Saturday, March 21, 2020

The 4 Mitosis PhasesProphase, Metaphase, Anaphase, Telophase

The 4 Mitosis PhasesProphase, Metaphase, Anaphase, Telophase SAT / ACT Prep Online Guides and Tips In order to heal an injury, your body needs to replace damaged cells with healthy new ones...and mitosis plays a crucial role in this process! Mitosis is a process of cell division that helps you stay alive and healthy. In other words, in the world of cell biology, mitosis is kind of a big deal! But like with anything science-related, mitosis can be sort of confusing when you first try to understand it. The key idea is that the process of mitosis involves four phases, or steps, that you need to understand if you want to understand how mitosis works. In this article, we’re going to do the following things to break down the four steps of mitosis for you and help you get acquainted with the mitosis phases: Briefly define mitosis and eukaryotic cells Break down the four phases of mitosis, in order Provide mitosis diagrams for the stages of mitosis Give you five resources for learning more about the phases of mitosis Now, let’s dive in! Feature image: Jpablo cadand Juliana Osorio/Wikimedia Commons (Marek Kultys/Wikimedia Commons) What Is Mitosis? Mitosis is a process that occurs during the cell cycle. The role of mitosis in the cell cycle is to replicate the genetic material in an existing cell- known as the â€Å"parent cell†- and distribute that genetic material to two new cells, known as â€Å"daughter cells.† In order to pass its genetic material to the two new daughter cells, a parent cell must undergo cell division, or mitosis. Mitosis results in two new nuclei- which contain DNA- that eventually become two identical cells during cytokinesis. Mitosis occurs in eukaryotic (animal) cells. Eukaryotic cells have a nucleus that contains the cell’s genetic material. A crucial part of mitosis involves breaking down the nuclear membrane that surrounds the cell’s DNA so that the DNA can be replicated and separated into new cells. Other types of cells, like prokaryotes, don’t have a nuclear membrane surrounding their cellular DNA, which is why mitosis only occurs in eukaryotic cells. The main purpose of mitosis is to accomplish cell regeneration, cell replacement, and growth in living organisms. Mitosis is important because it ensures that all new cells that are generated in a given organism will have the same number of chromosomes and genetic information. In order to accomplish this goal, mitosis occurs in four discrete, consistently consecutive phases: 1) prophase, 2) metaphase, 3) anaphase, and 4) telophase. Our in-depth post on mitosis is coming soon, so you can think of this as an intro to what mitosis is and how it works! What we want to focus on in more detail here are the 4 stages of mitosis: prophase, metaphase, anaphase, telophase, and what happens during those phases! So let’s get down to it. The 4 Phases of Mitosis: Prophase, Metaphase, Anaphase, Telophase So what are the stages of mitosis? The four stages of mitosis are known as prophase, metaphase, anaphase, telophase. Additionally, we’ll mention three other intermediary stages (interphase, prometaphase, and cytokinesis) that play a role in mitosis. During the four phases of mitosis, nuclear division occurs in order for one cell to split into two. Sounds simple enough, right? But different things occur in each step of mitosis, and each step is crucial to cell division occurring properly. That means successful cell division depends on the precision and regulation of each phase of mitosis. That’s why it’s important to be able to understand and articulate the role of each phase in mitosis overall. Also: you may have seen or heard the parts of mitosis called different things: mitosis phases, the stages of mitosis, the steps of mitosis, or maybe even something else. All of those different phrases refer to the exact same process. As long as you remember that the phases/stages/steps of mitosis always happen in the same order, it doesn’t really matter which of those phrases you use! Next, we’re going to breakdown the four phases of mitosis in order so you can understand how mitosis occurs through each phase. (Ph. Immel/Wikimedia Commons) Interphase: What Happens Before Mitosis We can think of interphase as a transitional phase. Interphase is when the parent cell prepares itself for mitosis. This phase isn’t considered part of mitosis, but understanding what happens during interphase can help the steps of mitosis make a little more sense. You can think of interphase kind of like the opening act. They aren’t the band you came to see, but they get the audience warmed up for the main event. Interphase occurs prior to the beginning of mitosis and encompasses what’s called stage G1, or first gap, stage S, or synthesis, and stage G2, or second gap. Stages G1, S, and G2 must always occur in this order. The cell cycle begins with stage G1, which is a part of interphase. So how does the parent cell prep itself for mitosis during interphase? During interphase, the cell is busy growing. It’s producing proteins and cytoplasmic organelles during the G1 phase, duplicating its chromosomes during the S phase, then continuing to grow in preparation for mitosis in the G2 phase. In the cell cycle, interphase doesn’t just occur before mitosis- it also alternates with mitosis. It’s important to remember that this is a recurring cycle. When mitosis ends, interphase starts up again! In fact, in the grand scheme of the cell cycle, mitosis is a much shorter phase than interphase. (Kelvinsong/Wikimedia Commons) Phase 1: Prophase Prophase is the first step of mitosis. This is when the genetic fibers within the cell’s nucleus, known as chromatin, begin to condense and become tightly compacted together. During interphase, the parent cell’s chromosomes are replicated, but they aren’t yet visible. They’re just floating around in the form of loosely collected chromatin. During prophase, that loose chromatin condenses and forms into visible, individual chromosomes. Since each of the parent cell’s chromosomes were replicated during interphase, there are two copies of each chromosome in the cell during prophase. Once the chromatin has condensed into individual chromosomes, the genetically-identical chromosomes come together to form an â€Å"X† shape, called sister chromatids. These sister chromatids carry identical DNA and are joined at the center (in the middle of the â€Å"X† shape) at a point called the centromere. The centromeres will serve as anchors that’ll be used to pull the sister chromatids apart during a later phase of mitosis. And that’s what’s happening inside the nucleus during prophase! After the sister chromatids form, two structures called centrosomes move away from each other outside of the nucleus. As they move to opposite sides of the cell, the centrosomes form something called the mitotic spindle. The mitotic spindle will eventually be responsible for separating the identical sister chromatids into two new cells and is made up of long protein strands, called microtubules. Late Prophase: Prometaphase Prometaphase is often referred to as â€Å"late prophase.