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History of the Food and Drug Administration
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This article is about the history of the United States Food and Drug Administration.
Contents
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1 Early history
1.1 Origins of federal food and drug regulation
1.2 The 1906 Food and Drug Act and creation of the FDA
1.3 The 1938 Food, Drug, and Cosmetic Act
2 Regulation of human drugs and medical devices after 1938
2.1 Early FD&C Act amendments: 1938–1958
2.2 Expansion of premarket approval process: 1959–1985
2.3 FDA reforms in the AIDS era
2.4 Challenges to FDA authority by states
2.5 Regulation of living organisms
3 Timeline of food and drug legislation
4 References
5 Further reading
Early history[edit]
Origins of federal food and drug regulation[edit]
Up until the 20th century, there were few federal laws regulating the contents and sale of domestically produced food and pharmaceuticals, with one exception being the short-lived Vaccine Act of 1813. A patchwork of state laws provided varying degrees of protection against unethical sales practices, such as misrepresenting the ingredients of food products or therapeutic substances. The history of the FDA can be traced to the latter part of the 19th century and the U.S. Department of Agriculture's Division of Chemistry (later Bureau of Chemistry). Under Harvey Washington Wiley, appointed chief chemist in 1883, the Division began conducting research into the adulteration and misbranding of food and drugs on the American market. Although they had no regulatory powers, the Division published its findings from 1887 to 1902 in a ten-part series entitled Foods and Food Adulterants. Wiley used these findings, and alliances with diverse organizations such as state regulators, the General Federation of Women's Clubs, and national associations of physicians and pharmacists, to lobby for a new federal law to set uniform standards for food and drugs to enter into interstate commerce. Wiley's advocacy came at a time when the public had become aroused to hazards in the marketplace by muckraking journalists like Upton Sinclair, and became part of a general trend for increased federal regulations in matters pertinent to public safety during the Progressive Era.[1] The 1902 Biologics Control Act was put in place after diphtheria antitoxin was collected from a horse named Jim who contracted tetanus, resulting in several deaths. Much credit is given to the deaths of many people in the 1930s, including Eben Byers in 1932 from the ingestion of radithor and many women, some known as The Radium Girls, to making the FDA into the much more powerful organization we know today.[2][3][4][5]
The 1906 Food and Drug Act and creation of the FDA[edit]
In June 1906, President Theodore Roosevelt signed into law the Food and Drug Act, also known as the "Wiley Act" after its chief advocate.[1] The Act prohibited, under penalty of seizure of goods, the interstate transport of food which had been "adulterated," with that term referring to the addition of fillers of reduced "quality or strength," coloring to conceal "damage or inferiority," formulation with additives "injurious to health," or the use of "filthy, decomposed, or putrid" substances. The act applied similar penalties to the interstate marketing of "adulterated" drugs, in which the "standard of strength, quality, or purity" of the active ingredient was not either stated clearly on the label or listed in the United States Pharmacopoeia or the National Formulary. The act also banned "misbranding" of food and drugs.[6] The responsibility for examining food and drugs for such "adulteration" or "misbranding" was given to Wiley's USDA Bureau of Chemistry.[1]
Wiley used these new regulatory powers to pursue an aggressive campaign against the manufacturers of foods with chemical additives, but the Chemistry Bureau's authority was soon checked by judicial decisions, as well as by the creation of the Board of Food and Drug Inspection and the Referee Board of Consulting Scientific Experts as separate organizations within the USDA in 1907 and 1908 respectively. A 1911 Supreme Court decision ruled that the 1906 act did not apply to false claims of therapeutic efficacy,[7] in response to which a 1912 amendment added "false and fraudulent" claims of "curative or therapeutic effect" to the Act's definition of "misbranded." However, these powers continued to be narrowly defined by the courts, which set high standards for proof of fraudulent intent.[1] In 1927, the Bureau of Chemistry's regulatory powers were reorganized under a new USDA body, the Food, Drug, and Insecticide organization. This name was shortened to the Food and Drug Administration (FDA) three years later.[8]
The 1938 Food, Drug, and Cosmetic Act[edit]
By the 1930s, muckraking journalists, consumer protection organizations, and federal regulators began mounting a campaign for stronger regulatory authority by publicizing a list of injurious products which had been ruled permissible under the 1906 law, including radioactive beverages, the mascara Lash lure, which caused blindness, and worthless "cures" for diabetes and tuberculosis. The resulting proposed law was unable to get through the Congress of the United States for five years, but was rapidly enacted into law following the public outcry over the 1937 Elixir Sulfanilamide tragedy, in which over 100 people died after using a drug formulated with a toxic, untested solvent. The only way that the FDA could even seize the product was due to a misbranding problem: an "Elixir" was defined as a medication dissolved in ethanol, not the diethylene glycol used in the Elixir Sulfanilamide. Had it been labeled a "solution" instead, it is argued, the agency could have done nothing to track down and confiscate what medication remained in the public's hands.[9]
