Secondary Plasma Research Articles

Characteristics of cold atmospheric plasma source based on low-current pulsed discharge with coaxial electrodes

This work investigates the characteristics of the gas discharge system used to create an atmospheric pressure plasma flow. The plasma jet design with a cylindrical graphite cathode and an anode rod located on the axis of the system allows to realize regularly reproducible spark breakdowns mode with a frequency ∼ 5 kHz and a duration ∼ 40 μs. The device generates a cold atmospheric plasma flame with 1 cm in diameter in the flow of various plasma forming gases including nitrogen and air at about 100 mA average discharge current. In the described construction the cathode spots of individual spark channels randomly move along the inner surface of the graphite electrode creating the secondary plasma stream time-average distributed throughout the whole exit aperture area after the decay of numerous filamentary discharge channels. The results of the spectral diagnostics of plasma in the discharge gap and in the stream coming out of the source are presented. Despite the low temperature of atoms and molecules in plasma stream the cathode spots operation with temperature of ∼ 4000 °C at a graphite electrode inside a discharge system enables to saturate the plasma by CN-radicals and atomic carbon in the case of using nitrogen as the working gas.

Determination of Plasma Screening Effects for Thermonuclear Reactions in Laser-generated Plasmas

Abstract Due to screening effects, nuclear reactions in astrophysical plasmas may behave differently than in the laboratory. The possibility to determine the magnitude of these screening effects in colliding laser-generated plasmas is investigated theoretically, having as a starting point a proposed experimental setup with two laser beams at the Extreme Light Infrastructure facility. A laser pulse interacting with a solid target produces a plasma through the Target Normal Sheath Acceleration scheme, and this rapidly streaming plasma (ion flow) impacts a secondary plasma created by the interaction of a second laser pulse on a gas jet target. We model this scenario here and calculate the reaction events for the astrophysically relevant reaction 13C(4He, n)16O. We find that it should be experimentally possible to determine the plasma screening enhancement factor for fusion reactions by detecting the difference in reaction events between two scenarios of ion flow interacting with the plasma target and a simple gas target. This provides a way to evaluate nuclear reaction cross-sections in stellar environments and can significantly advance the field of nuclear astrophysics.

Investigation of sewage sludge treatment using air plasma assisted gasification

This study presents an experimental investigation of downdraft gasification process coupled with a secondary thermal plasma reactor in order to perform experimental investigations of sewage sludge gasification, and compare process parameters running the system with and without the secondary thermal plasma reactor.The experimental investigation were performed with non-pelletized mixture of dried sewage sludge and wood pellets. To estimate the process performance, the composition of the producer gas, tars, particle matter, producer gas and char yield were measured at the exit of the gasification and plasma reactor. The research revealed the distribution of selected metals and chlorine in the process products and examined a possible formation of hexachlorobenzene.It determined that the plasma assisted processing of gaseous products changes the composition of the tars and the producer gas, mostly by destruction of hydrocarbon species, such as methane, acetylene, ethane or propane. Plasma processing of the producer gas reduces their calorific value but increases the gas yield and the total produced energy amount. The presented technology demonstrated capability both for applying to reduce the accumulation of the sewage sludge and production of substitute gas for drying of sewage sludge and electrical power.

Experimental observation of self excited co-rotating multiple vortices in a dusty plasma with inhomogeneous plasma background

We report an experimental observation of multiple co-rotating vortices in an extended dust column in the background of an inhomogeneous diffused plasma. An inductively coupled rf discharge is initiated in the background of argon gas in the source region. This plasma was later found to diffuse into the main experimental chamber. A secondary DC glow discharge plasma is produced to introduce dust particles into the plasma volume. These micron-sized poly-disperse dust particles get charged in the background of the DC plasma and are transported by the ambipolar electric field of the diffused plasma. These transported particles are found to be confined in an electrostatic potential well, where the resultant electric field due to the diffused plasma (ambipolar E–field) and glass wall charging (sheath E–field) holds the micron–sized particles against the gravity. Multiple co-rotating (anti–clockwise) dust vortices are observed in the dust cloud for a particular discharge condition. The transition from multiple vortices to a single dust vortex is observed when input rf power is lowered. The occurrence of these vortices is explained on the basis of the charge gradient of dust particles, which is orthogonal to the ion drag force. The charge gradient is a consequence of the plasma inhomogeneity along the dust cloud length. The detailed nature and the reason for multiple vortices are still under investigation through further experiments; however, preliminary qualitative understanding is discussed based on the characteristic scale length of the dust vortex. There is a characteristic size of the vortex in the dusty plasma; therefore, multiple vortices could possibly be formed in an extended dusty plasma with inhomogeneous plasma background. The experimental results on the vortex motion of particles are compared with a theoretical model and are found to be in close agreement.