† (Though it’s also sometimes called â€Å"early metaphase† or referred to as a distinct phase entirely!) Regardless, some really important things occur during prometaphase that propel cell division along and that help explain what happens in metaphase. Prometaphase is the phase of mitosis following prophase and preceding metaphase. The short version of what happens during prometaphase is that the nuclear membrane breaks down. Here’s the long version of what happens during prometaphase: first, the nuclear membrane or nuclear envelope (i.e. the lipid bilayer surrounding the nucleus and encasing the genetic material in the nucleus) breaks apart into a bunch of membrane vesicles. Once the nuclear envelope breaks apart, the sister chromatids that were stuck inside the nucleus break free. Now that the nucleus’s protective covering is gone, kinetochore microtubules move near the sister chromatids and attach to them at the centromere (that spot at the center of the â€Å"X†). Now these kinetochore microtubules are anchored at opposite poles on either end of the cell, so they’re extending themselves toward the sister chromatids and connecting them to one of the edges of the cell. It’s kind of like catching a fish with a fishing pole- eventually, the chromatids are going to be separated and drawn to opposite ends of the cell. And that’s the end of prometaphase. After prometaphase ends, metaphase- the second official phase of mitosis- begins. (Kelvinsong/Wikimedia Commons) Phase 2: Metaphase Metaphase is the phase of mitosis that follows prophase and prometaphase and precedes anaphase. Metaphase begins once all the kinetochore microtubules get attached to the sister chromatids’ centromeres during prometaphase. So here’s how it happens: the force generated during prometaphase causes the microtubules to start pulling back and forth on the sister chromatids. Since the microtubules are anchored at opposite ends of the cell, their back-and-forth pulling on different sides of the sister chromatids gradually shifts the sister chromatids to the middle of the cell. This equal and opposite tension causes the sister chromatids to align along an imaginary- but very important!- line trailing down the middle of the cell. This imaginary line dividing the cell down the middle is called the metaphase plate or equatorial plane. Now, in order for metaphase to progress on to anaphase, the sister chromatids must be equitably distributed across that metaphase plate. That’s where the metaphase checkpoint comes in: the metaphase checkpoint ensures that the kinetochores are properly attached to the mitotic spindles and that the sister chromatids are evenly distributed and aligned across the metaphase plate. If they are, the cell gets the green light to move on to the next phase of mitosis. The checkpoint is very important because it helps the cell make sure that it mitosis will result in two new, identical cells with the same DNA! Only once the cell passes the metaphase checkpoint successfully can the cell proceed to the next stage of mitosis: anaphase. (Kelvinsong/Wikimedia Commons) Phase 3: Anaphase The third phase of mitosis, following metaphase and preceding telophase, is anaphase. Since the sister chromatids began attaching to centrosomes on opposite ends of the cell in metaphase, they’re prepped and ready to start separating and forming genetically-identical daughter chromosomes during anaphase. During anaphase, the centromeres at the center of the sister chromatids are severed. (It sounds worse than it is!) Remember how the sister chromatids are attached to the mitotic spindle? The spindle is made up of microtubules, which start shrinking during this phase of mitosis. They gradually pull the severed sister chromatids toward opposite poles of the cell. Anaphase ensures that each chromosome receives identical copies of the parent cell’s DNA. The sister chromatids split apart down the middle at their centromere and become individual, identical chromosomes. Once the sister chromatids split during anaphase, they’re called sister chromosomes. (They’re actually more like identical twins!) These chromosomes will function independently in new, separate cells once mitosis is complete, but they still share identical genetic information. Finally, during the second half of anaphase, the cell begins to elongate as polar microtubules push against each other. It goes from looking like one round cell to...well, more like an egg as the new chromosome sets pull further away from each other. At the end of anaphase, chromosomes reach their maximum condensation level. This helps the newly separated chromosomes stay separated and prepares the nucleus to re-form . . . which occurs in the final phase of mitosis: telophase. (Kelvinsong/Wikimedia Commons) Phase 4: Telophase Telophase is the last phase of mitosis. Telophase is when the newly separated daughter chromosomes get their own individual nuclear membranes and identical sets of chromosomes. Toward the end of anaphase, the microtubules began pushing against each other and causing the cell to elongate. Those polar microtubules keep elongating the cell during telophase! In the meantime, the separated daughter chromosomes that are being pulled to opposite ends of the cell finally arrive at the mitotic spindle. Once the daughter chromosomes have fully separated to opposite poles of the cell, the membrane vesicles of the parent cell’s old, broken down nuclear envelope form into a new nuclear envelope. This new nuclear envelope forms around the two sets of separated daughter chromosomes, creating two separate nuclei inside the same cell. You might think of the events of telophase as a reversal of the events that occur during prophase and prometaphase. Remember how prophase and prometaphase are all about the nucleus of the parent cell starting to break down and separate? Telophase is about the reformation of the nuclear envelope around new nuclei to separate them from each cell’s cytoplasm. Now that the two sets of daughter chromosomes are encased in a new nuclear envelope, they begin to spread out again. When this occurs, it is the end of telophase, and mitosis is complete. (LadyofHats/Wikimedia Commons) Cytokinesis: What Happens After Mitosis Like interphase, cytokinesis isn’t a part of mitosis, but it’s definitely an important part of the cell cycle that is essential to completing cell division. Sometimes, the occurrence of the events of cytokinesis overlaps with telophase and even anaphase, but cytokinesis is still considered a separate process from mitosis. Cytokinesis is the actual division of the cell membrane into two discrete cells. At the end of mitosis, there are two new nuclei contained within the existing parent cell, which has stretched out into an oblong shape. So at this point, there’s actually two complete nuclei hanging out in one cell! So how does one cell become two cells? Cytokinesis is responsible for completing the process of cell division by taking those new nuclei, separating the old cell in half, and ensuring that each of the new daughter cells contains one of the new nuclei. Here’s how the separation of the old cell is accomplished during cytokinesis: remember that imaginary line running down the middle of the cell and dividing the centrosomes, called the metaphase plate? During cytokinesis, a contractile ring made of protein filaments develops where that metaphase plate used to be. Once the contractile ring forms down the middle of the cell, it starts shrinking, which pulls the cell’s outer plasma membrane inward. You can think of it like a belt that just keeps tightening around the middle of the cell, squeezing it into two sections. Eventually, the contractile ring shrinks so much that the plasma membrane pinches off and the separated nuclei are able to form into their own cells. The end of cytokinesis signifies the end of the M-phase of the cell cycle, of which mitosis is also a part. At the end of cytokinesis, the division part of the cell cycle has officially ended. 