Falling birth rates and world population decline: A quantitative discussion (1950-2040)

The UN data (1950-2010) and projections (both medium and low-fertility variants for 2015- 2040) show that fertility rates are already below replacement level in all continents except Africa. In this paper we develop a simple new approach for population projections based on a Improved Rate Equations (IRE) model. Population projections under the (1) Malthusian assumption, (2) an (IRE) model fitting and extrapolating from actual UN population data up to 2040, and (3) UN projections (low-fertility variant), are compared. The model fits quite well actual data and suggests a world population decline in the 21st Century. The economic, social and political consequences of this new and global circumstance would be far reachin

Constraints on the general solutions of Einstein cosmological equations by Hubble parameter times cosmic age: a historical perspective

A version of this paper is in Arxiv.org: arXiv:1306.0238In a historical perspective, compact solutions of Einstein’s equations, including the cosmological constant and the curvature terms, are obtained, starting from two recent observational estimates of the Hubble’s parameter (H0) and the “age” of the universe (t0). Cosmological implications for ΛCDM (Λ Cold Dark Matter), KOFL (k Open FriedmanLemaitre), plus two mixed solutions are investigated, under the constraints imposed by the relatively narrow current uncertainties. Quantitative results obtained for the KOFL case seem to be compatible with matter density and the highest observed red-shifts from distant galaxies, while those obtained for the ΛCDM may be more difficult to reconcile

Physicochemical and biological changes downstream from a trout farm outlet: comparing 1986 and 2006 sampling surveys

In this investigation we compare the results obtained in the 1986 and 2006 sampling surveys regarding physicochemical and biological changes caused by a trout farm effluent in the upper Tajuña River (Guadalajara, Spain). For this comparison three sampling sites were selected: S-1, placed upstream from the trout farm, was used as a reference station; S-2 and S-3 were respectively placed about 10 m and 1000 m downriver from the trout farm outlet. In both surveys, the concentration of nutrients (ammonia, nitrite, nitrate, phosphate) increased downstream from the trout farm, whereas the concentration of dissolved oxygen decreased. Gammaridae, Heptageniidae, Elmidae, Perlidae, Ancylidae, Hydrobiidae, Glossosomatidae and Sericostomatidae significantly decreased their abundances downstream from the trout farm outlet. On the contrary, Tubificidae, Erpobdellidae, Glossiphoniidae, Planorbidae, Sphaeridae and Chironomidae were clearly favoured. The water quality in ecological terms, as assessed by biotic indices, was markedly reduced, with average scores (ASPT, ASPT', a-BMWQ) showing a better indicator value than total scores (BMWP, BMWP', BMWQ). Shredders and scrapers were the functional feeding groups most severely affected, whereas collectors were clearly favoured. We conclude that the wastewater depuration system of the trout farm must be improved since, during the last twenty years, it has been insufficient to prevent significant alterations in the recipient river.En esta investigación comparamos los resultados obtenidos durante las campañas de muestreo de 1986 y 2006 para los cambios físico-químicos y biológicos producidos por el vertido de una piscifactoría en el tramo alto del río Tajuña (Guadalajara, España). Para ello se seleccionaron tres puntos de muestreo: S-1, aguas arriba de la piscifactoría, sirvió de punto control; S-2 y S-3 se emplazaron, respectivamente, a 10 m y 1000 m aguas abajo del punto de vertido. En ambas campañas, la concentración de nutrientes (amoniaco, nitrito, nitrato, fosfato) aumentó río abajo de la piscifactoría, mientras que la concentración de oxígeno disuelto disminuyó. Gammaridae, Heptageniidae, Elmidae, Perlidae, Ancylidae, Hydrobiidae, Glossosomatidae y Sericostomatidae redujeron significativamente sus abundancias aguas abajo del punto de vertido. Por el contrario, Tubificidae, Erpobdellidae, Glossiphoniidae, Planorbidae, Sphaeridae y Chironomidae fueron claramente favorecidos. La calidad del agua en términos ecológicos, evaluada por medio de índices bióticos, empeoró marcadamente, con las puntuaciones medias (ASPT, ASPT', a-BMWQ) mostrando un mejor valor indicador que las puntuaciones totales (BMWP, BMWP', BMWQ). Desmenuzadores y raspadores fueron los grupos tróficos más severamente afectados, mientras que los recolectores fueron claramente favorecidos. Concluimos que el sistema de depuración de las aguas residuales de la piscifactoría tiene que ser mejorado ya que, durante los últimos veinte años, ha sido insuficiente para prevenir alteraciones significativas en el río receptor

