Some properties of zeros of Sobolev-type orthogonal polynomials

9 pages, no figures.-- MSC1991 code: 33C45.MR#: MR1391618 (97f:33008)Zbl#: Zbl 0862.33005For polynomials orthogonal with respect to a discrete Sobolev product, we prove that, for each n, Qn has at least n − m zeros on the convex hull of the support of the measure, where m denotes the number of terms in the discrete part. Interlacing properties of zeros are also described.Research by first (M.A.) and third (M.L.R.) authors was partially supported by Diputación General de Aragón P CB-12/91 and by Comisión Interministerial de Ciencia y Tecnología (CICYT-Spain) PB93-0228-C02-02.Publicad

Self-assembly of Fmoc-tetrapeptides based on the RGDS cell adhesion motif

Self-assembly in aqueous solution has been investigated for two Fmoc [Fmoc ¼ N-(fluorenyl)-9-methoxycarbonyl] tetrapeptides comprising the RGDS cell adhesion motif from fibronectin or the scrambled sequence GRDS. The hydrophobic Fmoc unit confers amphiphilicity on the molecules, and introduces aromatic stacking interactions. Circular dichroism and FTIR spectroscopy show that the self-assembly of both peptides at low concentration is dominated by interactions among Fmoc units, although Fmoc-GRDS shows b-sheet features, at lower concentration than Fmoc-RGDS. Fibre X-ray diffraction indicates b-sheet formation by both peptides at sufficiently high concentration. Strong alignment effects are revealed by linear dichroism experiments for Fmoc-GRDS. Cryo-TEM and smallangle X-ray scattering (SAXS) reveal that both samples form fibrils with a diameter of approximately 10 nm. Both Fmoc-tetrapeptides form self-supporting hydrogels at sufficiently high concentration. Dynamic shear rheometry enabled measurements of the moduli for the Fmoc-GRDS hydrogel, however syneresis was observed for the Fmoc-RGDS hydrogel which was significantly less stable to shear. Molecular dynamics computer simulations were carried out considering parallel and antiparallel b-sheet configurations of systems containing 7 and 21 molecules of Fmoc-RGDS or Fmoc-GRDS, the results being analyzed in terms of both intermolecular structural parameters and energy contributions

PERICARDITIS CONSTRICTIVA EN UNA MUJER DE 36 AÑOS / Constrictive Pericarditis in a 36 year-old woman

ResumenPaciente femenina, de 36 años de edad, con antecedentes de dos gestaciones, dos partos y ningún aborto, que en el año 2003 tras su segundo parto, distócico por cesárea, desarrolla una pericarditis de causa no precisada que produjo un derrame pericárdico grave con signos de taponamiento cardíaco, y requirió ingreso hospitalario y pericardiocentesis. Siete años después se identifican, en la consulta de Cardiología, síntomas clínicos de una pericarditis constrictiva, corroborada por ecocardiograma y cateterismo derecho; actualmente ingresa para pericardiectomía, evaluada como alto riesgo quirúrgico. / Abstract36 year-old female patient, with a history of two pregnancies, two births and no abortion, who in 2003 after her second delivery (cesarean for dystocia) she developed pericarditis of undetermined cause that produced a severe pericardial effusion with signs of cardiac tamponade and required hospital admission and pericardiocentesis. Seven years later, in the Cardiology service, clinical symptoms of constrictive pericarditis are identified and confirmed by echocardiography and right heart catheterization. This patient has been recently admitted for pericardiectomy, and evaluated as high surgical risk

The influence of dietary lipid composition on skeletal muscle mitochondria from mice following eight months of calorie restriction

PMCID: PMC4138957.-- et al.Calorie restriction (CR) has been shown to decrease reactive oxygen species (ROS) production and retard aging in a variety of species. It has been proposed that alterations in membrane saturation are central to these actions of CR. As a step towards testing this theory, mice were assigned to 4 dietary groups (control and 3 CR groups) and fed AIN-93G diets at 95 % (control) or 60 % (CR) of ad libitum for 8 months. To manipulate membrane composition, the primary dietary fats for the CR groups were soybean oil (also used in the control diet), fish oil or lard. Skeletal muscle mitochondrial lipid composition, proton leak, and H2O2 production were measured. Phospholipid fatty acid composition in CR mice was altered in a manner that reflected the n-3 and n-6 fatty acid profiles of their respective dietary lipid sources. Dietary lipid composition did not alter proton leak kinetics between the CR groups. However, the capacity of mitochondrial complex III to produce ROS was decreased in the CR lard compared to the other CR groups. The results of this study indicate that dietary lipid composition can influence ROS production in muscle mitochondria of CR mice. It remains to be determined if lard or other dietary oils can maximize the CRinduced decreases in ROS production. © 2014 Institute of Physiology v.v.i.This work was supported by the National Institutes of Health grants R01 AG028125 and P01 AG025532.Peer Reviewe

