Centaur AC-8 Postflight Guidance Analysis

Centaur AC-8 postflight guidance and control analysi

Hilbert number for a family of piecewise nonautonomous equations

For family $x'=(a_0+a_1\cos t+a_2 \sin t)|x|+b_0+b_1 \cos t+b_2 \sin t$, we solve three basic problems related with its dynamics. First, we characterize when it has a center (Poincar\'e center focus problem). Second, we show that each equation has a finite number of limit cycles (finiteness problem), and finally we give a uniform upper bound for the number of limit cycles (Hilbert's 16th problem).Comment: 16 pages, no figure

Phonon assisted dynamical Coulomb blockade in a thin suspended graphite sheet

The differential conductance in a suspended few layered graphene sample is fou nd to exhibit a series of quasi-periodic sharp dips as a function of bias at l ow temperature. We show that they can be understood within a simple model of dyn amical Coulomb blockade where energy exchanges take place between the charge carriers transmitted trough the sample and a dissipative electromagnetic envir onment with a resonant phonon mode strongly coupled to the electrons

USE OF SYNTHETIC TANINES DURING THE SKIN CURTITION PROCESS OF Cavia porcellus (CUY) IN FINE PELETERY

The Cavia porcellus skin (Cuy), after receiving a tanning process, using synthetic tannins, becomes a high quality leather, very suitable in the articles manufacture of high quality. Its main objective was the evaluation of different levels of synthetic tannin (6, 7, 8%) during the tanning process of guinea pig skins with hair; using 48 skins, with an average mass of 200 g each. The experimental units modeled with a Completely Random Design (DCA. Once the experimental phase was completed, it observed that the most skin tanning suitable level the guinea pig (retaining hair) is 6 % of synthetic tanning agent; it´s supported by the excellent results the tests performed. The physical resistance evaluation determined that the best tensile strength (1945.75 N/cm2) it´s reached whit 6 % of synthetic tannin and the best percentage of elongation (89.69 %) achieved with the use of 7 % of tannin (which fully meet the requirements quality the Spanish Leather Association). The most efficient sensorial characteristics obtained with 6 % of tannin: fullness 4.88; softness 4.63 and roundness 4.75 points, respectively; producing a very soft, flexible skin and above all with the fullness suitable for the fine articles manufacture. Keywords: tanning, skins, guinea pig, synthetic tannins. Resumen La piel del Cavia porcellus (Cuy), después de curtida, empleando taninos sintéticos, se convierte en un cuero de alta calidad, muy adecuado en la peletería fina. Esta investigación tuvo por objetivo fundamental la evaluación de diferentes niveles de tanino sintético (6, 7, 8 %) durante el proceso de curtición de pieles de cuyes con pelo; utilizando para ello un total de 48 pieles, con una masa promedio de 200 g cada una. Las unidades experimentales fueron modeladas con un Diseño Completamente al Azar (DCA). Una vez culminada la fase experimental, se pudo constatar que el nivel más adecuado para la curtición de la piel de cuy (conservando el pelo) es del 6 % de curtiente sintético; lo cual quedó avalado por los excelentes resultados de las pruebas practicadas. La evaluación de las resistencias físicas determinó que la mejor resistencia a la tensión (1945,75 N/cm2) se alcanzó al curtir con 6 % de tanino sintético, y el mejor porcentaje de elongación (89,69 %), se logró con la utilización de 7 % de tanino (que satisfacen completamente con las exigencias de calidad de la Asociación Española del Cuero). Las características sensoriales más eficientes fueron logradas al curtir las pieles con 6 % de tanino: llenura 4,88; blandura 4,63 y redondez 4,75 puntos, respectivamente; produciéndose una piel muy suave, flexible y sobre todo con la llenura adecuada para la confección de artículos de peletería fina. Palabras Clave: Clave: curtición, pieles, cuy, taninos sintéticos

Effect of organic loading rate on the production of Polyhydroxyalkanoates from sewage sludge

The aim of this work was to study the effect of organic loading rate on the production of Polyhydroxyalkanoates (PHA) from sewage sludge. Synthesis of PHA using sewage sludge as platform was achieved in this work. Three pilot-scale selection-sequencing batch reactors (S-SBR) were used for obtaining a culture able to accumulate PHA following a strategy of aerobic dynamic feeding (ADF) at different volumetric organic-loading-rate (vOLR): 1.3, 1.8 and 0.8 g COD L-1 d-1 for S-SBR 1, S-SBR 2 and S-SBR 3, respectively. Decreasing the vOLR enhanced the general performance of the process as for organic matter removal (from 99.2% ± 0.3% in S-SBR-3 to 92 ± 2 in S-SBR-2) while the opposite trend was recorded for PHA production (6.0 PHA % w/w in S-SBR-3 vs 13.7 PHA % w/w in S-SBR-2 at the end of the feast phase). Furthermore, indirect and direct emissions, as N2O, were evaluated during the process for the first time. Finally, three accumulation tests were performed achieving 24% w/w

