The explicit presentation of the mathematics involved in the Arrhenius equation (Michels, Tsong, and Smith 1983) rendered the parameters involved in glass hydration understandable. However, the actual implementation of the physical processes described in the mathematical equations into a model replicating the natural environment is a complicated problem hard to solve (Stevenson 1998).
THE DEVELOPMENT OF MODELS FOR THE UNDERSTANDING OF OBSIDIAN HYDRATION RATES
In order to understand the obsidian hydration dating method, a model that can demonstrate the process of glass hydration under a certain range of environmental conditions is needed. To implement this, the nature of the concerned materials i.e. glass and water should be adequately known so that the interaction between them can be predicted on the basis of the properties of each substance (Stevenson et al. 1998). There is no consensus among archaeologists and geochemists on how best to model hydration rates. They have long debated on how hydration-rind thickness could tell us about time. The confusion seems to be based on two points. First, after hydration begins, water is no longer reacting with the pure glass. Rather it reacts with an already hydrated layer. The classic diffusion model breaks down at this point. Second, the different variables that determine the hydration rate are mutually interacting. Several researchers have observed a shift from classic diffusion between hydration-rind thickness and time to a linear relation, based on changes in pH. In turn, pH, in a closed system, is influenced by how long the hydration has occurred (Tremaine 1989). As alkali ions leach into solution and are replaced by hydrogen or hydronium ions, the pH of the solution will increase (Bra...
... middle of paper ...
...dity variation, largely because RH is not a variable expressed in the Arrhenius equation. It is likely that the Copan researchers, like the experimental parameters of Michels and colleagues (1983) might consider the RH of tropical soils to be always 100 percent. For contexts deeper than 50 cm, this may be a reasonable assumption. However, it should be borne in mind that the majority of the variability in hydration rates occurs between RH values of 90 and 100 percent, and a 1 percent change in RH translates to approximately a 3 percent change in hydration rate (Tremaine 1989). So if blades from Copan were recovered from contexts with 90 percent RH, their OHD dates would be in error by approximately 30 percent, excluding all other sources of error.
Braswell (1992) was hence right to have questioned the validity of the hydration dates obtained from the Copan region.
The settlements in the complex show a multimodal distribution which means that there is an extensive use of shaped and faced stone walling. Out of the three sites there are, only one has produced stone walling and that is Lago de Handel. Obsidian flows were identified in the Amontillado region and their products ca...
To understand the unique aspects of a gorge created in just a few days, it is necessary to look back to the events which occurred 100,000 years ago. Described by James Lovelock in his book, The Age...
...under H₂O-undersaturated conditions, water was structurally bound up to the greenschist facies and then at the start of anatexis the excess water maximized the amount of H₂O-undersaturated melt generated. Furthermore the dissolution of accessory minerals can provide melts with structural components which in turn give clues about melting history and melting conditions, even during rapid melting. The analysis and mass balance of trace elements found in the glasses and residual phases and melt extraction data, together provided evidence that significant amounts of LILE were retained in residual feldspars and biotite crystals up to a high degree of partial melting of the crustal protolith. This is interpreted as meaning that higher temperatures of partial melting are needed to more efficiently differentiate the crust in these mostly incompatible trace elements.
Have you ever wondered why the plastic bag that you left on the porch during winter cracks or breaks more easily than when you left it during summer time but a piece of wood which was left just like the plastic bag has no effect whatsoever? This is because of a phenomenon, which only happens to polymers, known as the glass transition. For each polymer, there is a certain temperature at which the amorphous polymers undergo a second order phase transition from a rubbery and viscous amorphous solid to a brittle and glassy amorphous solid called the glass transition temperature, Tg.1 When the polymer, or in this case, the plastic bag, is cooled below their glass transition temperature, it becomes hard and brittle like a glass but when it is used above their glass transition temperatures, it might have a different effect than when used at room temperature or below the glass transition temperature as normally, different types of polymers like clothes, food packaging, insulations for wires, etc. are either used above their glass transition temperatures or
Relying on the assumption that the channels could not have been accessed at a date later than the construction of the Fountain House, and that debris could not have made its way into the channels or surrounding areas after construction, Paga seems to be able to provide rather compelling evidence to support her dating of the Fountain House at circa 480-450 BCE. Most convincingly, she notes a saltcellar and a black-gloss Vicup or kylix base (Figure 15, Pg. 372 and Figure 12, Pg. 370 respectively). Saltcellars “are generally associated with the first quarter of the 5th century and rarely appear before 500,” (Paga, 374) and Vicups are “a particular type of cup that was manufactured for a brief time, perhaps for only a single generation, and almost all of its examples date to the second quarter of the 5th century,” (Paga, 374). However, Paga never distinguishes why the black-gloss base is “more likely,” (Paga, 374) from a Vicup than a less esoteric kylix, leaving reason to doubt the evidence she extrapolates from the shard originating as a part of a Vicup. Furthermore, and more significantly, the assumption Paga makes with regards to debris access to the areas the ceramics were found seems unfounded. While she is more than comfortable with the assumption, she does not identify why “such a hypothesis—that the later sherds [sic] represent an intrusion...seems highly unlikely,” (Paga, 376), she only identifies that—to her—it does. In contrast to this, Paga's supporting of her ideas with evidence from the pipelines themselves is more potentially more
In today’s society not many people realize that they are thankful to wake up and live another day. Just imagine being lost at night in an area you are completely unfamiliar with. Imagine it being cold, and you having no clothing. You don’t have any money and you are starving. Now, all your ears hear are the screams of the one’s around you being killed. To add to the torture, you are unable to control your next move, nor the next. There is constant death, starvation, and suffering happening all around you, but you cannot do anything to help the situation besides fending for yourself to survive. This is the devastating and cruel world that Chanrithy Him’s When Broken Glass Floats introduces to its readers.
