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There are some M. hoffmannii jaws with evidence of infectious diseases as a result of physical injuries. Two examples include IRSNB R25 and IRSNB R27, both having fractures and other pathologies in their dentaries. IRSNB R25 preserves a complete fracture near the sixth tooth socket. Extensive amounts of bony callus alm... | Mosasaurus | Wikipedia | 363 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
In 2006, Schulp and colleagues published a study describing a quadrate of M. hoffmannii with multiple unnatural openings and an estimated of tissue destroyed. This was likely a severe bone infection initiated by septic arthritis, which progressed to the point where a large portion of the quadrate was reduced to absces... | Mosasaurus | Wikipedia | 442 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
Unnatural fusion of tail vertebrae has been documented in Mosasaurus, which occurs when the bones remodel themselves after damage from trauma or disease. A 2015 study by Rothschild and Everhart surveyed 15 Mosasaurus specimens from North America and Belgium and found cases of fused tail vertebrae in three of them. Two ... | Mosasaurus | Wikipedia | 434 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
Paleoecology
Distribution, ecosystem, and ecological impactMosasaurus had a transatlantic distribution, with its fossils having been found in marine deposits on both sides of the Atlantic Ocean. These localities include the Midwest and East Coast of the United States, Canada, Europe, Turkey, Russia, the Levant, the Afr... | Mosasaurus | Wikipedia | 273 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
The northern Tethyan margin was located around the paleolatitudes of 30–40°N, consisting of what is now the European continent, Turkey, and New Jersey. At the time, Europe was a scattering of islands with most of the modern continental landmass being underwater. The margin provided a warm-temperate climate with habitat... | Mosasaurus | Wikipedia | 419 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
The southern Tethyan margin was located along the equator between 20°N and 20°S, resulting in warmer tropical climates. Seabeds bordering the cratons in Africa and Arabia and extending to the Levant and Brazil provided vast shallow marine environments. These environments were dominated by mosasaurs and marine side-neck... | Mosasaurus | Wikipedia | 462 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
The biogeography of the region has been subdivided into two Interior Subprovinces characterized by different climates and faunal structures, and their borders are separated in modern-day Kansas. The oceanic climate of the Northern Interior Subprovince was likely a cool temperate one, while the Southern Interior Subprov... | Mosasaurus | Wikipedia | 173 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
In what is now Alabama within the Southern Interior Subprovince, most of the key genera including sharks like Cretoxyrhina and the mosasaurs Clidastes, Tylosaurus, Globidens, Halisaurus, and Platecarpus disappeared and were replaced by Mosasaurus. During the Navesinkan Age, Mosasaurus dominated the whole region, accoun... | Mosasaurus | Wikipedia | 398 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
AntarcticaMosasaurus is known from late Maastrichtian deposits in the Antarctic Peninsula, specifically the López de Bertodano Formation in Seymour Island. Located within the polar circle at around 65°S, temperatures at medium to large water depths would have been around on average, while sea surface temperatures may ... | Mosasaurus | Wikipedia | 445 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
δ13C is also correlated with a marine animal's feeding habitat as isotope levels deplete when habitat is farther from the shoreline, so some scientists interpreted isotope levels as a proxy for habitat preference. Separate studies involving multiple Mosasaurus specimens have yielded consistently low δ13C levels of toot... | Mosasaurus | Wikipedia | 356 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
A study published in 2013 by Schulp and colleagues specifically tested how mosasaurs such as M. hoffmannii and P. saturator were able to coexist in the same localities through δ13C analysis. The scientists utilized an interpretation that differences in isotope values can help explain the level of resource partitioning ... | Mosasaurus | Wikipedia | 374 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
Nevertheless, competitive engagement evidently could not be entirely avoided. There is also evidence of aggressive interspecific combat between Mosasaurus and other large mosasaur species. This is shown from a fossil skull of a subadult M. hoffmannii with fractures caused by a massive concentrated blow to the braincase... | Mosasaurus | Wikipedia | 198 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
By the end of the Cretaceous, mosasaurs were at the height of their evolutionary radiation, and their extinction was a sudden event. During the late Maastrichtian, global sea levels dropped, draining the continents of their nutrient-rich seaways and altering circulation and nutrient patterns, and reducing the number of... | Mosasaurus | Wikipedia | 360 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
One enigmatic occurrence of Mosasaurus sp. fossils is in the Hornerstown Formation, a deposit typically dated to be from the Paleocene Danian age, which was immediately after the Maastrichtian age. The fossils were found in association with fossils of Squalicorax, Enchodus, and various ammonites within a uniquely fossi... | Mosasaurus | Wikipedia | 279 | 2051142 | https://en.wikipedia.org/wiki/Mosasaurus | Biology and health sciences | Prehistoric squamates | Animals |
