4,562 research outputs found

    Reação do solo e retenção de enxofre (SO24) em um Podzolico Vermelho Amarelo latossolico distrofico cultivado com milho.

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    O trabalho teve por objetivo a determinação do efeito da reação do solo e da precipitação na retenção do sulfato em profundidade em um Podzolico Vermelho Amarelo latossolico distrofico em Piracicaba (SP)

    Efeitos da extração pela cultura do milho e de fertilizantes nitrogenados na acidificação de um Podzolico Vermelho Amarelo latossolico distrofico.

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    Este trabalho teve por objetivo a determinação dos níveis de influência de dois fertilizantes nitrogenados (sulfato e nitrato de amonio) no processo de acidificação do solo, sendo realizado um ensaio em solo de textura media, utilizando-se a cultura do milho, com cultivo previo de tremoço

    Measuring topology in a laser-coupled honeycomb lattice: From Chern insulators to topological semi-metals

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    Ultracold fermions trapped in a honeycomb optical lattice constitute a versatile setup to experimentally realize the Haldane model [Phys. Rev. Lett. 61, 2015 (1988)]. In this system, a non-uniform synthetic magnetic flux can be engineered through laser-induced methods, explicitly breaking time-reversal symmetry. This potentially opens a bulk gap in the energy spectrum, which is associated with a non-trivial topological order, i.e., a non-zero Chern number. In this work, we consider the possibility of producing and identifying such a robust Chern insulator in the laser-coupled honeycomb lattice. We explore a large parameter space spanned by experimentally controllable parameters and obtain a variety of phase diagrams, clearly identifying the accessible topologically non-trivial regimes. We discuss the signatures of Chern insulators in cold-atom systems, considering available detection methods. We also highlight the existence of topological semi-metals in this system, which are gapless phases characterized by non-zero winding numbers, not present in Haldane's original model.Comment: 30 pages, 12 figures, 4 Appendice

    Smectic Layering: Landau theory for a complex-tensor order parameter

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    Composed of microscopic layers that stack along one direction while maintaining fluid-like positional disorder within layers, smectics are excellent systems for exploring topology, defects and geometric memory in complex confining geometries. However, the coexistence of crystalline-like characteristics in one direction and fluid-like disorder within layers makes lamellar liquid crystals notoriously difficult to model—especially in the presence of defects and large distortions. Nematic properties of smectics can be comprehensively described by the Q ̲ ̲ -tensor; however, lamellar order can exist independent of nematic alignment. To capture the features of the smectic layering alone, we develop a phenomenological Landau theory for a complex-tensor order parameter E ̲ ̲ , which is capable of describing the local degree of lamellar ordering, layer displacement, and orientation of the layers. This theory accounts for both parallel and perpendicular elastic contributions. In addition to resolving the potential ambiguities inherent to complex scalar order parameter models, this model reduces to previously employed models of simple smectics, and opens new possibilities for numerical studies on smectics possessing many defects, within complex geometries and under extreme confinement

    Inhibiting IRE1α-endonuclease activity decreases tumor burden in a mouse model for hepatocellular carcinoma

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    Hepatocellular carcinoma (HCC) is a liver tumor that usually arises in patients with cirrhosis. Hepatic stellate cells are key players in the progression of HCC, as they create a fibrotic micro-environment and produce growth factors and cytokines that enhance tumor cell proliferation and migration. We assessed the role of endoplasmic reticulum (ER) stress in the cross-talk between stellate cells and HCC-cells. Mice with a fibrotic HCC were treated with the IRE1α-inhibitor 4μ8C, which reduced tumor burden and collagen deposition. By co-culturing HCC-cells with stellate cells, we found that HCC-cells activate IREα in stellate cells, thereby contributing to their activation. Inhibiting IRE1α blocked stellate cell activation, which then decreased proliferation and migration of tumor cells in different in vitro 2D and 3D co-cultures. In addition, we also observed cell-line specific direct effects of inhibiting IRE1α in tumor cells

    Comparison of 35 and 50 {\mu}m thin HPK UFSD after neutron irradiation up to 6*10^15 neq/cm^2

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    We report results from the testing of 35 {\mu}m thick Ultra-Fast Silicon Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison of these new results to data reported before on 50 {\mu}m thick UFSD produced by HPK. The 35 {\mu}m thick sensors were irradiated with neutrons to fluences of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr \b{eta}-source. The leakage current, capacitance, internal gain and the timing resolution were measured as a function of bias voltage at -20C and -27C. The timing resolution was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction method for both. Within the fluence range measured, the advantage of the 35 {\mu}m thick UFSD in timing accuracy, bias voltage and power can be established.Comment: 9 pages, 9 figures, HSTD11 Okinawa. arXiv admin note: text overlap with arXiv:1707.0496

    Optical lattice quantum simulator for QED in strong external fields: spontaneous pair creation and the Sauter-Schwinger effect