The purpose of this experiment is to investigate the effect of changing the concentration of sodium chloride solution on the rate of osmosis in tubes of potatoes. This was maintained using equal measurements of the potato tubes and applying them into the different concentrations of sodium chloride, 0%, 2%, 5%, 10%, 20% and 26%, in beakers then measuring the change in mass of the potato tubes afterwards. The time taken for all potato tubes to be placed in solution was 15 minutes. Can the concentration gradient of the sodium chloride solution influence on the rate of osmotic diffusion undergone by the potato tubes?
Ever think you are in control only to find out that you are not and you are in way over your head? Well, that is the life that Kristina Georgia Snow has everyone follow in Glass. Glass is the continuing book of Crank. Crank is about a innocent,17 year old girl named Kristina, who is on her way to graduating early when she has to go spend one month in the summer with her estranged father. While at her fathers house, she tries crank for the first time and falls in love with the monster. The book follows her journey with the monster and the consequences that come with it like hurting her friends and loved ones. The book ends with the teen becoming pregnant due to a product of rape. Glass picks up shortly after Kristina Snow, also known by her "alter ego" Bree, has the baby. She names her baby Hunter Seth.
Dehydration can happen at any age and from a variety of primary causes including diarrhea, vomiting, use of diuretics, exercise, and exposure to extreme heat. The body has compensatory mechanisms to balance mild dehydration or fluid deficit of 2-4%; however, moderate fluid deficit of 5-8% can lead to electrolyte imbalances, postural hypotension, and dryness in skin and mucous membranes (Porth, 2011). In severe dehydration, or fluid deficits greater than 8% severe hypotension and shock can occur (Porth, 2011). The circulatory system has its own compensatory mechanisms for fluid volume deficits. These include changes in cardiac output, heart rate, and blood pressure.
The mixed alkali effect in the glass materials has been the subject of study in the recent years. Many properties of glasses show non linear behaviour of exhibiting a minimum or maximum, as a function of alkali content, if one of the alkali ions is gradually replaced by another alkali keeping total alkali content constant. This behaviour is called mixed alkali effect. The general formula for mixed alkali oxide glass is y[x.A2O + (1-x) B2O] + (1-y) glass former, where A and B are alkalis. The extent of departure from linearity, the direction of variation (positive or negative) depends on the property examined and the glass system. The behavior of mixed alkali effect is independent of glass forming oxides. It is being observed in silicates, borates, phosphates, germanates, tellurites, boro alluminate, alumino silicates, borotellurate etc., glasses. It is also observed that properties related to cationic movement are more sensitive to mixed alkali effect [1-3].
Say you finished on top of your high school year. You were set up for success, but you still felt lost after high school and reality smacks you in the face and invites you to the real world. In The Graduate by Mike Nichols the main character has finished high school and is lost about his future. Straight out the gate you see to two symbolic item in water and glass. Throughout the film you need to think about the third and that is openness. Each time these symbolic item are shown there is a sense of fear and
For example, a study from the Voice Institute of New York found that drinking alkaline water with a pH of 8.8 can help deactivate pepsin. Pepsin is the main enzyme that causes acid reflux. Another study published in the Shanghai Journal of Preventive Medicine suggests that drinking alkaline water may be beneficial for people who suffer from high blood pressure, diabetes, and high cholesterol. Meanwhile, the study from the University of Alberta concludes, “it would be prudent to consider an alkaline diet to reduce morbidity and mortality of chronic disease that are plaguing our aging
It might be easier to live a healthy life for many people, but for others it can be very challenging. I have tried to be healthy so many times, but I always fell off the wagon. For many days I would “feel” healthy, but in reality I was not the healthiest person mentally or physically. I knew that I had to change my behavior, and become healthier (or at least almost healthy) if I wanted to live a longer life. I began my journey by drinking more water, balancing my eating with exerting, all while trying to stay mentally well.
Water is one of the most essential non-renewable natural resources on the Earth. Technically, an un-hydrated human being can live no more than three days. In the United States, people consume water mainly from tap water and bottle water. However, the consumption between these two sources is not even but lean to one side heavily. According to the Natural Resources Defense Council, people consume from 240 to over 10000 times more per gallon for bottled water than they usually do for tap water. (NRDC) In addition, according to a survey from US National Library of Medicines, only 17% of the participants prefer to drink tap water exclusively.(US National Library) Compared to the bottled water which is shining like a superstar, tap water is like a diligent worker in the shade, unpopular but useful. The extremely unbalance of bottled water consumption implies that a commonly hold conception exists: bottle water is superior to tap water. In fact, scientific evidence proves that tap water is nothing different than bottle water. More importantly, the excessive consumption of bottled water is an irrational use of resources and creates severe environmental issues.
Less than 1% of the water supply on earth can be used as drinking water.