sábado, 30 de julio de 2016

Genetic diversity,

Genetic diversity and the r/K gradient in animals.
The average per-day fecundity is on the x axis and the average size of eggs or juveniles is on the y axis; each dot is for a family (one to four species each). The colour scale indicates the average...
Genetic diversity and the r/K gradient in animals.
The average per-day fecundity is on the x axis and the average size of eggs or juveniles is on the y axis; each dot is for a family (one to four species each). The colour scale indicates the average nucleotide diversity at synonymous positions, expressed in per cent. The negative correlation reflects a trade-off between quantity and size of offspring. r-strategists (bottom right; for example, blue mussels, heart urchins and lumbricid earthworms) are more polymorphic than K-strategists (top-left; for example, penguins, Galapagos tortoises and subterranean termites).
from the article “Determinants of genetic diversity” by NATURE REVIEWS GENETICS.

jueves, 21 de julio de 2016

lunes, 18 de julio de 2016

Graphic Biology

Sometimes figures created by scientists are striking, some others are just ugly and misleading the message. Wrong fonts, unfitting alignment of elements, excessive use of colors, dense strokes and unnecessary repetition of information, are among the issues that scientific figures can present. As a learning process, Graphic Biology will show technical images/illustrations that are accurate, self-explanatory and clear from scientific results and conclusions.Graphic Biology will try to expose the best visual examples of scientific communication from now and from the past. Tips from graphic design, cognitive psychology and semiotics will be also part of the journey. The encounter between science and art will be celebrated.
Enjoy the ride!

viernes, 15 de julio de 2016

Emil Erlenmeyer and the Erlenmeyer Flask

Whether you know it as an Erlenmeyer flask, conical flask, or by some other name, it’s a piece of glassware most of us, chemists or not, have likely used at some point. The Erlenmeyer flask is the most stereotypical piece of chemistry glassware there is, and today marks its creator’s birthday. Emil Erlenmeyer was born on 28 June in 1825; here we take a look at his eponymous flask, as well as some of his other achievements.
Firstly, to give Erlenmeyer his full name: Richard August Carl Emil Erlenmeyer. Perhaps not surprising that he chose to shorten it! He was a German chemist who originally specialised in pharmacy, but eventually gravitated back toward chemistry. During his career, he synthesised or isolated numerous organic compounds for the first time, and also made some significant contributions to our understanding of the structure of organic molecules.
Despite this, the flask that bears his name is what Erlenmeyer is invariably remembered for, though in some countries it’s known by other names. In the UK, hearing it referred to as a conical flask is more common, whereas in Italy they sometimes call it a ‘beuta’. Erlenmeyer designed his flask in the late 1850s; he first described it in a paper published at the beginning of 1860, by which point he had already arranged its commercial production and sale.

domingo, 10 de julio de 2016

The Chemistry of a Football Shirt – Euro 2016 Edition

With Euro 2016 in full swing, it seemed a good time to update this look at the chemicals that make up your average football shirt. Even if the tournament isn’t the kind of event to fill you with excitement, it’s still intriguing from a chemistry perspective to examine the different chemical materials used and the properties that they lend the finished shirt.
In the past, before polymers were widely used in clothing, football shirts were made from cotton, or even woollen materials. These had the obvious disadvantage of being a little on the warm side of things, and additionally soaked up any sweat produced, making them rather uncomfortable to wear. The first team to buck the trend of cotton shirts, and wear shirts made of an artificial material, were Bolton Wanderers in 1953’s FA Cup Final. Sadly, the precise material used doesn’t seem to be recorded anywhere that I could find, only being described as a ‘shiny material’.
It seems similarly hard to track down when exactly polyester shirts came into common use, but by the 1990s polyester shirts were the norm for the majority of clubs. Polyester is actually a name for a large range of polymers; polymers are long, chain-like molecules formed from many smaller molecules, often referred to as monomers. In the case of simple polymers, such as polyethene, the monomers are all the same, but in the case of polyesters, two different sets of molecules are needed: an alcohol and a carboxylic acid. The polymerisation reaction can be carried out in a number of ways – the most commonly utilised uses a diol (a molecule with two alcohol functional groups) and a dicarboxylic acid (a molecule with two carboxylic acid functional groups). It proceeds via a condensation reaction, giving off water as a byproduct.
Polyethylene terephthalate, often abbreviated to PET, is the most commonly used polyester. It has a huge range of uses – from plastic bottles, to food trays, to thin plastic films, and of course in clothing. In clothes, polyesters have a large advantage over the more traditional cotton fibres in that they absorb much less water. Cotton can absorb 7% of its weight in water, whereas polyester only absorbs about 0.4% of its weight. This makes it much less likely to get soaked in sweat during a game of football. Instead, the sweat can run down the fibres of the shirt and evaporate; because of this it is referred to as a ‘wicking’ fabric, or more generally as one that is ‘breathable’. It’s also durable, and doesn’t crease easily.
Whilst some football shirts are 100% polyester, it’s also common for other fibres to be woven in with it to alter its properties. Elastane is another polymer that’s often utilised – more commonly known as spandex or lycra. In its manufacture, a prepolymer is first formed from glycol and diisocyanate compounds, reacted in a 1:2 ratio. This prepolymer is then reacted further with a diamine, to produce a liquid of the elastane polymer. The liquid is subsequently spun in a cylindrical cell, and heated in the presence of nitrogen gas, to convert it to solid polymer strands.
Whilst elastane is not as breathable as polyester, it has other beneficial properties. One of these is that it can be stretched to approximately 600% of its length before eventually rupturing, a trait that’s very useful in the modern game where shirt-tugging is commonplace. It also easily returns to its original shape.
A final type of polymer commonly used in the manufacture of football shirts is polyurethane. Again, this is the name for a class of polymers, rather than a specific polymer; we’ve actually already mentioned polyurethanes in a previous post, as they’re also one of the polymers used in the manufacture of footballs. Polyurethanes are built up from compounds called isocyantes and polyols. The middle parts of these molecules can be varied to give different polyurethanes with differing properties. In football shirts, they’re often the material that the letters, numbers, and sponsors on the shirt are made from, although fabrics or other materials can also on occasion be used. They can be thermally bonded onto the shirt using a heat-sealer, and unlike other fabrics, they have the benefit of being water resistant.

viernes, 1 de julio de 2016

España eleva a 188.000 metros cúbicos el total de desechos nucleares a gestionar hasta 2024

España estima que deberá gestionar unos 188.000 metros cúbicos de residuos radiactivos y combustible gastado generado hasta 2024, año en el que caduca la última de las licencias de explotación de una central atómica (la de Trillo, Guadalajara).
La estimación viene reflejada en el primer informe nacional remitido por España a la Unión Europea sobre la gestión responsable y segura del combustible nuclear gastado y residuos radiactivos (en cumplimiento de la directiva sobre la materia), proporcionado por el Consejo de Seguridad Nuclear (CSN).

Infografía explicativa de la gestión de residuos nucleares en España. /  Efe