Steel profiles for repairing deteriorated timber beam ends

Se describe un procedimiento para la consolidación de viguetas de forjado de madera con deterioro en las cabezas mediante perfiles de acero conectados a la madera desde la cara superior del forjado. La pieza de refuerzo es un perfil en U de acero S275 conformado en frío con pletinas soldadas insertadas en la madera y conectada mediante tirafondos. Se ensayaron 30 piezas a flexión obteniendo la rigidez y la capacidad de carga. Las probetas se dividieron en tres grupos. El primero compuesto por 10 piezas de madera laminada encolada de abeto con una sección de 180 x 200 mm y una longitud de 4.000 mm; el segundo consistía en 10 piezas de madera aserrada de pino silvestre con la misma sección y longitud y, el tercero, estaba formado por otras 10 piezas de madera del género Pinus con una sección de 130 x 150 mm y 3.000 mm de longitud, procedentes de un edificio de Madrid con 120 años de antigüedad. Cada grupo de 10 piezas se dividió a su vez en dos grupos de 5 piezas. El primer subgrupo estaba formado por las piezas completas de madera y constituía el grupo de referencia. Las piezas del segundo subgrupo tenían una longitud inferior que se salvaba con una extensión del refuerzo metálico. Los resultados indican que el sistema de refuerzo metálico permite resolver los problemas de falta de apoyo de la vigueta por deterioro de la madera que afecte en una longitud limitada (aproximadamente entre el 10 y el 20% de la longitud)

Hepatitis A, B y D en Chocó

A study to compile and analyse the existing epidemiological information concerning hepatitis A, B and D in the Chocó department of Colombia was carried out from 1976-1993. One study reported a hepatitis A virus antibody prevalence of 85.7 per thousand, in a representative population sample. There was evidence of transmission amongst al1 age groups. In the same sample a hepatitis B surface antigen prevalence of 4.2 per thousand was found. Acute fulminant hepatitis foci for hepatitis D have been detected in the town of Riosucio in the Truandó-Salaquí region, where hepatitis B infection prevalence of 915 per thousand and 200 per thousand hepatitis B surface antigen prevalence was found. The main transmission axis is vertical-horizontal. The principal important transmission riskfactors in this area are: overcrowding, promiscuity, the 15-24 female age group and the evidence of transmission in any family member. Two foci of acute fulminant hepatitis have been identified in Bebaramá and Guarandó in the rural zone of Quibdó, hepatitis B infection prevalencies of 74% and 85% having been found. A study carried out with health personnel, whose objective was to identify groups most at risk, found infection prevalencies between 27% and 33%. Furthermore, hepatitis B sutface antigen prevalence was 13.3% and 13.6%, principally in nursing and laboratory personnel. Finally, integral solution alternatives were planned for hepatitis A and B based on health promotion activities, preventative measures (such as hepatitis B vaccination), vigilante and control.Se realiza una recopilación y análisis de la información epidemiológica existente sobre hepatitis A, B y delta en el departamento de Chocó en el período 1976-1993. En un estudio anterior, se informó una prevalencia de anticuerpos contra el virus de la hepatitis A de 85,7 por mil, en una muestra representativa de la población, con evidencia de transmisión en todos los grupos de edad; en la misma muestra, se encontró una prevalencia de antigeno de superficie de hepatitis B de 4,2/1.000. Se han detectado focos de hepatitisfulminante aguda por hepatitis delta en la región de Truandó-Salaquí, en el municipio de Riosucio, donde se encontró una prevalencia de infección por hepatitis B de 915/1.000 y una prevalencia de antígeno de superficie de hepatitis B de 200/1.000, El principal patrón de transmisión es vertical-horizontal. Los principales factores de riesgo de importancia en la transmisión en esa área son el hacinamiento, la promiscuidad, los grupos femeninos de 15 a 24 años y la evidencia de transmisión en algún miembro de la familia. En la zona rural de Quibdó, se han identificado dos focos de hepatitis fulminante aguda en las localidades de Bebaramá y Guarandó, encontrándose prevalencias de infección por hepatitis B de 74 y 85%. En un estudio realizado en personal de salud cuyo objetivo era identificar los grupos con mayor riesgo, se encontraron prevalencias de infección entre 27 y 33%; además, la prevalencia de antígeno de superficie de hepatitis B fue 13,3 a 13,6 %, principalmente en personal de enfermería y laboratorio. Finalmente, se plantean alternativas integrales de solución para hepatitis A y B basadas en actividades de promoción de la salud, medidas de prevención como la vacunación contra hepatitis B, la vigilancia y el control

Efecto de Tres Crioprotectores en la Criopreservación de Espermatozoides Epididimarios de Alpaca

