A Brief History of the Microscope

During that historic period known as the Renaissance, after the dark Middle Ages, there occurred the inventions of printing, gunpowder and the mariners compass, followed by the discovery of America. Equally remarkable was the invention of the light microscope: an instrument that enables the human eye, by means of a lens or combinations of lenses, to observe enlarged images of tiny objects. It made visible the fascinating details of worlds within worlds. Invention of Glass Lenses Long before, in the hazy unrecorded past, someone picked up a piece of transparent crystal thicker in the middle than at the edges, looked through it, and discovered that it made things look larger. Someone also found that such a crystal would focus the suns rays and set fire to a piece of parchment or cloth. Magnifiers and burning glasses or magnifying glasses are mentioned in the writings of Seneca and Pliny the Elder, Roman philosophers during the first century A. D., but apparently they were not used much until the invention of spectacles, toward the end of the 13th century. They were named lenses because they are shaped like the seeds of a lentil. The earliest simple microscope was merely a tube with a plate for the object at one end and, at the other, a lens which gave a magnification less than ten diameters -- ten times the actual size. These excited general wonder when used to view fleas or tiny creeping things and so were dubbed flea glasses. Birth of the Light Microscope About 1590, two Dutch spectacle makers, Zaccharias Janssen and his son Hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged. That was the forerunner of the compound microscope and of the telescope. In 1609, Galileo, father of modern physics and astronomy, heard of these early experiments, worked out the principles of lenses, and made a much better instrument with a focusing device. Anton van Leeuwenhoek (1632-1723) The father of microscopy, Anton van Leeuwenhoek of Holland, started as an apprentice in a dry goods store where magnifying glasses were used to count the threads in cloth. He taught himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270 diameters, the finest known at that time. These led to the building of his microscopes and the biological discoveries for which he is famous. He was the first to see and describe bacteria, yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries. During a long life, he used his lenses to make pioneer studies on an extraordinary variety of things, both living and non-living and reported his findings in over a hundred letters to the Royal Society of England and the French Academy. Robert Hooke Robert Hooke, the English father of microscopy, re-confirmed Anton van Leeuwenhoeks discoveries of the existence of tiny living organisms in a drop of water. Hooke made a copy of Leeuwenhoeks light microscope and then improved upon his design. Charles A. Spencer Later, few major improvements were made until the middle of the 19th century. Then several European countries began to manufacture fine optical equipment but none finer than the marvelous instruments built by the American, Charles A. Spencer, and the industry he founded. Present day instruments, changed but little, give magnifications up to 1250 diameters with ordinary light and up to 5000 with blue light. Beyond the Light Microscope A light microscope, even one with perfect lenses and perfect illumination, simply cannot be used to distinguish objects that are smaller than half the wavelength of light. White light has an average wavelength of 0.55 micrometers, half of which is 0.275 micrometers. (One micrometer is a thousandth of a millimeter, and there are about 25,000 micrometers to an inch. Micrometers are also called microns.) Any two lines that are closer together than 0.275 micrometers will be seen as a single line, and any object with a diameter smaller than 0.275 micrometers will be invisible or, at best, show up as a blur. To see tiny particles under a microscope, scientists must bypass light altogether and use a different sort of illumination, one with a shorter wavelength. The Electron Microscope The introduction of the electron microscope in the 1930s filled the bill. Co-invented by Germans, Max Knoll, and Ernst Ruska in 1931, Ernst Ruska was awarded half of the Nobel Prize for Physics in 1986 for his invention. (The other half of the Nobel Prize was divided between Heinrich Rohrer and Gerd Binnig for the STM.) In this kind of microscope, electrons are speeded up in a vacuum until their wavelength is extremely short, only one hundred-thousandth that of white light. Beams of these fast-moving electrons are focused on a cell sample and are absorbed or scattered by the cells parts so as to form an image on an electron-sensitive photographic plate. Power of the Electron Microscope If pushed to the limit, electron microscopes can make it possible to view objects as small as the diameter of an atom. Most electron microscopes used to study biological material can see down to about 10 angstroms--an incredible feat, for although this does not make atoms visible, it does allow researchers to distinguish individual molecules of biological importance. In effect, it can magnify objects up to 1 million times. Nevertheless, all electron microscopes suffer from a serious drawback. Since no living specimen can survive under their high vacuum, they cannot show the ever-changing movements that characterize a living cell. Light Microscope Vs Electron Microscope Using an instrument the size of his palm, Anton van Leeuwenhoek was able to study the movements of one-celled organisms. Modern descendants of van Leeuwenhoeks light microscope can be over 6 feet tall, but they continue to be indispensable to cell biologists because, unlike electron microscopes, light microscopes enable the user to see living cells in action. The primary challenge for light microscopists since van Leeuwenhoeks time has been to enhance the contrast between pale cells and their paler surroundings so that cell structures and movement can be seen more easily. To do this they have devised ingenious strategies involving video cameras, polarized light, digitizing computers, and other techniques that are yielding vast improvements, in contrast, fueling a renaissance in light microscopy.

