive disease.

  1. Inductively generated streaming plasma ion source

    DOEpatents

    Glidden, Steven C.; Sanders, Howard D.; Greenly, John B.

    2006-07-25

    A novel pulsed, neutralized ion beam source is provided. The source uses pulsed inductive breakdown of neutral gas, and magnetic acceleration and control of the resulting plasma, to form a beam. The beam supplies ions for applications requiring excellent control of ion species, low remittance, high current density, and spatial uniformity.

  2. Plasma treatment for next-generation nanobiointerfaces.

    PubMed

    Levchenko, Igor; Keidar, Michael; Mai-Prochnow, Anne; Modic, Martina; Cvelbar, Uros; Fang, Jinghua; Ostrikov, Kostya Ken

    2015-06-23

    Energy deficiency, global poverty, chronic hunger, chronic diseases, and environment conservation are among the major problems threatening the whole mankind. Nanostructure-based technologies could be a possible solution. Such techniques are now used for the production of many vitally important products including cultured and fermented food, antibiotics, various medicines, and biofuels. On the other hand, the nanostructure-based technologies still demonstrate low efficiency and controllability, and thus still are not capable to decisively address the global problems. Furthermore, future technologies should ensure lowest possible environmental impact by implementing green production principles. One of the most promising approaches to address these challenges are the sophisticatedly engineered biointerfaces. Here, the authors briefly evaluate the potential of the plasma-based techniques for the fabrication of complex biointerfaces. The authors consider mainly the atmospheric and inductively coupled plasma environments and show several examples of the artificial plasma-created biointerfaces, which can be used for the biotechnological and medical processes, as well as for the drug delivery devices, fluidised bed bioreactors, catalytic reactors, and others. A special attention is paid to the plasma-based treatment and processing of the biointerfaces formed by arrays of carbon nanotubes and graphene flakes.

  3. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    SciTech Connect

    Fisch, Nathaniel J

    2014-01-08

    I. Grant Objective The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereasthefficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  4. A research program in magnetogasdynamics utilizing hypervelocity coaxial plasma generators

    NASA Technical Reports Server (NTRS)

    Spight, C.

    1976-01-01

    A broadly-gauged research program in magnetogasdynamics utilizing hypervelocity coaxial plasma generators is presented. A complete hypervelocity coaxial plasma generator facility was assembled and tested. Significant progress was made in the direction of understanding the important processes in the interaction of hypervelocity MGD flow with transverse applied fields. It is now proposed to utilize the accumulated experimental capability and theoretical analysis in application to the analysis and design parameterization of pulsed magnetogasdynamic direct energy convertor configurations.

  5. Hydrogen Generation from the Dissociation of Water Using Microwave Plasmas

    NASA Astrophysics Data System (ADS)

    Yong, Ho Jung; Soo Ouk, Jang; Hyun Jong, You

    2013-06-01

    Hydrogen is produced by direct dissociation of water vapor, i.e., splitting water molecules by the electrons in water plasma at low pressure (<10-50 Torr) using microwave plasma discharge. This condition generates a high electron temperature, which facilitates the direct dissociation of water molecules. A microwave plasma source is developed, utilizing the magnetron of a microwave oven and a TE10 rectangular waveguide. The quantity of the generated hydrogen is measured using a residual gas analyzer. The electron density and temperature are measured by a Langmuir probe, and the neutral temperature is calculated from the OH line intensity.

  6. Optimum plasma conditions for the efficient high-order harmonic generation in platinum plasma

    SciTech Connect

    Ganeev, Rashid A.; Elouga Bom, Luc B.; Kieffer, Jean-Claude; Ozaki, Tsuneyuki

    2007-06-15

    We studied the optimum plasma conditions that are required for efficient high-order harmonic generation in platinum plume. Harmonics up to the 49th order ({lambda}=16.32 nm) are analyzed under various conditions of laser-plasma interaction. Time-resolved ultraviolet spectra of platinum plasma at both optimum and nonoptimum conditions of harmonic generation are presented. We calculated the ionization states of the plasma, free electron density, and singly charged ion density at different prepulse intensities and compared them with experimental results.

  7. A portable microchip for ultrasensitive and high-throughput assay of thrombin by rolling circle amplification and hemin/G-quadruplex system.

    PubMed

    Lin, Xuexia; Chen, Qiushui; Liu, Wu; Li, Haifang; Lin, Jin-Ming

    2014-06-15

    In this work, a convenient and high-throughput colorimetric assay was developed on an aptamer-modified microchip for ultrasensitive detection of thrombin using rolling circle amplification and G-quadruplex DNAzyme. This system consisted of an aptamer-modified microchip and a secondary aptamer. The secondary aptamer contained a thrombin aptamer and a primer with a G-quadruplex circular template. RCA technology was used to improve the sensitivity by producing the multiple G-quadruplex units. To generate colorimetric signal, G-quadruplex DNAzyme was used to catalyze the H2O2-mediated oxidation of 2,2'-azinobis (3-ethylbenzothiozoline)-6-sulfonic acid. At the optimal conditions, the linear range for thrombin was 0.100-50.000 pg/mL, and the limit of detection was down to 0.083 pg/mL. Moreover, the developed method was successfully applied to detect thrombin from human plasma and serum, indicating that this approach has great potential in clinical diagnosis and medical investigation.

  8. Dense Plasma Heating and Radiation Generation.

    DTIC Science & Technology

    1980-05-30

    INSTRUCTIONS ~~~~~~ B OUET ~iNPGEFORE COMPLETING FORM I. RPORTmumsZ. GVT AC INNo.i S. ACCIPIENT’S CATALOG MUM694 ~~ 80-0981 F,6-~IS~ � 4. r r~ejandsw... p M. Kristiansen and M.O. Hagler AFOSR 74-2639 ~ 9. 9%RFOR4fpN ORGAMIZAT1om NAME ANO ADDRESS 10. PROGRAM ELEMEN T. DRO.IECT, TASK Plasma Laboratory...8217AA P ’t1JIMIS Dept. of Electrical Engineering 2301/A Texas Tech University, Lubbock, Texas 79409, 61102F 20Il It. CONTROLLING OFFICE MAMIE AND AOhESS

  9. A large volume uniform plasma generator for the experiments of electromagnetic wave propagation in plasma

    SciTech Connect

    Yang Min; Li Xiaoping; Xie Kai; Liu Donglin; Liu Yanming

    2013-01-15

    A large volume uniform plasma generator is proposed for the experiments of electromagnetic (EM) wave propagation in plasma, to reproduce a 'black out' phenomenon with long duration in an environment of the ordinary laboratory. The plasma generator achieves a controllable approximate uniform plasma in volume of 260 mm Multiplication-Sign 260 mm Multiplication-Sign 180 mm without the magnetic confinement. The plasma is produced by the glow discharge, and the special discharge structure is built to bring a steady approximate uniform plasma environment in the electromagnetic wave propagation path without any other barriers. In addition, the electron density and luminosity distributions of plasma under different discharge conditions were diagnosed and experimentally investigated. Both the electron density and the plasma uniformity are directly proportional to the input power and in roughly reverse proportion to the gas pressure in the chamber. Furthermore, the experiments of electromagnetic wave propagation in plasma are conducted in this plasma generator. Blackout phenomena at GPS signal are observed under this system and the measured attenuation curve is of reasonable agreement with the theoretical one, which suggests the effectiveness of the proposed method.

  10. On the generation of magnetic field enhanced microwave plasma line

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Zhao, Ying; Wu, Kenan; Wang, Qi; Meng, Yuedong; Ren, Zhaoxing

    2016-12-01

    Microwave linear plasmas sustained by surface waves have attracted much attention due to the potential abilities to generate large-scale and uniform non-equilibrium plasmas. An external magnetic field was generally applied to enhance and stabilize plasma sources because the magnetic field decreased the electron losses on the wall. The effects of magnetic field on the generation and propagation mechanisms of the microwave plasma were tentatively investigated based on a 2-D numerical model combining a coupled system of Maxwell's equations and continuity equations. The mobility of electrons and effective electric conductivity of the plasma were considered as a full tensor in the presence of magnetic field. Numerical results indicate that both cases of magnetic field in the axial-direction and radial-direction benefit the generation of a high-density plasma; the former one allows the microwave to propagate longer in the axis direction compared to the latter one. The time-averaged power flow density and the amplitude of the electric field on the inner rod of coaxial waveguide attenuate with the propagation of the microwave for both cases of with and without external magnetic field. The attenuation becomes smaller in the presence of appropriately higher axial-direction magnetic field, which allows more microwave energies to transmit along the axial direction. Meanwhile, the anisotropic properties of the plasma, like electron mobility, in the presence of the magnetic field confine more charged particles in the direction of the magnetic field line.

  11. Characterization of inductively coupled plasma generated by a quadruple antenna

    NASA Astrophysics Data System (ADS)

    Shafir, G.; Zolotukhin, D.; Godyak, V.; Shlapakovski, A.; Gleizer, S.; Slutsker, Ya; Gad, R.; Bernshtam, V.; Ralchenko, Yu; Krasik, Ya E.

    2017-02-01

    The results of the characterization of large-scale RF plasma for studying nonlinear interaction with a high-power (˜400 MW) short duration (˜0.8 ns) microwave (˜10 GHz) beam are presented. The plasma was generated inside a Pyrex tube 80 cm in length and 25 cm in diameter filled by either Ar or He gas at a pressure in the range 1.3-13 Pa using a 2 MHz RF generator with a matching system and a quadruple antenna. Good matching was obtained between the plasma parameters, which were determined using different methods including a movable Langmuir probe, microwave cut-off, interferometry, and optical emission spectroscopy. It was shown that, depending on the gas pressure and RF power delivered to the antenna, the plasma density and electron temperature can be controlled in the range 1 × 1010-5 × 1012 cm-3 and 1-3.5 eV, respectively. The plasma density was found to be uniform in terms of axial (˜60 cm) and radial (˜10 cm) dimensions. Further, it was also shown that the application of the quadruple antenna, with resonating capacitors inserted in its arms, decreases the capacitive coupling of the antenna and the plasma as well as the RF power loss along the antenna. These features make this plasma source suitable for microwave plasma wake field experiments.

  12. Thrombin Induces Inositol Trisphosphate-Mediated Spatially Extensive Responses in Lung Microvessels.

    PubMed

    Escue, Rachel; Kandasamy, Kathirvel; Parthasarathi, Kaushik

    2017-04-01

    Activation of plasma membrane receptors initiates compartmentalized second messenger signaling. Whether this compartmentalization facilitates the preferential intercellular diffusion of specific second messengers is unclear. Toward this, the receptor-mediated agonist, thrombin, was instilled into microvessels in a restricted region of isolated blood-perfused mouse lungs. Subsequently, the thrombin-induced increase in endothelial F-actin was determined using confocal fluorescence microscopy. Increased F-actin was evident in microvessels directly treated with thrombin and in those located in adjoining thrombin-free regions. This increase was abrogated by inhibiting inositol trisphosphate-mediated calcium release with Xestospongin C (XeC). XeC also inhibited the thrombin-induced increase in the amplitude of endothelial cytosolic Ca(2+) oscillations. Instillation of thrombin and XeC into adjacent restricted regions increased F-actin in microvessels in the thrombin-treated and adjacent regions but not in those in the XeC-treated region. Thus, inositol trisphosphate, and not calcium, diffused interendothelially to the spatially remote thrombin-free microvessels. Thus, activation of plasma membrane receptors increased the ambit of inflammatory responses via a second messenger different from that used by stimuli that induce cell-wide increases in second messengers. Thrombin however failed to induce the spatially extensive response in microvessels of mice lacking endothelial connexin43, suggesting a role for connexin43 gap junctions. Compartmental second messenger signaling and interendothelial communication define the specific second messenger involved in exacerbating proinflammatory responses to receptor-mediated agonists.

  13. Plasma Physics Simulations on Next Generation Platforms

    NASA Astrophysics Data System (ADS)

    Koniges, Alice

    2013-10-01

    The current high-performance computing revolution provides opportunity for major increases in computational power over the next several years, if it can be harnessed. This transition from simply increasing the single-processor and network performance to a different architectural paradigms forces application programmers to rethink the basic models of parallel programming from both the language and problem division standpoints. One of the major computing facilities available to researchers in fusion energy is the National Energy Research Scientific Computing Center. As the mission computing center for DOE, Office of Science, NERSC is tasked with helping users to overcome the challenges of this revolution both through the use of new parallel constructs and languages and also by enabling a broader user community to take advantage of multi-core performance. We discuss the programming model challenges facing researchers in fusion and plasma physics in for a variety of simulations ranging from particle-in-cell to fluid-gyrokinetic and MHD models.

  14. Targeting thrombin: an inflammatory neurotoxin in Alzheimer's disease.

    PubMed

    Grammas, Paula; Martinez, Joseph M

    2014-01-01

    The Alzheimer's disease (AD) epidemic proceeds unabated. Estimates suggest 5.4 million Americans and 36 million people worldwide have AD. No single mechanism or pathologic mediator can account for AD progression. Currently no disease modifying therapies are available. There is a large literature documenting an association among cardiovascular risk factors (CVRFs), especially diabetes and hypoxia, with increased AD incidence. CVRFs directly impair vascular function and could mediate cerebrovascular dysfunction in AD. This is important as cerebrovascular dysfunction precedes cognitive decline and onset of neurodegenerative changes in AD and AD animal models. In this review we present evidence that thrombin may be a heretofore unexplored target for AD therapy. This idea is based on the following observations. Thrombin is elevated in the brain and cerebral microvasculature in AD, is directly neurotoxic, and causes pro-inflammatory effects in endothelial cells, microglia, and astrocytes. Diabetes- and hypoxia-induced cerebrovascular effects are mediated by thrombin. Thrombin inhibitors block the effects of hypoxia on brain endothelial cells and reduce vascular inflammation in transgenic AD mice. Based on reports that reducing cerebrovascular expression of inflammatory proteins in AD mice is associated with improved cognition, we propose thrombin inhibitors could prove useful for improving cognition in AD patients. The next generation of AD therapeutics should not focus on single target drugs but rather employ a multi-component cocktail approach. We propose thrombin inhibitors be considered as potential contributors to the dementia therapy pharmacopeia. The urgent need for disease-modifying drugs in AD demands new thinking about disease pathogenesis and exploration of novel drug targets.

  15. Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

    DOEpatents

    Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

    2013-09-17

    Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

  16. Spontaneous generation of rotation in tokamak plasmas

    SciTech Connect

    Parra Diaz, Felix

    2013-12-24

    Three different aspects of intrinsic rotation have been treated. i) A new, first principles model for intrinsic rotation [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has been implemented in the gyrokinetic code GS2. The results obtained with the code are consistent with several experimental observations, namely the rotation peaking observed after an L-H transition, the rotation reversal observed in Ohmic plasmas, and the change in rotation that follows Lower Hybrid wave injection. ii) The model in [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has several simplifying assumptions that seem to be satisfied in most tokamaks. To check the importance of these hypotheses, first principles equations that do not rely on these simplifying assumptions have been derived, and a version of these new equations has been implemented in GS2 as well. iii) A tokamak cross-section that drives large intrinsic rotation has been proposed for future large tokamaks. In large tokamaks, intrinsic rotation is expected to be very small unless some up-down asymmetry is introduced. The research conducted under this contract indicates that tilted ellipticity is the most efficient way to drive intrinsic rotation.

  17. Charge-exchange plasma generated by an ion thruster

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.

    1977-01-01

    The charge exchange plasma generated by an ion thruster was investigated experimentally using both 5 cm and 15 cm thrusters. Results are shown for wide ranges of radial distance from the thruster and angle from the beam direction. Considerations of test environment, as well as distance from the thruster, indicate that a valid simulation of a thruster on a spacecraft was obtained. A calculation procedure and a sample calculation of charge exchange plasma density and saturation electron current density are included.

  18. Edge Plasma Boundary Layer Generated By Kink Modes in Tokamaks

    SciTech Connect

    L.E. Zakharov

    2010-11-22

    This paper describes the structure of the electric current generated by external kink modes at the plasma edge using the ideally conducting plasma model. It is found that the edge current layer is created by both wall touching and free boundary kink modes. Near marginal stability, the total edge current has a universal expression as a result of partial compensation of the δ-functional surface current by the bulk current at the edge. The resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  19. Generation of auroral kilometric radiation in inhomogeneous magnetospheric plasma

    NASA Astrophysics Data System (ADS)

    Burinskaya, T. M.; Shevelev, M. M.

    2017-01-01

    The generation of auroral kilometric radiation in a narrow 3D plasma cavity, in which a weakly relativistic electron flow is propagated along the magnetic field against a low-density cold background plasma, is studied. The time dynamics of the propagation and intensification of waves are analyzed using geometric optics equations. The waves have different wave vector components and start from the cavity center at an altitude of about the Earth's radius at plasma parameters typical for the auroral zone at this altitude. It is shown that the global inhomogeneity of the Earth's magnetic field is of key importance in shaping the auroral kilometric radiation spectra.

  20. Magnetic Cusp Configuration of the SPL Plasma Generator

    SciTech Connect

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier

    2011-09-26

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  1. Generation of low-temperature air plasma for food processing

    NASA Astrophysics Data System (ADS)

    Stepanova, Olga; Demidova, Maria; Astafiev, Alexander; Pinchuk, Mikhail; Balkir, Pinar; Turantas, Fulya

    2015-11-01

    The project is aimed at developing a physical and technical foundation of generating plasma with low gas temperature at atmospheric pressure for food industry needs. As known, plasma has an antimicrobial effect on the numerous types of microorganisms, including those that cause food spoilage. In this work an original experimental setup has been developed for the treatment of different foods. It is based on initiating corona or dielectric-barrier discharge in a chamber filled with ambient air in combination with a certain helium admixture. The experimental setup provides various conditions of discharge generation (including discharge gap geometry, supply voltage, velocity of gas flow, content of helium admixture in air and working pressure) and allows for the measurement of the electrical discharge parameters. Some recommendations on choosing optimal conditions of discharge generation for experiments on plasma food processing are developed.

  2. A study of single and binary ion plasma expansion into laboratory-generated plasma wakes

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth Herbert, Jr.

    1988-01-01

    Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory.

  3. Harmonic generation by circularly polarized laser beams propagating in plasma

    SciTech Connect

    Agrawal, Ekta; Hemlata,; Jha, Pallavi

    2015-04-15

    An analytical theory is developed for studying the phenomenon of generation of harmonics by the propagation of an obliquely incident, circularly polarized laser beam in homogeneous, underdense plasma. The amplitudes of second and third harmonic radiation as well as detuning distance have been obtained and their variation with the angle of incidence is analyzed. The amplitude of harmonic radiation increases with the angle of incidence while the detuning distance decreases, for a given plasma electron density. It is observed that the generated second and third harmonic radiation is linearly and elliptically polarized, respectively. The harmonic radiation vanishes at normal incidence of the circularly polarized laser beam.

  4. Analysis of plasmas generated by fission fragments. [nuclear pumped lasers and helium plasma

    NASA Technical Reports Server (NTRS)

    Deese, J. E.; Hassan, H. A.

    1977-01-01

    A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.

  5. Thrombin and exercise similarly influence expression of cell cycle genes in cultured putative endothelial progenitor cells.

    PubMed

    Lockard, Michael M; Witkowski, Sarah; Jenkins, Nathan T; Spangenburg, Espen E; Obisesan, Thomas O; Hagberg, James M

    2010-06-01

    Acute exercise and exercise training may influence putative endothelial progenitor cell (EPC) number and colony forming units (CFU-ECs), although the mechanisms remain unclear. This study examined the effects of in vitro thrombin supplementation and acute exercise on CFU-EC gene expression, associated with cellular proliferation and differentiation. The effect of habitual physical activity was evaluated through analysis of EPCs from chronically high- and low-active men. Participants were healthy high- and low-active men (n=23), aged 55-80 yr. Circulating CD34+/VEGFR2+ number, CFU-ECs, plasma prothrombin fragment (F1+2), and thrombin-antithrombin III were measured at rest and after 30 min of exercise. Gene expression of cyclin A2, cyclin D1, p27, VE-cadherin, and VEGFR2 was assessed in postexercise CFU-ECs and resting CFU-ECs treated with 0, 1, 5, or 10 U/ml of thrombin. Outcomes were compared between high- and low-active participants. F1+2 and thrombin-antithrombin III, but not CD34+/VEGFR2+ number and CFU-ECs, increased with exercise. Exercise-induced changes in F1+2 correlated with changes in CD34+/VEGFR2+ number in both groups. Thrombin treatments and acute exercise increased cyclin A2 and cyclin D1 expression and decreased p27 expression. One unit per milliliter thrombin increased VEGFR2 and VE-cadherin expression, whereas 5 U/ml, 10 U/ml, and acute exercise did not elicit any changes. An exercise training effect was observed with greater decreases in p27 expression with 5 and 10 U/ml thrombin and greater increases in VEGFR2 and VE-cadherin expression with 1 U/ml thrombin in high-active men. Exercise-induced changes in putative EPC gene expression are associated with thrombin production and may be modulated by long-term exercise training.

  6. Thrombin and exercise similarly influence expression of cell cycle genes in cultured putative endothelial progenitor cells

    PubMed Central

    Lockard, Michael M.; Witkowski, Sarah; Jenkins, Nathan T.; Spangenburg, Espen E.; Obisesan, Thomas O.

    2010-01-01

    Acute exercise and exercise training may influence putative endothelial progenitor cell (EPC) number and colony forming units (CFU-ECs), although the mechanisms remain unclear. This study examined the effects of in vitro thrombin supplementation and acute exercise on CFU-EC gene expression, associated with cellular proliferation and differentiation. The effect of habitual physical activity was evaluated through analysis of EPCs from chronically high- and low-active men. Participants were healthy high- and low-active men (n = 23), aged 55–80 yr. Circulating CD34+/VEGFR2+ number, CFU-ECs, plasma prothrombin fragment (F1+2), and thrombin-antithrombin III were measured at rest and after 30 min of exercise. Gene expression of cyclin A2, cyclin D1, p27, VE-cadherin, and VEGFR2 was assessed in postexercise CFU-ECs and resting CFU-ECs treated with 0, 1, 5, or 10 U/ml of thrombin. Outcomes were compared between high- and low-active participants. F1+2 and thrombin-antithrombin III, but not CD34+/VEGFR2+ number and CFU-ECs, increased with exercise. Exercise-induced changes in F1+2 correlated with changes in CD34+/VEGFR2+ number in both groups. Thrombin treatments and acute exercise increased cyclin A2 and cyclin D1 expression and decreased p27 expression. One unit per milliliter thrombin increased VEGFR2 and VE-cadherin expression, whereas 5 U/ml, 10 U/ml, and acute exercise did not elicit any changes. An exercise training effect was observed with greater decreases in p27 expression with 5 and 10 U/ml thrombin and greater increases in VEGFR2 and VE-cadherin expression with 1 U/ml thrombin in high-active men. Exercise-induced changes in putative EPC gene expression are associated with thrombin production and may be modulated by long-term exercise training. PMID:20378705

  7. Thrombostatin FM compounds: direct thrombin inhibitors - mechanism of action in vitro and in vivo

    SciTech Connect

    Nieman, M T; Burke, F; Warnock, M; Zhou, Y; Sweigart, J; Chen, A; Ricketts, D; Lucchesi, B R; Chen, Z; Cera, E Di; Hilfinger, J; Kim, J S; Mosberg, H I; Schmaier, A H

    2008-04-29

    Novel pentapeptides called Thrombostatin FM compounds consisting mostly of D-isomers and unusual amino acids were prepared based upon the stable angiotensin converting enzyme breakdown product of bradykinin - RPPGF. These peptides are direct thrombin inhibitors prolonging the thrombin clotting time, activated partial thromboplastin time, and prothrombin time at ≥0.78, 1.6, and 1.6 μm, respectively. They competitively inhibit α-thrombin-induced cleavage of a chromogenic substrate at 4.4--8.2 μm. They do not significantly inhibit plasma kallikrein, factor (F) XIIa, FXIa, FIXa, FVIIa-TF, FXa, plasmin or cathepsin G. One form, FM19 [rOicPaF(p-Me)], blocks α-thrombin-induced calcium flux in fibroblasts with an IC50 of 6.9 ± 1.2 μm. FM19 achieved 100% inhibition of threshold α- or γ-thrombin-induced platelet aggregation at 8.4 ± 4.7 μm and 16 ± 4 μm, respectively. The crystal structure of thrombin in complex with FM19 shows that the N-terminal D-Arg retrobinds into the S1 pocket, its second residue Oic interacts with His-57, Tyr-60a and Trp-60d, and its C-terminal p-methyl Phe engages thrombin's aryl binding site composed of Ile-174, Trp-215, and Leu-99. When administered intraperitoneal, intraduodenal, or orally to mice, FM19 prolongs thrombin clotting times and delays carotid artery thrombosis. FM19, a low affinity reversible direct thrombin inhibitor, might be useful as an add-on agent to address an unmet need in platelet inhibition in acute coronary syndromes in diabetics and others who with all current antiplatelet therapy still have reactive platelets.

  8. Zinc modulates thrombin adsorption to fibrin

    SciTech Connect

    Hopmeier, P.; Halbmayer, M.; Fischer, M.; Marx, G. )

    1990-05-01

    Human thrombin with high affinity to Sepharose insolubilized fibrin monomers (high-affinity thrombin) was used to investigate the effect of Zn(II) on the thrombin adsorption to fibrin. Results showed that at Zn(II) concentrations exceeding 100 mumols/l, thrombin binding to fibrin was decreased concomitant with the Zn(II) concentration and time; at lower Zn(II) concentrations, thrombin adsorption was enhanced. Experimental results were identical by using 125I-labelled high-affinity alpha-thrombin or by measuring the thrombin activity either by chromogenic substrate or by a clotting time method. In contrast, Ca(II) alone (final conc. 3 mmol/l) or in combination with Zn(II) was not effective. However, at higher Ca(II) concentrations (7.5-15 mmol/l), thrombin adsorption was apparently decreased. Control experiments revealed that Zn(II) had no impact on the clottability of fibrinogen, and that the results of the experiments with Ca(II) were not altered by possible cross-linking of fibrin. We conclude that unlike Ca(II), Zn(II) is highly effective in modulating thrombin adsorption to fibrin.

  9. Opacity measurements in shock-generated argon plasmas

    SciTech Connect

    Erskine, D.

    1993-07-01

    Dense plasmas having uniform and constant density and temperature are generated by passage of a planar shock wave through gas. The opacity of the plasma is accurately measured versus wavelength by recording the risetime of emitted light. This technique is applicable to a wide variety of species and plasma conditions. Initial experiments in argon have produced plasmas with 2 eV temperatures, 0.004--0.04 g/cm{sup 3} densities, and coupling parameters {Gamma} {approximately}0.3--0.7. Measurements in visible light are compared with calculations using the HOPE code. An interesting peak in the capacity at 400 nm is observed for the first time and is identified with the 4s-5p transition in excited neutral argon atoms.

  10. Generation of radiation by intense plasma and electromagnetic undulators

    SciTech Connect

    Joshi, C.

    1991-10-01

    We examine the characteristics of the classical radiation emission resulting from the interaction of a relativistic electron beam that propagates perpendicularly through a large amplitude relativistic plasma wave. Such a study is useful for evaluating the feasibility of using relativistic plasma waves as extremely short wavelength undulators for generating short wavelength radiation. The electron trajectories in a plasma wave undulator and in an ac FEL undulator are obtained using perturbation techniques. The spontaneous radiation frequency spectrum and angular distribution emitted by a single electron oscillating in these two undulators are then calculated. The radiation gain of a copropagating electromagnetic wave is calculated. The approximate analytic results for the trajectories, spontaneous radiation and gain are compared with 3-D simulation results. The characteristics of the plasma wave undulator are compared with the ac FEL undulator and linearly polarized magnetic undulator. 50 refs., 26 figs., 3 tabs.

  11. Preliminary characterization of a laser-generated plasma sheet

    SciTech Connect

    Keiter, P. A.; Malamud, G.; Trantham, M.; Fein, J.; Davis, J.; Klein, S. R.; Drake, R. P.

    2014-12-10

    We present the results from recent experiments to create a flowing plasma sheet. Two groups of three laser beams with nominally 1.5 kJ of energy per group were focused to separate pointing locations, driving a shock into a wedge target. As the shock breaks out of the wedge, the plasma is focused on center, creating a sheet of plasma. Measurements at 60 ns indicate the plasma sheet has propagated 2825 microns with an average velocity of 49 microns/ns. These experiments follow previous experiments, which are aimed at studying similar physics as that found in the hot spot region of cataclysmic variables. Krauland et al created a flowing plasma, which represents the flowing plasma from the secondary star. This flow interacted with a stationary object, which represented the disk around the white dwarf. A reverse shock is a shock formed when a freely expanding plasma encounters an obstacle. Reverse shocks can be generated by a blast wave propagating through a medium. As a result, they can also be found in binary star systems where the flowing gas from a companion star interacts with the accretion disk of the primary star.

  12. Secondary electron emission from plasma-generated nanostructured tungsten fuzz

    NASA Astrophysics Data System (ADS)

    Patino, M.; Raitses, Y.; Wirz, R.

    2016-11-01

    Recently, several researchers [e.g., Yang et al., Sci. Rep. 5, 10959 (2015)] have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports the direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40%-63% lower than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus, the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.

  13. Preliminary characterization of a laser-generated plasma sheet

    DOE PAGES

    Keiter, P. A.; Malamud, G.; Trantham, M.; ...

    2014-12-10

    We present the results from recent experiments to create a flowing plasma sheet. Two groups of three laser beams with nominally 1.5 kJ of energy per group were focused to separate pointing locations, driving a shock into a wedge target. As the shock breaks out of the wedge, the plasma is focused on center, creating a sheet of plasma. Measurements at 60 ns indicate the plasma sheet has propagated 2825 microns with an average velocity of 49 microns/ns. These experiments follow previous experiments, which are aimed at studying similar physics as that found in the hot spot region of cataclysmicmore » variables. Krauland et al created a flowing plasma, which represents the flowing plasma from the secondary star. This flow interacted with a stationary object, which represented the disk around the white dwarf. A reverse shock is a shock formed when a freely expanding plasma encounters an obstacle. Reverse shocks can be generated by a blast wave propagating through a medium. As a result, they can also be found in binary star systems where the flowing gas from a companion star interacts with the accretion disk of the primary star.« less

  14. Secondary electron emission from plasma-generated nanostructured tungsten fuzz

    SciTech Connect

    Patino, M.; Raitses, Y.; Wirz, R.

    2016-11-14

    Recently, several researchers (e.g., Q. Yang, Y.-W. You, L. Liu, H. Fan, W. Ni, D. Liu, C. S. Liu, G. Benstetter, and Y. Wang, Scientific Reports 5, 10959 (2015)) have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40-63% lower than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.:7px

  15. Secondary electron emission from plasma-generated nanostructured tungsten fuzz

    DOE PAGES

    Patino, M.; Raitses, Y.; Wirz, R.

    2016-11-14

    Recently, several researchers (e.g., Q. Yang, Y.-W. You, L. Liu, H. Fan, W. Ni, D. Liu, C. S. Liu, G. Benstetter, and Y. Wang, Scientific Reports 5, 10959 (2015)) have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40-63% lowermore » than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.:7px« less

  16. Generation of nano roughness on fibrous materials by atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Kulyk, I.; Scapinello, M.; Stefan, M.

    2012-12-01

    Atmospheric plasma technology finds novel applications in textile industry. It eliminates the usage of water and of hazard liquid chemicals, making production much more eco-friendly and economically convenient. Due to chemical effects of atmospheric plasma, it permits to optimize dyeing and laminating affinity of fabrics, as well as anti-microbial treatments. Other important applications such as increase of mechanical resistance of fiber sleeves and of yarns, anti-pilling properties of fabrics and anti-shrinking property of wool fabrics were studied in this work. These results could be attributed to the generation of nano roughness on fibers surface by atmospheric plasma. Nano roughness generation is extensively studied at different conditions. Alternative explanations for the important practical results on textile materials and discussed.

  17. Air spark-like plasma source for antimicrobial NOx generation

    NASA Astrophysics Data System (ADS)

    Pavlovich, M. J.; Ono, T.; Galleher, C.; Curtis, B.; Clark, D. S.; Machala, Z.; Graves, D. B.

    2014-12-01

    We demonstrate and analyse the generation of nitrogen oxides and their antimicrobial efficacy using atmospheric air spark-like plasmas. Spark-like discharges in air in a 1 L confined volume are shown to generate NOx at an initial rate of about 1.5  ×  1016 NOx molecules/J dissipated in the plasma. Such a discharge operating in this confined volume generates on the order of 6000 ppm NOx in 10 min. Around 90% of the NOx is in the form of NO2 after several minutes of operation in the confined volume, suggesting that NO2 is the dominant antimicrobial component. The strong antimicrobial action of the NOx mixture after several minutes of plasma operation is demonstrated by measuring rates of E. coli disinfection on surfaces and in water exposed to the NOx mixture. Some possible applications of plasma generation of NOx (perhaps followed by dissolution in water) include disinfection of surfaces, skin or wound antisepsis, and sterilization of medical instruments at or near room temperature.

  18. Design and fabrication of a 30 second pulsed plasma generator

    SciTech Connect

    Biagi, L.A.; Ehlers, K.W.; Lietzke, A.F.; Matuk, C.A.; Maruyama, Y.; Paterson, J.A.; Tanabe, J.T.

    1983-10-01

    The design and fabrication techniques for a large hybrid magnetic cusp plasma generator developed for 30 sec pulse length are described. Included are the magnetic cusp geometry features, water cooling characteristics, filament structures, and the high energy density actively cooled anode and electron dump employed.

  19. Use of Plasma Actuators as a Moving-Wake Generator

    NASA Technical Reports Server (NTRS)

    Corke, Thomas C.; Thomas, Flint O.; Klapetzky Michael J.

    2007-01-01

    The work documented in this report tests the concept of using plasma actuators as a simple and easy way to generate a simulated moving-wake and the disturbances associated with it in turbines. This wake is caused by the blades of the upstream stages of the turbine. Two types of devices, one constructed of arrays of NACA 0018 airfoils, and the one constructed of flat plates were studied. The airfoils or plates were equipped with surface mounted dielectric barrier discharge (DBD) plasma actuators, which were used to generate flow disturbances resembling moving-wakes. CTA hot-wire anemometry and flow visualization using a smoke-wire were used to investigate the wake independence at various spacings and downstream locations. The flat plates were found to produce better results than the airfoils in creating large velocity fluctuations in the free-stream flow. Different dielectric materials, plasma actuator locations, leading edge contours, angles of attack and plate spacings were investigated, some with positive results. The magnitudes of the velocity fluctuations were found to be comparable to existing mechanical moving-wake generators, thus proving the feasibility of using plasma actuators as a moving-wake generator.

  20. Intense ion beam generation, plasma radiation source and plasma opening switch research

    NASA Astrophysics Data System (ADS)

    Hammer, D. A.; Coleman, M. D.; Qi, N.; Similon, P. L.; Sudan, R. N.

    1989-04-01

    This report describes research on intense ion beam diodes, plasma opening switches and dense z-pinch plasma radiators. Laser induced fluorescence spectroscopy has been used to map the electrostatic potential profile in a plasma-prefilled magnetically insulated ion diode. In a simple planar diode, the measured profile is inconsistent with the electrons being confined in a sheath near the cathode by the magnetic field. Rather, the profile implies the presence of electrons throughout the accelerating gap. A theoretical model of the penetration of current and magnetic field into a plasma, and of the current-driven effective collision frequency has been developed. The snowplow action of the rising magnetic field causes a steep rise in the plasma density at the leading edge. The subsequent multistreaming of the ions caused by ion reflection at the current layer could lead to ion heating through collective effects. The two-dimensional electron flow in the plasma cathode vacuum gap is also treated. Dense z-pinch plasma radiation source experiments have been initiated on the LION accelerator using gas puff and fine wire loads. The x-pinch was found to be a more effective way to generate soft x-rays than a single wire pinch or a gas puff implosion. Plasma opening switch experiments being initiated, and plasma anode ion diode development work being terminated are also briefly described.

  1. STIM1 and Orai1 mediate thrombin-induced Ca(2+) influx in rat cortical astrocytes.

    PubMed

    Moreno, Claudia; Sampieri, Alicia; Vivas, Oscar; Peña-Segura, Claudia; Vaca, Luis

    2012-12-01

    In astrocytes, thrombin leads to cytoplasmic Ca(2+) elevations modulating a variety of cytoprotective and cytotoxic responses. Astrocytes respond to thrombin stimulation with a biphasic Ca(2+) increase generated by an interplay between ER-Ca(2+) release and store-operated Ca(2+) entry (SOCE). In many cell types, STIM1 and Orai1 have been demonstrated to be central components of SOCE. STIM1 senses the ER-Ca(2+) depletion and binds Orai1 to activate Ca(2+) influx. Here we used immunocytochemistry, overexpression and siRNA assays to investigate the role of STIM1 and Orai1 in the thrombin-induced Ca(2+) response in primary cultures of rat cortical astrocytes. We found that STIM1 and Orai1 are endogenously expressed in cortical astrocytes and distribute accordingly with other mammalian cells. Importantly, native and overexpressed STIM1 reorganized in puncta under thrombin stimulation and this reorganization was reversible. In addition, the overexpression of STIM1 and Orai1 increased by twofold the Ca(2+) influx evoked by thrombin, while knockdown of endogenous STIM1 and Orai1 significantly decreased this Ca(2+) influx. These results indicate that STIM1 and Orai1 underlie an important fraction of the Ca(2+) response that astrocytes exhibit in the presence of thrombin. Thrombin stimulation in astrocytes leads to ER-Ca(2+) release which causes STIM1 reorganization allowing the activation of Orai1 and the subsequent Ca(2+) influx.

  2. Thrombin selectively induces transcription of genes in human monocytes involved in inflammation and wound healing.

    PubMed

    López, Mercedes L; Bruges, Gustavo; Crespo, Gustavo; Salazar, Victor; Deglesne, Pierre-Antoine; Schneider, Heike; Cabrera-Fuentes, Hector; Schmitz, M Lienhard; Preissner, Klaus T

    2014-11-01

    Thrombin is essential for blood coagulation but functions also as a mediator of cellular signalling. Gene expression microarray experiments in human monocytes revealed thrombin-induced upregulation of a limited subset of genes, which are almost exclusively involved in inflammation and wound healing. Among these, the expression of F3 gene encoding for tissue factor (TF) was enhanced indicating that this physiological initiator of coagulation cascade may create a feed-forward loop to enhance blood coagulation. Activation of protease-activated receptor type 1 (PAR1) was shown to play a main role in promoting TF expression. Moreover, thrombin induced phosphorylation of ERK1/2, an event that is required for expression of thrombin-regulated genes. Thrombin also increased the expression of TF at the protein level in monocytes as evidenced by Western blot and immunostaining. Furthermore, FXa generation induced by thrombin-stimulated monocytes was abolished by a TF blocking antibody and therefore it is entirely attributable to the expression of tissue factor. This cellular activity of thrombin provides a new molecular link between coagulation, inflammation and wound healing.

  3. Generation of filamentary structures by beam-plasma interaction

    SciTech Connect

    Wang, X.Y.; Lin, Y.

    2006-05-15

    The previous simulations by Wang and Lin [Phys. Plasmas. 10, 3528 (2003)] showed that filaments, frequently observed in space plasmas, can form via the interaction between an ion beam and a background plasma. In this study, the physical mechanism for the generation of the filaments is investigated by a two-dimensional hybrid simulation, in which a field-aligned ion beam with relative beam density n{sub b}=0.1 and beam velocity V{sub b}=10V{sub A} is initiated in a uniform plasma. Right-hand nonresonant ion beam modes, consistent with the linear theory, are found to be dominant in the linear stage of the beam-plasma interaction. In the later nonlinear stage, the nonresonant modes decay and the resonant modes grow through a nonlinear wave coupling. The interaction among the resonant modes leads to the formation of filamentary structures, which are the field-aligned structures (k perpendicular B) of magnetic field B, density, and temperature in the final stage. The filaments are nonlinearly generated in a prey-predator fashion by the parallel and oblique resonant ion beam modes, which meanwhile evolve into two types of shear Alfven modes, with one mainly propagating along the background field B{sub 0} and the other obliquely propagating. The filamentary structures are found to be phase standing in the plasma frame, but their amplitude oscillates with time. In the dominant filament mode, fluctuations in the background ion density, background ion temperature, and beam density are in phase with the fluctuations in B, whereas the significantly enhanced beam temperature is antiphase with B. It is found that the filaments are produced by the interaction of at least two ion beam modes with comparable amplitudes, not by only one single mode, thus their generation mechanism is different from other mechanisms such as the stimulated excitation by the decay of an Alfven wave.

  4. Template-assisted generation of nanocavities within plasma polymer films.

    PubMed

    Vasilev, Krasimir; Casanal, Ana; Challougui, Hela; Griesser, Hans J

    2009-05-21

    The generation of nanosized cavities within thin film layers is of interest for a number of fundamental and applied reasons. One challenge is to make such systems sufficiently robust mechanically. Plasma polymer (pp) films possess excellent mechanical stability if deposition conditions are selected such as to achieve a sufficient density of cross-linking and resistance to extraction of polymeric material by solvents. In this study, gold nanoparticles of 15 and 70 nm diameter were used as sacrificial templates to generate nanocavities in pp films of various thickness values in the tens of nanometers range. A first pp layer was deposited onto substrates using n-heptylamine (HA) to a thickness of 20 nm. Carboxy-thiolated gold nanoparticles were electrostatically bound onto the surface amine groups of the n-heptylamine plasma polymer (HApp) layer. A second HApp layer was then coated to various thicknesses onto the nanoparticle/HApp surface. The template particles embedded thus in-between the two HApp layers were then dissolved using aqueous KCN solution; monitoring of the plasmon resonance band of the gold nanoparticles enabled verification of template stripping and measurement of the kinetics of stripping. AFM topography images showed little change on extraction of the template nanoparticles, indicating that the plasma polymer layer maintained structural integrity upon template extraction and subsequent drying, and thereby prevented collapse of the empty nanocavities. The concept of template stripping to generate controlled size free volume in thin plasma polymer layers is thus shown to produce robust structures.

  5. A method to measure thrombin activity in a mixture of fibrinogen and thrombin powders

    PubMed Central

    DeAnglis, Ashley P.; Nur, Israel; Gorman, Anne J.; Meidler, Roberto

    2017-01-01

    Thrombin and fibrinogen powders are the active components of advanced surgical hemostasis products including the EVARREST Fibrin Sealant Patch. Measuring the enzymatic activity of thrombin in the presence of fibrinogen is challenging, as hydration of the powders in a neutral aqueous environment will cause the enzyme to rapidly react with the fibrinogen to form a fibrin clot, which in turn binds and entraps the enzyme thus preventing subsequent measurement of thrombin activity. A novel approach has been developed to overcome this challenge. After isolation of the mixture of powders, an alkaline carbonate solution is used to solubilize the proteins, while reversibly inhibiting the activity of thrombin and preventing clot formation. Once the powders have been fully solubilized, thrombin activity can be restored by neutralization in a buffered fibrinogen solution resulting in fibrin clot formulation. The rate of clot formation can be quantified in a coagulometer to determine the thrombin activity of the original powder. Samples coated with powders containing fibrinogen and varying amounts of thrombin were tested using the method described herein. The results demonstrated that the method could consistently measure the activity of (alpha) thrombin in the presence of fibrinogen over a broad range of thrombin activity levels. The test was successfully validated according to International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use Guidelines and thus is suitable for use as part of a commercial manufacturing process. A method has been developed that enables thrombin activity to be measured in a mixture of fibrinogen and thrombin powders. PMID:26991860

  6. Dynamics and interactions of pulsed laser generated plasma bubbles in dusty plasma liquids

    SciTech Connect

    Chu Hongyu; Liao Chenting; I Lin

    2005-10-31

    The plasma bubble with dust particle depletion can be generated by a nano-second laser pulse focused on one of the dust particles suspended in a strongly coupled dusty plasma liquid. The bubble dynamics at different time scales, including the initial forming and later traveling stages are investigated. In the first stage, dust particles are pushed outward by the outward ion flow associated with the plume generated by the more intensed plasma. The bubble then travels downward at a speed about 60 mm/s associated with a surrounding dipole-like dust flow field. Two bubbles can also be simultaneously generated at different locations by separated laser pulses to study their interactions. Strong coupling is observed between two vertical bubbles. However, two horizontal bubbles are weakly coupled. The possible mechanism is discussed.