Distinct T helper cell dependence of memory B‐cell proliferation versus plasma cell differentiation

Several memory B-cell subclasses with distinct functions have been described, of which the most effective is the class-switched (CS) memory B-cell population. We have previously shown, using virus-like particles (VLPs), that the proliferative potential of these CS memory B cells is limited and they fail to re-enter germinal centres (GCs). However, VLP-specific memory B cells quickly differentiated into secondary plasma cells (PCs) with the virtue of elevated antibody production compared with primary PCs. Whereas the induction of VLP+ memory B cells was strongly dependent on T helper cells, we were wondering whether re-stimulation of VLP+ memory B cells and their differentiation into secondary PCs would also require T helper cells. Global absence of T helper cells led to strongly impaired memory B cell proliferation and PC differentiation. In contrast, lack of interleukin-21 receptor-dependent follicular T helper cells or CD40 ligand signalling strongly affected proliferation of memory B cells, but differentiation into mature secondary PCs exhibiting increased antibody production was essentially normal. This contrasts with primary B-cell responses, where a strong dependence on CD40 ligand but limited importance of interleukin-21 receptor was seen. Hence, T helper cell dependence differs between primary and secondary B-cell responses as well as between memory B-cell proliferation and PC differentiation.

Influence of the target material on secondary plasma formation underwater and its laser induced breakdown spectroscopy (LIBS) signal

The significant influence of the target material properties on subsequent plasma and bubble formation in underwater laser ablation is demonstrated through the examples of α-alumina and pure Al targets.

Proteome alterations associated with transformation of multiple myeloma to secondary plasma cell leukemia.

Plasma cell leukemia is a rare and aggressive plasma cell neoplasm that may either originate de novo (primary PCL) or by leukemic transformation of multiple myeloma (MM) to secondary PCL (sPCL). The prognosis of sPCL is very poor, and currently no standard treatment is available due to lack of prospective clinical studies. In an attempt to elucidate factors contributing to transformation, we have performed super-SILAC quantitative proteome profiling of malignant plasma cells collected from the same patient at both the MM and sPCL stages of the disease. 795 proteins were found to be differentially expressed in the MM and sPCL samples. Gene ontology analysis indicated a metabolic shift towards aerobic glycolysis in sPCL as well as marked down-regulation of enzymes involved in glycan synthesis, potentially mediating altered glycosylation of surface receptors. There was no significant change in overall genomic 5-methylcytosine or 5-hydroxymethylcytosine at the two stages, indicating that epigenetic dysregulation was not a major driver of transformation to sPCL. The present study constitutes the first attempt to provide a comprehensive map of the altered protein expression profile accompanying transformation of MM to sPCL in a single patient, identifying several candidate proteins that can be targeted by currently available small molecule drugs. Our dataset furthermore constitutes a reference dataset for further proteomic analysis of sPCL transformation.

Pilot Study of Anti-CD19 Chimeric Antigen Receptor T Cells (CTL019) in Conjunction with Salvage Autologous Stem Cell Transplantation for Advanced Multiple Myeloma

