Two monochromatic lights of different frequencies can combine to show interference patterns. At time t=0, the waves interfere constructively. This gives a maximum in the added plot. The waves get more out of phase. This leads to destructive interference and a minimum in the added plot. From one peak maximum to the next is a "cycle". So when looking at two monochromatic lights, they can be graphed as two lines in the frequency-domain (this plot shows power, P(ν), as a function of frequency). The same two lights can be plotted as the sum of their waves in the time-domain (this plot shows power, P(t), as a function of time).
Spectroscopy done with visible or infrared radiation involves wavelengths of 10 to 10 Hz. Phototransducers (instruments that convert light to information readable by a computer) cannot make measurements that quickly. What is needed, then, is a way to make these high-frequency signals into low-frequency signals. For optical spectroscopy (such as infrared spectroscopy) the most common way to do this is by using a "Michelson interferometer".
Monochromatic light traveling through a Michelson interferometer is split into two beams by a beam splitter. These beams travel to mirrors, reflect, and then recombine at the beam splitter. One of the mirrors can be moved. If the two mirrors are the same distance apart, they meet at the beam splitter in-phase and show constructive interference. As the one mirror is moved, the beams become slightly more out of phase. When the movable mirror has moved a distance equal to ¼ of the light's wavelength, the extra distance it travels is ½ the light's wavelength. This means that when the two beams combine at the beam splitter, they destructively interfere. So moving the mirror a total distance of ½ the wavelength of light means the spectra will show one complete cycle. One could then plot the power of radiation as a function of distance traveled by the movable mirror. However, by knowing the speed of the movable mirror the power of radiation can be plotted as a function of time.
Most time-domain spectroscopy experiments involve broadband radiation (radiation that consists of a large range of wavelengths).
Time-domain spectroscopy is used very often in infrared spectroscopy (FT-IR) and NMR spectroscopy(FT-NMR). It has several advantages over frequency-domain spectroscopy. In frequency-domain experiments, each wavelength must be measured one at a time. This means scans can take several minutes. A single time-domain experiment takes no longer than a minute. Usually it only takes seconds. This means that many scans may be taken for a given sample, and that the scans can be averaged. So not only is the time-domain experiment faster, but it can also have a better signal to noise ratio.
D.A. Skoog, F.J. Holler, S.R. Crouch. 2007. " Principles of Instrumental Analysis". 6th ed, Thompson and Brooks/Cole: Canada.
Merle Haggard
Merle Ronald Haggard (April 6, 1937 – April 6, 2016) was an American country music singer and songwriter. He was known for his song "Okie from Muskogee". He was inducted into the Oklahoma Music Hall of Fame. He was involved with the growing outlaw country movement in the 1970s. Haggard won three Grammy Awards.
On April 6, 2016, Haggard died at his home in Palo Cedro, California from complications of pneumonia. He was 79 years old.
Battlefield 3
Battlefield 3 (BF3) is a first-person shooter video game. It was made by EA Digital Illusions CE and it was published by Electronic Arts. The game was released in October 2011. It is available for Microsoft Windows, PlayStation 3 and Xbox 360. Battlefield 3 is the 11th game in the "Battlefield" video games series, and it is next part of "Battlefield 2" (2005). On 29 June 2012, EA revealed that the game has sold 15 million copies.
Gut flora
Gut flora consists of microorganisms that live in the digestive system of animals. It is the largest reservoir of microbes in the human microbiome.
The human body, consisting of about 100 trillion cells, carries about ten times as many microorganisms in the intestines. The metabolic activities performed by these bacteria resemble those of an organ, leading some to call gut flora a 'forgotten organ'. It is estimated that these gut flora have around 100 times as many genes in aggregate as there are in the human genome.
Bacteria make up most of the flora in the colon and up to 60% of the dry mass of faeces. Somewhere between 300 and 1000 different species live in the gut, with most estimates at about 500. However, it is probable that 99% of the bacteria come from about 30 or 40 species. Fungi and protozoa also make up a part of the gut flora, but little is known about their activities.
Research suggests that the relationship between gut flora and humans is not merely commensal (a non-harmful coexistence), but rather a symbiotic relationship. Though people can survive without gut flora, the microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful, pathogenic bacteria, regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones to direct the host to store fats. However, in some conditions, some species can cause disease by producing an infection or increasing cancer risk for the host.
Such food compounds as polyphenols, oligosaccharides and polysaccharides may be useful for good bacteria and help reduce pathogenic species of human gut flora.
Over 99% of the bacteria in the gut are anaerobic, but in the cecum, aerobic bacteria reach high densities.
The traditional view is that no metazoan phylum can break down cellulose by producing the enzyme cellulase. Instead, herbivores contain, in their gut, microorganisms which produce cellulase. This is important because cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (the cellulose content of cotton is 90% and that of wood is 40–50%). Recently, evidence has emerged that some animals do produce their own cellulase. The question is not yet quite settled.
First-past-the-post voting
First-past-the-post is a voting system used by some countries to elect their governments or the members of their parliaments. In a first-past-the-post system, a country is divided into constituencies. In these constituencies people known as candidates, each of whom usually represents a different political party, will stand for election to the country's parliament. In the individual constituencies, the candidate who gets the most votes from people, wins the race to be elected to a seat in parliament. Plurality is another name for such an electoral system. It is in contrast to the majority system, where the winning candidate must have more votes than "all other candidates combined".
If a party wins over 50% of the seats, it can form a majority government. If no single party wins over 50% of the seats, then either the party with the most seats can form a minority government, or a coalition government can be formed from two or more of the other political parties who together have over 50% of the seats.
Countries using first-past-the-post include the United Kingdom, Canada, India and partly in the United States.
First-past-the-post, often called 'plurality voting', is the most common method for electing representatives in the United States and some other countries. Voters vote for one candidate, and the candidate with the most votes wins.
Political parties often use a primary in order to avoid splitting their party vote in a general election. For example, if 60% of the voters are Republican, and 40% Democrat, but two Republicans run for the same office and each get 30% of the vote, the Democrat would win with 40%, since that is the most votes, even if 60% of voters least preferred the Democrat.