5,925 research outputs found
Coordinated corrective control for transient stability enhancement in future Great Britain transmission system
This paper demonstrates a corrective control strategy through fast actuators (TCSC FACTS and HVDC links, both LCC and VSC) in order to enhance the transient stability in the future Great Britain (GB) transmission network. A model predictive control (MPC) scheme that relies on system wide-area measurements is employed for coordinated control action through these power electronic devices with the aim of preserving the system stability without having to constrain pre-fault transfer levels. Case studies employing detailed dynamic models are presented to demonstrate the effectiveness of the proposed approach for different formulations on a representative equivalent model of the future GB transmission grid
Time resolved pattern evolution in a large aperture laser
We have measured quasi-instantaneous transverse patterns in a broad aperture
laser. Non-ordered patterns yielding to boundary determined regular structures
in progressive time-integrated recording are observed. The linear analysis and
numerical integration of the full Maxwell-Bloch equations allow us to interpret
the features of the experiment. We show that this system being far from
threshold cannot be fully understood with a perturbative model.Comment: 7 pages, 5 GIF figures . To be published in Phys. Rev. Let
One-loop corrections to ALP couplings
The plethora of increasingly precise experiments which hunt for axion-like particles (ALPs), as well as their widely different energy reach, call for the theoretical understanding of ALP couplings at loop-level. We derive the one-loop contributions to ALP-SM effective couplings, including finite corrections. The complete leading-order — dimension five — effective linear Lagrangian is considered. The ALP is left off-shell, which is of particular impact on LHC and accelerator searches of ALP couplings to γγ, ZZ, Zγ, WW, gluons and fermions. All results are obtained in the covariant Rξ gauge. A few phenomenological consequences are also explored as illustration, with flavour diagonal channels in the case of fermions: in particular, we explore constraints on the coupling of the ALP to top quarks, that can be extracted from LHC data, from astrophysical sources and from Dark Matter direct detection experiments such as PandaX, LUX and XENON1T. Furthermore, we clarify the relation between alternative ALP bases, the role of gauge anomalous couplings and their interface with chirality-conserving and chirality-flip fermion interactions, and we briefly discuss renormalization group aspect
Generalized Arago-Fresnel laws: The EME-flow-line description
We study experimentally and theoretically the influence of light polarization
on the interference patterns behind a diffracting grating. Different states of
polarization and configurations are been considered. The experiments are
analyzed in terms of electromagnetic energy (EME) flow lines, which can be
eventually identified with the paths followed by photons. This gives rise to a
novel trajectory interpretation of the Arago-Fresnel laws for polarized light,
which we compare with interpretations based on the concept of "which-way" (or
"which-slit") information.Comment: 14 pages, 6 figure
Non-stationary Rayleigh-Taylor instability in supernovae ejecta
The Rayleigh-Taylor instability plays an important role in the dynamics of
several astronomical objects, in particular, in supernovae (SN) evolution. In
this paper we develop an analytical approach to study the stability analysis of
spherical expansion of the SN ejecta by using a special transformation in the
co-moving coordinate frame. We first study a non-stationary spherical expansion
of a gas shell under the pressure of a central source. Then we analyze its
stability with respect to a no radial, non spherically symmetric perturbation
of the of the shell. We consider the case where the polytropic constant of the
SN shell is and we examine the evolution of a arbitrary shell
perturbation. The dispersion relation is derived. The growth rate of the
perturbation is found and its temporal and spatial evolution is discussed. The
stability domain depends on the ejecta shell thickness, its acceleration, and
the perturbation wavelength.Comment: 16 page
Antioxidant activity of isolated compounds in non-volatile residue from orange essential oil
6 páginas, 3 figuras.[ES] Existe un creciente interés en la industria alimentaria y en la medicina
preventiva por la búsqueda de «antioxidantes naturales», por
lo que nos planteamos evaluar la actividad antioxidante del residuo
no volátil del aceite esencial de naranja contra la oxidación del aceite
de oliva sin retinar y de reciente extracción. Mediante destilación
del aceite esencial de naranja se obtuvo el residuo no-volátil, el cual
se fraccionó en columna de silica gel 60. La actividad antioxidante
fue medida por el valor de peróxidos producidos por el aceite de oliva
al provocar la oxidación por calentamiento a 70 °C durante 48 h.
