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50,723,919 | https://en.wikipedia.org/wiki/Cortinarius%20jenolanensis | Cortinarius jenolanensis is a fungus native to Australia. It was described in 2009 by Alec Wood, from a specimen collected at the Jenolan Caves on 30 April 1988. It has also been recorded from Tidbinbilla Nature Reserve in the Australian Capital Territory.
It is not closely related to the group of dark purple webcaps (subgenus Cortinarius) that contains Cortinarius kioloensis and Cortinarius violaceus.
The fruit body has a wide dark violet cap that is initially dome-shaped and becomes flattish as it matures. The cap surface is dry and smooth. The thin crowded wide dark purple gills are adnate to decurrent, and become more rusty brown as the spores mature. The stipe is high and wide. It is the same colour as the cap with a paler base. The remnants of the veil are sparse. The oval spores are 8.4 to 10.2 long by 5.7 to 6.9 μm wide. They have few warts, unlike those of C. kioloensis and relatives.
See also
List of Cortinarius species
References
External links
Fungi described in 2009
Fungi native to Australia
jenolanensis
Fungus species | Cortinarius jenolanensis | Biology | 251 |
25,520,865 | https://en.wikipedia.org/wiki/Index%20Filicum | Index Filicum is a discontinued series of botanical indices on ferns, started by Carl Christensen in 1906 and continued in the form of seven supplements by Christensen and other authors until 1997. As of supplement 5, the index also covered lycophytes and horsetails. There was an earlier work of the same name by Thomas Moore, published in eight volumes between 1857 and 1863.
The forward to supplement seven stated that the supplements would be issued every five years from then on. However, since then, no further volume has been issued. Kew Gardens, the publisher of the two most recent supplements, has decided instead to rely on the International Plant Names Index (http://www.ipni.org/index.html — online).
Index Filicum volumes
Index Filicum, sive Enumeratio Omnium Generum Specierumque Filicum et Hydropteridum, ab Anno 1753 ad Finem Anni 1905, Descriptorum adjectis Synonymis Principalibus, Area Geographica, etc.. by Christensen, Carl Frederik Albert. Hafniae apud H. Hagerup. 1906. lx/744/(2) pp., hardcover.
Supplement I: Index Filicum, Supplementum (I) 1906-1912. by Christensen, Carl Frederik Albert. Hafniae apud H. Hagerup. 1913. vi/132 pp, hardcover.
Supplement II: Index Filicum, Supplementum Preliminaire (II), pour les Annees 1913, 1914, 1915, 1916. by Christensen, Carl Frederik Albert. S. A. I Le Prince Bonaparte, Hafniae. 1917. iv/60 pp, hardcover.
Supplement III: Index Filicum, Supplementum Tertium, pro Annis 1917-1933. by Christensen, Carl Frederik Albert. apud H. Hagerup. 1934. 220 pp, hardcover.
Supplement IV: Index Filicum, Supplementum Quartum, pro Annis 1934-1960. by Pichi-Sermolli, Rudolfo E. G. International Bureau for Plant Taxonomy and Nomenclature, Utrecht, Netherlands. 1965. vi/370 pp, softcover.
Supplement V: Index Filicum, Supplementum Quintum pro Annis 1961-1975. by Jarrett, F. M., with collab. of T. A. Bence et al. Clarendon Press, Oxford. 1985. 400 pp, hardcover. ; B 84–29402.
Supplement VI: Index Filicum: Supplementum Sextum [Supplement 6] pro annis 1976-1990. by Johns, R. J. Royal Botanic Gardens, Kew, UK. 1996. 414pp, softcover. .
Supplement VII: Index Filicum: Supplementum Septimum [Supplement 7] Pro Annis 1991-1995. by Johns, R. J., P. J. Edwards, R. Davies and K. Challis. Royal Botanic Gardens, Kew, UK. 1997. 124pp, softcover. .
Other Relevant Indices
Grimes, J. W., and B. S. Parris. Index of Thelypteridaceae. Kew Publishing, Kew Royal Botanical Garden, United Kingdom. 1986. 54pp, PB. .
Herter, W. G. Index Lycopodiorum. W. G. Herter, Basel. 1949.
Øllgaard, Benjamin. Index of the Lycopodiaceae. Kongel. Danske Vidensk. Selsk., Biol. Skr. 34. Copenhagen. 1989. .
Reed, Clyde F. Index to Equisetophyta. Reed Herbarium, Baltimore, MD. 1971.
Reed, Clyde F. Index Selaginellarum. Memorias da Sociedade Broteriana. 1966.
Reed, Clyde F. Index Isoetales. Boletim da Sociedade Broteriana. 1953.
Reed, Clyde F. Index Psilotales. Boletim da Sociedade Broteriana, Vol. XL. 30/2 pp., PB. 1966.
References
Ferns | Index Filicum | Biology | 865 |
12,684,962 | https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates%20shuffle | The Fisher–Yates shuffle is an algorithm for shuffling a finite sequence. The algorithm takes a list of all the elements of the sequence, and continually determines the next element in the shuffled sequence by randomly drawing an element from the list until no elements remain. The algorithm produces an unbiased permutation: every permutation is equally likely. The modern version of the algorithm takes time proportional to the number of items being shuffled and shuffles them in place.
The Fisher–Yates shuffle is named after Ronald Fisher and Frank Yates, who first described it. It is also known as the Knuth shuffle after Donald Knuth. A variant of the Fisher–Yates shuffle, known as Sattolo's algorithm, may be used to generate random cyclic permutations of length n instead of random permutations.
Fisher and Yates' original method
The Fisher–Yates shuffle, in its original form, was described in 1938 by Ronald Fisher and Frank Yates in their book Statistical tables for biological, agricultural and medical research. Their description of the algorithm used pencil and paper; a table of random numbers provided the randomness. The basic method given for generating a random permutation of the numbers 1 through N goes as follows:
Write down the numbers from 1 through N.
Pick a random number k between one and the number of unstruck numbers remaining (inclusive).
Counting from the low end, strike out the kth number not yet struck out, and write it down at the end of a separate list.
Repeat from step 2 until all the numbers have been struck out.
The sequence of numbers written down in step 3 is now a random permutation of the original numbers.
Provided that the random numbers picked in step 2 above are truly random and unbiased, so will be the resulting permutation. Fisher and Yates took care to describe how to obtain such random numbers in any desired range from the supplied tables in a manner which avoids any bias. They also suggested the possibility of using a simpler method — picking random numbers from one to N and discarding any duplicates—to generate the first half of the permutation, and only applying the more complex algorithm to the remaining half, where picking a duplicate number would otherwise become frustratingly common.
The modern algorithm
The modern version of the Fisher–Yates shuffle, designed for computer use, was introduced by Richard Durstenfeld in 1964 and popularized by Donald E. Knuth in The Art of Computer Programming as "Algorithm P (Shuffling)". Neither Durstenfeld's article nor Knuth's first edition of The Art of Computer Programming acknowledged the work of Fisher and Yates; they may not have been aware of it. Subsequent editions of Knuth's The Art of Computer Programming mention Fisher and Yates' contribution.
The algorithm described by Durstenfeld is more efficient than that given by Fisher and Yates: whereas a naïve computer implementation of Fisher and Yates' method would spend needless time counting the remaining numbers in step 3 above, Durstenfeld's solution is to move the "struck" numbers to the end of the list by swapping them with the last unstruck number at each iteration. This reduces the algorithm's time complexity to compared to for the naïve implementation. This change gives the following algorithm (for a zero-based array).
-- To shuffle an array a of n elements (indices 0..n-1):
for i from n−1 down to 1 do
j ← random integer such that 0 ≤ j ≤ i
exchange a[j] and a[i]
An equivalent version which shuffles the array in the opposite direction (from lowest index to highest) is:
-- To shuffle an array a of n elements (indices 0..n-1):
for i from 0 to n−2 do
j ← random integer such that i ≤ j ≤ n-1
exchange a[i] and a[j]
Examples
Pencil-and-paper method
This example permutes the letters from A to H using Fisher and Yates' original method, starting with the letters in alphabetical order:
A random number j from 1 to 8 is selected. If j=3, for example, then one strikes out the third letter on the scratch pad and writes it down as the result:
A second random number is chosen, this time from 1 to 7. If the number is 4, then one strikes out the fourth letter not yet struck off the scratch pad and adds it to the result:
The next random number is selected from 1 to 6, and then from 1 to 5, and so on, always repeating the strike-out process as above:
Modern method
In Durstenfeld's version of the algorithm, instead of striking out the chosen letters and copying them elsewhere, they are swapped with the last letter not yet chosen. Starting with the letters from A to H as before:
Select a random number j from 1 to 8, and then swap the jth and 8th letters. So, if the random number is 6, for example, swap the 6th and 8th letters in the list:
The next random number is selected from 1 to 7, and the selected letter is swapped with the 7th letter. If it is 2, for example, swap the 2nd and 7th letters:
The process is repeated until the permutation is complete:
After eight steps, the algorithm is complete and the resulting permutation is G E D C A H B F.
Python Implementation
This example shows a simple Python implementation of the Fisher-Yates shuffle.import random
def shuffle(n: int) -> list[int]:
numbers = list(range(n))
shuffled = []
while numbers:
k = random.randint(0, len(numbers) - 1)
shuffled.append(numbers[k])
numbers.pop(k)
return shuffled
JavaScript Implementation
This example shows a simple JavaScript implementation of the Fisher-Yates shuffle.function shuffleArray(array) {
for (let i = array.length - 1; i >= 1; i--) {
const j = Math.floor(Math.random() * (i + 1));
[array[i], array[j]] = [array[j], array[i]];
}
}
Variants
The "inside-out" algorithm
The Fisher–Yates shuffle, as implemented by Durstenfeld, is an in-place shuffle. That is, given a preinitialized array, it shuffles the elements of the array in place, rather than producing a shuffled copy of the array. This can be an advantage if the array to be shuffled is large.
To simultaneously initialize and shuffle an array, a bit more efficiency can be attained by doing an "inside-out" version of the shuffle. In this version, one successively places element number i into a random position among the first i positions in the array, after moving the element previously occupying that position to position i. No separate initialization is needed. Because source is never altered during execution, there is considerable flexibility in how the values are obtained. In the common case where source is defined by some simple function, such as the integers from 0 to n − 1, source may simply be replaced with the function.
To initialize an array a[] of n elements to a randomly shuffled copy of source[], both 0-based:
for i from 0 to n − 1 do
j ← random integer such that 0 ≤ j ≤ i
a[i] ← source[i]
a[i] ← a[j]
a[j] ← source[i]
The apparently redundant initial assignment to a[i] is there to ensure that the following access to a[j] is not an uninitialized variable in the case that i = j. The initialization value does not matter; zero would serve just as well. In that case, the value copied in the second assignment to a[i] does not matter either, as it is immediately overwritten by the assignment to a[j], but many popular languages (specifically including C and C++, with limited exceptions which do not apply here) state that simply reading an uninitialized value is undefined behavior and thus a programming error. If this access is, in practice, harmless (as it is on almost all common computers), the initial assignment may be omitted.
You could alternatively test whether i = j and skip any assignment to a[i] if they are equal, but the saving of n redundant assignments comes at the cost of n conditional branches, Hn ≈ ln n + γ of which will be unpredictable. For moderate n, this may well be more expensive than the assignments.
The inside-out shuffle can be seen to be correct by induction. After loop iteration i, the first i elements of the array contain a random permutation. Each loop iteration maintains this property while increasing i. Alternatively, it can be shown that there are n! different sequences of random numbers j, and each corresponds with a different permutation. Thus, each permutation is obtained exactly once. Assuming a perfect random number generator, they will all occur with equal probability.
Another advantage of this variant is that n, the number of elements in the source, does not need to be known in advance; we only need to be able to detect the end of the source data when it is reached. Below, the array a is built iteratively starting from empty, and a.length represents the current number of elements seen:
To initialize an empty array a to a randomly shuffled copy of source whose length is not known:
while source.moreDataAvailable
j ← random integer such that 0 ≤ j ≤ a.length
if j = a.length
a.append(source.next)
else
a.append(a[j])
a[j] ← source.next
Choosing k out of n elements
It is interesting to compare the regular and reverse shuffle when choosing k ≤ n out of n elements. The regular algorithm requires an n-entry array initialized with the input values, but then requires only k iterations to choose a random sample of k elements. Thus, it takes O(k) time and n space.
The inside-out algorithm can be implemented using only a k-element array a. Elements a[i] for i ≥ k are simply not stored. During iteration i ≥ k, if j < k, source[i] is stored there and the previous value is discarded. If j ≥ k, then source[i] is discarded.
Assuming the source can be generated procedurally and so takes no space, this requires performing all n iterations to finalize the output, but only k elements of storage. Compared to the regular algorithm, the space and time requirements are reversed.
Another difference is that the regular algorithm needs to know n ahead of time, but not k; it is not necessary to decide in advance how much output is enough. The reverse algorithm needs to know (an upper bound on) k ahead of time, but not n; it is not necessary to decide in advance how much input is enough.
Sattolo's algorithm
A very similar algorithm was published in 1986 by Sandra Sattolo for generating uniformly distributed cycles of (maximal) length n. The only difference between Durstenfeld's and Sattolo's algorithms is that in the latter, in step 2 above, the random number j is chosen from the range between 1 and i−1 (rather than between 1 and i) inclusive. This simple change modifies the algorithm so that the resulting permutation always consists of a single cycle.
In fact, as described below, it is quite easy to accidentally implement Sattolo's algorithm when the ordinary Fisher–Yates shuffle is intended. This will bias the results by causing the permutations to be picked from the smaller set of (n−1)! cycles of length N, instead of from the full set of all n! possible permutations.
The fact that Sattolo's algorithm always produces a cycle of length n can be shown by induction. Assume by induction that after the initial iteration of the loop, the remaining iterations permute the first n − 1 elements according to a cycle of length n − 1 (those remaining iterations are just Sattolo's algorithm applied to those first n − 1 elements). This means that tracing the initial element to its new position p, then the element originally at position p to its new position, and so forth, one only gets back to the initial position after having visited all other positions. Suppose the initial iteration swapped the final element with the one at (non-final) position k, and that the subsequent permutation of first n − 1 elements then moved it to position l; we compare the permutation π of all n elements with that remaining permutation σ of the first n − 1 elements. Tracing successive positions as just mentioned, there is no difference between π and σ until arriving at position k. But then, under π the element originally at position k is moved to the final position rather than to position l, and the element originally at the final position is moved to position l. From there on, the sequence of positions for π again follows the sequence for σ, and all positions will have been visited before getting back to the initial position, as required.
As for the equal probability of the permutations, it suffices to observe that the modified algorithm involves (n−1)! distinct possible sequences of random numbers produced, each of which clearly produces a different permutation, and each of which occurs—assuming the random number source is unbiased—with equal probability. The (n−1)! different permutations so produced precisely exhaust the set of cycles of length n: each such cycle has a unique cycle notation with the value n in the final position, which allows for (n−1)! permutations of the remaining values to fill the other positions of the cycle notation.
A sample implementation of Sattolo's algorithm in Python is:
from random import randrange
def sattolo_cycle(items) -> None:
"""Sattolo's algorithm."""
i = len(items)
while i > 1:
i = i - 1
j = randrange(i) # 0 <= j <= i-1
items[j], items[i] = items[i], items[j]
Parallel variants
Several parallel shuffle algorithms, based on Fisher—Yates have been developed.
In 1990, Anderson developed a parallel version for machines with a small number of processors accessing shared memory. The algorithm generates a random permutations uniformly so long as the hardware operates in a fair manner.
In 2015, Bacher et al. produced MERGESHUFFLE, an algorithm that divides the array into blocks of roughly equal size, uses Fisher—Yates to shuffle each block, and then uses a random merge recursively to give the shuffled array.
Comparison with other shuffling algorithms
The asymptotic time and space complexity of the Fisher–Yates shuffle are optimal. Combined with a high-quality unbiased random number source, it is also guaranteed to produce unbiased results. Compared to some other solutions, it also has the advantage that, if only part of the resulting permutation is needed, it can be stopped halfway through, or even stopped and restarted repeatedly, generating the permutation incrementally as needed.
Naïve method
The naïve method of swapping each element with another element chosen randomly from all elements is biased. Different permutations will have different probabilities of being generated, for every , because the number of different permutations, , does not evenly divide the number of random outcomes of the algorithm, . In particular, by Bertrand's postulate there will be at least one prime number between and , and this number will divide but not divide .
from random import randrange
def naive_shuffle(items) -> None:
"""A naive method. This is an example of what not to do -- use Fisher-Yates instead."""
n = len(items)
for i in range(n):
j = randrange(n) # 0 <= j <= n-1
items[j], items[i] = items[i], items[j]
Sorting
An alternative method assigns a random number to each element of the set to be shuffled and then sorts the set according to the assigned numbers. The sorting method has the same asymptotic time complexity as Fisher–Yates: although general sorting is O(n log n), numbers are efficiently sorted using Radix sort in O(n) time. Like the Fisher–Yates shuffle, the sorting method produces unbiased results. However, care must be taken to ensure that the assigned random numbers are never duplicated, since sorting algorithms typically do not order elements randomly in case of a tie. Additionally, this method requires asymptotically larger space: O(n) additional storage space for the random numbers, versus O(1) space for the Fisher–Yates shuffle. Finally, the sorting method has a simple parallel implementation, unlike the Fisher–Yates shuffle, which is sequential.
A variant of the above method that has seen some use in languages that support sorting with user-specified comparison functions is to shuffle a list by sorting it with a comparison function that returns random values. However, this is very likely to produce highly non-uniform distributions, which in addition depend heavily on the sorting algorithm used.
For instance suppose quicksort is used as sorting algorithm, with a fixed element selected as first pivot element. The algorithm starts comparing the pivot with all other elements to separate them into those less and those greater than it, and the relative sizes of those groups will determine the final place of the pivot element. For a uniformly distributed random permutation, each possible final position should be equally likely for the pivot element, but if each of the initial comparisons returns "less" or "greater" with equal probability, then that position will have a binomial distribution for p = 1/2, which gives positions near the middle of the sequence with a much higher probability for than positions near the ends. Randomized comparison functions applied to other sorting methods like merge sort may produce results that appear more uniform, but are not quite so either, since merging two sequences by repeatedly choosing one of them with equal probability (until the choice is forced by the exhaustion of one sequence) does not produce results with a uniform distribution; instead the probability to choose a sequence should be proportional to the number of elements left in it. In fact no method that uses only two-way random events with equal probability ("coin flipping"), repeated a bounded number of times, can produce permutations of a sequence (of more than two elements) with a uniform distribution, because every execution path will have as probability a rational number with as denominator a power of 2, while the required probability 1/n! for each possible permutation is not of that form.
In principle this shuffling method can even result in program failures like endless loops or access violations, because the correctness of a sorting algorithm may depend on properties of the order relation (like transitivity) that a comparison producing random values will certainly not have.
While this kind of behaviour should not occur with sorting routines that never perform a comparison whose outcome can be predicted with certainty (based on previous comparisons), there can be valid reasons for deliberately making such comparisons. For instance the fact that any element should compare equal to itself allows using them as sentinel value for efficiency reasons, and if this is the case, a random comparison function would break the sorting algorithm.
Potential sources of bias
Care must be taken when implementing the Fisher–Yates shuffle, both in the implementation of the algorithm itself and in the generation of the random numbers it is built on, otherwise the results may show detectable bias. A number of common sources of bias have been listed below.
Implementation errors
A common error when implementing the Fisher–Yates shuffle is to pick the random numbers from the wrong range. The flawed algorithm may appear to work correctly, but it will not produce each possible permutation with equal probability, and it may not produce certain permutations at all. For example, a common off-by-one error would be choosing the index j of the entry to swap in the example above to be always strictly less than the index i of the entry it will be swapped with. This turns the Fisher–Yates shuffle into Sattolo's algorithm, which produces only permutations consisting of a single cycle involving all elements: in particular, with this modification, no element of the array can ever end up in its original position.
Similarly, always selecting j from the entire range of valid array indices on every iteration also produces a result which is biased, albeit less obviously so. This can be seen from the fact that doing so yields nn distinct possible sequences of swaps, whereas there are only n! possible permutations of an n-element array. Since nn can never be evenly divisible by n! when n > 2 (as the latter is divisible by n−1, which shares no prime factors with n), some permutations must be produced by more of the nn sequences of swaps than others. As a concrete example of this bias, observe the distribution of possible outcomes of shuffling a three-element array [1, 2, 3]. There are 6 possible permutations of this array (3! = 6), but the algorithm produces 27 possible shuffles (33 = 27). In this case, [1, 2, 3], [3, 1, 2], and [3, 2, 1] each result from 4 of the 27 shuffles, while each of the remaining 3 permutations occurs in 5 of the 27 shuffles.
The matrix to the right shows the probability of each element in a list of length 7 ending up in any other position. Observe that for most elements, ending up in their original position (the matrix's main diagonal) has lowest probability, and moving one slot backwards has highest probability.
Modulo bias
Doing a Fisher–Yates shuffle involves picking uniformly distributed random integers from various ranges. Most random number generators, however — whether true or pseudorandom — will only directly provide numbers in a fixed range from 0 to RAND_MAX, and in some libraries, RAND_MAX may be as low as 32767. A simple and commonly used way to force such numbers into a desired range is to apply the modulo operator; that is, to divide them by the size of the range and take the remainder. However, the need in a Fisher–Yates shuffle to generate random numbers in every range from 0–1 to 0–n almost guarantees that some of these ranges will not evenly divide the natural range of the random number generator. Thus, the remainders will not always be evenly distributed and, worse yet, the bias will be systematically in favor of small remainders.
For example, assume that your random number source gives numbers from 0 to 99 (as was the case for Fisher and Yates' original tables), which is 100 values, and that you wish to obtain an unbiased random number from 0 to 15 (16 values). If you simply divide the numbers by 16 and take the remainder, you will find that the numbers 0–3 occur about 17% more often than others. This is because 16 does not evenly divide 100: the largest multiple of 16 less than or equal to 100 is 6×16 = 96, and it is the numbers in the incomplete range 96–99 that cause the bias. The simplest way to fix the problem is to discard those numbers before taking the remainder and to keep trying again until a number in the suitable range comes up. While in principle this could, in the worst case, take forever, the expected number of retries will always be less than one.
A method of obtaining random numbers in the required ranges that is unbiased and nearly never performs the expensive modulo operation was described in 2018 by Daniel Lemire.
A related problem occurs with implementations that first generate a random floating-point number—usually in the range [0,1]—and then multiply it by the size of the desired range and round down. The problem here is that random floating-point numbers, however carefully generated, always have only finite precision. This means that there are only a finite number of possible floating point values in any given range, and if the range is divided into a number of segments that does not divide this number evenly, some segments will end up with more possible values than others. While the resulting bias will not show the same systematic downward trend as in the previous case, it will still be there.
The extra cost of eliminating "modulo bias" when generating random integers for a Fisher-Yates shuffle depends on the approach (classic modulo, floating-point multiplication or Lemire's integer multiplication), the size of the array to be shuffled, and the random number generator used.
Pseudorandom generators
An additional problem occurs when the Fisher–Yates shuffle is used with a pseudorandom number generator or PRNG: as the sequence of numbers output by such a generator is entirely determined by its internal state at the start of a sequence, a shuffle driven by such a generator cannot possibly produce more distinct permutations than the generator has distinct possible states. Even when the number of possible states exceeds the number of permutations, the irregular nature of the mapping from sequences of numbers to permutations means that some permutations will occur more often than others. Thus, to minimize bias, the number of states of the PRNG should exceed the number of permutations by at least several orders of magnitude.
For example, the built-in pseudorandom number generator provided by many programming languages and/or libraries may often have only 32 bits of internal state, which means it can only produce 232 different sequences of numbers. If such a generator is used to shuffle a deck of 52 playing cards, it can only ever produce a very small fraction of the 52! ≈ 2225.6 possible permutations. It is impossible for a generator with less than 226 bits of internal state to produce all the possible permutations of a 52-card deck.
No pseudorandom number generator can produce more distinct sequences, starting from the point of initialization, than there are distinct seed values it may be initialized with. Thus, a generator that has 1024 bits of internal state but which is initialized with a 32-bit seed can still only produce 232 different permutations right after initialization. It can produce more permutations if one exercises the generator a great many times before starting to use it for generating permutations, but this is a very inefficient way of increasing randomness: supposing one can arrange to use the generator a random number of up to a billion, say 230 for simplicity, times between initialization and generating permutations, then the number of possible permutations is still only 262.
A further problem occurs when a simple linear congruential PRNG is used with the divide-and-take-remainder method of range reduction described above. The problem here is that the low-order bits of a linear congruential PRNG with modulo 2e are less random than the high-order ones: the low n bits of the generator themselves have a period of at most 2n. When the divisor is a power of two, taking the remainder essentially means throwing away the high-order bits, such that one ends up with a significantly less random value. Different rules apply if the LCG has prime modulo, but such generators are uncommon. This is an example of the general rule that a poor-quality RNG or PRNG will produce poor-quality shuffles.
See also
Permutation, The Fisher-Yates shuffle does not depend on the elements being shuffled. The properties of the permutations of the standard set have been extensively studied.
RC4, a stream cipher based on shuffling an array
Reservoir sampling, in particular Algorithm R which is a specialization of the Fisher–Yates shuffle
References
External links
An interactive example Mike Bostock provides examples in JavaScript with visualizations showing how the modern (Durstenfeld) Fisher-Yates shuffle is more efficient than other shuffles. The example includes link to a matrix diagram that illustrates how Fisher-Yates is unbiased while the naïve method (select naïve swap i -> random) is biased. Select Fisher-Yates and change the line to have pre-decrement --m rather than post-decrement m-- giving i = Math.floor(Math.random() * --m);, and you get Sattolo's algorithm where no item remains in its original position.
Combinatorial algorithms
Randomized algorithms
Permutations
Monte Carlo methods
Articles with example pseudocode
Articles with example Python (programming language) code
Ronald Fisher | Fisher–Yates shuffle | Physics,Mathematics | 5,955 |
7,373,637 | https://en.wikipedia.org/wiki/Oblique%20correction | In particle physics, an oblique correction refers to a particular type of radiative correction to the electroweak sector of the Standard Model. Oblique corrections are defined in four-fermion scattering processes, ( + → + ) at the CERN Large Electron–Positron Collider. There are three classes of radiative corrections to these processes: vacuum polarization corrections, vertex corrections, and box corrections. The vacuum polarization corrections are referred to as oblique corrections, since they only affect the mixing and propagation of the gauge bosons and they do not depend on which type of fermions appear in the initial or final states. (The vertex and box corrections, which depend on the identity of the initial and final state fermions, are called nonoblique corrections.)
Any new particles charged under the electroweak gauge groups can contribute to oblique corrections. Therefore, the oblique corrections can be used to constrain possible new physics beyond the Standard Model. To affect the nonoblique corrections, on the other hand, the new particles must couple directly to the external fermions.
The oblique corrections are usually parameterized in terms of the Peskin–Takeuchi parameters S, T, and U.
See also
Initial and final state radiation
References
Standard Model
Physics beyond the Standard Model | Oblique correction | Physics | 266 |
5,717,580 | https://en.wikipedia.org/wiki/Active%20appearance%20model | An active appearance model (AAM) is a computer vision algorithm for matching a statistical model of object shape and appearance to a new image. They are built during a training phase. A set of images, together with coordinates of landmarks that appear in all of the images, is provided to the training supervisor.
The model was first introduced by Edwards, Cootes and Taylor in the context of face analysis at the 3rd International Conference on Face and Gesture Recognition, 1998. Cootes, Edwards and Taylor further described the approach as a general method in computer vision at the European Conference on Computer Vision in the same year. The approach is widely used for matching and tracking faces and for medical image interpretation.
The algorithm uses the difference between the current estimate of appearance and the target image to drive an optimization process.
By taking advantage of the least squares techniques, it can match to new images very swiftly.
It is related to the active shape model (ASM). One disadvantage of ASM is that it only uses shape constraints (together with some information about the image structure near the landmarks), and does not take advantage of all the available information – the texture across the target object. This can be modelled using an AAM.
References
Some reading
T. F. Cootes, C. J. Taylor, D. H. Cooper, and J. Graham. Training models of shape from sets of examples. In Proceedings of BMVC'92, pages 266–275, 1992
S. C. Mitchell, J. G. Bosch, B. P. F. Lelieveldt, R. J. van der Geest, J. H. C. Reiber, and M. Sonka. 3-d active appearance models: Segmentation of cardiac MR and ultrasound images. IEEE Trans. Med. Imaging, 21(9):1167–1178, 2002
T.F. Cootes, G. J. Edwards, and C. J. Taylor. Active appearance models. ECCV, 2:484–498, 1998[pdf]
External links
Professor Tim Cootes AAM Code Free Tools for experimenting with AAMs from Manchester University (for research use only).
Professor Tim Cootes AAM Page Co-creator of AAM page from Manchester University.
IMM AAM Code Dr Mikkel B. Stegmann's home page of AAM-API, C++ AAM implementation (non-commercial use only).
Matlab AAM Code Open-source Matlab implementation of the original AAM algorithm.
AAMtools An Active Appearance Modelling Toolbox in Matlab by Dr George Papandreou.
DeMoLib AAM Toolbox in C++ by Dr Jason Saragih and Dr Roland Goecke.
Computer vision | Active appearance model | Engineering | 569 |
1,344,838 | https://en.wikipedia.org/wiki/AT%26T%20Hobbit | The AT&T Hobbit is a microprocessor design developed by AT&T Corporation in the early 1990s. It was based on the company's CRISP (C-language Reduced Instruction Set Processor) design resembling the classic RISC pipeline, and which in turn grew out of the C Machine design by Bell Labs of the late 1980s. All were optimized for running code compiled from the C programming language. The design concentrates on fast instruction decoding, indexed array access, and procedure calls.
The project was ended in March 1994 because the Hobbit failed to achieve commercially viable sales.
History
The C Machine Project at Bell Labs had been underway since 1975 to develop computer architectures to run C programming language programs efficiently, aiming for a design that would offer an order of magnitude performance improvement over commercially available computers while remaining competitive in terms of cost. The design methodology for the C Machine architecture involved an iterative development approach informed by measurements of C program characteristics, involving the formulation and implementation of new computer architecture revisions, the development of a compiler to target each new revision, the compilation of "a large body of UNIX software", and the analysis of the compiled software. The results from such measurements then informed subsequent architecture revisions.
Following on from the stabilization of the C Machine architecture in 1981 for an uncompleted ECL implementation, a design team was formed for CRISP in April 1983, and CRISP was first produced in a silicon implementation in 1986. The performance objectives were largely met by the fabricated processor, running at 16 MHz and delivering a Dhrystone benchmark score over 13 times greater than the VAX-11/750, achieving approximately 7.7 VAX MIPS. This was competitive with the MIPS R2000 as delivered in the MIPS M/500 Development System (an 8 MHz device delivering around 7.4 VAX MIPS) although some benchmarks showed somewhat stronger performance by the CRISP processor. Compared to the R2000 which required numerous support chips when incorporated into a computer system, the CRISP was a "complete" processor incorporating on-chip caches and had "substantially" reduced board area requirements.
It was subsequently reoriented toward low-power applications and commercialized, resulting in the Hobbit. It was introduced in 1992 in the form of the 92010 and aimed at the personal communicator market. Operating at 3.3V, its reported performance is up to 13.5 VAX MIPS. Initial pricing in multiples of 10,000 units was given as $35 per unit, with the full chipset below $100. Several support chips were produced:
AT&T 92011 System Management Unit
AT&T 92012 PCMCIA Controller
AT&T 92013 Peripheral Controller
AT&T 92014 Display Controller
AT&T followed in 1993 with the 92020 family of processors, introducing new support chipsets targeting different applications. These devices can run at 3.3V or at 5V with an elevated clock frequency. The 92020S is pin-compatible with the 92010, has a larger 6 KB instruction cache (as opposed to the 3 KB cache of the 92010), and performs the equivalent of 16 VAX MIPS with a typical power consumption of 210 mW. The 92020S was intended to be used in conjunction with most of the original 92010 chipset, excluding the 92013 peripheral controller. Meanwhile, the 92020M and 92020MX processors were intended for use with the new support chips, also employing a multiplexed address and data bus for reduced pin count, and offering lower levels of performance, with the 92020M also utilizing a 6 KB cache and achieving similar performance to the original 92010. The updated support chips are as follows:
AT&T 92021M System Management Unit
AT&T 92021MX System Management Unit
AT&T 92024M Display Controller
The most highly integrated processor, the 92020MX, preserved the 3 KB cache of the 92010 but has a single-channel PCMCIA interface and a display controller supporting resolutions of up to . Costing $32 per unit in 10,000 unit quantities, it presented opportunities for cost reduction with certain devices when compared to the original Hobbit chipset.
Apple Computer approached AT&T and paid it to develop a newer version of the CRISP suitable for low-power use in the Newton handheld computer. The Hobbit-based Newton was never produced. According to Larry Tesler, "The Hobbit was rife with bugs, ill-suited for our purposes, and overpriced. We balked after AT&T demanded not one but several million more dollars in development fees." Apple rejected the Hobbit and adopted the ARM610 for the Newton, also partnering with Acorn Computers and VLSI Technology to form Advanced RISC Machines (ARM) in late 1990 with a $2.5 million investment. Apple sold its stake in ARM years later for a net $800 million.
The Active Book Company (founded by Hermann Hauser, who also founded Acorn Computers), which had been using an ARM in its Active Book personal digital assistant (PDA), was later purchased by AT&T and was subsumed by AT&T's Eo subsidiary, which produced an early PDA, the EO Personal Communicator, running PenPoint OS from the GO Corporation.
AT&T made early announcements in 1992 of broad vendor adoption. Hobbit was used in the earliest prototypes of the BeBox until in 1993, AT&T announced discontinuation of Hobbit. AT&T closed its Eo operations which were responsible for the only commercially released product using the Hobbit, and finally discontinued the Hobbit in 1994.
Design
In a traditional RISC design implementing a load–store architecture, memory is accessed through instructions that explicitly load data into registers and store data back to memory, with instructions that manipulate data working solely on the registers. By seeking to limit the data processing operations to a single clock cycle, a simpler control mechanism can be employed to dispatch instructions, making it easier to tune the instruction pipelines, and add superscalar support. However, programming languages do not actually operate in this fashion. Generally they use a stack containing local variables and other information for subroutines known as a stack frame or activation record. The compiler writes code to create activation records using the underlying processor's load-store design.
The C Machine in its CRISP implementation, and the Hobbit that followed directly, both aim to support the types of memory access that programming languages use, with the C programming language being a particular consideration. Instructions can access memory directly, referencing values in structures and arrays held within memory and updating memory with computation results. Although this memory-to-memory model is typical of the earlier CISC designs, the C Machine as implemented by CRISP differs from both CISC and RISC designs, including the earlier Bellmac 32, by providing no directly accessible registers. Instead, a "stack cache" of 32-bit register entries is provided, 32 entries in CRISP but extended to 64 entries in Hobbit, mapped to the address space corresponding to the top of the program stack, these being purely accessible using a stack-relative addressing mode. The CRISP architecture was described as a "2½ address memory-to-memory machine", where instructions can employ zero, one, or two memory addresses and can employ a stack entry called the accumulator for computation results. Reminiscent of the Bellmac 32 architecture, various instructions designed to support procedure calling are provided by the CRISP architecture: call saves the return address and branches to a routine; enter allocates a stack frame for a routine, flushing stack cache entries if necessary; return deallocates the stack frame and branches to the caller's return address; catch restores stack entries from memory.
One side effect of the Hobbit design is that it inspired designers of the Dis virtual machine (an offshoot of Plan 9 from Bell Labs) to use a memory-to-memory-based system that more closely matches the internal register-based workings of real-world processors. They found, as RISC designers would have expected, that without a load-store design it was difficult to improve the instruction pipeline and thereby operate at higher speeds. They decided that all future processors would thus move to a load-store design, and built Inferno to reflect this. In contrast, Java and .NET virtual machines are stack-based, a side effect of being designed by language programmers as opposed to chip designers. Translating from a stack-based language to a register-based assembly language is a "heavyweight" operation; Java's virtual machine (VM) and compiler are many times larger and slower than the Dis VM and the Limbo (the most common language compiled for Dis) compiler. The VMs for Android (Dalvik), Parrot, and Lua are also register-based.
See also
Jazelle
References
External links
The BeBox Zone - Prototype Hobbit BeBox Gallery (archived version)
Computer Industry Report 1992 article - Hobbit - AT&T Microelectronics' most visible new product - takes on Intel, ARM, Motorola, Microsoft - Intel Corp.; Motorola Inc.; Microsoft Corp
Sculley's Dream: The Story Behind the Newton, by Tom Hormby, Low End Mac
Hobbit
Inferno (operating system)
Plan 9 from Bell Labs
32-bit microprocessors | AT&T Hobbit | Technology | 1,956 |
64,718,903 | https://en.wikipedia.org/wiki/SAM%20%28automotive%29 | SAM (from Samochód Amatorski Motoru; Amateur Motor Car), in Polish law, is a kind of vehicle, usually car, motorcycle or tractor made by yourself or in a workshop. It is made in a single copy, less often in a small series. It is created by a thorough alteration of a serial vehicle or by building it from scratch. A vehicle brand "SAM" under the Act is a vehicle built using body, chassis or frame, own design. The construction uses many components of serial vehicles. The name derives from the popular in the 1950s in Poland by the competition of the weekly called Auto Amatorski Motoru, in which the editors of the magazine presented handcrafted constructions by workers or craftsmen .
"SAM" tractors are used in agriculture and horticulture, most often without approval and registration - hence they are not allowed for road traffic on public roads.
Vehicle registration requires technical inspection .
The scope of tests allowing for admission to traffic is specified in the regulation by the Minister of Infrastructure of October 22, 2004 (Journal of Laws No. 238, item 2395) on tests of compliance of historic vehicles and "SAM" brand vehicles with technical conditions .
Reservations regarding registration:
Self-built vehicle using Body, Chassis or frame of own design, brand of which is referred to as "SAM" without specifying model type
Engine and you cannot build it yourself - documents for the complete engine assembly must be submitted for registration.
Footnotes
External links
Examples of "SAM" vehicles:
Car "SAM"
Vehicle "SAM"
:pl:Sam (motoryzacja)
Vehicles
Agricultural machinery
Kit vehicles
Vehicles of Poland | SAM (automotive) | Physics | 332 |
22,416,330 | https://en.wikipedia.org/wiki/Intramolecular%20aglycon%20delivery | Intramolecular aglycon delivery is a synthetic strategy for the construction of glycans. This approach is generally used for the formation of difficult glycosidic linkages.
Introduction
Glycosylation reactions are very important reactions in carbohydrate chemistry, leading to the synthesis of oligosaccharides, preferably in a stereoselective manner. The stereoselectivity of these reactions has been shown to be affected by both the nature and the configuration of the protecting group at C-2 on the glycosyl donor ring. While 1,2-trans-glycosides (e.g. α-mannosides and β-glucosides) can be synthesised easily in the presence of a participating group (such as OAc, or NHAc) at the C-2 position in the glycosyl donor ring, 1,2-cis-glycosides are more difficult to prepare. 1,2-cis-glycosides with the α configuration (e.g. glucosides or galactosides) can often be prepared using a non-participating protecting group (such as Bn, or All) on the C-2 hydroxy group. However, 1,2-cis-glycosides with the β configuration are the most difficult to achieve, and present the greatest challenge in glycosylation reactions.
One of the most recent approaches to prepare 1,2-cis-β-glycosides in a stereospecific manner is termed ‘Intramolecular Aglycon Delivery’, and various methods have been developed based on this approach.
In this approach, the glycosyl acceptor is tethered onto the C-2-O-protecting group (X) in the first step. Upon activation of the glycosyl donor group (Y) (usually SR, OAc, or Br group) in the next step, the tethered aglycon traps the developing oxocarbenium ion at C-1, and is transferred from the same face as OH-2, forming the glycosidic bond stereospecifically. The yield of this reaction drops as the bulkiness of the alcohol increases.
Intramolecular Aglycon Delivery (IAD) methods
Carbon tethering
Acid-catalysed tethering to enol ethers
In this method, the glycosyl donor is protected at the C-2 position by an OAc group. The C-2-OAc protecting group is transformed into an enol ether by the Tebbe reagent (Cp2Ti=CH2), and then the glycosyl acceptor is tethered to the enol ether under acid-catalysed conditions to generate a mixed acetal. In a subsequent step, the β-mannoside is formed upon activation of the anomeric leaving group (Y), followed by work up.
Iodonium tethering to enol ethers
This method is similar to the previous method in that the glycosyl donor is protected at C-2 by an OAc group, which is converted into an enol ether by the Tebbe reagent. However, in this approach, N-iodosuccinimide (NIS) is used to tether the glycosyl acceptor to the enol ether, and in a second step, activation of the anomeric leaving group leads to intramolecular delivery of the aglycon to C-1 and formation of the 1,2-cis-glycoside product.
Iodonium tethering to prop-1-enyl ethers
The glycosyl donor is protected at C-2 by OAll group. The allyl group is then isomerized to a prop-1-enyl ether using a rhodium hydride generated from Wilkinson's catalyst ((PPh3)3RhCl) and butyllithium (BuLi). The resulting enol ether is then treated with NIS and the glycosyl acceptor to generate a mixed acetal. The 1,2-cis (e.g. β-mannosyl) product is formed in a final step through activation of the anomeric leaving group, delivery of the aglycon from the mixed acetal and finally hydrolytic work-up to remove the remains of the propenyl ether from O-2.
Oxidative tethering to para-methoxybenzyl (PMB) ethers
In this method, the glycosyl donor is protected at C-2 by a para-methoxybenzyl (PMB) group. The glycosyl acceptor is then tethered at the benzylic position of the PMB protecting group in the presence of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The anomeric leaving group (Y) is then activated, and the developing oxocarbenium ion is captured by the tethered aglycon alcohol (OR) to give 1,2-cis β-glycoside product.
Solid-supported oxidative tethering to para-alkoxybenzyl ethers
This is a modification of the method of oxidative tethering to a para-methoxybenzyl ether. The difference here is that the para-alkoxybenzyl group is attached to a solid support; the β-mannoside product is released into the solution phase in the last step, while the by-products remain attached to the solid phase. This makes the purification of the β-glycoside easier; it is formed as the almost exclusive product.
Silicon tethering
The initial step in this method involves the formation of a silyl ether at the C-2 hydroxy group of the glycosyl donor upon addition of dimethyldichlorosilane in the presence of a strong base such as butyllithium (BuLi); then the glycosyl acceptor is added to form a mixed silaketal. Activation of the anomeric leaving group in the presence of a hindered base then leads to the β-glycoside.
A modified silicon-tethering method involves mixing of the glycosyl donor with the glycosyl acceptor and dimethyldichlorosilane in the presence of imidazole to give the mixed silaketal in one pot. Activation of the tethered intermediate then leads to the β-glycoside product.
See also
Chemical glycosylation
Glycosyl halide
References
Carbohydrate chemistry | Intramolecular aglycon delivery | Chemistry | 1,416 |
27,387,028 | https://en.wikipedia.org/wiki/Fort%20de%20Leveau | The Fort de Leveau, also known as Fort Schouller, is located in the commune of Feignies, France. It is part of the fortifications of Maubeuge, located to the northwest of the city, overlooking the railroad to Mons. The Séré de Rivières system fort was built 1882–1884, one of six forts built at the time. It is maintained as a museum by the town of Feignies.
Description
The fort is a typical example of a Séré de Rivières system, with a low wall, surrounded by a ditch, which is in turn defended by caponiers. The roof of the barracks is concreted and supports an artillery platform, or cavalier. The ditch was traversed by a drawbridge, no longer extant. The position was heavily bombarded in 1914. In 1893, four 120mm guns were mounted on the cavalier, while additional armament including 90mm guns were added in casemates. A 1914 project added a turret for two 75mm guns. However, the turret was not armed and equipped at the outbreak of World War I.
In the 1930s the fort was chosen as a site for fortifications associated with the Maginot Line extension around Maubeuge, part of the "New Fronts" program. An observation post, a casemate and a blockhouse were built on the fort. The casemate was furnished with a 25mm anti-tank gun, a machine gun port and an automatic rifle port.
History
In 1870, France was partly occupied by the Prussian army. As a result of this defeat, the Séré de Rivières system of fortifications was planned and constructed to defend the nation. Maubeuge, located close by the border between France and Belgium, received a complete ring of forts. Construction started in 1882, completing in 1884 for a garrison of 97 men. The armament was improved in 1893, and the fort was renovated again in 1914.
In the opening stages of World War I the German army laid siege to Maubeuge, beginning 29 August 1914. On 7 September, the Fort de Leveau was bombarded by 25 42 cm projectiles and a number of 30.5 cm rounds, heavily damaging the fort, with one shot hitting the barracks and killing up to 120. At 1400 on the 7th, French forces evacuated the fort, shortly before the general surrender of the Maubeuge fortress. After occupying the fort, the Germans blew up the caponiers, the unfinished 75mm gun turret and other portions of the fort.
In the 1930s, France invested in the construction of the Maginot Line, which covered the eastern frontiers of France. The frontier with Belgium was regarded as a lesser priority because France's war plan called for the French Army to advance into Belgium and conduct an offensive there. Belatedly, France began construction of a limited series of defenses around Maubeuge in the mid-1930s. These fortifications were individually assaulted and captured in the opening phases of World War II. The Leveau fortifications were attacked on 18 May 1940 and were subdued that afternoon, with one defender dead. In 1944 the fort saw fighting between Resistance and German forces.
The site was acquired by the town of Feignies in 1993 and is administered as a museum by the Association de Sauvegrade du Fort de Leveau. In 1998, excavations recovered the remains of nine soldiers killed in the 1914 siege, who were re-interred at the Assevent cemetery.
References
External links
Official site
Fort de Leveau (59) at Chemins de mémoire
The Fort de Leveau on the website "Remembrance Trails of the Great War in Northern France"
Fortifications of Maubeuge
Séré de Rivières system
World War I museums in France
World War II museums in France | Fort de Leveau | Engineering | 763 |
558,379 | https://en.wikipedia.org/wiki/Dirham | The dirham, dirhem or drahm is a unit of currency and of mass. It is the name of the currencies of Morocco, the United Arab Emirates and Armenia, and is the name of a currency subdivision in Jordan, Libya, Qatar and Tajikistan. It was historically a silver coin.
Unit of mass
The dirham was a unit of mass used across North Africa, the Middle East, Persia and Ifat; later known as Adal, with varying values.
The value of Islamic dirham was 14 qirat. 10 dirham equals 7 mithqal (2.975 gm of silver).
In the late Ottoman Empire (), the standard dirham was 3.207 g; 400 dirhem equal one oka. The Ottoman dirham was based on the Sasanian drachm (in Middle Persian: 𐭦𐭥𐭦𐭭 drahm), which was itself based on the Greek dram/drachma.
In Egypt in 1895, it was equivalent to 47.661 troy grains (3.088 g).
There is currently a movement within the Islamic world to revive the dirham as a unit of mass for measuring silver, although the exact value is disputed (either 3 or 2.975 grams).
History
The word "dirham" ultimately comes from drachma (δραχμή), the Greek coin. The Greek-speaking Byzantine Empire lay partially in the Levant and traded with Arabia, circulating the coin there in pre-Islamic times and afterward. It was this currency which was initially adopted as a Persian word (Middle Persian drahm or dram); then near the end of the 7th century the coin became an Islamic currency bearing the name of the sovereign and a religious verse. The Arabs introduced their own coins.
The Islamic dirham was 8 daniq. The dirham was struck in many Mediterranean countries, including Al-Andalus (Moorish Spain) and the Byzantine Empire (miliaresion), and could be used as currency in Europe between the 10th and 12th centuries, notably in areas with Viking connections, such as Viking York and Dublin.
Dirham in Jewish orthodox law
The dirham is frequently mentioned in Jewish orthodox law as a unit of weight used to measure various requirements in religious functions, such as the weight in silver specie pledged in Marriage Contracts (Ketubbah), the quantity of flour requiring the separation of the dough-portion, etc. Jewish physician and philosopher, Maimonides, uses the Egyptian dirham to approximate the quantity of flour for dough-portion, writing in Mishnah Eduyot 1:2: "And I found the rate of the dough-portion in that measurement to be approximately five-hundred and twenty dirhams of wheat flour, while all these dirhams are the Egyptian [dirham]." This view is repeated by Maran's Shulhan Arukh (Hil. Hallah, Yoreh Deah § 324:3) in the name of the Tur. In Maimonides' commentary of the Mishnah (Eduyot 1:2, note 18), Rabbi Yosef Qafih explains that the weight of each Egyptian dirham was approximately 3.333 grams, or what was the equivalent to 16 carob-grains which, when taken together, the minimum weight of flour requiring the separation of the dough-portion comes to approx. 1 kilo and 733 grams. Rabbi Ovadiah Yosef, in his Sefer Halikhot ʿOlam (vol. 1, pp. 288–291), makes use of a different standard for the Egyptian dirham, saying that it weighed approx. 3.0 grams, meaning the minimum requirement for separating the priest's portion is 1 kilo and 560 grams. Others (e.g. Rabbi Avraham Chaim Naeh) say the Egyptian dirham weighed approx. 3.205 grams, which total weight for the requirement of separating the dough-portion comes to 1 kilo and 666 grams. Rabbi Shelomo Qorah (Chief Rabbi of Bnei Barak) wrote that the traditional weight used in Yemen for each dirham weighed 3.20 grams for a total of 31.5 dirhams given as the redemption of one's firstborn son (pidyon haben), or 3.36 grams for the 30 dirhams required by the Shulhan Arukh (Yoreh De'ah 305:1), and which in relation to the separation of the dough-portion made for a total weight of 1 kilo and 770.72 grams.
The word drachmon (), used in some translations of Maimonides' commentary of the Mishnah, has in all places the same connotation as dirham.
Modern-day currency
Currently the valid national currencies with the name dirham are:
Modern currencies with the subdivision dirham or diram are:
The unofficial modern gold dinar, issued and/or proposed by several states and proto-states, is also divided into dirhams.
