Life And Time One of the first ways in which we learn to classify objects is into two groups: In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter. Nevertheless, the task of defining “life” is both difficult and subtle; something that at once becomes evident if we stop to think. Consider a caterpillar crawling over a rock. The caterpillar is alive, but the rock is not; as you guess at once, since the caterpillar is moving and the rock is not. Yet what if the caterpillar were crawling over the trunk of a tree? The trunk isn’t moving, yet it is as alive as the caterpillar. Or what if a drop of water were trickling down the trunk of the tree? The water in motion would not be alive, but the motionless tree trunk would be. It would be expecting much of anyone to guess that an oyster were alive if he came across one for the first time with a closed shell.
Abstract Titanite sphene has great potential as a petrogenetic indicator and mineral geochronometer, as it can host high concentrations of a range of trace elements and it occurs in diverse rock types. In this paper we describe a natural titanite standard material that may be used to calibrate chemical and isotopic analysis of titanite of varying age and origin.
Through comprehensive bulk analysis of mm-size crystal fragments and in situ microanalysis, we show that the titanite, named MKED1, is largely free of inclusions and is homogenous at the level of analytical precision for major element, U—Pb isotope and Sm—Nd isotope composition. There is some minor zoning in trace element composition, but these zones are easily recognised using backscattered electron imaging and the trace element concentrations of each of these zones are also very homogenous.
Cross calibration with other titanite standards demonstrates that MKED1 can be used as a primary standard for determining U—Pb ages of titanite ranging in age from Precambrian to Neogene. MKED1 may also be used as a standard for in situ trace element microanalysis on the provision that locations for analytical sampling are selected with consideration to grain-scale elemental zoning.
Laser ablation has become a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material.
Radioactive decay[ edit ] Example of a radioactive decay chain from lead Pb to lead Pb. The final decay product, lead Pb , is stable and can no longer undergo spontaneous radioactive decay. All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus.
Additionally, elements may exist in different isotopes , with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable. That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide.
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. The above calculations make several assumptions, such as that the level of 14 C in the atmosphere has remained constant over time. The calculations involve several steps and include an intermediate value called the “radiocarbon age”, which is the age in “radiocarbon years” of the sample: Radiocarbon ages are still calculated using this half-life, and are known as “Conventional Radiocarbon Age”.
Since the calibration curve IntCal also reports past atmospheric 14 C concentration using this conventional age, any conventional ages calibrated against the IntCal curve will produce a correct calibrated age. When a date is quoted, the reader should be aware that if it is an uncalibrated date a term used for dates given in radiocarbon years it may differ substantially from the best estimate of the actual calendar date, both because it uses the wrong value for the half-life of 14 C, and because no correction calibration has been applied for the historical variation of 14 C in the atmosphere over time.
The glands of the endocrine system that regulate a women’s menstrual cycle are the hypothalamus, pituitary gland, and the ovaries. The hypothalamus is the master gland of the system; it secretes Luteinizing Hormone Releasing Hormones (LHRH) and stimulates the pituitary gland to release Luteinizing Hormone (LH) and Follicle-‐Stimulating Hormone (FSH).
To Jenkins’ Spoiler-Laden Guide to Isaac Asimov Introduction Though perhaps best known throughout the world for his science fiction, Isaac Asimov was also regarded as one of the great explainers of science. His essays exemplified his skill at making complex subjects understandable, and were written in an unformal style, liberally sprinkled with personal anecdotes that endeared him to a legion of faithful readers. It was all a labor of love; in particular Asimov often remarked that of all his writing, his essays for The Magazine of Fantasy and Science Fiction were his favorite, despite the fact that he received the lowest word-rate payment for them.
From November to February , an essay of his appeared in the magazine every month, without fail. With the advent of Isaac Asimov’s Science Fiction Magazine in , he began a series of editorials that appeared at the beginning of each issue. In addition he wrote essays and introductions for literally hundreds of magazines, newspapers, books, and trade publications. All together he wrote over essays.
Ayurveda Research Papers (CCA Student papers)
For more examples, see my article: Yet it’s a vacuum there. The thing is that of course it was a sunny day for the astronauts – you tend to forget when you see the black sky. On Earth some of the light comes to the landscape from the sun and some reaches us indirectly from the blue sky and the clouds.
Devil In The Dark () The Horta was an example of Silicon life.; Now we are really sailing off into terra incognito. “Here be dragons” and all that. But if you have starships, you almost have to have aliens (Isaac Asimov’s Foundation trilogy being the most notable exception).The “science” is called Astrobiology, the famous “science in search of a subject”.
Chemotherapy and radiation therapy in select cases Enchondromas, which are benign cartilage tumors, are usually found incidentally, most commonly in the bones of the hand and feet Enneking, Occasionally, very mild endosteal scalloping will occur, however true cortical invasion and the involvement of adjacent soft tissues is rare Enneking, Histologically, islands of normal hyaline cartilage are found surrounded by lamellar bone.
On rare occasion, enchondromas will become symptomatic, or lead to pathologic fracture, and will require surgical treatment. Juxtacortical chondrosarcoma arises on the surface of bone and is histologically identical to conventional intramedullary chondrosarcoma. Chondrosarcomas may also be classified by their histologic sub-type.
These sub-types include clear cell, mesenchymal, and de-differentiated. Clear cell chondrosarcomas are low-grade tumors with significant amounts of glycogen. They typically involve the proximal portion of femur, tibia or humerus. Histologically, cells have abundant clear cytoplasm embedded in a loose hyaline cartilaginous matrix and an infiltrative growth pattern.
