Лампы для проекторов
Дешевые лампы для проекторов, качество которых при этом остается безупречно высоким, вы всегда можете приобрести в нашем интернет-магазине. Цены на подобную продукцию формируются в соответствии с актуальными исследованиями рынка продаж и рынка закупки. Такие расходные материалы для видео проекторов зачастую распространяются по очень завышенным ценам, что негативно сказывается на продажах самого оборудования. Для бюджетных моделей стоимость лампы может превышать или быть такой же, как цена самого проектора, что нельзя назвать правильным.
Лампы для проектора в нашем интернет-магазине предлагаются по доступным ценам, которые не только приближаются к стоимости самого оборудования, но и являются значительно более низкими. Наш каталог содержит достаточно широкий ассортимент продукции от многих популярных на сегодняшний день производителей, в том числе:Benq, Epson, Infocus, Panasonic, Sanyo, Sony, Toshiba, Hitachi и других. При этом каждая модель полностью соответствует таким актуальным сегодня требованиям, как яркость, надежность и долговечность.
Любая лампа для мультимедийного проектора является высокотехнологичным расходным элементом, от которого непосредственно зависят все основные характеристики работы прибора. Современные лампы при производстве оснащаются специальным фильтром и защитным футляром, что позволяет самостоятельно производить их замену без необходимости вызова специалистов. Однако при покупке важно точно назвать модель проектора или самой лампы, так как универсальных комплектующих, подходящих к любой марке прибора, просто не существует. Если у вас возникнут какие-либо трудности с выбором, вы всегда можете обратиться к нашим сотрудникам, которые помогут вам определиться с покупкой и способом доставки.
Лампы для проекторов представляют собой не просто расходный материал, но во многом определяют особенности проецируемого при работе оборудования изображения:
Яркость;
Контрастность;
Разрешение;
Комфортность для глаз.
Именно такой высокотехничный элемент является необходимым для получения реалистичного изображения с насыщенной цветовой гаммой. Если краски достаточно контрастны, пользователю предоставляются более широкие возможности для регулировки параметров картинки. Этим и объясняется дороговизна продукции, однако мы делаем все возможное, чтобы вы смогли приобрести лучший товар по адекватным ценам!
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Success Stories - Telegraph Dating members share their experiences
8 Dating Turnoffs Men Over 50 Should Stop Doing
Here's a heads up for the post 50 single men out there. We ladies are so excited when you choose us as the "girl" you want to meet. Hours before our date with you, we are worrying whether you'll like us. Our bedroom floor is littered with clothes as we look for just the perfect outfit to impress you. We do our best to look good, hoping the two of us click. Then the date happens and sometimes we're bewildered by who we meet.
1. Gentlemen, please dress like you care about yourself. You don't have to wear a suit to impress us but it would be nice if you didn't wear your baggiest jeans and a stained shirt. You may be losing weight but there are a zillion discount stores out there that will gladly sell you a nice pair of jeans and a polo style shirt for less than $50. It's worth the investment if you want to get a second date with us.
2. Women are really turned off and have no interest in kissing your bad teeth or skimming their lips over visible skin tags on your neck. Aging takes its toll on all of us physically, but don't let that be an excuse for being sloppy. You may be the greatest guy on the planet with the most sensual lips but if your teeth are missing or your skin has developed tags, then I guarantee you're getting passed over for an issue that can be easily fixed with a quick visit to your doctor or dentist.
3. Please choose a picture that looks like you for your online dating profile. A friend recently had a date with a man who was 100 pounds heavier than his online picture revealed. She got to the restaurant and was unable to identify her date. She resorted to calling him, figuring the guy who picked his phone up was her date. Show us who you really are. Doing a bait and switch with your pictures, hoping we'll like you in person only makes us wonder what else you're hiding.
4. Please don't start our date by telling us gross stories like your dog has fleas, especially if we've hugged you. A client of mine actually had this happen. There's no way we want to expose ourselves to situations that might be contagious. If anything, we'll want to leave so we can go home and fumigate our clothes. Yuck!
