67 research outputs found
Control of Inverter-Interfaced Distributed Generation Units for Voltage and Current Harmonics Compensation in Grid-Connected Microgrids
In this paper, a new approach is proposed for voltage and current harmonics compensation in grid-connected microgrids (MGs). If sensitive loads are connected to the point of common coupling (PCC), compensation is carried out in order to reduce PCC voltage harmonics. In absence of sensitive loads at PCC, current harmonics compensation scenario is selected in order to avoid excessive injection of harmonics by the main grid. In both scenarios, compensation is performed by the interface converters of distributed generation (DG) units. Also, to decrease the asymmetry among phase impedances of MG, a novel structure is proposed to generate virtual impedance. At fundamental frequency, the proposed structure for the virtual impedance improves the control of the fundamental component of power, and at harmonic frequencies, it acts to adaptively improve nonlinear load sharing among DG units. In the structures of the proposed harmonics compensator and the proposed virtual impedance, a self-tuning filter (STF) is used for separating the fundamental component from the harmonic components. This STF decreases the number of phase locked loops (PLLs). Simulation results in MATLAB/SIMULINK environment show the efficiency of the proposed approach in improving load sharing and decreasing voltage and current harmonics
Measurement of rat brain tumor kinetics using an intravascular MR contrast agent and DCEâMRI nested model selection
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109323/1/jmri24469.pd
Approximately Ternary Homomorphisms and Derivations on C
We investigate the stability and superstability of ternary homomorphisms between C*-ternary algebras and derivations on C*-ternary algebras, associated with the following functional equation f((x2-x1)/3)+f((x1-3x3)/3)+f((3x1+3x3-x2)/3)=f(x1)
Targeting bone marrow to potentiate the anti-tumor effect of tyrosine kinase inhibitor in preclinical rat model of human glioblastoma
Antiangiogenic agents caused paradoxical increase in pro-growth and pro-angiogenic factors and caused tumor growth in glioblastoma (GBM). It is hypothesized that paradoxical increase in pro-angiogenic factors would mobilize Bone Marrow Derived Cells (BMDCs) to the treated tumor and cause refractory tumor growth. The purposes of the studies were to determine whether whole body irradiation (WBIR) or a CXCR4 antagonist (AMD3100) will potentiate the effect of vatalanib (a VEGFR2 tyrosine kinase inhibitor) and prevent the refractory growth of GBM. Human GBM were grown orthotopically in three groups of rats (control, pretreated with WBIR and AMD3100) and randomly selected for vehicle or vatalanib treatments for 2 weeks. Then all animals underwent Magnetic Resonance Imaging (MRI) followed by euthanasia and histochemical analysis. Tumor volume and different vascular parameters (plasma volume (vp), forward transfer constant (Ktrans), back flow constant (kep), extravascular extracellular space volume (ve) were determined from MRI. In control group, vatalanib treatment increased the tumor growth significantly compared to that of vehicle treatment but by preventing the mobilization of BMDCs and interaction of CXCR4-SDF-1 using WBIR and ADM3100, respectively, paradoxical growth of tumor was controlled. Pretreatment with WBIR or AMD3100 also decreased tumor cell migration, despite the fact that ADM3100 increased the accumulation of M1 and M2 macrophages in the tumors. Vatalanib also increased Ktrans and ve in control animals but both of the vascular parameters were decreased when the animals were pretreated with WBIR and AMD3100. In conclusion, depleting bone marrow cells or CXCR4 interaction can potentiate the effect of vatalanib
Intravenous Formulation of HET0016 Decreased Human Glioblastoma Growth and Implicated Survival Benefit in Rat Xenograft Models
Glioblastoma (GBM) is a hypervascular primary brain tumor with poor prognosis. HET0016 is a selective CYP450 inhibitor, which has been shown to inhibit angiogenesis and tumor growth. Therefore, to explore novel treatments, we have generated an improved intravenous (IV) formulation of HET0016 with HPĂCD and tested in animal models of human and syngeneic GBM. Administration of a single IV dose resulted in 7-fold higher levels of HET0016 in plasma and 3.6-fold higher levels in tumor at 60âmin than that in IP route. IV treatment with HPĂCD-HET0016 decreased tumor growth, and altered vascular kinetics in early and late treatment groups (pâ\u3câ0.05). Similar growth inhibition was observed in syngeneic GL261 GBM (pâ\u3câ0.05). Survival studies using patient derived xenografts of GBM811, showed prolonged survival to 26 weeks in animals treated with focal radiation, in combination with HET0016 and TMZ (pâ\u3câ0.05). We observed reduced expression of markers of cell proliferation (Ki-67), decreased neovascularization (laminin and αSMA), in addition to inflammation and angiogenesis markers in the treatment group (pâ\u3câ0.05). Our results indicate that HPĂCD-HET0016 is effective in inhibiting tumor growth through decreasing proliferation, and neovascularization. Furthermore, HPĂCD-HET0016 significantly prolonged survival in PDX GBM811 model
Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices
Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PEDOT:PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced âburn-inâ effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions
Quantitative Comparison of Organic Photovoltaic Bulk Heterojunction Photostability Under Laser Illumination
A versatile microfluidic chip for millisecond time-scale kinetic studies by electrospray mass spectrometry
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