130 research outputs found
Contribution of windfarms to ancillary services
International audienceIn the last décade, wind energy has expericnced a substantial growth in Europe with an increase in génération capaciiy from 2,5 GW in 1995 to 34 GW at (lie end of 2004 This incTease has raised new probîems and constraints which led System opéra tors, electric utilities, governments or regulatory boards to define lechnical requirements for the grid connection of wind farms and more generaily of distributed génération (DG) units. At flrst, the requirements for wind fanns were rather "soft" (at least softer than for other DG units) and were mainîy intended to limit the "disturbances" caused by wind energy on power quality and grid opération. But with the ever increasing developmenl of wind power, the impacts on the grids become more and more significant leading to the définition of more and more "scvcrc" requiremcnts, In parltcular, wind farms (WF) arc now more and more often askcd to provide some son of anciilary services such as contribution to voltage/réactive power control and rrequency/active power control. This paper focuscs on the possible provision of such anciilary services by wind faims. Regarcling réactive power and voltage contTOl:-Doubly-fed Induction GÊaerarors (DFIG) and Synchronous or Induction GeneratoTS with full power électron ics interfaces (SIG) can liave réactive power control capabilities (both in production and absorption) depending on the rating of their power electronics converters. Thèse capabilities {characterized by a fast dynamie respon.se) can be used to perform voltage control. Moreover, if required, extemal reactive power compensation device.s niay also be installed.-Classical Induction G encrât ors (OG) do not hâve such réactive power control capahilities and therefore require externat devices for reactive power and voltage control.-Simulations carried oui show that WFs with voltage control capabilîties can significantly sustaîn the network voltage in case of grid events and mus may efficiently support the power System stability.Regard ing frequency control: the resuits show that when the Wind Turbine Generator (WTG) is full y loaded (maximum active power génération], appre-priate use or the pitch control may enabic the WTG (DFIG, SIG or CIG) to contribute to frequency control. In case of partial toad. the contribution to frequency conlrol can be achieved either by "disoplimizing'" the wind energy conversion by mcans of aie pitch control. or by setting a non-optimal rotor speed for DFIG or SIG. However, a judicious way to use variable speed ge&eratCffS may also be looperate them as mertial flywheels
The Cooperation between hMena Overexpression and HER2 Signalling in Breast Cancer
hMena and the epithelial specific isoform hMena11a are actin cytoskeleton regulatory proteins belonging to the Ena/VASP family. EGF treatment of breast cancer cell lines upregulates hMena/hMena11a expression and phosphorylates hMena11a, suggesting cross-talk between the ErbB receptor family and hMena/hMena11a in breast cancer. The aim of this study was to determine whether the hMena/hMena11a overexpression cooperates with HER-2 signalling, thereby affecting the HER2 mitogenic activity in breast cancer. In a cohort of breast cancer tissue samples a significant correlation among hMena, HER2 overexpression, the proliferation index (high Ki67), and phosphorylated MAPK and AKT was found and among the molecular subtypes the highest frequency of hMena overexpressing tumors was found in the HER2 subtype. From a clinical viewpoint, concomitant overexpression of HER2 and hMena identifies a subgroup of breast cancer patients showing the worst prognosis, indicating that hMena overexpression adds prognostic information to HER2 overexpressing tumors. To identify a functional link between HER2 and hMena, we show here that HER2 transfection in MCF7 cells increased hMena/hMena11a expression and hMena11a phosphorylation. On the other hand, hMena/hMena11a knock-down reduced HER3, AKT and p44/42 MAPK phosphorylation and inhibited the EGF and NRG1-dependent HER2 phosphorylation and cell proliferation. Of functional significance, hMena/hMena11a knock-down reduced the mitogenic activity of EGF and NRG1. Collectively these data provide new insights into the relevance of hMena and hMena11a as downstream effectors of the ErbB receptor family which may represent a novel prognostic indicator in breast cancer progression, helping to stratify patients
Harmonin-b, an actin-binding scaffold protein, is involved in the adaptation of mechanoelectrical transduction by sensory hair cells