5. If you ask us out for a first date, please pay. We're happy to share the bill with you at a later date but whoever does the asking should be the one pulling their wallet out. Please don't ask us out if you can't even afford a cup of coffee. Get your financial situation straightened out before dating.
6. We know if you like us, you want to impress us with all you do and have. You drone on and on about all the great things in your life, even showing us pictures of your house, your car, your landscaping and your dog. We want to get to know you, but a one-way monologue is boring. We were taught as little girls to make you feel good so we listen. Most of us are not sure where to interject without appearing rude. It would be so helpful if you asked us questions too. Dialogue is much more fun!
7. Men, as you've aged you've become far more passionate in your political views. Many a woman has been forced to listen to you pontificate about the world and how you feel it should be run. There's nothing wrong with sharing your views. Just don't lecture us for an hour and then expect us to go out with you again. After 10 minutes, you've totally turned us off.
8. Lastly, please don't stick your tongue down our throats at the end of a first date when you like us. A gentle kiss feels so much nicer. Women are far more into romantic love and a slow gentle kiss will make us want you more. The tongue thrust makes us think you're at best overly aggressive and at worst a creep.
Okay, over 50's men out there, this was tough on you. My next article will be the biggest things women do to turn you off. If fact, feel free to make suggestions for what I should include in the comments.
In the meantime, if you really want to impress a woman consider keeping these eight turnoffs out of your dating repertoire. You'll have far better luck finding the woman of your dreams when you do.
Find out more about Lisa Copeland at www. FindAQualityMan. com .
Best Christian Dating Sites in 2014. How to Pick the Right One for You
There’s a lot of information on the web about the best Christian dating sites . but as Christian singles ourselves, we haven’t found much of it to be truly helpful in our decision-making process. So we figured instead of complaining about it, we’d try to help solve that problem.
Best Christian Dating Sites
We’ve created a comparison chart and detailed resource of the best Christian dating sites. We update it regularly as we get feedback from readers and do further research. Hey, we’re just trying to help a brother or sister out and keep it real. Just doing our part…
But here you are…
So before we go any further, let’s agree that we’re going to accept online dating for what it is: a tool that aids us in the search for Mr. or Miss Right. There’s no shame in using tools.
We’ve searched high and low for reliable information that would guide us to make an informed decision when choosing the best Christian dating sites . and there really aren’t many places that offer information from actual Christians.
We’ve done our fair share of online dating, and we just thought we’d offer our experience and research to those of you who want it. A piggyback ride, perhaps? After all, if we’re still single, we’d at least like to think our money went to something more useful than some awkward first dates.
We plan to update this page as new information arises, so check back often as our reviews of Christian dating sites grow. And if you have anything to contribute to the discussion, we’d love to hear it. Use a pseudonym if you don’t want to use your real name. There’s no shame in that either. We just want to hear your take on any site you’ve had experience with.
DOLLA-DOLLA BILLS, Y’ALL!
Everyone wants to talk about money first. This is evident from our own lives, our conversations with friends, and from the surveys we’ve conducted among online Christian daters.
If you show them the money, will they show you the love?
Money is a big issue.
So let’s talk scratch: Just because a site costs less doesn’t mean you’re necessarily getting a good deal. That being said, just because it costs more doesn’t mean you get a better site either.
Many of the seven sites we’ve reviewed offer a free trial membership. While you’re probably not going to fall in love in ten days or less, miracles can happen. And if you want to test-drive a site, a free trial is a good way to go.
But if you’re ready to go all in, you should know that many factors can change the price of subscription to a Christian dating site. Depending on how long you commit, you can easily make the price per month decrease. The average price for a one-month membership on Match, Chemistry. com and Christian Cafe runs close to $35, Christian Mingle is priced for about $30 for a month, and eHarmony will cost you around $60/month.
Suffice it to say: If you’re choosing strictly based on price, then Marry Well is the front-runner at $12 for a one-month subscription. You can get three months for $25 on Marry Well (less than one month on Christian Mingle). They even have an $8 monthly plan for “cash-strapped” college and graduate students and a scholarship program for people involved in ministry.