Background: Though CD19 is expressed only rarely on multiple myeloma (MM) plasma cells (PC), rare CD19+ B cells can be identified in MM patients that are clonally related to the MM PC. These clonotypic B cells may exhibit properties of cancer stem cells (enhanced MM-propagating properties and drug resistance compared to MM PC) and thus be a potential therapeutic target in conjunction with therapies that target MM PC. CTL019 consists of autologous T cells transduced via lentiviral vector with an anti-CD19 scFv coupled to CD3-zeta and 4-1BB signaling domains and expanded ex vivo with anti-CD3/CD28-conjugated beads. To target both clonotypic B cells and MM PC, we conducted a pilot clinical trial of CTL019 administered after high-dose melphalan and autologous stem cell transplantation (ASCT) in relapsed/refractory MM patients who had previously undergone first-line ASCT with short progression-free survival (PFS).Methods: Subjects were required to be medically fit for ASCT and have progressed within 1 year of a prior ASCT performed as part of first-line therapy. Study therapy consisted of ASCT with melphalan 140-200 mg/m2 followed by 1-5x107 CTL019 cells 12-14 days later. The primary endpoint was safety and feasibility of CTL019 manufacturing and administration in this clinical setting. Secondary endpoints included assessments of CTL019 in vivo persistence and activity against normal B cells, plasma cell immunophenotype as a response biomarker, and PFS after ASCT + CTL019 in comparison to PFS after initial ASCT.Results: Twelve subjects enrolled, and 10 received study therapy; autologous T cells failed to expand ex vivo in one enrolled subject, and one enrolled subject elected to pursue off-study therapy. Median age was 61 (range 48-68). Median prior lines of therapy was 6 (range 2-10). Poor-prognosis features were present in 8/10 subjects (6/10 with poor-prognosis cytogenetics, 2/10 with BRAF V600E mutations, 1/10 with secondary plasma cell leukemia). Median PFS after first-line ASCT was 258 days (range 100-342). In pre-ASCT bone marrow (BM), the dominant MM PC population was CD19-negative by flow cytometry in 9/9 evaluable subjects, though 7/9 exhibited rare CD19+ subsets comprising 0.05-1.5% of MM PC. Melphalan dose was 140 (N=7) or 200 (N=3) mg/m2. All subjects infused received the maximum target dose of 5x107 CTL019 cells. Adverse events (AE) consisted mostly of expected ASCT toxicities. Grade ³3 AE that were at least possibly related to CTL019 included grade 3 autologous GVHD (N=1, resolved with corticosteroids) and oral mucositis (N=1). Grade 1 cytokine release syndrome occurred in 1 subject. There was no ASCT-related mortality. After infusion, CTL019 cells were detectable in peripheral blood (PB) of all subjects and persisted for median of 44 days (range 14-156). Presence of PB CTL019 cells was associated with absence of PB B cells. Notably, CTL019 cells were detected in BM in 9/10 subjects at day 42 and/or 100 post-ASCT. Median PFS after ASCT + CTL019 was 185 days (range 42-479); all subjects have progressed. The peak BM CTL019 frequency correlated significantly with favorable PFS (SpearmanÕs rho=0.77, P=0.009). There was no association between PFS and peak frequency of CTL019 or duration of CTL019 persistence in PB. In 3/10 subjects, PFS after ASCT + CTL019 met or exceeded PFS after first-line ASCT (Figure). For comparison, in a historical cohort of 18 patients who received first-line and salvage ASCT at our institution since 2008, no patients exhibited longer PFS after salvage ASCT.Conclusion: CTL019 manufacturing and administration post-ASCT is safe and feasible in patients with advanced MM. Correlation of PFS with CTL019 frequency in BM and prolonged PFS in 3 subjects is suggestive of clinical efficacy. A phase-two study of CTL019 using a 10-fold higher dose after first-line ASCT in high-risk MM patients is ongoing. [Display omitted] DisclosuresGarfall:Medimmune: Consultancy; Bioinvent: Research Funding; Novartis: Consultancy, Research Funding. Stadtmauer:Novartis: Consultancy; Takada: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Teva: Consultancy; Celgene: Consultancy. Maus:Novartis: Patents & Royalties: related to CTL019, Research Funding. Hwang:Novartis: Research Funding. Vogl:Takeda: Consultancy, Research Funding; GSK: Research Funding; Calithera: Research Funding; Teva: Consultancy; Constellation: Research Funding; Celgene: Consultancy; Acetylon: Research Funding; Karyopharm: Consultancy. Cohen:Bristol-Meyers Squibb: Consultancy, Research Funding; Janssen: Consultancy. Weiss:Novartis: Consultancy. Porter:Genentech: Employment; Novartis: Patents & Royalties, Research Funding. Frey:Novartis: Research Funding; Amgen: Consultancy. Milone:Novartis: Patents & Royalties, Research Funding. Mangan:Novartis: Speakers Bureau. Lacey:Novartis: Research Funding. Melenhorst:Novartis: Patents & Royalties: Novartis, Research Funding. Ambrose:Novartis: Research Funding. Chen:Novartis: Research Funding. Kulikovskaya:Novartis: Research Funding. Levine:Novartis: Patents & Royalties, Research Funding; GE Healthcare Bio-Sciences: Consultancy. June:Johnson & Johnson: Honoraria; Tmunity Therapeutics: Equity Ownership; Novartis: Honoraria, Patents & Royalties, Research Funding; Immune Design: Consultancy, Equity Ownership; Celldex: Consultancy, Equity Ownership; Novartis: Honoraria, Patents & Royalties, Research Funding; Pfizer: Honoraria.