Electroencephalography (EEG)
is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex. It is typically non-invasive, with the EEG electrodes place... | Electroencephalography | Wikipedia | 341 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
A healthy human EEG will show certain patterns of activity that correlate with how awake a person is. The range of frequencies one observes are between 1 and 30 Hz, and amplitudes will vary between 20 and 100 μV. The observed frequencies are subdivided into various groups: alpha (8–13 Hz), beta (13–30 Hz), delta (0.5–4... | Electroencephalography | Wikipedia | 502 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG is the gold standard diagnostic procedure to confirm epilepsy. The sensitivity of a routine EEG to detect interictal epileptiform discharges at epilepsy centers has been reported to be in the range of 29–55%. Given the low to moderate sensitivity, a routine EEG (typically with a duration of 20–30 minutes) can be n... | Electroencephalography | Wikipedia | 268 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Epilepsy Monitoring Unit (EMU)
At times, a routine EEG is not sufficient to establish the diagnosis or determine the best course of action in terms of treatment. In this case, attempts may be made to record an EEG while a seizure is occurring. This is known as an ictal recording, as opposed to an interictal recording,... | Electroencephalography | Wikipedia | 479 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Other brain disorders
An EEG might also be helpful for diagnosing or treating the following disorders:
Brain tumor
Brain damage from head injury
Brain dysfunction that can have a variety of causes (encephalopathy)
Inflammation of the brain (encephalitis)
Stroke
Sleep disorders
It can also:
distinguish epilepti... | Electroencephalography | Wikipedia | 309 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
If a patient with epilepsy is being considered for resective surgery to treat epilepsy, it is often necessary to localize the focus (source) of the epileptic brain activity with a resolution greater than what is provided by scalp EEG. In these cases, neurosurgeons typically implant strips and grids of electrodes or pen... | Electroencephalography | Wikipedia | 507 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Advantages
Several other methods to study brain function exist, including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), magnetoencephalography (MEG), nuclear magnetic resonance spectroscopy (NMR or MRS), electrocorticography (ECoG), single-photon emission computed tomography (SPECT),... | Electroencephalography | Wikipedia | 501 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG does not involve exposure to radioligands, unlike positron emission tomography.
ERP studies can be conducted with relatively simple paradigms, compared with IE block-design fMRI studies
Relatively non-invasive, in contrast to electrocorticography, which requires electrodes to be placed on the actual surface of th... | Electroencephalography | Wikipedia | 68 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG also has some characteristics that compare favorably with behavioral testing:
EEG can detect covert processing (i.e., processing that does not require a response)
EEG can be used in subjects who are incapable of making a motor response
EEG is a method widely used in the study of sport performance, valued for its... | Electroencephalography | Wikipedia | 506 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
With other neuroimaging techniques
Simultaneous EEG recordings and fMRI scans have been obtained successfully, though recording both at the same time effectively requires that several technical difficulties be overcome, such as the presence of ballistocardiographic artifact, MRI pulse artifact and the induction of elec... | Electroencephalography | Wikipedia | 512 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Mechanisms
The brain's electrical charge is maintained by billions of neurons. Neurons are electrically charged (or "polarized") by membrane transport proteins that pump ions across their membranes. Neurons are constantly exchanging ions with the extracellular milieu, for example to maintain resting potential and to pr... | Electroencephalography | Wikipedia | 483 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
In conventional scalp EEG, the recording is obtained by placing electrodes on the scalp with a conductive gel or paste, usually after preparing the scalp area by light abrasion to reduce impedance due to dead skin cells. Many systems typically use electrodes, each of which is attached to an individual wire. Some system... | Electroencephalography | Wikipedia | 490 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
The digital EEG signal is stored electronically and can be filtered for display. Typical settings for the high-pass filter and a low-pass filter are 0.5–1 Hz and 35–70 Hz respectively. The high-pass filter typically filters out slow artifact, such as electrogalvanic signals and movement artifact, whereas the low-pass f... | Electroencephalography | Wikipedia | 480 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Sequential montage Each channel (i.e., waveform) represents the difference between two adjacent electrodes. The entire montage consists of a series of these channels. For example, the channel "Fp1-F3" represents the difference in voltage between the Fp1 electrode and the F3 electrode. The next channel in the montage, "... | Electroencephalography | Wikipedia | 446 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