Christian Cafe
It’s hard to figure out what kind of numbers these sites are pulling in. They’re not too keen on publishing exactly how many active members you’ll have access to.
A recent Christian Mingle’s commercial states that they have gained 2 million members in the past year alone. What does that mean for your search? Well, anyone can create a free profile on the site (or most sites). Just because there are a ton of profiles does not mean that there are that many actively paying members in which to communicate with.
Marry Well is still a new site, and a quick search from a metropolitan area such as Dallas/Fort Worth showed a much smaller selection of profiles than the sites that have been around for years such as eHarmony, Match, Christian Cafe, Chemistry. com, and Christian Mingle.
Here’s what you need to consider: If you live in a small town or rural area and you’re not into long-distance relationships, the number of online dating profiles within your geographical region is already slim. You’ll need to either expand your driving distance or choose one of the sites that boast millions of profiles to choose from.
With the exception of Marry Well, all 5 of the other sites generally include hundreds to thousands of profiles for Christians to choose from that are within a reasonable driving distance (under 2-3 hours). Marry Well has potential, but it might be a bit longer before we can wholeheartedly recommend it for its large membership.
Membership Numbers. SingleRoots Recommends
Better dates with eHarmony
The best first dates are the ones that stick in your mind long after the evening is over. When the fear-induced butterflies at the beginning get replaced with tingles of anticipation about your next encounter. When you feel like you’ve known each other for years even though it’s only been a few hours.
At eHarmony we think every date should feel like that. Dating isn’t a numbers game. It’s about finding someone uniquely right for you – without having to go on hundreds of dead-end dates first. We make sure each match we send you is perfectly suited to your personality, interests and values – leaving you more time to have fun.
Dating the eHarmony way
Searching for love shouldn’t just be about the number of people you meet. Like most things in life, it’s quality, not quantity that’s important. Here at eHarmony we believe there’s a better approach to online dating than being bombarding with profiles and pictures. We think the dates our members go on should be amazing, memorable occasions. Join eHarmony today and ensure your first meeting has that ‘wow’ moment.
Radiocarbon dating
From Wikipedia, the free encyclopedia
Radiocarbon dating is a method of determining the age of an object by using the properties of radiocarbon. a radioactive isotope of carbon. The method was invented by Willard Libby in the late 1940s and soon became a standard tool for archaeologists. It depends on the fact that radiocarbon, often abbreviated as 14
C. is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting radiocarbon combines with atmospheric oxygen to form radioactive carbon dioxide. This is then incorporated into plants by photosynthesis. and animals acquire 14
C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point the amount of 14
C it contains begins to reduce as the 14
C undergoes radioactive decay. Measuring the amount of 14
C in a sample from a dead plant or animal such as piece of old wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The oldest dates that can be reliably measured by radiocarbon dating are around 50,000 years ago, though special preparation methods occasionally permit dating of older samples.
While the idea behind radiocarbon dating is straightforward, years of additional work were required to develop the technique to the point where accurate dates could be obtained. Research has been going on since the 1960s to determine what the proportion of 14
C in the atmosphere has been over the past fifty thousand years. The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's actual calendar age. In addition to this curve, other corrections must be made to account for different proportions of 14
C in different types of organism (fractionation) and different 14
C levels in different parts of the biosphere (reservoir effects).
Measurement of radiocarbon was originally done by beta-counting devices, so called because they counted the amount of beta radiation emitted by decaying 14
C atoms in a sample. More recently, accelerator mass spectrometry has become the method of choice; it can be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly.
The development of radiocarbon dating has had a profound impact on archaeology. In addition to permitting more accurate dating within archaeological sites than did methods previously in use, it also allows comparison of dates of events across great distances. Histories of archaeology often refer to the early impact of the new method as the “radiocarbon revolution”. Occasionally, the method is used for items of popular interest such as the Shroud of Turin. which is claimed to show an image of the body of Jesus Christ. A sample of linen from the shroud was tested in 1988 and found to date from the 1200s or 1300s, casting doubt on its authenticity.