5 (Free!) Resources for Further Study of the Steps of Mitosis Mitosis is a complex process, and the mitosis phases involve a lot of big words and unfamiliar concepts that you might want to learn more about. If you’re interested in diving more deeply into the 4 stages of mitosis, take a look at our five suggested resources for further study of the steps of mitosis, explained below! #1: Mitosis Animations Online Reading all about mitosis can definitely be helpful, but what if visuals really help you understand how things work? That’s where web animations of mitosis might come in handy for you. Watching mitosis in action through web animations can help give you an idea of what all those verbal descriptions really mean. They can also help you picture what the phases of mitosis might look like under a real microscope! There are probably a lot of web animations of mitosis that you could take a look at, but we recommend these three: John Kyrk’s Mitosis Animation The Biology Project’s â€Å"Online Onion Root Tips† Cells Alive’s â€Å"Animal Cell Mitosis† We particularly like Cells Alive’s â€Å"Animal Cell Mitosis† animation because it allows you to pause the animation as it loops through the phases of mitosis in order to take a fine-grained look at how mitosis works. Cells Alive’s version also juxtaposes its animation of the mitosis phases with footage of mitosis occurring under a microscope, so you’ll know what you’re looking for if you’re ever tasked with observing cell mitosis in the lab. iframe width="560" height="315" src="https://www.youtube.com/embed/L0k-enzoeOM" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen/iframe #2: â€Å"Mitosis: Splitting Up Is Hard To Do† by Crash Course If you’re a bit exhausted from reading dense material and need someone else to put the stages of mitosis into more accessible terms, head over to YouTube and watch Crash Course’s 10 minute video on mitosis, called â€Å"Mitosis: Splitting Up Is Hard to Do.† The nice thing about this video is that, while being a bit more thorough than some of the other YouTube videos you might find out there on mitosis, it’s also really funny. More importantly, it explains mitosis in terms of familiar, everyday biological processes, like when you get a cut and need your body to make new cells to heal. If you need help thinking about the real-world relevance of the mitosis phases beyond just being something you have to memorize for a lab or exam, this is a great resource. #3: â€Å"Phases of Mitosis† by Khan Academy Here’s another YouTube video, but the tone and style of this explanation of the steps of mitosis by Khan Academy is a little different. Watching this tutorial on the mitosis phases feels a bit like you’re sitting in biology class and your teacher/professor is drawing out diagrams of mitosis while talking you through the entire process (except in this case, your teacher is sort of cool and only uses neon colors to draw the diagrams). If you’re looking for a step-by-step tutorial that takes a slow pace and deals with the steps of mitosis thoroughly, Khan Academy has you covered! #4: Creating a Mitosis Flip Book For some learners, the process of creating something to show your knowledge can help with memorization of difficult concepts and/or developing a thorough understanding of how things work. That’s why we suggest trying out some old-school tactics to build your knowledge of the 4 stages of mitosis! A tried-and-true approach to learning the mitosis phases, vetted by biology teachers, is creating a mitosis flip book. Post-It provides a step-by-step guide on how you can create a mitosis flip book on your own, but it’s really pretty simple: you get something to draw with, grab small note cards or sticky notes to draw on, and draw what each phase of the cell cycle looks like on individual note cards/sticky notes! When you’ve finished drawing your version of the stages of mitosis on your cards, you either stick, tape, or staple them together, and voila! You can flip through your mitosis flip book from beginning to end and watch the progression of mitosis through the four phases. Activities like this one can help imprint on your memory what each step of mitosis looks like. Plus, when you finish your flip book, you’ve got a pocket-sized resource that you can carry with you as a part of your study guide or a quick resource for review before a quiz or exam! #5: â€Å"Mitosis Study Set† by ProProfs Flashcards Maybe you’re feeling pretty good about your knowledge of the stages of mitosis but you want some help in testing that knowledge before a formal quiz or exam. That’s where ProProfs Flashcards’ â€Å"Mitosis Study Set,† an online study guide that provides an array of flashcards to help you test your knowledge of the stages of mitosis, comes in. What’s fun about this flashcard set is that you can choose different assessment styles depending on where you are in your knowledge of mitosis. The flashcard set provides traditional question-and-answer flashcards, a flashcard function specifically geared toward memorization, a multiple choice quiz, and matching. If you want to practice being tested on the steps of mitosis before the actual test, check out this resource! ProProfs Flashcards provides several study sets on other topics related to or involving mitosis, so if you need to test your knowledge of mitosis beyond just the four phases, this resource could help out there as well. What's Next? If you want more traditional resources to help you learn about the cell cycle, our list of the best AP Biology study guides has you covered. You’ll probably need to know about more than just mitosis to ace your AP Biology exam. Here’s an expert guide to the test to get your studying started off on the right foot! Taking science classes in high school (and doing well in them!) is an important step on your journey to get into the university of your dreams. Check out this article about which science classes you need to take before applying for college to figure out which classes are right for you.