See also
Dinar
Gold dinar
Fals
Notes
References
Denominations (currency)
Silver coins
Obsolete units of measurement
Ottoman units of measurement
Units of mass
Islamic banking
Islamic banking and finance terminology
Medieval currencies | Dirham | Physics,Mathematics | 1,084 |
4,682,498 | https://en.wikipedia.org/wiki/Semi-empirical%20quantum%20chemistry%20method | Semi-empirical quantum chemistry methods are based on the Hartree–Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where the full Hartree–Fock method without the approximations is too expensive. The use of empirical parameters appears to allow some inclusion of electron correlation effects into the methods.
Within the framework of Hartree–Fock calculations, some pieces of information (such as two-electron integrals) are sometimes approximated or completely omitted. In order to correct for this loss, semi-empirical methods are parametrized, that is their results are fitted by a set of parameters, normally in such a way as to produce results that best agree with experimental data, but sometimes to agree with ab initio results.
Type of simplifications used
Semi-empirical methods follow what are often called empirical methods where the two-electron part of the Hamiltonian is not explicitly included. For π-electron systems, this was the Hückel method proposed by Erich Hückel. For all valence electron systems, the extended Hückel method was proposed by Roald Hoffmann.
Semi-empirical calculations are much faster than their ab initio counterparts, mostly due to the use of the zero differential overlap approximation. Their results, however, can be very wrong if the molecule being computed is not similar enough to the molecules in the database used to parametrize the method.
Preferred application domains
Methods restricted to π-electrons
These methods exist for the calculation of electronically excited states of polyenes, both cyclic and linear. These methods, such as the Pariser–Parr–Pople method (PPP), can provide good estimates of the π-electronic excited states, when parameterized well. For many years, the PPP method outperformed ab initio excited state calculations.
Methods restricted to all valence electrons.
These methods can be grouped into several groups:
Methods such as CNDO/2, INDO and NDDO that were introduced by John Pople. The implementations aimed to fit, not experiment, but ab initio minimum basis set results. These methods are now rarely used but the methodology is often the basis of later methods.
Methods that are in the MOPAC, AMPAC, SPARTAN and/or CP2K computer programs originally from the group of Michael Dewar. These are MINDO, MNDO, AM1, PM3, PM6, PM7 and SAM1. Here the objective is to use parameters to fit experimental heats of formation, dipole moments, ionization potentials, and geometries. This is by far the largest group of semiempirical methods.
Methods whose primary aim is to calculate excited states and hence predict electronic spectra. These include ZINDO and SINDO. The OMx (x=1,2,3) methods can also be viewed as belonging to this class, although they are also suitable for ground-state applications; in particular, the combination of OM2 and MRCI is an important tool for excited state molecular dynamics.
Tight-binding methods, e.g. a large family of methods known as DFTB, are sometimes classified as semiempirical methods as well. More recent examples include the semiempirical quantum mechanical methods GFNn-xTB (n=0,1,2), which are particularly suited for the geometry, vibrational frequencies, and non-covalent interactions of large molecules.
The NOTCH method includes many new, physically-motivated terms compared to the NDDO family of methods, is much less empirical than the other semi-empirical methods (almost all of its parameters are determined non-empirically), provides robust accuracy for bonds between uncommon element combinations, and is applicable to ground and excited states.
See also
List of quantum chemistry and solid-state physics software
References | Semi-empirical quantum chemistry method | Chemistry | 794 |
10,946,060 | https://en.wikipedia.org/wiki/Jun%20dimerization%20protein | Jun dimerization protein 2 (JUNDM2) is a protein that in humans is encoded by the JDP2 gene. The Jun dimerization protein is a member of the AP-1 family of transcription factors.
JDP 2 was found by a Sos-recruitment system, to dimerize with c-Jun to repress AP-1-mediated activation. It was later identified by the yeast-two hybrid system to bind to activating transcription factor 2 (ATF2) to repress ATF-mediated transcriptional activation. JDP2 regulates 12-O-tetradecanoylphorbol-13-acetate (TPA) response element (TRE)- and cAMP-responsive element (CRE)-dependent transcription.
The JDP2 gene is located on human chromosome 14q24.3 (46.4 kb, 75,427,715 bp to 75,474,111 bp) and mouse chromosome 12 (39 kb, 85,599,105 bp to 85,639,878 bp), which is located at about 250 kbp in the Fos-JDP2-BATF locus. Alternative splicing of JDP2 generates at least two isoforms. The protein JDP2 has 163 amino acids, belongs to the family of basic leucine zipper (bZIP), and shows high homology with the ATF3 bZIP domain. The bZIP domain includes the amino acids from position 72 to 135, the basic motif from position 74 to 96, and the leucine zipper from 100 to 128. The molecular weight of the canonical JDP2 is 18,704 Da. The histone-binding region is located from position 35 to 72 and the inhibition of the histone acetyltransferase (INHAT) region is from position 35 to 135, which is located before the DNA-binding domain.
JDP2 is expressed ubiquitously but is detected mainly in the cerebellum, brain, lung, and testis. A JDP2 single nucleotide polymorphism (SNP) was detected in Japanese, Korean, and Dutch cohorts, and is associated with an increased risk of intracranial aneurysms.
Posttranscriptional and post translational modifications
Phosphorylation of the threonine (Thr) residue at position 148 is mediated by c-Jun N-terminal kinase (MAPK8; JNK1) and p38 MAPK. Phosphorylated ATF2 inhibits the formation with JDP2 in vitro while phosphorylated JDP2 undergoes proteosomal degradation. It contains putative SUMO modification of lysine (Lys) residue at position 65, and recruits interferon regulatory factor 2 binding protein 1 (IRF2BP1), which acts as an E3 ligase. Phosphorylation of Thr at position 148 is detected in response to various stress conditions such as UV irradiation, oxidative stress, and anisomycin treatment or JDP2 is also regulated by other kinases such as p38 MAPK and doublecortin like protein kinase. Polyubiquitination of JDP2 protein is induced by IRF2BP1. JDP2 displays histone-binding and histone-chaperone activity. and inhibition of p300/CBP induced histone acetylation (INHAT). JDP2 recruits histone deacetylases HDAC1 and HDAC2, HDAC6 and HDAC3. JDP2 has INHAT activity and inhibits histone methylation in vitro.
Function
Phenotypes of gene knockout and transgenic mice
Gene knockout mice have a shorter tail, are smaller, have low neutrophil count. and cell proliferation, and commit to cell cycle arrest because of AP-1 repression. TransgenicJDP2 mice display atrial dilation and myocardial hypertrophy.
Dimer formation and interacting molecules
JDP2 functions as a transcription activator or repressor depending on the leucine zipper protein member it is associated with. JDP2 forms a homodimer or heterodimer with c-Jun, JUNB, JUND, Fra2, ATF2. and acts as a general repressor. On the other hand, JDP2 form a stable heterodimer with CHOP10 to enhance TRE- but not CRE-dependent transcription. In addition, JDP2 has been shown to directly associate with the progesterone receptor (PR) and functionally acts as a coactivator of progesterone-dependent PR-mediated gene transcription. Other proteins such as interferon regulatory factor-2-binding protein-1 (IRF2BP1). CCAAT/enhancer-binding protein gamma (C/EBPγ), HDAC3 and HDAC6 have also been demonstrated to associate with JDP2.
Cell differentiation
JDP2 plays a role in cell differentiation in several systems. Ectopic expression of JDP2 inhibits the retinoic acid-induced differentiation of F9 cells and adipocyte differentiation. By contrast, JDP2 induces terminal muscle cell differentiation in C2 myoblasts and reduces the tumorigenicity of rhabdomyosarcoma cells and restored their ability to differentiate into myotubes. It is also reported that JDP2 plays an important role in the RANK-mediated osteoclast differentiation. Further, JDP2 is involved in neutrophil differentiation and transcription factor Tbx3-mediated osteoclastogenesis for host defense and bone homeostasis. Methylome mapping suggests that JDP2 plays a role in cell progenitor differentiation of megakaryocytes.
Regulation of cell cycle and p53 signaling
JDP2 induces cell cycle arrest through cyclin D, p53, and cyclin A transcription, by increasing JUNB, JUND, and Fra2, and by decreasing c-JUN through the loss of p27kip1. JDP2 downregulates p53 transcription, which promotes leukemogenesis. Mouse p53 protein negatively regulates the JDP2 promoter in F9 cells as part of the JDP2˗p53 autoregulatory circuit. By contrast, JDP2-knockout mice exhibit in downregulation of p53 and p21 proteins.
Apoptosis and senescence
JDP2 appears to be involved in the inhibition of apoptosis. Depletion of JDP2 induces cell death similar to apoptosis. A study also demonstrated that UV irradiation induces JDP2 expression, which in turn down-regulates expression of p53 and thereby protects cells from UV-mediated programmed cell death. Heart-specific JDP2 overexpression protects cardiomyocytes against hypertrophic growth and TGFβ–induced apoptosis. In other settings, JDP2 has been shown to play an important role in the regulation of cellular senescence. JDP2-deficient mouse embryonic fibroblasts are resistant to replicative senescence by recruiting polycomb-repressive complexes (PRC1 and PRC2) to the promoters at the p16Ink4a locus.
Oxidative stress and antioxidative response
The increased accumulation of intracellular reactive oxygen species (ROS) and 8-oxo-dGuo, one of the major products of DNA oxidation, and the reduced expression of several transcripts involved in ROS metabolism in Jdp2-deficient MEFs argue that JDP2 is required to hold ROS levels in check. Furthermore, JDP2 binds directly to the antioxidant responsive element (ARE) core sequence, associates with Nrf2 and MafK (Nrf2–MafK) via basic leucine zipper domains, and increases DNA-binding activity of the Nrf2–MafK complex to the ARE and the transcription of ARE-dependent genes such as HO1 and NQO1. Therefore, JDP2 functions as an integral component of the Nrf2–MafK complex to modulate antioxidant and detoxification programs.
Nuclear reprogramming
JDP2, which has been shown to regulate Wnt signaling pathway and prevent ROS production, may play roles in cell reprogramming. Indeed, a study demonstrated that DAOY medulloblastoma cells can be reprogrammed successfully by JDP2 and the defined factor OCT4 to become induced pluripotent stem cells (iPSC)-like cells. This iPSC-like cells expressed stem cell-like characteristics including alkaline phosphatase activity and some stem cell markers, including SSEA3, SSEA4 and Tra-1-60. Later, another study also showed that JDP2 can substitute Oct4 to generate iPSCs with Klf4, Sox2 and Myc (KSM) or KS from somatic cells. Moreover, they showed that JDP2 anchors five non-Yamanaka factors (ID1, JHDM1B, LRH1, SALL4, and GLIS1) to reprogram mouse embryonic fibroblasts into iPSCs.
Oncogene or tumor suppressor gene
JDP2 may act as a double-edge sword in tumorigenesis. It is reported that JDP2 inhibits Ras-dependent cell transformation in NIH3T3 cells and tumor development in xenografts transplanted into SCID mice. Constitutive expression of JDP2 in rhabdomyosarcoma cells reduced their tumorigenic characteristics. On the other hand, JDP2 induces partial oncogenic transformation of chicken embryonic fibroblasts. Studies using high throughput viral insertional mutagenesis analysis also revealed that JDP2 functions as an oncogene. JDP2-transgenic mice display potentiation of liver cancer, higher mortality and increase number and size of tumors, especially when JDP2 expression is at the promotion stage.
Cancer and disease markers
JDP2 shows the gene amplification of head and neck squamous-cell carcinoma. In pancreatic carcinoma, downregulation of JDP2 is correlated with lymph node metastasis and distant metastasis and strongly associated with the post-surgery survival time, indicating that JDP2 may serve as a biomarker to predict the prognosis of patients with pancreatic cancer. In addition, JDP2 overexpression reverses the epithelial-to-mesenchymal transition (EMT) induced by co-treatment with TGF-β1 and EGF in human pancreatic BxPC-3 cells, suggesting that JDP2 may be a molecular target for pancreatic carcinoma intervention. Furthermore, it has been shown that the expression level of JDP2 gene upon acute myocardial infarction (AMI) is highly specific and a sensitive biomarker for predicting heart failure. In T cell acute lymphoblastic leukaemia, JDP2 regulates pro-survival signalling through direct transcriptional regulation of MCL1 and leads to steroid resistance in vivo.
JDP2 targets and JDP2-regulated genes
JDP2 is involved in the modulation of gene expression. For example, JDP2 regulates MyoD gene expression with c-Jun and gene for galectin-7. JDP2 functionally associated with HDAC3 and acts as a repressor to inhibit the amino acid regulation of CHOP transcription. JDP2 and ATF3 are involved in recruiting HDACs to the ATF3 promoter region resulting in transcriptional repression of ATF3. JDP2 inhibits the promoter of the Epstein–Barr virus (EBV) immediate early gene BZLF1 for the regulation of the latent-lytic switch in EBV infection.
Interactions
JDP2 (gene) has been shown to interact with Activating transcription factor 2.
Notes
References
Further reading
External links
Transcription factors | Jun dimerization protein | Chemistry,Biology | 2,525 |
10,670,746 | https://en.wikipedia.org/wiki/Peroxin-7 | Peroxin-7 is a receptor associated with Refsum's disease and rhizomelic chondrodysplasia punctata type 1.
See also
Peroxin
External links
GeneReviews/NCBI/NIH/UW entry on Refsum Disease
GeneReviews/NIH/NCBI/UW entry on Rhizomelic Chondrodysplasia Punctata Type 1 | Peroxin-7 | Chemistry,Biology | 91 |
3,879,598 | https://en.wikipedia.org/wiki/Tension%20%28physics%29 | Tension is the pulling or stretching force transmitted axially along an object such as a string, rope, chain, rod, truss member, or other object, so as to stretch or pull apart the object. In terms of force, it is the opposite of compression. Tension might also be described as the action-reaction pair of forces acting at each end of an object.
At the atomic level, when atoms or molecules are pulled apart from each other and gain potential energy with a restoring force still existing, the restoring force might create what is also called tension. Each end of a string or rod under such tension could pull on the object it is attached to, in order to restore the string/rod to its relaxed length.
Tension (as a transmitted force, as an action-reaction pair of forces, or as a restoring force) is measured in newtons in the International System of Units (or pounds-force in Imperial units). The ends of a string or other object transmitting tension will exert forces on the objects to which the string or rod is connected, in the direction of the string at the point of attachment. These forces due to tension are also called "passive forces". There are two basic possibilities for systems of objects held by strings: either acceleration is zero and the system is therefore in equilibrium, or there is acceleration, and therefore a net force is present in the system.
Tension in one dimension
Tension in a string is a non-negative vector quantity. Zero tension is slack. A string or rope is often idealized as one dimension, having fixed length but being massless with zero cross section. If there are no bends in the string, as occur with vibrations or pulleys, then tension is a constant along the string, equal to the magnitude of the forces applied by the ends of the string. By Newton's third law, these are the same forces exerted on the ends of the string by the objects to which the ends are attached. If the string curves around one or more pulleys, it will still have constant tension along its length in the idealized situation that the pulleys are massless and frictionless. A vibrating string vibrates with a set of frequencies that depend on the string's tension. These frequencies can be derived from Newton's laws of motion. Each microscopic segment of the string pulls on and is pulled upon by its neighboring segments, with a force equal to the tension at that position along the string.
If the string has curvature, then the two pulls on a segment by its two neighbors will not add to zero, and there will be a net force on that segment of the string, causing an acceleration. This net force is a restoring force, and the motion of the string can include transverse waves that solve the equation central to Sturm–Liouville theory:
where is the force constant per unit length [units force per area], is the ...., is the ...., and are the eigenvalues for resonances of transverse displacement on the string, with solutions that include the various harmonics on a stringed instrument.
Tension of three dimensions
Tension is also used to describe the force exerted by the ends of a three-dimensional, continuous material such as a rod or truss member. In this context, tension is analogous to negative pressure. A rod under tension elongates. The amount of elongation and the load that will cause failure both depend on the force per cross-sectional area rather than the force alone, so stress = axial force / cross sectional area is more useful for engineering purposes than tension. Stress is a 3x3 matrix called a tensor, and the element of the stress tensor is tensile force per area, or compression force per area, denoted as a negative number for this element, if the rod is being compressed rather than elongated.
Thus, one can obtain a scalar analogous to tension by taking the trace of the stress tensor.
System in equilibrium
A system is in equilibrium when the sum of all forces is zero.
For example, consider a system consisting of an object that is being lowered vertically by a string with tension, T, at a constant velocity. The system has a constant velocity and is therefore in equilibrium because the tension in the string, which is pulling up on the object, is equal to the weight force, mg ("m" is mass, "g" is the acceleration caused by the gravity of Earth), which is pulling down on the object.
System under net force
A system has a net force when an unbalanced force is exerted on it, in other words the sum of all forces is not zero. Acceleration and net force always exist together.
For example, consider the same system as above but suppose the object is now being lowered with an increasing velocity downwards (positive acceleration) therefore there exists a net force somewhere in the system. In this case, negative acceleration would indicate that .
In another example, suppose that two bodies A and B having masses and , respectively, are connected with each other by an inextensible string over a frictionless pulley. There are two forces acting on the body A: its weight () pulling down, and the tension in the string pulling up. Therefore, the net force on body A is , so . In an extensible string, Hooke's law applies.
Strings in modern physics
String-like objects in relativistic theories, such as the strings used in some models of interactions between quarks, or those used in the modern string theory, also possess tension. These strings are analyzed in terms of their world sheet, and the energy is then typically proportional to the length of the string. As a result, the tension in such strings is independent of the amount of stretching.
See also
Continuum mechanics
Fall factor
Surface tension
Tensile strength
Traction (mechanics)
Hydrostatic pressure
References
Solid mechanics | Tension (physics) | Physics | 1,192 |
69,828,148 | https://en.wikipedia.org/wiki/Desmethylsibutramine | Desmethylsibutramine (also known as norsibutramine and BTS-54354) is an active metabolite of the anorectic drug sibutramine. It is a more potent monoamine reuptake inhibitor than sibutramine and has been sold as an ingredient in weight loss products sold as dietary supplements, along with related compounds such as the N-ethyl and 3,4-dichloro derivatives.
See also
α-PHiP
4-Chloro-alpha-pyrrolidinovalerophenone
Chlorosipentramine
Isohexylone
Venlafaxine
References
Anorectics
4-Chlorophenyl compounds
Cyclobutanes
Phenethylamines
Serotonin–norepinephrine–dopamine reuptake inhibitors
Stimulants
Substituted amphetamines | Desmethylsibutramine | Chemistry | 184 |
20,719,072 | https://en.wikipedia.org/wiki/Ice%20cloud | An ice cloud is a colloid of ice particles dispersed in air. The term has been used to refer to clouds of both water ice and carbon dioxide ice on Mars.
Such clouds can be sufficiently large and dense to cast shadows on the Martian surface.
Cirrus and noctilucent clouds on Earth contain ice particles.
See also
IceCube (spacecraft), a satellite used to map ice clouds
References
Atmosphere of Mars | Ice cloud | Astronomy | 88 |
24,798,057 | https://en.wikipedia.org/wiki/Thymidine%20diphosphate%20glucose | Thymidine diphosphate glucose (often abbreviated dTDP-glucose or TDP-glucose) is a nucleotide-linked sugar consisting of deoxythymidine diphosphate linked to glucose. It is the starting compound for the syntheses of many deoxysugars.
Biosynthesis
DTDP-glucose is produced by the enzyme glucose-1-phosphate thymidylyltransferase and is synthesized from dTTP and glucose-1-phosphate. Pyrophosphate is a byproduct of the reaction.
Uses within the cell
DTDP-glucose goes on to form a variety of compounds in nucleotide sugars metabolism. Many bacteria utilize dTDP-glucose to form exotic sugars that are incorporated into their lipopolysaccharides or into secondary metabolites such as antibiotics. During the syntheses of many of these exotic sugars, dTDP-glucose undergoes a combined oxidation/reduction reaction via the enzyme dTDP-glucose 4,6-dehydratase, producing dTDP-4-keto-6-deoxy-glucose.
References
Biochemistry
Nucleotides
Monosaccharides | Thymidine diphosphate glucose | Chemistry,Biology | 243 |
25,133,016 | https://en.wikipedia.org/wiki/Wiki%20hosting%20service | A wiki hosting service, or wiki farm, is a server or an array of servers that offers users tools to simplify the creation and development of individual, independent wikis.
Prior to wiki farms, someone who wanted to operate a wiki had to install the software and manage the server(s) themselves. With a wiki farm, the farm's administration installs the core wiki code once on its own servers, centrally maintains the servers, and establishes unique space on the servers for the content of each individual wiki with the shared core code executing the functions of each wiki.
Both commercial and non-commercial wiki farms are available for users and online communities. While most of the wiki farms allow anyone to open their own wiki, some impose restrictions. Many wiki farm companies generate revenue through the insertion of advertisements, but often allow payment of a monthly fee as an alternative to accepting ads.
Some examples of wiki hosting services are: Fandom (originally called Wikia), a for-profit wiki-hosting service created by Jimmy Wales and Angela Beesley Starling in 2004, and Miraheze, a non-profit wiki-hosting service created by John Lewis and Ferran Tufan in 2015.
Comparison of wiki hosting services
This comparison of wiki hosting services or wiki farms is not comprehensive, it details only those 'notable' enough (in Wikipedia terms) to be included. A useful comprehensive comparison of wiki farms can be found on MediaWiki's site, at mw:Hosting services.
Online services which host wiki-style editable web pages. General characteristics of cost, presence of advertising, licensing are compared, as are technical differences in editing, features, wiki engine, multilingual support and syntax support.
This table compares general information for several of the more than 100 wiki hosting services that exist.
All the mentioned services have WYSIWYG editing.
Deprecated wiki hosts
This section is for hosts that were previously in the list above but no longer are up and running.
Wikispaces
Notes
References
External links
Computers/Software/Groupware/Wiki/Wiki Farms at Curlie
Wikimatrix, with interactive selection of wikifarms based on user preference, now only available through the Wayback Machine.
Web hosting | Wiki hosting service | Technology | 475 |
39,032,561 | https://en.wikipedia.org/wiki/Design-Oriented%20Programming | Design-oriented programming is a way to author computer applications using a combination of text, graphics, and style elements in a unified code-space. The goal is to improve the experience of program writing for software developers, boost accessibility, and reduce eye-strain. Good design helps computer programmers to quickly locate sections of code using visual cues typically found in documents and web page authoring.
User interface design and graphical user interface builder research are the conceptual precursors to design-oriented programming languages. The former focus on the software experience for end users of the software application and separate editing of the user interface from the code-space. The important distinction is that design-oriented programming involves user experience of programmers themselves and fully merges all elements into a single unified code-space.
See also
User interface design
Graphical user interface builder
Elements of graphical user interfaces
Visual programming language
Experience design
User experience design
Usability
References
Visual programming
Intro to Design-Oriented Programming Languages
Computer programming | Design-Oriented Programming | Technology,Engineering | 191 |
58,100,243 | https://en.wikipedia.org/wiki/Spider%20shot | Spider shot was a variation of chain shot with multiple chains.
See also
Round shot
Heated shot
Canister shot
Grapeshot
References
Projectiles
Artillery ammunition
Balls
Chains
Metallic objects | Spider shot | Physics | 34 |
8,612,835 | https://en.wikipedia.org/wiki/Kluyveromyces%20marxianus | Kluyveromyces marxianus in ascomycetous yeast and member of the genus, Kluyveromyces. It is the sexual stage (teleomorph) of Atelosaccharomyces pseudotropicalis also known as Candida kefyr. This species has a homothallic mating system and is often isolated from dairy products.
History
Taxonomy
This species was first described in the genus Saccharomyces as S. marxianus by the Danish mycologist, Emil Christian Hansen from beer wort. He named the species for the zymologist, Louis Marx of Marseille who first isolated it from grape. The species was transferred to the genus Kluyveromyces by van der Walt in 1956. Since then, 45 species have been recognized in this genus.
The anamorphic basionym Saccharomyces kefyr was created by Beijerinck, M.W. in 1889 in an article titled Sur le kéfir ("On kefir" in English); the type material is a grain of kefir. The other commonly-used anamorphic basionym Endomyces pseudotropicalis was coined by Castell. in 1911, its type strain having been isolated from a Sri Lankan patient.
Phylogeny
The closest relative of Kluyveromyces marxianus is the yeast Kluyveromyces lactis, often used in the dairy industry. Both Kluyveromyces and Saccharomyces are considered a part of the "Saccharomyces complex", subclade of the Saccharomycetes. Using 18S rRNA gene sequencing, it was suggested that K. marxianus, K. aestuarii, K. dobzhanskii, K. lactic, K. wickerhamii, K. blattae, K. thermotolerans, and collectively constituted a distinct clade of separate ancestry from the central clade in the genus Kluyveromyces. Within this complex, two categories are defined based on the presence in certain taxa of a whole-genome duplication event: the two clades are referred to as pre-Whole Genome Duplication (WGD) and post-WGD. Kluyveromyces species are affiliated with the first of this clades while species of Saccharomyces belong to the latter. Separation of these clades based on the presence of the WGD event explains why, even though the two species are closely related, fundamental differences exist between them.
Growth and morphology
Colonies of K. marxianus are cream to brown in colour with the occasional pink pigmentation due to production of the iron chelate pigment, pulcherrimin. When grown on Wickerham's Yeast-Mold (YM) agar, the yeast cells appear globose, ellipsoidal or cylindrical, 2–6 x 3–11 μm in size. In a glucose-yeast extract broth, K. marxianus grows to produce a ring composed of sediment. A thin pellicle may be formed. In a Dalmau plate culture containing cornmeal agar and Polysorbate 80, K. marxianus forms a rudimentary to branched pseudomycelium with few blastospores. K. marxianus is thermotolerant, exhibiting a high growth rate at .
Physiology and reproduction
Kluyveromyces marxianus is an aerobic yeast capable of respiro-fermentative metabolism that consists of simultaneously generating energy from both respiration via the TCA cycle and ethanol fermentation. The balance between respiration and fermentation metabolisms is strain specific. This species also ferments inulin, glucose, raffinose, sucrose and lactose into ethanol. K. marxianus is widely used in industry because of its ability to use lactose. Two genes, LAC12 and LAC4, allow K. marxianus to absorb and use lactose as a carbon source. This species is considered to be a "crabtree negative fungus", meaning it is unable to convert sugars into ethanol as effectively as crabtree positive taxa such as S. cerevisiae. Studies, however, deem it to be crabtree positive which is likely due to strain differences since K. marxianus possesses the necessary genes to be crabtree positive. K. marxianus is highly thermotolerant and able to withstand temperatures up to . K. marxianus is also able to use multiple carbon substrata at the same time making it highly suited to industrial use. When glucose concentrations become depleted to 6 g/L, the lactose co-transport initiates.
The formation of the ascospores occurs through the conjugation of the haploid cells preceding the formation of the ascus. Alternatively, ascosporogensis can arise directly from diploid cells. Each ascus contains 1–4 ascospores. The ploidy of K. marxianus was originally thought to be a haploid but recent research has shown that many strains used in research and industry are diploid. These conflicting findings suggest that K. marxianus can exist in vegetative form either as a haploid and a diploid.
Habitat and ecology
Kluyveromyces marxianus has been isolated in dairy products, sisal leaves, and sewage from sugar manufacturing factories. It is also a naturally occurring colonist of plants, including corn.
Human disease
Kluyveromyces marxianus is not usually an agent of human disease, although infection in humans can occur in immunocompromised individuals. This species has been associated with candidemia and has been recovered from catheters. It has also found in biofilms on other indwelling devices such as pacemakers and prosthetic heart valves. Between 1–3 % of cases involving K. marxianus that have been reported oncology patients, surgical wards, female genital infections and upper respiratory infections. Treatment with amphotericin B have been effective against K. marxianus in one case report.
Industrial applications
Industrial use of K. marxianus is chiefly in the conversion of lactose to ethanol as a precursor for the production of biofuel. The ability for K. marxianus to reduce lactose is useful because of the potential to transform industrial whey waste, a problematic waste product for disposal, into useful biomass for animal feed, food additives or fuel. Certain strains of the fungus can also be used to convert whey to ethyl acetate, an alternative fuel source. K. marxianus is also used to produce the industrial enzymes: inulinase, β-galactosidase, and pectinase. Due to the heat tolerance of K. marxianus, high heat fermentations are feasible, reducing the costs normally expended for cooling as well as the potential for contamination by other fungi or bacteria. In addition, fermentations at higher temperatures occur more rapidly, making production much more efficient. Due to the ability of K. marxianus to simultaneously utilize lactose and glucose, the prevalence of K. marxianus in industrial settings is high as it decreases production time and increases productivity. Recent efforts have attempted to use K. marxianus in the production of food flavourings from waste products tomato and pepper pomaces as substrata.
References
External links
Yeasts
Saccharomycetaceae
Fungi described in 1888
Fungus species | Kluyveromyces marxianus | Biology | 1,568 |
4,139,340 | https://en.wikipedia.org/wiki/Federation%20of%20German%20Scientists | The Federation of German Scientists - VDW (Vereinigung Deutscher Wissenschaftler e. V.) is a German non-governmental organization.
History
Since its founding 1959 by Carl Friedrich von Weizsäcker, Otto Hahn, Max Born and further prominent nuclear scientists, known as Göttinger 18, who had previously publicly declared their position against the nuclear armament of the German Bundeswehr, the Federation has been committed to the ideal of responsible Wissenschaft. The founders were almost identical to the "Göttinger 18" (compare the historical Göttingen Seven). Both the "Göttingen Manifesto" and the formation of the VDW were an expression of the new sense of responsibility felt by Otto Hahn and some scientists after the dropping of atomic bombs on Hiroshima and Nagasaki. The VDW tried to mirror the American Federation of Atomic Scientists. VDW has been identified as Western Germany's Pugwash group.
Members of VDW feel committed to taking into consideration the possible military, political and economical implications and possibilities of atomic misuse when carrying out their scientific research and teaching. The Federation of German Scientists comprises around 400 scholars of different fields. The Federation of German Scientists addresses both interested members of the public and decision-makers on all levels of politics and society with its work. The politician Egon Bahr was a longstanding member. Georg Picht presented a radio series about the Limits of growth on behalf of the VDW in the 1970s. In 2005/2006, the VDW was the patron and main contributor to the Potsdam Manifesto‚ 'We have to learn to think in a new way’ and the Potsdam Denkschrift under co-authorship of Hans Peter Duerr and Daniel Dahm, together with Rudolf zur Lippe. Since 2022 Ulrike Beisiegel and Götz Neuneck are co-chairs of the VDW.
VDW was closely connected with the German Friedensbewegung (peace movement) in the 1980s. After 1999 VDW tried to regain public interest with the establishment of the Whistleblower Prize, awarded together with the German branch of the International Association of Lawyers Against Nuclear Arms (IALANA).
Whistleblower Prize
The Whistleblower Prize worth 3,000 euro, is given biannually and was established in 1999. In 2015, the selection of Gilles-Éric Séralini generated some controversy. Ulrich Bahnsen in Die Zeit described VDW and IALANA as consisting of busybodies with best wills - and worst possible outcome in the case of this award. The opinion piece, featured in Zeit Online, described the awarding of Séralini as a failure, and viewed his status as a "whistleblower" as questionable, in light of his use of "junk science" to support anti-GMO activism.
Recipients
1999 Alexander Nikitin
2001 Margrit Herbst
2003 Daniel Ellsberg
2005 Theodore A. Postol and Arpad Puztai
2007 Brigitte Heinisch and Liv Bode, in relation with the alleged Bornavirus
2009 Rudolf Schmenger and Frank Wehrheim, taxation experts in the state of Hessen
2011 Chelsea Manning and Rainer Moormann
2013 Edward Snowden
2015 Gilles-Éric Séralini and Brandon Bryant
References
External links
Website of the Federation of German Scientists - VDW
Website Goettinger 18
Anti–nuclear weapons movement
Organizations established in 1959
1959 establishments in West Germany
Pacifism in Germany
Science advocacy organizations
Pugwash Conferences on Science and World Affairs
Ethics of science and technology | Federation of German Scientists | Technology | 720 |
37,868,550 | https://en.wikipedia.org/wiki/C36H22O18 | {{DISPLAYTITLE:C36H22O18}}
The molecular formula C36H22O18 (molar mass: 742.52 g/mol, exact mass: 742.0806128 u) may refer to:
Dieckol, an eckol-type phlorotannin
6,6'-Bieckol, an eckol-type phlorotannin
8,8′-Bieckol, an eckol-type phlorotannin | C36H22O18 | Chemistry | 111 |
50,769,242 | https://en.wikipedia.org/wiki/Clean%20ring | In mathematics, a clean ring is a ring in which every element can be written as the sum of a unit and an idempotent. A ring is a local ring if and only if it is clean and has no idempotents other than 0 and 1. The endomorphism ring of a continuous module is a clean ring. Every clean ring is an exchange ring. A matrix ring over a clean ring is itself clean.
References
Ring theory | Clean ring | Mathematics | 94 |
42,071,787 | https://en.wikipedia.org/wiki/Indira%20Paryavaran%20Bhawan | Indira Paryavaran Bhawan is India's first on-site net-zero building located in New Delhi, India. The building houses the Ministry of Environment, Forest and Climate Change (MoEFCC) accommodating three ministers and their offices along with about 600 officials. The building, designed and constructed by the Central Public Works Department (CPWD), was completed in 2013 at a cost of INR 209 Crore.
The inauguration of the building, 28 February 2014, was conducted by the then prime minister Dr. Manmohan Singh. The building is rated as a five-star GRIHA (Green Rating for Integrated Habitat Assessment) by MNRE and LEED India Platinum by Indian Green Building Council (IGBC) rating. The building has its own solar power plant, sewage treatment facility, fully automatic robotic multi-level car parking system facility & puzzle parking facility, and geothermal heat exchange system.
Details
Indira Paryavaran Bhawan consists of two blocks within the premises connected through a corridor. Each block is a G+7 storey structure with 3 basements. The total floor area of the campus is 32,000 sq.metre. Each floor consists of office spaces, meeting rooms, conference rooms etc. The building consists of 7 elevators and a central atrium located in between the two blocks.
Indira Paryavaran Bhawan is located in a composite climate zone, a mix of hot, dry, humid, and cold climatic conditions, and the design involves multiple active, passive, and renewable strategies to achieve net zero goal. The building is divided into 5 sections: Vayu (Wind), Agni (Fire), Jal (Water), Prithvi (Earth), and Aakash (Space) depicting the 5 elements that all matters are composed of, as per Hinduism. Indira Paryavaran Bhawan is a set example that impinges on society's consciousness towards environmental awareness for adopting green building concepts in India.
The Union environment ministry is facing a challenge of a garden variety - bird droppings, soiling the courtyard of Indira Paryavaran Bhawan, which houses it, and is amongst the India's highest green-rated buildings. Individuals or organizations which will offer the best solution will be awarded an amount of ₹1 lakh.
Design
Passive Design Strategies
Orientation
The orientation of the building is set towards north south direction, to accommodate natural daylight and air movement in the building, a central atrium and corridor provide cross ventilation within the building.
Landscaping and Horticulture
More than 50% of the area outside the building is covered with plantations, to conserve as many existing trees as possible, out of a total of 79 trees, only 19 trees are cut and 11 trees are transplanted. The pathways and circulation roads in the building are made with grass paver blocks for ground water percolation and ground water recharge. The 7th floor of building also consists of a terrace garden.
Daylighting and Ventilation
The building is designed to ensure daylight in more than 75% of the floor space and to reduce dependency on active lighting devices. The central atrium located between the two blocks allows natural movement of air due to stack effect. The provision of windows further enhances the process of cross ventilation.
Building Envelope and Fenestration
The building envelope construction comprises heavy weight construction. The external wall consists of 30 cm thick Autoclave Aerated Concrete (AAC) block, 7 cm thick mineral wool insulation, 12 cm thick air gap and 12 cm thick 'Fal-G' [proprietary blend of fly ash (Fa), lime (L) and gypsum (G)] block brick, and has a U-value of .221 W/m2K. The external roof of the building consists of 2 cm thick clay tile, 6 cm thick cement mortar, 4 cm thick PUF insulation, 6 cm thick brick bat coba, 6 cm thick cement mortar,10 cm thick concrete. High reflectance terrace tiles are installed on the building roof for roof cool treatment - low heat ingress, high strength and hard wearing. Windows installed in the building with uPVC (Unplasticized Polyvinyl Chloride) frame are hermetically sealed double glazed with gas filling with a U-Value of 0.26 W/m2K and SHGC of 0.32 and aluminium frame.
Material and Construction technique
Fly ash bricks and heat-insulating Autoclave Aerated Concrete blocks along with fly ash-based mortar and plaster are used for walls. Low energy materials and locally available stones are utilized for flooring. Bamboo jute composite that is rapidly renewable is used for door frames and shutters. Low VOC paints are used to improvise indoor air quality.
Active Design Strategies
Lighting Design
Energy efficient lights are provided in the interior and exterior lighting system of the building. To maximize energy efficiency in lighting, the artificial lighting in the building is regulated using a lux-level sensor. The lighting power density is kept close to 5 W/m2 which is 50% more efficient than the Energy Conservation Building Code 2007 requirement (Lighting Power Density = 11 W/m2). The lighting load is supplied by the building integrated photovoltaic (BIPV) power plant.
Optimized HVAC System
The building is centrally air conditioned. Chilled beam system technology is used to meet 160 TR air conditioning load of the building. The process of air conditioning happens by convection currents rather than air supply by ducts. The chilled beams are used from second to sixth floor and this system has reduced energy utilization by up to 50% as compared to the conventional system. Integrated building management is utilized to control HVAC equipment and to monitor related systems. For energy efficiency, the room temperature is maintained at 26 ±1 °C.
Geothermal Heat Exchange System
To minimize the load on the HVAC system, a vertical closed loop system of geothermal heat exchange system is implemented. This is the first time it has been adopted on a large scale in a government building in India. The system takes advantage of the difference between the ambient temperature and the temperature below the ground level.
The vertical closed loop system consists of 180 vertical bores all over the premises to a depth of 80 meters. A minimum distance of 3 meters between any two bores is retained. Every bore has a 32mm outer diameter HDPE pipe U-loop and is connected in the central air conditioning plant room to the condenser water pipe system. A single U-Loop with a heat rejection capacity of 0.9TR results in a heat rejection capacity of 160TR from 180 vertical bores, resulting in reduction of cooling tower load and subsequent reduction in water consumption.
Renewable Energy Systems
A building integrated photovoltaic (BIPV) Power Plant has been installed on the entire roof surface of the building and court area. This clean and green renewable energy system has helped in meeting the energy demand of the building to achieve the target of net-zero energy.
Robotic Car Parking
Automated parking system is used on all 3 levels of the basement. The first basement is designed for the lobby and puzzle parking system for car entry and exit. The second and third basement floors use robotic dolly parking systems. The capacity for the first basement is 49, the second basement is 126, and the third basement is 170.
Water Management
The landscape and horticulture design of planting native species along with efficient irrigation systems are utilized leading up to 50% reduction in water requirement. The remaining water demand is met by recycling and reusing wastewater, and by implementation of rainwater harvesting systems. Additionally, low discharge and efficient water fixtures are installed including sensor urinals and dual flow cisterns.
Savings
Awards
The building has received the following awards.
References
Low-energy building
Sustainable building
Energy economics
Environmental design
Environment of India
Government buildings in Delhi
Ministry of Environment, Forest and Climate Change | Indira Paryavaran Bhawan | Engineering,Environmental_science | 1,586 |
4,444,657 | https://en.wikipedia.org/wiki/Animal%20repellent | An animal repellent consists of any object or method made with the intention of keeping animals away from personal items as well as food, plants or yourself. Plants and other living organisms naturally possess a special ability to emit chemicals known as semiochemicals as a way to defend themselves from predators. Humans purposely make use of some of those and create a way to repel animals through various forms of protection.
Overview
Repellents generally work by taking advantage of an animal's natural aversion to something, and often the thing chosen is something that the animal has learned to avoid (or instinctively avoids) in its natural environment.
Chemical repellents fall into two main categories, odor and taste. The former work better in the warm season and the latter, which ward off an animal only after it eats, in the cold season. (For example, the smell of the lawn fertilizer Milorganite is claimed to make it an effective repellent.) Such repellents mimic natural substances that deter animals and/or are designed to be so irritating to a specific animal or type of animal that it will avoid the protected object or area. Contact plant-origin repellents such as pepper, peppermint, tarragon, garlic, various essential oils, and castor oil, as well as diatomaceous earth and putrescent egg solids, are examples.
Further, some repellents function by inducing fear in the target animal. Such a repellent may contain animal urine, dried blood, or hair. Some animals will avoid anything that has the odor of the urine of their predators. Tiger urine is thus very effective at keeping away animals. Coyote urine has gained currency as a deer repellent. Fox urine is used to repel rabbits, groundhogs, woodchucks, squirrels and chipmunks. Bobcat urine repels moles, mice, voles and other rodents. Wolf urine is used to repel moose. Used cat litter is also effective. Domestic dogs can be repelled by vinegar.
Other repellents are not chemical. A simple electrified or barbed-wire fence can mechanically repel livestock or predator animals. Some electrical repellent systems have been tested against sharks. High-frequency whistles are used on vehicles to drive deer away from highways, and similar devices are used to deter certain types of insects or rodents. Repellents of this kind for domestic cats and dogs include ultrasonic devices which emit a high-frequency noise that does not affect humans. These types of non-chemical repellents are controversial, both because their effectiveness varies from animal to animal and because there have been few scientific studies conducted to prove that they work. They are, however, safe and humane, as are motion-activated sprinklers and electronic pet barriers, which latter are used by pet owners to confine their own pets to designated areas.
Flashing lights are used to repel lions in Kenya.
The ideal repellent is completely specific for the target animal; that is, it drives away the animal that one wishes to repel without affecting or harming any other animals or people. One type of animal repellent may be effective for raccoons, while another animal repellent may be more effective for skunks. It can be difficult to design a repellent method that drives away only undesirable animals while having no effect on people or other creatures.
Snake repellents
Research has shown that cinnamon oil, clove oil, and eugenol are effective snake repellents. Snakes will retreat when sprayed directly with these oils and will exit cargo or other confined spaces when these oils are introduced to the area.
In ancient times the Greek historian Herodotus noted that Arabian harvesters of frankincense used burning resin from Styrax trees to repel poisonous snakes that lived in the trees.
Camphor
Moth balls
The roots and other parts of Acacia polyacantha subsp. campylacantha emit chemical compounds that repel animals including rats, snakes and crocodiles. For snakes, roots are placed in the rafters of houses.
See also
Bird control spike
Cat repellent
Electronic pest control
Insect repellent
Shark repellent
Chemical ecology
References
External links
Pest control techniques
Chemical ecology
Horticultural techniques
Agronomy
Habitat management equipment and methods
Organic farming | Animal repellent | Chemistry,Biology | 877 |
69,680,149 | https://en.wikipedia.org/wiki/Dysprosium%20phosphide | Dysprosium phosphide is an inorganic compound of dysprosium and phosphorus with the chemical formula DyP.
Synthesis
The compound can be obtained by the reaction of phosphorus and dysprosium at high temperature.
4 Dy + P4 → 4 DyP
Physical properties
DyP has a NaCl structure (a=5.653 Å), where dysprosium is +3 valence. Its band gap is 1.15 eV, and the Hall mobility (μH) is 8.5 cm3/V·s.
DyP forms crystals of a cubic system, space group Fm3m.
Uses
The compound is a semiconductor used in high power, high frequency applications and in laser diodes.
References
Phosphides
Dysprosium compounds
Semiconductors
Rock salt crystal structure | Dysprosium phosphide | Physics,Chemistry,Materials_science,Engineering | 172 |
42,013,569 | https://en.wikipedia.org/wiki/St.%20Johns%20Racquet%20Center | Portland Tennis & Education (formally St. Johns Racquet Center) offers a variety of classes, drills, mixers, & private lessons for tennis & pickleball players of all levels. As a public facility, we welcome everyone. Our court fees are a flat rate that include ball machine access & racquet rental at no extra cost! Racquet stringing service is also offered at affordable prices. Every dollar earned on our public courts is poured directly back into our nonprofit program that offers academic support, tennis & athletic enrichment, life skills, family resources & mental health support to K-12 students enrolled in our after school & summer programs. Every time you play tennis or pickleball, you 'play a point' for PT&E students & families
Since our founding in 1996, 100% of 12th grade PT&E program graduates have graduated from high school on-time and gone on to pursue the post-secondary path of their choosing!
History
The St. Johns Racquet Center was planned in 1976 but delayed until 1979 after problems with shipment from the manufacturer Hess Building Company. The 27,500 ft. prefabricated building cost US$648,000 (US$ adjusted for inflation) was designed by Richard L. Glassford and Associations and manufactured in the Midwest United States. The total construction cost reached US$883,537 (US$ adjusted for inflation), most of which came from Economic Development Administration, when the building was erected. A failed plan in 1981 called for part of the racquet center be made a roller rink.
In October 1981, a National Association of Intercollegiate Athletics (NAIA) round robin tournament was held at the racquet center. The maximum capacity of the building in accordance to the fire code is 20 people. Threats to close the center came in 1983 from Portland Parks & Recreation commissioner Charles Jordan. Instead the hours of operations were cut.
A racquetball club known as the "Smashers" was organized at the center in 1984. The center held a table tennis tournament in 1987 and 1988. Plans to allow a private company operate the center were drawn up in 1994 but were quickly abandoned. A similar plan came up in 2006 and also failed. A plan to tear the center down to construct an apartment building was proposed in 2007 but was shelved and it was never recommended again. The center hosts several Portland Interscholastic League tennis matches. It is currently operated by Portland After-School Tennis & Education (PASTE).
See also
List of sports venues in Portland, Oregon
References
External links
St Johns Racquet Center — PortlandOregon.gov
[./Http://www.ptande.org Portland Tennis & Education]
St Johns Racquet Club — TennisPoint.com
1979 establishments in Oregon
Sports venues completed in 1979
Sports venues in Portland, Oregon
Tennis venues in the United States
Racquetball in the United States
Parks in Portland, Oregon
Buildings and structures in St. Johns, Portland, Oregon
Prefabricated buildings | St. Johns Racquet Center | Engineering | 610 |
51,745,258 | https://en.wikipedia.org/wiki/Isolation%20to%20facilitate%20abuse | Isolation (physical, social or emotional) is often used to facilitate power and control over someone for an abusive purpose. This applies in many contexts such as workplace bullying, elder abuse, domestic abuse, child abuse, and cults.
Isolation reduces the opportunity of the abused to be rescued or escape from the abuse. It also helps disorient the abused and makes the abused more dependent on the abuser. The degree of power and control over the abused is contingent upon the degree of their physical or emotional isolation.
Isolation of the victim from the outside world is an important element of psychological control. Isolation includes controlling a person's social activity: whom they see, whom they talk to, where they go and any other method to limit their access to others. It may also include limiting what material they can read or watch. It can also include insisting on knowing where they are and requiring permission for medical care. The abuser exhibits hypersensitive and reactive jealousy.
Isolation can be aided by:
economic abuse thus limiting the victim's actions as they may then lack the necessary resources to resist or escape from the abuse
smearing or discrediting the abused amongst their community so the abused does not get help or support from others
divide and conquer
In cults
Various isolation techniques may be used by cults:
separating from family and community
taking control of the handling of the victim's resources and property
undoing (mind control)
physical isolation
extortion/dependency tactics
controlling victim's access to necessities.
In workplace bullying
Isolation is a common element of workplace bullying. It includes preventing access to opportunities, physical or social isolation, withholding necessary information, keeping the target "out of the loop", ignoring or excluding.
Workplace isolation is a defined category in the workplace power and control wheel.
References
Power (social and political) concepts
Control (social and political)
Abuse
Workplace harassment and bullying
Psychological abuse
Domestic violence | Isolation to facilitate abuse | Biology | 385 |
48,782,005 | https://en.wikipedia.org/wiki/Astrophysical%20fluid%20dynamics | Astrophysical fluid dynamics is a branch of modern astronomy which deals with the motion of fluids in outer space using fluid mechanics, such as those that make up the Sun and other stars. The subject covers the fundamentals of fluid mechanics using various equations, such as continuity equations, the Navier–Stokes equations, and Euler's equations of collisional fluids. Some of the applications of astrophysical fluid dynamics include dynamics of stellar systems, accretion disks, astrophysical jets, Newtonian fluids, and the fluid dynamics of galaxies.
Introduction
Astrophysical fluid dynamics applies fluid dynamics and its equations to the movement of the fluids in space. The applications are different from regular fluid mechanics in that nearly all calculations take place in a vacuum with zero gravity.
Most of the interstellar medium is not at rest, but is in supersonic motion due to supernova explosions, stellar winds, radiation fields and a time dependent gravitational field caused by spiral density waves in the stellar discs of galaxies. Since supersonic motions almost always involve shock waves, shock waves must be accounted for in calculations. The galaxy also contains a dynamically significant magnetic field, meaning that the dynamics are governed by the equations of compressible magnetohydrodynamics. In many cases, the electrical conductivity is large enough for the ideal MHD equations to be a good approximation, but this is not true in star forming regions where the gas density is high and the degree of ionization is low.
Star formation
An example problem is that of star formation. Stars form out of the interstellar medium, with this formation mostly occurring in giant molecular clouds such as the Rosette Nebula. An interstellar cloud can collapse due to its self-gravity if it is large enough; however, in the ordinary interstellar medium this can only happen if the cloud has a mass of several thousands of solar masses—much larger than that of any star. Stars may still form, however, from processes that occur if the magnetic pressure is much larger than the thermal pressure, which is the case in giant molecular clouds. These processes rely on the interaction of magnetohydrodynamic waves with a thermal instability. A magnetohydrodynamic wave in a medium in which the magnetic pressure is much larger than the thermal pressure can produce dense regions, but they cannot by themselves make the density high enough for self-gravity to act. However, the gas in star forming regions is heated by cosmic rays and is cooled by radiative processes. The net result is that a gas in a thermal equilibrium state in which heating balances cooling can exist in three different phases at the same pressure: a warm phase with a low density, an unstable phase with intermediate density and a cold phase at low temperature. An increase in pressure due to a supernova or a spiral density wave can shift the gas from the warm phase to the unstable phase, with a magnetohydrodynamic wave then being able to produce dense fragments in the cold phase whose self-gravity is strong enough for them to collapse into stars.
