56 research outputs found
Attractive Potential around a Thermionically Emitting Microparticle
We present a simulation study of the charging of a dust grain immersed in a
plasma, considering the effect of electron emission from the grain (thermionic
effect). It is shown that the OML theory is no longer reliable when electron
emission becomes large: screening can no longer be treated within the
Debye-Huckel approach and an attractive potential well forms, leading to the
possibility of attractive forces on other grains with the same polarity. We
suggest to perform laboratory experiments where emitting dust grains could be
used to create non-conventional dust crystals or macro-molecules.Comment: 3 figures. To appear on Physical Review Letter
Very High Mach Number Electrostatic Shocks in Collisionless Plasmas
The kinetic theory of collisionless electrostatic shocks resulting from the
collision of plasma slabs with different temperatures and densities is
presented. The theoretical results are confirmed by self-consistent
particle-in-cell simulations, revealing the formation and stable propagation of
electrostatic shocks with very high Mach numbers (), well above the
predictions of the classical theories for electrostatic shocks.Comment: 6 pages, submitted to Phys. Rev. Let
The hematopoietic cell transplantation comorbidity index (HCT-CI) predicts clinical outcomes in lymphoma and myeloma patients after reduced-intensity or non-myeloablative allogeneic stem cell transplantation
Magnetic field amplification and electron acceleration to near-energy equipartition with ions by a mildly relativistic quasi-parallel plasma protoshock
The prompt emissions of gamma-ray bursts are seeded by radiating
ultrarelativistic electrons. Internal shocks propagating through a jet launched
by a stellar implosion, are expected to amplify the magnetic field & accelerate
electrons. We explore the effects of density asymmetry & a quasi-parallel
magnetic field on the collision of plasma clouds. A 2D relativistic PIC
simulation models the collision of two plasma clouds, in the presence of a
quasi-parallel magnetic field. The cloud density ratio is 10. The densities of
ions & electrons & the temperature of 131 keV are equal in each cloud. The mass
ratio is 250. The peak Lorentz factor of the electrons is determined, along
with the orientation & strength of the magnetic field at the cloud collision
boundary. The magnetic field component orthogonal to the initial plasma flow
direction is amplified to values that exceed those expected from shock
compression by over an order of magnitude. The forming shock is
quasi-perpendicular due to this amplification, caused by a current sheet which
develops in response to the differing deflection of the incoming upstream
electrons & ions. The electron deflection implies a charge separation of the
upstream electrons & ions; the resulting electric field drags the electrons
through the magnetic field, whereupon they acquire a relativistic mass
comparable to the ions. We demonstrate how a magnetic field structure
resembling the cross section of a flux tube grows in the current sheet of the
shock transition layer. Plasma filamentation develops, as well as signatures of
orthogonal magnetic field striping. Localized magnetic bubbles form. Energy
equipartition between the ion, electron & magnetic energy is obtained at the
shock transition layer. The electronic radiation can provide a seed photon
population that can be energized by secondary processes (e.g. inverse Compton).Comment: 12 pages, 15 Figures, accepted to A&
Multicenter Experience Using Total Lymphoid Irradiation and Antithymocyte Globulin as Conditioning for Allografting in Hematological Malignancies
A non myeloablative conditioning with total lymphoid irradiation (TLI) and antithymocyte globulin (ATG) was shown to protect against graft-versus-host disease (GVHD). To evaluate the effects of TLI-ATG in a multicenter study, 45
heavily pretreated patients, median age 51, with lymphoid (n = 38) and myeloid (n = 7) malignancies were enrolled at 9 centers. Twenty-eight patients (62%) received at least 3 lines of treatment before allografting, and 13 (29%) had refractory/relapsed disease at the time of transplantation. Peripheral blood hematopoietic cells were from HLA identical sibling (n = 30), HLA-matched (n = 9), or 1 antigen HLA-mismatched (n = 6) unrelated donors. A cumulative TLI dose of 8 Gy was administered from day -11 through -1 with ATG at the dose of 1.5 mg/kg/day (from day -11 through -7). GVHD prophylaxis consisted of cyclosporine and mycophenolate mofetil. Donor engraftment was reached in 95% of patients. Grade II to IV acute GVHD (aGVHD) developed in 6 patients (13.3%), and in 2 of these patients, it developed beyond day 100. Incidence of chronic GVHD (cGVHD) was 35.8%. One-year nonrelapse mortality was 9.1%. After a median follow-up of 28 months (range, 3-57 months) from transplantation, median overall survival was not
reached, whereas median event-free survival was 20 months. This multicenter experience confirms that TLI-ATG protects against GVHD and maintains graft-vs-tumor effects
Analysis of Large Phenotypic Variability of EEC and SHFM4 Syndromes Caused by K193E Mutation of the TP63 Gene
EEC (ectrodactyly, ectodermal dysplasia, clefting; OMIM 604292) is an autosomal dominant developmental disorder resulting mainly from pathogenic mutations of the DNA-binding domain (DBD) of the TP63 gene. In this study, we showed that K193E mutation in nine affected individuals of a four-generation kindred with a large degree of phenotypic variability causes four different syndromes or TP63-related disorders: EEC, Ectrodactyly-ectodermal dysplasia (EE), isolated ectodermal dysplasia, and isolated Split Hand/Foot Malformation type 4 (SHFM4). Genotype-phenotype and DBD structural modeling analysis showed that the K193-located loop L2-A is associated with R280 through hydrogen bonding interactions, while R280 mutations also often cause large phenotypic variability of EEC and SHFM4. Thus, we speculate that K193 and several other DBD mutation-associated syndromes may share similar pathogenic mechanisms, particularly in the case of the same mutation with different phenotypes. Our study and others also suggest that the phenotypic variability of EEC is attributed, at least partially, to genetic and/or epigenetic modifiers
Myeloablative conditioning with thiotepa-busulfan-fludarabine does not improve the outcome of patients transplanted with active leukemia: final results of the GITMO prospective trial GANDALF-01
The outcome of refractory/relapsed (R/R) acute leukemias is still dismal and their treatment represents an unmet clinical need. However, allogeneic transplantation (allo-HSCT) remains the only potentially curative approach in this setting. A prospective study (GANDALF-01, NCT01814488; EUDRACT:2012-004008-37) on transplantation with alternative donors had been run by GITMO using a homogeneous myeloablative conditioning regimen with busulfan, thiotepa and fludarabine while GVHD prophylaxis was stratified by donor type. The study enrolled 101 patients; 90 found an alternative donor and 87 ultimately underwent allo-HSCT. Two-year overall survival of the entire and of the transplant population (primary endpoint) were 19% and 22%, without significant differences according to disease, donor type and disease history (relapsed vs refractory patients). Two-year progression-free survival was 19% and 17% respectively. The cumulative incidences of relapse and non-relapse mortality were 49% and 33% at two years. Acute grade II-IV and chronic GVHD occurred in 23 and 10 patients. Dose intensification with a myeloablative two-alkylating regimen as sole strategy for transplanting R/R acute leukemia does seem neither to improve the outcome nor to control disease relapse. A pre-planned relapse prevention should be included in the transplant strategy in this patient population
Phase II Study of Perifosine and Sorafenib Dual-Targeted Therapy in Patients with Relapsed or Refractory Lymphoproliferative Diseases
Acceleration of dust grains by means of electromagnetic cyclotron waves
It is shown that charged dust grains can be accelerated by the nonuniform space charge electric fields that are created by the ponderomotive force of circularly polarized electromagnetic cyclotron waves. The relevance of our investigation to dust energization in the Earth's mesospheric plasma is stressed
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