261 research outputs found
A novel fast simulation technique for axisymmetric PWFA configurations in the blowout regime
In the blowout regime of plasma wakefield acceleration (PWFA), which is the
most relevant configuration for current and future applications and
experiments, the plasma flow that is excited by the ultra-relativistic drive
beam is highly nonlinear. Thus, fast and accurate simulations codes are
indispensable tools in the study of this extremely important problem. We have
developed a novel algorithm that deals with the propagation of axisymmetric
bunches of otherwise arbitrary profile through a cold plasma of uniform
density. In contrast to the existing PWFA simulation tools, our code PLEBS
(PLasma-Electron Beam Simulations) uses a new computational scheme which
ensures that the transverse and longitudinal directions are completely
decoupled---a feature which significantly enhances the speed and robustness of
the new method. Our numerical results are benchmarked against the QuickPic code
and excellent agreement is established between the two approaches. Moreover,
our new technique provides a very convenient framework for studying issues such
as beam loading and short-range wakefields within the plasma cavity
Microbunched Electron Cooling with Amplification Cascades
The Microbunched Electron Cooling (MBEC) is a promising cooling technique
that can find applications in future hadron and electron-ion colliders to
counteract intrabeam scattering that limits the maximum achievable luminosity
of the collider. To minimize the cooling time, one would use amplification
cascades consisting of a drift section followed by a magnetic chicane. In this
paper, we first derive and optimize the gain factor in an amplification section
for a simplified one-dimensional model of the beam. We then deduce the cooling
rate of a system with one and two amplification cascades. We also analyze the
noise effects that counteract the cooling process through the energy diffusion
in the hadron beam. Our analytical formulas are confirmed by numerical
simulations for a set of model parameters.Comment: arXiv admin note: text overlap with arXiv:1806.0278
Even-odd flux quanta effect in the Fraunhofer oscillations of an edge-channel Josephson junction
We calculate the beating of and periodic oscillations of the
flux-dependent critical supercurrent through a quantum spin-Hall
insulator between two superconducting electrodes. A conducting pathway along
the superconductor connects the helical edge channels via a non-helical
channel, allowing an electron incident on the superconductor along one edge to
be Andreev reflected along the opposite edge. In the limit of small Andreev
reflection probability the resulting even-odd effect is described by
, with proportional to the
probability for phase-coherent inter-edge transmission. Because the sign of
depends on microscopic details, a sample-dependent inversion of the alternation
of large and small peaks is a distinctive feature of the beating mechanism for
the even-odd effect
Even-odd flux quanta effect in the Fraunhofer oscillations of an edge-channel Josephson junction
Involvement of Mhc Loci in immune responses that are not Ir-gene-controlled
Twenty-nine randomly chosen, soluble antigens, many of them highly complex, were used to immunize mice of two strains, C3H and B10.RIII. Lymphnode cells from the immunized mice were restimulated in vitro with the priming antigens and the proliferative response of the cells was determined. Both strains were responders to 28 of 29 antigens. Eight antigens were then used to immunize 11 congenic strains carrying different H-2 haplotypes, and the T-cell proliferative responses of these strains were determined. Again, all the strains responded to seven of the eight antigens. These experiments were then repeated, but this time -antibodies specific for the A (AA) or E (EE) molecules were added to the culture to block the in vitro responsiveness. In all but one of the responses, inhibition with both A-specific and E-specific antibodies was observed. The response to one antigen (Blastoinyces) was exceptional in that some strains were nonresponders to this antigen. Furthermore, the response in the responder strains was blocked with A-specific, but not with E-specific, antibodies. The study demonstrates that responses to antigens not controlled by Irr genes nevertheless require participation of class II Mhc molecules. In contrast to Ir gene-controlled responses involving either the A- or the E-molecule controlling loci (but never both), the responses not Ir-controlled involve participation of both A- and E-controlling loci. The lack of Ir-gene control is probably the result of complexity of the responses to multiple determinants. There is thus no principal difference between responses controlled and those not controlled by Ir genes: both types involve the recognition of the antigen, in the context of Mhc molecules
GeneLink: a database to facilitate genetic studies of complex traits