Contents
Background [ edit ]
History [ edit ]
In the early 1930s Willard Libby was a chemistry student at the University of Berkeley. receiving his Ph. D. in 1933. He remained there as an instructor until the end of the decade. In 1939 the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research. It was soon discovered that 14
C 's half-life was far longer than had been previously thought, and in 1940 this was followed by proof that the interaction of slow neutrons with 14
N was the main pathway by which 14
C was created. It had previously been thought 14
C would be more likely to be created by deuterons interacting with 13
C. At about this time Libby read a paper by W. E. Danforth and S. A. Korff, published in 1939, which predicted the creation of 14
C in the atmosphere by neutrons from cosmic rays which had been slowed down by collisions with molecules of atmospheric gas. It was this paper that first gave Libby the idea that radiocarbon dating might be possible. [ 1 ]
In 1945, Libby moved to the University of Chicago. He published a paper in 1946 in which he proposed that the carbon in living matter might include 14
C as well as non-radioactive carbon. [ 2 ] [ 3 ] Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained radioactive 14
C. By contrast, methane created from petroleum had no radiocarbon activity. The results were summarized in a paper in Science in 1947, and the authors commented that their results implied it would be possible to date materials containing carbon of organic origin. [ 2 ] [ 4 ]
Libby and James Arnold proceeded to experiment with samples of wood of known age. For example, two wood samples taken from the tombs of two Egyptian kings, Zoser and Sneferu. independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years. These results were published in Science in 1949. [ 5 ] [ 6 ] In 1960, Libby was awarded the Nobel Prize in Chemistry for this work. [ 2 ]
Physical and chemical details [ edit ]
In nature, carbon exists as two stable, nonradioactive isotopes. carbon-12 ( 12
C ), and a radioactive isotope, carbon-14 ( 14
C ), also known as "radiocarbon". The half-life of 14
C (the time it takes for half of a given amount of 14
C to decay ) is about 5,730 years, so its concentration in the atmosphere might be expected to reduce over thousands of years. However, 14
C is constantly being produced in the lower stratosphere and upper troposphere by cosmic rays. which generate neutrons that in turn create 14
C when they strike nitrogen-14 ( 14
N ) atoms. [ 2 ] The 14
C creation process is described by the following nuclear reaction :
Once produced, the 14
C quickly combines with the oxygen in the atmosphere to form carbon dioxide ( CO
2 ). Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is taken up by plants via photosynthesis. Animals eat the plants, and ultimately the radiocarbon is distributed throughout the biosphere. The ratio of 14
Principles [ edit ]
During its life, a plant or animal is exchanging carbon with its surroundings, so the carbon it contains will have the same proportion of 14
C as the biosphere and the carbon exchange reservoir. Once it dies, it ceases to acquire 14
C. but the 14
C within its biological material at that time will continue to decay, and so the ratio of 14
C to 12
C in its remains will gradually reduce. Because 14
C decays at a known rate, the proportion of radiocarbon can be used to determine how long it has been since a given sample stopped exchanging carbon—the older the sample, the less 14
C will be left. [ 8 ]
The equation governing the decay of a radioactive isotope is: [ 2 ]
where N 0 is the number of atoms of the isotope in the original sample (at time t = 0, when the organism from which the sample was taken died), and N is the number of atoms left after time t . [ 2 ] ? is a constant that depends on the particular isotope; for a given isotope it is equal to the reciprocal of the mean-life — i. e. the average or expected time a given atom will survive before undergoing radioactive decay. [ 2 ] The mean-life, denoted by ? . of 14
C is 8,267 years, so the equation above can be rewritten as: [ 11 ]
The sample is assumed to have originally had the same 14
C / 12
C ratio as the ratio in the biosphere, and since the size of the sample is known, the total number of atoms in the sample can be calculated, yielding N 0 . the number of 14
C atoms in the original sample. Measurement of N . the number of 14
C atoms currently in the sample, allows the calculation of t . the age of the sample, using the equation above. [ 8 ]
The half-life of a radioactive isotope (the time it takes for half of the sample to decay, usually denoted by t 1/2 ) is a more familiar concept than the mean-life, so although the equations above are expressed in terms of the mean-life, it is more usual to quote the value of 14
C 's half-life than its mean-life. [ note 1 ] The currently accepted value for the half-life of 14
C is 5,730 years. [ 2 ] This means that after 5,730 years, only half of the initial 14
C will have remained; a quarter will have remained after 11,460 years; an eighth after 17,190 years; and so on.