The EEG is read by a clinical neurophysiologist or neurologist (depending on local custom and law regarding medical specialities), optimally one who has specific training in the interpretation of EEGs for clinical purposes. This is done by visual inspection of the waveforms, called graphoelements. The use of computer s... | Electroencephalography | Wikipedia | 386 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
In 1999 researchers at Case Western Reserve University, in Cleveland, Ohio, led by Hunter Peckham, used 64-electrode EEG skullcap to return limited hand movements to quadriplegic Jim Jatich. As Jatich concentrated on simple but opposite concepts like up and down, his beta-rhythm EEG output was analysed using software t... | Electroencephalography | Wikipedia | 446 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Limitations
EEG has several limitations. Most important is its poor spatial resolution. EEG is most sensitive to a particular set of post-synaptic potentials: those generated in superficial layers of the cortex, on the crests of gyri directly abutting the skull and radial to the skull. Dendrites which are deeper in the... | Electroencephalography | Wikipedia | 498 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG vis-à-vis fMRI, fNIRS, fUS and PET
EEG has several strong points as a tool for exploring brain activity. EEGs can detect changes over milliseconds, which is excellent considering an action potential takes approximately 0.5–130 milliseconds to propagate across a single neuron, depending on the type of neuron. Other ... | Electroencephalography | Wikipedia | 435 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
The EEG is typically described in terms of (1) rhythmic activity and (2) transients. The rhythmic activity is divided into bands by frequency. To some degree, these frequency bands are a matter of nomenclature (i.e., any rhythmic activity between 8–12 Hz can be described as "alpha"), but these designations arose becaus... | Electroencephalography | Wikipedia | 490 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Theta is the frequency range from 4 Hz to 7 Hz. Theta is seen normally in young children. It may be seen in drowsiness or arousal in older children and adults; it can also be seen in meditation. Excess theta for age represents abnormal activity. It can be seen as a focal disturbance in focal subcortical lesions; it can... | Electroencephalography | Wikipedia | 474 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Gamma is the frequency range approximately 30–100 Hz. Gamma rhythms are thought to represent binding of different populations of neurons together into a network for the purpose of carrying out a certain cognitive or motor function.
Mu range is 8–13 Hz and partly overlaps with other frequencies. It reflects the synchro... | Electroencephalography | Wikipedia | 393 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
The normal EEG also varies depending on state. The EEG is used along with other measurements (EOG, EMG) to define sleep stages in polysomnography. Stage I sleep (equivalent to drowsiness in some systems) appears on the EEG as drop-out of the posterior basic rhythm. There can be an increase in theta frequencies. Santama... | Electroencephalography | Wikipedia | 361 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG is an extremely useful technique for studying brain activity, but the signal measured is always contaminated by artifacts which can impact the analysis of the data. An artifact is any measured signal that does not originate within the brain. Although multiple algorithms exist for the removal of artifacts, the probl... | Electroencephalography | Wikipedia | 506 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Ocular artifacts
Ocular artifacts affect the EEG signal significantly. This is due to eye movements involving a change in electric fields surrounding the eyes, distorting the electric field over the scalp, and as EEG is recorded on the scalp, it therefore distorts the recorded signal. A difference of opinion exists am... | Electroencephalography | Wikipedia | 444 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
The propagation of the ocular artifact is impacted by multiple factors including the properties of the subject's skull, neuronal tissues and skin but the signal may be approximated as being inversely proportional to the distance from the eyes squared. The electrooculogram (EOG) consists of a series of electrodes measur... | Electroencephalography | Wikipedia | 401 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Environmental artifacts
In addition to artifacts generated by the body, many artifacts originate from outside the body. Movement by the patient, or even just settling of the electrodes, may cause electrode pops, spikes originating from a momentary change in the impedance of a given electrode. Poor grounding of the EEG ... | Electroencephalography | Wikipedia | 477 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
EEG diagnostics
The Department of Defense (DoD) and Veteran's Affairs (VA), and U.S Army Research Laboratory (ARL), collaborated on EEG diagnostics in order to detect mild to moderate Traumatic Brain Injury (mTBI) in combat soldiers. Between 2000 and 2012, 75 percent of U.S. military operations brain injuries were cla... | Electroencephalography | Wikipedia | 342 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Economics
Inexpensive EEG devices exist for the low-cost research and consumer markets. Recently, a few companies have miniaturized medical grade EEG technology to create versions accessible to the general public. Some of these companies have built commercial EEG devices retailing for less than US$100.