Response-Adapted Therapy for Newly Diagnosed Myeloma

Background: Before SWOG S0777 (Durie BGM at al. ASH 2015, abstract #25) it was not clear whether standard upfront regimens VRd (bortezomib, lenalidomide, dexamethasone) or Rd (lenalidomide, dexamethasone) yield different survival outcomes for newly diagnosed myeloma patients (pts.) but it was known that the higher response rate of VRd comes at a higher risk for severe peripheral neuropathy. Since no test predicts who requires the more toxic regimen to avoid adverse myeloma effects we designed a carepath that tailors therapy according to early response endpoints.Methods: Newly diagnosed symptomatic MM patients (pts) with measurable disease who were not eligible for or elected against a clinical trial were advised to begin a 2-drug regimen of lenalidomide (R) and weekly dexamethasone (d) or, if cast nephropathy suspected or R copay too high, bortezomib (V) and dexamethasone (D). Depending on response assessment per IMWG 2011 criteria after each cycle, treatment intensity was to be increased with sequential addition of agents (R or V, cyclophosphamide, and then liposomal doxorubicin) when there was not at least minor response (MR) after the first, or at least partial response (PR) after the second cycle of an administered combination. Once PR was reached, pts. were evaluated for high dose melphalan (HDM) and ASCT or consolidation with their induction regimen followed in either case by lenalidomide or bortezomib maintenance. After IRB approval, pts treated on carepath were identified through our registry and electronic medical records were reviewed.Results: From Oct 2012 to Dec 2015 the carepath was used in 91 pts. Their median age at treatment start was 64 years (34-84), 40 (44%) were ≥ 65, 11 (12%) ≥ 75 years old; at least one cytogenetic risk study (MyPRS®, FISH panel, karyotype analysis) was obtained in 81 (89%) and of them 23 (28.4%) had high risk features (MyPRS® score > 45.2, del17p, 1q amp, t4;14, t;14;16 and non-hyperdiploid karyotype abnormalities), 33 (36%) had ISS stage III and 21 (23%) had serum creatinine ≥ 2mg/dL, 6 (7%) were on dialysis. At median follow up of 20.5 months (1.7-44.6), at least PR was achieved in 84 pts (92%), at least very good partial remission (VGPR) in 63 (69%), with negative immunofixation in blood and urine in 24 (26%) and complete remission (CR) documented by bone marrow exam in 6 (7%). Only one pt (1%) had progressive disease as best response, stable disease and MR were seen in 3 pts. (3%) each. Induction required 2, 3, 4 and 5 drugs in 49 (54%), 33 (36%), 8 (9%), 1 (1%) pts, respectively, and was followed by high dose melphalan and autologous stem cell transplant in 19 (21%). Sixty-three pts. (69%) remain on carepath treatment without progression, while 28 (31%) have experienced progression with skeletal events in 4 (4%) and ARF in 2 pts. (2%). Nine pts. (10%) have died, 4 while in remission of whom 3 suffered a bleed while anticoagulated for DVT or pre-existing A-fib and died 1 after transition to hospice; the remaining 5 died after progression, of infection (3), secondary plasma cell leukemia (1), or after transition to hospice (2). No patient developed shingles or second primary malignancies so far; mild peripheral neuropathy (PNP) occurred in 27 pts (30%), severe or painful PNP in 4 (4%) and 8 pts. (9%) suffered venous thromboembolism (9%) on DVT prophylaxis with aspirin.Conclusions: Carepath therapy required only two drugs during induction in over 50% of patients to achieve an overall response rate of 92% with ≥ VGPR in 69% in a real-world setting without exclusion of patients on dialysis. Reduction in costs and side effects compared to upfront use of VRd for everyone were accompanied by promising early Kaplan-Meier estimates for progression-free and overall survival (Fig. 1) supporting the carepath principle and future randomized comparison of response-adapted therapy to fixed regimens like the new SWOG S0777 defined standard triplet VRd. [Display omitted] DisclosuresReu:Novartis: Research Funding; Takeda: Research Funding; Celgene: Research Funding; Signal Genetics: Consultancy. Valent:Celgene: Speakers Bureau; Takeda: Speakers Bureau. Faiman:Celgene: Consultancy, Speakers Bureau; Amgen: Consultancy; Takeda: Consultancy. Hamilton:Takeda: Speakers Bureau. Smith:Celgene: Honoraria; Spectrum: Honoraria; Genentech: Honoraria; Abbvie: Research Funding.

