band theory

Examples of band theory in the following topics:

• Conductors

  • In describing conductors using the concept of band theory, it is best to focus on conductors that conduct electricity using mobile electrons.
  • According to band theory, a conductor is simply a material that has its valence band and conduction band overlapping, allowing electrons to flow through the material with minimal applied voltage.
  • Band theory models the behavior of electrons in solids by postulating the existence of energy bands.
  • Bands may also be viewed as the large-scale limit of molecular orbital theory.
  • Apply the concept of band theory to explain the behavior of conductors.

• Semiconductors

  • Most of the states with low energy (closer to the nucleus) are occupied, up to a particular band called the valence band.
  • In semiconductors, only a few electrons exist in the conduction band just above the valence band, and an insulator has almost no free electrons.
  • In semiconductors, the band gap is small, allowing electrons to populate the conduction band.
  • As the energy in the system increases, electrons leave the valence band and enter the conduction band.
  • Compare N-type and P-type semi-conductors, distinguishing them from semi-conductors and insulators using band theory.

• Psychological Pricing

  • Psychological pricing is a marketing practice based on the theory that certain prices have meaning to many buyers.
  • The psychological pricing theory is based on one or more of the following hypotheses:
  • When items are listed in a way that is segregated into price bands (such as an online real estate search), the price ending is used to keep an item in a lower band, to be seen by more potential purchasers.

• Coloring Agents

  • This approach is described by the ligand field theory (LFT) and the molecular orbital theory (MO).
  • Ligand field theory, introduced in 1935 and built from molecular orbital theory, can handle a broader range of complexes.
  • The chemical applications of group theory can aid in the understanding of crystal or ligand field theory, by allowing simple, symmetry-based solutions to the formal equations.
  • Most transitions that are related to colored metal complexes are either d–d transitions or charge transfer bands.
  • A charge transfer band entails promotion of an electron from a metal-based orbital into an empty ligand-based orbital (Metal-to-Ligand Charge Transfer or MLCT).

• Introduction to The Sampling Theorem

  • Such a function is said to be band limited; it contains frequencies only in the band $[-2\pi f_s, 2\pi f_s]$ .
  • Clearly a band limited function has a finite inverse Fourier transform
  • A generation after Nyquist's pioneering work Claude Shannon, also at Bell Labs, laid the broad foundations of modern communication theory and signal processing.
  • Shannon (Born: April 1916 in Gaylord, Michigan; Died: Feb 2001 in Medford, Massachusetts) was the founder of modern information theory.
  • Shannon's paper and many other influential papers on communication are compiled in the book Key papers in the development of information theory.

• Microwaves

  • Extremely high frequency (EHF) is the highest microwave frequency band.
  • This frequency range corresponds to a wavelength range of 10 to 1 millimeter, so it is sometimes called the millimeter band.
  • This band is commonly used in radio astronomy and remote sensing.
  • This band of frequencies is known also as the centimeter band because the wavelengths range from ten to one centimeters.
  • The Cosmic Microwave Background Radiation (CMBR) is microwave radiation that permeates all of space, and its discovery supports the Big Bang theory of the origin of the universe.

• Introduction to deviance

  • Other examples include white hip-hop acts like Eminem and Nu-Metal bands like Limp Bizkit that mimic lower or middle class people in order to use their socioeconomic credentials for profit, despite their true socioeconomic status.
  • Sociological interest in deviance includes both interests in measuring formal deviance (statistics of criminal behavior; see below), examining how people (individually and collectively) define some things deviant and others normative, and a number of theories that try to explain both the role of deviance in society and its origins.
  • This chapter will cover the theories of deviance used by sociologists and will also cover current crime statistics.

• Sliding Filament Model of Contraction

  • The I-band is spanned by the titin molecule connecting the Z-line with a myosin filament.
  • The region between two neighboring, parallel I-bands is known as the A-band and contains the entire length of single myosin myofilaments.
  • Within the A-band is a region known as the H-band, which is the region not superimposed by actin myofilaments.
  • The myofilaments themselves do not contract or expand and so the A-band remains constant.
  • During stretching this tension is release and the I and H bands expand.

• Early Lifestyles

  • However, the traditional theory has been that these early migrants moved into the Beringia land bridge between eastern Siberia and present-day Alaska around 40,000–17,000 years ago, when sea levels were significantly lowered due to the Quaternary glaciation. 
  • This early Lithic reduction tool adaptation was utilized by highly mobile bands consisting of approximately 20 to 60 members of an extended family.
  • Small bands utilized hunting and gathering during the spring and summer months, then broke into smaller direct family groups for the fall and winter.
  • During much of the Early and Middle Paleo-Indian periods, inland bands are thought to have subsisted primarily through hunting now-extinct megafauna. 

• Functions of the State

  • For example, in debates over education, the National Education Association, a union of teachers, might be considered one special interest group, while a group of parents could band together to form another interest group.
  • Most political theories of the state can roughly be classified into two categories.
  • Theories of this variety view the state as a neutral entity distinct from both society and the economy.
  • Within the pluralist tradition, Robert Dahl developed the theory of the state as a neutral arena for contending interests.
  • Classify the different political theories concerning the function of the state in society