  7. A novel, all-dielectric, microwave plasma generator towards development of plasma metamaterials

    NASA Astrophysics Data System (ADS)

    Cohick, Zane; Luo, Wei; Perini, Steven; Baker, Amanda; Wolfe, Douglas; Lanagan, Michael

    2016-11-01

    A proof of concept for a microwave microplasma generator that consists of a halved dielectric resonator is presented. The generator functions via leaking electric fields of the resonant modes — TE01δ and HEM12δ modes are explored. Computational results illustrate the electric fields, whereas the stability of resonance and coupling are studied experimentally. Finally, a working device is presented. This generator promises potentially wireless and low-loss operation. This device may find relevance in plasma metamaterials; each resonator may generate the plasma structures necessary to manipulate electromagnetic radiation. In particular, the all-dielectric nature of the generator will allow low-loss interaction with high-frequency (GHz-THz) waves.

  8. Generation of pulsed discharge plasma in water with fine bubbles

    NASA Astrophysics Data System (ADS)

    Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu; Goto laboratory Team

    2015-09-01

    Recently, some researchers have proposed electric discharge methods with bubbles in water because the discharge plasma inside bubble was easy to be generated compared to that in water. Almost all of these methods introduced bubbles in the order of millimeter size from a nozzle placed in water. In these methods, bubbles rose one after another owing to high rising speed of millibubble, leading to inefficient gas consumption. We proposed fine bubbles introduction at the discharge area in water. A fine bubble is determined a bubble with less than 100 μm in a diameter. Fine bubbles exhibit extremely slow rising speed. Fine bubbles decrease in size during bubble rising and subsequently collapse in water with OH radical generation. Therefore, combining the discharge plasma with fine bubbles is expected to generate more active species with small amount of gas consumption. In this work, fine bubbles were introduced in water and pulsed discharge plasma was generated between two cylindrical electrodes which placed in water. We examined effects of fine bubbles on electric discharge in water when argon or oxygen gas was utilized as feed gas. Fine bubbles enhanced optical emission of hydrogen and oxygen atoms from H2O molecules, but that of feed gas was not observed. The formation mechanism of H2O2 by electric discharge was supposed to be different from that with no bubbling. Dissolved oxygen in water played a role in H2O2 formation by the discharge with fine bubbles.

  9. Electric probe investigations of microwave generated, atmospheric pressure, plasma jets

    SciTech Connect

    Porteanu, H. E.; Kuehn, S.; Gesche, R.

    2010-07-15

    We examine the applicability of the Langmuir-type of characterization for atmospheric pressure plasma jets generated in a millimeter-size cavity microwave resonator at 2.45 GHz. Wide range I-V characteristics of helium, argon, nitrogen, air and oxygen are presented for different gas fluxes, distances probe-resonator, and microwave powers. A detailed analysis is performed for the fine variation in the current around the floating potential. A simplified theory specially developed for this case is presented, considering the ionic and electronic saturation currents and the floating potential. Based on this theory, we conclude that, while the charge carrier density depends on gas flow, distance to plasma source, and microwave absorbed power, the electron temperature is quite independent of these parameters. The resulting plasma parameters for helium, argon, and nitrogen are presented.

  10. Advanced targets, diagnostics and applications of laser-generated plasmas

    NASA Astrophysics Data System (ADS)

    Torrisi, L.

    2015-04-01

    High-intensity sub-nanosecond-pulsed lasers irradiating thin targets in vacuum permit generation of electrons and ion acceleration and high photon yield emission in non-equilibrium plasmas. At intensities higher than 1015 W/cm2 thin foils can be irradiated in the target-normal sheath acceleration regime driving ion acceleration in the forward direction above 1 MeV per charge state. The distributions of emitted ions in terms of energy, charge state and angular emission are controlled by laser parameters, irradiation conditions, target geometry and composition. Advanced targets can be employed to increase the laser absorption in thin foils and to enhance the energy and the yield of the ion acceleration process. Semiconductor detectors, Thomson parabola spectrometer and streak camera can be employed as online plasma diagnostics to monitor the plasma parameters, shot by shot. Some applications in the field of the multiple ion implantation, hadrontherapy and nuclear physics are reported.

  11. Electromagnetic radiation generated by arcing in low density plasma

    NASA Technical Reports Server (NTRS)

    Vayner, Boris V.; Ferguson, Dale C.; Snyder, David B.; Doreswamy, C. V.

    1996-01-01

    An unavoidable step in the process of space exploration is to use high-power, very large spacecraft launched into Earth orbit. Obviously, the spacecraft will need powerful energy sources. Previous experience has shown that electrical discharges occur on the surfaces of a high-voltage array, and these discharges (arcs) are undesirable in many respects. Moreover, any high voltage conductor will interact with the surrounding plasma, and that interaction may result in electrical discharges between the conductor and plasma (or between two conductors with different potentials, for example, during docking and extravehicular activity). One very important aspect is the generation of electromagnetic radiation by arcing. To prevent the negative influence of electromagnetic noise on the operation of spacecraft systems, it seems necessary to determine the spectra and absolute levels of the radiation, and to determine limitations on the solar array bias voltage that depend on the parameters of LEO plasma and the technical requirements of the spacecraft equipment. This report describes the results of an experimental study and computer simulation of the electromagnetic radiation generated by arcing on spacecraft surfaces. A large set of high quality data was obtained during the Solar Array Module Plasma Interaction Experiment (SAMPIE, flight STS-62) and ground test. These data include the amplitudes of current, pulse forms, duration of each arc, and spectra of plasma waves. A theoretical explanation of the observed features is presented in this report too. The elaborated model allows us to determine the parameters of the electromagnetic noise for different frequency ranges, distances from the arcing site, and distinct kinds of plasma waves.

  12. A reusable aptasensor of thrombin based on DNA machine employing resonance light scattering technique.

    PubMed

    Hou, Yining; Liu, Jifeng; Hong, Min; Li, Xia; Ma, Yanhua; Yue, Qiaoli; Li, Chen-Zhong

    2017-06-15

    The design of molecular nanodevices attracted great interest in these years. Herein, a reusable, sensitive and specific aptasensor was constructed based on an extension-contraction movement of DNA interconversion for the application of human thrombin detection. The present biosensor was based on resonance light scattering (RLS) using magnetic nanoparticles (MNPs) as the RLS probe. MNPs coated with streptavidin can combine with biotin labeled thrombin aptamers. The combined nanoparticles composite is monodispersed in aqueous medium. When thrombin was added a sandwich structure can form on the surface of MNPs, which induced MNPs aggregation. RLS signal was therefore enhanced, and there is a linear relationship between RLS increment and thrombin concentration in the range of 60pM-6.0nM with a limit of detection at 3.5pM (3.29SB/m, according to the recent recommendation of IUPAC). The present aptasensor can be repeatedly used for at least 6 cycling times by heat to transfer G-quadruplex conformation to single strand of DNA sequence and release thrombin. MNPs can be captured by applying the external magnetic field. Furthermore, the proposed biosensor was successfully applied to detect thrombin in human plasma.

  13. Thrombin use in surgery: an evidence-based review of its clinical use

    PubMed Central

    Ham, Sung W; Lew, Wesley K; Weaver, Fred A

    2010-01-01

    When surgical ligation of bleeding fails, or is not possible, surgeons rely on a number of hemostatic aids, including thrombin. This review discusses the history, pharmacology and clinical application of thrombin as a surgical hemostat. The initial thrombin was bovine in origin, but its use has been complicated by the formation of antibodies that cross-react with human coagulation factors. This has been associated with life-threatening bleeding and in some circumstances anaphylaxis and death. Human thrombin, isolated from pooled plasma of donors, was developed in an effort to minimize these risks, but its downsides are its limited availability and the potential for transmitting blood-borne pathogens. Recently a recombinant thrombin has been developed, and approved for use by the FDA. It has the advantage of being minimally antigenic and devoid of the risk of viral transmission. Thrombin is often used in conjunction with other hemostatic aids, including absorbable agents such as Gelfoam, and with fibrinogen in fibrin glues. The last part of this review will discuss these agents in detail, and review their clinical applications. PMID:22282693

  14. Thrombin Production and Human Neutrophil Elastase Sequestration by Modified Cellulosic Dressings and Their Electrokinetic Analysis

    PubMed Central

    Edwards, Judson Vincent; Prevost, Nicolette

    2011-01-01

    Wound healing is a complex series of biochemical and cellular events. Optimally, functional material design addresses the overlapping acute and inflammatory stages of wound healing based on molecular, cellular, and bio-compatibility issues. In this paper the issues addressed are uncontrolled hemostasis and inflammation which can interfere with the orderly flow of wound healing. In this regard, we review the serine proteases thrombin and elastase relative to dressing functionality that improves wound healing and examine the effects of charge in cotton/cellulosic dressing design on thrombin production and elastase sequestration (uptake by the wound dressing). Thrombin is central to the initiation and propagation of coagulation, and elastase is released from neutrophils that can function detrimentally in a stalled inflammatory phase characteristic of chronic wounds. Electrokinetic fiber surface properties of the biomaterials of this study were determined to correlate material charge and polarity with function relative to thrombin production and elastase sequestration. Human neutrophil elastase sequestration was assessed with an assay representative of chronic wound concentration with cotton gauze cross-linked with three types of polycarboxylic acids and one phosphorylation finish; thrombin production, which was assessed in a plasma-based assay via a fluorogenic peptide substrate, was determined for cotton, cotton-grafted chitosan, chitosan, rayon/polyester, and two kaolin-treated materials including a commercial hemorrhage control dressing (QuickClot Combat Gauze). A correlation in thrombin production to zeta potential was found. Two polycarboxylic acid cross linked and a phosphorylated cotton dressing gave high elastase sequestration. PMID:24956451

  15. Generation and Diagnostics of Microwave Discharge Expanding Nitrogen Plasma

    NASA Astrophysics Data System (ADS)

    Shibata, Tomohiko; Yoshida, Kazuyuki; Nezu, Atsushi; Matsuura, Haruaki; Akatsuka, Hiroshi

    2008-10-01

    We examine a microwave discharge expanding nitrogen plasma on its vibrational and rotational temperatures (Tv, Tr) by using optical emission spectroscopy (OES), and on its electron density and temperature by using a double probe. In the present study, we generated microwave discharge plasma in a cylindrical quartz tube (26 mm i.d.) and the plasma flowed and expanded rapidly into a rarefied gas wind tunnel with its pressure 2.6x10-3 torr. The microwave output power was set at 300 W. The gas flow rate was set at 300 ml/min. In OES measurement, we measured the band spectra of 1stPS and 2ndPS. We compare the experimentally measured spectrum with the calculate one to determine Tv and Tr of the generated plasma. Electron temperature did not reduce monotonically, which is due to complicated energy relaxation process contributed by metastables or vibrational levels. Intensity of 2ndPS decreased more rapidly than that of 1stPS, which is considered to be mainly due to the lowering of Te. We found different way of variation in Tv of 1stPS and that of 2ndPS.

  16. Mechanism for blob generation in the TORPEX toroidal plasma

    SciTech Connect

    Furno, I.; Labit, B.; Fasoli, A.; Poli, F. M.; Ricci, P.; Theiler, C.; Brunner, S.; Diallo, A.; Graves, J. P.; Podesta, M.; Mueller, S. H.

    2008-05-15

    The mechanism for blob generation is detailed in the toroidal magnetized plasma of the TORPEX device [Fasoli et al., Phys. Plasmas 13, 055902 (2006)] using an experimental configuration, which features a plasma region dominated by a coherent wave and a region on the low field side characterized by the propagation of blobs. Predictions from linearized 2D drift-reduced Braginskii equations are compared with experimental data, revealing the interchange nature of the coherent wave. The dynamics of blob formation is investigated using time-resolved measurements of two-dimensional profiles of electron density, temperature, plasma potential and ExB velocity. Blobs form from radially elongated structures associated with the interchange wave. When a blob is generated, the following sequence of events is observed: 1) A decrease of local pressure gradient length provides an increase of the interchange mode drive; 2) in response, the interchange mode increases in amplitude and expands in the radial direction forming a radially elongated structure from the wave crest; 3) the elongated structure is convected by the ExB flow and is eventually sheared off, forming a blob on the low field side. The dependence of the blob amplitude upon the minimum pressure radial scale length before the blob ejection is also investigated.

  17. Status of the plasma generator of the superconducting proton linac

    SciTech Connect

    Kronberger, M.; Lettry, J.; Paoluzzi, M.; Pereira, H.; Arias, J. Sanchez; Schmitzer, C.; Scrivens, R.; Faircloth, D.

    2012-02-15

    In the framework of the superconducting proton linac (SPL) study at CERN, a new non-cesiated H{sup -} plasma generator driven by an external 2 MHz RF antenna has been developed and successfully operated at repetition rates of 50 Hz, pulse lengths of up to 3 ms, and average RF powers of up to 3 kW. The coupling efficiency of RF power into the plasma was determined by the cooling water temperatures and the analysis of the RF forward and reflected power and the antenna current and amounts to 50%-60%. The plasma resistance increases between 10 kW and 40 kW RF power from about 0.45 {Omega} to 0.65 {Omega}. Measurements of RF power dissipated in the ferrites and the magnets on a test bench show a 5-fold decrease of the power losses for the magnets when they are contained in a Cu box, thus validating the strategy of shielding the magnets with a high electrical conductivity material. An air cooling system was installed in the SPL plasma generator to control the temperatures of the ferrites despite hysteresis losses of several Watts.

  18. The Interaction of Explosively Generated Plasma with Explosives

    NASA Astrophysics Data System (ADS)

    Tasker, Douglas; LANL Team

    2015-06-01

    It has been shown that the temperature of explosively generated plasma (EGP) is of the order of 1 eV and plasma ejecta can be focused to achieve velocities as high as 25 km/s. These high velocity plasma can readily penetrate a wide range of materials including metals. Proof-of-principle tests were performed to determine if EGP could be used for explosive ordnance demolition and other applications. The test goals were: to benignly disable ordnance containing relatively sensitive high performance explosives (PBX-9501); and to investigate the possibility of interrupting an ongoing detonation in a powerful high explosive (again PBX-9501) with EGP. Experiments were performed to establish the optimum sizes of plasma generators for the benign deactivation of high explosives, i.e., the destruction of the ordnance without initiating a detonation or comparable violent event. These experiments were followed by attempts to interrupt an ongoing detonation by the destruction of the unreacted explosive in its path. The results were encouraging. First, it was demonstrated that high explosives could be destroyed without the initiation of a detonation or high order reaction. Second, ongoing detonations were successfully interrupted with EGP. LA-UR-15-20612.

  19. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, D.; Esarey, E.; Kim, J.K.

    1997-06-10

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

  20. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, Donald; Esarey, Eric; Kim, Joon K.

    1997-01-01

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

  1. Reversibility of thrombin-induced decrease in platelet glycoprotein Ib function.

    PubMed

    Lu, H; Menashi, S; Garcia, I; Cramer, E M; Li, H; Tenza, D; De Romeuf, C; Soria, J; Soria, C

    1993-09-01

    Thrombin induces a redistribution of glycoprotein (GP) Ib/GP IX complex from the platelet surface into the surface connected canalicular system (SCCS). This redistribution results in a reduced interaction of platelet GP Ib with von Willebrand factor (vWF) bound to subendothelium leading to impaired platelet adhesion. In this study we show that the platelet aggregation and degranulation require concentrations of thrombin above 0.05 U/ml, while the decrease in GP Ib function (about 50% of control value), as determined by ristocetin induced platelet agglutination, can be induced by lower concentrations (0.01-0.04 U/ml). Moreover, we show that when adding thrombin inhibitors to the platelets preincubated with < 0.04 U/ml thrombin for 5 min, their agglutinability by ristocetin was gradually recovered within 30 min, indicating that in these conditions the decrease in platelet adhesiveness is reversible. Immuno-electromicroscopic study showed that this restoration of platelet GP Ib function was associated with a reversed translocation of GP Ib from the SCCS to the plasma membrane. The data obtained from counting gold particles showed that the ratio of GP Ib immunolabelling on the external membrane versus that on the SCCS was 3.31 +/- 0.90 for resting platelets, down-regulated to 0.84 +/- 0.13 (P < 0.05 versus resting platelets) for the platelets treated with 0.04 U/ml thrombin and returned to 2.63 +/- 2.21 (P > 0.05 versus resting platelets) after incubation for 30 min with hirudin. However, the translocation of GP Ib was poorly reversed by thrombin inhibitors when higher concentrations of thrombin were used which induced platelet aggregation and large extent of degranulation. We conclude that thrombin affects platelets in a dose dependent manner, and that at low concentrations the decrease in platelet GP Ib related function is a reversible phenomenon.

  2. Improved Magnetic Field Generation Efficiency and Higher Temperature Spheromak Plasmas

    SciTech Connect

    Wood, R D; Hill, D N; McLean, H S; Hooper, E B; Hudson, B F; Moller, J M; Romero-Talamas, C A

    2008-09-15

    New understanding of the mechanisms governing the observed magnetic field generation limits on the sustained spheromak physics experiment has been obtained. Extending the duration of magnetic helicity injection during the formation of a spheromak and optimizing the ratio of injected current to bias flux produce higher magnetic field plasmas with record spheromak electron temperatures. To explore magnetic field buildup efficiency limits, the confinement region geometry was varied resulting in improved field buildup efficiencies.

  3. Theoretical modeling and experimental validation of surface stress in thrombin aptasensor.

    PubMed

    Lim, Yang Choon; Kouzani, Abbas Z; Kaynak, Akif; Dai, Xiujuan J; Littlefair, Guy; Duan, Wei

    2014-12-01

    Adsorption of target molecules on the immobilized microcantilever surface produced beam displacement due to the differential surface stress generated between the immobilized and non-immobilized surface. Surface stress is caused by the intermolecular forces between the molecules. Van der Waals, electrostatic forces, hydrogen bonding, hydrophobic effect and steric hindrance are some of the intermolecular forces involved. A theoretical framework describing the adsorption-induced microcantilever displacement is derived in this paper. Experimental displacement of thrombin aptamer-thrombin interactions was carried out. The relation between the electrostatic interactions involved between adsorbates (thrombin) as well as adsorbates and substrates (thrombin aptamer) and the microcantilever beam displacement utilizing the proposed mathematical model was quantified and compared to the experimental value. This exercise is important to aid the designers in microcantilever sensing performance optimization.

  4. Flowing dusty plasma experiments: generation of flow and measurement techniques

    NASA Astrophysics Data System (ADS)

    Jaiswal, S.; Bandyopadhyay, P.; Sen, A.

    2016-12-01

    A variety of experimental techniques for the generation of subsonic/supersonic dust fluid flows and means of measuring such flow velocities are presented. The experiments have been carried out in a \\Pi -shaped dusty plasma experimental device with micron size kaolin/melamine formaldehyde particles embedded in a background of argon plasma created by a direct current glow discharge. A stationary dust cloud is formed over the cathode region by precisely balancing the pumping speed and gas flow rate. A flow of dust particles/fluid is generated by additional gas injection from a single or dual locations or by altering the dust confining potential. The flow velocity is then estimated by three different techniques, namely, by super particle identification code, particle image velocimetry analysis and the excitation of dust acoustic waves. The results obtained from these three different techniques along with their merits and demerits are discussed. An estimation of the neutral drag force responsible for the generation as well as the attenuation of the dust fluid flow is made. These techniques can be usefully employed in laboratory devices to investigate linear and non-linear collective excitations in a flowing dusty plasma.

  5. Nonthermal Argon Plasma Generator and Some Potential Applications

    NASA Astrophysics Data System (ADS)

    Bunoiu, M.; Jugunaru, I.; Bica, I.; Balasoiu, M.

    2015-12-01

    A laboratory - made nonthermal plasma generator is presented. It has a diameter of 0.020 m and length of 0.155 m and contains two electrodes. The first electrode is a 2% Th-W alloy, 0.002 m in diameter bar, centred inside the generator's body by means of a four channel teflon piece; the other three channels, 0.003 m in diameter, are used for Ar supply. The second electrode is a nozzle of 0.002 m - 0.008 m diameter and 0.005m length. A ~500 kV/m electric field is generated between the two electrodes by a high frequency source (13.56 MHz ±5%), equipped with a OT-1000 (Tungsram) power triode. For Ar flows ranging from 0.00008 m3/s to 0.00056 m3/s, a plasma jet of length not exceeding 0.015 m and temperature below 315 K is obtained. Anthurium andraeanumis sample , blood matrix, human hair and textile fibers may be introduced in the plasma jet. For time periods of 30 s and 60 s, various effects like, cell detexturization, fast blood coagulation or textile fiber or hair cleaning and smoothing are obtained. These effects are presented and discussed in the paper.

  6. Laser plasma simulations of the generation processes of Alfven and collisionless shock waves in space plasma

    NASA Astrophysics Data System (ADS)

    Prokopov, P. A.; Zakharov, Yu P.; Tishchenko, V. N.; Shaikhislamov, I. F.; Boyarintsev, E. L.; Melekhov, A. V.; Ponomarenko, A. G.; Posukh, V. G.; Terekhin, V. A.

    2016-11-01

    Generation of Alfven waves propagating along external magnetic field B0 and Collisionless Shock Waves propagating across B0 are studied in experiments with laser- produced plasma and magnetized background plasma. The collisionless interaction of interpenetrating plasma flows takes place through a so-called Magnetic Laminar Mechanism (MLM) or Larmor Coupling. At the edge of diamagnetic cavity LP-ions produce induction electric field Eφ which accelerates BP-ions while LP-ions rotate in opposite direction. The ions movement generates sheared azimuthal magnetic field Bφ which could launches torsional Alfven wave. In previous experiments at KI-1 large scale facility a generation of strong perturbations propagating across B0 with magnetosonic speed has been studied at a moderate value of interaction parameter δ∼0.3. In the present work we report on experiments at conditions of 5∼R2 and large Alfven-Mach number MA∼10 in which strong transverse perturbations traveling at a scale of ∼1 m in background plasma at a density of ∼3*1013 cm-3 is observed. At the same conditions but smaller MA ∼ 2 a generation, the structure and dynamic of Alfven wave with wavelength ∼0.5 m propagating along fields B0∼100÷500 G for a distance of ∼2.5 m is studied.

  7. Platelet-rich plasma stimulated by pulse electric fields: Platelet activation, procoagulant markers, growth factor release and cell proliferation.

    PubMed

    Frelinger, A L; Torres, A S; Caiafa, A; Morton, C A; Berny-Lang, M A; Gerrits, A J; Carmichael, S L; Neculaes, V B; Michelson, A D

    2016-01-01

    Therapeutic use of activated platelet-rich plasma (PRP) has been explored for wound healing, hemostasis and antimicrobial wound applications. Pulse electric field (PEF) stimulation may provide more consistent platelet activation and avoid complications associated with the addition of bovine thrombin, the current state of the art ex vivo activator of therapeutic PRP. The aim of this study was to compare the ability of PEF, bovine thrombin and thrombin receptor activating peptide (TRAP) to activate human PRP, release growth factors and induce cell proliferation in vitro. Human PRP was prepared in the Harvest SmartPreP2 System and treated with vehicle, PEF, bovine thrombin, TRAP or Triton X-100. Platelet activation and procoagulant markers and microparticle generation were measured by flow cytometry. Released growth factors were measured by ELISA. The releasates were tested for their ability to stimulate proliferation of human epithelial cells in culture. PEF produced more platelet-derived microparticles, P-selectin-positive particles and procoagulant annexin V-positive particles than bovine thrombin or TRAP. These differences were associated with higher levels of released epidermal growth factor after PEF than after bovine thrombin or TRAP but similar levels of platelet-derived, vascular-endothelial, and basic fibroblast growth factors, and platelet factor 4. Supernatant from PEF-treated platelets significantly increased cell proliferation compared to plasma. In conclusion, PEF treatment of fresh PRP results in generation of microparticles, exposure of prothrombotic platelet surfaces, differential release of growth factors compared to bovine thrombin and TRAP and significant cell proliferation. These results, together with PEF's inherent advantages, suggest that PEF may be a superior alternative to bovine thrombin activation of PRP for therapeutic applications.

  8. Laser-plasma mirrors: from electron acceleration to harmonics generation

    NASA Astrophysics Data System (ADS)

    Thévenet, Maxence; Bocoum, Maïmouna; Faure, Jérôme; Leblanc, Adrien; Vincenti, Henri; Quéré, Fabien

    2016-10-01

    Accelerating electrons in the > 10 TV/m fields inside an ultrashort ultraintense laser pulse has been a long-standing goal in experimental physics, motivated by promising theoretical predictions. The biggest hurdle was to have electrons injected in the center of the laser pulse. Recent experimental and numerical results showed that this problem could be solved using a plasma mirror, i.e. an overdense plasma with a sharp (generation mechanisms on plasma mirrors, giving new insights into the motion of the plasma mirror surface. funded by the European Research Council, Contract No. 306708, ERC Starting Grant FEMTOELEC.

  9. The interaction of explosively generated plasma with explosives

    NASA Astrophysics Data System (ADS)

    Tasker, Douglas G.; Whitley, Von H.; Johnson, Carl E.

    2017-01-01

    It has been shown that the temperature of explosively generated plasma (EGP) is of the order of 1 eV and plasma ejecta can be focused to achieve velocities as high as 25 km/s. Proof-of-principle tests were performed to determine if EGP could be used for explosive ordnance demolition and other applications. The goals were: to benignly disable ordnance containing relatively sensitive high performance explosives (PBX-9501); and to investigate the possibility of interrupting an ongoing detonation in a powerful high explosive (again PBX-9501) with EGP. Experiments were performed to establish the optimum sizes of plasma generators for the benign deactivation of high explosives, i.e., the destruction of the ordnance without initiating a detonation or comparable violent event. These experiments were followed by attempts to interrupt an ongoing detonation by the benign disruption of the unreacted explosive in its path. The results were encouraging. First, it was demonstrated that high explosives could be destroyed without the initiation of a detonation or high order reaction. Second, ongoing detonations were successfully interrupted with EGP. [LA-UR-15-25350

  10. Theoretical and numerical predictions of hypervelocity impact-generated plasma

    NASA Astrophysics Data System (ADS)

    Li, Jianqiao; Song, Weidong; Ning, Jianguo

    2014-08-01

    The hypervelocity impact generated plasmas (HVIGP) in thermodynamic non-equilibrium state were theoretically analyzed, and a physical model was presented to explore the relationship between plasma ionization degree and internal energy of the system by a group of equations including a chemical reaction equilibrium equation, a chemical reaction rate equation, and an energy conservation equation. A series of AUTODYN 3D (a widely used software in dynamic numerical simulations and developed by Century Dynamic Inc.) numerical simulations of the impacts of hypervelocity Al projectile on its targets at different incident angles were performed. The internal energy and the material density obtained from the numerical simulations were then used to calculate the ionization degree and the electron temperature. Based on a self-developed 2D smooth particle hydrodynamic (SPH) code and the theoretical model, the plasmas generated by 6 hypervelocity impacts were directly simulated and their total charges were calculated. The numerical results are in good agreements with the experimental results as well as the empirical formulas, demonstrating that the theoretical model is justified by the AUTODYN 3D and self-developed 2D SPH simulations and applicable to predict HVIGPs. The study is of significance for astrophysical and cosmonautic researches and safety.

  11. Theoretical and numerical predictions of hypervelocity impact-generated plasma

    SciTech Connect

    Li, Jianqiao; Song, Weidong Ning, Jianguo

    2014-08-15

    The hypervelocity impact generated plasmas (HVIGP) in thermodynamic non-equilibrium state were theoretically analyzed, and a physical model was presented to explore the relationship between plasma ionization degree and internal energy of the system by a group of equations including a chemical reaction equilibrium equation, a chemical reaction rate equation, and an energy conservation equation. A series of AUTODYN 3D (a widely used software in dynamic numerical simulations and developed by Century Dynamic Inc.) numerical simulations of the impacts of hypervelocity Al projectile on its targets at different incident angles were performed. The internal energy and the material density obtained from the numerical simulations were then used to calculate the ionization degree and the electron temperature. Based on a self-developed 2D smooth particle hydrodynamic (SPH) code and the theoretical model, the plasmas generated by 6 hypervelocity impacts were directly simulated and their total charges were calculated. The numerical results are in good agreements with the experimental results as well as the empirical formulas, demonstrating that the theoretical model is justified by the AUTODYN 3D and self-developed 2D SPH simulations and applicable to predict HVIGPs. The study is of significance for astrophysical and cosmonautic researches and safety.

  12. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich

    2008-12-09

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron: 3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, and municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  13. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich; Shiryaev, Vasili Nikolaevich

    2010-03-02

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron:3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  14. Zero-plasma-current equilibria generated by tilted planar coils

    NASA Astrophysics Data System (ADS)

    Li, J.; Israeli, B.; Hammond, K. C.; Volpe, F. A.

    2016-10-01

    It is known that a periodic toroidal arrangement of tilted planar coils, combined with vertical field coils, can generate a helical magnetic field. One question, though, is: is this coil-set a generator or an amplifier of rotational transform? In other words, is a finite plasma-current needed? A numerical scan of coil-currents shows that configurations exist, for which no plasma-current is needed, and yet torsatron plasmas of finite volume can be obtained. The case of six tilted circular coils has been examined in great detail because of its relevance to the CIRCUS device operated by Columbia, a generalization of the two-tilted-coil CNT stellarator, also at Columbia. More axisymmetric configurations featuring a higher number of tilted circular coils are also being investigated. The calculations are performed with the aid of a numerical field-line tracer and the VMEC equilibrium solver, slightly modified to reflect the simplicity of the coil geometry: the coils are not discretized; instead, their field is evaluated by means of analytical expressions. This allows for faster calculations and rapid, fine scans of large parameter spaces.

  15. Apparatus for recording emissions from a rapidly generated plasma from a single plasma producing event

    DOEpatents

    Tan, Tai Ho; Williams, Arthur H.

    1985-01-01

    An optical fiber-coupled detector visible streak camera plasma diagnostic apparatus. Arrays of optical fiber-coupled detectors are placed on the film plane of several types of particle, x-ray and visible spectrometers or directly in the path of the emissions to be measured and the output is imaged by a visible streak camera. Time and spatial dependence of the emission from plasmas generated from a single pulse of electromagnetic radiation or from a single particle beam burst can be recorded.

  16. Apparatus for recording emissions from a rapidly generated plasma from a single plasma producing event

    DOEpatents

    Tan, T.H.; Williams, A.H.

    An optical fiber-coupled detector visible streak camera plasma diagnostic apparatus. Arrays of optical fiber-coupled detectors are placed on the film plane of several types of particle, x-ray and visible spectrometers or directly in the path of the emissions to be measured and the output is imaged by a visible streak camera. Time and spatial dependence of the emission from plasma generated from a single pulse of electromagnetic radiation or from a single particle beam burst can be recorded.

  17. Significance of thrombin-receptors of thrombocytes for the interaction of heparins and low-molecular-weight heparin in human whole blood clotting.

    PubMed

    Harenberg, J; Schuler, M; Zimmermann, R; Heptner, W

    1988-01-01

    We describe in the present paper the results of the influence of normal and low-molecular-weight heparin on the interaction of human fibrinogen and thrombocytes in human whole blood cotting ex vivo. During the coagulation process sequential measurements of fibrinopeptide A reflect fibrin formation and determination of platelet factor 4 indicate activation of thrombocytes. The data show that low-molecular-weight heparin inhibits plasma thrombin generation in vivo for longer than normal heparin and it affects the fibrinogen platelet binding less. There is good evidence that a lonely factor Xa inhibition mediates this anticoagulant mechanism. Therefore, these data favor the hypothesis that antifactor Xa activity prevents indeed blood clotting.

  18. High-order Harmonic Generation in Ultra Thin Plasma Foil

    NASA Astrophysics Data System (ADS)

    Shuai, Bin; Shen, Baifei; Li, Ruxin; Xu, Zhizhan

    Via l-D Particle In Cell (PIC) simulations, we investigated the high-order harmonic emission from flim plasma foils irradiated by two circular- polarized, counter-propagating laser pulses with their electrical vectors rotating in different directions. More than 200 harmonics can be generated with a laser intensity of 1021 W/cm2. When the duration of laser gets shorter, the frequencies of harmonics were severely modulated due to the Doppler shift caused by the movement of the plasma boundary when the foil is being compressed. The Doppler shift can be estimated by the simulation results, and this effect can also be reduced or modified by introducing frequency chirping to the pump pulse.

  19. Plasma generating device with hairpin-shaped cathode filaments

    DOEpatents

    Ehlers, Kenneth W.

    1979-01-01

    A device for generating a homogeneous ion-electron plasma from which a large ion beam can be extracted. The device utilizes hairpin-shaped filaments lining at least portions of the wall of the chamber which have been rotated 90 degrees from prior known approaches. This provides a very significant result in that the DC current flowing through the filaments produces a small solenoidal magnetic field that impedes the emitted electrons from striking the walls of the chamber, which may be of a cylindrical or rectangular configuration. This improves the efficiency of the ion source and provides additional space for more filaments, while providing a very uniform plasma density profile which is noise-free.

  20. On the generation of plasma waves in Saturn's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Barbosa, D. D.; Kurth, W. S.

    1993-06-01

    Voyager 1 plasma wave measurements of Saturn's inner magnetosphere are reviewed with regard to interpretative aspects of the wave spectrum. A comparison of the wave emission profile with the electron plasma frequency obtained from in situ measurements of the thermal ion density shows good agreement with various features in the wave data identified as electrostatic modes and electromagnetic radio waves. Theoretical calculations of the critical flux of superthermal electrons able to generate whistler-mode waves and electrostatic electron cyclotron harmonic waves through a loss-cone instability are presented. The comparison of model results with electron measurements shows excellent agreement, thereby lending support to the conclusion that a moderate perpendicular anisotropy in the hot electron distribution is present in the equatorial region of L = 5-8.

  1. SOLAR WIND STRAHL BROADENING BY SELF-GENERATED PLASMA WAVES

    SciTech Connect

    Pavan, J.; Gaelzer, R.; Vinas, A. F.; Yoon, P. H.; Ziebell, L. F. E-mail: rudi@ufpel.edu.br E-mail: yoonp@umd.edu

    2013-06-01

    This Letter reports on the results of numerical simulations which may provide a possible explanation for the strahl broadening during quiet solar conditions. The relevant processes involved in the broadening are due to kinetic quasi-linear wave-particle interaction. Making use of static analytical electron distribution in an inhomogeneous field, it is found that self-generated electrostatic waves at the plasma frequency, i.e., Langmuir waves, are capable of scattering the strahl component, resulting in energy and pitch-angle diffusion that broadens its velocity distribution significantly. The present theoretical results provide an alternative or complementary explanation to the usual whistler diffusion scenario, suggesting that self-induced electrostatic waves at the plasma frequency might play a key role in broadening the solar wind strahl during quiet solar conditions.

  2. Solar Wind Strahl Broadening by Self-Generated Plasma Waves

    NASA Technical Reports Server (NTRS)

    Pavan, J.; Vinas, A. F.; Yoon, P. H.; Ziebell, L. F.; Gaelzer, R.

    2013-01-01

    This Letter reports on the results of numerical simulations which may provide a possible explanation for the strahl broadening during quiet solar conditions. The relevant processes involved in the broadening are due to kinetic quasi-linear wave-particle interaction. Making use of static analytical electron distribution in an inhomogeneous field, it is found that self-generated electrostatic waves at the plasma frequency, i.e., Langmuir waves, are capable of scattering the strahl component, resulting in energy and pitch-angle diffusion that broadens its velocity distribution significantly. The present theoretical results provide an alternative or complementary explanation to the usual whistler diffusion scenario, suggesting that self-induced electrostatic waves at the plasma frequency might play a key role in broadening the solar wind strahl during quiet solar conditions.

  3. Electromagnetic Properties of Impact-Generated Plasma, Vapor and Debris

    SciTech Connect

    Crawford, D.A.; Schultz, P.H.

    1998-11-02

    Plasma, vapor and debris associated with an impact or explosive event have been demonstrated in the laboratory to produce radiofrequency and optical electromagnetic emissions that can be diagnostic of the event. Such effects could potentially interfere with communications or remote sensing equipment if an impact occurred, for example, on a satellite. More seriously, impact generated plasma could end the life of a satellite by mechanisms that are not well understood and not normally taken into account in satellite design. For example, arc/discharge phenomena resulting from highly conductive plasma acting as a current path across normally shielded circuits may have contributed to the loss of the Olympus experimental communications satellite on August 11, 1993. The possibility of significant storm activity during the Leonid meteor showers of November 1998, 1999 and 2000 (impact velocity, 72 km/s) has heightened awareness of potential vulnerabilities from hypervelocity electromagnetic effects to orbital assets. The concern is justified. The amount of plasma, electrostatic charge and the magnitude of the resulting currents and electric fields scale nearly as the cube of the impact velocity. Even for microscopic Leonid impacts, the amount of plasma approaches levels that could be dangerous to spacecraft electronics. The degree of charge separation that occurs during hypervelocity impacts scales linearly with impactor mass. The resulting magnetic fields increase linearly with impactor radius and could play a significant role in our understanding of the paleomagnetism of planetary surfaces. The electromagnetic properties of plasma produced by hypervelocity impact have been exploited by researchers as a diagnostic tool, invoked to potentially explain the magnetically jumbled state of the lunar surface and blamed for the loss of the Olympus experimental communications satellite. The production of plasma in and around an impact event can lead to several effects: (1) the

  4. Shock Generation and Control Using DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Patel, Mehul P.; Cain, Alan B.; Nelson, Christopher C.; Corke, Thomas C.; Matlis, Eric H.

    2012-01-01

    This report is the final report of a NASA Phase I SBIR contract, with some revisions to remove company proprietary data. The Shock Boundary Layer Interaction (SBLI) phenomena in a supersonic inlet involve mutual interaction of oblique shocks with boundary layers, forcing the boundary layer to separate from the inlet wall. To improve the inlet efficiency, it is desired to prevent or delay shock-induced boundary layer separation. In this effort, Innovative Technology Applications Company (ITAC), LLC and the University of Notre Dame (UND) jointly investigated the use of dielectric-barrier-discharge (DBD) plasma actuators for control of SBLI in a supersonic inlet. The research investigated the potential for DBD plasma actuators to suppress flow separation caused by a shock in a turbulent boundary layer. The research involved both numerical and experimental investigations of plasma flow control for a few different SBLI configurations: (a) a 12 wedge flow test case at Mach 1.5 (numerical and experimental), (b) an impinging shock test case at Mach 1.5 using an airfoil as a shock generator (numerical and experimental), and (c) a Mach 2.0 nozzle flow case in a simulated 15 X 15 cm wind tunnel with a shock generator (numerical). Numerical studies were performed for all three test cases to examine the feasibility of plasma flow control concepts. These results were used to guide the wind tunnel experiments conducted on the Mach 1.5 12 degree wedge flow (case a) and the Mach 1.5 impinging shock test case (case b) which were at similar flow conditions as the corresponding numerical studies to obtain experimental evidence of plasma control effects for SBLI control. The experiments also generated data that were used in validating the numerical studies for the baseline cases (without plasma actuators). The experiments were conducted in a Mach 1.5 test section in the University of Notre Dame Hessert Laboratory. The simulation results from cases a and b indicated that multiple

  5. Reversal of trauma-induced amnesia in mice by a thrombin receptor antagonist.

    PubMed

    Itzekson, Zeev; Maggio, Nicola; Milman, Anat; Shavit, Efrat; Pick, Chaim G; Chapman, Joab

    2014-05-01

    Minimal traumatic brain injury (mTBI) is associated with the existence of retrograde amnesia and microscopic bleeds containing activated coagulation factors. In an mTBI model, we report that thrombin induces amnesia through its receptor protease-activated receptor 1 (PAR-1). Thrombin activity was significantly elevated (32 %, p < 0.05) 5 min following mTBI compared to controls. Amnesia was assessed by the novel object recognition test in mTBI animals and in animals injected intracerebroventricularly (ICV) with either thrombin or a PAR-1 agonist 1 h after the acquisition phase. Saline-injected controls had a preference index of over 0.3 while mTBI animals and those injected with thrombin or the PAR-1 agonist spent equal time with both objects indicating no recall of the object presented to them 24 h previously (p < 0.05). Co-injecting a PAR-1 antagonist (SCH79797) completely blocked the amnestic effects of mTBI, thrombin, and the PAR-1 agonist. Long-term potentiation, measured in hippocampal slices 24 h after mTBI, ICV thrombin or the PAR-1 agonist, was significantly impaired and this effect was completely reversed by the PAR-1 antagonist. The results support a crucial role for PAR-1 in the generation of amnesia following mTBI, revealing a novel therapeutic target for the cognitive effects of brain trauma.

  6. Plasma motor generator tether system for orbit reboost

    NASA Technical Reports Server (NTRS)

    Hulkower, Neal D.; Rusch, Roger J.

    1988-01-01

    This paper describes a comprehensive study of an electrodynamic tether used as a Plasma Motor Generator (PMG). The paper summarizes the work performed in the study and includes: (1) a detailed design of a 2 kW PMG tether system to be used for orbit reboost, (2) the selection of the Orbiting Maneuvering Vehicle (OMV) and the European Retrievable Carrier (EURECA) as the primary candidate spacecraft to host the experimental system, (3) analysis of the integration of the PMG tether system with these two spacecraft, (4) the simulation of the deployment of the tether, and (5) an engineering design and development plan leading to a flight demonstration of this PMG tether.

  7. Electron distribution function in a plasma generated by fission fragments

    NASA Technical Reports Server (NTRS)

    Hassan, H. A.; Deese, J. E.

    1976-01-01

    A Boltzmann equation formulation is presented for the determination of the electron distribution function in a plasma generated by fission fragments. The formulation takes into consideration ambipolar diffusion, elastic and inelastic collisions, recombination and ionization, and allows for the fact that the primary electrons are not monoenergetic. Calculations for He in a tube coated with fissionable material shows that, over a wide pressure and neutron flux range, the distribution function is non-Maxwellian, but the electrons are essentially thermal. Moreover, about a third of the energy of the primary electrons is transferred into the inelastic levels of He. This fraction of energy transfer is almost independent of pressure and neutron flux.

  8. Protein C inhibits endocytosis of thrombin-thrombomodulin complexes in A549 lung cancer cells and human umbilical vein endothelial cells

    SciTech Connect

    Maruyama, I.; Majerus, P.W.