In 2004 OpenEE... | Electroencephalography | Wikipedia | 404 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
In 2014, OpenBCI released an eponymous open source brain-computer interface after a successful kickstarter campaign in 2013. The board, later renamed "Cyton", has 8 channels, expandable to 16 with the Daisy module. It supports EEG, EKG, and EMG. The Cyton Board is based on the Texas Instruments ADS1299 IC and the Ardui... | Electroencephalography | Wikipedia | 235 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Future research
The EEG has been used for many purposes besides the conventional uses of clinical diagnosis and conventional cognitive neuroscience. An early use was during World War II by the U.S. Army Air Corps to screen out pilots in danger of having seizures; long-term EEG recordings in epilepsy patients are still... | Electroencephalography | Wikipedia | 454 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
In research, currently EEG is often used in combination with machine learning. EEG data are pre-processed then passed on to machine learning algorithms. These algorithms are then trained to recognize different diseases like schizophrenia, epilepsy or dementia. Furthermore, they are increasingly used to study seizure de... | Electroencephalography | Wikipedia | 435 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
German physiologist and psychiatrist Hans Berger (1873–1941) recorded the first human EEG in 1924. Expanding on work previously conducted on animals by Richard Caton and others, Berger also invented the electroencephalograph (giving the device its name), an invention described "as one of the most surprising, remarkable... | Electroencephalography | Wikipedia | 482 | 21402632 | https://en.wikipedia.org/wiki/Electroencephalography | Technology | Diagnostic technologies | null |
Ironing is the use of an iron, usually heated, to remove wrinkles and unwanted creases from fabric. The heating is commonly done to a temperature of , depending on the fabric. Ironing works by loosening the bonds between the long-chain polymer molecules in the fibres of the material. While the molecules are hot, the fi... | Ironing | Wikipedia | 510 | 21402762 | https://en.wikipedia.org/wiki/Ironing | Technology | Household appliances | null |
When the fabric is heated, the molecules are more easily reoriented. In the case of cotton fibres, which are derivatives of cellulose, the hydroxyl groups that crosslink the cellulose polymer chains are reformed at high temperatures and become somewhat "locked in place" upon cooling the item. In permanent press pressed... | Ironing | Wikipedia | 90 | 21402762 | https://en.wikipedia.org/wiki/Ironing | Technology | Household appliances | null |
The Marinoan glaciation, sometimes also known as the Varanger glaciation, was a period of worldwide glaciation.
Its beginning is poorly constrained, but occurred no earlier than 654.5 Ma (million years ago).