The study aimed to evaluate the effect of three cryoprotectants: Dimetil Sulfoxide (DMSO), Ethylene glycol (EG) and Glycerol (GL) on the cryopreservation of epididymal alpaca sperm. Testicles of alpacas older than 3 years were used. The epididymides were separated and the tails were dissected. The spermatozoa were recovered with fraction A of the extender (cow skim milk, egg yolk and fructose), selecting samples with sperm motility equal or higher than 50% (n=18, motility = 69%, sperm membrane functional integrity = 48%). The fraction A with the sperm was refrigerated (cooling rate of 1 ºC/5 min) until 5 ºC. The fraction was divided in three and added the same volume of fraction B with the cryoprotectant (DMSO: 7%, 0.9M; EG: 7%, 0.9M; GL: 7%, 1.2M). Then, 0.5 ml straws were filled with the final dilution and frozen in liquid nitrogen. After 7 days of storage, the post-thaw motilities were 31, 8 and 24% and percentages of sperm membrane functional integrity were 28, 17 and 26% for DMSO, EG and GL respectively. An in vitro fertilization trial was conducted with thawed sperm from groups DMSO and GL, where the cleavage rate at 72 h post-fertilization was 47 and 27% respectively and without statistical difference. The results suggest that dimetil sulfoxide and glycerol are more efficient cryoprotective agents in comparison to the ethylene glycol.El estudio tuvo por objetivo evaluar el efecto de tres crioprotectores: Dimetil Sulfóxido (DMSO), Etilenglicol (EG) y Glicerol (GL) sobre la criopreservación de espermatozoides epididimarios de alpaca. Se trabajó con testículos de alpacas mayores de tres años. Se separaron los epidídimos y se diseccionaron las colas. Los espermatozoides fueron recuperados con la fracción A del dilutor (leche descremada, yema de huevo y fructosa) y se emplearon las muestras con motilidad espermática igual o mayor a 50% (n=18, motilidad = 69%, integridad funcional de membrana espermática = 48%). La fracción A con los espermatozoides fue refrigerada (1 ºC/5 min) hasta alcanzar 5 ºC. Esta fracción se dividió en tres y se añadió un volumen igual de la fracción B conteniendo un crioprotector (DMSO: 7%, 0.9M; EG: 7%, 0.9M; GL: 7%, 1.2M). Se llenaron pajillas de 0.5 ml con la dilución final y se congelaron en nitrógeno líquido. Después de 7 días de almacenamiento, las motilidades posdescongelación fueron de 31, 8 y 24% y los porcentajes de integridad funcional de la membrana espermática fueron de 28, 17 y 26% para DMSO, EG y GL, respectivamente. Se llevó a cabo un ensayo de fecundación in vitro con los espermatozoides descongelados de los grupos DMSO y GL, donde la tasa de división a las 72 h posfecundación fue de 47 y 27%, respectivamente, sin diferencias significativas. Los resultados sugieren que el dimetil sulfóxido y el glicerol son agentes crioprotectores más efectivos en comparación al etilenglicol

Deployment requirements for deorbiting electrodynamic tether technology

In the last decades, green deorbiting technologies have begun to be investigated and have raised a great interest in the space community. Among the others, electrodynamic tethers appear to be a promising option. By interacting with the surrounding ionosphere, electrodynamic tethers generate a drag Lorentz force to decrease the orbit altitude of the satellite, causing its re-entry in the atmosphere without using propellant. In this work, the requirements that drive the design of the deployment mechanism proposed for the H2020 Project E.T.PACK\u2014Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit\u2014are presented and discussed. Additionally, this work presents the synthesis of the reference profiles used by the motor of the deployer to make the tethered system reach the desired final conditions. The result is a strategy for deploying electrodynamic tape-shaped tethers used for deorbiting satellites at the end of their operational life

Exact 4He Spectral Function in a Semirealistic NN Potential Model

The spectral function of 4He is calculated with the Lorentz integral transform method in a large energy and momentum range. The excitation spectrum of the residual 3N-system is fully taken into account. The obtained spectral function is used to calculate the quasi elastic longitudinal (e,e') response R_l of 4He for q=300, 400, and 500 MeV/c. Comparison with the exact R_l shows a rather sizeable disagreement except in the quasi elastic peak, where the differences reduce to about 10% at q=500 MeV/c. It is shown as well that very simple momentum distribution approximations for the spectral function provide practically the same results for R_l as the exact spectral function.Comment: 7 pages, Latex (Revtex), 4 Postscript figures, to appear in Phys. Rev.

Use of Native Grassland in Small-Scale Dairy Systems in the Highlands of Central Mexico. A Case Study

Small-scale dairy systems in Mexico comprise 78% of specialized dairy farms and provide 37% of national production. They are small farms with herds 3-35 cows plus replacements, and rely on family labour (Posadas-Domínguez et al., 2014). In the highlands, many farms have native grasslands, grazed during the rainy season, and supplemented with other feeds as maize straw, maize grain and maize ears. Native grasslands have not been studied in this context. This is a case study on the use of native grassland in a small-scale dairy farm. The objective was to determine how native grasslands are integrated in feeding milking dairy cows, and the feeding costs involved

Solutions of the Faddeev-Yakubovsky equations for the four nucleons scattering states