Plasma Cell Leukaemia. Experience from Tertiary Referral Centres in Abu Dhabi

Plasma cell neoplasms range from an indolent disease (MGUS) to highly aggressive and relatively rare Plasma Cell Leukaemia (PCL). The diagnostic criteria for PCL is well established and includes plasmacytosis of greater than 20% of total white cell count or an absolute plasma cell count of greater than 2 X 109/L in peripheral blood. It is classified as either primary (pPCL) if there is no antecedent history of Multiple Myeloma (MM) or secondary (sPCL) arising as a leukemic event of MM. The median survival of PCL remains poor despite the use of novel agents and stem cell transplant. Here we report our experience with PCL.Method:Retrospective review of the medical records of patients with plasma cell dyscrasia identified through the tumour registry between January 2008 and March 2016. Eight patients were identified with diagnosis of PCL.Results:The median age was 53.5 years (range 34-77 years), male to female ratio was 5:3. There were four cases of sPCL while the other four patients had pPCL. The median time for transformation in sPCL was 199 weeks (range 163 to 244 weeks).All 4 patients with sPCL had received treatment with novel agents including bortezomib and IMIDS (lenalidomide/thalidomide) as part of their myeloma therapy. At the time of transformation two patients were unfit for any therapy while the other two patients were re-induced with bortezomib, lenalidomide and dexamethasone (RVd) with no response. None of the four patients had undergone autologous stem cell transplantation (due to unavailability of hematopoietic stem cell transplant facilities in UAE as well as socioeconomic reasons). The median survival after diagnosis of sPCL was 5.4 weeks (range 4-11 weeks).Patients with pPCL were treated with RVd (n=3) and VMP N=1. One patient also had an autologous stem cell transplant. Patients with primary PCL had a better median survival of 37 weeks (range 14 - 133 weeks) with one patient alive and under therapy 14 weeks after diagnosis.Conclusion:Plasma cell leukaemia remains a disease with extreme poor prognosis and an overall mortality of 88 per cent in our experience. Interestingly two patients with pPCL were noted to have evidence of plasma cell disorder (elevated total protein) a median of 8 months before the diagnosis of pPCL. Whether these two cases truly represent pPCL or 2ndry event because of under diagnosis of MM remains speculative at best. One of the above two patients also had a diagnosis of chronic myeloid leukaemia on Imatinib and was in a major molecular remission. Patients with primary plasma cell leukaemia tend to do relatively better as compared to secondary plasma cell leukaemia where the transformation is catastrophic with a very short median survival. The difference in survival between pPCL and sPCL is most likely because the sPCL has a more resistant disease due to previous treatment and clonal evolution of their disease.Second generation novel agents including carfizlomib and the monoclonal antibodies daratumomab and elotuzumab should be evaluated in the induction and maintenance strategy to improve the outcome of PCL. DisclosuresAlam:BMS: Consultancy, Honoraria; Biologix: Honoraria.