Wednesday, March 4, 2020

Toxic Chemicals from Peeing in the Pool

Toxic Chemicals from Peeing in the Pool Lets face it. Its not just babies who pee in the pool! Is that guy on the other side of the pool trying to look cool or is he concentrating on a little public urination? You dont know, because there isnt a chemical you can put in the pool as a urine indicator that wouldnt be toxic or respond to a whole host of other fluids. The Water Quality and Health Council conducted a survey that revealed one in five Americans admit to urinating in the pool. So, unless that pool was filled an hour ago, youre swimming in pee. But, urine doesnt just sit there in the water or harmlessly disperse. It reacts with chemical treatments in the water. For the same reason you dont want to rinse out a really nasty kitty litter box with bleach, you might not want to inhale too deeply in a pool full of people. The chemical reactions form two particularly nasty compounds: cyanogen chloride (CNCl) and trichloramine (NCl3). In high concentrations, these are chemical warfare agents. In the minute quantities produced in a pool, you wont die, but youre not doing your lungs any favors, not to mention your nervous and circulatory systems. Chlorine treatments, in particular, react with uric acid from urine to form toxic chemicals. The pool treatments themselves often aggravate respiratory and other health problems, since chlorine is (you guessed it) a toxic chemical agent. Its really not something to worry about, as researchers have found levels of the chemicals are lower than the World Health Organization (WHO) limits for public drinking water. However, if it bothers you, you have a few options. Swim in an outdoor pool rather than an indoor one, so vapors become diluted in the air rather than trapped in an enclosed space. Switch to a different pool disinfection method. Or, you can build your very own private pool and resist the urge to pee in it. Reference:  Volatile Disinfection Byproducts Resulting from Chlorination of Uric Acid: Implications for Swimming Pools,  Lushi Lian, Yue E, Jing Li, and Ernest R. Blatchley , III,  Environ. Sci. Technol.,  2014,  48  (6), pp 3210–3217.