The Faddeev-Yakubowsky equations in configuration space have been solved for the four nucleon system. The results with an S-wave interaction model in the isospin approximation are presented. They concern the bound and scattering states below the first three-body threshold. The elastic phase-shifts for the N+NNN reaction in different ($S,T$) channels are given and the corresponding low energy expansions are discussed. Particular attention is payed to the n+t elastic cross section. Its resonant structure is well described in terms of a simple NN interaction. First results concerning the S-matrix for the coupled N+NNN-NN+NN channels and the strong deuteron-deuteron scattering length are obtained.Comment: latex.tar.gz, 36 pages, 10 figures, 11 tables. To be published in Physical Review

Electromagnetic response functions of few-nucleon systems

Inclusive electromagnetic reactions in few-nucleon systems are studied basing on accurate three- and four-body calculations. The longitudinal 4He(e,e') response function obtained at q\le 600 MeV/c completely agrees with experiment. The exact 4He spectral function obtained in a semirealistic potential model is presented, and the accuracy of the quasielastic response calculated with its help is assessed, as well as the accuracy of some simpler approximations for the response. The photodisintegration cross section of 3He obtained with the realistic AV14 NN force plus UrbanaVIII NNN force agrees with experiment. It is shown that this cross section is very sensitive to underlying nuclear dynamics in the E_\gamma\simeq 70-100 MeV region. In particular, the NNN nuclear force clearly manifests itself in this region.Comment: 10 pages, Latex, style file is included, 7 ps figures, to appear in Proc. of the 2nd Int. Conf. on Perspectives in Hadronic Physics, ITCP, Triest, May 1999, World Sci., Singapor

Femtometer Toroidal Structures in Nuclei

The two-nucleon density distributions in states with isospin $T=0$, spin $S$=1 and projection $M_S$=0 and $\pm$1 are studied in $^2$H, $^{3,4}$He, $^{6,7}$Li and $^{16}$O. The equidensity surfaces for $M_S$=0 distributions are found to be toroidal in shape, while those of $M_S$=$\pm$1 have dumbbell shapes at large density. The dumbbell shapes are generated by rotating tori. The toroidal shapes indicate that the tensor correlations have near maximal strength at $r<2$ fm in all these nuclei. They provide new insights and simple explanations of the structure and electromagnetic form factors of the deuteron, the quasi-deuteron model, and the $dp$, $dd$ and $\alpha d$ $L$=2 ($D$-wave) components in $^3$He, $^4$He and $^6$Li. The toroidal distribution has a maximum-density diameter of $\sim$1 fm and a half-maximum density thickness of $\sim$0.9 fm. Many realistic models of nuclear forces predict these values, which are supported by the observed electromagnetic form factors of the deuteron, and also predicted by classical Skyrme effective Lagrangians, related to QCD in the limit of infinite colors. Due to the rather small size of this structure, it could have a revealing relation to certain aspects of QCD.Comment: 35 pages in REVTeX, 25 PostScript figure

Deorbit kit demonstration mission

In Low Earth Orbit, it is possible to use the ambient plasma and the geomagnetic field to exchange momentum with the Earth's magnetosphere without using propellant. A device that allows an efficient momentum exchange is the electrodynamic tether (EDT), a long conductor attached to the satellite. EDT technology has been demonstrated in several past missions, being the Plasma Motor Generator mission (NASA 1993) one of the most successful. Nevertheless, it is not until today that reality has imposed a strong need and a concrete use case for developing this technology. In March 2019, the European Commission project Electrodynamic Tether technology for PAssive Consumable-less deorbit Kit (E.T.PACK) started the design of a new generation EDT. After completing the design phase, the consortium manufactured and is currently testing a Deorbit Kit Demonstrator (DKD) breadboard based on EDT technology. The objective of E.T.PACK is to reach Technology Readiness Level equal to 4 by 2022. The DKD is a standalone 24-kg satellite with the objective to demonstrate the performances of the improved EDT solution and validate its ultra-compact deployment system. The DKD is composed of two modules that will separate in orbit extending a 500-m long tape-like tether. The deployed bare-Aluminium tether will capture electrons from the ambient plasma passively and the circuit will be closed with the ionospheric plasma by using an active electron emitter. E.T.PACK tether will take advantage of several novelties with respect to the mission flown in the past that will allow to optimize the system volume and mass. Once successful demonstrated in orbit, the team plans to develop a suite of EDT systems capable of deorbiting satellites between 200 and 1000 kg from an altitude up to 1200 km in a few months. The work presents the current design status of the de-orbit kit demonstrator breadboard, the simulations of the system deorbit performances and the development approach.This work was supported by the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No.828902 (3M€ E.T.PACK project) and No.101034874 (100K€ BMOM project). SG is supported by an Industrial Ph.D funded by Comunidad de Madrid (135K€ IND2019/TIC17198). The team has recently got 2.5M€ additional financial support from European Union (ETPACK-F project No. 101058166) for the manufacturing and qualification of the In Orbit Demonstration (IOD) by the end of 2025