The above calculations make several assumptions, such as that the level of 14
C in the biosphere has remained constant over time. [ 2 ] In fact, the level of 14
C in the biosphere has varied significantly and as a result the values provided by the equation above have to be corrected by using data from other sources in the form of a calibration curve, which is described in more detail below. [ 12 ] For over a decade after Libby's initial work, the accepted value of the half-life for 14
C was 5,568 years; this was improved in the early 1960s to 5,730 years, which meant that many calculated dates in published papers were now incorrect (the error is about 3%). However, it is possible to incorporate a correction for the half-life value into the calibration curve, and so it has become standard practice to quote measured radiocarbon dates in "radiocarbon years", meaning that the dates are calculated using Libby's half-life value and have not been calibrated. [ 13 ] [ note 2 ] This approach has the advantage of maintaining consistency with the early papers, and also avoids the risk of a double correction for the Libby half-life value. [ 15 ]
Carbon exchange reservoir [ edit ]
Simplified version of the carbon exchange reservoir, showing proportions of carbon and relative activity of the 14
The different elements of the carbon exchange reservoir vary in how much carbon they store, and in how long it takes for the 14
C generated by cosmic rays to fully mix with them. [ 2 ] The atmosphere, which is where 14
C is generated, contains about 1.9% of the total carbon in the reservoirs, and the 14
C it contains mixes in less than seven years. [ 16 ] [ 17 ] The ratio of 14
C to 12
C in the atmosphere is taken as the baseline for the other reservoirs: if another reservoir has a lower ratio of 14
C to 12
C. it indicates that the carbon is older and hence that some of the 14
C has decayed. [ 12 ] The ocean surface is an example: it contains 2.4% of the carbon in the exchange reservoir, [ 16 ] but there is only about 95% as much 14
C as would be expected if the ratio were the same as in the atmosphere. [ 2 ] The time it takes for carbon from the atmosphere to mix with the surface ocean is only a few years, [ 18 ] but the surface waters also receive water from the deep ocean, which has over 90% of the carbon in the reservoir. [ 12 ] Water in the deep ocean takes about 1,000 years to circulate back through surface waters, and so the surface waters contain a combination of older water, with depleted 14
C. and water recently at the surface, with 14
C in equilibrium with the atmosphere. [ 12 ]
Creatures living at the ocean surface have the same 14
C ratios as the water they live in, and as a result of the reduced 14
C / 12
C ratio, the radiocarbon age of marine life is typically about 400 years. [ 19 ] [ note 4 ] Organisms on land, however, are in closer equilibrium with the atmosphere and have the same 14
C / 12
C ratio as the atmosphere. [ 2 ] These organisms contain about 1.3% of the carbon in the reservoir; sea organisms have a mass of less than 1% of those on land and are not shown on the diagram. [ 16 ] Accumulated dead organic matter, of both plants and animals, exceeds the mass of the biosphere by a factor of nearly 3, and since this matter is no longer exchanging carbon with its environment, it has a 14
C / 12
Dating considerations [ edit ]
The variation in the 14
C / 12
C ratio in different parts of the carbon exchange reservoir means that a straightforward calculation of the age of a sample based on the amount of 14
C it contains will often give an incorrect result. There are several other possible sources of error that need to be considered. The errors are of four general types:
variations in the 14
C / 12
C ratio in the atmosphere, both geographically and over time;
isotopic fractionation;
variations in the 14
C / 12
C ratio in different parts of the reservoir;
contamination.
