Monday 30 March 2015

Operación Flecha Rota

   
The 1966 Palomares B-52 crash or Palomares incident occurred on 17 January 1966, when a B-52G bomber of the United States Air Force's Strategic Air Command collided with a KC-135 tanker during mid-air refuelling at 31,000 feet (9,450 m) over the Mediterranean Sea, off the coast of Spain. The KC-135 was completely destroyed when its fuel load ignited, killing all four crew members. The B-52G broke apart, killing three of the seven crew members aboard.[1]
Of the four Mk28-type hydrogen bombs the B-52G carried,[2] three were found on land near the small fishing village of Palomares in the municipality of Cuevas del Almanzora, Almería, Spain. The non-nuclear explosives in two of the weapons detonated upon impact with the ground, resulting in the contamination of a 2-square-kilometer (490-acre) (0.78 square mile) area by plutonium. The fourth, which fell into the Mediterranean Sea, was recovered intact after a 2½-month-long search
The casings of two B28 nuclear bombs involved in the Palomares incident are on display at the National Museum of Nuclear Science and History, in Albuquerque, NM

http://elpais.com/diario/2003/05/08/ultima/1052344801_850215.html

Operación Flecha Rota

Salen a la luz imágenes inéditas del accidente nuclear de Palomares

Era una especie de juego de niño grande. Al escuchar el ruido de los aviones sobre el cielo de Palomares (Almería), el agricultor Julio Ponce miraba su reloj y comprobaba satisfecho que eran las diez y media de la mañana, a veces un minuto arriba, a veces un minuto abajo. Hacía nueve años que Ponce se dedicaba, por encargo del boticario de Vera, a llevar un registro diario de las precipitaciones en Palomares. Aquella mañana del 17 de enero de 1966, el agricultor también esperaba que las dos parejas de aviones llegaran puntuales a su cita. Hacía mucho viento, y Ponce lo anotó en su libreta.
Ni él ni ninguno de sus vecinos llegaron a sospechar nunca a qué se debía tanto trajín aéreo. Nadie les había dicho que se trataba de dos superbombarderos norteamericanos B-52, cargados cada uno con cuatro bombas termonucleares de 1,5 megatones -75 veces más potentes que las lanzadas sobre Hiroshima y Nagasaki-. Aquellos aviones cubrían cada día la misma ruta. Procedentes de Estados Unidos, entraban por el noroeste de la península Ibérica, eran abastecidos en vuelo por dos aviones cisternas KC-135 a la altura de Zaragoza y seguían su camino por el Mediterráneo hasta la frontera de Turquía con las entonces repúblicas soviéticas de Georgia y Azerbaiyán. Allí se mantenían en vuelo circular hasta que llegaba el relevo. Era al regreso cuando entraban en España por el sureste en vuelo visual.
Ni el agricultor Ponce ni mucho menos Gracia la Gitana, una mujer que, montada en un borrico, visitaba los pueblos vendiendo ropa de ajuar a las muchachas casaderas, sabían que aquellos aviones se guiaban por la desembocadura del río Almanzora para repostar combustible de vuelta a casa. Ni que, desde 1957, habían transitado sobre sus cabezas 23.360 bombas de hidrógeno, con un poder total de 258.420 megatones, más que suficientes para haber convertido la Tierra en un desierto vacío.
Lo cierto es que aquella mañana de 1966, los dos B-52 llegaron a la cita con ocho minutos de adelanto. Uno de ellos colisionó con su nodriza y se estrelló sobre el campo de Palomares dejando caer cuatro bombas termonucleares. Dos de ellas liberaron 3 kilogramos de plutonio 239, otra se recuperó intacta y la cuarta cayó al mar, localizándose unos meses después gracias al testimonio de un pescador que hasta entonces se había llamado Francisco Simó y desde ese día pasó a ser Paco el de la Bomba. ¿Qué ocurrió entonces en Palomares?
La respuesta tenía hasta ahora mucho de misterio. Lo único que se difundió fue que el entonces ministro de Información y Turismo, Manuel Fraga Iribarne, viajó a la zona acompañado por el embajador norteamericano, Angier Biddle Duke, para darse un baño juntos y tranquilizar a la población, momento que oportunamente recogieron las cámaras del NO-DO. Y hasta eso, aun con cámaras de por medio, tiene mucho de leyenda: hay quien sigue sosteniendo que Fraga y sus acompañantes se bañaron en Mojácar, a 15 kilómetros de Palomares. Pero el resto -lo verdaderamente importante- quedó tan oculto a los ojos de la opinión pública como lo habían estado antes los vuelos de los B-52.
