Friday, February 27, 2009
Wednesday, February 25, 2009
Tuesday, February 24, 2009
Also known as "fat Tuesday," this pre-Lenten festival is celebrated in Roman Catholic countries and communities. In a strict sense, Mardi Gras, or Shrove Tuesday, is celebrated by the French as the last of the three days of Shrovetide and is a time of preparation immediately before Ash Wednesday and the start of the fast of Lent. Mardi Gras is thus the last opportunity for merrymaking and indulgence in food and drink. In practice, the festival is generally celebrated for one full week before Lent. Mardi Gras is marked by spectacular parades featuring floats, pageants, elaborate costumes, masked balls, and people dancing in the streets.
Mardi Gras originated as one of the series of carnival days held in all Roman Catholic countries between Twelfth Night, or Epiphany, and Ash Wednesday; these carnivals had their origin in pre-Christian spring fertility rites. The most famous modern Mardi Gras festivities are those held in New Orleans, La.; Rio de Janeiro, Brazil; Nice, France; and Cologne, Germany.
The first American Mardi Gras was celebrated near modern-day New Orleans on March 3, 1699. It wasn't until the mid-1800s did official parade organizations start to form with the Mystick Krewe of Comus in 1856 and the Krewe of Rex in 1872. The tradition is still carried on in New Orleans with many other krewes represented on floats in a myriad of parades. The official colors of Mardi Gras are purple, green and gold (representing justice, faith and power).
Mardi Gras celebrations can start as early as January 6, on the feast of Epiphany. The festivities end at midnight on Tuesday--the day before Ash Wednesday and the beginning of Lent. Mardi Gras day falls on any Tuesday between February 3 and March 9. Like Ash Wednesday, the date Mardi Gras falls on depends on the date of Easter--always occurring 46 days before Easter.
Fat Tuesday is, in a sense, like many pagan holidays "converted" to Christianity; all things within it are taken to extremes, amplified as though the original was a song and Christianity a loudspeaker. Any inherent moderation is removed, because, like all human beings, we wish to throw off the shackles of strict morality, and yet need a day set aside for that purpose, so we may feel justified in doing so. The complex paradox of Christianity is that, while we desire freedom, we construct a strict framework around it in which it is sullenly legitimized. The original pagan rituals suffered no such complexity, as their morality differed from ours. It was, in a way, more "natural," less "forced." While we celebrate because we desperately need an excuse to binge before the self-deprecating season of Lent is upon us, they celebrated because it was spring, and the babies (humans and animals) were about to be born.
And so today I'm wearing beads.
Monday, February 16, 2009
Friday, February 13, 2009
- In numerology, the number twelve is considered the number of completeness, as reflected in the twelve months of the year, twelve signs of the zodiac, twelve hours of the clock, twelve tribes of Israel, twelve Apostles of Jesus, twelve gods of Olympus, etc., whereas the number thirteen was considered irregular, transgressing this completeness. There is also a superstition, thought by some to derive from the Last Supper or a Norse myth, that having thirteen people seated at a table will result in the death of one of the diners.
- Friday has been considered an unlucky day at least since the 14th century's The Canterbury Tales, and many other professions have regarded Friday as an unlucky day to undertake journeys or begin new projects. Black Friday has been associated with stock market crashes and other disasters since the 1800s.It has also been suggested that Friday was the day that Jesus was crucified. 
Tuesday, February 10, 2009
Haplogroup U: Toward the Black Sea
Ancestral line: "Eve" > L1/L0 > L2 > L3 > N > R > U
Descending from the R group, a woman gave rise to people who now constitute haplogroup U. Because of the great genetic diversity found in haplogroup U, it is likely that this woman lived around 50,000 years ago.
Her descendants gave rise to several different subgroups, some of which exhibit very specific geographic homelands. The very old age of these subgroups has led to a wide distribution; today they harbor specific European, northern African, and Indian components, and are found in Arabia, the northern Caucasus Mountains, and throughout the Near East.
One interesting subgroup is U6, which branched off from haplogroup R while still in the Middle East, moved southward, and today is found in parts of northern Africa. Today, U6 individuals are found in around ten percent of people living in North Africa.