Atmospheric variation [ edit ]
In the early years of using the technique, it was understood that it depended on the atmospheric 14
C / 12
C ratio having remained the same over the preceding few thousand years. To verify the accuracy of the method, several artefacts that were datable by other techniques were tested; the results of the testing were in reasonable agreement with the true ages of the objects. However, in 1958, Hessel de Vries was able to demonstrate that the 14
C / 12
C ratio had changed over time by testing wood samples of known ages and showing there was a significant deviation from the expected ratio. This discrepancy, often called the de Vries effect, was resolved by the study of tree rings. [ 20 ] [ 21 ] Comparison of overlapping series of tree rings allowed the construction of a continuous sequence of tree-ring data that spanned 8,000 years. [ 20 ] (Since that time the tree-ring data series has been extended to 13,900 years.) [ 22 ] Carbon-dating the wood from the tree rings themselves provided the check needed on the atmospheric 14
C / 12
C ratio: with a sample of known date, and a measurement of the value of N (the number of atoms of 14
C remaining in the sample), the carbon-dating equation allows the calculation of N 0 – the number of atoms of 14
C in the sample at the time the tree ring was formed – and hence the 14
C / 12
C ratio in the atmosphere at that time. [ 20 ] Armed with the results of carbon-dating the tree rings, it became possible to construct calibration curves designed to correct the errors caused by the variation over time in the 14
C / 12
C ratio. [ 23 ] These curves are described in more detail below .
Atmospheric 14
C. New Zealand [ 24 ] and Austria. [ 25 ] The New Zealand curve is representative of the Southern Hemisphere; the Austrian curve is representative of the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of 14
C in the Northern Hemisphere. [ 9 ] The date that the Partial Test Ban Treaty (PTBT) went into effect is marked on the graph.
Coal and oil began to be burned in large quantities during the 1800s. Both coal and oil are sufficiently old that they contain little detectable 14
C and, as a result, the CO
2 released substantially diluted the atmospheric 14
C / 12
C ratio. Dating an object from the early 20th century hence gives an apparent date older than the true date. For the same reason, 14
C concentrations in the neighbourhood of large cities are lower than the atmospheric average. This fossil fuel effect (also known as the Suess effect, after Hans Suess. who first reported it in 1955) would only amount to a reduction of 0.2% in 14
C activity if the additional carbon from fossil fuels were distributed throughout the carbon exchange reservoir, but because of the long delay in mixing with the deep ocean, the actual effect is a 3% reduction. [ 20 ] [ 26 ]
A much larger effect comes from above-ground nuclear testing, which released large numbers of neutrons and created 14
C. From about 1950 until 1963, when atmospheric nuclear testing was banned, it is estimated that several tonnes of 14
C were created. If all this extra 14
C had immediately been spread across the entire carbon exchange reservoir, it would have led to an increase in the 14
C / 12
C ratio of only a few per cent, but the immediate effect was to almost double the amount of 14
C in the atmosphere, with the peak level occurring in about 1965. The level has since dropped, as the "bomb carbon" (as it is sometimes called) percolates into the rest of the reservoir. [ 20 ] [ 26 ] [ 27 ]
Isotopic fractionation [ edit ]
Photosynthesis is the primary process by which carbon moves from the atmosphere into living things. In both photosynthetic pathways (C3 and C4 ) 12
C is absorbed slightly more easily than 13
C. which in turn is more easily absorbed than 14
C ratios in plants that differ from the ratios in the atmosphere. This effect is known as isotopic fractionation. [ 28 ] [ 29 ]
To determine the degree of fractionation that takes place in a given plant, the amounts of both 12
C and 13
C isotopes are measured, and the resulting 13
C / 12
C ratio is then compared to a standard ratio known as PDB. [ note 5 ] The 13
C / 12
C ratio is used instead of 14
C / 12
C because the former is much easier to measure, and the latter can be easily derived: the depletion of 13
C relative to 12
C is proportional to the difference in the atomic masses of the two isotopes, so the depletion for 14
C is twice the depletion of 13
C. [ 12 ] The fractionation of 13
C. known as ? 13 C. is calculated as follows: [ 28 ]
where the ‰ sign indicates parts per thousand. [ 28 ] Because the PDB standard contains an unusually high proportion of 13
C. [ note 6 ] most measured ? 13 C values are negative.
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