142 research outputs found
On self-complementation
We prove that, with very few exceptions, every graph of order n, n - 0, 1(mod 4) and size at most n - 1, is contained in a self-complementary graph of order n. We study a similar problem for digraphs
Embedding digraphs of small size
AbstractLet D=(V,A) be a digraph without loops and multiple arcs of order n ⩾ 2. We say that D is embeddable if there is a permutation φ : V → V (called complementing permutation) such that (φ(x), φ(y)) ∉ A for every arc (x, y) ϵ A. In this paper we prove that if | A | < [3(n - 2)/2] then D is embeddable and, moreover, there is a complementing permutation which is a composition of disjoint transpositions when n is even or a composition of disjoint transpositions and a fixed point when n is odd
Laser-driven plasma waves in capillary tubes
The excitation of plasma waves over a length of up to 8 centimeters is, for
the first time, demon- strated using laser guiding of intense laser pulses
through hydrogen filled glass capillary tubes. The plasma waves are diagnosed
by spectral analysis of the transmitted laser radiation. The dependence of the
spectral redshift, measured as a function of filling pressure, capillary tube
length and incident laser energy, is in excellent agreement with simulation
results. The longitudinal accelerating field inferred from the simulations is
in the range 1 -10 GV/m
Familial Alzheimer's Disease Lymphocytes Respond Differently Than Sporadic Cells to Oxidative Stress: Upregulated p53-p21 Signaling Linked with Presenilin 1 Mutants
Familial (FAD) and sporadic (SAD) Alzheimer's disease do not share all pathomechanisms, but knowledge on their molecular differences is limited. We previously reported that cell cycle control distinguishes lymphocytes from SAD and FAD patients. Significant differences were found in p21 levels of SAD compared to FAD lymphocytes. Since p21 can also regulate apoptosis, the aim of this study was to compare the response of FAD and SAD lymphocytes to oxidative stress like 2-deoxy-D-ribose (2dRib) treatment and to investigate the role of p21 levels in this response. We report that FAD cells bearing seven different PS1 mutations are more resistant to 2dRib-induced cell death than control or SAD cells: FAD cells showed a lower apoptosis rate and a lower depolarization of the mitochondrial membrane. Despite that basal p21 cellular content was lower in FAD than in SAD cells, in response to 2dRib, p21 mRNA and protein levels significantly increased in FAD cells. Moreover, we found a higher cytosolic accumulation of p21 in FAD cells. The transcriptional activation of p21 was shown to be dependent on p53, as it can be blocked by PFT-α, and correlated with the increased phosphorylation of p53 at Serine 15. Our results suggest that in FAD lymphocytes, the p53-mediated increase in p21 transcription, together with a shift in the nucleocytoplasmic localization of p21, confers a survival advantage against 2dRib-induced apoptosis. This compensatory mechanism is absent in SAD cells. Thus, therapeutic and diagnostic designs should take into account possible differential apoptotic responses in SAD versus FAD cells
Study of electron acceleration and X-ray radiation as a function of plasma density in capillary-guided laser wakefield accelerators
Laser wakefield electron acceleration in the blow-out regime and the associated betatron X-rayradiation were investigated experimentally as a function of the plasma density in a configuration where the laser is guided. Dielectric capillary tubes were employed to assist the laser keeping self-focused over a long distance by collecting the laser energy around its central focal spot. With a 40 fs, 16 TW pulsed laser, electron bunches with tens of pC charge were measured to be accelerated to an energy up to 300 MeV, accompanied by X-ray emission with a peak brightness of the order of 10 21 ph/s/mm 2 / mrad 2 /0.1%BW. Electron trapping and acceleration were studied using the emitted X-ray beamdistribution to map the acceleration process; the number of betatron oscillations performed by theelectrons was inferred from the correlation between measured X-ray fluence and beam charge. A studyof the stability of electron and X-ray generation suggests that the fluctuation of X-ray emission can be reduced by stabilizing the beam charge. The experimental results are in good agreement with 3D particle-in-cell (PIC) simulation.Fil: Ju, L.. Universite de Paris Xi; Francia;Fil: Svensson, K.. Lund University; SueciaFil: Ferrari, Hugo Emilio. Comisión Nacional de EnergÃa Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de FÃsica (centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Döpp, A.. Universite de Paris Xi; Francia;Fil: Cassou, K.. Universite de Paris Xi; Francia;Fil: Genoud, G.. Lund University; Suecia;Fil: Wojda, F.. Lund University; Suecia;Fil: Burza, M.. Lund University; Suecia;Fil: Persson, A.. Lund University; Suecia;Fil: Lundh, O.. Lund University; Suecia;Fil: Wahlström, C. G.. Lund University; Suecia;Fil: Cros, B.. Universite de Paris Xi; Francia
