Blood Oxygenation Level Dependent FMRI Psychology Essay

Blood Oxygenation Level Dependent FMRI Psychology Essay Functional magnetic resonance (fMRI) is the most widely used and powerful method of understanding the brain function and mapping neuroanatomy of the human brain. The most basic fMRI technique is blood oxygen level dependent (BLOD-fMRI). Paramagnetic deoxyhemoglobin in venous blood is a natural contrast agent for magnetic resonance imaging (MRI). Basic principles and methodological applications of BOLD-MRI as an introduction are presented in this article, and the relationship between neural activation and a magnetic resonance signal change is represented in much detail. Introduction Functional magnetic resonance (fMRI) is a widely recognized technique for brain mapping and providing the anatomical information of brain activity. It has been demonstrated that this method bases on the local hemodynamic changes that influence deoxyhemoglobin changes in venous blood. Furthermore, susceptibility changes produced by deoxyhemoglobin changes lead to the changes of MR signal strength. This effect is called blood oxygenation level dependent (BOLD) contract (1). High spatial and temporal resolution brain mapping can be structured by this basic method. Currently, it has become the most powerful study of brain function techniques. Compared with the traditional neuroimaging methods, including positron emission tomography (PET) and intrinsic signal optical reflection imaging, BOLD-fMRI can provide high spatial and temporal resolution sufficiently using internal concentration of oxygenation in human bodies as a natural contrast agent. Blood oxygen level dependent (BOLD) effect was firstly presented by Ogawa etc in 1990. They found that the magnetic resonance signal reduces when the concentration of oxyhemoglobin decreases. Also, their research showed that the reduction of signal not only occurs in blood, but also outside the blood vessels. Thus, they assert that this effect is caused by the property of magnetic field changes. After that, many researchers performed a large number of theoretical and experimental works to summarize the basis of BOLD-fMRI imaging. When neuron is activated, regional cerebral blood flow and oxygen consumption volume increase, but there are differences between the two increases, which is that the increase in cerebral blood flow is more than the oxygen consumption. Due to this difference, the venous oxygen concentration in active regions is significantly higher than the surrounding tissue and the concentration of deoxyhemoglobin reduces relatively. BOLD contrast has its origin in the fact that when normally diamagnetic oxyhemoglobin gives up its oxygen, the resulting deoxyhemoglobin is paramagnetic (2). Deoxyhemoglobin is a paramagnetic material which can produce local gradient magnetic field in the blood vessels and surroundings. Hence, it has effect on reducing T2. When brain areas are activated, the effect of reducing T2 decreases result from the reduction of deoxyhemoglobin. Compared with the resting state, T2 or T2* is relatively extended in local brain regions. Therefore, the signal is relatively enhanced on the T2 weighting or T2* weighting functional magnetic resonance imaging maps. Current MRI brain mapping studies all focus on off-on subtraction mode, which is the fMRI signal in active condition minus the signal under control conditions. The signal is extremely weak, and the relative increasing strength is 2%-5% generally. During imaging, the functional image of corresponding brain areas can be obtained if superimposing the high signal in different colors of active area on the high-resolution T1 weighting anatomical maps. This method is called blood oxygen level dependent contrast fMRI due to it depends on the level of oxygen in local blood vessels (1). This article reviews the basic principles and available methodological information and research on blood oxygen level dependent (BLOD-fMRI). This review begins with some basic principles on BOLD-fMRI. Furthermore, the methods for BOLD-fMRI will be described in detail including block design and event-related design. Also, the results of BOLD-fMRI studies will be presented and the advantages and limitations of the current research will be discussed as well. Finally, the key points and important aspects of the BOLD-fMRI will be summarized as a conclusion. Materials and Methods BOLD-fMRI experiment steps include: firstly, make experimental planning