The Village of Dier Yassin - 1935 Words

The Village of Dier Yassin Dier Yassin is a village inside the British mandate of Palestine. In 1948, at the time of the Israeli war of independence, from the 9-11 of April Dier Yassin was attacked. Over 100 Arabs were killed on the Haganna and Stern Gang war path between Jaffa and Jerusalem. This was a turning point in the Arab Israeli conflict and some claim that it started the Palestinian refugee crisis. This attack, however, was a small part of a bigger conflict in which the Arab contingent started war on the newly created Israel. The conflictarose from decades of old competing nationalists and as a†¦show more content†¦His main aim to create sympathy for the Arab nation thus enforcing their claim to the land. As stated earlier the source is written by the PLO and is part of a propaganda leaflet, it is a biased account from one of the fighting sides; it attempts to discredit the Israelis and so cultivate support for the Palestinians. The author was probably not an eyewitness as the source is written in 1984, which is over 30yrs after the event. Often, secondary sources written after the event can be useful and reliable as they reflect a wider picture and writers have access to a wider range of sources. Moreover the source was written by an official spokesman for the PLO, who would have access to a lot of information. Some of the information in the source can be corroborated through cross reverence to other souces. However, in this case I think, because of the writer’s obvious views, the lapse in time will have given rise to a myth of error in account: indeed some of the language noted above is very myth-like. There may also be a question that they were allowed to speak freely; although it was written by the PLO in Palestine, Israel still had a lot of control over the Palestinian territories. I think this source is aimed at Arabs and other countries, apart from Israel, to both enrol freedom fighters and to create hatred of Israel.