President Franklin Delano Roosevelt signed the new Food, Drug, and Cosmetic Act (FD&C Act) into law on June 24, 1938. The new law significantly increased federal regulatory authority over drugs by mandating a pre-market review of the safety of all new drugs, as well as banning false therapeutic claims in drug labeling without requiring that the FDA prove fraudulent intent. The law also authorized factory inspections and expanded enforcement powers, set new regulatory standards for foods, and brought cosmetics and therapeutic devices under federal regulatory authority. This law, though extensively amended in subsequent years, remains the central foundation of FDA regulatory authority to the present day.[1]
Regulation of human drugs and medical devices after 1938[edit]
Early FD&C Act amendments: 1938–1958[edit]
Soon after passage of the 1938 Act, the FDA began to designate certain drugs as safe for use only under the supervision of a medical professional, and the category of "prescription-only" drugs was securely codified into law by the 1951 Durham-Humphrey Amendment.[1] While pre-market testing of drug efficacy was not authorized under the 1938 FD&C Act, subsequent amendments such as the Insulin Amendment and Penicillin Amendment did mandate potency testing for formulations of specific lifesaving pharmaceuticals.[8] The FDA began enforcing its new powers against drug manufacturers who could not substantiate the efficacy claims made for their drugs, and the United States Court of Appeals for the Ninth Circuit ruling in Alberty Food Products Co. v. United States (1950) found that drug manufacturers could not evade the "false therapeutic claims" provision of the 1938 act by simply omitting the intended use of a drug from the drug's label. These developments confirmed extensive powers for the FDA to enforce post-marketing recalls of ineffective drugs.[1] Much of the FDA's regulatory attentions in this era were directed towards abuse of amphetamines and barbiturates, but the agency also reviewed some 13,000 new drug applications between 1938 and 1962. While the science of toxicology was in its infancy at the start of this era, rapid advances in experimental assays for food additive and drug safety testing were made during this period by FDA regulators and others.[1]
Expansion of premarket approval process: 1959–1985[edit]
In 1959, Senator Estes Kefauver began holding congressional hearings into concerns about pharmaceutical industry practices, such as the perceived high cost and uncertain efficacy of many drugs promoted by manufacturers. There was significant opposition, however, to calls for a new law expanding the FDA's authority. This climate was rapidly changed by the thalidomide tragedy, in which thousands of European babies were born deformed after their mothers took that drug - marketed for treatment of nausea - during their pregnancies. Thalidomide had not been approved for use in the U.S. due to the concerns of an FDA reviewer, Frances Oldham Kelsey, about thyroid toxicity. However, thousands of "trial samples" had been sent to American doctors during the "clinical investigation" phase of the drug's development, which at the time was entirely unregulated by the FDA. Individual members of Congress cited the thalidomide incident in lending their support to expansion of FDA authority.[10]
The 1962 Kefauver-Harris Amendment to the FD&C act represented a "revolution" in FDA regulatory authority.[11] The most important change was the requirement that all new drug applications demonstrate "substantial evidence" of the drug's efficacy for a marketed indication, in addition to the existing requirement for pre-marketing demonstration of safety. This marked the start of the FDA approval process in its modern form. Drugs approved between 1938 and 1962 were also subject to FDA review of their efficacy, and to potential withdrawal from the market. Other important provisions of the 1962 amendments included the requirement that drug companies use the "established" or "generic" name of a drug along with the trade name, the restriction of drug advertising to FDA-approved indications, and expansion of FDA powers to inspect drug manufacturing facilities.
These reforms had the effect of increasing the time required to bring a drug to market.[12] In the mid-1970s, 13 of the 14 drugs the FDA saw as most important to approve were on the market in other countries before the United States.[12]
One of the most important statutes in establishing the modern American pharmaceutical market was the 1984 Drug Price Competition and Patent Term Restoration Act, more commonly known as the "Hatch-Waxman Act" after its chief sponsors. This act was intended to correct two unfortunate interactions between the new regulations mandated by the 1962 amendments, and existing patent law (which is not regulated or enforced by the FDA, but rather by the United States Patent and Trademark Office). Because the additional clinical trials mandated by the 1962 amendments significantly delayed the marketing of new drugs, without extending the duration of the manufacturer's patent, "pioneer" drug manufacturers experienced a decreased period of lucrative market exclusivity. On the other hand, the new regulations could be interpreted to require complete safety and efficacy testing for generic copies of approved drugs, and "pioneer" manufacturers obtained court decisions which prevented generic manufacturers from even beginning the clinical trial process while a drug was still under patent. The Hatch-Waxman Act was intended as a compromise between the "pioneer" and generic drug manufacturers which would reduce the overall cost of bringing generics to market and thus, it was hoped, reduce the long-term price of the drug, while preserving the overall profitability of developing new drugs.
