Highlights d The g-tubulin ring complex (gTuRC) nucleates microtubules and caps their minus ends d Microtubule nucleation from purified gTuRC is highly cooperative, yet inefficient d A partly open, asymmetric structure of gTuRC explains inefficient nucleation d Actin and MZT2 stabilize the closed part of the gTuRC structure
The high proliferation of converter-dominated Distributed Renewable Energy Sources (DRESs) at the distribution grid level has gradually replaced the conventional synchronous generators (SGs) of the transmission system, resulting in emerging stability and security challenges. The inherent characteristics of the SGs are currently used for providing ancillary services (ASs), following the instructions of the Transmission System Operator, while the DRESs are obliged to offer specific system support functions, without being remunerated for these functions, but only for the energy they inject. This changing environment has prompted the integration of energy storage systems as a solution for transfusing new characteristics and elaborating their business in the electricity markets, while the smart grid infrastructure and the upcoming microgrid architectures contribute to the transformation of the distribution grid. This review investigates the existing ASs in transmission system with the respective markets (emphasizing the DRESs’ participation in these markets) and proposes new ASs at distribution grid level, with emphasis to inertial response, active power ramp rate control, frequency response, voltage regulation, fault contribution and harmonic mitigation. The market tools and mechanisms for the procurement of these ASs are presented evolving the existing role of the Operators. Finally, potential barriers in the technical, regulatory, and financial framework have been identified and analyzed.
Abstract-The intermittent and uncertain nature of renewables represents a major challenge for large scale adoption of sustainable energy resources. Of particular concern is the need to maintain both quality of grid frequency and low costs of regulation reserves in the face of increasing fluctuations in renewables. To this end, we propose an integrated dynamic market mechanism (DMM) which combines real-time market and frequency regulation allowing market players, including renewable generators and flexible consumers, to iteratively negotiate electricity prices at the wholesale level while using the most recent information on the available wind power and the quality of grid frequency. Main features of the integrated DMM are (i) a Newton-Raphson-based method which leads to fast convergence to the optimal dispatch, (ii) use of an aggregated frequency error as a feedback signal for the negotiation process which leads to reduced regulation capacity requirements. The benefits of this DMM are illustrated via simulations on the IEEE 118 bus system.
Understanding smart grid cyber attacks is key for developing appropriate protection and recovery measures. Advanced attacks pursue maximized impact at minimized costs and detectability. This paper conducts risk analysis of combined data integrity and availability attacks against the power system state estimation. We compare the combined attacks with pure integrity attacks -false data injection (FDI) attacks. A security index for vulnerability assessment to these two kinds of attacks is proposed and formulated as a mixed integer linear programming problem. We show that such combined attacks can succeed with fewer resources than FDI attacks. The combined attacks with limited knowledge of the system model also expose advantages in keeping stealth against the bad data detection. Finally, the risk of combined attacks to reliable system operation is evaluated using the results from vulnerability assessment and attack impact analysis. The findings in this paper are validated and supported by a detailed case study.Index Terms-Combined integrity and availability attack, false data injection, risk analysis, power system state estimation arXiv:1708.08349v1 [cs.CR]
Amylin is normally secreted in a regulated fashion by the pancreatic beta-cells in parallel with insulin and has been reported to have bone-conserving properties. Type I diabetes mellitus results in a low-turnover osteopenia in the presence of decreased amylin, which is in contrast to type II diabetes where less bone loss, in the presence of high amylin levels, occurs. We investigated the effects of amylin on bone mineral metabolism in normal and diabetic (streptozotocin-induced) rats, in order to ascertain whether amylin would modify the streptozotocin-induced diabetic osteopenia. Ten-week-old male Sprague-Dawley rats were randomized as follows: group A (n = 18) received normal saline; group B (n = 18) received amylin; group C, diabetic rats (n = 23), received normal saline; and group D, diabetic rats (n = 23), received amylin. Amylin (100 pmol/100 g b.w.) was administered by a daily subcutaneous injection. Double calcein-labeled tibiae were removed for histomorphometric analysis followed sacrifice on day 19. Results showed no difference in blood ionized calcium between groups. Blood glucose remained above 600 mg/dl in the diabetic animals and was not affected by the administration of amylin. Serum osteocalcin, insulin-like growth factor-1 (IGF-1), parathyroid hormone (PTH), and 1,25 dihydroxyvitamin D [1,25(OH)2D] were significantly lower in the diabetic rats compared with control group A by day 19. Amylin produced higher levels of serum osteocalcin in group B on day 9 (P < 0.05) compared with controls but returned to control values (group A) by day 19; no such change occurred in the diabetic group.(ABSTRACT TRUNCATED AT 250 WORDS)
The exosome plays an important role in RNA degradation and processing. In archaea, three Rrp41:Rrp42 heterodimers assemble into a barrel like structure that contains a narrow RNA entrance pore and a lumen that contains three active sites. Here, we demonstrate that this quaternary structure of the exosome is important for efficient RNA degradation. We find that the entrance pore of the barrel is required for nM substrate affinity. This strong interaction is crucial for processive substrate degradation and prevents premature release of the RNA from the enzyme. Using methyl TROSY NMR techniques, we establish that the 3′ end of the substrate remains highly flexible inside the lumen. As a result, the RNA jumps between the three active sites that all equally participate in substrate degradation. The RNA jumping rate is, however, much faster than the cleavage rate, indicating that not all active site:substrate encounters result in catalysis. Enzymatic turnover therefore benefits from the confinement of the active sites and substrate in the lumen, which ensures that the RNA is at all times bound to one of the active sites. The evolution of the exosome into a hexameric complex and the optimization of its catalytic efficiency were thus likely co-occurring events.
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