Athiesms Problem Essay Example For Students

Athiesms Problem Essay To any of you who doubt the presence and magnificence of our Lord, Jesus Christ; first, I must say that I understand exactly where you are coming from. I, too, at one point was a non-believer. Moreover, I was violently anti-Christian to the point of persecuting these children of God. The following is a letter of my conversion to Christianity. It reads through from my early years and the person that I was at that time through to my troubled childhood and teen years all the way to where I am right now. I will focus on and demonstrate the many ways in which I know that Jesus Christ is Lord and God. Hopefully, you will listen with an open heart and realize the wonderful truth that took me so long to see. At the end are a few easy Bible verses to read for further study. My childhood was much like any other. I was born on January 13, 1980 to loving parents and a solid home. Everything was as good as things could be. I very vibrantly remember when I was two years old writing my name on a piece of paper and running around to show my mother what I had done. It was very important to me even at that young ago to feel respected and loved. I remember playing with my sister and chasing her around the house. We loved each other and our situation. When I was very young, my mother and father divorced and my father left us completely. That was the deal; if he left, it was going to be a clean break. I still remember seeing him for the last time when I was four years old. In the coming years, I would end up seeing him again, but not before much damage had been inflicted in our home. My mother remarried a friend of my fathers and things again went quite smoothly indeed. I had a fairly strong bond with my stepfather. We did many exciting and interesting things toget her. I very much enjoyed our time and could not get enough of it. When I was seven, I gave the word that I desired to quit Cub Scouts. This was one of the stronger bonding opportunities between the two of us. I did mention that I had good reasons for my request, but I knew at that very moment that things would never be the same. Storms came and washed away the happiness of my youth. Pressing financial difficulties coupled along with my familys growing lusts for material possessions drove us out into the wilderness of lies. From about this time, I was fascinated by everything mechanical, electrical and involving biology. My spare time at home was spent going through encyclopedia books in a concerted attempt to appease my desire for knowledge and at the same time to draw my mind away from my home life. At home, I would make various gadgets and take them to school. My classmates would marvel at the things I was doing. This, eventually, would be one of the many undoings of my life witho ut God. As the years passed, my former friends became very weary of my trinkets and tricks. They began to call me names and taunt me all the day. This escalated into a full torment which lasted approximately until I was 16. During this time, I fell into a deeper and deeper depression that never faded not even for an instant. I would go to sleep at night hating my life and hating everything else around me. The searing hate and unyielding depression would permeate my mind up until the moment that I fell asleep. Even in my dreams, I would hate myself. In the morning, I would open my eyes and the first thing that would pop into my mind was how angry and let down I was that I woke up again. My typical day would consist of waking up with a burning rage at 5:00 in the morning and going to school, where people would follow me around telling me to kill myself. I was followed around everywhere. No one would ever leave me alone. I even had a few teachers taunt me teachers that I didnt even have class with. I literally had no friends and no family. No one to turn to at all to vent my feelings to. Something happened along the way and my ability to actually feel any form of joy suddenly and inexplicable disappeared. When I was about eight years of age, my sense of pleasure, accomplishment, amusement and happiness simply vanished. I distinctly remember on many occasions trying desperately to laugh at anything in this world. I would do things such as watch television shows like Friends and no matter what I did, I was physically an emotionally unable to laugh. Everyone around me was laughing and talking about how funny these things on television were. I would move the air in and out of my lungs to fake a laugh because I didnt want anyone to know what was going on inside my head. Days ran into each other and there was no way to tell one from another. I no longer had days; I simply had one long never-ending day. This strengthened the non-stop barrage of condescending hate that drove me quite literally insane. After years of taunts and torment, all of a sudden, out of nowhere, everyone who used to follow me around and tease me just ended their torture and I was left all alone in my own mind. When I was 12, I discovered music. Up until this point, I had never listened to music because the only bands that I had ever come into contact with were terribly unmusical ones. This is the time that I discovered my bad music. The music I was listening to did very much make me feel better at the time and made me realize that I was not the only one in the world feeling this way. It did, however, help to drag my spirit even further down without my knowledge. Through years of torment, coupled with a uniquely strong video recorder-like memory and an uncontrollable ability to continually run through my day over and over again, I eventually did go insane. Because of my memory, even when people were leaving me alone (which in itself may have even been worse to be completely ignored) I constantly played back what they did do to me. When I would re-experience the memories over and over again, all of the accompanying emotions would play back along with the images. The burning hate and rage an d depression was right there in the memories, too. In my mind, I quite literally was going through a constant torture even when I was perfectly alone. At some point during these years, the pressure built up in me and other than being extremely susceptible to illness, I began to develop a tightening in my chest. It began as what would feel like a tension that would come and go, but after a while, it never left. Slowly, this tight feeling in my chest began to grow and manifest itself in much more powerful ways. The tight feeling I was having grew more and more unbearable and its hold on me was too much to take. These pains felt as though a car was actually parked on top of my chest. As this phenomenon grew in intensity, it also expanded in duration. No longer was I getting pangs of chest pain, now I was having in all-out non-stop flood of physical pain that was so intense I had to fight in order to breathe sometimes. It was incapacitating. Eventually, it came to a point where it would never go away for even a second. From the very instant I woke up in the morning to the last thing I remember at night, these extreme chest pains were t orturing me. It got to the point that I would have done anything to get rid of them. Business Ethics EssayI can see now just how much God loved me all through my early years even when I screamed at Him and cursed His name and even when I didnt believe he was real. I now am at ease with life because of Him. Sure, life is not easy, but its different now. I have my mind set on a new focus and it has changed me. No longer am I ruled by what doctors or science may say or what evil may come my way. I have a great protector that is very real and fights my battles for me. It is true. If you believe that Jesus Christ is Lord and came to earth to die for your sins and on the third day was resurrected from the dead, then you are a child of God and you may follow in his steps. The wages of sin is death and Jesus is the only one who can take away your sins. As long as you believe in Him and try your best to follow Him, then he will do the rest for you. He truly is a marvelous God. But beware, because there is a very real battle being waged in the spiritual realm. One that I was stuck right in the middle of, but God won me over to the winning side and gave me life! Be on guard because after reading these words, if you decide to give your life to God, there will initially be an enormous opposition and you will be pulled in two different ways. As long as you are not of God, you are siding with the devilthere is no middle ground. If you are not for God, then you will be used for evil even unknowingly. I was on a path to be a very powerful instrument of evil in this world. If only I had known that I was helping out the very one who was destroying my life, I would have stopped and reconsidered where I was going. Please, just take a step back from yourself for a moment and consider all the things you have done today that may have helped the evil to spread just a little farther in this world. Every time you said an unkind word to someone or lied to someone or cheated them you have helped to bring a little more evil into this world. I was so blinded to all this before my conversion, but now it is all so very clear that at times I am amazed how I didnt see it before. In closing, I testify that all these words are true and I hope and pray that this has helped you in some way to understand God and why we Christians love and trust in Him. This is not some unseen force which may or may not exist. We can actually feel His love and care. When we pray, our prayers are answered. When we are attacked, we call His name and He gives us relief. On top of that, some of us have seen amazing and sometimes even frightening things which can only be explained by the fact that God is real. Some of us have even prophesied the future in the name of the Christ to watch it come true in front of our own eyes. So, if you realize how much you cant go through life alone or have something pressing down on you so hard you think you may die, call out His name and ask that He show you His love so that you may believe. God desires all to come to Him, no matter who they are or how bad they may be. If I can be forgiven, anyone can. I was the worst of all and the Lord called me ou t personally to fight for Him. Remember, many will come claiming to be God and claiming to know the way. Test everything and never believe a word unless it can be backed up by verse. God be with you all.

