#62 Why do we shiver? (English)

Why do we shiver?

Its well-known that we shiver when we are cold but why do we shiver? Is there a specific and biological reason why we shiver?

The answer is yes! The human body needs to be at a constant temperature of 37 degrees Celsius in order for us to work properly. Your brain has a gland called the hypothalamus gland which helps control your body temperature. In order to prevent things such as hypothermia and other diseases, your brain must be very careful with your body temperature. Your skin contains receptor cells which send messages to your brain telling your brain if your body temperature to go up or down and uses different tacts to do this.

Shivering is a tactic your brain uses in order to keep your body temperature at 37 degrees Celsius. In order to shiver, your muscles contract and relax very quickly repeated times. Twitching enables your muscles to produce heat which will in turn make your body temperature warmer. Your brain sends signals and some of these signals may also go to your jaw which is why, sometimes, your teeth start to chatter as your whole body are getting signals and some may get sent to your jaw. When your muscles produce heat, your muscles release the hormone Irisn which helps to heat your core temperature back to 37 degrees Celsius.

Some may argue that shivering is the opposite as sweating, which in fact, it is! Instead of helping you cool down like sweating does, shivering helps you warm up meaning that it helps your core temperature heat up.

This is why, next time you feel shivers down your spine, it may mean that you should grab another sweater and sit by a fire!

Resources:
http://www.livescience.com/32475-why-do-we-shiver-when-cold.html
http://blog.zocdoc.com/shiver-cold-weird-science-daily-life/

PRM

#61 Why does food taste different on airplanes? (English)

Why does food taste different on airplanes?

We have all at in point in time complained about the bland, sometimes disgusting food on an airplane. Many people think that it’s due to the low cost food that the airline provides, but recent studies suggest that might not be the case at all. Ever noticed how your ears pop when you reach a high altitude? Well, that’s not the only thing that changes in your body. Your taste buds change when you take off too! This is due to low air pressure so it can affect the way things taste? Also sense of smell and background noise can effect flavor perception.

Your sense of smell is directly related to the humidity in the cabin. This means that when you take off and air pressure decreases, so does humidity. At worst the air can be drier than the desert, causing your taste buds to be less sensitive to sweet and salty foods, whereas bitter, spicy and sour  foods are not changed that much. Also, smell can affect how a food tastes. Smell relies on nasal mucus, but in a dry plane there is less, which affects the smell of the food. Ultimately what you smell is what you taste, so the taste of the food can be perceived differently. Airlines try to combat this problem by using more salt, sugar and spices to food (this is often why airline food is not the healthiest) so foods such as curry can be more flavorful in the air. Just remember this the next time  you fly: having slightly less salty, sweet or flavorsome food is a very small price to pay for being able fly across the globe so quickly and if you really can stand airplane food, wait until the flight has ended and your taste buds have gone back to normal before enjoying a meal!

SJS

#60 Why does plastic degrade slower than other substances (English)

Why does plastic degrade slower than other substances

                  An important definition to know when talking about degrading is the term, biodegradable. Biodegradable means materials that can be broken down by microorganisms into organic matter. For example, vegetables may degrade in a month or so, while metals might take longer than a month. This shows that one of the factors affecting biodegradability is the type of material that makes up the object. Another factor affecting biodegradability is the environment. Air, water, and light all affect the biodegradability. In the case of plastics, they are not affected by air, water, or light, and therefore do not biodegrade to any significant degree. One of the reasons that plastics degrade slowly, is because the links joining the atoms are linked more intricately. In things like wood or cotton, the atoms are linked to each other naturally, therefore allowing bacteria to easily break down the links. The conditions for plastic to decompose is limited to ultraviolet light or heat, neither of which are found naturally in landfills where plastic is discarded after its use.

             When we normally consider biodegradables, we think of the materials degrading in landfills. However, it has recently been found that certain plastics degrade in water. Not only that, but they also break down within a year of contact with water. Although this may seem positive for people finding ways to speed up the degradation of plastic, it poses a threat to the underwater ecosystems. The plastics that break down in the water are made up of a molecule called polystyrene, a chemical pollutant. The plastic not only releases this dangerous molecule into the water, it also introduces chemicals not found near the water, to the water. These chemicals have the power to create cancer in humans, and simpler creatures in the water may be more susceptible to these harsh chemicals. In the food chain, the animals at the top would be consuming the highest amount of these dangerous chemicals, potentially threatening the entire ecosystem as we know it.