Radiographs show a lytic defect at epiphyseal end of long bones that is sharply demarcated with sclerotic margins. They carry a low recurrence rate and a good prognosis with wide resection. Mesenchymal chondrosarcomas are highly aggressive tumors that are radiographically and histologically distinct from conventional and dedifferentiated types.
They are eccentrically located in bone and commonly extend into soft tissues.
I should start by saying that I was raised Catholic. The concepts of reconciliation and absolution are completely ingrained in me. I grew up going to confession at a beautiful monastery where Father Francis, an elderly monk, held my hand as we walked the grounds, and I asked for forgiveness for my transgressions. My spiritual beliefs have evolved and changed over the years, but the idea of forgiveness is still critical to how I walk through life.
Introduction Though perhaps best known throughout the world for his science fiction, Isaac Asimov was also regarded as one of the great explainers of science.
Laser ablation has become a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample remove a portion of a material. The advantages of laser-ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition.
Since then the word ablation has been adopted in the analytical community to describe the direct removal of material from samples of interest for subsequent chemical analysis. There are many excellent review papers related to the techniques presented here 3— However, since this column installment is meant to be an introduction to the field, rather than an exhaustive review, they could not all be included here. For ablation to occur, energy absorption is needed.
The energy can be provided in the form of electrical discharges for example, an arc and spark or in the form of light such as a laser. Laser ablation results in the formation of a gaseous vapor, luminous plasma, and the production of fine particles. Laser ablation is a universally accepted approach for direct sampling in chemical analysis with an extensive field of applications, including the analysis of counterfeit products 11 , nuclear forensics 12,13 , bioimaging 14,15 , food analysis 16,17 , and geochemistry 18, The benefits are well documented and include little-to-no sample preparation, no consumables and minimal waste products, real-time measurements, exceptional spatial resolution, and laboratory and field measurements.
The two primary implementations of laser ablation involve measuring elemental optical emission from the laser-induced plasma at the sample surface, referred to as laser-induced breakdown spectroscopy LIBS , and by transporting the ablated mass referred to as LA to a second atomization and ionization source such as inductively coupled plasma—mass spectrometry ICP-MS or ICP-optical emission spectroscopy OES detection.
At higher temperatures, CO 2 has poor solubility in water, which means there is less CO 2 available for the photosynthetic reactions. The enrichment of bone 13 C also implies that excreted material is depleted in 13 C relative to the diet. This increase in 14 C concentration almost exactly cancels out the decrease caused by the upwelling of water containing old, and hence 14 C depleted, carbon from the deep ocean, so that direct measurements of 14 C radiation are similar to measurements for the rest of the biosphere.
Correcting for isotopic fractionation, as is done for all radiocarbon dates to allow comparison between results from different parts of the biosphere, gives an apparent age of about years for ocean surface water.
Jul 22, · Earlier this year, the realms of law and new media collided when Lori Drew was hit with federal charges for creating a fake MySpace page and harassing a .
In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter. Nevertheless, the task of defining “life” is both difficult and subtle; something that at once becomes evident if we stop to think. Consider a caterpillar crawling over a rock. The caterpillar is alive, but the rock is not; as you guess at once, since the caterpillar is moving and the rock is not.
Yet what if the caterpillar were crawling over the trunk of a tree? The trunk isn’t moving, yet it is as alive as the caterpillar. Or what if a drop of water were trickling down the trunk of the tree? The water in motion would not be alive, but the motionless tree trunk would be. It would be expecting much of anyone to guess that an oyster were alive if he came across one for the first time with a closed shell.
Could a glance at a clump of trees in midwinter, when all are standing leafless, easily distinguish those which are alive and will bear leaves in the spring from those which are dead and will not? Is it easy to tell a live seed from a dead seed, or either from a grain of sand? For that matter, is it always easy to tell whether a man is merely unconscious or quite dead? Modern medical advances are making it a matter of importance to decide the moment of actual death, and that is not always easy.
A Guide to Isaac Asimov’s Essays
It reports that, except for isolated cases, most fluoroelastomers are synthesized by radical co-, ternary or tetrapolymerizations. Hence, after reminding the most known syntheses of fluoroalkenes involved in the preparation of these fluoropolymers and recent achievements of block, graft and alternating copolymers, several academic laws and concepts e. The section dealing with the synthesis of fluoroelastomers is divided into two parts: This section also points out recent syntheses on novel reactive functional trifluorovinyl or vinyl ether monomers for easy curing of original fluoropolymers.
Perhaps lunar miners could use something analogous to Bruce Damer’s idea for asteroids of using CO in an enclosure warmed by the sunlight and iron and nickel extracted in attached 3D printer – .
Some quite large development programs have come and gone in efforts to overcome practical problems associated with what should ideally be a simple, inexpensive, safe, and controllable rocket motor. More recent work has produced variations that have the promise to overcome many of the historical problems. A rocket motor is a device that encloses a high-energy exothermic chemical reaction in a chamber with an exit orifice.
The energies required to perform this feat are enormous. This is why many early tests of various rocket types result in spectacular explosions and even proven types will occasionally experience a malfunction that results in events that can be devastating. In theory, rocket motors are the simplest of devices as they have no requirement to convert heat into mechanical motion, as in the case of a piston or turbine engine.
What could be simpler than burning some stuff in a tube and letting the gas out? In practice, the devil is in the detail and the end result is that rocket motors are very complex, difficult to understand, and hard to predict.