Primary Plasma Cell Leukemia Has a Poor Prognosis Even in the Era of Novel Agents - a Multicenter Case Series

Introduction: Primary plasma cell leukemia (PPCL) is a rare and aggressive variant of multiple myeloma (MM), characterized by the presence of 20% and/or 2X109/L plasma cells (PCs) in the peripheral blood (PB) of the patient. Data regarding this entity are scarce and based on case reports and few retrospective case series. Most of the reports are dated prior to the incorporation of novel agents into MM treatment. The aim of this multicenter retrospective study was to evaluate the response and survival of PPCL patients in the era of the novel agents.Methods: We searched for the diagnosis of PPCL, during the years 2002-2016, in the medical summaries of 16 medical centers in Israel which routinely treat patients with MM. Patients with the presence of plasma cells in the blood during the course of MM (secondary plasma cell leukemia) were excluded.Results: 40 PPCL patients were identified in 11 of the 16 medical centers. It is probable that several patients were recorded as MM and thus not identified as PPCL. The characteristics of the patients and their disease are available for 35 patients and are summarized in table 1. One third of the patients presented with light chain disease and over two thirds had hypercalcemia at diagnosis. The median age was 60 and 3 patients were aged less than 35 years at diagnosis. The median number of treatments was 2. 83% of the patients received at least one IMiD or proteosome inhibitor (PI), 51% received both IMiD and PI. 17% of the patients received more than one line of IMiDs and a similar number of patients received more than one line of PIs (Fig. 1). The type of novel agents that were used are shown in figure 2. 45.7% of the patients underwent hematopoietic stem cell transplant (HSCT), of those, 4 patients (11%) have undergone tandem auto-allo HSCT and 1 (3%) - tandem auto-auto HSCT.29% of the patients did not responded to induction therapy and 57% achieved PR or better response. 13 out of 35 patients (37%) are still alive and one is lost to follow-up. The median overall survival (OS) was 11 months.7 patients (20%) survived less than 2 months while 13 (37%) survived more than 24 months, including 7 who survived more than 48 months.Among the 16 patients who underwent HSCT, all the 4 who underwent tandem auto-allo-transplant survived more than 32 months.Conclusions: Despite the modest size of this patient cohort, several inferences may be made. Patients with PPCL have unique characteristics compared to MM patients; lower median age, more frequent light chain disease and hypercalcemia at presentation. Extreme leukocytosis or leukopenia are rare. Despite intensive use of novel agents, the median OS of this cohort remains poor - 11 months. The best results were seen in patients who received tandem auto-allo HSCT, suggesting that the immunotherapeutic graft-versus-myeloma effect may offer the best hope for long-term survival to patients with PPCL. [Display omitted] [Display omitted] [Display omitted] DisclosuresAvivi:Tel Aviv Sourasky Medical center: Consultancy, Other: consultancy to :BMS Roche.

Interaction of powerful hot plasma and fast ion streams with materials in dense plasma focus devices

A process of irradiating and ablating solid-state targets with hot plasma and fast ion streams in two Dense Plasma Focus (DPF) devices – PF-6 and PF-1000 was examined by applying a number of diagnostics of nanosecond time resolution. Materials perspective for use in chambers of the mainstream nuclear fusion facilities (mainly with inertial plasma confinement like NIF and Z-machine), intended both for the first wall and for constructions, have been irradiated in these simulators. Optical microscopy, SEM, Atomic Emission Spectroscopy, images in secondary electrons and in characteristic X-ray luminescence of different elements, and X-ray elemental analysis, gave results on damageability for a number of materials including low-activated ferritic and austenitic stainless steels, β-alloy of Ti, as well as two types of W and a composite on its base. With an increase of the number of shots irradiating the surface, its morphology changes from weakly pronounced wave-like structures or ridges to strongly developed ones. At later stages, due to the action of the secondary plasma produced near the target materials they melted, yielding both blisters and a fracturing pattern: first along the grain and then “in-between” the grains creating an intergranular net of microcracks. At the highest values of power flux densities multiple bubbles appeared. Furthermore, in this last case the cracks were developed because of microstresses at the solidification of melt. Presence of deuterium within the irradiated ferritic steel surface nanolayers is explained by capture of deuterons in lattice defects of the types of impurity atoms, pores and oxycarbonitride particles existed in the material.