    1987-05-01

    We investigated the effect of protein C on the endocytosis of thrombin-thrombomodulin complexes. We previously showed that exposure of umbilical vein endothelial cells to thrombin stimulated the internalization and degradation of thrombin. A similar internalization was stimulated by a monoclonal antithrombomodulin antibody. We have repeated these studies in the presence of protein C and found that endocytosis of /sup 125/I-thrombin-thrombomodulin complexes, but not /sup 125/I-antithrombomodulin-thrombomodulin complexes, is inhibited. Activated protein C did not inhibit endocytosis of thrombin-thrombomodulin complexes. Protein C inhibited both internalization and degradation of /sup 125/I-thrombin and diisopropylphosphoryl (DIP) /sup 125/I-thrombin in human lung cancer cells (A549). These effects were observed at protein C concentrations found in human plasma. Protein S had no effect on the inhibition of endocytosis of thrombin-thrombomodulin complexes by protein C. We propose that protein C may regulate the rate of endocytosis of thrombin-thrombomodulin complexes in vivo and thereby control the capacity for endothelium to activate protein C.

  9. Closed cycle MHD generator with nonuniform gas-plasma flow driving recombinated plasma clots

    SciTech Connect

    Slavin, V.S.; Danilov, V.V.; Sokolov, V.S.

    1996-12-31

    A new concept of a closed cycle MHD generator without alkali seed has been suggested. The essence of it is the phenomenon of frozen conductivity for recombined plasma which appears for noble gas at T{sub e} > 4,000 K. At the inlet of the MHD channel in supersonic flow of noble gas (He or Ar) the plasma clots with electron density about 10{sup 15} cm{sup {minus}3} are formed by pulsed intense electron beam with energy about 300 keV. Gas flow drives these clots in a cross magnetic field along the MHD channel which has electrodes connected with the load by Faraday scheme. The gas flow pushes plasma layers and produces electric power at the expense of enthalpy extraction. The numerical simulation has shown that a supersonic gas flow, containing about 4 plasma layers in the MHD channel simultaneously, is braked without shock waves creation. This type of the MHD generator can provide more than 30% enthalpy extraction ratio and about 80% isentropic efficiency. The advantages of the new concept are the following: (a) possibility of working at higher pressure and lower temperature, (b) operation with alkali seed.

  10. THz Radiation Generation via Laser Plasma Interaction Experiments

    NASA Astrophysics Data System (ADS)

    Yugami, Noboru; Higashiguchi, Takeshi

    2008-12-01

    Recently radiation generation from the interaction between laser and plasma is studied. Terahertz radiation from photo-conductive antenna which is based on semiconductor technology is widely used, The power is in the order of nano-watt level so that it is hard to use for application. On the other hand, terahertz radiation from laser plasma interaction is much higher than that of semiconductor technology. In our experiments, we have studied by use DARC (dc to ac radiation converter) mechanism by using YAG laser with nano-second pulse duration. DARC is novel radiation source using the interaction between laser-created ionization front and static electric field. The frequency of radiation is determined by both plasma density of ionization front and the geometry of DARC structure. We observed radiation pulse of frequency of 1.2 THz and pulse duration of 2 ps with ZnSe crystal as media detected by EO (electro-optics) sampling technique. Note from Publisher: This article contains the abstract only.

  11. Charge-exchange plasma generated by an ion thruster

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.

    1975-01-01

    The use of high voltage solar arrays greatly reduces or eliminates power processing requirements in space electric propulsion systems. This use also requires substantial areas of solar array to be at high positive potential relative to space and most of the spacecraft. The charge exchange plasma conducts electrons from the ion beam to such positive surfaces, and thereby electrically load the high voltage solar array. To evaluate this problem, the charge-exchange plasma generated by an ion beam was investigated experimentally. Based upon the experimental data, a simple model was derived for the charge-exchange plasma. This model is conservative in the sense that both the electron/ion density and the electron current density should be equal to, or less than, the preducted value for all directions in the hemisphere upstream of the ion beam direction. Increasing the distance between a positive potential surface (such as a high voltage solar array) and the thruster is the simplest way to control interactions. Both densities and currents vary as the inverse square of this distance.

  12. Design and characterization of hirulogs: A novel class of bivalent peptide inhibitors of thrombin

    SciTech Connect

    Maraganore, J.M.; Bourdon, P.; Jablonski, J.; Ramachandran, K.L. ); Fenton, J.W. II )

    1990-07-31

    A novel class of synthetic peptides has been designed that inhibit the thrombin catalytic site and exhibit specificity for the anion-binding exosite (ABE) of {alpha}-thrombin. These peptides, called hirulogs, consist of (i) an active-site specificity sequence with a restricted Arg-Pro scissile bond, (ii) a polymeric linker of glycyl residues from 6 to 18 {angstrom} in length, and (iii) an ABE recognition sequence such as that in the hirudin C-terminus. Hirulog-1 ((D-Phe)-Pro-Arg-Pro-(Gly){sub 4}-Asn-Gly-Asp-Phe-Glu-Glu-Ile-Pro-Glu-Tyr-Leu) inhibits the thrombin-catalyzed hydrolysis of a tripeptide p-nitroanilide substrate with K{sub i} = 2.3 nM. In contrast, the synthetic C-terminal hirudin peptide S-Hir{sub 53-64}, which binds to the thrombin ABE, blocked the fibrinogen clotting activity of the enzyme with K{sub i} = 144 nM but failed to inhibit the hydrolysis of p-nitroanilide substrates at concentrations as high as 1 mM. Hirulog-1, but not S-Hir{sub 53-64}, was found to inhibit the incorporation of ({sup 14}C)diisopropyl fluorophosphate in thrombin. Hirulog-1 appears specific for thrombin as it lacks inhibitory activities toward human factor Xa, human plasmin, and bovine trypsin at inhibitor:enzyme concentrations 3 orders of magnitude higher than those required to inhibit thrombin. The optimal inhibitory activity of hirulog-1 depends upon all three components of its structure. Comparison of anticoagulant activities of hirulog-1, hirudin, and S-Hir{sub 53-64} showed that the synthetic hirulog-1 is 2-fold more potent than hirudin and 100-fold more active than S-Hir{sub 53-64} in increasing the activated partial thromboplastin time of normal human plasma.

  13. Ion Beam Analysis applied to laser-generated plasmas

    NASA Astrophysics Data System (ADS)

    Cutroneo, M.; Macková, A.; Havranek, V.; Malinsky, P.; Torrisi, L.; Kormunda, M.; Barchuk, M.; Ullschmied, J.; Dudzak, R.

    2016-04-01

    This paper presents the research activity on Ion Beam Analysis methods performed at Tandetron Laboratory (LT) of the Institute of Nuclear Physics AS CR, Rez, Czech Republic. Recently, many groups are paying attention to implantation by laser generated plasma. This process allows to insert a controllable amount of energetic ions into the surface layers of different materials modifying the physical and chemical properties of the surface material. Different substrates are implanted by accelerated ions from plasma through terawatt iodine laser, at nominal intensity of 1015 W/cm2, at the PALS Research Infrastructure AS CR, in the Czech Republic. This regime of the laser matter interaction generates, multi-MeV proton beams, and multi-charged ions that are tightly confined in time (hundreds ps) and space (source radius of a few microns). These ion beams have a much lower transverse temperature, a much shorter duration and a much higher current than those obtainable from conventional accelerators. The implementation of protons and ions acceleration driven by ultra-short high intensity lasers is exhibited by adopting suitable irradiation conditions as well as tailored targets. An overview of implanted targets and their morphological and structural characterizations is presented and discussed.

  14. Bernstein wave aided laser third harmonic generation in a plasma

    NASA Astrophysics Data System (ADS)

    Tyagi, Yachna; Tripathi, Deepak; Kumar, Ashok

    2016-09-01

    The process of Bernstein wave aided resonant third harmonic generation of laser in a magnetized plasma is investigated. The extra-ordinary mode (X-mode) laser of frequency ω 0 and wave number k → 0 , travelling across the magnetic field in a plasma, exerts a second harmonic ponderomotive force on the electrons imparting them an oscillatory velocity v → 2 ω0 , 2 k → 0 . This velocity beats with the density perturbation due to the Bernstein wave to produce a density perturbation at cyclotron frequency shifted second harmonic. The density perturbation couples with the oscillatory velocity v → ω0 , k → 0 of X-mode of the laser to produce the cyclotron frequency shifted third harmonic current density leading to harmonic radiation. The phase matching condition for the up shifted frequency is satisfied when the Bernstein wave is nearly counter-propagating to the laser. As the transverse wave number of the Bernstein wave is large, it is effective in the phase matched third harmonic generation, when the laser frequency is not too far from the upper hybrid frequency.

  15. High duty factor plasma generator for CERN's Superconducting Proton Linac.

    PubMed

    Lettry, J; Kronberger, M; Scrivens, R; Chaudet, E; Faircloth, D; Favre, G; Geisser, J-M; Küchler, D; Mathot, S; Midttun, O; Paoluzzi, M; Schmitzer, C; Steyaert, D

    2010-02-01

    CERN's Linac4 is a 160 MeV linear accelerator currently under construction. It will inject negatively charged hydrogen ions into CERN's PS-Booster. Its ion source is a noncesiated rf driven H(-) volume source directly inspired from the one of DESY and is aimed to deliver pulses of 80 mA of H(-) during 0.4 ms at a 2 Hz repetition rate. The Superconducting Proton Linac (SPL) project is part of the luminosity upgrade of the Large Hadron Collider. It consists of an extension of Linac4 up to 5 GeV and is foreseen to deliver protons to a future 50 GeV synchrotron (PS2). For the SPL high power option (HP-SPL), the ion source would deliver pulses of 80 mA of H(-) during 1.2 ms and operate at a 50 Hz repetition rate. This significant upgrade motivates the design of the new water cooled plasma generator presented in this paper. Its engineering is based on the results of a finite element thermal study of the Linac4 H(-) plasma generator that identified critical components and thermal barriers. A cooling system is proposed which achieves the required heat dissipation and maintains the original functionality. Materials with higher thermal conductivity are selected and, wherever possible, thermal barriers resulting from low pressure contacts are removed by brazing metals on insulators. The AlN plasma chamber cooling circuit is inspired from the approach chosen for the cesiated high duty factor rf H(-) source operating at SNS.

  16. PREFACE: Acceleration and radiation generation in space and laboratory plasmas

    NASA Astrophysics Data System (ADS)

    Bingham, R.; Katsouleas, T.; Dawson, J. M.; Stenflo, L.

    1994-01-01

    Sixty-six leading researchers from ten nations gathered in the Homeric village of Kardamyli, on the southern coast of mainland Greece, from August 29-September 4, 1993 for the International Workshop on Acceleration and Radiation Generation in Space and Laboratory Plasmas. This Special Issue represents a cross-section of the presentations made at and the research stimulated by that meeting. According to the Iliad, King Agamemnon used Kardamyli as a dowry offering in order to draw a sulking Achilles into the Trojan War. 3000 years later, Kardamyli is no less seductive. Its remoteness and tranquility made it an ideal venue for promoting the free exchange of ideas between various disciplines that do not normally interact. Through invited presen tations, informal poster discussions and working group sessions, the Workshop brought together leaders from the laboratory and space/astrophysics communities working on common problems of acceleration and radiation generation in plasmas. It was clear from the presentation and discussion sessions that there is a great deal of common ground between these disciplines which is not at first obvious due to the differing terminologies and types of observations available to each community. All of the papers in this Special Issue highlight the role collective plasma processes play in accelerating particles or generating radiation. Some are state-of-the-art presentations of the latest research in a single discipline, while others investi gate the applicability of known laboratory mechanisms to explain observations in natural plasmas. Notable among the latter are the papers by Marshall et al. on kHz radiation in the magnetosphere ; Barletta et al. on collective acceleration in solar flares; and by Dendy et al. on ion cyclotron emission. The papers in this Issue are organized as follows: In Section 1 are four general papers by Dawson, Galeev, Bingham et al. and Mon which serves as an introduction to the physical mechanisms of acceleration

  17. Promoting Plasma Physics as a Career: A Generational Approach

    NASA Astrophysics Data System (ADS)

    Morgan, James

    2005-10-01

    A paradigm shift is occurring in education physics programs. Educators are shifting from the traditional teaching focus to concentrate on student learning. Students are unaware of physics as a career, plasma physics or the job opportunities afforded to them with a physics degree. The physics profession needs to promote itself to the younger generations, or specifically the millennial generation (Born in the 1980's-2000's). Learning styles preferred by ``Millennials'' include a technological environment that promotes learning through active task performance rather than passive attendance at lectures. Millennials respond well to anything experiential and will be motivated by opportunities for creativity and challenging learning environments. The open-ended access to information, the ability to tailor learning paths, and continuous and instantaneous performance assessment offer flexibility in the design of curricula as well as in the method of delivery. Educators need to understand the millennial generation, appeal to their motivations and offer a learning environment designed for their learning style. This poster suggests promoting a physics career by focusing on generational learning styles and preferences.

  18. A mathematical model of thrombin production in blood coagulation, Part I: The sparsely covered membrane case.

    PubMed

    Baldwin, S A; Basmadjian, D

    1994-01-01

    This paper presents the first attempt to model the blood coagulation reactions in flowing blood. The model focuses on the common pathway and includes activation of factor X and prothrombin, including feedback activation of cofactors VIII and V by thrombin, and plasma inhibition of factor Xa and thrombin. In this paper, the first of two, the sparsely covered membrane (SCM) case is presented. This considers the limiting situation where platelet membrane binding sites are in excess, such that no membrane saturation or binding competition occurs. Under these conditions, the model predicts that the two positive feedback loops lead to multiple steady-state behavior in the range of intermediate mass transfer rates. It will be shown that this results in three parameter regions exhibiting very different thrombin production patterns. The model predicts the effect of flow on steady-state and dynamic thrombin production and attempts to explain the difference between venous and arterial thrombi. The reliance of thrombin production on precursor procoagulant protein concentrations is also assessed.

  19. Bufadienolides from Kalanchoe daigremontiana as thrombin inhibitors-In vitro and in silico study.

    PubMed

    Kolodziejczyk-Czepas, Joanna; Sieradzka, Malgorzata; Moniuszko-Szajwaj, Barbara; Pecio, Łukasz; Ponczek, Michal B; Nowak, Pawel; Stochmal, Anna

    2017-06-01

    Thrombin is an active plasma coagulation factor II, critical for the formation of fibrin clot during blood coagulation. For that reason, this protein is also a crucial target for different anti-thrombotic therapies. The work is based on in vitro evaluation of the inhibitory effect of bufadienolide-rich fraction, isolated from roots of Kalanchoe daigremontiana (1-50μg/ml) on enzymatic properties of a serine proteinase - thrombin. The efficacy of the inhibition of amidolytic activity of thrombin (measured as a hydrolysis of the chromogenic substrate S-2238, Chromogenix) attained about 10 and 66%, respectively. The IC50, established for the examined bufadienolide fraction was 2.79μg/ml, while the IC50 calculated for argatroban (reference compound) was 0.78μg/ml. Linearization conducted using Lineweaver-Burk plot indicated that the K. daigremontiana fraction contains compounds that are uncompetitive inhibitors of thrombin. K. daigremontiana fraction was also able to reduce the proteolytic activity of thrombin towards its physiological substrate, i.e. fibrinogen. Additionally, this study is supported by in silico analysis of interactions of the most common compounds, identified in the examined in Kalanchoe extract to crystal structure of this enzyme.

  20. The routine determination of the endogenous thrombin potential, first results in different forms of hyper- and hypocoagulability.

    PubMed

    Wielders, S; Mukherjee, M; Michiels, J; Rijkers, D T; Cambus, J P; Knebel, R W; Kakkar, V; Hemker, H C; Béguin, S

    1997-04-01

    The area under the thrombin generation curve (the endogenous thrombin potential; ETP) has been proposed as a parameter for plasma-based hypercoagulability and to monitor anticoagulant treatment. We present an ETP assay for the routine laboratory using a centrifugal analyser. Throughput is 30 samples/h, within and between run imprecision is 4-5.6%. Suitable substrates were developed for the ranges of 10-500% and 2-100% of normal. Independent of tissue factor concentration (if > 4 pM), the normal value of the extrinsic ETP is 384.8 +/- 51.7 nM.min. The intrinsic ETP, triggered by ellagic acid, is 414 +/- 41 nM.min. The ETP is decreased to 15 and 35% of normal by oral anticoagulation (INR 2.5-4.0) and by heparin administration (APTT 1.5-2.5 x control). The ETP is increased in untreated subjects with congenital antithrombin deficiency and in women using oral contraceptives. In deep vein thrombosis (phlebographically confirmed), it is increased by 29.4% (extrinsic) and 53% (intrinsic). In (angiographically assessed) coronary artery disease the increase is by 10% and 17% respectively.

  1. Magnetohydrodynamic Power Generation in the Laboratory Simulated Martian Entry Plasma

    NASA Technical Reports Server (NTRS)

    Vuskovic, L.; Popovic, S.; Drake, J.; Moses, R. W.

    2005-01-01

    This paper addresses the magnetohydrodynamic (MHD) conversion of the energy released during the planetary entry phase of an interplanetary vehicle trajectory. The effect of MHD conversion is multi-fold. It reduces and redirects heat transferred to the vehicle, and regenerates the dissipated energy in reusable and transportable form. A vehicle on an interplanetary mission carries about 10,000 kWh of kinetic energy per ton of its mass. This energy is dissipated into heat during the planetary atmospheric entry phase. For instance, the kinetic energy of Mars Pathfinder was about 4220 kWh. Based on the loss in velocity, Mars Pathfinder lost about 92.5% of that energy during the plasma-sustaining entry phase that is approximately 3900 kWh. An ideal MHD generator, distributed over the probe surface of Mars Pathfinder could convert more than 2000 kWh of this energy loss into electrical energy, which correspond to more than 50% of the kinetic energy loss. That means that the heat transferred to the probe surface can be reduced by at least 50% if the converted energy is adequately stored, or re-radiated, or directly used. Therefore, MHD conversion could act not only as the power generating, but also as the cooling process. In this paper we describe results of preliminary experiments with light and microwave emitters powered by model magnetohydrodynamic generators and discuss method for direct use of converted energy.

  2. Enhanced ionospheric plasma bubble generation in more active ITCZ

    NASA Astrophysics Data System (ADS)

    Li, Guozhu; Otsuka, Yuichi; Ning, Baiqi; Abdu, M. A.; Yamamoto, M.; Wan, Weixing; Liu, Libo; Abadi, Prayitno

    2016-03-01

    A close link between the atmospheric Intertropical Convergence Zone (ITCZ) and ionospheric plasma bubble has been proposed since the last century. But this relationship has often appeared to be less than convincing due to the simultaneous roles played by several other factors in shaping the global distribution of ionospheric bubbles. From simultaneous collaborative radar multibeam steering measurements at Kototabang (0.2°S, 100.3°E) and Sanya (18.4°N, 109.6°E), conducted during September-October of 2012 and 2013, we find that the total numbers of nights with bubble (i.e., occurrence rates) at the two closely located longitudes (Kototabang and Sanya) are comparable. But interestingly, the total number of nights with locally generated bubble (i.e., generation rate) over Kototabang is clearly more than that over Sanya. Further analysis reveals that a more active ITCZ is situated around the longitude of Kototabang. We surmise that the enhanced ionospheric bubble generation at Kototabang longitude could be caused by a higher gravity wave activity associated with the more active ITCZ.

  3. Mechanisms of polymer degradation using an oxygen plasma generator

    NASA Technical Reports Server (NTRS)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  4. Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

    NASA Technical Reports Server (NTRS)

    Singh, N.; Leung, W. C.; Moore, T. E.; Craven, P. D.

    2001-01-01

    The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the Polar satellite is studied by using a three-dimensional particle-in-cell (PIC) code. When the satellite passes through the region of low-density plasma, the satellite charges to positive potentials as high as 40-50 V, owing to the photoelectron emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, ion-rich xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at approximately 2 V. Accordingly, in our three-dimensional PIC simulation we considered that the potential of the satellite is 2 V as a fixed bias. Considering the relatively high density of the xenon plasma in the sheath (10-10(exp 3)/cc), the ambient plasma of low density (<1/cc) is neglected. In the simulations the electric fields and plasma dynamics are calculated self-consistently. We found that an 'apple'-shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission a high positive potential hill develops. Near the Thermal Ion Dynamics Experiment detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations it takes only about a couple of tens of electron gyroperiods for the sheath to reach a quasi steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. After this time the expansion of the sheath in directions transverse to the ambient magnetic field slows down because the electrons are magnetized. Using the quasi steady sheath, we performed trajectory calculations to characterize the detector response to a

  5. Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

    NASA Technical Reports Server (NTRS)

    Leung, Wing C.; Singh, Nagendra; Moore, Thomas E.; Craven, Paul D.

    2000-01-01

    The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the POLAR satellite is studied by using a 3-dimensional Particle-In-Cell (PIC) code. When the satellite passes through the region of low density plasma, the satellite charges to positive potentials as high as 4050Volts due to the photoelectrons emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, an ion-rich Xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at about 2Volts. Accordingly, in our 3-dimensional PIC simulation, we considered that the potential of the satellite is 2Volts as a fixed bias. Considering the relatively high density of the Xenon plasma in the sheath (approx. 10 - 10(exp 3)/cc), the ambient plasma of low density (less than 1/cc) is neglected. In the simulations, the electric fields and plasma dynamics are calculated self-consistently. We found that an "Apple" shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission, a high positive potential hill develops. Near the Thermal Ion Detection Experiment (TIDE) detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations, it takes about a hundred electron gyroperiods for the sheath to reach a quasi-steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. Using the steady state sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the

  6. Plasma-Enhanced Chemical Vapor Deposition of SiOx Films Using Electron Beam Generated Plasmas

    DTIC Science & Technology

    2009-09-28

    special relation to the substrate or e-beam. A total flow of 100 sccm was used in all cases . For the gas flows mentioned above, the individual flows...beam generated plasmas. In this case , molecular hydrogen, formed primarily by recombination of atomic hydrogen on system walls, will not be...the films was large (> 130 nm/min), which implied a high porosity for all cases except for low TEOS flow (≤ 2 sccm) at the higher (300 °C) temperature

  7. Osteopontin Fragments with Intact Thrombin-Sensitive Site Circulate in Cervical Cancer Patients

    PubMed Central

    Lim, Pak-Leong; Cheung, Tak-Hong; Wong, Raymond R. Y.; Yim, So-Fan; Ng, Margaret H. L.; Tam, Frankie C. H.; Chung, Tony K. H.; Wong, Yick-Fu

    2016-01-01

    We investigated whether circulating osteopontin (OPN) could be used as a biomarker for cervical cancer. We employed a monoclonal antibody (mAb 659) specific for the unique and intact thrombin-sensitive site in OPN using an inhibition ELISA. We found significantly higher levels of OPN in 33 cervical cancer patients in both the plasma (mean +/- SD, 612 +/- 106 ng/mL) and serum (424 +/- 121 ng/mL) compared to healthy subjects [409 +/- 56 ng/mL, from 31 plasma samples (P < 0.0001), and 314 +/- 98 ng/mL, from 32 serum samples (P = 0.0002), respectively]. Similar results were obtained when the plasma from a bigger group (147 individuals) of cervical cancer patients (560 +/- 211 ng/mL) were compared with the same plasma samples of the healthy individuals (P = 0.0014). More significantly, the OPN level was highest in stage III-IV disease (614 +/- 210 ng/mL, from 52 individuals; P = 0.0001) and least and non-discriminatory in stage I (473 +/- 110 ng/mL, from 40 individuals; P = 0.5318). No such discrimination was found when a mAb of a different specificity (mAb 446) was used in a similar inhibition ELISA to compare the two groups in the first study; a commercial capture ELISA also failed. The possibility that the target epitope recognized by the antibody probe in these assays was absent from the circulating OPN due to protein truncation was supported by gel fractionation of the OPN found in patients’ plasma: 60–64 kDa fragments were found instead of the presumably full-length OPN (68 kDa) seen in healthy people. How these fragments are generated and what possible role they play in cancer biology remain interesting questions. PMID:27494141

  8. Cleavage at Arg-1689 influences heavy chain cleavages during thrombin-catalyzed activation of factor VIII.

    PubMed

    Newell, Jennifer L; Fay, Philip J

    2009-04-24

    The procofactor, factor VIII, is activated by thrombin or factor Xa-catalyzed cleavage at three P1 residues: Arg-372, Arg-740, and Arg-1689. The catalytic efficiency for thrombin cleavage at Arg-740 is greater than at either Arg-1689 or Arg-372 and influences reaction rates at these sites. Because cleavage at Arg-372 appears rate-limiting and dependent upon initial cleavage at Arg-740, we investigated whether cleavage at Arg-1689 influences catalysis at this step. Recombinant B-domainless factor VIII mutants, R1689H and R1689Q were prepared and stably expressed to slow and eliminate cleavage, respectively. Specific activity values for the His and Gln mutations were approximately 50 and approximately 10%, respectively, that of wild type. Thrombin activation of the R1689H variant showed an approximately 340-fold reduction in the rate of Arg-1689 cleavage, whereas the R1689Q variant was resistant to thrombin cleavage at this site. Examination of heavy chain cleavages showed approximately 4- and 11-fold reductions in A2 subunit generation and approximately 3- and 7-fold reductions in A1 subunit generation for the R1689H and R1689Q mutants, respectively. These results suggest a linkage between light chain cleavage and cleavages in heavy chain. Results obtained evaluating proteolysis of the factor VIII mutants by factor Xa revealed modest rate reductions (<5-fold) in generating A2 and A1 subunits and in cleaving light chain at Arg-1721 from either variant, suggesting little dependence upon prior cleavage at residue 1689 as compared with thrombin. Overall, these results are consistent with a competition between heavy and light chains for thrombin exosite binding and subsequent proteolysis with binding of the former chain preferred.

  9. Microwave plasmas generated in bubbles immersed in liquids for hydrocarbons reforming

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Sharma, Ashish; Raja, Laxminarayan L.

    2016-06-01

    We present a computational modeling study of microwave plasma generated in cluster of atmospheric-pressure argon bubbles immersed in a liquid. We demonstrate that the use of microwaves allows the generation of a dense chemically active non-equilibrium plasma along the gas-liquid interface. Also, microwaves allow generation of overdense plasma in all the bubbles considered in the cluster which is possible because the collisional skin depth of the wave exceeds the bubble dimension. These features of microwave plasma generation in bubbles immersed in liquids are highly desirable for the large-scale liquid hydrocarbon reforming technologies.

  10. Terahertz generation by beating two Langmuir waves in a warm and collisional plasma

    SciTech Connect

    Zhang, Xiao-Bo; Qiao, Xin; Cheng, Li-Hong; Tang, Rong-An; Zhang, Ai-Xia; Xue, Ju-Kui

    2015-09-15

    Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length.

  11. Evaluation of antithrombotic activity of thrombin DNA aptamers by a murine thrombosis model.

    PubMed

    Zavyalova, Elena; Samoylenkova, Nadezhda; Revishchin, Alexander; Golovin, Andrey; Pavlova, Galina; Kopylov, Alexey

    2014-01-01

    Aptamers are nucleic acid based molecular recognition elements with a high potential for the theranostics. Some of the aptamers are under development for therapeutic applications as promising antithrombotic agents; and G-quadruplex DNA aptamers, which directly inhibit the thrombin activity, are among them. RA-36, the 31-meric DNA aptamer, consists of two thrombin binding pharmacophores joined with the thymine linker. It has been shown earlier that RA-36 directly inhibits thrombin in the reaction of fibrinogen hydrolysis, and also it inhibits plasma and blood coagulation. Studies of both inhibitory and anticoagulation effects had indicated rather high species specificity of the aptamer. Further R&D of RA-36 requires exploring its efficiency in vivo. Therefore the development of a robust and adequate animal model for effective physiological studies of aptamers is in high current demand. This work is devoted to in vivo study of the antithrombotic effect of RA-36 aptamer. A murine model of thrombosis has been applied to reveal a lag and even prevention of thrombus formation when RA-36 was intravenous bolus injected in high doses of 1.4-7.1 µmol/kg (14-70 mg/kg). A comparative study of RA-36 aptamer and bivalirudin reveals that both direct thrombin inhibitors have similar antithrombotic effects for the murine model of thrombosis; though in vitro bivalirudin has anticoagulation activity several times higher compared to RA-36. The results indicate that both RA-36 aptamer and bivalirudin are direct thrombin inhibitors of different potency, but possible interactions of the thrombin-inhibitor complex with other components of blood coagulation cascade level the physiological effects for both inhibitors.

  12. Evaluation of Antithrombotic Activity of Thrombin DNA Aptamers by a Murine Thrombosis Model

    PubMed Central

    Zavyalova, Elena; Samoylenkova, Nadezhda; Revishchin, Alexander; Golovin, Andrey; Pavlova, Galina; Kopylov, Alexey

    2014-01-01

    Aptamers are nucleic acid based molecular recognition elements with a high potential for the theranostics. Some of the aptamers are under development for therapeutic applications as promising antithrombotic agents; and G-quadruplex DNA aptamers, which directly inhibit the thrombin activity, are among them. RA-36, the 31-meric DNA aptamer, consists of two thrombin binding pharmacophores joined with the thymine linker. It has been shown earlier that RA-36 directly inhibits thrombin in the reaction of fibrinogen hydrolysis, and also it inhibits plasma and blood coagulation. Studies of both inhibitory and anticoagulation effects had indicated rather high species specificity of the aptamer. Further R&D of RA-36 requires exploring its efficiency in vivo. Therefore the development of a robust and adequate animal model for effective physiological studies of aptamers is in high current demand. This work is devoted to in vivo study of the antithrombotic effect of RA-36 aptamer. A murine model of thrombosis has been applied to reveal a lag and even prevention of thrombus formation when RA-36 was intravenous bolus injected in high doses of 1.4–7.1 µmol/kg (14–70 mg/kg). A comparative study of RA-36 aptamer and bivalirudin reveals that both direct thrombin inhibitors have similar antithrombotic effects for the murine model of thrombosis; though in vitro bivalirudin has anticoagulation activity several times higher compared to RA-36. The results indicate that both RA-36 aptamer and bivalirudin are direct thrombin inhibitors of different potency, but possible interactions of the thrombin-inhibitor complex with other components of blood coagulation cascade level the physiological effects for both inhibitors. PMID:25192011

  13. The thrombin receptor extracellular domain contains sites crucial for peptide ligand-induced activation.

    PubMed Central

    Bahou, W F; Coller, B S; Potter, C L; Norton, K J; Kutok, J L; Goligorsky, M S

    1993-01-01

    A thrombin receptor (TR) demonstrating a unique activation mechanism has recently been isolated from a megakaryocytic (Dami) cell line. To further study determinants of peptide ligand-mediated activation phenomenon, we have isolated, cloned, and stably expressed the identical receptor from a human umbilical vein endothelial cell (HUVEC) library. Chinese hamster ovary (CHO) cells expressing a functional TR (CHO-TR), platelets, and HUVECs were then used to specifically characterize alpha-thrombin- and peptide ligand-induced activation responses using two different antibodies: anti-TR34-52 directed against a 20-amino acid peptide spanning the thrombin cleavage site, and anti-TR1-160 generated against the NH2-terminal 160 amino acids of the TR expressed as a chimeric protein in Escherichia coli. Activation-dependent responses to both alpha-thrombin (10 nM) and peptide ligand (20 microM) were studied using fura 2-loaded cells and microspectrofluorimetry. Whereas preincubation of CHO-TR with anti-TR34-52 abolished only alpha-thrombin-induced [Ca2+]i transients, preincubation with anti-TR1-160 abrogated both alpha-thrombin- and peptide ligand-induced responses. This latter inhibitory effect was dose dependent and similar for both agonists, with an EC50 of approximately 90 micrograms/ml. Anti-TR1-160 similarly abolished peptide ligand-induced [Ca2+]i transients in platelets and HUVECs, whereas qualitatively different responses characterized by delayed but sustained elevations in [Ca2+]i transients were evident using alpha-thrombin. Platelet aggregation to low concentrations of both ligands was nearly abolished by anti-TR1-160, although some shape change remained; anti-TR34-52 only inhibited alpha-thrombin-induced aggregation. These data establish that a critical recognition sequence for peptide ligand-mediated receptor activation is contained on the NH2-terminal portion of the receptor, upstream from the first transmembrane domain. Furthermore, alpha-thrombin

  14. Naphthalene and acenaphthene decomposition by electron beam generated plasma application

    SciTech Connect

    Ostapczuk, A.; Hakoda, T.; Shimada, A.; Kojima, T.

    2008-08-15

    The application of non-thermal plasma generated by electron beam (EB) was investigated in laboratory scale to study decomposition of polycyclic aromatic hydrocarbons like naphthalene and acenaphthene in flue gas. PAH compounds were treated by EB with the dose up to 8 kGy in dry and humid base gas mixtures. Experimentally established G-values gained 1.66 and 3.72 mol/100 eV for NL and AC at the dose of 1 kGy. NL and AC removal was observed in dry base gas mixtures showing that the reaction with OH radical is not exclusive pathway to initialize PAH decomposition; however in the presence of water remarkably higher decomposition efficiency was observed. As by-products of NL decomposition were identified compounds containing one aromatic ring and oxygen atoms besides CO and CO{sub 2}. It led to the conclusion that PAH decomposition process in humid flue gas can be regarded as multi-step oxidative de-aromatization analogical to its atmospheric chemistry.

  15. Plasma generation in mass-limited water targets

    NASA Astrophysics Data System (ADS)

    Hah, Jungmoo; Liberty, Kirk; Nees, John; Krushelnick, Karl; Thomas, Alexander

    2014-10-01

    One major problem associated with high repetition-rate experiment is obtaining a suitable new target for each shot, while maintaining shot-to-shot spatial stability. For high repetition-rate laser experiments with solid targets, rotating stage is usually used for moving a target point, which causes stability and size problems. To solve these problems, some researchers have tried to replace solid targets with liquid stream or droplet. Here, we use a syringe pump, a piezoelectric device and a tungsten needle to make continuous and stable water droplets with a diameter of ~ 2 μm. These mass-limited water droplets as a target have some advantages. First, heat dissipation is blocked, so the target is entirely heated. Second, effective spatial contrast is improved by reducing the interaction between lower intensity spatial wings of the beam and a single-micron target. Third, at the relativistic laser intensities, a smaller target allows for higher electron densities at the target's back surface, which enhances field's strength for ion acceleration. For these advantages, it is required that we understand plasma generation processes. Therefore, we investigate the processes by irradiating fs laser pulses to mass-limited droplets and these interactions are captured by CCD.

  16. Comparative evaluation of direct thrombin and factor Xa inhibitors with antiplatelet agents under flow and static conditions: an in vitro flow chamber model.

    PubMed

    Hosokawa, Kazuya; Ohnishi, Tomoko; Sameshima, Hisayo; Miura, Naoki; Koide, Takehiko; Maruyama, Ikuro; Tanaka, Kenichi A

    2014-01-01

    Dabigatran and rivaroxaban are novel oral anticoagulants that specifically inhibit thrombin and factor Xa, respectively. The aim of this study is to elucidate antithrombotic properties of these anticoagulant agents under arterial and venous shear conditions. Whole blood samples treated with dabigatran or rivaroxaban at 250, 500, and 1000 nM, with/without aspirin and AR-C66096, a P2Y12 antagonist, were perfused over a microchip coated with collagen and tissue thromboplastin at shear rates of 240 and 600 s(-1). Fibrin-rich platelet thrombus formation was quantified by monitoring flow pressure changes. Dabigatran at higher concentrations (500 and 1000 nM) potently inhibited thrombus formation at both shear rates, whereas 1000 nM of rivaroxaban delayed, but did not completely inhibit, thrombus formation. Dual antiplatelet agents weakly suppressed thrombus formation at both shear rates, but intensified the anticoagulant effects of dabigatran and rivaroxaban. The anticoagulant effects of dabigatran and rivaroxaban were also evaluated under static conditions using thrombin generation (TG) assay. In platelet-poor plasma, dabigatran at 250 and 500 nM efficiently prolonged the lag time (LT) and moderately reduce peak height (PH) of TG, whereas rivaroxaban at 250 nM efficiently prolonged LT and reduced PH of TG. In platelet-rich plasma, however, both anticoagulants efficiently delayed LT and reduced PH of TG. Our results suggest that dabigatran and rivaroxaban may exert distinct antithrombotic effects under flow conditions, particularly in combination with dual antiplatelet therapy.

  17. Spatio-temporal optimization of a laser produced Al-plasma: Generation of highly ionized species

    NASA Astrophysics Data System (ADS)

    Smijesh, N.; H. Rao, Kavya; Klemke, N.; Philip, R.; Litvinyuk, I. V.; Sang, R. T.

    2016-11-01

    Laser produced plasmas are transient in nature, and their properties, which depend on the laser parameters as well as the material properties and the irradiation conditions, can be tailored for different applications. Highly ionized Al plasmas generated using 7 ns and negatively chirped 60 ps pulses are optimized for the purpose of generating Al IV and Al III, respectively. The plasma is optimized spatio-temporally for Al IV or Al III with irradiation energy as the control parameter using time-resolved optical emission spectroscopy. Plasmas attuned for higher charged states could be utilized as a good alternative source for the generation of high order harmonics.

  18. Radiofrequency plasma antenna generated by femtosecond laser filaments in air

    SciTech Connect

    Brelet, Y.; Houard, A.; Point, G.; Prade, B.; Carbonnel, J.; Andre, Y.-B.; Mysyrowicz, A.; Arantchouk, L.; Pellet, M.

    2012-12-24

    We demonstrate tunable radiofrequency emission from a meter-long linear plasma column produced in air at atmospheric pressure. A short-lived plasma column is initially produced by femtosecond filamentation and subsequently converted into a long-lived discharge column by application of an external high voltage field. Radiofrequency excitation is fed to the plasma by induction and detected remotely as electromagnetic radiation by a classical antenna.

  19. Population Inversions in Ablation Plasmas Generated by Intense Electron Beams.

    DTIC Science & Technology

    1986-11-30

    beam driven carbon anode plasmas. Diode closure results ..,.in three phases of beam-plasma evolution which are summarized below: Stage I: Deposited...enough for anode plasma forma- tion before the diode shorts. Spectroscopic data for noncrowbarred shots (dose 1 500-800 J/g) indicate the presence of CII...inconsistent with previously proposed kinetic mechanisms for the N2 laser pumped by helium. With a simple- model of the chemical kinetics, we have shown

  20. Effect of preformed plasma on terahertz-wave emission from the plasma generated by two-color laser pulses

    SciTech Connect

    Minami, Yasuo; Nakajima, Makoto; Suemoto, Tohru

    2011-02-15

    We introduced a weak prepulse 0-2 ns before the main pulse in the formation of a terahertz (THz) wave in air plasma by laser pulses composed of fundamental and second-harmonic waves. The prepulse suppressed the THz wave generated by the main pulse. We analyzed the suppression factor as a function of the time interval between the prepulse and the main pulse and found that the THz wave from the main pulse decreases immediately after the prepulse, recovers partially within several hundred picoseconds, and then recovers slowly. This suppression is attributed to the dense plasma, which absorbs and screens the generated THz wave, since the relaxation time is close to the lifetime of the fluorescence from the plasma. The results support the idea that the major mechanism of THz wave generation is explained by the plasma current model.

  1. Cylindrical plasmas generated by an annular beam of ultraviolet light

    SciTech Connect

    Thomas, D. M.; Allen, J. E.

    2015-07-15

    We investigate a cylindrical plasma system with ionization, by an annular beam of ultraviolet light, taking place only in the cylinder's outer region. In the steady state, both the outer and inner regions contain a plasma, with that in the inner region being uniform and field-free. At the interface between the two regions, there is an infinitesimal jump in ion density, the magnitude approaching zero in the quasi-neutral (λ{sub D} → 0) limit. The system offers the possibility of producing a uniform stationary plasma in the laboratory, hitherto obtained only with thermally produced alkali plasmas.

  2. Pencil lead plasma for generating multimicrojoule high-order harmonics with a broad spectrum

    SciTech Connect

    Pertot, Y.; Elouga Bom, L. B.; Ozaki, T.; Bhardwaj, V. R.

    2011-03-07

    Using the plasma harmonic method, we show the generation of efficient and intense high-order harmonics from plasma of pencil lead. We demonstrate multimicrojoule energy in each harmonic order for the 11th to the 17th order of a Ti:sapphire laser. By analyzing the target morphology and the plasma composition, we conclude that these intense harmonics are generated from nanoparticles of graphitic carbon.

  3. Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Sakawa, Y.; Morita, T.; Yamaura, Y.; Kuramitsu, Y.; Moritaka, T.; Sano, T.; Shimoda, R.; Tomita, K.; Uchino, K.; Matsukiyo, S.; Mizuta, A.; Ohnishi, N.; Crowston, R.; Woolsey, N.; Doyle, H.; Gregori, G.; Koenig, M.; Michaut, C.; Pelka, A.; Yuan, D.; Li, Y.; Zhang, K.; Zhong, J.; Wang, F.; Takabe, H.

    2016-03-01

    One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm × 3 mm × 10 μm) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering.

  4. A plasma generator utilizing the high intensity ASTROMAG magnets

    NASA Technical Reports Server (NTRS)

    Sullivan, James D.; Post, R. S.; Lane, B. G.; Tarrh, J. M.

    1986-01-01

    The magnet configuration for the proposed particle astrophysics magnet facility (ASTROMAG) on the space station includes a cusp magnetic field with an intensity of a few tesla. With these large magnets (or others) located in the outer ionosphere, many quite interesting and unique plasma physics experiments become possible. First there are studies utilizing the magnet alone to examine the supersonic, sub-Alfvenic interaction with the ambient medium; the scale length for the magnet perturbation is approx. 20 m. The magnetic field geometry when combined with the Earth's and their relative motion will give rise to a host of plasma phenomena: ring nulls, x-points, ion-acoustic and lower-hybrid shocks, electron heating (possible shuttle glow without a surface) launching of Alfvenwaves, etc. Second, active experiments are possible for a controlled study of fundamental plasma phenomena. A controlled variable species plasma can be made by using an RF ion source; use of two soft iron rings placed about the line cusp would give an adequate resonance zone (ECH or ICH) and a confining volume suitable for gas efficiency. The emanating plasma can be used to study free expansion of plasma along and across field lines (polar wind), plasma flows around the space platform, turbulent mixing in the wake region, long wavelength spectrum of convecting modes, plasma-dust interactions, etc.

  5. Cavitational Iron Microparticles Generation By Plasma Procedures For Medical Applications

    NASA Astrophysics Data System (ADS)

    Bica, Ioan; Bunoiu, Madalin; Chirigiu, Liviu; Spunei, Marius; Juganaru, Iulius

    2012-12-01

    The paper presents the experimental installation for the production, in argon plasma, of cavitational iron microparticles (pore microspheres, microtubes and octopus-shaped microparticles). Experimental results are presented and discussed and it is shown that absorbant particles with a minimum iron content are obtained by the plasma procedures

  6. Lupus anticoagulants form immune complexes with prothrombin and phospholipid that can augment thrombin production in flow.

    PubMed

    Field, S L; Hogg, P J; Daly, E B; Dai, Y P; Murray, B; Owens, D; Chesterman, C N

    1999-11-15

    Lupus anticoagulants (LA) are a family of autoantibodies that are associated with in vitro anticoagulant activity but a strong predisposition to in vivo thrombosis. They are directed against plasma phospholipid binding proteins, including prothrombin. We found that a murine monoclonal antiprothrombin antibody and 7 of 7 LA IgGs tested enhanced binding of prothrombin to 25:75 phosphatidyl serine:phosphatidyl choline vesicles in a concentration-dependent manner. We hypothesized that enhanced binding of prothrombin to phospholipid in the presence of LA IgG might result in increased thrombin production when reactions are performed in flow. Thrombin production by purified prothrombinase components was measured in a phospholipid-coated flow reactor. The flow reactor was incubated with prothrombin, calcium ions, and the IgGs and then perfused with prothrombin, calcium ions, the IgGs, factor Va, and factor Xa. A murine monoclonal antiprothrombin antibody and 4 of 6 LA IgGs from patients with a history of thrombosis increased thrombin production up to 100% over control in the first 15 minutes. In summary, LA IgGs concentrate prothrombin on a phospholipid surface that can augment thrombin production by prothrombinase in flow. These observations suggest that LA might propagate coagulation in flowing blood by facilitating prothrombin interaction with the damaged blood vessel wall.