Basic concepts
Concepts of fluid dynamics
Many regular fluid dynamics equations are used in astrophysical fluid dynamics. Some of these equations are:
Continuity equations
The Navier–Stokes equations
Euler's equations
Conservation of mass
The continuity equation is an extension of conservation of mass to fluid flow. Consider a fluid flowing through a fixed volume tank having one inlet and one outlet. If the flow is steady (no accumulation of fluid within the tank), then the rate of fluid flow at entry must be equal to the rate of fluid flow at the exit for mass conservation. If, at an entry (or exit) having a cross-sectional area m2, a fluid parcel travels a distance in time , then the volume flow rate ( m3s−1) is given by:
but since is the fluid velocity ( ms−1) we can write:
The mass flow rate ( kgs−1) is given by the product of density and volume flow rate
Because of conservation of mass, between two points in a flowing fluid we can write . This is equivalent to:
If the fluid is incompressible, () then:
This result can be applied to many areas in astrophysical fluid dynamics, such as neutron stars.
References
Further reading
Clarke, C.J. & Carswell, R.F. Principles of Astrophysical Fluid Dynamics, Cambridge University Press (2014)
Introduction to Magnetohydrodynamics by P. A. Davidson, Cambridge University Press
Astrophysics
Fluid dynamics
Astronomical sub-disciplines | Astrophysical fluid dynamics | Physics,Chemistry,Astronomy,Engineering | 905 |
5,822,644 | https://en.wikipedia.org/wiki/Basic%20helix-loop-helix%20leucine%20zipper%20transcription%20factors | Basic helix-loop-helix leucine zipper transcription factors are, as their name indicates, transcription factors containing both Basic helix-loop-helix and leucine zipper motifs.
Examples include Microphthalmia-associated transcription factor and Sterol regulatory element binding protein (SREBP).
External links
Gene expression
Transcription factors | Basic helix-loop-helix leucine zipper transcription factors | Chemistry,Biology | 67 |
342,086 | https://en.wikipedia.org/wiki/War%20of%20the%20currents | The war of the currents was a series of events surrounding the introduction of competing electric power transmission systems in the late 1880s and early 1890s. It grew out of two lighting systems developed in the late 1870s and early 1880s; arc lamp street lighting running on high-voltage alternating current (AC), and large-scale low-voltage direct current (DC) indoor incandescent lighting being marketed by Thomas Edison's company. In 1886, the Edison system was faced with new competition: an alternating current system initially introduced by George Westinghouse's company that used transformers to step down from a high voltage so AC could be used for indoor lighting. Using high voltage allowed an AC system to transmit power over longer distances from more efficient large central generating stations. As the use of AC spread rapidly with other companies deploying their own systems, the Edison Electric Light Company claimed in early 1888 that high voltages used in an alternating current system were hazardous, and that the design was inferior to, and infringed on the patents behind, their direct current system.
In the spring of 1888, a media furor arose over electrical fatalities caused by pole-mounted high-voltage AC lines, attributed to the greed and callousness of the arc lighting companies that operated them. In June of that year Harold P. Brown, a New York electrical engineer, claimed the AC-based lighting companies were putting the public at risk using high-voltage systems installed in a slipshod manner. Brown also claimed that alternating current was more dangerous than direct current and tried to prove this by publicly killing animals with both currents, with technical assistance from Edison Electric. The Edison company and Brown colluded further in their parallel goals to limit the use of AC with attempts to push through legislation to severely limit AC installations and voltages. Both also colluded with Westinghouse's chief AC rival, the Thomson-Houston Electric Company, to make sure the first electric chair was powered by a Westinghouse AC generator.
By the early 1890s, the war was winding down. Further deaths caused by AC lines in New York City forced electric companies to fix safety problems. Thomas Edison no longer controlled Edison Electric, and subsidiary companies were beginning to add AC to the systems they were building. Mergers reduced competition between companies, including the merger of Edison Electric with their largest competitor, Thomson-Houston, forming General Electric in 1892. Edison Electric's merger with their chief alternating current rival brought an end to the war of the currents and created a new company that now controlled three quarters of the US electrical business. Westinghouse won the bid to supply electrical power for the World's Columbian Exposition in 1893 and won the major part of the contract to build Niagara Falls hydroelectric project later that year (partially splitting the contract with General Electric). DC commercial power distribution systems declined rapidly in numbers throughout the 20th century; the last DC utility in New York City was shut down in 2007.
Background
The war of the currents grew out of the development of two lighting systems; arc lighting running on alternating current and incandescent lighting running on direct current. Both were supplanting gas lighting systems, with arc lighting taking over large area/street lighting, and incandescent lighting replacing gas for business and residential indoor lighting.
Arc lighting
By the late 1870s, arc lamp systems were beginning to be installed in cities, powered by central generating plants. Arc lighting was capable of lighting streets, factory yards, or the interior of large buildings. Arc lamp systems used high voltages (above 3,000 volts) to supply current to multiple series-connected lamps, and some ran better on alternating current.
1880 saw the installation of large-scale arc lighting systems in several US cities including a central station set up by the Brush Electric Company in December 1880 to supply a length of Broadway in New York City with a 3,500–volt demonstration arc lighting system. The disadvantages of arc lighting were: it was maintenance intensive, buzzed, flickered, constituted a fire hazard, was really only suitable for outdoor lighting, and, at the high voltages used, was dangerous to work with.
Edison's direct current company
In 1878 inventor Thomas Edison saw a market for a system that could bring electric lighting directly into a customer's business or home, a niche not served by arc lighting systems. By 1882 the investor-owned utility Edison Illuminating Company was established in New York City. Edison designed his utility to compete with the then established gas lighting utilities, basing it on a relatively low 110-volt direct current supply to power a high resistance incandescent lamp he had invented for the system. Edison direct current systems would be sold to cities throughout the United States, making it a standard with Edison controlling all technical development and holding all the key patents. Direct current worked well with incandescent lamps, which were the principal load of the day. Direct-current systems could be directly used with storage batteries, providing valuable load-leveling and backup power during interruptions of generator operation. Direct-current generators could be easily paralleled, allowing economical operation by using smaller machines during periods of light load and improving reliability. Edison had invented a meter to allow customers to be billed for energy proportional to consumption, but this meter worked only with direct current. Direct current also worked well with electric motors, an advantage DC held throughout the 1880s. The primary drawback with the Edison direct current system was that it ran at 110 volts from generation to its final destination giving it a relatively short useful transmission range: to keep the size of the expensive copper conductors down generating plants had to be situated in the middle of population centers and could only supply customers less than a mile from the plant.
Westinghouse and alternating current
In 1884 Pittsburgh, Pennsylvania inventor and entrepreneur George Westinghouse entered the electric lighting business when he started to develop a DC system and hired William Stanley, Jr. to work on it. In 1885 he read an article in UK technical journal Engineering that described alternating current systems under development. By that time alternating current had gained a key advantage over direct current with the development of transformers that allowed the voltage to be "stepped up" to much higher transmission voltages and then dropped down to a lower end user voltage for business and residential use. The high voltages allowed a central generating station to supply a large area, up to long circuits. Westinghouse saw this as a way to build a truly competitive system instead of simply building another barely competitive DC lighting system using patents just different enough to get around the Edison patents. The Edison DC system of centralized DC plants with their short transmission range also meant there was a patchwork of un-supplied customers between Edison's plants that Westinghouse could easily supply with AC power.
In 1885 Westinghouse purchased the US patents rights to a transformer developed by French engineer Lucien Gaulard (financed by British engineer John Dixon Gibbs). He imported several of these "Gaulard–Gibbs" transformers as well as Siemens AC generators to begin experimenting with an AC-based lighting system in Pittsburgh. That same year William Stanley used the Gaulard-Gibbs design and designs from the Hungarian Ganz company's Z.B.D. transformer to develop the first practical transformer. The Westinghouse Electric Company was formed at the beginning of 1886.
In March 1886 Stanley, with Westinghouse's backing, installed the first multiple-voltage AC power system, a demonstration incandescent lighting system, in Great Barrington, Massachusetts. Expanded to the point where it could light 23 businesses along main street with very little power loss over 4000 feet, the system used transformers to step 500 AC volts at the street down to 100 volts to power incandescent lamps at each location. By fall of 1886 Westinghouse, Stanley, and Oliver B. Shallenberger had built the first commercial AC power system in the US in Buffalo, New York.
The spread of AC
By the end of 1887 Westinghouse had 68 alternating current power stations to Edison's 121 DC-based stations. To make matters worse for Edison, the Thomson-Houston Electric Company of Lynn, Massachusetts (another competitor offering AC- and DC-based systems) had built 22 power stations. Thomson-Houston was expanding their business while trying to avoid patent conflicts with Westinghouse, arranging deals such as coming to agreements over lighting company territory, paying a royalty to use the Stanley AC transformer patent, and allowing Westinghouse to use their Sawyer-Man incandescent bulb patent. Besides Thomson-Houston and Brush there were other competitors at the time, including the United States Illuminating Company and the Waterhouse Electric Light Company. All of the companies had their own electric power systems, arc lighting systems, and even incandescent lamp designs for domestic lighting, leading to constant lawsuits and patent battles between themselves and with Edison.
Safety concerns
Elihu Thomson of Thomson-Houston was concerned about AC safety and put a great deal of effort into developing a lightning arrestor for high-tension power lines as well as a magnetic blowout switch that could shut the system down in a power surge, a safety feature the Westinghouse system did not have. Thomson also worried about what would happen with the equipment after they sold it, assuming customers would follow a risky practice of installing as many lights and generators as they could get away with. He also thought the idea of using AC lighting in residential homes was too dangerous and had the company hold back on that type of installation until a safer transformer could be developed.
Due to the hazards presented by high voltage electrical lines most European cities and the city of Chicago in the US required them to be buried underground. The City of New York did not require burying and had little in the way of regulation so by the end of 1887 the mishmash of overhead wires for telephone, telegraph, fire and burglar alarm systems in Manhattan were now mixed with haphazardly strung AC lighting system wires carrying up to 6,000 volts. Insulation on power lines was rudimentary, with one electrician referring to it as having as much value "as a molasses covered rag", and exposure to the elements was eroding it over time. A third of the wires were simply abandoned by defunct companies and slowly deteriorating, causing damage to, and shorting out the other lines. Besides being an eyesore, New Yorkers were annoyed when a large March 1888 snowstorm (the Great Blizzard of 1888) tore down a large number of the lines, cutting off utilities in the city. This spurred on the idea of having these lines moved underground but it was stopped by a court injunction obtained by Western Union. Legislation to give all the utilities 90 days to move their lines into underground conduits supplied by the city was slowly making its way through the government but that was also being fought in court by the United States Illuminating Company, who claimed their AC lines were perfectly safe.
Edison's anti-AC stance
As AC systems continued to spread into territories covered by DC systems, with the companies seeming to impinge on Edison patents including incandescent lighting, things got worse for the company. The price of copper was rising, adding to the expense of Edison's low voltage DC system, which required much heavier copper wires than higher voltage AC systems. Thomas Edison's own colleagues and engineers were trying to get him to consider AC. Edison's sales force was continually losing bids in municipalities that opted for cheaper AC systems and Edison Electric Illuminating Company president Edward Hibberd Johnson pointed out that if the company stuck with an all DC system it would not be able to do business in small towns and even mid-sized cities. Edison Electric had a patent option on the ZBD transformer, and a 1886 confidential in-house report by electrical engineer Frank Sprague had recommended that the company go AC, but Thomas Edison was against the idea.
After Westinghouse installed his first large scale system, Edison wrote in a November 1886 private letter to Edward Johnson, "Just as certain as death Westinghouse will kill a customer within six months after he puts in a system of any size, He has got a new thing and it will require a great deal of experimenting to get it working practically." Edison seemed to hold a view that the very high voltage used in AC systems was too dangerous and that it would take many years to develop a safe and workable system. Safety and avoiding the bad press of killing a customer had been one of the goals in designing his DC system and he worried that a death caused by a mis-installed AC system could hold back the use of electricity in general. Edison's understanding of how AC systems worked seemed to be extensive. He noted what he saw as inefficiencies and that, combined with the capital costs in trying to finance very large generating plants, led him to believe there would be very little cost savings in an AC venture. Edison was also of the opinion that DC was a superior system (a fact that he was sure the public would come to recognize) and inferior AC technology was being used by other companies as a way to get around his DC patents.
In February 1888 Edison Electric president Edward Johnson published an 84-page pamphlet titled "A Warning from the Edison Electric Light Company" and sent it to newspapers and to companies that had purchased or were planning to purchase electrical equipment from Edison competitors, including Westinghouse and Thomson-Houston, stating that the competitors were infringing on Edison's incandescent light and other electrical patents.
Execution by electricity
As arc lighting systems spread, so did stories of how the high voltages involved were killing people, usually unwary linemen, a strange new phenomenon that seemed to instantaneously strike a victim dead. One such story in 1881 of a drunken dock worker dying after he grabbed a large electric dynamo led Buffalo, New York dentist Alfred P. Southwick to seek some application for the curious phenomenon. He worked with local physician George E. Fell and the Buffalo ASPCA, electrocuting hundreds of stray dogs, to come up with a method to euthanize animals via electricity. Southwick's 1882 and 1883 articles on how electrocution could be a replacement for hanging, using a restraint similar to a dental chair (an electric chair) caught the attention of New York State politicians who, following a series of botched hangings, were desperately seeking an alternative. An 1886 commission appointed by New York governor David B. Hill, which including Southwick, recommended in 1888 that executions be carried out by electricity using the electric chair.
There were early indications that this new form of execution would become mixed up with the war of currents. As part of their fact-finding, the commission sent out surveys to hundreds of experts on law and medicine, seeking their opinions, as well as contacting electrical experts, including Elihu Thomson and Thomas Edison. In late 1887, when death penalty commission member Southwick contacted Edison, the inventor stated he was against capital punishment and wanted nothing to do with the matter. After further prompting, Edison hit out at his chief electric power competitor, George Westinghouse, in what may have been the opening salvo in the war of currents, stating in a December 1887 letter to Southwick that it would be best to use current generated by "'alternating machines,' manufactured principally in this country by Geo. Westinghouse". Soon after the execution by electricity bill passed in June 1888, Edison was asked by a New York government official what means would be the best way to implement the state's new form of execution. "Hire out your criminals as linemen to the New York electric lighting companies" was Edison's tongue-in-cheek answer.
Anti-AC backlash
As the number of deaths attributed to high voltage lighting around the country continued to mount, a cluster of deaths in New York City in the spring of 1888 related to AC arc lighting set off a media frenzy against the "deadly arc-lighting current" and the seemingly callous lighting companies that used it. These deaths included a 15-year-old boy killed on April 15 by a broken telegraph line that had been energized with alternating current from a United States Illuminating Company line; a clerk killed two weeks later by an AC line; and a Brush Electric Company lineman killed in May by the AC line he was cutting. The press in New York seemed to switch overnight from stories about electric lights vs gas lighting to "death by wire" incidents, with each new report seeming to fan public resentment against high voltage AC and the dangerously tangled overhead electrical wires in the city.
Harold Brown's crusade
At this point an electrical engineer named Harold P. Brown, who at that time seemed to have no connection to the Edison company, sent a June 5, 1888 letter to the editor of the New York Post claiming the root of the problem was the alternating current (AC) system being used. Brown argued that the AC system was inherently dangerous and "damnable" and asked why the "public must submit to constant danger from sudden death" just so utilities could use a cheaper AC system.
At the beginning of attacks on AC, Westinghouse, in a June 7, 1888 letter, tried to defuse the situation. He invited Edison to visit him in Pittsburgh and said "I believe there has been a systemic attempt on the part of some people to do a great deal of mischief and create as great a difference as possible between the Edison Company and The Westinghouse Electric Co., when there ought to be an entirely different condition of affairs". Edison thanked him but said "My laboratory work consumes the whole of my time".
On June 8, Brown was lobbying in person before the New York Board of Electrical Control, asking that his letter to the paper be read into the meeting's record and demanding severe regulations on AC including limiting voltage to 300 volts, a level that would make AC next to useless for transmission. There were many rebuttals to Brown's claims in the newspapers and letters to the board, with people pointing out he was showing no scientific evidence that AC was more dangerous than DC. Westinghouse pointed out in letters to various newspapers the number of fires caused by DC equipment and suggested that Brown was obviously being controlled by Edison, something Brown continually denied.
A July edition of The Electrical Journal covered Brown's appearance before the New York Board of Electrical Control and the debate in technical societies over the merits of DC and AC, noting that:
At a July meeting Board of Electrical Control, Brown's criticisms of AC and even his knowledge of electricity was challenged by other electrical engineers, some of whom worked for Westinghouse. At this meeting, supporters of AC provided anecdotal stories from electricians on how they had survived shocks from AC at voltages up to 1000 volts and argued that DC was the more dangerous of the two.
Brown's demonstrations
Brown, determined to prove alternating current was more dangerous than direct current, at some point contacted Thomas Edison to see if he could make use of equipment to conduct experiments. Edison immediately offered to assist Brown in his crusade against AC companies. Before long, Brown was loaned space and equipment at Edison's West Orange, New Jersey laboratory, as well as laboratory assistant Arthur Kennelly.
Brown paid local children to collect stray dogs off the street for his experiments with direct and alternating current. After much experimentation killing a series of dogs, Brown held a public demonstration on July 30 in a lecture room at Columbia College. With many participants shouting for the demonstration to stop and others walking out, Brown subjected a caged dog to several shocks with increasing levels of direct current up to 1,000 volts, which the dog survived. Brown then applied 330 volts of alternating current which killed the dog. Four days later he held a second demonstration to answer critics' claims that the DC probably weakened the dog before it died. In this second demonstration, three dogs were killed in quick succession with 300 volts of AC. Brown wrote to a colleague that he was sure this demonstration would get the New York Board of Electrical Control to limit AC installations to 300 volts. Brown's campaign to restrict AC to 300 volts was unsuccessful but legislation did come close to passing in Ohio and Virginia.
Collusion with Edison
What brought Brown to the forefront of the debate over AC and his motives remain unclear, but historians note there grew to be some form of collusion between the Edison company and Brown. Edison records seem to show it was Edison Electric Light treasurer Francis S. Hastings who came up with the idea of using Brown and several New York physicians to attack Westinghouse and the other AC companies in retaliation for what Hastings thought were unscrupulous bids by Westinghouse for lighting contracts in Denver and Minneapolis. Hasting brought Brown and Edison together and was in continual contact with Brown. Edison Electric seemed to be footing the bill for some of Brown's publications on the dangers of AC. In addition, Thomas Edison himself sent a letter to the city government of Scranton, Pennsylvania recommending Brown as an expert on the dangers of AC. Some of this collusion was exposed in letters stolen from Brown's office and published in August 1889.
Patents and mergers
During this period Westinghouse continued to pour money and engineering resources into the goal of building a completely integrated AC system. To gain control of the Sawyer-Man lamp patents he bought Consolidated Electric Light in 1887. He bought the Waterhouse Electric Light Company in 1888 and the United States Illuminating Company in 1890, giving Westinghouse their own arc lighting systems as well as control over all the major incandescent lamp patents not controlled by Edison. In April 1888 Westinghouse engineer Oliver B. Shallenberger developed an induction meter that used a rotating magnetic field for measuring alternating current, giving the company a way to calculate how much electricity a customer used. In July 1888 Westinghouse paid a substantial amount to license Nikola Tesla's US patents for a poly-phase AC induction motor and obtained a patent option on Galileo Ferraris' induction motor design. Although the acquisition of a feasible AC motor gave Westinghouse a key patent in building a completely integrated AC system, the general shortage of cash the company was going through by 1890 meant development had to be put on hold for a while. The difficulties of obtaining funding for such a capital intensive business was becoming a serious problem for the company and 1890 saw the first of several attempts by investor J. P. Morgan to take over Westinghouse Electric.
Thomson-Houston was continuing to expand, buying seven smaller electric companies including a purchase of the Brush Electric Company in 1889. By 1890 Thomson-Houston controlled the majority of the arc lighting systems in the US and a collection of its own US AC patents. Several of the business deals between Thomson-Houston and Westinghouse fell apart and in April 1888 a judge rolled back part of Westinghouse's original Gaulard Gibbs patent, stating it only covered transformers linked in series.
With the help of the financier Henry Villard the Edison group of companies also went through a series of mergers: Edison Lamp Company, a lamp manufacturer in East Newark, New Jersey; Edison Machine Works, a manufacturer of dynamos and large electric motors in Schenectady, New York; Bergmann & Company, a manufacturer of electric lighting fixtures, sockets, and other electric lighting devices; and Edison Electric Light Company, the patent-holding company and the financial arm backed by J.P. Morgan and the Vanderbilt family for Edison's lighting experiments, merged. The new company, Edison General Electric Company, was formed in January 1889 with the help of Drexel, Morgan & Co. and Grosvenor Lowrey with Villard as president. It later included the Sprague Electric Railway & Motor Company.
The peak of the war
Through the fall of 1888 a battle of words with Brown specifically attacking Westinghouse continued to escalate. In November George Westinghouse challenged Brown's assertion in the pages of the Electrical Engineer that the Westinghouse AC systems had caused 30 deaths. The magazine investigated the claim and found at most only two of the deaths could be attributed to Westinghouse installations.
Associating AC and Westinghouse with the electric chair
Although New York had a criminal procedure code that specified electrocution via an electric chair, it did not spell out the type of electricity, the amount of current, or its method of supply, since these were still relative unknowns. The New York Medico-Legal Society, an informal society composed of doctors and lawyers, was given the task of working out the details and in late 1888 through early 1889 conducted a series of animal experiments on voltage amounts, electrode design and placement, and skin conductivity. During this time they sought the advice of Harold Brown as a consultant. This ended up expanding the war of currents into the development of the chair and the general debate over capital punishment in the US.
After the Medico-Legal Society formed their committee in September 1888 chairman Frederick Peterson, who had been an assistant at Brown's July 1888 public electrocution of dogs with AC at Columbia College, had the results of those experiments submitted to the committee. The claims that AC was more deadly than DC and was the best current to use was questioned, with some committee members pointing out that Brown's experiments were not scientifically carried out and were on animals smaller than a human being. At their November meeting the committee recommended 3,000 volts although the type of electricity, direct current or alternating current, was not determined.
In order to more conclusively prove to the committee that AC was more deadly than DC, Brown contacted Edison Electric Light treasurer Francis S. Hastings to arrange the use of the West Orange laboratory. There on December 5, 1888 Brown set up an experiment with members of the press, members of the Medico-Legal Society, the chairman of the death penalty commission, and Thomas Edison looking on. Brown used alternating current for all of his tests on animals larger than a human, including 4 calves and a lame horse, all dispatched with 750 volts of AC. Based on these results the Medico-Legal Society's December meeting recommended the use of 1,000–1,500 volts of alternating current for executions and newspapers noted the AC used was half the voltage used in the power lines over the streets of American cities.
Westinghouse criticized these tests as a skewed self-serving demonstration designed to be a direct attack on alternating current. On December 13 in a letter to the New York Times, Westinghouse spelled out where Brown's experiments were wrong and claimed again that Brown was being employed by the Edison company. Brown's December 18 letter refuted the claims and Brown even challenged Westinghouse to an electrical duel, with Brown agreeing to be shocked by ever-increasing amounts of DC power if Westinghouse submitted himself to the same amount of increasing AC power, first to quit loses. Westinghouse declined the offer.
In March 1889 when members of the Medico-Legal Society embarked on another series of tests to work out the details of electrode composition and placement they turned to Brown for technical assistance. Edison treasurer Hastings tried unsuccessfully to obtain a Westinghouse AC generator for the test. They ended up using Edison's West Orange laboratory for the animal tests.
Also in March, Superintendent of Prisons Austin Lathrop asked Brown if he could supply the equipment needed for the executions as well as design the electric chair. Brown turned down the job of designing the chair but did agree to fulfill the contract to supply the necessary electrical equipment. The state refused to pay up front, and Brown apparently turned to Edison Electric as well as Thomson-Houston Electric Company to help obtaining the equipment. This became another behind-the-scenes maneuver to acquire Westinghouse AC generators to supply the current, apparently with the help of the Edison company and Westinghouse's chief AC rival, Thomson-Houston. Thomson-Houston arranged to acquire three Westinghouse AC generators by replacing them with new Thomson-Houston AC generators. Thomson-Houston president Charles Coffin had at least two reasons for obtaining the Westinghouse generators; he did not want his company's equipment to be associated with the death penalty and he wanted to use one to prove a point, paying Brown to set up a public efficiency test to show that Westinghouse's sales claim of manufacturing 50% more efficient generators was false.
That spring Brown published "The Comparative Danger to Life of the Alternating and Continuous Electrical Current" detailing the animal experiments done at Edison's lab and claiming they showed AC was far deadlier than DC. This 61-page professionally printed booklet (possibly paid for by the Edison company) was sent to government officials, newspapers, and businessmen in towns with populations greater than 5,000 inhabitants.
In May 1889 when New York had its first criminal sentenced to be executed in the electric chair, a street merchant named William Kemmler, there was a great deal of discussion in the editorial column of the New York Times as to what to call the then-new form of execution. The term "Westinghoused" was put forward as well as "Gerrycide" (after death penalty commission head Elbridge Gerry), and "Browned". The Times hated the word that was eventually adopted, electrocution, describing it as being pushed forward by "pretentious ignoramuses". One of Edison's lawyers wrote to his colleague expressing an opinion that Edison's preference for dynamort, ampermort and electromort were not good terms but thought Westinghoused was the best choice.
The Kemmler appeal
William Kemmler was sentenced to die in the electric chair around June 24, 1889, but before the sentence could be carried out an appeal was filed on the grounds that it constituted cruel and unusual punishment under the U.S. Constitution. It became obvious to the press and everyone involved that the politically connected (and expensive) lawyer who filed the appeal, William Bourke Cockran, had no connection to the case but did have connection to the Westinghouse company, obviously paying for his services.
During fact-finding hearings held around the state beginning on July 9 in New York City, Cockran used his considerable skills as a cross-examiner and orator to attack Brown, Edison, and their supporters. His strategy was to show that Brown had falsified his test on the killing power of AC and to prove that electricity would not cause certain death and simply lead to torturing the condemned. In cross examination he questioned Brown's lack of credentials in the electrical field and brought up possible collusion between Brown and Edison, which Brown again denied. Many witnesses were called by both sides to give firsthand anecdotal accounts about encounters with electricity and evidence was given by medical professionals on the human body's nervous system and the electrical conductivity of skin. Brown was accused of fudging his tests on animals, hiding the fact that he was using lower current DC and high-current AC. When the hearing convened for a day at Edison's West Orange lab to witness demonstrations of skin resistance to electricity, Brown almost got in a fight with a Westinghouse representative, accusing him of being in the Edison laboratory to conduct industrial espionage. Newspapers noted the often contradictory testimony was raising public doubts about the electrocution law but after Edison took the stand many accepted assurances from the "wizard of Menlo Park" that 1,000 volts of AC would easily kill any man.
After the gathered testimony was submitted and the two sides presented their case, Judge Edwin Day ruled against Kemmler's appeal on October 9 and US Supreme Court denied Kemmler's appeal on May 23, 1890.
When the chair was first used, on August 6, 1890, the technicians on hand misjudged the voltage needed to kill William Kemmler. After the first jolt of electricity Kemmler was found to be still breathing. The procedure had to be repeated and a reporter on hand described it as "an awful spectacle, far worse than hanging." George Westinghouse commented: "They would have done better using an axe."
Brown's collusion exposed
On August 25, 1889 the New York Sun ran a story headlined:
The story was based on 45 letters stolen from Brown's office that spelled out Brown's collusion with Thomson-Houston and Edison Electric. The majority of the letters were correspondence between Brown and Thomson-Houston on the topic of acquiring the three Westinghouse generators for the state of New York as well as using one of them in an efficiency test. They also showed that Brown had received $5,000 from Edison Electric to purchase the surplus Westinghouse generators from Thomson-Houston. Further Edison involvement was contained in letters from Edison treasurer Hastings asking Brown to send anti-AC pamphlets to all the legislators in the state of Missouri (at the company's expense), Brown requesting that a letter of recommendation from Thomas Edison be sent to Scranton, Pennsylvania, as well as Edison and Arthur Kennelly coaching Brown in his upcoming testimony in the Kemmler appeal trial.
Brown was not slowed down by this revelation and characterized his efforts to expose Westinghouse as the same as going after a grocer who sells poison and calls it sugar.
The "Electric Wire Panic"
1889 saw another round of deaths attributed to alternating current including a lineman in Buffalo, New York, four linemen in New York City, and a New York fruit merchant who was killed when the display he was using came in contact with an overhead line. NYC Mayor Hugh J. Grant, in a meeting with the Board of Electrical Control and the AC electric companies, rejected the claims that the AC lines were perfectly safe saying "we get news of all who touch them through the coroners office". On October 11, 1889, John Feeks, a Western Union lineman, was high up in the tangle of overhead electrical wires working on what were supposed to be low-voltage telegraph lines in a busy Manhattan district. As the lunchtime crowd below looked on he grabbed a nearby line that, unknown to him, had been shorted many blocks away with a high-voltage AC line. The jolt entered through his bare right hand and exited his left steel studded climbing boot. Feeks was killed almost instantly, his body falling into the tangle of wire, sparking, burning, and smoldering for the better part of an hour while a horrified crowd of thousands gathered below. The source of the power that killed Feeks was not determined although United States Illuminating Company lines ran nearby.
Feeks' public death sparked a new round of people fearing the electric lines over their heads in what has been called the "Electric Wire Panic". The blame seemed to settle on Westinghouse since, Westinghouse having bought many of the lighting companies involved, people assumed Feeks' death was the fault of a Westinghouse subsidiary. Newspapers joined into the public outcry following Feeks' death, pointing out men's lives "were cheaper to this monopoly than insulated wires" and calling for the executives of AC companies to be charged with manslaughter. The October 13, 1889, New Orleans Times-Picayune noted "Death does not stop at the door, but comes right into the house, and perhaps as you are closing a door or turning on the gas you are killed." Harold Brown's reputation was rehabilitated almost overnight with newspapers and magazines seeking his opinion and reporters following him around New York City where he measured how much current was leaking from AC power lines.
At the peak of the war of currents, Edison himself joined the public debate for the first time, denounced AC current in a November 1889 article in the North American Review titled "The Dangers of Electric Lighting". Edison put forward the view that burying the high-voltage lines was not a solution, and would simply move the deaths underground and be a "constant menace" that could short with other lines threatening people's homes and lives. He stated the only way to make AC safe was to limit its voltage and vowed Edison Electric would never adopt AC as long as he was in charge.
George Westinghouse was characterized as a villain trying to defend pole-mounted AC installations that he knew were unsafe, and fumbled his replies to the questions put to him by reporters, attempting to point out all the other things in a large city that were more dangerous than AC. However, his subsequent response, printed in the North American Review, was much improved, highlighting that his AC/transformer system actually used lower household voltages than the Edison DC system. He also pointed out 87 deaths in one year caused by street cars and gas lighting, versus only 5 accidental electrocutions and no in-home deaths attributed to AC current.
The crowd that watched Feeks contained many New York aldermen due to the site of the accident being near the New York government offices and the horrifying affair galvanized them into the action of passing the law on moving utilities underground. The electric companies involved obtained an injunction preventing their lines from being cut down immediately but shut down most of their lighting until the situation was settled, plunging many New York streets into darkness. The legislation ordering the cutting down of all of the utility lines was finally upheld by the New York Supreme Court in December. The AC lines were cut down, keeping many New York City streets in darkness for the rest of the winter, since little had been done by the overpaid Tammany Hall city supervisors who were supposed arrange the building of the underground "subways" to house them.
The current war ends
Even with the Westinghouse propaganda losses, the war of currents itself was winding down with direct current on the losing side. This was due in part to Thomas Edison himself leaving the electric power business. Edison was becoming marginalized in his own company, having lost majority control in the 1889 merger that formed Edison General Electric. In 1890, he told president Henry Villard he thought it was time to retire from the lighting business and moved on to an iron ore refining project that preoccupied his time. Edison's dogmatic anti-AC values were no longer controlling the company. By 1889, Edison's Electric's own subsidiaries were lobbying to add AC power transmission to their systems, and in October 1890, Edison Machine Works began developing AC-based equipment.
With Thomas Edison no longer involved with Edison General Electric, the war of currents came to a close with a financial merger. Edison president Henry Villard, who had engineered the merger that formed Edison General Electric, was continually working on the idea of merging that company with Thomson-Houston or Westinghouse. He saw a real opportunity in 1891. The market was in a general downturn causing cash shortages for all the companies concerned and Villard was in talks with Thomson-Houston, which was now Edison General Electric's biggest competitor. Thomson-Houston had a habit of saving money on development by buying, or sometimes stealing, patents. Patent conflicts were stymieing the growth of both companies and the idea of saving on some 60 ongoing lawsuits as well as saving on profit losses of trying to undercut each other by selling generating plants below cost pushed forward the idea of this merger in financial circles. Edison hated the idea and tried to hold it off, but Villard thought his company, now winning its incandescent light patent lawsuits in the courts, was in a position to dictate the terms of any merger. As a committee of financiers, which included J.P. Morgan, worked on the deal in early 1892, things went against Villard. In Morgan's view, Thomson-Houston looked on the books to be the stronger of the two companies and engineered a behind the scenes deal announced on April 15, 1892, that put the management of Thomson-Houston in control of the new company, now called General Electric (dropping Edison's name). Thomas Edison was not aware of the deal until the day before it happened.
The fifteen electric companies that existed five years before had merged down to two: General Electric and Westinghouse. The war of currents came to an end, and this merger of the Edison company, along with its lighting patents, and the Thomson-Houston, with its AC patents, created a company that controlled three quarters of the US electrical business. From this point on, General Electric and Westinghouse were both marketing alternating current systems. Edison put on a brave face, noting to the media how his stock had gained value in the deal, but privately he was bitter that his company and all of his patents had been turned over to the competition.
Aftermath
Even though the institutional war of currents had ended in a financial merger, the technical difference between direct and alternating current systems followed a much longer technical merger. Due to innovation in the US and Europe, alternating current's economy of scale with very large generating plants linked to loads via long-distance transmission was slowly being combined with the ability to link it up with all of the existing systems that needed to be supplied. These included single phase AC systems, poly-phase AC systems, low-voltage incandescent lighting, high voltage arc lighting, and existing DC motors in factories and street cars. In the engineered universal system these technological differences were temporarily being bridged via the development of rotary converters and motor–generators that allowed the large number of legacy systems to be connected to the AC grid. These stopgaps were slowly replaced as older systems were retired or upgraded.
In May 1892, Westinghouse Electric managed to underbid General Electric on the contract to electrify the World's Columbian Exposition in Chicago and, although they made no profit, their demonstration of a safe, effective and highly flexible universal alternating current system powering all of the disparate electrical systems at the Exposition led to them winning the bid at the end of that year to build an AC power station at Niagara Falls. General Electric was awarded contracts to build AC transmission lines and transformers in that project and further bids at Niagara were split with GE who were quickly catching up in the AC field due partly to Charles Proteus Steinmetz, a Prussian mathematician who was the first person to fully understand AC power from a solid mathematical standpoint. General Electric hired many talented new engineers to improve its design of transformers, generators, motors and other apparatus.
A three-phase three-wire transmission system had already been deployed in Europe at the International Electro-Technical Exhibition of 1891, where Mikhail Dolivo-Dobrovolsky used this system to transmit electric power over a distance of 176 km with 75% efficiency. In 1891 he also created a three-phase transformer, the short-circuited (squirrel-cage) induction motor and designed the world's first three-phase hydroelectric power plant.
Patent lawsuits were still hampering both companies and bleeding off cash, so in 1896, J. P. Morgan engineered a patent sharing agreement between the two companies that remained in force for 11 years.
In 1897 Edison sold his remaining stock in Edison Electric Illuminating of New York to finance his iron ore refining prototype plant. In 1908, Edison said to George Stanley, son of AC transformer inventor William Stanley, Jr., "Tell your father I was wrong", likely an admission that he had underestimated the developmental potential of alternating current.
Remnant and existent DC systems
Some cities continued to use DC well into the 20th century. For example, central Helsinki had a DC network until the late 1940s, and Stockholm lost its dwindling DC network as late as the 1970s. A mercury-arc valve rectifier station could convert AC to DC where networks were still used. Parts of Boston, Massachusetts, along Beacon Street and Commonwealth Avenue still used 110 volts DC in the 1960s, causing the destruction of many small appliances (typically hair dryers and phonographs) used by Boston University students, who ignored warnings about the electricity supply.
New York City's electric utility company, Consolidated Edison, continued to supply direct current to customers who had adopted it early in the twentieth century, mainly for elevators. The New Yorker Hotel, constructed in 1929, had a large direct-current power plant and did not convert fully to alternating-current service until well into the 1960s. This was the building in which AC pioneer Nikola Tesla spent his last years, and where he died in 1943. New York City's Broadway theaters continued to use DC services until 1975, requiring the use of outmoded manual resistance dimmer boards operated by several stagehands. This practice ended when the musical A Chorus Line introduced computerized lighting control and thyristor (SCR) dimmers to Broadway, and New York theaters were finally converted to AC.
In January 1998, Consolidated Edison started to eliminate DC service. At that time there were 4,600 DC customers. By 2006, there were only 60 customers using DC service, and on November 14, 2007, the last direct-current distribution by Con Edison was shut down. Customers still using DC were provided with on-site AC to DC rectifiers. In 2012, Pacific Gas and Electric Company still provided DC power to some locations in San Francisco, primarily for elevators, supplied by close to 200 rectifiers each providing power for 7–10 customers.
The Central Electricity Generating Board in the UK maintained a 200–volt DC generating station at Bankside Power Station in London until 1981. It exclusively powered DC printing machinery in Fleet Street, then the heart of the UK's newspaper industry. It was decommissioned later in 1981 when the newspaper industry moved into the developing docklands area further down the river (using modern AC-powered equipment).
High-voltage direct current (HVDC) systems are used for bulk transmission of energy from distant generating stations, for underwater lines, and for interconnection of separate alternating-current systems.
See also
Format war
History of electric power transmission
History of electronic engineering
Timeline of electrical and electronic engineering
Topsy (elephant) – in popular culture associated with the war of currents
References
Citations
Bibliography
Further reading
External links
(AC vs DC an online video mini-history).
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Thomas Edison
Scientific rivalry | War of the currents | Physics,Engineering | 9,388 |
752,310 | https://en.wikipedia.org/wiki/RCA%20Dome | The RCA Dome (originally Hoosier Dome) was a domed stadium in Indianapolis. It was the home of the Indianapolis Colts NFL franchise for 24 seasons (1984–2007).
It was completed at a cost of $77.5 million, as part of the Indiana Convention Center, with the costs split between private and public money. The largest crowd to attend an event at the Dome was 62,167 for WrestleMania VIII in 1992. It was demolished on December 20, 2008, as part of a project to expand the attached convention center.
Description
The Birdair-designed dome was made up of teflon-coated fiberglass and weighed , which was held up by the air pressure inside the building. The ceiling was high, though the height varied up to as the materials expanded and contracted with the weather.
Like other domes of this style (the Hubert H. Humphrey Metrodome, BC Place, the JMA Wireless Dome, and the Pontiac Silverdome) there were warning signs posted cautioning patrons of the high winds at the doors when exiting the facility.
History
Construction for the Hoosier Dome began in May 1982.
The domed stadium was similar in design and appearance to the Metrodome and the previous BC Place roof, owing in great part to the involvement of engineers David Geiger and Walter Bird, pioneers in air-supported roofs.
The stadium was originally named the Hoosier Dome until 1994 when RCA paid $10 million for the naming rights for 10 years, with two 5-year options to RCA at a cost of $3.5 million if invoked. The stadium seated 56,127 for football, the smallest in the NFL. Modifications were made to the stadium in 1999 to expand the suites and add club seating. Before that, the maximum seating for a football crowd was 60,272. The stadium was built to lure a National Football League team to Indianapolis, and as the stadium was being completed, the Baltimore Colts relocated to Indianapolis on March 29, 1984.
The Dome was officially dedicated on August 11, 1984, as a sellout crowd watched the Indianapolis Colts defeat the New York Giants in an NFL preseason game. The Buffalo Bills and Chicago Bears played a preseason game at the Hoosier Dome on August 26, 1984, which had been scheduled prior to the Colts moving in.
The football playing surface was originally AstroTurf, and replaced with FieldTurf in 2005.
The Colts moved into the new, retractable-roof, Lucas Oil Stadium for the 2008 NFL season. The RCA Dome was replaced by additional space for the adjacent Indiana Convention Center. The new convention space connects to Lucas Oil Stadium in much the same way that the existing Indiana Convention Center had been connected to the RCA Dome (although the new connecting walkway now passes under a railroad track).
Demolition
On September 24, 2008, the roof of the Dome was deflated, which took about 35 minutes. The building itself was imploded on December 20, 2008, by Controlled Demolition, Inc., and was featured on the second series premiere of the National Geographic show Blowdown.
An Indianapolis nonprofit, People for Urban Progress, rescued of the Dome roof. They work with local Indianapolis designers to recycle the material into community shade structures and art installations, as well as wallets, purses and bags.
Events
Football
Although the RCA Dome never hosted any Super Bowls, it played host to the 2006 AFC Championship Game, which saw the Colts erase a 21–3 deficit for a come-from-behind 38–34 win over the New England Patriots in what would ultimately be the only AFC Championship Game hosted at the RCA Dome.
The RCA Dome also hosted three AFC Divisional Round games in 1999, 2005, and 2007, with the Colts posting an 0–3 record in those games; the 2005 game, which saw the heavily favored Colts lose to the Pittsburgh Steelers 21–18 in one of the biggest upsets in NFL history (en route to the Steelers' victory in Super Bowl XL), is best remembered for Colts cornerback Nick Harper recovering a Jerome Bettis fumble only for Mike Vanderjagt to miss the game-tying field goal at the end of the game. The RCA Dome also hosted three AFC wild card games in 2003, 2004, and 2006, with the Colts winning all three games. The Colts' 28–24 loss to the San Diego Chargers in the 2007 Divisional Round proved to be the stadium's final game before the Colts moved on to Lucas Oil Stadium the following season.
Basketball
In addition to football, the RCA Dome hosted several basketball games. The first was an exhibition game in 1984 between an NBA All-Star team led by home-state hero Larry Bird and the United States Olympic Men's Basketball team, coached by Bob Knight, who was at the time the coach of Indiana University. The Dome hosted the 1985 NBA All-Star Game in February, where an NBA-record crowd of 43,146 saw the Western Conference beat the host Eastern Conference 140–129. The Indiana High School Athletic Association's 1990 boys and girls basketball finals were held at the stadium; 41,046 attended the boys semifinals and finals, setting the record for the largest crowd at a high school basketball game. Later, it hosted many NCAA Men's Division I Basketball Championship games, including four Final Fours (1991, 1997, 2000, 2006). The NCAA, whose headquarters are in Indianapolis, has committed to holding the Final Four in the city once every five years. The RCA Dome hosted its only Women's Final Four in 2005. It served as one of two sites for the FIBA Men's Basketball World Championship in 2002, sharing the honors with Gainbridge Fieldhouse, the home of the Indiana Pacers.
Other sports
During the 1987 Pan American Games, the RCA Dome hosted the Gymnastics and Handball competitions as well as the closing ceremonies.
In 1991, the Dome hosted the 1991 World Artistic Gymnastics Championships. In 1992, the Dome hosted WrestleMania VIII for the World Wrestling Federation.
Monster Jam hosted events at the venue every year, with the last event being held in 2008 a few months before the venue was demolished.
In addition, it hosted the NCAA Men's Division I Indoor Track and Field Championships from 1989 to 1999, and the 1990 General Conference Session of Seventh-day Adventists. Additionally, the RCA Dome served as the site of the Indiana State School Music Association State Marching Band Competition, the Bands of America Grand Nationals, and the Drum Corps International Midwestern Regional, along with the NFL Scouting Combine in February of each year. The 2004 U.S. Olympic Team Wrestling Trials were held in the Dome. It also hosted a PBR Built Ford Tough Series bull riding event in 2004.
The Thunder in the Dome was a midget car race held from 1985 to 2001. The Dome also hosted an AMA Supercross Championship round from 1992 to 2008.
Concerts
Many concerts took place in this venue, such as the 1987 Pink Floyd reunion, the Rolling Stones, the Monsters of Rock Festival in 1988 (Van Halen, Metallica, Scorpions, Dokken, and Kingdom Come), and Farm Aid IV in 1990 (Elton John, Guns N' Roses, Lou Reed, John Mellencamp, Genesis, CSN&Y, Willie Nelson, Iggy Pop, Don Henley & Bonnie Raitt).
References
External links
RCA Dome Demolition
RCA
American football venues in Indiana
Basketball venues in Indiana
Sports venues demolished in 2008
Covered stadiums in the United States
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Event venues established in 1983
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2008 disestablishments in Indiana
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Sports venues in Indianapolis
Demolished sports venues in Indiana
Indoor track and field venues in Indiana
Air-supported structures
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Buildings and structures demolished by controlled implosion
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Handball venues in the United States
Defunct covered stadiums | RCA Dome | Engineering | 1,576 |
1,203,002 | https://en.wikipedia.org/wiki/Crew%20resource%20management | Crew resource management or cockpit resource management (CRM) is a set of training procedures for use in environments where human error can have devastating effects. CRM is primarily used for improving aviation safety and focuses on interpersonal communication, leadership, and decision making in aircraft cockpits. Its founder is David Beaty, a former Royal Air Force and a BOAC pilot who wrote The Human Factor in Aircraft Accidents (1969). Despite the considerable development of electronic aids since then, many principles he developed continue to prove effective.
CRM in the US formally began with a National Transportation Safety Board (NTSB) recommendation written by NTSB Air Safety Investigator and aviation psychologist Alan Diehl during his investigation of the 1978 United Airlines Flight 173 crash. The issues surrounding that crash included a DC-8 crew running out of fuel over Portland, Oregon, while troubleshooting a landing gear problem.
The term "cockpit resource management"—which was later generalized to "crew resource management"—was coined in 1979 by NASA psychologist John Lauber, who for several years had studied communication processes in cockpits. While retaining a command hierarchy, the concept was intended to foster a less-authoritarian cockpit culture in which co-pilots are encouraged to question captains if they observed them making mistakes.
CRM grew out of the 1977 Tenerife airport disaster, in which two Boeing 747 aircraft collided on the runway, killing 583 people. A few weeks later, NASA held a workshop on the topic, endorsing this training. In the US, United Airlines was the first airline to launch a comprehensive CRM program, starting in 1981. By the 1990s, CRM had become a global standard.
United Airlines trained their flight attendants to use CRM in conjunction with the pilots to provide another layer of enhanced communication and teamwork. Studies have shown the use of CRM by both work groups reduces communication barriers and problems can be solved more efficiently, leading to increased safety. CRM training concepts have been modified for use in a wide range of activities including air traffic control, ship handling, firefighting, and surgery, in which people must make dangerous, time-critical decisions.
Overview
The current generic term "crew resource management" (CRM) has been widely adopted but is also known as cockpit resource management; flightdeck resource management; and command, leadership and resource management. When CRM techniques are applied to other arenas, they are sometimes given unique labels, such as maintenance resource management, bridge resource management, or maritime resource management.
CRM training encompasses a wide range of knowledge, skills, and attitudes including communications, situational awareness, problem solving, decision making, and teamwork; together with all the attendant sub-disciplines which each of these areas entails. CRM can be defined as a system that uses resources to promote safety within the workplace.
CRM is concerned with the cognitive and interpersonal skills needed to manage resources within an organized system rather than with the technical knowledge and skills required to operate equipment. In this context, cognitive skills are defined as the mental processes used for gaining and maintaining situational awareness, for solving problems and for making decisions. Interpersonal skills are regarded as communications and a range of behavioral activities associated with teamwork. In many operational systems, skill areas often overlap and are not confined to multi-crew craft or equipment, and relate to single operator equipment or craft.
Aviation organizations including major airlines and military aviation have introduced CRM training for crews. CRM training is now a mandated requirement for commercial pilots working under most regulatory bodies, including the FAA (US) and EASA (Europe). The NOTECHS system is used to evaluate non-technical skills. Following the lead of the commercial airline industry, the US Department of Defense began training its air crews in CRM in the mid 1980s. The U.S. Air Force and U.S. Navy require all air crew members to receive annual CRM training to reduce human-error-caused mishaps. The U.S. Army has its own version of CRM called Aircrew Coordination Training Enhanced (ACT-E).
Case studies
United Airlines Flight 173
When the crew of United Airlines Flight 173 was making an approach to Portland International Airport on the evening of Dec 28, 1978, they experienced a landing gear abnormality. The captain decided to enter a holding pattern so they could troubleshoot the problem. The captain focused on the landing gear problem for an hour, ignoring repeated hints from the first officer and the flight engineer about their dwindling fuel supply, and only realized the situation when the engines began flaming out. The aircraft crash-landed in a suburb of Portland, Oregon, over short of the runway. Of the 189 people aboard, two crew members and eight passengers died. The NTSB Air Safety Investigator Alan Diehl wrote in his report:
Diehl was assigned to investigate this accident and realized it was similar to several other major airline accidents including the crash of Eastern Air Lines Flight 401 and the runway collision between Pan Am and KLM Boeing 747s at Tenerife.
United Airlines Flight 232
Captain Al Haynes, pilot of United Airlines Flight 232, credits CRM as being one of the factors that saved his own life, and many others, in the Sioux City, Iowa, crash of July 1989:
Air France 447
One analysis blames failure to follow proper CRM procedures as being a contributing factor that led to the 2009 fatal crash into the Atlantic Ocean of Air France Flight 447 from Rio de Janeiro to Paris. The final report concluded the aircraft crashed after temporary inconsistencies between the airspeed measurements—likely due to the aircraft's pitot tubes being obstructed by ice crystals—caused the autopilot to disconnect, after which the crew reacted incorrectly, causing the aircraft to enter an aerodynamic stall from which it did not recover.