Highly Segmented Thermal Barrier Coatings Deposited by Suspension Plasma Spray: Effects of Spray Process on Microstructure

Effects of the ceramic powder size used for suspension as well as several processing parameters in suspension plasma spraying of YSZ were investigated experimentally, aiming to fabricate highly segmented microstructures for thermal barrier coating (TBC) applications. Particle image velocimetry (PIV) was used to observe the atomization process and the velocity distribution of atomized droplets and ceramic particles travelling toward the substrates. The tested parameters included the secondary plasma gas (He versus H2), suspension injection flow rate, and substrate surface roughness. Results indicated that a plasma jet with a relatively higher content of He or H2 as the secondary plasma gas was critical to produce highly segmented YSZ TBCs with a crack density up to ~12 cracks/mm. The optimized suspension flow rate played an important role to realize coatings with a reduced porosity level and improved adhesion. An increased powder size and higher operation power level were beneficial for the formation of highly segmented coatings onto substrates with a wider range of surface roughness.

Talking to the dead: using Post-mortem data in the assessment of stress in tiger sharks (Galeocerdo cuvier) (Péron and Lesueur, 1822).

Sharks are very sensitive to stress and prone to a high mortality rate after capture. Since approximately 50million of sharks are caught as bycatch every year, and current recommendations to reduce the impact of commercial fishing strongly support immediate release, it is imperative to better understand post-release mortality caused by the stress of capture and handling. Blood samples allow the assessment of stress levels which are valuable tools to reduce mortality in commercial, recreational and scientific fishing, being essential for the improvement in those conservation measures. Biochemical analyses are widely used for sharks as stress indicators, with secondary plasma parameters (lactate, glucose and ions) being the most often employed assays. However, it is virtually impossible to determine baseline plasma parameters in free-ranging sharks, since blood withdrawal involves animal capture and restrain, which are stressful procedures. This study aims at analyzing secondary parameters of five healthy tiger sharks captured with circular hooks and handlines in Fernando de Noronha (Northeastern Brazil) and comparing them with secondary parameters of three dead tiger sharks caught off Recife (also Northeastern Brazil). The results showed that the analysis of some plasma constituents in dead animals may be an efficient tool to assess stress and lethality. However, traditional parameters such as glucose and calcium, need to be used with caution. The results also demonstrated the extreme importance of urea and phosphorus for assessing stress response and mortality in tiger sharks, both parameters frequently neglected and of utmost importance for shark's homeostasis.

ZBTB32 Restricts the Duration of Memory B Cell Recall Responses.

Memory B cell responses are more rapid and of greater magnitude than are primary Ab responses. The mechanisms by which these secondary responses are eventually attenuated remain unknown. We demonstrate that the transcription factor ZBTB32 limits the rapidity and duration of Ab recall responses. ZBTB32 is highly expressed by mouse and human memory B cells but not by their naive counterparts. Zbtb32(-/-) mice mount normal primary Ab responses to T-dependent Ags. However, Zbtb32(-/-) memory B cell-mediated recall responses occur more rapidly and persist longer than do control responses. Microarray analyses demonstrate that Zbtb32(-/-) secondary bone marrow plasma cells display elevated expression of genes that promote cell cycle progression and mitochondrial function relative to wild-type controls. BrdU labeling and adoptive transfer experiments confirm more rapid production and a cell-intrinsic survival advantage of Zbtb32(-/-) secondary plasma cells relative to wild-type counterparts. ZBTB32 is therefore a novel negative regulator of Ab recall responses.