  7. Different duplex/quadruplex junctions determine the properties of anti-thrombin aptamers with mixed folding.

    PubMed

    Russo Krauss, Irene; Spiridonova, Vera; Pica, Andrea; Napolitano, Valeria; Sica, Filomena

    2016-01-29

    Mixed duplex/quadruplex oligonucleotides have attracted great interest as therapeutic targets as well as effective biomedical aptamers. In the case of thrombin-binding aptamer (TBA), the addition of a duplex motif to the G-quadruplex module improves the aptamer resistance to biodegradation and the affinity for thrombin. In particular, the mixed oligonucleotide RE31 is significantly more effective than TBA in anticoagulation experiments and shows a slower disappearance rate in human plasma and blood. In the crystal structure of the complex with thrombin, RE31 adopts an elongated structure in which the duplex and quadruplex regions are perfectly stacked on top of each other, firmly connected by a well-structured junction. The lock-and-key shape complementarity between the TT loops of the G-quadruplex and the protein exosite I gives rise to the basic interaction that stabilizes the complex. However, our data suggest that the duplex motif may have an active role in determining the greater anti-thrombin activity in biological fluids with respect to TBA. This work gives new information on mixed oligonucleotides and highlights the importance of structural data on duplex/quadruplex junctions, which appear to be varied, unpredictable, and fundamental in determining the aptamer functional properties.

  8. Microwave plasma generation of hydrogen atoms for rocket propulsion

    NASA Technical Reports Server (NTRS)

    Chapman, R.; Filpus, J.; Morin, T.; Snellenberger, R.; Asmussen, J.; Hawley, M.; Kerber, R.

    1981-01-01

    A flow microwave plasma reaction system is used to study the conversion of hydrogen to hydrogen atoms as a function of pressure, power density, cavity tuning, cavity mode, and time in the plasma zone. Hydrogen atom concentration is measured down-stream from the plasma by NOCl titration. Extensive modeling of the plasma and recombination zones is performed with the plasma zone treated as a backmix reaction system and the recombination zone treated as a plug flow. The thermodynamics and kinetics of the recombination process are examined in detail to provide an understanding of the conversion of recombination energy to gas kinetic energy. It is found that cavity tuning, discharge stability, and optimum power coupling are critically dependent on the system pressure, but nearly independent of the flow rate.

  9. Generation of reactive species by an atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Kelly, S.; Turner, M. M.

    2014-12-01

    The role of gas mixing in reactive species delivery to treatment surfaces for an atmospheric pressure capacitively coupled plasma helium jet is investigated by numerical modelling. Atomic oxygen in the jet effluent is shown to quickly convert to ozone for increasing device to surface separation due to the molecular oxygen present in the gas mixture. Surface profiles of reactive oxygen species show narrow peaks for atomic oxygen and broader surface distributions for ozone and metastable species. Production efficiency of atomic oxygen to the helium plasma jet by molecular oxygen admixture is shown to be dependent on electro-negativity. Excessive molecular oxygen admixture results in negative ion dominance over electrons which eventually quenches the plasma. Interaction of the plasma jet with an aqueous surface showed hydrogen peroxide as the dominant species at this interface. Gas heating by the plasma is found to be dominated by elastic electron collisions and positive ion heating. Comparison with experimental measurements for atomic oxygen shows good agreement.

  10. Atmospheric-pressure plasma jet induces apoptosis involving mitochondria via generation of free radicals.

    PubMed

    Ahn, Hak Jun; Kim, Kang Il; Kim, Geunyoung; Moon, Eunpyo; Yang, Sang Sik; Lee, Jong-Soo

    2011-01-01

    The plasma jet has been proposed as a novel therapeutic method for anticancer treatment. However, its biological effects and mechanism of action remain elusive. Here, we investigated its cell death effects and underlying molecular mechanisms, using air and N₂ plasma jets from a micro nozzle array. Treatment with air or N₂ plasma jets caused apoptotic death in human cervical cancer HeLa cells, simultaneously with depolarization of mitochondrial membrane potential. In addition, the plasma jets were able to generate reactive oxygen species (ROS), which function as surrogate apoptotic signals by targeting the mitochondrial membrane potential. Antioxidants or caspase inhibitors ameliorated the apoptotic cell death induced by the air and N₂ plasma jets, suggesting that the plasma jet may generate ROS as a proapoptotic cue, thus initiating mitochondria-mediated apoptosis. Taken together, our data suggest the potential employment of plasma jets as a novel therapy for cancer.

  11. Atmospheric-Pressure Plasma Jet Induces Apoptosis Involving Mitochondria via Generation of Free Radicals

    PubMed Central

    Kim, Geunyoung; Moon, Eunpyo; Yang, Sang Sik; Lee, Jong-Soo

    2011-01-01

    The plasma jet has been proposed as a novel therapeutic method for anticancer treatment. However, its biological effects and mechanism of action remain elusive. Here, we investigated its cell death effects and underlying molecular mechanisms, using air and N2 plasma jets from a micro nozzle array. Treatment with air or N2 plasma jets caused apoptotic death in human cervical cancer HeLa cells, simultaneously with depolarization of mitochondrial membrane potential. In addition, the plasma jets were able to generate reactive oxygen species (ROS), which function as surrogate apoptotic signals by targeting the mitochondrial membrane potential. Antioxidants or caspase inhibitors ameliorated the apoptotic cell death induced by the air and N2 plasma jets, suggesting that the plasma jet may generate ROS as a proapoptotic cue, thus initiating mitochondria-mediated apoptosis. Taken together, our data suggest the potential employment of plasma jets as a novel therapy for cancer. PMID:22140530

  12. Dust generation at interaction of plasma jet with surfaces

    NASA Astrophysics Data System (ADS)

    Ticos, Catalin; Toader, Dorina; Banu, Nicoleta; Scurtu, Adrian; Oane, Mihai

    2013-10-01

    Coatings of W and C with widths of a few microns will be exposed to plasma jet for studying the erosion of the surface and detachment of micron size dust particles. A coaxial plasma gun has been built inside a vacuum chamber for producing supersonic plasma jets. Its design is based on a 50 kJ coaxial plasma gun which has been successfully used for accelerating hypervelocity dust. Initial shots were carried out for a capacitor bank with C = 12 μF and charged up to 2 kV. Currents of tens of amps were measured with a Rogowsky coil and plasma flow speeds of 4 km/s were inferred from high-speed images of jet propagation. An upgrade consisting in adding capacitors in parallel will be performed in order to increase the energy up to 2 kJ. A coil will be installed at the gun muzzle to compress the plasma flow and increase the energy density of the jet on the sample surface. A CCD camera with a maximum recording speed of 100 k fps and a maximum resolution of 1024 × 1024 pixels was set for image acquisition of the plasma and dust. A laser system used to illuminate the ejected dust from the surface includes a laser diode emitting at 650 nm with a beam power of 25 mW. The authors acknowledge support from EURATOM WP13-IPH-A03-P2-02-BS22.

  13. Generation and remote delivery of plasma activated species

    NASA Astrophysics Data System (ADS)

    Maguire, Paul; Mahony, Charles; Kelsey, Colin; Rutherford, David; Mariotti, Davide; Macias-Montero, Manuel; Perez-Martin, Fatima; Diver, Declan

    2016-09-01

    Plasma interactions with microdroplets offer new opportunities to deliver active chemical agents and nanoparticles to remote substrates downstream with many potential applications from cancer theranostics and wound healing in biomedicine, gentle food decontamination and seed germination in plasma agriculture to catalyst production and photonic structures fabrication, among others. We demonstrate plasma-liquid based pristine nanomaterials synthesis in flight and subsequent delivery up to 120mm from the atmospheric pressure plasma source. Monosized and non-aggregating metal nanoparticles are formed in the rf plasma in less than 100us, representing an increase in precursor reduction rate that is many (>4) orders of magnitude faster than that observed with standard colloidal chemistry or via high energy radiolytic techniques. Also the collection and purification limitations of the latter are avoided. Plasma activated liquid including OH radicals and H2O2 are transported over 120mm and have demonstrated high efficacy bacterial decontamination. These results will be compared with charge species and radical transport from the rf plasma without microdroplets. Reaction models based on high solvated surface electron concentrations will be presented. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  14. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Bers, Abraham

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to estalish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated inthe plasma.

  15. System and method for generating steady state confining current for a toroidal plasma fusion reactor

    DOEpatents

    Fisch, Nathaniel J.

    1981-01-01

    A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to establish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated in the plasma.

  16. Measurement of plasma-generated RONS in the cancer cells exposed by atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Joh, Hea Min; Baek, Eun Jeong; Kim, Sun Ja; Chung, Tae Hun

    2015-09-01

    The plasma-induced reactive oxygen and nitrogen species (RONS) could result in cellular responses including DNA damages and apoptotic cell death. These chemical species, O, O2-,OH, NO, and NO2-,exhibit strong oxidative stress and/or trigger signaling pathways in biological cells. Each plasma-generated chemical species having biological implication should be identified and quantitatively measured. For quantitative measurement of RONS, this study is divided into three stages; plasma diagnostics, plasma-liquid interactions, plasma-liquid-cell interactions. First, the optical characteristics of the discharges were obtained by optical emission spectroscopy to identify various excited plasma species. And the characteristics of voltage-current waveforms, gas temperature, and plume length with varying control parameters were measured. Next, atmospheric pressure plasma jet was applied on the liquid. The estimated OH radical densities were obtained by ultraviolet absorption spectroscopy at the liquid surface. And NO2-is detected by Griess test and compared between the pure liquid and the cell-containing liquid. Finally, bio-assays were performed on plasma treated human lung cancer cells (A549). Intracellular ROS production was measured using DCF-DA. Among these RONS, productions of NO and OH within cells were measured by DAF-2DA and APF, respectively. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas, liquids, and cells.

  17. Parasitic current losses due to solar electric propulsion generated plasmas

    NASA Technical Reports Server (NTRS)

    Katz, I.; Parks, D. E.; Mandell, M. J.; Schnuelle, G. W.

    1981-01-01

    Solar electric propulsion is a leading candidate for many upcoming space missions. Under many circumstances plasma produced by charge-exchange reactions within the ion beam dominates the ambient environment near the spacecraft. The calculations presented here contain a predictive hydrodynamic model for the charge-exchange plasma expansion, and a fully three-dimensional model for the structure of the plasma sheath around the solar array wing. Results of calculations for several configurations and voltage levels indicate that with kilovolt biases power losses of approximately 10 percent or more are likely, even with only one engine in operation, and that ameliorative measures should focus on the inboard portion of the solar arrays.

  18. Thrombin regulates the function of human blood dendritic cells

    SciTech Connect

    Yanagita, Manabu; Kobayashi, Ryohei; Kashiwagi, Yoichiro; Shimabukuro, Yoshio; Murakami, Shinya E-mail: ipshinya@dent.osaka-u.ac.jp

    2007-12-14

    Thrombin is the key enzyme in the coagulation cascade and activates endothelial cells, neutrophils and monocytes via protease-activated receptors (PARs). At the inflammatory site, immune cells have an opportunity to encounter thrombin. However little is known about the effect of thrombin for dendritic cells (DC), which are efficient antigen-presenting cells and play important roles in initiating and regulating immune responses. The present study revealed that thrombin has the ability to stimulate blood DC. Plasmacytoid DC (PDC) and myeloid DC (MDC) isolated from PBMC expressed PAR-1 and released MCP-1, IL-10, and IL-12 after thrombin stimulation. Unlike blood DC, monocyte-derived DC (MoDC), differentiated in vitro did not express PAR-1 and were unresponsive to thrombin. Effects of thrombin on blood DC were significantly diminished by the addition of anti-PAR-1 Ab or hirudin, serine protease inhibitor. Moreover, thrombin induced HLA-DR and CD86 expression on DC and the thrombin-treated DC induced allogenic T cell proliferation. These findings indicate that thrombin plays a role in the regulation of blood DC functions.

  19. Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects

    NASA Astrophysics Data System (ADS)

    Lu, X.; Naidis, G. V.; Laroussi, M.; Reuter, S.; Graves, D. B.; Ostrikov, K.

    2016-05-01

    Non-equilibrium atmospheric-pressure plasmas have recently become a topical area of research owing to their diverse applications in health care and medicine, environmental remediation and pollution control, materials processing, electrochemistry, nanotechnology and other fields. This review focuses on the reactive electrons and ionic, atomic, molecular, and radical species that are produced in these plasmas and then transported from the point of generation to the point of interaction with the material, medium, living cells or tissues being processed. The most important mechanisms of generation and transport of the key species in the plasmas of atmospheric-pressure plasma jets and other non-equilibrium atmospheric-pressure plasmas are introduced and examined from the viewpoint of their applications in plasma hygiene and medicine and other relevant fields. Sophisticated high-precision, time-resolved plasma diagnostics approaches and techniques are presented and their applications to monitor the reactive species and plasma dynamics in the plasma jets and other discharges, both in the gas phase and during the plasma interaction with liquid media, are critically reviewed. The large amount of experimental data is supported by the theoretical models of reactive species generation and transport in the plasmas, surrounding gaseous environments, and plasma interaction with liquid media. These models are presented and their limitations are discussed. Special attention is paid to biological effects of the plasma-generated reactive oxygen and nitrogen (and some other) species in basic biological processes such as cell metabolism, proliferation, survival, etc. as well as plasma applications in bacterial inactivation, wound healing, cancer treatment and some others. Challenges and opportunities for theoretical and experimental research are discussed and the authors' vision for the emerging convergence trends across several disciplines and application domains is presented to

  20. Thrombin-induced increase in albumin permeability across the endothelium

    SciTech Connect

    Garcia, J.G.; Siflinger-Birnboim, A.; Bizios, R.; Del Vecchio, P.J.; Fenton, J.W. 2d.; Malik, A.B.

    1986-07-01

    We studied the effect of thrombin on albumin permeability across the endothelial monolayer in vitro. Bovine pulmonary artery endothelial cells were grown on micropore membranes. Morphologic analysis confirmed the presence of a confluent monolayer with interendothelial junctions. Albumin permeability was measured by the clearance of 125I-albumin across the endothelial monolayer. The control 125I-albumin clearance was 0.273 +/- 0.02 microliter/min. The native enzyme, alpha-thrombin (10(-6) to 10(-10) M), added to the luminal side of the endothelium produced concentration-dependent increases in albumin clearance (maximum clearance of 0.586 +/- 0.08 microliter/min at 10(-6) M). Gamma (gamma) thrombin (10(-6) M and 10(-8) M), which lacks the fibrinogen recognition site, also produced a concentration-dependent increase in albumin clearance similar to that observed with alpha-thrombin. Moreover, the two proteolytically inactive forms of the native enzyme, i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin, increased the 125I-albumin clearance (0.610 +/- 0.09 microliter/min and 0.609 +/- 0.02 microliter/min for i-Pr2 P-alpha-thrombin and D-Phe-Pro-Arg-CH2-alpha-thrombin at 10(-6) M, respectively). Since the modified forms of thrombin lack the fibrinogen recognition and active serine protease sites, the results indicate that neither site is required for increased albumin permeability. The increase in albumin clearance with alpha-thrombin was not secondary to endothelial cell lysis because lactate dehydrogenase concentration in the medium following thrombin was not significantly different from baseline values. There was also no morphological evidence of cell lysis. Moreover, the increase in 125I-albumin clearance induced by alpha-thrombin was reversible by washing thrombin from the endothelium.

  1. High density plasma gun generates plasmas at 190 kilometers per second

    NASA Technical Reports Server (NTRS)

    Espy, P. N.

    1971-01-01

    Gun has thin metal foil disc which positions or localizes gas to be ionized during electrical discharge cycle, overcoming major limiting factor in obtaining such plasmas. Expanding plasma front travels at 190 km/sec, compared to plasmas of 50 to 60 km/sec previously achieved.

  2. Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes

    SciTech Connect

    Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.

    2012-02-15

    Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

  3. Electrostatic interactions in hirudin-thrombin binding.

    PubMed

    Sharp, K A

    1996-08-30

    Hirudin is a good anticoagulant owing to potent inhibition of the serine protease thrombin. An aspartate- and glutamate-rich portion of hirudin plays an important part in its tight binding to thrombin through a ladder of salt bridges, and these residues have previously been mutated to asparagine or glutamine. Detailed calculations of the electrostatic contribution to changes in binding from these mutations have been performed using the finite-difference Poisson-Boltzmann method which include charge--charge interactions, solvation interactions, the residual electrostatic interaction of mutant residues, pKa shifts, and ionic strength. Single mutant effects on binding energy were close to experimental values, except for the D55N mutant whose effect is overestimated, perhaps because of displacement of a bound chloride ion from the site where it binds. Multiple mutation values were generally overestimated. The effect of pKa shifts upon the binding is significant for one hirudin residue E58, but this appears to be due to a poor salt bridge with thrombin caused by crystal contacts. Electrostatic interaction between the acidic residues is unfavorable. However, analysis of experimental multiple mutation/single mutation data shows apparently negative interactions between these residues, from which it is concluded that structural changes can occur in the complex to relieve an unfavorable interaction when more than one acidic residue is mutated. In all cases, there is a loss in stability of the complex from mutations due to loss of favorable charge--charge interactions with thrombin, but this is largely compensated for by reduced unfavorable desolvation interactions, and by residual polar interactions in the Asn/Gln mutants.

  4. Pulse compression in plasma: Generation of femtosecond pulses without CPA

    SciTech Connect

    G. Shvets; N. J. Fisch; A. Pukhov; J. Meyer-ter-Vehn

    2000-07-20

    Laser pulses can be efficiently compressed to femtosecond duration when a smaller-frequency short pulse collides with high frequency long pulse in rare plasma, absorbing most of its energy. The mechanism of short pulse amplification is nonlinear superradiance.

  5. Experiments With Radiatively Cooled Supersonic Plasma Jets Generated in Conical Wire Array Z-Pinches

    NASA Astrophysics Data System (ADS)

    Lebedev, S. V.; Ampleford, D. J.; Bland, S. N.; Chittenden, J. P.; Ciardi, A.; Naz, N.; Haines, M. G.; Frank, A.; Blackman, E.; Gardiner, T.

    2002-12-01

    We present results of astrophysically relevant experiments where highly supersonic plasma jets are generated via conically convergent plasma flows in a conical wire array Z-pinch. Stagnation of plasma flow on the axis of symmetry forms a standing conical shock effectively collimating the flow in the axial direction. This scenario is essentially similar to that discussed by Canto and collaborators [1] as a purely hydrodynamic mechanism for jet formation in astrophysical systems. Experiments using different materials (Al, Fe and W) show that a hypersonic (M ~ 20), well-collimated jet is generated when the radiative cooling rate of the plasma is significant.

  6. Numerical Simulation of Flow in the Chamber of the Water-Argon Plasma Generator

    NASA Astrophysics Data System (ADS)

    Hlbočan, Peter; Varchola, Michal; Knížat, Branislav; Mlkvik, Marek; Olšiak, Róbert

    2012-12-01

    The paper describes the CFD simulation of the flow of gas and plasma in a plasma generator with a hybrid stabilization of the electric arc. The momentum equations of the model also take Lorentz forces into account. In the energy equation, Joule heat is introduced as an energy source. The introduction of boundary conditions is also explained, as along with plasma transport properties and a method of solution. The paper presents selected results of pressure and velocity fields in the chamber of the plasma generator.

  7. Studies of HED Plasmas with Self-Generated Magnetic Field

    SciTech Connect

    Medvedev, Mikhail

    2016-02-08

    High-amplitude sub-Larmor-scale electromagnetic turbulence is ubiquitous in high-energy density environments, such as laboratory plasmas produced by high-intensity lasers, e.g., NIF, Omega-EP, Trident, and others, and in astrophysical and space plasmas, e.g., at high-Mach-number collisionless shocks in weakly magnetized plasmas upstream regions of quasi-parallel shocks, sites of magnetic reconnection and others. Studies of plasmas and turbulence in these environments are important for fusion energy sciences and the inertial confinement concept, in particular, as well as to numerous astrophysical systems such as gamma-ray bursts, supernovae blast waves, jets of quasars and active galactic nuclei, shocks in the interplanetary medium, solar flares and many more. Such turbulence can be of various origin and thus have rather different properties, from being purely magnetic (Weibel) turbulence to various types of electromagnetic turbulence (for example, whistler wave turbulence or turbulence produced by filamentation or Weibel-type streaming instability), to purely electrostatic Langmuir turbulence. In this project we use analytical and numerical tools to study the transport, radiative, and magneto-optical properties of plasmas with sub-Larmor-scale turbulence. We discovered the connection of transport/diffusion properties to certain spectral benchmark features of (jitter) radiation produced by the plasma and radiation propagation through it. All regimes, from the relativistic to non-relativistic, were thoroughly investigated and predictions were made for laboratory plasmas and astrophysical plasmas. Thus, all the tasks outlined in the proposal were fully and successfully accomplished.

  8. High power, fast, microwave components based on beam generated plasmas

    NASA Astrophysics Data System (ADS)

    Manheimer, W. M.; Fernsler, R. F.; Gitlin, M. S.

    1998-10-01

    It is shown that the agile mirror plasma, under development as a device to simply and cheaply give electronic steering to microwave beams, also has application as a fast, electronically controlled, high power reflector, or phase shifter. In a radar system, this can lead to such applications as pulse to pulse polarization agility and electronic control of antenna gain, as well as to innovative approaches to high power millimeter wave circulators. The basic theory of the enhanced glow plasma is also developed.

  9. Elongation of plasma channel generated by temporally shaped femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Chen, Anmin; Li, Suyu; Qi, Hongxia; Jiang, Yuanfei; Hu, Zhan; Huang, Xuri; Jin, Mingxing

    2017-01-01

    Temporally shaped femtosecond laser pulse is used to generate the air plasma channel. The length of plasma channel is optimized by a genetic algorithm. Compared with the transform-limited pulse, the temporally shaped femtosecond laser produced by the spatial light modulator with the genetic algorithm can lead to a significant increase in length and brightness of plasma channel in atmosphere. In particular, the length of the plasma channel produced by the optimized shaped pulse can be extended by 50%. This method can be especially advantageous in the context of femtosecond laser-induced plasma channel.

  10. Electro-physical property of plasma jet generated by burning chemicals as antenna

    NASA Astrophysics Data System (ADS)

    Zhong-Cai, Yuan; Jia-Ming, Shi; Xiao-Po, Wu; Zong-Shen, Chen; Zong-Shen

    2013-02-01

    The application of pulsed power to transient radiofrequency/microwave radiation for warhead/projectile payloads is currently a significant area of research. In this paper, the far-field radiative property of a plasma antenna is analyzed. Then, a plasma jet is generated by burning chemicals, in which the electron concentration and collision frequency are diagnosed, and the electric conductance is calculated. Finally, the feasibility to apply the plasma jet as antenna is investigated by analyzing the radiative pattern. The dependency of pattern on plasma electron density, collision frequency, and plasma wake radius is calculated and analyzed.

  11. Generation and diagnostics of atmospheric pressure CO{sub 2} plasma by laser driven plasma wind tunnel

    SciTech Connect

    Matsui, Makoto; Yamagiwa, Yoshiki; Tanaka, Kensaku; Arakawa, Yoshihiro; Nomura, Satoshi; Komurasaki, Kimiya

    2012-08-01

    Atmospheric pressure CO{sub 2} plasma was generated by a laser driven plasma wind tunnel. At an ambient pressure of 0.38 MPa, a stable plasma was maintained by a laser power of 1000 W for more than 20 min. The translational temperature was measured using laser absorption spectroscopy with the atomic oxygen line at 777.19 nm. The measured absorption profiles were analyzed by a Voigt function considering Doppler, Stark, and pressure-broadening effects. Under the assumption of thermochemical equilibrium, all broadening effects were consistent with each other. The measured temperature ranged from 8500 K to 8900 K.

  12. Ground-Based Simulation of Low-Earth Orbit Plasma Conditions: Plasma Generation and Characterization

    NASA Technical Reports Server (NTRS)

    Williams, John D.; Farnell, Casey C.; Shoemaker, Paul B.; Vaughn, Jason A.; Schneider, Todd A.

    2004-01-01

    A 16-cm diameter plasma source operated on argon is described that is capable of producing a plasma environment that closely simulates the low Earth orbit (LEO) conditions experienced by satellites in the altitude range between 300 to 500 km. The plasma source uses a transverse-field magnetic filter, and has been successful in producing low electron temperature plasmas that contain streaming ion populations. Both of these characteristics are important because the plasma in LEO is relatively cold (e.g., Te approx. 0.1 eV) and the ram energy of the ions due to the motion of the satellite relative to the LEO plasma is high (e.g., 7,800 m/s which corresponds to approx. 5 eV for O+ ions). Plasma source operational conditions of flow rate and discharge power are presented that allow the electron temperature to be adjusted over a range from 0.14 to 0.4 eV. The expanding plasma flow field downstream of the source contains both low-energy, charge-exchange ions and streaming ions with energies that are adjustable over a range from 4 eV to 6 eV. At low flow rates and low facility pressures, the streaming ion component of the ion population comprises over 90% of the total plasma density. In the work described herein, a large area retarding potential analyzer was used to measure both electron and ion energy distribution functions in the low density, expanding plasma produced downstream of the plasma source. The benefits of using this type of plasma diagnostic tool in easily perturbed, low-density plasma are identified, and techniques are also discussed that can be used to perform real-time measurements of electron temperature. Finally, recommendations are made that may enable lower electron temperatures to be produced while simultaneously decreasing the plasma source flow rate below 1 to 2 sccm.

  13. Phospholipase C-beta3 mediates the thrombin-induced Ca2+ response in glial cells.

    PubMed

    Hwang, Jong-Ik; Shin, Kum-Joo; Oh, Yong-Seok; Choi, Jung-Woong; Lee, Zee-Won; Kim, Daesoo; Ha, Kwon-Soo; Shin, Hee-Sup; Ryu, Sung Ho; Suh, Pann-Ghill

    2005-06-30

    Phospholipase C-beta (PLC-beta) hydrolyses phosphatidylinositol 4,5-bisphosphate and generates inositol 1,4,5-trisphosphate in response to activation of various G protein-coupled receptors (GPCRs). Using glial cells from knock-out mice lacking either PLC-beta1 [PLC-beta1 (-/-)] or PLC-beta3 [PLC-beta3 (-/-)], we examined which isotype of PLC-beta participated in the cellular signaling events triggered by thrombin. Generation of inositol phosphates (IPs) was enhanced by thrombin in PLC-beta1 (-/-) cells, but was negligible in PLC-beta3 (-/-) cells. Expression of PLC-beta3 in PLC-beta3 (-/-) cells resulted in an increase in pertussis toxin (PTx)-sensitive IPs in response to thrombin as well as to PAR1-specific peptide, while expression of PLC-beta1 in PLC-beta1 (-/-) cells did not have any effect on IP generation. The thrombin-induced [Ca2+]i increase was delayed and attenuated in PLC-beta3 (-/-) cells, but normal in PLC-beta1 (-/-) cells. Pertussis toxin evoked a delayed [Ca2+]i increase in PLC-beta3 (-/-) cells as well as in PLC-beta1 (-/-) cells. These results suggest that activation of PLC-beta3 by pertussis toxin-sensitive G proteins is responsible for the transient [Ca2+]i increase in response to thrombin, whereas the delayed [Ca2+]i increase may be due to activation of some other PLC, such as PLC-beta4, acting via PTx-insensitive G proteins.

  14. Chemically reactive species in liquids generated by atmospheric-pressure plasmas and their roles in plasma medicine

    SciTech Connect

    Hamaguchi, Satoshi

    2013-07-11

    Plasmas whose gas temperatures are close to room temperature may be generated in ambient air or a gas at atmospheric pressure with the use of low-frequency high voltage or low-power radio-frequency (RF) or microwave power applied to electrodes. Such plasmas can serve as a powerful source of free radicals and/or chemically reactive species that arise from atoms and molecules of the ambient gas. Recently use of such plasmas for medical purposes has attracted much attention as they can be implemented in possible medical devices that can cause blood coagulation, heal wounds, facilitate angiogenesis, sterilize surgical devices as well as living tissues without harming healthy cells, and selectively inactivate cancer cells. Especially of interest among reactive species generated by atmospheric-pressure plasmas (APP) are reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are generated in liquid phase. Since most living tissues and cells are immersed in liquids (such as blood or culture media), reactive species generated by APPs in the gas phase are transported to the liquid phase and possibly converted to different types of reactive species therein before causing some influence on the tissues or cells. In this study, the rate equations are solved to evaluate concentrations of various reactive species in pure water that are originated by plasma reactions in atmosphere and possible effects of such species (including ROS/RNS) on living tissues and cells are discussed.

  15. Chemically reactive species in liquids generated by atmospheric-pressure plasmas and their roles in plasma medicine

    NASA Astrophysics Data System (ADS)

    Hamaguchi, Satoshi

    2013-07-01

    Plasmas whose gas temperatures are close to room temperature may be generated in ambient air or a gas at atmospheric pressure with the use of low-frequency high voltage or low-power radio-frequency (RF) or microwave power applied to electrodes. Such plasmas can serve as a powerful source of free radicals and/or chemically reactive species that arise from atoms and molecules of the ambient gas. Recently use of such plasmas for medical purposes has attracted much attention as they can be implemented in possible medical devices that can cause blood coagulation, heal wounds, facilitate angiogenesis, sterilize surgical devices as well as living tissues without harming healthy cells, and selectively inactivate cancer cells. Especially of interest among reactive species generated by atmospheric-pressure plasmas (APP) are reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are generated in liquid phase. Since most living tissues and cells are immersed in liquids (such as blood or culture media), reactive species generated by APPs in the gas phase are transported to the liquid phase and possibly converted to different types of reactive species therein before causing some influence on the tissues or cells. In this study, the rate equations are solved to evaluate concentrations of various reactive species in pure water that are originated by plasma reactions in atmosphere and possible effects of such species (including ROS/RNS) on living tissues and cells are discussed.

  16. Arc plasma generator of atomic driver for steady-state negative ion source

    SciTech Connect

    Ivanov, A. A.; Belchenko, Yu. I.; Davydenko, V. I.; Ivanov, I. A.; Kolmogorov, V. V.; Listopad, A. A. Mishagin, V. V.; Shulzhenko, G. I.; Putvinsky, S. V.; Smirnov, A.

    2014-02-15

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB{sub 6} cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  17. Arc plasma generator of atomic driver for steady-state negative ion source.

    PubMed

    Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A

    2014-02-01

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  18. Study of Plasma Motor Generator (PMG) tether system for orbit reboost

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Detailed designs were produced for a 2 kW plasma motor generator tether system based largely on existing hardware and hardware designs. Specifically, the hollow cathode design and electronics are derived from ion propulsion equipment. A prototype tether was constructed and will be tested for deployment, strength, resistance to breakage and abrasion and electrical properties. In addition, laboratory development models of the electronics will be used to operate two plasma motor generator hollow cathode assemblies with this tether to verify electrical performance parameters for the complete system. Results show that a low cost demonstration of a plasma motor generator tether system appears to be feasible by the middle of the 1990s.

  19. Temporal evolution of electron beam generated Argon plasma in pasotron device

    NASA Astrophysics Data System (ADS)

    Khandelwal, Neha; Pal, U. N.; Prakash, Ram; Choyal, Y.

    2016-10-01

    The plasma- assisted slow wave oscillator (PASOTRON) is a high power microwave source in which the electron beam in the interaction region is confined by the background plasma. The plasma is generated by impact ionization of background gas with the electron beam. A model has been developed for temporal evolution of Argon plasma in pasotron device. In this model, we consider electron beam of energy E interacting with Argon gas. The resulting ionization creates quasi neutral argon plasma composed of argon Ar atoms, singly ionized ions Ar+1and electrons having energy from 0 to E. Electron impact excitation, ionization, radiative decay, radiative recombination and three body recombination processes are considered in this model. Population of ground and excited states of argon atom, ground state of argon ion as well as the population of electron energy groups is calculated by solving time dependent rate equations. Temporal evolution of electron beam generated plasma is given.

  20. Laser-induced plasma generation and evolution in a transient spray.

    PubMed

    Kawahara, Nobuyuki; Tsuboi, Kazuya; Tomita, Eiji

    2014-01-13

    The behaviors of laser-induced plasma and fuel spray were investigated by visualizing images with an ultra-high-speed camera. Time-series images of laser-induced plasma in a transient spray were visualized using a high-speed color camera. The effects of a shockwave generated from the laser-induced plasma on the evaporated spray behavior were investigated. The interaction between a single droplet and the laser-induced plasma was investigated using a single droplet levitated by an ultrasonic levitator. Two main conclusions were drawn from these experiments: (1) the fuel droplets in the spray were dispersed by the shockwave generated from the laser-induced plasma; and (2) the plasma position may have shifted due to breakdown of the droplet surface and the lens effect of droplets.

  1. Generation of high-power electromagnetic radiation by a beam-driven plasma antenna

    NASA Astrophysics Data System (ADS)

    Annenkov, V. V.; Volchok, E. P.; Timofeev, I. V.

    2016-04-01

    In this paper we study how efficiently electromagnetic radiation can be generated by a relativistic electron beam with a gigawatt power level during its injection into a thin magnetized plasma. It is shown that, if the transverse beam and plasma size is compared with the radiation wavelength and the plasma density is modulated along the magnetic field, such a beam-plasma system can radiate electromagnetic waves via the antenna mechanism. We propose a theoretical model describing generation of electromagnetic waves by this plasma antenna and calculate its main radiation characteristics. In the two-dimensional case theoretical predictions on the radiation efficiency are shown to be confirmed by the results of particle-in-cell simulations, and the three-dimensional variant of this theory is used to estimate the peak power of sub-terahertz radiation that can be achieved in beam-plasma experiments in mirror traps.

  2. High frequency plasma generators for ion thruster applications

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Komatsu, G. K.; Christensen, T.

    1981-01-01

    Two concepts for high frequency discharge ion thrusters are described. Both sources are designed for use with 30 cm grid sets and argon propellant and utilize multi-cusp permanent magnet geometries for plasma confinement. The RF induction source is a conventional design representing a synthesis of the RIT and multi-cusp concepts. The preliminary data (without system optimization) indicate a discharge efficiency comparable to that obtained in 30 cm hollow cathode multi-cusp argon thrusters. The electron cyclotron heating source is electrodeless and exhibits plasma characteristics which should lead to greatly reduced discharge chamber and screen sputter rates with the optimization of the magnetic fields, microwave frequency, and feed configuration.

  3. Generation of collisionless shock in laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Fiuza, Frederico

    2015-08-01

    Collisionless shocks are ubiquitous in astrophysical environments and are tightly connected with magnetic-field amplification and particle acceleration. The fast progress in high-power laser technology is bringing the study of high Mach number shocks into the realm of laboratory plasmas, where in situ measurements can be made helping us understand the fundamental kinetic processes behind shocks. I will discuss the recent progress in laser-driven shock experiments at state-of-the-art facilities like NIF and Omega and how these results, together with ab initio massively parallel simulations, can impact our understanding of magnetic field amplification and particle acceleration in astrophysical plasmas.

  4. Laser driven terahertz generation in hot plasma with step density profile

    SciTech Connect

    Kumar, Manoj Jeong, Young Uk; Tripathi, Vipin Kumar

    2015-06-15

    An analytical formalism of terahertz (THz) radiation generation by beating of two lasers in a hot plasma with step density profile is developed. The lasers propagate obliquely to plasma surface normal, and the nonlinearity arises through the ponderomotive force. The THz is emitted in the specular reflection direction, and the yield is enhanced due to coupling with the Langmuir wave when the plasma frequency is close to THz frequency. The power conversion efficiency maximizes at an optimum angle of incidence.

  5. Wakefields generated by collisional neutrinos in neutral-electron-positron-ion plasma

    SciTech Connect

    Tinakiche, Nouara

    2015-12-15

    A classical fluid description is adopted to investigate nonlinear interaction between an electron-type neutrino beam and a relativistic collisionless unmagnetized neutral-electron-positron-ion plasma. In this work, we consider the collisions of the neutrinos with neutrals in the plasma and study their effect on the generation of wakefields in presence of a fraction of ions in a neutral-electron-positron plasma. The results obtained in the present work are interpreted and compared with previous studies.

  6. Time-resolved spectroscopy of plasma plumes: A versatile approach for optimization of high-order harmonic generation in laser plasma

    SciTech Connect

    Ganeev, R. A.; Elouga Bom, L. B.; Ozaki, T.

    2011-08-15

    The time-resolved studies of laser-produced Ag, In, Pt, V, Mn, and Ga plasmas are presented from the point of view of plasma application as the nonlinear optical medium for high-order harmonic generation of laser radiation. We show that optimization of plasma formation using this technique allows the enhancement of harmonic generation efficiency and extension of maximal harmonic order.

  7. Hypersensitivity to thrombin of platelets from hypercholesterolemic rats

    SciTech Connect

    Winocour, P.D.; Rand, M.L.; Kinlough-Rathbone, R.L.; Mustard, J.F.

    1986-03-01

    Hypersensitivity of platelets to thrombin has been associated with hypercholesterolemia. The authors have examined the mechanisms involved in this hypersensitivity. Rats were given diets rich in milk fat and containing added cholesterol and taurocholate to produce hypercholesterolemia (HC) (262 +/- 25 mg%) or added sitosterol as a normocholesterolemic control (NC) (89 +/- 6 mg%). Washed platelets were prelabelled with /sup 14/C-serotonin. In the presence of acetylsalicyclic acid (ASA) (to inhibit thromboxane A/sub 2/ (TXA/sub 2/) formation) and creatine phosphate/creatine phosphokinase (CP/CPK) (to remove released ADP), HC platelets aggregated more (26 +/- 1%) and released more /sup 14/C (9.1 +/- 2.0%) than NC platelets (aggregation: 0%, p < 0.001; /sup 14/C release: 1.5 +/- 0.5%, p < 0.002) in response to thrombin (0.075 U/ml). Thus, a pathway independent of released ADP or TXA/sub 2/ formation is involved in the hypersensitivity of HC platelets to thrombin. Total binding of /sup 125/I-thrombin to HC platelets was less than that to NC platelets but HC platelets were smaller and had less protein than NC platelets; the thrombin binding per mg platelet protein was the same for HC and NC platelets, indicating that hypersensitivity to thrombin of HC platelets does not result from increased thrombin binding. Thus, hypersensitivity of HC platelets to thrombin is not due to TXA/sub 2/ formation, the action of released ADP or increased thrombin binding.

  8. Early detection of thrombin activity in neuroinflammatory disease

    PubMed Central

    Davalos, Dimitrios; Baeten, Kim M; Whitney, Michael A; Mullins, Eric S; Friedman, Beth; Olson, Emilia S; Ryu, Jae Kyu; Smirnoff, Dimitri S; Petersen, Mark A; Bedard, Catherine; Degen, Jay L; Tsien, Roger Y; Akassoglou, Katerina

    2014-01-01

    Although multiple sclerosis (MS) has been associated with the coagulation system, the temporal and spatial regulation of coagulation activity in neuroinflammatory lesions is unknown. Using a novel molecular probe, we characterized the activity pattern of thrombin, the central protease of the coagulation cascade, in experimental autoimmune encephalomyelitis. Thrombin activity preceded onset of neurological signs, increased at disease peak, and correlated with fibrin deposition, microglial activation, demyelination, axonal damage, and clinical severity. Mice with a genetic deficit in prothrombin confirmed the specificity of the thrombin probe. Thrombin activity might be exploited for developing sensitive probes for preclinical detection and monitoring of neuroinflammation and MS progression. PMID:24740641

  9. The role of topical thrombin in skin grafting.

    PubMed Central

    Ofodile, F. A.; Sadana, M. K.

    1991-01-01

    A prospective study to evaluate the efficacy of thrombin as a hemostatic agent in burn patients was conducted on 24 patients undergoing debridement and skin grafting. All patients also acted as their own control. Results showed a 43.5% reduction in bleeding on the thrombin-treated sites compared with the control sites. There was no adverse effect on the rate of wound healing from the thrombin, and no difference in the nature of the scar seen at the thrombin-treated site compared with the control site. Images Figure 1 PMID:1875421

  10. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    SciTech Connect

    Sydorenko, D.; Kaganovich, I. D.; Chen, L.; Ventzek, P. L. G.

    2015-12-15

    Generation of anomalously energetic suprathermal electrons was observed in simulation of a high-voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in the discharge via a two-stream instability. The energy transfer from the beam to the plasma electrons is ensured by the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The waves with short wavelength near the anode accelerate plasma bulk electrons to suprathermal energies. The sheath near the anode reflects some of the accelerated electrons back into the plasma. These electrons travel through the plasma, reflect near the cathode, and enter the accelerating area again but with a higher energy than before. Such particles are accelerated to energies much higher than after the first acceleration. This mechanism plays a role in explaining earlier experimental observations of energetic suprathermal electrons in similar discharges.

  11. Generation of electromagnetic emission during the injection of dense supersonic plasma flows into arched magnetic field

    NASA Astrophysics Data System (ADS)

    Viktorov, Mikhail; Golubev, Sergey; Mansfeld, Dmitry; Vodopyanov, Alexander

    2016-04-01

    Interaction of dense supersonic plasma flows with an inhomogeneous arched magnetic field is one of the key problems in near-Earth and space plasma physics. It can influence on the energetic electron population formation in magnetosphere of the Earth, movement of plasma flows in magnetospheres of planets, energy release during magnetic reconnection, generation of electromagnetic radiation and particle precipitation during solar flares eruption. Laboratory study of this interaction is of big interest to determine the physical mechanisms of processes in space plasmas and their detailed investigation under reproducible conditions. In this work a new experimental approach is suggested to study interaction of supersonic (ion Mach number up to 2.7) dense (up to 1015 cm-3) plasma flows with inhomogeneous magnetic field (an arched magnetic trap with a field strength up to 3.3 T) which opens wide opportunities to model space plasma processes in laboratory conditions. Fully ionized plasma flows with density from 1013 cm-3 to 1015 cm-3 are created by plasma generator on the basis of pulsed vacuum arc discharge. Then plasma is injected in an arched open magnetic trap along or across magnetic field lines. The filling of the arched magnetic trap with dense plasma and further magnetic field lines break by dense plasma flow were experimentally demonstrated. The process of plasma deceleration during the injection of plasma flow across the magnetic field lines was experimentally demonstrated. Pulsed plasma microwave emission at the electron cyclotron frequency range was observed. It was shown that frequency spectrum of plasma emission is determined by position of deceleration region in the magnetic field of the magnetic arc, and is affected by plasma density. Frequency spectrum shifts to higher frequencies with increasing of arc current (plasma density) because the deceleration region of plasma flow moves into higher magnetic field. The observed emission can be related to the

  12. Cold atmospheric plasma jet-generated RONS and their selective effects on normal and carcinoma cells.

    PubMed

    Kim, Sun Ja; Chung, T H

    2016-02-03

    Cold atmospheric helium plasma jets were fabricated and utilized for plasma-cell interactions. The effect of operating parameters and jet design on the generation of specific reactive oxygen and nitrogen species (RONS) within cells and cellular response were investigated. It was found that plasma treatment induced the overproduction of RONS in various cancer cell lines selectively. The plasma under a relatively low applied voltage induced the detachment of cells, a reduction in cell viability, and apoptosis, while the plasma under higher applied voltage led to cellular necrosis in our case. To determine whether plasma-induced reactive oxygen species (ROS) generation occurs through interfering with mitochondria-related cellular response, we examined the plasma effects on ROS generation in both parental A549 cells and A549 ρ(0) cells. It was observed that cancer cells were more susceptible to plasma-induced RONS (especially nitric oxide (NO) and nitrogen dioxide (NO2(-)) radicals) than normal cells, and consequently, plasma induced apoptotic cell responses mainly in cancer cells.