and determine the most optimal stimulus or task programs. Secondly, high T1 WL resolution anatomical images and a great number of original images in stimulation and rest states can be obtained by scanning. Lastly, functional active maps should be obtained by experimental data analysis. Block design bases on cognitive subtraction mode to show the stimulus task in block form. A tropical block design contains two basic tasks which are experimental tasks and control tasks, and the two intervals of blocks appear. Task-related brain activities can be understudied by the comparison of regional cerebral blood oxygen reaction through stimulation and control tasks. It is widely used in locating brain function. It is the early main method to do functional magnetic resonance imaging experiments. The advantages are simple and easy to perform tasks. However, the drawback is that the BOLD signal changes larger result in long stimulation time and the high rate of oxygen reaction. In blocked designs, regardless of stimulus presentation or task performance interdigitated with rest, observing the relationship of the time course of BOLD response to activation paradigm is possible (3). Also, more than one image can be obtained during every experimental and rest period. The signal time course should be assumed to be activated, and it can be tested. A simple example is presented in Figure 1(a). Firstly, switch on and off the visual stimulation (black and green) quickly for 10 times. It is shown that the time course of pixels follows the stimulation paradigm. However, the difference between the stimulation and time course is quite obviously (p

How Xerophytes Are Adapted for Water Loss Essay

Biology essay: describe the adaptations shown by xerophytes to reduce water loss A Xerophyte is a type of plant that is well adapted to water. Water loss is something that is very bad for the plants if the ratio of water lost to water taken in is too drastic. The cells may lose their turgidity and may even submit to plasmolysis, which will result in the plant wilting and eventually dying. Water loss via transpiration (loss of water vapour from the aerial parts of a plant due to evaporation) is fundamentally inevitable due to the fact that plants exchange gases with the atmosphere, via their stomata-the pores in a leafs epidermis . The bad aspect of this is the fact that the plants must photosynthesise in order to acquire the energy vital for their survival; for this exchange to occur the plant must be able to allow the gases in and out of the leaves, and to do this the stomata must open, meaning that water can be lost due to the opening of an exit, and also the change in the water va pour potential gradient. Water potential is the measure of the tendency/ability of water to move freely in a solution. Water moves from an area of high water potential to an area of lower water potential, and this is what causes the water vapour in the plant to be lost to the outside atmosphere, due to the difference in the water potential gradient, and we call this â€Å"moving along the water potential gradient†. If the water potential outside the plant was higher than the water potential inside the plant, then the plant would absorb water vapour rather than lose it, but because of the extreme weather conditions, and the difference in water potential the plant loses rather than gains water. The potential of water vapour is the same concept, and simply means the same thing but in terms of the gaseous form of water. Most plants can reduce water loss by structural and behavioural adaptations such as: * A waxy cuticle on the leaf will reduce water loss due to evaporation through the epidermis * The stom ata are often found on the undersurface of leaves, not on the top surface- this reduces the evaporation due to direct heating from the sun * Most stomata are closed at night, when there is no light for photosynthesis * Deciduous plants lose their leaves in winter, when the ground may be frozen (making water less available) and when temperatures may be too low for photosynthesis. However although xerophytes do execute these adaptations, they also have a number of adaptations specific to their own requirements that reduce the rate of water loss. Firstly, the surface area. Xerophytes have much smaller leaves, often shaped like needles. This reduces the surface area of the leaves significantly; hence the total leaf surface area is also reduced. This means that there is a much smaller