Monday, February 17, 2020

African slavery and African Catholicism Essay Example | Topics and Well Written Essays - 1250 words

African slavery and African Catholicism - Essay Example Many historians and scholars hold that the domination of European rule in Africa caused African slavery and the development of African Catholicism. However, there is much evidence showing that the development of African slavery and African Catholicism occurred due to deep rooted African systems and an already established traditional form of religion. It will also provide evidence of the roots and development of African slavery. Roots and Development of African Catholicism and African Slavery Many scholars view Christianity in Kongo, especially Catholicism as a foreign religion introduced by the colonizers during the 15th and 16th centuries. In addition, these scholars often deem this form of religion as serving the interests of foreigners more than the indigenous Kongo people. The result of this assertion is that Christianity overlooked the independence of Kongo people. In addition, this caused most historians to view the deemed introduced Christianity as a form of colonization and d omination by the Portuguese in Kongo. Moreover, these historians also assert that the conversion of Kongo to Christianity and the development of African Catholicism was a direct effect of westernization of Kongo (Thornton, 147). The history of religion and African Catholicism was quite different from the assertions of these historians and scholars. The conversion of Kongo in to Christianity was under a free will. Consequently, it is evident that the Kongo people and leaders highly determined the structure of the church and its doctrines as well as practices. It is also evident that the Portuguese attempted to control the church under political terms. However, this was not possible since Kongo highly controlled the activities and practices of the church. Even though contemporary studies reveal that there was substantial syncretism in Christian doctrines in Kongo, the European clergy who visited Kongo, recognized it as conventional (Thornton, 148). In the case of African slavery, ther e are misconceptions by most scholars as to what prompted slave trade in the region. Most of these scholars considered the roots of African slavery as a product of economic underdevelopment in Africa, in which forced labor dominated the economy rather than free labor. However, this was not the case but there was the spirit of slavery rooted deep in the African institutional and legal structures of communities of Africa. In addition, this kind of slavery occurred very differently from the form of slavery in Europe. The main reason that slavery occurred widely in the Atlantic Africa was that in African law, slaves were the only recognized form of private ownership. It became very perverse in the African society because there lacked landed private property (Thornton, 74). The incorporation of Christianity as a part of indigenous religion is the main reason it survived and hence the documentation of the cult dates from the early sixteenth century to the present day. In the nineteenth ce ntury, Christianity briefly disappeared from Kongo. However, the disappearance was not due to a lack on the part of Kongo, a failure on the part of the clergy or a resurgence of suppressed local religion. Rather, it was because of the changing definition among European clergy including Rome as to what made up Christianity, together with more chauvinistic attitudes towards non-Western and particularly colonial peoples that happened after I850 (Thornton, 148). In African law, one could only establish a claim on a product through taxation and slavery rather than through the fiction of land ownership. However, this did not make the African legal system backward or egalitarian, but only legally divergent. Due to this

Monday, February 3, 2020

Case Study Plaskor Inc.Accounting Information Systems Internal

Plaskor Inc.Accounting Information Systems Internal Controls and Risks in IT Systems - Case Study Example Thus, Plaskor Inc. has underscored implementation of this strategy in carrying out manufacturing of automotive parts since it needs to trade with other partners. a) This section of the paper seeks to describe the extra IT system risks that Plaskor should consider as it evaluates whether to buy or develop an Internet EDI system. According to Segev, Porrar, and Roldan (n.d.), the main risk that can be faced by Plaskor is related to the aspect of security. Whether to buy or develop the system, there are certain risks that are likely to be faced. For instance, the system can be intruded by hackers who are bent on stealing business information belonging to other organizations. The security risk is more threatening to the viability of business since this can impact its operations. The system is also likely to be infiltrated by spyware which can affect the operations of the company. The company can lose vital information as a result of spyware that can be picked from the Internet. Therefore, there is a need to build strong firewalls in order to protect data from being stolen by other unscrupulous people. Plaskor can choose to develop the EDI system, which implies that it should also develop translators which can code the data so that it can be exchanged smoothly between two different companies. However, the risk likely to be encountered is that the translators may not be compatible with transmission and security systems and back end systems that ultimately process EDI instructions (Segev, Porrar, & Roldan, n.d.). This may affect the seamless flow of information, hence the need to put concerted efforts in order to ensure that the translators are compatible with the internal systems of the company. Failure to do so may impact the smooth flow of information between linked computers. b) This section of the paper seeks to describe IT internal controls that should be incorporated into an Internet EDI system. Systematic scheduling has to be put in