  13. Flow and delta-P dictate where thrombin, fibrin, and von Willebrand Factor will be found.

    PubMed

    Diamond, Scott L

    2016-05-01

    Hemostasis occurs in two different topological scenarios: complete severing of a vessel or disruption of the vessel wall. Either to meet the daily rigors of active life or during an acute trauma, hemostasis involves the regulated and self-limiting production of thrombin to stop bleeding. In contrast, arterial and venous thrombosis typically involves the unregulated, intraluminal growth of a clot, in the absence of bleeding. For either hemostasis or thrombosis, the presence of flow and pressure gradients (delta-P, ΔP) dictates when and where thrombin and fibrin are located and in what quantity. For hemostatic clots, fibrin formation helped limit clot growth. We found that γ'-fibrinogen had a role in limiting clot growth via anti-thrombin activity at venous, but not arterial conditions. For hemophilic blood, severe factor deficiency (<1% healthy) led to a defect in both platelet and fibrin deposition under flow. However, moderate deficiency, which is associated with a less severe bleeding phenotype, had normalized platelet function but still lacked fibrin production. We conclude signaling levels of thrombin can be generated during moderate hemophilia to sufficiently activate platelets to achieve primary hemostasis, even if fibrin formation remains defective. Finally, as a clot grows, shear stresses can become sufficiently extreme in diseased arteries to drive von Willebrand Factor self-association into massive fibers, potentially the final burst of clot growth towards full thrombotic occlusion.

  14. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    NASA Astrophysics Data System (ADS)

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-01

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  15. Generation of terahertz radiation by focusing femtosecond bichromatic laser pulses in a gas or plasma

    SciTech Connect

    Chizhov, P A; Volkov, Roman V; Bukin, V V; Ushakov, A A; Garnov, Sergei V; Savel'ev-Trofimov, Andrei B

    2013-04-30

    The generation of terahertz radiation by focusing two-frequency femtosecond laser pulses is studied. Focusing is carried out both in an undisturbed gas and in a pre-formed plasma. The energy of the terahertz radiation pulses is shown to reduce significantly in the case of focusing in a plasma. (extreme light fields and their applications)

  16. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    SciTech Connect

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-14

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  17. Generation of Radio Frequency Plasmas in Pure Water within Hole in Insulating Plate

    NASA Astrophysics Data System (ADS)

    Maehara, Tsunehiro; Matsutomo, Shinya; Yamamoto, Shin; Mukasa, Shinobu; Tanaka, Ayaka; Kawashima, Ayato

    2015-09-01

    Recently, various types of plasmas in water have been investigated. In some cases, it has been observed that plasmas in water are not in contact with the metal electrodes. In these systems, no metal electrodes contaminate water. Our research group has carried out experimental investigations on RF plasma enclosed in a bubble within a hole in an insulating plate. RF power was applied between two electrodes, and an insulating plate was placed between them. RF plasmas in pure water (0.2mS/m) and 1 wt% NaCl solution can be generated within the hole, apart from the electrodes. When hole diameter is 3-10 mm, the plasmas can be maintained stably. From finite element method, the electric field and heat density before breakdown were estimated, and on the basis of those calculations it was shown that bubble formation is a key factor for plasma generation, that is, in both the cases, the existence of a bubble increases the electric field at the side of the bubble increases. These facts suggest plasma generation occurs at around the side of the bubble. However, solution can be treated as a conductor in 1 wt% NaCl solution. On the other hand, in pure water, water behaves as an insulator. Therefore, different mechanisms lead to the plasma generation.

  18. Characterization of a copper spark discharge plasma in argon atmosphere used for nanoparticle generation

    NASA Astrophysics Data System (ADS)

    Kohut, Attila; Galbács, Gábor; Márton, Zsuzsanna; Geretovszky, Zsolt

    2017-04-01

    Spark discharge nanoparticle generation is a dynamically developing application of discharge plasmas. In the present study a spark plasma used for nanoparticle generation is characterized by means of spatially and temporally resolved optical emission spectroscopy (OES) supplemented by fast imaging. The data acquired during the generation of copper nanoparticles in argon ambient is used to describe the spatial and temporal evolution of the species in the spark gap and to derive plasma parameters such as excitation temperature and electron concentration on one hand, and the concentration of the Cu species eroded by a single spark on the other. It is shown that temporally and spatially resolved OES together with a simple equilibrium model are efficient tools to estimate the characteristics of the spark discharge plasma that typically exists in spark discharge nanoparticle generators.

  19. Plasma convection and ion beam generation in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.; Smith, R. A.

    1991-01-01

    Because of the dawn-dusk electric field E(dd), plasma in the magnetotail convects from the lobe toward the central plasma sheet (CPS). In the absence of space or velocity diffusion due to plasma turbulence, convection would yield a steady state distribution function f = V exp (-2/3) g(v exp 2 V exp 2/3), where V is the flux tube volume. Starting with such a distribution function and a plasma beta which varies from beta greater than 1 in the CPS to beta much smaller than 1 in the lobe, the evolution of the ion distribution function was studied considering the combined effects of ion diffusion by kinetic Alfven waves (KAW) in the ULF frequency range (1-10 mHz) and convection due to E(dd) x B drift in the plasma sheet boundary layer (PSBL) and outer central plasma sheet (OCPS). The results show that, during the early stages after launching the KAWs, a beamlike ion distribution forms in the PSBL and at the same time the plasma density and temperature decrease in the OCPS. Following this stage, ions in the beams convect toward the CPS resulting in an increase of the plasma temperature in the OCPS.

  20. On uniform plasma generation for the large area plasma processing in intermediate pressures

    SciTech Connect

    Kim, Hyun Jun; Hwang, Hye-Ju; Cho, Jeong Hee; Chae, Hee Sun; Kim, Dong Hwan; Chung, Chin-Wook

    2015-04-21

    Radial plasma discharge characteristics in the range of 450 mm were studied in a dual inductively coupled plasma (ICP) source, which consisted of a helical ICP and the side type ferrite ICPs. Since the energy relaxation length is shorter than the distance between each of the ferrite ICPs in an intermediate pressure (600 mTorr), local difference in the plasma ignition along the antenna position were observed. In addition, large voltage drop in the discharge of the ferrite ICPs causes an increase in the displacement current to the plasma, and separate discharge mode (E and H mode) according to the antenna position was observed. This results in non-uniform plasma distribution. For the improvement in the discharge of the ferrite ICPs, a capacitor which is placed between the ends of antenna and the ground is adjusted to minimize the displacement current to the plasma. As a result, coincident transitions from E to H mode were observed along the antenna position, and radially concave density profile (edge focused) was measured. For the uniform density distribution, a helical ICP, which located at the center of the discharge chamber, was simultaneously discharged with the ferrite ICPs. Due to the plasma potential variation through the simultaneous discharge of helical ICP and ferrite ICPs, uniform radial distribution in both plasma density and electron temperature are achieved.

  1. Core-shell nanostructures for ultrasensitive detection of α-thrombin

    NASA Astrophysics Data System (ADS)

    Chen, Xia; Liu, Hongli; Zhou, Xiaodong; Hu, Jiming

    2010-12-01

    We have synthesized a stable, sensitive and specific surface-enhanced Raman tag, and demonstrated its application in human α-thrombin detection. The tag consists of aptamer-modified core-shell nanoparticles with hydrophobic Au@Ag as core and silica as shell encapsulating Raman active molecules. By taking advantage of the Raman signal enhancement effect by metallic nanostructures, high stability and robustness of glass-coated core-shell nanostructures and the recognition capabilities of aptamers, we designed a sandwich detection for protein identification with high selectivity and sensitivity. In this way, we realized the ultrasensitive detection of α-thrombin. GDNs (glass-coated, dye-tagged nanoparticles), which were conjugated with oligonucleotides or antibodies, were extremely soluble in water, and had mechanical and chemical stability, easily controllable-size distribution and friendly biocompatibility. Specifically, the glass coating renders the particles amenable to use in many solvents without altering the Raman spectral response and makes agglomeration a nonfactor. All these merits open the door of the real applications in diagnostics or medical investigations in complex biofluids, such as human plasma and serum. Using the aptamer-modified GDNs as Raman tags, we successfully performed the detection of α-thrombin in human plasma. Furthermore, the overall method have been proved effective and selective, and may be implemented for multiplex target analysis simultaneously.

  2. Dense electron-positron plasmas and bursts of gamma-rays from laser-generated quantum electrodynamic plasmas

    SciTech Connect

    Ridgers, C. P.; Bell, A. R.; Brady, C. S.; Bennett, K.; Arber, T. D.; Duclous, R.; Kirk, J. G.

    2013-05-15

    In simulations of a 12.5 PW laser (focussed intensity I=4×10{sup 23}Wcm{sup −2}) striking a solid aluminum target, 10% of the laser energy is converted to gamma-rays. A dense electron-positron plasma is generated with a maximum density of 10{sup 26}m{sup −3}, seven orders of magnitude denser than pure e{sup −} e{sup +} plasmas generated with 1PW lasers. When the laser power is increased to 320 PW (I=10{sup 25}Wcm{sup −2}), 40% of the laser energy is converted to gamma-ray photons and 10% to electron-positron pairs. In both cases, there is strong feedback between the QED emission processes and the plasma physics, the defining feature of the new “QED-plasma” regime reached in these interactions.

  3. Plasma generation for controlled microwave-reflecting surfaces in plasma antennas

    SciTech Connect

    Bliokh, Yury P.; Felsteiner, Joshua; Slutsker, Yakov Z.

    2014-04-28

    The idea of replacing metal antenna elements with equivalent plasma objects has long been of interest because of the possibility of switching the antenna on and off. In general, two kinds of designs have so far been reported: (a) Separate plasma “wires” which are thin glass tubes filled with gas, where plasma appears due to discharge inside. (b) Reflecting surfaces, consisting of tightly held plasma wires or specially designed large discharge devices with magnetic confinement. The main disadvantages of these antennas are either large weight and size or too irregular surfaces for proper reflection. To design a microwave plasma antenna in the most common radar wavelength range of 1–3 cm with a typical gain of 30 dB, a smooth plasma mirror having a 10–30 cm diameter and a proper curvature is required. The plasma density must be 10{sup 12}–10{sup 14} cm{sup −3} in order to exceed the critical density for the frequency of the electromagnetic wave. To achieve this we have used a ferromagnetic inductively coupled plasma (FICP) source, where a thin magnetic core of a large diameter is fully immersed in the plasma. In the present paper, we show a way to adapt the FICP source for creating a flat switchable microwave plasma mirror with an effective diameter of 30 cm. This mirror was tested as a microwave reflector and there was found no significant difference when compared with a copper plate having the same diameter.

  4. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2001-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime (about 40 ps), high frequency (about 5G hz), high power bursts of low-duty factor microwaves sufficient to generate a dielectric barrier discharge and passing a gas to treated through the discharge so as to cause dissociative reduction of the exhaust gases. The invention also includes a reactor for generating the non-thermal plasma.

  5. A reflex electron beam discharge as a plasma source for electron beam generation

    SciTech Connect

    Murray, C.S.; Rocca, J.J.; Szapiro, B. )

    1988-10-01

    A reflex electron beam glow discharge has been used as a plasma source for the generation of broad-area electron beams. An electron current of 120 A (12 A/cm/sup 2/) was extracted from the plasma in 10 ..mu..s pulses and accelerated to energies greater than 1 keV in the gap between two grids. The scaling of the scheme for the generation of multikiloamp high-energy beams is discussed.

  6. PLASMA-WAVE GENERATION IN A DYNAMIC SPACETIME

    SciTech Connect

    Yang, Huan; Zhang, Fan

    2016-02-01

    We propose a new electromagnetic (EM)-emission mechanism in magnetized, force-free plasma, which is driven by the evolution of the underlying dynamic spacetime. In particular, the emission power and angular distribution of the emitted fast-magnetosonic and Alfvén waves are separately determined. Previous numerical simulations of binary black hole mergers occurring within magnetized plasma have recorded copious amounts of EM radiation that, in addition to collimated jets, include an unexplained, isotropic component that becomes dominant close to the merger. This raises the possibility of multimessenger gravitational-wave and EM observations on binary black hole systems. The mechanism proposed here provides a candidate analytical characterization of the numerical results, and when combined with previously understood mechanisms such as the Blandford–Znajek process and kinetic-motion-driven radiation, it allows us to construct a classification of different EM radiation components seen in the inspiral stage of compact-binary coalescences.

  7. Magnetic-Field Generation and Amplification in an Expanding Plasma

    NASA Astrophysics Data System (ADS)

    Schoeffler, K. M.; Loureiro, N. F.; Fonseca, R. A.; Silva, L. O.

    2014-05-01

    Particle-in-cell simulations are used to investigate the formation of magnetic fields B in plasmas with perpendicular electron density and temperature gradients. For system sizes L comparable to the ion skin depth di, it is shown that B˜di/L, consistent with the Biermann battery effect. However, for large L/di, it is found that the Weibel instability (due to electron temperature anisotropy) supersedes the Biermann battery as the main producer of B. The Weibel-produced fields saturate at a finite amplitude (plasma β≈100), independent of L. The magnetic energy spectra below the electron Larmor radius scale are well fitted by the power law with slope -16/3, as predicted by Schekochihin et al. [Astrophys. J. Suppl. Ser. 182, 310 (2009)].

  8. Explosive-Driven Hemispherical Implosions for Generating Fusion Plasmas

    DTIC Science & Technology

    1982-03-01

    facility in order to provide a small region of extremely high pressures and temperatures (13-25). The implosion chamber had originally been used as a...exploding wire) and reflects, leaving behind a very small pocket (1 mm3 ) of extremely high-temperature, high- pressure and high-density plasma. In the present...Fig. 1.4). The cavity in the capsule serves to produce a second compression and heating stage in order to produce extremely high temperatures, pressures

  9. Population Inversions in Ablation Plasmas Generated by Intense Electron Beams.

    DTIC Science & Technology

    1988-11-01

    light weight design, and moderate cost. The Soviets have investigated intense proton beam pumped plasma lasers , however, the University of Michigan...interpretations have been verified by moving the position of the probe laser beam away from the surface of the anode (from 0.1 cm to 0.4 cm) and noting the changes...Properties Effects on Ultraviolet Laser induced Flashover of Angled Plastic insulators in Vacuum", C.L. Ensloe and R. M. Gilgenbach, IEEE 3 Trans. on

  10. High Magnetic field generation for laser-plasma experiments

    SciTech Connect

    Pollock, B B; Froula, D H; Davis, P F; Ross, J S; Fulkerson, S; Bower, J; Satariano, J; Price, D; Glenzer, S H

    2006-05-01

    An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system suppling 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented.

  11. Characterization of Plasma Generated in a Commercial Grade Plasma Etching system

    NASA Astrophysics Data System (ADS)

    Bessinger, Gabriella; Drake, Dereth; Popovic, Svetozar; Vuskovic, Leposava

    2014-10-01

    The use of plasma for etching and cleaning of many types of metal surfaces is becoming more prominent in industry. This is primarily due to the fact that plasma etching can reduce the amount of time necessary to clean/etch the surface and does not require large amounts of environmentally hazardous chemicals. Most plasma etching systems are designed and built in academic institutions. These systems provide reasonable etching rates and easy accessibility for monitoring plasma parameters. The downside is that the cost is typically high. Recently a number of commercial grade plasma etchers have been introduced on the market. These etching systems cost near a fraction of the price, making them a more economical choice for researchers in the field. However, very few academicians use these devices because their effectiveness has not yet been adequately verified in the current literature. We will present the results from experiments performed in a commercial grade plasma etching system, including analysis of the pulse characteristics observed by a photo diode and the plasma parameters obtained with optical emission spectroscopy.

  12. Optical Characterization of Plasma Generated in a Commercial Grade Plasma Etching System

    NASA Astrophysics Data System (ADS)

    Hardy, Ashley; Drake, Dereth

    2015-11-01

    The use of plasma for etching and cleaning of many types of metal surfaces is becoming more prominent in industry. This is primarily due to the fact that plasma etching can reduce the amount of time necessary to clean/etch the surface and does not require large amounts of environmentally hazardous chemicals. Most plasma etching systems are designed and built in academic institutions. These systems provide reasonable etching rates and easy accessibility for monitoring plasma parameters. The downside is that the cost is typically high. Recently a number of commercial grade plasma etchers have been introduced on the market. These etching systems cost near a fraction of the price, making them a more economical choice for researchers in the field. However, very few academics use these devices because their effectiveness has not yet been adequately verified in the current literature. We will present the results from experiments performed in a commercial grade plasma etching system, including analysis of the pulse characteristics observed by a photo diode and the plasma parameters obtained with optical emission spectroscopy.

  13. Terahertz generation by two cross focused laser beams in collisional plasmas

    SciTech Connect

    Sharma, R. P. Singh, Ram Kishor

    2014-07-15

    The role of two cross-focused spatial-Gaussian laser beams has been studied for the high power and efficient terahertz (THz) radiation generation in the collisional plasma. The nonlinear current at THz frequency arises on account of temperature dependent collision frequency of electrons with ions in the plasma and the presence of a static electric field (applied externally in the plasma) and density ripple. Optimisation of laser-plasma parameters gives the radiated THz power of the order of 0.23  MW.

  14. Magnetic filter apparatus and method for generating cold plasma in semicoductor processing

    DOEpatents

    Vella, Michael C.

    1996-01-01

    Disclosed herein is a system and method for providing a plasma flood having a low electron temperature to a semiconductor target region during an ion implantation process. The plasma generator providing the plasma is coupled to a magnetic filter which allows ions and low energy electrons to pass therethrough while retaining captive the primary or high energy electrons. The ions and low energy electrons form a "cold plasma" which is diffused in the region of the process surface while the ion implantation process takes place.

  15. Magnetic filter apparatus and method for generating cold plasma in semiconductor processing

    DOEpatents

    Vella, M.C.

    1996-08-13

    Disclosed herein is a system and method for providing a plasma flood having a low electron temperature to a semiconductor target region during an ion implantation process. The plasma generator providing the plasma is coupled to a magnetic filter which allows ions and low energy electrons to pass therethrough while retaining captive the primary or high energy electrons. The ions and low energy electrons form a ``cold plasma`` which is diffused in the region of the process surface while the ion implantation process takes place. 15 figs.

  16. Higher-Order Harmonic Generation from Fullerene by Means of the Plasma Harmonic Method

    SciTech Connect

    Ganeev, R. A.; Bom, L. B. Elouga; Abdul-Hadi, J.; Ozaki, T.; Wong, M. C. H.; Brichta, J. P.; Bhardwaj, V. R.

    2009-01-09

    We demonstrate, for the first time, high-order harmonic generation from C{sub 60} by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C{sub 60}-rich epoxy and C{sub 60} films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.

  17. Use of extended laser plasma for generation of high-order harmonics of picosecond duration

    SciTech Connect

    Ganeev, R A; Boltaev, G S; Reyimbaev, Sh; Sherniyozov, Kh; Usmanov, T

    2015-07-31

    We report the results of experimental investigations on the generation of picosecond radiation harmonics in extended laser plasma produced on the surface of different metal targets. The effect of plasma length, heating pulse duration and delay between the heating and transformable pulses on the efficiency of conversion to higher harmonics is studied. The λ = 1064 nm radiation conversion to a short-wavelength (down to 50 nm, 21st harmonic) range in extended plasma of several metals is demonstrated. (interaction of laser radiation with matter. laser plasma)

  18. Structure of the bipolar plasma sheath generated by SPEAR I

    SciTech Connect

    Katz, I.; Jongeward, G.A.; Davis, V.A.; Mandell, M.J.; Kuharski, R.A.; Lilley, J.R. Jr. ); Raitt, W.J. ); Cooke, D.L. ); Torbert, R.B.; Larson, G.; Rau, D. )

    1989-02-01

    The Space Power Experiment Aboard Rockets I (SPEAR I) biased two 10-cm radius spheres as high as 46,000 V positive with respect to an aluminum rocket body. The experiment measured the steady state current to the spheres and the floating potential of the rocket body. Three-dimensional calculations performed using NASCAP/LEO and POLAR 2.0 show that both ion-collecting and electron-collecting sheaths were formed. The rocket body potential with respect to the ionospheric plasma adjusted to achieve a balance between the electron current collected by the spheres and the secondary electron-enhanced ion current to the rocket body. This current balance was obtained with a large ion-collecting sheath that enveloped most of the electron-collecting sheath and reduced the area for collection of ionospheric electrons. The calculated current is in agreement with the flight measurement of a steady state current of less than 1/10 A. The calculations show that the rocket body was driven thousands of volts negative with respect to the ionospheric plasma. The calculated rocket potential is within the uncertainty of that inferred from ion spectrometer data. The current flowed through the space plasma. There was almost no direct charge transport between the spheres and the rocket body.

  19. Simulation study of wakefield generation by two color laser pulses propagating in homogeneous plasma

    SciTech Connect

    Kumar Mishra, Rohit; Saroch, Akanksha; Jha, Pallavi

    2013-09-15

    This paper deals with a two-dimensional simulation of electric wakefields generated by two color laser pulses propagating in homogeneous plasma, using VORPAL simulation code. The laser pulses are assumed to have a frequency difference equal to the plasma frequency. Simulation studies are performed for two similarly as well as oppositely polarized laser pulses and the respective amplitudes of the generated longitudinal wakefields for the two cases are compared. Enhancement of wake amplitude for the latter case is reported. This simulation study validates the analytical results presented by Jha et al.[Phys. Plasmas 20, 053102 (2013)].

  20. Apparatus for generating quasi-free-space microwave-driven plasmas.

    PubMed

    Hoff, Brad W; French, David M; Reid, Remington R; Lawrance, Julie E; Lepell, P David; Maestas, Sabrina S

    2016-03-01

    An apparatus for generating quasi-free-space microwave-driven plasmas has been designed, constructed, and tested. The plasma is driven by a multi-kW, ∼5 GHz microwave beam focused at the center of a vacuum chamber using a Koch-type metal plate lens. Sustained plasma discharges have been generated in argon at pressures ranging from 150 to 200 mTorr, at beam power levels ranging from 5 to 10 kW, and at gas flow rates of approximately 200 SCCM.

  1. High-order harmonic generation from plasma plume pumped by 400 nm wavelength laser

    SciTech Connect

    Ganeev, Rashid A.; Elouga Bom, Luc B.; Ozaki, Tsuneyuki

    2007-09-24

    The authors present their study on high-order harmonic generation pumped by 400 nm wavelength laser from plasma plumes produced on the surfaces of various solid-state targets. The maximum harmonic cutoff was observed for Be plasma (31st harmonic, {lambda}=12.9 nm). They compared these results with harmonic generation pumped by 800 nm wavelength laser. The authors demonstrated single harmonic enhancement for Cr, Sn, Sb, and Mn plasmas. They also studied the use of varying the chirp of the pump laser to control the enhancement of single harmonics within the plateau.

  2. Generation and evolution of magnetic field in the relativistic plasma following q-nonextensive distribution

    NASA Astrophysics Data System (ADS)

    Lin, Fu-Jun; Chen, Zong-Hua; Li, Xiao-Qing; Liao, Jing-Jing; Zhu, Yun

    2017-02-01

    A GigaGauss quasi-steady magnetic field can be generated in astrophysical plasmas and laser-produced plasmas with high-frequency electromagnetic radiation through wave-wave and wave-particle interactions. A set of governing equations for this field are obtained in the plasma consisting of ultra-relativistic electrons following q-nonextensive distribution. The numerical results show that the initial field is unstable and can collapse to generate various spatially intermittent magnetic flux tubes. It can also be found that the behavior of the magnetic field is greatly dependent on the nonextensive index q, which may be helpful in understanding the magnetic turbulence.

  3. Dynamic high pressure generation through plasma implosion driven by an intense laser pulse

    NASA Astrophysics Data System (ADS)

    Li, M.; Wang, J. X.; Yuan, T.; Xu, Y. X.; Zhu, W. J.

    2017-03-01

    When an intense laser pulse is loaded upon solids, very high impact pressure can be generated on the surface. In this letter, we simulate this process through one-dimensional particle-in-cell simulation and find that the pressure as high as 0.13 TPa can be generated after the laser pulse with intensity 1015 W/cm2 and 5 picosecond duration is injected upon a nanometer solid-density plasma. The peak pressure is shown to be resulted from an energetic high-density plasma bunch, produced through plasma implosion under extremely high light pressure.

  4. Decomposition of chlorinated ethylenes and ethanes in an electron beam generated plasma reactor

    SciTech Connect

    Vitale, Steven A.

    1996-02-01

    An electron beam generated plasma reactor (EBGPR) is used to determine the plasma chemistry kinetics, energetics and decomposition pathways of six chlorinated ethylenes and ethanes: 1,1,1-trichloroethane, 1,1-dichloroethane, ethyl chloride, trichloroethylene, 1,1-dichloroethylene, and vinyl chloride. A traditional chemical kinetic and chemical engineering analysis of the data from the EBGPR is performed, and the following hypothesis was verified: The specific energy required for chlorinated VOC decomposition in the electron beam generated plasma reactor is determined by the electron attachment coefficient of the VOC and the susceptibility of the molecule to radical attack. The technology was demonstrated at the Hanford Reservation to remove VOCs from soils.

  5. Targeting cancer cells with reactive oxygen and nitrogen species generated by atmospheric-pressure air plasma.

    PubMed

    Ahn, Hak Jun; Kim, Kang Il; Hoan, Nguyen Ngoc; Kim, Churl Ho; Moon, Eunpyo; Choi, Kyeong Sook; Yang, Sang Sik; Lee, Jong-Soo

    2014-01-01

    The plasma jet has been proposed as a novel therapeutic method for cancer. Anticancer activity of plasma has been reported to involve mitochondrial dysfunction. However, what constituents generated by plasma is linked to this anticancer process and its mechanism of action remain unclear. Here, we report that the therapeutic effects of air plasma result from generation of reactive oxygen/nitrogen species (ROS/RNS) including H2O2, Ox, OH-, •O2, NOx, leading to depolarization of mitochondrial membrane potential and mitochondrial ROS accumulation. Simultaneously, ROS/RNS activate c-Jun NH2-terminal kinase (JNK) and p38 kinase. As a consequence, treatment with air plasma jets induces apoptotic death in human cervical cancer HeLa cells. Pretreatment of the cells with antioxidants, JNK and p38 inhibitors, or JNK and p38 siRNA abrogates the depolarization of mitochondrial membrane potential and impairs the air plasma-induced apoptotic cell death, suggesting that the ROS/RNS generated by plasma trigger signaling pathways involving JNK and p38 and promote mitochondrial perturbation, leading to apoptosis. Therefore, administration of air plasma may be a feasible strategy to eliminate cancer cells.

  6. Turbulent jet flow generated downstream of a low temperature dielectric barrier atmospheric pressure plasma device

    PubMed Central

    Whalley, Richard D.; Walsh, James L.

    2016-01-01

    Flowing low temperature atmospheric pressure plasma devices have been used in many technological applications ranging from energy efficient combustion through to wound healing and cancer therapy. The generation of the plasma causes a sudden onset of turbulence in the inhomogeneous axisymmetric jet flow downstream of the plasma plume. The mean turbulent velocity fields are shown to be self-similar and independent of the applied voltage used to generate the plasma. It is proposed that the production of turbulence is related to a combination of the small-amplitude plasma induced body forces and gas heating causing perturbations in the unstable shear layers at the jet exit which grow as they move downstream, creating turbulence. PMID:27561246

  7. Turbulent jet flow generated downstream of a low temperature dielectric barrier atmospheric pressure plasma device.

    PubMed

    Whalley, Richard D; Walsh, James L

    2016-08-26

    Flowing low temperature atmospheric pressure plasma devices have been used in many technological applications ranging from energy efficient combustion through to wound healing and cancer therapy. The generation of the plasma causes a sudden onset of turbulence in the inhomogeneous axisymmetric jet flow downstream of the plasma plume. The mean turbulent velocity fields are shown to be self-similar and independent of the applied voltage used to generate the plasma. It is proposed that the production of turbulence is related to a combination of the small-amplitude plasma induced body forces and gas heating causing perturbations in the unstable shear layers at the jet exit which grow as they move downstream, creating turbulence.

  8. Negative-permittivity plasma generation in negative-permeability space with high-energy metamaterials

    NASA Astrophysics Data System (ADS)

    Sakai, Osamu; Nakamura, Yoshihiro; Iwai, Akinori; Iio, Satoshi

    2016-10-01

    Plasma generation by electromagnetic waves in negative-permeability space is analyzed using experimental results and theoretical models. Installation of negative-permeability metamaterials triggers drastic changes to the propagation of electromagnetic waves. Unlike usual cases in which permeability is  +1, negative permeability induces evanescent modes in a space without plasma. However, if permittivity becomes negative due to high-electron-density or overdense plasma, electromagnetic waves can propagate because negative-refractive-index states emerge. In this study, reviewing our previous experimental data, we study the underlying physical processes in plasma generation in terms of wave propagation and parameters of wave media. We confirm nonlinear (transition) processes in the phase of density evolution up to the negative permittivity state and negative-refractive-index states in the quasi-steady phase. We also note that such energetic metamaterials are built up when we use plasma, unlike conventional metamaterials composed of solid-state materials.

  9. Turbulent jet flow generated downstream of a low temperature dielectric barrier atmospheric pressure plasma device

    NASA Astrophysics Data System (ADS)

    Whalley, Richard D.; Walsh, James L.

    2016-08-01

    Flowing low temperature atmospheric pressure plasma devices have been used in many technological applications ranging from energy efficient combustion through to wound healing and cancer therapy. The generation of the plasma causes a sudden onset of turbulence in the inhomogeneous axisymmetric jet flow downstream of the plasma plume. The mean turbulent velocity fields are shown to be self-similar and independent of the applied voltage used to generate the plasma. It is proposed that the production of turbulence is related to a combination of the small-amplitude plasma induced body forces and gas heating causing perturbations in the unstable shear layers at the jet exit which grow as they move downstream, creating turbulence.

  10. Urokinase has direct catalytic activity against fibrinogen and renders it less clottable by thrombin.

    PubMed Central

    Weitz, J I; Leslie, B

    1990-01-01

    Recently, we demonstrated that tissue plasminogen activator directly releases fibrinopeptides A and B (FPA and FPB) from fibrinogen. The purpose of this study was to determine whether urokinase has similar activity. Incubation of urokinase with fibrinogen or heparinized plasma results in concentration-dependent FPB release unaccompanied by FPA cleavage. For equivalent amidolytic activity, high molecular weight urokinase releases twofold more FPB than the low molecular weight species. In contrast, prourokinase does not release FPB until activated to urokinase. Contaminating thrombin or plasma is not responsible for urokinase-mediated FPB release because this activity is unaccompanied by FPA or B beta 1-42 cleavage, and is unaffected by heparin, hirudin, a monospecific antibody against thrombin, aprotinin, or alpha 2-antiplasmin. FPB release reflects a direct action of urokinase on fibrinogen because release is completely inhibited by a monospecific antibody against the enzyme. Further, urokinase releases FPB from the FPB-containing substrate B beta 1-42, thus confirming its specificity for the B beta 14 (Arg)-B beta 15 (Gly) bond. In addition to FPB release, SDS-PAGE analysis of the time course of urokinase-mediated fibrinogenolysis indicates progressive proteolysis of both the A alpha- and B beta-chains of fibrinogen that occurs after FPB release is completed. As a consequence of urokinase-mediated fibrinogenolysis, there is progressive prolongation of the thrombin clotting time. These studies indicate that urokinase has direct catalytic activity against fibrinogen. By releasing FPB, a potent chemoattractant, and by rendering fibrinogen less clottable by thrombin, urokinase may participate in processes extending beyond fibrinolysis. Images PMID:2365816

  11. Generation of electromagnetic emission during the injection of dense supersonic plasma flows into arched magnetic field

    NASA Astrophysics Data System (ADS)

    Mansfeld, Dmitry; Golubev, Sergey; Viktorov, Mikhail; Vodopyanov, Alexander; Yushkov, George

    2015-11-01

    Interaction of dense supersonic plasma flows with an inhomogeneous arched magnetic field is one of the key problems in near-Earth and space plasma physics. In this work a new experimental approach is suggested to study interaction of supersonic (ion Mach number up to 2.7) dense (up to 1015cm-3) plasma flows with inhomogeneous magnetic field (an arched magnetic trap with a field strength up to 3.3 T) which opens wide opportunities to model space plasma processes in laboratory conditions. Fully ionized plasma flows with density from 1013cm-3 to 1015cm-3 are created by plasma generator on the basis of pulsed vacuum arc discharge and injected into open magnetic trap across magnetic field lines. The filling of the arched magnetic trap with plasma and further magnetic field lines break by dense plasma flow was accompanied by pulsed electromagnetic emission at electron cyclotron frequency range, which can generated by electrons in the place of intensive deceleration of plasma flow in magnetic field. Grant of Ministry of Education 14.Z50.31.0007.

  12. Thrombin-activatable fibrinolysis inhibitor in hypothyroidism and hyperthyroxinaemia.

    PubMed

    Verkleij, Chantal J N; Stuijver, Danka J F; van Zaane, Bregje; Squizzato, Alessandro; Brandjes, Dees P M; Büller, Harry R; Meijers, Joost C M; Gerdes, Victor E A

    2013-02-01

    Endocrine disorders affect both the coagulation and fibrinolytic systems, and have been associated with the development of cardiovascular diseases. Thrombin-activatable fibrinolysis inhibitor (TAFI) is a link between coagulation and the fibrinolytic system. The aim of this study was to determine the effect of thyroid hormone excess and deficiency on TAFI levels and function. The effect of hyperthyroxinemia on TAFI was studied in healthy volunteers who were randomised to receive levothyroxine or no medication for 14 days in a crossover design. The effect of hypothyroidism on TAFI was studied in a multicentre observational cohort study. Blood was drawn before treatment of patients with newly diagnosed hypothyroidism and when euthyroidism was achieved. Plasma clot-lysis times, activated TAFI (TAFIa)-dependent prolongation of clot-lysis and TAFI levels were measured. Thyroid hormone excess resulted in a hypofibrinolytic condition and in an enhanced TAFIa-dependent prolongation of clot lysis. A trend towards decreased plasma TAFI levels was observed in healthy volunteers who used levothyroxine. Hypothyroidism resulted in hyperfibrinolysis and a reduced TAFIa-dependent prolongation of clot lysis. In conclusion, alterations of TAFIa-dependent prolongation of clot lysis in patients with thyroid disorders may cause an impaired haemostatic balance. The disturbed haemostatic balance in patients with hyperthyroidism might make them prone to thrombosis, while the risk for bleeding may increase in patients with hypothyroidism.

  13. Advanced properties of extended plasmas for efficient high-order harmonic generation

    SciTech Connect

    Ganeev, R. A.; Suzuki, M.; Kuroda, H.

    2014-05-15

    We demonstrate the advanced properties of extended plasma plumes (5 mm) for efficient harmonic generation of laser radiation compared with the short lengths of plasmas (∼0.3–0.5 mm) used in previous studies. The harmonic conversion efficiency quadratically increased with the growth of plasma length. The studies of this process along the whole extreme ultraviolet range using the long plasma jets produced on various metal surfaces, particularly including the resonance-enhanced laser frequency conversion and two-color pump, are presented. Such plasmas could be used for the quasi-phase matching experiments by proper modulation of the spatial characteristics of extended ablating area and formation of separated plasma jets.

  14. Helium generated cold plasma finely regulates activation of human fibroblast-like primary cells.

    PubMed

    Brun, Paola; Pathak, Surajit; Castagliuolo, Ignazio; Palù, Giorgio; Brun, Paola; Zuin, Matteo; Cavazzana, Roberto; Martines, Emilio

    2014-01-01

    Non-thermal atmospheric pressure plasmas are being developed for a wide range of health care applications, including wound healing. However in order to exploit the potential of plasma for clinical applications, the understanding of the mechanisms involved in plasma-induced activation of fibroblasts, the cells active in the healing process, is mandatory. In this study, the role of helium generated plasma in the tissue repairing process was investigated in cultured human fibroblast-like primary cells, and specifically in hepatic stellate cells and intestinal subepithelial myofibroblasts. Five minutes after treatment, plasma induced formation of reactive oxygen species (ROS) in cultured cells, as assessed by flow cytometric analysis of fluorescence-activated 2',7'-dichlorofluorescein diacetate probe. Plasma-induced intracellular ROS were characterized by lower concentrations and shorter half-lives with respect to hydrogen peroxide-induced ROS. Moreover ROS generated by plasma treatment increased the expression of peroxisome proliferator activated receptor (PPAR)-γ, nuclear receptor that modulates the inflammatory responses. Plasma exposure promoted wound healing in an in vitro model and induced fibroblast migration and proliferation, as demonstrated, respectively, by trans-well assay and partitioning between daughter cells of carboxyfluorescein diacetate succinimidyl ester fluorescent dye. Plasma-induced fibroblast migration and proliferation were found to be ROS-dependent as cellular incubation with antioxidant agents (e.g. N-acetyl L-cysteine) cancelled the biological effects. This study provides evidence that helium generated plasma promotes proliferation and migration in liver and intestinal fibroblast-like primary cells mainly by increasing intracellular ROS levels. Since plasma-evoked ROS are time-restricted and elicit the PPAR-γ anti-inflammatory molecular pathway, this strategy ensures precise regulation of human fibroblast activation and can be considered a

  15. Time Resolved Temperature Measurement of Hypervelocity Impact Generated Plasma Using a Global Optimization Method

    NASA Astrophysics Data System (ADS)

    Hew, Y. M.; Linscott, I.; Close, S.

    2015-12-01

    Meteoroids and orbital debris, collectively referred to as hypervelocity impactors, travel between 7 and 72 km/s in free space. Upon their impact onto the spacecraft, the energy conversion from kinetic to ionization/vaporization occurs within a very brief timescale and results in a small and dense expanding plasma with a very strong optical flash. The radio frequency (RF) emission produced by this plasma can potentially lead to electrical anomalies within the spacecraft. In addition, space weather, such as solar activity and background plasma, can establish spacecraft conditions which can exaggerate the damages done by these impacts. During the impact, a very strong impact flash will be generated. Through the studying of this emission spectrum of the impact, we hope to study the impact generated gas cloud/plasma properties. The impact flash emitted from a ground-based hypervelocity impact test is long expected by many scientists to contain the characteristics of the impact generated plasma, such as plasma temperature and density. This paper presents a method for the time-resolved plasma temperature estimation using three-color visible band photometry data with a global pattern search optimization method. The equilibrium temperature of the plasma can be estimated using an optical model which accounts for both the line emission and continuum emission from the plasma. Using a global pattern search based optimizer, the model can isolate the contribution of the continuum emission versus the line emission from the plasma. The plasma temperature can thus be estimated. Prior to the optimization step, a Gaussian process is also applied to extract the optical emission signal out of the noisy background. The resultant temperature and line-to-continuum emission weighting factor are consistent with the spectrum of the impactor material and current literature.

  16. Helium Generated Cold Plasma Finely Regulates Activation of Human Fibroblast-Like Primary Cells

    PubMed Central

    Brun, Paola; Pathak, Surajit; Castagliuolo, Ignazio; Palù, Giorgio; Brun, Paola; Zuin, Matteo; Cavazzana, Roberto; Martines, Emilio

    2014-01-01

    Non-thermal atmospheric pressure plasmas are being developed for a wide range of health care applications, including wound healing. However in order to exploit the potential of plasma for clinical applications, the understanding of the mechanisms involved in plasma-induced activation of fibroblasts, the cells active in the healing process, is mandatory. In this study, the role of helium generated plasma in the tissue repairing process was investigated in cultured human fibroblast-like primary cells, and specifically in hepatic stellate cells and intestinal subepithelial myofibroblasts. Five minutes after treatment, plasma induced formation of reactive oxygen species (ROS) in cultured cells, as assessed by flow cytometric analysis of fluorescence-activated 2′,7′-dichlorofluorescein diacetate probe. Plasma-induced intracellular ROS were characterized by lower concentrations and shorter half-lives with respect to hydrogen peroxide-induced ROS. Moreover ROS generated by plasma treatment increased the expression of peroxisome proliferator activated receptor (PPAR)-γ, nuclear receptor that modulates the inflammatory responses. Plasma exposure promoted wound healing in an in vitro model and induced fibroblast migration and proliferation, as demonstrated, respectively, by trans-well assay and partitioning between daughter cells of carboxyfluorescein diacetate succinimidyl ester fluorescent dye. Plasma-induced fibroblast migration and proliferation were found to be ROS-dependent as cellular incubation with antioxidant agents (e.g. N-acetyl L-cysteine) cancelled the biological effects. This study provides evidence that helium generated plasma promotes proliferation and migration in liver and intestinal fibroblast-like primary cells mainly by increasing intracellular ROS levels. Since plasma-evoked ROS are time-restricted and elicit the PPAR-γ anti-inflammatory molecular pathway, this strategy ensures precise regulation of human fibroblast activation and can be

  17. Thrombelastographic characterization of the thrombin-like activity of Crotalus simus and Bothrops asper venoms.

    PubMed

    Nielsen, Vance G; Boyer, Leslie V; Redford, Daniel T; Ford, Paul

    2016-06-16

    Annually, thousands suffer venomous snake-bite from Crotalus simus and Bothrops asper vipers in central and South America. The goals of the present study were to generally characterize the thrombin-like effects of venom from these snakes in human plasma with viscoelastic methods. Human plasma was exposed to the venom of three different C. simus subspecies and venoms obtained from B. asper vipers located in three different locations in Mexico. To characterize the factor X-activating and thrombin-like activity of these venoms, plasma (normal or factor XIII deficient) was pretreated with a variety of additives (e.g., heparin) in the absence or presence of calcium prior to exposure to 2.0 μg/ml of each viper's venom. These profiles were compared with plasma without venom that had contact activation of coagulation. Coagulation kinetics were determined with thrombelastography. All venoms had thrombin-like activity, with C. s. simus creating a slow growing, weak clot that was likely mediated by metalloproteinases. In contrast, B. asper venoms had rapid onset of coagulation and a high velocity of thrombus growth. Further, B. asper venom activity was calcium-independent, activated prothrombin, activated factor XIII, and independently polymerized fibrinogen. The viscoelastic methods used were able to differentiate subspecies of C. simus and specimens of B. asper, and provide insight into the mechanisms by which the venoms acted on plasma. These methods may be useful in the profiling of similar venoms and perhaps can assist in the assessment of interventions designed to treat envenomation (e.g., antivenom).

  18. Application of nanoparticle-containing laser plasmas for optical harmonic generation

    SciTech Connect

    Ganeev, R. A.; Bom, L. B. Elouga; Ozaki, T.

    2009-07-15

    Nanoparticle-containing media can be used for efficient high-order harmonic generation of laser radiation. We present the results of studies of the harmonics generated in the laser-produced plasmas containing Cr{sub 2}O{sub 3}, Ag, Cu, and Au nanoparticles. These results are compared with the harmonics generated in the plasma produced on the surface of bulk targets at different delays between the subnanosecond heating prepulse and femtosecond pulse and different intensities of prepulse on the target surface. We discuss the harmonic enhancement, which was observed in the case of nanoparticle-containing plumes with regard to the monoparticle-containing plasmas. Morphological studies of plasma debris confirmed the presence and integrity of nanoparticles in the plumes.