It ended approximately 632.3 ± 5.9 Ma
during the Cryogenian period. This glaciation possibly covered the enti... | Marinoan glaciation | Wikipedia | 463 | 21407814 | https://en.wikipedia.org/wiki/Marinoan%20glaciation | Physical sciences | Events | Earth science |
Emerging evidence suggests that the Earth underwent a number of glaciations during the Neoproterozoic era. There were three (or possibly four) significant ice ages during the late Neoproterozoic. These periods of nearly complete glaciation of Earth are often referred to as "Snowball Earth", where it is hypothesized tha... | Marinoan glaciation | Wikipedia | 505 | 21407814 | https://en.wikipedia.org/wiki/Marinoan%20glaciation | Physical sciences | Events | Earth science |
According to Eyles and Young, the Marinoan is a second episode of Neoproterozoic glaciation (680–690 Ma) occurring in the Adelaide Geosyncline. According to them, "It is separated from the Sturtian by a thick succession of sedimentary rocks containing no evidence of glaciation. This glacial phase could correspond to th... | Marinoan glaciation | Wikipedia | 129 | 21407814 | https://en.wikipedia.org/wiki/Marinoan%20glaciation | Physical sciences | Events | Earth science |
Sloths are a Neotropical group of xenarthran mammals constituting the suborder Folivora, including the extant arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of movement, tree sloths spend most of their lives hanging upside down in the trees of the tropical rainforests of South Amer... | Sloth | Wikipedia | 479 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Sloths belong to the superorder Xenarthra, a group of placental mammals believed to have evolved in the continent of South America around 60 million years ago. One study found that xenarthrans broke off from other placental mammals around 100 million years ago. Anteaters and armadillos are also included among Xenarthra... | Sloth | Wikipedia | 203 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
†Megalocnidae: the Greater Antilles sloths, a basal group that arose about 32 million years ago and became extinct about 5,000 years ago.
Superfamily Megatherioidea
Bradypodidae, the three-toed sloths, contains four extant species:
The brown-throated three-toed sloth (Bradypus variegatus) is the most common of the ex... | Sloth | Wikipedia | 449 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Hoffmann's two-toed sloth (Choloepus hoffmanni) which inhabits tropical forests. It has two separate ranges, split by the Andes. One population is found from eastern Honduras in the north to western Ecuador in the south, and the other in eastern Peru, western Brazil, and northern Bolivia.
†Mylodontidae: ground sloths t... | Sloth | Wikipedia | 129 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Evolution
The common ancestor of the two existing sloth genera dates to about 28 million years ago, with similarities between the two- and three- toed sloths an example of convergent evolution to an arboreal lifestyle, "one of the most striking examples of convergent evolution known among mammals". The ancient Xenarth... | Sloth | Wikipedia | 493 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Recently obtained molecular data from collagen and mitochondrial DNA sequences fall in line with the diphyly (convergent evolution) hypothesis but have overturned some of the other conclusions obtained from morphology. These investigations consistently place two-toed sloths close to mylodontids and three-toed sloths wi... | Sloth | Wikipedia | 494 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Physiology
Sloths have colour vision but have poor visual acuity. They also have poor hearing. Thus, they rely on their sense of smell and touch to find food.
Sloths have very low metabolic rates (less than half of that expected for a mammal of their size), and low body temperatures: when active, and still lower whe... | Sloth | Wikipedia | 480 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Sloths move only when necessary and even then, very slowly. They usually move at an average speed of per minute but can move at a marginally higher speed of per minute if they are in immediate danger from a predator. While they sometimes sit on top of branches, they usually eat, sleep, and even give birth hanging fro... | Sloth | Wikipedia | 477 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Two-toed sloths are omnivorous, with a diverse diet of insects, carrion, fruits, leaves and small lizards, ranging over up to . Three-toed sloths, on the other hand, are almost entirely herbivorous (plant eaters), with a limited diet of leaves from only a few trees, and no other mammal digests its food as slowly.
They... | Sloth | Wikipedia | 374 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
Reproduction
The pale- and brown-throated three-toed sloths mate seasonally, while the maned three-toed sloth breeds at any time of the year. The reproduction of pygmy three-toed sloths is currently unknown. Litters are of one newborn only, after six months' gestation for three-toed, and 12 months for two-toed. Newbor... | Sloth | Wikipedia | 495 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
The Sloth Institute Costa Rica is known for caring, rehabilitating and releasing sloths back into the wild. Also in Costa Rica, the Aviarios Sloth Sanctuary cares for sloths. It has rehabilitated and returned about 130 individuals to the wild. However, a report in May 2016 featured two former veterinarians from the fac... | Sloth | Wikipedia | 91 | 5168174 | https://en.wikipedia.org/wiki/Sloth | Biology and health sciences | Pilosa | null |
A genet (pronounced or ) is a member of the genus Genetta, which consists of 17 species of small African carnivorans. The common genet is the only genet present in Europe and occurs in the Iberian Peninsula, Italy and France.