Sunday, January 26, 2020

The Invention Of The Revolver History Essay

The Invention Of The Revolver History Essay Revolvers are repeating firearms that consist of a cylinder containing multiple chambers, with at least one barrel for firing. The name revolver comes from the short-form of its original name, revolving gun. As its name suggests, the revolver is uniquely designed such that the chambers of a revolver revolve around an axis. 2. The Invention of the Revolver The first inventor of the revolver was Elisha Haydon Collier. Collier invented the flintlock revolver, which was a single-action, self-priming weapon with automatic release of gunpowder into the pan when the gun hammer was cocked. Patented in 1818, the flintlock revolvers single barrel allowed greater accuracy and faster reloading time (Shaver, 2004 ). Today, the revolvers that we are familiar with are an adaptation of Colliers revolver. One of the most significant pioneers in revolver technology was Samuel Colt. There are many variations as to how Colt first came up with the idea for his revolver, ranging from an eureka moment while shooting whales, to stealing Colliers idea in India (Hosley, 1996 ). Colt patented the percussion cap revolver in December 1835, which enabled muzzle-loading firearms to fire reliably regardless of weather. This was an improvement from Colliers flintlock revolver, which was prone to misfire in wet weather. The shooter would load the chambers of the cylinder with gunpowder and a projectile, and put in place several percussion caps. While this loading procedure might be tedious, it allowed the shooter to have rounds fully prepared ahead of time (Harris, 2011 ). Bullet cartridges were soon introduced in revolvers in the 1870s, replacing gunpowder and caps. The cartridges are a combination of a projectile (the bullet), a propellant (gunpowder) and a primer (the explosive cap), all contained within a metal casing. 3. Evolution of Revolvers 3.1 Type of innovation 3.1.1 Product Innovation The first revolvers invented by Collier were a product innovation. The patent was bought by John Evans and Son of London. It manufactured about 10,000 revolvers to sell mainly to the British forces in India and they are embodied as its outputs (Flemming, 2012). 3.1.2 Incremental Innovation Before the revolvers were invented, other types of handguns such as the single shot and multi barreled pistols existed. Revolvers improved on these handguns and hence were an incremental innovation. Firstly in the past, guns were mostly limited to a single shot except the pepper box however it was heavy and difficult to load since it had multiple barrels for each bullet. The revolver has the capability to deliver multiple loads to a single handgun barrel in quick succession (Delman ,2010). Revolvers are also different in terms of having lower chances of malfunction and thus provide greater reliability. Rounds which fail to fire can usually be cleared by merely pulling the trigger which will cycle the cylinder and place the next available round in a firing position (Riverwalker, 2009). Several malfunctions are however common in pistols that require more complex methods to clear them. Revolvers also have a sturdier design due partly to their heavier construction which allows them to shoot more powerful rounds (Riverwalker, 2009). 3.1.3 Component Innovation The revolver is a component innovation since its major change in handgun design is in creating a rotating cylinder which would come into alignment with a single barrel to fire successive bullets (Harris,2010). Collier combined this with a flintlock mechanism to create the first revolver. 3.1.3 Competence Enhancing vs Competence Destroying Originally, Colliers flintlock revolver was competence enhancing for John Evans and Son of London. However the revolver had several problems and by the 1840s, Colts Patent Fire Arms Manufacturing Company had adapted the revolvers based on the percussion cap system and mass produced them. This was competence destroying for Colliers company while competence enhancing for Colts (Delman, 2010). 3.2 Mechanics of the Revolver Over the years, the revolver has been constantly evolving and many different variations of the revolver have been invented. Despite this, the fundamental design of the revolver still remains the same, with several firing chambers arranged in a circle in a cylindrical block. This differs from other repeating firearms that use a single firing chamber with a different mechanism to load and extract cartridges. In modern revolvers, there is a spring-loaded hammer located at one end of the cylinder, in line with the barrel (Fig. 1). By cocking the hammer back, a new cartridge is lined up between the hammer and the barrel. To release the bullet, a pull of the trigger would result in the spring throwing the hammer forward so it hits the primer at the back of the bullet. The primer explodes, igniting the propellant and driving the bullet down the barrel. Macintosh HD:Users:helpdesk:Desktop:Screen Shot 2013-03-02 at 1.21.04 AM.png Figure 1 The inside of the barrel is lined with spiralling grooves, which increases the stability of the bullet by spinning it. A longer barrel not only improves stability, but also increases the speed of the bullet. 3.2.1 Actions (Mechanism) Single-Action Mechanism Single-action revolvers are revolvers that require the user to cock the weapon manually. The act of pulling back the cock rotates the cylinder and the user can then pull the trigger to fire it. Colts original revolver design involved a ratchet and pawl mechanism to hold the cylinders in place. Double-Action Mechanism Most revolvers today are double-action revolvers that perform two functions: cocking, and then firing the gun. Robert Adams, a British gunsmith, invented double-action revolvers in 1851. In this mechanism, pulling the trigger halfway automatically rotates the cylinder and releases the cocked hammer. Pulling back the trigger even more releases the cocked hammer. This would allow the user to fire the double-action revolver in one trigger pull. 3.3 How it has evolved 4. Uses Applications 4.1 Self Defence In the US where private gun ownership is legalized, a third of all gun sales can be attributed to handguns, including revolvers (Harris, 2013). Many Americans choose the revolver as a self-defense weapon due to its ease of use, maintenance and general reliability. To fire a revolver, a novice gun owner merely needs to aim and pull the trigger for double action revolvers or cock the hammer and then pull the trigger for single action revolvers. Their simplicity in design allows an average person to shoot safely and competently without much training. They are also relatively more affordable and sustainable due to the ability to withstand neglect (Riverwalker, 2009). 4.2 Combat Military The revolver was first adopted in combat by the Texas Rangers against the hostile native Indians who outnumbered them in Texas (Brown, 2013). Later on it was introduced into the U.S army in 1846 when the Mexican War began as Capt. Samuel H. Walker collaborated with Colt to design a novel and more powerful revolver (Colt Defense LLC, 2013). Throughout US military history up till 1985, revolvers had been the standard firearm, to arm the soldiers on battlefields such as during the Civil War, World War I and II. Although later on they were replaced by higher ammunition and faster reloading semi-automatic pistols, today they continued to be employed largely by guards, Navy Shore Patrol, and intelligence and counterintelligence operatives (Olive-Drab, 2013). 4.3 Sporting Hunting Handgun hunting has become a popular sport and most hunters use revolvers since they provide the reliability needed to hunt all types of big game (Hampton, 2013). Hunting with revolvers is more challenging and hones a hunters skills since the guns have comparatively shorter sight radius and less powerful ammunition. Hunters must also stalk closer to the prey to kill it humanely and this gives it greater chance of escaping from the hunters. A significant amount of practice is required to develop accuracy and marksmanship in revolver hunting (Wilson, 2010). 