See also: Geologic time scale and Timeline of evolutionary history of life For earlier events, see Timeline of the formation of the Universe. Main articles: History of the Earth and Geological history of Earth Axis scale: millions of years. also see {{Human timeline}} and {{Nature timeline}} This timeline of natural history summarizes significant geological and biological events from the formation of the Earth to the arrival of modern humans. Times are listed in millions of years, or megaanni (Ma). NGC 188 star cluster forms Axis scale: billions of years. also see {{Human timeline}} and {{Life timeline}} Main articles: Formation and evolution of the Solar System and Nebular hypothesis In the earliest solar system history, the Sun, the planetesimals and the jovian planets were formed. The inner solar system aggregated more slowly than the outer, so the terrestrial planets were not yet formed, including Earth and Moon. The Geologic record is the strata (layers) of rock in the planet’s crust and the science of geology is much concerned with the age and origin of all rocks to determine the history and formation of Earth and to understand the forces that have acted upon it.

Geologic time is the timescale used to calculate dates in the planet’s geologic history from its origin (currently estimated to have been some 4,600 million years ago) to the present day. Radiometric dating measures the steady decay of radioactive elements in an object to determine its age. It is used to calculate dates for the older part of the planet’s geological record. The theory is very complicated but, in essence, the radioactive elements within an object decay to form isotopes of each chemical element. Isotopes are atoms of the element that differ in mass but share the same general properties. Geologists are most interested in the decay of isotopes carbon-14 (into nitrogen-14) and potassium-40 (into argon-40). Carbon-14 aka radiocarbon dating works for organic materials that are less than about 50,000 years old. For older periods, the potassium-argon dating process is more accurate. Radiocarbon dating is carried out by measuring how much of the carbon-14 and nitrogen-14 isotopes are found in a material.

The ratio between the two is used to estimate the material’s age. Suitable materials include wood, charcoal, paper, fabrics, fossils and shells. It is assumed that rock exists in layers according to age, with older beds below later ones. This is the basis of stratigraphy. The ages of more recent layers are calculated primarily by the study of fossils, which are remains of ancient life preserved in the rock. envion air purifier reviewsThese occur consistently and so a theory is feasible. enso aroma diffuser air purifier humidifierMost of the boundaries in recent geologic time coincide with extinctions (e.g., the dinosaurs) and with the appearances of new species (e.g., hominids).iwata airbrush desktop cleaning station

The Proterozoic (from c.2500 Ma to c.541 Ma) saw the first traces of biological activity. Fossil remains of bacteria and algae. also see {{Life timeline}} and {{Nature timeline}} For later events, see Timeline of human prehistory. ^ According to isotopicAges, the Ca-Al-I's (= Ca-Al-rich inclusions) here formed in a proplyd (= protoplanetary disk]). ^ Taylor, G. Jeffrey (2006), "Wandering Gas Giants and Lunar Bombardment: Outward migration of Saturn might have triggered a dramatic increase in the bombardment rate on the Moon 3.9 billion years ago, an idea testable with lunar samples" [1] ^ Cowan, G (1976), A natural fission reactor (Scientific American, 235) ^ Bernstein H, Bernstein C, Michod RE (2012). DNA repair as the primary adaptive function of sex in bacteria and eukaryotes. Chapter 1: pp.1-49 in: DNA Repair: New Research, Sakura Kimura and Sora Shimizu editors. RESORT-STYLE LIVING IN THE HEART OF SILICON VALLEY! North Park Apartment Village in North San Jose surrounding beautiful five-acre Moitozo Park offer studio, one, two and three bedroom apartment homes, plus townhomes.

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Welcome to Thermal Products Incorporated We offer Replacement Heat Exchanger Tube Bundles Regardless of your industry, Thermal Products, Inc has the right equipment for your process requirements. The dependability of our product line can satisfy even the most demanding and versatile clients. Please contact us for more information or if you need a quotation. DOWNLOAD OUR LINE CARDWhen a UV lamp stops curing within the UV system, it’s generally down to a number of common occurrences. These general issues result in decreased output of UV light intensity, primarily due to the deterioration of the lamp and the transparency of the quartz body. UV radiation can no longer pass through the quartz wall, due to divitrification and the deteriorated electrodes are no longer capable of sparking a plasma arc. Longer wavelengths transmit through the quartz body fairly easily but shorter wavelengths are absorbed in ageing or poorly maintained UV lamps.Problem: The basis of natural “devitrification” occurs when quartz converts back into a crystalline structure which acts as a very poor UV transmitter.