area for the water vapour to escape from, this works well because the smaller the surface area, the smaller the quantity of water that can escape, therefore the less water lost. The thorn like structures reduce the area exposed for transpiration. Pine trees are prime examples of this, as they have small needle-shaped â€Å"leaves† that h ave a small surface area, therefore are able to retain more water as a result, because less of the area is exposed, and so transpiration cannot occur as abundantly. Next, includes the way mesophyll, the spongy inner tissue of a leaf that is composed of loosely arranged cells of irregular shape, is densely packed together. This reduces the cell surface area that is exposed to the air inside the leaves, meaning that the space for water to have access to is reduced, because the cells are more compact, thus creating a sealed wall where water cannot escape into and less water will evaporate into the leaf air spaces as a result, hence reducing the rate of water loss. A third factor of xerophytes that they have adapted themselves to include the waxy cuticle, which appears on all plants, is a lot thicker than the typical cuticle. The waxiness reduces evaporation further, particularly cuticular transpiration, where water escapes from fissures through the cuticle. This is because the cuticle, found at the epidermal (outermost) layer of cells, is made up of a complex formula of waxy substances known as Cutin, which acts sort of like a waterproof layer to p revent the loss of water from the surface cells, therefore reducing the amount of water that could be lost to the atmosphere. Fourthly, closing the stomata when water availability is low will reduce water loss and so reduce the need to take up water. This is because when the stomata is open for various reasons including gas exchange, water can escape from the openings made by the stomata, this is bad or a plant like a xerophyte which wants to retain as much after as possible, therefore keeping the stomata closed as much as possible increases the plants chances of retaining water, particularly when water is scarce. Next, hairs on the surface of the leaf trap a layer of air close to the surface. This air can become saturated with moisture and will reduce the diffusion of water vapour out through the stomata. This is because the gradient of the water vapour potential between the inside of the leaf and the outside has been reduced, for if there is a â€Å"barrier† of water between the inside of the cell and the out, then the gradient of water potential is significantly reduced, because the difference in water potential is less, hence water will not want to move from an area of high water potential to an area of low water potential. Pits containing stomata at their base also trap air that can become saturated with water vapour, and so also reduce the rate of water loss. This will reduce the gradient in the water vapour potential between inside and outside the lea, so reducing loss by diffusion. Behavioural aspects of adaptations that xerophytes achieve include rolling their leaves up so that the lower epidermis is not exposed to the atmosphere which can trap air that becomes saturated. This is another way to reduce or even eliminate the water potential gradient. Another point to make is that some plants have a low water potential inside their leaf cells. This is achieved by maintaining a high salt concentration in the cells. The low water potential reduces the evaporation o water from the cell surfaces as the water potential gradient between the cells and the leaf air spaces is reduced. An excellent example of a xerophyte is marram grass. A dense green plant with protruding spikes that appears in tufts, which you often see dotted along the coastal scenery. Its principal habitat is sand dunes and the conditions are very severe and can be particularly brutal at times, with winds and salty, dry terrain. The features described above mirror a lot of the characteristics that marram grass possess, such as rolling up its leaves to trap air inside as well as a thick waxy cuticle to reduce water evaporation rom surface cells, and hence is a very good example of a xerophyte. In conclusion, xerophytes are very durable plants that have adapted exceedingly well to living in such harsh conditions. Their features allow them to retain water incredibly well, and that provides them with an advantage to living in places such as the desert in comparison with a normal plant.