The act extended the patent exclusivity terms of new drugs, and importantly tied those extensions, in part, to the length of the FDA approval process for each individual drug. For generic manufacturers, the Act created a new approval mechanism, the Abbreviated New Drug Application (ANDA), in which the generic drug manufacturer need only demonstrate that their generic formulation has the same active ingredient, route of administration, dosage form, strength, and pharmacokinetic properties ("bioequivalence") as the corresponding brand-name drug. This act has been credited with essentially creating the modern generic drug industry.[13]
FDA reforms in the AIDS era[edit]
Concerns about the length of the drug approval process were brought to the fore early in the AIDS epidemic. In the mid- and late 1980s, ACT-UP and other HIV activist organizations accused the FDA of unnecessarily delaying the approval of medications to fight HIV and opportunistic infections, and staged large protests, such as a confrontational October 11, 1988 action at the FDA campus which resulted in nearly 180 arrests.[14] In August 1990, Dr. Louis Lasagna, then chairman of a presidential advisory panel on drug approval, estimated that thousands of lives were lost each year due to delays in approval and marketing of drugs for cancer and AIDS.[15]
Partly in response to these criticisms, the FDA issued new rules to expedite approval of drugs for life-threatening diseases, and expanded pre-approval access to drugs for patients with limited treatment options.[16] The first of these new rules was the "IND exemption" or "treatment IND" rule, which allowed expanded access to a drug undergoing phase II or III trials (or in extraordinary cases even earlier) if it potentially represented a safer or better alternative to treatments currently available for terminal or serious illness. A second new rule, the "parallel track policy", allowed a drug company to set up a mechanism for access to a new potentially lifesaving drug by patients who for various reasons would be unable to participate in ongoing clinical trials. The "parallel track" designation could be made at the time of IND submission. The accelerated approval rules were further expanded and codified in 1992.[17]
All of the initial drugs approved for the treatment of HIV/AIDS were approved through accelerated approval mechanisms. For example, a "treatment IND" was issued for the first HIV drug, AZT, in 1985, and approval was granted just two years later in 1987.[18] Three of the first five drugs targeting HIV were approved in the United States before they were approved in any other country.[citation needed]
Challenges to FDA authority by states[edit]
In two instances, state governments have sought to legalize drugs which have not been approved by the FDA. Because federal law passed pursuant to Constitutional authority overrules conflicting state laws,[citation needed] federal authorities still claim the authority to seize, arrest, and prosecute for possession and sales of these substances, even in states where they are legal under state law.
The first wave was the legalization by 27 states of laetrile in the late 1970s. This drug was used as a treatment for cancer, but scientific studies both before and after this legislative trend found it to be ineffective.[19][20] Federal law enforcement prevented interstate shipment, making the drug infeasible to manufacture and sell. Further studies based on a Mexican formulation also showed no effectiveness in treating cancer, but did find that some patients experienced symptoms of cyanide poisoning. Though the political movement died out in the 1980s, FDA enforcement actions against laetrile purveyors continued into the 2000s.[20]
The second wave concerned medical marijuana in the 1990s and 2000s. Though Virginia passed a law with limited effect in 1979, a more widespread trend began in California in 1996. In 2009, the Obama Administration de-prioritized enforcement of federal law against patients using the drug in compliance with state law, but reversed this policy in 2011.[21] Recreational marijuana remains illegal (but not necessarily criminal) in all states and at the federal level, as of 2009.
Further information: Medical cannabis in the United States
Regulation of living organisms[edit]
With acceptance of premarket notification 510(k) k033391 in January 2004, the FDA granted Dr. Ronald Sherman permission to produce and market medical maggots for use in humans or other animals as a prescription medical device. Medical maggots represent the first living organism allowed by the Food and Drug Administration for production and marketing as a prescription medical device.
In June 2004, the FDA cleared Hirudo medicinalis (medicinal leeches) as the second living organism to be used as a medical devices.
Timeline of food and drug legislation[edit]
Most federal laws concerning the FDA are part of the Food, Drug and Cosmetic Act,[22] (first passed in 1938 and extensively amended since) and are codified in Title 21, Chapter 9 of the United States Code. Other significant laws enforced by the FDA include the Public Health Service Act, parts of the Controlled Substances Act, the Federal Anti-Tampering Act, as well as many others. In many cases these responsibilities are shared with other federal agencies.
Important enabling legislation for the FDA includes:
1902 – Biologics Control Act
1906 – Pure Food and Drug Act
1938 – Federal Food, Drug, and Cosmetic Act
1944 – Public Health Service Act
1951 – 1951 Food, Drug, and Cosmetics Act Amendments PL 82–215
1962 – 1962 Food, Drug, and Cosmetics Act Amendments PL 87–781
1966 – Fair Packaging and Labeling Act PL 89–755
1976 – Medical Device Regulation Act PL 94–295
1987 – Prescription Drug Marketing Act
1988 – Anti-Drug Abuse Act of 1988 PL 100–690
1990 – Nutrition Labeling and Education Act PL 101–535
1992 – Prescription Drug User Fee Act PL 102–571
1994 – Dietary Supplement Health and Education Act
1997 – Food and Drug Administration Modernization Act 105-115
2002 – Bioterrorism Act 107-188
2002 – Medical Device User Fee and Modernization Act (MDUFMA) PL 107-250
2003 – Animal Drug User Fee Act PL 108-130
2007 – Food and Drug Administration Amendments Act of 2007
2009 – Family Smoking Prevention and Tobacco Control Act
2010 – FDA Food Safety Modernization Act
2012 – Food and Drug Administration Safety and Innovation Act
References[edit]
^ Jump up to: a b c d e f g h A History of the FDA
Jump up ^ "The Radioactive Death of Eben Byers". Medical Curiosities. Retrieved 26 March 2012.
Jump up ^ "Medical Curiosities". The Radium Girls. /. Retrieved 26 March 2012.
Jump up ^ "Radithor Radioactive Health Water!". Esmeralda's Quiet Life. Retrieved 26 March 2012.
Jump up ^ "Medicine: Radium Drinks". Time Magazine. 11 April 1932. Retrieved 26 March 2012.