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    Spontaneous creation of electron-positron pairs out of the vacuum due to a strong electric field is a spectacular manifestation of the relativistic energy-momentum relation for the Dirac fermions. This fundamental prediction of Quantum Electrodynamics (QED) has not yet been confirmed experimentally as the generation of a sufficiently strong electric field extending over a large enough space-time volume still presents a challenge. Surprisingly, distant areas of physics may help us to circumvent this difficulty. In condensed matter and solid state physics (areas commonly considered as low energy physics), one usually deals with quasi-particles instead of real electrons and positrons. Since their mass gap can often be freely tuned, it is much easier to create these light quasi-particles by an analogue of the Sauter-Schwinger effect. This motivates our proposal of a quantum simulator in which excitations of ultra-cold atoms moving in a bichromatic optical lattice represent particles and antiparticles (holes) satisfying a discretized version of the Dirac equation together with fermionic anti-commutation relations. Using the language of second quantization, we are able to construct an analogue of the spontaneous pair creation which can be realized in an (almost) table-top experiment.Comment: 21 pages, 10 figure

    Efficient algorithm to compute the Berry conductivity

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    We propose and construct a numerical algorithm to calculate the Berry conductivityin topological band insulators. The method is applicable to cold atomsystems as well as solid state setups, both for the insulating case where the Fermienergy lies in the gap between two bulk bands as well as in the metallic regime.This method interpolates smoothly between both regimes. The algorithm isgauge-invariant by construction, efficient, and yields the Berry conductivity withknown and controllable statistical error bars. We apply the algorithm to severalparadigmatic models in the field of topological insulators, including Haldaneʼsmodel on the honeycomb lattice, the multi-band Hofstadter model, and the BHZmodel, which describes the 2D spin Hall effect observed in CdTe/HgTe/CdTequantum well heterostructures

    DARA-VD VERSUS DARA-RD AS SALVAGE THERAPY FOR PATIENTS WITH MYELOMA. INITIAL FOLLOW-UP OF AN ITALIAN MULTICENTER RETROSPECTIVE CLINICAL EXPERIENCE BY RETE EMATOLOGICA PUGLIESE

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    Background: Daratumumab is a CD38 monoclonal antibody approved in monotherapy or in combination with bortezomib and dexamethasone (Dara-Vd) or lenalidomide and dexamethasone (Dara-Rd) for the treatment of relapsed or refractory myeloma (rrMM). Aims: We report here an initial multicenter retrospective analysis of 126 consecutive patients with rrMM treated with daratumumab in combination with bortezomib or lenalidomide as salvage therapy at 9 haematological centers in Puglia, conducted to evaluate the outcomes, as well as the toxicity profile of these combination in a daily practice setting outside clinical trials. Methods: Of 126 patients, 122 were evaluable for response and toxicity. Forty-two patients (33%) (15 F and 27 M) received Dara-Vd and 84 patients (67%) (41 F and 43 M) with Dara-Rd; 74% of them had relapsed MM and 26% MM refractory to one or more previous treatment lines. The median age at diagnosis was 62 years (range 36-77) in the Vd-group, 66 years (range 32-83) in the Rd-group. The median time to initiation of daratumumab from diagnosis was 5 years (range 3-9) in the Vd-group, 3 years (range 1-10) in the Rd-group. Patients had received a median 2 prior lines of therapy (range 1-6) in the Vd-group, a median 1 prior course of therapy (range 1-4) in the Rd-group. Twenty patients (48%) in the Vd-group and 30 patients (37%) in the Rd-group had previously undergone single or tandem ASCT. In the Vd-group all patients were previously exposed to at least one proteasome inhibitor (91% of patients to bortezomib, 37% of patients to carfilzomib), in the Rd-group only 18% of patients was exposed to lenalidomide. Results: The median number of administered cycles was 9 (range 1-23) in the VD-group and 8.5 (range 1-23) in the Rd-group. The ORR was 68.2% in the Vd-group (CR 4.8%, VGPR 12.2%, PR 51.2%) and 81.5% in the Rd-group (CR 21%, VGPR 35.8%, pr 24.7%). Median TTR was 2 months (range 1-6) in the Vd-group and 1.5 months (range 1-5) in the Rd-group. Median PFS was 10 months (range 8-16; 95% > CI) in the Vd-group; median PFS was not reached in the Rd-group (fig.1). Grade 3/4 neutropenia (37%) was the most common adverse event in the Rd-group, grade 3/4 thrombocytopenia (24%) was the most common adverse event in the Vd-group. Seventeen (41%) patients in the Vd-group discontinued treatment due to relapse, 16 patients (19%) in the Rd-group because of haematological toxicity (4.5%), relapse (7.5%), death (6%) and the development of urological cancer (1%). Summary/Conclusion: A higher rate of ORR (81.5% vs 68.2%) and very good partial response or better (responses > VGPR 56.8% vs 17%) was observed in the Dara-Rd group compared to Dara-Vd group. This difference could be due to the fact that: 1) in the Dara- Rd group the patients had received a lower number of prior antimyeloma therapies compared to Dara-Vd group; 2) the patients in the Dara-Rd group had a more indolent myeloma (median ISS 1) compared to the patients in the Dara-Vd group, who had a more advanced disease (median ISS 3); 3) in the Rd-group only 18% of patients was exposed to lenalidomide, in the Vd-group all patients were previously exposed to at least one proteasome inhibitor. Unfortunately, the interference of daratumumab with immunofixation and serum protein electrophoresis assays may lead to underestimation of CR
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