PoS 
 

#59 Meningitis (English)

Meningitis

 Meningitis is a disease caused by the inflammation of the protective membranes covering the brain and spinal cord known as the meinges. The inflammation is usually caused by an infection of the fluid that surrounds the brain and the spinal cord. Meningitis can develop for many reasons including: bacteria, viruses, physical injury, cancer, and in some rare cases, drugs. It is important to know what caused meningitis for each person because how you contracted the disease affects the severity of the disease. There are two types of the disease, viral meningitis is fairly common and does not cause serious illness, however, bacterial meningitis is not as common, but if not treated immediately, can cause brain damage and death. The disease is easy to identify as symptoms come in seven hours to two days and include: sudden high fever, severe headache, stiff neck, vomiting, seizures, sensitivity to light, and confusion. If it is not recognized and treated properly, it could potentially lead to: hearing loss, memory difficulty, learning disabilities, brain damage, walking problems, and even death.
In order to find out if you have meningitis or not, you must have a lumbar puncture done. A lumbar puncture is when a long thin needle is inserted into the spinal canal. It is used to collect samples of spinal fluid to check for bacteria and viruses. Depending on the type of meningitis contracted, there are different methods of treatment. For viral meningitis, you will only have to drink more liquids and take medicine for pain and fever. For bacterial meningitis, the use of medicines, as well oxygen therapy. We can prevent ourselves from contracting meningitis by getting vaccinations for measles, mumps, rubella, and chicken pox. We get these shots to prevent germs from causing some of the diseases that lead to meningitis.

PoS

#58 Why do cats purr? (English)

Why do cats purr?

For many, a cat’s purr seems to be a sign of contentment and a rather positive message. Cats are known to purr when they are being pet but do we really know what a purr signifies? Does a purr really mean that cats are happy or could they be purring for another reason?

Scientists have seen that purring can show happiness but it may also indicate other things such as nervousness or pain. Some scientists even think that purring may actually be a way of self-healing for cats. According to livescience.com, the frequency of between 25 to 150 Hertz is the frequency at which bones and muscles best repair themselves. This frequency range is also the frequency range of domestic cats. Cats may also use their purrs to signify their hunger so it is not only created to show pain or contentment but also hunger. It has also been shown that mothers of litters teaches their newborn kittens to purr when they are only a few days old and this may therefore show us that purring may also be a form of communication between cats.

Some scientists however believe that purring may only be the equivalent of a smile. They say this as we too sometimes smile when we are happy, when we are anxious and as a form of communication.
Therefore the reasons why cats purr is still not clear. Scientists have different reasons to why they purr for different circumstances therefore purring may just be a common occurrence for cats and a form of communication.

Resources: http://www.livescience.com/40377-why-do-cats-purr.html

PRM

#57 Mutaciones (Español)

Mutaciones

Estas se denominan como la alteración en la descendencia, producto de un cambio de la información genética de uno o ambos padres.

Causas e importancia:

Las mutaciones son importantes porque constituyen la base para la variabilidad en los seres vivos. La mayoría de las mutaciones son perjudícales porque hacen al individuo menos eficiente para sobrevivir en su ambiente. Muchas mutaciones son de carácter recesivo por lo que se mantienen entre generación. Hay unas que lleven a al muerte inmediata del individuo y por eso se les conoce como mutaciones letales, pero también hay otras que son benéficas para el ser vivo y así por selección natural llevan a la formación de una nueva especie. 

Las mutaciones ocurren espontáneamente de la naturaleza, algunas pueden ocurrir por errores en la replicación del ADN, otras pueden ser producto de la exposición a la radiación o a los agentes físicos y químicos de los alrededores del ambiente. Los factores ambientales causantes de la mutaciones se llaman agentes muta génicos y estos pueden ser bióticos o abióticos.

Los bióticos muta génicos se encuentran en ciertos virus y bacterias los cuales se asocian con el ADN de la célula parasita y originan cambios en el material genético de la célula huésped, lo cual provoca tumores y malformaciones.