BACKGROUND: In contrast to gene-mapping studies of simple Mendelian disorders, genetic analyses of complex traits are far more challenging, and high quality data management systems are often critical to the success of these projects. To minimize the difficulties inherent in complex trait studies, we have developed GeneLink, a Web-accessible, password-protected Sybase database. RESULTS: GeneLink is a powerful tool for complex trait mapping, enabling genotypic data to be easily merged with pedigree and extensive phenotypic data. Specifically designed to facilitate large-scale (multi-center) genetic linkage or association studies, GeneLink securely and efficiently handles large amounts of data and provides additional features to facilitate data analysis by existing software packages and quality control. These include the ability to download chromosome-specific data files containing marker data in map order in various formats appropriate for downstream analyses (e.g., GAS and LINKAGE). Furthermore, an unlimited number of phenotypes (either qualitative or quantitative) can be stored and analyzed. Finally, GeneLink generates several quality assurance reports, including genotyping success rates of specified DNA samples or success and heterozygosity rates for specified markers. CONCLUSIONS: GeneLink has already proven an invaluable tool for complex trait mapping studies and is discussed primarily in the context of our large, multi-center study of hereditary prostate cancer (HPC). GeneLink is freely available at
Cytotoxic T-cell precursor frequencies to HER-2 (369 – 377) in patients with HER-2/neu-positive epithelial tumours
HER-2/neu oncoprotein contains several major histocompatibility complex class I-restricted epitopes, which are recognised by cytotoxic T lymphocyte (CTL) on autologous tumours and therefore can be used in immune-based cancer therapies. Of these, the most extensively studied is HER-2(9(369)). In the present report, we used dendritic cells pulsed with HER-2(9(369)) to stimulate, in the presence of IL-7 and IL-12, the production of IFN-gamma by patients' CTL detected by the enzyme-linked immunosorbent spot-assay. Frequencies of peptide-specific precursors were estimated in HLA-A2, HLA-A3 and HLA-A26 patients with HER-2/neu-positive (+) breast, ovarian, lung, colorectal and prostate cancers and healthy individuals. We found increased percentages of such precursors in HLA-A2 (25%) and HLA-A26 (30%) patients, which were significantly higher (60%) in HLA-A3 patients. Our results demonstrate for the first time that pre-existing immunity to HER-2(9(369)) occurs in patients with colorectal, lung and prostate cancer. They also suggest that HER-2(9(369)) can be recognised by CTL, besides HLA-A2, also in the context of HLA-A3 and HLA-A26, thus increasing the applicability of HER-2(9(369))-based vaccinations in a considerably broader patients' population.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe
Prothymosin alpha: a ubiquitous polypeptide with potential use in cancer diagnosis and therapy
The thymus is a central lymphoid organ with crucial role in generating T cells and maintaining homeostasis of the immune system. More than 30 peptides, initially referred to as “thymic hormones,” are produced by this gland. Although the majority of them have not been proven to be thymus-speciWc, thymic peptides comprise an eVective group of regulators, mediating important immune functions. Thymosin fraction Wve (TFV) was the Wrst thymic extract shown to stimulate lymphocyte proliferation and diVerentiation. Subsequent fractionation of TFV led to the isolation and characterization of a series of immunoactive peptides/polypeptides, members of the thymosin family. Extensive research on prothymosin (proT) and thymosin 1 (T1) showed that they are of clinical signiWcance and potential medical use. They may serve as molecular markers for cancer prognosis and/or as therapeutic agents for treating immunodeWciencies, autoimmune diseases and malignancies. Although the molecular mechanisms underlying their eVect are yet not fully elucidated proT and T1 could be considered as candidates for cancer immunotherapy. In this review, we will focus in principle on the eventual clinical utility of proT, both as a tumor biomarker and in triggering anticancer immune responses. Considering the experience acquired via the use of T1 to treat cancer patients, we will also discuss potential approaches for the future introduction of proT into the clinical setting
Functional studies on the role of Notch signaling in Hydractinia development
The function of Notch signaling was previously studied in two cnidarians, Hydra and Nematostella, representing the lineages Hydrozoa and Anthozoa, respectively. Using pharmacological inhibition in Hydra and a combination of pharmacological and genetic approaches in Nematostella, it was shown in both animals that Notch is required for tentacle morphogenesis and for late stages of stinging cell maturation. Surprisingly, a role for Notch in neural development, which is well documented in bilaterians, was evident in embryonic Nematostella but not in adult Hydra. Adult neurogenesis in the latter seemed to be unaffected by DAPT, a drug that inhibits Notch signaling. To address this apparent discrepancy, we studied the role of Notch in Hydractinia echinata, an additional hydrozoan, in all life stages. Using CRISPR-Cas9 mediated mutagenesis, transgenesis, and pharmacological interference we show that Notch is dispensable for Hydractinia normal neurogenesis in all life stages but is required for the maturation of stinging cells and for tentacle morphogenesis. Our results are consistent with a conserved role for Notch in morphogenesis and nematogenesis across Cnidaria, and a lineage-specific loss of Notch dependence in neurogenesis in hydrozoans
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