Jump up ^ Original Text of the 1906 Food and Drugs Act and Amendments
Jump up ^ United States v. Johnson (1911) , 6df1b297de555a5c 221 U.S. 488 (31 S. Ct. 627 May 29, 1911, decided).
^ Jump up to: a b Milestones in U.S. Food and Drug Law History
Jump up ^ Hamowy, Ronald (February 2010). "Medical Disasters and the Growth of FDA" (PDF): 7. Retrieved 28 September 2011.
Jump up ^ Report of Congressman Morris Udall on thalidomide and the Kefauver hearings.
Jump up ^ Temple R (2002). "Policy developments in regulatory approval". Statistics in Medicine. 21 (19): 2939–2948. PMID 12325110. doi:10.1002/sim.1298.
^ Jump up to: a b Frum, David (2000). How We Got Here: The '70s. New York, New York: Basic Books. p. 180. ISBN 0-465-04195-7.
Jump up ^ Karki L (2005). "Review of FDA Law Related to Pharmaceuticals: The Hatch-Waxman Act, Regulatory Amendments and Implications for Drug Patent Enforcement". Journal of the Patent & Trademark Office Society. 87: 602–620.
Jump up ^ ACT-UP NY timeline
Jump up ^ Faster Approval of AIDS Drugs Is Urged, The New York Times, August 16, 1990, Thursday, Late Edition – Final, Section B; Page 12, Column 4; National Desk, 830 words, By ROBERT PEAR, Special to The New York Times, Washington, Aug. 15
Jump up ^ FDA Website: Expanded Access and Expedited Approval of New Therapies Related to HIV/AIDS
Jump up ^ Orlando V (1999). "The FDA's Accelerated Approval Process: Does the Pharmaceutical Industry Have Adequate Incentives for Self-Regulation?". American Journal of Law and Medicine. 25 (4): 543–68. PMID 10629734.
Jump up ^ FDA report on accelerated approval process Archived 2009-05-25 at the Wayback Machine.
Jump up ^ NPR.org
^ Jump up to: a b Quackwatch.com
Jump up ^ Kampia, Rob (4 May 2012). "Medical marijuana meets hostility from Obama administration". The Washington Post. Retrieved 24 June 2012.
Jump up ^ Food, Drug and Cosmetic Act Web Version
Further reading[edit]
Henninger, Daniel (2002). "Drug Lag". In David R. Henderson (ed.). Concise Encyclopedia of Economics (1st ed.). Library of Economics and Liberty. CS1 maint: Extra text: editors list (link) OCLC 317650570, 50016270, 163149563
[show]
v
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Food and Drug Administration of the United States
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Federal Food, Drug, and Cosmetic Act
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Energy levels for an electron in an atom: ground state and excited states. After absorbing energy, an electron may "jump" from the ground state to a higher energy excited state.
Quantum mechanics
H ^ | ψ ( t ) ⟩ = i ℏ ∂ ∂ t | ψ ( t ) ⟩ {\displaystyle {\hat {H}}|\psi (t)\rangle =i\hbar {\frac {\partial }{\partial t}}|\psi (t)\rangle }
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A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy levels. The term is commonly used for the energy levels of electrons in atoms, ions, or molecules, which are bound by the electric field of the nucleus, but can also refer to energy levels of nuclei or vibrational or rotational energy levels in molecules. The energy spectrum of a system with such discrete energy levels is said to be quantized.
In chemistry and atomic physics, an electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on farther and farther from the nucleus. The shells correspond with the principal quantum numbers (n = 1, 2, 3, 4 ...) or are labeled alphabetically with letters used in the X-ray notation (K, L, M, …).
Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.[1] Since electrons are electrically attracted to the nucleus, an atom's electrons will generally occupy outer shells only if the more inner shells have already been completely filled by other electrons. However, this is not a strict requirement: atoms may have two or even three incomplete outer shells. (See Madelung rule for more details.) For an explanation of why electrons exist in these shells see electron configuration.[2]
If the potential energy is set to zero at infinite distance from the atomic nucleus or molecule, the usual convention, then bound electron states have negative potential energy.
If an atom, ion, or molecule is at the lowest possible energy level, it and its electrons are said to be in the ground state. If it is at a higher energy level, it is said to be excited, or any electrons that have higher energy than the ground state are excited. If more than one quantum mechanical state is at the same energy, the energy levels are "degenerate". They are then called degenerate energy levels.
Contents
[hide]
1 Explanation
2 History
3 Atoms
3.1 Intrinsic energy levels
3.1.1 Orbital state energy level: atom/ion with nucleus + one electron
3.1.2 Electron-electron interactions in atoms
3.1.3 Fine structure splitting
3.1.4 Hyperfine structure
3.2 Energy levels due to external fields
3.2.1 Zeeman effect
3.2.2 Stark effect
4 Molecules
4.1 Energy level diagrams
5 Energy level transitions
6 Crystalline materials
7 See also
8 References
Explanation[edit]
Wavefunctions of a hydrogen atom, showing the probability of finding the electron in the space around the nucleus. Each stationary state defines a specific energy level of the atom.
Quantized energy levels result from the relation between a particle's energy and its wavelength. For a confined particle such as an electron in an atom, the wave function has the form of standing waves. Only stationary states with energies corresponding to integral numbers of wavelengths[clarification needed] can exist; for other states the waves interfere destructively[clarification needed], resulting in zero probability density. Elementary examples that show mathematically how energy levels come about are the particle in a box and the quantum harmonic oscillator.