  19. Electron beam generated whistler emissions in a laboratory plasma

    SciTech Connect

    Van Compernolle, B. Pribyl, P.; Gekelman, W.; An, X.; Bortnik, J.; Thorne, R. M.

    2015-12-10

    Naturally occurring whistler mode emissions in the magnetosphere, are important since they are responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Recently, we reported on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced [1]. A beam of energetic electrons is launched into a cold plasma and excites both chirping whistler waves and broadband waves. Here we extend our previous analysis by comparing the properties of the broadband waves with linear theory.

  20. 21 CFR 864.7875 - Thrombin time test.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Thrombin time test. 864.7875 Section 864.7875 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7875 Thrombin time test....

  1. Acidosis, magnesium and acetylsalicylic acid: Effects on thrombin

    NASA Astrophysics Data System (ADS)

    Borisevich, Nikolaj; Loznikova, Svetlana; Sukhodola, Aleksandr; Halets, Inessa; Bryszewska, Maria; Shcharbin, Dzmitry

    2013-03-01

    Thrombin, an enzyme from the hydrolase family, is the main component of the blood coagulation system. In ischemic stroke it acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin forming blood clots in the brain. It has been found to phosphoresce at room temperature in the millisecond and microsecond ranges. The phosphorescence of thrombin was studied under physiological conditions, in acidosis (decrease of pH from 8.0 to 5.0) and on the addition of salts (magnesium sulfate and sodium chloride) and of acetylsalicylic acid, and its connection with thrombin function is discussed. Acidosis significantly increased the internal dynamics of thrombin. We propose that lactate-acidosis plays a protective role in stroke, preventing the formation of clots. The addition of NaCl and MgSO4 in different concentrations increased the internal dynamics of thrombin. Also, the addition of MgSO4 decreased thrombin-induced platelet aggregation. However, magnesium sulfate and acetylsalicylic acid in the therapeutic concentrations used for treatment of ischemic stroke had no effect on thrombin internal dynamics. The data obtained will help to elucidate the conformational stability of thrombin under conditions modulating lactate-acidosis and in the presence of magnesium sulfate.

  2. 21 CFR 864.7875 - Thrombin time test.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Thrombin time test. 864.7875 Section 864.7875 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7875 Thrombin time test....

  3. 21 CFR 864.7875 - Thrombin time test.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Thrombin time test. 864.7875 Section 864.7875 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7875 Thrombin time test....

  4. 21 CFR 864.7875 - Thrombin time test.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Thrombin time test. 864.7875 Section 864.7875 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Hematology Kits and Packages § 864.7875 Thrombin time test....

  5. A thrombin receptor in resident rat peritoneal macrophages

    SciTech Connect

    Kudahl, K.; Fisker, S.; Sonne, O. )

    1991-03-01

    Resident rat peritoneal macrophages possess 6 x 10(2) high-affinity binding sites per cell for bovine thrombin with a Kd of 11 pM, and 7.5 x 10(4) low-affinity sites with a Kd of 5.8 nM. These binding sites are highly specific for thrombin. Half-maximal binding of {sup 125}I-labeled bovine thrombin is achieved after 1 min at 37{degrees}C, and after 12 min at 4 degrees C. The reversibly bound fraction of the ligand dissociates according to a biexponential time course with the rate constants 0.27 and 0.06 min-1 at 4 degrees C. Part of the tracer remains cell-associated even after prolonged incubation, but all cell-associated radio-activity migrates as intact thrombin upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bound thrombin is minimally endocytosed as judged by the resistance to pH 3 treatment, and the receptor does not mediate a quantitatively important degradation of the ligand. The binding is not dependent on the catalytic site of thrombin, since irreversibly inactivated thrombin also binds to the receptor. {sup 125}I-labeled thrombin covalently cross-linked to its receptor migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a Mr 160,000, corresponding to an approximate receptor size of Mr 120,000.

  6. Development of a plasma generator for a long pulse ion source for neutral beam injectors

    SciTech Connect

    Watanabe, K.; Dairaku, M.; Tobari, H.; Kashiwagi, M.; Inoue, T.; Hanada, M.; Jeong, S. H.; Chang, D. H.; Kim, T. S.; Kim, B. R.; Seo, C. S.; Jin, J. T.; Lee, K. W.; In, S. R.; Oh, B. H.; Kim, J.; Bae, Y. S.

    2011-06-15

    A plasma generator for a long pulse H{sup +}/D{sup +} ion source has been developed. The plasma generator was designed to produce 65 A H{sup +}/D{sup +} beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and {+-}7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm{sup 2}.

  7. Plasma generation near an Ion thruster disharge chamber hollow cathode

    NASA Technical Reports Server (NTRS)

    Katz, Ira; Anderson, John R.; Goebel, Dan M.; Wirz, Richard; Sengupta, Anita

    2003-01-01

    In gridded electrostatic thrusters, ions are produced by electron bombardment in the discharge chamber. In most of these thrusters, a single, centrally located hollow cathode supplies the ionizing electrons. An applied magnetic field in the discharge chamber restricts the electrons leaving the hollow cathode to a very narrow channel. In this channel, the high electron current density ionizes both propellant gas flowing from the hollow cathode, and other neutrals from the main propellant flow from the plenum. The processes that occur just past the hollow cathode exit are very important. In recent engine tests, several cases of discharge cathode orifice place and keeper erosion have been reported. In this paper we present results from a new 1-D, variable area model of the plasma processes in the magnetized channel just downstream of the hollow cathode keeper. The model predicts plasma densities, and temperatures consistent with those reported in the literature for the NSTAR engine, and preliminary results from the model show a potential maximum just downstream of the cathode.

  8. Collimated fast electron beam generation in critical density plasma

    SciTech Connect

    Iwawaki, T. Habara, H.; Morita, K.; Tanaka, K. A.; Baton, S.; Fuchs, J.; Chen, S.; Nakatsutsumi, M.; Rousseaux, C.; Filippi, F.; Nazarov, W.

    2014-11-15

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 10{sup 14 }W/cm{sup 2}, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 10{sup 14 }W/cm{sup 2}, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  9. Generation of Gigabar Pressures for High-Energy-Density Plasmas

    NASA Astrophysics Data System (ADS)

    Theobald, W.; Betti, R.; Bose, A.; Seka, W.; Stoeckl, C.; Mangino, D.; Casner, A.; Beg, F. N.; Llor Aisa, E.; Ribeyre, X.; Wei, M. S.; Schoff, M. E.; Florido, R.; Mancini, R. C.

    2016-10-01

    Experiments on the OMEGA laser were performed to study gigabar pressures in small (50- μm-diam) Ti and Cu target samples for high-energy-density plasma applications. The samples were precisely placed (better than 10 μm) at the center of a spherical plastic matrix that is irradiated at incident laser intensities of 5 ×1015 W /cm2 . The laser launches a spherical shock wave that converges in the center in order to reach Gbar pressures in the sample. The shock convergence produces a short burst ( 30ps) of x-ray emission. Time-resolved and time-integrated x-ray spectroscopy provides the means to diagnose the plasma conditions in the sample. The time-resolved spectra are compared to predictions from radiation-hydrodynamic simulations to infer the material conditions at Gbar pressures. A second x-ray flash delayed by 600ps caused by the breakout of the rebounded shock through the outer surface of the compressed plastic was observed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by the Fusion Science Center under Grant No. DE-FC02-04ER54789.

  10. Planar Hall magnetoresistive aptasensor for thrombin detection.

    PubMed

    Sinha, B; Ramulu, T S; Kim, K W; Venu, R; Lee, J J; Kim, C G

    2014-09-15

    The use of aptamer-based assays is an emerging and attractive approach in disease research and clinical diagnostics. A sensitive aptamer-based sandwich-type sensor is presented to detect human thrombin using a planar Hall magnetoresistive (PHR) sensor in cooperation with superparamagnetic labels. A PHR sensor has the great advantages of a high signal-to-noise ratio, a small offset voltage and linear response in the low-field region, allowing it to act as a high-resolution biosensor. In the system presented here, the sensor has an active area of 50 µm × 50 µm with a 10-nm gold layer deposited onto the sensor surface prior to the binding of thiolated DNA primary aptamer. A polydimethylsiloxane well of 600-µm radius and 1-mm height was prepared around the sensor surface to maintain the same specific area and volume for each sensor. The sensor response was traced in real time upon the addition of streptavidin-functionalized magnetic labels on the sensor. A linear response to the thrombin concentration in the range of 86 pM-8.6 µM and a lower detection limit down to 86 pM was achieved by the proposed present method with a sample volume consumption of 2 µl. The proposed aptasensor has a strong potential for application in clinical diagnosis.

  11. Development of a new atmospheric pressure cold plasma jet generator and application in sterilization

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Liu, Peng; Xu, Lei; Zhang, Li-Ye; Zhan, Ru-Juan; Zhang, Wen-Rui

    2006-07-01

    This paper reports that a new plasma generator at atmospheric pressure, which is composed of two homocentric cylindrical all-metal tubes, successfully generates a cold plasma jet. The inside tube electrode is connected to ground, the outside tube electrode is connected to a high-voltage power supply, and a dielectric layer is covered on the outside tube electrode. When the reactor is operated by low-frequency (6 kHz-20 kHz) AC supply in atmospheric pressure and argon is steadily fed as a discharge gas through inside tube electrode, a cold plasma jet is blown out into air and the plasma gas temperature is only 25-30°C. The electric character of the discharge is studied by using digital real-time oscilloscope (TDS 200-Series), and the discharge is capacitive. Preliminary results are presented on the decontamination of E.colis bacteria and Bacillus subtilis bacteria by this plasma jet, and an optical emission analysis of the plasma jet is presented in this paper. The ozone concentration generated by the plasma jet is 1.0×1016cm-3 which is acquired by using the ultraviolet absorption spectroscopy.

  12. Spectroscopic study of unique line broadening and inversion in low-pressure microwave generated water plasmas

    NASA Astrophysics Data System (ADS)

    Mills, R. L.; Ray, P. C.; Mayo, R. M.; Nansteel, M.; Dhandapani, B.; Phillips, J.

    2005-12-01

    It was demonstrated that low pressure (˜0.2 torr) water vapor plasmas generated in a 10 mm inner diameter quartz tube with an Evenson microwave cavity show at least two features that are not explained by conventional plasma models. First, significant (gt2.5Å) hydrogen Balmer alpha line broadening, of constant width, up to 5 cm from the microwave coupler was recorded. Only hydrogen, and not oxygen, showed significant line broadening. This feature, observed previously in hydrogen-containing mixed gas plasmas generated with high voltage dc and rf discharges, was explained by some researchers as resulting from acceleration of hydrogen ions near the cathode. This explanation cannot apply to the line broadening observed in the (electrodeless) microwave plasmas generated in this work, particularly at distances as great as 5 cm from the microwave coupler. Second, inversion of the line intensities of both the Lyman and Balmer series, again at distances up to 5 cm from the coupler, were observed. The line inversion suggests the existence of a hitherto unknown source of pumping of the optical power in plasmas. Finally, it is notable that other aspects of the plasma including the OH* rotational temperature and low electron concentrations are quite typical of plasmas of this type.

  13. Resistive wall tearing mode generated finite net electromagnetic torque in a static plasma

    NASA Astrophysics Data System (ADS)

    Hao, G. Z.; Liu, Y. Q.; Wang, A. K.; Xu, M.; Qu, H. P.; Peng, X. D.; Wang, Z. H.; Xu, J. Q.; Qiu, X. M.

    2014-01-01

    The MARS-F code [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] is applied to numerically investigate the effect of the plasma pressure on the tearing mode stability as well as the tearing mode-induced electromagnetic torque, in the presence of a resistive wall. The tearing mode with a complex eigenvalue, resulted from the favorable averaged curvature effect [A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], leads to a re-distribution of the electromagnetic torque with multiple peaking in the immediate vicinity of the resistive layer. The multiple peaking is often caused by the sound wave resonances. In the presence of a resistive wall surrounding the plasma, a rotating tearing mode can generate a finite net electromagnetic torque acting on the static plasma column. Meanwhile, an equal but opposite torque is generated in the resistive wall, thus conserving the total momentum of the whole plasma-wall system. The direction of the net torque on the plasma is always opposite to the real frequency of the mode, agreeing with the analytic result by Pustovitov [Nucl. Fusion 47, 1583 (2007)]. When the wall time is close to the oscillating time of the tearing mode, the finite net torque reaches its maximum. Without wall or with an ideal wall, no net torque on the static plasma is generated by the tearing mode. However, re-distribution of the torque density in the resistive layer still occurs.

  14. Resistive wall tearing mode generated finite net electromagnetic torque in a static plasma

    SciTech Connect

    Hao, G. Z. Wang, A. K.; Xu, M.; Qu, H. P.; Peng, X. D.; Wang, Z. H.; Xu, J. Q.; Qiu, X. M.; Liu, Y. Q.

    2014-01-15

    The MARS-F code [Y. Q. Liu et al., Phys. Plasmas 7, 3681 (2000)] is applied to numerically investigate the effect of the plasma pressure on the tearing mode stability as well as the tearing mode-induced electromagnetic torque, in the presence of a resistive wall. The tearing mode with a complex eigenvalue, resulted from the favorable averaged curvature effect [A. H. Glasser et al., Phys. Fluids 18, 875 (1975)], leads to a re-distribution of the electromagnetic torque with multiple peaking in the immediate vicinity of the resistive layer. The multiple peaking is often caused by the sound wave resonances. In the presence of a resistive wall surrounding the plasma, a rotating tearing mode can generate a finite net electromagnetic torque acting on the static plasma column. Meanwhile, an equal but opposite torque is generated in the resistive wall, thus conserving the total momentum of the whole plasma-wall system. The direction of the net torque on the plasma is always opposite to the real frequency of the mode, agreeing with the analytic result by Pustovitov [Nucl. Fusion 47, 1583 (2007)]. When the wall time is close to the oscillating time of the tearing mode, the finite net torque reaches its maximum. Without wall or with an ideal wall, no net torque on the static plasma is generated by the tearing mode. However, re-distribution of the torque density in the resistive layer still occurs.

  15. Generation of Shock-Wave Disturbances at Plasma-Vapor Bubble Oscillation

    NASA Astrophysics Data System (ADS)

    Kuznetsova, N. S.; Yudin, A. S.; Voitenko, N. V.

    2015-11-01

    The complex physical and mathematical model describing all steps of plasma-vapor bubble evolution in the system of the water-ground condensed media is presented. Discharge circuit operation, discharge plasma channel expansion, its transformation into the vapor-plasma bubble and its pulsation, pressure wave generation and propagation of the mechanical stress waves in the ground are self-consistently considered in the model. The model allows investigation of the basic laws of stored energy transformation into the discharge plasma channel, next to the plasma-vapor bubble and transformation of this energy to the energy of pressure wave compressing the surrounding ground. Power characteristics of wave disturbances generated by gas-vapor bubble oscillation in liquid depending on the circuit parameters are analyzed for the prediction of the ground boundary displacement. The dynamics of the shock-wave propagation in water-ground condensed media depending on the rate of the plasma channel energy release is investigated. Simulation of the shock-wave phenomena at a plasma-vapor bubble oscillation in condensed media consecutively describes the physical processes underlying technology for producing piles by electro-discharge stuffing. The quantitative model verified by physical experimental tests will allow optimization of pulse generator parameters and electrode system construction of high-voltage equipment.

  16. Research progress on ionic plasmas generated in an intense hydrogen negative ion source

    SciTech Connect

    Takeiri, Y. Tsumori, K.; Nagaoka, K.; Kaneko, O.; Ikeda, K.; Nakano, H.; Kisaki, M.; Tokuzawa, T.; Osakabe, M.; Kondo, T.; Sato, M.; Shibuya, M.; Komada, S.; Sekiguchi, H.; Geng, S.

    2015-04-08

    Characteristics of ionic plasmas, observed in a high-density hydrogen negative ion source, are investigated with a multi-diagnostics system. The ionic plasma, which consists of hydrogen positive- and negative-ions with a significantly low-density of electrons, is generated in the ion extraction region, from which the negative ions are extracted through the plasma grid. The negative ion density, i.e., the ionic plasma density, as high as the order of 1×10{sup 17}m{sup −3}, is measured with cavity ring-down spectroscopy, while the electron density is lower than 1×10{sup 16}m{sup −3}, which is confirmed with millimeter-wave interferometer. Reduction of the negative ion density is observed at the negative ion extraction, and at that time the electron flow into the ionic plasma region is observed to conserve the charge neutrality. Distribution of the plasma potential is measured in the extraction region in the direction normal to the plasma grid surface with a Langmuir probe, and the results suggest that the sheath is formed at the plasma boundary to the plasma grid to which the bias voltage is applied. The beam extraction should drive the negative ion transport in the ionic plasma across the sheath formed on the extraction surface. Larger reduction of the negative ions at the beam extraction is observed in a region above the extraction aperture on the plasma grid, which is confirmed with 2D image measurement of the Hα emission and cavity ring-down spectroscopy. The electron distribution is also measured near the plasma grid surface. These various properties observed in the ionic plasma are discussed.

  17. Radiatively cooled supersonic plasma jets generated in wire array Z-pinches

    NASA Astrophysics Data System (ADS)

    Bland, Simon; Lebedev, Sergey; Chittenden, Jerry; Beg, F. N.; Ciardi, A.; Haines, M. G.

    2000-10-01

    We will present experiments on the generation of a highly supersonic plasma jet by a convergent plasma flow, produced by electrodynamic acceleration of plasma in a conical array of fine metallic wires (a modification of the wire array Z-pinch [1]). Stagnation of the plasma flow on the axis of symmetry forms a standing conical shock, which effectively collimates the flow in the axial direction. This scenario is essentially similar to that discussed by Cantó et al. [2] as a possible, purely hydrodynamic mechanism of jet formation in young stellar objects. Experiments using different materials (Al, Fe and W) show that a highly supersonic (M 20) and a well-collimated jet is generated when the radiative cooling rate of the plasma is significant. The interaction of this jet with a plasma target could be used for scaled [3] laboratory astrophysical experiments on hydrodynamic instabilities in decelerated plasma flow. [1] M.K. Matzen, Phys. Plasmas v.4, 1519 (1997) [2] J. Cantó, et. al. Astron. Astrophys. v.192, 287 (1994). [3] D. Ryutov et al., ApJ, v.518, 821 (1999)

  18. Fast camera studies at an electron cyclotron resonance table plasma generator

    SciTech Connect

    Rácz, R.; Biri, S.

    2014-02-15

    A simple table-size ECR plasma generator operates in the ATOMKI without axial magnetic trap and without any particle extraction tool. Radial plasma confinement is ensured by a NdFeB hexapole. The table-top ECR is a simplified version of the 14 GHz ATOMKI-ECRIS. Plasma diagnostics experiments are planned to be performed at this device before installing the measurement setting at the “big” ECRIS. Recently, the plasma generator has been operated in pulsed RF mode in order to investigate the time evolution of the ECR plasma in two different ways. (1) The visible light radiation emitted by the plasma was investigated by the frames of a fast camera images with 1 ms temporal resolution. Since the visible light photographs are in strong correlation with the two-dimensional spatial distribution of the cold electron components of the plasma it can be important to understand better the transient processes just after the breakdown and just after the glow. (2) The time-resolved ion current on a specially shaped electrode was measured simultaneously in order to compare it with the visible light photographs. The response of the plasma was detected by changing some external setting parameters (gas pressure and microwave power) and was described in this paper.

  19. Self-consistent modeling of radio-frequency plasma generation in stellarators

    SciTech Connect

    Moiseenko, V. E. Stadnik, Yu. S.; Lysoivan, A. I.; Korovin, V. B.

    2013-11-15

    A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

  20. The role of plasma slowdown in the generation of Rhea's Alfvén wings

    NASA Astrophysics Data System (ADS)

    Khurana, Krishan K.; Fatemi, Shahab; Lindkvist, Jesper; Roussos, Elias; Krupp, Norbert; Holmström, Mats; Russell, Christopher T.; Dougherty, Michele K.

    2017-02-01

    Alfvén wings are known to form when a conducting or mass-loading object slows down a flowing plasma in its vicinity. Alfvén wings are not expected to be generated when an inert moon such as Rhea interacts with Saturn's magnetosphere, where the plasma impacting the moon is absorbed and the magnetic flux passes unimpeded through the moon. However, in two close polar passes of Rhea, Cassini clearly observed magnetic field signatures consistent with Alfvén wings. In addition, observations from a high-inclination flyby (Distance > 100 RRh) of Rhea on 3 June 2010 showed that the Alfvén wings continue to propagate away from Rhea even at this large distance. We have performed three-dimensional hybrid simulations of Rhea's interaction with Saturn's magnetosphere which show that the wake refilling process generates a plasma density gradient directed in the direction of corotating plasma. The resulting plasma pressure gradient exerts a force directed toward Rhea and slows down the plasma streaming into the wake along field lines. As on the same field lines, outside of the wake, the plasma continues to move close to its full speed, this differential motion of plasma bends the magnetic flux tubes, generating Alfvén wings in the wake. The current system excited by the Alfvén wings transfers momentum to the wake plasma extracting it from plasma outside the wake. Our work demonstrates that Alfvén wings can be excited even when a moon does not possess a conducting exosphere.

  1. A simplified analytic form for generation of axisymmetric plasma boundaries

    NASA Astrophysics Data System (ADS)

    Luce, T. C.

    2017-04-01

    An improved method has been formulated for generating analytic boundary shapes as input for axisymmetric MHD equilibria. This method uses the family of superellipses as the basis function, as previously introduced. The improvements are a simplified notation, reduction of the number of simultaneous nonlinear equations to be solved, and the realization that not all combinations of input parameters admit a solution to the nonlinear constraint equations. The method tests for the existence of a self-consistent solution and, when no solution exists, it uses a deterministic method to find a nearby solution. Examples of generation of boundaries, including tests with an equilibrium solver, are given.

  2. Structure and behavior of human α-thrombin upon ligand recognition: thermodynamic and molecular dynamics studies.

    PubMed

    Silva, Vivian de Almeira; Cargnelutti, Maria Thereza; Giesel, Guilherme M; Palmieri, Leonardo C; Monteiro, Robson Q; Verli, Hugo; Lima, Luis Mauricio T R

    2011-01-01

    Thrombin is a serine proteinase that plays a fundamental role in coagulation. In this study, we address the effects of ligand site recognition by alpha-thrombin on conformation and energetics in solution. Active site occupation induces large changes in secondary structure content in thrombin as shown by circular dichroism. Thrombin-D-Phe-Pro-Arg-chloromethyl ketone (PPACK) exhibits enhanced equilibrium and kinetic stability compared to free thrombin, whose difference is rooted in the unfolding step. Small-angle X-ray scattering (SAXS) measurements in solution reveal an overall similarity in the molecular envelope of thrombin and thrombin-PPACK, which differs from the crystal structure of thrombin. Molecular dynamics simulations performed with thrombin lead to different conformations than the one observed in the crystal structure. These data shed light on the diversity of thrombin conformers not previously observed in crystal structures with distinguished catalytic and conformational behaviors, which might have direct implications on novel strategies to design direct thrombin inhibitors.

  3. Toward understanding allosteric activation of thrombin: a conjecture for important roles of unbound Na(+) molecules around thrombin.

    PubMed

    Kurisaki, Ikuo; Takayanagi, Masayoshi; Nagaoka, Masataka

    2015-03-05

    We shed light on important roles of unbound Na(+) molecules in enzymatic activation of thrombin. Molecular mechanism of Na(+)-activation of thrombin has been discussed in the context of allostery. However, the recent challenge to redesign K(+)-activated thrombin revealed that the allosteric interaction is insufficient to explain the mechanism. Under these circumstances, we have examined the roles of unbound Na(+) molecule in maximization of thrombin-substrate association reaction rate. We performed all-atomic molecular dynamics (MD) simulations of thrombin in the presence of three different cations; Li(+), Na(+), and Cs(+). Although these cations are commonly observed in the vicinity of the S1-pocket of thrombin, smaller cations are distributed more densely and extensively than larger ones. This suggests the two observation rules: (i) thrombin surrounded by Na(+) is at an advantage in the initial step of association reaction, namely, the formation of an encounter complex ensemble, and (ii) the presence of Na(+) molecules does not necessarily have an advantage in the final step of association reaction, namely, the formation of the stereospecific complex. In conclusion, we propose a conjecture that unbound Na(+) molecules also affect the maximization of rate constant of thrombin-substrate association reaction through optimally forming an encounter complex ensemble.

  4. Intense terahertz-pulse generation by four-wave mixing process in induced gas plasma

    NASA Astrophysics Data System (ADS)

    Wicharn, S.; Buranasiri, P.

    2015-08-01

    In this article, we have numerically investigated an intense terahertz (THz) pulses generation in gaseous plasma based on the third-order nonlinear effect, four-wave mixing rectification (FWMR). We have proposed that the fundamental fields and second-harmonic field of ultra-short pulse lasers are combined and focused into a very small gas chamber to induce a gaseous plasma, which intense THz pulse is produced. To understand the THz generation process, the first-order multiple-scale perturbation method (MSPM) has been utilized to derive a set of nonlinear coupled-mode equations for interacting fields such as two fundamental fields, a second-harmonic field, and a THz field. Then, we have simulate the intense THz-pulse generation by using split step-beam propagation method (SS-BPM) and calculated output THz intensities. Finally, the output THz intensities generated from induced air, nitrogen, and argon plasma have been compared.

  5. New approaches for the reduction of plasma arc drop in second-generation thermionic converters

    NASA Astrophysics Data System (ADS)

    Hatziprokopiou, M. E.; Shaw, D. T.

    1981-03-01

    Investigations of ion generation and recombination mechanisms in the cesium plasma are described with respect to the advanced mode thermionic energy converter. The changes in plasma density and temperature within the converter were studied under the influence of several promising auxiliary ionization candidate sources. Three novel approaches of external cesium ion generation were studied in some detail, namely vibrationally excited N2 as an energy source of ionization of Cs ions in a dc discharge, microwave power as a means of resonant sustenance of the cesium plasma, and ion generation in a pulse N2-Cs mixture. The data obtained show that all three techniques - i.e., the non-LTE high voltage pulsing, the energy transfer from vibrationally excited diatomic gases, and the external pumping with a microwave power have considerable promise as schemes in auxiliary ion generation applicable to the advanced thermionic energy converter.

  6. Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probe.

    PubMed

    Schmitzer, C; Kronberger, M; Lettry, J; Sanchez-Arias, J; Störi, H

    2012-02-01

    The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H(-) volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e(-) and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H(-) ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H(-) ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

  7. Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probea)

    NASA Astrophysics Data System (ADS)

    Schmitzer, C.; Kronberger, M.; Lettry, J.; Sanchez-Arias, J.; Störi, H.

    2012-02-01

    The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H- volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e- and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H- ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H- ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

  8. Two-Color Laser High-Harmonic Generation in Cavitated Plasma Wakefields

    SciTech Connect

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

    2016-10-03

    A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highly-stripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

  9. Second harmonic generation of Cosh-Gaussian laser beam in collisional plasma with nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Singh, Navpreet; Gupta, Naveen; Singh, Arvinder

    2016-12-01

    This paper investigates second harmonic generation (SHG) of an intense Cosh-Gaussian (ChG) laser beam propagating through a preformed underdense collisional plasma with nonlinear absorption. Nonuniform heating of plasma electrons takes place due to the nonuniform irradiance of intensity along the wavefront of laser beam. This nonuniform heating of plasma leads to the self-focusing of the laser beam and thus produces strong density gradients in the transverse direction. The density gradients so generated excite an electron plasma wave (EPW) at pump frequency that interacts with the pump beam to produce its second harmonics. To envision the propagation dynamics of the ChG laser beam, moment theory in Wentzel-Kramers-Brillouin (W.K.B) approximation has been invoked. The effects of nonlinear absorption on self-focusing of the laser beam as well as on the conversion efficiency of its second harmonics have been theoretically investigated.

  10. Generation of a longitudinal current upon interaction of a transverse electromagnetic wave with degenerate plasma

    NASA Astrophysics Data System (ADS)

    Latyshev, A. V.; Yushkanov, A. A.

    2017-02-01

    We consider degenerate plasma that is located in the field of a transverse electromagnetic wave. An electric current generated in the plasma by the electromagnetic field is sought. During classical description of the interaction of the electromagnetic wave with the plasma, the Vlasov kinetic equation is used, while, in quantum description, the quantum kinetic equation with the Wigner integral is applied. A nonlinear analysis has shown that that the electric current in the plasma has two nonzero components. One component of the electric current is directed along the vector potential of the electromagnetic field. The other nonzero component of the current is directed along the wave vector. In the present work, we analyze this component of the electric current. The case of collisionless plasma is examined.

  11. Comparison Between Dust Particle Generation In CH4 or CH4/N2 Mixing RF Plasmas

    SciTech Connect

    Pereira, Jeremy; Massereau-Guilbaud, Veronique; Geraud-Grenier, Isabelle; Plain, Andre

    2005-10-31

    Dust particles have been spontaneously generated either in pure CH4 or in CH4/N2 r.f. plasmas. The dust particle formation results from homogeneous nucleation in the plasma and is detected by laser light scattering (Ar+, {lambda} = 514.5 nm). The temporal and spatial behaviour of dust particles is studied. In pure methane gas, particles are trapped in well defined clouds at the plasma sheath boundaries. In a CH4/N2 mixture, the nitrogen addition leads to an expansion of the clouds. For nitrogen contents higher than 50%, the space between the electrodes is nearly completely filled with dust particles leading to plasma instabilities and a void appears in the center of the discharge. The particles are spherical with diameters in the range 0.8-2 {mu}m. For nitrogen-rich plasmas, the particles growth is improved and leads to a rough shape with an orange-peel-type surface texture.

  12. Characteristics of the NASA Lewis bumpy-torus plasma generated with positive applied potentials

    NASA Technical Reports Server (NTRS)

    Roth, J. R.; Gerdin, G. A.; Richardson, R. W.

    1976-01-01

    Experimental observations were made during steady-state operation of a bumpy-torus plasma at input powers up to 150 kW in deuterium and helium gas and with positive potentials applied to the midplane electrodes. In this steady-state ion heating method a modified Penning discharge is operated such that the plasma is acted upon by a combination of strong electric and magnetic fields. Experimental investigation of a deuterium plasma revealed electron temperatures from 14 to 140 eV and ion kinetic temperatures from 160 to 1785 eV. At least two distinct modes of operation exist. Experimental data shows that the average ion residence time in the plasma is virtually independent of the magnetic field strength. Data was taken when all 12 anode rings were at high voltage, and in other symmetric configurations in which the toroidal plasma was generated by applying positive potentials to six anode rings, three anode rings, and a single anode ring.

  13. Exogenous nitric oxide (NO) generated by NO-plasma treatment modulates osteoprogenitor cells early differentiation

    NASA Astrophysics Data System (ADS)

    Elsaadany, Mostafa; Subramanian, Gayathri; Ayan, Halim; Yildirim-Ayan, Eda

    2015-09-01

    In this study, we investigated whether nitric oxide (NO) generated using a non-thermal plasma system can mediate osteoblastic differentiation of osteoprogenitor cells without creating toxicity. Our objective was to create an NO delivery mechanism using NO-dielectric barrier discharge (DBD) plasma that can generate and transport NO with controlled concentration to the area of interest to regulate osteoprogenitor cell activity. We built a non-thermal atmospheric pressure DBD plasma nozzle system based on our previously published design and similar designs in the literature. The electrical and spectral analyses demonstrated that N2 dissociated into NO under typical DBD voltage-current characteristics. We treated osteoprogenitor cells (MC3T3-E1) using NO-plasma treatment system. Our results demonstrated that we could control NO concentration within cell culture media and could introduce NO into the intracellular space using NO-plasma treatment with various treatment times. We confirmed that NO-plasma treatment maintained cell viability and did not create any toxicity even with prolonged treatment durations. Finally, we demonstrated that NO-plasma treatment induced early osteogenic differentiation in the absence of pro-osteogenic growth factors/proteins. These findings suggest that through the NO-plasma treatment system we are able to generate and transport tissue-specific amounts of NO to an area of interest to mediate osteoprogenitor cell activity without subsequent toxicity. This opens up the possibility to develop DBD plasma-assisted tissue-specific NO delivery strategies for therapeutic intervention in the prevention and treatment of bone diseases.

  14. High Power, Solid-State RF Generation for Plasma Heating

    NASA Astrophysics Data System (ADS)

    Prager, James; Ziemba, Timothy; Miller, Kenneth; Pierren, Chris

    2016-10-01

    Radio Frequency heating systems are rarely used by the small-scale validation platform experiments due to the high cost and complexity of these systems. Eagle Harbor Technologies (EHT), Inc. is developing an all-solid-state RF plasma heating system that uses EHT's nanosecond pulser technology in an inductive adder configuration to drive nonlinear transmission lines (NLTL). The system under development does not require the use of vacuum tube technology, is inherently lower cost, and is more robust than traditional high power RF heating schemes. The inductive adder can produce 0 to20 kV pulses into 50 Ohms with sub-10 ns rise times. The inductive adder has been used to drive NLTLs near 2 GHz with other frequencies to be tested in the future. EHT will present experimental results, including RF measurements with D-dot probes and capacitve voltage probes. During this program, EHT will test the system on Helicity Injected Torus at the University of Washington and the High Beta Tokamak at Columbia University.

  15. Simulation of terahertz generation in corrugated plasma waveguides.

    PubMed

    Pearson, Andrew J; Palastro, John; Antonsen, Thomas M

    2011-05-01

    We simulate the response of a corrugated plasma channel to an ultrashort laser pulse in two dimensions with the goal of demonstrating the production of terahertz frequency electromagnetic modes. Corrugated channels support electromagnetic modes that have a Floquet-type dispersion relation and thus consist of a sum of spatial harmonics with subluminal phase velocities. This allows the possibility of phase matching between the ponderomotive potential associated with the laser pulse and the electromagnetic modes of the channel. Since the bandwidth of an ultrashort pulse includes terahertz frequencies, significant excitation of terahertz radiation is possible. Here we consider realistic density profiles to obtain predictions of the terahertz power output and mode structure for a channel with periodic boundary conditions. We then estimate pulse depletion effects from our simulation results. The fraction of laser energy converted to terahertz is independent of laser pulse energy in the linear regime, and we find it to be around 1%. Extrapolating to a pulse energy of 0.5 J gives a terahertz power output of 6 mJ with a pulse depletion length of less than 20 cm.

  16. Modelling Of Generation And Growth Of Nanoparticles In Low-Pressure Plasmas

    SciTech Connect

    Gordiets, B. F.

    2008-09-07

    Theoretical kinetic models of generation and growth of clusters and nanoparticles in low-pressure plasma are briefly rewired. The relatively simple kinetic model is discussed more detail. Simple formulas and equations are given for monomer density; cluster dimension distribution; critical cluster dimension; rate of particle production; particle density and average dimension as well as plasma characteristics. The analytical formula is also obtained for the time delay of the measured LIPEE signal in the 'Laser Induced Particle Explosive Evaporation' experimental method.

  17. Scaled-Up Nonequilibrium Air Plasmas Generated by DC and Pulsed Discharges

    DTIC Science & Technology

    2010-09-08

    scalability of nonequilibrium plasmas produced by electrical discharges in atmospheric pressure air. Both DC and repetitively pulsed discharges ...Key results demonstrate that both DC glow discharge and pulsed transient spark generate air plasmas of required parameters. Glow discharge is easier...Corona discharge as a temperature probe was developed to diagnose the microwave torch preheated air. A new concept of the DC-driven pulsed

  18. Microwave Plasma Based Single-Step Method for Generation of Carbon Nanostructures

    DTIC Science & Technology

    2013-07-01

    31st ICPIG, July 14-19, 2013, Granada, Spain Microwave plasma based single-step method for generation of carbon nanostructures A. Dias 1 , E...Nowadays, carbon based two-dimensional (2D) nanostructures are one of the ongoing strategic research areas in science and technology. Graphene, an...fabrication, to obtain transferable sheets [1]. A plasma based method to synthesize substrate free, i.e., “free–standing” graphene at ambient conditions has

  19. Improvement of the lifetime of radio frequency antenna for plasma generation

    SciTech Connect

    Reijonen, J.; Eardley, M.; Gough, R.; Keller, R.; Leung, K.; Thomae, R.; Pickard, D.; Williams, M. D.

    2000-02-01

    At Lawrence Berkeley National Laboratory different antenna protection schemes have been investigated for the radio frequency-driven multicusp ion source. It was found that the antenna lifetime can be greatly enhanced by an additional shielding, which consists of porcelain, quartz or boron nitride. Different antenna configurations and their influence on the plasma generation will be discussed. Antenna life time greater than 500 hours continuous wave operation has been demonstrated in hydrogen plasma using a novel quartz antenna design. (c)

  20. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2002-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime, high frequency, high power bursts of low-duty factor microwaves sufficient to generate a plasma discharge and passing a gas to be treated through the discharge so as to cause dissociative reduction of the exhaust gases and enhanced catalyst reactivity through application of the pulsed microwave fields directly to the catalyst material sufficient to cause a polarizability catastrophe and enhanced heating of the metal crystallite particles of the catalyst, and in the presence or absence of the plasma. The invention also includes a reactor for aftertreatment of exhaust gases.

  1. Low Temperature Plasmas Generated and Sustained Indefinitely Using a Focused Microwave Beam

    NASA Astrophysics Data System (ADS)

    Reid, Remington; Hoff, Brad; Lepell, Paul; AFRL Team

    2016-10-01

    The Air Force Research Laboratory has constructed a device that can initiate a plasma discharge in a focused microwave beam and sustain it indefinitely. A 10 kW, 4.5 GHz beam is passed through a vacuum chamber outfitted with pressure windows that are transparent to 4.5 GHz radiation. The pressure windows are large enough in diameter to prevent any interactions between the beam and the metallic chamber. The entire experiment is housed inside an anechoic chamber to minimize reflections. This novel plasma source generates low temperature, low density plasmas that have no contact with the walls which minimizes contamination and sheath formation.

  2. Generating vorticity and magnetic fields in plasmas in general relativity: Spacetime curvature drive

    SciTech Connect

    Asenjo, Felipe A.; Mahajan, Swadesh M.; Qadir, Asghar

    2013-02-15

    Using the generally covariant magnetofluid formalism for a hot plasma, a spacetime curvature driven mechanism for generating seed vorticity/magnetic field is presented. The 'battery' owes its origin to the interaction between the gravity modified Lorentz factor of the fluid element and the inhomogeneous plasma thermodynamics. The general relativistic drive is evaluated for two simple cases: seed formation in a simplified model of a hot plasma accreting in stable orbits around a Schwarzschild black hole and for particles in free fall near the horizon. Some astrophysical applications are suggested.

  3. Characteristic measurements of silicon dioxide aerogel plasmas generated in a Planckian radiation environment

    SciTech Connect

    Dong Quanli; Wang Shoujun; Li Yutong; Zhang Yi; Zhao Jing; Wei Huigang; Shi Jianrong; Zhao Gang; Zhang Jiyan; Gu Yuqiu; Ding Yongkun; Wen Tianshu; Zhang Wenhai; Hu Xin; Liu Shenye; Zhang Lin; Tang Yongjian; Zhang Baohan; Zheng Zhijian; Nishimura, Hiroaki

    2010-01-15

    The temporally and spatially resolved characteristics of silicon dioxide aerogel plasmas were studied using x-ray spectroscopy. The plasma was generated in the near-Planckian radiation environment within gold hohlraum targets irradiated by laser pulses with a total energy of 2.4 kJ in 1 ns. The contributions of silicon ions at different charge states to the specific components of the measured absorption spectra were also investigated. It was found that each main feature in the absorption spectra of the measured silicon dioxide aerogel plasmas was contributed by two neighboring silicon ionic species.

  4. NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK

    SciTech Connect

    WALKER, ML; FERRON, JR; HUMPHREYS, DA; JOHNSON, RD; LEUER, JA; PENAFLOR, BG; PIGLOWSKI, DA; ARIOLA, M; PIRONTI, A; SCHUSTER, E

    2002-10-01

    OAK A271 NEXT-GENERATION PLASMA CONTROL IN THE DIII-D TOKAMAK. The advanced tokamak (AT) operating mode which is the principal focus of the DIII-D tokamak requires highly integrated and complex plasma control. Simultaneous high performance regulation of the plasma boundary and internal profiles requires multivariable control techniques to account for the highly coupled influences of equilibrium shape, profile, and stability control. This paper describes progress towards the DIII-D At mission goal through both significantly improved real-time computational hardware and control algorithm capability.

  5. Broadband radio frequency plasma generation in a Penning-Malmberg trap

    NASA Astrophysics Data System (ADS)

    Paroli, B.; De Luca, F.; Maero, G.; Pozzoli, R.; Romé, M.

    2010-08-01

    Plasma generation is observed in a cylindrical Penning-Malmberg trap in the ultra-high vacuum pressure regime for a large bandwidth of low-power radio frequency (RF) excitations. The process of plasma formation is investigated by measuring the density profiles and a simplified model is developed to characterize the electron heating mechanism. The total charge confined at equilibrium is systematically studied for RF drives in the 0.1-20 MHz range and with different geometrical configurations. With electron densities of some 106 cm-3 at least, the scheme represents an alternative source of non-neutral plasmas for Penning-Malmberg traps.

  6. Effect of resveratrol, a natural polyphenolic compound, on platelet activation induced by endotoxin or thrombin.

    PubMed

    Olas, Beata; Wachowicz, Barbara; Saluk-Juszczak, Joanna; Zieliński, Tomasz

    2002-08-15

    Resveratrol (3, 4', 5-trihydroxystilbene), a natural polyphenol, is found in some plants that are used in human nutrition. Grapes are a major source for resveratrol, and a significant amount can also be found in red wine. Several experimental studies have demonstrated biological properties of resveratrol, especially its anti-inflammatory, antioxidant, anti-platelet and antitumor effects. In the present study, we investigated the first step of platelet activation-platelet adhesion stimulated by lipopolysaccharide (LPS) from Proteus mirabilis (weak stimulator) and thrombin (strong activator) in the presence of resveratrol. Our studies show that endotoxin (0.3 microg/10(8) platelets), like thrombin (0.2 U/10(8) platelets), induced the adhesion of platelets (expressed as absorbance of cell attached proteins) to collagen and fibrinogen. Preincubation of washed platelets with resveratrol at physiological plasma concentrations (25-100 microg/ml, 30 min, 37 degrees C) had an inhibitory effect on adhesion of platelets to collagen after activation by LPS alone or LPS with thrombin. The strongest effect on this process was caused by resveratrol at the concentration of 100 microg/ml. Pretreatment of platelets with resveratrol (25-100 microg/ml, 30 min, 37 degrees C) had also inhibitory effects on adhesion of platelets to fibrinogen after stimulation of these cells by LPS alone or by LPS with thrombin at the same concentration. In conclusion, we suggest that resveratrol present in human diet may be an important compound responsible for the reduction of platelet adhesion and changed reactivity of blood platelets in inflammatory process.