A family of Nikishin systems with periodic recurrence coefficients

Suppose we have a Nikishin system of $p$ measures with the $k$th generating measure of the Nikishin system supported on an interval \Delta_k\subset\er with $\Delta_k\cap\Delta_{k+1}=\emptyset$ for all $k$. It is well known that the corresponding staircase sequence of multiple orthogonal polynomials satisfies a $(p+2)$-term recurrence relation whose recurrence coefficients, under appropriate assumptions on the generating measures, have periodic limits of period $p$. (The limit values depend only on the positions of the intervals $\Delta_k$.) Taking these periodic limit values as the coefficients of a new $(p+2)$-term recurrence relation, we construct a canonical sequence of monic polynomials $\{P_{n}\}_{n=0}^{\infty}$, the so-called \emph{Chebyshev-Nikishin polynomials}. We show that the polynomials $P_{n}$ themselves form a sequence of multiple orthogonal polynomials with respect to some Nikishin system of measures, with the $k$th generating measure being absolutely continuous on $\Delta_{k}$. In this way we generalize a result of the third author and Rocha \cite{LopRoc} for the case $p=2$. The proof uses the connection with block Toeplitz matrices, and with a certain Riemann surface of genus zero. We also obtain strong asymptotics and an exact Widom-type formula for the second kind functions of the Nikishin system for $\{P_{n}\}_{n=0}^{\infty}$.Comment: 30 pages, minor change

The galaxy major merger fraction to z ~ 1

Aims. The importance of disc-disc major mergers in galaxy evolution remains uncertain. We study the major merger fraction in a SPITZER/IRAC-selected catalogue in the GOODS-S field up to z ~ 1 for luminosity- and mass-limited samples. Methods. We select disc-disc merger remnants on the basis of morphological asymmetries/distortions, and address three main sources of systematic errors: (i) we explicitly apply morphological K-corrections; (ii) we measure asymmetries in galaxies artificially redshifted to z_d = 1.0 to deal with loss of morphological information with redshift; and (iii) we take into account the observational errors in z and A, which tend to overestimate the merger fraction, though use of maximum likelihood techniques. Results. We obtain morphological merger fractions (f_m^mph) below 0.06 up to z ~ 1. Parameterizing the merger fraction evolution with redshift as f_m^mph (z) = f_m^mph (0)(1 + z)^m, we find that m = 1.8 ± 0.5 for M(B)≤ -20 galaxies, while m = 5.4 ± 0.4 for M_* ≥ 10^10 M_⨀ galaxies. When we translate our merger fractions to merger rates (R_m^mph), their evolution, parameterized as R_m^mph (z) = R_m^mph (0)(1+ z)^n, is quite similar in both cases: n = 3.3 ± 0.8 for M(B) ≤ -20 galaxies, and n = 3.5 ± 0.4 for M_* ≥10^10 M_⨀ galaxies. Conclusions. Our results imply that only similar to 8% of today's M(star) ≥ 10^10 M_⨀ galaxies have undergone a disc-disc major merger since z ~ 1. In addition, ~ 21% of M_* ≥ 10(10) M_⨀ galaxies at z ~ 1 have undergone one of these mergers since z similar to 1.5. This suggests that disc-disc major mergers are not the dominant process in the evolution of M_* ≥ 10(10) M_⨀ galaxies since z 1, with only 0.2 disc-disc major mergers per galaxy, but may be an important process at z > 1, with ~ 1 merger per galaxy at 1 < z < 3

Transference Impedance Estimation of IEC60318 Couplers by Image Processing and finite Element Modelling

In order to know the acoustic transference impedance of acoustic coupler described in IEC60318 standard it is necessary to make measures based on the reciprocity technique. This technique is used for microphones calibration as is defined in IEC61094-2 standard. This calibration method is complex enough to execute, and therefore it would be very interesting to look for alternative procedures that allow knowing the coupler acoustic impedance. In this paper an acoustic impedance calibration methodfor type I coupler is proposed based on non invasive X-ray inspection, virtual instrumentation image processing application and computer simulation. This new approach requires knowing the coupler's geometry and use offinite element model approach for acoustic coupler behavior determination. In order to establish a precise mechanical model of the couplers described in IEC60318 standard it is necessary to know the geometry and key dimensions of the coupler. These dimensions are obtained with non-invasive measurement techniques, based on X-ray inspection. Then the use of a finite element model allows prediction of the coupler acoustic impedance values. This modeling is quite differentfrom the "lumped parameter model" proposed in the IEC60318 standard Lumped parameter modeling has limitations in its application because the dimensions of the coupler's elements are comparable with the acoustic signal wavelength. Moreover, when the sound propagates in narrow cavities and ducts the losses produced by viscosity and thermal effects must be taken into account. All these effects are not reflected with accuracy in the classic lumped model. The result of finite element simulation can provide more detailed information about the interior acoustic behavior of the coupler and therefore provide a more realistic and accurate value of acoustic impedance in order to calibrate the device. The comparison of the data obtained with this new approach and the values defined in the current version of IEC60318-1 standard (291633/CDV) confirm the validity ofthe method