Among his multiple contributions to world science is the synthesis on October 15,when Miramontes was only 26 years old, of norethisterone norethindronethat was to become the progestin used in one of the first three oral contraceptives combined oral contraceptive pills. For this reason, Luis Miramontes is considered by Lilia Miramontes to be its inventor.
December 8, NASA: Life with arsenic December 7, Last week, in a much publicized news conference, NASA announced the discovery of a bacterium that can use arsenic instead of phosphorus.
The news media covered it with a flourish -- and produced much nonsense. The paper was posted at the Science magazine web site, so we can look at what was really shown.
Whatever the hype that the news media added, it is an interesting -- but incomplete -- story. The figure at left shows a key experiment; this is Figure 1B of the paper.
The graph shows the growth of the bacteria under different conditions. Number of cells on the y-axis log scale ; time on the x-axis. The three conditions are, from the top: Importantly, if there is no addition, the bacteria grow very little, if at all lower curve.
Then, arsenic in the form of arsenate does indeed stimulate growth middle curve. So does phosphate; in fact, it is better upper curve. The above experiment along with other measurements does seem to establish the basic point: But now let's look at some of the limitations of the story -- as we have it so far.
First, the bug prefers P to As: You can see this in the graph above. They explicitly do not claim that the bug requires or prefers As, merely that it can use it.
Second and more importantly, the growth medium with no added P contains a trace level of P.
This probably comes from low levels of P contaminating other chemicals they use. It's not enough to support growth alone lower curve in the graphbut it does mean that when the bugs are growing on As, they also have a small amount of P available.
In fact, analysis of the bacteria grown on As shows a weight ratio of about 7 As: On a mole basis, the ratio would be about half that. Thus there still is considerable P in the bacteria. They cannot claim a total replacement of As for P. The paper recognizes this limitation, but some of the news coverage does not.Use the Latin names in Google to locate pictures of the plant, and references to the scientific literature.
Use a slash to open a dialog box where you can type the sinhala name in roman letters (e.g., Ehela, or Aehaela, Waraka or Varaka) to locate the botanical (Latin) name.
Artwork by Dean Ellis (for The Last Hurrah Of The Golden Horde); There is a nice basic overview of propulsion systems here.. You can spend lots of time researching spacecraft propulsion systems.
Separation of mixtures into the respective parts. 2.
In chromatography, components of a mixture distribute themselves between the stationary phase and the mobile phase. We Will Write A Custom Essay Sample On Chem Lab Chromatography FOR YOU For Only $/page. order now. Abiogenesis, or informally the origin of life, is the natural process by which life arises from non-living matter, such as simple organic compounds.
The transition from non-living to living entities was not a single event, but a gradual process of increasing complexity that involved molecular self-replication, self-assembly, autocatalysis and cell membranes.
Moles and Percents Why do we need Moles? A chemical mole, or mol, is a unit of measure, just like a gram or an ounce. It is used internationally so that all chemists speak the same measurement language. International Scholars Tuition School International Scholars Tuition School (IST) tutors are dedicated to teaching the most comprehensive lessons for the 11+ Common Entrance Exams (CEE), UKiset, Verbal Reasoning, Non-Verbal Reasoning, 13+ Common Entrance Exams (CEE), 13+ Common Academic Scholarship Exams (CASE), and Eton College King’s Scholarship Exams, to Hong Kong students who .