  7. APTAMER-BASED SERRS SENSOR FOR THROMBIN DETECTION

    SciTech Connect

    Cho, H; Baker, B R; Wachsmann-Hogiu, S; Pagba, C V; Laurence, T A; Lane, S M; Lee, L P; Tok, J B

    2008-07-02

    We describe an aptamer-based Surface Enhanced Resonance Raman Scattering (SERRS) sensor with high sensitivity, specificity, and stability for the detection of a coagulation protein, human a-thrombin. The sensor achieves high sensitivity and a limit of detection of 100 pM by monitoring the SERRS signal change upon the single step of thrombin binding to immobilized thrombin binding aptamer. The selectivity of the sensor is demonstrated by the specific discrimination of thrombin from other protein analytes. The specific recognition and binding of thrombin by the thrombin binding aptamer is essential to the mechanism of the aptamer-based sensor, as shown through measurements using negative control oligonucleotides. In addition, the sensor can detect 1 nM thrombin in the presence of complex biofluids, such as 10% fetal calf serum, demonstrating that the immobilized, 5{prime}-capped, 3{prime}-capped aptamer is sufficiently robust for clinical diagnostic applications. Furthermore, the proposed sensor may be implemented for multiplexed detection using different aptamer-Raman probe complexes.

  8. S-Duct Engine Inlet Flow Control Using SDBD Plasma Streamwise Vortex Generators

    NASA Astrophysics Data System (ADS)

    Kelley, Christopher; He, Chuan; Corke, Thomas

    2009-11-01

    The results of a numerical simulation and experiment characterizing the performance of plasma streamwise vortex generators in controlling separation and secondary flow within a serpentine, diffusing duct are presented. A no flow control case is first run to check agreement of location of separation, development of secondary flow, and total pressure recovery between the experiment and numerical results. Upon validation, passive vane-type vortex generators and plasma streamwise vortex generators are implemented to increase total pressure recovery and reduce flow distortion at the aerodynamic interface plane: the exit of the S-duct. Total pressure recovery is found experimentally with a pitot probe rake assembly at the aerodynamic interface plane. Stagnation pressure distortion descriptors are also presented to show the performance increase with plasma streamwise vortex generators in comparison to the baseline no flow control case. These performance parameters show that streamwise plasma vortex generators are an effective alternative to vane-type vortex generators in total pressure recovery and total pressure distortion reduction in S-duct inlets.

  9. Investigation on plasma generated during hypervelocity impact at different impact velocities and angles

    SciTech Connect

    Song, Weidong Lv, Yangtao; Wang, Cheng; Li, Jianqiao

    2015-12-15

    A 3D Smoothed Particle Hydrodynamics code was developed to investigate plasma generation by considering a chemical reaction process in hypervelocity impacts of an aluminum projectile on an aluminum target. The chemical reaction process was described by the reaction rate based on the Arrhenius equation and used to calculate the plasma generation during the impact simulation. The predicted result was verified by empirical formulas and a new empirical formula was proposed based on the comparisons and analyses. The influence of the impact angle was discussed for different impact velocities. Then, the application of both the new and original empirical formulas for protection design from plasma generated by hypervelocity impact was discussed, which demonstrated that the code and model were useful in the prediction of hypervelocity impacts on spacecraft.

  10. Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror.

    PubMed

    Chen, Zi-Yu; Pukhov, Alexander

    2016-08-17

    Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser-plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser-plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications.

  11. Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror

    PubMed Central

    Chen, Zi-Yu; Pukhov, Alexander

    2016-01-01

    Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser–plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser–plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047

  12. Plasma wave generation near the inner heliospheric shock

    NASA Technical Reports Server (NTRS)

    Macek, W. M.; Cairns, I. H.; Kurth, W. S.; Gurnett, D. A.

    1991-01-01

    There is mounting evidence that the Voyager 1 and 2 and Pioneer 11 spacecraft may approach the inner (termination) heliospheric shock near the end of this century. It is argued here, by analogy with planetary bow shocks, that energetic electrons backstreaming from the heliospheric shock along the magnetic field should be unstable to the generation of Langmuir waves by the electron beam instability. Analytic expressions for the cutoff velocity, corresponding to the beam speed of the electrons backstreaming from the shock, are derived for a standard solar wind model. At the front side of the heliosphere the maximum beam velocity is expected to be at the meridian passing through the nose of the shock, which is assumed to be aligned with the Very Local Inter-Stellar Medium flow. This foreshock region and the associated Langmuir waves are relevant to both the expected in situ observations of the heliospheric boundaries, and to the low-frequency (2-3 kHz) radio emissions observed by the Voyager spacecraft in the outer heliosphere. Provided that these radio emissions are generated by Langmuir waves, the minimum Langmuir wave electric fields at the remote source are estimated to be greater than about 3 - 30 microV/m.

  13. Second harmonic generation by self-focusing of intense hollow Gaussian laser beam in collisionless plasma

    SciTech Connect

    Purohit, Gunjan Rawat, Priyanka; Gauniyal, Rakhi

    2016-01-15

    The effect of self focused hollow Gaussian laser beam (HGLB) (carrying null intensity in center) on the excitation of electron plasma wave (EPW) and second harmonic generation (SHG) has been investigated in collisionless plasma, where relativistic-ponderomotive and only relativistic nonlinearities are operative. The relativistic change of electron mass and the modification of the background electron density due to ponderomotive nonlinearity lead to self-focusing of HGLB in plasma. Paraxial ray theory has been used to derive coupled equations for the self focusing of HGLB in plasma, generation of EPW, and second harmonic. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, electric field associated with the excited EPW, and the power of SHG. Second harmonic emission is generated due to nonlinear coupling between incident HGLB and EPW satisfying the proper phase matching conditions. The results show that the effect of including the ponderomotive nonlinearity is significant on the generation of EPW and second harmonic. The electric field associated with EPW and the power of SHG are found to be highly sensitive to the order of the hollow Gaussian beam.

  14. Second harmonic generation by self-focusing of intense hollow Gaussian laser beam in collisionless plasma

    NASA Astrophysics Data System (ADS)

    Purohit, Gunjan; Rawat, Priyanka; Gauniyal, Rakhi

    2016-01-01

    The effect of self focused hollow Gaussian laser beam (HGLB) (carrying null intensity in center) on the excitation of electron plasma wave (EPW) and second harmonic generation (SHG) has been investigated in collisionless plasma, where relativistic-ponderomotive and only relativistic nonlinearities are operative. The relativistic change of electron mass and the modification of the background electron density due to ponderomotive nonlinearity lead to self-focusing of HGLB in plasma. Paraxial ray theory has been used to derive coupled equations for the self focusing of HGLB in plasma, generation of EPW, and second harmonic. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, electric field associated with the excited EPW, and the power of SHG. Second harmonic emission is generated due to nonlinear coupling between incident HGLB and EPW satisfying the proper phase matching conditions. The results show that the effect of including the ponderomotive nonlinearity is significant on the generation of EPW and second harmonic. The electric field associated with EPW and the power of SHG are found to be highly sensitive to the order of the hollow Gaussian beam.

  15. On generation of dark solitons by gravitational waves in a strongly magnetized pulsar plasma

    SciTech Connect

    Mofiz, U. A.

    2007-11-15

    In this paper, the propagation of gravitational wave perpendicular to a superstrong magnetic field immersed in an electron-positron pulsar plasma is considered. On the basis of the Einstein-Maxwell system of magnetohydrodynamic equations, both the linear and nonlinear interactions of the wave with plasma are investigated. In near-resonant interaction, a relation between gravitation perturbations to electromagnetic field perturbations shows that the field perturbations are directly proportional to the product of ambient magnetic field and the gravitational wave perturbation. Thus, a weak gravitational wave may resonate an effective field perturbation in the strongly magnetized plasma in an astrophysical context. A coupled system of equations describing the nonlinear interaction between gravitational wave and field perturbations in the magnetized plasma is obtained. The equations are solved in resonant approximation, and it is found that a linearly polarized electric field is generated with a frequency close to the plasma frequency. For nonresonant interaction, the solution shows that both electric and magnetic field perturbations in the plasma are produced. Density perturbation and field intensity variation in the plasma lead to a nonlinear frequency shift and the slowly varying field amplitude obeys the nonlinear Schroedinger equation. The solution of the equation is the dark soliton, the amplitude of which may be very significant in the case of a superstrong magnetic field in the pulsar plasma.

  16. Bacithrocins A, B and C, novel thrombin inhibitors.

    PubMed

    Kamiyama, T; Umino, T; Nakamura, Y; Itezono, Y; Sawairi, S; Satoh, T; Yokose, K

    1994-09-01

    Novel thrombin inhibitors, bacithrocins A, B and C, have been isolated from the culture broth of Bacillus laterosporus Laubach NR 2988. The structures of these inhibitors have been determined to be N-acyl-L-phenylalanyl-DL-arginal by the 2D-NMR experiments on their oxidation products and by amino acid analysis. Bacithrocin A inhibits thrombin, factor Xa and trypsin with IC50s of 48, 13 and 0.65 microM, respectively, which are similar to those of bacithrocins B and C. Bacithrocins prolong the clotting time induced by thrombin and factor Xa.

  17. High-current lanthanum-hexaboride electron emitter for a quasi-stationary arc plasma generator

    SciTech Connect

    Davydenko, V. I. Ivanov, A. A. Shul’zhenko, G. I.

    2015-11-15

    A high-current electron emitter on the basis of lanthanum hexaboride is developed for quasi-stationary arc plasma generators of ion sources. The emitter consists of a set of LaB{sub 6} washers interleaved with washers made of thermally extended graphite. The emitter is heated by the current flowing through the graphite washers. The thermal regime of emitter operation during plasma generation is considered. The emitter has been successfully used in the ion sources of the diagnostic injectors of fast hydrogen atomic beams.

  18. Generation of large sheet-like ionospheric plasma irregularities at Arecibo

    NASA Astrophysics Data System (ADS)

    Lee, M. C.; Riddolls, R. J.; Burke, W. J.; Sulzer, M. P.; Kuo, S. P.; Klien, E. M. C.

    Large-scale ionospheric plasma irregularities, generated by O-mode heater waves at Arecibo, are shown for the first time to have “sheet-like” structures. The irregularities are aligned with the magnetic meridional plane and have scale sizes ranging from a few hundred meters to a few kilometers. This interpretation is based on detailed considerations of sequential measurements of radar backscatter power, the controlling magnetic field geometry, and the deduced E × B plasma drift. The alignment of O-mode-generated irregularities with the magnetic meridional plane, and their disappearance during X-mode heating intervals are consistent with predictions of the thermal filamentation instability model.

  19. Maximizing the yield and cutoff of high-order harmonic generation from plasma plume

    SciTech Connect

    Ganeev, Rashid A.; Elouga Bom, Luc B.; Ozaki, Tsuneyuki; Redkin, Pavel V.

    2007-11-15

    We study high-order harmonic generation (HHG) from various lowly ionized laser plasmas. We study harmonic generation from targets of Al (Z=13) to Bi (Z=83). Varying the wavelength, chirp, and pulse duration of the femtosecond pump laser resulted in the change in the harmonic distribution, cutoff, and conversion efficiency of HHG. We also study the use of doubly charged ions, and resonances for some materials. We were able to obtain high HHG conversion efficiency and harmonic cutoff by implementing the above approaches and by observing the time-resolved spectra of the laser plasma.

  20. Experimental Observation of the Blob-Generation Mechanism from Interchange Waves in a Plasma

    SciTech Connect

    Furno, I.; Labit, B.; Podesta, M.; Fasoli, A.; Poli, F. M.; Ricci, P.; Theiler, C.; Brunner, S.; Diallo, A.; Graves, J.; Mueller, S. H.

    2008-02-08

    The mechanism for blob generation in a toroidal magnetized plasma is investigated using time-resolved measurements of two-dimensional structures of electron density, temperature, and plasma potential. The blobs are observed to form from a radially elongated structure that is sheared off by the ExB flow. The structure is generated by an interchange wave that increases in amplitude and extends radially in response to a decrease of the radial pressure scale length. The dependence of the blob amplitude upon the pressure radial scale length is discussed.

  1. Analysis and characterization of microwave plasma generated with rectangular all-dielectric resonators

    NASA Astrophysics Data System (ADS)

    Kourtzanidis, K.; Raja, L. L.

    2017-04-01

    We report on a computational modeling study of small scale plasma discharge formation with rectangular dielectric resonators (DR). An array of rectangular dielectric slabs, separated by a gap of millimeter dimensions is used to provide resonant response when illuminated by an incident wave of 1.26 GHz. A coupled electromagnetic (EM) wave–plasma model is used to describe the breakdown, early response and steady state of the argon discharge. We characterize the plasma generation with respect to the input power, background gas pressure and gap size. It is found that the plasma discharge is generated mainly inside the gaps between the DR at positions that correspond to the antinodes of the resonant enhanced electric field pattern. The enhancement of the electric field inside the gaps is due to a combination of leaking and displacement current radiation from the DR. The plasma is sustained in over-critical densities due to the large skin depth with respect to the gap and plasma size. Electron densities are calculated in the order of {10}18{--}{10}19 {{{m}}}-3 for a gas pressure of 10 Torr, while they exceed 1020 {{{m}}}-3 in atmospheric conditions. Increase of input power leads to more intense ionization and thus faster plasma formation and results to a more symmetric plasma pattern. For low background gas pressure the discharge is diffusive and extends away from the gap region while in high pressure it is constricted inside the gap. An optimal gap size can be found to provide maximum EM energy transfer to the plasma. This fact demonstrates that the gap size dictates to a certain extent the resonant frequency and the Q-factor of the dielectric array and the breakdown fields can not be determined in a straight-forward way but they are functions of the resonators geometry and incident field frequency.

  2. X-ray Generation in Strongly Nonlinear Plasma Waves

    NASA Astrophysics Data System (ADS)

    Kiselev, S.; Pukhov, A.; Kostyukov, I.

    2004-09-01

    We show that a laser wake field in the “bubble” regime [

    A. Pukhov and J. Meyer-ter-Vehn Appl. Phys. BAPBOEM0946-2171 74, 355 (2002)10.1007/s003400200795
    ], works as a compact high-brightness source of x-rays. The self-trapped relativistic electrons make betatron oscillations in the transverse fields of the bubble and emit a bright broadband x-ray radiation with a maximum about 50 keV. The emission is confined to a small angle of about 0.1 rad. In addition, we make simulations of x-ray generation by an external 28.5 GeV electron bunch injected into the bubble. γ quanta with up to GeV energies are observed in the simulation in good agreement with analytical results. The energy conversion is efficient, leading to a significant stopping of the electron bunch over 5 mm interaction distance.

  3. Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

    NASA Astrophysics Data System (ADS)

    van Helden, J. H.; Wagemans, W.; Yagci, G.; Zijlmans, R. A. B.; Schram, D. C.; Engeln, R.; Lombardi, G.; Stancu, G. D.; Röpcke, J.

    2007-02-01

    We investigated the efficiency and formation mechanism of ammonia generation in recombining plasmas generated from mixtures of N2 and H2 under various plasma conditions. In contrast to the Haber-Bosch process, in which the molecules are dissociated on a catalytic surface, under these plasma conditions the precursor molecules, N2 and H2, are already dissociated in the gas phase. Surfaces are thus exposed to large fluxes of atomic N and H radicals. The ammonia production turns out to be strongly dependent on the fluxes of atomic N and H radicals to the surface. By optimizing the atomic N and H fluxes to the surface using an atomic nitrogen and hydrogen source ammonia can be formed efficiently, i.e., more than 10% of the total background pressure is measured to be ammonia. The results obtained show a strong similarity with results reported in literature, which were explained by the production of ammonia at the surface by stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals. Furthermore, our results indicate that the ammonia production is independent of wall material. The high fluxes of N and H radicals in our experiments result in a passivated surface, and the actual chemistry, leading to the formation of ammonia, takes place in an additional layer on top of this passivated surface.

  4. Magnetic field generation in Rayleigh-Taylor unstable inertial confinement fusion plasmas.

    PubMed

    Srinivasan, Bhuvana; Dimonte, Guy; Tang, Xian-Zhu

    2012-04-20

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion implosions are expected to generate magnetic fields. A Hall-MHD model is used to study the field generation by 2D single-mode and multimode RTI in a stratified two-fluid plasma. Self-generated magnetic fields are predicted and these fields grow as the RTI progresses via the ∇n(e)×∇T(e) term in the generalized Ohm's law. Scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, Atwood number, and perturbation wavelength.

  5. Hemalin, a thrombin inhibitor isolated from a midgut cDNA library from the hard tick Haemaphysalis longicornis.

    PubMed

    Liao, Min; Zhou, Jinlin; Gong, Haiyan; Boldbaatar, Damdinsuren; Shirafuji, Rika; Battur, Banzragch; Nishikawa, Yoshifumi; Fujisaki, Kozo

    2009-02-01

    A full-length sequence of a thrombin inhibitor (designated as hemalin) from the midgut of parthenogenetic Haemaphysalis longicornis has been identified. Sequence analysis shows that this gene belongs to the Kunitz-type family, containing two Kunitz domains with high homology to boophilin, the thrombin inhibitor from Rhipicephalus (Boophilus) microplus. The recombinant protein expressed in insect cells delayed bovine plasma clotting time and inhibited both thrombin-induced fibrinogen clotting and platelet aggregation. A 20-kDa protein was detected from the midgut lysate with antiserum against recombinant hemalin. The gene is expressed at all stages of the tick except for the egg stage, and hemalin mRNA mainly in the midgut of the female adult tick. Real-time PCR analysis shows that this gene has a distinctly high expression level in the rapid bloodsucking period of the larvae, nymphs, and adults. Disruption of the hemalin gene by RNA interference led to a 2-day extension of the tick blood feeding period, and 27.7% of the RNA-treated ticks did not successfully complete the blood feeding. These findings indicate that the newly identified thrombin inhibitor from the midgut of H. longicornis might play an important role in tick blood feeding.

  6. A Multiple Z-Pinch Configuration for the Generation of High-Density, Magnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Tarditi, Alfonso G.

    2015-11-01

    The z-pinch is arguably the most straightforward and economical approach for the generation and confinement of hot plasmas, with a long history of theoretical investigations and experimental developments. While most of the past studies were focused on countering the natural tendency of z-pinches to develop instabilities, this study attempts to take advantage of those unstable regimes to form a quasi-stable plasma, with higher density and temperature, possibly of interest for a fusion reactor concept. For this purpose, a configuration with four z-pinch discharges, with axis parallel to each other and symmetrically positioned, is considered. Electrodes for the generation of the discharges and magnetic coils are arranged to favor the formation of concave discharge patterns. The mutual attraction from the co-streaming discharge currents enhances this pattern, leading to bent plasma streams, all nearing towards the axis. This configuration is intended to excite and sustain a ``kink'' unstable mode for each z-pinch, eventually producing either plasmoid structures, detached from each discharge, or sustained kink patterns: both these cases appear to lead to plasmas merging in the central region. The feasibility of this approach in creating a higher density, hotter, meta-stable plasma regime is investigated computationally, addressing both the kink excitation phase and the dynamics of the converging plasma columns.

  7. Fast electron generation and transport in a turbulent, magnetized plasma

    SciTech Connect

    Stoneking, Matthew Randall

    1994-05-01

    The nature of fast electron generation and transport in the Madison Symmetric Torus (MST) reversed field pinch (RFP) is investigated using two electron energy analyzer (EEA) probes and a thermocouple calorimeter. The parallel velocity distribution of the fast electron population is well fit by a drifted Maxwellian distribution with temperature of about 100 eV and drift velocity of about 2 x 106 m/s. Cross-calibration of the EEA with the calorimeter provides a measurement of the fast electron perpendicular temperature of 30 eV, much lower than the parallel temperature, and is evidence that the kinetic dynamo mechanism (KDT) is not operative in MST. The fast electron current is found to match to the parallel current at the edge, and the fast electron density is about 4 x 1011 cm-3 independent of the ratio of the applied toroidal electric field to the critical electric field for runaways. First time measurements of magnetic fluctuation induced particle transport are reported. By correlating electron current fluctuations with radial magnetic fluctuations the transported flux of electrons is found to be negligible outside r/a~0.9, but rises the level of the expected total particle losses inside r/a~0.85. A comparison of the measured diffusion coefficient is made with the ausilinear stochastic diffusion coefficient. Evidence exists that the reduction of the transport is due to the presence of a radial ambipolar electric field of magnitude 500 V/m, that acts to equilibrate the ion and electron transport rates. The convective energy transport associated with the measured particle transport is large enough to account for the observed magnetic fluctuation induced energy transport in MST.

  8. Expression screening of bacterial libraries of recombinant alpha-1 proteinase inhibitor variants for candidates with thrombin inhibitory capacity.

    PubMed

    Bhakta, Varsha; Gierczak, Richard F; Sheffield, William P

    2013-12-01

    Exhaustive mutagenesis studies of the reactive centre loop (RCL), a key structural component of proteins belonging to the serpin superfamily of protease inhibitors, are complicated by the size of the RCL, serpin conformational complexity, and, for most serpins, the lack of a serpin-dependent phenotype of expressing cells. Here, we describe a thrombin capture assay that distinguished thrombin-inhibitory recombinant human alpha-1 proteinase inhibitor (API M358R) from non-inhibitory API variants in Escherichia coli lysates prepared from either single clones or pools. Binding of API proteins in the lysates to thrombin immobilized on microtiter plate wells was quantified via colour generated by a peroxidase-coupled anti-API antibody. Bacterial expression plasmids encoding inhibitory API M358R were mixed 1:99 with plasmids encoding non-inhibitory API T345R/M358R and the resulting library screened in pools of 10. All above-background signals arising from pools or subsequently re-probed single clones were linked to the presence of plasmids encoding API M358R. Screening of a portion of another expression library encoding hypervariable API with all possibilities at codons 352-358 also yielded only novel, thrombin-inhibitory variants. Probing a smaller library expressing all possible codons at Ala347 yielded the wild type, 6 different functional variants, one partially active variant, and two variants with no thrombin-inhibitory activity. API antigen levels varied considerably less among Ala347 variants than activity levels, and comparison of rate constants of inhibition of purified API variants to their corresponding thrombin capture assay lysate values was used to establish the sensitivity and specificity of the assay. The results indicate that the approach is sufficiently robust to correctly identify functional versus non-functional candidates in API expression libraries, and could be of value in systematically probing structure/function relationships not only in the API

  9. Ar plasma treated polytetrafluoroethylene films for a highly efficient triboelectric generator

    NASA Astrophysics Data System (ADS)

    Kim, Dong Yeong; Kim, Hyun Soo; Jung, Jong Hoon

    2016-12-01

    We report an Ar plasma treated polytetrafluoroethylene (PTFE) film based triboelectric device for a highly enhanced electric power generation. The plasma treatment of the PTFE in flowing Ar gas results in a sharp increase in surface roughness ( 46 nm), as compared with the as-received film ( 25 nm). In addition, the F ion content decreases whereas the O ion increases with increasing plasma reaction time. Because of the increased number of polar O ions, the surface becomes hydrophilic, as confirmed by water contact angle measurements. After the Ar plasma treatment, the PTFE based triboelectric device, which is periodically contacted with and separated from the ITO electrode, generates a 715 V open-circuit voltage and a 16 μA closed-circuit current, which are almost 79 and 32 times larger than those for as-received PTFE based device. Using the Ar plasma treated PTFE based triboelectric generator, we can turn on the 120 light emitting diodes (LEDs) without any batteries.

  10. Generation and detection of whistler wave induced space plasma turbulence at Gakona, Alaska

    NASA Astrophysics Data System (ADS)

    Rooker, L. A.; Lee, M. C.; Pradipta, R.; Watkins, B. J.

    2013-07-01

    We report on high-frequency wave injection experiments using the beat wave technique to study the generation of very-low-frequency (VLF) whistler waves in the ionosphere above Gakona, Alaska. This work is aimed at investigating whistler wave interactions with ionospheric plasmas and radiation belts. The beat wave technique involves injecting two X-mode waves at a difference frequency in the VLF range using the High-frequency Active Auroral Research Program (HAARP) heating facility. A sequence of beat wave-generated whistler waves at 2, 6.5, 7.5, 8.5, 9.5, 11.5, 15.5, 22.5, 28.5 and 40.5 kHz were detected in our 2011 experiments. We present Modular Ultra-high-frequency Ionospheric Radar (MUIR) (446 MHz) measurements of ion lines as the primary diagnosis of ionospheric plasma effects caused by beat wave-generated whistler waves. A magnetometer and digisonde were used to monitor the background ionospheric plasma conditions throughout the experiments. Our theoretical and data analyses show that VLF whistler waves can effectively interact with ionospheric plasmas via two different four-wave interaction processes leading to energization of electrons and ions. These preliminary results support our Arecibo experiments to study NAU-launched 40.75 kHz whistler wave interactions with space plasmas.

  11. High-Power Tunable Laser Pulse Driven Terahertz Generation in Corrugated Plasma Waveguides

    NASA Astrophysics Data System (ADS)

    Miao, Chenlong; Palastro, John; Antonsen, Thomas

    2016-10-01

    Excitation of terahertz radiation by the interaction of an ultra-short laser pulse and the fields of a miniature, corrugated plasma waveguide is considered. Plasma structures of this type have been realized experimentally and they can support electromagnetic (EM) channel modes with properties that allow for radiation generation. In particular, the mode have subluminal field components, thus allowing phase matching between the generated THz modes and the ponderomotive potential of the laser pulse. Theoretical analysis and full format PIC simulations are conducted. We find THz generated by this slow wave phase matching mechanism is characterized by lateral emission and a coherent, narrow band, tunable spectrum with relatively high power and conversion efficiency. We investigated two different types of channels, and a range of realistic laser pulses and plasma profile parameters are considered with the goal of increasing the conversion of optical energy to THz radiation. We find high laser intensities strongly modify the THz spectrum by exciting higher order channel modes. Enhancement of a specific channel mode can be realized by using an optimum pulse duration and plasma density. As an example, a fixed drive pulse (0.55 J) with spot size of 15 µm and pulse duration of 15 fs excites 37.8 mJ of THz radiation in a 1.5 cm corrugated plasma waveguide with on axis average density of 1.4×1018cm-3, conversion efficiency exceeding 8% is achieved.

  12. Efficient second- and third-harmonic radiation generation from relativistic laser-plasma interactions

    SciTech Connect

    Singh, Mamta; Gupta, D. N.; Suk, H.

    2015-06-15

    We propose an idea to enhance the efficiency of second- and third-harmonic generation by considering the amplitude-modulation of the fundamental laser pulse. A short-pulse laser of finite spot size is modeled as amplitude modulated in time. Amplitude-modulation of fundamental laser contributes in quiver velocity of the plasma electrons and produces the strong plasma-density perturbations, thereby increase in current density at second- and third-harmonic frequency. In a result, the conversion efficiency of harmonic generation increases significantly. Power conversion efficiency of harmonic generation process is the increasing function of the amplitude-modulation parameter of the fundamental laser beam. Harmonic power generated by an amplitude modulated laser is many folds higher than the power obtained in an ordinary case.

  13. Generation of Alfven waves by high power pulse at the electron plasma frequency

    NASA Astrophysics Data System (ADS)

    van Compernolle, Bart Gilbert

    The physics of the interaction between plasmas and high power waves with frequencies in the electron plasma frequency range is of importance in many areas of space and plasma physics. A great deal of laboratory research has been done on the interaction of microwaves in a density gradient when o = ope in unmagnetized plasmas. [SWK74, WS78, KSW74]. Extensive studies of HF-ionospheric modifications have been performed [Fej79] as evidenced by experiments at Arecibo [HMD92, BHK86, CDF92, FGI85], at the HAARP facility [RKK98] in Alaska, at the EISCAT observatory in Norway [IHR99], and at SURA in Russia [FKS99]. This dissertation focusses on the interaction with a fully magnetized plasma, capable of supporting Alfven waves. The experiment is performed in the upgraded LArge Plasma Device (LAPD) at UCLA [GPL91] (Helium, n = 1012 cm-3, B = 1 kG - 2.5 kG). A number of experiments have been done at LAPD using antennas, skin depth scale currents and laser produced plasmas to generate Alfven waves [LGM99, GVL97a, GVL97b, VGV01]. In this work a high power pulse 6th, frequency in the electron plasma frequency range is launched into the radial density gradient, perpendicular to the background magnetic field. The microwave pulses last on the order of one ion gyro period and has a maximum power of |E|2/ nT ≃ .5 in the afterglow. The absorption of these waves leads to a pulse of field aligned suprathermal electrons. This electron current pulse then launches with Alfven wave with o ≤ o ci. The experiment was performed bath in ordinary node (O-mode) and extraordinary (X-mode), for different background magnetic fields B0, different temperatures (afterglow vs discharge) and different power levels of the incoming microwaves. It was found that the Alfven wave generation can be explained by Cherenkov radiation of Alfven waves by the suprathermal electron pulse. Theoretical solutions for the perturbed magnetic field due to a pulse of field aligned electrons were obtained, and shown to be

  14. High-Density Plasma Sources and Technology for the Next Generation

    NASA Astrophysics Data System (ADS)

    Sugai, Hideo

    1998-10-01

    These days, rapid progress in semiconductor devices such as LSI, flat panel displays and solar cells requires technical innovation in plasma-aided deposition and etching. Due to the primary importance of plasma sources, a great deal of effort has been made to develop high-density large-diameter sources and to control reactive plasmas for the next generation. Here I briefly review high-density sources developed so far, focusing mainly on current understanding of nonlinear coupling from RF antenna to high density sources, and on chemistry control of highly dissociated plasmas. First of all, I introduce various high density sources such as ECR, helicon, inductively-coupled and surface-wave plasmas; then they are classified into three categories depending on the antenna-induced electromagnetic fields. In general, antenna-plasma coupling is nonlinear, which causes plasma density jump with a discharge power increase in most high-density sources. I describe such examples of helicon,(H. Sugai et al., Plasma Phys. Control. Fusion) 39 (1997) A445. and surface wave discharges along with a model explaining the mechanism. In the case of inductive RF discharge, power transfer efficiency measurements(K. Suzuki, K. Nakamura, H. Ohkubo, H. Sugai, Plasma Sources Sci. Technol.) 7 (1998) 13. enable discrimination of electrostatic coupling from inductive coupling, and a few methods to reduce the electrostatic coupling will be presented. The wave excitation and absorption processes in surface wave discharge(H. Sugai, I. Ghanashev, M. Nagatsu, Plasma Sources Sci. Technol.) 7 (1998) 192. will then be discussed, but only qualitatively as the physics involved there is not clearly understood yet. Besides the discharge physics described above, plasma chemistry significantly influences the processing performance in high density plasmas. The radical composition is markedly different from the low density case, due to secondary processes accompanied with electron-impact dissociation of radicals

  15. Manipulation of laser-generated energetic proton spectra in near critical density plasma

    NASA Astrophysics Data System (ADS)

    Palmer, Charlotte A. J.; Dover, Nicholas P.; Pogorelsky, Igor; Streeter, Matthew J. V.; Najmudin, Zulfikar

    2015-01-01

    We present simulations that demonstrate the production of quasi-monoenergetic proton bunches from the interaction of a CO2 laser pulse train with a near-critical density hydrogen plasma. The multi-pulse structure of the laser leads to a steepening of the plasma density gradient, which the simulations show is necessary for the formation of narrow-energy spread proton bunches. Laser interactions with a long, front surface, scale-length (>> c/ωp ) plasma, with linear density gradient, were observed to generate proton beams with a higher maximum energy, but a much broader spectrum compared to step-like density profiles. In the step-like cases, a peak in the proton energy spectra was formed and seen to scale linearly with the ratio of laser intensity to plasma density.

  16. A reference protocol for comparing the biocidal properties of gas plasma generating devices

    NASA Astrophysics Data System (ADS)

    Shaw, A.; Seri, P.; Borghi, C. A.; Shama, G.; Iza, F.

    2015-12-01

    Growing interest in the use of non-thermal, atmospheric pressure gas plasmas for decontamination purposes has resulted in a multiplicity of plasma-generating devices. There is currently no universally approved method of comparing the biocidal performance of such devices and in the work described here spores of the Gram positive bacterium Bacillus subtilis (ATCC 6633) are proposed as a suitable reference biological agent. In order to achieve consistency in the form in which the biological agent in question is presented to the plasma, a polycarbonate membrane loaded with a monolayer of spores is proposed. The advantages of the proposed protocol are evaluated by comparing inactivation tests in which an alternative microorganism (methicillin resistant Staphylococcus aureus—MRSA) and the widely-used sample preparation technique of directly pipetting cell suspensions onto membranes are employed. In all cases, inactivation tests with either UV irradiation or plasma exposure were more reproducible when the proposed protocol was followed.

  17. Antithrombotic effects of bromophenol, an alga-derived thrombin inhibitor

    NASA Astrophysics Data System (ADS)

    Shi, Dayong; Li, Xiaohong; Li, Jing; Guo, Shuju; Su, Hua; Fan, Xiao

    2010-01-01

    Thrombin, the ultimate proteinase of the coagulation cascade, is an attractive target for the treatment of a variety of cardiovascular diseases. A bromophenol derivative named (+)-3-(2,3-dibromo-4, 5-dihydroxy-phenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroiso-benzofuran 1, isolated from the brown alga Leathesia nana exhibited significant thrombin inhibitory activity. In this study, we investigated the inhibition of human thrombin in vitro with this bromophenol derivative, and its antithrombotic efficacy in vivo using the arteriovenous shunt model and the ferric chloride-induced arterial thrombosis model in rats. The results show that the bromophenol derivative is a potential inhibitor of thrombin (IC50=1.03 nmol/L). In antithrombotic experiments in vivo, the bromophenol derivative also shows good effect comparing with the control group. These data indicate that the bromophenol derivative is a potential drug for prophylaxis and the treatment of thrombotic diseases.

  18. Electron Acoustic Waves Generated in SRS by Beam-Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Focia, R. J.; Bers, A.; Ram, A. K.; Shoucri, M. M.

    2001-10-01

    In recent single hot spot laser-plasma experiments on the Los Alamos National Laboratory TRIDENT laser, stimulated scattering was observed at a frequency and phase velocity (ω ≈ 0.4 ω_pe, v_φ ≈ 1.4 v_e) below that of the usual SRS electron plasma wave (EPW).(D. S. Montgomery et al., LANL Report LA-UR-01-1857.) This mode has the characteristics of an electron acoustic wave (EAW). We suggest that this new mode is generated by the interaction of an energetic beam of electrons, produced by nonlinear trapping in the SRS-EPW, with the background plasma. Using a bi-Maxwellian electron distribution function to model the beam-plasma system, we find that, in addition to the usual beam-plasma mode, there exists another mode with characteristic features of an EAW. The weakly damped EAW, obtained from the dispersion relation with the complete plasma dispersion function, exists for parameters consistent with the experiments. EAW features will be presented. The validity of the beam-plasma model is also being studied with an Eulerian-Vlasov code which allows for the nonlinear evolution of the electron distribution function in SRS.

  19. Numerical Modeling on Plasma Gases in an Explosively-Driven Magnetohydrodynamic Generator

    NASA Astrophysics Data System (ADS)

    Kim, Deok-Kyu; Seo, Min Su; Kim, Inho

    2002-11-01

    A time-dependent one-dimensional simulation has been carried out on the argon and air plasmas in an explosively-driven magnetohydrodynamic (MHD) power generator. To compute the thermodynamic properties of the plasma gases during the shock compression and jet extraction, we utilize the equation-of-state data calculated from a detailed physical model. The plasma conductivities are given by the mixing rule that compromises the weakly-ionized and fully-ionized limits. The effects of initial gas pressure and applied magnetic field strength are investigated for optimal design of the MHD power generator. For the case of the initial channel pressure of 400 torr and the magnetic field 0.3 T, the maximum output power is estimated up to 0.1 GW with the pulse duration 20 ms, which shows a good agreement with the measured profile.

  20. Theory of coherent transition radiation generated at a plasma-vacuum interface

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim P.

    2003-06-26

    Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources.

  1. Ultrabroad Terahertz Spectrum Generation from an Air-Based Filament Plasma

    NASA Astrophysics Data System (ADS)

    Andreeva, V. A.; Kosareva, O. G.; Panov, N. A.; Shipilo, D. E.; Solyankin, P. M.; Esaulkov, M. N.; González de Alaiza Martínez, P.; Shkurinov, A. P.; Makarov, V. A.; Bergé, L.; Chin, S. L.

    2016-02-01

    We have solved the long-standing problem of the mechanism of terahertz (THz) generation by a two-color filament in air and found that both neutrals and plasma contribute to the radiation. We reveal that the contribution from neutrals by four-wave mixing is much weaker and higher in frequency than the distinctive plasma lower-frequency contribution. The former is in the forward direction while the latter is in a cone and reveals an abrupt down-shift to the plasma frequency. Ring-shaped spatial distributions of the THz radiation are shown to be of universal nature and they occur in both collimated and focusing propagation geometries. Experimental measurements of the frequency-angular spectrum generated by 130-fs laser pulses agree with numerical simulations based on a unidirectional pulse propagation model.

  2. Generation of bioactive peptide hydrolysates from cattle plasma using plant and fungal proteases.

    PubMed

    Bah, Clara S F; Bekhit, Alaa El-Din A; McConnell, Michelle A; Carne, Alan

    2016-12-15

    Four protease preparations from plant and fungal sources (papain, bromelain, FP400 and FPII) were used to hydrolyse plasma which was separated from slaughterhouse cattle blood. The o-phthaldialdehyde assay was used to follow the release of TCA-soluble peptides over a 24h period. Hydrolysis profiles were displayed using SDS-PAGE. The in vitro antioxidant and antimicrobial activities of the hydrolysates were determined. The results showed that hydrolysates of cattle plasma generated with fungal protease FPII had higher antioxidant activities. Overall than hydrolysates generated with papain, bromelain and FP400. None of the hydrolysates demonstrated antimicrobial activity. The FPII peptide hydrolysate was fractionated using gel permeation chromatography, OFFGEL isoelectric focusing and RP-HPLC. The RP-HPLC fraction with highest antioxidant activity contained 15 novel peptide sequences. The use of protease FPII to hydrolyse cattle plasma resulted in a hydrolysate with high antioxidant properties and unique peptide sequences.

  3. Effect of nonlinear chirped Gaussian laser pulse on plasma wake field generation

    SciTech Connect

    Afhami, Saeedeh; Eslami, Esmaeil

    2014-08-15

    An ultrashort laser pulse propagating in plasma can excite a nonlinear plasma wake field which can accelerate charged particles up to GeV energies within a compact space compared to the conventional accelerator devices. In this paper, the effect of different kinds of nonlinear chirped Gaussian laser pulse on wake field generation is investigated. The numerical analysis of our results depicts that the excitation of plasma wave with large and highly amplitude can be accomplished by nonlinear chirped pulses. The maximum amplitude of excited wake in nonlinear chirped pulse is approximately three times more than that of linear chirped pulse. In order to achieve high wake field generation, chirp parameters and functions should be set to optimal values.

  4. Strong terahertz radiation generation by beating of two spatial-triangular beams in collisional magnetized plasma

    NASA Astrophysics Data System (ADS)

    Hematizadeh, Ayoob; Bakhtiari, Farhad; Jazayeri, Seyed Masud; Ghafary, Bijan

    2016-05-01

    A scheme of terahertz (THz) radiation generation is proposed by beating of two spatial-triangular laser beams in plasma with a spatially periodic density when electron-neutral collisions have taken into account. In this process, the laser beams exert a ponderomotive force on the electrons of the plasma and impart the oscillatory velocity at the difference frequency in the presence of a static magnetic field which is applied parallel to the direction of the lasers. We show that higher efficiency and stronger THz radiation are achieved when the parallel magnetic field is used to compare the perpendicular magnetic field. The effects of beam width of lasers, collision frequency, periodicity of density ripples, and magnetic field strength are analyzed for strong THz radiation generation. The THz field of the emitted radiations is found to be highly sensitive to collision frequency and magnetic field strength. In this scheme with the optimization of plasma parameters, the efficiency of order 21% is achieved.

  5. THz generation by self-focusing of hollow Gaussian laser beam in magnetised plasma

    NASA Astrophysics Data System (ADS)

    Hussain, Saba; Singh, Monika; Kishor Singh, Ram; Sharma, R. P.

    2014-09-01

    A scheme of terahertz (THz) generation is proposed by the self-focusing of a high-power laser beam having hollow Gaussian intensity profile in a collissionless magnetized plasma, where ponderomotive nonlinearity is operative. THz waves are resonantly excited at the difference frequency of laser and electron plasma wave (EPW) satisfying the proper phase matching conditions. In this paper first we have investigated the filamentation of the circularly polarized hollow Gaussian beam (HGB) propagating parallel to the direction of a static background magnetic field within the paraxial approximation, subsequently this filamented HG laser beam interplay with the electron plasma wave to generate a nonlinear current in the transverse direction, thereby producing THz radiations. The intensity of the emitted radiations are found to be highly sensitive to the order of the HGB. For the current scheme the power level of THz wave comes out to be ˜ 0.05 gigawatts.

  6. Plasma Processing of SRF Cavities for the next Generation Of Particle Accelerators

    SciTech Connect

    Vuskovic, Leposava

    2015-11-23

    The cost-effective production of high frequency accelerating fields are the foundation for the next generation of particle accelerators. The Ar/Cl2 plasma etching technology holds the promise to yield a major reduction in cavity preparation costs. Plasma-based dry niobium surface treatment provides an excellent opportunity to remove bulk niobium, eliminate surface imperfections, increase cavity quality factor, and bring accelerating fields to higher levels. At the same time, the developed technology will be more environmentally friendly than the hydrogen fluoride-based wet etching technology. Plasma etching of inner surfaces of standard multi-cell SRF cavities is the main goal of this research in order to eliminate contaminants, including niobium oxides, in the penetration depth region. Successful plasma processing of multi-cell cavities will establish this method as a viable technique in the quest for more efficient components of next generation particle accelerators. In this project the single-cell pill box cavity plasma etching system is developed and etching conditions are determined. An actual single cell SRF cavity (1497 MHz) is plasma etched based on the pill box cavity results. The first RF test of this plasma etched cavity at cryogenic temperature is obtained. The system can also be used for other surface modifications, including tailoring niobium surface properties, surface passivation or nitriding for better performance of SRF cavities. The results of this plasma processing technology may be applied to most of the current SRF cavity fabrication projects. In the course of this project it has been demonstrated that a capacitively coupled radio-frequency discharge can be successfully used for etching curved niobium surfaces, in particular the inner walls of SRF cavities. The results could also be applicable to the inner or concave surfaces of any 3D structure other than an SRF cavity.

  7. Surface composition, chemistry, and structure of polystyrene modified by electron-beam-generated plasma.

    PubMed

    Lock, Evgeniya H; Petrovykh, Dmitri Y; Mack, Paul; Carney, Tim; White, Richard G; Walton, Scott G; Fernsler, Richard F

    2010-06-01

    Polystyrene (PS) surfaces were treated by electron-beam-generated plasmas in argon/oxygen, argon/nitrogen, and argon/sulfur hexafluoride environments. The resulting modifications of the polymer surface energy, morphology, and chemical composition were analyzed by a suite of complementary analytical techniques: contact angle goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and reflection electron energy loss spectroscopy (REELS). The plasma treatments produced only minimal increases in the surface roughness while introducing the expected chemical modifications: oxygen-based after Ar/O(2) plasma, oxygen- and nitrogen-based after Ar/N(2) plasma, and fluorine-based after Ar/SF(6) plasma. Fluorinated PS surfaces became hydrophobic and did not significantly change their properties over time. In contrast, polymer treated in Ar/O(2) and Ar/N(2) plasmas initially became hydrophilic but underwent hydrophobic recovery after 28 days of aging. The aromatic carbon chemistry in the top 1 nm of these aged surfaces clearly indicated that the hydrophobic recovery was produced by reorientation/diffusion of undamaged aromatic polymer fragments from the bulk rather than by contamination. Nondestructive depth profiles of aged plasma-treated PS films were reconstructed from parallel angle-resolved XPS (ARXPS) measurements using a maximum-entropy algorithm. The salient features of reconstructed profiles were confirmed by sputter profiles obtained with 200 eV Ar ions. Both types of depth profiles showed that the electron-beam-generated plasma modifications are confined to the topmost 3-4 nm of the polymer surface, while valence band measurements and unsaturated carbon signatures in ARXPS and REELS data indicated that much of the PS structure was preserved below 9 nm.