Biography of Polycarp, Christian Bishop and Martyr

Polycarp (60-155 CE), also known as Saint Polycarp, was a Christian bishop of Smyrna, the modern city of Izmir in Turkey. He was an Apostolic father, meaning he was a student of one of the original disciples of Christ; and he was known to other important figures in the early Christian church, including Irenaeus, who knew him as a youth, and Ignatius of Antioch, his colleague in the Eastern Catholic church. His surviving works include a Letter to the Philippians, in which he quotes the Apostle Paul, some of which quotes appear in the books of the New Testament and the Apocrypha. Polycarps letter has been used by scholars to identify Paul as the probable writer of those books. Polycarp was tried and executed as a criminal by the Roman empire in 155 C.E., becoming the 12th Christian martyr in Smyrna; the documentation of his martyrdom is an important document in the history of the Christian church. Birth, Education, and Career Polycarp was likely born in Turkey, about 69 C.E. He was a student of the obscure disciple John the Presbyter, sometimes considered to be the same as John the Divine. If John the Presbyter was a separate apostle, he is credited with writing the book of Revelations. As Bishop of Smyrna, Polycarp was a father figure and mentor to Irenaeus of Lyons (ca 120–202 C.E.), who heard his preachings and mentioned him in several writings. Polycarp was a subject of the historian Eusebius (ca 260/265–ca 339/340 C.E.), who wrote about his martyrdom and connections with John. Eusebius is the earliest source separating out John the Presbyter from John the Divine. Irenaeus Letter to the Smyrneans is one of the sources recounting Polycarps martyrdom. Martyrdom of Polycarp The Martyrdom of Polycarp or Martyrium Polycarpi in Greek and abbreviated MPol in the literature, is one of the earliest examples of the martyrdom genre, documents which recount the history and legends surrounding a particular Christian saints arrest and execution. The date of the original story is unknown; the earliest extant version was composed in the early 3rd century. Polycarp was 86 years old when he died, an old man by any standard, and he was the bishop of Smyrna. He was considered a criminal by the Roman state because he was a Christian. He was arrested at a farmhouse and taken to the Roman amphitheater in Smyrna where he was burned and then stabbed to death. Mythic Events of the Martyrdom Supernatural events described in MPol include a dream Polycarp had that he would die in flames (rather than being torn apart by lions), a dream that MPol says was fulfilled. A disembodied voice emanating from the arena as he entered entreated Polycarp to be strong and show yourself a man. When the fire was lit, the flames did not touch his body, and the executioner had to stab him; Polycarps blood gushed out and put out the flames. Finally, when his body was found in the ashes, it was said to have not been roasted but rather baked as bread; and a sweet aroma of frankincense was said to have arisen from the pyre. Some early translations say a dove rose out of the pyre, but there is some debate about the accuracy of the translation. With the MPol and other examples of the genre, martyrdom was being shaped into a highly public sacrificial liturgy: in Christian theology, the Christians were Gods choice for martyrdom who were trained for the sacrifice. Martyrdom as Sacrifice In the Roman empire, criminal trials and executions were highly structured spectacles that dramatized the power of the state. They attracted mobs of people to see the state and criminal square off in a battle that the state was supposed to win. Those spectacles were intended to impress on the minds of the spectators how powerful the Roman Empire was, and what a bad idea it was to attempt to go against them. By turning a criminal case into a martyrdom, the early Christian church emphasized the brutality of the Roman world, and explicitly converted the execution of a criminal into a sacrifice of a holy person. The MPol reports that Polycarp and the writer of the MPol considered Polycarps death a sacrifice to his god in the Old Testament sense. He was bound like a ram taken out of a flock for sacrifice and made an acceptable burnt-offering unto God. Polycarp prayed that he was happy to have been found worthy to be counted among the martyrs, I am a fat and acceptable sacrifice. Epistle of St. Polycarp to the Philippians The only surviving document known to have been written by Polycarp was a letter (or perhaps two letters) he wrote to the Christians at Philippi. The Phillippians had written to Polycarp and asked him to write an address to them, as well as to forward a letter they had written to the church of Antioch, and to send them any epistles of Ignatius he might have. The importance of Polycarps epistle is that it explicitly ties the apostle Paul to several pieces of writing in what would eventually become the New Testament. Polycarp uses expressions such as as Paul teaches to quote several passages which are today found in different books of the New Testament and the Apocrypha, including Romans, 1 and 2 Corinthians, Galatians, Ephesians, Philippians, 2 Thessalonians, 1 and 2 Timothy, 1 Peter, and 1 Clement. Sources Ari, Bryen. Martyrdom, Rhetoric, and the Politics of Procedure. Classical Antiquity 33.2 (2014): 243–80. Print.Bacchus, Francis Joseph. St. Polycarp. The Catholic Encyclopedia. Vol. 12. New York City: Robert Appleton Company, 1911. Print.Berding, Kenneth. Polycarp of Smyrnas View of the Authorship of 1 and 2 Timothy. Vigiliae Christianae 53.4 (1999): 349–60. Print.Moss, Candida R. On the Dating of Polycarp: Rethinking the Place of the Martyrdom of Polycarp in the History of Christianity. Early Christianity 1.4 (2010): 539–74. Print.Norris, Frederick W. Ignatius, Polycarp, and I Clement: Walter Bauer Reconsidered. Vigiliae Christianae 30.1 (1976): 23–44. Print.Pionius, Alexander Roberts, and James Donaldson. [English Translation of ]the Martyrdom of Polycarp. Ante-Nicene Fathers. Eds. Roberts, Alexander, James Donaldson and A. Cleveland Coxe. Vol. 1. Buffalo, New Yokr: Christian Literature Publishing Co., 1888 Print.Thompson, Leonard L. The Martyrdom of Pol ycarp: Death in the Roman Games. The Journal of Religion 82.1 (2002): 27–52. Print.