History[edit]
The first evidence of quantization in atoms was the observation of spectral lines in light from the sun in the early 1800s by Joseph von Fraunhofer and William Hyde Wollaston. The notion of energy levels was proposed in 1913 by Danish physicist Niels Bohr in the Bohr theory of the atom. The modern quantum mechanical theory giving an explanation of these energy levels in terms of the Schrödinger equation was advanced by Erwin Schrödinger and Werner Heisenberg in 1926.
Atoms[edit]
Intrinsic energy levels[edit]
In the formulas for energy of electrons at various levels given below in an atom, the zero point for energy is set when the electron in question has completely left the atom, i.e. when the electron's principal quantum number n = ∞. When the electron is bound to the atom in any closer value of n, the electron's energy is lower and is considered negative.
Orbital state energy level: atom/ion with nucleus + one electron[edit]
Assume there is one electron in a given atomic orbital in a hydrogen-like atom (ion). The energy of its state is mainly determined by the electrostatic interaction of the (negative) electron with the (positive) nucleus. The energy levels of an electron around a nucleus are given by :
E n = − h c R ∞ Z 2 n 2 {\displaystyle E_{n}=-hcR_{\infty }{\frac {Z^{2}}{n^{2}}}}
(typically between 1 eV and 103 eV), where R∞ is the Rydberg constant, Z is the atomic number, n is the principal quantum number, h is Planck's constant, and c is the speed of light. For hydrogen-like atoms (ions) only, the Rydberg levels depend only on the principal quantum number n.
This equation is obtained from combining the Rydberg formula for any hydrogen-like element (shown below) with E = h ν = h c / λ assuming that the principal quantum number n above = n1 in the Rydberg formula and n2 = ∞ (principal quantum number of the energy level the electron descends from, when emitting a photon). The Rydberg formula was derived from empirical spectroscopic emission data.
1 λ = R Z 2 ( 1 n 1 2 − 1 n 2 2 ) {\displaystyle {\frac {1}{\lambda }}=RZ^{2}\left({\frac {1}{n_{1}^{2}}}-{\frac {1}{n_{2}^{2}}}\right)}
An equivalent formula can be derived quantum mechanically from the time-independent Schrödinger equation with a kinetic energy Hamiltonian operator using a wave function as an eigenfunction to obtain the energy levels as eigenvalues, but the Rydberg constant would be replaced by other fundamental physics constants.
Electron-electron interactions in atoms[edit]
If there is more than one electron around the atom, electron-electron-interactions raise the energy level. These interactions are often neglected if the spatial overlap of the electron wavefunctions is low.
For multi-electron atoms, interactions between electrons cause the preceding equation to be no longer accurate as stated simply with Z as the atomic number. A simple (though not complete) way to understand this is as a shielding effect, where the outer electrons see an effective nucleus of reduced charge, since the inner electrons are bound tightly to the nucleus and partially cancel its charge. This leads to an approximate correction where Z is substituted with an effective nuclear charge symbolized as Zeff that depends strongly on the principal quantum number.
E n , l = − h c R ∞ Z e f f 2 n 2 {\displaystyle E_{n,l}=-hcR_{\infty }{\frac {{Z_{\rm {eff}}}^{2}}{n^{2}}}\ }
In such cases, the orbital types (determined by the azimuthal quantum number ℓ) as well as their levels within the molecule affect Zeff and therefore also affect the various atomic electron energy levels. The Aufbau principle of filling an atom with electrons for an electron configuration takes these differing energy levels into account. For filling an atom with electrons in the ground state, the lowest energy levels are filled first and consistent with the Pauli exclusion principle, the Aufbau principle, and Hund's rule.
Fine structure splitting[edit]
Fine structure arises from relativistic kinetic energy corrections, spin–orbit coupling (an electrodynamic interaction between the electron's spin and motion and the nucleus's electric field) and the Darwin term (contact term interaction of s shell[which?] electrons inside the nucleus). These affect the levels by a typical order of magnitude of 10−3 eV.
Hyperfine structure[edit]
Main article: Hyperfine structure
This even finer structure is due to electron–nucleus spin–spin interaction, resulting in a typical change in the energy levels by a typical order of magnitude of 10−4 eV.
Energy levels due to external fields[edit]
Zeeman effect[edit]
Main article: Zeeman effect
There is an interaction energy associated with the magnetic dipole moment, μL, arising from the electronic orbital angular momentum, L, given by
U = − μ L ⋅ B {\displaystyle U=-{\boldsymbol {\mu }}_{L}\cdot \mathbf {B} }
with
− μ L = e ℏ 2 m L = μ B L {\displaystyle -{\boldsymbol {\mu }}_{L}={\dfrac {e\hbar }{2m}}\mathbf {L} =\mu _{B}\mathbf {L} } .
Additionally taking into account the magnetic momentum arising from the electron spin.
Due to relativistic effects (Dirac equation), there is a magnetic momentum, μS, arising from the electron spin
− μ S = − μ B g S S {\displaystyle -{\boldsymbol {\mu }}_{S}=-\mu _{B}g_{S}\mathbf {S} } ,
with gS the electron-spin g-factor (about 2), resulting in a total magnetic moment, μ,
μ = μ L + μ S {\displaystyle {\boldsymbol {\mu }}={\boldsymbol {\mu }}_{L}+{\boldsymbol {\mu }}_{S}} .