Fue precisamente ayer cuando el Centro Andaluz de la Fotografía, que dirige Manuel Falces, inauguró en Almería una exposición titulada Operación Flecha Rota donde se muestran 60 fotografías inéditas sobre el accidente nuclear de Palomares. Y lo que se ve en esas fotografías forma parte de la memoria que nunca tuvieron los vecinos de Palomares. Apenas tres cuartos de hora después de producirse el accidente, los norteamericanos pusieron en funcionamiento un plan de emergencia llamado Broken Arrow (Flecha Rota) y acotaron junto a la playa de Quitapellejos una zona cerrada que bautizaron como Campamento Wilson.
Ningún vecino de Palomares supo nunca a ciencia cierta qué estaba pasando tras la valla de Villa Jarapa -lo de Wilson era demasiado difícil de pronunciar-; ni a qué se dedicaban los 800 soldados americanos allí trasladados.Y es eso precisamente lo que desvela, 36 años después del accidente nuclear, la exposición inaugurada ayer.
"La localización del material", explican Antonio Sánchez Picón y José Herrera, coordinadores de la muestra, "fue fruto de una mezcla de azar y labor de investigación. Cuando conseguimos acceder a los fondos desclasificados de los Archivos Nacionales de Estados Unidos nos quedamos muy sorprendidos: 36 registros contenían filmaciones en 16 milímetros, en color y mudas, fechadas entre enero y marzo de 1966, realizadas en Palomares y sus alrededores". Una vez conseguidas las películas, Sánchez Picón y Herrera se quedaron impresionados. Allí tenían toda la memoria robada: ocho horas y media de filmación, 700.000 fotogramas de los que han seleccionado 60 para la exposición, sólo un anticipo de la película que quieren hacer.
Allí aparecen los restos de los aviones y de las bombas, los trabajos de los hombres rana, los 4.810 barriles con la tierra contaminada -los norteamericanos rasparon y envasaron 105 hectáreas-, las reuniones del alto mando, la actuación de un grupo de música pop traído expresamente para elevar la moral de la tropa, ya que el contacto con los nativos estaba restringido...
También aparece -y es igualmente esclarecedor- lo que los americanos vieron y les impresionó de España. Hombres con boinas y camisas abotonadas hasta el cuello que saludaban militarmente para congraciarse con los soldados, una niña comiéndose un tomate para demostrar que no había peligro, Juana la Gitana y su marido encima del borrico, un guardia civil flaco y con tricornio intentando entenderse con un oficial de la Sandia Corporation...; niños y adultos arremolinándose junto al camión de reparto de alimentos. La España que nunca salía en el NO-DO fue filmada por los americanos y guardada durante tres décadas en los Archivos Nacionales de Estados Unidos. De aquella época sólo queda Fraga y el fantasma de la radioactividad en Palomares.

Tuesday 24 March 2015

http://www.sharksavers.org/en/education/biology/differences-between-sharks-and-bony-fish-more-than-just-a-skeleton/

Differences between sharks and bony fish: more than just the skeleton

Around 400 million years ago, fish evolved into two very different ‘classes’, or groups. One of them is ‘Class Chondrichthyes’, which includes sharks, rays and chimeras. This class of fish is also known as ‘cartilaginous’ fish because they have skeletons made of cartilage.
The other class is ‘Class Osteichthyes’, which gave rise to the modern day bony fish, also called ‘teleost’, and their primitive relatives such as the sturgeon.  Although the two groups once shared a common ancestor, there are several major biological differences between them.
Teleosts, the bony fish, are some of the most abundant vertebrates on the planet with nearly 25,000 living species.  In contrast, the chondrichthians represent only about 1,100 species of extant species of. In the past, however, the chondrichthians were much more abundant, according to the fossil record.
There are a few differences between cartilaginous fish and bony fish that are pretty apparent.