4.4 Law Enforcement Since the 1870s American police forces have relied on revolvers to arrest criminals and protect civilians. The most popular revolver used in law enforcement history was the Colt Official Police invented in 1927 which sold up to 400,000 units by 1970 (Scarlata, 2011). It was the top choice across numerous American police departments for one third of a century. Although production of this model has ceased today, other types of revolvers still play a significant role as back up and off duty firearms among American police officers. 5. Impacts of the Revolver 5.1 Military As an important tool for the military, the revolver has transformed major warfare in history and especially assisted in westward expansion. In the American Civil War in 1860, revolvers were one of the new and powerful weapons that forced armies to change their battle techniques. The Lemat and Colt revolvers were the most common firearms used. For example, Samuel Colt alone produced 200,000 of his guns for the Union and Confederate troops (Elbehri, 2010). These guns were more accurate and required less time to reload since they could fire multiple shots at one time. Combat at the time occurred at short distances and cavalrymen had to charge into formations of the enemy and use firearms and sabers to disrupt them and spread panic. At close ranges, revolvers were very powerful and handy especially while the cavalrymen were in saddles. This allowed armies to attack enemies more easily and aggressively. After the war, the US military adopted the Single Action Army revolver as the standard firearm and they aided the front troops to fight in the Indian war, Spanish-American War and Philippine-American War (military factory, 2011). In World War I, although the Americans had started switching to semi-automatic pistols, the M1917 revolvers continued to play a key role in filling the urgent need for guns. The British-made Webley revolvers also served as the standard sidearm for British soldiers in the war (Lewis, 2012). This sudden popularity in the armies was due to the revolvers small size which allowed airmen and tank operators to be armed under their space constrained environments (Duffey, 2009). Additionally, given its sturdy design and dependability, it was ideally suited to muddy and adverse conditions of trench warfare (Lewis, 2012). In World War II, the British and American troops continued using .38 calibre revolvers until finally afterwards, semi-automatic pistols replaced the revolvers in most militaries worldwide. 5.2 Societal Impacts Due to the strong gun culture that exists in U.S., this report will only be studying the societal impacts that revolvers have caused in U.S. Among the developed countries in the world today, U.S. has the highest number of gun owners. About 9 in 10 Americans own more than 270 million guns (Alpers, Philip and Wilson, 2013). That is 5% of the worlds population owning 35-50% of the worlds civilian-owned firearms, of which around 30% are revolvers (Stray, 2013). Sadly, the U.S. is also well known for clinching the highest number of gun homicides. The points below illustrated how the gun industry has severely impacted the society. Homicides Gun-rights advocates might be right when they argue that there might not be a connection between level gun ownership and homicide. However, numerous surveys and studies have concluded that there is an association between the number of homicides and gun ownership in developed countries. A study by Hemenway found that U.S. firearm homicide rates were 19.5 times higher than other developed countries (Kenny, 2013). Accidental Deaths In addition, unintentional firearm deaths in the U.S. were more than five times higher than in the other countries. Among these 23 countries, the U.S. accounted for 80 percent of all firearm deaths; 87 percent of all children under 15 killed by firearms were American children. Homes with guns are 12 times more likely to have household members or guests killed or injured by the weapon than by an intruder (Kenny, 2013). Self Defense and Reassurance of Safety However, the revolver  Data from the National Crime Victimization Survey suggest that a gun is used in self-defense  about 60,000 to 120,000 times each year. Several other surveys confirm this estimate. Facilitating Crimes each year about a million violent crimes involve guns This means guns are used to commit a crime about 10 times as often as they are used for self-defense. 5.3 Government 5.3.1 Laws Policy Making The Federal legislation enacted the Gun Control Act in 1968 that defines who was not allowed to possess a gun and barred anyone under 21 years old from buying handgun. However, they guarantee the right to gun ownership by law. There are restrictions though. The   National Firearms Act of 1934  restricts civilians from owning automatic weapons, short-barrelled shotguns, hand grenades, and other powerful arms without appropriate registration. People are free to carry guns both openly or hidden, outside, with the exception of federal facilities where guns are prohibited. The buyer of firearm is not obliged to allow official background checks before taking possession of guns. However, the  Brady Handgun Violence Prevention Act  of 1993 requires licensed gun dealers to perform background checks. Each state may have different jurisdiction, but overall, in the United States, if you do not have a criminal record and have not been adjudicated as mentally incompetent, you can buy guns. 5.4 Economic Impacts Over the years, the U.S. gun industry has been profiting by illegally trafficking firearms into Mexico. However, these firearms were used to arm drug cartels and thus, caused the deaths of thousands of civilians. Nearly 90 percent of weapons seized in Mexico are trafficked from the U.S. The market is extremely strong, especially because of the high demand and lack of strict control in the sale of weapons in U.S. Furthermore, in 2005, the Congress granted gun dealers blanket immunity from civil damages resulting from the misuse. Thus, the tyranny of the drug cartels and mafia reigns on (Kenny, 2013). The gun industry has faced its own share of ups and downs throughout the history but to date, it is still going strong. In 2012, the industry is expected to earn $11.7 billion in sale and $993 million in profit, according to analysts at IBIS World.(Brad, 2012) In 2011, about half of the six million guns manufactured in the United States were pistols and revolvers. Thats up from just one-third in 2001,  according to a report  from First Research.  Rifles now account for 35 percent of the market, with shotguns and other guns making up the rest. U.S. firearms manufacturers will export some $4.4 billion worth of guns and ammunition to other countries this year. The biggest customers are Canada, the United Kingdom, and Australia, who accounted for nearly 40 percent of exports in 2012 (its mainly law enforcement and military agencies doing the buying, as private gun ownership is heavily regulated in those nations). IBIS World expects exports to keep surging in the coming years, with ammunition and ordnance being an especially popular item overseas. The economic impact of the firearms industry is up 66 percent since the beginning of the Great Recession, providing an unexpected shot in the arm for the economy, according to a new study. The  National Shooting Sports Foundation  says the economic impact of firearm sales a figure that includes jobs. taxes and sales hit $31 billion in 2011, up from $19 billion in 2008. Jobs in the firearms business jumped 30 percent from 2008 to 2011, when the industry employed 98,750. The industry paid $2.5 billion in federal taxes in 2011, up 66 percent in three years. Ours is an industry with a rich history and heritage that remains vital and important to the American economy today,  NSSF  Senior Vice President  Lawrence G. Keane  said in a statement. To millions of Americans our industrys products represent liberty, security and recreation. Some in the industry attribute the jump in sales to fears the  Obama administration  will tighten gun control laws in a possible second term. Theres a concern that in the second term the  Obama administration  would lead an attempt to restrict gun ownership,  Mr. Keane  said. That concern, known in the industry as the Obama factor, has led many gun owners to purchase now in hopes of avoiding more restrictions and regulations later. (Devaney 2012)