Following recovery of the black box two years later, independent analyses were published before and after the official report was issued by the BEA, France's air safety board. One was a French report in the book "Erreurs de Pilotage" written by Jean-Pierre Otelli, which leaked the final minutes of recorded cockpit conversation. According to Popular Mechanics, which examined the cockpit conversation just before the crash:
The men are utterly failing to engage in an important process known as crew resource management, or CRM. They are failing, essentially, to cooperate. It is not clear to either one of them who is responsible for what, and who is doing what.
First Air Flight 6560
The Canadian Transportation Safety Board (CTSB) determined a failure of crew resource management was largely responsible for the crash of First Air Flight 6560, a Boeing 737-200, in Resolute, Nunavut, on August 20, 2011. A malfunctioning compass gave the crew an incorrect heading, although the instrument landing system and Global Positioning System indicated they were off course. The first officer made several attempts to indicate the problem to the captain but a failure to follow airline procedures and a lack of a standardized communication protocol to indicate a problem led to the captain dismissing the first officer's warnings. Both pilots were also overburdened with making preparations to land, resulting in neither being able to pay full attention to what was happening.
First Air increased the time dedicated to CRM in their training as a result of the accident, and the CTSB recommended regulatory bodies and airlines to standardize CRM procedures and training in Canada.
Qantas Flight 32
The success of the Qantas Flight 32 flight has been attributed to teamwork and CRM skills. Susan Parson, the editor of the Federal Aviation Administration (FAA) Safety Briefing wrote; "Clearly, the QF32 crew's performance was a bravura example of the professionalism and airmanship every aviation citizen should aspire to emulate".
Carey Edwards, author of Airmanship wrote:
Their crew performance, communications, leadership, teamwork, workload management, situation awareness, problem solving and decision making resulted in no injuries to the 450 passengers and crew. QF32 will remain as one of the finest examples of airmanship in the history of aviation.
Adoption in other fields
Transportation
The basic concepts and ideology of CRM have proven successful in other related fields. In the 1990s, several commercial aviation firms and international aviation safety agencies began expanding CRM into air traffic control, aircraft design, and aircraft maintenance. The aircraft maintenance section of this training expansion gained traction as maintenance resource management (MRM). To attempt to standardize industry-wide MRM training, the FAA issued Advisory Circular 120–72, "Maintenance Resource Management Training" in September 2000.
Following a study of aviation mishaps between 1992 and 2002, the United States Air Force determined that close to 18% of its aircraft mishaps were directly attributable to human error in maintenance, which often occurred long before the flight in which the problems were discovered. These "latent errors" include failures to follow published aircraft manuals, lack of assertive communication among maintenance technicians, poor supervision, and improper assembly practices. In 2005, to address these human-error-induced aircraft mishaps, Lt Col Doug Slocum, Chief of Safety at the Air National Guard's (ANG) 162nd Fighter Wing, Tucson, directed the modification of the base's CRM program into a military version called maintenance resource management (MRM).
In mid-2005, the Air National Guard's Aviation Safety Division converted Slocum's MRM program into a national program available to the Air National Guard's flying wings in 54 U.S. states and territories. In 2006, the Defense Safety Oversight Council (DSOC) of the U.S. Department of Defense (DoD) recognized the mishap-prevention value of this maintenance safety program by partially funding a variant of ANG MRM for training throughout the U.S. Air Force. This ANG initiated, DoD-funded version of MRM became known as Air Force Maintenance Resource Management (AF-MRM) and is now widely used in the U.S. Air Force.
The Rail Safety Regulators Panel of Australia has adapted CRM to rail as rail resource management and developed a free resource kit. Operating train crews at the National Railroad Passenger Corporation (Amtrak) in the United States are instructed on CRM principles during yearly training courses.
CRM has been adopted by merchant shipping worldwide. The STCW Convention and STCW Code, 2017 edition, published by the I.M.O. states the requirements for bridge resource management and engine room resource management training. These are approved shore-based training, simulator training, or approved in-service experience. Most maritime colleges hold courses for deck and engine room officers. Refresher courses are held every five years. These are referred to as maritime resource management.
Firefighting
Following its successful use in aviation training, CRM was identified as a potential safety improvement program for the fire services. Ted Putnam advocated for improved attention to human factors that contribute to accidents and near misses, building on CRM principles. In 1995, Dr. Putnam organized the first Human Factors Workshop for wildland fire. Dr. Putnam also wrote a paper that applied CRM concepts to the violent deaths of 14 Wildland firefighters on the South Canyon Fire in Colorado.
From this paper, a movement was initiated in the Wildland and Structural Fire Services to apply CRM concepts to emergency response situations. Various programs have since been developed to train emergency responders in these concepts and to help track breakdowns in these stressful environments.
The International Association of Fire Chiefs published its first CRM manual for the fire service in 2001. It is currently in its third edition. Several industry-specific textbooks have also been published.
Healthcare
Elements of CRM have been applied in US healthcare since the late 1990s, specifically in infection prevention.
For example, the "central line bundle" of best practices recommends using a checklist when inserting a central venous catheter. The observer checking off the checklist is usually lower-ranking than the person inserting the catheter. The observer is encouraged to communicate when elements of the bundle are not executed; for example if a breach in sterility has occurred.
TeamSTEPPS
The Agency for Healthcare Research and Quality (AHRQ), a division of the United States Department of Health and Human Services, also provides training based on CRM principles to healthcare teams. This training, called Team Strategies and Tools to Enhance Performance and Patient Safety (TeamSTEPPS), and the program is currently being implemented in hospitals, long-term care facilities, and primary care clinics around the world. TeamSTEPPs was designed to improve patient safety by teaching healthcare providers how to better collaborate with each other by using tools such as huddles, debriefs, handoffs, and check-backs. Implementing TeamSTEPPS has been shown to improve patient safety. There is evidence TeamSTEPPS interventions are difficult to implement and are not universally effective. There are strategies healthcare leaders can use to improve their chance of implementation success, such as using coaching, supporting, empowering, and supporting behaviors.
See also
British European Airways Flight 548
Stress in the aviation industry
Impact of culture on aviation safety
Line-oriented flight training
Saudia Flight 163
SHELL model
Single pilot resource management
Sterile cockpit rule
The Checklist Manifesto – primarily a justification of the application of these ideas to safety in medical operating rooms.
Maritime resource management
Threat and error management
References
External links
Military Human Factors
Crew Resource Management Current Regulatory Paper
Crew Resource Management for the Fire Service
TeamSTEPPS Program from the U.S. Dept. of Health and Human Services
Flight-crew human factors handbook (CAP 737)
Aviation safety
Error detection and correction | Crew resource management | Engineering | 2,772 |
36,505,783 | https://en.wikipedia.org/wiki/Anaikoddai%20seal | The Anaikoddai seal is a soapstone seal that was found in Anaikoddai, Sri Lanka during archeological excavations of a megalithic burial site by a team of researchers from the University of Jaffna. The seal was originally part of a signet ring and contains one of the oldest Brahmi inscriptions mixed with megalithic graffiti symbols found on the island. It was dated paleographically to the early third century BC.
Inscription
Although many pottery fragments have been found in excavations throughout Sri Lanka and South India that had both Brahmi and megalithic graffiti symbols side by side, the Anaikoddai seal is distinguished by having each written in a manner that indicates that the megalithic graffiti symbols may be a translation of the Brahmi. Read from right to left, the legend is read by most scholars in early Tamil as Koveta (Ko-ve-ta ). 'Ko' and 'Veta' both mean 'King' in Tamil and refers to a chieftain here. It is comparable to such names as Ko Ataṉ and Ko Putivira occurring in contemporary Tamil-Brahmi inscriptions. The trident symbol is equated with 'King', and is also found after a Tamil-Brahmi inscription of the Chera dynasty, thus supporting this interpretation.
Investigators disagree on whether megalithic graffiti symbols found in South India and Sri Lanka constitute an ancient writing system that preceded the introduction and widespread acceptance of Brahmi variant scripts or non-lithic symbols. The purpose of usage remains unclear.
See also
Early Indian epigraphy
South Indian Inscriptions
Tamil inscriptions in Sri Lanka
References
Cited literature
Ancient Indian culture
Archaeology of India
Indian inscriptions
Inscriptions in undeciphered writing systems
Iron Age Asia
Megalithic symbols
Sri Lankan Tamil history
Sri Lanka inscriptions
Tamil Brahmi script
Tamil inscriptions in Sri Lanka
Tamilakam | Anaikoddai seal | Mathematics | 363 |
78,259,584 | https://en.wikipedia.org/wiki/Facer.io | Facer is one of the largest watch face platforms for Apple Watch, Wear OS, and Tizen-based smartwatches, developed by Los Angeles-based Little Labs, Inc. It allows users to select from over 500,000 premade watch faces or create custom designs through its web-based editor.
Overview
Facer was launched in 2015 as a platform for Android and Wear OS smartwatches. In March 2016, the platform expanded to support iOS and Apple Watch. The service gained popularity for providing users with a large selection of watch faces, both from independent designers and branded partnerships. Facer has licensing agreements with brands, such as Star Trek, Fallout, US Air Force, Atari, Barbie, DOOM, Dungeons and Dragons, U.S. Space Force, Tetris, Teenage Mutant Ninja Turtles and more.
The platform supports all major smartwatches, including Wear OS, watchOS and Tizen. Facer hosts a library of over 500,000 watch faces designed by more than 50,000 creators. The platform allows users to browse and download a wide variety of designs themed around various genres and styles. Users can access the platform for free, though some premium watch faces require in-app purchases. Facer also allows users interested in designing to create their own watch faces through its web-based editor, Facer Creator.
Little Labs, Inc., the company behind Facer, is headquartered in Los Angeles, California.
References
American websites
Smartwatches | Facer.io | Technology | 298 |
72,031,127 | https://en.wikipedia.org/wiki/Lauren%20B.%20Hitchcock | Lauren Blakely Hitchcock (March 18, 1900 – October 15, 1972) was a chemical engineer and early opponent of air pollution.
Hitchcock was born in Paris to Frank Lauren Hitchcock, a mathematician and physicist, and Margaret Johnson Blakely, and was raised in Belmont, Massachusetts. He received his undergraduate (1920), master's (1927), and doctorate degree (1933) from Massachusetts Institute of Technology. He taught at the University of Virginia from 1928 to 1935 and then moved into private industry.
Hitchcock became president of the Southern California Air Pollution Foundation (APF) in 1954, which had been formed to fight smog. Hitchcock identified automobile exhaust and backyard incinerators as the cause and advised that significant steps would be needed--comparable to wartime efforts--to fight the problem in a meaningful way. In 1963, Hitchcock was appointed to the faculty at University at Buffalo, where his work papers are now archived.
References
External links
Hitchcock (Lauren B.) Papers, 1923-1966, at University at Buffalo Archives
1972 deaths
1900 births
Chemical engineers
Massachusetts Institute of Technology alumni
People from Belmont, Massachusetts | Lauren B. Hitchcock | Chemistry,Engineering | 223 |
19,732,690 | https://en.wikipedia.org/wiki/John%20Tyler | John Tyler (March 29, 1790 – January 18, 1862) was the tenth president of the United States, serving from 1841 to 1845, after briefly holding office as the tenth vice president in 1841. He was elected vice president on the 1840 Whig ticket with President William Henry Harrison, succeeding to the presidency following Harrison's death 31 days after assuming office. Tyler was a stalwart supporter and advocate of states' rights, including regarding slavery, and he adopted nationalistic policies as president only when they did not infringe on the states' powers. His unexpected rise to the presidency posed a threat to the presidential ambitions of Henry Clay and other Whig politicians and left Tyler estranged from both of the nation's major political parties at the time.
Tyler was born into a prominent slaveholding Virginia family. He became a national figure at a time of political upheaval. In the 1820s, the Democratic-Republican Party, at the time the nation's only political party, split into several factions. Initially a Jacksonian Democrat, Tyler opposed President Andrew Jackson during the nullification crisis as he saw Jackson's actions as infringing on states' rights and criticized Jackson's expansion of executive power during Jackson's veto on banks. This led Tyler to ally with the southern faction of the Whig Party. He served as a Virginia state legislator and governor, U.S. representative, and U.S. senator. Tyler was a regional Whig vice-presidential nominee in the 1836 presidential election; they lost. He was the sole nominee on the 1840 Whig presidential ticket as William Henry Harrison's running mate. Under the campaign slogan "Tippecanoe and Tyler Too", the Harrison–Tyler ticket defeated incumbent president Martin Van Buren.
President Harrison died just one month after taking office, and Tyler became the first vice president to succeed to the presidency. Amid uncertainty as to whether a vice president succeeded a deceased president, or merely took on his duties, Tyler immediately took the presidential oath of office, setting a lasting precedent. He signed into law some of the Whig-controlled Congress's bills, but he was a strict constructionist and vetoed the party's bills to create a national bank and raise tariff rates. He believed that the president, rather than Congress, should set policy, and he sought to bypass the Whig establishment led by Senator Henry Clay. Almost all of Tyler's cabinet resigned shortly into his term and the Whigs expelled him from the party and dubbed him "His Accidency". Tyler was the first president to have his veto of legislation overridden by Congress. He faced a stalemate on domestic policy, although he had several foreign-policy achievements, including the Webster–Ashburton Treaty with Britain and the Treaty of Wanghia with China. Tyler was a believer in manifest destiny and saw the annexation of Texas as economically and internationally advantageous to the United States, signing a bill to offer Texas statehood just before leaving office.
When the American Civil War began in 1861, Tyler at first supported the Peace Conference. When it failed, he sided with the Confederacy. He presided over the opening of the Virginia Secession Convention and served as a member of the Provisional Congress of the Confederate States. Tyler subsequently won election to the Confederate House of Representatives but died before it assembled. Some scholars have praised Tyler's political influence, but historians have generally put Tyler near the bottom quartile when ranking U.S. presidents. Tyler is praised for helping in the creation of the Webster–Ashburton Treaty, which peacefully settled the border between Maine and Canada. He also helped in stopping African slave trafficking, which was made illegal under the Jefferson administration. Today, Tyler is seldom remembered when in comparison to other presidents and maintains only a limited presence in American cultural memory.
Early life and education
John Tyler was born on March 29, 1790, to a prominent slave-owning Virginia family. Tyler hailed from Charles City County, Virginia, and was descended from the First Families of Virginia. The Tyler family traced its lineage to English settlers and 17th-century colonial Williamsburg. His father, John Tyler Sr., commonly known as Judge Tyler, was a personal and political friend and college roommate of Thomas Jefferson and served in the Virginia House of Delegates alongside Benjamin Harrison V, father of William Henry Harrison. The elder Tyler served four years as Speaker of the Virginia House of Delegates before becoming a state court judge and later governor of Virginia and a judge on the U.S. District Court for the Eastern District of Virginia at Richmond. His wife, Mary Marot (Armistead), was the daughter of prominent New Kent County plantation owner and one-term delegate, Robert Booth Armistead. She died of a stroke in 1797 when her son John was seven years old.
With his two brothers and five sisters, Tyler was reared on Greenway Plantation, a estate with a six-room manor house his father had built. Enslaved labor tended various crops, including wheat, corn and tobacco. Judge Tyler paid high wages for tutors who challenged his children academically. Tyler was of frail health, thin and prone to diarrhea. At age 12, he continued a Tyler family tradition and entered the preparatory branch of the College of William and Mary. Tyler graduated from the school's collegiate branch in 1807, at age 17. Adam Smith's The Wealth of Nations helped form his economic views, and he acquired a lifelong love of William Shakespeare. Bishop James Madison, the college's president, served as a second father and mentor to Tyler.
After graduation, Tyler read the law with his father, then a state judge, and later with Edmund Randolph, former United States Attorney General.
Planter and lawyer
Tyler was admitted to the Virginia bar at the age of 19 (too young to be eligible, but the admitting judge neglected to ask his age). By this time, his father was governor of Virginia, and Tyler started a legal practice in Richmond, the state capital. According to the 1810 federal census, one "John Tyler" (presumably his father) owned eight slaves in Richmond, and possibly five slaves in adjoining Henrico County, and possibly 26 slaves in Charles City County.
In 1813, the year of his father's death, the younger Tyler purchased Woodburn plantation, where he lived until 1821. As of 1820, Tyler owned 24 enslaved persons at Woodburn, after having inherited 13 enslaved persons from his father, although only eight were listed as engaged in agriculture in that census.
Political rise
Start in Virginia politics
In 1811, at age 21, Tyler was elected to represent Charles City County in the House of Delegates. He served five successive one-year terms (the first alongside Cornelius Egmon and later with Benjamin Harrison). As a state legislator, Tyler sat on the Courts and Justice Committee. His defining positions were on display by the end of his first term in 1811—strong, staunch support of states' rights and opposition to a national bank. He joined fellow legislator Benjamin W. Leigh in supporting the censure of U.S. senators William Branch Giles and Richard Brent of Virginia who had, against the Virginia legislature's instructions, voted for the recharter of the First Bank of the United States.
War of 1812
Like most Southern Americans of his day, Tyler was anti-British, and at the onset of the War of 1812, he urged support for military action in a speech to the House of Delegates. After the British capture of Hampton, Virginia, in the summer of 1813, Tyler eagerly organized a militia company, the Charles City Rifles, to defend Richmond, which he commanded with the rank of captain. No attack came, and he dissolved the company two months later. For his military service, Tyler received a land grant near what later became Sioux City, Iowa.
Tyler's father died in 1813, and Tyler inherited 13 slaves along with his father's plantation. In 1816, he resigned his legislative seat to serve on the Governor's Council of State, a group of eight advisers elected by the General Assembly.
U.S. House of Representatives
The death of U.S. Representative John Clopton in September 1816 created a vacancy in Virginia's 23rd congressional district. Tyler sought the seat, as did his friend and political ally Andrew Stevenson. Since the two men were politically alike, the race was, for the most part, a popularity contest. Tyler's political connections and campaigning skills narrowly won him the election. He was sworn into the Fourteenth Congress on December 17, 1816, to serve as a Democratic-Republican, the major political party in the Era of Good Feelings.
While the Democratic-Republicans had supported states' rights, many members urged a stronger central government in the wake of the War of 1812. A majority in Congress wanted to see the federal government help to fund internal improvements such as ports and roadways. Tyler held fast to his strict constructionist beliefs, rejecting such proposals on constitutional and personal grounds. He believed each state should construct necessary projects within its borders using locally generated funds. Virginia was not "in so poor a condition as to require a charitable donation from Congress", he contended. He was chosen to participate in an audit of the Second Bank of the United States in 1818 as part of a five-man committee, and was appalled by the corruption which he perceived within the bank. He argued for the revocation of the bank charter, although Congress rejected any such proposal. His first clash with General Andrew Jackson followed Jackson's 1818 invasion of Florida during the First Seminole War. While praising Jackson's character, Tyler condemned him as overzealous for the execution of two British subjects. Tyler was elected for a full term without opposition in early 1819.
The major issue of the Sixteenth Congress (1819–1821) was whether Missouri should be admitted to the Union and whether slavery would be permitted in the new state. Acknowledging the ills of slavery, he hoped that by letting it expand, there would be fewer slaves in the East as slaves and masters journeyed west, making it feasible to consider abolishing the institution in Virginia. Thus, slavery would be abolished through the action of individual states as the practice became rare, as had been done in some Northern states. Tyler believed that Congress did not have the power to regulate slavery and that admitting states based on whether they were slave or free was a recipe for sectional conflict; therefore, the Missouri Compromise was enacted without Tyler's support. It admitted Missouri as a slave state and Maine as a free one, and it also forbade slavery in states formed from the northern part of the territories. Throughout his time in Congress, he voted against bills that would restrict slavery in the territories.
Tyler declined to seek renomination in late 1820, citing frequently ill health. He privately acknowledged his dissatisfaction with the position, as his opposing votes were largely symbolic and did little to change the political culture in Washington; he also observed that funding his children's education would be difficult on a congressman's low salary. He left office on March 3, 1821, endorsing his former opponent Stevenson for the seat, and returned to private law practice full-time.
Return to state politics
Restless and bored after two years at home practicing law, Tyler sought election to the House of Delegates in 1823. Neither member from Charles City County was seeking reelection, and Tyler was elected easily that April, finishing first among the three candidates seeking the two seats. As the legislature convened in December, Tyler found the chamber debating the impending presidential election of 1824. The congressional nominating caucus, an early system for choosing presidential candidates, was still used despite its growing unpopularity. Tyler tried to convince the lower house to endorse the caucus system and choose William H. Crawford as the Democratic-Republican candidate. Crawford captured the legislature's support, but Tyler's proposal was defeated. His most enduring effort in this second legislative tenure was saving the College of William and Mary, which risked closure from waning enrollment. Rather than move it from rural Williamsburg to the more populated capital at Richmond, as some suggested, Tyler proposed administrative and financial reforms. These were passed into law and were successful; by 1840, the school achieved its highest enrollment.
Tyler's political fortunes were growing; he was considered a possible candidate in the legislative deliberation for the 1824 U.S. Senate election. He was nominated in December 1825 for governor of Virginia, a position which was then appointed by the legislature. Tyler was elected 131–81 over John Floyd. The office of governor was powerless under the original Virginia Constitution (1776–1830), lacking even veto authority. Tyler enjoyed a prominent oratorical platform but could do little to influence the legislature. His most visible act as governor was delivering the funeral address for former president Jefferson, a Virginian and a former governor, who had died on July 4, 1826. Tyler was deeply devoted to Jefferson, and his eloquent eulogy was well received.
Tyler's governorship was otherwise uneventful. He promoted states' rights and adamantly opposed any concentration of federal power. To thwart federal infrastructure proposals, he suggested Virginia actively expand its road system. A proposal was made to expand the state's poorly funded public school system, but no significant action was taken. Tyler was unanimously reelected to a second one-year term in December 1826.
In 1829, Tyler was elected as a delegate to the Virginia Constitutional Convention of 1829–1830 from the district encompassing the cities of Richmond and Williamsburg and Charles City County, James City County, Henrico County, New Kent County, Warwick County, and York County. There, he served alongside Chief Justice John Marshall (a Richmond resident), Philip N. Nicholas and John B. Clopton. The leadership assigned him to the Committee on the Legislature. Tyler's service in various capacities at a state level included as president of the Virginia Colonization Society and much later as rector and chancellor of the College of William and Mary.
U.S. Senate
In January 1827, the General Assembly considered whether to elect U.S. Senator John Randolph for a full six-year term. Randolph was a contentious figure; although he shared the staunch views on states' rights held by most of the Virginia legislature, he had a reputation for fiery rhetoric and erratic behavior on the Senate floor, which put his allies in an awkward position. Furthermore, he had made enemies by fiercely opposing President John Quincy Adams and Kentucky Senator Henry Clay. The nationalists of the Democratic-Republican Party, who supported Adams and Clay, were a sizable minority in the Virginia legislature. They hoped to unseat Randolph by capturing the vote of states' rights supporters who were uncomfortable with the senator's reputation. They approached Tyler and promised their endorsement if he sought the seat. Tyler repeatedly declined the offer, endorsing Randolph as the best candidate, but the political pressure continued to mount. Eventually, he agreed to accept the seat if chosen. On the day of the vote, one assemblyman argued there was no political difference between the candidates—Tyler was more agreeable than Randolph. The incumbent's supporters contended that Tyler's election would be a tacit endorsement of the Adams administration. The legislature selected Tyler in a vote of 115–110, and he resigned his governorship on March 4, 1827, as his Senate term began.
Democratic maverick
By the time of Tyler's senatorial election, the 1828 campaign for president was in progress. Adams, the incumbent president, was challenged by Andrew Jackson. The Democratic-Republicans had splintered into Adams's National Republicans and Jackson's Democrats. Tyler disliked both candidates for their willingness to increase the federal government's power, but was increasingly drawn to Jackson, hoping that he would not seek to spend as much federal money on internal improvements as Adams. Of Jackson, he wrote, "Turning to him I may at least indulge in hope; looking on Adams I must despair."
When the Twentieth Congress began in December 1827, Tyler served alongside his Virginia colleague and friend Littleton Waller Tazewell, who shared his strict constructionist views and uneasy support of Jackson. Throughout his tenure, Tyler vigorously opposed national infrastructure bills, feeling these were matters for individual states to decide. He and his Southern colleagues unsuccessfully opposed the protectionist Tariff of 1828, known to its detractors as the "Tariff of Abominations". Tyler suggested that the tariff's only positive outcome would be a national political backlash, restoring a respect for states' rights. He remained a strong supporter of states' rights, saying, "they may strike the Federal Government out of existence by a word; demolish the Constitution and scatter its fragments to the winds".
Tyler was soon at odds with President Jackson, frustrated by Jackson's newly emerging spoils system, describing it as an "electioneering weapon". He voted against many of Jackson's nominations when they appeared to be unconstitutional or motivated by patronage. Opposing the nominations of a president of his party was considered "an act of insurgency" against his party. Tyler was particularly offended by Jackson's use of the recess appointment power to name three treaty commissioners to meet with emissaries from the Ottoman Empire and introduced a bill chastising Jackson for this.
In some matters, Tyler was on good terms with Jackson. He defended Jackson for vetoing the Maysville Road funding project, which Jackson considered unconstitutional. He voted to confirm several of Jackson's appointments, including Jackson's future running mate Martin Van Buren as United States Minister to Britain. The leading issue in the 1832 presidential election was the recharter of the Second Bank of the United States, which both Tyler and Jackson opposed. Congress voted to recharter the bank in July 1832, and Jackson vetoed the bill for constitutional and practical reasons. Tyler voted to sustain the veto and endorsed Jackson in his successful bid for reelection.
Break with the Democratic Party
Tyler's uneasy relationship with his party came to a head during the 22nd Congress, as the nullification crisis of 1832–1833 began. South Carolina, threatening secession, passed the Ordinance of Nullification in November 1832, declaring the "Tariff of Abominations" null and void within its borders. This raised the constitutional question of whether states could nullify federal laws. Jackson, who denied such a right, prepared to sign a Force Bill allowing the federal government to use military action to enforce the tariff. Tyler, who sympathized with South Carolina's reasons for nullification, rejected Jackson's use of military force against a state and gave a speech in February 1833 outlining his views. He supported Clay's Compromise Tariff, enacted that year, to gradually reduce the tariff over ten years, alleviating tensions between the states and the federal government.
In voting against the Force Bill, Tyler knew he would permanently alienate the pro-Jackson faction of the Virginia legislature, even those who had tolerated his irregularity up to this point. This jeopardized his reelection in February 1833, in which he faced the pro-administration Democrat James McDowell, but with Clay's endorsement, Tyler was reelected by a margin of 12 votes.
Jackson further offended Tyler by moving to dissolve the Bank by executive fiat. In September 1833, Jackson issued an executive order directing Treasury Secretary Roger B. Taney to transfer federal funds from the Bank to state-chartered banks immediately. Tyler saw this as "a flagrant assumption of power", a breach of contract, and a threat to the economy. After months of agonizing, he decided to join with Jackson's opponents. Sitting on the Senate Finance Committee, he voted for two censure resolutions against the president in March 1834. By this time, Tyler had become affiliated with Clay's newly formed Whig Party, which held control of the Senate. On March 3, 1835, with only hours remaining in the congressional session, the Whigs voted Tyler President pro tempore of the Senate as a symbolic gesture of approval. He is the only U.S. president to have held this office.
Shortly after that, the Democrats took control of the Virginia House of Delegates. Tyler was offered a judgeship in exchange for resigning his seat, but he declined. He understood what was to come: the legislature would soon force him to vote against his constitutional beliefs. Senator Thomas Hart Benton of Missouri had introduced a bill expunging Jackson's censure. By resolution of the Democratic-controlled legislature, Tyler could be instructed to vote for the bill. If he disregarded the instructions, he would violate his own principles: "the first act of my political life was a censure on Messrs. Giles and Brent for opposition to instructions", he noted. Over the next few months he sought the counsel of his friends, who gave him conflicting advice. By mid-February he felt that his Senate career was likely at an end. He issued a letter of resignation to Vice President Van Buren on February 29, 1836, saying in part:
1836 presidential election
While Tyler wished to attend to his private life and family, he was soon occupied with the 1836 presidential election. He had been suggested as a vice presidential candidate since early 1835, and the same day the Virginia Democrats issued the expunging instruction, the Virginia Whigs nominated him as their candidate. The new Whig Party was not organized enough to hold a national convention and name a single ticket against Van Buren, Jackson's chosen successor. Instead, Whigs in various regions put forth their own preferred tickets, reflecting the party's tenuous coalition: the Massachusetts Whigs nominated Daniel Webster and Francis Granger, the Anti-Masons of the Northern and border states backed William Henry Harrison and Granger, and the states' rights advocates of the middle and lower South nominated Hugh Lawson White and John Tyler. In Maryland, the Whig ticket was Harrison and Tyler and in South Carolina it was Willie P. Mangum and Tyler. The Whigs wanted to deny Van Buren a majority in the Electoral College, throwing the election into the House of Representatives, where deals could be made. Tyler hoped electors would be unable to elect a vice president, and that he would be one of the top two vote-getters, from whom the Senate, under the Twelfth Amendment, must choose.
Following the custom of the times—that candidates not appear to seek the office—Tyler stayed home throughout the campaign, and made no speeches. He received only 47 electoral votes, from Georgia, South Carolina and Tennessee, in the November 1836 election, trailing both Granger and the Democratic candidate, Richard Mentor Johnson of Kentucky. Harrison was the leading Whig candidate for president, but he lost to Van Buren. The presidential election was settled by the Electoral College, but for the only time in American history, the vice-presidential election was decided by the Senate, which selected Johnson over Granger on the first ballot.
National political figure
Tyler had been drawn into Virginia politics as a U.S. senator. From October 1829 to January 1830, he served as a member of the state constitutional convention, a role he had been reluctant to accept. The original Virginia Constitution gave outsize influence to the state's more conservative eastern counties, as it allocated an equal number of legislators to each county regardless of population and granted suffrage only to property owners. The convention gave the more populous and liberal counties of western Virginia an opportunity to expand their influence. A slaveowner from eastern Virginia, Tyler supported the existing system, but largely remained on the sidelines during the debate, not wishing to alienate any of the state's political factions. He was focused on his Senate career, which required a broad base of support, and gave speeches during the convention promoting compromise and unity.
After the 1836 election, Tyler thought his political career was over, and planned to return to private law practice. In the fall of 1837 a friend sold him a sizable property in Williamsburg. Unable to remain away from politics, Tyler successfully sought election to the House of Delegates and took his seat in 1838. He was a national political figure by this point, and his third delegate service touched on such national issues as the sale of public lands.
Tyler's successor in the Senate was William Cabell Rives, a conservative Democrat. In February 1839, the General Assembly considered who should fill that seat, which was to expire the following month. Rives had drifted away from his party, signalling a possible alliance with the Whigs. As Tyler had already fully rejected the Democrats, he expected the Whigs would support him. Still, many Whigs found Rives a more politically expedient choice, as they hoped to ally with the conservative wing of the Democratic Party in the 1840 presidential election. This strategy was supported by Whig leader Henry Clay, who nevertheless admired Tyler at that time. With the vote split among three candidates, including Rives and Tyler, the Senate seat remained vacant for almost two years, until January 1841.
1840 presidential election
Adding Tyler to the ticket
When the 1839 Whig National Convention convened in Harrisburg, Pennsylvania, to choose the party's ticket, the nation was in the third year of a serious recession following the Panic of 1837. Van Buren's ineffective efforts to deal with the situation cost him public support. With the Democratic Party torn into factions, the head of the Whig ticket would likely be the next president. Harrison, Clay, and General Winfield Scott all sought the nomination. Tyler attended the convention and was with the Virginia delegation, although he had no official status. Because of bitterness over the unresolved Senate election, the Virginia delegation refused to make Tyler its favorite son candidate for vice president. Tyler himself did nothing to aid his chances. If his favored candidate for the presidential nomination, Clay, was successful, he would likely not be chosen for the second place on the ticket, which would probably go to a Northerner to assure geographic balance.
The convention deadlocked among the three main candidates, with Virginia's votes going to Clay. Many Northern Whigs opposed Clay, and some, including Pennsylvania's Thaddeus Stevens, showed the Virginians a letter by Scott in which he apparently displayed abolitionist sentiments. The influential Virginia delegation then announced that Harrison was its second choice, causing most Scott supporters to abandon him in favor of Harrison, who gained the presidential nomination.
The vice presidential nomination was considered immaterial; no president had failed to complete his elected term. Not much attention was given to the choice, and the specifics of how Tyler came to gain it are unclear. Chitwood pointed out that Tyler was a logical candidate: as a Southern slaveowner, he balanced the ticket and also assuaged the fears of Southerners who felt Harrison might have abolitionist leanings. Tyler had been a vice-presidential candidate in 1836, and having him on the ticket might win Virginia, the most populous state in the South. One of the convention managers, New York publisher Thurlow Weed, alleged that "Tyler was finally taken because we could get nobody else to accept"—though he did not say this until after the subsequent break between President Tyler and the Whig Party. Other Tyler foes claimed that he had wept himself into the White House, after crying at Clay's defeat; this was unlikely, as the Kentuckian had backed Tyler's opponent Rives in the Senate election. Tyler's name was submitted in the balloting, and though Virginia abstained, he received the necessary majority. As president, Tyler was accused of having gained the nomination by concealing his views, and responded that he had not been asked about them. His biographer Robert Seager II held that Tyler was selected because of a dearth of alternative candidates. Seager concluded, "He was put on the ticket to draw the South to Harrison. No more, no less."
General election
There was no Whig platform—the party leaders decided that trying to put one together would tear the party apart. So the Whigs ran on their opposition to Van Buren, blaming him and his Democrats for the recession. In campaign materials, Tyler was praised for integrity in resigning over the state legislature's instructions. The Whigs initially hoped to muzzle Harrison and Tyler, lest they make policy statements that alienated segments of the party. But after Tyler's Democratic rival, Vice President Johnson, made a successful speaking tour, Tyler was called upon to travel from Williamsburg to Columbus, Ohio, and there address a local convention, in a speech intended to assure Northerners that he shared Harrison's views. In his journey of nearly two months, Tyler made speeches at rallies. He could not avoid questions, and after being heckled into an admission that he supported the Compromise Tariff (many Whigs did not), resorted to quoting from Harrison's vague speeches. In his two-hour speech at Columbus, Tyler entirely avoided the issue of the Bank of the United States, one of the major questions of the day.
To win the election, Whig leaders decided they had to mobilize people across the country, including women, who could not then vote. This was the first time that an American political party included women in campaign activities on a widespread scale, and women in Tyler's Virginia were active on his behalf. The party hoped to avoid issues and win through public enthusiasm, with torchlight processions and alcohol-fueled political rallies. The interest in the campaign was unprecedented, with many public events. When the Democratic press depicted Harrison as an old soldier, who would turn aside from his campaign if given a barrel of hard cider to drink in his log cabin, the Whigs eagerly seized on the image, and the log cabin campaign was born. The fact that Harrison lived on a palatial estate along the Ohio River and that Tyler was well-to-do was ignored, while log cabin images appeared everywhere, from banners to whiskey bottles. Cider was the favored beverage of many farmers and tradesmen, and Whigs claimed that Harrison preferred that drink of the common man.
The presidential candidate's military service was emphasized, thus the well-known campaign jingle, "Tippecanoe and Tyler Too", referring to Harrison's victory at the Battle of Tippecanoe. Glee clubs sprouted all over the country, singing patriotic and inspirational songs: one Democratic editor stated that he found the songfests in support of the Whig Party to be unforgettable. Among the lyrics sung were "We shall vote for Tyler therefore/Without a why or wherefore". Louis Hatch, in his history of the vice presidency, noted, "the Whigs roared, sang, and hard-cidered the 'hero of Tippecanoe' into the White House".
Clay, though embittered by another of his many defeats for the presidency, was appeased by Tyler's withdrawal from the still-unresolved Senate race, which would permit the election of Rives, and campaigned in Virginia for the Harrison/Tyler ticket. Tyler predicted the Whigs would easily take Virginia; he was embarrassed when he was proved wrong, but was consoled by an overall victory—Harrison and Tyler won by an electoral vote of 234–60 and with 53% of the popular vote. Van Buren took only seven states out of 26. The Whigs gained control of both houses of Congress.
Vice presidency (1841)
As vice president-elect, Tyler remained quietly at his home in Williamsburg. He privately expressed hopes that Harrison would prove decisive and not allow intrigue in the Cabinet, especially in the first days of the administration. Tyler did not participate in selecting the Cabinet, and did not recommend anyone for federal office in the new Whig administration. Beset by office seekers and the demands of Senator Clay, Harrison twice sent Tyler letters asking his advice as to whether a Van Buren appointee should be dismissed. In both cases, Tyler recommended against, and Harrison wrote, "Mr. Tyler says they ought not to be removed, and I will not remove them." The two men met briefly in Richmond in February, and reviewed a parade together, though they did not discuss politics.
Tyler was sworn in on March 4, 1841, in the Senate chamber, and delivered a three-minute speech about states' rights before swearing in the new senators and then attending Harrison's inauguration. Following the new president's two-hour speech before a large crowd in freezing weather, Tyler returned to the Senate to receive the president's Cabinet nominations, presiding over the confirmations the following day—a total of two hours as president of the Senate. Expecting few responsibilities, he then left Washington, quietly returning to his home in Williamsburg. Seager later wrote, "Had William Henry Harrison lived, John Tyler would undoubtedly have been as obscure as any vice-president in American history."
Meanwhile, Harrison struggled to keep up with the demands of Clay and others who sought offices and influence in his administration. Harrison's age and fading health were no secret during the campaign, and the question of presidential succession was on every politician's mind. The first few weeks of the presidency took a toll on Harrison's health, and after being caught in a rainstorm in late March he came down with pneumonia and pleurisy. Secretary of State Daniel Webster sent word to Tyler of Harrison's illness on April 1; two days later, Richmond attorney James Lyons wrote with the news that the president had taken a turn for the worse, remarking, "I shall not be surprised to hear by tomorrow's mail that Gen'l Harrison is no more." Tyler decided not to travel to Washington, not wanting to appear unseemly in anticipating Harrison's death. At dawn on April 5, Webster's son Fletcher, chief clerk of the State Department, arrived at Tyler's Williamsburg home to officially inform him of Harrison's death the morning before. Tyler left Williamsburg and arrived in Washington at dawn the next day.
Presidency (1841–1845)
Harrison's death in office was an unprecedented event that caused considerable uncertainty about presidential succession. Article II, Section 1, Clause 6 of the United States Constitution, which governed intra-term presidential succession at the time (now superseded by the Twenty-fifth Amendment), states:
Interpreting this Constitutional prescription led to the question of whether the actual office of president devolved upon Tyler, or merely its powers and duties. The Cabinet met within an hour of Harrison's death and, according to a later account, determined that Tyler would be "vice-president acting president". But Tyler firmly and decisively asserted that the Constitution gave him the full and unqualified powers of the office. Accordingly, he had himself sworn in immediately as president, moved into the White House and assumed full presidential powers. This set a critical precedent for an orderly transfer of power following a president's death, though it was not codified until the passage of the 25th Amendment in 1967. Judge William Cranch administered the presidential oath in Tyler's hotel room. Tyler considered the oath redundant to his oath as vice president, but wished to quell any doubt over his accession. When he took office, Tyler, at 51, became the youngest president to that point. His record was in turn surpassed by his immediate successor James Polk, who was inaugurated at the age of 49.
"Fearing that he would alienate Harrison's supporters, Tyler decided to keep Harrison's entire cabinet even though several members were openly hostile to him and resented his assumption of the office." At his first cabinet meeting, Webster informed him of Harrison's practice of making policy by a majority vote. (This was a dubious assertion, since Harrison had held few cabinet meetings and had boldly asserted his authority over the cabinet in at least one.) The Cabinet fully expected the new president to continue this practice. Tyler was astounded and immediately corrected them:
Tyler delivered an informal written inaugural address to the Congress on April 9, in which he reasserted his belief in fundamental tenets of Jeffersonian democracy and limited federal power. Tyler's claim to be president was not immediately accepted by opposition members of Congress such as John Quincy Adams, who felt that Tyler should be a caretaker under the title of "acting president", or remain vice president in name. Among those who questioned Tyler's authority was Clay, who had planned to be "the real power behind a fumbling throne" while Harrison was alive, and intended the same for Tyler. Clay saw Tyler as the "vice-president" and his presidency as a mere "regency".
Ratification of the decision by Congress came through the customary notification that it makes to the president, that it is in session and available to receive messages. In both houses, unsuccessful amendments were offered to strike the word "president" in favor of language including the term "vice president" to refer to Tyler. Mississippi Senator Robert J. Walker, in opposition, said that the idea that Tyler was still vice president and could preside over the Senate was absurd. On May 31, 1841, the House passed a joint resolution confirming Tyler as "President of the United States" for the remainder of his term. On June 1, 1841, the Senate voted in favor of the resolution. Most importantly, Senators Clay and John C. Calhoun voted with the majority to reject Walker's amendment.
Tyler's opponents never fully accepted him as president. He was called by many mocking nicknames, including "His Accidency". But Tyler never wavered from his conviction that he was the rightful president; when his political opponents sent correspondence to the White House addressed to the "vice president" or "acting president", Tyler had it returned unopened.
Tyler was considered a strong leader for his decisive action on his accession to the presidency. But he generally held a limited view of presidential power, that legislation should be initiated by Congress, and the presidential veto should be only used when a law was unconstitutional or against the national interest.
Economic policy and party conflicts
Like Harrison, Tyler had been expected to adhere to Whig Party Congressional public policies and to defer to Whig party leader Clay. The Whigs especially demanded that Tyler curb the veto power, in response to Jackson's perceived authoritarian presidency. Clay had envisioned Congress to be modeled after a parliamentary-type system where he was the leader. Initially Tyler concurred with the new Whig Congress, signing into law the preemption bill granting "squatters' sovereignty" to settlers on public land, a Distribution Act (discussed below), a new bankruptcy law, and the repeal of the Independent Treasury. But when it came to the great banking question, Tyler was soon at odds with the Congressional Whigs, and twice vetoed Clay's legislation for a national banking act. Although the second bill was originally tailored to meet his objections in the first veto, its final version did not. This practice, designed to protect Clay from having a successful incumbent president as a rival for the Whig nomination in 1844, became known as "heading Captain Tyler", a term coined by Whig Representative John Minor Botts of Virginia. Tyler proposed an alternative fiscal plan known as the "Exchequer", but Clay's friends who controlled the Congress would have none of it.
On September 11, 1841, after the second bank veto, members of the cabinet entered Tyler's office one by one and resigned—an orchestration by Clay to force Tyler's resignation and place his own lieutenant, Senate President pro tempore Samuel L. Southard, in the White House. The only exception was Webster, who remained to finalize what became the 1842 Webster–Ashburton Treaty, and to demonstrate his independence from Clay. When told by Webster that he was willing to stay, Tyler is reported to have said, "Give me your hand on that, and now I will say to you that Henry Clay is a doomed man." On September 13, when the president did not resign or give in, the Whigs in Congress expelled Tyler from the party. Tyler was lambasted by Whig newspapers and received hundreds of letters threatening his assassination. Whigs in Congress were so angry with Tyler that they refused to allocate funds to fix the White House, which had fallen into disrepair.
Tariff and distribution debate
By mid-1841, the federal government faced a projected budget deficit of $11 million. Tyler recognized the need for higher tariffs, but wished to stay within the 20% rate created by the 1833 Compromise Tariff. He also supported a plan to distribute to the states any revenue from the sales of public land, as an emergency measure to manage the states' growing debt, even though this would cut federal revenue. The Whigs supported high protectionist tariffs and national funding of state infrastructure, and so there was enough overlap to forge a compromise. The Distribution Act of 1841 created a distribution program, with a ceiling on tariffs at 20%; a second bill increased tariffs to that figure on previously low-tax goods. Despite these measures, by March 1842 it had become clear that the federal government was still in dire fiscal straits.
The root of the trouble was an economic crisis—initiated by the Panic of 1837—that was entering its sixth year in 1842. A speculative bubble had burst in 1836–39, causing a collapse of the financial sector and a subsequent depression. The country became deeply divided over the best response to the crisis. Conditions got even worse in early 1842 because a deadline was looming. A decade earlier, when the economy was strong, Congress had promised Southern states that there would be a reduction in hated federal tariffs. Northern states welcomed tariffs, which protected their infant industries. But the South had no industrial base and depended on open access to British markets for their cotton. In a recommendation to Congress, Tyler lamented that it would be necessary to override the Compromise Tariff of 1833 and raise rates beyond the 20 percent limit. Under the previous deal, this would suspend the distribution program, with all revenues going to the federal government.
The defiant Whig Congress would not raise tariffs in a way that would affect the distribution of funds to states. In June 1842 they passed two bills that would raise tariffs and unconditionally extend the distribution program. Believing it improper to continue distribution at a time when federal revenue shortage necessitated increasing the tariff, Tyler vetoed both bills, burning any remaining bridges between himself and the Whigs. Congress tried again, combining the two into one bill; Tyler vetoed it again, to the dismay of many in Congress, who nevertheless failed to override the veto. As some action was necessary, Whigs in Congress, led by the House Ways and Means chairman Millard Fillmore, passed in each house (by one vote) a bill restoring tariffs to 1832 levels and ending the distribution program. Tyler signed the Tariff of 1842 on August 30, pocket vetoing a separate bill to restore distribution.
New York Customs House reform
In May 1841, President Tyler appointed three private citizens to investigate fraud in the New York Customs House that supposedly took place under President Martin Van Buren. The commission was led by George Poindexter, former governor, and Mississippi U.S. Senator. The commission uncovered fraudulent activities by Jesse D. Hoyt, the New York Collector under Van Buren. The commission's investigation caused controversy with the Whig-controlled Congress, which demanded to see the investigation report and was upset that Tyler paid the commission without Congressional approval. Tyler responded and said it was his constitutional duty to enforce the laws. When the report was finished on April 29, 1842, the House asked for the report, and Tyler complied. Poindexter's report proved embarrassing to the Whig New York Collector as well as to Hoyt. To curb Tyler's power, Congress passed an appropriations law that made it illegal for the president to appropriate money to investigators without Congressional approval.
House petition of impeachment
Shortly after the tariff vetoes, Whigs in the House of Representatives initiated that body's first impeachment proceedings against a president. The congressional ill will towards Tyler derived from the basis for his vetoes; until the presidency of the Whigs' archenemy Andrew Jackson, presidents rarely vetoed bills, and then only on grounds of constitutionality. Tyler's actions were in opposition to the presumed authority of Congress to make policy. Congressman John Botts, who opposed Tyler, introduced an impeachment resolution on July 10, 1842. Botts levied nine formal articles of impeachment for "high crimes and misdemeanors" against Tyler. Six of the charges against Tyler pertained to political abuse of power, while three concerned his alleged misconduct in office. Additionally, Botts called for a nine-member committee to investigate Tyler's behavior, with the expectation of a formal impeachment recommendation. Clay found this measure prematurely aggressive and favored a more moderate progression toward Tyler's "inevitable" impeachment. Botts's resolution was tabled until January 1843 when it was rejected by a vote of 127 to 83.
A House select committee headed by John Quincy Adams, an ardent abolitionist who disliked slaveholders like Tyler, condemned Tyler's use of the veto and assailed his character. While the committee's report did not formally recommend impeachment, it clearly established the possibility, and in August 1842 the House endorsed the committee's report. Adams sponsored a constitutional amendment to change both houses' two-thirds requirement for overriding vetoes to a simple majority, but neither house approved it. The Whigs were unable to pursue further impeachment proceedings in the subsequent 28th Congress—in the elections of 1842, they retained a majority in the Senate but lost control of the House. On the last full day of Tyler's term in office, March 3, 1845, Congress overrode his veto of a minor bill relating to revenue cutters—the first override of a presidential veto.
Tyler was not without support in Congress, including fellow Virginia Congressman Henry Wise. A handful of House members, known as the "Corporal's Guard", led by Wise, supported Tyler throughout his struggles with the Whigs. As a reward, Tyler appointed Wise U.S. Minister to Brazil in 1844.
Foreign affairs
Tyler's difficulties in domestic policy contrasted with his accomplishments in foreign policy. He had long been an advocate of expansionism toward the Pacific and free trade, and was fond of evoking themes of national destiny and the spread of liberty in support of these policies. His positions were largely in line with Jackson's earlier efforts to promote American commerce across the Pacific. Eager to compete with Great Britain in international markets, he sent lawyer Caleb Cushing to China, where he negotiated the terms of the Treaty of Wanghia (1844). The same year, he sent Henry Wheaton as a minister to Berlin, where he negotiated and signed a trade agreement with the Zollverein, a coalition of German states that managed tariffs. This treaty was rejected by the Whigs, mainly as a show of hostility toward the Tyler administration. Tyler advocated an increase in military strength and this drew praise from naval leaders, who saw a marked increase in warships.
In an 1842 special message to Congress, Tyler also applied the Monroe Doctrine to Hawaii (dubbed the "Tyler Doctrine"), told Britain not to interfere there, and began a process that led to the eventual annexation of Hawaii by the United States.
Webster-Ashburton treaty
A foreign crisis erupted in an offshoot of the Aroostook War, that ended in 1839. Citizens of Maine clashed with citizens of New Brunswick over disputed territory, that covered 12,000 square miles. In 1841, an American ship, the Creole, was transporting slaves from Virginia to New Orleans. A mutiny took place, and the ship was captured by the British and taken to the Bahamas. The British refused to return the slaves to their masters. Tyler's Secretary of State, Daniel Webster, eager to settle the matter with England, had Tyler's full support and confidence. In 1842, the British dispatched emissary Lord Ashburton (Alexander Baring) to the United States. Soon, favorable negotiations were started.
The negotiations culminated in the Webster–Ashburton Treaty, which determined the border between Maine and Canada. That issue had caused tension between the U.S. and Britain for decades and had brought the two countries to the brink of war on several occasions. The treaty improved Anglo-American diplomatic relations. To resolve the slave issue, the U.S. and England agreed to grant the "right to visit" when ships from both nations were suspected of holding slaves. Additionally, in a joint oceanic venture, a U.S. squadron, and the British fleet would cooperate and stop slave trafficking off of African waters.