Monte Carlo critical isotherms for Ising lattices

Monte Carlo investigations of magnetization versus field, $M_c(H)$, at the critical temperature provide direct accurate results on the critical exponent $\delta^{-1}$ for one, two, three and four-dimensional lattices: $\delta_{1D}^{-1}$=0, $\delta_{2D}^{-1}$=0.0666(2)$\simeq$1/15, $\delta_{3D}^{-1}$=0.1997(4)$\simeq$1/5, $\delta_{4D}^{-1}$=0.332(5)$\simeq$1/3. This type of Monte Carlo data on $\delta$, which is not easily found in studies of Ising lattices in the current literature, as far as we know, defines extremely well the numerical value of this exponent within very stringent limits.Comment: 5 pages, 4 figures. Sent to Europhysics Letter

The Endoplasmic Reticulum Glucosyltransferase Recognizes Nearly Native Glycoprotein Folding Intermediates

The UDP-Glc:glycoprotein glucosyltransferase (GT), a key player in the endoplasmic reticulum (ER) quality control of glycoprotein folding, only glucosylates glycoproteins displaying non-native conformations. To determine whether GT recognizes folding intermediates or irreparably misfolded species with nearly native structures, we generated and tested as GT substrates neoglycoprotein fragments derived from chymotrypsin inhibitor 2 (GCI2) bearing from 53 to 64 (full-length) amino acids. Fragment conformations mimicked the last stage-folding structures adopted by a glycoprotein entering the ER lumen. GT catalytic efficiency (V(max)/K(m)) remained constant from GCI2-(1-53) to GCI2-(1-58) and then steadily declined to reach a minimal value with GCI2-(1-64). The same parameter showed a direct hyperbolic relationship with solvent accessibility of the single Trp residue but only in fragments exposing hydrophobic amino acid patches. Mutations introduced (GCI2-(1-63)V63S and GCI2-(1-64)V63S) produced slight structural destabilizations but increased GT catalytic efficiency. This parameter presented an inverse exponential relationship with the free energy of unfolding of canonical and mutant fragments. Moreover, the catalytic efficiency showed a linear relationship with the fraction of unfolded species in water. It was concluded that the GT-derived quality control may be operative with nearly native conformers and that no alternative ER-retaining mechanisms are required when glycoproteins approach their proper folding.Fil: Caramelo, Julio Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Castro, Olga Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: de Prat Gay, Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Parodi, Armando José A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

Prospects of world population decline in the near future: a short note

An article in Science (4 November 1960) proposed Friday 13 November AD 2026 as the "Doomsday" of planet Earth, a doomsday produced by the "world population" going to infinity. In that paper, a rudimentary rate equation describing the evolution of the world population with time, was approximated in such a way that a quantitative calculation produced that particular date. In this note, we give a more realistic rate equation which respects general conservation principles and we compare previous results and the results of our calculation, with actual UN data for 1960-2010 and UN medium term projections. At present there is disagreement among experts as to what can be expected for the world population in the future. Some think that the population is still growing out control, some say it will be approximating a constant level by 2050, whilst others expect it to be clearly in decline somewhere between 2050 and the end of 21st century. Our model shows conclusively that if no drastic and unexpected changes take place soon, the world population will be decreasing at an accelerated rate after 2050. Our rate equation approach is similar to that used in condensed matter physics and chemical physics to describe the evolution of a two level system under an external perturbation. The result is much more realistic than a purely exponential result as has been generally assumed in the last decades of the last centur

Pyroelectric Charge Release in Rhombohedral PZT

A new experimental set-up controlled by computer has been made to measure the pyroelectric charge of ferroelectric materials with a relatively high conductivity at slow rates of temperature variation. It allowed us to obtain the polarisation vs. temperature behaviour of PZT with various compositions in the whole range of temperatures with a high accuracy. The ferroelectric Zr-rich region of the PZT phase diagram, where the isostructural phase transition FRL-FRH takes place, has been studied