Effect of buoyancy on power deposition in microwave cavity hydrogen plasma source

A self-consistent model describing the coupling of resonant microwave radiation and plasma has been constructed. This model improves upon the models developed by Hassouni et al and Hagelaar et al, in 1999 and 2004, respectively with inclusion of hydrodynamic effects. The model has been used to study the effect of buoyancy on power deposition in microwave assisted hydrogen plasmas at different operating pressures over the range 25–300 mbar and power over the range 400 and 4000 W. Three cases viz. normal reactor (g = −9.81 m s−2, negative buoyancy), pure diffusion (g = 0 m s−2) and the inverted case (g = 9.81 m s−2, positive buoyancy) were considered. Buoyancy effects in the cavity become important at high power / pressure operating conditions. The formation of a secondary plasma zone is strongly increased in the presence of negative buoyancy, while positive buoyancy and diffusion cases are more stable. Also the density of atomic hydrogen close to the substrate is larger with a wider radial spread for the positive buoyancy case over normal operating conditions which augurs well for achieving good deposition of diamond.

Design and numerical simulation of a high power capacity relativistic backward wave oscillator with an electron collection cavity

A high power capacity relativistic backward wave oscillator with an electron collection cavity (ECC) placed at the downstream of the slow wave structure (SWS) is presented. The breakdown threshold is increased, and the density of seed electron is suppressed by preventing the secondary electron, plasma, and powder generated from the bombardment of spent electron beam on the surface of the collector drifting to the extractor and beam-wave interaction region. The maximum longitudinal electric field in the device is reduced through extension of the span between electron beam and slow wave structure and weakening the Cerenkov radiation. The conversion efficiency reaches up to 52% owing to enhanced transit time radiation taking place at the entrance of the ECC. The maximum longitudinal electric field is 1.1 MV/cm on the surface of SWSs when the output power is 7.3 GW and the power capacity improves significantly.

Experimental investigation on the characteristics of the plasma jet of a low-current vacuum arc in axial magnetic fields

In this paper, the characteristics of the plasma jet of a low-current vacuum arc with a single cathode spot (CS) in an external axial magnetic field (AMF) up to 150 mT is investigated experimentally, at a constant arc current ranging from 20 A to 60 A. The experiments are conducted with Cu butt contacts in a demountable vacuum chamber. Images of the plasma jets are photographed with a high-speed digital camera with an exposure time of 2 μs. The uniform constant AMF (Bn) within the inter-contacts region is supplied by Nd–Fe–B permanent magnets. The influence of the external AMF on the shape of the jet near the anode surface as well as in the arc column is mainly investigated. A luminous ‘spot’ is observed on the anode surface facing the position of the CS under a relatively strong AMF. The mechanism of the appearance of the luminous ‘spot’ is proposed to be connected to the secondary plasma originating from the anode. Moreover, with the increase in the strength of the AMF, the spreading angle of the cone-shaped plasma jet in the arc–column region decreases gradually. The plasma jet, subjected to a relatively strong AMF (120 mT and 150 mT), becomes cylindrical in shape in the arc–column region and conical in shape in the near-electrode regions. The overall geometry of the plasma jet looks like a dumbbell.

Vapor shielding models and the energy absorbed by divertor targets during transient events

The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level Emax. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that Emax depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the Emax is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Thus, Emax cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.

Secondary plasma formation after single pulse laser ablation underwater and its advantages for laser induced breakdown spectroscopy (LIBS).

In this work we present studies of spatial and temporal plasma evolution after single pulse ablation of an aluminium target in water. The laser ablation was performed using 20 ns long pulses emitted at 1064 nm. The plasma characterization was performed by fast photography, the Schlieren technique, shadowgraphy and optical emission spectroscopy. The experimental results indicate the existence of two distinct plasma stages: the first stage has a duration of approximately 500 ns from the laser pulse, and is followed by a new plasma growth starting from the crater center. The secondary plasma slowly evolves inside the growing vapor bubble, and its optical emission lasts over several tens of microseconds. Later, the hot glowing particles, trapped inside the vapor cavity, were detected during the whole cycle of the bubble, where the first collapse occurs after 475 μs from the laser pulse. Differences in the plasma properties during the two evolution phases are discussed, with an accent on the optical emission since its detection is of primary importance for LIBS. Here we demonstrate that the LIBS signal quality in single pulse excitation underwater can be greatly enhanced by detecting only the secondary plasma emission, and also by applying long acquisition gates (in the order of 10-100 μs). The presented results are of great importance for LIBS measurements inside a liquid environment, since they prove that a good analytical signal can be obtained by using nanosecond pulses from a single commercial laser source and by employing cost effective, not gated detectors.