The issue of the Oregon border in the West was another matter and was attempted to be resolved during the negotiations of the Webster–Ashburton Treaty. At this time Britain and the United States shared Oregon by joint occupation, according to the Convention of 1818. American settlement had been minimal compared to the British, whose fur trading Hudson Bay Company established posts in the Columbia River Valley northward. During the negotiations, the British wanted to divide the territory on the Columbia River. This was unacceptable to Webster, who demanded that Britain pressure Mexico to cede California's San Francisco Bay to the United States. The Tyler administration was unsuccessful in concluding a treaty with the British to fix Oregon's boundaries.
Oregon and the West
Tyler had an interest in the vast territory west of the Rockies known as Oregon, which extended from the northern boundary of California (42° parallel) to the southern boundary of Alaska (54°40′ north latitude). As early as 1841, he urged Congress to establish a chain of American forts from Council Bluffs, Iowa, to the Pacific. The American forts would be used to protect American settlers on a route or trail to Oregon.
Tyler's presidency had two popular successes in western exploration, including Oregon, Wyoming, and California. Captain John C. Frémont completed two interior scientific expeditions (1842 and 1843–1844), which opened the West to American emigration. In his 1842 expedition, Frémont boldly climbed a mountain in Wyoming, Frémont's Peak (13,751 feet), planted an American flag, and symbolically claimed the Rocky Mountains and the West for the United States. In his second expedition starting in 1843, Frémont and his party entered Oregon following the Oregon Trail. Traveling west on the Columbia River, Frémont sighted the Cascade Range peaks and mapped Mount St. Helens and Mount Hood. In early March 1844, Frèmont and his party descended the American River Valley to Sutter's Fort in Mexican California. Given a cordial greeting by John Sutter, Frémont talked to American settlers, who were growing numerous, and discovered Mexican authority over California was very weak. Upon Frémont's triumphal return from his second expedition, at General Winfield Scott's request, Tyler promoted Frémont with a double brevet.
Florida
On Tyler's last full day in office, March 3, 1845, Florida was admitted to the Union as the 27th state.
Dorr Rebellion
In May 1842, when the Dorr Rebellion in Rhode Island came to a head, Tyler pondered the request of the governor and legislature to send in federal troops to help suppress it. The insurgents under Thomas Dorr had armed themselves and proposed to install a new state constitution. Before such acts, Rhode Island had been following the same constitutional structure that was established in 1663. Tyler called for calm on both sides and recommended that the governor enlarge the franchise to let most men vote. Tyler promised that in case an actual insurrection should break out in Rhode Island he would employ force to aid the regular, or Charter, government. He made it clear that federal assistance would be given only to put down an insurrection once underway, and would not be available until violence had taken place. After listening to reports from his confidential agents, Tyler decided that the "lawless assemblages" had dispersed and expressed his confidence in a "temper of conciliation as well as of energy and decision" without the use of federal forces. The rebels fled the state when the state militia marched against them, but the incident led to broader suffrage in the state.
Indian affairs
The Seminoles were the last remaining Indians in the South who had been induced to sign a fraudulent treaty in 1833, taking away their remaining lands. Under Chief Osceola, the Seminoles for a decade resisted removal harassed by U.S. troops. Tyler brought the long, bloody, and inhumane Seminole War to an end in May 1842, in a message to Congress. Tyler expressed interest in the forced cultural assimilation of Native Americans.
In May 1842, the House demanded President Tyler's Secretary of War John Spencer hand over information of an investigation by the U.S. Army into the matter of alleged Cherokee frauds. In June, Tyler ordered Spencer not to comply. Tyler, whose executive privilege was challenged, insisted the matter was ex parte and against the public interest. The House responded with three resolutions, in part, that claimed the House had a right to demand information from Tyler's cabinet. The House also ordered the Army officer in charge of the investigation into the Cherokee frauds to turn over the information. Tyler made no attempt to respond until Congress returned from recess in January.
Administration and cabinet
The battles between Tyler and the Whigs in Congress resulted in a number of his cabinet nominees being rejected. He received little support from Democrats and, without much support from either major party in Congress, a number of his nominations were rejected without regard for the qualifications of the nominee. It was then unprecedented to reject a president's nominees for his Cabinet (though in 1809, James Madison withheld the nomination of Albert Gallatin as Secretary of State because of opposition in the Senate). Four of Tyler's Cabinet nominees were rejected, the most of any president. These were Caleb Cushing (Treasury), David Henshaw (Navy), James Porter (War), and James S. Green (Treasury). Henshaw and Porter served as recess appointees before their rejections. Tyler repeatedly renominated Cushing, who was rejected three times in one day, March 3, 1843, the last day of the 27th Congress. No cabinet nomination failed after Tyler's term until Henry Stanbery's nomination as Attorney General was rejected by the Senate in 1868.
Judicial appointments
Two vacancies occurred on the Supreme Court during Tyler's presidency, as Justices Smith Thompson and Henry Baldwin died in 1843 and 1844, respectively. Tyler, ever at odds with Congress—including the Whig-controlled Senate—nominated several men to the Supreme Court to fill these seats. However, the Senate successively voted against confirming John C. Spencer, Reuben Walworth, Edward King and John M. Read (Walworth was rejected three times, King rejected twice). One reason cited for the Senate's actions was the hope that Clay would fill the vacancies after winning the 1844 presidential election. Tyler's four unsuccessful nominees are the most by a president.
Finally, in February 1845, with less than a month remaining in his term, Tyler's nomination of Samuel Nelson to Thompson's seat was confirmed by the Senate—Nelson, a Democrat, had a reputation as a careful and noncontroversial jurist. Still, his confirmation came as a surprise. Baldwin's seat remained vacant until James K. Polk's nominee, Robert Grier, was confirmed in 1846.
Tyler was able to appoint only six other federal judges, all to United States district courts.
Annexation of Texas
Tyler made the annexation of the Republic of Texas part of his agenda soon after becoming president. Tyler knew he was a President without a party, and was emboldened to challenge party leaders Clay and Van Buren, unconcerned how Texas annexation would affect the Whigs or Democrats. Texas had declared independence from Mexico in the Texas Revolution of 1836, although Mexico still refused to acknowledge its sovereignty. The people of Texas actively pursued joining the Union, but Jackson and Van Buren had been reluctant to inflame tensions over slavery by annexing another Southern state. Though Tyler intended annexation to be the focal point of his administration, Secretary Webster was opposed, and convinced Tyler to concentrate on Pacific initiatives until later in his term. Tyler's desire for western expansionism is acknowledged by historians and scholars, but views differ regarding the motivations behind it. Biographer Edward C. Crapol notes that during the presidency of James Monroe, Tyler (then in the House of Representatives) had suggested slavery was a "dark cloud" hovering over the Union, and that it would be "well to disperse this cloud" so that with fewer blacks in the older slave states, a process of gradual emancipation would begin in Virginia and other upper Southern states. Historian William W. Freehling, however, wrote that Tyler's official motivation in annexing Texas was to outmaneuver suspected efforts by Great Britain to promote an emancipation of slaves in Texas that would weaken the institution in the United States.
Early attempts
In early 1843, having completed the Webster–Ashburton treaty and other diplomatic efforts, Tyler felt ready to pursue Texas. Now lacking a party base, he saw annexation of the republic as his only pathway to independent election in 1844. For the first time in his career he was willing to play "political hardball" to see it through. As a trial balloon he dispatched his ally Thomas Walker Gilmer, then a U.S. Representative from Virginia, to publish a letter defending annexation, which was well received. Despite his successful relationship with Webster, Tyler knew he would need a Secretary of State who supported the Texas initiative. With the work on the British treaty now completed, he forced Webster's resignation and installed Hugh S. Legaré of South Carolina as an interim successor.
With the help of newly appointed Treasury Secretary John C. Spencer, Tyler cleared out an array of officeholders, replacing them with pro-annexation partisans, in a reversal of his former stand against patronage. He elicited the help of political organizer Michael Walsh to build a political machine in New York. In exchange for an appointment as consul to Hawaii, journalist Alexander G. Abell wrote a flattering biography, Life of John Tyler, which was printed in large quantities and given to postmasters to distribute. Seeking to rehabilitate his public image, Tyler embarked on a nationwide tour in the spring of 1843. The positive reception of the public at these events contrasted with his ostracism back in Washington. The tour centered on the dedication of the Bunker Hill Monument in Boston, Massachusetts. Shortly after the dedication, Tyler learned of Legaré's sudden death, which dampened the festivities and caused him to cancel the rest of the tour.
Tyler appointed Abel P. Upshur, a popular Secretary of the Navy and close adviser, as his new Secretary of State, and nominated Gilmer to fill Upshur's former office. Tyler and Upshur began quiet negotiations with the Texas government, promising military protection from Mexico in exchange for a commitment to annexation. Secrecy was necessary, as the Constitution required congressional approval for such military commitments. Upshur planted rumors of possible British designs on Texas to garner support among Northern voters, who were wary of admitting a new pro-slavery state. By January 1844 Upshur told the Texas government that he had found a large majority of senators in favor of an annexation treaty. The republic remained skeptical, and finalization of the treaty took until the end of February.
USS Princeton disaster
A ceremonial cruise down the Potomac River was held aboard the newly built on February 28, 1844, the day after completion of the annexation treaty. Aboard the ship were 400 guests, including Tyler and his cabinet, as was the world's largest naval gun, the "Peacemaker". The gun was ceremoniously fired several times in the afternoon to the great delight of the onlookers, who then filed downstairs to offer a toast. Several hours later, Captain Robert F. Stockton was convinced by the crowd to fire one more shot. As the guests moved up to the deck, Tyler paused briefly to watch his son-in-law, William Waller, sing a ditty.
At once an explosion was heard from above: the gun had malfunctioned. Tyler was unhurt, having remained safely below deck, but a number of others were killed instantly, including his crucial cabinet members, Gilmer and Upshur. Also killed or mortally wounded were Virgil Maxcy of Maryland, Rep. David Gardiner of New York, Commodore Beverley Kennon, Chief of Construction of the United States Navy, and Armistead, Tyler's black slave and body servant. The death of David Gardiner had a devastating effect on his daughter, Julia, who fainted and was carried to safety by the president himself. Julia later recovered from her grief and married Tyler on June 26.
For Tyler, any hope of completing the Texas plan before November (and with it, any hope of re-election) was instantly dashed. Historian Edward P. Crapol later wrote that "Prior to the Civil War and the assassination of Abraham Lincoln", the Princeton disaster "unquestionably was the most severe and debilitating tragedy ever to confront a President of the United States".
Ratification issue
In what the Miller Center of Public Affairs considers "a serious tactical error that ruined the scheme [of establishing political respectability for him]", Tyler appointed former Vice President John C. Calhoun in early March 1844 as his Secretary of State. Tyler's good friend, Virginia Representative Henry A. Wise, wrote that following the Princeton disaster, Wise on his own volition extended Calhoun the position as a self-appointed emissary of the president and Calhoun accepted. When Wise went to tell Tyler what he had done, the president was angry but felt that the action had to stand. Calhoun was a leading advocate of slavery, and his attempts to get an annexation treaty passed were resisted by abolitionists as a result. When the text of the treaty was leaked to the public, it met political opposition from the Whigs, who opposed anything that might enhance Tyler's status, as well as from foes of slavery and those who feared a confrontation with Mexico, which had announced that it would view annexation as a hostile act by the United States. Both Clay and Van Buren, the respective frontrunners for the Whig and Democratic nominations, decided in a private meeting at Van Buren's home to come out against annexation. Knowing this, Tyler was pessimistic when he sent the treaty to the Senate for ratification in April 1844.
Secretary of State Calhoun sent a controversial letter informing the British minister to the U.S. that the motivation for Texas annexation was to protect American slavery from British intrusion. The letter also claimed Southern slaves were better off than Northern free blacks and English white laborers.
Election of 1844
Following Tyler's break with the Whigs in 1841, he attempted a return to his old Democratic party, but its members, especially the followers of Van Buren, were not ready to accept him. As the election of 1844 approached, Van Buren appeared to have a lock on the Democratic nomination, while Clay was certain to be the Whig candidate. With little chance of election, the only way to salvage his presidential legacy was to threaten to run for president and force public acceptance of Texas annexation. Tyler used his vast presidential patronage power, and formed a third party, the Tyler Party, with the officeholders and political networks he had built over the previous year. Multiple supportive newspapers across the country issued editorials promoting his candidacy throughout the early months of 1844. Reports of meetings held throughout the country suggest that support for the president was not limited to officeholders, as is widely assumed. Just as the Democratic Party was holding its presidential nomination in Baltimore, Maryland, the Tyler supporters, in that very city, were holding signs reading "Tyler and Texas!", and with their own high visibility and energy, they gave Tyler their nomination. His party nominated Tyler for the presidency on May 27, 1844. However, Tyler's party was loosely organized, failed to nominate a vice president, and had no platform.
Regular Democrats were forced to call for annexation of Texas in their platform, but there was a bitter battle for the presidential nomination. Ballot after ballot, Van Buren failed to win the necessary super-majority of Democratic votes, and slowly fell in the rankings. It was not until the ninth ballot that the Democrats turned their sights to James K. Polk, a less prominent candidate who supported annexation. They found him to be perfectly suited for their platform, and he was nominated with two-thirds of the vote. Tyler considered his work vindicated, and implied in an acceptance letter that annexation was his true priority rather than election.
In the spring of 1844, Tyler ordered Secretary of State John C. Calhoun to begin negotiations with Texas president Sam Houston for the annexation of Texas. To bolster annexation and keep Mexico at bay, Tyler boldly ordered the U.S. Army to the Texas border on western Louisiana. He strongly supported Texas annexation.
Annexation achieved
Tyler was unfazed when the Whig-controlled Senate rejected his treaty by a vote of 16–35 in June 1844; he felt that annexation was now within reach by joint resolution rather than by treaty, and made that request to Congress. Former President Andrew Jackson, a staunch supporter of annexation, persuaded Polk to welcome Tyler back into the Democratic Party and ordered Democratic editors to cease their attacks on him. Satisfied by these developments, Tyler dropped out of the race in August and endorsed Polk for the presidency. Polk's narrow victory over Clay in the November election was seen by the Tyler administration as a mandate for completing the resolution. Tyler announced in his annual message to Congress that "a controlling majority of the people and a large majority of the states have declared in favor of immediate annexation". On February 26, 1845, the joint resolution that Tyler, the lame-duck president, had strongly lobbied for, passed Congress. The House approved a joint resolution offering annexation to Texas by a substantial margin, and the Senate approved it by a bare 27–25 majority. On his last day in office, March 3, 1845, Tyler signed the bill into law. Immediately afterward, Mexico broke diplomatic relations with the U.S., mobilized for war, and would recognize Texas only if Texas remained independent. But after some debate, Texas accepted the terms and entered the union on December 29, 1845, as the 28th state.
Post-presidency (1845–1862)
Tyler left Washington with the conviction that the newly inaugurated President Polk had the best interest of the nation. Tyler retired to a Virginia plantation, originally named Walnut Grove (or "the Grove"), located on the James River in Charles City County. He renamed it Sherwood Forest, in a reference to the folk legend Robin Hood, to signify that he had been "outlawed" by the Whig Party. He did not take farming lightly and worked hard to maintain large yields. His neighbors, largely Whigs, appointed him to the minor office of overseer of roads in 1847 in an effort to mock him. To their displeasure, he treated the job seriously, frequently summoning his neighbors to provide their slaves for road work, and continuing to insist on carrying out his duties even after his neighbors asked him to stop.
The former president spent his time in a manner common to Virginia's First Families, with parties, visiting or being visited by other aristocrats, and spending summers at the family's seaside home, "Villa Margaret". In 1852, Tyler happily rejoined the ranks of the Virginia Democratic Party and thereafter kept interested in political affairs. However, Tyler rarely received visits from his former allies and was not sought out as an adviser. Occasionally requested to deliver a public speech, Tyler spoke during the unveiling of a monument to Henry Clay. He acknowledged their political battles but spoke highly of his former colleague, whom he had always admired for bringing about the Compromise Tariff of 1833.
Prelude to the American Civil War
After John Brown's raid on Harpers Ferry ignited fears of an abolitionist attempt to free the slaves or an actual slave rebellion, several Virginia communities organized militia units or re-energized existing ones. Tyler's community organized a cavalry troop and a home guard company; Tyler was chosen to command the home guard troops with the rank of captain.
On the eve of the Civil War, Tyler re-entered public life as presiding officer of the Washington Peace Conference held in Washington, D.C., in February 1861 as an effort to prevent the conflict from escalating. The convention sought a compromise to avoid civil war even as the Confederate Constitution was being drawn up at the Montgomery Convention. Despite his leadership role in the Peace Conference, Tyler opposed its final resolutions. He felt that they were written by the free state delegates, did not protect the rights of slave owners in the territories, and would do little to bring back the lower South and restore the Union. He voted against the conference's seven resolutions, which the conference sent to Congress for approval late in February 1861 as a proposed Constitutional amendment.
On the same day the Peace Conference started, local voters elected Tyler to the Virginia Secession Convention. He presided over the opening session on February 13, 1861, while the Peace Conference was still underway. Tyler abandoned hope of compromise and saw secession as the only option, predicting that a clean split of all Southern states would not result in war. In mid-March, he spoke against the Peace Conference resolutions. On April 4, he voted for secession even when the convention rejected it. On April 17, after the attack on Fort Sumter and Lincoln's call for troops, Tyler voted with the new majority for secession. He headed a committee that negotiated the terms for Virginia's entry into the Confederate States of America and helped set the pay rate for military officers. On June 14, Tyler signed the Ordinance of Secession, and one week later the convention unanimously elected him to the Provisional Confederate Congress. Tyler was seated in the Confederate Congress on August 1, 1861, and he served until just before his death in 1862. In November 1861, he was elected to the Confederate House of Representatives but he died of a stroke in his room at the Ballard Hotel in Richmond before the first session could open in February 1862.
Death
Throughout his life, Tyler suffered from poor health. As he aged, he suffered more frequently from colds during the winter. On January 12, 1862, after complaining of chills and dizziness, he vomited and collapsed. Despite treatment, his health failed to improve, and he made plans to return to Sherwood Forest by the 18th. As he lay in bed the night before, he began suffocating, and Julia summoned his doctor. Just after midnight, Tyler took a sip of brandy, and told his doctor, "Doctor, I am going", to which the doctor replied, "I hope not, Sir." Tyler then said, "Perhaps it is best." Tyler died in his room at the Exchange Hotel in Richmond shortly thereafter, most likely due to a stroke. He was 71.
Tyler's death was the only one in presidential history not to be officially recognized in Washington, because of his allegiance to the Confederate States of America. He had requested a simple burial, but Confederate President Jefferson Davis devised a grand, politically pointed funeral, painting Tyler as a hero to the new nation. Accordingly, at his funeral, the coffin of the tenth president of the United States was draped with a Confederate flag; he remains the only U.S. president ever laid to rest under a flag not of the United States. Tyler had been more loyal to Virginia and his own principles than to the Union of which he had been president.
Tyler was buried in Hollywood Cemetery in Richmond, Virginia, nearby the gravesite of President James Monroe. He has since been the namesake of several U.S. locations, including the city of Tyler, Texas, named for him because of his role in the annexation of Texas.
Historical reputation and legacy
Tyler's presidency has provoked highly divided responses among political commentators. It is generally held in low esteem by historians; Edward P. Crapol began his biography John Tyler, the Accidental President (2006) by noting: "Other biographers and historians have argued that John Tyler was a hapless and inept chief executive whose presidency was seriously flawed." In The Republican Vision of John Tyler (2003), Dan Monroe observed that the Tyler presidency "is generally ranked as one of the least successful". Seager wrote that Tyler "was neither a great president nor a great intellectual", adding that despite a few achievements, "his administration has been and must be counted an unsuccessful one by any modern measure of accomplishment". A survey of historians conducted by C-SPAN in 2021 ranked Tyler as 39th of 44 men to hold the office.
In 2002, bucking the trend of historically poor evaluations of Tyler's presidency, historian Richard P. McCormick said "[contrary] to accepted opinion, John Tyler was a strong President. He established the precedent that the vice president, on succeeding to the presidential office, should be president. He had firm ideas on public policy, and he was disposed to use the full authority of his office." McCormick said that Tyler "conducted his administration with considerable dignity and effectiveness."
Tyler's assumption of complete presidential powers "set a hugely important precedent", according to a biographical sketch by the University of Virginia's Miller Center of Public Affairs. Tyler's successful insistence that he was president, and not a caretaker or acting president, was a model for the succession of seven other vice presidents (Millard Fillmore, Andrew Johnson, Chester A. Arthur, Theodore Roosevelt, Calvin Coolidge, Harry S. Truman, and Lyndon B. Johnson) to the presidency over the 19th and 20th centuries upon the death of the president. The propriety of Tyler's action in assuming both the title of the presidency and its full powers was legally affirmed in 1967, when it was codified in the Twenty-fifth Amendment to the United States Constitution.
Some scholars have praised Tyler's foreign policy. Monroe credits him with "achievements like the Webster–Ashburton treaty which heralded the prospect of improved relations with Great Britain, and the annexation of Texas, which added millions of acres to the national domain". Crapol argued that Tyler "was a stronger and more effective president than generally remembered", while Seager wrote, "I find him to be a courageous, principled man, a fair and honest fighter for his beliefs. He was a president without a party." Author Ivan Eland, in an update of his 2008 book Recarving Rushmore, rated all 44 US presidents by the criteria of peace, prosperity, and liberty; with the finished ratings, John Tyler was ranked the best president of all time. In a History Today article, Louis Kleber wrote that Tyler brought integrity to the White House at a time when many in politics lacked it, and refused to compromise his principles to avoid the anger of his opponents. Crapol argues that Tyler's allegiance to the Confederacy overshadows much of the good he did as president: "Tyler's historical reputation has yet to fully recover from that tragic decision to betray his loyalty and commitment to what he had once defined as 'the first great American interest'—the preservation of the Union."
In her book on Tyler's presidency, Norma Lois Peterson suggests that Tyler's general lack of success as president was due to external factors that would have affected whoever was in the White House. Chief among them was Henry Clay, who brooked no opposition to his grand economic vision for America. In the aftermath of Jackson's determined use of the powers of the executive branch, the Whigs wanted the president to be dominated by Congress, and Clay treated Tyler as a subordinate. Tyler resented this, leading to the conflict between the branches that dominated his presidency. Pointing to Tyler's advances in foreign policy, she deemed Tyler's presidency "flawed ... but ... not a failure".
While academics have both praised and criticized Tyler, the general American public has little awareness of him. Several writers have portrayed Tyler as among the nation's most obscure presidents. As Seager remarked: "His countrymen generally remember him, if they have heard of him at all, as the rhyming end of a catchy campaign slogan."
Family, personal life, slavery
Tyler fathered more children than any other American president. His first wife was Letitia Christian (November 12, 1790 – September 10, 1842), with whom he had eight children: Mary (1815–1847), Robert (1816–1877), John (1819–1896), Letitia (1821–1907), Elizabeth (1823–1850), Anne (1825–1825), Alice (1827–1854), and Tazewell (1830–1874).
Letitia died of a stroke in the White House in September 1842. On June 26, 1844, Tyler married Julia Gardiner (July 23, 1820 – July 10, 1889), with whom he had seven children: David (1846–1927), John Alexander (1848–1883), Julia (1849–1871), Lachlan (1851–1902), Lyon (1853–1935), Robert Fitzwalter (1856–1927), and Margaret Pearl (1860–1947).
Although Tyler's family was dear to him, during his political rise he was often away from home for extended periods. When he chose not to seek reelection to the House of Representatives in 1821 because of illness, he wrote that he would soon be called upon to educate his growing family. It was difficult to practice law while away in Washington for part of the year and his plantation was more profitable when Tyler was available to manage it himself. By the time he entered the Senate in 1827, he had resigned himself to spending part of the year away from his family. Still, he sought to remain close to his children through letters.
Tyler was a slaveholder, at one point keeping 40 slaves at Greenway. Although he regarded slavery as an evil and did not attempt to justify it, he never freed any of his slaves. Tyler considered slavery a part of states' rights, and that therefore the federal government lacked the authority to abolish it. The living conditions of his slaves are not well documented, but historians surmise that he cared for their well-being and abstained from physical violence against them. In December 1841, Tyler was attacked by the abolitionist publisher Joshua Leavitt, with the unsubstantiated allegation that Tyler had fathered several sons with his slaves, and later sold them. A number of black families today maintain a belief in their descent from Tyler, but there is no evidence of such genealogy. At least four of his sons served in the government or military forces of the Confederacy; Robert Tyler Jones, his grandson by his daughter Mary, joined Company K of the 53rd Virginia Infantry Regiment on 25 June 1861, and was wounded on 3 July 1863 while taking part in Pickett's Charge as a color-bearer in the Army of Northern Virginia during the Battle of Gettysburg.
Tyler's personal net worth is estimated to have exceeded $50 million when adjusting for inflation by modern standards (according to peak valuation circa 2020), but he became indebted during the Civil War, and died with a greatly reduced fortune.
Tyler and his son Lyon remarried much younger women and fathered children at advanced ages, such that Tyler's daughter Pearl did not die until the 157th year after her father's birth. , Tyler still has one living grandson (234 years after John Tyler's birth) through Lyon, making him the earliest former president with a living grandchild. This grandson, Harrison Ruffin Tyler was born in 1928 and maintains the family home, Sherwood Forest Plantation, in Charles City County, Virginia.
See also
List of presidents of the United States
List of presidents of the United States by previous experience
List of presidents of the United States who owned slaves
Notes
References
Bibliography
Books
Leahy, Christopher J. President Without a Party: The Life of John Tyler (LSU, 2020), a scholarly biography; excerpt also online book review
; also see online book review
Morgan, Robert J. A Whig embattled; the Presidency under John Tyler (U of Nebraska Press, 1954) online
online
Articles
Cash, Jordan T. "The isolated presidency: John Tyler and unilateral presidential power." American Political Thought 7.1 (2018): 26–56. online
Crapol, Edward P. "President John Tyler, Henry Clay, and the Whig Party." in A Companion to the Antebellum Presidents 1837–1861 (2014): 173–194.
Kesilman, Sylvan H. "John Tyler as President: An Old School Republican in Search of Vindication", in The Moment of Decision: Biographical Essays on American Character and Regional Identity, R. M. Miller and J. R. McGivigan, eds. Westport. CT: Greenwood Press, 1994.
McCormick, Richard P. "William Henry Harrison and John Tyler" in Henry Graff, The Presidents: A Reference History 2d ed. (1996) pp 143–154.
Tyler, Lyon G. "President John Tyler and the Ashburton Treaty." William and Mary Quarterly 25.1 (1916): 1–8. online
Primary sources
Lyon Gardiner Tyler, ed. The Letters and Times of the Tylers (3 vols. 1884–1896). online
The personal papers of the Tyler family, including John Tyler, can be found at the Special Collections Research Center at the College of William and Mary.
The executive papers of John Tyler while he was Governor of Virginia can be found at the Library of Virginia.
External links
John Tyler at Miller Center, U Virginia
John Tyler: A Resource Guide from the Library of Congress
U.S. Senate Historian's Office: Vice Presidents of the United States – John Tyler
John Tyler in Union or Secession: Virginians Decide at the Library of Virginia
Biography at Encyclopedia Virginia/Library of Virginia
Finding aid of the Tyler Family Papers, Group A
A Guide to the Governor John Tyler Executive Papers, 1825–1827 at The Library of Virginia
"Life Portrait of John Tyler", from C-SPAN's American Presidents: Life Portraits, May 17, 1999
"John Tyler: The Accidental President", presentation by Edward Crapol at the Kansas City Public Library, April 11, 2012
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19th-century members of the United States House of Representatives | John Tyler | Chemistry | 16,970 |
3,868,748 | https://en.wikipedia.org/wiki/Table%20of%20Newtonian%20series | In mathematics, a Newtonian series, named after Isaac Newton, is a sum over a sequence written in the form
where
is the binomial coefficient and is the falling factorial. Newtonian series often appear in relations of the form seen in umbral calculus.
List
The generalized binomial theorem gives
A proof for this identity can be obtained by showing that it satisfies the differential equation
The digamma function:
The Stirling numbers of the second kind are given by the finite sum
This formula is a special case of the kth forward difference of the monomial xn evaluated at x = 0:
A related identity forms the basis of the Nörlund–Rice integral:
where is the Gamma function and is the Beta function.
The trigonometric functions have umbral identities:
and
The umbral nature of these identities is a bit more clear by writing them in terms of the falling factorial . The first few terms of the sin series are
which can be recognized as resembling the Taylor series for sin x, with (s)n standing in the place of xn.
In analytic number theory it is of interest to sum
where B are the Bernoulli numbers. Employing the generating function its Borel sum can be evaluated as
The general relation gives the Newton series
where is the Hurwitz zeta function and the Bernoulli polynomial. The series does not converge, the identity holds formally.
Another identity is
which converges for . This follows from the general form of a Newton series for equidistant nodes (when it exists, i.e. is convergent)
See also
Binomial transform
List of factorial and binomial topics
Nörlund–Rice integral
Carlson's theorem
References
Philippe Flajolet and Robert Sedgewick, "Mellin transforms and asymptotics: Finite differences and Rice's integrals", Theoretical Computer Science 144 (1995) pp 101–124.
Finite differences
Factorial and binomial topics
Newton series | Table of Newtonian series | Mathematics | 404 |
45,150,748 | https://en.wikipedia.org/wiki/Customer%20knowledge | Customer knowledge (CK) is the combination of experience, value and insight information which is needed, created and absorbed during the transaction and exchange between the customers and enterprise.
Campbell (2003) defines customer knowledge as: "organized and structured information about the customer as a result of systematic processing". According to Mitussis et al. (2006), customer knowledge is identified as one of the more complex types of knowledge, since customer knowledge can be captured from different sources and channels.
Classification
Various classifications exist:
Gebert et al. (2002), classified customer knowledge from an organization's perspective into three types:
Knowledge about customers: Is gained mainly by service management, offer management, complaint management and, if available, contract management. The main user processes of knowledge regarding the customer are campaign management and service management, because both processes personalize their services based on user criteria. Knowledge about the customer must be transparent within the company; although its distribution beyond the border of the company must be controlled, as this type of knowledge can often be directly transformed into competitive advantages. The development of such knowledge is also expensive, because knowledge revelation is quite time-consuming.
Knowledge for customers: Is mainly developed in processes within the company, for example, the research and development section or a production department. Collecting this knowledge is the responsibility of campaign management. It should be refined according to the customer's requirements. It is then disseminated to the other customer relationship management (CRM) processes, mainly: contract management, offer management, and service management. CRM manages knowledge, transparency and dissemination of knowledge for customers. Maintaining the balance between comprehensibility and precision is the main challenge when managing this kind of knowledge.
Knowledge from customers: Can be obtained in the same ways as knowledge about customers. Capturing knowledge from customers is based on the important fact that customers who obtain their own expertise when utilizing a service or product can be seen as equal partners. This concept is not regularly understood in the business world and its effects have been poorly researched in academia (Garcia-Murillo and Annabi, 2002).
The same categorization of customer knowledge has been made by others such as Bueren et al. (2005) and Feng and Tian (2005).
In another categorization, Crié and Micheaux (2006) divide customer knowledge into two types, namely: "behavioural" (or quantitative) and "attitudinal" (or qualitative). Behavioral knowledge is easy to acquire and is basically quantitative by nature; that is, containing customer transactional relationship with the company. On the other hand, attitudinal knowledge is difficult to acquire because it deals with a customer's state of mind; but meanwhile it is an important factor for enhancement of customer knowledge because they are directly related to a customer's thoughts and insights.
Customer knowledge management
Customer knowledge management (CKM) concept emerges as a crucial element for customer-oriented value creation. CKM is important for collecting, collaborating, compositing and communicating customer knowledge.
See also
Consumer privacy
Customer intelligence
Customer relationship management
Customer success
Knowledge engineering
Knowledge management
Knowledge transfer
Journals:
Electronic Journal of Knowledge Management
Journal of Knowledge Management
Journal of Knowledge Management Practice
References
Intellectual capital
Information systems
Customer relationship management
Groupware
Business terms
Hypertext | Customer knowledge | Technology | 668 |
1,741,642 | https://en.wikipedia.org/wiki/1%2C2-rearrangement | A 1,2-rearrangement or 1,2-migration or 1,2-shift or Whitmore 1,2-shift is an organic reaction where a substituent moves from one atom to another atom in a chemical compound. In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible. In the example below the substituent R moves from carbon atom C2 to C3.
The rearrangement is intramolecular and the starting compound and reaction product are structural isomers. The 1,2-rearrangement belongs to a broad class of chemical reactions called rearrangement reactions.
A rearrangement involving a hydrogen atom is called a 1,2-hydride shift. If the substituent being rearranged is an alkyl group, it is named according to the alkyl group's anion: i.e. 1,2-methanide shift, 1,2-ethanide shift, etc.
Reaction mechanism
A 1,2-rearrangement is often initialised by the formation of a reactive intermediate such as:
a carbocation by heterolysis in a nucleophilic rearrangement or anionotropic rearrangement
a carbanion in an electrophilic rearrangement or cationotropic rearrangement
a free radical by homolysis
a nitrene.
The driving force for the actual migration of a substituent in step two of the rearrangement is the formation of a more stable intermediate. For instance a tertiary carbocation is more stable than a secondary carbocation and therefore the SN1 reaction of neopentyl bromide with ethanol yields tert-pentyl ethyl ether.
Carbocation rearrangements are more common than the carbanion or radical counterparts. This observation can be explained on the basis of Hückel's rule. A cyclic carbocationic transition state is aromatic and stabilized because it holds 2 electrons. In an anionic transition state on the other hand 4 electrons are present thus antiaromatic and destabilized. A radical transition state is neither stabilized or destabilized.
The most important carbocation 1,2-shift is the Wagner–Meerwein rearrangement. A carbanionic 1,2-shift is involved in the benzilic acid rearrangement.
Radical 1,2-rearrangements
The first radical 1,2-rearrangement reported by Heinrich Otto Wieland in 1911 was the conversion of bis(triphenylmethyl)peroxide 1 to the tetraphenylethane 2.
The reaction proceeds through the triphenylmethoxyl radical A, a rearrangement to diphenylphenoxymethyl C and its dimerization. It is unclear to this day whether in this rearrangement the cyclohexadienyl radical intermediate B is a transition state or a reactive intermediate as it (or any other such species) has thus far eluded detection by ESR spectroscopy.
An example of a less common radical 1,2-shift can be found in the gas phase pyrolysis of certain polycyclic aromatic compounds. The energy required in an aryl radical for the 1,2-shift can be high (up to 60 kcal/mol or 250 kJ/mol) but much less than that required for a proton abstraction to an aryne (82 kcal/mol or 340 kJ/mol). In alkene radicals proton abstraction to an alkyne is preferred.
1,2-Rearrangements
The following mechanisms involve a 1,2-rearrangement:
1,2-Wittig rearrangement
Alpha-ketol rearrangement
Beckmann rearrangement
Benzilic acid rearrangement
Brook rearrangement
Criegee rearrangement
Curtius rearrangement
Dowd–Beckwith ring expansion reaction
Favorskii rearrangement
Friedel–Crafts reaction
Fritsch–Buttenberg–Wiechell rearrangement
Halogen dance rearrangement
Hofmann rearrangement
Lossen rearrangement
Pinacol rearrangement
Seyferth–Gilbert homologation
SN1 reaction (generally)
Stevens rearrangement
Stieglitz rearrangement
Wagner–Meerwein rearrangement
Westphalen–Lettré rearrangement
Wolff rearrangement
References
Rearrangement reactions | 1,2-rearrangement | Chemistry | 926 |
34,306,243 | https://en.wikipedia.org/wiki/Biodegradation%20%28journal%29 | Biodegradation is a peer-reviewed scientific journal covering biotransformation, mineralization, detoxification, recycling, amelioration or treatment of chemicals or waste materials by naturally occurring microbial strains, microbial associations or recombinant organisms.
According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.909. The editor-in-chief of the journal is Claudia K. Gunsch (Duke University).
References
Springer Science+Business Media academic journals
English-language journals
Waste management journals
Biodegradation | Biodegradation (journal) | Chemistry,Environmental_science | 115 |
68,498,249 | https://en.wikipedia.org/wiki/Civilian%20victimization | Civilian victimization is the intentional use of violence against noncombatants in a conflict. It includes both lethal forms of violence (such as killings), as well as non-lethal forms of violence such as torture, forced expulsion, and rape. According to this definition, civilian victimization is only a subset of harm that occurs to civilians during conflict, excluding that considered collateral damage of military activity. However, "the distinction between intentional and unintentional violence is highly ambivalent" and difficult to determine in many cases.
Scholars have identified various factors that may either provide incentives for the use of violence against civilians, or create incentives for restraint. Violence against civilians occurs in many types of civil conflict, and can include any acts in which force is used to harm or damage civilians or civilian targets. It can be lethal or nonlethal. During periods of armed conflict, there are structures, actors, and processes at a number of levels that affect the likelihood of violence against civilians.
Violence towards civilians is not “irrational, random, or the result of ancient hatreds between ethnic groups.” Rather, violence against civilians may be used strategically in a variety of ways, including attempts to increase civilian cooperation and support; increase costs to an opponent by targeting their civilian supporters; and physically separate an opponent from its civilian supporters by removing civilians from an area.
Patterns of violence towards civilians can be described at a variety of levels and a number of determinants of violence against civilians have been identified.
Describing patterns of violence
Francisco Gutiérrez-Sanín and Elisabeth Jean Wood have proposed a conceptualization of political violence that describes an actor in terms of its pattern of violence, based on the "repertoire, targeting, frequency, and technique in which it regularly engages." Actors can include any organized group fighting for political objectives. Repertoire covers the forms of violence used; targeting identifies the those attacked in terms of social group; frequency is the measurable occurrence of violence; and techniques are the types of weapons or technology used. This framework can be applied to observed patterns of violence without considering the intentionality of the actor. Other frameworks focus on motivation of the actor.
Repertoires may include both lethal forms of violence against civilians such as killings, massacres, bombings, and terrorist attacks, and nonlethal forms of violence, such as forced displacement and sexual violence. In indirect violence heavy weapons such as tanks or fighter planes are used remotely and unilaterally. In direct violence perpetrators act face-to-face with the victims using small weapons such as machetes or rifles.
Targets may be chosen collectively, as members of a particular ethnic, religious, or political group. This is sometimes referred to as categorical violence. Targets may also be chosen selectively, identifying specific individuals who are seen as opposing a political group or aiding its opponents.
Techniques can vary greatly depending on the level of technology and amount of resources available to combatants. There are considerable impacts of technology over time, including the introduction of new technologies of rebellion. For example, changes in communication infrastructure may affect violence against civilians. If such technology facilitates organization by armed groups and increases contests over territory, violence against civilians in those areas is also likely to increase.
As government surveillance of digital information increases, the use of targeted, selective violence against civilians by governments has been shown to increase.
Analysis of levels of violence
Theoretical explanations at various levels of analysis can co-exist and interact with one another. The following levels of analysis can be useful in understanding such dynamics:
International
At the international level, institutions, ideologies and the distribution of power and resources shape technologies of rebellion and political interactions, including both international and domestic wars. During the Cold War, the United States and the Soviet Union provided military and financial backing to both governments and rebellious groups, who engaged in irregular civil wars. Such conflicts frequently involve the use of violence to control civilians and territory. The decade following the dissolution of the Soviet Union was marked by a decline in worldwide battle deaths and the number of armed conflicts in the world.
International norms and ideas also influence conflict and the use of violence against civilians. The period following World War II, from 1946 to 2013, has also been regarded as showing a decline in conflict.
The United Nations General Assembly adopted the Universal Declaration of Human Rights in 1946.
International actors signed the Genocide Convention in 1948 and the Geneva Conventions in 1949, formalizing protections for noncombatants and international norms for human rights and humanitarian standards.
Transnational non-governmental organizations such as Human Rights Watch and Amnesty International have become active in surfacing information, advocating for human rights, mobilizing international public opinion, and influencing both social norms and international law.
Interactions between foreign governments and rebel groups who receive their support can affect violence against civilians. Groups receiving external support become less dependent on local civilian populations and have less incentive to limit violence against civilians. Foreign aid to rebels is associated with higher levels of both combat-related death and civilian targeting. However, foreign actors that are democracies or have strong human rights lobbies are less likely to support groups that engage in violence against civilians.
The international strategic environment also shapes government perceptions of threat. Perceptions of threat due to external military intervention may lead to increases in governmental mass killing of civilians and violence against domestic out-groups.
The scrutiny and criticism of international and domestic actors can affect government use of violence, by increasing the perceived costs of violence against civilians. Governments and rebel groups that are vulnerable domestically and that seek international legitimacy are more likely to comply with international humanitarian law and exercise restraint toward civilians.
Domestic and subnational
Political organization occurs not just at a national level, but at many levels, including provinces, states, legislative districts, and cities. In many countries, national and local politics differ in scale and in the extent to which subnational governments afford and support their citizen's political rights and civil liberties.
Relationships between government (at various levels), armed groups and domestic populations affect violence against civilians. Governments that rely on a broad base of domestic and institutional support are more likely to exercise restraint toward civilians. These may include democratic governments, inclusive governments, and governments in which institutions have not consolidated power.
Similarly, rebel groups that need the support of a broad domestic constituency or of local civilians are less likely to target civilians and to engage in terrorism. Rebel groups whose political constituents live in the area that they control are more likely to use governance structures like elections to obtain cooperation and less likely to use political violence. Rebel groups that control areas inhabited by nonconstituents are more likely to use violence to obtain resources and cooperation.
Ideology may strongly influence the ways in which governments and rebels define their constituencies, affecting patterns of violence. Where national, subnational or local institutions follow exclusionary ideologies, ethnic or other out-groups may become identified as nonconstituents and targeted, sometimes to the point of displacement, ethnic cleansing or genocide.
Violence against civilians may vary over space and time with the extent to which military forces are contesting a territory. Stathis Kalyvas has theorized that selective violence is more likely to occur where control is asymmetric, with one group exercising dominant but not complete control of an area. Indiscriminate violence may be more likely to occur where one side controls an area. It has also been shown that indiscriminate violence is more likely to occur at a distance from a country's center of power.
Opinions differ widely on whether there is a relationship between the relative military capacity of a government or rebel group and the likelihood that it will engage in patterns of violence against civilians. This may also vary depending on the type of violence involved. However, there is evidence that cutting off access to external sources of support may cause a group to become more dependent on the support of its local population and less likely to engage in violence against civilians.
Organizational
At the organizational level, researchers have examined the dynamics and ideology of armed groups: how they recruit and train their members, how organizational norms about the use of violence against civilians are established and maintained, and the role of group leaders and political ideology in shaping organizations and behavior. While some studies argue that violence against civilians reflects a lack of control over an organization's members and the absence of norms that inhibit violence, other researchers emphasize the social dynamics of armed groups and ways in which they may actively break down social norms that inhibit violence.
Jeremy Weinstein has argued that armed groups develop certain organizational structures and characteristics as a result of their available resources. According to this view, organizations that depend on external resources are predicted to attract low-commitment members, and have trouble controlling their use of violence against civilians. Organizations that are dependent on local resources will tend to attract higher-commitment, ideologically motivated members from local communities, which will help to control their use of violence against civilians.
Other researchers focus on organizational structure and its effects on behavior, without assuming that they are driven by resource endowment. They suggest that processes of education, training, and organizational control are important both in producing strategic violence and in establishing restraints against the use of violence against civilians.
The ideology of armed groups is a key factor influencing both their organizational structure and member behavior.
Some Marxist groups, which emphasize political education, have been less likely to use violence against civilians. The ideology of other armed groups, including governments, can actively promote violence and direct it at particular targets. Such groups often use "exclusionary ethnic or national ideologies or narratives" which have resulted in mass killings and genocide.
Accounts from multiple countries have documented the "practice, norms, and other socialization processes" which armed groups have used to gain recruits, socialize group members, establish new norms of behavior and build group cohesion. Methods can include forced recruitment, systematic brutalization, and gang rape. Such groups create a “culture of violence” in which "horrifying acts of cruelty" are directed at both group members and civilians and become routine. The risk to civilians from such organizations is high.
Individual
On an individual level, people may be influenced to participate in armed conflicts due to economic motivations or incentive structures. Research in this area often views violence against civilians as a by-product of economic processes such as competition for resources.
Researchers have also studied emotional and psychological factors relating to the use of violence, which are generally related to other factors such as strategy, opportunity, socialization, and other group-level processes. The emotions of shame, disgust, resentment, and anger have been linked to violence against civilians. While research suggests that emotions such as fear affect the polarization of attitudes, material and structural opportunities are important mediators of the expression of violence.
At the individual level, researchers are examining the category of “civilian" in greater detail, to better understand the use of violence against different types of noncombatants. Such research also emphasizes the agency of civilians who are themselves actors during wartime and the ways in which they may respond to armed groups.
There is evidence to suggest that local civilian institutions can sometimes mitigate violence by governments and rebel groups.
Research also examines concerns such as the use of violence against humanitarian aid workers, and the targeting of women.
Consequences of violence against civilians
A relatively new area of research asks how individuals, groups, communities and domestic and international audiences respond to violence against civilians. Legacies of violence can last for many years and across generations, long after the violence occurred. Evidence on the effects of wartime violence on ethnic polarization is mixed.
Research from various countries suggests that civilian responses to violence are not uniform. However, civilians do blame actors who have acted violently against their communities, and may withdraw their support, provide support to opposing forces, or vote for an opposing political party in elections. Such outcomes are more likely to occur in the area where the violence was experienced, and when the perpetrators of violence are considered outsiders.
Individuals are likely to respond to violence by rejecting the ideology of the perpetrating group, particularly if the violence was severe.
Those exposed to violence are likely to engage in prosocial behavior and to increase their political engagement.
Research on the effectiveness of groups using violence against civilians in gaining political ends is mixed.
Macro-level evidence suggests that rebel groups are likely to gain support from Western international actors in situations where governments are employing violence against civilians and rebel groups are showing restraint towards civilians.
The United Nations is more likely to deploy peacekeepers when conflicts involve high levels of violence towards civilians. However, peacekeeping missions are more likely to be effective at protecting civilians from rebel groups than from governments.
See also
Child murder
Civilian casualty ratio
Collective punishment
Dehumanization
Gaza Strip famine
Genocide
Incitement to genocide
Indiscriminate attack
State crime
References
Civil affairs
Global health
Social conflict
Human rights abuses
Civilians in war | Civilian victimization | Biology | 2,560 |
77,944,608 | https://en.wikipedia.org/wiki/IC%204687 | IC 4687 known as IRAS 18093-5744 or F18093-5744, is an Sb spiral galaxy located in the constellation of Pavo. It is located 250 million light years from Earth and was discovered by Royal Harwood Frost on August 1, 1904, who described the object "as brighter middle with magnitude of 14. It has a surface brightness of 12.5.
Characteristics
IC 4687 is classified as a luminous infrared galaxy. It has an infrared-luminosity of 1011.3 LΘ, compatible with a star formation rate of 30 MΘ yr−1. Through it has an energy output dominated by its star formation, the galaxy has a weak active galactic nucleus.
The regions of IC 4687 are also known to contain high amounts of molecular gas surface densities of log ΣH2 (MΘ pc−2) = 2.9 ± 0.2. In additional, the galaxy is known to produce stars at a rapid rate when compared to normal star forming galaxies with the regions having log ΣSFR (MΘ yr−1 kpc−2) = 0.7 ± 0.4. This units are considered ~ 10 factor higher when compared to extreme values of nearby galaxies. Not to mention, IC 4687 has a velocity field mainly controlled by rotation. It also has a defined kinematic center that is synchronous with its nucleus.
IC 4687 forms an interacting galaxy trio with two other galaxies, IC 4686 and IC 4689. Both of these galaxies are located ~ 10 and ~ 20 kiloparsecs away from IC 4687 and are classified as spiral-like with their velocity fields influenced by kinematic and rotation centers. Because of its close merger with IC 4686, a starburst and wolf-raynet galaxy, IC 4687 appears distorted. The Hubble images shows the galaxy has a distorted morphology with interstellar dust and gas apparently obscuring its companion. Not to mention, IC 4687 has large curly tidal tail as a result of the merger. It is possible the weak interaction from IC 4686 might triggered its starburst.
References
External links
at SIMBAD
4687
Pavo (constellation)
Barred spiral galaxies
061602
140-IG10
IRAS catalogue objects
Luminous infrared galaxies
Interacting galaxies
Discoveries by Royal Harwood Frost
Astronomical objects discovered in 1904 | IC 4687 | Astronomy | 490 |
16,413,876 | https://en.wikipedia.org/wiki/Biotechnology%20consulting | Biotechnology consulting (or biotech consulting) refers to the practice of assisting organizations involved in research and commercialization of biotechnology in improving their methods and efficiency of production, and approaches to R&D. This assistance is usually provided in the form of specialized technological advice and sharing of expertise. Both start-up and established organizations would hire biotechnology consultants mainly to receive an independent and professional advice from key opinion leaders, individuals with extensive knowledge and experience in a particular area of biotechnology or biological sciences, and, often, to outsource their projects for implementation by well qualified individuals. Large management consulting firms would often be able to provide technological advice as well, depending on the qualifications of their consulting team. With the growth of pharmaceutical companies, biotechnology consulting has recently developed into an industry of its own and separated from the management consulting industry that traditionally also provides technological advice on R&D projects to various industries. This has also been fueled by the impact various conflicts of interests can have on commercialization when biotechnology organizations contract services from academic institutions or government scientists
This is exemplified by the successful emergence of many consulting companies dedicated exclusively to servicing the biotech industry. Occasionally, university professors and Phd students engage in biotechnology consulting, either commercially or free of charge.
A special type of consulting is patent strategy and management consulting or simply patent consulting which specifically emphasizes on the scope of patent rights versus R&D in industry. It also assets successful commercialization of patentable matter. The primary aim of patent consulting company is to assist various small, medium and large corporation in realizing their research project toward successful patent registration with minimized danger of infringement and other risks that patent registrations may be subjected to prior to commercialization. One example of patent consulting firm is The Patent World.