The way of being Essay Example For Students

The way of being Essay Interdependence between this two issues is very close. Li is one that contains Ren and it cannot be separated. According to your rites and cultural behavior you become humane and according to humanness you become culturally developed. To be Li is to be moral so that means to be kind and benevolence to surrounding people. We everyday interact with people who are our parents, friends, relatives, colleges, group mates and other we try to be polite ands nice so to be Ren and according to this we behave in a moral way with them so this is wise. Ren, also in my opinion, refers to honesty. We will write a custom essay on The way of being specifically for you for only $16.38 $13.9/page Order now You have to honestly say if you know something or if you do not know something and it will be wise so this is Li, from my point of view. If you make such kind of confession for yourself that will be wise. Also, responsibility refers to be a wise man so Ren should be wise. To keep your promise if you have done. Do not be a friend for someone who is worse than you, because from him or her you will not get something useful and good. This also means that you have to think before saying something so to be careful in actions. This also some kind of responsibility, because you are responsible for all that you say. This is Li that is a part of Ren and this is moral behavior according to all people who are around you. So I think there is straight relationship between these two issues. Wisdom and knowledge plays a huge role in analects of Confucius. According to Confucius wisdom is absolute welfare of human minds. Also, wisdom is to use knowledge in the right way. However, not always to have much knowledge means to be wise. You can possess a lot of knowledge, but you can be bad and angry man so this is not concerning Li and Ren. Human nature have to be cultural, if human kind is not moral so he cannot be kind and polite. Human nature is evil according to Confucius, he has to study to become kind. Person born with greediness and meanness, but unlike animals, person has intellect that can correct the low human nature. To become cultural person has to work with himself in order to possess kindness. .To be wise means to keep all in balanced: Ren, Li, and Knowledge. Everything have to be interrelated. To be wise means to use your knowledge in the right way, to use knowledge skillfully means to be wise, to be wise and have knowledge means to be Ren and Li, to be humane and to be in accordance with your rites means to be wise. To my mind, interdependence between Ren and Li is very close. For instance, I appreciate my parents and show respect toward them. I am polite with them and kind and while I have a chance I look after them and try to do my best for them. Ren cannot be without Li and Li cannot be without Ren. As for me, reading and analyzing those analects provided me some ideas about constructing and making future plans of my life. I agree that benevolence , virtue, respect, clearness in thoughts are the parts of success. On the other hand being too much benevolent like unable to express own opinion is not right, man should have freedom to innovate, to improve skills and to grow up in mind. Freedom is tool of discovering and inventing new. Of course, people can be shown by someone way to follow if this way is noble, but only show. Thus, people should always try to make their living memorable for everyone, because only like this people can get peace of mind, soul and interacting with others. Ren and Li makes people refine makes the human nature more wise, polite, kind.