New Horizons
New Horizons is an interplanetary space probe that was launched as a part of NASA’s New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow, which as of 2019 includes 2014 MU69.It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.
Henry Moseley
Mendeleev’s table was nine tenths of the way there, but needed one important modification before it became the modern periodic table – the use of atomic number as the organizing principle for the periods. According to Moseley, similar properties recur periodically when elements are arranged according to increasing atomic number. Atomic numbers, not weights, determine the factor of chemical properties.
Mendeleev ordered his elements in order of their relative atomic mass, and this gave him some problems. For example, iodine has a lower relative atomic mass than tellurium, so it should come before tellurium in Mendeleev’s table – but in order to get iodine in the same group as other elements with similar properties such as fluorine, chlorine and bromine, he had to put it after tellurium, so breaking his own rules. In his invention of the Periodic Table of the Elements, Mendeleev had interchanged the orders of a few pairs of elements in order to put them in more appropriate places in this table of the elements. For example, the metals cobalt and nickel had been assigned the atomic numbers 27 and 28, respectively, based on their known chemical and physical properties, even though they have nearly the same atomic masses. In fact, the atomic mass of cobalt is slightly larger than that of nickel, which would have placed them in backwards order if they had been placed in the Periodic Table blindly according to atomic mass.
Moseley’s experiments in X-ray spectroscopy showed directly from their physics that cobalt and nickel have the different atomic numbers, 27 and 28, and that they are placed in the Periodic Table correctly by Moseley’s objective measurements of their atomic numbers. Using atomic number instead of atomic mass as the organizing principle was first proposed by the British chemist Henry Moseley in 1913, and it solved anomalies like this one. Iodine has a higher atomic number than tellurium – so, even though he didn’t know why, Mendeleev was right to place it after tellurium after all!
Sickle Cell Disease
Sickle cell disease is a group of inherited red blood cells disorders. People who have sickle cell disease have an abnormal protein in their red blood cells.Because the disease runs in families, couples planning to have children can have genetic testing.
Early signs and symptoms of sickle cell disease include swelling of the hands and feet; symptoms of anemia, including fatigue, or extreme tiredness; and jaundice. Over time, sickle cell disease can lead to complications such as infections, delayed growth, and episodes of pain, called pain crises. Most children who have sickle cell disease are pain-free between crises, but adolescents and adults may also suffer with chronic, ongoing pain. Over a lifetime, sickle cell disease can harm a patient’s spleen, brain, eyes, lungs, liver, heart, kidneys, penis, joints, bones, or skin.
A blood and bone marrow transplant is currently the only cure for sickle cell disease, and only a small number of people who have sickle disease are able to have the transplant. There are effective treatments that can reduce symptoms and prolong life. Early diagnosis and regular medical care to prevent complications also contribute to improved well-being. Sickle cell disease is a life-long illness. The severity of the disease varies widely from person to person.