Understanding States Rights and the 10th Amendment

In American government, states’ rights are the rights and powers reserved by the state governments rather than the national government according to the U.S. Constitution. From the Constitutional Convention in 1787 to the Civil War in 1861 to the civil rights movement of the 1960s, to today’s marijuana legalization movement, the question of the rights of the states to govern themselves has been the focus of the American political landscape for well over two centuries. Key Takeaways: States' Rights States’ rights refer to the political rights and powers granted to the states of the United States by the U.S. Constitution.Under the doctrine of states’ rights, the federal government is not allowed to interfere with the powers of the states reserved or implied to them by the 10th Amendment to the U.S. Constitution.In issues such as slavery, civil rights, gun control, and marijuana legalization, conflicts between states’ rights and the powers of the federal government have been a part of civic debate for over two centuries. The doctrine of states’ rights holds that the federal government is barred from interfering with certain rights â€Å"reserved† to the individual states by the 10th Amendment to the U.S. Constitution. The 10th Amendment The debate over states’ rights started with the writing of the Constitution and Bill of Rights. During the Constitutional Convention, the Federalists, led by John Adams, argued for a powerful federal government, while the Anti-federalists, led by Patrick Henry, opposed the Constitution unless it contained a set of amendments specifically listing and ensuring certain rights of the people and the states. Fearing that the states would fail to ratify the Constitution without it, the Federalists agreed to include the Bill of Rights. In establishing American government’s power-sharing system of federalism, the Bill of Rights 10th Amendment holds that all rights and powers not specifically reserved to Congress by Article I, Section 8, of the Constitution or to be shared concurrently by the federal and state governments are reserved by either the states or by the people. In order to prevent the states from claiming too much power, the Constitution’s Supremacy Clause (Article VI, Clause 2) holds that all laws enacted by the state governments must comply with the Constitution, and that whenever a law enacted by a state conflicts with a federal law, the federal law must be applied. The Alien and Sedition Acts The issue of states’ rights versus the Supremacy Clause was first tested in 1798 when the Federalist-controlled Congress enacted the Alien and Sedition Acts. Anti-federalists Thomas Jefferson and James Madison believed the Acts’ restrictions on freedom of speech and freedom of the press violated the Constitution. Together, they secretly wrote the Kentucky and Virginia Resolutions supporting states’ rights and calling on the state legislatures to nullify federal laws they considered unconstitutional. Madison, however, would later come to fear that such unchecked applications of states’ rights could weaken the union, and argued that in ratifying the Constitution, the states had yielded their sovereignty rights to the federal government. The Issue of States’ Rights in the Civil War While slavery and its abolition are the most visible, the question of states’ rights was the underlying cause of the Civil War. Despite the overarching reach of the Supremacy Clause, proponents of states’ rights like Thomas Jefferson continued to believe the states should have the right to nullify federal acts within their boundaries. In 1828 and again in 1832, Congress enacted protective trade tariffs, which while helping the industrial northern states, hurt the agricultural southern states. Outraged by what it called the â€Å"Tariff of Abominations,† the South Carolina legislature, on November 24, 1832, enacted an Ordinance of Nullification declaring the federal tariffs of 1828 and 1832 â€Å"null, void, and no law, nor binding upon this State, its officers or citizens.