This cool season grass requires an added level of consideration. Because naturally occurring tall fescue is often infected with an endophyte toxic to broodmares and cattle, extensive research has gone into developing new, safe varieties of tall fescue. As a result, there are more varieties of tall fescue commercially available than most other grasses, and greater performance differences among them. There is also tremendous misunderstanding surrounding tall fescue varieties, so take the time to learn about each. Tall fescue can be one of three types: Endophyte free, Novel Endophyte infected or Toxic Endophyte infected. For your reference, the endophyte status of each variety is listed in the 2019 Tall Fescue and Bromegrass Report.
When lights of different colors shine on the same spot on a white surface, the light reflecting from that spot to your eyes is called an additive mixture because it is the sum of all the light. We can learn about human color perception by using colored lights to make additive color mixtures.
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An implication of one boiling point is that lighter components never cleanly "boil first". At boiling point, all volatile components boil, but for a component, its percentage in the vapor is the same as its percentage of the total vapor pressure. Lighter components have a higher partial pressure and, thus, are concentrated in the vapor, but heavier volatile components also have a (smaller) partial pressure and necessarily vaporize also, albeit at a lower concentration in the vapor. Indeed, batch distillation and fractionation succeed by varying the composition of the mixture. In batch distillation, the batch vaporizes, which changes its composition; in fractionation, liquid higher in the fractionation column contains more lights and boils at lower temperatures. Therefore, starting from a given mixture, it appears to have a boiling range instead of a boiling point, although this is because its composition changes: each intermediate mixture has its own, singular boiling point.
Interactions between the components of the solution create properties unique to the solution, as most processes entail non-ideal mixtures, where Raoult's law does not hold. Such interactions can result in a constant-boiling azeotrope which behaves as if it were a pure compound (i.e., boils at a single temperature instead of a range). At an azeotrope, the solution contains the given component in the same proportion as the vapor, so that evaporation does not change the purity, and distillation does not effect separation. For example, ethyl alcohol and water form an azeotrope of 95.6% at 78.1 C.
Another factor in addition to the packing shape and surface area that affects the performance of random or structured packing is the liquid and vapor distribution entering the packed bed. The number of theoretical stages required to make a given separation is calculated using a specific vapor to liquid ratio. If the liquid and vapor are not evenly distributed across the superficial tower area as it enters the packed bed, the liquid to vapor ratio will not be correct in the packed bed and the required separation will not be achieved. The packing will appear to not be working properly. The height equivalent to a theoretical plate (HETP) will be greater than expected. The problem is not the packing itself but the mal-distribution of the fluids entering the packed bed. Liquid mal-distribution is more frequently the problem than vapor. The design of the liquid distributors used to introduce the feed and reflux to a packed bed is critical to making the packing perform to it maximum efficiency. Methods of evaluating the effectiveness of a liquid distributor to evenly distribute the liquid entering a packed bed can be found in references.[44][45] Considerable work has been done on this topic by Fractionation Research, Inc. (commonly known as FRI).[46]
Exposure Contact with a substance by swallowing, breathing, or touching the skin or eyes. Exposure may be short-term [acute exposure], of intermediate duration, or long-term [chronic exposure].
Minimal risk level (MRL) An ATSDR estimate of daily human exposure to a hazardous substance at or below which that substance is unlikely to pose a measurable risk of harmful (adverse), noncancerous effects. MRLs are calculated for a route of exposure (inhalation or oral) over a specified time period (acute, intermediate, or chronic). MRLs should not be used as predictors of harmful (adverse) health effects [see reference dose].
Statistics A branch of mathematics that deals with collecting, reviewing, summarizing, and interpreting data or information. Statistics are used to determine whether differences between study groups are meaningful.
Toxicological profile An ATSDR document that examines, summarizes, and interprets information about a hazardous substance to determine harmful levels of exposure and associated health effects. A toxicological profile also identifies significant gaps in knowledge on the substance and describes areas where further research is needed.