Skeleton

The main difference between the two groups is what defines them, the composition of their skeleton.
  • The teleosts have an ‘ossified’ internal skeleton, meaning it is made of calcified bone, just like ours.  Sharks and their relatives have a skeleton made of cartilage, the same lightweight, flexible connective tissue found around our joints and the flexible part of our nose. 
  • The upper jaw of a shark is not attached to the skull as it is in bony fish and can move independently.  Some bony fish also have a secondary set of jaws, pharyngeal jaws, which are used to further breakdown food, an element absent from sharks. 
  • The skull of a shark is made of only 10 cartilaginous elements while a bony fish skull has about 63 bones. 
  • Bony fish have pleural ribs formed from dermal bone and sharks lack these ribs.
  • Unlike bony fish that have a protective bony plate covering their vulnerable gills, the gill slits of a shark are exposed and visible.

Eyelids

Shark species have eyelids and some can even protect their eye with a tough third eyelid called a nictating membrane.  Other species, like the great white shark, have muscles that can roll the eye back into the socket for protection.  Bony fish lack eyelids or the ability to protect their eyes.

Heart and Blood

The circulatory system of the two groups is also different.
  • All fish have four compartments in their hearts but the 4th compartment differs between sharks and bony fish.  The compartment in sharks is called the conus arteriosus, a contractile cardiac muscle.  The 4th compartment of a bony fish heart is called the bulbous arteriosus and is made of non-contractile smooth muscle and elastic fibers.
  • Some studies suggest that sharks have larger and fewer red blood cells.
  • Sharks do not have bone so there is no bone marrow for hemopoiesis, the making of red blood cells.  So red blood cells are made by organs like the Leydig organ, spleen, thymus, and epigonal organ, exclusive to sharks.
  • Sharks and bony fish have to deal with comparable amounts of acid levels in their blood after a period of exertion but sharks have the ability to maintain high hemoglobin content in their blood and their blood oxygen carrying capacity is not affected.  This means shark’s blood is better equipped to deliver oxygen to muscles more efficiently.

External Features

The outer design of sharks and bony fish is also contrasting.
  • Shark skin is covered by dermal denticles, toothlike placoid scales that are covered with enamel.  This design is successful in minimizing drag and maximizing swimming efficiency.  Bony fish are covered in flat scales, either cycloid, ctenoid or ganoid, that grow as the fish grows.  The rings on these scales can be used to estimate age in bony fish, just as you would count the rings on a tree.  However, dermal denticles do not grow with the shark so they can not be used in age estimation.
  • Shark fins are stiff and lack the fine bony spines and muscle control found in teleost.  Flexible fins mean bony fish can swim forwards and backwards but sharks are stuck only going forward.
  • Both sharks and bony fish have caudal fins, or tail fins with two lobes.  The caudal fin of a shark is considered heterocercal, meaning the two lobes are unequal in size and the vertebral column extends up into the top lobe.  Bony fish caudal fins are homocercal, having symmetrical lobes that extend past the end of the vertebral column.

Buoyancy

Because all fish live in a three dimensional environment, they have to control their position to keep from floating up to the surface or sinking to the bottom to the sea floor.  This is known as neutral buoyancy, a state that SCUBA divers know well.
Bony fish have an internal organ known as the swim bladder that keeps them achieve neutral buoyancy by exchanging gases with the blood vessels.  Sharks lack this structure but rely on a lighter cartilaginous skeleton, hydrodynamic planing, the low density oils in their relatively large livers, and even some gulp air from the surface to keep neutral.

Digestion and Evacuation

  • The intestine of the shark is shortened but spirals internally to increase surface area for nutrient absorption. 
  • Shark kidneys and genitals empty into only one opening called the cloaca.  Bony fish have two separate openings, a rectum and an anus.  It has been hypothesized that is also takes a shark considerably longer to evacuate a meal, inferring that the digestive processes may be quite disparate as well.