This process occurs after surface contamination and is  accelerated when the UV lamp becomes too hot. Devitrification appears as many white spots on the surface of the quartz body, which causes a reduction of quartz transparency to UV light.Problem: Over-cooling results in a combination of tungsten from the electrode and mercury, condensing onto the inside of the lamp ends giving it a mirror coated effect.3) Black Ends / Electrode ErosionProblem: Although tungsten has a high melting point, natural “blackening” occurs during the lifetime of a UV lamp, due to very high arc temperatures operating between each electrode. During normal operation the electrodes start to erode and the tungsten material starts to sputter depositing on the inside of the quartz body. When the transparency of quartz body is compromised, UV output potential is significantly reduced.Problem: The UV Lamp has overheated due to poor air circulation within the UV System, this is more common with longer lamps due to increased requirement for airflow across a larger surface area.

Overheating of the lamp body softens the quartz which starts to sag under gravity or deforms from pressure differences.Problem: External contamination of a UV lamp happens when foreign contaminants such as finger prints or spray from powders, paper dust and ink, stick onto the outside surface of the quartz body. Sometimes contamination even occurs where the system reflector itself has come into direct contact with the lamp. These contaminants cause ditivtrification (recrystallization) on the quartz body, as such UV radiation is no longer able to pass through.Problem: If a UV lamp is exposed to a current overload, or excessively high temperatures, the electrical connection can break down. Over current situations are generally due to power supply faults, not a fault in the lamp design itself. The electrical connections at the end of each UV lamp are designed to withstand temperatures of no more than 250 °C.  This problem causes electrical arching between the lamp and the lamp holder, which can result in a hole being burnt through the cap, destroy the lamp and potentially even damage the UV system.

Problem: In compressed air cooling systems, airflow contamination occurs, this causes spot devitrification, donated by the alignment of the cooling holes within the uv system reflector.Problem: Spiralling is when the plasma arc is no longer wall stabalised. The plasma arc spirals out of control, repeatedly hitting the inside surface of the lamp body, softening the quartz. Risk of spiralling is higher when:Problem: In the unlikely event the UV lamp doesn’t strike out of the box, it is possible this is due to leaking – which means air is entering into the lamp envelope. The only way to confirm this technical issue, is by using a high frequency lamp tester. A constricted purple or blue arc as shown above, or no discharge at all, indicates there may be a small leak in the seal, which is unlikely to be visible to the naked eye.10) Dirty / Distorted UV ReflectorsProblem: There are many different types of reflectors installed in various UV systems, from plain aluminium to extrusions, fabrications and dichroic coatings.

Around 60% of UV radiation that hits the substrate is actually reflected UV, loss of radiation causes significant loss of UV curing results. As such it is imperative that system reflectors are maintained and cleaned regularly. Poorly focused / distorted reflectors are also a very common reason for UV systems failing to cure.11) UV Light Below Full IntensityProblem: If UV light falls below full intensity, the UV lamp will not reach the necessary levels required for the curing of inks, adhesives and varnishes. Similarly other processes such as the disinfection of air and water or surface treatment.Problem: Lamps operate at high voltages, if they are too close to any metal work or humidity is high, an earth fault can occur, as the arc jumps to ground. Most control systems will instantly trip out.Check UV reflectors are not distorted / too close to the lamp body13) Inks / Coatings / Adhesives – Poorly FormulatedProblem: Ultraviolet curable inks, coatings and adhesives when not properly mixed can lead to unequally distributed photo-initiators, which can negatively effect the curing results.14) How to Enhance Lifetime of a UV Lamp Problem: Natural degradation of UV output occurs during the lifetime of a lamp.