The interaction energy therefore becomes
U B = − μ ⋅ B = μ B B ( M L + g S M S ) {\displaystyle U_{B}=-{\boldsymbol {\mu }}\cdot \mathbf {B} =\mu _{B}B(M_{L}+g_{S}M_{S})} .
Stark effect[edit]
Main article: Stark effect
Molecules[edit]
Chemical bonds between atoms in a molecule form because they make the situation more stable for the involved atoms, which generally means the sum energy level for the involved atoms in the molecule is lower than if the atoms were not so bonded. As separate atoms approach each other to covalently bond, their orbitals affect each other's energy levels to form bonding and antibonding molecular orbitals. The energy level of the bonding orbitals is lower, and the energy level of the antibonding orbitals is higher. For the bond in the molecule to be stable, the covalent bonding electrons occupy the lower energy bonding orbital, which may be signified by such symbols as σ or π depending on the situation. Corresponding anti-bonding orbitals can be signified by adding an asterisk to get σ* or π* orbitals. A non-bonding orbital in a molecule is an orbital with electrons in outer shells which do not participate in bonding and its energy level is the same as that of the constituent atom. Such orbitals can be designated as n orbitals. The electrons in an n orbital are typically lone pairs. [3] In polyatomic molecules, different vibrational and rotational energy levels are also involved.
Roughly speaking, a molecular energy state, i.e. an eigenstate of the molecular Hamiltonian, is the sum of the electronic, vibrational, rotational, nuclear, and translational components, such that:
E = E e l e c t r o n i c + E v i b r a t i o n a l + E r o t a t i o n a l + E n u c l e a r + E t r a n s l a t i o n a l {\displaystyle E=E_{\rm {electronic}}+E_{\rm {vibrational}}+E_{\rm {rotational}}+E_{\rm {nuclear}}+E_{\rm {translational}}\,}
where Eelectronic is an eigenvalue of the electronic molecular Hamiltonian (the value of the potential energy surface) at the equilibrium geometry of the molecule.
The molecular energy levels are labelled by the molecular term symbols.
The specific energies of these components vary with the specific energy state and the substance.
In molecular physics and quantum chemistry, an energy level is a quantized energy of a bound quantum mechanical state.
Energy level diagrams[edit]
There are various types of energy level diagrams for bonds between atoms in a molecule.
Examples
Molecular orbital diagrams, Jablonski diagrams, and Franck–Condon diagrams.
Energy level transitions[edit]
Further information: atomic electron transition and molecular electron transition
An increase in energy level from E1 to E2 resulting from absorption of a photon represented by the red squiggly arrow, and whose energy is h ν
A decrease in energy level from E2 to E1 resulting in emission of a photon represented by the red squiggly arrow, and whose energy is h ν
Electrons in atoms and molecules can change (make transitions in) energy levels by emitting or absorbing a photon (of electromagnetic radiation), whose energy must be exactly equal to the energy difference between the two levels. Electrons can also be completely removed from a chemical species such as an atom, molecule, or ion. Complete removal of an electron from an atom can be a form of ionization, which is effectively moving the electron out to an orbital with an infinite principal quantum number, in effect so far away so as to have practically no more effect on the remaining atom (ion). For various types of atoms, there are 1st, 2nd, 3rd, etc. ionization energies for removing the 1st, then the 2nd, then the 3rd, etc. of the highest energy electrons, respectively, from the atom originally in the ground state. Energy in corresponding opposite quantities can also be released, sometimes in the form of photon energy, when electrons are added to positively charged ions or sometimes atoms. Molecules can also undergo transitions in their vibrational or rotational energy levels. Energy level transitions can also be nonradiative, meaning emission or absorption of a photon is not involved.
If an atom, ion, or molecule is at the lowest possible energy level, it and its electrons are said to be in the ground state. If it is at a higher energy level, it is said to be excited, or any electrons that have higher energy than the ground state are excited. Such a species can be excited to a higher energy level by absorbing a photon whose energy is equal to the energy difference between the levels. Conversely, an excited species can go to a lower energy level by spontaneously emitting a photon equal to the energy difference. A photon's energy is equal to Planck's constant (h) times its frequency (f) and thus is proportional to its frequency, or inversely to its wavelength (λ).[3]
ΔE = h f = h c / λ,
since c, the speed of light, equals to f λ[3]
Correspondingly, many kinds of spectroscopy are based on detecting the frequency or wavelength of the emitted or absorbed photons to provide information on the material analyzed, including information on the energy levels and electronic structure of materials obtained by analyzing the spectrum.
An asterisk is commonly used to designate an excited state. An electron transition in a molecule's bond from a ground state to an excited state may have a designation such as σ → σ*, π → π*, or n → π* meaning excitation of an electron from a σ bonding to a σ antibonding orbital, from a π bonding to a π antibonding orbital, or from an n non-bonding to a π antibonding orbital. [3] [4] Reverse electron transitions for all these types of excited molecules are also possible to return to their ground states, which can be designated as σ* → σ, π* → π, or π* → n.