A numerical study of the development of bulk scale-free structures upon growth of self-affine aggregates

During the last decade, self-affine geometrical properties of many growing aggregates, originated in a wide variety of processes, have been well characterized. However, little progress has been achieved in the search of a unified description of the underlying dynamics. Extensive numerical evidence has been given showing that the bulk of aggregates formed upon ballistic aggregation and random deposition with surface relaxation processes can be broken down into a set of infinite scale invariant structures called "trees". These two types of aggregates have been selected because it has been established that they belong to different universality classes: those of Kardar-Parisi-Zhang and Edward-Wilkinson, respectively. Exponents describing the spatial and temporal scale invariance of the trees can be related to the classical exponents describing the self-affine nature of the growing interface. Furthermore, those exponents allows us to distinguish either the compact or non-compact nature of the growing trees. Therefore, the measurement of the statistic of the process of growing trees may become a useful experimental technique for the evaluation of the self-affine properties of some aggregates.Comment: 19 pages, 5 figures, accepted for publication in Phys.Rev.

Extended States in a One-dimensional Generalized Dimer Model

The transmission coefficient for a one dimensional system is given in terms of Chebyshev polynomials using the tight-binding model. This result is applied to a system composed of two impurities located between $N$ sites of a host lattice. It is found that the system has extended states for several values of the energy. Analytical expressions are given for the impurity site energy in terms of the electron's energy. The number of resonant states grows like the number of host sites between the impurities. This property makes the system interesting since it is a simple task to design a configuration with resonant energy very close to the Fermi level $E_F$.Comment: 4 pages, 3 figure

Neocortical tissue recovery in severe congenital obstructive hydrocephalus after intraventricular administration of bone marrow-derived mesenchymal stem cells

BACKGROUND: In obstructive congenital hydrocephalus, cerebrospinal fluid accumulation is associated with high intracranial pressure and the presence of periventricular edema, ischemia/hypoxia, damage of the white matter, and glial reactions in the neocortex. The viability and short time effects of a therapy based on bone marrow-derived mesenchymal stem cells (BM-MSC) have been evaluated in such pathological conditions in the hyh mouse model. METHODS: BM-MSC obtained from mice expressing fluorescent mRFP1 protein were injected into the lateral ventricle of hydrocephalic hyh mice at the moment they present a very severe form of the disease. The effect of transplantation in the neocortex was compared with hydrocephalic hyh mice injected with the vehicle and non-hydrocephalic littermates. Neural cell populations and the possibility of transdifferentiation were analyzed. The possibility of a tissue recovering was investigated using 1H High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance (1H HR-MAS NMR) spectroscopy, thus allowing the detection of metabolites/osmolytes related with hydrocephalus severity and outcome in the neocortex. An in vitro assay to simulate the periventricular astrocyte reaction conditions was performed using BM-MSC under high TNFα level condition. The secretome in the culture medium was analyzed in this assay. RESULTS: Four days after transplantation, BM-MSC were found undifferentiated and scattered into the astrocyte reaction present in the damaged neocortex white matter. Tissue rejection to the integrated BM-MSC was not detected 4 days after transplantation. Hyh mice transplanted with BM-MSC showed a reduction in the apoptosis in the periventricular neocortex walls, suggesting a neuroprotector effect of the BM-MSC in these conditions. A decrease in the levels of metabolites/osmolytes in the neocortex, such as taurine and neuroexcytotoxic glutamate, also indicated a tissue recovering. Under high TNFα level condition in vitro, BM-MSC showed an upregulation of cytokine and protein secretion that may explain homing, immunomodulation, and vascular permeability, and therefore the tissue recovering. CONCLUSIONS: BM-MSC treatment in severe congenital hydrocephalus is viable and leads to the recovery of the severe neurodegenerative conditions in the neocortex. NMR spectroscopy allows to follow-up the effects of stem cell therapy in hydrocephalus.España Instituto Carlos III , PI15/00619 (to AJJ), PI19/00778 (to AJJ and PPG), PI15/00796, and PI18/01557España Ministerio de Educación, Cultura y Deporte FPU13/02906España, Ministerio de Economía y Competitividad RYC-2014-16980España, FEDER Andalucía y Universidad de Málaga UMA18-FEDERJA-27