Controlling the spectrum of x-rays generated in a laser-plasma accelerator by tailoring the laser wavefront
By tailoring the wavefront of the laser pulse used in a laser-wakefield
accelerator, we show that the properties of the x-rays produced due to the
electron beam's betatron oscillations in the plasma can be controlled. By
creating a wavefront with coma, we find that the critical energy of the
synchrotron-like x-ray spectrum can be significantly increased. The coma does
not substantially change the energy of the electron beam, but does increase its
divergence and produces an energy-dependent exit angle, indicating that changes
in the x-ray spectrum are due to an increase in the electron beam's oscillation
amplitude within the wakefield.Comment: 7 pages, 2 figures, submitted to Appl. Phys. Let
4-1BBL-containing leukemic extracellular vesicles promote immunosuppressive effector regulatory T cells
Chronic and acute myeloid leukemia evade immune system surveillance and induce immunosuppression by expanding proleukemic Foxp31 regulatory T cells (Tregs). High levels of immunosuppressive Tregs predict inferior response to chemotherapy, leukemia relapse, and shorter survival. However, mechanisms that promote Tregs in myeloid leukemias remain largely unexplored. Here, we identify leukemic extracellular vesicles (EVs) as drivers of effector proleukemic Tregs. Using mouse model of leukemia-like disease, we found that Rab27adependent secretion of leukemic EVs promoted leukemia engraftment, which was associated with higher abundance of activated, immunosuppressive Tregs. Leukemic EVs attenuated mTOR-S6 and activated STAT5 signaling, as well as evoked significant transcriptomic changes in Tregs. We further identified specific effector signature of Tregs promoted by leukemic EVs. Leukemic EVs-driven Tregs were characterized by elevated expression of effector/tumor Treg markers CD39, CCR8, CD30, TNFR2, CCR4, TIGIT, and IL21R and included 2 distinct effector Treg (eTreg) subsets: CD301CCR8hiTNFR2hi eTreg1 and CD391TIGIThi eTreg2. Finally, we showed that costimulatory ligand 4-1BBL/CD137L, shuttled by leukemic EVs, promoted suppressive activity and effector phenotype of Tregs by regulating expression of receptors such as CD30 and TNFR2. Collectively, our work highlights the role of leukemic extracellular vesicles in stimulation of immunosuppressive Tregs and leukemia growth. We postulate that targeting of Rab27a-dependent secretion of leukemic EVs may be a viable therapeutic approach in myeloid neoplasms
Thermosensitivity of the Saccharomyces cerevisiae gpp1gpp2 double deletion strain can be reduced by overexpression of genes involved in cell wall maintenance
A Saccharomyces cerevisiae strain in which the GPP1 and GPP2 genes, both encoding glycerol-3-phosphate phosphatase isoforms, are deleted, displays both osmo- and thermosensitive (ts) phenotypes. We isolated genes involved in cell wall maintenance as multicopy suppressors of the gpp1gpp2 ts phenotype. We found that the gpp1gpp2 strain is hypersensitive to cell wall stress such as treatment with β-1,3-glucanase containing cocktail Zymolyase and chitin-binding dye Calcofluor-white (CFW). Sensitivity to Zymolyase was rescued by overexpression of SSD1, while CFW sensitivity was rescued by SSD1, FLO8 and WSC3-genes isolated as multicopy suppressors of the gpp1gpp2 ts phenotype. Some of the isolated suppressor genes (SSD1, FLO8) also rescued the lytic phenotype of slt2 deletion strain. Additionally, the sensitivity to CFW was reduced when the cells were supplied with glycerol. Both growth on glycerol-based medium and overexpression of SSD1, FLO8 or WSC3 had additive suppressing effect on CFW sensitivity of the gpp1gpp2 mutant strain. We also confirmed that the internal glycerol level changed in cells exposed to cell wall perturbation. © 2007 Springer-Verlag
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