Other members of the larger haplogroup U descend from a group that moved northward out of the Near East. These women crossed the rugged Caucasus Mountains in southern Russia, and moved on to the steppes of the Black Sea. These individuals represent movements from the Black Sea steppes west into regions that comprise the present-day Baltic States and western Eurasia. This grassland then served as the home base for subsequent movements north and west. Today, members of these lineages are found in Europe and the eastern Mediterranean at frequencies of almost seven percent of the population.
While you do share distant ancestry with these subgroups of U, your genetic lineage went in a different direction.
Haplogroup U5: Your Branch on the Tree
Ancestral line: "Eve" > L1/L0 > L2 > L3 > N > R > U > U5
We finally arrive at your own clan, a group of individuals who descend from a woman in the U branch of the tree. Her descendants, and the most recent common ancestor for all U5 individuals, broke off from the rest of the group and headed north into Scandinavia. Even though U5 is descended from an ancestor in haplogroup U, it is also ancient, estimated to be around 50,000 years old.
U5 is quite restricted in its variation to Scandinavia, and particularly to Finland. This is likely the result of the significant geographical, linguistic, and cultural isolation of the Finnish populations, which would have restricted geographic distribution of this subgroup and kept it fairly isolated genetically. The Saami, reindeer hunters who follow the herds from Siberia to Scandinavia each season, have the U5 lineage at a very high frequency of around 50 percent, indicating that it may have been introduced during their movements into these northern territories.
The U5 lineage is found outside of Scandinavia, though at much lower frequencies and at lower genetic diversity. Interestingly, the U5 lineage found in the Saami has also been found in some North African Berber populations in Morocco, Senegal, and Algeria. Finding similar genetic lineages in populations living thousands of miles apart is certainly unexpected, and is likely the result of re-expansions that occurred after the last glacial maximum around 15,000 years ago. Humans who had been confined to narrow patches in southern Europe began to move outward again, recolonizing ancient territories and bringing new genetic lineages with them.
In addition to being present in some parts of North Africa, U5 individuals also live sporadically in the Near East at two percent—about one-fifth as frequent as in parts of Europe—and are completely absent from Arabia. Their distribution in the Near East is largely confined to surrounding populations, such as Turks, Kurds, Armenians, and Egyptians. Because these individuals contain lineages that first evolved in Europe, their presence in the Near East is the result of a back-migration of people who left northern Europe and headed south, as though retracing the migratory paths of their own ancestors.
Thursday, February 5, 2009
In a fascinating paper just published in Physical Review Letters (January of this year), a small research group from the University of Rome describes their elaborate numerical simulations of micromotors (micron-scale gears, essentially) in a chaotic bacterial bath.
For some time, microscopic motors, driven by tiny mule-teams of bacteria or other self-propelling entities, have been considered an interesting and plausible way of converting chemical energy to useful mechanical energy. The PRL describes how such a mechanism might just be constructed.
Starting with relatively simple models for the bacteria themselves (oblong spheroids, self-propelled but subject to tumbling, Brownian motion, hydrodynamics, etc) and two different shapes for the "rotor" (one symmetric and one asymmetric), the forces and torques exerted on and by each of 1092 simulated bacteria are calculated, and the equations of motion for each numerically integrated using a Runge-Kutta method. Though many of the initial parameters were derived from a great deal of physics and biology, the process itself is very simple: press start and iteratively watch what happens.
And something incredible does happen - the rotor starts to turn (see figure 1 above; note the arrow). The asymmetric rotor "spins up" and then hovers around a non-zero, non-negligible angular momentum (see figure 2 below). The symmetric rotor, on the other hand, stays essentially stationary. It appears as though the asymmetry is the key to spontaneously "rectifying" the chaotic and random motion of the bacteria into the usable, directed motion of a rotor.
While this paper describes only a few numerical simulations (a forthcoming paper is planned to discuss the results of all the different input parameters), it is a tremendous step toward actually creating a method for deriving mechanical energy from something we typically try to avoid - bacteria. Billboards of the future will exclaim, in great blue letters, "Let bacteria work for you!" alongside photos of happy families with their home's lights blazing.
Ok, perhaps it's still a bit far off, but until then, I'm happy to read about some interesting and beneficial results that were spawned by a simple numerical code.
Luca Angelani, Roberto Di Leonardo, Giancarlo Ruocco (2009). Self-Starting Micromotors in a Bacterial Bath Physical Review Letters, 102 (4) DOI: 10.1103/PhysRevLett.102.048104