† On December 10, 1832, President Andrew Jackson responded by issuing a â€Å"Proclamation to the People of South Carolina,† demanding that the state observe the Supremacy Clause and threatening to send federal troops to enforce the tariffs. After Congress passed a compromise bill reducing the tariffs in the southern states, the South Carolina legislature rescinded its Ordinance of Nullification on March 15, 1832. While it made President Jackson a hero to nationalists, the so-called Nullification Crisis of 1832 reinforced the growing feeling among Southerners that they would continue to be vulnerable to the Northern majority as long as their states remained a part of the union. Over the next three decades, the main battle over states’ rights shifted from economics to slavery. Did the southern states, whose largely agricultural economy depended on slave labor, have the right to maintain the slave trade in defiance of federal laws abolishing it? By 1860, that question, along with the election of anti-slavery President Abraham Lincoln, drove 11 southern states to secede from the union. Though secession was not intended to create an independent nation, Lincoln viewed it as an act of treason conducted in violation of both the Supremacy Clause and federal law.   Civil Rights Movement From the day in 1866, when the U.S. Congress passed America’s first civil rights law, public and legal opinions have been divided on whether the federal government overrides states’ rights in attempting to ban racial discrimination nationwide. Indeed, key provisions of the Fourteenth Amendment dealing with racial equality were largely ignored in the South until the 1950s. During the Civil Rights Movement of the 1950s and 1960s, southern politicians who supported the continuation of racial segregation and enforcement of state-level â€Å"Jim Crow† laws denounced anti-discrimination laws like the Civil Rights Act of 1964 as federal interference with states’ rights. Even after passage of the Civil Rights Act of 1964 and the Voting Rights Act of 1965, several southern states passed â€Å"Interposition Resolutions† contending that the states retained the right to nullify the federal laws. Current States Rights Issues As an inherent byproduct of federalism, questions of states’ rights will undoubtedly continue to be a part of American civic debate for years to come. Two highly visible examples of current states’ rights issues include marijuana legalization and gun control. Marijuana Legalization While at least 10 states have enacted laws allowing their residents to possess, grow, and sell marijuana for recreational and medical use, the possession, production, and sale of marijuana continues to be a violation of federal drug laws. Despite previously rolling back an Obama-era hands-off approach to prosecuting violations of federal marijuana laws in pot-legal states, former Attorney General Jeff Sessions clarified on March 8, 2018 that federal law enforcement officers would go after dealers and drug gangs, rather than casual users. Gun Control Both the federal and state governments have been enacting gun control laws for over 180 years. Due to an increase in incidents of gun violence and mass shootings, state gun control laws are now often more restrictive than federal laws. In these cases, gun rights advocates often argue that the states have actually exceeded their rights by ignoring both the Second Amendment and the Supremacy Clause of the Constitution. In the 2008 case of District of Columbia v. Heller, the U.S. Supreme Court ruled that a District of Columbia law completely banning its citizens from possessing handguns violated the Second Amendment. Two years later, the Supreme Court ruled that its Heller decision applied to all U.S. states and territories. Other current states’ rights issues include same-sex marriage, the death penalty, and assisted suicide. Sources and Further Reference Drake, Frederick D., and Lynn R. Nelson. 1999. States Rights and American Federalism: A Documentary History. Westport, Conn.: Greenwood Press. ISBN 978-0-313-30573-3.Mason, Alpheus Thomas. 1972. The States Rights Debate: Antifederalism and the Constitution. New York: Oxford Univ. Press. ISBN-13; 978-0195015539McDonald, Forrest. 2000. States Rights and the Union: Imperium in Imperio, 1776-1876. Lawrence: Univ. Press of Kansas.Interposition. Center for the Study of Federalism.