In this section, we examine the effects of several intervention studies that aimed to teach students questioning skills and discuss the significance of their findings. These studies were carried out mainly in the contexts of: (a) reading science texts; (b) formulating researchable questions for science investigations; and (c) learning new content material through group discussions.
In general, the American Cancer Society does not determine if something causes cancer (that is, if it is a carcinogen). Instead, we rely on the determinations of other respected agencies, such as the International Agency for Research on Cancer (IARC, part of the World Health Organization) and the US National Toxicology Program (NTP).
Surface winds drive currents in the upper ocean. Deep below the surface, however, ocean circulation is primarily driven by changes in seawater density, which is determined by salinity and temperature. In some regions such as the North Atlantic near Greenland, cooled high-salinity surface waters can become dense enough to sink to great depths. The 'Global Conveyor Belt' visualization (below) shows a simplified model of how this type of circulation would work as an interconnected system.The ocean stores more heat in the uppermost three (3) meters than the entire atmosphere. Thus density-controlled circulation is key to transporting heat in the ocean and maintaining Earth's climate. Excess heat associated with the increase in global temperature during the last century is being absorbed and moved by the ocean. In addition, studies suggest that seawater is becoming fresher in high latitudes and tropical areas dominated by rain, while in sub-tropical high evaporation regions, waters are getting saltier. Such changes in the water cycle could significantly impact not only ocean circulation but also the climate in which we live.
For the most effective hand washing, you must use soap and you must be thorough. Work up a lather because the friction helps lift dirt and oils from your skin, according to the Centers for Disease Control and Prevention (CDC). How long you should scrub depends on how dirty your hands are, but most health authorities recommend at least 20 seconds, or as long as it takes to sing "Happy Birthday" twice. And don't forget to scrape underneath your fingernails. That area is prime real estate for germs.
"Consumers may think antibacterial washes are more effective at preventing the spread of germs, but we have no scientific evidence that they are any better than plain soap and water," Dr. Janet Woodcock, the director of the FDA's Center for Drug Evaluation and Research (CDER), said in a statement. "In fact, some data suggests that antibacterial ingredients may do more harm than good over the long term."
To know that boiling point has been reached, bubbles of vapour are produced inside the liquid. If the heating rate is turned up, the temperature of the reactants does not change, but the rate at which the boiling liquid changes into vapour form increases. This increase is caused by the increased supply of energy that facilitates more liquid molecules into overcoming their intermolecular interactions to enter the gas phase.
Distillation of crude oil and production of petrochemicals - Crude oil is a mixture of hundreds of hydrocarbons that also contains some solids and some gaseous hydrocarbons dissolved in it from the alkane family (mainly it is CH4 and C2H6, but it can be C3H8 or C4H10). Crude oil is first heated into a furnace then the resultant mixture is fed as a vapour to the fractional distillation tower. The fractional distillation column separates the mixture into different compartments called fractions. There exists a temperature gradient in the distillation tower where the top is cooler than the base. The mixture of liquid and vapour fractions gets separated in the tower depending on their weight and boiling point (boiling point is the temperature at which the liquid phase changes into gaseous). When the vapours evaporate and meet a liquid fraction whose temperature is below the boiling point of vapor, it partly condenses. These vapours of evaporating crude oil condense at different temperature in the tower. Vapours (gases) of the lightest fractions (gasoline and petroleum gas), flow to the top of the tower, intermediate weight liquid fractions (kerosene and diesel oil distillates), lingers in the middle, heavier liquids (called gas oils) separate lower down, while the heaviest fractions (solids) with the highest boiling points remain at the base of the tower. Each fraction in the column contains hydrocarbons with a similar number of carbon atoms, smaller molecules are towards the top and longer molecules nearer the bottom of the column (Ref). In this way, petroleum is decomposed into petroleum gas, gasoline, paraffin (kerosene), naphtha, light oil, heavy oil, etc. 2ff7e9595c
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