146 research outputs found
Constraints for the existence of flat and stable non-supersymmetric vacua in supergravity
We further develop on the study of the conditions for the existence of
locally stable non-supersymmetric vacua with vanishing cosmological constant in
supergravity models involving only chiral superfields. Starting from the two
necessary conditions for flatness and stability derived in a previous paper
(which involve the Kahler metric and its Riemann tensor contracted with the
supersymmetry breaking auxiliary fields) we show that the implications of these
constraints can be worked out exactly not only for factorizable scalar
manifolds, but also for symmetric coset manifolds. In both cases, the
conditions imply a strong restriction on the Kahler geometry and constrain the
vector of auxiliary fields defining the Goldstino direction to lie in a certain
cone. We then apply these results to the various homogeneous coset manifolds
spanned by the moduli and untwisted matter fields arising in string
compactifications, and discuss their implications. Finally, we also discuss
what can be said for completely arbitrary scalar manifolds, and derive in this
more general case some explicit but weaker restrictions on the Kahler geometry.Comment: 22 pages, Latex, no figure
Transformaciones de haz mediante microlentes selfoc activas
[EN]: In this paper light propagation in an active selfoc microlens with complex refractive index and gradient parameter are examined. The ray-transfer matrix of an active material regarded as a diffraction-free first order optical system is presented to describe the beam transformations in active selfoc microlenses. Results concerning Gaussian beam transformationsand on-axis irradiance through the active selfoc microlens are discussed and commented. © Sociedad Española de Óptica.[ES]: En este trabajo se estudia la propagación de la luz a través de una microlente selfoc activa con un índice de refracción y parámetro de gradiente complejos. La matriz de transferencia de rayos, vista como un sistema óptico de primer orden libre de efectos de difracción, es introducida para describir las transformaciones que puede sufrir un haz en microlentes selfoc activas. Por último se presentan y comentan los resultados correspondientes a las transformaciones de haces Gaussianos y a la irradiancia en eje a través de la microlente selfoc activa.This work has been sponsored by Xunta de Galicia/Feder (INCITE08PXIB206013PR), Ministerio de Ciencia e Innovación (MAT2010-18519) and CDTI (SURFALUX SOL-00030930), Spain. Besides, Ana I. Gomez-Varela wants to acknowledge the financial support from the FPU (Formación de Profesorado Universitario) grant 2009 (Ministerio de Educación, Spain).Peer Reviewe
The lightest scalar in theories with broken supersymmetry
We study the scalar mass matrix of general supersymmetric theories with local
gauge symmetries, and derive an absolute upper bound on the lightest scalar
mass. This bound can be saturated by suitably tuning the superpotential, and
its positivity therefore represents a necessary and sufficient condition for
the existence of metastable vacua. It is derived by looking at the subspace of
all those directions in field space for which an arbitrary supersymmetric mass
term is not allowed and scalar masses are controlled by supersymmetry-breaking
splitting effects. This subspace includes not only the direction of
supersymmetry breaking, but also the directions of gauge symmetry breaking and
the lightest scalar is in general a linear combination of fields spanning all
these directions. We present explicit results for the simplest case of theories
with a single local gauge symmetry. For renormalizable gauge theories, the
lightest scalar is a combination of the Goldstino partners and its square mass
is always positive. For more general non-linear sigma models, on the other
hand, the lightest scalar can involve also the Goldstone partner and its square
mass is not always positive.Comment: 30 pages, 3 figures; v2 introduction expanded, paragraph added in
section 5 and two references adde
Structural and optical characterisation of planar waveguides obtained via sol-gel
8 páginas, 6 figuras, 1 tabla.-- Trabajo presentado a la "International Conference on Applications of Optics and Photonics" celebrada en Braga (Portugal) en Mayo del 2011.Planar waveguides of SiO2:TiO2 (multilayer structure) and SiO2:CeO2 (thick layer) were prepared onto commercial glass
substrates using a sol-gel technique combined with dip-coating. These glassy coatings were structural characterised by
Transmission Electron Microscopy (TEM) Energy Dispersive X-ray analysis and by Confocal Microscopy. Thicknesses
of 1230 nm and 4,15 μm and refractive indices of 1.59 and 1.48 for SiO2:TiO2 (70:30) and SiO2:CeO2 (95:5) waveguides
were obtained, respectively, by Spectroscopic Ellypsometry. Losses of 0.8 dB/cm were measured by double prism
method in the SiO2:CeO2 system.The authors acknowledge funding from MICINN (TEC2006-10469, CEN 2007-2014, SURFALUX SOL-00030930 and
MAT2010-18519), from DGA (Group of Excellence in Laser Material Processing and Characterisation) and XUNTA
DE GALICIA (INCITE08PXIB206013PR).Peer reviewe
Metastable supergravity vacua with F and D supersymmetry breaking
We study the conditions under which a generic supergravity model involving
chiral and vector multiplets can admit viable metastable vacua with
spontaneously broken supersymmetry and realistic cosmological constant. To do
so, we impose that on the vacuum the scalar potential and all its first
derivatives vanish, and derive a necessary condition for the matrix of its
second derivatives to be positive definite. We study then the constraints set
by the combination of the flatness condition needed for the tuning of the
cosmological constant and the stability condition that is necessary to avoid
unstable modes. We find that the existence of such a viable vacuum implies a
condition involving the curvature tensor for the scalar geometry and the charge
and mass matrices for the vector fields. Moreover, for given curvature, charges
and masses satisfying this constraint, the vector of F and D auxiliary fields
defining the Goldstino direction is constrained to lie within a certain domain.