  8. Cleavage of a specific bond in troponin C by thrombin.

    PubMed

    Leavis, P C; Rosenfeld, S; Lu, R C

    1978-08-21

    Limited proteolysis of rabbit skeletal troponin C with bovine thrombin yielded two fragments, TH1 (Mr = 11000) containing Ca2+ binding regions I--III and TH2 (Mr = 6000) containing region IV. Determination of the partial sequences of the fragments established the site of cleavage at Arg120-Ala121. Secondary cleavage by thrombin at other arginyl or lysyl residues in troponin C was ruled out by the sequence data and by the amino acid compositions of the two fragments.

  9. Diode Dynamics, Beam Generation and Transport and Plasma Erosion Opening Switch Development.

    DTIC Science & Technology

    1983-05-17

    provide standoff protecti.on for the ion diode~s) b) allow close packing of multipla generators saround a coamion target :IiaT.Lr and c) facili- tate tim...beam and plasma parame:ers in w1hich the very intense ion bea= ms behave like weak beams in prescribed electromagnetic fields. As a result, concepts of

  10. Exposure of Mice to Topical Bovine Thrombin Induces Systemic Autoimmunity

    PubMed Central

    Schoenecker, Jonathan G.; Johnson, Rachel K.; Lesher, Aaron P.; Day, Jarrod D.; Love, Stephanie D.; Hoffman, Maureane R.; Ortel, Thomas L.; Parker, William; Lawson, Jeffrey H.

    2001-01-01

    Bovine thrombin is used as an aid to hemostasis in medical and surgical procedures. At least 500,000 Americans are exposed to this therapeutic annually and reports suggest that exposure is associated with the development of autoreactive antibodies. To determine whether bovine thrombin can induce pathological autoimmunity we exposed nonautoimmune-prone galactose-α1-3-galactose-deficient mice to the two bovine thrombin preparations currently approved for use in the United States. We found that, like humans exposed to bovine thrombin, mice developed an immune response against the therapeutic and the xenogeneic carbohydrate galactose-α1-3-galactose, and some mice developed autoantibodies against clotting factors. Further, unexpectedly, a single exposure to this therapeutic also induced autoimmunity with features characteristic of systemic lupus erythematosus including antibodies against nuclear antigens, native DNA, double-stranded DNA, and cardiolipin. High levels of these autoantibodies correlated with glomerulonephritis in all mice evaluated. This autoimmune syndrome was detected in mice 15 weeks after a secondary exposure to bovine thrombin and female mice were found to develop the syndrome at a significantly greater frequency than males. Thus, these studies indicate that exposure to bovine thrombin preparations can induce a pathological systemic autoimmune syndrome with lupus-like serology. PMID:11696457

  11. The platelet strip. II. Pharmacomechanical coupling in thrombin-activated human platelets.

    PubMed

    Salganicoff, L; Sevy, R W

    1985-09-01

    A model of contracted, irreversibly aggregated thrombin-activated human platelets relaxes when treated with ethyleneglycol-bis(beta-aminoethylether-N,N'-tetraacetic acid (EGTA) in the presence of Mg2+. Inhibition of the cyclooxygenase or blockade of the thromboxane A2 receptor decreases the tension partially, but EGTA treatment is needed for full relaxation. After a stable relaxation has been achieved (3-4 h), Ca2+ addition in a cumulative manner does not reinduce contraction. Whether in the absence or presence of external Ca2+, the relaxed preparation contracts when stimulated with ADP, epinephrine, thromboxane A2 or its analogues, or thrombin. At supramaximal doses, each of the agonists activates only a partial amount of the total tension capable of being generated. Addition of an agonist of a different class to the partially contracted preparation further increases its force. The contractile responses are reversible on washout, with kinetics dependent on the class of agonist and time of contact with the preparation. The contraction induced by the prolonged simultaneous stimulation with ADP, arachidonate, and thrombin reverts very slowly on washout of the agonists and for all practical purposes reproduces the initial state of irreversible platelet contraction.

  12. Effect of thrombin and endotoxin on the in vivo metabolism of antithrombin III (AT III) in dogs

    SciTech Connect

    Tanaka, H.; Kobayashi, N.; Maekawa, T.

    1985-11-01

    Effect of thrombin and endotoxin on the metabolism of I-125-labelled canine AT III was studied in mongrel dogs. Under control condition, mean total amount of intravascular AT III with standard deviation was 23.4 +/- 2.4 mg/kg, plasma half life of i.v. injected I-125-AT III was 1.7 +/- 0.2 days, and the fractional catabolic flux (j3x) was 16.3 +/- 1.6 mg/kg/day. The total amount of intra- and extra-vascular AT III was 36.0 +/- 0.34 mg/kg. Neither a 3 hour infusion of a small dose (30 units/kg/hr) of thrombin nor i.v. injection of a large amount of thrombin (5,000-15,000 units/day) with heparin significantly affected AT III metabolism except for a transient decrease in AT III concentration in the latter case, although decrease in plasma fibrinogen concentration and platelet count was observed in both cases. Two injections with 200 micrograms/kg of endotoxin resulted in an evident acceleration of AT III metabolism with significant decrease in the plasma AT III, fibrinogen concentrations and platelet count. More marked changes in AT III metabolism were induced by a single infusion with 1 mg/kg of endotoxin. Changes in hemostatic system coincided with those observed in DIC.

  13. Atmospheric plasma generates oxygen atoms as oxidizing species in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mokhtar Hefny, Mohamed; Pattyn, Cedric; Lukes, Petr; Benedikt, Jan

    2016-10-01

    A remote microscale atmospheric pressure plasma jet (µAPPJ) with He, He/H2O, He/O2, and He/O2/H2O gas mixtures was used to study the transport of reactive species from the gas phase into the liquid and the following aqueous phase chemistry. The effects induced by the µAPPJ in water were quantitatively studied using phenol as a chemical probe and by measuring H2O2 concentration and pH values. These results were combined with the analysis of the absolute densities of the reactive species and the modeling of convective/diffusion transport and recombination reactions in the effluent of the plasma jet. Additionally, modified plasma jets were used to show that the role of emitted photons in aqueous chemistry is negligible for these plasma sources. The fastest phenol degradation was measured for the He/O2 plasma, followed by He/H2O, He/O2/H2O, and He plasmas. The modeled quantitative flux of O atoms into the liquid in the He/O2 plasma case was highly comparable with the phenol degradation rate and showed a very high transfer efficiency of reactive species from the plasma into the liquid, where more than half of the O atoms leaving the jet nozzle entered the liquid. The results indicate that the high oxidative effect of He/O2 plasma was primarily due to solvated O atoms, whereas OH radicals dominated the oxidative effects induced in water by plasmas with other gas mixtures. These findings help to understand, in a quantitative way, the complex interaction of cold atmospheric plasmas with aqueous solutions and will allow a better understanding of the interaction of these plasmas with water or buffered solutions containing biological macromolecules, microorganisms, or even eukaryotic cells. Additionally, the µAPPJ He/O2 plasma source seems to be an ideal tool for the generation of O atoms in aqueous solutions for any future studies of their reactivity.

  14. Ultracold electron bunch generation via plasma photocathode emission and acceleration in a beam-driven plasma blowout.

    PubMed

    Hidding, B; Pretzler, G; Rosenzweig, J B; Königstein, T; Schiller, D; Bruhwiler, D L

    2012-01-20

    Beam-driven plasma wakefield acceleration using low-ionization-threshold gas such as Li is combined with laser-controlled electron injection via ionization of high-ionization-threshold gas such as He. The He electrons are released with low transverse momentum in the focus of the copropagating, nonrelativistic-intensity laser pulse directly inside the accelerating or focusing phase of the Li blowout. This concept paves the way for the generation of sub-μm-size, ultralow-emittance, highly tunable electron bunches, thus enabling a flexible new class of an advanced free electron laser capable high-field accelerator.

  15. Aptamer/Protein Proximity Binding-Triggered Molecular Machine for Amplified Electrochemical Sensing of Thrombin.

    PubMed

    Yang, Jianmei; Dou, Baoting; Yuan, Ruo; Xiang, Yun

    2017-04-13

    The development of convenient and sensitive methods without involving any enzymes or complex nanomaterials for the monitoring of proteins is of great significance in disease diagnostics. In this work, we describe the validation of a new aptamer/protein proximity binding-triggered molecular machinery amplification strategy for sensitive electrochemical assay of thrombin in complex serum samples. The sensing interface is prepared by self-assembly of three-stranded DNA complexes on the gold electrode. The association of two distinct functional aptamers with different sites of thrombin triggers proximity binding-induced displacement of one of the short single-stranded DNAs (ssDNAs) from the surface-immobilized three-stranded DNA complexes, exposing a prelocked toehold domain to hybridize with a methylene blue (MB)-tagged fuel ssDNA strand (MB-DNA). Subsequent toehold-mediated strand displacement by the MB-DNA leads to the release and recycling of the aptamer/protein complexes and the function of the molecular machine. Eventually, a large number of MB-DNA strands are captured by the sensor surface, generating drastically amplified electrochemical responses from the MB tags for sensitive detection of thrombin. Our signal amplified sensor is completely enzyme-free and shows a dynamic range from 5 pM to 1 nM with a detection limit of 1.7 pM. Such sensor also has a high specificity for thrombin assay in serum samples. By changing the affinity probe pairs, the developed sensor can be readily expanded as a more general platform for sensitive detection of different types of proteins.

  16. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    SciTech Connect

    Jablonowski, H.; Hammer, M. U.; Reuter, S.; Bussiahn, R.; Weltmann, K.-D.; Woedtke, Th. von

    2015-12-15

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  17. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    NASA Astrophysics Data System (ADS)

    Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

    2015-12-01

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  18. Enhancement of the high-order harmonic generation from the gold plume using the time-resolved plasma spectroscopy

    SciTech Connect

    Ganeev, Rashid A.; Elouga Bom, Luc B.; Ozaki, Tsuneyuki

    2007-10-01

    We present systematic time-resolved investigations of plasma conditions for achieving the maximum cutoff and maximum conversion efficiency of high-order harmonic generation from gold plasma within the plateau. We analyzed harmonic generation under different laser-plasma conditions. We also performed simulations to calculate the ionization state of the gold plasma, the free electron density, and singly charged ion density at different prepulse intensities. By optimizing the plasma conditions, we observed a harmonic cutoff at the 53rd order ({lambda}=15.09 nm). We estimate the conversion efficiency of the harmonics within the plateau region to be 2x10{sup -6}.

  19. Method for generating extreme ultraviolet with mather-type plasma accelerators for use in Extreme Ultraviolet Lithography

    DOEpatents

    Hassanein, Ahmed; Konkashbaev, Isak

    2006-10-03

    A device and method for generating extremely short-wave ultraviolet electromagnetic wave uses two intersecting plasma beams generated by two plasma accelerators. The intersection of the two plasma beams emits electromagnetic radiation and in particular radiation in the extreme ultraviolet wavelength. In the preferred orientation two axially aligned counter streaming plasmas collide to produce an intense source of electromagnetic radiation at the 13.5 nm wavelength. The Mather type plasma accelerators can utilize tin, or lithium covered electrodes. Tin, lithium or xenon can be used as the photon emitting gas source.

  20. Differential proteolytic activation of factor VIII-von Willebrand factor complex by thrombin

    SciTech Connect

    Hill-Eubanks, D.C.; Parker, C.G.; Lollar, P. )

    1989-09-01

    Blood coagulation factor VIII (fVIII) is a plasma protein that is decreased or absent in hemophilia A. It is isolated as a mixture of heterodimers that contain a variably sized heavy chain and a common light chain. Thrombin catalyzes the activation of fVIII in a reaction that is associated with cleavages in both types of chain. The authors isolated a serine protease from Bothrops jararacussu snake venom that catalyzes thrombin-like heavy-chain cleavage but not light-chain cleavage in porcine fVIII as judged by NaDodSO{sub 4}/PAGE and N-terminal sequence analysis. Using a plasma-free assay of the ability of activated {sup 125}I-fVIII to function as a cofactor in the activation of factor X by factor IXa, they found that fVIII is activated by the venom enzyme. The venom enzyme-activated fVIII was isolated in stable form by cation-exchange HPLC. von Willebrand factor inhibited venom enzyme-activated fVIII but not thrombin-activated fVIII. These results suggest that the binding of fVIII to von Willebrand factor depends on the presence of an intact light chain and that activated fVIII must dissociate from von Willebrand factor to exert its cofactor effect. Thus, proteolytic activation of fVIII-von Willebrand factor complex appears to be differentially regulated by light-chain cleavage to dissociate the complex and heavy-chain cleavage to activate the cofactor function.

  1. Nitrogen Gas Plasma Generated by a Static Induction Thyristor as a Pulsed Power Supply Inactivates Adenovirus

    PubMed Central

    Sakudo, Akikazu; Toyokawa, Yoichi; Imanishi, Yuichiro

    2016-01-01

    Adenovirus is one of the most important causative agents of iatrogenic infections derived from contaminated medical devices or finger contact. In this study, we investigated whether nitrogen gas plasma, generated by applying a short high-voltage pulse to nitrogen using a static induction thyristor power supply (1.5 kilo pulse per second), exhibited a virucidal effect against adenoviruses. Viral titer was reduced by one log within 0.94 min. Results from detection of viral capsid proteins, hexon and penton, by Western blotting and immunochromatography were unaffected by the plasma treatment. In contrast, analysis using the polymerase chain reaction suggested that plasma treatment damages the viral genomic DNA. Reactive chemical products (hydrogen peroxide, nitrate, and nitrite), ultraviolet light (UV-A) and slight temperature elevations were observed during the operation of the gas plasma device. Viral titer versus intensity of each potential virucidal factor were used to identify the primary mechanism of disinfection of adenovirus. Although exposure to equivalent levels of UV-A or heat treatment did not inactivate adenovirus, treatment with a relatively low concentration of hydrogen peroxide efficiently inactivated the virus. Our results suggest the nitrogen gas plasma generates reactive chemical products that inactivate adenovirus by damaging the viral genomic DNA. PMID:27322066

  2. Modeling of the plasma generated in a rarefied hypersonic shock layer

    SciTech Connect

    Farbar, Erin D.; Boyd, Iain D.

    2010-10-15

    In this study, a rigorous numerical model is developed to simulate the plasma generated in a rarefied, hypersonic shock layer. The model uses the direct simulation Monte Carlo (DSMC) method to treat the particle collisions and the particle-in-cell (PIC) method to simulate the plasma dynamics in a self-consistent manner. The model is applied to compute the flow along the stagnation streamline in front of a blunt body reentering the Earth's atmosphere at very high velocity. Results from the rigorous DSMC-PIC model are compared directly to the standard DSMC modeling approach that uses the ambipolar diffusion approximation to simulate the plasma dynamics. It is demonstrated that the self-consistent computation of the plasma dynamics using the rigorous DSMC-PIC model captures many physical phenomena not accurately predicted by the standard modeling approach. These computations represent the first assessment of the validity of the ambipolar diffusion approximation when predicting the rarefied plasma generated in a hypersonic shock layer.

  3. High-Intensity High-order Harmonics Generated from Low-Density Plasma

    SciTech Connect

    Ozaki, T.; Bom, L. B. Elouga; Abdul-Hadi, J.; Ganeev, R. A.; Haessler, S.; Salieres, P.

    2009-07-25

    We study the generation of high-order harmonics from lowly ionized plasma, using the 10 TW, 10 Hz laser of the Advanced Laser Light Source (ALLS). We perform detailed studies on the enhancement of a single order of the high-order harmonic spectrum generated in plasma using the fundamental and second harmonic of the ALLS beam line. We observe quasi-monochromatic harmonics for various targets, including Mn, Cr, Sn, and In. We identify most of the ionic/neutral transitions responsible for the enhancement, which all have strong oscillator strengths. We demonstrate intensity enhancements of the 13th, 17th, 29th, and 33rd harmonics from these targets using the 800 nm pump laser and varying its chirp. We also characterized the attosecond nature of such plasma harmonics, measuring attosecond pulse trains with 360 as duration for chromium plasma, using the technique of 'Reconstruction of Attosecond Beating by Interference of Two-photon Transitions'(RABBIT). These results show that plasma harmonics are intense source of ultrashort coherent soft x-rays.

  4. Evaluation of Ash Toxicity Generated From the Thermal Plasma Pyrolysis of Used Automobile Tires

    NASA Astrophysics Data System (ADS)

    Chang, J. S.; Novog, D. R.; Jamal, S.

    1996-10-01

    The disposal of used tires represents a severe environmental problem. As the heat content of the rubber tires is even higher than that of coal it should be considered as a future source of alternate fuel for power generation. There have been attempts to burn old tires directly in cofired boilers for production of electricity. However, there are several environmental concerns since the combustion flue gas may contain a significant concentration heavy metals (Fe, Zn, Cd, As, etc.). One technique currently being developed is the pyrolyzation of rubber tires by a thermal plasma to produce combustible gases. In this work, ashes generated during the plasma pyrolysis of used automobile tires using a DC Argon thermal plasma were analyzed using Neutron Activation Analysis (NAA) and produced syngas composition was analyzed by FT-IR.. The gas analysis indicates a significant quantity of combustible gases (CH4, C2H2, C2H4, CO, H2 etc..) was produced from the thermal plasma pyrolysis of used tires. The results also indicate that a majority of the heavy metals present in used tires were concentrated in the ashes deposited in reaction chamber wall and in the two-stage filtering system. Furthermore the heavy metal concentration decreases significantly with increasing distance from the plasma torch. Toxic components such as Zn, As and Cl were also collected in the filtering process.

  5. Scavenging of hydroxyl radicals generated in human plasma following X-ray irradiation.

    PubMed

    Hosokawa, Yoichiro; Sano, Tomoaki

    2015-11-01

    There are various antioxidant materials that scavenge free radicals in human plasma. It is possible that the radical-scavenging function causes a radiation protective effect in humans. This study estimated the hydroxyl (OH) radical-scavenging activity induced by X-ray irradiation in human plasma. The test subjects included 111 volunteers (75 males and 36 females) ranging from 22 to 35 years old (average, 24.0). OH radicals generated in irradiated human plasma were measured by electron spin resonance (ESR). The relationships between the amount of the OH radical and chemical and biological parameters [total protein, total cholesterol, triglycerides and hepatitis B surface (HBs) antibodies] were estimated in the plasma of the 111 volunteers by a multivariate analysis. The presence of HBs antibodies had the greatest influence on OH radical-scavenging activity. One volunteer who did not have the HBs antibody was given an inoculation of the hepatitis B vaccine. There was a remarkable decrease in the amount of OH radical generated from plasma after the HBs antibody was produced. The results indicate that the HBs antibody is an important factor for the scavenging of OH radicals initiated by X-ray irradiation in the human body.

  6. Study of an Atmospheric Pressure Plasma Jet of Argon Generated by Column Dielectric Barrier Discharge

    NASA Astrophysics Data System (ADS)

    Nur, M.; Kinandana, A. W.; Winarto, P.; Muhlisin, Z.; Nasrudin

    2016-11-01

    An atmospheric of argon plasma jet was generated by using column dielectric barrier discharge has been investigated. In this study, argon gas was passed through the capillary column by regulating the flow rate of gas. This atmospheric pressure plasma jet (APPJ) was generated by a sinusoidal AC high voltage in the range of 0.4 kV to 10 kV and at frequencies of 15 kHz and 26 kHz. APPJ has been produced with flow rate of argon gas from 1 litter/min - 10 litters/min. The electric current has been taken with variation of voltage and each interval argon gas flow rate of 1 litter/min. The results show that electric current increase linearly and then it trends to saturation condition by the increasing of applied voltage. We found also that the length of the plasma jet increase by augmenting of applied voltage both for frequencies of 15 kHz and 26 kHz. Furthermore, our results show that length of plasma jet optimum for flow rate of argon gas of 2 litters/minute. In addition, we obtained that the larger applied voltage, the greater the temperature of the plasma jet.

  7. Third harmonic generation in air ambient and laser ablated carbon plasma

    SciTech Connect

    Singh, Ravi Pratap Gupta, Shyam L.; Thareja, Raj K.

    2015-12-15

    We report the third harmonic generation of a nanosecond laser pulse (1.06 μm) in air ambient and in the presence of nanoparticles from laser ablated carbon plasma. Significant decrease in the threshold of third harmonic generation and multi-fold increment in the intensity of generated third harmonic is observed in presence of carbon plasma. The third harmonic in air is due to the quasi-resonant four photon process involving vibrationally excited states of molecular ion of nitrogen due to electron impact ionization and laser pulse. Following optical emission spectroscopic observations we conclude that the presence of C{sub 2} and CN in the ablated plume play a vital role in the observed third harmonic signals.

  8. High-order harmonic generation from C{sub 60}-rich plasma

    SciTech Connect

    Ganeev, R. A.; Elouga Bom, L. B.; Ozaki, T.; Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.; Redkin, P. V.

    2009-10-15

    We performed systematic investigation of high-order harmonic generation from fullerene-rich laser-produced plasmas. We studied harmonic generation by varying several experimental parameters, such as the delay between the ablation and driving pulses, and divergence and polarization of the pump laser. Enhancement of harmonic yield is observed near 20 eV, which is attributed to the influence of a broadband plasmon resonance of C{sub 60} on the nonlinear optical response of fullerene-rich plasma. This increase in the harmonic intensity occurs despite the increased absorption by C{sub 60} at these wavelengths. Using simulations based on time-dependent density-functional theory, we confirm that this effect is due to the influence of collective excitations. We compare harmonic generation from fullerenes using lasers with 793 nm and 396 nm wavelengths, which show the influence of plasmon resonance on the conversion efficiency of high-order harmonics for different laser wavelengths.

  9. Free radical generation and concentration in a plasma polymer: the effect of aromaticity.

    PubMed

    Ershov, Sergey; Khelifa, Farid; Lemaur, Vincent; Cornil, Jérôme; Cossement, Damien; Habibi, Youssef; Dubois, Philippe; Snyders, Rony

    2014-08-13

    Plasma polymer films (PPF) have increasing applications in many fields due to the unique combination of properties of this class of materials. Among notable features arising from the specifics of plasma polymerization synthesis, a high surface reactivity can be advantageously used when exploited carefully. It is related to the presence of free radicals generated during the deposition process through manifold molecular bond scissions in the energetic plasma environment. In ambient atmosphere, these radicals undergo autoxidation reactions resulting in undesired polymer aging. However, when the reactivity of surface radicals is preserved and they are put in direct contact with a chemical group of interest, a specific surface functionalization or grafting of polymeric chains can be achieved. Therefore, the control of the surface free radical density of a plasma polymer is crucially important for a successful grafting. The present investigation focuses on the influence of the hydrocarbon precursor type, aromatic vs aliphatic, on the generation and concentration of free radicals on the surface of the PPF. Benzene and cyclohexane were chosen as model precursors. First, in situ FTIR analysis of the plasma phase supplemented by density functional theory calculations allowed the main fragmentation routes of precursor molecules in the discharge to be identified as a function of energy input. Using nitric oxide (NO) chemical labeling in combination with X-ray photoelectron spectroscopy analysis, a quantitative evaluation of concentration of surface free radicals as a function of input power has been assessed for both precursors. Different evolutions of the surface free radical density for the benzene- and cyclohexane-based PPF, namely, a continuous increase versus stabilization to a plateau, are attributed to different plasma polymerization mechanisms and resulting structures as illustrated by PPF characterization findings. The control of surface free radical density can be

  10. Modeling and experiments on differential pumping in linear plasma generators operating at high gas flows

    SciTech Connect

    Eck, H. J. N. van; Koppers, W. R.; Rooij, G. J. van; Goedheer, W. J.; Cardozo, N. J. Lopes; Kleyn, A. W.; Engeln, R.; Schram, D. C.

    2009-03-15

    The direct simulation Monte Carlo (DSMC) method was used to investigate the efficiency of differential pumping in linear plasma generators operating at high gas flows. Skimmers are used to separate the neutrals from the plasma beam, which is guided from the source to the target by a strong axial magnetic field. In this way, the neutrals are prevented to reach the target region. The neutral flux to the target must be lower than the plasma flux to enable ITER relevant plasma-surface interaction (PSI) studies. It is therefore essential to control the neutral gas dynamics. The DSMC method was used to model the expansion of a hot gas in a low pressure vessel where a small discrepancy in shock position was found between the simulations and a well-established empirical formula. Two stage differential pumping was modeled and applied in the linear plasma devices Pilot-PSI and PLEXIS. In Pilot-PSI a factor of 4.5 pressure reduction for H{sub 2} has been demonstrated. Both simulations and experiments showed that the optimum skimmer position depends on the position of the shock and therefore shifts for different gas parameters. The shape of the skimmer has to be designed such that it has a minimum impact on the shock structure. A too large angle between the skimmer and the forward direction of the gas flow leads to an influence on the expansion structure. A pressure increase in front of the skimmer is formed and the flow of the plasma beam becomes obstructed. It has been shown that a skimmer with an angle around 53 deg. gives the best performance. The use of skimmers is implemented in the design of the large linear plasma generator Magnum-PSI. Here, a three stage differentially pumped vacuum system is used to reach low enough neutral pressures near the target, opening a door to PSI research in the ITER relevant regime.

  11. Formation of the compression zone in a plasma flow generated by a magnetoplasma compressor

    SciTech Connect

    Solyakov, D. G. Petrov, Yu. V.; Garkusha, I. E.; Chebotarev, V. V.; Ladygina, M. S.; Cherednichenko, T. N.; Morgal’, Ya. I.; Kulik, N. V.; Stal’tsov, V. V.; Eliseev, D. V.

    2013-12-15

    Processes occurring in a plasma flow generated by a magnetoplasma compressor (MPC) during the formation of the compression zone are discussed. The paper presents results of measurements of the spatial distribution of the electric current in the plasma flow, the temporal and spatial (along the flow) distributions of the plasma density, and the profiles of the velocity of individual flow layers along the system axis. The spatial distribution of the electromagnetic force in the flow is analyzed. It is shown that the plasma flow is decelerated when approaching the compression zone and reaccelerated after passing it. In this case, the plasma flow velocity decreases from ν = (2–3) × 10{sup 7} cm/s at the MPC output to ν < 10{sup 6} cm/s in the region of maximum compression and then again increases to 10{sup 7} cm/s at a distance of 15–17 cm from the MPC output. In some MPC operating modes, a displacement of the magnetic field from the compression zone and the formation of toroidal electric current vortices in the plasma flow after passing the compression zone were detected.

  12. Nitric Oxide Studies in Low Temperature Plasmas Generated with a Nanosecond Pulse Sphere Gap Electrical Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David Dean

    This dissertation presents studies of NO kinetics in a plasma afterglow using various nanosecond pulse discharges across a sphere gap. The discharge platform is developed to produce a diffuse plasma volume large enough to allow for laser diagnostics in a plasma that is rich in vibrationally-excited molecules. This plasma is characterized by current and voltage traces as well as ICCD and NO PLIF images that are used to monitor the plasma dimensions and uniformity. Temperature and vibrational loading measurements are performed via coherent anti-Stokes Raman spectroscopy (CARS). Absolute NO concentrations are obtained by laser-induce fluorescence (LIF) measurements, and N and O densities are found using two photon absorption laser-induced fluorescence (TALIF). For all dry air conditions studied, the NO behavior is characterized by a rapid rate of formation consistent with an enhanced Zeldovich process involving electronically-excited nitrogen species that are generated within the plasma. After several microseconds, the NO evolution is entirely controlled by the reverse Zeldovich process. These results show that under the chosen range of conditions and even in extreme instances of vibrational loading, there is no formation channel beyond ~2 musec. Both the NO formation and consumption mechanisms are strongly affected by the addition of fuel species, producing much greater NO concentrations in the afterglow.

  13. Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Namihira, T.; Sakai, S.; Matsuda, M.; D., Wang; Kiyan, T.; Akiyama, H.; Okamoto, K.; Toda, K.

    2007-12-01

    Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.

  14. Dense pair plasma generation by two laser pulses colliding in a cylinder channel

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Xun; Ma, Yan-Yun; Yu, Tong-Pu; Zhao, Jun; Yang, Xiao-Hu; Zou, De-Bin; Zhang, Guo-Bo; Zhao, Yuan; Yang, Jing-Kang; Li, Han-Zhen; Zhuo, Hong-Bin; Shao, Fu-Qiu; Kawata, Shigeo

    2017-03-01

    An all-optical scheme for high-density pair plasmas generation is proposed by two laser pulses colliding in a cylinder channel. Two dimensional particle-in-cell simulations show that, when the first laser pulse propagates in the cylinder, electrons are extracted out of the cylinder inner wall and accelerated to high energies. These energetic electrons later run into the second counter-propagating laser pulse, radiating a large amount of high-energy gamma photons via the Compton back-scattering process. The emitted gamma photons then collide with the second laser pulse to initiate the Breit–Wheeler process for pairs production. Due to the strong self-generated fields in the cylinder, positrons are confined in the channel to form dense pair plasmas. Totally, the maximum density of pair plasmas can be 4.60× {10}27 {{{m}}}-3, for lasers with an intensity of 4× {10}22 {{W}}\\cdot {{cm}}-2. Both the positron yield and density are tunable by changing the cylinder radius and the laser parameters. The generated dense pair plasmas can further facilitate investigations related to astrophysics and particle physics. Project supported by the National Natural Science Foundation (Grant Nos. 11475260, 11305264, 11622547, 11375265, and 11474360), the National Basic Research Program of China (Grant No. 2013CBA01504), the Research Project of National University of Defense Technology, China (Contract No. JC14-02-02), and the Science Challenge Program, China (Grant No. JCKY2016212A505).

  15. Intense Ion Beam Generation, Plasma Radiation Source and Plasma Opening Switch Research

    DTIC Science & Technology

    1989-04-01

    ion source on the 150 kV, ls pulse , ifl LONG- SHOT pulsed power generator under NRL support. The completion of this task 2 will demonstrate both higher...following paragraph. This research is continuing under a new NRL-supported grant. 3 The POS system is pulsed by a 1.9MAF Scyllac capacitor charged to 50 kV...electric field measurements made in a surface flashover MID using emission spectroscopy by Maron et al.’ This LIF potential measuring technique could

  16. Effect of plasma temperature on electrostatic shock generation and ion acceleration by laser

    SciTech Connect

    Zhang Xiaomei; Shen Baifei; Yu, M. Y.; Li Xuemei; Jin Zhangying; Wang Fengchao; Wen Meng

    2007-11-15

    The effect of plasma temperature on electrostatic shock generated by a circularly polarized laser pulse in overdense plasma is studied by particle-in-cell simulation. Ion reflection and transmission in the collisionless electrostatic shock (CES) are investigated analytically. As the initial ion temperature is varied, a distinct transition from the laser-driven piston scenario with all ions being reflected to the CES scenario with partial ion reflection is found. The results show that at low but finite temperatures the ions are much more accelerated than if they were cold.

  17. Generation of a uranium plasma at near gaseous core reactor conditions.

    NASA Technical Reports Server (NTRS)

    Davis, J. F., III; Schnitzler, B. G.; Schneider, R. T.

    1971-01-01

    A constricted sliding spark discharge is used to generate a high density, high temperature uranium plasma. Uranium particle densities up to 10 to the 20th power per cu cm are obtained over a temperature range of 30,000 to 50,000 K. The device consists of a capillary discharge channel lined with pressed and sintered UO2. A 250 joule capacitor bank is discharged into the channel, producing a plasma of 10-20 microsec duration. Spectroscopic observations are made over the spectral range of 1300 to 2500 A.

  18. Surface plasma wave assisted second harmonic generation of laser over a metal film

    SciTech Connect

    Chauhan, Santosh; Parashar, J.

    2015-01-15

    Second harmonic generation of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal–vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second harmonic ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second harmonic surface plasma wave.

  19. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    SciTech Connect

    Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

    2015-03-15

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

  20. Impedance Mismatch study between the Microwave Generator and the PUPR Plasma Machine

    SciTech Connect

    Gaudier, Jorge R.; Castellanos, Ligeia; Encarnacion, Kabir; Zavala, Natyaliz; Rivera, Ramon; Farahat, Nader; Leal, Edberto

    2006-12-04

    Impedance mismatch inside the connection from the microwave power generator to the plasma machine is studied. A magnetron power generator transmits microwaves of 2.45 GHz and variable power from 50W to 5000W, through a flexible rectangular waveguide to heat plasma inside a Mirror Cusp devise located at the Polytechnic University of Puerto Rico. Before the production of plasma, the residual gas of the devise must be extracted by a vacuum system (5Torr or better), then Argon gas is injected to the machine. The microwaves heat the Argon ions to initiate ionization and plasma is produced. A dielectric wall is used inside the rectangular waveguide to isolate the plasma machine and maintain vacuum. Even though the dielectric will not block the wave propagation, some absorption of microwaves will occur. This absorption will cause reflection, reducing the efficiency of the power transfer. Typically a thin layer of Teflon is used, but measurements using this dielectric show a significant reflection of power back to the generator. Due to the high-power nature of the generator (5KW), this mismatch is not desirable. An electromagnetic field solver based on the Finite Difference Time Domain Method(FDTD) is used to model the rectangular waveguide connection. The characteristic impedance of the simulation is compared with the analytical formula expression and a good agreement is obtain. Furthermore the Teflon-loaded guide is modeled using the above program and the input impedance is computed. The reflection coefficient is calculated based on the transmission line theory with the characteristic and input impedances. Based on the simulation results it is possible to optimize the thickness, shape and dielectric constant of the material, in order to seal the connection with a better match.

  1. Generation of Streamer Discharge Plasma in Water by All Solid-State Pulsed Power

    NASA Astrophysics Data System (ADS)

    Sakugawa, Takashi; Yamaguchi, Takahiro; Yamamoto, Kunihiro; Choi, Jaegu; Kiyan, Tsuyoshi; Namihira, Takao; Katsuki, Sunao; Akiyama, Hidenori

    Pulsed power has been used to produce non-thermal plasmas in gases that generate a high electric field at the tip of streamer discharges, where high energy electrons, free radicals, and ozone are produced. Recently, all solid-state pulsed power generators, which are operated with high repetition rate, long lifetime and high reliability, have been developed for industrial applications, such as high repetition rate pulsed gas lasers, high energy density plasma (EUV sources) and water discharges. We have studied and developed repetitive all solid-state pulsed power system for discharge in water. The developed system consists of a photo-voltaic generator, a Pb battery, an inverter, a controller, a command charger, a high-speed thyristor, a magnetic pulse compression circuit and a pulse transformer, and has mobility. This system can generate an output peak voltage of over 100 kV with voltage rise time of 200 ns. In this work, large volume streamer like discharges in water were produced by the developed system and this discharge plasma used to treat algae (Microcystis) with point-to-plane simple electrodes.

  2. Megagauss field generation for high-energy-density plasma science experiments.

    SciTech Connect

    Rovang, Dean Curtis; Struve, Kenneth William; Porter, John Larry Jr.

    2008-10-01

    There is a need to generate magnetic fields both above and below 1 megagauss (100 T) with compact generators for laser-plasma experiments in the Beamlet and Petawatt test chambers for focused research on fundamental properties of high energy density magnetic plasmas. Some of the important topics that could be addressed with such a capability are magnetic field diffusion, particle confinement, plasma instabilities, spectroscopic diagnostic development, material properties, flux compression, and alternate confinement schemes, all of which could directly support experiments on Z. This report summarizes a two-month study to develop preliminary designs of magnetic field generators for three design regimes. These are, (1) a design for a relatively low-field (10 to 50 T), compact generator for modest volumes (1 to 10 cm3), (2) a high-field (50 to 200 T) design for smaller volumes (10 to 100 mm3), and (3) an extreme field (greater than 600 T) design that uses flux compression. These designs rely on existing Sandia pulsed-power expertise and equipment, and address issues of magnetic field scaling with capacitor bank design and field inductance, vacuum interface, and trade-offs between inductance and coil designs.

  3. Divertor conditions relevant for fusion reactors achieved with linear plasma generator

    SciTech Connect

    Eck, H. J. N. van; Lof, A.; Meiden, H. J. van der; Rooij, G. J. van; Scholten, J.; Zeijlmans van Emmichoven, P. A.; Kleyn, A. W.

    2012-11-26

    Intense magnetized hydrogen and deuterium plasmas have been produced with electron densities up to 3.6 Multiplication-Sign 10{sup 20} m{sup -3} and electron temperatures up to 3.7 eV with a linear plasma generator. Exposure of a W target has led to average heat and particle flux densities well in excess of 4 MW m{sup -2} and 10{sup 24} m{sup -2} s{sup -1}, respectively. We have shown that the plasma surface interactions are dominated by the incoming ions. The achieved conditions correspond very well to the projected conditions at the divertor strike zones of fusion reactors such as ITER. In addition, the machine has an unprecedented high gas efficiency.

  4. Effective factors on twisted terahertz radiation generation in a rippled plasma

    NASA Astrophysics Data System (ADS)

    Sobhani, Hassan; Dadar, Elham; Feili, Sahar

    2017-02-01

    Based on the beating of two Laguerre-Gaussian laser beams in a rippled plasma medium, the effective factors such as plasma density, Gouy phase and orbital angular momentums of input lasers on the output twisted terahertz radiation are investigated. As a result, the amplitude of the generated vortex terahertz radiation is an increasing function of plasma density. The vortex terahertz intensity is strongly dependent on the orbital angular momentum of the input lasers. The terahertz output amplitude increases by decreasing the orbital angular momentum of the Laguerre-Gaussian input lasers. Here, by employing a suitably ripple wavenumber, the destroyer effect of the relative Gouy phase of the input lasers is removed, and perfect phase matching is satisfied.

  5. Transport and Deposition of Hydrocarbons in the Plasma Generator PSI-2

    NASA Astrophysics Data System (ADS)

    Naujoks, D.; Bohmeyer, W.; Markin, A.; Arkhipov, I.; Carl, P.; Koch, B.; Reiner, H.-D.; Schröder, D.; Fussmann, G.

    A series of experiments dedicated to the analysis of transport and sticking of hydrocarbon molecules have been performed in the plasma generator PSI-2. As a source of hydrocarbons defined amounts of CH4 and C2H4 have been injected. After injection the molecules undergo a series of ionisation and dissociation reactions. The thickness change of deposited layers on temperature controlled collector surfaces (outside the plasma column) was measured in-situ by means of an optical spectroscopy for different plasma conditions (density, working gas, injection position) and as function of the collector temperature. It was found that the flux of atomic hydrogen mainly determines whether net-deposition or net-erosion occurs. For the simulation of the experiments the 3D Monte Carlo code ERO was applied allowing a numerical description of the emission, transport, deposition and re-erosion cycle of hydrocarbon molecules.

  6. Integral equation for electrostatic waves generated by a point source in a spatially homogeneous magnetized plasma

    SciTech Connect

    Podesta, John J.

    2012-08-15

    The electric field generated by a time varying point charge in a three-dimensional, unbounded, spatially homogeneous plasma with a uniform background magnetic field and a uniform (static) flow velocity is studied in the electrostatic approximation which is often valid in the near field. For plasmas characterized by Maxwell distribution functions with isotropic temperatures, the linearized Vlasov-Poisson equations may be formulated in terms of an equivalent integral equation in the time domain. The kernel of the integral equation has a relatively simple mathematical form consisting of elementary functions such as exponential and trigonometric functions (sines and cosines), and contains no infinite sums of Bessel functions. Consequently, the integral equation is amenable to numerical solutions and may be useful for the study of the impulse response of magnetized plasmas and, more generally, the response to arbitrary waveforms.

  7. Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Lopez-Quintas, I.; Benítez-Cañete, A.; de Nalda, R.; Castillejo, M.

    2017-01-01

    Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium.

  8. Mechanistic Modeling of the Effects of Acidosis on Thrombin Generation

    DTIC Science & Technology

    2015-08-01

    protocol. Thus, in the case of the default initial concentrations, we used Figure 1. Relative enzyme activity as a function of pH . For every con- sidered...acidotic pH level, the pH factor values (which express enzy- matic activity relative to that at pH 7.4) were sampled uniformly from the interval...trajectories, onset time and activation time increased, while maximum slope and final level decreased. For every acidotic pH level, the pattern FC

  9. Fast ion generation in the cathode plasma jet of a multipicosecond laser-triggered vacuum discharge

    SciTech Connect

    Moorti, A.; Naik, P. A.; Gupta, P. D.

    2010-03-15

    Ion generation in the cathode plasma jet of a moderate-current ({approx}2.3 kA), low-energy ({<=}20 J) vacuum spark discharge triggered by {approx}27 ps, 10 mJ laser pulses is studied using time of flight technique. Fastest ion velocity and velocity corresponding to the peak of the time of flight signals for Al cathode were measured to be {approx}5.25x10{sup 8} cm/s (energy of {approx}143 keV/u) and {approx}8.1x10{sup 7} cm/s (energy of {approx}3.4 keV/u), respectively. Corresponding velocities in the case of ions generated from laser-produced Al plasma (energy of {approx}550 mJ, intensity of {approx}10{sup 14} W/cm{sup 2}) were found to be much smaller, viz., {approx}1.05x10{sup 8} cm/s (energy of {approx}5.75 keV/u) and {approx}2.63x10{sup 7} cm/s (energy of {approx}0.36 keV/u), respectively. Study shows efficient acceleration of ions in a current-carrying cathode plasma jet of a small-energy multipicosecond laser-triggered spark discharge as compared with that in a high-energy multipicosecond laser-produced plasma plume.

  10. Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

    NASA Astrophysics Data System (ADS)

    Tamura, Jun; Kumaki, Masafumi; Kondo, Kotaro; Kanesue, Takeshi; Okamura, Masahiro

    2016-02-01

    We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe21+) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe19+). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

  11. Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

    SciTech Connect

    Tamura, Jun; Kumaki, Masafumi; Kondo, Kotaro; Kanesue, Takeshi; Okamura, Masahiro

    2016-02-15

    We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe{sup 21+}) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe{sup 19+}). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

  12. Demonstration of the 101st harmonic generated from a laser-produced manganese plasma

    SciTech Connect

    Ganeev, R. A.; Bom, L. B. Elouga; Kieffer, J.-C.; Ozaki, T.; Suzuki, M.; Kuroda, H.

    2007-08-15

    We demonstrate the generation of the 101st harmonic (wavelength {lambda}=7.9 nm) from manganese plasma, which is generated using the plasma high-order harmonic technique. We also investigate the variation of the high-order harmonic distribution from the manganese plasma plume as a function of the prepulse and main pulse intensities. The harmonic cutoff was at the 31st order, for pump intensities below the barrier suppression intensity for singly charged Mn ions. However, by using higher prepulse and main pulse intensities, the harmonic cutoff was extended to the 101st order, with an appearance of second plateau for harmonics higher than the 31st order. In this case, the low-order harmonics decreased in intensity, or completely disappeared, and the spectrum for wavelengths longer than 27.6 nm was dominated by plasma line emission. The origin of the harmonics appearing at this short wavelength plateau is attributed to the interaction of the intense main pump laser field with doubly charged manganese ions.

  13. Aptamer functionalized hydrophilic polymer monolith with gold nanoparticles modification for the sensitive detection of human α-thrombin.

    PubMed

    Chen, Yuanbo; Deng, Nan; Wu, Ci; Liang, Yu; Jiang, Bo; Yang, Kaiguang; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2016-07-01

    Low abundant proteins of body fluids participate nearly all physiological processes and indicate various kinds of diseases. The