Osmoregulation

This is the process that all organisms use to control the levels of water and mineral salts in the blood.  The water in the marine environment is saltier than the water inside a fish, both bony and cartilaginous and each group has developed distinct strategies to cope with this.  The less salty water inside a fish is tends to rush out of the body to reach an equilibrium with the saltier seawater, which can leave a fish quite dehydrated.  Bony fish deal with this uneven concentration by drinking a lot of seawater to stay hydrated and excreting the concentrated salts through the gills and gut.  Sharks have evolved the ability to reabsorb the urea created by the breakdown of protein back into their tissue which helps level out the concentration differences so they do not lose as much water.  Salts are still diffused into their body but are excreted over the gills, within the urine, and by the rectal gland that extracts salt from the blood. Read more...

Life History

Sharks have developed a life history strategy that requires slow growth to a relatively large size.  It takes a long time for most sharks to reach maturity.  When they reproduce, they have low numbers of advanced offspring (shark pups are miniature versions of adult sharks and are on their own from birth) and repeat these reproductive events over a long life.
Most bony fish demonstrate rapid growth, reach maturity younger, an increased ability to reproduce resulting in the creation of thousands of minuscule offspring that is scantily developed. Some bony fish have a single breeding event and then they die.  The difference in these two strategies magnify why sharks and bony fish need to be managed in different ways.  Bony fish on the fast track have the ability to replace itself in a population quickly but all of the characteristics listed above mean sharks take a lot longer.

Reproduction

All shark reproduction is internal.  Male sharks have mixoptyerigia, or pelvic claspers, an extension of the cartilaginous skeleton that serve as the sperm conducting structure for internal fertilization.  No such structure is found on bony fish. Read more...

Diversity Patterns

As a group, the diversity of shark species is lowest in the Pacific Ocean region but bony fish have a pattern of lowest species diversity in the eastern Atlantic Ocean
Resultado de imagen de jurel




Resultado de imagen de pintarroja


Cartilaginous fish of the Mediterranean sea.






http://www.indiastudychannel.com/attachments/Resources/124345-16628-Shark-Anatomy.jpg









Monday 23 March 2015

Fish dissection.

http://www.dec.ny.gov/education/92833.html
Living things are similar to and different from each other. When we look at the inside of a fish, we will learn that certain organs and systems in fish are similar to those in humans; and other organs and systems are not. Stomach contents can tell us much about a fish's habit. The external anatomical features (outside body parts) of fish can also tell us a lot about a species--where it lives in the water, how it finds food, and how it protects itself from predators.

Vocabulary

  • Anal Fin - fin located near the anal opening; used for balance and steering.
  • Caudal or Tail Fin - fin at the tail of a fish; used for propulsion.
  • Circulatory System - delivers blood and oxygen throughout the body via the heart.
  • Digestive System - breaks down and processes proteins, carbohydrates and fats.
  • Dorsal Fin - backside (top) fin on a fish; used for balance and protection.
  • External Anatomy - the outside body parts, such as, fins, scales, mouth.
  • Gills - organ used to obtain oxygen from the water and rid carbon dioxide.
  • Gill Rakers - filter feed tiny prey; appendages along the front edge of the gill arch.
  • Gonads - the sex organs; males have testes, females have ovaries. Some fish are hermaphroditic, meaning having both sets of gonads (male & female) in one fish.
  • Lateral Line - organ of microscopic pores that sense low vibrations and water pressure.
  • Nares - organ to smell; similar to nostrils.
  • Nervous System - organs receiving and interpreting stimuli for nares, eyes, lateral line, muscles, and other tissues.
  • Pectoral Fin - fins on the sides; used for balance and assist turning.
  • Pelvic Fin - belly fins on a fish; used for balance and steering.
  • Pyloric Caece - "finger-like" organ that aids in digestion, using bile from the liver.
  • Reproductive System - the organs and tissues involved in reproduction, including gonads, eggs, sperm.
  • Respiratory System - organs and tissues involved in the oxygen & carbon dioxide gas exchange, including gills, gill rakers, and gill filaments.
  • Scales - protective cover on a fish; similar to skin.
  • Slime - slippery covering on scales, protecting fish from bacteria, parasites, etc.
  • Swim bladder - found only in "ray-finned" fish; a double sac used to assist in buoyancy.
  • Urinary System - the kidneys remove nitrogen (ammonia) from the blood and regulate water balance in the blood and tissues.
  • Vertebrate - an organism with a backbone or spine.
 
A drawing of a fish with all external parts marked
Resultado de imagen de fish dissection ny