Saturday, January 18, 2020

Larry Crowne

Based on the movie â€Å"Larry Crowne† I feel that college is going to be great. This movie really taught me a lot about college and how it’s never to late until your dead. I can only hope that my college experience is like Larry’s : fun , exciting , and a place to meet new people. However this movie also taught me that there are up and downs that come with college, but as long as you try and care you can make it through just fine. The first topic I would like to touch on is the fact that college is a great chance to meet new people, but now only new people but lifetime friends.There are so many different â€Å"characters† or personalities is college, where as it may have not been the same is your high school or city. I’m the type of person that loves to meet new people so that would be just great for me. This also helps me to see that being shy is college is not going to help you get through. Some people might introduce themselves to you like the y oung lady did Larry & other you have to make the first move. Having friends will get you through college and they’re always there for you as you saw in the movie.Moving on to the next topic , I’d say the teachers in college are a lot different. It’s like they understand your older and mature so they are more relaxed and you have more freedom. But one thing that I notice is that they give you work but your responsible for getting it in cause they won’t ask you for it. Also from watching the movie the class room atmosphere is way more relaxed in college but also not everything has the â€Å"Green-light† so to speak.College can be very fun, but I believe that all depends on what you go there with your mind set on. If you go just to party then you won’t be there long. However if you go with a mind to get you education like Larry Crowne then you do what he did which is get his degree so that he could never have to worry about getting fired again. To me because of what Larry had his mind set on doing when he went he was to able to get the job done, have fun after class and sometimes during , and on top of all that he was able to manage a job.I believe he was only able to get it done because he had is priorities set , in order , and he followed through with them. Hence , after viewing this movie feel like I am somewhat ready for college, I’m definitely excited for it. There are a few things that I have to still work on i. e. work and study habits. If you noticed in the end you’d see Larry studying for finals , class etc. when and where ever he could. And in the end it all paid off.College is not an option for me – it’s a must – so there for I have to go. Larry didn’t have to go he wanted to. I wonder how would it have been Larry to just stay out of school and do nothing. Instead he wanted his education and went In with a positive attitude. And no matter when I start college I want to go with that attitude from the get go cause as I witnessed from the movie it’s a much more smoother process. So that’s what I learned from this movie. It really taught me a lesson. h

Thursday, January 9, 2020

Unbiased Report Exposes the Unanswered Questions on American Dream Essay Samples

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