The effect of vector multiplets relative to chiral multiplets is maximal when
the masses of the vector fields are comparable to the gravitino mass. When the
masses are instead much larger or much smaller than the gravitino mass, the
effect becomes small and translates into a correction to the effective
curvature. We finally apply our results to some simple classes of examples, to
illustrate their relevance.Comment: 40 pages; v2 some clarifications added in the introduction; v3 some
typos correcte
The incidence of tuberculosis in patients treated with certolizumab pegol across indications: impact of baseline skin test results, more stringent screening criteria and geographic region
Objectives We report the incidence of tuberculosis (TB) across certolizumab pegol (CZP) clinical trials in rheumatoid arthritis (RA), psoriasis, psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA), before and after the introduction of stricter TB screening.
Methods TB incidence rates (IRs) were assessed and stratified according to screening guidelines used at the time of CZP trials. Before 2007 (original trials), purified protein derivative (PPD) tuberculin skin test positivity varied according to local standards (induration ≥5 up to ≥20 mm). Since 2007, all CZP trial protocols have been amended, including trials spanning (intermediate) and initiated after 2007 (current), mandating that any patient with PPD≥5 mm receives treatment for latent TB infection (LTBI). All cases of suspected TB or PPD≥5 mm, in pooled data from 5402 CZP patients across all CZP trials up to 2012, underwent blinded central review by independent experts.
Results 44 TB cases were confirmed in pooled CZP RA trials (IR 0.47/100PY, patient-years) with no cases in Japanese RA trials (J-RAPID, HIKARI). Single TB cases were confirmed in psoriasis and axSpA trials (RAPID-axSpA), and no cases in the PsA trial (RAPID-PsA). IR of TB was 0.51/100PY across original or intermediate RA trials and 0.18/100PY in current trials. The majority of TB cases in RA occurred in Eastern (IR 1.02/100PY) and Central Europe (IR 0.58/100PY). Of 242/370 PPD≥5 mm patients who received 9 months isoniazid (INH) treatment for latent TB infection (LTBI), none developed TB, versus 7.8% of 128 untreated PPD≥5 mm patients.
Conclusions Implementation of more stringent LTBI screening, plus treatment for LTBI, reduced the IR of TB, even when INH was administered after starting CZP therapy.This study was funded by UCB PharmaS
Electronic structure and exotic exchange splitting in spin-density-wave states of BaFeAs
The magnetic properties in the parent compounds are often intimately related
to the microscopic mechanism of superconductivity. Here we report the first
direct measurements on the electronic structure of a parent compound of the
newly discovered iron-based superconductor, BaFeAs, which provides a
foundation for further studies. We show that the energy of the spin density
wave (SDW) in BaFeAs is lowered through exotic exchange splitting of
the band structure, rather than Fermi surface nesting of itinerant electrons.
This clearly demonstrates that a metallic SDW state could be solely induced by
interactions of local magnetic moments, resembling the nature of
antiferromagnetic order in cuprate parent compounds.Comment: 5 pages, 4 figure
Identification of novel adipokines in the joint.Differential expression in healthy and osteoarthritis tissues
OBJECTIVES: Emerging data suggest that several metabolic factors, released mainly by white adipose tissue (WAT) and joint tissues, and collectively named adipokines, might have a role in the pathophysiology of OA. Recently, novel adipokines such as SERPINE2, WISP2, GPNMB and ITIH5 have been identified in WAT. The main goal of this study was to analyse the expression of these novel adipokines in synovium, infrapatellar fat pad and chondrocytes and to compare the expression of these molecules in healthy and OA tissues. METHODS: Synovial tissues, infrapatellar fat pad and chondrocytes were obtained from 36 OA patients (age 52-85; mean BMI 28.9) who underwent total knee replacement surgery. Healthy synovial tissues and infrapatellar fat pad were obtained from 15 traumatic knee patients (age 23-53; mean BMI 23.5). mRNA and protein expression were determined by qRT-PCR and western blot analysis respectively. RESULTS: All the novel adipokines, matter of our study, are expressed in OA synovium, infrapatellar fat pad and chondrocytes. Moreover, we detected a differential expression of SERPINE2 and ITIH5 in OA synovial tissues as compared to healthy samples. Finally, we also observed an increased expression of WISP2 in OA infrapatellar fat pad in comparison to healthy controls. CONCLUSIONS: In this study we demonstrated for the first time the expression of four novel adipokines in different joint tissues and how these molecules are differentially expressed in healthy and OA joint tissues.Xunta de Galicia/SERGASInstituto de Salud Carlos III (ISCIII)Fundación Ramón DomínguezMinisterio de Educación de Españ
Clinical features and outcomes of COVID-19 in patients with rheumatic diseases treated with biological and synthetic targeted therapies
- …