Genet fossils from the Late Miocene and later have been found at sites in Ethiopia, Kenya an... | Genet (animal) | Wikipedia | 493 | 5171924 | https://en.wikipedia.org/wiki/Genet%20%28animal%29 | Biology and health sciences | Other carnivora | Animals |
The South African small-spotted genet lives in woodland savanna, grassland, thickets, dry vlei areas in Angola, Namibia, South Africa and Zambia.
The rusty-spotted genet is widely distributed in sub-Saharan woodland savannah, savannah-forest mosaic, rain forest and montane forest up to an elevation of in Ethiopia.
T... | Genet (animal) | Wikipedia | 489 | 5171924 | https://en.wikipedia.org/wiki/Genet%20%28animal%29 | Biology and health sciences | Other carnivora | Animals |
In 2014, a camera trap in the Hluhluwe–Imfolozi Park captured a large spotted genet riding on the back of two different buffalo and a rhinoceros. This was the first time a genet was recorded hitch-hiking.
Females have up to five young in a litter. They rear their young alone.
Common genet females become sexually matu... | Genet (animal) | Wikipedia | 498 | 5171924 | https://en.wikipedia.org/wiki/Genet%20%28animal%29 | Biology and health sciences | Other carnivora | Animals |
In theoretical physics, scalar field theory can refer to a relativistically invariant classical or quantum theory of scalar fields. A scalar field is invariant under any Lorentz transformation.
The only fundamental scalar quantum field that has been observed in nature is the Higgs field. However, scalar quantum fields... | Scalar field theory | Wikipedia | 498 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
The factors in the expansion are introduced because they are useful in the Feynman diagram expansion of the quantum theory, as described below.
The corresponding Euler–Lagrange equation of motion is now
Dimensional analysis and scaling
Physical quantities in these scalar field theories may have dimensions of lengt... | Scalar field theory | Wikipedia | 450 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
The reason that not all actions are invariant is that one usually thinks of the parameters m and as fixed quantities, which are not rescaled under the transformation above. The condition for a scalar field theory to be scale invariant is then quite obvious: all of the parameters appearing in the action should be dime... | Scalar field theory | Wikipedia | 437 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
Kink solutions
The 4 theory with a negative 2 also has a kink solution, which is a canonical example of a soliton. Such a solution is of the form
where is one of the spatial variables ( is taken to be independent of , and the remaining spatial variables). The solution interpolates between the two different vacua ... | Scalar field theory | Wikipedia | 438 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
This can be generalised to a theory of N scalar fields transforming in the vector representation of the O(N) symmetry. The Lagrangian for an O(N)-invariant scalar field theory is typically of the form
using an appropriate O(N)-invariant inner product. The theory can also be expressed for complex vector fields, i.e. f... | Scalar field theory | Wikipedia | 487 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
Applying all possible combinations of creation operators to the vacuum constructs the relevant Hilbert space: This construction is called Fock space. The vacuum is annihilated by the Hamiltonian
where the zero-point energy has been removed by Wick ordering. (See canonical quantization.)
Interactions can be included... | Scalar field theory | Wikipedia | 415 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
The integral with g = 0 can be treated as a product of infinitely many elementary Gaussian integrals: the result may be expressed as a sum of Feynman diagrams, calculated using the following Feynman rules:
Each field (p) in the n-point Euclidean Green's function is represented by an external line (half-edge) in the g... | Scalar field theory | Wikipedia | 455 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
Beta-functions are usually computed in an approximation scheme, most commonly perturbation theory, where one assumes that the coupling constant is small. One can then make an expansion in powers of the coupling parameters and truncate the higher-order terms (also known as higher loop contributions, due to the number of... | Scalar field theory | Wikipedia | 313 | 5173456 | https://en.wikipedia.org/wiki/Scalar%20field%20theory | Physical sciences | Particle physics: General | Physics |
In organic chemistry, a ring flip (also known as a ring inversion or ring reversal) is the interconversion of cyclic conformers that have equivalent ring shapes (e.g., from a chair conformer to another chair conformer) that results in the exchange of nonequivalent substituent positions. The overall process generally ta... | Ring flip | Wikipedia | 255 | 3823804 | https://en.wikipedia.org/wiki/Ring%20flip | Physical sciences | Stereochemistry | Chemistry |
Cyclohexane
There exist many different conformations for cyclohexane, such as chair, boat, and twist-boat, but the chair conformation is the most commonly observed state for cyclohexanes because it requires the least amount of energy. The chair conformation minimizes both angle strain and torsional strain by having all... | Ring flip | Wikipedia | 494 | 3823804 | https://en.wikipedia.org/wiki/Ring%20flip | Physical sciences | Stereochemistry | Chemistry |