References
Consulting by type
Biotechnology organizations | Biotechnology consulting | Engineering,Biology | 353 |
22,819,905 | https://en.wikipedia.org/wiki/Acaulospora%20polonica | Acaulospora polonica is a species of fungus in the family Acaulosporaceae. It forms arbuscular mycorrhiza and vesicles in roots. Found in Poland growing under Thuja occidentalis, it was described as a new species in 1988.
References
Diversisporales
Fungi described in 1988
Fungi of Europe
Fungus species | Acaulospora polonica | Biology | 76 |
3,241,848 | https://en.wikipedia.org/wiki/Chan%E2%80%93Paton%20factor | In theoretical physics, the Chan–Paton factor (named after Jack E. Paton and Hong-Mo Chan) is a multivalued index associated with the endpoints of an open string. An open string can be interpreted as a flux tube connecting a quark and its antiparticle. The two Chan–Paton factors make the string transform as a tensor under a gauge group whose charges are carried by the endpoints of the strings.
The procedure of enabling isospin factors to be added to the Veneziano model is known as Chan–Paton rules or Chan–Paton method.
After the second superstring revolution in 1995, Chan–Paton factors are interpreted as labels that identify which (spacetime-filling) D-branes the stringy endpoints are attached to. The Chan–Paton factors have become a special case of a more general concept.
References
String theory | Chan–Paton factor | Astronomy | 188 |
70,688,323 | https://en.wikipedia.org/wiki/Auricularia%20mesenterica | Auricularia mesenterica, commonly known as the tripe fungus, is a species of fungus in the family Auriculariaceae. Basidiocarps (fruit bodies) are gelatinous and typically formed in coalescing tiers on stumps and logs. They are partly pileate, with hirsute, zoned caps, and partly resupinate, with smooth to wrinkled undersurfaces that spread over the wood. Auricularia mesenterica is a saprotroph on dead deciduous trees and shrubs. The species is restricted to Europe and Central Asia.
Taxonomy and etymology
Auricularia mesenterica was described from England in 1785 by James Dickson as Helvella mesenterica and transferred to the genus Auricularia by Christiaan Hendrik Persoon in 1822. The species was considered to be cosmopolitan and was subsequently applied to collections from America, Asia, and Australia as well as Europe.
Molecular research, based on cladistic analysis of DNA sequences, has however shown that Auricularia mesenterica (as previously understood) is a complex of related species and that A. mesenterica sensu stricto is confined to Europe and Central Asia, with superficially similar but distinct species occurring elsewhere.
The specific epithet is a Latin adjective formed from the Ancient Greek word (mesentérion), "middle intestine", from (meso-, "middle, center") and (énteron, "intestine"), referring to its shape.
Description
This species forms bracket-like fruit bodies that first appear pale, rubbery, and button-like, expanding to typically across and hardening with age. The fruit bodies often merge into compound structures sometimes running along fallen trunks and branches for more than . The upper surface is grey to brown or buff, tomentose to hispid with concentric zones, while the underside is thickly gelatinous, irregularly folded radially and reddish brown. The spore print is white. Microscopically the basidia are auricularioid (tubular with three lateral septa) and the basidiospores are allantoid (sausage-shaped), 14 to 17 by 4.5 to 5 μm.
Distribution and habitat
Originally described from England, the species is known to occur throughout Europe and into Central Asia as far as Uzbekistan. Basidiocarps are formed on various deciduous tree stumps and logs.
Similar species
Other species in the Auricularia mesenterica complex include Auricularia brasiliensis in South America, A. pusio in Australia, A. africana in East Africa, and A. asiatica, A. orientalis, A. srilankensis, and A. submesenterica in Asia. Other species of Auricularia lack the zoned, hirsute upper surface found in the A. mesenterica complex. Some unrelated Stereum species may have similarly zoned caps, but their fruit bodies are leathery (not gelatinous) and their undersurfaces are often yellowish to orange.
Uses
Before the fruit body fully matures and hardens, young specimens are said to be edible, but in some local populations, these fungi tend to bioaccumulate high levels of heavy metals from their environment. A. mesenterica has shown to have high levels of phenols, flavonoids, and antioxidant activity, having potential as antitumor agent.
References
Auriculariales
Taxa named by James Dickson (botanist)
Fungi described in 1785
Fungi of Europe
Fungus species | Auricularia mesenterica | Biology | 746 |
72,463,442 | https://en.wikipedia.org/wiki/Amanita%20flavipes | Amanita flavipes is a species of Amanita found in oak and conifer forest of China, India, Japan, Pakistan, and South Korea.
References
External links
flavipes
Fungi of Asia
Fungi described in 1933
Fungus species | Amanita flavipes | Biology | 50 |
22,603,423 | https://en.wikipedia.org/wiki/Terrabacteria | Terrabacteria is a taxon containing approximately two-thirds of prokaryote species, including those in the gram positive phyla (Actinomycetota and Bacillota) as well as the phyla "Cyanobacteria", Chloroflexota, and Deinococcota.
It derives its name (terra = "land") from the evolutionary pressures of life on land. Terrabacteria possess important adaptations such as resistance to environmental hazards (e.g., desiccation, ultraviolet radiation, and high salinity) and oxygenic photosynthesis. Also, the unique properties of the cell wall in gram-positive taxa, which likely evolved in response to terrestrial conditions, have contributed toward pathogenicity in many species. These results now leave open the possibility that terrestrial adaptations may have played a larger role in prokaryote evolution than currently understood.
Terrabacteria was proposed in 2004 for Actinomycetota, "Cyanobacteria", and Deinococcota and was expanded later to include Bacillota and Chloroflexota. Other phylogenetic analyses have supported the close relationships of these phyla. Most species of prokaryotes not placed in Terrabacteria were assigned to the taxon Hydrobacteria, in reference to the moist environment inferred for the common ancestor of those species. Some molecular phylogenetic analyses have not supported this dichotomy of Terrabacteria and Hydrobacteria, but the most recent genomic analyses, including those that have focused on rooting the tree, have found these two groups to be monophyletic.
Terrabacteria and Hydrobacteria were inferred to have diverged approximately 3 billion years ago, suggesting that land (continents) had been colonized by prokaryotes at that time. Together, Terrabacteria and Hydrobacteria form a large group containing 97% of prokaryotes and 99% of all species of Bacteria known by 2009, and placed in the taxon Selabacteria, in allusion to their phototrophic abilities (selas = light). Currently, the bacterial phyla that are outside of Terrabacteria + Hydrobacteria, and thus justifying the taxon Selabacteria, are debated and may or may not include Fusobacteria.
The name “Glidobacteria” included some members of Terrabacteria but excluded the large gram positive groups, Bacillota and Actinomycetota, and is not supported by molecular phylogenetic data. Moreover, the article naming Glidobacteria did not include a molecular phylogeny or statistical analyses and did not follow the widely used three-domain system. For example, it claimed that eukaryotes split from Archaea very recently (~900 Mya), which is contradicted by the fossil record, and that lineage of eukaryotes + Archaea was nested within Bacteria as a close relative of Actinomycetota.
In 2022, new rules were introduced for kingdom-level taxa of prokaryotes, and the same two authors who proposed those new rules, proposed new names in 2024. They concluded that “the taxonomically preferable solution for bacterial kingdoms seems to be to accept the subdivision apparent in the study by Battistuzzi and Hedges,” with refinement. The new (and only valid) name is Bacillati.
Phylogeny
The phylogenetic tree according to the phylogenetic analyses of Battistuzzi and Hedges (2009) is the following and with a molecular clock calibration.
Recent molecular analyses have found roughly the following relationships including other phyla, whose relationships were uncertain.
On the other hand, Coleman et al. named the clade composed of Thermotogota, Deinococcota, Synergistota and related as DST and furthermore the analysis suggests that ultra-small bacteria (CPR group) may belong to Terrabacteria being more closely related to Chloroflexota. According to this study the phylum Aquificota sometimes included belongs to Hydrobacteria and that the phylum Fusobacteriota can belong to both Terrabacteria and Hydrobacteria. The result was the following:
References
Bacterial nomenclature | Terrabacteria | Biology | 901 |
67,558,499 | https://en.wikipedia.org/wiki/Bovhyaluronidase%20azoximer | Bovhyaluronidase azoximer, sold under the brand name Longidaze, is a conjugate of proteolytic enzyme hyaluronidase with high- molecular weight copolymer that forms a component of combination therapy regimens for treatment and prevention of diseases associated with connective tissue hyperplasia.
The most frequently observed adverse reactions seen with bovhyaluronidase azoximer include pain at site of injection and injection site reactions such as skin redness, itching and oedema. Local reactions typically resolve themselves in 48–72 hours.
Clinical data
Type: Hyaluronidases
Other names: hyaluronidase conjugate with co-polymer of N-oxide 1,4-ethylenepiperazine and (N-carboxymethyl)-1,4- ethylenepiperazine bromide
Pharmaceutical form: suppositories
Pharmacotheapeutic group: enzymes
ATC Code: V03AX
Medical uses
Bovhyaluronidase azoximer is a porous white or white with a yellowish or brownish tint mass and prepared in ampules 1500 IU or 3000 IE with mannitol excipient (up to 15 mg [for 1500 IE dos] or up to 20 mg (for 3000 IE dose).
The active ingredient belongs to the hyaluronidases family of enzymes that catalyse the degradation of hyaluronic acid. By catalyzing the hydrolysis of hyaluronan, a constituent of the body's extracellular matrix (ECM), hyaluronidase lowers the viscosity of hyaluronan, thereby increasing tissue permeability... It is, therefore, often used in medicine in conjunction with other drugs to speed their dispersion and delivery. It also increases the absorption rate of parenteral fluids given by hypodermoclysis, and is an adjunct in subcutaneous urography for improving resorption of radiopaque agents. Hyaluronidases are also used for extravasation of hyperosmolar solutions.
Approved applications include:
Gynaecology: treatment and prevention of adhesive process in lesser pelvis during inflammatory diseases of internal genital organs, including tubo-peritoneal infertility, intrauterine synechiae, chronic endometritis.
Urology: treatment of chronic prostatitis, interstitial cystitis.
Pulmonology and phthisiology: treatment of pneumosclerosis,
fibrosing alveolitis, and tuberculosis (fibro-cavity, infiltrative, tuberculoma).
Orthopaedics: treatment of joint contracture, arthrosis, Marie-Striinipell disease, haematomas.
History
Medicines incorporating hyaluronidase have been used in medical applications for over 60 years. The US Food and Drug Administration has approved hyaluronidase for the following indications: (1) subcutaneous fluid infusion (hypodermoclysis), (2) as an adjuvant to accelerate the absorption and dispersion of drugs in subcutaneous tissue or to manage extravasation, and (3) as an adjunct to promote the absorption of contrast media in urinary tract angiography (subcutaneous urography). They have also been approved and used for the purpose of increasing hematoma absorption in Europe. Hyaluronidase has a variety of uses in addition to its approved indications. Its current off-label uses include dissolving hyaluronic acid fillers, treating granulomatous foreign body reactions, and treating skin necrosis associated with filler injections.
Recognised limitations for hyaluronidase-based medicines include allergenic properties, presence of ballast impurities, loss of enzymatic activity due to temperature and inhibitors of blood serum. Since administration is via a parenteral route of administration, the enzyme is inactivated by blood serum inhibitors, which shortens its half-life.
Conjugation (covalent binding) of hyaluronidase with polymeric carriers prevents the unfolding of enzyme globule Hyal, increasing resistance to denaturation and the action of inhibitors while preserving the enzymes native structure and activity, thus prolonging its activity. The water-soluble copolymer 1,4-ethylene-piperazine N-oxide and (N-carboxymethyl)-1,4-ethylene-piperazinium bromide, itself an immunomodulator with anti-inflammatory properties, was found to confer increased stability. A comparative study of the stability of commercial hyaluronidase (Lydase®) and bovhyaluronidase azoximer showed a 20-fold increase in length of activity at 37 °C (24 hours vs. 20 days, respectively).
Safety and tolerability
Frequently observed adverse events include (≥ 1/100 to < 1/10) – pain at injection site. Less frequent adverse events (≥ 1/1,000 to < 1/100) include injection site reaction such as skin redness, itching and oedema. All local reactions resolve themselves in 48 – 72 hours. Very rare (< 1/10000) – allergic reactions.
Use of bovhyaluronidase azoximer is contraindicated in known cases of hypersensitivity to hyaluronidase, acute infectious diseases, pulmonary haemorrhage and haemoptysis, recent vitreous haemorrhage, malignant neoplasms, acute renal failure, age under 18 years (no clinical study data available). It should also be used with caution in cases of chronic liver failure (administer not more than once per week) and is contraindicated for use in pregnant and breast-feeding women.
Concomitant medications
Bovhyaluronidase azoximer can be prescribed with other medications such as antifungal drugs, bronchial spasmolytics, antibiotics and antivirals. When administered in combination with other medicinal product (antibiotics, local anesthetics, diuretics) bovhyaluronidase azoximer increases their bioavailability and enhances their effect. In case of co-administration with high doses of salicylates, cortisone, adrenocorticotrophic hormone (ACTH), estrogens or antihistaminic drugs bovhyaluronidase azoximer enzymatic activity can decrease. It is advised that bovhyaluronidase azoximer is not administered with medicinal products containing furosemide, benzodiazepines, phenytoin.
References
Further reading
External links
Biopharmaceuticals
Copolymers | Bovhyaluronidase azoximer | Chemistry,Biology | 1,436 |
30,332,244 | https://en.wikipedia.org/wiki/Bandicam | Bandicam (stylized as BANDICAM) is a closed-source screen capture and screen recording software originally developed by Bandisoft and later by Bandicam Company that can take screenshots or record screen changes.
Bandicam consists of three main modes. One is the Screen Recording mode, which can be used for recording a certain area on the PC screen. The other is the Game Recording mode, which can record the target created in DirectX or OpenGL. And the last is the Device Recording mode which records Webcams and HDMI devices.
Bandicam displays an FPS count in the corner of the screen while the DirectX/OpenGL window is in active mode. When the FPS count is shown in green, it means the program is ready to record, and when it starts recording, it changes the color of the FPS count to red. The FPS count is not displayed when the program is recording in the Screen Recording mode. This software has a maximum frame rate of 480 FPS.
Bandicam is shareware, meaning that it can be tested free of charge with limited functionality (It is often called crippleware). The free version of Bandicam places its name as a watermark at the top of every recorded video, and each recorded video is limited to 10 minutes in length. However, users can adjust the screen margin with the video screen so that the watermark is off-screen from the video.
The created video can be saved in AVI or MP4 formats. Bandicam can also capture screenshots and save them as BMP, PNG, or JPG. Bandicam features an autocomplete recording mode which can limit the video capture process to a specified size or time value.
It supports hardware acceleration through Nvidia NVENC AV1/HEVC/H.264, CUDA, AMD APP AV1/HEVC/H.264 and Intel Quick Sync Video AV1/HEVC/H.264.
See also
Crippleware
Comparison of screencasting software
References
External links
Official Reseller
2009 software
Screencasting software
Screenshot software
Windows-only proprietary software | Bandicam | Technology | 445 |
14,204,445 | https://en.wikipedia.org/wiki/Mazur%20manifold | In differential topology, a branch of mathematics, a Mazur manifold is a contractible, compact, smooth four-dimensional manifold-with-boundary which is not diffeomorphic to the standard 4-ball. Usually these manifolds are further required to have a handle decomposition with a single -handle, and a single -handle; otherwise, they would simply be called contractible manifolds. The boundary of a Mazur manifold is necessarily a homology 3-sphere.
History
Barry Mazur and Valentin Poenaru discovered these manifolds simultaneously. Akbulut and Kirby showed that the Brieskorn homology spheres , and are boundaries of Mazur manifolds, effectively coining the term `Mazur Manifold.' These results were later generalized to other contractible manifolds by Casson, Harer and Stern. One of the Mazur manifolds is also an example of an Akbulut cork which can be used to construct exotic 4-manifolds.
Mazur manifolds have been used by Fintushel and Stern to construct exotic actions of a group of order 2 on the 4-sphere.
Mazur's discovery was surprising for several reasons:
Every smooth homology sphere in dimension is homeomorphic to the boundary of a compact contractible smooth manifold. This follows from the work of Kervaire and the h-cobordism theorem. Slightly more strongly, every smooth homology 4-sphere is diffeomorphic to the boundary of a compact contractible smooth 5-manifold (also by the work of Kervaire). But not every homology 3-sphere is diffeomorphic to the boundary of a contractible compact smooth 4-manifold. For example, the Poincaré homology sphere does not bound such a 4-manifold because the Rochlin invariant provides an obstruction.
The h-cobordism Theorem implies that, at least in dimensions there is a unique contractible -manifold with simply-connected boundary, where uniqueness is up to diffeomorphism. This manifold is the unit ball . It's an open problem as to whether or not admits an exotic smooth structure, but by the h-cobordism theorem, such an exotic smooth structure, if it exists, must restrict to an exotic smooth structure on . Whether or not admits an exotic smooth structure is equivalent to another open problem, the smooth Poincaré conjecture in dimension four. Whether or not admits an exotic smooth structure is another open problem, closely linked to the Schoenflies problem in dimension four.
Mazur's observation
Let be a Mazur manifold that is constructed as union a 2-handle. Here is a sketch of Mazur's argument that the double of such a Mazur manifold is . is a contractible 5-manifold constructed as union a 2-handle. The 2-handle can be unknotted since the attaching map is a framed knot in the 4-manifold . So union the 2-handle is diffeomorphic to . The boundary of is . But the boundary of is the double of .
References
Differential topology
Manifolds | Mazur manifold | Mathematics | 640 |
77,347,365 | https://en.wikipedia.org/wiki/Disitamab%20vedotin | Disitamab vedotin (trade name Aidixi) is a drug for the treatment of various types of solid tumors. It is an antibody-drug conjugate that consists of an immunoglobulin G1 antibody that is linked to the antitumor agent vedotin (monomethyl auristatin E).
History
In China, disitamab vedotin was approved in 2021 for the treatment of patients with HER2-overexpressing locally advanced or metastatic gastric cancer, including gastroesophageal junction adenocarcinoma, who have received at least two systemic chemotherapy regimens. In the United States, the FDA has granted disitamab vedotin a breakthrough therapy designation for the treatment of patients with HER2-positive locally advanced or metastatic urothelial carcinoma following treatment with platinum-based chemotherapy.
References
Antibody-drug conjugates | Disitamab vedotin | Biology | 192 |
318,598 | https://en.wikipedia.org/wiki/Paul%20Halmos | Paul Richard Halmos (; 3 March 3 1916 – 2 October 2006) was a Hungarian-born American mathematician and probabilist who made fundamental advances in the areas of mathematical logic, probability theory, operator theory, ergodic theory, and functional analysis (in particular, Hilbert spaces). He was also recognized as a great mathematical expositor. He has been described as one of The Martians.
Early life and education
Born in the Kingdom of Hungary into a Jewish family, Halmos immigrated to the United States at age 13. He obtained his B.A. from the University of Illinois, majoring in mathematics while also fulfilling the requirements for a degree in philosophy. He obtained the degree after only three years, and was 19 years old when he graduated. He then began a Ph.D. in philosophy, still at the Champaign–Urbana campus. However, after failing his masters' oral exams, he shifted to mathematics and graduated in 1938. Joseph L. Doob supervised his dissertation, titled Invariants of Certain Stochastic Transformations: The Mathematical Theory of Gambling Systems.
Career
Shortly after his graduation, Halmos left for the Institute for Advanced Study, lacking both job and grant money. Six months later, he was working under John von Neumann, which proved a decisive experience. While at the Institute, Halmos wrote his first book, Finite Dimensional Vector Spaces, which immediately established his reputation as a fine expositor of mathematics.
From 1967 to 1968 he was the Donegall Lecturer in Mathematics at Trinity College Dublin.
Halmos taught at Syracuse University, the University of Chicago (1946–60), the University of Michigan (~1961–67), the University of Hawaii (1967–68), Indiana University (1969–85), and the University of California at Santa Barbara (1976–78). From his 1985 retirement from Indiana until his death, he was affiliated with the Mathematics department at Santa Clara University (1985–2006).
Accomplishments
In a series of papers reprinted in his 1962 Algebraic Logic, Halmos devised polyadic algebras, an algebraic version of first-order logic differing from the better known cylindric algebras of Alfred Tarski and his students. An elementary version of polyadic algebra is described in monadic Boolean algebra.
In addition to his original contributions to mathematics, Halmos was an unusually clear and engaging expositor of university mathematics. He won the Lester R. Ford Award in 1971 and again in 1977 (shared with W. P. Ziemer, W. H. Wheeler, S. H. Moolgavkar, J. H. Ewing and W. H. Gustafson). Halmos chaired the American Mathematical Society committee that wrote the AMS style guide for academic mathematics, published in 1973. In 1983, he received the AMS's Leroy P. Steele Prize for exposition.
In the American Scientist 56(4): 375–389 (Winter 1968), Halmos argued that mathematics is a creative art, and that mathematicians should be seen as artists, not number crunchers. He discussed the division of the field into and , further arguing that mathematicians and painters think and work in related ways.
Halmos's 1985 "automathography" I Want to Be a Mathematician is an account of what it was like to be an academic mathematician in 20th century America. He called the book "automathography" rather than "autobiography", because its focus is almost entirely on his life as a mathematician, not his personal life. The book contains the following quote on Halmos' view of what doing mathematics means:
In these memoirs, Halmos claims to have invented the "iff" notation for the words "if and only if" and to have been the first to use the "tombstone" notation to signify the end of a proof, and this is generally agreed to be the case. The tombstone symbol ∎ (Unicode U+220E) is sometimes called a halmos.
In 1994, Halmos received the Deborah and Franklin Haimo Award for Distinguished College or University Teaching of Mathematics.
In 2005, Halmos and his wife Virginia Halmos funded the Euler Book Prize, an annual award given by the Mathematical Association of America for a book that is likely to improve the view of mathematics among the public. The first prize was given in 2007, the 300th anniversary of Leonhard Euler's birth, to John Derbyshire for his book about Bernhard Riemann and the Riemann hypothesis: Prime Obsession.
In 2009 George Csicsery featured Halmos in a documentary film also called I Want to Be a Mathematician.
Books by Halmos
Books by Halmos have led to so many reviews that lists have been assembled.
1942. Finite-Dimensional Vector Spaces. Springer-Verlag.
1950. Measure Theory. Springer Verlag.
1951. Introduction to Hilbert Space and the Theory of Spectral Multiplicity. Chelsea.
1956. Lectures on Ergodic Theory. Chelsea.
1960. Naive Set Theory. Springer Verlag.
1962. Algebraic Logic. Chelsea.
1963. Lectures on Boolean Algebras. Van Nostrand.
1967. A Hilbert Space Problem Book. Springer-Verlag.
1973. (with Norman E. Steenrod, Menahem M. Schiffer, and Jean A. Dieudonne). How to Write Mathematics. American Mathematical Society.
1978. (with V. S. Sunder). Bounded Integral Operators on L² Spaces. Springer Verlag
1985. I Want to Be a Mathematician. Springer-Verlag.
1987. I Have a Photographic Memory. Mathematical Association of America.
1991. Problems for Mathematicians, Young and Old, Dolciani Mathematical Expositions, Mathematical Association of America.
1996. Linear Algebra Problem Book, Dolciani Mathematical Expositions, Mathematical Association of America.
1998. (with Steven Givant). Logic as Algebra, Dolciani Mathematical Expositions No. 21, Mathematical Association of America.
2009. (posthumous, with Steven Givant), Introduction to Boolean Algebras, Springer.
See also
Crinkled arc
Commutator subspace
Invariant subspace problem
Naive set theory
Criticism of non-standard analysis
The Martians (scientists)
Notes
References
Includes a bibliography of Halmos's writings through 1991.
External links
"Paul Halmos: A Life in Mathematics", Mathematical Association of America (MAA)
Finite-Dimensional Vector Spaces
"Examples of Operators" a series of video lectures on operators in Hilbert Space given by Paul Halmos during his 2-week stay in Australia, Briscoe Center Digital Collections
1916 births
2006 deaths
20th-century Hungarian mathematicians
20th-century American mathematicians
Algebraists
American logicians
American people of Hungarian-Jewish descent
American statisticians
Donegall Lecturers of Mathematics at Trinity College Dublin
Functional analysts
Hungarian emigrants to the United States
Hungarian Jews
Indiana University faculty
Jewish American scientists
Mathematical analysts
Measure theorists
Operator theorists
Probability theorists
American set theorists
The American Mathematical Monthly editors
University of Chicago faculty
University of Illinois Urbana-Champaign alumni
University of Michigan faculty | Paul Halmos | Mathematics | 1,411 |
73,295,978 | https://en.wikipedia.org/wiki/Burnt%20Village | Burnt village is an oil-on-canvas painting by Finnish painter Albert Edelfelt completed in 1879.
The painting depicts an imaginary scene from the time of the Cudgel War of 1596–1597, a peasant uprising in Finland, which was then part of the Kingdom of Sweden. In the painting, a Finnish peasant family has fled their home village, which has been burnt down by a military force. The creator Albert Edelfelt donated the painting to Cygnaeus Gallery in Helsinki, Finland, where it is on display.
Edelfelt made a study in oils for the painting in 1878–79.
Study
References
1879 paintings
Paintings by Albert Edelfelt
Paintings in the Ateneum
Paintings of people
Oil on canvas paintings
Destruction of buildings
War paintings | Burnt Village | Engineering | 154 |
27,197,456 | https://en.wikipedia.org/wiki/A%20Passage%20to%20Infinity | A Passage to Infinity: Medieval Indian Mathematics from Kerala and Its Impact is a 2009 book by George Gheverghese Joseph chronicling the social and mathematical origins of the Kerala school of astronomy and mathematics. The book discusses the highlights of the achievements of Kerala school and also analyses the hypotheses and conjectures on the possible transmission of Kerala mathematics to Europe.
An outline of the contents
Introduction
The Social Origins of the Kerala School
The Mathematical Origins of the Kerala School
The Highlights of Kerala Mathematics and Astronomy
Indian Trigonometry: From Ancient Beginnings to Nilakantha
Squaring the Circle: The Kerala Answer
Reaching for the Stars: The Power Series for Sines and Cosines
Changing Perspectives on Indian Mathematics
Exploring Transmissions: A Case Study of Kerala Mathematics
A Final Assessment
See also
Indian astronomy
Indian mathematics
History of mathematics
References
Further references
In association with the Royal Society's 350th anniversary celebrations in 2010, Asia House presented a talk based on A Passage to Infinity. See :
For an audio-visual presentation of George Gheverghese Joseph's views on the ideas presented in the book, see :
The Economic Times talks to George Gheverghese Joseph on The Passage to Infinity. See :
Review of "A PASSAGE TO INFINITY: Medieval Indian Mathematics from Kerala and its impact" by M. Ram Murty in Hardy-Ramanujan Journal, 36 (2013), 43–46.
Hindu astronomy
Indian mathematics
Kerala school of astronomy and mathematics
Astronomy books | A Passage to Infinity | Astronomy | 298 |
21,500,262 | https://en.wikipedia.org/wiki/Electronic%20document%20and%20records%20management%20system | Electronic document and records management system (EDRMS) is a type of content management system and refers to the combined technologies of document management and records management systems as an integrated system.
Use
Typically, systems consider a document or file to be a work-in-progress until it has undergone review, approval, lock-down, and (potentially) publication, where it will wait to be used. The version of the form that is saved containing user content will become a formal record within the organization.
Once a document achieves the status of a record, the organization may apply best-practice or legally enforced retention policies which state how the second half of the record life-cycle will progress. This typically involves retention (and protection from change), until some events occur which relate to the record and which trigger the final disposition schedule to apply to the record. Eventually, typically at a set time after these events, the record undergoes destruction.
EDRMS software
A range of software vendors offer these systems at an enterprise level (i.e. targeted at managing all documents and records within an enterprise).
These vendors have historically provided electronic document management systems and have acquired smaller records management system companies. The seamlessness of the integration and the original intention of the records-management component to manage electronic records typically sets the complexity of deploying and potentially of using the final system.
Associated technologies
Business process management (BPM)
Case management and matter management
Enterprise content management (ECM)
Scanning
Web content management (WCM)
Professional organizations
Notable professional organizations for documents and records include:
Association of Records Managers and Administrators (ARMA International)
Information and Records Management Society (IRMS)
References
Content management systems
Information management
Records management
Records management technology | Electronic document and records management system | Technology | 345 |
76,573,038 | https://en.wikipedia.org/wiki/PHL%205038 | PHL 5038AB (or just PHL 5038) is a binary system consisting out of a white dwarf and a brown dwarf on a wide orbit. The system is 240 light years (74 parsec) distant from earth.
The white dwarf PHL 5038A was discovered in 2006 in data from the Sloan Digital Sky Survey and the brown dwarf companion was discovered in 2009 from UKIDSS infrared excess and confirmed with Gemini North to be a spacially resolved binary. It was only the fourth known brown dwarf to orbit a white dwarf at the time. The others were GD 165B, WD 0137-349B and GD 1400B.
Physical parameters
The white dwarf was first classified as a DA white dwarf, which indicates a hydrogen-dominated atmosphere without any metal pollution. A later work found weak pollution due to calcium in the atmosphere of the white dwarf thanks to XSHOOTER spectra from the Very Large Telescope. The calcium is detected as the K-line in two spectra. No infrared excess due to a disk was detected. PHL 5038A has either accreted all debris or is surrounded by a thin disk. The mass and temperature was also overestimated in the past and later works found a mass of around 0.53 to 0.57 , an effective temperature of around 7500 to 7800 Kelvin and a surface gravity of around 7.9 dex. The progenitor main-sequence star had a mass of around 1.07 and it existed for around 9 billion years until it became an AGB star and around 1 billion years ago it became a white dwarf.
The brown dwarf has a spectral type of around L8-L9. Its mass was initially estimated to be 60 , but this mass was likely an underestimate and more recent estimates find a mass of around 0.070 (or 73 ) and an effective temperature of 1425 K.
The same team that discovered the metal pollution of the white dwarf also re-observed the system with Gemini North to determine the orbital parameters. The semi-major axis is astronomical units and the inclination is 132 ±11°. The eccentricity is unconstrained, but likely lower than 0.615. In the past the white dwarf was more massive, making the semi-major axis half as large at 33 AU.
Evolution
Casewell et al. suggest the following evolution of the system:
The PHL 5038 system during the main-sequence had a star with a mass similar or more massive than the sun and it had a brown dwarf at an orbit of 33 AU, similar to the orbital distance of Neptune. It also likely had rocky debris in the form of planetesimals in orbit around the star, maybe similar to the asteroid belt. At the end of its lifetime the star became an AGB star with a size smaller than 2.5 AU, leaving the rocky debris mostly intact. As the star lost around half of its mass, the orbit of the brown dwarf and the planetesimals increased. The debris would be stable within 17-32 AU (circular orbit of the brown dwarf) or 5-8 AU (e=0.6 for the brown dwarf orbit). A debris belt with an increased size might be close to the edge of this stable zone and gravitational interactions with the brown dwarf would scatter planetesimals into all kinds of directions, eroding the edge of the debris belt. Some of these planetesimals will be scattered inwards and are being disrupted by the tidal forces of the white dwarf, leading to the pollution of the white dwarf atmosphere. Alternatively the disk could have been larger than the stable zone, resulting in chaotic scattering at the beginning of the white dwarf stage, until the scattering decreased.
See also
List of exoplanets and planetary debris around white dwarfs
GD 165B is the first brown dwarf discovered around a white dwarf
References
White dwarfs
L-type brown dwarfs
Binary stars
Aquarius (constellation) | PHL 5038 | Astronomy | 804 |
6,432 | https://en.wikipedia.org/wiki/Caelum | Caelum is a faint constellation in the southern sky, introduced in the 1750s by Nicolas Louis de Lacaille and counted among the 88 modern constellations. Its name means "chisel" in Latin, and it was formerly known as Caelum Sculptorium ("Engraver's Chisel"); it is a rare word, unrelated to the far more common Latin caelum, meaning "sky", "heaven", or "atmosphere". It is the eighth-smallest constellation, and subtends a solid angle of around 0.038 steradians, just less than that of Corona Australis.
Due to its small size and location away from the plane of the Milky Way, Caelum is a rather barren constellation, with few objects of interest. The constellation's brightest star, Alpha Caeli, is only of magnitude 4.45, and only one other star, (Gamma) γ1 Caeli, is brighter than magnitude 5 . Other notable objects in Caelum are RR Caeli, a binary star with one known planet approximately away; X Caeli, a Delta Scuti variable that forms an optical double with γ1 Caeli; and HE0450-2958, a Seyfert galaxy that at first appeared as just a jet, with no host galaxy visible.
History
Caelum was incepted as one of fourteen southern constellations in the 18th century by Nicolas Louis de Lacaille, a French astronomer and celebrated of the Age of Enlightenment.
It retains its name Burin among French speakers, latinized in his catalogue of 1763 as Caelum Sculptoris (“Engraver's Chisel”).
Francis Baily shortened this name to Caelum, as suggested by John Herschel. In Lacaille's original chart, it was shown as a pair of engraver's tools: a standard burin and more specific shape-forming échoppe tied by a ribbon, but came to be ascribed a simple chisel. Johann Elert Bode stated the name as plural with a singular possessor, Caela Scalptoris – in German (die ) Grabstichel (“the Engraver’s Chisels”) – but this did not stick.
Characteristics
Caelum is bordered by Dorado and Pictor to the south, Horologium and Eridanus to the east, Lepus to the north, and Columba to the west. Covering only 125 square degrees, it ranks 81st of the 88 modern constellations in size.
Its main asterism consists of four stars, and twenty stars in total are brighter than magnitude 6.5 .
The constellation's boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are a 12-sided polygon. In the equatorial coordinate system, the right ascension coordinates of these borders lie between and and declinations of to . The International Astronomical Union (IAU) adopted the three-letter abbreviation “Cae” for the constellation in 1922.
Its main stars are visible in favourable conditions and with a clear southern horizon, for part of the year as far as about the 41st parallel north
These stars avoid being engulfed by daylight for some of every day (when above the horizon) to viewers in mid- and well-inhabited higher latitudes of the Southern Hemisphere. Caelum shares with (to the north) Taurus, Eridanus and Orion midnight culmination in December (high summer), resulting in this fact. In winter (such as June) the constellation can be observed sufficiently inset from the horizons during its rising before dawn and/or setting after dusk as it culminates then at around mid-day, well above the sun. In South Africa, Argentina, their sub-tropical neighbouring areas and some of Australia in high June the key stars may be traced before dawn in the east; near the equator the stars lose night potential in May to June; they ill-compete with the Sun in northern tropics and sub-tropics from late February to mid-September with March being unfavorable as to post-sunset due to the light of the Milky Way.
Notable features
Stars
Caelum is a faint constellation: It has no star brighter than magnitude 4 and only two stars brighter than magnitude 5.
Lacaille gave six stars Bayer designations, labeling them Alpha (α ) to Zeta (ζ ) in 1756, but omitted Epsilon (ε ) and designated two adjacent stars as Gamma (γ ). Bode extended the designations to Rho (ρ ) for other stars, but most of these have fallen out of use. Caelum is too far south for any of its stars to bear Flamsteed designations.
The brightest star, (Alpha) α Caeli, is a double star, containing an F-type main-sequence star of magnitude 4.45 and a red dwarf of magnitude 12.5 , from Earth. (Beta) β Caeli, another F-type star of magnitude 5.05 , is further away, being located from Earth. Unlike α, β Caeli is a subgiant star, slightly evolved from the main sequence. (Delta) δ Caeli, also of magnitude 5.05 , is a B-type subgiant and is much farther from Earth, at .
(Gamma) γ1Caeli is a double-star with a red giant primary of magnitude 4.58 and a secondary of magnitude 8.1 . The primary is from Earth. The two components are difficult to resolve with small amateur telescopes because of their difference in visual magnitude and their close separation. This star system forms an optical double with the unrelated X Caeli (previously named γ2Caeli), a Delta Scuti variable located from Earth. These are a class of short-period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study astroseismology. The only other variable star in Caelum visible to the naked eye is RV Caeli, a pulsating red giant of spectral type M1III, which varies between magnitudes 6.44 and 6.56 .
Three other stars in Caelum are still occasionally referred to by their Bayer designations, although they are only on the edge of naked-eye visibility. (Nu) ν Caeli is another double star, containing a white giant of magnitude 6.07 and a star of magnitude 10.66, with unknown spectral type. The system is approximately away. (Lambda) λ Caeli, at magnitude 6.24, is much redder and farther away, being a red giant around from Earth. (Zeta) ζ Caeli is even fainter, being only of magnitude 6.36 . This star, located away, is a K-type subgiant of spectral type K1. The other twelve naked-eye stars in Caelum are not referred to by Bode's Bayer designations anymore, including RV Caeli.
One of the nearest stars in Caelum is the eclipsing binary star RR Caeli, at a distance of . This star system consists of a dim red dwarf and a white dwarf. Despite its closeness to the Earth, the system's apparent magnitude is only 14.40 due to the faintness of its components, and thus it cannot be easily seen with amateur equipment. The system is a post-common-envelope binary and is losing angular momentum over time, which will eventually cause mass transfer from the red dwarf to the white dwarf. In approximately 9–20 billion years, this will cause the system to become a cataclysmic variable. In 2012, the system was found to contain a giant planet, and there is evidence for a second substellar body. , it is believed two planets orbit RR Caeli.
Another nearby star is LHS 1678, an astrometric binary located some 65 light-years away. The primary star is a red dwarf hosting three close-in exoplanets, all smaller than Earth, the secondary component is a likely brown dwarf. This system is notable as the closest star to Alpha Caeli, just 3.3 light-years distant. Due to its closeness, α Caeli would shine at magnitude from LHS 1678, brighter than Sirius in our sky.
Deep-sky objects
Due to its small size and location away from the plane of the Milky Way, Caelum is rather devoid of deep-sky objects, and contains no Messier objects. The only deep-sky object in Caelum to receive much attention is HE0450-2958, an unusual Seyfert galaxy. Originally, the jet's host galaxy proved elusive to find, and this jet appeared to be emanating from nothing. Although it has been suggested that the object is an ejected supermassive black hole, the host is now agreed to be a small galaxy that is difficult to see due to light from the jet and a nearby starburst galaxy.
The 13th magnitude planetary nebula PN G243-37.1 is also in the eastern regions of the constellation. It is one of only a few planetary nebulae found in the galactic halo, being light-years below the Milky Way's 1000 light-year-thick disk.
Galaxies NGC 1595, NGC 1598, and the Carafe galaxy are known as the Carafe group. The Carafe galaxy is a Seyfert galaxy with ring. Its location is 4:28 / -47°54' (2000.0).
Notes
References
External links
Starry Night Photography – Caelum Constellation
Southern constellations
Constellations listed by Lacaille | Caelum | Astronomy | 1,962 |
344,542 | https://en.wikipedia.org/wiki/Multiplicative%20order | In number theory, given a positive integer n and an integer a coprime to n, the multiplicative order of a modulo n is the smallest positive integer k such that .
In other words, the multiplicative order of a modulo n is the order of a in the multiplicative group of the units in the ring of the integers modulo n.
The order of a modulo n is sometimes written as .
Example
The powers of 4 modulo 7 are as follows:
The smallest positive integer k such that 4k ≡ 1 (mod 7) is 3, so the order of 4 (mod 7) is 3.
Properties
Even without knowledge that we are working in the multiplicative group of integers modulo n, we can show that a actually has an order by noting that the powers of a can only take a finite number of different values modulo n, so according to the pigeonhole principle there must be two powers, say s and t and without loss of generality s > t, such that as ≡ at (mod n). Since a and n are coprime, a has an inverse element a−1 and we can multiply both sides of the congruence with a−t, yielding as−t ≡ 1 (mod n).
The concept of multiplicative order is a special case of the order of group elements. The multiplicative order of a number a modulo n is the order of a in the multiplicative group whose elements are the residues modulo n of the numbers coprime to n, and whose group operation is multiplication modulo n. This is the group of units of the ring Zn; it has φ(n) elements, φ being Euler's totient function, and is denoted as U(n) or U(Zn).
As a consequence of Lagrange's theorem, the order of a (mod n) always divides φ(n). If the order of a is actually equal to φ(n), and therefore as large as possible, then a is called a primitive root modulo n. This means that the group U(n) is cyclic and the residue class of a generates it.
The order of a (mod n) also divides λ(n), a value of the Carmichael function, which is an even stronger statement than the divisibility of φ(n).
Programming languages
Maxima CAS : zn_order (a, n)
Wolfram Language : MultiplicativeOrder[k, n]
Rosetta Code - examples of multiplicative order in various languages
See also
Discrete logarithm
Modular arithmetic
References
External links
Modular arithmetic | Multiplicative order | Mathematics | 549 |
68,377,413 | https://en.wikipedia.org/wiki/Near-field%20radiative%20heat%20transfer | Near-field radiative heat transfer (NFRHT) is a branch of radiative heat transfer which deals with situations for which the objects and/or distances separating objects are comparable or smaller in scale or to the dominant wavelength of thermal radiation exchanging thermal energy. In this regime, the assumptions of geometrical optics inherent to classical radiative heat transfer are not valid and the effects of diffraction, interference, and tunneling of electromagnetic waves can dominate the net heat transfer. These "near-field effects" can result in heat transfer rates exceeding the blackbody limit of classical radiative heat transfer.
History
The origin of the field of NFRHT is commonly traced to the work of Sergei M. Rytov in the Soviet Union. Rytov examined the case of a semi-infinite absorbing body separated by a vacuum gap from a near-perfect mirror at zero temperature. He treated the source of thermal radiation as randomly fluctuating electromagnetic fields. Later in the United States, various groups theoretically examined the effects of wave interference and evanescent wave tunneling. In 1971, Dirk Polder and Michel Van Hove published the first fully correct formulation of NFRHT between arbitrary non-magnetic media. They examined the case of two half-spaces separated by a small vacuum gap. Polder and Van Hove used the fluctuation-dissipation theorem to determine the statistical properties of the randomly fluctuating currents responsible for thermal emission and demonstrated definitively that evanescent waves were responsible for super-Planckian (exceeding the blackbody limit) heat transfer across small gaps.
Since the work of Polder and Van Hove, significant progress has been made in predicting NFRHT. Theoretical formalisms involving trace formulas, fluctuating surface currents, and dyadic Green's functions, have all been developed. Though identical in result, each formalism can be more or less convenient when applied to different situations. Exact solutions for NFRHT between two spheres, ensembles of spheres, a sphere and a half-space, and concentric cylinders have all been determined using these various formalisms. NFRHT in other geometries has been addressed primarily through finite element methods. Meshed surface and volume methods have been developed which handle arbitrary geometries. Alternatively, curved surfaces can be discretized into pairs of flat surfaces and approximated to exchange energy like two semi-infinite half spaces using a thermal proximity approximation (sometimes referred to as the Derjaguin approximation). In systems of small particles, the discrete dipole approximation can be applied.
Theory
Fundamentals
Most modern works on NFRHT express results in the form of a Landauer formula. Specifically, the net heat power transferred from body 1 to body 2 is given by
,
where is the reduced Planck constant, is the angular frequency, is the thermodynamic temperature, is the Bose function, is the Boltzmann constant, and
.
The Landauer approach writes the transmission of heat in terms discrete of thermal radiation channels, . The individual channel probabilities, , take values between 0 and 1.
NFRHT is sometimes alternatively reported as a linearized conductance, given by
.
Two half-spaces
For two half-spaces, the radiation channels, , are the s- and p- linearly polarized waves. The transmission probabilities are given by
where is the component of the wavevector parallel to the surface of the half-space. Further,
where:
are the Fresnel reflection coefficients for polarized waves between media 0 and ,
is the component of the wavevector in the region 0 perpendicular to the surface of the half-space,
is the separation distance between the two half-spaces, and
is the speed of light in vacuum.
Contributions to heat transfer for which arise from propagating waves whereas contributions from arise from evanescent waves.
Applications
Thermophotovoltaic energy conversion
Thermal rectification
Localized cooling
Heat-assisted magnetic recording
References
Heat transfer
Mechanical engineering
Electromagnetism
Optics
Light | Near-field radiative heat transfer | Physics,Chemistry,Engineering | 813 |
16,231,138 | https://en.wikipedia.org/wiki/Shilov%20system | The Shilov system is a classic example of catalytic C-H bond activation and oxidation which preferentially activates stronger C-H bonds over weaker C-H bonds for an overall partial oxidation.
Overview
The Shilov system was discovered by Alexander E. Shilov in 1969-1972 while investigating H/D exchange between isotopologues of CH4 and H2O catalyzed simple transition metal
coordination complexes. The Shilov cycle is the partial oxidation of a hydrocarbon to an alcohol or alcohol precursor (RCl) catalyzed by PtIICl2 in an aqueous solution with [PtIVCl6]2− acting as the ultimate oxidant. The cycle consists of three major steps, the electrophilic activation of the C-H bond, oxidation of the complex, and the nucleophilic oxidation of the alkane substrate. An equivalent transformation is performed industrially by steam reforming methane to syngas then reducing the carbon monoxide to methanol. The transformation can also performed biologically by methane monooxygenase.
Overall Transformation
RH + H2O + [PtCl6]2− → ROH + 2H+ + PtCl2 + 4Cl−
Major steps
The initial and rate limiting step involving the electrophilic activation of RH2C-H by a PtII center to produce a PtII-CH2R species and a proton. The mechanism of this activation is debated. One possibility is the oxidative addition of a sigma coordinated C-H bond followed by the reductive removal of the proton. Another is a sigma-bond metathesis involving the formation of the M-C bond and a H-Cl or H-O bond. Regardless it is this step that kinetically imparts the chemoselectivity to the overall transformation. Stronger, more electron-rich bonds are activated preferentially over weaker, more electron-poor bonds of species that have already been partially oxidized. This avoids a problem that plagues many partial oxidation processes, namely, the over-oxidation of substrate to thermodynamic sinks such as H2O and CO2.
In the next step the PtII-CH2R complex is oxidized by [PtIVCl6]2− to a PtIV-CH2R complex. There have been multiple studies to find a replacement oxidant that is less expensive than [PtIVCl6]2− or a method to regenerate [PtIVCl6]2−. It would be most advantageous to develop an electron train which would use oxygen as the ultimate oxidant. It is important that the oxidant preferentially oxidizes the PtII-CH2R species over the initial PtII species since PtIV complexes will not electrophilically activate a C-H bond of the alkane (although PtIV complexes electrophilically substitute hydrogens in aromatics - see refs. [1] and [2] ). Such premature oxidation shuts down the catalysis.
Finally the PtIV-CH2R undergoes nucleophilic attack by OH− or Cl− with the departure of PtII complex to regenerate the catalyst.
References
Organometallic chemistry
Catalysis
Soviet inventions | Shilov system | Chemistry | 673 |
66,678,699 | https://en.wikipedia.org/wiki/Heinz%20Nixdorf%20MuseumsForum | The Heinz Nixdorf MuseumsForum (HNF) in Paderborn, Germany, is a computer museum named after the Paderborn computer pioneer and entrepreneur Heinz Nixdorf.
History
In 1977, Heinz Nixdorf received numerous gifts in the form of historic office machines at the celebrations for the company anniversary of 25 years of Nixdorf Computer AG, which gave him the idea of expanding them into a collection for a computer museum. The museum idea became more concrete in 1983/1984 through purchases with the support of the Cologne office machine expert Uwe Breker. In 1985, the entrepreneur had his first exhibition concept drawn up by Prof. Ludwig Thürmer and his partners, but it was still undecided on the location. In 1986, Heinz Nixdorf died unexpectedly. The Nixdorf employee Willi Lenz, also a member of the "Computermuseum" working group, had the idea of a museum in discussion with the city of Paderborn and in 1990 obtained a positive city council resolution to establish it.
Between 1992 and 1996, the HNF was designed and built on the premises of the former headquarters of Nixdorf Computer AG by the Berlin architects Ludwig Thürmer and Gerhard Diel, and a scientific team led by the mathematician Norbert Ryska. In the presence of the then Federal Chancellor Helmut Kohl, the museum was opened on 24 October 1996. has an average of over 110,000 visitors annually. The institution is supported by the Westphalia Foundation and the Heinz Nixdorf Foundation, formed from the estate of Heinz Nixdorf.
Exhibits
In its permanent exhibition space, the museum presents 5,000 years of information and communications technology (ICT). In a historical journey through time, the story is presented from the origin of writing in Mesopotamia around 3,000 BC to current topics such as the Internet, artificial intelligence, and robotics. In the 6,000 square meters available, more than 5,000 exhibits can be seen, organized on two floors. The museum stores around 25,000 objects in total. Some museum objects are available for access via an online database.
The museum consists of three parts: early history before computers, the history of computers since the 1950s and a possible temporary exhibition.
Further reading
References
External links
1996 establishments in Germany
Nixdofr, Heinz, MuseumsForum
Buildings and structures in Paderborn (district)
Computer museums
Museums established in 1996
Paderborn
Technology museums in Germany | Heinz Nixdorf MuseumsForum | Technology | 488 |
61,981,734 | https://en.wikipedia.org/wiki/Germanium%28II%29%20dicationic%20complexes | Ge(II) dicationic complexes refer to coordination compounds of germanium with a +2 formal oxidation state, and a +2 charge on the overall complex. In some of these coordination complexes, the coordination is strongly ionic, localizing a +2 charge on Ge, while in others the bonding is more covalent, delocalizing the cationic charge away from Ge. Examples of dicationic Ge(II) complexes are much rarer than monocationic Ge(II) complexes, often requiring the use of bulky ligands to shield the germanium center. Dicationic complexes of Ge(II) have been isolated with bulky isocyanide and carbene ligands. Much more weakly coordinated Germanium (II) dications have been isolated as complexes with polyether ligands, such as crown ethers and [2.2.2]cryptand. Crown ethers and cryptands are typically known for their ability to bind metal cations, however these ligands have also been employed in stabilizing low-valent cations of heavier p-block elements. A Ge2+ ion's valence shell consists of a filled valence s orbital but empty valence p orbitals, giving rise to atypical bonding in these complexes. Germanium is a metalloid of the carbon group, typically forming compounds with mainly covalent bonding, contrasting with the dative bonding observed in these coordination complexes.