Los abióticos muta génicos se conoce a : los rayos X, rayos ultravioleta, radiaciones nucleares, nicotina, dióxido de carbono, parafina,  gas mostaza, los colorantes artificiales en bebidas y otros.

Clasificación de las mutaciones según el material de cambio:

·         Mutaciones puntuales

Estas mutaciones se original al nivel del ADN y los cambios se pueden dar: por perdida ( cuando un nucleótido desaparece),  por duplicación ( nucleótido se duplica), por adicción (cuando se le añaden nucleótidos a la información) y por sustitución ( nucleótidos se sustituyen por otros).

·         Mutaciones cromosómicas

Estas pueden ocurrir durante el proceso de división celular y se presentan por:

Ø  Perdida de mas de un segmento de cromosoma

Ø  Translocación, es el intercambio de material genético de un segmento del cromosoma a otra.

Ø  Inversión, que consiste en la alteración de la secuencia de los genes de los cromosomas y en la eliminación del entrecruzamiento.

Ø  Duplicación, cuando hay repetición de una parte del cromosoma.

Estos cambios estructurales causan retraso mental, malformaciones y  malformaciones congénitas.

·         Mutaciones genómicas

El numero de cromosomas y la forma que presentan suele ser constante en una especie. Por ejemplo la especie humana tiene 46 cromosomas, 44 autosomas y dos sexuales. Hay ocasiones en que ocurren accidentes genéticos que producen una distribución anormal de cromosomas. Cuando no o mas pares de cromosomas dejan de separarse ocurre lo que se llama no-disyunción y esto trae como consecuencia que una de las células hijas reciba un cromosoma menos o uno extra. A esto se le llama aneuploidia.

El síndrome de Klinefelter ocurre por la no-disyunción durante la división meiótica y  el espermatozoides presenta un numero anormal de cromosomas que son XY, y fecunda a un ovulo que tiene un cromosoma X. El individuo resultante tendrá un cromosoma demás en la carga genética  que determina el sexo: XXY, este error cromosómico ocurre en los varones y produce: testículos que no producen espermatozoides, esterilidad y retraso mental.

Existen otras alteraciones como el síndrome de Turner que presenta fenotipo femenino y e da cuando el ovario produce óvulos sin el cromosoma X, y a cruzar es un individuo que presenta el genotipo XO.  El resultado es no ovular, no menstruar y un coeficiente intelectual bajo.

AAM

#56 Se nourrir au IIIe millénaire (Français)

Se nourrir au IIIe millénaire

Bonjour à tous, je voudrais vous parler des alternatives alimentaires. c'est une phénomène mondiale car la population a tendance à augmenter abruptement. Comme la pénurie des ressources est un enjeu quotidien. On a besoin de prendre des mesures pour nourrir le monde. Bien qu'il existe une possibilité d'un grave effet sur la santé, la culture en laboratoire est prometteuse. De plus, on pourrait dépasser quelques générations de cultures grâce à la culture en espace. Enfin, je souligne l'importance de la réduction du gaspillage d'aliments.

D'abord, et si on pouvait préserver les animaux et se nourrir en même temps? C'est une idée géniale! Les cellules qui sont des extraits d'animaux sont cultivées en laboratoire. Par conséquent, les viandes fabriquées n'est pas encore prête à être instaurée.

 Ensuite, l'environnement de l'espace - l'absence de la gravité - provoque des mutations de légumes. Autrement dit, c'est idéal pour leur culture. Non seulement, les légumes spéciaux atteignent une grande taille, mais la quantité fournie est également énorme.

Pour finir, la nourriture pour l'avenir est un sujet brûlant: le gaspillage d'aliments, en Europe surtout. Si on commence à consommer un petit peu moins qu'avant, on peut se nourrir 200 ans de plus selon une article par Le Monde Diplomatique. À mon avis, l'imposition d'une amende est primordiale pour empêcher le gaspillage.

En conclusion, c'est évident qu'on sera confrontés à un problème de manque d'aliments. En revanche, il existe plusieurs solutions pour l'avenir. Cependant, pour chaque remède que j'ai mentionné, il existe toujours des davantage. C'est nécessaire de poursuivre nos efforts pour ralentir cet événement.

KSJ