Diaxial interactions or axial-axial interactions is what the steric strain between an axial substituent and another axial group, typically a hydrogen, on the same side of a chair conformation ring. The interaction is labeled by the carbon number they come from. A 1,3-diaxial interaction happens between the atoms connec... | Ring flip | Wikipedia | 492 | 3823804 | https://en.wikipedia.org/wiki/Ring%20flip | Physical sciences | Stereochemistry | Chemistry |
Tetrodotoxin is one of the world's most potent toxins. It is made up of multiple six member rings set in chair conformations, with each ring but one containing an atom other than carbon. | Ring flip | Wikipedia | 44 | 3823804 | https://en.wikipedia.org/wiki/Ring%20flip | Physical sciences | Stereochemistry | Chemistry |
Subfossil lemurs are lemurs from Madagascar that are represented by recent (subfossil) remains dating from nearly 26,000 years ago to approximately 560 years ago (from the late Pleistocene until the Holocene). They include both extant and extinct species, although the term more frequently refers to the extinct giant le... | Subfossil lemur | Wikipedia | 389 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Subfossil remains were first discovered on Madagascar in the 1860s, but giant lemur species were not formally described until the 1890s. The paleontological interest sparked by the initial discoveries resulted in an overabundance of new species names, the allocation of bones to the wrong species, and inaccurate reconst... | Subfossil lemur | Wikipedia | 449 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
All but one species, the giant aye-aye, are thought to have been active during the day. Not only were they unlike the living lemurs in both size and appearance, they also filled ecological niches that no longer exist or are now left unoccupied. Their remains have been found in most parts of the island, except for the e... | Subfossil lemur | Wikipedia | 492 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
These traits are shared among both living and extinct lemurs, but are uncommon among primates in general. Two prevailing hypotheses to explain these unique adaptations are the energy frugality hypothesis by Patricia Wright (1999) and the evolutionary disequilibrium hypothesis by Carel van Schaik and Peter M. Kappeler (... | Subfossil lemur | Wikipedia | 456 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Their skeletons suggest that most subfossil lemurs were tree-dwellers, adapted for living in forests and possibly limited to such habitats. Unlike some of the living species, the subfossil lemurs lacked adaptations for leaping. Instead, suspension, used by some indriids and ruffed lemurs, was extensively used in some l... | Subfossil lemur | Wikipedia | 449 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Koala lemurs
The koala lemurs of the family Megaladapidae most closely resemble marsupial koalas from Australia. According to genetic evidence they were most closely related to the family Lemuridae, although for many years they were paired with the sportive lemurs of the family Lepilemuridae due to similarities in thei... | Subfossil lemur | Wikipedia | 422 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
An extinct, giant relative of the living aye-aye, the giant aye-aye shared at least two of the aye-aye's bizarre traits: ever-growing central incisors and an elongated, skinny middle finger. These shared features suggest a similar lifestyle and diet, focused on percussive foraging (tapping with the skinny digit and lis... | Subfossil lemur | Wikipedia | 285 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Determining the phylogeny of subfossil lemurs has been problematic because studies of morphology, developmental biology, and molecular phylogenetics have sometimes yielded conflicting results. All studies agree that the family Daubentoniidae (including the giant aye-aye) diverged first from the other lemurs at least 60... | Subfossil lemur | Wikipedia | 300 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Subfossil sites in Madagascar have yielded the remains of more than just extinct lemurs. Extant lemur remains have also been found, and radiocarbon dating has demonstrated that both types of lemur lived at the same time. In some cases living species are locally extinct for the area in which their subfossil remains were... | Subfossil lemur | Wikipedia | 431 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
As a group, the lemurs of Madagascar are extremely diverse, having evolved in isolation and radiated over the past 40 to 60 million years to fill many ecological niches normally occupied by other primates. In the recent past, their diversity was significantly greater, with 17 extinct species sharing body proportions an... | Subfossil lemur | Wikipedia | 349 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Species of both extinct and living (extant) lemur vary in size based on habitat conditions, despite their differences in niche preference. Within related groups, larger species tend to inhabit wetter, more productive habitats, while smaller sister taxa are found in drier, less productive habitats. This pattern suggests... | Subfossil lemur | Wikipedia | 459 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