History
In 2007, a Ge(II) based dication was reported by Rupar, Staroverov, Ragogna and Baines in which a Ge(II) unit is coordinated by three bulky N-heterocyclic carbene ligands. Later in 2008, Rupar, Staroverov and Baines isolated a weakly coordinate Ge(II) dication using cryptand[2.2.2], also the first example of a non-metallic mononuclear dication complexed with a cryptand. In this report, a Ge(II) cation is encapsulated within [2.2.2]cryptand with two triflate counter ions. The crystal structure of this Ge cryptand[2.2.2] (CF3SO3)2 salt reveals a lack of coordination between the encapsulated Ge(II) cation and the triflate anions. Since these reports, similar cationic Ge(II) complexes have been prepared employing crown ethers, azamacrocycles, and bulky isocyanide ligands.
Synthesis
In the preparation of Ge(II) cationic complexes, triflate is often chosen as a counter anion as it is relatively weakly coordinating. GeCl2•dioxane is often used as a starting material, as it is a convenient source of Ge(II).
Ge(II) cryptand[2.2.2]
The Ge(II) cryptand[2.2.2] complex was prepared by the addition of cryptand to a solution of N-heterocyclic carbene stabilized GeCl(CF3SO3) in tetrahydrofuran. The products obtained from this reaction are summarized below. The germanium cryptand salt precipitated from solution as a white powder, and the identity was established using proton NMR and crystal X-ray diffraction. The carbene stabilized germanium chloride side products (structures given below) were identified in solution after the reaction.
Ge(II) crown ethers
Ge(II) cationic species have been isolated with several crown ether ligands, including [12]crown-4, [15]crown-5, and [18]crown-6. Rupar et al. reported the synthesis of various germanium crown ethers employing GeCl2•dioxane as the source of Ge(II). Trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) was used to displace chloride ligands with a more weakly associating triflate ligand. The resulting germanium crown ether complexes can adopt different geometries and cation charges depending on the size of the crown ether and the nature of the anionic ligand, summarized in the figure below. Only the Ge complex with [12]crown-4 is able to fully exclude counter anions from coordinating to Ge to give a dicationic complex. The larger crown ethers do not form sandwich complexes with Ge, and leave room for an anion to associate with the encapsulated Ge. These complexes were characterized with NMR, X-ray crystallography, Raman spectroscopy, and mass spectrometry.
Ge(II) carbene complex
The Ge(II) carbene stabilized dication reported by Rupar et al. was prepared by treating GeCl2•dioxane with an N-heterocyclic carbene (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) to give the GeCl2 carbene complex. Upon treatment with trimethylsilyl iodide and excess carbene, the dicationic complex consisting of three carbene ligands to one Ge atom was formed.
Ge(II) 2,6-dimethylphenyl isocyanide complex
A Ge(II) dication stabilized by 4 isocyanide ligands was prepared by mixing GeCl2•dioxane and 2,6-dimethylphenyl isocyanide in toluene (scheme given below). Three molecules of GeCl2 are required per four molecules of the isocyanide ligand, as the counter anion is GeCl3−. This complex was crystallized from toluene, and was characterized by X-ray crystallography and NMR spectroscopy.
Structure and bonding
The geometry of these Ge(II) complexes is not adequately described by VSEPR theory due to the nature of the lone pair on Ge(II). VSEPR theory is used to predict geometric distortions about atoms with nonbonding electrons (lone pairs), but in some cases heavier main group elements can violate VSEPR theory, displaying a stereochemically inactive or "spherically symmetric" lone pair, deemed the inert-pair effect. Ge(II) complexes can possess stereochemically active or inactive lone pairs, depending on the ligand. To further assess the nature of the electronic structure of Ge(II) dicationic complexes, natural bond orbital (NBO) computational analysis is often employed.
Cryptand and crown ethers
The bonding in such Ge(II) polyether complexes is believed to be mainly ionic in character, differing from the expected mainly covalent character typical of most germanium compounds. This lack of a covalent interaction is exemplified in the relatively long Ge-O distances observed in crystal structures of Ge crown ether and Ge cryptand complexes. Ge-O covalent single bonds are expected to be approximately 1.8 Å in length. The crystal structure of the Ge(II) cryptand[2.2.2] complex reveals a much longer Ge-O distance of 2.49 Å, similarly the Ge-O distances range from 2.38-2.49 Å in the Ge(II) ([12]crown-4)2 sandwich complex. For the Ge(II) cryptand[2.2.2] complex, NBO analysis reveals the Ge(II) cation does not participate in any covalent bonding and that the lone pair on the Ge(II) resides in a purely s orbital, indicating a stereochemically inactive lone pair. This lone pair orbital of Ge(II) within cryptand[2.2.2] is depicted to the right. In the Ge(II) crown ether complexes presented above, only the sandwich complex with [12]crown-4 clearly bears a stereochemically inactive lone pair, suggested by the high symmetry of the complex. The Ge(II) complexes with [15]crown-5, and [18]crown-6 show geometric distortions likely due to the activity of the Ge(II) lone pair.
Carbenes and isocyanides
The bonding in Ge(II) dications stabilized by carbenes and isocyanides is believed to be more covalent in nature compared with the bonding in the polyether complexes. Furthermore, the positive charge in these complexes can be quite delocalized.
In the Ge(II) carbene dication complex reported by Rupar et al., the Ge-C bonds are 2.07 Å in length, only marginally longer than expected Ge-C bond lengths. This suggests that the Ge-carbene interaction is not dative, but more covalent in nature. Limiting resonance forms for the Ge(II) carbene dication can be drawn (shown below), with the Ge(II) bearing the full +2 charge, or with the carbenes forming covalent bonds to the Ge center giving each ligand a +1 charge and the Ge a -1 charge. Natural population analysis, a computational technique associated with NBO assigns a charge of +0.64 to the Ge atom, indicating that charge delocalization is significant, and that the structure is best described as an intermediate between the two limiting representations. This compound adopts a pyramidal geometry, with a stereochemically active lone pair on Ge.
Similar to the Ge(II) carbene complex, the Ge-C bond lengths in the Ge(II) (2,6-dimethylphenyl isocyanide)3 structure range between 2.03-2.07 Å, typical for expected Ge-C bonds. The ligands adopt a distorted tetrahedral structure about the germanium center in the crystal structure. NBO analysis of the Ge(II) isocyanide dication reveals a partially filled Ge p orbital as a frontier orbital of this complex, depicted to the right. The nature of the frontier orbitals change upon consideration of the GeCl3− counter anions in the NBO analysis. The NBO analysis also reveals a charge of +0.74 on Ge, with some positive charge delocalized on the isocyanide ligands. Geometry optimizations for both singlet and triplet electron configurations were performed for this complex, and the singlet was found to be favored by 48.6 kcal/mol.
Reactivity
The weakly coordinated Ge(II) cations are Lewis acids. Due to this weak coordination, such Ge(II) crown ether complexes could be useful for the preparation of other germanium compounds. Bandyopadhyay et al. have investigated the reactivity of a GeOTf+ [15]crown-5 complex, and found that the weakly coordinating triflate could be exchanged for H2O or NH3. Addition of water to a solution of GeOTf+ [15]crown-5 in dichloromethane results in the formation of the dicationic water complex, as depicted in the figure below. This water adduct was isolated and the structure was determined by X-ray crystallography, making it the first characterized Ge(II)-water adduct. Further addition of bulk water to this complex results in decomposition.
Upon treatment with base, this water adduct [Ge[15]crown-5·OH2]2+can be deprotonated to give the hydroxide adduct [Ge[15]crown-5·OH]+. Upon deprotonation to give the hydroxide adduct, the Ge-O bond becomes shorter and stronger. NBO analysis identifies the H2O-Ge[15]crown-5 interaction as a donor-acceptor interaction, while the HO-Ge[15]crown-5 interaction is identified as a polar single bond. This reactivity presents a potential strategy for the preparation of new Ge complexes.
The empty p orbitals of Ge(II) dications make them potential π-acceptors for transition metal complexes. Intriguingly, dicationic Ge(II) complexes have been shown to act as ligands for Au(I) and Ag(I). Raut and Majumdar report the use of a bis(α-iminopyridine) ligand to prepare a Ge(II) dicationic complex that coordinates to the electron rich Au(I) or Ag(I) metal centers. The bonding in such complexes is best described by σ-donation of the Ge(II) lone pair to the transition metal, and π-back donation from the filled transition metal d orbitals to the vacant Ge(II) p orbitals. This unusual activity for Ge(II) is under investigation for possible applications in catalysis.
See also
Cryptand
Host–guest chemistry
Organogermanium compounds
References
Germanium(II) compounds
Coordination complexes | Germanium(II) dicationic complexes | Chemistry | 2,673 |
41,405,104 | https://en.wikipedia.org/wiki/Torus%20action | In algebraic geometry, a torus action on an algebraic variety is a group action of an algebraic torus on the variety. A variety equipped with an action of a torus T is called a T-variety. In differential geometry, one considers an action of a real or complex torus on a manifold (or an orbifold).
A normal algebraic variety with a torus acting on it in such a way that there is a dense orbit is called a toric variety (for example, orbit closures that are normal are toric varieties).
Linear action of a torus
A linear action of a torus can be simultaneously diagonalized, after extending the base field if necessary: if a torus T is acting on a finite-dimensional vector space V, then there is a direct sum decomposition:
where
is a group homomorphism, a character of T.
, T-invariant subspace called the weight subspace of weight .
The decomposition exists because the linear action determines (and is determined by) a linear representation and then consists of commuting diagonalizable linear transformations, upon extending the base field.
If V does not have finite dimension, the existence of such a decomposition is tricky but one easy case when decomposition is possible is when V is a union of finite-dimensional representations ( is called rational; see below for an example). Alternatively, one uses functional analysis; for example, uses a Hilbert-space direct sum.
Example: Let be a polynomial ring over an infinite field k. Let act on it as algebra automorphisms by: for
where
= integers.
Then each is a T-weight vector and so a monomial is a T-weight vector of weight . Hence,
Note if for all i, then this is the usual decomposition of the polynomial ring into homogeneous components.
Białynicki-Birula decomposition
The Białynicki-Birula decomposition says that a smooth projective algebraic T-variety admits a T-stable cellular decomposition.
It is often described as algebraic Morse theory.
See also
Sumihiro's theorem
GKM variety
Equivariant cohomology
monomial ideal
References
A. Bialynicki-Birula, "Some Theorems on Actions of Algebraic Groups," Annals of Mathematics, Second Series, Vol. 98, No. 3 (Nov., 1973), pp. 480–497
M. Brion, C. Procesi, Action d'un tore dans une variété projective, in Operator algebras, unitary representations, and invariant theory (Paris 1989), Prog. in Math. 92 (1990), 509–539.
Algebraic geometry
Algebraic groups | Torus action | Mathematics | 548 |
23,579,534 | https://en.wikipedia.org/wiki/C19H24N2O4 | {{DISPLAYTITLE:C19H24N2O4}}
The molecular formula C19H24N2O4 (molar mass: 344.40 g/mol, exact mass: 344.1736 u) may refer to:
Arformoterol
Formoterol
Tolamolol | C19H24N2O4 | Chemistry | 65 |
1,464,418 | https://en.wikipedia.org/wiki/COLLADA | COLLADA (for 'collaborative design activity') is an interchange file format for interactive 3D applications. It is managed by the nonprofit technology consortium, the Khronos Group, and has been adopted by ISO as a publicly available specification, ISO/PAS 17506.
COLLADA defines an open standard XML schema for exchanging digital assets among various graphics software applications that might otherwise store their assets in incompatible file formats. COLLADA documents that describe digital assets are XML files, usually identified with a .dae (digital asset exchange) filename extension.
History
Originally created at Sony Computer Entertainment by Rémi Arnaud and Mark C. Barnes, it has since become the property of the Khronos Group, a member-funded industry consortium, which now shares the copyright with Sony. The COLLADA schema and specification are freely available from the Khronos Group. The COLLADA DOM uses the SCEA Shared Source License 1.0.
Several graphics companies collaborated with Sony from COLLADA's beginnings to create a tool that would be useful to the widest possible audience, and COLLADA continues to evolve through the efforts of Khronos contributors. Early collaborators included Alias Systems Corporation, Criterion Software, Autodesk, Inc., and Avid Technology. Dozens of commercial game studios and game engines have adopted the standard.
In March 2011, Khronos released the COLLADA Conformance Test Suite (CTS). The suite allows applications that import and export COLLADA to test against a large suite of examples, ensuring that they conform properly to the specification. In July 2012, the CTS software was released on GitHub, allowing for community contributions.
ISO/PAS 17506:2012 Industrial automation systems and integration -- COLLADA digital asset schema specification for 3D visualization of industrial data was published in July 2012.
Software tools
COLLADA was originally intended as an intermediate format for transporting data from one digital content creation (DCC) tool to another application. Applications exist to support the usage of several DCCs, including:
Game engines
Originally intended as an interchange format, many game engines now support COLLADA, including:
Applications
Some games and 3D applications have started to support COLLADA:
Physics
As of version 1.4, physics support was added to the COLLADA standard. The goal is to allow content creators to define various physical attributes in visual scenes. For example, one can define surface material properties such as friction. Furthermore, content creators can define the physical attributes for the objects in the scene. This is done by defining the rigid bodies that should be linked to the visual representations. More features include support for ragdolls, collision volumes, physical constraints between physical objects, and global physical properties such as gravitation.
Physics middleware products that support this standard include Bullet Physics Library, Open Dynamics Engine, PAL and NVIDIA's PhysX. These products support by reading the abstract found in the COLLADA file and transferring it into a form that the middleware can support and represent in a physical simulation. This also enables different middleware and tools to exchange physics data in a standardized manner.
The Physics Abstraction Layer provides support for COLLADA Physics to multiple physics engines that do not natively provide COLLADA support including JigLib, OpenTissue, Tokamak physics engine and True Axis. PAL also provides support for COLLADA to physics engines that also feature a native interface.
Versions
1.0: October 2004
1.2: February 2005
1.3: June 2005
1.4.0: January 2006; added features such as character skinning and morph targets, rigid body dynamics, support for OpenGL ES materials, and shader effects for multiple shading languages including the Cg programming language, GLSL, and HLSL. First release through Khronos.
1.4.1: July 2006; primarily a patch release.
1.5.0: August 2008; added kinematics and B-rep as well as some FX redesign and OpenGL ES support. Formalised as ISO/PAS 17506:2012.
See also
glTF (Graphics Library Transmission Format)
FBX (Filmbox)
List of vector graphics markup languages
Open Game Engine Exchange (OpenGEX)
Universal Scene Description (USD)
Universal 3D (U3D)
VRML
WebGL
X3D (Extensible 3D Graphics)
References
External links
2004 software
3D graphics file formats
3D graphics software
CAD file formats
Graphics standards
XML-based standards | COLLADA | Technology | 925 |
37,689,732 | https://en.wikipedia.org/wiki/International%20Institute%20of%20Air%20and%20Space%20Law | The International Institute of Air and Space Law (IIASL) is a leading research and teaching institution. It specialises in legal and policy issues for aviation and space activities. It forms part of the Leiden Law School at Leiden University.
The institute co-operates with many sister institutions and maintains contact with national and international organisations throughout the world.
It is guided by an International Advisory Board populated by people professionally involved with the development of aviation and space-related activities who meet at least once per year.
It organises courses and conferences on all aspects of aviation and space law and policy.
History
The first professor appointed to teach air law was Daniel Goedhuis in 1938. A chair in air law was created in 1947 and extended to space law in 1961. Professor Goedhuis held it until 1977. His successor Professor Henri Wassenbergh was the catalyst for the creation of the current institute.
The institute held its Silver Jubilee in August 2011
Purpose
The purpose of the institute is to contribute to the development of aviation and space law and related policy by conducting and promoting research and teaching at university level.
Facilities
The Institute possesses a modern library.
References
External links
Official website
Space organizations
Aviation law
Space law
Aviation research institutes
Scientific organizations established in 1985 | International Institute of Air and Space Law | Astronomy | 249 |
323,705 | https://en.wikipedia.org/wiki/Newman%E2%80%93Shanks%E2%80%93Williams%20prime | In mathematics, a Newman–Shanks–Williams prime (NSW prime) is a prime number p which can be written in the form
NSW primes were first described by Morris Newman, Daniel Shanks and Hugh C. Williams in 1981 during the study of finite simple groups with square order.
The first few NSW primes are 7, 41, 239, 9369319, 63018038201, … , corresponding to the indices 3, 5, 7, 19, 29, … .
The sequence S alluded to in the formula can be described by the following recurrence relation:
The first few terms of the sequence are 1, 1, 3, 7, 17, 41, 99, … . Each term in this sequence is half the corresponding term in the sequence of companion Pell numbers. These numbers also appear in the continued fraction convergents to .
Further reading
External links
The Prime Glossary: NSW number
Classes of prime numbers
Unsolved problems in mathematics | Newman–Shanks–Williams prime | Mathematics | 200 |
73,900,375 | https://en.wikipedia.org/wiki/Angela%20Schoellig | Angela P. Schoellig is a German computer scientist whose research involves the application of machine learning to the control theory of robot motion, especially for quadcopters and other flying devices. She is an Alexander von Humboldt Professor for Robotics and Artificial Intelligence at the Technical University of Munich, and an associate professor in the University of Toronto Institute for Aerospace Studies (UTIAS).
Education and career
After high school in Backnang, near Stuttgart, Schoellig studied engineering science and mechanics in the US at Georgia Tech, earning a master's degree there in 2007 under the supervision of Magnus Egerstedt. She returned to Germany for a second master's degree in engineering cybernetics at the University of Stuttgart, in 2008, working there with Frank Allgöwer. She completed a doctorate in 2013 at ETH Zurich in Switzerland, with Raffaello D'Andrea as her doctoral advisor.
After continued postdoctoral research at ETH Zurich, she became an assistant professor at the University of Toronto in 2013, was given a Canada Research Chair in 2019, and was promoted to associate professor in 2020. In 2021 she was given the Alexander von Humboldt Professorship in Artificial Intelligence at the Technical University of Munich, where she holds the Chair of Safety, Performance and Reliability for Learning Systems in the Department of Computer Engineering.
References
External links
Home page at U. Toronto
Home page at TU Munich
Year of birth missing (living people)
Living people
German computer scientists
German women computer scientists
Control theorists
German roboticists
Women roboticists
Georgia Tech alumni
University of Stuttgart alumni
ETH Zurich alumni
Academic staff of the University of Toronto
Canada Research Chairs
Academic staff of the Technical University of Munich | Angela Schoellig | Engineering | 334 |
28,149,071 | https://en.wikipedia.org/wiki/Maxwell%27s%20thermodynamic%20surface | Maxwell’s thermodynamic surface is an 1874 sculpture made by Scottish physicist James Clerk Maxwell (1831–1879). This model provides a three-dimensional space of the various states of a fictitious substance with water-like properties. This plot has coordinates volume (x), entropy (y), and energy (z). It was based on the American scientist Josiah Willard Gibbs’ graphical thermodynamics papers of 1873. The model, in Maxwell's words, allowed "the principal features of known substances [to] be represented on a convenient scale."
Construction of the model
Gibbs' papers defined what Gibbs called the "thermodynamic surface," which expressed the relationship between the volume, entropy, and energy of a substance at different temperatures and pressures. However, Gibbs did not include any diagrams of this surface. After receiving reprints of Gibbs' papers, Maxwell recognized the insight afforded by Gibbs' new point of view and set about constructing physical three-dimensional models of the surface. This reflected Maxwell's talent as a strong visual thinker and prefigured modern scientific visualization techniques.
Maxwell sculpted the original model in clay and made several plaster casts of the clay model, sending one to Gibbs as a gift, keeping two in his laboratory at Cambridge University. Maxwell's copy is on display at the Cavendish Laboratory of Cambridge University, while Gibbs' copy is on display at the Sloane Physics Laboratory of Yale University, where Gibbs held a professorship. Two copies reside at the National Museum of Scotland, one via Peter Tait and the other via George Chrystal. Another was sent to Thomas Andrews. A number of historic photographs were taken of these plaster casts during the middle of the twentieth century – including one by James Pickands II, published in 1942 – and these photographs exposed a wider range of people to Maxwell's visualization approach.
Uses of the model
As explained by Gibbs and appreciated by Maxwell, the advantage of a U-V-S (energy-volume-entropy) surface over the usual P-V-T (pressure-volume-temperature) surface was that it allowed to geometrically explain sharp, discontinuous phase transitions as emerging from a purely continuous and smooth state function ; Maxwell's surface demonstrated the generic behaviour for a substance that can exist in solid, liquid, and gaseous phases. The basic geometrical operation involved simply placing a tangent plane (such as a flat sheet of glass) on the surface and rolling it around, observing where it touches the surface. Using this operation, it was possible to explain phase coexistence, the triple point, to identify the boundary between absolutely stable and metastable phases (e.g., superheating and supercooling), the spinodal boundary between metastable and unstable phases, and to illustrate the critical point.
Maxwell drew lines of equal pressure (isopiestics) and of equal temperature (isothermals) on his plaster cast by placing it in the sunlight, and "tracing the curve when the rays just grazed the surface." He sent sketches of these lines to a number of colleagues. For example, his letter to Thomas Andrews of 15 July 1875 included sketches of these lines. Maxwell provided a more detailed explanation and a clearer drawing of the lines (pictured) in the revised version of his book Theory of Heat, and a version of this drawing appeared on a 2005 US postage stamp in honour of Gibbs.
As well as being on display in two countries, Maxwell's model lives on in the literature of thermodynamics, and books on the subject often mention it, though not always with complete historical accuracy. For example, the thermodynamic surface represented by the sculpture is often reported to be that of water, contrary to Maxwell's own statement.
Related models
Maxwell's model was not the first plaster model of a thermodynamic surface: in 1871, even before Gibbs' papers, James Thomson had constructed a plaster pressure-volume-temperature plot, based on data for carbon dioxide collected by Thomas Andrews.
Around 1900, the Dutch scientist Heike Kamerlingh Onnes, together with his student Johannes Petrus Kuenen and his assistant Zaalberg van Zelst, continued Maxwell's work by constructing their own plaster thermodynamic surface models. These models were based on accurate experimental data obtained in their laboratory, and were accompanied by specialised tools for drawing the lines of equal pressure.
See also
History of thermodynamics
Process leading from Gibbs' drawings to Maxwell's thermodynamic surface
References
External links
Photograph of one of the two Cambridge copies in the Museum at the Cavendish Laboratory; for better readable legends to go with the axes, see here
Thermodynamic Case Study: Gibbs' Thermodynamic Graphical Method at Virginia Tech's Laboratory for Scientific Visual Analysis
Maxwell’s thermodynamic surface at the "Encyclopedia of Human Thermodynamics"
1874 in science
1874 sculptures
Historical scientific instruments
Sculptures in England
Sculptures in the United States
Scottish sculpture
Numerical function drawing
Scientific models
Thermodynamics
Works by James Clerk Maxwell | Maxwell's thermodynamic surface | Physics,Chemistry,Mathematics | 1,046 |
860,507 | https://en.wikipedia.org/wiki/Centered%20polygonal%20number | In mathematics, the centered polygonal numbers are a class of series of figurate numbers, each formed by a central dot, surrounded by polygonal layers of dots with a constant number of sides. Each side of a polygonal layer contains one more dot than each side in the previous layer; so starting from the second polygonal layer, each layer of a centered k-gonal number contains k more dots than the previous layer.
Examples
Each centered k-gonal number in the series is k times the previous triangular number, plus 1. This can be formalized by the expression , where n is the series rank, starting with 0 for the initial 1. For example, each centered square number in the series is four times the previous triangular number, plus 1. This can be formalized by the expression .
These series consist of the
centered triangular numbers 1, 4, 10, 19, 31, 46, 64, 85, 109, 136, 166, 199, ... (),
centered square numbers 1, 5, 13, 25, 41, 61, 85, 113, 145, 181, 221, 265, ... (), which are exactly the sum of consecutive squares, i.e., n^2 + (n - 1)^2.
centered pentagonal numbers 1, 6, 16, 31, 51, 76, 106, 141, 181, 226, 276, 331, ... (),
centered hexagonal numbers 1, 7, 19, 37, 61, 91, 127, 169, 217, 271, 331, 397, ... (), which are exactly the difference of consecutive cubes, i.e. n3 − (n − 1)3,
centered heptagonal numbers 1, 8, 22, 43, 71, 106, 148, 197, 253, 316, 386, 463, ... (),
centered octagonal numbers 1, 9, 25, 49, 81, 121, 169, 225, 289, 361, 441, 529, ... (), which are exactly the odd squares,
centered nonagonal numbers 1, 10, 28, 55, 91, 136, 190, 253, 325, 406, 496, 595, ... (), which include all even perfect numbers except 6,
centered decagonal numbers 1, 11, 31, 61, 101, 151, 211, 281, 361, 451, 551, 661, ... (),
centered hendecagonal numbers 1, 12, 34, 67, 111, 166, 232, 309, 397, 496, 606, 727, ... (),
centered dodecagonal numbers 1, 13, 37, 73, 121, 181, 253, 337, 433, 541, 661, 793, ... (), which are also the star numbers,
and so on.
The following diagrams show a few examples of centered polygonal numbers and their geometric construction. Compare these diagrams with the diagrams in Polygonal number.
Centered square numbers
Centered hexagonal numbers
Formulas
As can be seen in the above diagrams, the nth centered k-gonal number can be obtained by placing k copies of the (n−1)th triangular number around a central point; therefore, the nth centered k-gonal number is equal to
The difference of the n-th and the (n+1)-th consecutive centered k-gonal numbers is k(2n+1).
The n-th centered k-gonal number is equal to the n-th regular k-gonal number plus (n-1)2.
Just as is the case with regular polygonal numbers, the first centered k-gonal number is 1. Thus, for any k, 1 is both k-gonal and centered k-gonal. The next number to be both k-gonal and centered k-gonal can be found using the formula:
which tells us that 10 is both triangular and centered triangular, 25 is both square and centered square, etc.
Whereas a prime number p cannot be a polygonal number (except the trivial case, i.e. each p is the second p-gonal number), many centered polygonal numbers are primes. In fact, if k ≥ 3, k ≠ 8, k ≠ 9, then there are infinitely many centered k-gonal numbers which are primes (assuming the Bunyakovsky conjecture). Since all centered octagonal numbers are also square numbers, and all centered nonagonal numbers are also triangular numbers (and not equal to 3), thus both of them cannot be prime numbers.
Sum of reciprocals
The sum of reciprocals for the centered k-gonal numbers is
, if k ≠ 8
, if k = 8
References
: Fig. M3826
Figurate numbers | Centered polygonal number | Mathematics | 1,008 |
22,166,915 | https://en.wikipedia.org/wiki/McCormack%20reaction | The McCormack reaction is a method for the synthesis of organophosphorus compounds. In this reaction, a 1,3-diene and a source of R2P+ are combined to give phospholenium cation. The reaction is named after W. B. McCormack, a research chemist at duPont.
An illustrative reaction involves phenyldichlorophosphine and isoprene:
The reaction proceeds via a pericyclic [2+4]-process. The resulting derivatives can be hydrolyzed to give the phosphine oxide. Dehydrohalogenation gives the phosphole.
References
Cycloadditions
Cheletropic reactions
Name reactions | McCormack reaction | Chemistry | 152 |
61,729,563 | https://en.wikipedia.org/wiki/Amazon%20Scout | Amazon Scout is a 6 wheeled delivery robot used to deliver packages for multinational company Amazon. Amazon Scout originally debuted on January 23, 2019, delivering packages to Amazon customers in Snohomish County, Washington. Amazon scouts move on sidewalks, at a walking pace. In August, 2019, the robots started delivering packages to customers Irvine, California on a test basis, with human monitors. The package is stored inside of the robot, and driven to the customer.
Amazon acquired the robotics company Dispatch to build the robot.
Amazon cancelled Amazon Scout in January 2023.
Vision and Technology
All Amazon Scout robots are fully electric, as a part of Amazon’s movement towards net zero carbon emission by 2040. Amazon plans to use Scout in place of common delivery carriers, and for it to be available with Amazon’s shipping options for Amazon Prime members, such as two-day shipping. Integration of Scout adds to Amazon’s use of automation in delivery infrastructure, as there are already robots in use at Amazon warehouses. It is also helping to transition the Prime program from two-day shipping to faster one-day shipping.
Amazon Scout has been developed to safely navigate around common neighborhood obstacles such as pets and pedestrians. Scout uses tech like sensors and machine learning to navigate streets, as GPS is not reliable or detailed enough. The risks of using Scout are small as well, in comparison to the risks associated with autonomous cars.
Rollout in Snohomish County, WA
Amazon’s first rollout of Scout began in Snohomish County, Washington, with only six devices being used. Scout robots operated Monday through Friday, during daylight hours. They autonomously followed a route set to their destination, but each robot was accompanied by an employee titled an "Amazon Scout Ambassador".
Delivery began in Irvine, California in August 2019 under the same operating conditions used in Snohomish County, WA.
Further Usage and Future Development
According to Amazon Vice President Sean Scott, Amazon is continuing its rollout of Scout in different locations around the US in order to “operate in varied neighborhoods with different climates”. As of November 2020, Amazon Scout robots operated in Atlanta, Georgia, and Franklin, Tennessee as well. Further Scout trials are being conducted at locations like college campuses and office complexes. Delivery with Scout around the US also continued through the COVID-19 pandemic to minimize human-to-human contact.
The current Amazon Scout development team includes former robotics professors who will be developing features like navigation, independent perception, and simulation testing, in order to optimize Scout for future widespread usage. In several ways, federal and local regulations are limiting further investment, development, and testing of Scout. For example, some regulations “limit the use of fully automated devices in public space”, which is why an accompanying Amazon employee has been necessary. There have also been concerns about robots like Scout replacing human workers, and concerns on how residents will react to camera-bearing robots in their neighborhoods.
See also
Amazon Robotics
List of mergers and acquisitions by Amazon
References
Robots
Amazon (company) | Amazon Scout | Physics,Technology | 614 |
68,226,603 | https://en.wikipedia.org/wiki/Halcon%20process | In chemistry, the Halcon process refers to technology for the production of propylene oxide by oxidation of propylene with tert-butyl hydroperoxide. The reaction requires metal catalysts, which typically contain molybdenum:
(CH3)3COOH + CH2=CHCH3 → (CH3)3COH + CH2OCHCH3
The byproduct tert-butanol is recycled or converted to other useful compounds. The process once operated at the scale of >2 billion kg/y.
The lighter analogue of propylene oxide, ethylene oxide, is produced by silver-catalyzed reaction of ethylene with oxygen. Attempts to implement this relatively simple technology to the conversion of propylene to propylene oxide fail. Instead only combustion predominates. The problems are attributed to the sensitivity of allylic C-H bonds.
Mechanism
The oxidation is thought to proceed by formation of Mo(η2-O2-tert-Bu) complexes. The peroxy O center is rendered highly electrophilic, leading to attack on the alkene.
History
The Halcon process was developed by Halcon International.
References
Catalysis | Halcon process | Chemistry | 251 |
7,887,563 | https://en.wikipedia.org/wiki/Black%20triangle%20%28pharmacovigilance%29 | A black triangle appearing after the trade name of a British medicine (or vaccine) indicates that the medication is new to the market, or that an existing medicine (or vaccine) is being used for a new reason or by a new route of administration.
Examples of how it might appear:
NewDrugTradeName▼
NewDrugTradeName▼
The black triangle also highlights the need for surveillance of any Adverse Drug Reactions (ADRs) that might arise from the use of a new medication. The Medicines and Healthcare products Regulatory Agency (MHRA) encourage anyone to voluntarily report ADRs (however minor) via the Yellow Card Scheme to gather more information and gain more understanding of a new medication.
After a new medicine (or vaccine) has been brought to the market there is still a lot that can be learned about the drug from its widespread use. Similarly, if an existing drug is being used in a situation where it was not used before or if it is being given by a different route of administration much can still be learned about its new or modified use.
The black triangle label generally stays with the new drug (or new use of an existing drug) for at least 5 years, when it is reviewed, and after this time the black triangle label may or may not be discontinued.
See also
Pharmacovigilance
EudraVigilance
Uppsala Monitoring Centre (WHO)
British National Formulary
References
Pharmaceutical industry
Pharmacy in the United Kingdom
ru:Чёрный треугольник | Black triangle (pharmacovigilance) | Chemistry,Biology | 298 |
16,065,426 | https://en.wikipedia.org/wiki/Roe%20solver | The Roe approximate Riemann solver, devised by Phil Roe, is an approximate Riemann solver based on the Godunov scheme and involves finding an estimate for the intercell numerical flux or Godunov flux at the interface between two computational cells and , on some discretised space-time computational domain.
Roe scheme
Quasi-linear hyperbolic system
A non-linear system of hyperbolic partial differential equations representing a set of conservation laws in one spatial dimension
can be written in the form
Applying the chain rule to the second term we get the quasi-linear hyperbolic system
where is the Jacobian matrix of the flux vector .
Roe matrix
The Roe method consists of finding a matrix that is assumed constant between two cells. The Riemann problem can then be solved as a truly linear hyperbolic system at each cell interface. The Roe matrix must obey the following conditions:
Diagonalizable with real eigenvalues: ensures that the new linear system is truly hyperbolic.
Consistency with the exact jacobian: when we demand that
Conserving:
Phil Roe introduced a method of parameter vectors to find such a matrix for some systems of conservation laws.
Intercell flux
Once the Roe matrix corresponding to the interface between two cells is found, the intercell flux is given by solving the quasi-linear system as a truly linear system.
See also
Riemann solver
References
Further reading
Toro, E. F. (1999), Riemann Solvers and Numerical Methods for Fluid Dynamics, Springer-Verlag.
Numerical differential equations
Conservation equations | Roe solver | Physics,Mathematics | 309 |
22,269,613 | https://en.wikipedia.org/wiki/Prp24 | Prp24 (precursor RNA processing, gene 24) is a protein part of the pre-messenger RNA splicing process and aids the binding of U6 snRNA to U4 snRNA during the formation of spliceosomes. Found in eukaryotes from yeast to E. coli, fungi, and humans, Prp24 was initially discovered to be an important element of RNA splicing in 1989. Mutations in Prp24 were later discovered in 1991 to suppress mutations in U4 that resulted in cold-sensitive strains of yeast, indicating its involvement in the reformation of the U4/U6 duplex after the catalytic steps of splicing.
Biological Role
The process of spliceosome formation involves the U4 and U6 snRNPs associating and forming a di-snRNP in the cell nucleus. This di-snRNP then recruits another member (U5) to become a tri-snRNP. U6 must then dissociate from U4 to bond with U2 and become catalytically active. Once splicing has been done, U6 must dissociate from the spliceosome and bond back with U4 to restart the cycle.
Prp24 has been shown to promote the binding of U4 and U6 snRNPs. Removing Prp24 results in the accumulation of free U4 and U6, and the subsequent addition of Prp24 regenerates U4/U6 and reduces the amount of free U4 and U6. Naked U6 snRNA is very compact and has little room to form base pairs with other RNA. However, when U6 snRNP associates with proteins such as Prp24, the structure is much more open, thus facilitating the binding to U4. Prp24 is not present in the U6/U4 duplex itself, and it has been suggested that Prp24 must leave the complex in order for proper base pairs to be formed. It has also been suggested that Prp24 may play a role in destabilizing U4/U6 in order for U6 to pair bases with U2.
Structure
Prp24 has a molecular weight of 50 kDa and has been shown to contain four RNA recognition motifs (RRMs) and a conserved 12-amino acid sequence at the C-terminus. RRMs 1 and 2 have been shown to be important for high-affinity binding of U6, while RRMs 3 and 4 bind at lower affinity sites on U6. The first three RRMs interact extensively with each other and contain canonical folds that contain a four-stranded beta-sheet and two alpha-helices. The electropositive surface of RRMs 1 and 2 is a RNA annealing domain while the cleft between RRMs 1 and 2 including the beta-sheet face of RRM2 is a sequence-specific RNA binding site. The C-terminal motif is required for association with LSm proteins and contributes to substrate (U6) binding and not the catalytic rate of splicing.
Interactions
Prp24 interacts with the U6 snRNA via its RRMs. It has been shown through chemical modification testing that nucleotides 39–57 of U6 (40–43 in particular) are involved in binding Prp24.
The LSm proteins are in a consistent configuration on the U6 RNA. It has been proposed that the LSm proteins and Prp24 interact both physically and functionally and the C-terminal motif of Prp24 is important for this interaction. The binding of Prp24 to U6 is enhanced by the binding of Lsm proteins to U6, as is binding of U4 and U6. It was revealed by electron microscopy that Prp24 may interact with the LSm protein ring at LSm2.
Homologs
Prp24 has a human homolog, SART3. SART3 is a tumor rejection antigen (SART3 stands for "squamous cell carcinoma antigen recognized by T cells, gene 3). The RRMs 1 and 2 in yeast are similar to RRMs in human SART3. The C-terminal domain is also highly conserved from yeast to humans. This protein, like Prp24, interacts with the LSm proteins for the recycling of U6 into the U4/U6 snRNP. It has been proposed that SART3 target U6 to a Cajal body or a nuclear inclusion as the site of assembly of the U4/U6 snRNP. SART3 is located on chromosome 12, and a mutation is likely the cause of disseminated superficial actinic porokeratosis.
References
External links
Biological Sciences at Lancaster University Explanation of pre-mRNA splicing
Gene expression
Molecular genetics
Spliceosome | Prp24 | Chemistry,Biology | 987 |
53,511,508 | https://en.wikipedia.org/wiki/International%20Beacon%20Project | The International Beacon Project (IBP) is a worldwide network of radio propagation beacons. It consists of 18 continuous wave (CW) beacons operating on five designated frequencies in the high frequency band. The IBP beacons provide a means of assessing the prevailing ionospheric signal propagation characteristics to both amateur and commercial high frequency radio users.
The project is coordinated by the Northern California DX Foundation (NCDXF) and the International Amateur Radio Union (IARU). The first beacon of the IBP started operations from Northern California in 1979. The network was expanded to include 8 and subsequently 18 international transmission sites.
History
The first beacon was put into operation in 1979 using the call sign . It transmitted a 1 minute-long beacon every 10 minutes on 14.1 MHz using custom built transmitter and controller hardware. The signal consisted of the beacon's call sign transmitted in Morse code at 100 watts, four 9 second long dashes, each at 100 watts, 10 watts, 1 watt, and 0.1 watt, followed by sign-out at 100 watts.
Northern California DX Foundation and seven partnering organizations from the United States, Finland, Portugal, Israel, Japan, and Argentina operated the first iteration of the beacon network. Due to difficulties encountered in building beacon hardware, each site used a Kenwood TS-120 transceiver keyed and controlled by a custom built beacon controller. The network operated on 14.1 MHz and the beacon format remained unchanged.
In 1995, work began to improve the existing beacon network, so it could operate on 5 designated frequencies on the high frequency band. The new beacon network used Kenwood TS-50 transceivers keyed and controlled by an upgraded beacon controller unit. The number of partner organizations were expanded to 18 and the new 10 second beacon format was adopted.
Notable Projects
Beyond helping amateur radio operators better understand HF radio propagation the project has aided scientists in better understanding the earths ionosphere,
improved prediction models,
and aided in radio direction finding.
Frequencies and transmission schedule
The beacons transmit around the clock on the frequencies
14.100 MHz
18.110 MHz
21.150 MHz
24.930 MHz
28.200 MHz
Each beacon transmits its signal once on each frequency, in sequence from low (14.100 MHz) to high (28.200 MHz), followed by a 130 second pause during which beacons at other sites transmit in turn on the same frequencies, after which the cycle repeats. Each transmission is 10 second-long, and consists of the call sign of the beacon transmitted at 22 words per minute () followed by four dashes. The call sign and the first dash is transmitted at 100 watts of power. Subsequent three dashes are transmitted at 10 watts, 1 watt, and 0.1 watt respectively.
All beacon transmissions are coordinated using GPS time. As such, at a given frequency, all 18 beacons transmit in succession once every 3 minutes.
Hardware
Beacons transmit using commercial HF transceivers (Kenwood TS-50 or Icom IC-7200) keyed and coordinated by a purpose-built, hardware beacon controller.
Beacons
The International Beacon Project operates the following beacons as of January 2024.
{| class="wikitable"
!
! Beacon region
! Call sign
! Transmit site
! Gridsquare
! Operator
|-
|style="text-align:center;"| 1
| United Nationsheadquarters
|
| New York City
|style="text-align:left;"|
| United Nations Staff Recreation CouncilAmateur Radio Club (UNRC)
|-
|style="text-align:center;"| 2
| northernCanada
| VE8AT
| Inuvik, NT
|style="text-align:left;"| CP 38 gh
| RAC/NARC
|-
|style="text-align:center;"| 3
| California,United States
|
| Mt. Umunhum
|style="text-align:left;"|
| Northern California DX Foundation (NCDXF)
|-
|style="text-align:center;"| 4
| Hawaii,United States
|
| Maui
|style="text-align:left;"|
| Maui Amateur Radio Club (Maui ARC)
|-
|style="text-align:center;"| 5
| New Zealand
|
| Masterton
|style="text-align:left;"|
| New Zealand Association of Radio Transmitters (NZART)
|-
|style="text-align:center;"| 6
| Western Australia
|
| Roleystone
|style="text-align:left;"|
| Wireless Institute of Australia (WIA)
|-
|style="text-align:center;"| 7
| Honshū, Japan
|
| Mt. Asama
|style="text-align:left;"|
| Japan Amateur Radio League (JARL)
|-
|style="text-align:center;"| 8
| Siberia, Russia
|
| Novosibirsk
|style="text-align:left;"|
| Russian Amateur Radio Union (SRR)
|-
|style="text-align:center;"| 9
| Hong Kong
|
| Hong Kong
|style="text-align:left;"|
| Hong Kong Amateur Radio Transmitting Society (HARTS)
|-
|style="text-align:center;"| 10
| Sri Lanka
|
| Colombo
|style="text-align:left;"|
| Radio Society of Sri Lanka (RSSL)
|-
|style="text-align:center;"| 11
| South Africa
|
| Pretoria
|style="text-align:left;"|
| South Africa Radio Society (SARL)
|-
|style="text-align:center;"| 12
| Kenya
|
| Kariobangi
|style="text-align:left;"|
| Amateur Radio Society of Kenya (ARSK)
|-
|style="text-align:center;"| 13
| Israel
|
| Tel Aviv
|style="text-align:left;"|
| Israel Amateur Radio Club (IARC)
|-
|style="text-align:center;"| 14
| Finland
|
| Lohja
|style="text-align:left;"|
| Finnish Amateur Radio League (SRAL)
|-
|style="text-align:center;"| 15
| Madeira Island,Portugal
|
| Santo da Serra
|style="text-align:left;"|
| Rede dos Emissores Portugueses (REP)
|-
|style="text-align:center;"| 16
| Argentina
|
| Buenos Aires
|style="text-align:left;"|
| Radio Club Argentino (RCA)
|-
|style="text-align:center;"| 17
| Peru
|
| Lima
|style="text-align:left;"|
| Radio Club Peruano (RCP)
|-
|style="text-align:center;"| 18
| northern Venezuela
|
| Caracas
|style="text-align:left;"|
| Radio Club Venezolano (RCV)
|}
References
Radio frequency propagation
Beacons | International Beacon Project | Physics | 1,501 |
61,644,953 | https://en.wikipedia.org/wiki/Orbital%20Insight | Orbital Insight is a Palo Alto, California-based geospatial analytics company. The company analyzes satellite, drone, balloon and other unmanned aerial vehicle images, including cell phone geolocation data, to study a range of human activity, and provides business and other strategic insights from the data.
James Crawford is the company's founder and chief executive officer.
History
Orbital Insight was founded in 2013 by James Crawford, who earlier worked with artificial intelligence systems at Bell Labs, with Google Books and with NASA's Mars rover project. Crawford saw an opportunity to combine commercial and government satellite images with government image sets. The company's first project was analyzing the health of corn crops.
In 2015, the company partnered with the World Bank to improve its poverty data, using building height and rooftop material analysis to approximate wealth.
In 2016, the US intelligence committee's research arm, In-Q-Tel, and Google Ventures (GV), along with CME Group's investment arm CME Ventures, invested in the company, joining previous investors Sequoia Capital, Lux Capital and Bloomberg Beta.
In May 2017, the company closed a $50M million series C round from Sequoia Capital, making it reportedly one of the most capitalized companies in the geospatial analytics industry. In October, it was reported that Orbital Insight was working with the US Department of Defense's Defense Innovation Unit (DIU) group to develop and apply advanced algorithms to extract insights from images obtained using prototype commercial Synthetic Aperture Radar (SAR) microsatellites. One goal was to improve imagery applications in poor weather or lighting conditions, for better identification of natural and manmade threats. In October, Orbital Insight partnered with commercial space imagery company DigitalGlobe to extract insights from DigitalGlobe's satellite imagery.
In June 2018, Orbital Insight partnered with e-GEOS, S.p.A., a joint venture between European spaceflight services company Telespazio and the Italian Space Agency (ASI), to provide emergency flood mapping services to the U.S. government. In July, financial technology and media company Bloomberg L.P. began using Orbital Insight's geospatial vendor analysis including car counts at over 80 retailers, as part of Bloomberg's traditional client data. In September, Orbital Insight partnered with aerospace company Airbus to build a suite of geospatial analytics and tools as part of Airbus' OneAtlas program. Also in September, the company acquired Boston-based FeatureX, a company that specialized in applying computer vision to satellite images in order to extract information. Also in September, Orbital Insight partnered with Royal Bank of Canada's RBC Capital Markets arm to use geospatial imagery to predict trends in energy, mining, and location intelligence fields. Also in September, the company extended a partnership with earth imaging company Planet Labs (Planet), allowing Orbital to use Planet's PlanetScope imagery and high resolution SkySat imagery of Earth.
In May 2019, the company released Orbital Insight GO, an application designed to allow customers to search satellite imagery and geolocation information on their own, and analyze the images and data for insights. Also in May, Orbital Insight announced Earth Monitor, the first product that came from its Airbus satellite imagery partnership, which was a white labeling of Orbital Insight GO with additional custom work to enable integration with Airbus' proprietary satellites and imagery purchasing web flows. Orbital Insight GO was renamed Terrascope and relaunched in late 2022.
In May 2024, Apple cofounder Steve Wozniak's firm Privateer Space announced its acquisition of Orbital Insight, following reporting from an independent journalist six months prior that the transaction was meant to save Orbital from bankruptcy. This will add mapping and intelligence services to Privateer's space data offerings, Privateer's chief executive officer told Reuters.
Business
Orbital Insight analyzes satellite, drone, balloon and other unmanned aerial vehicle images, along with phone geolocation data, by applying machine learning techniques with computer vision to extract information that can be used for business decisions. Images are tagged manually to assist with computer recognition. Applications of the technology include estimating retail revenue by studying car counts at malls, helping insurance companies estimate the extent of damages from natural disasters, gauging a country's fuel supply by counting oil storage facilities, and assisting with strategic defense applications for threat assessments.
The company's Global Geospatial Crude Index (GCI) monitors millions of barrels of oil on a daily basis by tracking 25,000 external floating roof tanks. The shadows on the roofs can be used to predict how full the tanks are.
Orbital Insight also acquires anonymized location data for smartphones, and uses the geolocation data to track various business activities, such as staffing levels at refineries and factories, to make economic predictions.
Other tools include Orbital Insight GO, a self service satellite imagery and geospatial data analysis tool for customers.
Clients include hedge funds trying to get information advantages to help their investors.
Operations
Orbital Insight is headquartered in Palo Alto, California. The company also has US offices in Arlington, VA, and New York City, and international offices in Tokyo and London.
Financial Distress and Indonesia's State Intelligence Agency
In September and October 2023 multiple articles were published stating the company was facing significant financial difficulties. While the company raised $130 million over the years it has devalued itself to $50 million to obtain a $3 million emergency loan to avoid bankruptcy. The company seem to have secured only $500 000 of the total $3 million. Slide Decks from June 2023 have shown that there were multiple Merger and Acquisition attempts that failed. The company sees its lifeline in a project called Alpha for the Indonesian' State Intelligence Agency. It vaguely mentions multiple prospective deals with Qatar Armed Forces, Israel Defense Forces, Armed Forces of Ukraine, Armed Forces of Saudi Arabia and United Arab Emirates Armed Forces.
References
External links
Official website
Companies based in Palo Alto, California
Technology companies established in 2013
2013 establishments in California
Spatial analysis
Remote sensing companies
American companies established in 2013 | Orbital Insight | Physics | 1,232 |
65,466,889 | https://en.wikipedia.org/wiki/Crude%20oil%20stabilisation | Crude oil stabilisation (or stabilization) is a partial distillation process that renders crude oil suitable for storage in atmospheric tanks, or of a quality suitable for sales or pipeline transportation. Stabilization is achieved by subjecting ‘live’ crude to temperature and pressure conditions in a fractionation vessel, which drives off light hydrocarbon components to form a ‘dead’ or stabilized crude oil with a lower vapor pressure.
Specification
Typically, the live crude from an oil production installation would have a vapor pressure of 120 psia at 100 °F (726 kPa at 37.8 °C) or 125 psig at 60 °F (862 kPa at 15.5 °C). After stabilisation dead crude would have a Reid vapor pressure of 9 – 10 psig at 100 °F (62 – 69 kPa at 37.8 °C).
The stabilization process
Live crude is heated in a furnace or heat exchanger to an elevated temperature. The crude oil is fed to a stabilizer which is typically a tray or packed tower column that achieves a partial fractionation or distillation of the oil. The heavier components, pentane (C5H12), hexane (C6H14), and higher hydrocarbons (C7+), flow as liquid down through the column where the temperature is increasingly higher. At the bottom of the column, some of the liquid is withdrawn and circulated through a reboiler which adds heat to the tower. Here the lighter fractions are finally driven off as a gas, which rises up through the column. At each tray or stage, the rising gas strips the light ends from heavy ends, and the rising gas becomes richer in the light components and leaner in the heavy ends.
Alternatively, if a finer separation is required the column may be provided with an upper section reflux system making it similar to a distillation column. As the reflux liquid flows down through the column it becomes leaner in light components and richer in heavy ends. Overhead gas from the stabilizer passes through a back pressure control valve that maintains the pressure in the stabilizer.