Se aislaron seis compuestos mediante H PLC preparativo de
los cuales cuatro tuvieron actividad antioxidante. Usando métodos
espectroscópicos se identificaron a-tocoferol y tres flavonas
metoxiladas. Con este estudio se confirmó que la fracción no volátil
del aceite esencial de naranja contiene antioxidantes naturales
diferentes al a-tocoferol.[EN] There has been a growing interest in the food industry and in
preventive medicine to search for «natural antioxidants». Therefore
the objetive of this study was to evaluate the antioxidant activity of
the non-volatile residue of essential orange oil in the oxidation of
unrefined and freshly extracted olive oil. Essential orange oil was
distilled to obtain a non-volatile residue and fracctionated on a Silica
Gel 60 column. The antioxidant activity was determined by measuring
peroxide value obtained after heating olive oil at 70 °C for 48 h.
Six compounds were isolated and purified, four of these had
antioxidant activity, a-tocopherol and three methoxylated flavones
were identified using spectroscopic methods. This study confirmed
that non-volatile fractions of essential orange oil contain natural
antioxidants diferent from a-tocopherol.Peer reviewe
Positive Experiences at Work and Daily Recovery: Effects on Couple’s Well-Being
The present diary study investigates, at the within-person level, how job satisfaction mediates the relationship between self-rated job performance and recovery experiences (i.e., psychological detachment from work and relaxation) during off-job time. Furthermore, we explore the effects of these two recovery experiences on couple´s well-being. Data were collected from 145 dual-earner couples (N = 290 participants; N = 1450 occasions) with a daily diary design (five consecutive working days). Multilevel analyses showed that daily job performance positively predicted psychological detachment and relaxation, and that daily job satisfaction partially mediated this relationship. In addition, we found that psychological detachment and relaxation have positive effects on own and partner´s indicators of well-being (i.e., relationship satisfaction and positive emotions). The benefits of recovery go beyond the individual and affect their partner´s level of well-being
Inositol 1,3,4,5,6-pentakisphosphate 2-kinase is a distant IPK member with a singular inositide binding site for axial 2-OH recognition
Inositol phosphates (InsPs) are signaling molecules with multiple roles in cells. In particular Graphic (InsP6) is involved in mRNA export and editing or chromatin remodeling among other events. InsP6 accumulates as mixed salts (phytate) in storage tissues of plants and plays a key role in their physiology. Human diets that are exclusively grain-based provide an excess of InsP6 that, through chelation of metal ions, may have a detrimental effect on human health. Ins(1,3,4,5,6)P5 2-kinase (InsP5 2-kinase or Ipk1) catalyses the synthesis of InsP6 from InsP5 and ATP, and is the only enzyme that transfers a phosphate group to the axial 2-OH of the myo-inositide. We present the first structure for an InsP5 2-kinase in complex with both substrates and products. This enzyme presents a singular structural region for inositide binding that encompasses almost half of the protein. The key residues in substrate binding are identified, with Asp368 being responsible for recognition of the axial 2-OH. This study sheds light on the unique molecular mechanism for the synthesis of the precursor of inositol pyrophosphates
Non-linear Higgs portal to Dark Matter
The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the dominant interactions of gauge bosons and the physical Higgs particle h to a scalar singlet Dark Matter candidate. Phenomenological consequences are also studied in detail, including the possibility of distinguishing this scenario from the standard Higgs portal in which the electroweak symmetry breaking is linearly realised. Two features of significant impact are: i) the connection between the electroweak scale v and the Higgs particle departs from the (v + h) functional dependence, as the Higgs field is not necessarily an exact electroweak doublet; ii) the presence of specific couplings that arise at different order in the non-linear and in the linear expansions. These facts deeply affect the Dark Matter relic abundance, as well as the expected signals in direct and indirect searches and collider phenomenology, where Dark Matter production rates are enhanced with respect to the standard portal
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