The diets of most subfossil lemurs, most notably Palaeopropithecus and Megaladapis, consisted primarily of C3 plants, which use a form of photosynthesis that results in higher water loss through transpiration. Other subfossil lemurs, such as Hadropithecus and Mesopropithecus, fed on CAM and C4 plants, which use more wa... | Subfossil lemur | Wikipedia | 237 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Seed dispersal
Giant subfossil lemurs are thought to have also played a significant role in seed dispersal, possibly targeting species that did not attract the seed dispersal services of the extinct elephant birds. Biogeochemistry studies have shown that they may have been the primary seed dispersers for the endemic an... | Subfossil lemur | Wikipedia | 470 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
The writings of French colonial governor Étienne de Flacourt in the mid-17th century introduced the existence of giant Malagasy mammals to Western science with recorded eye-witness accounts from the local people of dangerous animals, hornless "water cows", and a large lemur-like creature referred to locally as the or ... | Subfossil lemur | Wikipedia | 358 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
In 1905, Alfred Grandidier's son, Guillaume Grandidier, reviewed subfossil lemur taxonomy and determined that too many names had been created. His review established most of the presently known family and genera names for the extinct lemurs. Despite the taxonomic clarification, subfossil postcrania from different gener... | Subfossil lemur | Wikipedia | 429 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Excavations during the early 20th century by researchers like Lamberton failed to unearth any new extinct lemur genera. Fourteen of the approximately seventeen known species had previously been identified from field work in southern, western, and central Madagascar. When paleontological field work resumed in the early ... | Subfossil lemur | Wikipedia | 487 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
The number of Malagasy subfossil sites containing subfossil lemurs has increased significantly since the mid-20th century. At that time, subfossil lemurs had only been found in the center, south, and southwest of the island. Since then, only the eastern rainforests have not been represented, and paleodistributions are ... | Subfossil lemur | Wikipedia | 392 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
By region, the Central Highlands lost the greatest number of lemur species. It has lost nearly all of its woodland habitat, but some lemur species still survive in isolated forest patches. Lemur diversity is tightly linked with plant diversity, which in turn decreases with increased forest fragmentation. In extreme cas... | Subfossil lemur | Wikipedia | 448 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
As with the extinctions that occurred on other land masses during the late Pleistocene and Holocene (known as the Quaternary extinction event), the disappearance of Madagascar's megafauna is tightly linked with the arrival of humans, with nearly all extinctions dating to around the same time of the earliest evidence of... | Subfossil lemur | Wikipedia | 310 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
The extinction of Madagascar's megafauna, including the giant lemurs, was one of the most recent in history, with large lemur species like Palaeopropithecus ingens surviving until approximately 500 years ago and one bone of the extinct Hippopotamus laloumena radiocarbon dated to about 100 years BP. An even wider extinc... | Subfossil lemur | Wikipedia | 256 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
In the 20th century, six hypotheses for explaining the extinction of the giant subfossil lemurs have been proposed and tested. They are known as the "Great Fire", "Great Drought", "Blitzkrieg", "Biological Invasion", "Hypervirulent Disease", and "Synergy" hypotheses. The first was proposed in 1927 when Henri Humbert an... | Subfossil lemur | Wikipedia | 500 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Since the subfossil bones of extinct lemurs have been found alongside the remains of highly arboreal living lemur species, we know that much of Madagascar had been covered in forest prior to the arrival of humans; the forest coverage of the high plateau region has been debated. Humbert and other botanists suggested tha... | Subfossil lemur | Wikipedia | 320 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
Over-hunting by humans has been one of the most widely accepted hypotheses for the ultimate demise of the subfossil lemurs. The extinctions and human hunting pressure are associated due to the synchronicity of human arrival and species decline, as well as the suspected naïveté of the Malagasy wildlife during the early ... | Subfossil lemur | Wikipedia | 271 | 27653365 | https://en.wikipedia.org/wiki/Subfossil%20lemur | Biology and health sciences | Strepsirrhini | Animals |
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