Impact of Low Rotational Inertia on Power System Stability and Operation

Large-scale deployment of RES has led to significant generation shares of variable RES in power systems worldwide. RES units, notably inverter-connected wind turbines and PV that as such do not provide rotational inertia, are effectively displacing conventional generators and their rotating machinery. The traditional assumption that grid inertia is sufficiently high with only small variations over time is thus not valid for power systems with high RES shares. This has implications for frequency dynamics and power system stability and operation. Frequency dynamics are faster in power systems with low rotational inertia, making frequency control and power system operation more challenging. This paper investigates the impact of low rotational inertia on power system stability and operation, contributes new analysis insights and offers mitigation options for low inertia impacts.Comment: Presented at IFAC World Congress 2014, Capetown, South Africa (Flaws in Table I corrected.

Sorafenib prevents human retinal pigment epithelium cells from light-induced overexpression of VEGF, PDGF and PlGF

Background Cumulative light exposure is significantly associated with progression of age-related macular degeneration (AMD). Inhibition of vascular endothelial growth factor is the main target of current antiangiogenic treatment strategies in AMD. However, other growth factors, such as platelet-derived growth factor (PDGF) and placenta growth factor (PlGF), have a substantial impact on development of AMD. Previous reports indicate that sorafenib, an oral multikinase inhibitor, might have beneficial effects on exudative AMD. This study investigates the effects of sorafenib on light-induced overexpression of growth factors in human retinal pigment epithelial (RPE) cells. Methods Primary human RPE cells were exposed to white light and incubated with sorafenib. Viability, expression, and secretion of VEGF-A, PDGF-BB, and PlGF and their mRNA were determined by reverse transcription-polymerase chain reactions, immunohistochemistry and enzyme-linked immunosorbent assays. Results Light exposure decreased cell viability and increased expression and secretion of VEGF-A, PDGF-BB and PlGF. These light-induced effects were significantly reduced when cells were treated with sorafenib at a dose of 1 mu g/ml. Conclusion The results show that sorafenib has promising properties as a potential antiangiogenic treatment for AMD

Optimal planning of distribution grids considering active power curtailment and reactive power control

In this paper, a new planning methodology is proposed for existing distribution grids, considering both passive and active network measures. The method is designed to be tractable for large grids of any type, e.g., meshed or radial. It can be used as a decision-making tool by distribution system operators which need to decide whether to invest in new hardware, such as new lines and transformers, or to initiate control measures influencing the operational costs. In this paper, active power curtailment and reactive power control are taken into account as measures to prevent unacceptable voltage rises as well as element overloads, as these allow postponing network investments. A low-voltage, meshed grid with 27 nodes is used to demonstrate the proposed scheme. In this particular case, the results show that by using control measures, an active distribution system operator can defer investments and operate the existing infrastructure more efficiently. The methodology is able to account for variations in operational and investment costs coming from regulatory influences to provide an insight to the most cost-efficient decision

Laser treatment in diabetic retinopathy

Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel

Comparative Evaluation of Combined Navigated Laser Photocoagulation and Intravitreal Ranibizumab in the Treatment of Diabetic Macular Edema

Objective: To evaluate if a standardized combination therapy regimen, utilizing 3 monthly ranibizumab injections followed by navigated laser photocoagulation, reduces the number of total ranibizumab injections required for treatment of diabetic macular edema (DME). Research Design and Methods: A 12-month, prospective comparison of 66 patients with center-involving DME: 34 patients with combination therapy were compared to 32 patients treated with ranibizumab monotherapy. All patients initially received 3 monthly ranibizumab injections (loading phase) and additional injections pro re nata (PRN). Combination therapy patients additionally received navigated laser photocoagulation after the loading phase. Main outcome measures were mean number of injections after the loading phase and change in BCVA from baseline to month 12. Results: Navigated laser combination therapy and ranibizumab monotherapy similarly improved mean BCVA letter score (+8.41 vs. +6.31 letters, p=0.258). In the combination group significantly less injections were required after the 3 injection loading phase (0.88 +/- 1.23 vs. 3.88 +/- 2.32, p<=0.001). By month 12, 84% of patients in the monotherapy group had required additional ranibizumab injections as compared to 35% in the combination group (p<=0.001). Conclusions: Navigated laser combination therapy demonstrated significant visual gains in most patients. Retreatment rate and number of injections were significantly lower compared to ranibizumab monotherapy and compared to the results of conventional laser combination therapy previously reported in pivotal anti-VEGF studies

First-principles simulation of intrinsic collision cascades in KCl and NaCl to test interatomic potentials at energies between 5 and 350 eV

Theoretical interatomic potentials for KCl and NaCl are tested at energies 5–350 eV against experimental data from intrinsic collision cascades. The collisional scattering of Cl with Cl, K, and Na atoms was observed from Doppler-shifted γ rays depopulating an excited state in recoiling Cl36 produced through the thermal neutron capture Cl35(n,γ)36Cl. The collisional scattering was simulated with molecular dynamics. Interatomic potentials from the present Iab initioP atomic cluster calculations are proposed for the Cl-Cl, Cl-K, and Cl-Na interactions in KCl and NaCl.Peer reviewe