A transition in an energy level of an electron in a molecule may be combined with a vibrational transition and called a vibronic transition. A vibrational and rotational transition may be combined by rovibrational coupling. In rovibronic coupling, electron transitions are simultaneously combined with both vibrational and rotational transitions. Photons involved in transitions may have energy of various ranges in the electromagnetic spectrum, such as X-ray, ultraviolet, visible light, infrared, or microwave radiation, depending on the type of transition. In a very general way, energy level differences between electronic states are larger, differences between vibrational levels are intermediate, and differences between rotational levels are smaller, although there can be overlap. Translational energy levels are practically continuous and can be calculated as kinetic energy using classical mechanics.
Higher temperature causes fluid atoms and molecules to move faster increasing their translational energy, and thermally excites molecules to higher average amplitudes of vibrational and rotational modes (excites the molecules to higher internal energy levels). This means that as temperature rises, translational, vibrational, and rotational contributions to molecular heat capacity let molecules absorb heat and hold more internal energy. Conduction of heat typically occurs as molecules or atoms collide transferring the heat between each other. At even higher temperatures, electrons can be thermally excited to higher energy orbitals in atoms or molecules. A subsequent drop of an electron to a lower energy level can release a photon, causing a possibly colored glow.
An electron farther from the nucleus has higher potential energy than an electron closer to the nucleus, thus it becomes less bound to the nucleus, since its potential energy is negative and inversely dependent on its distance from the nucleus.[5]
Crystalline materials[edit]
Crystalline solids are found to have energy bands, instead of or in addition to energy levels. Electrons can take on any energy within an unfilled band. At first this appears to be an exception to the requirement for energy levels. However, as shown in band theory, energy bands are actually made up of many discrete energy levels which are too close together to resolve. Within a band the number of levels is of the order of the number of atoms in the crystal, so although electrons are actually restricted to these energies, they appear to be able to take on a continuum of values. The important energy levels in a crystal are the top of the valence band, the bottom of the conduction band, the Fermi level, the vacuum level, and the energy levels of any defect states in the crystal.
See also[edit]
Perturbation theory (quantum mechanics)
Computational chemistry
References[edit]
Jump up ^ Re: Why do electron shells have set limits ? madsci.org, 17 March 1999, Dan Berger, Faculty Chemistry/Science, Bluffton College
Jump up ^ Electron Subshells. Corrosion Source. Retrieved on 1 December 2011.
^ Jump up to: a b c d UV-Visible Absorption Spectra
Jump up ^ Theory of Ultraviolet-Visible (UV-Vis) Spectroscopy
Jump up ^ http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Electron-Density-and-Potential-Energy-899.html
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Piggly Wiggly
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Piggly Wiggly
Type
Private
Industry
Supermarket chain
Founded
Memphis, Tennessee, U.S. (1916)
Headquarters
Keene, New Hampshire, U.S.
Area served
Midwestern/Southern U.S.
Parent
C&S Wholesale Grocers
Website
www.pigglywiggly.com
Piggly Wiggly is an American supermarket chain operating in the Southern and Midwestern regions of the United States, run by Piggly Wiggly, LLC, an affiliate of C&S Wholesale Grocers.[1] Its first outlet opened in 1916 in Memphis, Tennessee, and is notable for having been the first true self-service grocery store, and the originator of various familiar supermarket features such as checkout stands, individual item price marking and shopping carts. The current company headquarters is in Keene, New Hampshire.[2] Currently, more than 600 independently owned Piggly Wiggly stores operate in 17 states, primarily in smaller cities and towns.
Piggly Wiggly operations in the U.S. as of 2018 (highlighted in blue and red)
Contents
[hide]
1 History
1.1 Name
2 Present company
3 See also
4 References
5 Further reading
6 External links
History[edit]
Historical marker near the site of the first Piggly Wiggly store in Memphis, Tennessee.
Piggly Wiggly was the first true self-service grocery store.[3] It was founded on September 6, 1916, at 79 Jefferson Avenue in Memphis, Tennessee, by Clarence Saunders. A replica of the original store has been constructed in the Memphis Pink Palace Museum and Planetarium, a mansion that Saunders built as his private residence, which was later sold to the city.
At the time of its founding, grocery stores did not allow their customers to gather their own goods. Instead, a customer would give a list of items to a clerk, who would then go through the store himself, gathering them. This created a greater cost, therefore higher prices. Piggly Wiggly introduced the innovation of allowing customers to go through the store, gathering their own goods. This cut costs, allowing for lower prices.[4] Others were initially experimenting with this format as well, which initially came to be known as a "grocerteria", reminding people of cafeterias, another relatively new, self-service idea.[5]
Piggly Wiggly Corporation secured the self-service format and issued franchises to hundreds of grocery retailers for the operation of its stores. The concept of the "self-serving store" was patented[6] by Saunders in 1917. Customers at Piggly Wiggly entered the store through a turnstile and walked through four aisles to view the store’s 605 items sold in packages and organized into departments. The customers selected merchandise as they continued through the maze to the cashier. Instantly, packaging and brand recognition became important to companies and consumers.