The stabilised crude oil, comprising pentane and higher hydrocarbons (C5+), is drawn from the base of the stabilizer and is cooled. This may be by heat exchange with the incoming live crude and by cooling water in a heat exchanger. The dead, stabilized crude flows to tanks for storage or to a pipeline for transport to customers such as an oil refinery.
The stabilization tower may typically operate at approximately 50 to 200 psig (345 – 1378 kPa). Where the crude oil contains high levels of hydrogen sulphide (H2S) a sour stabilization is undertaken. This entails operating the stabilizer at the lower end of the pressure range, whereas sweet (low H2S) stabilization would take place at a higher pressure.
Gas processing
The light hydrocarbons stripped from the crude are usually processed to yield useful products. Gas from the top of the stabilizer column is compressed and fed to a de-methanizer column. This column separates the lightest hydrocarbons, methane (CH4) and ethane (C2H6), from the heavier components. Methane and ethane are withdrawn from the top of the column and are used as fuel gas in the plant. Excess gas may be flared.
Liquid from the base of the de-methanizer is routed to the de-ethanizer. Gas from the top is principally ethane and is compressed and returned to the de-methanizer.
Liquid from the base of the de-ethanizer is routed to the de-propanizer. Gas from the top is principally propane (C3H8) and is compressed or chilled for storage and sales.
Liquid from the base of the de-propanizer is principally butane (C4H10) and some heavier components. Butane is stored and sold, and the heavier fraction is sold or spiked into the stabilized crude.
See also
Oil production plant
Oil platform
Upstream (oil industry)
Oil industry
Flotta oil terminal
Sullom Voe terminal
References
Petroleum technology
Oil refining
Distillation | Crude oil stabilisation | Chemistry,Engineering | 849 |
37,537,157 | https://en.wikipedia.org/wiki/Lithium%20tungstate | Lithium tungstate is the inorganic compound with the formula Li2WO4. It is a white solid that is soluble in water. The compound is one of the several orthotungstates, compounds that feature the tetrahedral WO42− anion.
Structure
The salt consists of tetrahedrally coordinated Li and W centres bridged by oxides. The W-O and Li-O bond distances are 1.79 and 1.96 Å, respectively. These differing bond lengths reflect the multiple bond character of the W-O interaction and the weaker ionic bonding between the Li-O interactions. The solid undergoes phase transitions at high pressures, such that the coordination geometry at tungsten becomes octahedral (six W-O bonds). For example at 40 kilobars, it adopts a structure related to wolframite.
Uses
Lithium tungstate is used to produce high density aqueous polytungstate (metatungstate) solutions. Like other high density fluids, such solutions are often used in the separation of minerals and other solids. These can achieve a density of 2.95 at 25 °C and up to 3.6 in hot water.
This use of lithium and sodium tungstate anions was developed in the 1980s and early 1990s to address toxicity and safety issues with the existing organic high density fluids. Unlike methylene iodide and bromoform, polytungstates and heteropolytungstates can be more safely be used in an indoor environment without a fume hood with only ordinary common sense safety precautions such as protective gloves and safety glasses.
References
Lithium salts
Tungstates | Lithium tungstate | Chemistry | 335 |
8,908,470 | https://en.wikipedia.org/wiki/Conodont%20Alteration%20Index | The Conodont Alteration Index (CAI) is used to estimate the maximum temperature reached by a sedimentary rock using thermal alteration of conodont fossils. Conodonts in fossiliferous carbonates are prepared by dissolving the matrix with weak acid, since the conodonts are composed of apatite and thus do not dissolve as readily as carbonate. The fossils are then compared to the index under a microscope. The index was first developed by Anita Epstein and colleagues at the United States Geological Survey.
The CAI ranges from 1 to 6, as follows:
The CAI is commonly used by paleontologists due to its ease of measurement and the abundance of Conodonta throughout marine carbonates of the Paleozoic. However, the organism disappears from the fossil record after the Triassic period, so the CAI is not available to analyze rocks younger than . Additionally, the index can be positively skewed in regions of hydrothermal alteration.
See also
Foraminiferal Colouration Index (FCI)
References
Epstein, A., Epstein, J., Harris, L. (1977). "Conodont Color Alteration - an Index to Organic Metamorphism." United States Geological Survey Professional Paper 995, 1-27.
(Image)
Conodonts
Fossil record of animals
Geochemistry
Sedimentology | Conodont Alteration Index | Chemistry | 264 |
16,481,963 | https://en.wikipedia.org/wiki/Lefschetz%20duality | In mathematics, Lefschetz duality is a version of Poincaré duality in geometric topology, applying to a manifold with boundary. Such a formulation was introduced by , at the same time introducing relative homology, for application to the Lefschetz fixed-point theorem. There are now numerous formulations of Lefschetz duality or Poincaré–Lefschetz duality, or Alexander–Lefschetz duality.
Formulations
Let M be an orientable compact manifold of dimension n, with boundary , and let be the fundamental class of the manifold M. Then cap product with z (or its dual class in cohomology) induces a pairing of the (co)homology groups of M and the relative (co)homology of the pair . Furthermore, this gives rise to isomorphisms of with , and of with for all .
Here can in fact be empty, so Poincaré duality appears as a special case of Lefschetz duality.
There is a version for triples. Let decompose into subspaces A and B, themselves compact orientable manifolds with common boundary Z, which is the intersection of A and B. Then, for each , there is an isomorphism
Notes
References
Duality theories
Manifolds | Lefschetz duality | Mathematics | 265 |
56,209,806 | https://en.wikipedia.org/wiki/Datroniella%20minuta | Datroniella minuta is a species of fungus in the family Polyporaceae. It was described in 2016 by mycologists Carla Rejane Sousa de Lira and Leif Ryvarden from collections made in northeast Brazil. The fungus is characterized by its tiny, cup-shaped fruit bodies that are reddish to dark brown, and microscopically by its large cylindrical spores that typically measure 9–10 by 3 μm.
References
Fungi of Brazil
Polyporaceae
Fungi described in 2016
Taxa named by Leif Ryvarden
Fungus species | Datroniella minuta | Biology | 111 |
164,501 | https://en.wikipedia.org/wiki/Nimber | In mathematics, the nimbers, also called Grundy numbers, are introduced in combinatorial game theory, where they are defined as the values of heaps in the game Nim. The nimbers are the ordinal numbers endowed with nimber addition and nimber multiplication, which are distinct from ordinal addition and ordinal multiplication.
Because of the Sprague–Grundy theorem which states that every impartial game is equivalent to a Nim heap of a certain size, nimbers arise in a much larger class of impartial games. They may also occur in partisan games like Domineering.
The nimber addition and multiplication operations are associative and commutative. Each nimber is its own additive inverse. In particular for some pairs of ordinals, their nimber sum is smaller than either addend. The minimum excludant operation is applied to sets of nimbers.
Uses
Nim
Nim is a game in which two players take turns removing objects from distinct heaps. As moves depend only on the position and not on which of the two players is currently moving, and where the payoffs are symmetric, Nim is an impartial game. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap. The goal of the game is to be the player who removes the last object. The nimber of a heap is simply the number of objects in that heap. Using nim addition, one can calculate the nimber of the game as a whole. The winning strategy is to force the nimber of the game to 0 for the opponent's turn.
Cram
Cram is a game often played on a rectangular board in which players take turns placing dominoes either horizontally or vertically until no more dominoes can be placed. The first player that cannot make a move loses. As the possible moves for both players are the same, it is an impartial game and can have a nimber value. For example, any board that is an even size by an even size will have a nimber of 0. Any board that is even by odd will have a non-zero nimber. Any board will have a nimber of 0 for all even and a nimber of 1 for all odd .
Northcott's game
In Northcott's game, pegs for each player are placed along a column with a finite number of spaces. Each turn each player must move the piece up or down the column, but may not move past the other player's piece. Several columns are stacked together to add complexity. The player that can no longer make any moves loses. Unlike many other nimber related games, the number of spaces between the two tokens on each row are the sizes of the Nim heaps. If your opponent increases the number of spaces between two tokens, just decrease it on your next move. Else, play the game of Nim and make the Nim-sum of the number of spaces between the tokens on each row be 0.
Hackenbush
Hackenbush is a game invented by mathematician John Horton Conway. It may be played on any configuration of colored line segments connected to one another by their endpoints and to a "ground" line. Players take turns removing line segments. An impartial game version, thereby a game able to be analyzed using nimbers, can be found by removing distinction from the lines, allowing either player to cut any branch. Any segments reliant on the newly removed segment in order to connect to the ground line are removed as well. In this way, each connection to the ground can be considered a nim heap with a nimber value. Additionally, all the separate connections to the ground line can also be summed for a nimber of the game state.
Addition
Nimber addition (also known as nim-addition) can be used to calculate the size of a single nim heap equivalent to a collection of nim heaps. It is defined recursively by
where the minimum excludant of a set of ordinals is defined to be the smallest ordinal that is not an element of .
For finite ordinals, the nim-sum is easily evaluated on a computer by taking the bitwise exclusive or (XOR, denoted by ) of the corresponding numbers. For example, the nim-sum of 7 and 14 can be found by writing 7 as 111 and 14 as 1110; the ones place adds to 1; the twos place adds to 2, which we replace with 0; the fours place adds to 2, which we replace with 0; the eights place adds to 1. So the nim-sum is written in binary as 1001, or in decimal as 9.
This property of addition follows from the fact that both and XOR yield a winning strategy for Nim and there can be only one such strategy; or it can be shown directly by induction: Let and be two finite ordinals, and assume that the nim-sum of all pairs with one of them reduced is already defined. The only number whose XOR with is is , and vice versa; thus is excluded.
On the other hand, for any ordinal , XORing with all of , and must lead to a reduction for one of them (since the leading 1 in must be present in at least one of the three); since
we must have either
thus is included as either
and hence is the minimum excluded ordinal.
Nimber addition is associative and commutative, with as the additive identity element. Moreover, a nimber is its own additive inverse. It follows that if and only if .
Multiplication
Nimber multiplication (nim-multiplication) is defined recursively by
Nimber multiplication is associative and commutative, with the ordinal as the multiplicative identity element. Moreover, nimber multiplication distributes over nimber addition.
Thus, except for the fact that nimbers form a proper class and not a set, the class of nimbers forms a ring. In fact, it even determines an algebraically closed field of characteristic 2, with the nimber multiplicative inverse of a nonzero ordinal given by
where is the smallest set of ordinals (nimbers) such that
is an element of ;
if and is an element of , then is also an element of .
For all natural numbers , the set of nimbers less than form the Galois field of order . Therefore, the set of finite nimbers is isomorphic to the direct limit as of the fields . This subfield is not algebraically closed, since no field with not a power of 2 is contained in any of those fields, and therefore not in their direct limit; for instance the polynomial , which has a root in , does not have a root in the set of finite nimbers.
Just as in the case of nimber addition, there is a means of computing the nimber product of finite ordinals. This is determined by the rules that
The nimber product of a Fermat 2-power (numbers of the form ) with a smaller number is equal to their ordinary product;
The nimber square of a Fermat 2-power is equal to as evaluated under the ordinary multiplication of natural numbers.
The smallest algebraically closed field of nimbers is the set of nimbers less than the ordinal , where is the smallest infinite ordinal. It follows that as a nimber, is transcendental over the field.
Addition and multiplication tables
The following tables exhibit addition and multiplication among the first 16 nimbers.
This subset is closed under both operations, since 16 is of the form .
(If you prefer simple text tables, they are .)
See also
Surreal number
Notes
References
which discusses games, surreal numbers, and nimbers.
Combinatorial game theory
Finite fields
Ordinal numbers | Nimber | Mathematics | 1,646 |
2,865,864 | https://en.wikipedia.org/wiki/List%20of%20unsolved%20problems%20in%20chemistry | This is a list of unsolved problems in chemistry. Problems in chemistry are considered unsolved when an expert in the field considers it unsolved or when several experts in the field disagree about a solution to a problem.
Physical chemistry problems
Can the transition temperature of high-temperature superconductors be brought up to room temperature?
How do the spin–orbit coupling, other relativistic corrections, and inter-electron effects modify the chemistry of the trans-actinides?
Is it possible to create a practically-useful lithium–air battery?
Organic chemistry problems
What is the origin of homochirality in biomolecules?
Why are accelerated kinetics observed for some organic reactions at the water-organic interface?
Do replacement reactions of aryl diazonium salts (dediazotizations) predominantly undergo SN1 or a radical mechanism?
Can an electrochemical cell reliably perform organic redox reactions?
Which "classic organic chemistry" reactions admit chiral catalysts?
Is it possible to construct a quaternary carbon atom with arbitrary (distinguishable) substituents and stereochemistry?
Can artificial enzymes replace the need for protecting groups when modifying sensitive compounds?
Inorganic chemistry problems
Are there any molecules that certainly contain a phi bond?
Is there a less labor- or energy-intensive technique for titanium refinement than the Kroll process?
Does nitrogen admit metastable allotropes under standard conditions?
Can new solvents or other techniques make direct carbon capture economical?
Can artificial photosynthesis make any common fuels?
What is a reliable synthesis and stabilization method for catenary allotropes of sulfur and carbon?
Biochemistry problems
Enzyme kinetics: Why do some enzymes exhibit faster-than-diffusion kinetics?
Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions? This has been achieved for several small globular proteins in recent years. In 2020, it was announced that Google's AlphaFold, a neural network based on DeepMind artificial intelligence, is capable of predicting a protein's final shape based solely on its amino-acid chain with an accuracy of around 90% on a test sample of proteins used by the team.
RNA folding problem: Is it possible to accurately predict the secondary, tertiary and quaternary structure of a polyribonucleic acid sequence based on its sequence and environment?
Protein design: Is it possible to design highly active enzymes de novo for any desired reaction?
Biosynthesis: Can desired molecules, natural products or otherwise, be produced in high yield through biosynthetic pathway manipulation?
See also
List of hypothetical technologies
List of paradoxes
List of philosophical problems
List of purification methods in chemistry
List of thermal conductivities
List of undecidable problems
List of unsolved deaths
List of unsolved problems in astronomy
List of unsolved problems in biology
List of unsolved problems in computer science
List of unsolved problems in economics
List of unsolved problems in fair division
List of unsolved problems in geoscience
List of unsolved problems in information theory
List of unsolved problems in mathematics
List of unsolved problems in neuroscience
List of unsolved problems in physics
List of unsolved problems in statistics
Lists of problems
Outline of chemistry
Outline of physics
Unsolved problems in medicine
References
External links
Unsolved Problems in Nanotechnology: Chemical Processing by Self-Assembly - Matthew Tirrell - Departments of Chemical Engineering and Materials, Materials Research Laboratory, California NanoSystems Institute, University of California, Santa Barbara [No doc at link, 20 Aug 2016]
Unsolved problems
chemistry
Scientific problems | List of unsolved problems in chemistry | Chemistry | 784 |
36,647,269 | https://en.wikipedia.org/wiki/Newar%20window | Newār window (; newār jhyāl) refers to the elaborately carved wooden window which is the distinguishing feature of traditional Newa architecture. The ornate windows have been described as a symbol of Newar culture and artistry. The level of design and carving of the Newar window reached its peak in the mid-18th century. They are found on palaces, private residences and sacred houses across Nepal Mandala.
The lintel, sill and jamb are ornamented with figures of deities, mythical beings, dragons, peacocks, auspicious jars and other elements. The window is surmounted by ritual parasols. Traditional Newar houses are usually of four stories and built of brick. Different types of windows are used on each floor according to their function.
Newar windows and bare-brick facade in the traditional style are making a comeback as an architectural trend due to the tourism industry and growing heritage awareness.
Types of windows
Among the many window designs, the following are the most common:
Sanjhyā (Devanagari: सँझ्या:) is a projecting bay window and the classic Newar window. A typical Sanjhyā consists of three units and is located in the center of a facade. The shutter consists of a lattice and opens upwards. It is usually located on the third floor.
Tikijhya(तिकिझ्या:) is a lattice window and the most common window in traditional architecture. It is located on the second floor. The window allows light and air to enter the room but does not permit a passerby to see inside.
Gājhyā (गा:झ्या:) is a projecting window located under a roof.
Pāsukhā Jhyā (पासुखा झ्या:) is a small window with five units symbolizing the Pancha Buddha (Five Buddhas). It is mostly found on the shrine house of monasteries.
Famous windows
A number of traditional carved windows in the Kathmandu Valley are celebrated for their uniqueness.
Desay Madu Jhya (देसय मदु झ्या:), set in a house in Kathmandu, means "the only window of its kind in the country".
Lunjhyā (लुँझ्याः) at Patan Durbar, Patan is a gilded window. The name means "golden window".
Mhaykhā Jhyā (म्हयखाझ्याः) at Bhaktapur means "peacock window" and depicts a fan tailed peacock.
Gallery
See also
Newa architecture
References
Windows
Newa architecture
Architectural elements
Kathmandu
Woodcarving
Woodworking
Newar
Cultural history of Nepal | Newar window | Technology,Engineering | 515 |
55,062,864 | https://en.wikipedia.org/wiki/EZCast | EZCast is a line of digital media players, built by Actions Microelectronics, that allows users to mirror media content from smart devices, including mobile devices, personal computers, and project to high-definition televisions.
History
The first generation of EZCast was developed in 2013, shipped 1 million units within a year, and accumulated more than 2 million EZCast app users worldwide. The latest device in the family, called EZCast 4K, was launched in November 2016 which supports 4K HEVC video streaming.
EZCast technology is built into a dongle that interacts with EZCast app to stream content from smart devices, and it works across Android, ChromeOS, iOS, macOS, Windows and Windows Phone.
EZCast SDK has been released to enable third party development on Android and iOS.
In 2018 became possible to voice control EZCast 2 and EZCast 4K devices using Google Assistant.
Technology
EZCast devices all come equipped with Actions Microelectronics SoCs and Linux-based software that supports Miracast/DLNA and/or USB video for iOS and Android.
References
Electronics companies of Taiwan
Wireless display technologies | EZCast | Technology | 242 |
3,559,472 | https://en.wikipedia.org/wiki/Axiomatic%20quantum%20field%20theory | Axiomatic quantum field theory is a mathematical discipline which aims to describe quantum field theory in terms of rigorous axioms. It is strongly associated with functional analysis and operator algebras, but has also been studied in recent years from a more geometric and functorial perspective.
There are two main challenges in this discipline. First, one must propose a set of axioms which describe the general properties of any mathematical object that deserves to be called a "quantum field theory". Then, one gives rigorous mathematical constructions of examples satisfying these axioms.
Analytic approaches
Wightman axioms
The first set of axioms for quantum field theories, known as the Wightman axioms, were proposed by Arthur Wightman in the early 1950s. These axioms attempt to describe QFTs on flat Minkowski spacetime by regarding quantum fields as operator-valued distributions acting on a Hilbert space. In practice, one often uses the Wightman reconstruction theorem, which guarantees that the operator-valued distributions and the Hilbert space can be recovered from the collection of correlation functions.
Osterwalder–Schrader axioms
The correlation functions of a QFT satisfying the Wightman axioms often can be analytically continued from Lorentz signature to Euclidean signature. (Crudely, one replaces the time variable with imaginary time the factors of change the sign of the time-time components of the metric tensor.) The resulting functions are called Schwinger functions. For the Schwinger functions there is a list of conditions — analyticity, permutation symmetry, Euclidean covariance, and reflection positivity — which a set of functions defined on various powers of Euclidean space-time must satisfy in order to be the analytic continuation of the set of correlation functions of a QFT satisfying the Wightman axioms.
Haag–Kastler axioms
The Haag–Kastler axioms axiomatize QFT in terms of nets of algebras.
Euclidean CFT axioms
These axioms (see e.g.) are used in the conformal bootstrap approach to conformal field theory in . They are also referred to as Euclidean bootstrap axioms.
See also
Dirac–von Neumann axioms
References
Quantum field theory | Axiomatic quantum field theory | Physics | 450 |
35,539,120 | https://en.wikipedia.org/wiki/Mueterschwanderberg | Mueterschwanderberg (also Mueterschwandenberg) is a ridge forming the southern shore of Alpnachersee, just northwest of Stanserhorn and west of the village of Ennetmoos, Nidwalden, Switzerland.
Its peak is at an elevation of 860 m (some 425 m above the lake surface).
The peak is known as Drachenflue (Drachenfluh), with the Drachenloch cave nearby, named for the dragon which according to legend was slain here by Heinrich von Winkelried.
Mueterschwanderberg is known for the historical artillery fortress built into the mountain, constructed during the Second World War, during 1941 to 1944.
Mueterschwanderberg was the largest such fortress in Switzerland. It remained in service throughout the Cold War period.
Its decommission was decided in 1998, and it was dismantled in 2007.
Mountains of Switzerland
Mountains of Nidwalden
Forts in Switzerland
Fortifications of Switzerland built in the 20th century
Mountains of the Alps
20th-century architecture in Switzerland | Mueterschwanderberg | Engineering | 221 |
41,650,491 | https://en.wikipedia.org/wiki/Google%20Free%20Zone | Google Free Zone was a global initiative undertaken by the Internet company Google in collaboration with mobile phone-based Internet providers, whereby the providers waive data (bandwidth) charges (also known as zero-rate) for accessing select Google products such as Google Search, Gmail, and Google+. In order to use this service, users were required to have a Google account and a phone that had access to an internet connection.
History
November 2012: Google Free Zone was announced by Google on November 8, 2012, with a launch in the Philippines in partnership with Globe Telecom, with the experimental round scheduled to run until March 31, 2013. Telkom Mobile in South Africa, then branded as 8ta, offered Google Free Zone 3 from 13 November 2012 but discontinued the service on 31 May 2013.
April 2013: launch in Sri Lanka on the Dialog mobile network.
June 2013: Google launched Google Free Zone in India in partnership with mobile Internet provider Airtel, and in Thailand on the AIS network.
December 2013: Airtel extended Google Free Zone to its services in Nigeria.
March 2014: Safaricom in Kenya had launched 60 day promotional Free Zone.
Reception and impact
A number of Internet commentators viewed Google Free Zone as both inspired by and a potential competitor to Facebook Zero.
The Subsecretaria de Telecomunicaciones of Chile ruled that Zero-rating services like Wikipedia Zero, Facebook Zero, and Google Free Zone, that subsidize mobile data usage, violate net neutrality laws and that the practice had to end by June 1, 2014.
See also
Alliance for Affordable Internet
Facebook Zero
Internet.org
Project Loon
Wikipedia Zero
Zero-rating Zero Rating / Toll Free Data / Toll Free Apps
References
Free Zone
Internet access
Net neutrality | Google Free Zone | Technology,Engineering | 351 |
46,560,320 | https://en.wikipedia.org/wiki/Joint%20Organisations%20Data%20Initiative | The Joint Organisations Data Initiative (JODI) is an international collaboration to improve the availability and reliability of data on petroleum and natural gas. First named the "Joint Oil Data Exercise", the collaboration was launched in April 2001 with six international organisations: Asia-Pacific Economic Cooperation (APEC), Statistical Office of the European Communities (Eurostat), International Energy Agency (IEA), (OLADE), Organization of the Petroleum Exporting Countries (OPEC), and United Nations Statistics Division (UNSD). In 2005, the effort was renamed JODI, joined by the International Energy Forum (IEF), and covered more than 90% of the global oil market. The Gas Exporting Countries Forum (GECF) joined as an eighth partner in 2014, enabling JODI also to cover nearly 90% of the global market for natural gas.
References
External links
Energy economics
International energy organizations
2001 establishments in the United States
Companies established in 2001 | Joint Organisations Data Initiative | Engineering,Environmental_science | 194 |
66,572,904 | https://en.wikipedia.org/wiki/TOI-561 | TOI-561 is an old, metal-poor, Sun-like star, known to have multiple small planets.
It is an orange dwarf, estimated to be 10.5 billion years old, and about 79% the mass and 85% the radius of Sol, Earth's sun. It is located in the constellation Sextans, near the border with Leo.
In January 2021, a team led by Lauren Weiss of the University of Hawaii at Manoa announced that, using data from NASA's Transiting Exoplanet Survey Satellite, they had found a Super-Earth in a very close orbit, as well as two outer Sub-Neptunes. The innermost planet, TOI-561 b, orbits in under one Earth day. Another team led by Gaia Lacedelli of the University of Padua independently announced the discovery in a paper published in December 2020. However, the two papers disagree on the structure of the system. While the innermost two planets were confirmed from data by both papers, Weiss proposes only a single third planet in a 16.3-day orbit, while Lacedelli argues that the system instead contains two further planets, in wider orbits of 25.6 and 77 days.
Discovery and nomenclature
TOI-561 is also designated 2MASS J09524454+0612589 in the 2MASS catalog and TIC 377064495 in the TESS Input Catalog. When its planets were first identified, it was renamed TOI-561, with TOI standing for "TESS Object of Interest".
The planetary system was independently confirmed and characterized by Lacedelli et al. 2020 and Weiss et al. 2021. Lacedelli et al. found evidence for four exoplanets: the Ultra-Short-Period (USP) Super-Earth TOI-561 b, and three Sub-Neptunes designated TOI-561 c, d, and e. The two planets TOI-561 d and TOI-561 e were originally listed as a single planet with a period of 16 days on ExoFOP, but Lacedelli could not detect a planet in that orbit using radial velocity data from HARPS, and instead interpreted it as two separate transits coming from planets correlating with periods of 25.6 and 77.2 days found by HARPS.
In January 2021, Lauren Weiss and her team's study on TOI-561 was published. Unlike Lacedelli, they kept the 16-day signal and designated it TOI-561 d; it is referred to as TOI-561 f on NASA's Exoplanet Archive to avoid confusion with the TOI-561 d from Lacedelli's paper.
Characteristics
TOI-561 is a yellow or orange star approximately 80% the size of the Sun. According to Lacedelli, it is 85% the radius and 79% the mass of the Sun, with a temperature of 5455 K. Weiss found the star to be 83.2% the radius and 80.5% the mass of the Sun, with a temperature of 5326 K and a luminosity just over half that of the Sun. Both teams found that TOI-561 has an extremely low abundance of metals, or any element heavier than hydrogen or helium, and is very old; Weiss calculates an age of roughly 10 billion years. It is also a part of the Galactic Thick-Disk and is the first of those stars to have confirmed transiting exoplanets.
Planetary system
Depending on the study, TOI-561 has either 3 (Weiss) or 4 (Lacedelli) planets. The discrepancy comes from different interpretations of the two transit events associated with TOI-561 d in Weiss 2020. Only two transits were observed by TESS, and a third transit for a 16-day period would have occurred in the middle of a data gap. Weiss attributes the two transits to that of a single Sub-Neptune sized planet. However, in the radial velocity analysis by Lacedelli 2020, the 16-day signal is not recovered, but there are two additional signals of 26 and 77 days that they attribute to one of the two transits each. The follow-up study in 2022 has confirmed the architecture of four-planet system. Additional, fifth planet on the 473 days orbit is suspected. The orbital parameters were refined with additional observations from CHEOPS and TESS in 2024, further confirming four transiting planets and a fifth non-transiting candidate.
TOI-561 b
TOI-561 b is an USP Super-Earth with a radius of roughly 1.4 Earths. It has an extremely short orbital period of under 11 hours, less than half of an Earth day, resulting in an equilibrium temperature of . The planet is believed to be far too small and irradiated to hold onto its primordial Hydrogen and Helium envelope. However, the composition of the planet varies greatly between the two studies. Weiss 2020 found a mass of around 3.2 Earths and a density of 5.5 grams per cubic centimetre, around the same as Earth and implying a rocky but iron-poor composition. Lacedelli 2020, on the other hand, found a mass of only 1.59 Earths and a density of 3.0 grams per cubic centimetre, abnormally low for a planet of its size and suggesting a composition made of 50% or more of water. Even their higher mass estimate of 1.83 Earths is still consistent with a water-world. With an insolation 5,100 times greater than Earth, TOI-561 b should have lost its gaseous layer and have little volatiles, so the authors believe if the planet has a significant amount of water, it has been evaporated into a puffy steam atmosphere that makes the planet seem larger, less dense, and more water-rich. If it is an extremely water-rich world, TOI-561 b would prove formation scenarios about Super-Earths forming beyond the "Snow Line" and migrating inwards.
TOI-561 c
TOI-561 c is a Mini-Neptune orbiting every 10.7 days with an equilibrium temperature of . With a radius of 2.9 Earths and a mass of 5.4 to 7.0 Earths, the planet has a Neptune-like density of 1.3 to 1.6 grams per cubic centimetre, implying that it is a small gas planet with a similar composition, albeit far hotter and closer to its star than our system's ice giants.
TOI-561 d/e/f
Two additional transit events were observed by TESS. The original planet candidate from the SPOC pipeline included both transits with a period of 16 days. Lacedelli et al. failed to find a significant radial velocity signal at that period, but found two others with periods of 25.6 and 77.2 days, and also noticed differences in the shape, duration, and depth of the two individual transits. They concluded that the 16-day signal was instead two separate single transit events from similarly sized but different planets, which corresponded with the additional signals found in their radial velocity analysis. They designated these planets TOI-561 d (25.6 days) and TOI-561 e (77.2 days). According to their analysis, both planets are slightly smaller than TOI-561 c at 2.5 and 2.7 Earths, but are both significantly more massive, at 12 and 16 times the mass of Earth. TOI-561 d and TOI-561 e are much denser at 4.1 and 4.6 grams per cubic centimetre, respectively. These are compatible with water-world compositions of >50% water by mass, or a thin H/He envelope on top of a water mantle and rocky core. Weiss et al. interprets the two transits as a single planet, and also interprets an extremely faint radial velocity signal corresponding to about 3 Earth masses; however, it is too imprecise to gain an accurate density estimate, and this scenario could be incorrect. To distinguish this from the previous reported TOI-561 e, the 16-day planet from Weiss et al. has been designated TOI-561 f on the Exoplanet Archive.
References
G-type main-sequence stars
Sextans
0561
Planetary systems with four confirmed planets
J09524454+0612589 | TOI-561 | Astronomy | 1,749 |
36,221,385 | https://en.wikipedia.org/wiki/HD%2097658 | HD 97658 is a star with an exoplanetary companion in the equatorial constellation of Leo. The star is too dim to be seen with the naked eye, having an apparent visual magnitude of 7.76. It is located at a distance of 70 light years based on parallax, but is slowly drifting closer with a radial velocity of −1.6 km/s.
This is an ordinary K-type main-sequence star with a stellar classification of K1V. The star has 77% of the mass and 73% of the radius of the Sun. Estimates of the star's age ranges from four to six billion years. It is spinning with a rotation period of around 39 days and shows a magnetic activity cycle of 9.6 years, which is slightly shorter than the solar cycle. The chromospheric activity is lower than average for stars of this class.
HD 97658 is radiating 35% of the luminosity of the Sun from its photosphere at an effective temperature of 5,212 K. The star has a low metallicity – the atmospheric abundance of elements with a higher atomic number than helium, which explains why it lies 0.46 magnitudes below average for main sequence stars of its type.
Planetary system
On November 1, 2010, a super-Earth was announced orbiting the star along with Gliese 785 b as part of the NASA-UC Eta-Earth program. The planet orbits in just under 9.5 days and was originally thought to have a minimum mass of 8.2 ± 1.2 M🜨. Spurred by the possibility of transits, additional data was acquired for less than a year which found a lower mass for the star and hence reduced the minimum mass of the planet to 6.4 ± 0.7 M🜨, and improved certainty on the time of possible transit. Transits of the planet were apparently detected and announced on September 12, 2011; this would make HD 97658 the second-to-brightest star with a transiting planet after 55 Cancri and indicating a low-density planet like Gliese 1214 b. However, the occurrence of transits was quietly retracted on April 11, 2012, and three days later it was announced that observations by the MOST space telescope could not confirm transits. Transits of radii larger than 1.87 R🜨 were ruled out.
Further transit measurements were taken in April 2012 and were confirmed with transit readings made in the following year, March and April 2013. It was determined that HD 97658 b had a diameter 2.34 times that of Earth. Using a radial velocity mass of 7.86 M🜨 and the radius measured from the transits taken in 2012 and 2013 and in early 2014, the density of the planet was calculated as 3.44 g cm−3. It is likely therefore that the super-Earth exoplanet HD 97658 b has a large rocky core covered with a thick layer of volatiles, either a deep ocean of water or a thick atmosphere possibly made up of a mixture of helium and hydrogen. The gravity on this exoplanet's surface is about 1.6 times greater than that of Earth's.
The planetary transmission spectrum of HD 97658 b taken in 2020 have revealed presence of clouds up to millibar pressure. Although no conclusion can be made on atmosphere composition, best model fitting is obtained with hydrogen-helium envelope with carbon monoxide and methane admixture. No helium was detected at HD 97658 b in 2020 though.
See also
List of stars in Leo
References
K-type main-sequence stars
Planetary transit variables
Planetary systems with one confirmed planet
Leo (constellation)
J11143316+2542374
BD+26 2184
3651
097658
054906 | HD 97658 | Astronomy | 771 |
1,241,529 | https://en.wikipedia.org/wiki/Spacebus | Spacebus is a satellite bus produced at the Cannes Mandelieu Space Center in France by Thales Alenia Space. Spacebuses are typically used for geostationary communications satellites, and seventy-four have been launched since development started in the 1980s. Spacebus was originally produced by Aérospatiale and later passed to Alcatel Alenia Space. In 2006, it was sold to Thales Group as Thales Alenia Space.
The first Spacebus satellite, Arabsat-1A, was launched in 1985. Since then, seventy-four have been launched, with one more completed, and six outstanding orders. The launch of the 50th Spacebus satellite, Star One C1, occurred in November 2007. It was a Spacebus 3000B3, launched by an Ariane 5 rocket flying from the Guiana Space Centre in Kourou, French Guiana.
Several variants have been built: the early Spacebus 100 and Spacebus 300; followed by the Spacebus 2000, optimised for launch on the Ariane 4 carrier rocket; and the subsequent modular Spacebus 3000 and 4000 series, designed for use with the Ariane 5 rocket.
History
Aérospatiale had produced a number of satellites, including Symphonie, with the German company Messerschmitt. On 9 December 1983, the two companies signed the Franco-German Spacebus Agreement. The Spacebus designation was first applied to satellites which were under construction by Aérospatiale when the programme started. These included three satellites for Arabsat, which became the Spacebus 100 series, and five further satellites: two for Deutsche Bundespost, two for TéléDiffusion de France, and the Swedish Space Corporation's Tele-X, which became the Spacebus 300 series. Later series' names were followed by a number indicating the approximate mass of the bus in kilograms. Spacebus designations were not retroactively applied to previously launched satellites.
Architecture
Spacebus satellites consist of a satellite bus, which provides power, propulsion, and other subsystems necessary for the satellite's operation, and a payload which is customisable according to the customer's requirements. The bus was designed to be adaptable to perform various missions; however, as of 2009, only communications satellites have been ordered. It was also designed to be adaptable when the capacity of launch systems increased.
The bus is made of carbon fibre with a composite honeycomb structure. It contains fuel tanks, equipment to interface with a carrier rocket, and other critical systems. External panels contain equipment such as solar panels, payload, and engine. The payload, developed separately from the bus, takes up three panels. Once it has been outfitted with transponders or other equipment, it is transported to Cannes-Mandelieu, where it is integrated onto the bus.
The satellites are powered by rigid solar panels. Several configurations are used depending on the amount of power the satellite requires. Batteries to store this power are produced by the Belgian company ETCA. Early satellites used nickel-hydrogen batteries, while later spacecraft use lithium-ion batteries.
Spacebus satellites use bipropellant, liquid-fuelled chemical engines to achieve orbit and subsequently perform station-keeping. Electric propulsion was used on the Stentor and Astra 1K satellites, both of which were subsequently involved in launch failures. Spacebus Neo will be an electric propulsion satellite. A three-axis stabilisation system is used for attitude control.
Models
Spacebus satellites are compatible with a large number of carrier rockets, particularly the Ariane family. As the Ariane's performance has increased, the satellites' capacities have increased accordingly.
Spacebus 100
Three Spacebus 100 satellites were produced for Arabsat to serve the 22 members of the Arab League.
One of the solar panels on the first satellite, Arabsat-1A, failed to deploy, resulting in reduced power. This, combined with gyroscope issues, caused it to spend most of its operational lifespan as a reserve satellite.
Spacebus 300
Five direct-to-home television satellites were built using the Spacebus 300 bus, which provided of power.
Spacebus 2000
The Spacebus 2000 series was developed to use additional capacity provided by the Ariane 4. Its solar panels generated .
Spacebus 3000
The Spacebus 3000 was introduced around the time the Ariane 5 entered service. Spacebus 3000 satellites have masses from and produce between 5 and 16 kW. Increasingly larger payload fairings allowed larger spacecraft to be produced. In 1991, Aérospatiale, Alenia and Space Systems/Loral joined to form the Satellite Alliance.
The first version of the Spacebus 3000 was the Spacebus 3000A, originally developed for Arabsat. They were also ordered by Shin Satellite of Thailand and China's Sino Satellite Communications Company.
Twelve 3000B2 satellites were ordered, five of them by Eutelsat for their W Series, one of which later became Eutelsat 28A. A sixth order from Eutelsat was for Eutelsat 8 West A. Nordic Satellite AB, a Scandinavian company that later became SES Sirius, ordered Sirius 2, a replacement for the Spacebus 300-based TeleX satellite. Spanish satellite operator Hispasat ordered two satellites, and Arabsat ordered one satellite, Arabsat-3A. The final two were ordered by the German Bundeswehr and were launched on 1 October 2009, and in May 2010, respectively.
Nine B3 satellites were ordered, three for Eutelsat, two for Star One of Brazil, GE-12 for GE Americom, Turksat 2A for Turksat, and the Stentor experimental communications satellite for CNES. Stentor was lost in a launch failure on the maiden flight of the Ariane 5ECA. Galaxy 17 was successfully launched in 2007 for Intelsat.
Spacebus 4000
The Spacebus 4000 series was derived from the 3000 series but featured upgraded avionics. The voltage of the electrical system was increased from 50 volts to 100 volts, and an integrated onboard computer, designed to be more flexible than previous versions, was added. It was also the first satellite bus to be equipped with an attitude and orbit control system with star trackers designed for use in geostationary orbit.
The B series used the same basic structure as the 3000 series. The C version had a base measuring .
Eight Spacebus 4000B2 satellites have been ordered: Bangabandhu-1 for Bangabandhu-1 of Bangladesh, Turksat 3A for Turksat, Thor 6 for Telenor of Norway, Nilesat 201 for Nilesat of Egypt, Athena-Fidus for the French and Italian space agencies CNES and ASI, and Sicral-2 for the Italian Ministry of Defence and the French Defence Procurement Agency (DGA), a contract worth about €295m in total, Koreasat-5A and Koreasat-7 for KTSAT and Telkom-3S for PT Telkom Indonesia.
Spacebus 4000B3 satellites are in height and generate 8.5 kilowatts of power. So far, five have been ordered, including two for the French Délégation Générale pour l'Armement and two for RascomStar-QAF.
The fifth, Palapa D1 for Indosat, uses the ITAR-free configuration, and was launched by a Long March 3B in September 2009, but was initially placed in a low orbit. Thales Alenia Space made corrections allowing the satellite to reach the planned geostationary transfer orbit on 3 September. It finally reached geostationary orbit on 9 September. It is now undergoing on-orbit testing upon its arrival at 113° East about mid-September, where it will be used to provide communications to Asia and Australia. It has enough fuel for 10 years of service, according to Reynald Seznec, President of Thales Alenia Space, instead of the planned 15 years due to the orbit-raising maneuvers.
The first Rascom satellite, Rascom-QAF1, suffered a propulsion system failure during its first apogee manoeuvre on 21 December 2007. It was confirmed to have reached its final geostationary orbit at a longitude of 2.85° east on 4 February 2008, but with only two years of expected operational life, compared to the fifteen expected prior to launch. On 9 September 2008, the Rascom-QAF1R satellite was ordered to replace it, also based on the 4000B3 bus.
The Spacebus 4000C1 has a height of , and is capable of generating 8.5 kilowatts of electricity. The only C1 to have been ordered so far is Koreasat 5 for Korea Telecom of South Korea. It was launched by a Sea Launch Zenit-3SL from the Ocean Odyssey platform on the equator, at 03:27 GMT on 22 August 2006.
The Spacebus 4000C2, which has a height of , generates 10.5 kilowatts of power. Five have been ordered, all using the ITAR-free option, by companies in the People's Republic of China. Chinasat, a state-owned company ordered two satellites, whilst the APT Satellite ordered three. All were launched by Long March 3B rockets from Launch Area 2 at the Xichang Satellite Launch Centre.
Eight Spacebus 4000C3 satellites, each of which has a height of and generates 13 kilowatts of power, have been ordered. SES Americom and Eutelsat ordered two spacecraft each. The Eutelsat spacecraft are being built using ITAR-free parts, and one of the satellites, Eutelsat W3B launched on an Ariane 5 on 2010-10-28 and was declared lost on 2010-10-30 due to a fuel leak. Eutelsat 21B was ordered by 9 June 2010.; and launched 10 November 2012; Eutelsat W3D ordered on 3 December 2010;, launched 2013-05-14; Russian satellite operator Gazprom also ordered two satellites for its Yamal (satellite constellation) programme—the first time it had procured Yamal spacecraft that were not manufactured in Russia. Only one will be a Spacebus, the second one is based on an Express-2000 platform.
The Spacebus 4000C4 bus is high and can generate 16 kilowatts of power with its solar panels. Four have been ordered so far: Ciel 2 for Ciel Satellite of Canada, which was launched on 10 December 2008, and three spacecraft for Eutelsat, W2A, W7, launched by Proton on 23 November 2009. and Eutelsat-8 West B, ordered on 11 October 2012.
Ekspress-4000
On 6 December 2007, Thales Alenia Space signed an agreement with NPO PM of Russia to jointly develop the Ekspress-4000 bus, based on the Spacebus 4000. The Ekspress-4000 is designed for direct injection into geostationary orbit by a Proton-M rocket.
Spacebus NEO
In 2014, Thales Alenia Space started the development of a new family - Spacebus NEO. These new platforms will be available in various propulsion versions, including an all-electric one. The all-electric Spacebus NEO, capable of carrying payloads weighing over 1,400 kg, and with power exceeding 16 kW, will be available starting in mid-2015.
See also
List of Spacebus satellites
Comparison of satellite buses
References
External links
Encyclopedia Astronautica, particularly the permanent following of satellite orbital positions
Gunter’s Space Page, and its exhaustive lists of platforms, satellites and chronologies for all launchers
The Spacecraft Encyclopedia and its chronological list of all satellites launched with detailed information
The Thales Alenia Space website Manufacturer documentation and press releases
Spacemart, press releases
Space Newsfeed, press releases
Watch an Ariane 5 launch
Satellite buses
European space programmes | Spacebus | Engineering | 2,405 |
33,042,691 | https://en.wikipedia.org/wiki/Op%20amp%20integrator | The operational amplifier integrator is an electronic integration circuit. Based on the operational amplifier (op-amp), it performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.
Applications
The integrator circuit is mostly used in analog computers, analog-to-digital converters and wave-shaping circuits.
A common wave-shaping use is as a charge amplifier and they are usually constructed using an operational amplifier though they can use high gain discrete transistor configurations.
Design
The input current is offset by a negative feedback current flowing in the capacitor, which is generated by an increase in output voltage of the amplifier. The output voltage is therefore dependent on the value of input current it has to offset and the inverse of the value of the feedback capacitor. The greater the capacitor value, the less output voltage has to be generated to produce a particular feedback current flow.
The input capacitance of the circuit is almost zero because of the Miller effect. This ensures that the stray capacitances (the cable capacitance, the amplifier input capacitance, etc.) are virtually grounded and have no influence on the output signal.
Ideal circuit
This circuit operates by passing a current that charges or discharges the capacitor during the time under consideration, which strives to retain the virtual ground condition at the input by off-setting the effect of the input current:
Referring to the above diagram, if the op-amp is assumed to be ideal, then the voltage at the inverting (-) input is held equal to the voltage at the non-inverting (+) input as a virtual ground. The input voltage passes a current through the resistor producing a compensating current flow through the series capacitor to maintain the virtual ground. This charges or discharges the capacitor over time. Because the resistor and capacitor are connected to a virtual ground, the input current does not vary with capacitor charge, so a linear integration that works across all frequencies is achieved (unlike ).
The circuit can be analyzed by applying Kirchhoff's current law at the inverting input:
For an ideal op-amp, amps, so:
Furthermore, the capacitor has a voltage-current relationship governed by the equation:
Substituting the appropriate variables:
For an ideal op-amp, volts, so:
Integrating both sides with respect to time:
If the initial value of is assumed to be 0 volts, the output voltage will simply be proportional to the integral of the input voltage:
Practical circuit
This practical integrator attempts to address a number of flaws of the ideal integrator circuit:
Real op-amps have a finite open-loop gain, an input offset voltage and input bias currents , which may not be well-matched and may be distinguished as going into the inverting input and going into the non-inverting input. This can cause several issues for the ideal design; most importantly, if , both the output offset voltage and the input bias current can cause current to pass through the capacitor, causing the output voltage to drift over time until the op-amp saturates. Similarly, if were a signal centered about zero volts (i.e. without a DC component), no drift would be expected in an ideal circuit, but may occur in a real circuit.
To negate the effect of the input bias current, it is necessary for the non-inverting terminal to include a resistor which simplifies to provided that is much smaller than the load resistance and the feedback resistance . Well-matched input bias currents then cause the same voltage drop of at both the inverting and non-inverting terminals, to effectively cancel out the effect of bias current at those inputs.
Also, in a DC steady state, an ideal capacitor acts as an open circuit. The DC gain of the ideal circuit is therefore infinite (or in practice, the open-loop gain of a non-ideal op-amp). Any DC (or very low frequency) component may then cause the op amp output to drift into saturation. To prevent this, the DC gain can be limited to a finite value by inserting a large resistor in parallel with the feedback capacitor. Note that some op amps have a large internal feedback resistor, and many real capacitors have leakage that is effectively a large feedback resistor.
The addition of these resistors turns the output drift into a finite, preferably small, DC error voltage:
Notes on offset: a variation of this circuit simply uses an adjustable voltage source instead of and some op amps with very low offset voltage may not even require offset correction. Offset correction is a bigger concern for older op amps, particularly BJT types. Another variation circuit to avoid offset correction that works for AC signals only is to capacitively-couple the input with large input capacitor before which will naturally charge up to the offset voltage. Additionally, because offset may drift over time and temperature, some op amps provide null offset pins, which can be connected to a potentiometer whose wiper connects to the negative supply to allow readjusting when conditions change. These methods may be combined.
Frequency response
Both the ideal and practical integrator have a gain of 1 at a single frequency called the unity gain frequency :
But the overall frequency response of the two circuits differ due to their different pole locations.
Ideal integrator
The ideal integrator's transfer function corresponds to the time-domain integration property of the Laplace transform. Since its denominator is just , the transfer function has a pole frequency at . Thus its frequency response has a steady -20 dB per decade slope across all frequencies and appears as a downward-sloping line in a Bode plot.
Practical integrator
The practical integrator's feedback resistor in parallel with the feedback capacitor turns the circuit into an active low-pass filter with a pole at the -3 dB cutoff frequency:
The frequency response has a relatively constant gain up to , and then decreases by 20 dB per decade. While this circuit is no longer an integrator for low frequencies around and below , the error is decreases to only 0.5% at one decade above and the response approaches that of an ideal integrator as the frequency increases. Real op amps also have a limited gain-bandwidth product (GBWP), which adds an additional high frequency pole. Integration only occurs along the -20 dB per decade slope, which is steady only from frequencies about a decade above to about a decade below the op amp's GBWP.
References
Analog circuits
Linear electronic circuits | Op amp integrator | Engineering | 1,386 |
43,355,620 | https://en.wikipedia.org/wiki/Musket%20Ball%20Cluster | The Musket Ball Cluster (DLSCL J0916.2+2951) is a galaxy cluster that exhibits separation between its baryonic matter and dark matter components. The cluster is a recent merger of two galaxy clusters. It is named after the Bullet Cluster, as it is a slower collision, and older than the Bullet Cluster. This cluster is further along the process of merger than the Bullet Cluster, being some 500 million years older, at 700 million years old. The cluster was discovered in 2011 by the Deep Lens Survey. As of 2012, it is one of the few galaxy clusters to show a separation between its dark matter and baryonic matter components.
Characteristics
As of 2012, it is one of seven galaxy clusters that exhibit a separation of dark matter and baryonic matter following cluster collision and merger. The separation between the galaxies and their dark matter components is on average . This separation may indicate that dark matter may interact with itself, through a dark force (a force that only interacts with dark matter) or a set of dark forces. The galaxy cluster itself is some across.
See also
Bullet Group
Other dissociative galaxy cluster mergers known at the time of discovery
Bullet Cluster (2006)
MACS J0025.4-1222 (2008)
Abell 520 (2007)
Abell 2744 (2011)
Abell 2163 (2011)
Abell 1759 (2011)
References
External links
Chandra X-Ray Observatory: "Musket Ball Cluster in 60 Seconds", April Hobart, 16 April 2012 (PODcast)
Galaxy clusters
Cancer (constellation) | Musket Ball Cluster | Astronomy | 322 |
37,177,771 | https://en.wikipedia.org/wiki/Psi%20Hydrae | Psi Hydrae (ψ Hydrae) is a star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 14.09 mas as seen from Earth, it is located around 231 light years away from the Sun. It is faintly visible to the naked eye with an apparent magnitude of 4.97.
System
This is a probable astrometric binary system. The primary, component A, is an evolved giant star with a stellar classification of K0 III. It is a red clump star that is generating energy through the fusion of helium at its core. The measured angular diameter is , which, at the estimated distance of Psi Hydrae, yields a physical size of about 10.6 times the radius of the Sun. It is radiating 56 times the solar luminosity from its photosphere at an effective temperature of 4,680. K.
Cultural significance
The Kalapalo people of Mato Grosso state in Brazil called this star and β Hya Kafanifani.
References
K-type giants
Horizontal-branch stars
Astrometric binaries
Hydra (constellation)
Hydrae, Psi
BD-22 3515
Hydrae, 45
114149
064166
4958 | Psi Hydrae | Astronomy | 243 |
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