We assessed the involvement of harmonin-b, a submembranous protein containing PDZ domains, in the mechanoelectrical transduction machinery of inner ear hair cells. Harmonin-b is located in the region of the upper insertion point of the tip link that joins adjacent stereocilia from different rows and that is believed to gate transducer channel(s) located in the region of the tip link's lower insertion point. In Ush1cdfcr-2J/dfcr-2J mutant mice defective for harmonin-b, step deflections of the hair bundle evoked transduction currents with altered speed and extent of adaptation. In utricular hair cells, hair bundle morphology and maximal transduction currents were similar to those observed in wild-type mice, but adaptation was faster and more complete. Cochlear outer hair cells displayed reduced maximal transduction currents, which may be the consequence of moderate structural anomalies of their hair bundles. Their adaptation was slower and displayed a variable extent. The latter was positively correlated with the magnitude of the maximal transduction current, but the cells that showed the largest currents could be either hyperadaptive or hypoadaptive. To interpret our observations, we used a theoretical description of mechanoelectrical transduction based on the gating spring theory and a motor model of adaptation. Simulations could account for the characteristics of transduction currents in wild-type and mutant hair cells, both vestibular and cochlear. They led us to conclude that harmonin-b operates as an intracellular link that limits adaptation and engages adaptation motors, a dual role consistent with the scaffolding property of the protein and its binding to both actin filaments and the tip link component cadherin-23
Role for a Novel Usher Protein Complex in Hair Cell Synaptic Maturation
The molecular mechanisms underlying hair cell synaptic maturation are not well understood. Cadherin-23 (CDH23), protocadherin-15 (PCDH15) and the very large G-protein coupled receptor 1 (VLGR1) have been implicated in the development of cochlear hair cell stereocilia, while clarin-1 has been suggested to also play a role in synaptogenesis. Mutations in CDH23, PCDH15, VLGR1 and clarin-1 cause Usher syndrome, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa. Here we show developmental expression of these Usher proteins in afferent spiral ganglion neurons and hair cell synapses. We identify a novel synaptic Usher complex comprised of clarin-1 and specific isoforms of CDH23, PCDH15 and VLGR1. To establish the in vivo relevance of this complex, we performed morphological and quantitative analysis of the neuronal fibers and their synapses in the Clrn1−/− mouse, which was generated by incomplete deletion of the gene. These mice showed a delay in neuronal/synaptic maturation by both immunostaining and electron microscopy. Analysis of the ribbon synapses in Ames waltzerav3J mice also suggests a delay in hair cell synaptogenesis. Collectively, these results show that, in addition to the well documented role for Usher proteins in stereocilia development, Usher protein complexes comprised of specific protein isoforms likely function in synaptic maturation as well
Procesos técnicos y culturales durante el Holoceno inicial en el noroeste de la PenÃnsula Ibérica. Los niveles B y Bb de La Cativera (El Catllar, Tarragona)
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External ballistics of Pleistocene hand-thrown spears: experimental performance data and implications for human evolution
The appearance of weaponry - technology designed to kill - is a critical but poorly established threshold
in human evolution. It is an important behavioural marker representing evolutionary changes in
ecology, cognition, language and social behaviours. While the earliest weapons are often considered
to be hand-held and consequently short-ranged, the subsequent appearance of distance weapons is a
crucial development. Projectiles are seen as an improvement over contact weapons, and are considered
by some to have originated only with our own species in the Middle Stone Age and Upper Palaeolithic.
Despite the importance of distance weapons in the emergence of full behavioral modernity, systematic
experimentation using trained throwers to evaluate the ballistics of thrown spears during fight and at
impact is lacking. This paper addresses this by presenting results from a trial of trained javelin athletes,
providing new estimates for key performance parameters. Overlaps in distances and impact energies
between hand-thrown spears and spearthrowers are evidenced, and skill emerges as a signifcant factor in
successful use. The results show that distance hunting was likely within the repertoire of hunting strategies
of Neanderthals, and the resulting behavioural flexibility closely mirrors that of our own specie
Gene Therapy Restores Auditory and Vestibular Function in a Mouse Model of Usher Syndrome Type 1c
Because there are currently no biological treatments for deafness, we sought to advance gene therapy approaches to treat genetic deafness. We reasoned that gene delivery systems that target auditory and vestibular sensory cells with high efficiency would be required to restore complex auditory and balance function. We focused on Usher Syndrome, a devastating genetic disorder that causes blindness, balance disorders and profound deafness, and used a knock-in mouse model, Ush1c c.216G>A, which carries a cryptic splice site mutation found in French-Acadian patients with Usher Syndrome type IC (USH1C). Following delivery of wild-type Ush1c into the inner ears of neonatal Ush1c c.216G>A mice, we find recovery of gene and protein expression, restoration of sensory cell function, rescue of complex auditory function and recovery of hearing and balance behavior to near wild-type levels. The data represent unprecedented recovery of inner ear function and suggest that biological therapies to treat deafness may be suitable for translation to humans with genetic inner ear disorders
The Chiquihuite Cave, a Real Novelty? Observations about the Still-ignored South American Prehistory
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