The original Piggly Wiggly Store, Memphis, Tennessee
Piggly Wiggly was the first to:
provide checkout stands.[7]
price mark every item in the store.[7]
provide shopping carts for customers, starting in the year 1937 in Oklahoma.[8]
The success of Piggly Wiggly was phenomenal, so much so that other independent and chain grocery stores changed to self-service in the 1920s and 1930s. At its peak in 1932 (see Clarence Saunders), the company operated 2,660 stores and posted annual sales in excess of $180 million. In November 1922, Saunders attempted a squeeze on the substantial short interest in the stock, running the share price up from 40 to 120 and profiting by millions on paper. The Stock Exchange Governors responded by deciding that a corner had been established in Piggly Wiggly and removed the stock from the Board eventually forcing Saunders to turn over his assets to the banks that had financed his leveraged position. Saunders reputedly lost nine million dollars in the attempted corner.[9]
Following these events, the company was divided into strategic units and sold to regional grocery chains, including Kroger, Safeway, National Tea, and Colonial.[10] In 1935 all 179 Canadian Piggly Wiggly were also sold to Canada Safeway, which merged with Sobeys in 2013.[citation needed]
After losing control of Piggly Wiggly, Saunders had no further association with the company although he remained interested in the concept of automated shopping which he experimented with initially with the Keedoozle store until his death in 1953.[11]
The smaller Piggly Wiggly Corporation continued to prosper as franchiser for the hundreds of independently owned grocery stores licensed to do business under the Piggly Wiggly name. During the decades following the 1920s divestment, the company has operated successfully under a variety of owners.
Management of the Toyota Corporation were inspired by Piggly Wiggly's Just-in-time inventory strategy and used this model to develop its Toyota Production System (TPS), a philosophy by which the company organizes its manufacturing and logistics, including its interactions with suppliers and customers.[12]
Name[edit]
According to the Piggly Wiggly website, Saunders was "reluctant" to explain the origin of the company's name. There are two theories:
One story says that, while riding a train, he looked out his window and saw several little pigs struggling to get under a fence, which prompted him to think of the rhyme. Someone once asked him why he had chosen such an unusual name for his organization, to which he replied, "So people will ask that very question."[11]
Present company[edit]
Fleming Companies bought Benson Wholesale located in Geneva, Alabama, the owner of the Piggly Wiggly name, in 1978.[13] Fleming filed for bankruptcy in 2003, and C&S Wholesale Grocers acquired most of the business, including Piggly Wiggly.[14][15]
A Piggly Wiggly store in Owasso, Oklahoma, in 2006
There are presently more than 600 independently owned and operated stores in 17 states. The company headquarters are located in Keene, New Hampshire.[11] Some of the stores have formed a retailers' cooperative to manage distribution, while using the Piggly Wiggly name (e.g., Piggly Wiggly Midwest and Piggly Wiggly Alabama Distributing Company). Piggly Wiggly stores are found predominantly in medium to smaller size cities, and remain a fixture in many rural communities. In many of the larger cities and more metropolitan areas within the company's territory (especially in the faster-growing regions), competitive national grocery chains have built larger supermarkets with greater variety and selection than Piggly Wiggly, targeting a more upscale clientele. In response, Piggly Wiggly has developed a loyalty card discount membership program similar to many other national merchants.
See also[edit]
Supermarkets in the United States
Houchens Industries
References[edit]
Jump up ^ Fleischauer, Eric (November 3, 2009). "2 Decatur Piggly Wigglys to become Food World stores". Decatur Daily. Archived from the original on July 29, 2012.
Jump up ^ "Where It Began..." PigglyWiggly.com. Piggly Wiggly LLC. Retrieved 2008-11-21.
Jump up ^ "See you at the Piggly Wiggly". Pink Palace Family of Museums. Archived from the original on 2007-10-14. Retrieved 2007-10-22.
Jump up ^ Piggly Wiggly
Jump up ^ A Quick History of the Supermarket
Jump up ^ US patent 1242872, C. Saunders, "Self-serving store", issued 1917-10-09
^ Jump up to: a b "Modern Marvels: The Supermarket". History Channel, first broadcast November 15, 2006.
Jump up ^ "Shopping Carts Will Track Consumers' Every Move". blogs.hbr.org. Retrieved 2015-09-03.
Jump up ^ "Business & Finance: Piggly Wiggly Man". Time. 1929-02-25. Retrieved 2010-05-22.
Jump up ^ Lebhar, Godfrey M. (1959) Chain Stores in America 1859–1959, Colonial Press: 31.
^ Jump up to: a b c "Piggly Wiggly: About Us". Piggly Wiggly LLC. Archived from the original on 2007-09-29. Retrieved 2007-10-22.
Jump up ^ Magee, David (November 2007), How Toyota Became #1 - Leadership Lessons from the World's Greatest Car Company, Portfolio Hardcover, ISBN 978-1-59184-179-1
Jump up ^ "Food Chains Bought by Fleming". Sarasota Herald-Tribune. March 12, 1974. Retrieved 2011-10-05.
Jump up ^ Hamstra, Mark (2003). "C&S Only Bidder for Fleming Assets, Some Resale Expected". Supermarket News.
Jump up ^ Zwiebach, Elliot (2003). "Wholesaler Exchange Boosts Both Operations". Supermarket News.
Further reading[edit]
Mike Freeman, Clarence Saunders and the Founding of Piggly Wiggly: The Rise & Fall of a Memphis Maverick (2011) excerpt
External links[edit]
Wikimedia Commons has media related to Piggly Wiggly.
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