Saturday, May 21, 2011

A nickname in biology: domino for whale shark

We all know the game domino, consisting of tiles with their front side divided into faces that are dotted with spots to represent number values. Dot patterns are common in the world of human design as well as in the natural world. The whale shark, a polka-dotted gentle giant living in tropical and warm-temperate seas, is nicknamed domino for the spots on its back [1].  A Mexican conservation group, which works on studying and protecting whale sharks, is accordingly called Proyecto Dominó.

The whale shark (Rhincodon typus) is a filter feeder, living of plankton and small fish [2]. Divers often get near dominoes. A diver swimming next to a domino is a good measuring unit. Peter Klimley reports [3]: a whale shark was five times longer than a diver with long flippers, 8 feet total, suggesting a fish length of 40 feet. The whale-like appearance and feeding behavior makes a domino a peaceful diving fellow, but carnivorous sharks such as hammerheads and blacktip reef sharks can be nearby, as Peter Klimley experienced on a diving trip in the waters above the Gorda Seamount off the tip of the peninsula of Baja California.

Domino spots are variously described as white, yellow or blue. Most intriguing, the spot patterns are unique and allow scientists to identify an individual domino per computer program—kind of a natural bar code system. Certainly, these “dot codes” didn't evolve for human- or computer-based pattern recognition. But what kind of advantage do they provide? Better mutual recognition, greater sex appeal or camouflage?

References and suggested reading
[1] Juliet Eilperin: Swimming with Sharks. Smithsonian June 2011, 42 (3), pp. 34-40.
[2] National Geographic: Whale Shark (Rhinocodon typus) [].
[3] A. Peter Klimley: The Secret Life of Sharks. Simon & Schuster, New York, 2003; pages 77 and 110.

Thursday, May 19, 2011

A word in geography: char for a constantly changing floodplain island

Char, a word that looks like shorthand for the word character or charcoal—and also is used that way—has a special meaning in geography and geomorphology: a constantly changing, vanishing and (re)appearing island on the floodplains of a river; in particular, of one of the three major rivers of Bangladesh—the Padma, Jamuna and Meghna [1]. A typical char is a sandbank island (channel bar), called island char, which is completely surrounded by water of a river channel. In addition, there are attached chars; as the name suggests, they are attached to a riverbank [2].

Chars can be dry or flooded depending on tide, season and rainfall. In Bangladesh, char dwellers have adapted their life to the river and char dynamics. They build movable houses (different from mobile homes) and grow crops on char ground and switch chars when water levels demand. Although vulnerable to erosion and flood hazards, chars have groundwater in addition to the river water and most chars provide grasslands for cattle grazing.

References and further reading
[1] Don Belt: Buoyant in Bangladesh. National Geographic May 2011, 219 (5), pp. 58-83 [].
[2] Banglapedia: Char [].

Tuesday, May 17, 2011

Acronym in materials science: NIB for neodymium-iron-boron

In materials science and engineering, the acronym NIB stands for three chemical elements: neodymium-iron-boron. The reason for grouping these three elements together is that they can be alloyed into strong magnets with an energy product of about 470 kJ·m-3 [1].

NIB-based alloys belong to a particular material class which is critical to the design of rare-earth magnets and named rare-earth iron alloys, typically referring to alloys with a composition of two rare earth atoms to 14 iron atoms and one boron atom [2].

In NIB the rare-earth element is neodymium, which may partially be substituted by dysprosium to obtain magnets for high-temperature applications, for example, in car engines. 
Change of chemical composition, by including other element types and varying atomic ratios, results in alloys with different magnetic properties (see Table IV-1 in [2]). In addition to dysprosium, samarium and praseodymium are used.

Iron atoms in NIB-based alloys have been substituted by copper, cobalt, zirconium and hafnium atoms. Corresponding energy products range from 130 to 400 kJ·m-3. But much higher values are desired for green technologies. A nanostructured, multilayered material composed of alternating Sm2Fe17N3 and Fe65Co35 layers can theoretically reach an energy product close to 1 MJ·m-3 [3]. But current technology has not yet reached the stage of fabrication to get magnets with energy products that come anywhere near this upper boundary.

References and detailed information
[1] Nicola Jones: The Pull of Stronger Magnets. Nature, April 7, 2011, 472 (7341), pp. 22-23. DOI: 10.1038/472022a.
[2] Magnetic Materials Producer Association: Standard Specifications for Permanent Magnet Materials [].
[3] Ralph Skomski and J. M. D. Coey:  Giant energy product in nanostructured two-phase magnets. Phys. Rev B. 1993, 48 (21), pp. 15812-15816. DOI: 10.1103/PhysRevB.48.15812.

Tuesday, May 10, 2011

An early mammal named Liaoconodon hui

 Liaoconodon hui is a Cretaceous eutriconodont mammal of the order Eutriconodonta, whose representatives are only known as fossils. The name indicates its geographic origin, anatomic signature and an honored researcher [1]:
  • Liao: short for the Liaoning Province in northeastern China, where the fossilized skeleton of the described species was found in the Jiufotang Formation,
  • conodon: a common, Latin-derived suffix for generic names in animal taxonomy, meaning cuspate tooth (tooth with a pointed or rounded projection on the chewing surface; the Latin word cuspis means point),
  • hui: after Yaoming Hu, a palaeontology student dedicated to the study of Mesozoic mammals.
The species is described as a medial-sized eutriconodont with a total body length (including the tail) of about 35 cm and with dental formula I3.CI.P2.M3/i2.c1.p2.m4 [1]; some knowledge you may want to impress your dentist with at your next visit.

This early mammal species is of interest in evolutionary biology: particularly in understanding the evolution of placental mammals and marsupials (Theria) and egg-laying mammals (monotremes) by studying the morphology and homologies of the middle ear [2].

Keywords: palaeontology, etymology, taxonomy, vertebrates, mammalia, cranium of mammals, ear ossicles

References and further reading
[1] J. Meng, Y. Wang and C. Li: Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont. Nature April 14, 2011, 472 (7342), pp. 181-185. DOI: 10.1038/nature09921.
[2] Posted by Taylor Reints: A newly Described Eutriconodont from the Early Cretaceous of Northeastern China possessing a Transitional Middle Ear [].

Thursday, May 5, 2011

When potassium or sodium bicarbonate was used in baking powders: saleratus (Latin for “salt” and “aerated”)

The word saleratus has its roots in New Latin: sal aeratus, meaning aerated salt [1]. Saleratus was the name for potassium bicarbonate (KHCO3) or sodium bicarbonate (NaHCO3), which was sold in the mid-19th century as baking powder  (baking soda) in paper packets [2]: in North America, settlers heading west and Civil War soldiers looking for fast food used saleratus to make “lightnin‘bread”  or “aerated bread” in skillets over campfire. Baking soda easily develops carbon dioxide gas on heating and contact with acidic substances such as vinegar, while yeast takes hours and some baking experience to achieve equally fluffy food.

Beyond baking: saleratus became a product of many uses including the treatment of burns, abrasions and indigestions as well as cleaning and odor elimination (such as sulfide odors) [3]. Although the name saleratus is rarely used today—other than in historical context—the ingredients of this “industrial revolution product” and their chemical reactivities are.

Keywords: chemical history, household products, baking, raising agent, alkali hydrogenecarbonates

[1] The Free Dictionary: saleratus [].
[2] Jane E. Boyd: Rise Up. Chemical Heritage Spring 201129 (1), page 9.
[3] sodium bicarbonate uses [].